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The anti-inflammatory activity of standard aqueous stem bark extract of Mangifera indica L. as evident in inhibition of Group IA sPLA2

ABSTRACT

The standard aqueous stem bark extract is consumed as herbal drink and used in the pharmaceutical formulations to treat patients suffering from various disease conditions in Cuba. This study was carried out to evaluate the modulatory effect of standard aqueous bark extract of M. indica on Group IA sPLA2. M. indica extract, dose dependently inhibited the GIA sPLA2 (NN-XIa-PLA2) activity with an IC50 value 8.1 µg/ml. M. indica extract effectively inhibited the indirect hemolytic activity up to 98% at ~40 µg/ml concentration and at various concentrations (0-50 µg/ml), it dose dependently inhibited the edema formation. When examined as a function of increased substrate and calcium concentration, there was no relieve of inhibitory effect on the GIA sPLA2. Furthermore, the inhibition was irreversible as evidenced from binding studies. It is observed that the aqueous extract ofM. indica effectively inhibits sPLA2 and it is associated inflammatory activities, which substantiate their anti-inflammatory properties. The mode of inhibition could be due to direct interaction of components present in the extract, with sPLA2 enzyme. Further studies on understanding the principal constituents, responsible for the anti-inflammatory activity would be interesting to develop this into potent anti-inflammatory agent.

Key words:
secretory phospholipase A2; anti-inflammatory; pro-inflammatory; inhibition; drug; plants

RESUMO

O extrato aquoso padrão da casca do caule é consumido como bebida à base de plantas e usado em formulações farmacêuticas para o tratamento de pacientes que sofrem de várias doenças em Cuba. Este estudo foi conduzido para avaliar o efeito modulador do extrato aquoso padrão da casca do caule de M. indica sobre o Grupo IA sPLA2. Extrato de M. indica inibiu, de forma dependente de dose, a atividade do GIA sPLA2 (NN-XIa-PLA2) com IC50 de 8,1 µg/ml. O extrato da M. indica inibiu efetivamente a atividade hemolítica indireta em até 98% em uma concentração de 40 µg/ml, e em várias concentrações (0-50 µg/ml), esse extrato inibiu a formação de edema de maneira dependente de dose. Quando examinado como uma função de aumento de concentrações de substrato e cálcio, não houve diminuição do efeito inibitório sobre GIA sPLA2. Adicionalmente, a inibição foi irreversível, como evidenciado em estudos de ligação. Foi observado que o extrato aquoso daM. indica inibe efetivamente sPLA2 e está associado a atividades anti-inflamatórias, o que corrobora suas pro­priedades anti-inflamatórias. A inibição pode ser devida a uma interação direta dos componentes presentes no extrato com a enzima sPLA2. Mais estudos sobre o entendimento dos principais constituintes responsáveis pela atividade anti-inflamatória seriam de interesse para o desenvolvimento destes componentes como potenciais agentes anti-inflamatórios.

Palavras-chave:
fosfolipase A2 secretória; anti-inflama­tório; pró-inflamatório; inibição; drogas; plantas

INTRODUCTION

Phospholipases A2 (PLA2) (PLA2, EC 3.1.1.1.4) are a family of key enzymes, that cleaves fatty acids at the sn-2 position of glycerol phospholipids to liberate free fatty acid and lysophospholipid (Nanda et al. 2007Nanda BL, Nataraju A, Rajesh R, Rangappa KS, Shekar MA and Vishwanath BS. 2007. PLA2 mediated arachidonate free radicals: PLA2 inhibition adn neutralization of free radicals by anti-oxidants-a new role as anti-inflammatory molecule. Curr Top Med Chem 7(8): 765-777. , Burke and Dennis 2009Burke JE and Dennis EA. 2009. Phospholipase A2structure/function, mechanism, and signaling. J Lipid Res 50: S237-S242. ). The released free fatty acid i.e., arachidonic acid, is known to liberate potent and short-lived pro-inflammatory mediators such as prostaglandins, thromboxanes, prostacyclins and leukotrienes; by the action of cyclooxygenase (COX) and lipooxy­genase (LOX) (Nanda et al. 2007,Vadas and Pruzanski 1984Vadas P and Pruzanski W. 1984. Role of extracellular phospholipase A2 in inflammation. Adv Inflam Res 7: 51-59., Diaz and Arm 2003Diaz BL and Arm JP. 2003. Phospholipase A2. Prostaglandins Leukot Essent Fatty Acids 69: 87-97.). The other sPLA2action product -lysophospholipid that is liberated has also been demostrated to serve as a substrate for the synthesis of pro-inflammatory platelet activating factors (PAF) (Burke and Dennis 2009Burke JE and Dennis EA. 2009. Phospholipase A2structure/function, mechanism, and signaling. J Lipid Res 50: S237-S242. , Diaz and Arm 2003Diaz BL and Arm JP. 2003. Phospholipase A2. Prostaglandins Leukot Essent Fatty Acids 69: 87-97.). Thus, it can be concluded that the release of archidonic acid from membrane lipids is the first regulatory and obligatory step in the synthesis of pro-inflammatory mediators in inflammatory. This arachidonic acid metabolic pathway is known to be regulated mainly by secretory phospholipase A2, suggesting the importance of enzyme in inflammation related processes (Nanda et al. 2007Nanda BL, Nataraju A, Rajesh R, Rangappa KS, Shekar MA and Vishwanath BS. 2007. PLA2 mediated arachidonate free radicals: PLA2 inhibition adn neutralization of free radicals by anti-oxidants-a new role as anti-inflammatory molecule. Curr Top Med Chem 7(8): 765-777. ). In snake venoms, only two groups of sPLA2s (GI and GII) have been identified. Group I (GIA) includes the svPLA2s fromElapinae and Hydrophiinae venoms with 115-120 amino acid residues and these svPLA2s are homologous to mammalian pancreatic GIB sPLA2. Group II (GIIA and GIIB) comprises the svPLA2s from Crotalinae andViperinae venoms with 120-125 amino acid residues and homologous to mammalian non-pancreatic Group II-A sPLA2 (Burke and Dennis 2009Burke JE and Dennis EA. 2009. Phospholipase A2structure/function, mechanism, and signaling. J Lipid Res 50: S237-S242. ). Group II PLA2s are in turn divided into different subgroups on the basis of amino acid residue in the 49th position: catalytically active D49 enzymes, catalytically inactive or with low activity K49, S49, N49 or R49 forms (Nevalainen et al. 2012Nevalainen TJ, Cardoso JC and Riikonen PT. 2012. Conserved domains and evolution of secreted phospho­lipases A(2). FEBS J 279: 636-649., Lomonte et al. 2009Lomonte B, Angulo Y, Sasa M and Gutiérrez JM. 2009. The phospholipase A2 homologues of snake venoms: Biological activities and their possible adaptive roles. Protein Pept Lett 16: 860-876.). The subgroups described above exhibit a wide variety of physiological and pathological effects including the inflammatory one (Doley et al. 2010Doley R, Zhou X and Kini RM. 2010. Snake Venom Phospholipase A2 Enzymes. In Handbook of Venoms and Toxins of Reptiles; Mackessy SP Ed., CRC Press: Boca Raton, FL, USA, p. 173-205., Kini 2003Kini RM. 2003. Excitement ahead: Structure, function and mechanism of snake venom phospholipase A2 enzymes. Toxicon 42: 827-840.).

An increased level of sPLA2 are found in inflammatory exudates such as synovial fluid, pleural fluid, ascitis fluid (Bomalaski and Clark 1993Bomalaski JS and Clark MA. 1993. Phospholipase A2 and arthritis. Arthritis Rheum 36: 190-198.) and also in plasma after an inflammatory challenge (Wright et al. 1990Wright GW, Ool CE, Weiss J and Elsbach P. 1990. Purification of a cellular (granulocyte) and extracellular (serum) phospholipase A2that participate in the destruction of Escherichia coli in a rabbit inflammatory exudates. J Biol Chem26: 6675-6681.). In addition, an excess level of sPLA2s is found to be associated with many physiopathological processes such as in cerebral illnesses, cardiovascular disorders, cancers, asthma, respiratory distress syndrome, and progression of tonsillitis (Mallat et al. 2010Mallat Z, Lambeau G and Tedgui A. 2010. Lipoprotein-associated and secreted phospholipases A2 in cardiovascular disease: roles as biological effectors and biomarkers. Circulation 122: 2183-2200., de Luca et al. 2011, Chalbot et al. 2011Chalbot S, Zetterberg H, Blennow K, Fladby T, Andreasen N, Grundke-Igbal I and Igbal K. 2011. Blood-cerebrospinal fluid barrier permeability in Alzheimer's disease. J Alzheimers Dis 25: 505-515., Farooqui et al. 1999Farooqui AA, Litsky ML, Farooqui T and Horrocks LA. 1999. Inhibitors of intracellular phospholipase A2 activity: their neurochemical effects and therapeutical importance for neurological disorders. Brain Res Bull 49: 139-153.). Furthermore, an increased level of sPLA2 activity is also observed in some brain tumors, in chronic neurological disorders associated with neurodegenerative diseases such as neural trauma, Alzheimer's, and Parkinson's diseases (Farooqui et al. 1999Farooqui AA, Litsky ML, Farooqui T and Horrocks LA. 1999. Inhibitors of intracellular phospholipase A2 activity: their neurochemical effects and therapeutical importance for neurological disorders. Brain Res Bull 49: 139-153., Sun et al. 2004Sun GY, Xu J, Jensen MD and Simonyi A. 2004. Phos­pholipase A2 in the central nervous system: implications for neurodegenerative diseases. J Lipid Res45: 205-213.). Several studies have demonstrated that the sPLA2inhibitors suppress inflammatory processes, which provides a strong evidence for their role in pathogenesis in inflammation (Nanda et al. 2007Nanda BL, Nataraju A, Rajesh R, Rangappa KS, Shekar MA and Vishwanath BS. 2007. PLA2 mediated arachidonate free radicals: PLA2 inhibition adn neutralization of free radicals by anti-oxidants-a new role as anti-inflammatory molecule. Curr Top Med Chem 7(8): 765-777. , Moses et al. 2006Moses GS, Jensen MD, Lue LF, Walker DG, Sun AY, Simonyi A and Sun GY. 2006. Secretory PLA2-IIA: a new inflammatory factor for Alzheimer`s diseases. J Neuroinflammation 3: 28., Balsinde et al. 1999Balsinde J, Balboa MA, Insel PA and Dennis EA. 1999. Regulation and inhibition of phospholipase A2. Annu Rev Pharmacol Toxicol 39: 175-189., Granata et al. 2003Granata F, Balestrieri B, Petraroli A, Giannattasio G, Marone G and Triggiani M. 2003. Secretory phos­pholipase A2 as multivalent mediators of inflammatory and allergic disorders. Int Arch Allergy Immunol 131: 153-163., Kim et al. 2004Kim HP, Son KH, Chang HW and Kang SS. 2004. Anti-inflammatory plant flavonoids and cellular action mechanism. J Pharmacol Sci 96: 229-245., Rosenson et al. 2010Rosenson RS, Fraser H, Trias J and Hislop C. 2010. Varespladib methyl in cardiovascular disease. Expert Opin Investig Drugs 19: 1245-1255.). It has been observed that effective inhibitors of sPLA2 are known to suppress the inflammation and its associated aspects (Nanda et al. 2007, Meyer et al. 2005Meyer MC, Rastogi P, Beckett CS and Mchowat J. 2005. Phospholipase A2 inhibitors as potential anti-inflammatory agents. Curr Pharm Des 11: 1301-1312., Narendra Sharath Chandra et al. 2007Narendra Sharath Chandra JN, Ponnappa KC, Sadashiva CT, Priya BS, Nanda BL, Gowda TV, Vishwanath BS and Rangappa KS. 2007. Chemistry and structural evaluation of different phospholipase A2 inhibitors in arachidonic acid pathway mediated inflammation and snake venom toxicity. Curr Top Med Chem7(8): 787-800.). Considering the role of sPLA2s in the inflammatory process, there is considerable pharmacological interest in finding potent and specific sPLA2 inhibitors from diverse sources (Nanda et al. 2007Nanda BL, Nataraju A, Rajesh R, Rangappa KS, Shekar MA and Vishwanath BS. 2007. PLA2 mediated arachidonate free radicals: PLA2 inhibition adn neutralization of free radicals by anti-oxidants-a new role as anti-inflammatory molecule. Curr Top Med Chem 7(8): 765-777. ,Narendra Sharath Chandra et al. 2007Narendra Sharath Chandra JN, Ponnappa KC, Sadashiva CT, Priya BS, Nanda BL, Gowda TV, Vishwanath BS and Rangappa KS. 2007. Chemistry and structural evaluation of different phospholipase A2 inhibitors in arachidonic acid pathway mediated inflammation and snake venom toxicity. Curr Top Med Chem7(8): 787-800.). In addition, considering the drawbacks and severe side effects exhibited by the current anti-inflammatory therapies (non-steroidal anti-inflammatory drugs) targets either LOX or COX-1/2 enzymes (Vane and Botting 1998Vane JR and Botting RM. 1998. Anti-inflammatory drugs and their mechanism of action. Inflamm Res 47: 78-87.), Therefore, it appears rational to develop or find effective inhibitors of sPLA2 which could deplete the downstream pro-inflammatory metabolites of arachidonic acid as well as PAF. Many plant extracts and its constituents are reported for their anti-inflammatory activity through inhibition of sPLA2s (Nanda et al. 2007Nanda BL, Nataraju A, Rajesh R, Rangappa KS, Shekar MA and Vishwanath BS. 2007. PLA2 mediated arachidonate free radicals: PLA2 inhibition adn neutralization of free radicals by anti-oxidants-a new role as anti-inflammatory molecule. Curr Top Med Chem 7(8): 765-777. , Narendra Sharath Chandra et al. 2007Narendra Sharath Chandra JN, Ponnappa KC, Sadashiva CT, Priya BS, Nanda BL, Gowda TV, Vishwanath BS and Rangappa KS. 2007. Chemistry and structural evaluation of different phospholipase A2 inhibitors in arachidonic acid pathway mediated inflammation and snake venom toxicity. Curr Top Med Chem7(8): 787-800., Springer 2001Springer DM. 2001. An update of inhibitors of human 14 kDa type II s- PLA2 in development. Curr Pharm Des 7: 181-198.); effective and specific inhibitors of sPLA2 are not available to date. Many studies have shown that sPLA2s (of Group I) have a very definite role in pathogenesis of inflammation (Granata et al. 2003Granata F, Balestrieri B, Petraroli A, Giannattasio G, Marone G and Triggiani M. 2003. Secretory phos­pholipase A2 as multivalent mediators of inflammatory and allergic disorders. Int Arch Allergy Immunol 131: 153-163., Kim et al. 2004Kim HP, Son KH, Chang HW and Kang SS. 2004. Anti-inflammatory plant flavonoids and cellular action mechanism. J Pharmacol Sci 96: 229-245., Rosenson et al. 2010Rosenson RS, Fraser H, Trias J and Hislop C. 2010. Varespladib methyl in cardiovascular disease. Expert Opin Investig Drugs 19: 1245-1255.), therefore, it would be beneficial to find plant extract/compounds exhibiting inhibitory activity against group I sPLA2, this would be of potential therapeutic relevance in many inflammatory diseased state (Scott et al. 2010Scott KF, Sajinovic M, Hein J, Nixdorf S, Galettis P, Liauw W, DeSouza P, Dong Q, Graham GG and Russell PJ. 2010. Emerging roles for phospholipase A2 enzymes in cancer. Biochimie 92: 601-610. , Dessì et al. 2013Dessì M, Noce A, Bertucci P, Manca Di Villahermosa S, Zenobi R, Castagnola V, Addessi E and DiDaniele N. 2013. Atherosclerosis, Dyslipidemia, and Inflammation: The Significant Role of polyundaturated Fatty acids. ISRN Inflamm 2013: 191823., Magrioti and Kokotos 2013Magrioti V and Kokotos G. 2013. Phospholipase A2inhibitors for the treatment of inflammatory diseases: a patent review (2010-present). Expert Opin Ther Pat 23: 333-344., Slesser et al. 2013Slesser AA, Bhangu A, Bower M, Goldin R and Tekkis PP. 2013. A systemic review of anal squamous cell carcinoma in inflammatory bowel disease. Surg Oncol 22: 230-237.).

Mangifera indica L. (Anacardiaceae), also known as mango, aam, grows in the tropical and sub tropical regions and is one of the most popular edible fruit yielding trees in the world. M. indica has been traditionally used to treat various diseases (Chopra et al. 1956Chopra RN, Nayar SL and Chopra IC. 1956. Glossary of Indian medicinal plants, CSIR publication, New Delhi, 330 p.,Coe and Anderson 1996Coe FG and Anderson GJ. 1996. Screening of medicinal plants used by the Garı´funa of eastern Nicaragua for bioactive compounds. J Ethnopharmacol 53: 29-50., Shah et al. 2010Shah KA, Patel MB, Patel RJ and Parmar PK. 2010. Mangifera indica (mango). Pharmacogn Rev 4: 42-48., Dhananjaya et al. 2011Dhananjaya BL, Zameer F, Girish KS and D'Souza CJ. 2011. Anti-venom potential of aqueous extract of stem bark of Mangifera indicaL. against Daboia russelii (Russell`s viper) venom. Indian J Biochem Biophys 48(3): 175-183.). The aqueous stem bark extract ofM. indica obtained by decoction has been traditionally used for the treatment of menorrhagia, scabies, diarrhea, syphilis, deabetes, cutaneous infections and anemia, as reported in the Naprolert database (Coe and Anderson 1996Coe FG and Anderson GJ. 1996. Screening of medicinal plants used by the Garı´funa of eastern Nicaragua for bioactive compounds. J Ethnopharmacol 53: 29-50., Shah et al. 2010Shah KA, Patel MB, Patel RJ and Parmar PK. 2010. Mangifera indica (mango). Pharmacogn Rev 4: 42-48.). This standard aqueous stem bark extract has been used in pharmaceutical formulations in Cuba under the brand name VIMANG(r), to treat patients suffering from increased stress (Guevara et al. 1998Guevara GM, Tamayo BD, Gonzalez LS, Paez BE, Oceguera J and Nunez-Selles AJ. 1998. Ethnopharmacologic study of Mangifera indica L. extract (QF-808). Abstract of 1stInternational congress pharmacology`98, ed., ORTOP, La Habana, p. 45.). Pharmacological studies have indicated that VIMANG(r) has immunomodulatory, analgestic, antinociceptive, antioxidant and anti-inflammatory effects (Makare et al. 2001Makare N, Bodhankar S and Rangari V. 2001. Immuno­modulatory activity of alcoholic extract of Mangifera indica L. in mice. J Ethnopharmacol78: 133-137., Garrido et al. 2004Garrido G, Gonzalez D, Lemus Y, Garcia D, Lodeiro L, Quintero G, Delporte C, Nunez-Selles AJ and Delgado R. 2004. In vivo and in vitro anti-inflammatory activity of Mangifera indica L. extract (VIMANG). Pharmacol Res 50: 143-149.). Previously, the standard aqueous extract was demonstrated to inhibit the edema induced by carrageen and formalin in mice, rats and guinea-pigs (Garrido et al. 2001Garrido G, González D, Delporte C, Backhouse N, Quintero G, Núñez-Sellés AJ and Morales MA. 2001. Analgestic and anti-inflammatory effects of Mangi­fera indica L. Extarct (Vimang). Phytother Res 15: 18-21., Ojewole 2005Ojewole JA. 2005. Antiinflammatory, analgesic and hypogly­cemic effects of Mangifera indica linn. (Anacardiaceae) stem-bark aqueous extract. Methods Find Exp Clin Pharmacol 27: 547-554.). Even though, M. indica extract is known to possess anti-inflammatory activities, no study has been conducted with regard to sPLA2 enzyme (main regulatory enzyme in arachidonic acid pathway) inhibition in support of its anti-inflammatory effects. Therefore, in this study, for the first time we report the investigations carried out to evaluate the modulatory effect of standard aqueous extract of M. indica on Group IA sPLA2 (i.e., purified NN-XIa-PLA2 phospholipase A2 enzyme from Naja naja venom), to substantiate their anti-inflammatory properties. Furthermore, this study provides an insight on the possible biochemical interaction of extract/components to bring about inhibition of sPLA2s and its inflammatory process.

MATERIALS AND METHODS

Venom of Naja naja (Indian Cobra) was purchased from Irula Co-operative Society Ltd., Chennai, India. All other reagents and chemicals used were of all analytical grades purchased from Sisco Research Laboratories (SRL), Bangalore, India.

Preparation of Extract

Mangifera indica stem bark collected in the campus of the university, which was authenticated at the university herbarium centre, Department of Botany, University of Mysore, Mysore, India, where a voucher specimen (UOM/DOSB/PL/82) was deposited. The stem bark extract of M. indica was prepared by decoction for 1 h in accordance to the method of Garrido et al. (2004Garrido G, Gonzalez D, Lemus Y, Garcia D, Lodeiro L, Quintero G, Delporte C, Nunez-Selles AJ and Delgado R. 2004. In vivo and in vitro anti-inflammatory activity of Mangifera indica L. extract (VIMANG). Pharmacol Res 50: 143-149.) as described earlier (Dhananjaya et al. 2011Dhananjaya BL, Zameer F, Girish KS and D'Souza CJ. 2011. Anti-venom potential of aqueous extract of stem bark of Mangifera indicaL. against Daboia russelii (Russell`s viper) venom. Indian J Biochem Biophys 48(3): 175-183.)\. The fine brown powder obtained after desiccation was dissolved in saline for neutralization assays. The amount of extract is expressed as dry weight.

Animals

Swiss Wistar albino mice weighing about 20-25 g were obtained from the central animal house facility. All protocols of animal experiments were approved by the Sri Adichunchangiri College of Pharmacy- Institutional Animal Care and Use Committee (IACUC). Animal care and handling were conducted in compliance with the national regulations for animal research.

Isolation of Group IA Secretary Phospholipase A2(NN-XIa-PLA2)

sPLA2 belonging to the group IA- NN-XIa-PLA2 from the venom of Naja naja (Southern region) was purified up to homogeneity as described previously by the method of Rudrammaji and Gowda (1998Rudrammaji LM and Gowda TV. 1998. Purification and characterization of three acidic, cytotoxic phospholipase A2 from Indian cobra (Naja naja) venom. Toxicon36: 921-932.). This protein was further used for evaluating the anti-inflammatory potential of aqueous extract of M. indica. The protein concentration was estimated according to the method of Lowry et al. (1951Lowry OH, Rosebrough NJ, Farr AL and Randall RJ. 1951. Protein measurement with the Folin phenol reagent. J Biol Chem193: 265-275.) using BSA as protein standard.

Inhibition of Phospholipase A2 Activity

The Phospholipase A2 assay was carried out according to the method described by Bhat and Gowda (1989Bhat MK and Gowda TV. 1989. Purification and charac­terization of a myotoxic phospholipase A2 from Indian cobra (Naja naja naja) venom. Toxicon 27: 861-873. ). Phosphatidyl choline (PC) was diluted with petroleum ether (60 - 80 °C) to a concentration of 1000 nmoles/50 ml. The reaction mixture containing NN-XIa-PLA2 (5 mg) was made up to 680 ml with water. To the reaction mixture, 200 ml of ether, 100 ml of Tris - HCl buffer (0.05M, pH 7.5), and 20 ml of CaCl2 (500 mM) was added. The total reaction mixture was incubated at 37 °C for 60 min. After incubation, 0.5 ml of Doles mixture (Isopropanol: Pet ether: 1NH2SO4, 40:10:1) was added, mixed and centrifuged at 1000 rpm for 3 min. To the organic phase 0.5 ml of CHCl3: Pet ether (1:5) was added, mixed and centrifuged at 1000 rpm for 3 min. To the upper phase cobalt reagent [1.35 vol. of Triethanolamine made up to 10 ml with solution A (6 g of CO(NO3)2.- 6H2O + 0.8 ml glacial acetic acid) and 7 ml of solution B (Saturated Na2SO4)] was added, mixed and centrifuged at 1000 rpm for 3 min. The upper organic phase was carefully transferred and 0.75 ml of a-nitroso-b-naphthol reagent (0.4% a-nitroso-b-naphthol in 96% ethanol) was added. The intensity of the orange colour is directly proportional to the amount of cobalt present. After 30 min 2 ml of ethanol was added to dilute the contents and absorbance was read at 540 nm. The amount of free fatty acid released was estimated using the standard linolenic acid curve. Enzyme activity was expressed as nmol of fatty acid released/min/mg of protein.

For inhibition studies, NN-XIa-PLA2 (5 mg) was preincubated with or without different concentrations of aqueous extract of M. indica (0 - 20 µg/ml) at 37 °C for 15 minutes. Appropriate controls were carried out and further experiments were conducted as described above. The inhibition is expressed as percentage (%) taking activity of venom alone as 100%. IC50 values were calculated using Graphpad version 5.0.

Effect of Substrate and Calcium Concentration on NN-XIa-PLA2Inhibition by Aqueous Extract of M. Indica

Effects of substrate and calcium concentrations on the inhibition of NN-XIa-PLA2 (5 mg) at IC50 concentration of extract were determined. In general, the reaction mixture containing NN-XIa-PLA2 alone and/or with the IC50 concentration of aqueous extract of M. indica, in 0.05M Tris- HCl buffer, pH 7.5, and 400 mM calcium was used for the PLA2 assay. In the substrate-dependent assay, substrate concentration in the range of 20 to 120 nM was used as in the final reaction mixture. The calcium-dependent assay was carried out with concentrations ranging from 0 to 15 mM in the final reaction mixture. After the reaction time, PLA2 assay was carried out as described above.

Determination of Binding Characteristics and Reversibility of Inhibition byM. Indica

The reaction mixture containing NN-XIa-PLA2 (5 µg) with the IC50 concentration of aqueous extract of M. indica in 0.05M Tris- HCl buffer, pH 7.5, and 40mM calcium were pre-incubated for 15 min. Following the reaction mixture was dialyzed against 1000 ml of 100mM Tris-HCl buffer, pH 7.5, containing 0.2 mM Ca at 4 °C in dialysis tubing (with a molecular weight cut off of 3000-6000) for 24 h with three buffer changes. The PLA2 activity was assayed before and after dialysis as described above.

Neutralization of Indirect Hemolytic Activity

Indirect hemolytic activity was assayed as described by Boman and Kaletta (1957Boman HG and Kaletta U. 1957. Chromatography of rattle snake venom, a separation of three phosphodiesterases. Biochim Biophys Acta 24: 619-631.). The substrate for the indirect hemolytic assay was prepared by suspending 1 ml of packed fresh human red blood cells and 1 ml fresh hen's egg yolk in 8 ml of phosphate buffered saline (PBS). Aqueous extract of M. indica (0 - 40 µg/ml) was pre-incubated with or without NN-XIa-PLA2 (4 μg), which showed 100% hemolytic activity, for 30 min at 37 °C. To the pre-incubated sample, 1 ml of substrate was added and allowed to react for 45 min at 37 °C. The reaction was stopped by adding 9 ml of ice-cold PBS. The suspension was mixed and centrifuged at 1500×g for 20 min. The released hemoglobin was read at 530 nm. A sample with venom alone served as positive control. The hydrolysis of erythrocyte caused by the addition of 9 ml of distilled water is taken as 100% hydrolysis. Appropriate controls were carried out and the inhibition is expressed as percentage (%). Values are presented as the mean of 4 independent determinations.

Neutralization of Edema Inducing Activity

The procedure of Yamakawa and Hokama (1976Yamakawa MM and Hokama NZ. 1976. Fractionation of Sakishima habu (Elegans T) venom and lethal hemorrhagic and edema forming activity of the fractions. In: Ohsaka A, Hayashi K and Sawai Y (Eds), Animal, plant and microbial toxins, Plenum Press, New York 1: 97.) as modified by Vishwanath et al. (1987Vishwanath BS, Kini RM and Gowda TV. 1987. Characterization of three edema inducing phospholipase A2 enzymes from habu (Trimeresurus flavovoridis) venom and their interaction with the alkaloid aristolochic acid. Toxicon25: 501-515. ) was followed. NN-XIa-PLA2 (6 mg) was preincubated without and/or with different concentration of aqueous extract of M. indica (0 - 50 µg/ml) in a total volume of 20 ml saline. The reaction mixture was injected into intra plantar surface of the right hind footpad of mice weighing 20-25 g. The left footpad that received 20 ml of saline served as control. After 45 min the mice were sacrificed giving anaesthesia (Pentobarbitone, 30 mg/kg, i.p.) and both hind limbs were removed at the ankle joint and weighed individually. The increase in weight due to edema is expressed as the ratio of the weight of oedematous limb to the weight of normal (sham injected) limb x 100. Minimum edema dose is defined as the microgram of protein causing an edema ratio of 120%. Injecting a fixed dose of protein into footpads of mice and sacrificing them at regular periods of time, provided time-course curve of edema inducing activity. Edema ratio was calculated and expressed as %.

Statistical Analyses

The IC50 values were calculated using Graph Pad version 5.0. Inhibition percentages were calculated from the difference between inhibitor-treated group and control animals, which received the vehicle. Student's t-test for comparisons of unpaired data was used for statistical evaluation.

RESULTS AND DISCUSSION

sPLA2 are groups of enzymes that are the main regulating enzymes in arachidonic acid pathway-derived pro-inflammatory mediators release, and thus play an important role in inflammatory processes (Nanda et al. 2007Nanda BL, Nataraju A, Rajesh R, Rangappa KS, Shekar MA and Vishwanath BS. 2007. PLA2 mediated arachidonate free radicals: PLA2 inhibition adn neutralization of free radicals by anti-oxidants-a new role as anti-inflammatory molecule. Curr Top Med Chem 7(8): 765-777. , Vadas and Pruzanski 1984Vadas P and Pruzanski W. 1984. Role of extracellular phospholipase A2 in inflammation. Adv Inflam Res 7: 51-59.). Considering the drawbacks and the severe side effects exhibited by current anti-inflammatory therapies that include the non-steroidal anti-inflammatory drugs that inhibit either of the LOX or COX-1/2 enzymes (Vane and Botting 1998Vane JR and Botting RM. 1998. Anti-inflammatory drugs and their mechanism of action. Inflamm Res 47: 78-87.). It appears rational to develop effective inhibitors of sPLA2 that could deplete the downstream pro-inflammatory metabolites of arachidonic acid as well as PAF (Nanda et al. 2007). It has been observed that effective inhibitors of sPLA2 are known to suppress the inflammation and its associated process (Nanda et al. 2007), thus there is renound interest among the researchers around the world for the search of new potent and specific sPLA2 inhibitors from different sources. Many sPLA2 inhibitors have been isolated from various medicinal plants (Nanda et al. 2007, Narendra Sharath Chandra et al. 2007Narendra Sharath Chandra JN, Ponnappa KC, Sadashiva CT, Priya BS, Nanda BL, Gowda TV, Vishwanath BS and Rangappa KS. 2007. Chemistry and structural evaluation of different phospholipase A2 inhibitors in arachidonic acid pathway mediated inflammation and snake venom toxicity. Curr Top Med Chem7(8): 787-800., Springer 2001Springer DM. 2001. An update of inhibitors of human 14 kDa type II s- PLA2 in development. Curr Pharm Des 7: 181-198.), however, effective and specific inhibitors of sPLA2 are still not available. In these line of studies, the aqueous steam bark extract of M. indicais evaluated for its anti-inflammatory potential by inhibiting inflammatory phospholipase A2 (PLA2) belonging to group IA i.e., NN-XIa-PLA2, which is isolated from Naja naja venom as per the previously described method of Rudrammaji and Gowda (1989). The sPLA2 belonging to group IA i.e., NN-XIa-PLA2 gave a specific activity of around 183.6±4.6, when measured using PC as substrate (Table I). When preincubated with different concentrations of extract it was observed that the aqueous extract of M. indica, inhibited the enzymatic activity in a concentration dependent manner as shown in Fig. 1. The result shows that the extent of inhibition was >95% at 40 µg/ml of extract used. The IC50 values calculated was 8.1 µg/ml (Table I). Most of the sPLA2 inhibitors are known to inhibit the activity either by binding to substrate or by chelating calcium, which is required for activity (Nanda et al. 2007). Furthermore, it was observed that the sPLA2 inhibitors affect the "Quality of interface" by modifying the phospholipids bilayer properties which render the phospholipids inaccessible to the enzyme. The steroid inducible inhibitors of sPLA2like lipocartin I and II are shown to inhibit by non-specific binding to the membrane phospholipids. It is also observed that their inhibition is relieved by increasing the substrate concentration (Davidson et al. 1987Davidson FF, Dennis EA, Powell M and Glenney Jr JR. 1987. Inhibition of Phospholipase A2 by "lipocortins' and calpactins. An effect of binding to substrate phospholipids. J Biol Chem 262: 1698-1705.). In our experiments, we observed that, when examined as a function of substrate concentration, there was no relieve of inhibition of the extract preincubated, and also when the substrate concentration was increased from 20 to 120 nM (Fig. 2). This suggests that the inhibition is independent of substrate concentration. Further­more, in the calcium dependent activity test, it was observed that an increase in calcium concentration from 2.5 to 15 mM, increased the NN-XIa-PLA2 enzymatic activity in a dose dependent manner. However, while when IC50 concentration of M. indica extract was preincubated and then used along with varying concentrations of calcium, there was no relieve of inhibition (Fig. 3), suggesting that the inhibition by M. indica extract is independent on calcium concentration. All these studies show that inhibition by aqueous extract ofM. indica is independent on substrate and calcium concentration. Furthermore, it is reported that some of the sPLA2inhibitors have been known to mediate displacement of catalytically essential calcium from the enzyme and consequently inhibition of enzymatic activity (Pruzanski et al. 1992). In the calcium binding experiments, it was found that the PLA2 enzyme activity, both before and after the dialysis of the enzyme inhibitor mixture, was unaltered i.e., the % of inhibitory activity ofM. indica extract was not decreased upon extensive dialysis, suggesting that the inhibition is irreversible, supporting the observation that inhibition by M. indica extract is independent on substrate and calcium concentration. These studies indicate that the inhibition could be due to direct interaction of components/molecules present in M. indicaextract at active site residues of the sPLA2 enzyme.

Figure 1
Dose dependent inhibition of in vitro PLA2(NN-XIa-PLA2) activity by aqueous stem bark extract ofM. indica. Briefly, Phosphatidyl choline (PC) corresponding to 1000 nmol/ml was made up to 680 ml with NN-XIa-PLA2 (5 mg), with or without aqueous stem bark extract of M. indica at various concentrations (0-20 µg/ml) and was incubated with other reaction mixture at 37 °C for 60 min and color developed was read at 540 nm. The results show ± S.E.M. for n=3.

Figure 2
Dose dependent inhibition of indirect hemolytic activity of NN-XIa-PLA2 by aqueous stem bark extract of M. indica. NN-XIa-PLA2 (4 mg) in 100 µl of phosphate-buffered Saline (PBS) was preincubated with or without aqueous stem bark extract of M. indica at various concentrations (0-40 µg/ml). The reaction was started by adding erythrocytes, egg yolk and PBS (1:1:8 v/v) incubated for 10 min at 37 °C. The released hemoglobin in the supernatant was measured by taking absorbance at 540 nm. The results show ± S.E.M. for n=3.

Figure 3
Dose dependent neutralization of edema inducing activity of NN-XIa-PLA2 by aqueous stem bark extract of M. indica. The reaction mixture 30 µl containing NN-XIa-PLA2 (6 µgs) was incubated for 30 min with increasing concentration of aqueous stem bark extract (0-50 µg/ml) ofM. indica. Saline (30 µl) injected into the mouse foot pad served as control. Data represents ± S.E.M for n=3.

TABLE I
IC50 value and specific activity of NN-XIa-PLA2

NN-XIa-PLA2 enzyme exhibited indirect hemolytic activity, which is an indirect way of measuring PLA2 activity using egg yolk and washed erythrocytes which is used as substrates. When the effect of aqueous extract ofM. indica at different concentrations (0-40 µg/ml) was tested, it was found that the extract in general effectively inhibited indirect hemolytic activity up to 98% at ~40 µg/ml concentration (Fig. 4). This in situ inhibition activity is well correlated with the inhibitory activity of the in vitro PLA2enzyme. Therefore, the inhibition of NN-XIa-PLA2 activity by molecules inM. indica extract could be attributed to the modulation of the catalytic activity of PLA2 at the interface itself, i.e., beyond the initial steps of enzyme adsorption and activation, probably through modifications of the intermolecular organization of the membrane components. It is well known that sPLA2s cause cell membrane asymmetry by degradation of glycerol phospholipids of the membranes (Granata et al. 2003Granata F, Balestrieri B, Petraroli A, Giannattasio G, Marone G and Triggiani M. 2003. Secretory phos­pholipase A2 as multivalent mediators of inflammatory and allergic disorders. Int Arch Allergy Immunol 131: 153-163.).

Figure 4
Effect of substrate concentration on inhibition of NN-XIa-PLA2 by aqueous stem bark extract of M. indica. The reaction mixture contained NN-XIa-PLA2enzyme in 0.05 M Tri-HCl buffer pH 7.5, 500 mM CaCl2, inhibitors, and increasing concentrations of substrate (0-120 nM). The reaction was carried out in the absence (rhombus) and presence of IC50 concentration of extract (open square) with increasing concentration of substrate. The figure inset represents the percent of inhibition in the presence of IC50 concentration. Data represents ± S.E.M for n=3.

Many of the inflammatory sPLA2s induce edema (inflammatory reactions) when injected into mouse footpad as demonstrated before (Vishwanath et al. 1988Vishwanath BS, Fawzy AA and Franson RC. 1988. Edema inducing activity of phospholipase A2 purified from human synovial fluid and inhibition by aristolochic acid. Inflammation 12: 549-561.). Several sPLA2 inhibitors are demonstrated to exhibit concomitant inhibition of enzyme activity and edema-inducing activity (Nanda et al. 2007Nanda BL, Nataraju A, Rajesh R, Rangappa KS, Shekar MA and Vishwanath BS. 2007. PLA2 mediated arachidonate free radicals: PLA2 inhibition adn neutralization of free radicals by anti-oxidants-a new role as anti-inflammatory molecule. Curr Top Med Chem 7(8): 765-777. , Mohamed et al. 2010Mohamed R, Dharmappa KK, Tarannum S, Jameel NM, Kannum SA, Ashrafulla HS, Rai L, Souza CJ, Shekhar MA and Vishwanath BS. 2010. Chemical modification of ascorbic acid and evaluation of its lipophilic derivatives as inhibitors of secretory phospholipase A(2) with anti-inflammatory activity. Mol Cell Biochem 345: 69-76.). Since in our study, the aqueous extract of M. indica effectively inhibited the in vitro sPLA2 activity and in situsPLA2 activity, the inhibitory potential of in vivoedema inducing activity of NN-XIa-PLA2 was tested. The edema inducing effect of NN-XIa-PLA2 (6 µg) was more than 175%, when compared to the saline injected mice. Figure 5 shows that aqueous extract of M. indica at different concentrations (0-50 µg/ml), dose dependently inhibited the edema formation, when co-injected with enzyme. In addition, M. indica extract at the tested dose alone did not cause edema when injected into footpads of mice. The neutralization of edema inducing activity is known to be well correlated with the in vitroenzymatic activity inhibition. It has been demonstrated that the standard extract ofM. indica, administered orally (50-200 mg/Kg body wt.) reduced ear edema induced by arachidonic acid (AA) and phorbol myristate acetate (PMA) in mice (Garrido et al. 2006Garrido G, González D, Lemus Y, Delporte C and Delgado R. 2006. Protective effects of a standard extarct of Mangifera indica L. (VIMANG) against mouse ear edemas and its inhibition of eicosanoid production in J7774 murine macrophages. Phytomedicine 13: 412-418.). In addition, the extract was demonstrated to inhibit the edema induced by carrageen and formalin in mice, rats and guinea-pigs (Garrido et al. 2001Garrido G, González D, Delporte C, Backhouse N, Quintero G, Núñez-Sellés AJ and Morales MA. 2001. Analgestic and anti-inflammatory effects of Mangi­fera indica L. Extarct (Vimang). Phytother Res 15: 18-21., Magrioti and Kokotos 2013Magrioti V and Kokotos G. 2013. Phospholipase A2inhibitors for the treatment of inflammatory diseases: a patent review (2010-present). Expert Opin Ther Pat 23: 333-344.). Furthermore, the extract has been shown to reduce the tumor necrosis factor alpha (TNF alpha) serum levels in both arachidonic acid (AA) and phorbol myristate acetate (PMA) induced models of inflammation in mice (Garrido et al. 2004Garrido G, Gonzalez D, Lemus Y, Garcia D, Lodeiro L, Quintero G, Delporte C, Nunez-Selles AJ and Delgado R. 2004. In vivo and in vitro anti-inflammatory activity of Mangifera indica L. extract (VIMANG). Pharmacol Res 50: 143-149.). It was demonstrated that the extract inhibited the induction of PGE2 and LTB4, when it was stimulated with pro-inflammatory stimuli lipopolysaccharide-interferon gamma (LPS-IFNg) or calcium ionophore A23187 in J774 macrophage cell lines (Garrido et al. 2006Garrido G, González D, Lemus Y, Delporte C and Delgado R. 2006. Protective effects of a standard extarct of Mangifera indica L. (VIMANG) against mouse ear edemas and its inhibition of eicosanoid production in J7774 murine macrophages. Phytomedicine 13: 412-418.). Recently, it has been shown that the aqueous stem bark extract of M. indica administration reduced TBARS levels and iNOS, COX-2, TNF-α and TNF R-2 expression in colonic tissue. A decrease in IL-6 and TNF-α serum levels was also observed (Márquez et al. 2010Márquez L, Pérez-Nievas BG, Gárate I, García-Bueno B, Madrigal JL, Menchén L, Garrido G and Leza JC. 2010. Anti-inflammatory effects of Mangifera indica L. Extract in a model of colitis. World J Gastroenterol 16: 4922-4931.).

Figure 5
Effect of calcium concentration on inhibition of NN-XIa-PLA2 by aqueous stem bark extract of M. indica. The reaction mixture contained NN-XIa-PLA2enzyme in 0.05 M Tri-HCl buffer pH 7.5, and 0-15mM CaCl2 in final volume. The reaction was initiated by adding substrate. The reaction was carried out in the absence (rhombus) and presence of IC50 concentration of extract (open square) with increasing concentration of calcium. The figure inset represents percentage inhibition in the presence of the IC50concentration. Data represents ± S.E.M for n=3.

Although the mechanism of action of the extract is unclear, the finding that no visible change was detected in electrophoretic pattern of NN-XIa-PLA2when incubated with extracts (data not shown), excludes the proteolytic degradation as a potential mechanism (Borges et al. 2000Borges MH et al. 2000. Effects of aqueous extract ofCasearia sylvestris (Flacourtiaceae) on actions of snake venom and bee venoms and on activity of phospholipase A2. Comp Biochem Physiol Biochem Mol Biol 127: 21-30.). Furthermore, considering the results of binding studies, the inhibition is known to be of irreversible nature. In addition, inhibiton is observed to be of independent of substrate and calcium concentration. The most likely mechanism for anti-inflammatory activities by this extract is probably due to the direct binding of the constituents of the extract with sPLA2s active site. The extract is known to contain a well-defined and standardized mixture of components such as polyphenols, terpenoids, steroids, fatty acids and microelements (Nunez-Selles et al. 2002Nunez-Selles AJ, Velez HT, Aguero J, Gonzalez J, Naddeo F, DeSimone F and Rastrelli L. 2002. Isolation and quantitative analysis of phenolic antioxidants, free sugars, and polyols from Mango (Mangifera indica L.) stem bark aqueous decoction used in Cuba as a nutritional supplement. J Agric Food Chem 50: 762-766., Shah et al. 2010Shah KA, Patel MB, Patel RJ and Parmar PK. 2010. Mangifera indica (mango). Pharmacogn Rev 4: 42-48.), and mangiferin (20%) being the predominant one. As with other polyphenols, the phenolic constituents of the extract like phenolic acids (Gallic acid, 3, 4 dihydroxy benzoic acid, benzoic acid) and phenolic esters (Gallic acidmethyl ester, gallic acid propylester, benzoic acid propyl ester), could also be involved in binding with sPLA2s, thus bringing about inhibition (Nunez-Selles et al. 2002Nunez-Selles AJ, Velez HT, Aguero J, Gonzalez J, Naddeo F, DeSimone F and Rastrelli L. 2002. Isolation and quantitative analysis of phenolic antioxidants, free sugars, and polyols from Mango (Mangifera indica L.) stem bark aqueous decoction used in Cuba as a nutritional supplement. J Agric Food Chem 50: 762-766.). In addition, the active constituents of this extract like mangiferin, amento flavone, friedelin, daucosterol and beta-sistosterol (Sanchez et al. 2000Sanchez GM, Re L, Giuliani A, Nunez-Selles AJ, Davison GP and Leon-Fernandez OS. 2000. Protective effects of Mangifera indicaL. extract, mangiferin and selected antioxidants against TPA-induced biomolecules oxidation and peritoneal macrophage activation in mice. Pharmacol Res42: 565-573.) seems to exhibit anti-inflammatory effect through quenching of free radicals, as they are involved in the mechanism of inflammatory process (Nanda et al. 2007Nanda BL, Nataraju A, Rajesh R, Rangappa KS, Shekar MA and Vishwanath BS. 2007. PLA2 mediated arachidonate free radicals: PLA2 inhibition adn neutralization of free radicals by anti-oxidants-a new role as anti-inflammatory molecule. Curr Top Med Chem 7(8): 765-777. ,Garrido et al. 2004Garrido G, Gonzalez D, Lemus Y, Garcia D, Lodeiro L, Quintero G, Delporte C, Nunez-Selles AJ and Delgado R. 2004. In vivo and in vitro anti-inflammatory activity of Mangifera indica L. extract (VIMANG). Pharmacol Res 50: 143-149., 2009, Márquez et al. 2012Márquez L, García-Bueno B, Madrigal JL and Leza JC. 2012. Mangiferin decreases inflammation and oxidative damage in rat brain after stress. Eur J Nutr 51: 729-739., Vyas et al. 2012Vyas A, Syeda K, Ahmad A, Padhye S and Sarkar FH. 2012. Perspectives on medicinal properties of mangiferin. Mini Rev Med Chem 12: 412-425.). Previously, it was demonstrated and concluded that the standardized aqueous extract of M. indica(VIMANG(r)) can be classified as a dual inhibitor, as it inhibits both COX and LOX pathways of arachidonate metabolism (Garrido et al. 2004Garrido G, Gonzalez D, Lemus Y, Garcia D, Lodeiro L, Quintero G, Delporte C, Nunez-Selles AJ and Delgado R. 2004. In vivo and in vitro anti-inflammatory activity of Mangifera indica L. extract (VIMANG). Pharmacol Res 50: 143-149.). This anti-inflammatory activity of the extract was believed to be due to the powerful antioxidant activities exhibited by the constituents like phenolic compounds including mangiferin. It has been demonstrated that VIMANG(r) and mangiferin, exhibit inhibitory activity against synovial fluid PLA2 activities (Garrido et al. 2004Garrido G, Gonzalez D, Lemus Y, Garcia D, Lodeiro L, Quintero G, Delporte C, Nunez-Selles AJ and Delgado R. 2004. In vivo and in vitro anti-inflammatory activity of Mangifera indica L. extract (VIMANG). Pharmacol Res 50: 143-149.).

The aqueous stem bark extract of M. indica inhibiting bothin vitro sPLA2 enzymatic activity and in vivo edema inducing activity of NN-XIa-PLA2, suggests a strong correlation between lipolytic activity and pro-inflammatory activity inhibition. It is to be noted that this standard aqueous stem bark extract ofM. indica has been tested in a broad set of toxicological studies with satisfactory results, including acute and subchronic toxicity, genotoxicity, and irritability and is classified as a non-toxic product (Garrido et al. 2009Garrido G, Rodeiro I, Hernández I, García G, Pérez G, Merino N, Núñez-Sellés A and Delgado R. 2009. In vivo acute toxicological studies of an antioxidant extract from Mangifera indica L. (Vimang). Drug Chem Toxicol 32: 53-58., Márquez et al. 2012Márquez L, García-Bueno B, Madrigal JL and Leza JC. 2012. Mangiferin decreases inflammation and oxidative damage in rat brain after stress. Eur J Nutr 51: 729-739., González et al. 2007González JE et al. 2007. Lack of in vivo embryotoxic and genotoxic activities of orally administered stem bark aqueous extract of Mangifera indica L. (Vimang). Food Chem Toxicol 45: 2526-2532.). Thus, M. indica bark extract can be developed for topical application, as it is non-toxic and an effective anti-inflammatory formula contains potent anti-inflammatory molecules.

CONCLUSIONS

The aqueous extract of M. indica effectively inhibited sPLA2 and its associated inflammatory activities. The inhibition is irreversible and also independent on substrate and calcium concentration, suggesting that the constituents of the extract might possibly directly interact to bring about inhibition. In addition, it was found that there is a strong correlation between lipolytic activity and pro-inflammatory activity inhibition. Therefore, the study suggests that the extract possesses potent anti-inflammatory agents, which could be developed as a potential therapeutic agent against inflammatory related diseases. This study also substantiates their anti-inflammatory properties. Further studies on compounds responsible for the anti-inflammatory activity would be interesting, as these are highly attractive candidates for clinical development as a new class of anti-inflammatory agents.

ACKNOWLEDGMENTS

DBL thanks Jain University for the constant encouragement to progress in research. DBL acknowledge DST, Govt of India for providing the grant INT/SLP/P-007/2012, dated 15th May, 2014. SS and DBL acknowledge the Adichunchanagiri Mahasamstana Mutt and Shikshana Trust for providing facilities in the Adichunchanagiri Biotechnology and Cancer Research Institute (ABCRI). We thank Balagangadharanatha Swamiji Institute for Technology (BGS-IT) and Sri Adichunchangiri College of Pharmacy for the support to carry out the research.

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Publication Dates

  • Publication in this collection
    04 Mar 2016
  • Date of issue
    Mar 2016

History

  • Received
    18 Dec 2014
  • Accepted
    03 Apr 2015
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