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Topical hydrogel containing Achyrocline satureioides oily extract (free and nanocapsule) has anti-inflammatory effects and thereby minimizes irritant contact dermatitis

Abstract

Inflammatory dermatoses are prevalent worldwide, with impacts on the quality of life of patients and their families. The aim of this study was to determine the anti-inflammatory effects of Achyrocline satureioides oily extracts and nanocapsules on the skin using a mouse model of irritant contact dermatitis induced by croton oil, and a skin inflammation model induced by ultraviolet B (UVB) radiation. The mice were treated with 15 mg/ear oily extract (HG-OLAS) or nanocapsules (HG-NCAS) of A. satureioides incorporated into Carbopol® 940 hydrogels. We found that HG-OLAS and HG-NCAS formulations reduced ear edema in croton oil-induced lesions with maximum inhibitions of 54±7% and 74±3%, respectively. HG-OLAS and HG-NCAS formulations decreased ear edema induced by UVB radiation (0.5 J/cm2), with maximum inhibitions of 68±6% and 76±2% compared to the UVB radiation group, respectively. HG-OLAS and HG-NCAS modulated myeloperoxidase (MPO) activity after croton oil induction. Furthermore, croton oil and UVB radiation for 6 and 24 h, respectively, stimulated polymorphonuclear cells infiltration. The topical treatments reduced inflammatory processes, as shown by histological analysis. Together, the data suggest that topical application of A. satureioides oily extracts and nanocapsules produced antiedematogenic and anti-inflammatory effects. They constitute a compelling alternative for treatment of skin injuries.

Key words
UVB radiation; croton oil; macela; nanocapsules; skin injuries; anti-inflammatory

INTRODUCTION

The skin operates as a barrier that protects the body against a variety chemical and physical agents, including those caused by ultraviolet (UV) radiation, chemical components and infectious agents (Pasparakis et al. 2014PASPARAKIS M, HAASE I & NESTLE FO. 2014. Mechanisms regulating skin immunity and inflammation. Nat Rev Immunol 14: 289-301. doi:10.1038/nri3646.). Losses in skin integrity contribute to the development of several inflammatory skin diseases, including psoriasis, allergic contact dermatitis (ACD) and irritant contact dermatitis (ICD) (Yeom et al. 2012YEOM M, KIM SH, LEE B, HAN JJ, CHUNG GH, CHOIN H-D, LEE H & HAHM D-H. 2012. Oral administration of glucosylceramide ameliorates inflammatory dry-skin condition in chronic oxazolone-induced irritant contact dermatitis in the mouse ear. J Dermatol Sci 67: 101-110. doi:10.1016/j.jdermsci.2012.05.009., Horinouchi et al. HORINOUCHI CDS, MENDES DAGB, SOLEY BS, PIETROVSKI EF, FACUNDO VA, SANTOS ARS, CABRINI DA & OTUKI MF. 2013. Combretum leprosum Mart. (Combretaceae): Potential as an antiproliferative and anti-inflammatory agent. J Ethnopharmacol 145: 311-319.2013). In ICD caused by contact with irritants (Pinto et al. 2015PINTO NDCC, MACHADO DC, DA SILVA JM, CONEGUNDES JLM, GUALBERTO ACM, GAMEIRO J, CHEDIER LM, CASTANON MCMN & SCIO E. 2015. Pereskia aculeata Miller leaves present in vivo topical anti-inflammatory activity in models of acute and chronic dermatitis. J Ethnopharmacol 173: 330-337. doi: 10.1016/j.jep.2015.07.032.), partial loss of skin integrity may progress to the release of pro-inflammatory mediators (monocytes and neutrophils) that play important roles in inflammation of the skin (Yeom et al. 2012YEOM M, KIM SH, LEE B, HAN JJ, CHUNG GH, CHOIN H-D, LEE H & HAHM D-H. 2012. Oral administration of glucosylceramide ameliorates inflammatory dry-skin condition in chronic oxazolone-induced irritant contact dermatitis in the mouse ear. J Dermatol Sci 67: 101-110. doi:10.1016/j.jdermsci.2012.05.009., Piana et al. 2016PIANA M, CAMPONOGARA C, BOLIGON AA, MACHADO MM, BRUM, TF, OLIVEIRA SM & BAUERMANN LF. 2016. Topical anti-inflammatory activity of Solanum corymbiflorum leaves. J Ethnopharmacol 179: 16-21. doi: 10.1016/j.jep.2015.12.036.).

Skin complications are commonly treated with non-steroidal anti-inflammatory and topical corticosteroids. Nevertheless, long-term use of topical corticosteroids gives rise to several adverse effects, including cutaneous atrophy, telangiectasias, changes in the healing process, intense pruritis, dryness, and burning sensations (Unzueta & Vargas 2013UNZUETA A & VARGAS HE. 2013. Nonsteroidal anti-inflammatory drug-induced hepatoxicity. Clin Liver Dis 17: 643-656. doi: 10.1016/j.cld.2013.07.009., Xiao et al. 2015XIAO X, XIE H, JIAN D, DENG Y, CHEN X & LI J. 2015. Rebounding triad (severe itching, dryness and burning) after facial corticosteroid discontinuation defines a specific class of corticosteroid-dependent dermatitis. J Dermatol 42: 697-702. doi: 10.1111/1346-8138.12877.). Non-steroidal anti-inflammatory drugs cause complications related to the cardiovascular, gastrointestinal, and renal systems (Unzueta & Vargas 2013UNZUETA A & VARGAS HE. 2013. Nonsteroidal anti-inflammatory drug-induced hepatoxicity. Clin Liver Dis 17: 643-656. doi: 10.1016/j.cld.2013.07.009.). These findings suggest that there is a need for safer and more effective therapies to improve the quality of life of patients afflicted by these diseases. The mainstay of treatment for skin damage involves restoring skin-barrier function.

Plant oils improve wound closure phases, promoting keratinocyte proliferation, remodeling of the extracellular matrix and controlling inflammation (Serra et al. 2017SERRA MB, BARROSO WA, DA SILVA NN, SILVA SN, BORGES ACR, ABREU IC & BORGES MO. 2017. From inflammation of current and alternative therapies involved in wound healing. Int J Inflam 2017: 3406215. doi: 10.1155/2017/3406215.). In Brazil, because of its substantial biodiversity, medicinal plants have become important sources of research into development of new therapeutic agents, many of which have already been accepted by the public health system (the SUS) (De Figueredo et al. 2014DE FIGUEREDO CA, GURGEL IGD & JUNIOR GDG. 2014. Fitoterápicos: construção, perspectivas e desafios. Physis 24: 381-400. doi: 10.1590/S0103.).

In Brazil, A. satureioides (Asteraceae family) is a plant widely used in popular culture in the form of infusion and decoction (Stolz et al. 2014STOLZ ED, MÜLLER LG, TROJAN-RODRIGUES M, BAUMHARDT E, RITTER MR & RATES SMK. 2014. Survey of plants popularly used for pain relief in Rio Grande do Sul, southern Brazil. Brazilian J Pharmacogn 24: 185-196. doi: 10.1016/j.bjp.2014.03.007., Yamane et al. 2016YAMANE LT, DE PAULA E, JORGE MP, DE FREITAS-BLANCO VS, JUNIOR IM, FIGUERA GM, ANHOLETO LA, DE OLIVEIRA PR & RODRIGUES RAF. 2016. Acmella oleracea and Achyrocline satureioides as sources of natural products in topical wound care. Evid Based Complement Alternat Med 2016: 9. doi: 10.1155/2016/3606820.). This plant is popularly known as macela or marcela. In traditional medicine, this plant is used to treat gastrointestinal, inflammatory, and respiratory complications, among others. The therapeutic effect may be associated with the presence of bioactive compounds that hypothetically act synergistically (Da Silva et al. 2016DA SILVA LM, FARIAS JAM, BOEING T, SOMENSI LB, BEBER AP, CURY BJ, SANTIN JR & ANDRADE SF. 2016. Hydroalcoholic extract from inflorescences of Achyrocline satureioides (Compositae) Ameliorates Dextran Sulphate sodium-induced colitis in mice by attenuation in the production of inflammatory cytokines and oxidative mediators. Evid Based Complement and Alternat Med 2016: 15. doi 10.1155/2016/3475356., Yamane et al. 2016YAMANE LT, DE PAULA E, JORGE MP, DE FREITAS-BLANCO VS, JUNIOR IM, FIGUERA GM, ANHOLETO LA, DE OLIVEIRA PR & RODRIGUES RAF. 2016. Acmella oleracea and Achyrocline satureioides as sources of natural products in topical wound care. Evid Based Complement Alternat Med 2016: 9. doi: 10.1155/2016/3606820.).

A. satureioides is widely cited in scientific research for its ability to induce cell proliferation in vivo, suggesting potential healing action, in addition to promoting the reduction of inflammatory mediators and the recruitment of leukocytes in vitro (Barioni et al. 2013BARIONI ED ET AL. 2013. Achyrocline satureioides (Lam.) D.C. Hydroalcoholic extract inhibits neutrophil functions related to innate host defense. Evidence-Based Complement Altern Med 2013: 1-12. https://doi.org/10.1155/2013/787916., Alerico et al. 2015ALERICO GC, BECKENKAMP A, VIGNOLI-SILVA M, BUFFON A & VON POSER GL. 2015. Proliferative effect of plants used for wound healing in Rio Grande do Sul state, Brazil. J Ethnopharmacol 176: 305-310. https://doi.org/10.1016/ j.jep.2015.11.001.). Nevertheless, plants substances are not very stable. Nanotechnology appears as a promising alternative to improve product stability and protect the active compounds from chemical or physical degradation (Guterres et al. 2007GUTERRES SS, ALVES MP & POHLMANN AR. 2007. Polymeric nanoparticles, nanospheres and nanocapsules, for cutaneous applications. Drug Target Insights 2: 147-157. doi: 10.1177/117739280700200002.).

Therefore, in this study, we investigated the topical anti-inflammatory effects of A. satureioides oily extracts and nanoencapsulation delivery mechanisms for treatment of skin inflammation and irritant contact dermatitis in mice.

MATERIALS AND METHODS

Headspace solid-phase microextraction-mass chromatograph – mass spectrometer (HS-SPME-GC-MS) analysis of Achyrocline satureioides oily extract

A. satureioides oily extract was purchased from Mundo dos Oleos S/A (Brasília, Brazil, 100% purity), obtained from A. satureioides flowers, leaves and stalks parts by maceration in natural oil. This was followed by cold pressing, filtration and headspace solid-phase microextraction (HS-SPME). Sample preparation and terpene extraction of A. satureioides oily extracts were performed. The compounds were analyzed using a gas chromatograph coupled a mass espectrometer (GC-MS) as described by Ivanova-Petropulos et al. (2015)IVANOVA-PETROPULOS V, MITREV S, STAFILOV T, MARKOVA N, LEITNER E, LANKMAYR E & SIEGMUND B. 2015. Characterisation of traditional Macedonian edible oils by their fatty acid composition and their volatile compounds. Food Res Int 77: 506-514. doi: 10.1016/j.foodres.2015.08.014., with modifications.

Polymer swelling test

Poly (ε-caprolactone) films were obtained by complete dissolution of 0.5 g of the polymer in 10 ml of acetone at 40 °C. The solvent was removed, and films were subsequently immersed in A. satureioides oily extract. The polymer swelling test was performed following the methodology of Venturini et al. (2015)VENTURINI CG, BRUINSMAN FA, CONTRI RV, FONSECA FN, FRANK LA, D`AMORE CM, RAFFIN RP, BUFFON A, POHLMANN AR & GUTERRES SS. 2015. Co-encapsulation of imiquimod and copaiba oil in novel nanostructured systems: promising formulations against skin carcinoma. Eur J Pharm Sci 79: 36-43. doi: 10.1016/j.ejps.2015.08.016. with some modifications. The films were removed from the oil, dried and weighed on an analytical balance at 0, 24, 48, 72, and 96 hours on days 7, 15, 30, 45, 60, and 90.

Nanocapsule formulation and characterization

A. satureioides oily extract nanocapsules suspensions were prepared according to the interfacial deposition of performed polymer (Fessi et al. 1989FESSI H, PUISIEUX F, DEVISSAGUET JP, AMMOURY N & BENITA S. 1989. Nanocapsule formation by interfacial polymer deposition following solvent displacement. Int J Pharm 55: 1-4. doi: 10.1016/0378-5173(89)90281-0.), described in detail by Ritter et al. (2017)RITTER CS ET AL. 2017. Achyrocline satureioides essential oil-loaded in nanocapsules reduces cytotoxic damage in liver of rats infected by Trypanosoma evansi. Microb Pathog 103: 149-154. doi: 10.1016/j.micpath.2016.12.023.. The organic phase was composed of poly(ϵ-caprolactone) (PCL) (1%), sorbitan monoestearate (0.766%), A. satureioides oily extract (3%) and acetone (67 ml). The aqueous phase was composed of polysorbate 80 (0.766%) and ultrapure water (134 ml). After homogenization of each step separately at 40 °C for 1 hour, the organic phase was poured into the aqueous phase and stirred for 10 minutes. Solvent removal was performed under reduced pressure on a rotary evaporator to a final volume of 25 ml.

The nanoparticles were characterized in terms of the mean particle size, polydispersity index (PdI) and zeta potential by electrophoresis using a Zeta sizer (nano-ZS model ZEN 3600, Malvern). The electrophoretic mobility technique was used and the formulations were diluted (500 times) in sodium chloride solution (10 mM), described in detail by Ritter et al. (2017)RITTER CS ET AL. 2017. Achyrocline satureioides essential oil-loaded in nanocapsules reduces cytotoxic damage in liver of rats infected by Trypanosoma evansi. Microb Pathog 103: 149-154. doi: 10.1016/j.micpath.2016.12.023.. For size and PdI evaluations, the formulations were diluted in ultrapure water (500 times) and analyzed using the dynamic light scattering technique. The hydrogen potential (pH) was evaluated using a potentiometer (DM-22, Digimed) previously calibrated with standard solutions of pH 4.0 and 7.0. The results were expressed as mean ± standard deviation from three lots (three readings from each lot) (De Godoi et al. 2017DE GODOI SN, QUATRIN PMI, SAGRILLO MR, NASCIMENTO K, WAGNER R, KLEIN B, SANTOS RCV & OURIQUE AF. 2017. Evaluation of Stability and in Vitro Security of Nanoemulsions Containing Eucalyptus globulus Oil. Biomed Res Int 2017: 1-10. doi: 10.1155/2017/2723418.).

Hydrogel preparation and characterization

Three hydrogel formulations were created: hydrogel containing nanocapsules of A. satureioides; hydrogel containing oily extract of A. satureioides; and base hydrogel. These were prepared according to the protocol described by Alves et al. (2005)ALVES PM, POHLMANN AR & GUTERRES SS. 2005. Semisolid topical formulations containing nimesulide-loaded nanocapsules, nanospheres or nanoemulsion: development and rheological characterization. Pharmazie 60: 900-904. with modifications. For development of hydrogels, Carbopol 940® (6 g), paraben preservative solution (1 g) and ultrapure water (91 ml) were used. The hydrogel containing nanocapsules was composed of the dispersion of Carbopol 940® (6%), triethanolamine (0.5%), sorbitol (5%), imidazolidinyl urea (1%) and 25 ml of nanocapsules containing A. satureioides oily extract. In the case of the hydrogel containing oily extract, the nanocapsules suspension was replaced by a dispersion of the oily extract (3%) polysorbate 80 (0.766%) and sorbitan monooleate (0.766%). In the base hydrogel, the addition of the nanocapsules suspension was omitted and was replaced with ultrapure water (25 ml).

The size and PdI of the hydrogels containing A. satureioides nanocapsules were determined after aqueous redispersion of the formulation using a dynamic light scattering technique. Briefly, 0.02 g of hydrogel were diluted in 10 ml of ultrapure water and subsequently filtered (0.45 μm) for analysis. To determine the pH of the hydrogel containing A. satureioides nanocapsules, hydrogel containing A. satureioides oily extract and base hydrogel, 1 g of the hydrogel was diluted in 10 ml of ultrapure water, and the values were determined using potentiometry (Marchiori et al. 2010MARCHIORI ML ET AL. 2010. Hydrogel containing dexamethasone-loaded nanocapsules for cutaneous administration: preparation, characterization, and in vitro drug release study. Drug Dev Ind Pharm 36: 962-971. doi: 10.3109/03639041003598960.).

Experimental design

Animals

For the in vivo study, the experiment design included 96 male Swiss mice, (up to 60 days, weighing 25 ± 5 g). Animals were maintained in boxes with five animals each, under a 12-h light/dark cycle with controlled temperature and humidity (25 °C, 70% respectively), respecting their circadian rhythm, and were fed with commercial feed and water ad libitum. All animals procedures were approved by the Ethics Committee on Animal of Universidade Federal de Santa Maria under protocol number (6581200716/2016).

Treatments

The experimental design was divided into two models: irritant contact dermatitis induced by croton oil, and skin inflammation induced by UVB radiation. The experimental groups for croton oil-induced irritant contact dermatitis model were composed by following groups (n = 8): naïve group (negative control); croton oil group; hydrogel group (treated with base hydrogel); HG-OLAS group (treated with hydrogel containing 3% A. satureioides oily extract); HG-NCAS group (treated with hydrogel containing 3% A. satureioides nanocapsules oily extract); and dexamethasone group (0.5% dexamethasone hydrogel as a positive control).

The UVB radiation-induced skin inflammation model included the following groups (n = 8): naïve group (negative control—no inflammation process induction and no topical treatment); UVB group; hydrogel group (treated with base hydrogel); HG-OLAS group (treated with hydrogel containing 3% A. satureioides oily extract); HG-NCAS group (treated with hydrogel containing 3% A. satureioides nanocapsule oily extract); and sulfadiazine group (sulfadiazine hydrogel 3% as a positive control).

Mice were topically treated on the ear surface with various semisolid formulations at 15 mg/ear immediately after the inflammatory stimulus.

Model of croton oil-induced ear edema

Irritant contact dermatitis was mimicked using a single topical administration of croton oil (1 mg/ear; diluted in 20 μl acetone) on the right ear. The hydrogel formulations (base hydrogel, HG-OLAS, HG-NCAS and dexamethasone) were applied immediately after irritant agent administration. Ear thickness (expressed in μm) was evaluated before and 6 h after croton oil application using a digital micrometer (Digimess) in animals anesthetized with isoflurane (Piana et al. 2016PIANA M, CAMPONOGARA C, BOLIGON AA, MACHADO MM, BRUM, TF, OLIVEIRA SM & BAUERMANN LF. 2016. Topical anti-inflammatory activity of Solanum corymbiflorum leaves. J Ethnopharmacol 179: 16-21. doi: 10.1016/j.jep.2015.12.036.). The micrometer was applied near the tip of the ear just distal to the cartilaginous ridges. Six hours after croton oil administration, the animals were euthanized and ear biopsies were taken for further analysis (De Brum et al. 2016DE BRUM TF, CAMPONOGARA C, DA SILVA JESUS R, BELKE BV, PIANA M, BOLIGON AA, PIRES FB, OLIVEIRA SM, DA ROSA MB & BAUERMANN LF. 2016. Ethnopharmacological study and topical anti-inflammatory activity of crude extract from Poikilacanthus glandulosus (Nees) Ariza leaves. J Ethnopharmacol 193: 60-67. doi: 10.1016/j.jep.2016.07.075., Piana et al. 2016PIANA M, CAMPONOGARA C, BOLIGON AA, MACHADO MM, BRUM, TF, OLIVEIRA SM & BAUERMANN LF. 2016. Topical anti-inflammatory activity of Solanum corymbiflorum leaves. J Ethnopharmacol 179: 16-21. doi: 10.1016/j.jep.2015.12.036.).

Model of UVB radiation-induced ear edema

The UVB radiation source was a Philips TL40W/12 RS lamp (Medical-Eindhoven, Holland) mounted 20 cm abe the table on which the animals were placed, using a continuous light spectrum exposure between 270 and 400 nm with peak emission at 313 nm. UVB output (80% of the total UV irradiation) was measured using a model IL-1700 Research Radiometer (International Light, USA; calibrated by IL service staff) with radiometer sensors for UV (SED005) and UVB (SED240). The UVB irradiation rate was 0.27 mW/cm2 and the dose used was 0.5 J/cm2. The mice were first anesthetized with a single intraperitoneal injection (90 mg/kg of ketamine and 3 mg/kg of xylazine) and then exposed to UVB radiation. Only the right ear of each animal was exposed to UVB radiation. The hydrogel formulations (base hydrogel, HG-OLAS, HGNCAS and silver sulfadiazine at 15 mg/ear) were immediately applied after the UVB radiation. Ear edema was measured before the inflammatory stimulus and 24 h after the UVB exposure, expressed as µm. Twenty-four hours after UVB radiation, the animals were euthanized and ear biopsies were taken for further analysis (Marchiori et al. 2017MARCHIORI MCL, RIGON C, CAMPONOGARA C, OLIVEIRA SM & CRUZ L. 2017. Hydrogel containing silibinin-loaded pomegranate oil based nanocapsules exhibits anti-inflammatory effects on skin damage UVB radiation-induced in mice. J Photochem Photobiol B Biol 170: 25-32. doi: 10.1016/j.jphotobiol.2017.03.015., Pegoraro et al. 2017PEGORARO NS, BARBIERI AV, CAMPONOGARA C, MATTIAZZI J, BRUM ES, MARCHIORI MCL, OLIVEIRA SM & CRUZ L. 2017. Nanoencapsulation of coenzyme Q10 and vitamin E acetate protects against UVB radiation-induced skin injury in mice. Colloids Surf B 150: 32-40. doi: 10.1016/j.colsurfb.2016.11.013.).

Assessment of leukocyte infiltration

Myeloperoxidase (MPO) enzyme activity was evaluated in the ear samples after 24 h (skin inflammation UVB-induced) or 6 h (irritant croton oil-induced) of stimulus. Tissue samples were removed and homogenized in a motor-driven homogenizer in acetate buffer (8 mM, pH 5.4) containing hexadecyltrimethylammonium bromide (Phanse et al. 2012PHANSE MA, PATIL MJ, ABBULU K, CHAUDHARI PD & PATEL B. 2012. In-vivo and in-vitro screening of medicinal plants for their anti-inflammatory activity: An overview. J Appl Pharm Sci 2: 19-33. doi: 10.7324/JAPS.2012.2704.), as previously described (Camponogara et al. 2019aCAMPONOGARA C, CASOTI R, BRUSCO I, PIANA M, BOLIGON AA, CABRINI DA, TREVISAN G, FERREIRA J, SILVA CR & OLIVEIRA SM. 2019a. Tabernaemontana catharinensis leaves effectively reduce the irritant contact dermatitis by glucocorticoid receptor-dependent pathway in mice. Biomed Phrmacother 109: 646-657. Doi: 10.1016/j.biopha.2018.10.132.). The enzyme activity value was assessed colorimetrically at 630 nm using a microplate reader. The results were expressed as optical density (OD)/ml of sample.

Histological analysis and polymorphonuclear cells

After 24 h (UVB-induced skin inflammation) or 6 h (croton oil-induced irritant contact dermatitis), the right ear was removed and fixed in an aflac solution (16:2:1 mixture of ethanol 80%, formaldehyde 40% and acetic acid). Each sample was embedded in paraffin, sectioned at 5 μm and stained with hematoxylin-eosin. A representative area was observed under a light microscope fitted with 20× and 40× objectives to assess the inflammatory cellular response (Piana et al. 2016PIANA M, CAMPONOGARA C, BOLIGON AA, MACHADO MM, BRUM, TF, OLIVEIRA SM & BAUERMANN LF. 2016. Topical anti-inflammatory activity of Solanum corymbiflorum leaves. J Ethnopharmacol 179: 16-21. doi: 10.1016/j.jep.2015.12.036., Marchiori et al. 2017MARCHIORI MCL, RIGON C, CAMPONOGARA C, OLIVEIRA SM & CRUZ L. 2017. Hydrogel containing silibinin-loaded pomegranate oil based nanocapsules exhibits anti-inflammatory effects on skin damage UVB radiation-induced in mice. J Photochem Photobiol B Biol 170: 25-32. doi: 10.1016/j.jphotobiol.2017.03.015.). The polymorphonuclear cells were counted at 20× and were expressed as number polymorphonuclear cells per field (two fields from three distinct histological slides of each group were analyzed).

Statistical analysis

The maximum inhibitory effect was calculated based on the response of the control groups. The statistical significance between the groups was assessed by one or two (repeated measures) one-way analysis of variance (ANOVA) followed by a post-hoc Tukey or Bonferroni tests, respectively. P <0.05 denoted significant differences between groups. All tests were carried out using GraphPad 6.0 Software (San Diego, CA, USA), and Image J software (inflammatory cells count). No statistical methods were used to predetermine sample sizes; nevertheless, our sample sizes were similar to those reported in previous publications in the field. The results were presented as mean ± standard error of mean (SEM) and as geometric means with their respective 95% confidence limits.

RESULTS

In vitro assay

Composition of A. satureioides oily extract

The headspace oily extract produced 17 volatile terpenoids compounds, in decreasing order of quantity: α-pinene (65.8%), limonene (7.9%), eucalyptol (5.0%), α-copaene (3.9%), o-xylene (2.8%), camphene (2.7%), α-phellandrene (2.6%), β-phellandrene (2.0%), cis-verbenol (1.5%), caryophyllene (1.2%), cis-alpha-bisabolene (1.0%), caryophyllene oxide (0.9%), methyl salicylate (0.8%), β-myrcene (0.7%), linalool (0.4%), p-xylene (0.4%) and anethole (0.3%).

Polymer swelling test

Polymeric films immersed in A. satureioides oily extract were evaluated. The polymer film masses remained constant over 90 days (Fig. 1), suggesting that the A. satureioides oily extract did not dissolve the polymer film, assuring the potential to obtain polymeric nanocapsules containing the oily extract.

Figure 1
The polymer swelling test over 90 days. Each bar represents the mean ± S.E.M (n = 3).

Characterization of nanocapsules and hydrogel containing A. satureioides oily extract or nanocapsules

The three suspensions were evaluated with respect to their physical-chemical properties. The characterization of nanocapsules and hydrogels containing A. satureioides oily extract or nanocapsulated are shown in Table I The hydrogen potential (pH) of the base hydrogel was 7.3 ± 0.04 and that of the oily extract hydrogel was 7.0 ± 0.04.

Table I
Characterization of Achyrocline satureioides nanocapsules and hydrogels containing nanocapsules after aqueous redispersion.

In vivo assay

Anti-inflammatory effect of A. satureioides oily extract hydrogel formulations on irritant contact dermatitis croton oil-induced

We measured the effect of hydrogel formulations on irritant contact dermatitis induced by croton oil application. A topical application of croton oil on the ears of the mice increased the ear thickness with an Emax of 160 ± 10 µm after 6 h, compared to the naïve group (Fig 2a). The HG-OLAS, HG-NCAS, and dexamethasone formulations reduced ear edema in croton oil-treated mice with Imax of 54 ± 7%, 74 ± 3%, and 66 ± 4%, respectively, when compared to the control oil group. HG-NCAS had an antiedematogenic effect as effective as positive control in the skin inflammation model induced by croton oil.

Figure 2
Anti-inflammatory effects of hydrogels containing A. satureioides oily extracts (HG-OLAS), hydrogel A. satureioides nanocapsule oily extracts (HG-NCAS) and dexamethasone hydrogel formulations on croton-oil-induced contact dermatitis in mice. Ear edema (a), myeloperoxidase activity (MPO) (b) and histological changes (c and d) in mice subjected to croton oil (1 mg/ear) administration. All formulations (15 mg/ear) were applied immediately after croton oil application. Each bar represents the mean + S.E.M (n = 6–8). The arrows indicate inflammatory cells in the ear tissue. ###P<0.001 when compared to the naive group. ***P <0.001, and *P <0.05 compared to the untreated croton oil group. &&P <0.01 when compared to the HG-OLAS and dexamethasone formulations [one- or two-way (repeated measures) ANOVA followed by post-Tukey or Bonferroni tests, respectively].

The irritant agent application by croton oil gave significantly greater MPO activity than that of the naïve group. All topical treatments reduced MPO enzymatic activity with an Imax of 30 ± 12% (HG-OLAS), 82 ± 1% (HG-NCAS) and 33 ± 9% (dexamethasone), when compared to the croton oil group. The nanoencapsulation process contributed to the HG-NCAS anti-inflammatory effect, as this hydrogel formulation was more effective in reducing MPO activity than were the hydrogel formulations (HG-OLAS and dexamethasone) (Fig. 2b).

Histologically, we performed quantitative analysis of numbers of polymorphonuclear cells at the ear tissue and observed that application of croton oil significantly increased polymorphonuclear cell infiltration (179 ± 10 inflammatory cells per field) at 6 h after the stimulus when compared to the number in the naïve group (Fig. 2c). All topical treatments showed lower levels of inflammatory cell infiltration (79 ± 6 to HG-OLAS, 35 ± 4 to HG-NCAS and 39 ± 5 to dexamethasone) when compared with the croton oil group. HG-NCAS was more effective in reducing inflammatory cell infiltration than was the HG-OLAS group.

These results were confirmed by histological sections of ear tissue, showing that the inflammatory process generated ear edema and inflammatory cell infiltration, and that all topical formulations were effective in reducing both these parameters (Fig. 2d).

Anti-inflammatory effects of A. satureioides oily extract hydrogel formulations on inflammation induced by UVB-radiation

To evaluate the anti-inflammatory effect of A. satureioides oily extract hydrogel formulations, as well as the influence of the nanoencapsulation process on the inflammatory parameters, a UVB irradiation-induced skin inflammation model was used. The UVB radiation on mice ear caused a marked increase in skin thickness with an Emax of 130 ± 12 µm) compared to the naïve group after 24 h of stimulus (Fig. 3a). The HG-OLAS and HG-NCAS formulations significantly decreased UVB radiation-induced ear edema with Imax of 68 ± 6% and 76 ± 2% compared to the UVB-irradiated group, respectively. The nanoencapsulation process enhanced the A. satureioides oily extract antiedematogenic effect compared to the treatment of hydrogel-containing A. satureioide free oily extract group. Silver sulfadiazine, used as a positive (treatment) control, reduced UVB radiation-induced ear edema by 87 ± 4% (Fig. 3b). The antiedematogenic effect of HG-NCAS was similar to that of the silver sulfadiazine group. Interestingly, no significant differences were observed in myeloperoxidase activity after 24 h UVB radiation between the analyzed groups (data not shown).

Figure 3
Anti-inflammatory effect of hydrogels containing A. satureioides oily extracts (HG-OLAS), A. satureioides nanocapsule oily extracts (HG-NCAS) and silver sulfadiazine hydrogel formulations on UVB-radiation-induced skin inflammation in mice. Ear edema (a) and histological changes (b and c) in mice subjected to UVB irradiation (0.5 J/cm2). All formulations (15 mg/ear) were applied immediately after UVB irradiation. Each bar represents the mean + S.E.M (n = 6–8). The arrows indicate inflammatory cells in the ear tissue. ###P<0.001 when compared to the naive group. ***P <0.001, **P <0.01 and *P <0.05 when compared to the untreated UVB-irradiated group. &P <0.05 when compared to HG-OLAS formulation [one- or two-way (repeated measures) ANOVA followed by post-Tukey or Bonferroni tesst, respectively].

The effect HG-OLAS and HG-NCAS on inflammatory cell infiltration was evaluated using histological analysis. The irradiation with a UVB source promoted a marked presence of edema characterized by intense increase of the skin thickness, especially at the dermis, in addition to intense inflammatory cell infiltration (150 ± 22 inflammatory cells per field) compared to the naïve group. All topical treatments reduced ear edema and inflammatory cell infiltration (79 ± 10 to HG-OLAS, 61 ± 12 to HG-NCAS and 42 ± 10 to silver sulfadiazine inflammatory cell per field) compared to the only UVB-irradiated group, evaluated at 24 h after UVB-irradiation (Fig. 3b and 3c).

DISCUSSION

The present study provides evidence that topical administration of A. satureioides oily extract, in free and nanocapsule form, exerts anti-inflammatory effects against irritant-induced contact dermatitis and UVB-induced skin inflammation. To the best of our knowledge, this is the first demonstration of topical application of A. satureioides oily extract and nanocapsules, showing anti-inflammatory activity in mouse models of skin inflammation.

Many bioactive compounds extracted from plants are very unstable, making their study impossible. In this context, research shows that the association of isolated bioactive compounds in nanotechnology-based distribution systems may present promising advantages when compared to conventional dosage forms, including improved stability, reduction of side-effects, controlled release of active compounds, and increased permeability of the products (Bidone et al. 2014BIDONE J, ZORZI GK, CARVALHO EL, SIMÕES CM, KOESTER LS, BASSANI VL & TEIXEIRA HF. 2014. Incorporation of Achyrocline satureioides (LAM.) DC extracts into topical nanoemulsions obtained by means of spontaneous emulsification procedure. Industrial Crops and Products 62: 421-429. doi: 10.1016/j.indcrop.2014.08.042.).

In terms of physico-chemical characterization, the particle size of nanocapsules and hydrogels containing nanocapsules showed similar values, confirming maintenance of the nanocapsule structure in the semisolid (Table I). These results corroborate those of Pegoraro et al. (2017)PEGORARO NS, BARBIERI AV, CAMPONOGARA C, MATTIAZZI J, BRUM ES, MARCHIORI MCL, OLIVEIRA SM & CRUZ L. 2017. Nanoencapsulation of coenzyme Q10 and vitamin E acetate protects against UVB radiation-induced skin injury in mice. Colloids Surf B 150: 32-40. doi: 10.1016/j.colsurfb.2016.11.013. and Terroso et al. (2009)TERROSO T, KÜLKAMP IC, JORNADA DS, POHLMANN AR & GUTERRES SS. 2009. Development of semi-solid cosmetic formulations containing coenzyme Q10-loaded nanocapsules. Lat Am J Pharm 28: 819-826., who showed that nanostructures remained unaltered even after semisolid aqueous redispersion. The nanocapsules maintained pH in the range of skin pH (4.8–5.6), as well as negative zeta potential, suggesting they are suitable for dermal application (Terroso et al. 2009TERROSO T, KÜLKAMP IC, JORNADA DS, POHLMANN AR & GUTERRES SS. 2009. Development of semi-solid cosmetic formulations containing coenzyme Q10-loaded nanocapsules. Lat Am J Pharm 28: 819-826., Silva et al. 2013SILVA MA ET AL. 2013. Antinociceptive and anti-inflammatory effects of Aloe saponaria Haw on thermal injury in rats. J Ethnopharmacol 146: 393-401. doi: 10.1016/j.jep.2012.12.055.). The hydrogel formulation presented pH values of 7.0–7.3, suitable for cutaneous administration, according to Alves et al. (2007)ALVES MP, SCARRONE AL, SANTOS M, POHLMANNAR & GUTERRES SS. 2007. Human skin penetration and distribution of nimesulide from hydrophilic gels containing nanocarriers. Int J Pharm 341: 215-220. doi: 10.1016/j.ijpharm.2007.03.031.. The polydispersity index remained between 0.14–0.15, suggesting homogenity of the systems (Terroso et al. 2009TERROSO T, KÜLKAMP IC, JORNADA DS, POHLMANN AR & GUTERRES SS. 2009. Development of semi-solid cosmetic formulations containing coenzyme Q10-loaded nanocapsules. Lat Am J Pharm 28: 819-826.). We also observed that the nanocapsules remained stable throughout the observation period of 90 days.

A. satureioides oily extract was effective in reducing all inflammatory parameters in the croton oil and UVB radiation models. Croton oil is an in vivo irritant contact dermatitis model widely used in the investigation of compounds with topical anti-inflammatory activity (Phanse et al. 2012PHANSE MA, PATIL MJ, ABBULU K, CHAUDHARI PD & PATEL B. 2012. In-vivo and in-vitro screening of medicinal plants for their anti-inflammatory activity: An overview. J Appl Pharm Sci 2: 19-33. doi: 10.7324/JAPS.2012.2704.). It contains phorbol esters, mainly 12-O-tetradecanoylphorbol-13-acetate (TPA); when applied topically, croton oil promotes an acute inflammatory response, resulting in vasodilatation, inflammatory cell infiltration and edema formation (Piana et al. 2016PIANA M, CAMPONOGARA C, BOLIGON AA, MACHADO MM, BRUM, TF, OLIVEIRA SM & BAUERMANN LF. 2016. Topical anti-inflammatory activity of Solanum corymbiflorum leaves. J Ethnopharmacol 179: 16-21. doi: 10.1016/j.jep.2015.12.036.) as observed in the present study after 6 h (Fig. 2a). These inflammatory events may happen because of protein kinase C (PKC) activation as well as increased phospholipase A2 (PLA2) levels resulting from production of inflammatory mediators (Pinto et al. 2015PINTO NDCC, MACHADO DC, DA SILVA JM, CONEGUNDES JLM, GUALBERTO ACM, GAMEIRO J, CHEDIER LM, CASTANON MCMN & SCIO E. 2015. Pereskia aculeata Miller leaves present in vivo topical anti-inflammatory activity in models of acute and chronic dermatitis. J Ethnopharmacol 173: 330-337. doi: 10.1016/j.jep.2015.07.032.). The hypothesis for the antiedematogenic and anti-inflammatory effect of A. satureioides oily extract may be linked to the inhibition process of proinflammatory cytokines induced by the chroton oil.

Nevertheless, UVB radiation exposure is the main cause of sunburn, characterized by inflammation and oxidative damage to the tissue (overproduction of reactive oxygen species and antioxidants systems depletion) (Martinez et al. 2017MARTINEZ RM ET AL. 2017. trans-Chalcone, a flavonoid precursor, inhibits UV-induced skin inflammation and oxidative stress in mice by targeting NADPH oxidase and cytokine production. Photochem Photobiol Sci 16: 1162-1173. doi:10.1039/C6PP00442C.). In this context, the possible effect of oily extract of A. satureioides in free and nanocapsulated on sunburn induced by UVB radiation is related to its anti-inflammatory action, as suggested in this study. However, its therapeutic effect may also be associated with activation of the antioxidant pathways and consequently with control of oxidative damage (Salgueiro et al. 2016SALGUEIRO AC, FOLMER V, DA ROSA HS, COSTA MT, BOLIGON AA, PAULA FR, ROOS DH & PUNTEL GO. 2016. In vitro and in silico antioxidant and toxicological activities of Achyrocline satureioides. J Ethnopharmacol 194: 6-14. doi: 10.1016/j.jep.2016.08.048.).

Skin inflammation is commonly characterized by intense inflammatory cell infiltration, in which neutrophil cells become the first line of defense against pathogens (Németh & Mócsai 2012NÉMETH T & MÓCSAI A. 2012. The role of neutrophils in autoimmune diseases. Immunol Lett 143: 9-19. doi: 10.1016/j.imlet.2012.01.013.). In this sense, both skin inflammation models caused induction of this inflammatory parameter and the topical formulations (HG-OLAS and HG-NCAS) were effective in decreasing it. It is worth mentioning that the nanoencapsulation process potentiated the effect of topical anti-inflammatory A. satureioides oily extract in this skin inflammation models.

Nanoparticles are effective drug delivery systems. Recently, many researchers reported that the advantage of nanoparticles is their ability to enhance solubility and bioavailability of certain drugs (Ye et al. 2015YE Y-J, WANG Y, LOU K-Y, CHEN Y-Z, CHEN R & GAO F. 2015. The preparation, characterization, and pharmacokinetic studies of chitosan nanoparticles loaded with paclitaxel/dimethyl-β-cyclodextrin inclusion complexes. Int J Nanomedicine 10: 4309-4319. doi: 10.2147/IJN.S83508.). Many studies showed the advantages of nanoencapsulation of bioactive compounds in terms of reducing cutaneous inflammation and oxidative damage (Pegoraro et al. 2017PEGORARO NS, BARBIERI AV, CAMPONOGARA C, MATTIAZZI J, BRUM ES, MARCHIORI MCL, OLIVEIRA SM & CRUZ L. 2017. Nanoencapsulation of coenzyme Q10 and vitamin E acetate protects against UVB radiation-induced skin injury in mice. Colloids Surf B 150: 32-40. doi: 10.1016/j.colsurfb.2016.11.013., Marchiori et al. 2017MARCHIORI MCL, RIGON C, CAMPONOGARA C, OLIVEIRA SM & CRUZ L. 2017. Hydrogel containing silibinin-loaded pomegranate oil based nanocapsules exhibits anti-inflammatory effects on skin damage UVB radiation-induced in mice. J Photochem Photobiol B Biol 170: 25-32. doi: 10.1016/j.jphotobiol.2017.03.015.).

Adoption of nanothecnology for use with natural products can be considered a promising alternative to treat skin inflammation diseases; many studies have already discussed such an approach (Camponogara et al. 2019aCAMPONOGARA C, CASOTI R, BRUSCO I, PIANA M, BOLIGON AA, CABRINI DA, TREVISAN G, FERREIRA J, SILVA CR & OLIVEIRA SM. 2019a. Tabernaemontana catharinensis leaves effectively reduce the irritant contact dermatitis by glucocorticoid receptor-dependent pathway in mice. Biomed Phrmacother 109: 646-657. Doi: 10.1016/j.biopha.2018.10.132., bCAMPONOGARA C, SILVA CR, BRUSCO I, PIANA M, FACCIN H, CARVALHO LM, SCHUCH A, TREVISAN G & OLIVEIRA SM. 2019b. Nasturtium officinale R. Br. effectively reduces the skin inflammation induced by croton oil via glucocorticoid receptor-dependent and NF-κB pathways without causing toxicological effects in mice. J Ethnopharmacol 229: 190-204. doi: 10.1016/j.jep.2018.10.011.). Moreover, presence of bioactive compound may explain their anti-inflammatory actions. Previous studies have already investigated the phytochemical profile of A. satureioides, demonstrating the presence and anti-inflammatory activity of terpenoids, steroids and flavonoids (Di Sotto et al. 2010DI SOTTO A, MAZZANTI G, CARBONE F, HRELIA P & MAFFEI F. 2010. Inhibition by β-caryophyllene of ethyl methanesulfonate-induced clastogenicity in cultured human lymphocytes. Mutat Res - Genet Toxicol Environ Mutagen 699: 23-28. doi: 10.1016/j.mrgentox.2010.04.008., Tsang et al. 2016TSANG M ET AL. 2016. Anti-inflammatory activities of pentaherbs formula, berberine, gallic acid and chlorogenic acid in atopic dermatitis-like skin inflammation. Molecules 21: 519. doi: 10.3390/molecules21040519.). Yamane et al. (2016)YAMANE LT, DE PAULA E, JORGE MP, DE FREITAS-BLANCO VS, JUNIOR IM, FIGUERA GM, ANHOLETO LA, DE OLIVEIRA PR & RODRIGUES RAF. 2016. Acmella oleracea and Achyrocline satureioides as sources of natural products in topical wound care. Evid Based Complement Alternat Med 2016: 9. doi: 10.1155/2016/3606820. showed that plants of the Asteraceae family have a composition rich in secondary metabolites with potential anti-inflammatory action. Compounds such as α-pinene, limonene, eucalyptol are described in the literature in terms of their potential anti-inflammatory, gastroprotective and analgesic effects (Kim et al. KIM DS ET AL. 2015. Alpha-pinene exhibits anti-inflammatory activity through the suppression of MAPKs and the NF-κB pathway in mouse peritoneal macrophages. Am J Chinese Med 43: 731-742. doi: 10.1142/S0192415X15500457.2015, Yin et al. 2019YIN C, LIU B, WANG P, LI X, LI Y, ZHENG X, TAI Y, WANG C & LIU B. 2019. Eucalyptol alleviates inflammation and pain responses in a mouse model of gout arthritis. Br J Pharmacol 177: 2042-2057. doi: 10.1111/bph.14967., de Souza et al. 2019DE SOUZA MC, VIEIRA AJ, BESERRA FP, PELLIZZON CH, NÓBREGA RH & ROZZA AL. 2019. Gastroprotective effect of limonene in rats: Influence on oxidative stress, inflammation and gene expression. Phytomedicine 53: 37-42. doi: 10.1016/j.phymed.2018.09.027.). Previous studies showed the potential anti-inflammatory effect of A. satureioides hydroalcoholic extract in in vivo and in silico models of ulcerative colitis (Da Silva et al. 2016DA SILVA LM, FARIAS JAM, BOEING T, SOMENSI LB, BEBER AP, CURY BJ, SANTIN JR & ANDRADE SF. 2016. Hydroalcoholic extract from inflorescences of Achyrocline satureioides (Compositae) Ameliorates Dextran Sulphate sodium-induced colitis in mice by attenuation in the production of inflammatory cytokines and oxidative mediators. Evid Based Complement and Alternat Med 2016: 15. doi 10.1155/2016/3475356.).

From this perspective, the possible anti-inflammatory effect of bioactives compounds of oily extract A. satureioides may be related to decreasing levels of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) and IL-1β and increasing levels of IL-10, by controlling the activity of enzymes and transcriptional inflammatory pathways mitogen-activated protein kinases (MAPKs), myeloperoxidase (MPO), nuclear factor-kappa β (NF-kβ). Reductions in levels of ROS may contribute to inhibition the inflammatory pathways because oxidative stress and inflammation act synergistically (Martinez et al. 2017MARTINEZ RM ET AL. 2017. trans-Chalcone, a flavonoid precursor, inhibits UV-induced skin inflammation and oxidative stress in mice by targeting NADPH oxidase and cytokine production. Photochem Photobiol Sci 16: 1162-1173. doi:10.1039/C6PP00442C., Camponogara et al. 2020CAMPONOGARA C, BRUM ES, BELKE BV, BRUM, TF, JESUS RS, PIANA M, BAUERMANN LF & OLIVEIRA SM. 2020. Casearia decandra leaves present anti-inflammatory efficacy in a skin inflammation model in mice. J Ethnopharmacol 249: 112436. doi: 10.1016/j.jep.2019.112436.). Further studies are need to elucidate the effect antioxidant of topical formulations tested in this study on skin inflammation models.

CONCLUSION

We demonstrated the feasibility of preparing hydrogels containing oily extracts and nanocapsules of A. satureioides that had satisfactory physico-chemical characteristics for cutaneous application and that were effective topical anti-inflammatories. The nanoencapsulation process enhanced the topical anti-inflammatory effect of A. satureioides oily extracts, suggesting that this is a technology that can generate promising treatments for skin injuries.

ACKNOWLEGMENTS

The authors acknowledge the financial support of CNPq/CAPES/FAPERGS (Process no. 17/2551-0001) (Conselho Nacional de Desenvolvimento Cientifico e Tecnológico -CNPq/Coordenação de Aperfeiçoamento de Pessoal de Nível Superior -CAPES/Fundação de Amparo a Pesquisa do Rio Grande do Sul- FAPERGS), Brazil. They also acknowledge fellowships from CNPq and CAPES.

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Publication Dates

  • Publication in this collection
    16 Nov 2020
  • Date of issue
    2020

History

  • Received
    9 Sept 2019
  • Accepted
    20 Apr 2020
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