RESUMO Objetivo Avaliar o efeito dos compostos ICI 182,780 (fulvestranto), um antagonista seletivo dos receptores de estrógeno alfa/beta (REα/REβ), e do G-1, um agonista seletivo de receptores de estrógeno acoplados a proteínas-G (GPER), na possível indução de autofagia em linhagens de câncer de mama MCF-7 e SKBr3, bem como o efeito de G-1 na viabilidade celular. Métodos A viabilidade celular de células MCF-7 e SKBr3 foi avaliada pelo ensaio com MTT. Para investigar a indução da autofagia, células MCF-7 foram transfectadas com GFP-LC3, um marcador de autofagossomos, e analisadas por microscopia de fluorescência em tempo real. As células MCF-7 e SKBr3 foram incubadas com o indicador de compartimentos ácidos laranja de acridina e analisadas por citometria de fluxo como indicativo para autofagia. Resultados Em células MCF-7, o ICI 182,780 e rapamicina após 48 horas levaram à diminuição da viabilidade celular, enquanto o G-1 não alterou a viabilidade no mesmo período de tratamento. Nem o ICI 182,780 e nem o G-1 induziram aumento na pontuação de GFP-LC3 em células MCF-7 até 4 horas. Já os ensaios de citometria de fluxo demonstraram que ICI 182,780 levou ao aumento de compartimentos ácidos em células MCF-7. O G-1 não aumentou estes parâmetros em ambas as linhagens. Por outro lado, ICI 182,780 e G-1 não induziram à redução da viabilidade em células SKBr3 e nem à formação de compartimentos ácidos, como etapa final do processo autofágico. Conclusão O aumento de compartimentos ácidos pelo ICI 182,780 em células de câncer de mama positivas para receptores de estrógeno parece estar associado com seu efeito inibidor de receptores de estrógeno, mas sem o envolvimento de GPER. A compreensão desses mecanismos pode direcionar estudos sobre o envolvimento dos receptores nos processos celulares de resistência do câncer de mama.

ABSTRACT Objective To investigate if ICI 182,780 (fulvestrant), a selective estrogen receptor alpha/beta (ERα/ERβ) antagonist, and G-1, a selective G-protein-coupled receptor (GPER) agonist, can potentially induce autophagy in breast cancer cell lines MCF-7 and SKBr3, and how G-1 affects cell viability. Methods Cell viability in MCF-7 and SKBr3 cells was assessed by the MTT assay. To investigate the autophagy flux, MCF-7 cells were transfected with GFP-LC3, a marker of autophagosomes, and analyzed by real-time fluorescence microscopy. MCF-7 and SKBr3 cells were incubated with acridine orange for staining of acidic vesicular organelles and analyzed by flow cytometry as an indicator of autophagy. Results Regarding cell viability in MCF-7 cells, ICI 182,780 and rapamycin, after 48 hours, led to decreased cell proliferation whereas G-1 did not change viability over the same period. The data showed that neither ICI 182,780 nor G-1 led to increased GFP-LC3 puncta in MCF-7 cells over the 4-hour observation period. The cytometry assay showed that ICI 182,780 led to a higher number of acidic vesicular organelles in MCF-7 cells. G-1, in turn, did not have this effect in any of the cell lines. In contrast, ICI 182,780 and G-1 did not decrease cell viability of SKBr3 cells or induce formation of acidic vesicular organelles, which corresponds to the final step of the autophagy process in this cell line. Conclusion The effect of ICI 182,780 on increasing acidic vesicular organelles in estrogen receptor-positive breast cancer cells appears to be associated with its inhibitory effect on estrogen receptors, and GPER does notseem to be involved. Understanding these mechanisms may guide further investigations of these receptors’ involvement in cellular processes of breast cancer resistance.

ABSTRACT Preservatives are widely used substances that are commonly added to various cosmetic and pharmaceutical products to prevent or inhibit microbial growth. In this study, we compared the in vitro cytotoxicity of different types of currently used preservatives, including methylparaben, imidazolidinyl urea (IMU), and sodium benzoate, using the human newborn fibroblast cell line CCD1072Sk. Of the tested preservatives, only IMU induced a reduction in cell viability, as shown using the MTT assay and propidium iodide staining (IMU>methylparaben>sodium benzoate). IMU was shown to promote homeostatic alterations potentially related to the initiation of programed cell death, such as decreased mitochondrial membrane potential and caspase-3 activation, in the treated cells. Methylparaben and sodium benzoate were shown to have a very low cytotoxic activity. Taken together, our results suggest that IMU induces programed cell death in human fibroblasts by a canonical intrinsic pathway via mitochondrial perturbation and subsequent release of proapoptotic factors.

Cancer is a leading cause of death worldwide, and its incidence is continually increasing. Although anticancer therapy has improved significantly, it still has limited efficacy for tumor eradication and is highly toxic to healthy cells. Thus, novel therapeutic strategies to improve chemotherapy, radiotherapy and targeted therapy are an important goal in cancer research. Macroautophagy (herein referred to as autophagy) is a conserved lysosomal degradation pathway for the intracellular recycling of macromolecules and clearance of damaged organelles and misfolded proteins to ensure cellular homeostasis. Dysfunctional autophagy contributes to many diseases, including cancer. Autophagy can suppress or promote tumors depending on the developmental stage and tumor type, and modulating autophagy for cancer treatment is an interesting therapeutic approach currently under intense investigation. Nutritional restriction is a promising protocol to modulate autophagy and enhance the efficacy of anticancer therapies while protecting normal cells. Here, the description and role of autophagy in tumorigenesis will be summarized. Moreover, the possibility of using fasting as an adjuvant therapy for cancer treatment, as well as the molecular mechanisms underlying this approach, will be presented.

Aumentos transientes no cálcio citosólico (Ca c2+) e mitocondrial (Ca m2+) são elementos essenciais no controle de muitos processos fisiológicos. No entanto, aumentos sustentados do Ca c2+ e do Ca m2+ podem contribuir para o estresse oxidativo ea morte celular. Muitos eventos estão relacionados ao aumentono Ca c2+, incluindo a regulação e ativação de várias enzimas dependentes de Ca2+ como as fosfolipases, proteases e nucleases. A mitocôndria e o retículo endoplasmático têm um papel central na manutenção da homeostase intracellular de Ca c2+ e na regulação da morte celular. Várias evidências mostraram que, na presença de certos estímulos apoptóticos, a ativação dos processos mitocondriais pode promover a liberação de citocromo c, seguida da ativação de caspases, fragmentação nuclear e morte celular por apoptose. O objetivo desta revisão é mostrar como aumentos na sinalização de Ca2+ podem estar relacionados aos eventos de indução da morte celular apoptótica. Além disso, evidenciar como a homeostase de Ca2+ pode ser importante e está envolvida nos mecanismos presentes nos processos de neurodegeneração e envelhecimento.

Transient increase in cytosolic (Cac2+) and mitochondrial Ca2+ (Ca m2+) are essential elements in the control of many physiological processes. However, sustained increases in Ca c2+ and Ca m2+ may contribute to oxidative stress and cell death. Several events are related to the increase in Ca m2+, including regulation and activation of a number of Ca2+ dependent enzymes, such as phospholipases, proteases and nucleases. Mitochondria and endoplasmic reticulum (ER) play pivotal roles in the maintenance of intracellular Ca2+ homeostasis and regulation of cell death. Several lines of evidence have shown that, in the presence of some apoptotic stimuli, the activation of mitochondrial processes maylead to the release of cytochrome c followed by the activation of caspases, nuclear fragmentation and apoptotic cell death. The aim of this review was to show how changes in calcium signaling can be related to the apoptotic cell death induction. Calcium homeostasis was also shown to be an important mechanism involved in neurodegenerative and aging processes.