Cytotoxicity of capsaicin on cultured human skin fibroblast

Background: Capsaicin has been shown to have different biologic and toxic effects, depending on non-neuronal cells and several transformed cells, however no study has been reported from cultured human skin fibroblast. Objective: Present study was aimed to evaluate the cytotoxicity and its mechanism of capsacin on the cultured human skin fibroblast. Material and method: Normal neonatal human fibroblasts were used, and changes of cell survival were measured by MTT assay after the cells were pre-treated with growth factors, receptor antagonist, antioxidants, calcium modulators were pre-treated or co-treated with capsaicin. Results: Suvival of fibroblast was significantly increased by treatment with EGF (10 ng/ml), bFGF (10 ng/ml), capsazepine (10 M) but inhibited by cycloheximide (1 g/ml). When 200 M capsaicin was added to fibroblasts, chromatin condensations were observed at 12 hours and cell survival rate was reduced to 25-50% at 24 hours. Vanilloid receptor antagonists, capsazepine and ruthenium red, did not prevent the toxic effect of capsaicin, and 10 M capsazepine paradoxically rather enhanced the cytotoxicity. In contrast to bFGF (10 ng/ml), EGF (10, 100 ng/ml) enhanced the cytotoxicity of capsaicin. Neuropeptides, substance P (1, 10 nM) and CGRP (1, 10 nM), and a structural analogue to capsaicin, tyrosine (0.3-1.2 mM) did not affect the cytotoxicity. However, antioxidants such as trolox (100 M) and ascorbic acid (0.1, 0.3 mM) reduced the capsaicin cytotoxicity. Of calcium modulating agents, nifedifine, a Ca2+ channel blocker (10, 20 M) and cyclopiazonic acid, a Ca2+-ATPase inhibitor in ER (10 M) did not influence the cytotoxicity, however BAPTA/AM (10M) as a chelater for cytoplasmic free calcium ion (10 M) significantly decreased capsaicin cytotoxicity. Unlike cycloheximide, z-VAD-FMK, a protein synthesis inhibitor and a non-specific caspase inhibitor, prevented the capsaicin cytotoxicity. The DNA ladder and TUNEL positive cells were observed among the capsaicin treated fibroblasts and Western blot revealed caspase-3 activity. Conclusion: The capsaicin-induced cytotoxicity on human skin fibroblasts is likely to suggest the mechanism of an apoptotic pathway, which can possibly be prevented by antioxidants.