Background: Several metallic elements with high atomic weight and density are serious systemic toxicants, and their wide environmental distribution increase the risk of their exposure to human. Silymarin (SL), a polyphenol from milk thistle (Silybum marianum) plant has shown protective role against heavy metal toxicity. However, its low aqueous solubility and rapid metabolism limits its therapeutic potential in clinic.
Methods: We compared the role of silymarin nanoliposomes (SL-L) against cadmium (Cd) toxicity in normal MRC-5 and A 549 cancer cells. MRC-5 and A 549 cells exposed to Cd at 25 and 0.25 µM respectively, were treated with various non-toxic SL-L concentrations (2.5, 5, 10 µM) and cells viability, reactive oxygen species (ROS) generation, apoptosis and levels of cleaved PARP and caspase-3 proteins were determined following incubation.
Results: Results indicated that Cd exposure significantly increased apoptosis due to ROS generation, and showed greater toxicity on cancer cells compared to normal cells. While SL-L at higher concentrations (25 µM and higher) exhibits pro-apoptotic features, lower concentrations (10 and 2.5 µM for MRC-5 and A 549 cancer cells, respectively) played a protective and anti-oxidant role in Cd induced toxicity in both cells. Further, lower SL-L was required to protect cancer cells against Cd toxicity. In general, treatment with SL-L significantly improved cell survival by decreasing ROS levels, cleaved PARP and caspase-3 in both MRC-5 and A 549 cells compared to free silymarin.
Conclusion: Results demonstrated that SL-L potential in protecting against Cd-induced toxicity depends on concentration-dependent antioxidant and anti-apoptotic balance.
Keywords: Apoptosis; Cadmium; Lung cells; Silymarin liposome; Toxicity.
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