ABSTRACT
Aims: In addition to reducing the respiratory function, crystalline silica (SiO2) disturbs the immune response by affecting immune cells during the progression of silicosis. Regulatory T cell (Treg) differentiation may play a key role in the abnormal polarization of T helper cell (Th)1 and Th2 cells in the development of silicosis-induced fibrosis. Alpha-lipoic acid (ALA) has immunomodulatory effects by promoting Tregs differentiation. Thus, ALA may have a therapeutic potential for treating autoimmune disorders in patients with silicosis. However, little is known regarding whether ALA regulates the immune system during silicosis development. Results: We found that the expression levels of collagen increased, and the antioxidant capacity was lower in the Lias-/-+SiO2 group than in the Lias+/++SiO2 group. The proportion of Tregs decreased in the peripheral blood and spleen tissue in mice exposed to SiO2. The proportion of Tregs in the Lias-/-+SiO2 group was significantly lower than that in the Lias+/++SiO2 group. Supplementary exogenous ALA attenuates the accumulation of inflammatory cells and extracellular matrix in lung tissues. ALA promotes the immunological balance between Th17 and Treg responses during the development of silicosis-induced fibrosis. Innovation and Conclusion: Our findings confirmed that low expression of lipoic acid synthase aggravates SiO2-induced silicosis, and that supplementary exogenous ALA has therapeutic potential by improving Tregs in silicosis fibrosis.
ABSTRACT
Silicosis is characterized by pulmonary interstitial fibrosis that arises as a result of chronic exposure to silica. The few available treatments only delay its progression. As α-lipoic acid (ALA) has been shown to have various beneficial effects, including mitoprotective, antioxidant, and anti-inflammatory effects, we hypothesized that it may exhibit therapeutic effects in pulmonary fibrosis. Therefore, in the present study, we used a murine model of silicosis to investigate whether supplementation with exogenous ALA could attenuate silica-induced pulmonary fibrosis by improving mitochondrial function. ALA was administered to the model mice via continuous intragastric administration for 28 days, and then the antioxidant and mitoprotective effects of ALA were evaluated. The results showed that ALA decreased the production of reactive oxygen species, protected mitochondria from silica-induced dysfunction, and inhibited extracellular matrix deposition. ALA also decreased hyperglycemia and hyperlipidemia. Activation of the mitochondrial AMPK/PGC1α pathway might be responsible for these ALA-mediated anti-fibrotic effects. Exogenous ALA blocked oxidative stress by activating NRF2. Taken together, these findings demonstrate that exogenous ALA effectively prevents the progression of silicosis in a murine model, likely by stimulating mitochondrial biogenesis and endogenous antioxidant responses. Therefore, ALA can potentially delay the progression of silica-induced pulmonary fibrosis.