Overexpression of endogenous lipoic acid synthase attenuates pulmonary fibrosis induced by crystalline silica in mice

Oxidative stress and inflammatory processes are proposed to mediate the development of silicosis. However, antioxidant therapy has not produced consistent results during the treatment of silicosis. alpha-Lipoic acid synthesized by lipoic acid synthase is a powerful anti-oxidant and helps protect mitochondria. Thus far, the effect of endogenous alpha-Lipoic acid on silicosis has not been elucidated yet. We established an experimental model of silicosis with wildtype and Lias(H/H) mice, a new antioxidant mouse model which has overexpressed Lias gene (similar to 150 %) relative to its wild type counterpart. We systemically examined main pathological changes of pulmonary fibrosis, and explored alpha-lipoic acid effects on oxidative stress, inflammatory and pulmonary fibrosis biomarkers in silica-instillated mice. In Lias(H/H) mice over-expression of lipoic acid alleviated the severity of major pathological alterations in the early stage of pulmonary fibrosis induced by silica compared with wild type mice. Silica significantly increased oxidative stress in both wild type and Lias(H/H) mice. The antioxidant defense was strengthen including increased NRF2 and LIAS production in Lias(H/H) mice. Relieved oxidative stress resulted in decreased inflammatory response and secretion of chemokines. Lias(H/H) mice reduced chronic inflammatory response and inhibition of NF-kappa B activity after silica instillation. The Lias(H/H) mouse model overexpression of lipoic acid synthase gene retarded the development of silica-induced pulmonary fibrosis. Strengthen antioxidant defense by increased lipoic acid synthase is a potential strategy for protection against silica-induced pulmonary fibrosis.