S-allylmercaptocysteine ameliorates lipopolysaccharide-induced acute lung injury in mice by inhibiting inflammation and oxidative stress via nuclear factor kappa B and Keap1/Nrf2 pathways

The garlic-derived organosulfur compound S-allylmercaptocysteine (SAMC) has been reported to exhibit anti-inflammatory and anti-oxidative activities, whereas its potential therapeutic effect on lipopolysaccharide (LPS)-induced acute lung injury (ALI) is unknown. In this study, we focused on exploring the therapeutic effects of SAMC on LPS-induced ALI mice and the involvement of underlying molecular mechanisms. BalB/c mice were treated with SAMC (10, 30 and 60 mg/kg) or positive control N-acetylcysteine (NAC, 500 mg/kg) by gavage after intratracheal instillation of LPS for 30 min and were sacrificed 24 h after LPS administration. Our results indicate that the treatment with SAMC not only ameliorated the histological changes but also decreased LPS-triggered lung edema. Moreover, SAMC displayed an anti-inflammatory effect through reducing inflammatory cells infiltration, myeloperoxidase (MPO) formation and inhibiting pro-inflammatory cytokines/mediator production including tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), interleukin-6 (IL-6), inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX2) via suppressing the activation of nuclear factor-kappaB (NF-κB) signaling pathway. Furthermore, SAMC attenuated oxidative stress evoked by LPS via diminishing malondialdehyde (MDA) formation and reversing glutathione (GSH) and superoxide dismutase (SOD) depletion. Meanwhile, SAMC up-regulated expressions of endogenous antioxidant/detoxifying proteins including heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1(NQO1) through reversing the suppression of Kelch-like ECH-associated protein 1 (Keap1)/nuclear factor erythroid-2 related factor 2 (Nrf2) signaling pathway. Our results demonstrate that SAMC effectively attenuated LPS-induced ALI which was largely dependent upon inhibition of inflammation and oxidative stress via NF-κB and Keap1/Nrf2 signaling pathways.

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