Synthesis, evaluation and mechanism study of novel pyrazole enamides to alleviate lung injury.

Particulate matter with diameter ≤2.5 μm particles (PM2.5) can trigger pulmonary inflammation and lung injury. However, there is still no specific and effective treatment. Lansiumamide B (LB) is a natural cis-enamide compound isolated from wampee seeds, and has potential anti-inflammatory effect. Herein, two series of pyrazole enamide analogues were designed and synthesized based on the scaffold hopping strategy. The inhibition rates of inflammatory cytokines on compound 11a were superior to other compounds and exhibited good dose-dependent manner and safety. Mechanism studies shown that 11a activated the Keap1/Nrf2/HO-1 signaling pathway and promoted Nrf2 entering into nucleus. Further, 11a alleviated pulmonary inflammation, collagen formation and mucus secretion in PM2.5 induced lung injury mice. Besides, 11a administration inhibited M1 macrophage polarization and neutrophil infiltration. Overall, 11a is an effective anti-inflammatory agent which might be a potent candidate to treat lung injury.