Exogenous spermine inhibits high glucose/oxidized LDL-induced oxidative stress and macrophage pyroptosis by activating the Nrf2 pathway

Evidence suggests that macrophage pyroptosis promotes the progression of diabetic atherosclerosis. Spermine, a natural cellular metabolite, demonstrates a protective effect against cardiovascular diseases. However, whether spermine has a protective effect against macrophage pyroptosis caused by high glucose (HG) and oxidized low-density lipoprotein (ox-LDL) conditions remains to be elucidated. To investigate the protective effect of spermine and the related underlying mechanism, THP-1 macrophages were treated with HG/ox-LDL, spermine, or the specific nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor ML385. Cell viability was detected using CCK-8, cell membrane permeability was analyzed using lactate dehydrogenase (LDH) and Hoechst/propidium iodide staining and pyroptosis-related gene and protein expression levels were evaluated using polymerase chain reaction and western blot analysis. Spermine showed a potent preventive effect on THP-1 macrophage pyroptosis and oxidative stress induced by HG/ox-LDL. Cells treated with spermine showed increased cell viability, reduced reactive oxygen species (ROS) production, decreased LDH levels in the supernatant and reduced cell swelling. In addition, spermine significantly reduced NLR family pyrin domain containing 3, cleaved caspase-1, N-gasdermin D and IL-1β expression, as well as IL-1β levels in the supernatant. This demonstrated that the inhibition of pyroptosis and oxidative stress due to spermine was Nrf2 dependent. Furthermore, spermine enhanced Nrf2 nuclear translocation, thereby increasing heme oxygenase-1 and NADPH quinone oxidoreductase-1 expression, which subsequently reduced ROS production. In addition, the anti-pyroptotic and antioxidant effects of spermine were reversed by ML385 inhibition of Nrf2. It was concluded that spermine prevented macrophage pyroptosis and increased ROS overproduction by activating the Nrf2 pathway. The data suggested that spermine may be a potential novel drug for the treatment of diabetic atherosclerosis because it targets macrophage pyroptosis.