Spermidine is a naturally occurring polyamine compound that has recently emerged with anti-aging properties and suppresses inflammation and oxidation. However, its mechanisms of action on anti-inflammatory and antioxidant effects have not been fully elucidated. In this study, the potential of spermidine for reducing pro-inflammatory and oxidative effects in lipopolysaccharide (LPS)-stimulated macrophages and zebrafish was explored. Our data indicate that spermidine significantly inhibited the production of pro-inflammatory mediators such as nitric oxide (NO) and prostaglandin E2 (PGE2), and cytokines including tumor necrosis factor-α and interleukin-1β in RAW 264.7 macrophages without any significant cytotoxicity. The protective effects of spermidine accompanied by a marked suppression in their regulatory gene expression at the transcription levels. Spermidine also attenuated the nuclear translocation of NF-κB p65 subunit and reduced LPS-induced intracellular accumulation of reactive oxygen species (ROS) in RAW 264.7 macrophages. Moreover, spermidine prevented the LPS-induced NO production and ROS accumulation in zebrafish larvae and was found to be associated with a diminished recruitment of neutrophils and macrophages. Although more work is needed to fully understand the critical role of spermidine on the inhibition of inflammation-associated migration of immune cells, our findings clearly demonstrate that spermidine may be a potential therapeutic intervention for the treatment of inflammatory and oxidative disorders.

During mammalian embryogenesis, the early embryo grows in a relatively hypoxic environment due to a restricted supply of oxygen. The molecular mechanisms underlying modulation of self-renewal and differentiation of mouse embryonic stem cells (mESCs) under such hypoxic conditions remain to be established. Here, we show that hypoxia inhibits mESC self-renewal and induces early differentiation in vitro, even in the presence of leukemia inhibitory factor (LIF). These effects are mediated by down-regulation of the LIF-STAT3 signaling pathway. Under conditions of hypoxia, hypoxia-inducible factor-1α (HIF-1α) suppresses transcription of LIF-specific receptor (LIFR) by directly binding to the reverse hypoxia-responsive element located in the LIFR promoter. Ectopic expression and small interference RNA knockdown of HIF-1α verified the inhibitory effect on LIFR transcription. Our findings collectively suggest that hypoxia-induced in vitro differentiation of mESCs is triggered, at least in part, by the HIF-1α-mediated suppression of LIF-STAT3 signaling.