Spermine Alleviates Acute Liver Injury by Inhibiting Liver-Resident Macrophage Pro-Inflammatory Response Through ATG5-Dependent Autophagy

Abstract

Liver-resident macrophages (Kupffer cells, KCs) and autophagy play critical roles in the pathogenesis of toxin-induced liver injury. Recent evidence indicates that autophagy can regulate macrophage M1/M2 polarization under different inflammatory conditions. Polyamines, including putrescine, spermidine, and spermine (SPM), are polycations with anti-oxidative, anti-aging, and cell autophagy induction properties. This study aimed to determine the mechanisms by which SPM protects against thioacetamide (TAA)-induced acute liver injury in a mouse model. Pretreatment with SPM significantly alleviated liver injury and reduced intrahepatic inflammation in TAA-induced liver injury compared to controls. SPM markedly inhibited M1 polarization, but promoted M2 polarization of KCs obtained from TAA-exposed livers, as evidenced by decreased IL-1β and iNOS gene induction but increased Arg-1 and Mrc-1 gene induction accompanied by decreased STAT1 activation and increased STAT6 activation. Furthermore, pretreatment with SPM enhanced autophagy, as revealed by increased LC3B-II levels, decreased p62 protein expression, and increased ATG5 protein expression in TAA-treated KCs. Knockdown of ATG5 in SPM-pretreated KCs by siRNA resulted in a significant increase in pro-inflammatory TNF-α and IL-6 secretion and decreased anti-inflammatory IL-10 secretion after TAA treatment, while no significant changes were observed in cytokine production in the TAA treatment alone. Additionally, the effect of SPM on regulation of KC M1/M2 polarization was abolished by ATG5 knockdown in TAA-exposed KCs. Finally, in vivo ATG5 knockdown in KCs abrogated the protective effect of SPM against TAA-induced acute liver injury. Our results indicate that SPM-mediated autophagy inhibits M1 polarization, while promoting M2 polarization of KCs in TAA-treated livers via upregulation of ATG5 expression, leading to attenuated liver injury. This study provides a novel target for the prevention of acute liver injury.

HMGB1‐associated necroptosis and Kupffer cells M1 polarization underlies remote liver injury induced by intestinal ischemia/reperfusion in rats

“…59 Another research also found that spermine-mediated autophagy inhibits M1 polarization but promoting M2 polarization of KCs leading to attenuated thioacetamide-induced liver injury. 60 Previous researches already demonstrated that systemic depletion of macrophages prevents hippocampal neuroinflammation and memory dysfunction after experimental tibial fracture, 61 improves renal I/R injury, 62 and decreases inflammatory mediators in endotoxin-treated rats. 63 Similarly, we found that liposomal clodronate led to effective depletion of the mature macrophage population in the liver and spleen, as a consequence, presented better-preserved liver architecture with lower injury scores and reduced serum ALT/AST levels after intestinal I/R.…”

The role of polyamines in the regulation of macrophage polarization and function

“…The spermine pre-treatment also resulted in a decrease of CCL2, CXCL-10, TNF-α and IL-6, but an increase of IL-10 in the tissues, thus suppressing the recruitment of immune cells (Zhou et al 2018). This is supported by low levels of proinflammatory markers and increased IL-10 in the serum, and evidence of less macrophage infiltration in the tissues (Zhou et al 2018). Knockdown of autophagy protein 5 (ATG5) mediates autophagy and increases M1 markers, while decreasing M2 markers (Zhou et al 2018) (Fig.…”

“…Spermine pre-treatment of Kupffer cells (resident liver macrophages) isolated from mice injected with thioacetamide, a hepatotoxin that causes acute and chronic liver injury, had reduced expression of Il1b and Nos2, but increased expression of Arg1 and Mrc1 (macrophage mannose receptor 1) (Zhou et al 2018). The spermine pre-treatment also resulted in a decrease of CCL2, CXCL-10, TNF-α and IL-6, but an increase of IL-10 in the tissues, thus suppressing the recruitment of immune cells (Zhou et al 2018). This is supported by low levels of proinflammatory markers and increased IL-10 in the serum, and evidence of less macrophage infiltration in the tissues (Zhou et al 2018).…”

RIP3 deficiency alleviates liver fibrosis by inhibiting ROCK1–TLR4–NF‐κB pathway in macrophages

“…Liver macrophages were isolated from mice after perfusion with liberase (Roche, Basel, Switzerland) and differential centrifugation in Percoll (17-0891-02; GE Healthcare, Waukesha, WI, USA) as previously described by Zhou et al (15). Primary hepatocytes and hepatic stellate cells (HSCs) were isolated from mice by collagenase (Roche) perfusion by subsequent density gradient centrifugation as previously described by Ma et al (16).…”