MicroRNA 181b‐3p and its target importin α5 regulate toll‐like receptor 4 signaling in Kupffer cells and liver injury in mice in response to ethanol

Abstract

Increased inflammatory signaling by Kupffer cells contributes to alcoholic liver disease (ALD). Here we investigated the impact of small-specific sized hyaluronic acid of ~35kD (HA35) on ethanol-induced sensitization of Kupffer cells, as well as ethanol-induced liver injury in mice. Un-biased analysis of microRNA (miRNA) expression in Kupffer cells identified miRNAs regulated by both ethanol and HA35. TLR4-mediated signaling was assessed in primary cultures of Kupffer cells from ethanol- and pair-fed rats after treatment with HA35. Female C57BL6/J mice were fed ethanol or pair-fed control diets and treated or not with HA35. TLR4 signaling was increased in Kupffer cells by ethanol; this sensitization was normalized by ex vivo treatment with HA35. Next Generation Sequencing of Kupffer cell miRNA identified miRNA181b-3p as sensitive to both ethanol and HA35. Importin α5, a protein involved in p65 translocation to the nucleus, was identified as a target of miR181b-3p; importin α5 protein was increased in Kupffer cells from ethanol-fed rats, but decreased by HA35 treatment. Overexpression of miR181b-3p decreased importin α5 expression and normalized LPS-stimulated TNFα expression in Kupffer cells from ethanol-fed rats. In a mouse model of ALD, ethanol feeding decreased miR181b-3p in liver and increased expression of importin α5 in non-parenchymal cells. Treatment with HA35 normalized these changes and also protected mice from ethanol-induced liver and intestinal injury. Conclusions miR181b-3p is dynamically regulated in Kupffer cells and mouse liver in response to ethanol and treatment with HA35. miR181b-3p modulates expression of importin α5 and sensitivity of TLR4-mediated signaling. To our knowledge, this study is the first to identify a miR181b-3p→importin α5 axis in regulating inflammatory signaling pathways in hepatic macrophages.

Noncoding RNAs in alcoholic liver disease

“…miR‐21 also has a positive correlation with activation of LPS signaling in response to ethanol (Alam & O'Neill, ). Decreased miR‐181b‐3p in liver and macrophages isolated from alcohol‐fed mice promotes expression of importin α5, a protein associated with translocation of p65 to the nucleus, and enhances sensitivity of TLR4 signaling (Saikia et al, ). In addition to TLR4, TLR7/let‐7 contributes to EtOH‐induced hepatic inflammation in AH (Massey et al, ).…”

Targeting inflammation for the treatment of alcoholic liver disease

“…Similarly, miRNA-217 is found to be increased in ethanol-treated macrophages/KCs and leads to inflammatory activity by disrupting Siruin1-lipin-1 signaling (Yin et al, 2015). More recently, Dr. Nagy’s group demonstrated that miR181b-3p in KCs plays an important role in the control of liver injury and inflammation in ethanol-fed mice via the regulation of importin α5 and sensitivity of TLR4-mediated signaling (Saikia et al, 2017). A small specific-sized hyaluronic acid 35 (HA35) treatment can normalize the dysregulated miR181b-3p in KCs and ameliorate ALD in mice, suggesting that HA35, miR-181b-3p, or combination may have therapeutic potential for the treatment of ALD (He & Gao, 2017; Saikia et al, 2017).…”

A small specific‐sized hyaluronic acid ameliorates alcoholic liver disease by targeting a small RNA: New hope for therapy?

“…Many potential targets against inflammation have been identified in preclinical studies of ALD, but none of them have been approved to be effective in the clinic for the treatment of patients with ALD yet. In this issue of Hepatology , Saikia et al add two more new targets including a small specific‐sized hyaluronic acid (HA) 35 (HA35) and microRNA (miRNA) 181b‐3p that may have therapeutic potential for the treatment of ALD. By screening a series of small specific‐sized HA fragments including HA7, HA12, HA59, HA35, and HA74 for their immunoregulatory effects on Kupffer cells from ethanol‐fed rats, the authors identified that only small specific‐sized HA of ∼35 kDa (HA35) completely normalized the overactivated Kupffer cells from ethanol‐fed rats in vitro and in vivo .…”

“…Dependent on the size and matrix structure of the HA molecules and interaction with various types of HA binding proteins and receptors, HA can act either as an anti‐inflammatory mediator or as a proinflammatory factor in response to tissue damage . The study by Saikia et al clearly demonstrated that HA35, but not several other small‐sized HAs they tested, acts as a potent anti‐inflammatory mediator to ameliorate ethanol‐induced overactivation of Kupffer cells in vivo and in vitro . Further mechanistic studies demonstrated that the inhibitory effect of HA35 on hepatic inflammation is mediated by restoring the miRNA‐181b‐3p expression in Kupffer cells that is down‐regulated by ethanol.…”

“…Moreover, Blaya et al have demonstrated that miR‐182 is the most highly up‐regulated miRNA in alcoholic hepatitis and mainly expressed in ductular reaction cells, playing an important role in promoting bile acid accumulation and inflammation. The study by Saikia et al identified miR‐181b‐3p as a critical negative regulator for Toll‐like receptor 4 signaling in Kupffer cells. Using next‐generation sequencing analysis, the authors demonstrated that 30 miRNAs were markedly down‐regulated by more than 2‐fold in Kupffer cells from ethanol‐fed rats compared to those from pair‐fed animals, and three miRNAs from these 30 down‐regulated miRNAs were restored by HA35 treatment.…”