Type I interferon (IFN) inhibits, by an unknown mechanism, the replication of human papillomaviruses (HPV), which are major human pathogens, Here, we present evidence that P56 (a protein), the expression of which is strongly induced by IFN, double-stranded RNA and viruses, mediates the anti-HPV effect of IFN. Ectopic expression of P56 inhibited HPV DNA replication and its ablation in IFN-treated cells alleviated the inhibitory effect of IFN on HPV DNA replication. Protein-protein interaction and mutational analyses established that the antiviral effect of P56 was mediated by its direct interaction with the DNA replication origin-binding protein E1 of several strains of HPV, through the tetratricopeptide repeat 2 in the N-terminal region of P56 and the C-terminal region of E1. In vivo, the interaction with P56, a cytoplasmic protein, caused translocation of E1 from the nucleus to the cytoplasm. In vitro, recombinant P56, or a small fragment derived from it, inhibited the DNA helicase activity of E1 and E1-mediated HPV DNA replication. These observations delineate the molecular mechanism of IFN's antiviral action against HPV.

Multiple pathways of programmed cell death are important in liver homeostasis. Hepatocyte death is associated with progression of nonalcoholic fatty liver disease (NAFLD) and inhibition of apoptosis partially protects against liver injury in response to high fat diets (HFD). However, the contribution of necroptosis, a caspase-independent pathway of cell death, to HFD-induced liver injury is not known. Wild-type C57BL/6 and receptor interacting protein (RIP) 3−/− mice were randomized to chow or HFD. HFD-fed C57BL/6 mice increased expression of RIP3, the master regulator of necroptosis, as well as phosphorylated mixed lineage kinase domain-like (pMLKL), an effector of necroptotic cell death, in liver. HFD did not increase pMLKL in RIP3−/− mice. HFD increased fasting insulin and glucose, as well as glucose intolerance, in C57BL/6 mice. RIP3−/− were glucose intolerant even on chow diets; HFD further increased fasting glucose and insulin, but not glucose intolerance. HFD also increased hepatic steatosis, plasma ALT activity, inflammation, oxidative stress and hepatocellular apoptosis in wild-type mice; these responses were exacerbated in RIP3−/− mice. Importantly, increased inflammation and injury was associated with early indicators of fibrosis in RIP3−/− compared to C57BL/6 mice. Culture of AML12 hepatocytes with palmitic acid increased cytotoxicity via apoptosis and necrosis. Inhibition of RIP1 with necrostatin-1 or siRNA knock-down of RIP3 reduced palmitic acid-induced cytotoxicity. Conclusion Absence of RIP3, a key mediator of necroptosis, exacerbated HFD-induced liver injury, associated with increased inflammation and hepatocyte apoptosis, as well as early fibrotic responses. These findings indicate that shifts in the mode of hepatocellular death can influence disease progression and have therapeutic implications because manipulation of hepatocyte cell death pathways is being considered as a target for treatment of NAFLD.

Alcoholic liver disease (ALD) develops in approximately 20% of alcoholics, with a higher prevalence in females. ALD progression is marked by fatty liver and hepatocyte necrosis, as well as apoptosis, inflammation, regenerating nodules, fibrosis, and cirrhosis 1. ALD develops via a complex process involving parenchymal and non-parenchymal cells, as well as recruitment of other cell types to the liver in response to damage and inflammation. Hepatocytes are damaged by ethanol, via generation of reactive oxygen species and induction of endoplasmic reticulum stress and mitochondrial dysfunction. Hepatocyte cell death via apoptosis and necrosis are markers of ethanol-induced liver injury. We review the mechanisms by which alcohol injures hepatocytes and the response of hepatic sinusoidal cells to alcohol-induced injury. We also discuss how recent insights into the pathogenesis of ALD will affect treatment and management of patients.

Toll like receptors (TLRs) recognize specific microbial products and elicit innate immune signals to activate specific transcription factors that induce protective proteins, such as interferon. TLR3 recognizes double-stranded (ds) RNA, generated by virus infected or apoptotic cells. TLR3 has been genetically linked to several human diseases, including some without viral etiology. Unlike other TLRs, TLR3 requires phosphorylation of two specific tyrosine residues, in its cytoplasmic domain, to initiate signaling. Here, we demonstrate that the two protein tyrosine kinases, the epidermal growth factor receptor ErbB1 and Src, bind sequentially to dsRNA-activated TLR3 and phosphorylate the two tyrosine residues, which is required for the recruitment of the adaptor protein, TRIF. Thus, these results reveal a connection between antiviral innate immunity and cell growth regulators.

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.