Role of butyrate, a short-chain fatty acid, in modulating HBV replication and hepatocellular carcinoma 

Butyrate is a short-chain fatty acid produced by the gut microbiota during the fermentation of dietary fibres or fermentable sugars. Our lab observed butyrate-induced apoptosis and autophagy via ROS production in Hepatocellular Carcinoma (HCC). The autophagy modulation happened through inhibited phosphorylation of akt and mTOR, leading to the upregulation of autophagic proteins, such as beclin 1, ATG 5, LC3-II, followed by increased autophagosome formation. (PMID: 28600122, DOI: 10.1016/j.cbi.2017.06.001 ). Butyrate is a class IV histone deacetylase inhibitor and an apoptosis inducer. Apoptosis happened through cytochrome c release, activation of caspase-3, and further inhibited cell growth & proliferation. This apoptosis modulation is accomplished by inhibiting SIRT-1 expression via induced miR-22 expression in hepatic cells. (PMID: 28288414, DOI: 10.1016/j.redox.2017.03.006 ). A similar mechanism of butyrate inhibiting SIRT-1 was observed in HBV replication inhibition. In HBV, Inhibition of SIRT-1 by butyrate increased the levels of Ac-p53, which in turn decreased p-akt, cyclin D1, and thereby inhibited cell proliferation. (PMID: 30501014, DOI: 10.1002/mc.22946 ).

Role of Augmenter of Liver Regeneration (ALR) in theLliver Regeneration

Liver regeneration is regulated by several growth factors, one of the key factors being the augmenter of liver regeneration (ALR). ALR has been observed to be involved in liver regeneration by not only overcoming cell cycle inhibition but by maintaining the stem cell pool as well. Previous studies showed that ALR could not itself initiate the process of liver regeneration but is still crucial for the progression of regeneration, and growth factors could initiate the regeneration, and ALR enhances it by promoting cell proliferation. The inherent mechanism of the increase in proliferation was not yet known. In our lab, we observed ALR-induced proliferation via upregulation of miRNA-26a, targeting the down-regulation of PTEN, resulting in enhanced p-Akt/cyclin D1 pathway in hepatic cells. (PMID: 31267617, DOI: 10.1111/hepr.13404 ). Not only in regeneration but also ALR was shown to inhibit liver fibrosis in mice model systems. The mechanisms by which it inhibited fibrosis were not known. In our lab, we observed TGF-β induced miRNA-181a, which in turn induced fibrosis and inhibited ALR expression. Overexpression of ALR inhibited TGF-β-induced fibrogenic changes, including the expression of miRNA-181a and E-cadherin. Hence we observed that ALR inhibited TGF-β action by decreasing the expression of TGFβ-RII, thereby inhibiting miRNA-181a expression and fibrosis markers which makes ALR a potential molecule to inhibit liver fibrosis. (PMID: 31166951, DOI: 10.1371/journal.pone.0214534 )

Role of miRNAs and Glucose Metabolism in the Progression of Non-Alcoholic Fatty Liver Disease to Hepatocellular Carcinoma

Non-alcoholic fatty liver disease (NAFLD) is one of the major health concerns in the World. The dietary free fatty acids (FFAs) affect the metabolic status of the hepatocytes by modulating cellular pathways. These are important regulators of the progression of NAFLD. Several studies have reported that the expression of multiple miRNAs is dysregulated among liver samples of NAFLD patients compared to normal controls. Apoptosis normally occurs in the liver during development and in the renewal of hepatocytes. However, apoptosis can also be initiated in various other conditions, such as viral infections and immunological, malignant, and drug-induced liver disease. In NAFLD, cell death is a predominant feature resulting from apoptosis. In our lab, we observed that FFAs-induced miR-181a-5p expression inhibited anti-apoptotic genes, XIAP and Bcl2, and enhanced proliferation-related PTEN protein in hepatic cells. (PMID: 35551953, DOI: 10.1016/j.lfs.2022.120625 ). One of the major functions of the liver is to maintain glucose homeostasis by switching from glucose storage to export. The pathogenesis of NAFLD is associated with increased fat deposition in the liver by decreasing fatty acid oxidation. But induction of fatty acid oxidation is required for gluconeogenesis, and hence this metabolic process will also be affected. In our lab, we observed FFAs in liver induced miR-22 expression, which in turn inhibited the expression of SIRT-1, which led to decreased expression of PGC-1α, an enhancer of gluconeogenesis. Hence on the whole FFAs lead to decreased gluconeogenesis via miR-22 in hepatic cells. (DOI: 10.1016/j.iliver.2023.01.002)

Identification and Characterization of Different HBV Interacting Host Proteins and Elucidation of their Mechanism of Action

Hepatitis B virus (HBV) infection is a global public health problem, and its chronic infection carries a high risk of developing liver cirrhosis and hepatocellular carcinoma (HCC). Upon entry into the host cells, HBV interacts with numerous cellular factors, such as the host immune system, miRNAs, and other cellular proteins, and modulates their expression to survive in the host cells. HBV infection targets host restriction factors that inhibit its replication and survival. HBV entry to the host cells and its successful infection depends on its ability to modulate the host restriction factors. The molecular mechanisms by which HBV survives and replicates in the host cells are yet to be explored more. In our lab, for the first time, we found that Barrier to autointegration factor1 (BANF1) inhibited HBV replication and restricted the viral load. HBV infection inhibited the intracellular expression of BANF1 via HBx-mediated upregulation of miR-203 expression. (PMID: 36519846, DOI: 10.1128/spectrum.01235-22 ). Another molecule, DEAD-box RNA helicase, DDX3, is shown to inhibit HBV replication. However, the exact mechanism of inhibition remains unclear. We observed that DDX3 upregulates miR-34 expression and thus inhibits autophagy in HBV-expressing cells, while HBx helps HBV evade DDX3-mediated inhibition by downregulating DDX3 expression in HBV-infected cells. (PMID: 36597176, DOI: 10.1111/jvh.13799 ).