Pseudogene RPL32P3 regulates the blood–tumor barrier permeability via the YBX2/HNF4G axis

The existence of the blood–tumor barrier (BTB) severely hinders the transport of anti-tumor drugs to brain tumor tissues. Selectively opening BTB is of great significance to improve the chemotherapy effect of glioma. Pseudogenes have been recognized as important regulators in various biologic processes. In this study, we identified that ribosomal protein L32 pseudogene 3 (RPL32P3) was highly expressed in glioma-exposed endothelial cells (GECs). Knockdown of RPL32P3 decreased the expression of tight junction-related proteins (TJPs) and increased BTB permeability. Subsequent analysis of the underlying mechanism indicated that RPL32P3 recruited lysine methyltransferase 2 A (KMT2A) to the Y-box binding protein 2 (YBX2) promoter region and mediated H3K4me3 to promote YBX2 transcription. Highly expressed YBX2 bound and stabilized hepatocyte nuclear factor 4 gamma (HNF4G) mRNA. Highly expressed HNF4G directly bound to the promoters of TJPs ZO-1, occludin and claudin-5 to promote their transcriptional activities and regulated BTB permeability. The simultaneous knockdown of RPL32P3, YBX2, and HNF4G combined with doxorubicin (DOX) increased the apoptosis of glioma cells. In conclusion, the current study indicated that RPL32P3 knockdown increased BTB permeability through the YBX2/HNF4G pathway. These findings may provide new targets for the comprehensive treatment of glioma.

GATA binding protein 4 promotes the expression and transcription of hepatitis B virus by facilitating hepatocyte nuclear factor 4 alpha in vitro

Background GATA binding protein 4 (GATA4) has been reported as a potential target of gene therapy for hepatocellular carcinoma (HCC). It is well known that the main cause of HCC is the chronic infection of hepatitis B virus (HBV). However, whether the effect of GATA4 on HBV has not yet been reported. Methods In this study, the regulation of GATA4 on HBV was analyzed in vitro. In turn, the effect of HBV on GATA4 was also observed in vitro, in vivo, and clinical HCC patients. Subsequently, we analyzed whether the effect of GATA4 on HBV was related to hepatocyte nuclear factor 4 alpha (HNF4α) in vitro. Results The results showed that GATA4 significantly promoted the secretion of HBV surface antigen (HBsAg) and HBV e antigen in the cell culture medium, improved the replication of HBV genomic DNA, and increased the level of HBV 3.5 kb pre-genomic RNA and HBV total RNA (P < 0.05). Moreover, it was showed that HBV had no significant effect on GATA4 in vitro and in vivo (P > 0.05). At the same time, GATA4 expression was decreased in 78.9% (15/19) of HCC patients regardless of the HBV and HBsAg status. Among them, there were 76.9% (10/13) in HBV-associated patients with HCC (HBV-HCC), and 83.3% (5/6) in non-HBV-HCC patients. In addition, the expression of HNF4α was also up-regulated or down-regulated accordingly when stimulating or interfering with the expression of GATA4. Furthermore, stimulating the expression of HNF4α could only alleviate the HBsAg level and HBV transcription levels, but had no significant effect on GATA4. Conclusions In summary, this study found that GATA4 has a positive effect on HBV, and the potential pathway may be related to another transcription factor HNF4α that regulates HBV.

Hepatocyte Nuclear Factor 4 Alpha Attenuated Lipotoxicity, But Increased Bile Acid Toxicity in Non-Alcoholic Fatty Liver Disease Model.

Background: It is known that hepatocyte nuclear factor 4 alpha (HNF4α) is key master nuclear receptor for hepatic fat and bile acid metabolic pathways. But the role of HNF4α in non-alcoholic fatty liver disease (NAFLD) is complex. The current study aimed to investigate role of HNF4α in NAFLD. Methods: Hepatic HNF4α expression evaluated in human NAFLD subjects. Free fatty acid induced lipotoxicity evaluated under HNF4α over- and down regulation. Chenodeoxy cholic acid (CDCA) induced bile acid toxicity evaluated under HNF4α in In Vitro NAFLD model. NAFLD activity score and fibrosis assessed after HNF4α silencing in methionine choline deficiency diet fed mice. Results: Hepatic HNF4α expression was higher in NAFLD than in control group. Overexpression of HNF4α reduced intracellular lipid contents via increasing mitochondria beta-oxidation and hepatic fat excretion. HNF4α overexpression attenuated palmitic acid (PA) induced lipotoxicity. Protective effects of HNF4α on cell death were reversed when CDCA co-treated with PA. CDCA mono-treatment did not affect cell viability, but co-treatment with PA and CDCA decreased cell viability. Bile acid toxicity of HNF4α was exaggerated under PA co-treatment with CDCA. HNF4α knock down using small interfering RNA recovered cell apoptosis and increased cell proliferation from PA and CDCA co-treatment condition. Inhibition of HNF4α using sh-HNF4α adenovirus vector did not reduce hepatic fat accumulation, but decreased intrahepatic inflammation and NAFLD activity score compared to control.Conclusions: HNF4α increased free fatty acid oxidation and attenuated lipotixicity, but increased bile acid toxicity in NAFLD animal model. Inhibition of HNF4α attenuated In vivo NAFLD model.

Serum transferrin as a biomarker of hepatocyte nuclear factor 4 alpha activity and hepatocyte function in liver diseases

Background Serum transferrin levels represent an independent predictor of mortality in patients with liver failure. Hepatocyte nuclear factor 4 alpha (HNF4α) is a master regulator of hepatocyte functions. The aim of this study was to explore whether serum transferrin reflects HNF4α activity. Methods Factors regulating transferrin expression in alcoholic hepatitis (AH) were assessed via transcriptomic/methylomic analysis as well as chromatin immunoprecipitation coupled to DNA sequencing. The findings were corroborated in primary hepatocytes. Serum and liver samples from 40 patients with advanced liver disease of multiple etiologies were also studied. Results In patients with advanced liver disease, serum transferrin levels correlated with hepatic transferrin expression (r = 0.51, p = 0.01). Immunohistochemical and biochemical tests confirmed reduced HNF4α and transferrin protein levels in individuals with cirrhosis. In AH, hepatic gene-gene correlation analysis in liver transcriptome revealed an enrichment of HNF4α signature in transferrin-correlated transcriptome while transforming growth factor beta 1 (TGFβ1), tumor necrosis factor α (TNFα), interleukin 1 beta (IL-1β), and interleukin 6 (IL-6) negatively associated with transferrin signature. A key regulatory region in transferrin promoter was hypermethylated in patients with AH. In primary hepatocytes, treatment with TGFβ1 or the HNF4α inhibitor BI6015 suppressed transferrin production, while exposure to TNFα, IL-1β, and IL-6 had no effect. The correlation between hepatic HNF4A and transferrin mRNA levels was also seen in advanced liver disease. Conclusions Serum transferrin levels constitute a prognostic and mechanistic biomarker. Consequently, they may serve as a surrogate of impaired hepatic HNF4α signaling and liver failure.

Hepatocyte-specific Hepatocyte Nuclear Factor 4 alpha (HNF4) deletion decreases resting energy expenditure by disrupting lipid and carbohydrate homeostasis

Hepatocyte Nuclear Factor 4 alpha (HNF4α) is required for hepatocyte differentiation and regulates expression of genes involved in lipid and carbohydrate metabolism including those that control VLDL secretion and gluconeogenesis. Whereas previous studies have focused on specific genes regulated by HNF4α in metabolism, its overall role in whole body energy utilization has not been studied. In this study, we used indirect calorimetry to determine the effect of hepatocyte-specific HNF4α deletion (HNF4α-KO) in mice on whole body energy expenditure (EE) and substrate utilization in fed, fasted, and high fat diet (HFD) conditions. HNF4α-KO had reduced resting EE during fed conditions and higher rates of carbohydrate oxidation with fasting. HNF4α-KO mice exhibited decreased body mass caused by fat mass depletion despite no change in energy intake and evidence of positive energy balance. HNF4α-KO mice were able to upregulate lipid oxidation during HFD suggesting that their metabolic flexibility was intact. However, only hepatocyte specific HNF4α-KO mice exhibited significant reduction in basal metabolic rate and spontaneous activity during HFD. Consistent with previous studies, hepatic gene expression in HNF4α-KO supports decreased gluconeogenesis and decreased VLDL export and hepatic Beta-oxidation in HNF4α-KO livers across all feeding conditions. Together, our data suggest deletion of hepatic HNF4α increases dependence on dietary carbohydrates and endogenous lipids for energy during fed and fasted conditions by inhibiting hepatic gluconeogenesis, hepatic lipid export, and intestinal lipid absorption resulting in decreased whole body energy expenditure. These data clarify the role of hepatic HNF4α on systemic metabolism and energy homeostasis.