Cellular and Molecular Gastroenterology and Hepatology最新文献

Background & aims: The SWI/SNF ATP-dependent chromatin remodeling complex regulates transcriptional machinery access and is critical in normal physiology and cancer development. PBRM1, a key subunit of this complex, is frequently mutated in intrahepatic cholangiocarcinoma (iCCA). This study aims to explore the role of PBRM1 in liver physiology and its involvement in iCCA development.

Methods: Liver-specific Pbrm1 knockout (Pbrm1 KO) mice were generated to assess the effects of Pbrm1 loss under various conditions. These mice were exposed to a 3,5-diethoxycarbonyl-1,4-dihydrocollidine diet to induce cholestatic injury and were also subjected to a high-fat diet to evaluate susceptibility to liver steatosis. Chromatin accessibility and gene expression under both normal and injury conditions were examined. Additionally, the impact of Pbrm1 loss was analyzed in combination with an activating Kras^G12D mutation to study cancer development.

Results: Pbrm1 KO mice exhibited increased susceptibility to cholestatic injury, with an enhanced ductular reaction. Loss of Pbrm1 reduced chromatin accessibility at hepatocyte-specific and metabolically important genes, although RNA expression remained unaffected during homeostasis. Following cholestatic injury, hepatocyte-specific gene expression was significantly reduced compared with wild-type controls. Pbrm1 KO mice also showed heightened vulnerability to high-fat diet-induced liver steatosis. When combined with Kras^G12D mutation, Pbrm1 KO/Kras^G12D mice had shorter survival and were more likely to develop cholangiocarcinomas, whereas Pbrm1 wild type/Kras^G12D mice predominantly developed hepatocellular neoplasms. PBRM1-deficient organoids were highly sensitive to the EZH2 inhibitor tazemetostat, whereas effects on allografts were limited.

Conclusions: PBRM1 maintains chromatin accessibility for hepatocyte differentiation-related genes. Its loss promotes differentiation toward cholangiocytes during injury or tumorigenesis, driving iCCA development.

Background & aims: The global incidence of metabolic dysfunction-associated steatotic liver disease (MASLD) has risen dramatically. The capillarization of liver sinusoidal endothelial cells (LSEC) represents a crucial target for intervention in MASLD. However, the regulatory mechanisms underlying LSEC capillarization in MASLD remain unclear. Angiopoietin-2 (Ang-2) serves as a key regulator of vascularization.

Methods: The role and molecular mechanism of lipotoxic hepatocyte-derived small extracellular vesicles (LTH-sEVs) on LSEC capillarization was assessed in both LSEC and high-fat diet (HFD)-induced MASLD mice. O-linked N-acetylglucosamine transferase (OGT) expression was assessed in serum sEV and liver samples from healthy individuals and patients with MASLD. The O-GlcNAcylation inhibitor Benzyl-α-GalNAc (BAGN) was utilized to HFD-induced MASLD mice.

Results: Here, we showed that LTH-sEV can upregulate the vascularization marker Ang-2 and promote LSEC capillarization in vivo and in vitro. Mechanistically, LTH-sEV may transport O-linked N-acetylglucosamine (O-GlcNAc) glycosyltransferase (OGT) to enhance the O-GlcNAc glycosylation (O-GlcNAcylation) of the hepatocyte nuclear factor 1-alpha (HNF1α) Ser471 site. This process facilitates the nuclear translocation of HNF1α and increases its transcriptional activation of Ang-2, thereby promoting the LSEC capillarization. Serum sEV derived from patients with MASLD exhibit elevated levels of OGT, which are positively correlated with alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels. Additionally, BAGN could dose-dependently reduce HNF1α O-GlcNAcylation, thereby alleviating LSEC capillarization and MASLD progression in HFD-induced mice.

Conclusions: LTH-sEV may transport OGT to enhance HNF1α O-GlcNAcylation and activate Ang-2 expression regulated by HNF1α transcription, thus promoting LSEC capillarization. Consequently, sEV-derived OGT may serve as a novel diagnostic and therapeutic target for MASLD.

Background & aims: Visceral pain is a cardinal symptom of many disorders affecting the gut and other abdominal organs. Modulators of gamma-aminobutyric acid (GABA) such as benzodiazepines may attenuate such pain but the specific contribution of peripheral GABA-A receptors (GABRAs) remains unclear as current agonists have prominent central effects.

Methods: Using medicinal chemistry optimization of the benzodiazepine scaffold, we developed a novel and potent positive allosteric modulator (PAM), LI-633, with no significant central nervous system (CNS) penetration.

Results: The locomotor activity of rats placed in an open field was unchanged with LI-633 at doses up to 30 mg/kg, confirming its lack of a CNS effect. LI-633 produced robust potentiation of GABA-induced inward current, with EC50 values ranging from 8 nM (α5β2γ2) to 128 nM (α3β2γ2). In vitro electrophysiological studies confirmed its ability to reduce excitability of human dorsal root ganglion (DRG) neurons by GABA. LI-633 potentiated muscimol-induced GABAergic currents in rat DRG neurons in a dose-dependent manner, with an EC₅₀ of 70.4 nM. In vivo, LI-633 significantly attenuated visceral hypersensitivity and pain behavior in a rat model of irritable bowel syndrome (IBS) and functional dyspepsia (FD), indicating the presence of physiologically relevant concentrations of GABA in the colon and stomach. In the IBS model, administration of the drug also resulted in decreased excitability of colon-specific DRG neurons and significantly reduced the colonic afferent response to balloon distention as measured by recordings of neural activity in dorsal ganglia rootlets.

Conclusions: These findings highlight the potential of targeting peripheral GABRAs for pain management in disorders associated with visceral hypersensitivity.