Inhibition of soluble epoxide hydrolase reduces portal pressure by protecting mesenteric artery myogenic responses in cirrhotic rats

Transcriptome analysis of mesenteric arterioles changes and its mechanisms in cirrhotic rats with portal hypertension

Portal hypertension (PHT) is a major cause of liver cirrhosis. The formation of portosystemic collateral vessels and splanchnic vasodilation contribute to the development of hyperdynamic circulation, which in turn aggravates PHT and increases the risk of complications. To investigate the changes in mesenteric arterioles in PHT, cirrhotic rat models were established by ligating the common bile ducts. After 4 weeks, the cirrhotic rats suffered from severe PHT and splanchnic hyperdynamic circulation, characterized by increased portal pressure (PP), cardiac output (CO), cardiac index (CI), and superior mesenteric artery (SMA) flow. Mesenteric arterioles in cirrhotic rats displayed remarkable vasodilation, vascular remodeling, and hypocontractility. RNA sequencing was performed based on these findings. A total of 1,637 differentially expressed genes (DEGs) were detected, with 889 up-regulated and 748 down-regulated genes. Signaling pathways related to vascular changes were enriched, including the vascular endothelial growth factor (VEGF), phosphatidylinositol-3-kinase-AKT (PI3K-AKT), and nuclear factor kappa light chain enhancer of activated B cells (NF-κB) signaling pathway, among others. Moreover, the top ten hub genes were screened according to the degree nodes in the protein-protein interaction (PPI) network. Functional enrichment analyses indicated that the hub genes were involved in cell cycle regulation, mitosis, and cellular response to oxidative stress and nitric oxide (NO). In addition, promising candidate drugs for ameliorating PHT, such as resveratrol, were predicted based on hub genes. Taken together, our study highlighted remarkable changes in the mesenteric arterioles of cirrhotic rats with PHT. Transcriptome analyses revealed the potential molecular mechanisms of vascular changes in splanchnic hyperdynamic circulation.

DPP4 inhibitor reduces portal hypertension in cirrhotic rats by normalizing arterial hypocontractility

AIMS

Dipeptidyl peptidase-4 inhibitor (DPP4i), a new antidiabetic agent, is reported to affect the progression of chronic liver diseases. The study aims to investigate the effects of DPP4i on contractile response, splanchnic hemodynamics, and portal pressure in cirrhotic rats.

MATERIALS AND METHODS

A rat model of carbon tetrachloride-induced cirrhosis was used in this study. Sixteen rats with cirrhosis were treated with DDP4i sitagliptin for 5 consecutive days. Portal and systemic pressures and portal blood flow were measured. Mesenteric arterioles were isolated, and concentration-response curves to norepinephrine (NE) were evaluated. The expression of NADPH oxidase (Nox)1, Nox2, Nox4, and soluble epoxide hydrolase (sEH) were detected. Reactive oxygen species (ROS) and epoxyeicosatrienoic acid (EET) levels in mesenteric arteries were also measured.

KEY FINDINGS

In cirrhotic rats, sitagliptin significantly reduced portal blood flow and portal pressure without effects on systemic pressure and reversed the decreased response of mesenteric arterioles to NE in an endothelium-dependent manner. Sitagliptin suppressed the increased Nox4 expression and ROS production. In vitro studies showed that Nox4 inhibitor enhanced arteriolar response to NE and reduced hydrogen peroxide (H2O2) level in cirrhotic rats. Sitagliptin also reduced EET levels and increased sEH expression of mesenteric vessels. Pre-incubation with sEH inhibitor in vitro reversed sitagliptin-induced augmentation of response to NE in cirrhotic rats.

SIGNIFICANCE

DPP4 inhibition by sitagliptin in vivo has beneficial effects on portal hypertension in cirrhotic rats through normalizing arterial hypocontractility. DDP4 inhibitor may be a novel strategy in the treatment of patients with cirrhosis and portal hypertension.

Advances in therapeutic options for portal hypertension

Portal hypertension represents one of the major clinical consequences of chronic liver disease, having a deep impact on patients' prognosis and survival. Its pathophysiology defines a pathological increase in the intrahepatic vascular resistance as the primary factor in its development, being subsequently aggravated by a paradoxical increase in portal blood inflow. Although extensive preclinical and clinical research in the field has been developed in recent decades, no effective treatment targeting its primary mechanism has been defined. The present review critically summarizes the current knowledge in portal hypertension therapeutics, focusing on those strategies driven by the disease pathophysiology and underlying cellular mechanisms.

Soluble epoxide hydrolase inhibition with t-TUCB alleviates liver fibrosis and portal pressure in carbon tetrachloride-induced cirrhosis in rats

BACKGROUND/AIMS

Fibrosis and increased intrahepatic vascular resistance are the hallmarks of chronic inflammatory disorders of the liver and cirrhosis. Inhibitors of the enzyme soluble epoxide hydrolase reduce fibrosis in several disease models. The present study aimed at investigating the effects of soluble epoxyhydrolase inhibition with t-TUCB in tetrachloride-induced cirrhosis in rats.

METHODS

The models were established by CCl₄ (2ml/kg) given subcutaneously for 14 weeks. t-TUCB was concomitantly administered from the tenth week of modelling time. After the models were successfully built, the rats were anesthetized with sodium phenobarbital and portal pressure was determined in the groups. After that, the rats were killed and part of liver tissues were taken for histological analysis. In addition, the levels of intrahepatic inflammatory message factors were measured using real-time polymerase chain reaction (PCR) analysis. The remaining liver samples were processed for assessment of oxidative stress.

RESULTS

t-TUCB administration significantly attenuated portal pressure relative to CCl₄-only rats. This improvement was associated with decreased deposition of collagen in liver, which was supported by reduced mRNA expression of α-smooth muscle actin (α-SMA), Collagen I, Collagen III, transforming growth factor (TGF)-β and tissue inhibitor of metalloproteinase-1 (TIMP-1) and increased matrix metalloproteinase-1, -13 (MMP-1, -13) mRNA expression. In addition, t-TUCB decreased the levels of proinflammatory cytokines, including IL-1β, IL-6, IL-10, tumor necrosis factor-α (TNF-α) and NF-κB, within cirrhotic hepatic tissue. Meanwhile, oxidative stress was also alleviated following inhibition of sEH in CCl₄-induced models, as evidenced by down-regulated levels of malondialdehyde (MDA) and up-regulated levels of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px).

CONCLUSION

The soluble epoxyhydrolase inhibitor, t-TUCB alleviates liver fibrosis and portal hypertension through attenuation of inflammatory response and oxidative stress in tetrachloride induced cirrhosis.