Dual Angiotensin Receptor and Neprilysin Inhibitor Ameliorates Portal Hypertension in Portal Hypertensive Rats

Abstract

Background: Portal hypertension is characterized by exaggerated activation of the renin-angiotensin-aldosterone axis. Natriuretic peptide system plays a counter-regulatory role, which is modulated by neprilysin. LCZ696 (sacubitril/valsartan) is a dual angiotensin receptor and neprilysin inhibitor. This study evaluated the effect of LCZ696 on portal hypertensive rats.

Methods: Portal hypertension was induced by partial portal vein ligation (PVL) in rats. LCZ696, valsartan (angiotensin receptor blocker), or normal saline (control) was administered in PVL rats for 10 days. Then, hemodynamic and biochemistry data were obtained. The hepatic histology and protein expressions were surveyed. On the parallel groups, the portal-systemic shunting degrees were determined.

Results: LCZ696 and valsartan reduced mean arterial pressure and systemic vascular resistance. LCZ696, but not valsartan, reduced portal pressure in portal hypertensive rats (control vs. valsartan vs. LCZ696: 15.4 ± 1.6 vs. 14.0 ± 2.3 vs. 12.0 ± 2.0 mmHg, control vs. LCZ696: P < 0.05). LCZ696 and valsartan improved liver biochemistry data and reduced intrahepatic Cluster of Differentiation 68 (CD68)-stained macrophages infiltration. Hepatic endothelin-1 (ET-1) protein expression was downregulated by LCZ696. The portal-systemic shunting was not affected by LCZ696 and valsartan.

Conclusion: LCZ696 and valsartan reduced mean arterial pressure through peripheral vasodilation. Furthermore, LCZ696 significantly reduced portal pressure in PVL rats via hepatic ET-1 downregulation.

Keywords: angiotensin receptor neprilysin inhibitor; natriuretic peptide; portal hypertension; renin-angiotensin-aldosterone system.

Figure 1

Biochemical data of partial portal vein ligation (PVL) rats treated by vehicle (control), valsartan, or LCZ696 (sacubitril/valsartan). Valsartan and LCZ696 significantly decreased the plasma levels of alanine aminotransferase (ALT) (both P < 0.05). In addition, valsartan decreased the plasma level of aspartate aminotransferase (AST) (P < 0.05). The total bilirubin and creatinine levels were not significantly affected by valsartan and LCZ696.

Figure 2

Liver histology and immunochemical staining of PVL rats treated by vehicle (control), valsartan, or LCZ696. The representative hematoxylin and eosin staining images show similar architecture of liver tissue among these 3 groups (magnification 200×, upper panel). Many Cluster of Differentiation 68 (CD68)-positive staining cells (the representative brown cell with irregular shape as indicated by green arrow) were noted in the control group. In contrast, they were nearly absent in those treated by valsartan and LCZ696 (magnification 200×, lower panel).

Figure 3

Portal-systemic shunting degree of PVL rats treated with vehicle, valsartan, or LCZ696. Valsartan and LCZ696 did not significantly affect the shunting degree (P > 0.05).

Figure 4

Hepatic protein expressions of control, valsartan-, LCZ696-treated PVL rats. The densitometric quantification and representative Western blot images are shown. The upper panel reveals that the endothelial-1 (ET-1) protein expression was significantly downregulated by LCZ696 compared to the control group. The vascular endothelial growth factor (VEGF), cyclooxygenase (COX)-1, and COX-2 protein expressions were not significantly different among control, valsartan-, and LCZ696-treated PVL rats. The lower panel indicates that the phosphorylated-endothelial nitric oxide synthase (eNOS) protein expressions were downregulated by valsartan and LCZ696 treatments. The phosphorylated-nuclear factor kappa B (NFκB) p65, phosphorylated-antinuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor alpha (IκBα), and phosphorylated-inducible nitric oxide synthase (iNOS) protein expressions were not affected by valsartan and LCZ696.