HPS (hepatopulmonary syndrome) is characterized by oxygen desaturation in patients with chronic liver disease. The initiation of HPS comes from abnormal pulmonary vasodilatation and/or angiogenesis. In the present study, we evaluated anti-angiogenesis therapy using sorafenib in experimental HPS animals. HPS was induced by CBDL (common bile duct ligation) in rats. A 2-week 10 mg·(kg of body weight)−1·day−1 treatment regimen of sorafenib or distilled water (control) was initiated 2 weeks after the surgical procedure. Haemodynamics, liver biochemistry, plasma VEGF (vascular endothelial growth factor) measurements and blood gas analysis of the CBDL rats were performed. The livers of the CBDL rats were dissected for histopathology examination, and the lungs were examined by immunohistochemical staining, real-time PCR and Western blot analysis. In another two parallel groups, intrapulmonary shunts were determined. The AaPO2 (alveolar–arterial O2 gradient) and plasma VEGF levels were reduced after sorafenib treatment [AaPO2, 7.2±3.4 mmHg in sorafenib-treated rats compared with 15.3±4.2 mmHg in controls (P=0.004); VEGF, 45.3±2.7 pg/ml in sorafenib-treated rats compared with 54.4±7.7 pg/ml in controls (P=0.021)]. Sorafenib attenuated pulmonary VEGF mRNA and VEGF, VEGFR-2 (VEGF receptor 2), phospho-VEGFR-2 and Akt protein expression. In addition, sorafenib significantly attenuated intrapulmonary angiogenesis and decreased the degree of intrapulmonary shunting by 33.7% (11.2±5.7% in sorafenib-treated rats compared with 16.9±5.9% in controls; P=0.003). Our findings suggest that sorafenib attenuates intrapulmonary shunting and decreases the AaPO2 in CBDL rats, implicating the improvement of HPS in this experimental animal model. The beneficial effect may be attributed to the reduction in intrapulmonary angiogenesis through inhibition of the VEGF/VEGFR-2/Akt pathway.

This study investigated the effect of vasopressin on portal-systemic collaterals in portal hypertensive rats and the influence of nitric oxide (NO) and prostaglandin on the responsiveness of collateral vessels to vasopressin. The vascular responsiveness to graded concentrations of vasopressin was tested with or without the incubation of n^ω-nitro-l-arginine (NNA) (100 μmol/L) and/or indomethacin (10 μmol/L) in perfused collateral vascular beds of rats with portal hypertension induced by partial portal vein ligation. In addition, concentration-response curves to vasopressin with incubation of a vasopressin V₁ receptor antagonist d(CH₂ )₅ Tyr(Me) arginine vasopressin and concentration-response curves to a V₂ receptor agonist 1-desamino-8-d-arginine vasopressin were performed. Vasopressin significantly increased the perfusion pressure of collaterals, and this effect was suppressed by the addition of the V₁ receptor antagonist. Perfusion with the V₂ receptor agonist had no effect on the collaterals. Incubation with NNA, indomethacin, or both significantly potentiated the response of collaterals to vasopressin. In addition, the pressor response to vasopressin in the combination group was significantly higher than that in the NNA-alone group. The results show that vasopressin produces a direct vasoconstrictive effect on the portal-systemic collaterals of portal hypertensive rats. This effect is mediated by the vasopressin V_1, but not V₂, receptors. The attenuation of the response to vasopressin by NO and prostaglandin suggest a function role of both mediators in the regulation of the portal-systemic collateral circulation in portal hypertensive rats.

Angiogenesis in liver cirrhosis leads to splanchnic hyperemia, increased portal inflow, and portosystemic collaterals formation, which may induce lethal complications, such as gastroesophageal variceal hemorrhage and hepatic encephalopathy. Cannabinoids (CBs) inhibit angiogenesis, but the relevant influences in cirrhosis are unknown. In this study, Spraque-Dawley rats received common bile duct ligation (BDL) to induce cirrhosis. BDL rats received vehicle, arachidonyl-2-chloroethylamide (cannabinoid receptor type 1 [CB₁] agonist), JWH-015 (cannabinoid receptor type 2 [CB₂] agonist), and AM630 (CB₂ antagonist) from days 35 to 42 days after BDL. On the 43rd day, hemodynamics, presence of CB receptors, severity of portosystemic shunting, mesenteric vascular density, vascular endothelial growth factor (VEGF), VEGFR-1, VEGFR-2, phospho-VEGFR-2, cyclooxygenase (COX)-1, COX-2, and endothelial nitric oxide synthase (eNOS) expressions as well as plasma VEGF levels were evaluated. Results showed that CB₁ and CB₂ receptors were present in left adrenal veins of sham rats, splenorenal shunts (the most prominent intra-abdominal shunts) of BDL rats, and mesentery of sham and BDL rats. CB₂ receptor was up-regulated in splenorenal shunts of BDL rats. Both acute and chronic JWH-015 treatment reduced portal pressure and superior mesenteric arterial blood flow. Compared with vehicle, JWH-015 significantly alleviated portosystemic shunting and mesenteric vascular density in BDL rats, but not in sham rats. The concomitant use of JWH-015 and AM630 abolished JWH-015 effects. JWH-133, another CB₂ agonist, mimicked the JWH-015 effects. JWH-015 decreased mesenteric COX-1, COX-2 messenger RNA expressions, and COX-1, COX-2, eNOS protein expressions. Furthermore, JWH-015 decreased intrahepatic angiogenesis and fibrosis. Conclusions: CB₂ agonist alleviates portal hypertension (PH), severity of portosystemic collaterals and mesenteric angiogenesis, intrahepatic angiogenesis, and fibrosis in cirrhotic rats. The mechanism is, at least partly, through COX and NOS down-regulation. CBs may be targeted in the control of PH and portosystemic collaterals. (HEPATOLOGY 2012;56:248–258)

Portal hypertension is associated with increased hepatic and collateral resistance to an increased portal blood flow. Endothelin–1 (ET–1) can induce intrahepatic vasoconstriction and consequently increase portal pressure. It is unknown if ET–1 also modulates portal pressure by a direct vasoconstrictive effect on collaterals. This study investigated the collateral vascular responses to ET–1, the receptors in mediation, and the regulation of ET–1 action by nitric oxide and prostaglandin. The portal–systemic collaterals of partially portal vein—ligated rats were tested by in situ perfusion. The concentration–response curves of collaterals to graded concentrations of ET–1 (10^-10–10^-7 mol/L) with or without BQ–123 (ET_A receptor antagonist, 2 × 10^-6 mol/L), BQ–788 (ET_B receptor antagonist, 10^-7 mol/L) or both were recorded. In addition, the collateral responses to ET–1 with preincubation of n^ω–nitro–L–arginine (NNA; 100 mol/L), indomethacin (INDO; 10 mol/L), or in combination were performed. ET–1 increased the perfusion pressure of collaterals and its effect was significantly suppressed by BQ–123 alone and BQ–123 plus BQ–788, but not BQ–788 alone (P < .05). Incubation with NNA, INDO, or both significantly enhanced the response of collaterals to ET–1 (P < .05). These results show that ET–1 produces a direct vasoconstrictive effect on the collateral vessels of portal hypertensive rats. This effect is mediated by ET_A, but not ET_B, receptors. Both nitric oxide and prostaglandin modulate the collateral vascular response to ET–1 and may therefore participate in the development and maintenance of portal hypertension.