P. Cejudo-Martin

Increased anandamide induced relaxation in mesenteric arteries of cirrhotic rats: role of cannabinoid and vanilloid receptors

Background and aims: Anandamide is an endocannabinoid that evokes hypotension by interaction with peripheral cannabinoid CB1 receptors and with the perivascular transient receptor potential vanilloid type 1 protein (TRPV1). As anandamide has been implicated in the vasodilated state in advanced cirrhosis, the study investigated whether the mesenteric bed from cirrhotic rats has an altered and selective vasodilator response to anandamide. Methods: We assessed vascular sensitivity to anandamide, mRNA and protein expression of cannabinoid CB1 receptor and TRPV1 receptor, and the topographical distribution of cannabinoid CB1 receptors in resistance mesenteric arteries of cirrhotic and control rats. Results: Mesenteric vessels of cirrhotic animals displayed greater sensitivity to anandamide than control vessels. This vasodilator response was reverted by CB1 or TRPV1 receptor blockade, but not after endothelium denudation or nitric oxide inhibition. Anandamide had no effect on distal femoral arteries. CB1 and TRPV1 receptor protein was higher in cirrhotic than in control vessels. Neither CB1 mRNA nor protein was detected in femoral arteries. Immunochemistry showed that CB1 receptors were mainly in the adventitia and in the endothelial monolayer, with higher expression observed in vessels of cirrhotic rats than in controls. Conclusions: These results indicate that anandamide is a selective splanchnic vasodilator in cirrhosis which predominantly acts via interaction with two different types of receptors, CB1 and TRPV1 receptors, which are mainly located in perivascular sensory nerve terminals of the mesenteric resistance arteries of these animals.

Nitric oxide synthase 3-dependent vascular remodeling and circulatory dysfunction in cirrhosis

Vascular remodeling is an active process that consists in important modifications in the vessel wall. Endothelium-derived nitric oxide (NO) plays a major role in this phenomenon. We assessed wall thickness (WT), total wall area (TWA), lumen diameter, and total nuclei number/cross-section (TN) in cirrhotic rats with ascites and in control rats. A second group of cirrhotic rats received the NO synthesis inhibitor, L-NAME, or vehicle daily for 11 weeks and systemic hemodynamics, arterial compliance, aortic NO synthase 3 (NOS3) protein expression, and vascular morphology were analyzed. Cirrhotic vessels showed a significant reduction in WT, TWA, and TN as compared to control vessels. Long-term inhibition of NOS activity in cirrhotic rats resulted in a significant increase in WT, TWA, and TN as compared to cirrhotic rats receiving vehicle. NOS3 protein abundance was higher in aortic vessels of nontreated cirrhotic animals than in controls. This difference was abolished by chronic treatment with L-NAME. NOS inhibition in cirrhotic rats resulted in higher arterial pressure and peripheral resistance and lower arterial compliance than cirrhotic rats receiving vehicle. Therefore, vascular remodeling in cirrhosis with ascites is a generalized process with significant functional consequences that can be negatively modulated by long-term inhibition of NOS activity.

Effect of the V1a/V2-AVP receptor antagonist, Conivaptan, on renal water metabolism and systemic hemodynamics in rats with cirrhosis and ascites

BACKGROUND Selective V(2)-AVP receptor antagonists are effective in inducing aquaresis in humans and rats with cirrhosis, hyponatremia and water retention. However, it is unknown whether dual V(1a)/V(2)-AVP antagonists are also efficacious as aquaretic agents under these conditions. This is important, particularly considering that blockade of V(1a)-AVP receptors could aggravate cardiocirculatory function in decompensated cirrhosis. AIMS To evaluate the renal, hormonal and hemodynamic effects induced by the chronic oral administration of the V(1a)/V(2)-AVP antagonist, Conivaptan, in rats with CCl(4)-induced cirrhosis, ascites and severe water retention. METHODS We assessed the aquaretic efficacy of 10-day chronic oral administration of Conivaptan (0.5mg/kg body weight (bw)) in cirrhotic rats with hyponatremia and water retention. Urine volume (UV), osmolality (UOsm), and sodium excretion (U(Na)V) were measured daily. At the end of the study arterial pressure was also measured. RESULTS Conivaptan produced an acute increase in UV, a reduction in UOsm and, at the end of the investigation, cirrhotic rats receiving the V(1a)/V(2)-AVP receptor antagonist did not show hyponatremia or hypoosmolality. Conivaptan also normalized U(Na)V without affecting creatinine clearance and arterial pressure. CONCLUSIONS Dual V(1a)/V(2)-receptor antagonists may be therapeutically useful for the treatment of water retention and dilutional hyponatremia in human cirrhosis.

Gene transduction of an active mutant of akt exerts cytoprotection and reduces graft injury after liver transplantation.

Akt is expected to be an effective target for the treatment of ischemia‐reperfusion injury (I/R) due to its anti‐apoptotic properties and its ability to activate the endothelial nitric oxide synthase (eNOS) enzyme. Therefore, this study was aimed to determine the efficacy of an active mutant of Akt (myr‐Akt) to decrease I/R injury in a model of orthotopic liver transplantation in pigs. In addition, we analyzed the contribution of nitric oxide in the Akt‐mediated effects by using an eNOS mutant (S1179DeNOS) that mimics the phosphorylation promoted by Akt in the eNOS sequence. Donors were treated with adenoviruses codifying for myr‐Akt, S1179DeNOS or β‐galactosidase 24 h before liver harvesting. Then, liver grafts were orthotopically transplanted into their corresponding recipients. Levels of transaminases and lactate dehydrogenase (LDH) increased in all recipients after 24 h of transplant. However, transaminases and LDH levels were significantly lower in the myr‐Akt group compared with vehicle. The percentage of apoptotic cells and the amount of activated‐caspase 3 protein were also markedly reduced in myr‐Akt‐treated grafts after 4 days of liver transplant compared with vehicle and S1179DeNOS groups. In conclusion, myr‐Akt gene therapy effectively exerts cytoprotection against hepatic I/R injury regardless of the Akt‐dependent eNOS activation.