Cannabinoid type 1 receptor antagonism delays ascites formation in rats with cirrhosis.

BACKGROUND & AIMS: Endocannabinoids contribute to hemodynamic abnormalities of cirrhosis. Whether this favors renal sodium retention and ascites formation is unknown. We determined whether cannabinoid type 1 receptor antagonism prevents sodium retention and ascites formation in preascitic cirrhotic rats. METHODS: Once renal sodium handling was impaired, rats with carbon tetrachloride-induced cirrhosis were randomized to receive either vehicle or rimonabant (3 [group 1] or 10 [group 2] mg x kg(-1) x day(-1)) for 2 weeks. Natriuresis, sodium intake, and sodium balance were measured daily. At the end of the protocol, systemic hemodynamics, renal blood flow, ascites volume, and liver fibrosis were assessed. RESULTS: A significant reduction in ascites formation (group 1: 54%; group 2: 10%; vehicle: 90%) and volume (group 1: 1.6 +/- 0.3 mL; group 2: 0.5 mL; vehicle: 5.5 +/- 0.8 mL) occurred in treated rats. Rimonabant significantly improved sodium balance during week 2 (group 1: 0.98 +/- 0.08 mmol; group 2: 0.7 +/- 0.08 mmol; vehicle: 3.05 +/- 0.11 mmol). Both treated groups showed lower cardiac output and higher mean arterial pressure, peripheral vascular resistance, and renal blood flow (P < .05). Liver fibrosis was reduced in group 2 by 30% (P < .05 vs vehicle). Mean arterial pressure inversely correlated with sodium balance (R = -0.61; P = .003), but not with fibrosis score. CONCLUSIONS: Rimonabant improves sodium balance and delays decompensation in preascitic cirrhosis. This is achieved though an improvement in systemic and renal hemodynamics, although it cannot be excluded that the antifibrotic effect of the drug may play a role.

Variable activation of phosphoinositide 3-kinase influences the response of liver grafts to ischemic preconditioning.

BACKGROUND/AIMS: The efficacy of ischemic preconditioning (IPC) in preventing reperfusion injury in human liver transplants is still questioned. Phosphoinositide-3-kinase (PI3K) is essential for IPC development in rodent livers. This work investigates whether PI3K-dependent signals might account for the inconsistent responses to IPC of transplanted human livers. METHODS: Forty livers from deceased donors were randomized to receive or not IPC before recovery. PI3K activation was evaluated in biopsies obtained immediately before IPC and 2 h after reperfusion by measuring the phosphorylation of the PI3K downstream kinase PKB/Akt and the levels of the PI3K antagonist phosphatase tensin-homologue deleted from chromosome 10 (PTEN). RESULTS: IPC increased PKB/Akt phosphorylation (p = 0.01) and decreased PTEN levels (p = 0.03) in grafts, but did not significantly ameliorate post-transplant reperfusion injury. By calculating T(2h)/T(0) PKB/Akt phosphorylation ratios, 10/19 (53%) of the preconditioned grafts had ratios above the control threshold (IPC-responsive), while the remaining nine grafts showed ratios comparable to controls (IPC-non-responsive). T(2h)/T(0) PTEN ratios were also decreased (p < or = 0.03) only in IPC-responsive grafts. The patients receiving IPC-responsive organs had ameliorated (p < or = 0.05) post-transplant aminotransferase and bilirubin levels, while prothrombin activity was unchanged. CONCLUSIONS: Impaired PI3K signaling might account for the variability in the responses to IPC of human grafts from deceased donors.

Insulin-like growth factor and epidermal growth factor treatment: new approaches to protecting steatotic livers against ischemia-reperfusion injury.

Hepatic steatosis is a major risk factor in ischemia-reperfusion (I/R). IGF-binding proteins (IGFBPs) modulate IGF-I action by transporting circulating IGF-I to its sites of action. Epidermal growth factor (EGF) stimulates IGF-I synthesis in vitro. We examined the effect of IGF-I and EGF treatment, separately or in combination, on the vulnerability of steatotic livers to I/R. Our results indicated that I/R impaired IGF-I synthesis only in steatotic livers. Only when a high dose of IGF-I (400 microg/kg) was given to obese animals did they show high circulating IGF-I:IGFBP levels, increased hepatic IGF-I levels, and protection against damage. In lean animals, a dose of 100 microg/kg IGF-I protected nonsteatotic livers. Our results indicated that the combined administration of IGF-I and EGF resulted in hepatic injury parameters in both liver types similar to that obtained by IGF-I and EGF separately. IGF-I increased egf expression in both liver types. The beneficial role of EGF on hepatic I/R injury may be attributable to p38 inhibition in nonsteatotic livers and to PPAR gamma overexpression in steatotic livers. In conclusion, IGF-I and EGF may constitute new pharmacological strategies to reduce the inherent susceptibility of steatotic livers to I/R injury.

Successful treatment of CCl4-induced acute liver failure with portal vein arterialization in the rat.

BACKGROUND: Optimization of the conditions for regeneration is a major goal in the management of patients with acute liver failure (ALF). Previous observations suggested that hyperoxygenation of the liver may improve its regenerative capacity. Thus, this study aimed to determine whether an additional supply of oxygenated blood achieved by portal vein arterialization (PVA) is protective in rat ALF caused by toxin administration or hepatectomy. METHODS: Sprague-Dawley rats were subjected or not to PVA after CCl(4) intoxication or extended hepatectomy. PVA was performed by interposing a stent between the left renal artery and splenic vein after left nephrectomy and splenectomy. Liver injury was evaluated by the serum ALT level and necrotic cell count. Hepatocyte regeneration was assessed by calculating the mitotic index and bromodeoxyuridine (BrdU) staining. The 10-day survival was assessed in separate experimental groups. RESULTS: The pO(2) in portal blood increased significantly following PVA. In the CCl(4)-induced ALF, serum ALT levels and necrosis were significantly reduced in arterialized than non-arterialized rats. PVA greatly promotes liver regeneration in both models. Finally, PVA significantly improved survival compared to controls (CCl(4): 100 versus 40%; 90% hepatectomy: 90 versus 30%). Interestingly, in the CCl(4)-induced ALF, survival was 100% even when the shunt was closed after 48 h. CONCLUSION: These data indicate that the additional supply of arterial oxygenated blood through PVA promotes a rapid regeneration leading to the resolution of toxic-induced massive liver necrosis and a faster restoration of liver mass after partial hepatectomy in rats. Thus, PVA may represent a novel tool for optimizing hepatocyte regeneration.

A novel sodium overload test predicting ascites decompensation in rats with CCl4-induced cirrhosis.

BACKGROUND/AIMS: We aimed to develop a non-invasive test to identify the initial alterations of sodium homeostasis and prospectively predict decompensation in preascitic cirrhotic rats. METHODS: The sodium overload test (SOT) was performed in control (CT) and CCl4-induced cirrhotic rats (CH) by calculating the percentage of sodium excreted in the urine after NaCl oral administration (0.5 g/kg). Liver fibrosis was quantified by image cytometry. RESULTS: From the 8th week of CCl4 intoxication, while the daily sodium balance did not change in CH and CT, SOT became significantly lower in the former (62.1+/-13.2 vs 78.8+/-13.2%; P=0.035). At sacrifice, ascites was only present in one animal. The degree of liver fibrosis correlated with SOT. In subsequent experiments, 17 cirrhotic rats developed ascites between the 9th and 14th weeks. SOT remained stable up to 3 weeks before ascites appearance, while it fell significantly to 35+/-19 and 26+/-21% at 2 and 1 week before ascites diagnosis, respectively. Nearly all the rats (95%) with a SOT<60% developed ascites within 3 weeks. CONCLUSIONS: In preascitic cirrhotic rats, SOT unveils sodium metabolism abnormalities earlier than the daily sodium balance and prospectively predicts ascites appearance, identifying rats in a homogeneous stage of cirrhosis, which is essential in pathophysiological studies on sodium retention.

The nutritional status modulates preservation-reperfusion injury in rat fatty liver.

BACKGROUND: Microcirculation disturbances are essential factors of preservation injury in fatty liver. However, hepatocyte injury is also markedly excessive in fatty liver resulting, at least in part, from energy metabolism impairment and oxidative stress. Thus, this study aimed to determine whether nutritional status influences preservation injury in fatty liver and whether energetic substrate supplementation, alone or with a vasodilator, is protective. MATERIALS AND METHODS: Normal or fatty livers induced by a choline-deficient diet were isolated from fed and fasted rats, preserved in University of Wisconsin solution at 4 degrees C for 18 h, and then reperfused with Krebs-Henseleit solution at 37 degrees C for 120 min. Fasted rats with fatty liver were also treated as follows: (1) Glucose supplementation: rats had access to a glucose solution for 18 h prior procurement; (2) Prostaglandin (PG): alprostadil was continuously infused during reperfusion; (3) Combined treatment: Glucose supplementation + PG. RESULTS: Fasting-induced liver injury was significantly greater in fatty than normal liver. In fatty livers from fasted rats, all treatments reduced the alanine aminotransaminase release. Hepatic oxygen consumption improved in the glucose and glucose + PG groups, while PG infusion had no effect. Glucose supplementation did not affect portal pressure, which, in contrast, was reduced in livers receiving PG. Finally, all treatments lowered oxidative injury. CONCLUSIONS: Preservation injury in fatty liver is greatly related to nutritional status. Energetic substrate supplementation may represent a clinically feasible protective strategy and a multistep approach adding vasodilators could offer further benefit by acting on different pathogenetic mechanisms.

Impairment of mitochondrial oxidative phosphorylation in rat fatty liver exposed to preservation-reperfusion injury.

BACKGROUND/AIMS: As the impairment of the cellular energy metabolism contributes to the failure of fatty liver grafts after transplantation, we aimed to determine whether steatosis affects the oxidative phosphorylation activity during preservation. METHODS: Rat normal and fatty livers were preserved for 18 h and then reperfused with warm oxygenated solution. The oxidative phosphorylation, the F(0)F(1)-ATPase and the Complex I activities were assessed in isolated mitochondria before and after preservation, and during reperfusion. The ALT release and portal pressure were monitored during reperfusion. RESULTS: The baseline phosphorylation activity was similar in normal and steatotic mitochondria. After cold preservation, the respiratory control index and state 3 respiration decreased significantly only in steatotic livers. Reperfusion induced a further deterioration in either group. Contrary to normal liver, uncoupling of fatty liver mitochondria allowed the recovery of the maximal respiration rate only using succinate (Complex II-dependent substrate), but not glutamate-malate (Complex I-dependent). Complex I dysfunction was confirmed spectrophotometrically. The ATPase activity was also significantly lower in fatty livers. Finally, ALT release and portal pressure were greater in steatotic livers. CONCLUSIONS: The alteration of the oxidative phosphorylation activity during preservation is greatly exacerbated by fatty infiltration likely resulting from damage of the respiratory chain Complex I and of the F(0)F(1)-ATP synthase.