[Experimental models for assessment of pulmonary alterations in hepatopulmonary syndrome]

Melatonin effects on pulmonary tissue in the experimental model of Hepatopulmonary Syndrome

Objective:

To evaluate the pulmonary alterations of animals with Hepatopulmonary Syndrome (HPS) submitted to Biliary Duct Ligature (BDL), as well as the antioxidant effect of Melatonin (MEL).

Methods:

Sixteen male Wistar rats, divided into four Sham groups: BDL group, Sham + MEL group and BDL + MEL. The pulmonary and hepatic histology, lipoperoxidation and antioxidant activity of lung tissue, alveolar-arterial O2 difference and lung / body weight ratio (%) were evaluated.

Results:

When comparing the groups, could be observed an increase of vasodilation and pulmonary fibrosis in the BDL group and the reduction of this in relation to the BDL + MEL group. It was also observed significant changes in the activity of catalase, ApCO2, ApO₂ in the LBD group when compared to the other groups.

Conclusion:

The use of MEL has been shown to be effective in reducing vasodilation, fibrosis levels and oxidative stress as well as gas exchange in an experimental HPS model.

Hepatopulmonary Syndrome: Oxidative Stress and Physical Exercise

Hepatopulmonary syndrome (HPS) may be defined by hepatic disease, gas exchange abnormalities that may lead to hypoxaemia, and the presence of pulmonary vascular dilations. The balance between the many substances involved in vasodilation and vasoconstriction is regulated by the liver; thus, liver damage may generate systemic changes throughout the body. The pulmonary tissue may be damaged by reactive oxygen species or nitric oxide. Dyspnoea is the most frequent pulmonary symptom, caused by tissue damage, and may become worse when an individual exercises. In experimental research the surgical model of bile duct ligation is the optimal model to simulate the typical lung alterations present in HPS, which results in an increase in oxidative stress in hepatic and pulmonary tissues. In liver injury, the muscular system may also be damaged, for example sarcopenia may seriously aggravate cirrhosis and is associated with cirrhotic patient mortality. Muscular changes can be explained by the actions of myostatin and insulin-like growth factor and the increase in body levels of ammonia. As a result of impaired cardiopulmonary and muscular conditions, HPS patients may exhibit a low exercise tolerance, low muscle strength, and low functionality. Liver disease can contribute to HPS oxidative stress and is one of the main factors responsible for the reduction of gas exchange. Physical exercise can be performed as a way of modifying this pathophysiological state. Studies that have investigated physical exercise as a therapy for cirrhosis suggest that this approach may be beneficial for cirrhotic patients, primarily with regard to muscular and cardiorespiratory injuries.

A comparison of two common bile duct ligation methods to establish hepatopulmonary syndrome animal models

The major drawback of the current common bile duct ligation (CBDL)-induced hepatopulmonary syndrome (HPS) animal model is the extremely high mortality rate that hinders experimental studies. The purpose of this study was to investigate an improved method of CBDL with the goal of developing a simple and reproducible rat HPS model after a single CBDL treatment. Two groups of male Sprague–Dawley rats underwent separate methods of CBDL: (1) the upper common bile duct ligation (UCBDL) group ( n = 40), in which the first ligature was made near the junction of the hepatic ducts, and the second ligature was made above the entrance of the pancreatic duct; (2) the middle of the common bile duct ligation (MCBDL) group ( n = 40), in which the first ligature was made in the middle of the common bile duct, and the second ligature was made above the entrance of the pancreatic duct. The CBDL-induced HPS rats were evaluated by pulse oximeter, arterial blood analysis, histopathology, and cerebral uptake of intravenous technetium-99m-labeled albumin macroaggregates (which reflects intrapulmonary vascular dilation). The mortality rates of the UCBDL group and the MCBDL group were 42.5% and 77.5%, respectively ( P < 0.05). These results suggest that the UCBDL, a single improved procedure, provides a better method compared to the established HPS model, because of the relatively high success rate and the decreased risk of complications.

Oxidative stress and pulmonary changes in experimental liver cirrhosis

The use of carbon tetrachloride (CCl₄) in rats is an experimental model of hepatic tissue damage; which leads to fibrosis, and at the long term, cirrhosis. Cirrhosis is the consequence of progressive continued liver damage, it may be reversible when the damaging noxae have been withdrawn. The aim of this study is to evaluate the changes caused by cirrhosis in lung and liver, through the experimental model of intraperitoneal CCI₄ administration. We used 18 male Wistar rats divided into three groups: control (CO) and two groups divided by the time of cirrhosis induction by CCI₄: G1 (11 weeks), G2 (16 weeks). We found significant increase of transaminase levels and lipid peroxidation (TBARS) in liver and lung tissue and also increased antioxidant enzymes SOD and CAT, as well as the expression of TNF-α and IL-1β in the lung of cirrhotic animals. We observed changes in gas exchange in both cirrhotic groups. We can conclude that our model reproduces a model of liver cirrhosis, which causes alterations in the pulmonary system that leads to changes in gas exchange and size of pulmonary vessels.