Prevention of hepatopulmonary syndrome and hyperdynamic state by pentoxifylline in cirrhotic rats

Inhibition of tumour necrosis factor-alpha (TNF-alpha), levels of which are increased in the blood of cirrhotic rats, prevents hyperdynamic circulatory state, mainly by decreasing the vascular overproduction of nitric oxide. Hepatopulmonary syndrome, which is characterised by intrapulmonary vascular dilatation and increased alveolar to arterial oxygen tension difference (PA-a,O-2), is mainly related to pulmonary overproduction of NO by macrophages accumulated in lung vessels. Since TNF-alpha is a potent activator of macrophagic inducible nitric oxide synthase (NOS), the aim of this study was to investigate whether TNF-alpha inhibition prevented hepatopulmonary syndrome and hyperdynamic circulatory state in rats with cirrhosis. TNF-alpha was inhibited by 5 weeks of pentoxifylline (10 mg(.)kg body weight(-1.)day(-1)) in rats with cirrhosis induced by common bile duct ligation. Cardiac output, pulmonary and systemic vascular resistance, PA-a,O-2 and cerebral uptake of intravenous technetium-99m-labelled albumin macroaggregates (which reflects intrapulmonary vascular dilatation) were similar in sham- and pentoxifylline-treated cirrhotic rats. Blood TNF-alpha concentrations and pulmonary intravascular macrophage sequestration, as assessed by morphometric analysis and radioactive colloid uptake, were decreased with pentoxifylline. Pentoxifylline also prevented increases in aorta and lung NOS activities and inducible NOS expression. Thus pentoxifylline prevents development of hyperdynamic circulatory state and hepatopulmonary syndrome, probably by inhibiting the effects of tumour necrosis factor-alpha on vascular nitric oxide synthase and intravascular macrophages. These results support an important role for tumour necrosis factor-alpha in the genesis of hepatopulmonary syndrome.