Losartan attenuates bleomycin induced lung fibrosis by increasing prostaglandin E2 synthesis.

BACKGROUND: The angiotensin system has a role in the pathogenesis of pulmonary fibrosis. This study examines the antifibrotic effect of losartan, an angiotensin II type 1 receptor antagonist, in bleomycin induced lung fibrosis and its possible implication in the regulation of prostaglandin E(2) (PGE(2)) synthesis and cyclooxygenase-2 (COX-2) expression. METHODS: Rats were given a single intratracheal instillation of bleomycin (2.5 U/kg). Losartan (50 mg/kg/day) was administrated orally starting one day before induction of lung fibrosis and continuing to the conclusion of each experiment. RESULTS: Losartan reduced the inflammation induced by bleomycin, as indicated by lower myeloperoxidase activity and protein content in the bronchoalveolar lavage fluid. Collagen deposition induced by bleomycin was inhibited by losartan, as shown by a reduction in the hydroxyproline content and the amelioration of morphological changes. PGE(2) levels were lower in fibrotic lungs than in normal lungs. Losartan significantly increased PGE(2) levels at both 3 and 15 days. A reduction in COX-2 expression by bleomycin was seen at 3 days which was relieved by losartan. CONCLUSIONS: The antifibrotic effect of losartan appears to be mediated by its ability to stimulate the production of PGE(2). Losartan, which is already widely used clinically, could be assessed as a new treatment in lung fibrosis.

Induction of c-fos messenger RNA by 3-(N-phenylamino)-1,2-propanediol esters, compounds related to Toxic Oil Syndrome.

The Toxic Oil Syndrome (TOS) was a toxic epidemic disease, related to the consumption of rapeseed oil denatured with aniline that affected more than 20,000 people in Spain and resulted in more than 330 deaths after its sudden appearance in 1981. It has been reported that the fatty acid esters of 3-(N-phenylamino)-1,2-propanediol (PAP) have shown a strong association with TOS. These PAP-esters could be absorbed and metabolized in a similar way than phospholipids. This is of interest because some products of phospholipid metabolism are important mediators in downstream pathways involved in the regulation of different nuclear factors. In particular, phospholipase D activity is involved in the activation of c-fos. Thus, we have investigated the effect of different PAP-esters in the induction of c-fos in lung fibroblasts. Results indicate that PAP-esters rapidly induced the expression of c-fos in a dose-dependent manner. In addition, both butanol and propranolol prevent this induction pointing to the involvement of phospholipase D in this activation. These results suggest that deregulation of some nuclear factors such as AP-1 could be involved in the pathogenesis of TOS.

Ischemic preconditioning: tolerance to hepatic ischemia-reperfusion injury.

Hepatic ischemia-reperfusion (I/R) injury still remains an unresolved problem in both liver resectional surgery and liver transplantation and may be responsible for liver failure, lung injury and death. The current review summarizes the findings reported to date on the effectiveness of ischemic preconditioning against liver and lung damage associated with hepatic I/R injury and the underlying protective mechanisms. The effect of ischemic preconditioning on the mechanisms potentially involved in hepatic I/R injury, including alterations in energy metabolism, neutrophil accumulation, microcirculatory disturbances, formation of proinflammatory mediators, such as endothelin and tumor necrosis factor-alpha, and reactive oxygen species generation have been evaluated. In this review, we address the role of preconditioning in the increased vulnerability of fatty livers to hepatic I/R injury. The effectiveness of ischemic preconditioning versus pharmacological strategies that could simulate the benefits of liver preconditioning has been also discussed.

Liver ischemic preconditioning: a new strategy for the prevention of ischemia-reperfusion injury.

Ischemic preconditioning renders the liver more tolerant to ischemia-reperfusion injury in warm and cold ischemia-reperfusion models. In general, the application of a 5 to 10-minute period of ischemia followed by 10 minutes of reperfusion confers early effective protection to the liver. Mechanisms responsible for this endogenous protective effect include: (1) transient nitric oxide production during liver preconditioning; (2) diminution of toxic reactive species generated on reperfusion; (3) remote effect on extrahepatic organs such as lung, kidney, and pancreas; (4) preservation of energy metabolism during ischemia; and (5) involvement of nuclear transcription factor and others.