The effects of peripheral benzodiazepine receptor ligands on inflammation and apoptosis in acute lung injury

This study was designed to investigate the effects of selective peripheral benzodiazepine receptor agonist 4'-chlorodiazepam (Ro 5-4864) on inflammation and apoptosis in acute lung injury induced by α-naphthylthiourea (ANTU). ANTU is applied to rats at 10 mg/kg dose via intraperitoneally. Development of acute lung injury has been investigated 4 hours after ANTU. Injection of ANTU (10 mg/kg i.p.) produced pulmonary edema as indicated by an increase in lung weight/body weight ratio (LW/BW) and pleural effusion (PE) reaching a maximum within 4 h in rat. Ro 5-4864 (2 and 4 mg/kg, i.p.) carried out to rats 30 min prior to ANTU. After 4 hours, the thorax was opened and pleural effusion was carefully collected by suction and lung weight was measured and hispathological examination of the lung tissue was conducted. In both groups, iNOS, TNF-α, peripheral benzodiazepine receptor, caspas-3 immunohistochemical staining applied to the lung tissue. In serum samples IL-1 α, IFN-γ ve MCP-1 levels are measured by ELISA method. Through Annexin V/propidium iodide staining, apoptosis assessment is made on the lung tissue. In acute lung damage model induced by ANTU, selective peripheral benzodiazepine receptor agonist caused a decrease in the lung weight/body weight (LW/BW) ratio at the doses of 2 ve 4 mg/kg Ro 5-4864. However, it is only considered statistically different in 2 mg/kg dose. Ro 5-4864 has decreased the effusion development (PE/VA) in statistically different levels in both doses and provided protection against the development of effusion. In histopathological assessment, it is observed that Ro 5-4864 has displayed protective activity on the inflammation at both doses, whereas reduced the hemorrhage at statistically different levels only at 2 mg/kg dose. When immunohistochemical analyses were considered, it is detected that Ro 5-4864 has no statistically different protective effect on iNOS in ANTU group. Significantly reduced the TNF and PBR at both doses in ANTU group, and reduced caspase-3 in ANTU group at only 2 mg/kg dose. IL-1 and IFN gamma levels did not display any difference between the groups. MCP-1 levels has increased in ANTU group and such increase reduced at statistically different levels with Ro 5-4864 at 2 and 4 mg/kg doses. When assessed with respect to apoptosis, necrosis were observed in ANTU group, and Ro 5-4864 at the doses of 2 and 4 mg/kg was found to provide protection atstatistically different levels against such situation. In conclusion selective peripheral benzodiazepine receptor agonist Ro 5-4864 displayed a protective effect in lung damaged caused by ANTU and effusion development. These results shows that benzodiazepines may display protective effect over the lung damage mechanisms through their peripheral receptors located at periphery as different from those located at central nervous system. This positive and protective effect of peripheral benzodiazepine receptors on tissue damage and inflammation will enable them to be used as a potential medication in lung diseases.