The effect of Intranasal Rho Kinase Inhibitor Y-27632 on pulmonary apoptosis in endotoxemia-induced acute lung injury in infant rats

Background and Aims: Sepsis is the leading clinical risk factor for acute lung injury(ALI) and acute respiratory distres syndrome(ARDS). Increased pulmonary cell apoptosis is responsible for the pathogenesis of endotoxemia-induced acute lung injury. The aim of this study is to evaluate the efficiency of intranasal Rho kinase inhibitor, Y-27632 on pulmonary apoptosis in endotoxemia-induced acute lung injury.Material and Methods: Forty-two infant rats were randomised to two experimental groups: (A)Intranasal group; (B)Intraperitoneal group. Each group has three subgroups: (1)Control group; (2)Acute lung injury group; (3) Acute lung injury + therapy group. Endotoxemia was induced in rats by intraperitoneal (i. p.) injection of lipopolysaccharide (Escherichia coli LPS serotype 0111:B4; 10 mg/kg). Rho kinase inhibitor (Sigma Chemical, St Louis, MO) was dissolved and diluted with physiological saline. It was administered both intraperitoneal and intranasal 5 mg/kg at three times, just after LPS injection, 8 hours after LPS injection and 16 hours after LPS injection. The control and LPS groups received only physiological saline in the same volume, instead of Y-27632. Infant rats were sacrified on the 24th hour of LPS injection and lung tissue samples were assessed by TUNEL, caspase-3 and hematoxilen eosin hystopathologically.Results: Lipopolysaccaride injection caused evident pulmonary injury and apoptosis in rat lung. In acute lung injury subgroup of intranasal group, hystologic grade was significantly high. Apoptosis was significantly high with TUNEL and caspase-3 stain in this subgroup. Both in intranasal and intraperitoneal groups, subgroup of ALI has lower hystological grade than the therapy subgroup and it is statistically significant. The number of TUNEL-positive and caspase-3-positive cell count and hystologic grade was detected fewer in the therapy subgroup of intranasal group and this finding is statistically significant. In ALI subgroup of intraperitoneal group, hystologic grade detected significantly high. In this subgroup apoptosis was significantly high with TUNEL and caspase-3 stain. In the therapy subgroup of intraperitoneal group, hystologic grade and the number of apopitotic cells stained with TUNEL and caspase-3 were significantly low. Intranasal and intraperitoneal administration of Rho kinase inhibitor, Y-27632 was found effective in each group. Comparing the therapy subgroups of intranasal and intraperitoneal groups there was no significant difference for hystologic grade and TUNEL stain. The number of caspase-3 positive cells in the therapy subgroup of Intraperitoneal group was significantly lower than the therapy subgroup of intranasal group (p=0.002).Conclusion: Rho kinase pathway has a important role for the regulation of pulmonary apoptosis in acute lung injury. In this study, it was found that intranasal and intraperitoneal administration of Rho kinase inhibitor has similar effect on apoptosis inhibition in endotoxemia-induced acute lung injury in infant rats. Intranasal administration of Rho kinase inhibitor has both low systemic side effect profile and easy usage so it gives hope to be a new alternative therapeutic agent.