Effects of pneumonia caused by klebsiella pneumoniae on apoptosis of thymocytes in rats

Objective To study the effects of pneumonia caused by Klebsiella pneumoniae on apoptosis of thymocytes in rats and its possible mechanism. Methods A total of 48 Sprague Dawley rats were randomly (random number) divided into 2 groups, namely the control group (n =24) and the infection group ( n = 24). The pneumonia models of rats were made with 0.3 mL Klebsiella pneumoniae suspension administered intratracheally per animal. On the 2nd, 4th, and 6th day after intratracheal instillation of bacteria, 1/ 3 of the rats in each group were sacrificed and TdT-mediated dUTP nick end labeling (TUN EL) method was used to assess the apoptosis of thymocytes. The expressions of cleaved Caspase-3, Bcl-2 and Fas in thympcytes of rats were detected with immunohistochemical staining. Results On each interval, apoptosis index of thymocytes, and the expressions of Cleaved Caspase-3 and Fas in the infection group were all higher than those in the control group (P < 0.01) , while the expressions of Bcl-2 lower than those in the control group (P<0.01). As more time consumed, the apoptotic index of thymocytes and the expressions of cleaved Caspase-3 in the infection group increased significantly (P<0.05). The expressions of Bcl-2 declined gradually (P < 0.05), but the expressions of Fas reached their peak 4th day after infection. There were no significant dynamic changes in all above mentioned variables in control group. Conclusions Pneumonia caused by Klebsiella Pneumoniae can lead to the increase in thymocyte apoptosis in rats. The mechanism may be associated with the decreased expression of Bcl-2 and the increased expression of Fas in thymocytes of rats with pneumonia caused by Klebsiella pneumoniae. The different apoptosis regulation pathways have different effects on different phase of pneumonia, that the effects of Fas decrease 4th day after pneumonia, while the effects of Bcl-2 increase further. Key words: Klebsiella pneumoniae;  Pneumonia;  Thymocyte;  Rat;  Apoptosis;  Cleaved Caspase-3;  Bcl-2;  Fas