Apoptosis-dependent acute pulmonary injury after intratracheal instillation of angiotensin II.

To test the hypothesis that exogenous purified angiotensin II (ANG) might cause apoptosis of alveolar epithelial cells (AECs) and acute lung injury, male Wistar rats were intratracheally instilled with purified ANG (10 mumol/L), ANG plus the caspase inhibitor ZVAD-fmk (60 mumol/L), ANG plus the ANG receptor AT1 antagonist losartan (LOS, 100 mumol/L) or sterile phosphate-buffered saline (PBS) vehicle alone. Six or 20 h later, the lungs were lavaged in situ for determination of bronchoalveolar lavage (BAL) fluid content of hemoglobin (Hb) and fluorescent (BODIPY)-albumin, a bolus of which was injected intravenously 15 min prior to BAL. Terminal deoxynucleotidyl transferase-mediated nick-end labeling (TUNEL) revealed that instillation of ANG, but not PBS alone, increased labeling of fragmented DNA in bronchiolar epithelial cells and in AECs (P<0.05) at 6 h post-ANG. Increased TUNEL was abrogated by concurrent instillation of ZVAD-fmk or LOS. Significant increased numbers of caspase-positive cells were observed by anti-caspase 3 immunolabeling after instillation of ANG (P<0.01); the same doses of LOS or ZVAD-fmk that blocked TUNEL also blocked the activation of caspase 3 (P<0.01). Intratracheal instillation of ANG also remarkably increased BAL BODIPY-albumin (P< 0.01) and Hb (P<0.05), both of which were eliminated by ZVAD-fmk or LOS. These data indicate that exposure of AECs to ANG in vivo is sufficient to induce apoptosis and alveolar epithelial barrier injury mediated by ANG receptor AT1.

[Study on the roles of the expression of bcl-2 and bax in experimental immunological liver injury in rats].

OBJECTIVE: To elucidate the roles of Bcl-2 and Bax in experimental immunological liver injury in rat and the effect of lowering serum levels on the expression and the injury. METHODS: 48 male Wistar rats were divided into six groups randomly. The animal model of iron low-load was created by intravenation of deferoxamine (DFO) or phlebotomy respectively, and immunological liver damage model was reproduced by injection of BCG (Bacilli Calmette Guein) and lipopolysaccharide (LPS). Then the following parameters were determined such as serum iron (SI) concentration, transferrin (TRF) concentration, total proteins (TP) volume, the serum activity of aspartate aminotransferase (AST), malondialdehyde (MDA) content, iron content (HIC), the expression of Bcl-2 and Bax proteins in liver tissue were assayed; the ratio of Bax to Bcl-2, apoptotic index (AI), and proliferative index (PI) were also calculated. RESULTS: (1) The amount of Bax expression in liver injury group was significantly higher than that of control one, but no change in Bcl-2 expression. The ratio of Bax to Bcl-2 and AI augmented significantly, along with increased serum activities of AST and level of MDA, reduced volume of TP in liver injury animals. (2) The serum activity of AST and TP volume in both of the control groups with DFO and phlebotomy pretreatment remained at control level. Although the expression of Bax and Bcl-2, Bax/Bcl-2 ratio and AI were all higher than those of blank controls, the increased magnitudes of Bax/Bcl-2 ratio and Al were significantly lower than those of the liver injury animals. (3) The expression amounts of Bcl-2 and Bax increased in the injury animals induced after injecting DFO or phlebotomy, thus Bax/Bcl-2 ratio and Al increased. However, Bax/Bcl-2 ratio and AI of them were less than those of the injuries without lowered SI, and the magnitude of increased serum activity of AST was lower than that of the injuries, but no change in TP volume in the rats with lowered SI. The MDA levels in the injuries with lower value of serum iron were lower than those of the animals without lower SI. CONCLUSION: The results show that the apoptotic process of hepatocyte accelerates in immunological liver injury, apoptosis may facilitate hepatocyte damage. Effect of iron on the expression of apoptosis regulating proteins have played an important role in apoptosis of immunological hepatic injury.