Ischemic preconditioning protects the mouse liver by inhibition of apoptosis through a caspase-dependent pathway

Abstract

A short period of ischemia and reperfusion, called ischemic preconditioning, protects various tissues against subsequent sustained ischemic insults. We previously showed that apoptosis of hepatocytes and sinusoidal endothelial cells is a critical mechanism of injury in the ischemic liver. Because caspases, calpains, and Bcl-2 have a pivotal role in the regulation of apoptosis, we hypothesized that ischemic preconditioning protects by inhibition of apoptosis through down-regulation of caspase and calpain activities and upregulation of Bcl-2. A preconditioning period of 10 minutes of ischemia followed by 15 minutes of reperfusion maximally protected livers subjected to prolonged ischemia. After reperfusion, serum aspartate transaminase (AST) levels were reduced up to 3-fold in preconditioned animals. All animals subjected to 75 minutes of ischemia died, whereas all those who received ischemic preconditioning survived. Apoptosis of hepatocytes and sinusoidal endothelial cells, assessed by in situ TUNEL assay and DNA fragmentation by gel electrophoresis, was dramatically reduced with preconditioning. Caspase activity, measured by poly (adenosine diphosphate ribose) polymerase (PARP) proteolysis and a specific caspase-3 fluorometric assay, was inhibited by ischemic preconditioning. The antiapoptotic mechanism did not involve calpain-like activity or Bcl-2 expression because levels were similar in control and preconditioned livers. In conclusion, ischemic preconditioning confers dramatic protection against prolonged ischemia via inhibition of apoptosis through down-regulation of caspase 3 activity, independent of calpain-like activity or

Ischemia/reperfusion accelerates the outgrowth of hepatic micrometastases in a highly standardized murine model

“…1F-G) (n ϭ 7 each group), as shown in similar I/R models. 21 Mortality was not observed in this model of left lobar I/R. In conclusion, this partial I/R model induces hepatic oxidative stress and tissue injury in a background of stable hemodynamic parameters.…”

“…Partial hepatic I/R was induced by occluding the vascular inflow of the left lateral liver lobe for 45 minutes, corresponding to approximately 40% of the liver mass. 21 All surgical procedures were performed under inhalation anesthesia with a 1.5% to 2% isoflurane/O 2 mixture using a mask. Buprenorfine (3 g/mouse) was administered intramuscularly before surgery to provide sufficient intraoperative and postoperative analgesia.…”

“…In pilot experiments, this preconditioning protocol proved to be the most optimal schedule in preventing elevation of liver enzymes (data not shown), as has also been recognized in other studies. 20,21 Intermittent clamping was performed by occluding the blood supply to the left liver lobe in three cycles of 15 minutes separated by 5 minutes of reperfusion, 35 leaving the total time of ischemia unaltered (45 minutes). Tissue levels of GSH and plasma levels of ALT and AST were assessed after 6 hours of reperfusion.…”

“…[17][18][19] These include alternative clamping techniques such as ischemic preconditioning 8,[20][21][22][23] and intermittent clamping [24][25][26] as well as pharmacological intervention with antioxidants such as ␣-tocopherol and ascorbic acid. [27][28][29][30][31][32] We evaluated whether those strategies cross-protect the liver against (accelerated) outgrowth of micrometastases in this model.…”

Platinum-(IV)-derivative satraplatin induced G2/M cell cycle perturbation via p53-p21waf1/cip1-independent pathway in human colorectal cancer cells

“…We have reported that satraplatin treatment induces the accumulation of apoptotic cells even in the p53-null model, thus overcoming chemoresistance by a p53-independent mechanism [14] . Generally, the protection of cells against apoptosis requires the down-regulation of proapoptotic activities or the up-regulation of anti-apoptotic mechanisms [23] . The Bcl-2 family is an important regulator of cellular apoptosis [24] .…”