Apoptosis and autophagy in cold preservation ischemia

Prolonged cold ischemia (CI) is a risk factor for the development of delayed graft function that predicts reduced 5-year kidney transplant survival. CI results in caspase-3 activation, tubular injury, and apoptosis. Autophagy, a highly conserved pathway that permits recycling of nutrients within the cell during stress, is linked to apoptosis. We hypothesized that CI during kidney preservation would induce autophagy. We sought to determine apoptosis and autophagic flux in CI.

Autophagic flux and apoptosis were examined in kidneys of wild-type and green fluorescent protein (GFP)-microtubule-associated protein1 light chain 3 (LC3) transgenic mice that were subjected to 48 hr of CI. Autophagic flux was determined by performing experiments with and without bafilomycin A1.

CI alone significantly increased the number of apoptotic cells/hpf, caspase-3/7 activity, and protein expression of autophagy markers LC3 II and autophagy-related protein 5. To determine the effect of inhibiting autophagic flux on apoptosis, kidneys of wild-type and GFP-LC3 transgenic mice were subjected to 48 hr of CI in the presence of lysosomal inhibitor bafilomycin A1. The combination of CI and bafilomycin A1 suppressed autophagic flux and significantly reduced the number of apoptotic cells/hpf, caspase-3/7 activity, LC3 II (both by immunoblot and in GFP-LC3 transgenic mice), and autophagy-related protein 5 protein expression.

In summary, we have shown that autophagy and autophagic flux are reduced in cold ischemic kidneys treated with bafilomycin A1. Reduced autophagy and autophagic flux were associated with a significant reduction in apoptotic cell death, which may provide a therapeutic rationale for including bafilomycin A1 in University of Wisconsin solution during organ preservation.