Autophagy in renal ischemia-reperfusion injury: effect of ischemic duration and modulation with trehalose

J.P. Decuypere, T.W. Wylin, V.H. Heedfeld, D. Monbaliu, W.M. Martinet, J. Pirenne, I.J. Jochmans

Friday 16 march 2018

11:10 - 11:20h at Van Weelde Zaal

Categories: Basic / translational research, Session (parallel)

Parallel session: Parallel session 12: Basic/translational research

The role of autophagy in renal ischemia-reperfusion (IR) injury is still unclear: both protective as well as detrimental functions have been described. Additionally, whether autophagy is actually enhanced or suppressed during IR likely depends on both ischemia and reperfusion time. We therefore analyzed several autophagy markers in a female rat renal IR injury model subjected to varying durations of ischemia (45-60 min) and reperfusion (0, 1, 3, 6, 24, 48 h and 7 days). Sixty min ischemia led to less survival (33%) compared to 45 min (100%) and was characterized by more renal injury as evidenced by plasma creatinine, AST and h-FABP levels together with positive TUNEL staining. Expression of stress markers ICAM-1 and Hsp70 were markedly increased after 60 min ischemia compared to 45 min. Interestingly, compared to Sham-operated rats, autophagosome marker LC3-II was significantly lower after 0 and 3 h reperfusion, regardless of ischemic duration (45 or 60 min ischemia). After 24 h of reperfusion however, LC3-II levels were significantly higher after 60 min compared to 45 min of ischemia, associated with increased mRNA expression of LC3. As expected, these effects were associated with lower levels of autophagy degradation substrate Sqstm1/p62 after 60 min compared to 45 min of ischemia.

As autophagy seemed to decrease during reperfusion, we analyzed the effect of trehalose, an mTOR-independent autophagy stimulator and natural disaccharide, in the rat IR model subjected to 60 min ischemia. Rats were administered PBS (vehicle) or trehalose (2 g/kg bw) daily 2 days prior to IR experiments. Trehalose increased LC3-I and LC3-II levels 24 h post-reperfusion. Interestingly, trehalose treatment did not reduce expression of inflammatory markers nor reduce renal injury 24 h post-reperfusion, but resulted in markedly less positive TUNEL-staining 7 days post-reperfusion and increased survival (83%) compared to vehicle treatment (50%).

In conclusion, autophagy levels are reduced at several time points after reperfusion. One day following IR, autophagy is higher with increased ischemic stress. Autophagy inducer trehalose did not attenuate the initial IR injury, but nonetheless resulted in less injury and better survival in the long run, suggesting that autophagy enhancement via trehalose is not involved in reducing injury, but in repair and recovery of kidneys after IR.