Hypothermic machine perfusion increases A20 expression which protects renal cells against ischemia/reperfusion injury by suppressing inflammation, apoptosis and necroptosis

There is an urgent need to improve the quality of donor organs obtained after cardiac death. In the present study, we examined the potential mechanisms through which A20 protects renal cells against ischemia/reperfusion injury (IRI) following either hypothermic machine perfusion (HMP) or static cold storage (CS) of the kidneys in a rabbit model. The expression of markers of apoptosis, necroptosis and inflammation in frozen kidney tissues were detected by western blot analysis, RT-qPCR and ELISA. Compared with the CS group, A20 expression was significantly higher in the tissue from the HMP group (P<0.01). By contrast, the expression of nuclear factor-κB (NF-κB) and tumor necrosis factor-α (TNF-α) was significantly lower in HMP group (P<0.01), whereas IκBα expression was significantly higher (P<0.01). The expression of apoptosis signal-regulating kinase 1 (ASK1), phosphorylated (p-)c-Jun N-terminal kinase (JNK) and activated caspase-3 in the HMP group was significantly downregulated compared with that in the CS group (all P<0.01). In addition, A20 inhibited receptor-interacting protein kinase 3 (RIPK3)-mediated necroptosis in the kidney. RIPK3 expression in the HMP group was significantly lower than that in the CS group (P<0.01), although the levels in both groups were higher than those in the sham group (P<0.01). Based on these findings, we propose a novel mechanism underlying the anti-apoptotic effect of A20 in renal cells in which A20 binds to ASK1 and promotes the degradation of ASK1 leading to the suppression of JNK activation and eventually, to the blockade of apoptosis. Thus, HMP reduces inflammation, apoptosis and necroptosis by upregulating the expression of A20; this mechanism may be responsible for protecting the kidney against IRI.