Receptor Interacting Protein Kinase-1 mediates murine acetaminophen toxicity independent of the necrosome and not through necroptosis

Abstract

Although necrosis in the acetaminophen (APAP) model is known to be regulated by c-Jun NH2- terminal kinase, (JNK) through interaction with mitochondria, the role of necroptosis through receptor interacting proteins 1 and 3 (RIPK1 and RIPK3) has also been suggested. Our aim was to determine the relationship between these two mechanisms of cell death. To verify the participation of RIPK1, we used antisense knockdown and confirmed protection comparable to the RIPK1 inhibitor, necrostatin in vivo and in vitro. However, we found no evidence that RIPK3 is expressed in primary mouse hepatocytes under basal conditions or after APAP and RIPK3−/− mice were not protected. RIPK3 was exclusively expressed in nonparenchymal cells. RIPK1 knockdown protected RIPK3−/− mice to the same extent as wild type mice, underscoring the independent role of RIPK1. We confirmed necroptosis is not involved in APAP toxicity by using mixed lineage kinase domain-like protein (MLKL) −/− mice, which were not protected from APAP. Next we addressed if there is interplay between RIPK1 and JNK. RIPK1 knockdown decreased the level of JNK activation and translocation to mitochondria and abrogated subsequent translocation of dynamin-related protein-1 (Drp1). Interestingly, APAP induced the translocation of RIPK1 to mitochondria which was unaffected by the knockdown of the mitochondrial JNK docking protein, Sh3 homology3 binding protein5 (Sab).

Conclusion

RIPK1 participates in APAP induced necrosis upstream of JNK activation while RIPK3 and MLKL are dispensable, indicating that necroptosis does not contribute to APAP-induced necrosis and RIPK1 has a unique, independent role.