Receptor-interacting protein kinase 3 (RIPK3)-mediated necroptosis is thought to be
the pathophysiologically predominant pathway that leads to regulated necrosis of parenchymal
cells in ischemia-reperfusion injury (IRI), and loss of either Fas-associated protein
with death domain (FADD) or caspase-8 is known to sensitize tissues to undergo spontaneous
necroptosis. Here, we demonstrate that renal tubules do not undergo sensitization
to necroptosis upon genetic ablation of either FADD or caspase-8 and that the RIPK1
inhibitor necrostatin-1 (Nec-1) does not protect freshly isolated tubules from hypoxic
injury. In contrast, irondependent ferroptosis directly causes synchronized necrosis
of renal tubules, as demonstrated by intravital microscopy in models of IRI and oxalate
crystal-induced acute kidney injury. To suppress ferroptosis in vivo, we generated
a novel third-generation ferrostatin (termed 16-86), which we demonstrate to be more
stable, to metabolism and plasma, and more potent, compared with the firstin- class
compound ferrostatin-1 (Fer-1). Even in conditions with extraordinarily severe IRI,
16-86 exerts strong protection to an extent which has not previously allowed survival
in any murine setting. In addition, 16-86 further potentiates the strong protective
effect on IRI mediated by combination therapy with necrostatins and compounds that
inhibit mitochondrial permeability transition. Renal tubules thus represent a tissue
that is not sensitized to necroptosis by loss of FADD or caspase-8. Finally, ferroptosis
mediates postischemic and toxic renal necrosis, which may be therapeutically targeted
by ferrostatins and by combination therapy.
