Targeting the [CL/cyt c] complex to protect electron transport and prevent ROS formation prevents mitochondrial IR injury without ROS scavenging (LB169)

SS‐31 (D‐Arg‐dimethylTyr‐Lys‐Phe‐NH2) is a ROS‐scavenging cardiolipin‐targeting tetrapeptide which is known to protect against oxidative stress‐induced ischemia‐reperfusion (IR) injury. The interaction of CL with cytochrome c (cyt c) is necessary for electron carrier function of cyt c but can also lead to a [CL/cyt c] complex formation, which prevents electron transfer and promotes superoxide and hydrogen peroxide generation. SS‐31 was shown to protect the carrier function of cyt c while preventing oxidative stress and optimizing bioenergetic efficiency. To distinguish between ROS scavenging and inhibition of ROS formation in mitochondrial protection during IR injury, we developed an analog of SS‐31 which lacks the ROS‐scavenging dimethylTyr moiety (SS‐20; Phe‐D‐Arg‐Phe‐Lys‐NH2). We showed that SS‐20 interacts specifically with CL in liposomes and mitochondria. In isolated mitochondria, SS‐20 increases oxygen respiration and reduces hydrogen peroxide formation. Although SS‐20 cannot scavenge ROS, it is as effective as SS‐31 at protecting cristae architecture during ischemia and accelerating ATP recovery upon reperfusion in a model of acute kidney ischemia. Thus we demonstrate that targeting the [CL/cyt c] complex to protect electron transport and prevent ROS formation prevents mitochondrial IR injury without ROS scavenging.