Activation of PKC epsilon-ALDH2 Axis Prevents 4-HNE-Induced Pain in Mice

Protein kinase C epsilon (PKC epsilon) is highly expressed in nociceptor neurons and its activation has been reported as pro-nociceptive. Intriguingly, we previously demonstrated that activation of the mitochondrial PKC epsilon substrate aldehyde dehydrogenase-2 (ALDH2) results in anti-nociceptive effects. ALDH2 is a major enzyme responsible for the clearance of 4-hydroxy-2-nonenal (4-HNE), an oxidative stress byproduct accumulated in inflammatory conditions and sufficient to induce pain hypersensitivity in rodents. Here we determined the contribution of the PKC epsilon-ALDH2 axis during 4-HNE-induced mechanical hypersensitivity. Using knockout mice, we demonstrated that PKC epsilon is essential for the nociception recovery during 4-HNE-induced hypersensitivity. We also found that ALDH2 deficient knockin mice display increased 4-HNE-induced nociceptive behavior. As proof of concept, the use of a selective peptide activator of PKC epsilon (psi epsilon HSP90), which favors PKC epsilon translocation to mitochondria and activation of PKC epsilon-ALDH2 axis, was sufficient to block 4-HNE-induced hypersensitivity in WT, but not in ALDH2-deficient mice. Similarly, psi epsilon HSP90 administration prevented mechanical hypersensitivity induced by endogenous production of 4-HNE after carrageenan injection. These findings provide evidence that selective activation of mitochondrial PKC epsilon-ALDH2 axis is important to mitigate aldehyde-mediated pain in rodents, suggesting that psi epsilon HSP90 and small molecules that mimic it may be a potential treatment for patients with pain.