Elucidating the structure and functions of Resolvin D6 isomers on nerve regeneration with a distinctive trigeminal transcriptome

Innervation sustains cornea integrity. Pigment epithelium-derived factor (PEDF) plus docosahexaenoic acid (DHA) regenerated damaged nerves by stimulating the synthesis of a new stereoisomer of Resolvin D6 (RvD6si). Here, we resolved the structure of this lipid isolated from mouse tears after injured corneas were treated with PEDF + DHA. RvD6si synthesis was inhibited by fluvoxamine, a cytochrome P450 inhibitor, but not by 15- or 5-LOX inhibitors, suggesting that the 4- and 17-hydroxy of DHA have an RR- or SR-configuration. The two compounds were chemically synthesized. Using chiral phase HPLC, four peaks of RvD6si(1-4) from tears were resolved. The RR-RvD6 standard eluted as a single peak with RvD6(1) while pure SR-RvD6 eluted with RvD6(3). The addition of these pure mediators prompted a trigeminal ganglion transcriptome response in injured corneas and showed that RR-RvD6 was the more potent, increasing cornea sensitivity and nerve regeneration. RR-RvD6 stimulates Rictor and hepatocyte growth factor (hgf) genes specifically as upstream regulators and a gene network involved in axon growth and suppression of neuropathic pain, indicating a novel function of this lipid mediator to maintain cornea integrity and homeostasis after injury.

Automated summary

Innervation is crucial for maintaining cornea integrity. The combination of PEDF and DHA can stimulate the synthesis of a new stereoisomer of RvD6si, which promotes nerve regeneration. RR-RvD6 is more potent than SR-RvD6 in increasing cornea sensitivity and nerve regeneration, indicating a novel function of this lipid mediator in maintaining cornea integrity and homeostasis after injury.