Neurokinin-1 Receptor Antagonism Ameliorates Ocular Pain and Immune Responses in Dry Eye Disease

Abstract

Purpose : Ocular pain is a common symptom of dry eye disease (DED). Our previous work has demonstrated increased levels of the neuropeptide substance P (SP) in DED. SP preferentially activates the neurokinin 1 receptor (NK1R) to mediate an inflammatory response. However, the direct effects of SP in ocular pain in DED are unknown. The purpose of this study was to determine the contributions of SP to ocular pain and inflammation in DED through antagonism of NK1R.

Methods : DED was induced in 6 week old C57BL/6 female mice by housing them in a controlled environment chamber for 14 days. Eye wiping test was performed to evaluate pain after instillation of hypertonic saline (2M NaCl) on days 0, 2, 4, 7, 10, and 14 during DED induction. L-733,060 (1μg/μl), an NK1R antagonist, was administered topically twice per day from day 0 to day 14 after DED induction. Cornea, draining lymph nodes (dLNs), and trigeminal nerve ganglion (TG) were collected on day 14. SP expression in TG and cornea were measured by ELISA. The frequency of MHC-II^highCD11b⁺ cells in dLNs was assessed using flow cytometry.

Results : Eye wipe behavior was significantly increased in the DED group compared to the normal group (P < 0.001) and the peak was reached on day 4 (P = 0.02). Application of L-733,060 to DED mice led to significantly decreased eye wipe behavior at day 4 and 14 (P = 0.03). Corneal SP expression levels were 25% lower in the L-733,060 group compared to the untreated DED group (724±24pg/100μg vs. 976±82pg/100μg, P = 0.051) at day 14. In the TG, no difference in SP level was observed amongst groups (P = 0.97). Additionally, the L-733,060 group showed significantly fewer MHC-II^highCD11b⁺cells compared to the untreated DED group at day 14 (2.82±0.26% vs. 4.46± 0.24%, P = 0.001).

Conclusions : Our data demonstrate that antagonism of NK1R simultaneously reduces ocular pain and suppresses inflammation in a murine model of DED, suggesting SP blockade as a new therapeutic strategy in the management of DED.

This is a 2021 ARVO Annual Meeting abstract.