Abstract
Purpose :
Ocular pain is a common symptom of dry eye disease (DED). Yet, there are no effective safe therapies available for DED pain. Sodium channels in nociceptive primary sensory neurons are required for action potential generation, and calcium channels are required for both synaptic transmission and for vesicular release of neuropeptides such as substance P (SP). Here, we employed a newly designed cationic dual sodium and calcium channel inhibitor (CNCB-2) to treat DED pain and inhibit the release of SP, which has been shown to be elevated in DED.
Methods :
To induce DED, 6-week-old C57BL/6 female mice were housed under desiccating stress in a controlled environment chamber for 14 days. The animals received CNCB-2 (0.5%) or PBS topically twice daily (N=5/group) and were evaluated on days 0, 4, 7, and 14. Corneal fluorescein staining (CFS) was scored (0-15) in a masked fashion using 2.5% fluorescein. To evaluate hyperalgesia, eye wiping count (EWC) was performed after instillation of hypertonic saline (2M NaCl). Allodynia was assessed by automated quantification of palpebral ratio (PR) via AI-assisted video analysis of the animals’ eyes after instillation of saline, iso-osmolar to tear (0.9 % NaCl). Corneas and trigeminal ganglions (TG) were collected to quantify SP via ELISA. All data were compared via one-way or two-way ANOVA followed by Tukey’s post-hoc test.
Results :
There was a significant increase in CFS (P<0.01) over time; however, treatment with CNCB-2 decreased CFS by 3.4 and 2.5 scores on day 7 (P<0.01) and day 14 (P<0.05). DED mice exhibited significant hyperalgesia (P<0.001) and allodynia (P=0.01), with a 36% increase in EWC and a 28% decrease in PR compared to the naïve animals (EWC= 13.1, PR= 0.54). CNCB-2 application significantly reduced EWC by 41% at all time points (P<0.001; P<0.001; P<0.01). The treated animals also exhibited significantly less allodynia in comparison to the vehicle group at all time points (P<0.01; P<0.001; P<0.01), with a 38% PR increase. SP level was significantly lower in the TG of the CNCB-2 group compared to the vehicle group (3389±383 vs 5057±178 pg/mg, P<0.01). Treatment also displayed a 10% decrease in corneal SP expression (12431±523 vs 14163±1185 pg/mg).
Conclusions :
Treatment with CNCB-2 shows a decrease in CFS, hyperalgesia, allodynia, and SP expression, suggesting the therapeutic potential of dual sodium and calcium channel blockers for DED.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.