Abstract
Purpose :
Corneal nerves and resident leukocytes are closely associated, and we have previously demonstrated that trigeminal ganglion (TG) neurons express various chemotactic neuropeptides/chemokines. The purpose of this study was to characterize alterations in neuropeptide expression in the TG and their subsequent effect on migration of leukocytes following capsaicin stimulation.
Methods :
We investigated if stimulation of TG neurons with capsaicin altered the expression of chemotactic molecules and affect the migration of leukocytes. To study the effect of capsaicin (30nM or 1mM) added to the culture media of TG neurons, mRNA and protein levels of neuropeptides were assessed in cultured TG neurons and media via RT-qPCR and ELISA. For the leukocyte migration assay, TG neurons with or without capsaicin treatment were co-cultured with splenic plasmacytoid dendritic cells (pDCs) isolated from pDC-GFP mice in a modified Boyden chamber, using transwell inserts with 5mm pore size.
Results :
Capsaicin treatment of the TG neurons reduced the mRNA expression of neuropeptides Substance P (2.07-fold decrease), CGRP (3.09-fold decrease), and Somatostatin (1.60-fold decrease) compared to vehicle controls (p<0.05) and no change in Urocortin expression (p>0.05). The respective protein level was also significantly lower in the culture media of TG neurons treated with capsaicin compared to untreated TG neuron controls (Substance P ELISA, p<0.05). TG neurons treated with capsaicin and co-cultured in the modified Boyden chamber with pDCs in the transwell had less pDCs migrating through the transwell membrane after 24 hours incubation period, compared to untreated TG neurons co-culture (3.78-fold decrease; p<0.05).
Conclusions :
Corneal nerves and resident corneal leukocytes share expression of neuropeptides and their respective receptors, suggesting a potential crosstalk. TG neurons exert chemotactic effects on leukocytes via neuropeptides and changes in expression levels of neuropeptides in the TG neurons following capsaicin stimulation affects the migration of leukocytes.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.