Abstract
Abstract: :
Purpose: We hypothesis that neurogenic inflammation mediated by the sensory neuropeptide substance P (SP), is involved in the pathogenesis of pterygium. Given pterygium is characterised in part by inflammation and expressed elevated IL–6 and IL–8, we investigate if pro–inflammatory cytokines expressed in pterygium could result from stimulation by SP. Methods: SP (10–10 to 10–6M) was added to primary epithelial cell cultures established from pterygium (n=2) or normal limbal (n=1) explants. After 24 hours, cell culture supernatants were collected and stored at –80oC. The supernatants were assayed for pro–inflammatory cytokines using the Bio–Plex suspension array system and a human cytokine assay purchased from Bio–rad. RT–PCR was used to detect IL–8 transcripts on SP stimulated cells. Results: SP induced secretion of IL–6, IL–8 and MCP–1 from both pterygium and normal limbal epithelial cell cultures. When normalised to basal conditions, SP induced a minimal 3–fold increase in IL–6, 14–fold increase in IL–8 and 4–fold increase in MCP–1 in the supernatants of pterygium epithelial cells. For normal limbal epithelial cells, a 2–fold increase in IL–6, 6–fold increase in IL–8 and 3–fold increase in MCP–1 was detected in the supernatants. IL–8 mRNA was not up–regulated by SP. Pterygium derived epithelial cell lines were more responsive to SP stimulation as compared to epithelial cells derived from normal limbus when measured by protein assays. Conclusions: SP induces secretion of the pro–inflammatory cytokines IL–6, IL–8 and MCP–1 in both normal limbal and pterygium epithelial cells in culture. Elevated cytokine secretion by pterygium epithelial cells in response to stimulation by SP could play a role in the pathogenesis of pterygium.
Keywords: Pterygium • cytokines/chemokines • neuropeptides