Effect of hyperglycemia and neuropeptides on interleukin-8 expression and angiogenesis in dermal microvascular endothelial cells

Abstract

Impaired wound healing is a major complication associated with diabetes, involving a dysregulation and impairments in the inflammatory and angiogenic phases of wound healing. Here, we examine the effects of the neuropeptides substance P (SP) and neuropeptide Y (NPY) on dermal microvascular endothelial cell (DMVEC) angiogenesis and interleukin-8 (IL-8) expression, a known effector of the neuropeptide pathways in normal and hyperglycemic conditions in vitro. DMVECs are treated with one of four glucose concentrations: 1) 5 mM glucose; 2) 10 mM glucose; 3) 30 mM glucose; or 4) 30 mM mannitol and cotreated with 100 nM NPY, 100 nM SP, or 10 ng/mL IL-8. Angiogenesis is assessed with proliferation and tube formation assays. IL-8 mRNA and protein expression are evaluated at days 1 and 7. As compared with noromoglycemia (5 mM glucose), hyperglycemia (30 mM glucose) decreases DMVEC proliferation and tube formation by 39% and 42%, respectively. SP cotreatment restores DMVEC proliferation (211%) and tube formation (152%), and decreases IL-8 expression (34%) in DMVECs exposed to hyperglycemic conditions. These effects are not observed with NPY. However, IL-8 treatment by itself does not affect proliferation or tube formation, suggesting that the effect of SP on DMVEC angiogenesis is unlikely through changes in IL-8 expression. Hyperglycemic conditions impair DMVEC proliferation and tube formation. SP mitigates the effect of hyperglycemia on DMVECs by increasing DMVEC proliferation and tube formation. These findings are not likely to be related to a dysregulation of IL-8 due to the lack of effects of hyperglycemia on IL-8 expression and the lack of effect of IL-8 on DMVEC proliferation and tube formation. The effect of SP on DMVECs makes SP a promising potential target for therapy in impaired wound healing in diabetes, but the exact mechanism remains unknown.