The effect of neurotensin in human keratinocytes – implication on impaired wound healing in diabetes

Abstract

Diabetic foot ulcers are an important complication of diabetes mellitus characterized by chronic, non-healing ulcers resulting from poor proliferation and migration of fibroblasts and keratinocytes, thus impairing a correct re-epithelialization of wounded tissues. This healing process can be modulated by neuropeptides released from peripheral nerves; however, little is known regarding the role of neurotensin (NT) as a modulator of human keratinocyte function under hyperglycemic conditions. Therefore, this work is focused on the effect of NT in human keratinocytes, under normal and hyperglycemic conditions at different functional levels, namely NT receptors, cytokine, and growth factor expression, as well as proliferation and migration. Human keratinocyte cells were maintained at either 10/30 mM glucose and treated with or without NT (10 nM). The results show that NT did not affect keratinocyte viability. In addition, NT and all NT receptor expression levels were significantly reduced by hyperglycemia; however, NT treatment stimulated expression of NT and neurotensin receptor 2 (NTR2) while neurotensin receptor 1 (NTR1) and neurotensin receptor 3 (NTR3) expression levels were unchanged. Keratinocyte proliferation was not affected by NT and hyperglycemia, while cell migration was reduced by NT treatment. These results demonstrated that hyperglycemic conditions strongly impaired endogenous NT and NTR2 expression in keratinocytes. Despite the addition of exogenous NT to stimulate the endogenous NT and NTR2 expression, these changes do not translate into functional modifications on keratinocytes, particularly in terms of migration, proliferation, and production of cytokines or growth factors. These results suggest that NT production by keratinocytes may exert a paracrine effect on other skin cells, namely fibroblasts, macrophages, and dendritic cells for correct wound healing.