Substance P and Secretoneurin in vitreous Aspirates of Patients With Various Vitreoretinal Diseases

Abstract

Purpose: : To detect the levels of substance P (SP) and secretoneurin (SN) in vitreous aspirates of patients with macular holes which served as controls, in patients with nonproliferative diabetic retinopathy (active PDR), inactive PDR, rhegmatogenous retinal detachment and proliferative vitreoretinopathy (PVR).

Methods: : Approximately 500 µl of vitreous fluid was aspirated at the beginning of vitrectomy and the concentration of both SP and SN was measured by a highly sensitive radioimmunoassay. SN-like immunoreactivities were characterized by reversed phase HPLC.

Results: : The concentration of SN was more than twenty-fold higher in macular holes when compared with SP and reversed phase HPLC revealed evidence that the vitreous levels of SN represent authentic SN. SN was significantly decreased in patients with nonproliferative diabetic retinopathy, active PDR and inactive PDR by more than 70 % whereas SP was increased in patients with rhegmatogenous retinal detachment.

Conclusions: : The decrease of SN in diabetic retinopathy seems to result from a reduced expression and/or secretion of the ciliary epithelium and a reduced release from the retina both due to diabetes mellitus, the increase of SP in rhegmatogenous retinal detachment from an enhanced outflow of the peptide through retinal breaks. Despite their proangiogenic activities, SP and SN are unlikely to be involved in the pathogenesis of neovascularizations of DR because of their unchanged and reduced levels, respectively, but the low levels of both peptides may facilitate the regression of vasoproliferations following laser photocoagulation. An involvement in the pathogenesis of PVR cannot be excluded and the significance of the high vitreous levels of SN remains to be clarified.

Keywords: neuropeptides • vitreous • retina