Interleukin 17 (IL17) Levels in Diabetic Patients is Associated With Diabetic Macular Edema and Diabetic Retinopathy

Abstract

Purpose: : Chronic inflammatory processes have been implicated in the pathogenesis of DR. Interleukin 17 (IL-17), a product of Th17 lymphocytes, has been recently shown to play a critical role in sustaining inflammatory processes associated with chronic conditions, such as rheumatoid arthritis and others. In the present study we wanted to investigate whether IL-17 was involved in the pathogenesis of DR.

Methods: : Clinical assessment of DR was conducted by fluorescein angiography following standard protocols. Flow cytometry analysis (FACS) was used to measure the ratio of Th17 lymphocytes within the CD4+ population of circulating immunocytes of diabetic patients (Type 1 = 25 and Type 2= 40) and compared to healthy, age-matched control volunteers (20). Multiplex ELISA was used to measure plasma levels of IL-17 in diabetic patients (Type 1 and Type 2) and in post-mortem vitrei obtained from diabetic donors (Georgia Eye Bank).

Results: : The ratio of Th17 lymphocytes, within the CD4+ immunocytes, was increased in all the diabetic patients and this effect was maximal in patients presenting signs of retinopathy (28%, p<0.03). Plasma circulating levels of IL-17 were also increased in both Type 1 and Type 2 diabetic patients and were significantly elevated in patients presenting signs of retinopathy (p<0.02) and in post-mortem vitrei although levels of IL-17 found in this tissue were more modest of the plasma levels. Finally, correlation studies also revealed that levels of IL-17 correlated with presence of macular edema in both Type 1 and Type 2 diabetic patients.

Conclusions: : The results of the present studies revealed that patients presenting clinical signs of DR, in particular macular edema, have increased levels of Th17 lymphocytes and plasma levels of IL-17. Given the emerging role of IL-17 in sustaining chronic inflammatory diseases, our data suggest a possible implication of this cytokine in the pathogenesis of DR.

Keywords: diabetic retinopathy • diabetes • inflammation