Diabetic Retinopathy Is Associated with Decreased Tyrosine Nitrosylation of Vitreous Interleukins IL-1α, IL-1β, and IL-7.

OBJECTIVE

To simultaneously evaluate tyrosine nitrosylation and phosphorylation levels of vitreous interleukins of patients with diabetic retinopathy, in which abnormal tyrosine phosphorylation has been previously described.

METHODS

Specific immunoprecipitation of interleukins IL-1α, IL-1β, IL-2 and IL-7 was carried out in samples obtained during vitrectomy performed for proliferative diabetic retinopathy in patients (n=12) and for macular hole in controls (n=12). Tyrosine nitrosylation and phosphorylation levels of the immunoprecipitated interleukins were analysed by Western blot with the respective specific antibodies and correlated. The results were also correlated with the total amount of immunoprecipitated interleukin protein. The mean phosphorylation/nitrosylation ratios of these proteins in vitreous humour of both the control group and diabetic patients were determined.

RESULTS

Diabetes was associated with decreased tyrosine nitrosylation of IL-1α, IL-1β and IL-7 and an increased tyrosine phosphorylation/nitrosylation ratio with respect to controls in IL-1α (1.58±0.22 vs. 2.74±0.39, respectively; p<0.05) and IL-7 (2.15±0.01 vs. 3.26±0.57, respectively; p<0.05). No significant changes were observed in nitrotyrosine or in the tyrosine phosphorylation/nitrosylation ratio of IL-2.

CONCLUSIONS

Proliferative diabetic retinopathy is associated with concomitant and simultaneous changes in both tyrosine phosphorylation and tyrosine nitrosylation status of specific pro-inflammatory interleukins present in the vitreous fluid such as IL-1α, IL-1β and IL-7. These changes could be related to the increase in pro-inflammatory activity detected in diabetes-induced retinopathy.