The Retinal Proteome in Experimental Diabetic Retinopathy

Abstract

Diabetic retinopathy is the leading cause of blindness in working age persons. Targeted studies have uncovered several components of the pathophysiology of the disease without unveiling the basic mechanisms. This study describes the use of complementary proteomic and genomic discovery methods that revealed that the proteins of the crystallin superfamily are increased dramatically in early diabetic retinopathy. Orthogonal methods confirmed that the amplitude of the up-regulation is greater than other changes described so far in diabetic retinopathy. A detailed time course study during diabetes showed differential up-regulation of the different isoforms of the crystallins superfamily. α- and β-crystallins were regulated primarily at the translation level, whereas γ-crystallins were also regulated transcriptionally. We also demonstrated cell-specific patterns of expression of the different crystallins in normal and diabetic rat retinas. In addition, systemic and periocular insulin treatments restored retinal crystallin protein expression during diabetes, indicating effects of phosphoinositide 3-kinase/Akt activity. Altogether this work shows the importance of proteomics discovery methods coupled with targeted approaches to unveil new disease mechanistic details and therapeutic targets. Diabetic retinopathy is the leading cause of blindness in working age persons. Targeted studies have uncovered several components of the pathophysiology of the disease without unveiling the basic mechanisms. This study describes the use of complementary proteomic and genomic discovery methods that revealed that the proteins of the crystallin superfamily are increased dramatically in early diabetic retinopathy. Orthogonal methods confirmed that the amplitude of the up-regulation is greater than other changes described so far in diabetic retinopathy. A detailed time course study during diabetes showed differential up-regulation of the different isoforms of the crystallins superfamily. α- and β-crystallins were regulated primarily at the translation level, whereas γ-crystallins were also regulated transcriptionally. We also demonstrated cell-specific patterns of expression of the different crystallins in normal and diabetic rat retinas. In addition, systemic and periocular insulin treatments restored retinal crystallin protein expression during diabetes, indicating effects of phosphoinositide 3-kinase/Akt activity. Altogether this work shows the importance of proteomics discovery methods coupled with targeted approaches to unveil new disease mechanistic details and therapeutic targets. Diabetic retinopathy is the leading cause of blindness in working age persons, and despite numerous studies, the pathophysiological mechanisms, especially during the early stages of diabetes, remain to be elucidated. Diabetic retinopathy develops, to some degree, in nearly all patients with diabetes and is the most common cause of new cases of blindness among adults. The predominant causes of vision loss are clinically significant macular edema and proliferative diabetic retinopathy, but vision impairment can be prevented or minimized if the retinopathy is identified in its early stages. Diabetic retinopathy includes microvascular and neuronal, glial, and microglial cell defects early in the course of the disease before clinically visible vascular lesions. Photoreceptor and ganglion cell death occurs as early as 2–4 weeks after the onset of diabetes (1Barber A.J. Lieth E. Khin S.A. Antonetti D.A. Buchanan A.G. Gardner T.W. Neural apoptosis in the retina during experimental and human diabetes. Early onset and effect of insulin.J. Clin. Investig. 1998; 102: 783-791Crossref PubMed Scopus (1038) Google Scholar, 2Martin P.M. Roon P. Van Ells T.K. Ganapathy V. Smith S.B. Death of retinal neurons in streptozotocin-induced diabetic mice.Investig. Ophthalmol. Vis. Sci. 2004; 45: 3330-3336Crossref PubMed Scopus (374) Google Scholar, 3Park S.H. Park J.W. Park S.J. Kim K.Y. Chung J