Inhibition of TXNIP expression in vivo blocks early pathologies of diabetic retinopathy

L Perrone,L P Singh,K-I Hosoya,T Terasaki,T S Devi

doi:10.1038/cddis.2010.42

Abstract

Evidence is mounting that proinflammatory and proapoptotic thioredoxin-interacting protein (TXNIP) has a causative role in the development of diabetes. However, there are no studies investigating the role of TXNIP in diabetic retinopathy (DR). Here, we show that, in diabetic rats, TXNIP expression and hexosamine biosynthesis pathway (HBP) flux, which regulates TXNIP, are elevated in the retina and correlates well with the induction of inflammatory cyclooxygenase 2 (Cox-2) and sclerotic fibronectin (FN). We blocked the expression of TXNIP in diabetic rat retinas by: (i) inhibiting HBP flux; (ii) inducing post-transcriptional gene silencing (PTGS) for TXNIP mRNA; and (iii) performing an in vivo transcriptional gene silencing (TGS) approach for TXNIP knockdown by promoter-targeted small interfering RNAs and cell-penetrating peptides as RNA interference (RNAi) transducers. Each of these methods is efficient in downregulating TXNIP expression, resulting in blockade of its target genes, Cox-2 and FN, demonstrating that TXNIP has a causative role in aberrant gene induction in early DR. RNAi TGS of TXNIP abolishes diabetes-induced retinal gliosis and ganglion injury. Thus, TXNIP has a critical role in inflammation and retinal injury in early stages of DR. The successful employment of TXNIP TGS and amelioration of its pathological effects open the way for novel therapeutic strategies aimed to block disease onset and progression of DR.

Highlights

thioredoxin-interacting protein (TXNIP) has been shown to inhibit thioredoxin activity and reduces cellular antioxidant capacity.[6]
We reported that TXNIP is required for RAGE-induced proinflammatory gene expression in retinal endothelial cells (ECs) under diabetic conditions in vitro and that TXNIP expression is significantly elevated in the diabetic rat retina.[14]
This study aims to elucidate two unexplored questions that are relevant to the understanding of the molecular mechanisms that underline the development of DR: (i) analyze the metabolic pathway and the molecular network responsible for HG-induced TXNIP expression; and (ii) investigate whether TXNIP has a causative role in early abnormalities of DR

Summary

Introduction

TXNIP has been shown to inhibit thioredoxin activity and reduces cellular antioxidant capacity.[6]. Owing to the emerging relevance of TXNIP in diabetic complications and the lack of studies of TXNIP function in DR, we investigated the molecular mechanisms responsible for hyperglycemia (HG)induced TXNIP expression in retinal EC in vitro and whether TXNIP has a causative role in early diabetic abnormalities in vivo in the retina of streptozotocin (STZ)-induced diabetic rats. Received 10.5.10; revised 26.5.10; accepted 10.6.10; Edited by M Federici expression and ECM gene expression in renal mesangial cells and diabetic kidney.[11,16] we investigated whether HG and diabetes induce TXNIP expression via elevated HBP flux in EC in culture and in the retina of diabetic rats in vivo. To elucidate the causative role of TXNIP in DR, we employed several methods to blunt TXNIP expression including a novel strategy to silence the expression of TXNIP in vivo by promoter-targeted small interfering RNA (siRNA) (RNA interference (RNAi))-mediated transcriptional gene silencing (TGS).[18,19] We show that TXNIP is required for diabetes-induced Cox-2 and FN expression, gliosis and neuronal apoptosis in the rat retina, shedding some light into a crucial role of TXNIP in disease initiation and progression of early DR

Objectives

Methods

Conclusion