JQ-1 attenuates microglial activation and retinal pathology in experimental diabetic retinopathy with modulation of Pagr1a/JAK2/STAT3 signaling.

Abstract

Diabetic retinopathy (DR) is a major vision-threatening complication of diabetes mellitus, in which chronic inflammation and retinal microglial activation contribute to disease progression. Bromodomain-containing protein 4 (BRD4) is an epigenetic regulator involved in inflammatory transcription; however, the downstream mediators associated with BET inhibition in diabetic retinal inflammation remain poorly characterized. In this study, high-glucose (HG)-stimulated BV2 microglia and streptozotocin (STZ)-induced diabetic mice were used to investigate the effects and mechanisms of the BET inhibitor JQ-1. Bulk RNA sequencing identified Pagr1a as a candidate mediator of JQ-1-associated transcriptional regulation. Candidate prioritization was based on HG responsiveness, the magnitude of JQ-1-associated reversal, and baseline expression abundance. BRD4 knockdown, BRD4 overexpression, promoter reporter assays, and ChIP-qPCR were used to examine the relationship between BRD4 and Pagr1a transcription. HG exposure was associated with increased BRD4 and Pagr1a expression, enhanced BRD4 occupancy at the Pagr1a promoter, and activation of JAK2/STAT3 signaling. BRD4 knockdown or JQ-1 treatment reduced Pagr1a expression and promoter activity. Pagr1a overexpression (Pagr1a-OE) partially attenuated the inhibitory effects of JQ-1 on JAK2/STAT3 phosphorylation and microglial inflammatory responses. In STZ-induced diabetic mice, short-term JQ-1 treatment reduced retinal microglial activation, inflammatory responses, oxidative stress, apoptosis, and structural injury without markedly altering systemic metabolic parameters. Retinal Pagr1a knockdown also reduced microglial JAK2/STAT3 activation and inflammatory marker expression, whereas combined JQ-1 and Pagr1a knockdown produced comparable or greater protection than JQ-1 alone in selected endpoints. These findings support a BRD4-associated Pagr1a/JAK2/STAT3 regulatory mechanism in diabetic retinal inflammation and identify Pagr1a as a candidate therapeutic target for further investigation.