Potential Combination Drug Therapy to Prevent Redox Stress and Mitophagy Dysregulation in Retinal Müller Cells under High Glucose Conditions: Implications for Diabetic Retinopathy

Abstract

Chronic hyperglycemia-induced thioredoxin-interacting protein (TXNIP) expression, associated oxidative/nitrosative stress (ROS/RNS), and mitochondrial dysfunction play critical roles in the etiology of diabetic retinopathy (DR). However, there is no effective drug treatment to prevent or slow down the progression of DR. The purpose of this study is to examine if a combination drug treatment targeting TXNIP and the mitochondria-lysosome pathway prevents high glucose-induced mitochondrial stress and mitophagic flux in retinal Müller glial cells in culture, relevant to DR. We show that diabetes induces TXNIP expression, redox stress, and Müller glia activation (gliosis) in rat retinas when compared to non-diabetic rat retinas. Furthermore, high glucose (HG, 25 mM versus low glucose, LG 5.5 mM) also induces TXNIP expression and mitochondrial stress in a rat retinal Müller cell line, rMC1, in in vitro cultures. Additionally, we develop a mitochondria-targeted mCherry and EGFP probe tagged with two tandem COX8a mitochondrial target sequences (adenovirus-CMV-2×mt8a-CG) to examine mitophagic flux in rMC1. A triple drug combination treatment was applied using TXNIP-IN1 (which inhibits TXNIP interaction with thioredoxin), Mito-Tempo (mitochondrial anti-oxidant), and ML-SA1 (lysosome targeted activator of transient calcium channel MCOLN1/TRPML1 and of transcription factor TFEB) to study the mitochondrial–lysosomal axis dysregulation. We found that HG induces TXNIP expression, redox stress, and mitophagic flux in rMC1 versus LG. Treatment with the triple drug combination prevents mitophagic flux and restores transcription factor TFEB and PGC1α nuclear localization under HG, which is critical for lysosome biosynthesis and mitogenesis, respectively. Our results demonstrate that 2×mt8a-CG is a suitable probe for monitoring mitophagic flux, both in live and fixed cells in in vitro experiments, which may also be applicable to in vivo animal studies, and that the triple drug combination treatment has the potential for preventing retinal injury and disease progression in diabetes.

Thioredoxin-interacting protein deficiency protects against severe acute pancreatitis by suppressing apoptosis signal-regulating kinase 1

“…Activated PSCs also secrete the neutrophil chemokine IL-8 and macrophage chemoattractant protein-1 (MCP-1) and express intracellular adhesion molecule-1 (ICAM-1) [ 36 , 37 ], suggesting that activated PSCs may be involved in exacerbating pancreatic inflammation by recruiting inflammatory cells. Studies have shown that pancreatic acinar cells secrete various inflammatory cytokines in response to the stimulation of pancreatitis [ 16 , 20 ]. The inflammatory response during SAP is characterized by the induction of a cascade of proinflammatory mediators which culminates in the recruitment of macrophages and neutrophils to the inflamed pancreas, thus leading to pancreatic acinar cell injury [ 38 ].…”

“…In a previous study, Kim et al found that TXNIP induced redox stress, inflammation, and apoptosis in diabetes and was also associated with the complications of diabetes [ 15 ]. Another study showed that melatonin alleviates lung inflammation caused by silica nanoparticles by downregulating TXNIP-related signaling pathways [ 16 ]. TXNIP can regulate AP through a variety of signaling pathways, and it was found that diosgenin derivative D can inhibit L-arginine-induced AP by mediating GSDMD in the endoplasmic reticulum through the TXNIP/HIF-1α pathway [ 17 ].…”

Contribution of Müller Cells in the Diabetic Retinopathy Development: Focus on Oxidative Stress and Inflammation

“…Apoptosis is described due to a decrease in Bcl-2 and an increase in Bax (bcl2 associated X) and caspase-3 levels [173][174][175]. Recently, several studies have shown the activation of pyroptosis and mitophagy/autophagy pathways [169,[176][177][178][179][180]. Corroborating these findings, various morphological and functional alterations have been described in MGC in diabetes experimental models.…”

The role of the mTOR pathway in diabetic retinopathy

“…On the other hand, rapamycin restores the autophagic machinery and protects cells from apoptosis, thus highlighting the role of autophagic dysfunction in these cells during DR ( 161 ). Along with these alterations, Müller cells undergo the dysregulation of mitophagy and become more susceptible to redox stress ( 162 ).…”