Thymoquinone Mediates Müller Cell Apoptosis via miR-29b/SP1 Pathway: A Potential Therapeutic Approach in Diabetic Retinopathy.

Abstract

This study aims to explore the therapeutic potential of thymoquinone (TQ) in DR by assessing its effects on Müller cell apoptosis through modulation of the miR-29b/SP1 pathway in a diabetic animal model.Healthy C57BL/6 mice (25 g) were used in the study. Retinal samples were collected from both normal and diabetic mice subjected to various treatments: TQ (1 mg/kg/day), glibenclamide (GLB, 250 mg/kg/day), sitagliptin (STG, 10 mg/kg/day), and metformin (MET, 5 mg/kg/day) over a period of 28 days. The study measured miR-29b and SP1 mRNA levels using qRT-PCR. Protein expressions of SP1, Bax, and bcl-2 were analyzed through western blotting, while Caspase-3 activity using an ELISA assay kit, and apoptosis levels by annexin V.TQ administration resulted in a 52% reduction in blood glucose levels. Similarly, GLB, STG, and MET treatments reduced blood glucose by 60%, 57%, and 61%, respectively (p<0.05). In addition, TQ upregulated miR-29b by 51.28% and downregulated SP1 mRNA by 32.52% (p<0.05). Bax protein expression levels were decreased by 64.99%, while Bcl-2 protein expression increased by 62.92% in the TQ treatment group as compared to the untreated diabetic controls. Furthermore, Caspase-3 activity was downregulated by 40.03% with TQ treatment (p<0.05). Interestingly, the effect TQ on SP1 mRNA expression was inhibited by a miR-29b blocker (p<0.05), while an miR-29b mimic enhanced this effect; this was associated with a mitigation of apoptosis of retinal Müller cells as measured by flow cytometry (p<0.05).These results indicate that TQ might be a possible option for DR via its effect on the miR-29b/SP1 pathway; and therefore, playing a significant role in the mechanism against cell death.