Minocycline as a therapeutic candidate in diabetic retinopathy: insights into pathophysiology and translational...

Diabetic retinopathy (DR) is a leading cause of vision loss worldwide and is increasingly recognized as a complex neurovascular disease characterized by early neuroinflammation, neurodegeneration, and microvascular dysfunction. Current therapies primarily target late-stage vascular complications and do not adequately address the upstream mechanisms involved in DR onset and progression. Minocycline, a second-generation semisynthetic tetracycline with high lipophilicity, has emerged as a promising therapeutic candidate because of its pleiotropic pharmacological effects beyond antimicrobial activity. Accumulating experimental evidence indicates that minocycline exerts anti-inflammatory, anti-apoptotic, mitochondrial-protective, and potentially epigenetic regulatory effects in diabetic retinal tissues and cellular models. Mechanistically, minocycline suppresses microglial activation, attenuates pro-inflammatory signaling, stabilizes the blood-retinal barrier, preserves mitochondrial function, inhibits matrix metalloproteinase activity, and has been associated with changes in histone acetylation and methylation under diabetic conditions. These actions may help preserve retinal neurovascular integrity and reduce neuronal and microvascular injury in experimental DR models. Despite promising preclinical findings, clinical evidence remains limited. Early-phase clinical studies indicate that oral minocycline is generally well tolerated; however, its efficacy has not been established in adequately powered clinical trials. This review summarizes the pharmacological properties of minocycline, critically examines its molecular mechanisms in DR pathogenesis, and discusses current clinical evidence, translational challenges, and future research directions. Although available data support further investigation of minocycline for DR, additional preclinical and clinical studies are needed to determine its therapeutic efficacy and clinical applicability.