Role of Oxidative Stress and Ca2+ Signaling on Molecular Pathways of Neuropathic Pain in Diabetes: Focus on TRP Channels

Diabetes mellitus, a debilitating chronic disease, affects similar to 100 million people. Peripheral neuropathy is one of the most common early complications of diabetes in similar to 66 % of these patients. Altered Ca2+ handling and Ca2+ signaling were detected in a huge variety of preparations isolated from animals with experimentally induced type 1 and 2 diabetes as well as patients suffering from the disease. We reviewed the role of Ca2+ signaling through cation channels and oxidative stress on diabetic neuropathic pain in sensory neurons. The pathogenesis of diabetic neuropathy involves the polyol pathway, advanced glycation end products, oxidative stress, protein kinase C activation, neurotrophism, and hypoxia. Experimental studies with respect to oxidative stress and Ca2+ signaling, inhibitor roles of antioxidants in diabetic neuropathic pain are also summarized in the review. We hypothesize that deficits in insulin, triggers alterations of sensory neurone phenotype that are critical for the development of abnormal Ca2+ homeostasis and oxidative stress and associated mitochondrial dysfunction. The transient receptor potential channels are a large family of proteins with six main subfamilies. The sheer number of different TRPs with distinct functions supports the statement that these channels are involved in a wide range of processes ranging in diabetic neuropathic pain and it seems that the TRPC, TRPM and TRPV groups are mostly responsible from diabetic neuropathic pain. In conclusion, the accumulating evidence implicating Ca2+ dysregulation and over production of oxidative stress products in diabetic neuropathic pains, along with recent advances in understanding of genetic variations in cation channels such as TRP channels, makes modulation of neuronal Ca2+ handling an increasingly viable approach for therapeutic interventions against the painful and degenerative aspects of many diabetic neuropathies.