Treatment with NADPH oxidase inhibitor apocynin alleviates diabetic neuropathic pain in rats

Abstract

Increased reactive oxygen species by the activation of NADPH oxidase (NOX) contributes to the development of diabetic complications. Apocynin, a NOX inhibitor, increases sciatic nerve conductance and blood flow in diabetic rats. We investigated potential protective effect of apocynin in rat diabetic neuropathy and its precise mechanism of action at molecular level. Rat models of streptozotocin-induced diabetes were treated with apocynin (30 and 100 mg/kg per day, intragastrically) for 4 weeks. Mechanical hyperalgesia and allodynia were determined weekly using analgesimeter and dynamic plantar aesthesiometer. Western blot analysis and histochemistry/immunohistochemistry were performed in the lumbar spinal cord and sciatic nerve respectively. Streptozotocin injection reduced pain threshold in analgesimeter, but not in aesthesiometer. Apocynin treatment increased pain threshold dose-dependently. Western blot analysis showed an increase in catalase and NOX-p47phox protein expression in the spinal cord. However, protein expressions of neuronal and inducible nitric oxide synthase (nNOS, iNOS), superoxide dismutase, glutathion peroxidase, nitrotyrosine, tumor necrosis factor-α, interleukin-6, interleukin-1β, aldose reductase, cyclooxygenase-2 or MAC-1 (marker for increased microgliosis) in the spinal cord remained unchanged. Western blot analysis results also demonstrated that apocynin decreased NOX-p47phox expression at both doses and catalase expression at 100 mg/kg per day. Histochemistry of diabetic sciatic nerve revealed marked degeneration. nNOS and iNOS immunoreactivities were increased, while S-100 immunoreactivity (Schwann cell marker) was decreased in sciatic nerve. Apocynin treatment reversed these changes dose-dependently. In conclusion, decreased pain threshold of diabetic rats was accompanied by increased NOX and catalase expression in the spinal cord and increased degeneration in the sciatic nerve characterized by increased NOS expression and Schwann cell loss. Apocynin treatment attenuates neuropathic pain by decelerating the increased oxidative stress-mediated pathogenesis in diabetic rats.

Downregulation of glucose-6-phosphate dehydrogenase contributes to diabetic neuropathic pain through upregulation of toll-like receptor 4 in rats

“…9 Increased reactive oxygen species by the activation of NADPH oxidase contributes to the development of diabetic neuropathic pain. 32 In the present study, we provided the evidence to prove for the first time that G6PD in DRGs was involved in the process of diabetic neuropathic pain. We showed that the mRNA and protein expression levels of G6PD in L4-L6 DRGs were significantly lower in diabetic rats than in age-matched CON rats.…”

Effective Accentuation of Voltage-Gated Sodium Current Caused by Apocynin (4′-Hydroxy-3′-methoxyacetophenone), a Known NADPH-Oxidase Inhibitor

“…Therefore, through ionic mechanisms shown herein, pyrethroids or other structurally similar compounds are able to adjust the functional activities of varying types of neuroendocrine or endocrine cells, or heart cells, if similar in vivo results exist [ 6 , 7 , 11 , 12 , 13 , 50 ]. To this end, the overall findings from our study highlight an important alternative aspect that has to be taken into account, inasmuch as there is the beneficial or ameliorating effect of aPO in various pathologic disorders, such as inflammatory or neurodegenerative diseases, and heart failure [ 1 , 3 , 6 , 7 , 9 , 10 , 11 , 12 , 13 , 16 , 42 ].…”

“…Of note, this compound has been widely used as a selective inhibitor of NADPH-dependent oxidase (NOX) [2][3][4][5]. Alternatively, it has been recognized to be one of the most promising drugs in a variety of pathophysiological disorders, such as inflammatory and neurodegenerative diseases, glioma, and cardiac failure [1,3,[5][6][7][8][9][10][11] aPO has been recently shown to ameliorate cardiac function (e.g., structural remodeling) in heart failure [6,7,[11][12][13]. Pituitary cells were previously demonstrated to be expressed in the activity of NOX [14,15].…”

“…Of note, this compound has been widely used as a selective inhibitor of NADPH-dependent oxidase (NOX) [ 2 , 3 , 4 , 5 ]. Alternatively, it has been recognized to be one of the most promising drugs in a variety of pathophysiological disorders, such as inflammatory and neurodegenerative diseases, glioma, and cardiac failure [ 1 , 3 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]…”

Selenium and Neurological Diseases: Focus on Peripheral Pain and TRP Channels

“…Oxidative stress and inflammation have a main role in diabetic neuropathic pain generation [ 13 , 163 - 165 ]. Inhibition of ROS generation may contribute to the reduction of diabetic neuropathy [ 166 ]. Antioxidant applications can also be useful for the attenuation of diabetes and hyperglycemia-induced neuropathy.…”