Abstract
Objectives. CXCR4 plays critical roles in the development of diabetic neuropathic pain (DNP) in rats, and its mechanism is unknown. This study was aimed at evaluating the potential therapeutic value of the antioxidant N-acetylcysteine (NAC) against DNP in rats and how CXCR4 participates in the formation of DNP. Methods. Control or streptozotocin- (STZ-) induced diabetic Sprague-Dawley rats received vehicle or NAC for four weeks starting one week after STZ injection. Von Frey and Hargreaves Apparatus were used to analyze the behavioral changes of mechanical allodynia and heat hyperalgesia. CXCR4, p-CXCR4, interleukin- (IL-) 6, and tumor necrosis factor- (TNF-) α in the spinal cord and the prefrontal cortex were detected by western blotting. Plasma IL-6, TNF-α, superoxide dismutase- (SOD-) 1, SOD-2, and lipid peroxidation products malondialdehyde (MDA) and 15-F2t-Isoprostane were detected by ELISA. Results. The values of paw withdrawal threshold (PWT) and paw withdrawal latencies (PWL) were reduced in diabetic rats compared to control rats that were concomitant with significant increases of CXCR4, p-CXCR4, IL-6, and TNF-α protein expressions in the spinal cord and prefrontal cortex. The treatment with NAC decreased the IL-6 and TNF-α protein expression and further increased CXCR4 and p-CXCR4 in the spinal cord and the cortex of diabetic rats that were accompanied with enhancement of PWT and PWL. NAC also significantly attenuated or reverted the increases of plasma IL-6, TNF-α, SOD-1, SOD-2, MDA, and 15-F2t-Isoprostane in diabetic rats. Conclusion. It is concluded that NAC treatment could effectively alleviate DNP and that induction of CXCR4 and p-CXCR4 may represent a mechanism whereby NAC attenuates DNP.
Highlights
Diabetic neuropathic pain (DNP) is one of the most common chronic complications of diabetes, which brings suffering to diabetic patients [1, 2]
Hyperglycemia-induced activation of the polyol and hexosamine pathway and formation of advanced glycation end products are known to increase the production of Reactive Oxygen Species (ROS) that contribute to nerve injury [4, 5]
Proinflammatory proteins tumor necrosis factor- (TNF-)α and IL-6 were significantly upregulated in the spinal cord, cortex, and plasma
Summary
Diabetic neuropathic pain (DNP) is one of the most common chronic complications of diabetes, which brings suffering to diabetic patients [1, 2]. Increased oxidative stress is a unifying mechanism in the causation of DNP [3]. Hyperglycemia-induced activation of the polyol and hexosamine pathway and formation of advanced glycation end products are known to increase the production of Reactive Oxygen Species (ROS) that contribute to nerve injury [4, 5]. Excessive generation of ROS initiates a vicious circle by activating stress-sensitive pathways such as NFKb, p38 MAPK, and protein kinase C [6] or proinflammatory cytokines that contribute to diabetic complications [7, 8]. Hyperglycemia induces higher levels of proinflammatory cytokines that have been shown to correlate with the incidence of neuropathy [9, 10]
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