The Effects Of VEGF And Its Receptor-2 In Primary Sensory Neuron On Neuropathic Pain

Introduction: The pathogenesis of neuropathic pain is complex. P2X3 and P2X2/3 receptors play a crucial role in nociception transduction of chronic pain. We investigated the effects of VEGF and its receptor-2 on the pain transmission in neuropathic pain states that mediated by P2X3 and P2X2/3 receptors in primary sensory neurons.Methods: Chronic constriction injury (CCI) rats were made as the neuropathic pain model. Sprague-Dawley male rats were randomly divided into three groups: Sham group (â… ) , CCI group(â…¡) and CCI+anti-rVEGF antibody group (â…¢) . Anti-rVEGF antibody was injected to the rats intrathecally in groupâ…¢, and PBS was injected in groupâ… andâ…¡respectively. The mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL) were measured every two days interval. After 14-day consecutive treatment, the L4-L6 DRG were isolated immediately from three group rats. The expressions of P2X2, P2X3, VEGF and VEGFR-2 mRNA and protein in L4-L6 dorsal root ganglia (DRG) were detected by in situ hybridization, RT-PCR, immunohistochemistry and western blotting.Results: (1) In behavioral studies, the MWT and TWL in groupâ…¡were lower than those in groupâ… andâ…¢(p<0.05) respectively; (2) In situ hybridization,the optical density(mean) of P2X2, P2X3, VEGF and VEGFR-2 mRNA in groupâ…¡were higher than those in groupâ… a ndâ…¢(p<0.05) respectively; (3) RT-PCR revealed that the expression levels of P2X2, P2X3, VEGF and VEGFR-2 mRNA in DRG of groupâ…¡w ere significantly higher than those in groupâ… andâ…¢( p<0.05) respectively; (4) In immunohistochemistry, the optical density(mean) of P2X2, P2X3, VEGF and VEGFR-2 in L4-L6 DRG in groupâ…¡were higher than those in groupâ… a ndâ…¢( p<0.05) respectively; (5) By western blotting, the protein levels of P2X2, P2X3, VEGF and VEGFR-2 in DRG of groupâ…¡were significantly enhanced compared with those in groupâ… andâ…¢(p<0.05) respectively. However, the expression levels of P2X3, P2X2, VEGF and VEGFR-2 mRNA and protein in DRG of groupâ…¢was just slightly higher than those in groupâ… ( p>0.05).Conclusions: These results indicated that the expression levels of P2X2, P2X3, VEGF and VEGFR-2 in DRG were enhanced in CCI group. The MWT and TWL were extended and the expression levels of P2X2 and P2X3 were reduced after CCI rats treated with anti-rVEGF antibody. All results above show that VEGF and VEGFR-2 may play an important role in the pathophysiology of neuropathic pain and the mechanism may be involved in P2X2/3 receptors in DRG.