The Role Of G Protein-coupled Receptor Kinase 2 In Diabetic Mechanical Hyperalgesia In Rats

ObjectiveWe aimed to study the relationship between G protein-coupled receptor kinase 2(GRK2)expression in the lumbar(L)dorsal root ganglion(DRG)and paw withdrawal threshold(PWT)in a diabetic mechanical hyperalgesia(DMH)rat model,and to explore the role of GRK2 in the pathogenesis of DMH.Methods102 Male Sprague-Dawley rats were fed adaptively for 1 week in a Specific Pathogen Free(SPF)rang animal house and were randomly divided into control(CON)group and streptozotocin(STZ)group.All rats in the STZ group were given a single intraperitoneal injection of STZ solution(65 mg/kg)for 2weeks and 33 DMH models were established.In the CON group,rats were intraperitoneally injected with the same volume of the sodium citrate buffer(20mg/ml,PH 4.3).CON group was randomly divided into 3 groups,group 1: normal group,no intrathecal injection.Group 2: normal AAV empty carrier group.AAV2/9-RFP(AAV empty carrier)was injected into the sheath.It was an empty vector without GRK2 gene and was used as a negative control of AAV-GRK2.Group 3: normal AAV-GRK2 group,AAV-GRK2 was injected into the sheath.It was used to upregulate GRK2 protein expression.DMH rats were randomly divided into 3 group,group 4: DMH CON group,no intrathecal injection.Group 5: DMH AAV empty vector group,AAV empty vector was injected into sheath.Group 6: DMH AAV-GRK2 group,AAV-GRK2 was injected into the sheath.The changes in PWT in rats in each group were detected using von Frey test.After 4 weeks of intrathecal injection,the GRK2 protein expression in rat L4-6 DRG was detected by immunoblotting and immunohistochemistry;the transfection of GRK2 gene was detected by immunofluorescence.ResultsThe rats were successfully transfected with GRK2 after 4 weeks of AAV-GRK2 intrathecal injection.Compared with the group 1,GRK2 protein expression decreased in the group 4 and group 5(P<0.01),and PWT was reduced(P<0.01).Compared with the group 5,GRK2 protein expression increased in the group 6(P<0.01);intrathecal injection of AAV-GRK2 vector increased GRK2 expression.The PWT began to increase after 2 weeks of AAV-GRK2 treatment and continued to increase until week 4(P<0.01).ConclusionsGRK2 expression was decreased in DMH rats.AAV-GRK2 vector could up-regulate GRK2 expression and relieve pain.