Cellular localization of kinin B(1 )receptor in the spinal cord of streptozotocin-diabetic rats with a fluorescent [N(α)-Bodipy]-des-Arg(9)-bradykinin

BACKGROUND: The kinin B(1 )receptor (B(1)R) is upregulated by pro-inflammatory cytokines, bacterial endotoxins and hyperglycaemia-induced oxidative stress. In animal models of diabetes, it contributes to pain polyneuropathy. This study aims at defining the cellular localization of B(1)R in thoracic spinal cord of type 1 diabetic rats by confocal microscopy with the use of a fluorescent agonist, [Nα-Bodipy]-des-Arg(9)-BK (BdABK) and selective antibodies. METHODS: Diabetes was induced by streptozotocin (STZ; 65 mg/kg, i.p.). Four days post-STZ treatment, B(1)R expression was confirmed by quantitative real-time PCR and autoradiography. The B(1)R selectivity of BdABK was determined by assessing its ability to displace B(1)R [(125)I]-HPP-desArg(10)-Hoe140 and B(2)R [(125)I]-HPP-Hoe 140 radioligands. The in vivo activity of BdABK was also evaluated on thermal hyperalgesia. RESULTS: B(1)R was increased by 18-fold (mRNA) and 2.7-fold (binding sites) in the thoracic spinal cord of STZ-treated rats when compared to control. BdABK failed to displace the B(2)R radioligand but displaced the B(1)R radioligand (IC(50 )= 5.3 nM). In comparison, IC(50 )values of B(1)R selective antagonist R-715 and B(1)R agonist des-Arg(9)-BK were 4.3 nM and 19 nM, respectively. Intraperitoneal BdABK and des-Arg(9)-BK elicited dose-dependent thermal hyperalgesia in STZ-treated rats but not in control rats. The B(1)R fluorescent agonist was co-localized with immunomarkers of microglia, astrocytes and sensory C fibers in the spinal cord of STZ-treated rats. CONCLUSION: The induction and up-regulation of B(1)R in glial and sensory cells of the spinal cord in STZ-diabetic rats reinforce the idea that kinin B(1)R is an important target for drug development in pain processes.