Research

Cellular localization of kinin B₁ receptor in the spinal cord of streptozotocin-diabetic rats with a fluorescent [N^α-Bodipy]-des-Arg⁹-bradykinin

Sébastien Talbot¹ , Patrick Théberge-Turmel¹ , Dalinda Liazoghli² , Jacques Sénécal¹ , Pierrette Gaudreau³ and Réjean Couture¹

¹  Department of Physiology, Faculty of Medicine, Université de Montréal, C.P. 6128, Succursale Downtown, Montréal, Québec, H3C 3J7, Canada

²  The Montreal Neurological Institute and Hospital, McGill University, 3801 University Street, Montreal, Québec, H3A 2B4, Canada

³  Laboratory of Neuroendocrinology of Aging, Centre Hospitalier de l'Université de Montréal Research Center, Angus Technopole, Montréal, Québec, H1W 4A4, Canada

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Journal of Neuroinflammation 2009, 6:11doi:10.1186/1742-2094-6-11

Published:	26 March 2009

Abstract

Background

The kinin B₁ receptor (B₁R) 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 B₁R in thoracic spinal cord of type 1 diabetic rats by confocal microscopy with the use of a fluorescent agonist, [Nα-Bodipy]-des-Arg⁹-BK (BdABK) and selective antibodies.

Methods

Diabetes was induced by streptozotocin (STZ; 65 mg/kg, i.p.). Four days post-STZ treatment, B₁R expression was confirmed by quantitative real-time PCR and autoradiography. The B₁R selectivity of BdABK was determined by assessing its ability to displace B₁R [¹²⁵I]-HPP-desArg¹⁰-Hoe140 and B₂R [¹²⁵I]-HPP-Hoe 140 radioligands. The in vivo activity of BdABK was also evaluated on thermal hyperalgesia.

Results

B₁R 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 B₂R radioligand but displaced the B₁R radioligand (IC₅₀ = 5.3 nM). In comparison, IC₅₀ values of B₁R selective antagonist R-715 and B₁R agonist des-Arg⁹-BK were 4.3 nM and 19 nM, respectively. Intraperitoneal BdABK and des-Arg⁹-BK elicited dose-dependent thermal hyperalgesia in STZ-treated rats but not in control rats. The B₁R 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 B₁R in glial and sensory cells of the spinal cord in STZ-diabetic rats reinforce the idea that kinin B₁R is an important target for drug development in pain processes.