Des-Arg 9-bradykinin increases intracellular Ca 2+ in bronchoalveolar eosinophils from ovalbumin-sensitized and -challenged mice

Abstract

The effects of the selective bradykinin B 1 receptor agonist, des-Arg 9-bradykinin and the bradykinin B 2 receptor agonist, bradykinin were studied on the intracellular free Ca 2+ concentration ([Ca 2+] i) in murine bronchoalveolar lavage cells from control and ovalbumin-sensitized mice using fura-2 microfluorimetry. The bronchoalveolar lavage cells of control mice, which were predominantly alveolar macrophages, showed an increase in [Ca 2+] i in response to bradykinin (1 μM) but not to des-Arg 9-bradykinin (1 μM), indicating the presence of functional bradykinin B 2 receptors and the absence of B 1 receptors. Such elevation in [Ca 2+] i induced by bradykinin was totally inhibited by the selective bradykinin B 2 receptor antagonist, d-Arg 0-Hyp 3-Thi 5- d-Tic 7-Oic 8-bradykinin (HOE-140; 10 μM). In contrast, bronchoalveolar lavage cells from ovalbumin-sensitized and -challenged mice significantly responded to both bradykinin and des-Arg 9-bradykinin, indicating the presence of both functional bradykinin B 1 and B 2 receptors. Eosinophils exhibited higher response to des-Arg 9-bradykinin (1 μM; 485% increase in [Ca 2+] i) compared to bradykinin (1 μM; 163% increase in [Ca 2+] i). This des-Arg 9-bradykinin-induced [Ca 2+] i increase was markedly inhibited by the selective bradykinin B 1 receptor antagonist, Ac-Lys-[ d-βNal 7, Ile 8]des-Arg 9-bradykinin (R-715; 10 μM). Des-Arg 9-bradykinin neither modified the basal [Ca 2+] i in lymphocytes nor in mononuclear cells from ovalbumin-sensitized and challenged mice, while bradykinin produced a [Ca 2+] i increase in both cell types. Our results further support the implication of the inducible bradykinin B 1 receptors in airway inflammatory response in ovalbumin-sensitized and challenged mice.