Neuroprotective role of bradykinin because of the attenuation of pro-inflammatory cytokine release from activated microglia |
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Authors: | Noda Mami Kariura Yukihiro Pannasch Ulrike Nishikawa Kaori Wang Liping Seike Toshihiro Ifuku Masataka Kosai Yuki Wang Bing Nolte Christiane Aoki Shunsuke Kettenmann Helmut Wada Keiji |
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Institution: | Laboratory of Pathophysiology, Graduate School of Pharmaceutical Sciences, Kyushu University, Fukuoka, Japan. |
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Abstract: | Bradykinin (BK) has been reported to be a mediator of brain damage in acute insults. Receptors for BK have been identified on microglia, the pathologic sensors of the brain. Here, we report that BK attenuated lipopolysaccharide (LPS)-induced release of tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta from microglial cells, thus acting as an anti-inflammatory mediator in the brain. This effect was mimicked by raising intracellular cAMP or stimulating the prostanoid receptors EP2 and EP4, while it was abolished by a cAMP antagonist, a prostanoid receptor antagonist, or by an inhibitor of the inducible cyclooxygenase (cyclooxygenase-2). BK also enhanced formation of prostaglandin E(2) and expression of microsomal prostaglandin E synthase. Expression of BK receptors and EP2/EP4 receptors were also enhanced. Using physiological techniques, we identified functional BK receptors not only in culture, but also in microglia from acute brain slices. BK reduced LPS-induced neuronal death in neuron-microglia co-cultures. This was probably mediated via microglia as it did not affect TNF-alpha-induced neuronal death in pure neuronal cultures. Our data imply that BK has anti-inflammatory and neuroprotective effects in the central nervous system by modulating microglial function. |
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Keywords: | bradykinin lipopolysaccharide microglia prostaglandin tumor necrosis factor-alpha |
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