trans-Arachidonic acids induce a heme oxygenase-dependent vasorelaxation of cerebral microvasculature

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• 作者：Amna Kooli ; Elsa Kermorvant-Duchemin ; Florian Sennlaub ; Michela Bossolasco ; Xin Hou ; Jean-Claude Honoré ; Phyllis A. Dennery ; Przemyslaw Sapieha ; Daya Varma ; Pierre Lachapelle ; Tang Zhu ; Sophie Tr
• 关键词：trans-Arachidonic acids ; Nitrative stress ; Cerebral vasorelaxation ; Heme oxygenase ; Carbon monoxide ; Cyclic GMP ; Large conductance calcium-dependent potassium channels ; Free radicals
• 刊名：Free Radical Biology and Medicine
• 出版年：2008
• 出版时间：1 March 2008
• 年：2008
• 卷：44
• 期：5
• 页码：815-825
• 全文大小：850 K

文摘

Nitrative stress is an important regulator of vascular tone. We have recently described that trans-arachidonic acids (TAA) are major products of NO₂^·–mediated isomerization of arachidonic acid in cell membranes and that nitrative stress increases TAA levels leading to neural microvascular degeneration. In the present study, we explored whether TAA exert acute effects on neuromicrovascular tone and investigated potential mechanisms thereof. TAA induced an endothelium-dependent vasorelaxation of rat brain pial microvasculature. This vasorelaxation was independent of nitric oxide, prostanoids, lipoxygenase products, and CYP₄₅₀ metabolite trans-hydroxyeicosatetraenoic acids. However, inhibition of heme oxygenase (using zinc protoporphyrin IX) and of dependent soluble guanylate cyclase (sGC; using ODQ) significantly diminished (by 70 % ) the TAA-induced vasorelaxation. Consistent with these findings, TAA stimulated heme oxygenase (HO)-2-dependent bilirubin (using siRNA HO-2) and cGMP formation, and the HO product carbon monoxide (using CO-releasing CORM-2) reproduced the sGC-dependent cGMP formation and vasorelaxation. Further exploration revealed that TAA-induced vasorelaxation and bilirubin formation (HO activation) were nearly abrogated by large-conductance calcium-dependent potassium channels (BK_Ca) (using TEA and iberiotoxin). Opening of BK_Ca with the selective activator NS1619 induced a concentration-dependent vasorelaxation, which was inhibited by HO and sGC inhibitors. Coimmunoprecipitation suggested a molecular complex interaction between BK_Ca and HO-2 (but not HO-1). Collectively, these findings identify new properties of TAA, specifically cerebral vasorelaxation through interactive activation of BK_Ca with HO-2 and, in turn, sGC. Our findings provide new insights into the characterization of nitrative stress-derived TAA products, by showing they can act as acute mediators of nitrative stress on neurovascular tone.