trans-Arachidonic acids induce a heme oxygenase-dependent vasorelaxation of cerebral microvasculature.
Nitrative stress is an important regulator of vascular tone. We have recently described that trans-arachidonic acids (TAA) are major products of NO(2)(.)-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 CYP(450) 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 approximately 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.
Kooli
Amna
A
Department of Paediatrics, Research Center of Hôpital Ste-Justine, Montréal, Quebec, Canada.
Kermorvant-Duchemin
Elsa
E
Sennlaub
Florian
F
Bossolasco
Michela
M
Hou
Xin
X
Honoré
Jean-Claude
JC
Dennery
Phyllis A
PA
Sapieha
Przemyslaw
P
Varma
Daya
D
Lachapelle
Pierre
P
Zhu
Tang
T
Tremblay
Sophie
S
Hardy
Pierre
P
Jain
Kavita
K
Balazy
Michael
M
Chemtob
Sylvain
S
D000818:Animals; D001095:Arachidonic Acids / Q000737:chemistry / Q000494:pharmacology*; D001663:Bilirubin / Q000378:metabolism; D002478:Cells, Cultured; D002560:Cerebrovascular Circulation / Q000187:drug effects* / Q000502:physiology; D000242:Cyclic AMP / Q000378:metabolism; D006152:Cyclic GMP / Q000378:metabolism; D004730:Endothelium, Vascular / Q000166:cytology / Q000378:metabolism; D006419:Heme Oxygenase (Decyclizing) / Q000378:metabolism*; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D009573:Nitrites / Q000378:metabolism; D015221:Potassium Channels / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013237:Stereoisomerism; D014664:Vasodilation / Q000187:drug effects*
D001095:Arachidonic Acids; C494842:Kcnma1 protein, rat; D051037:Large-Conductance Calcium-Activated Potassium Channel alpha Subunits; D009573:Nitrites; D015221:Potassium Channels; D012333:RNA, Messenger; D000242:Cyclic AMP; D006419:Heme Oxygenase (Decyclizing); D006152:Cyclic GMP; D001663:Bilirubin