Abstract:Aim: to analyze the signaling pathways involved in H₂O₂ vascular responses in hypertension. Methods: Vascular function, thromboxane A₂ (TXA₂) production, oxidative stress and protein expression were determined in mesenteric resistance arteries (MRA) from hypertensive (SHR) and normotensive WKY rats. Results: H₂O₂ and the TP agonist U46619 induced greater contractile responses in MRA from SHR than WKY. Moreover H₂O₂increased TXA₂production more in SHR than in WKY. The cSrc inhibitor PP1 reduced H₂O₂-and U46619-induced contraction and TXA₂ release in both strains. The ERK1/2 inhibitor PD98059 reduced H₂O₂but not U46619-induced contraction only in SHR arteries. The Rho Kinase inhibitor Y26372 reduced H₂O₂and U46619-induced contractions only in SHR arteries. Basal c-Src, ERK1/2 and Rho Kinase expression were greater in MRA from SHR than WKY. In SHR, the combination of PD98059 with the TP antagonist SQ29548 but not with Y27632, inhibited the H₂O₂contraction more than each inhibitor alone. H₂O₂and U46619 increased NAD(P)H Oxidase activity and O₂.-production and decreased mitochondrial membrane potential in vessels from SHR. The effects induced by H₂O₂were abolished by inhibitors of TXA₂synthase, ERK1/2 and c-Src. The mitochondrial antioxidant mitoTEMPO reduced H₂O₂-induced contraction and NAD(P)H Oxidase activation. Conclusions: In arteries from WKY, c-Src mediates H₂O₂ contractile responses by modulating TXA₂release and TXA₂ effect. In SHR, H₂O₂contraction is mediated by c-Src-dependent TXA₂ release which further activates Rho Kinase, c-Src and the relationship between mitochondria and NAD(P)H Oxidase. Moreover, ERK1/2 activation contributes to H₂O₂ contraction in SHR through effects on mitochondria/NAD(P)H Oxidase. We affirm that the present study is not under consideration by another journal, and that no part of the material has been published elsewhere. All persons acknowledged have seen and approved the mention of their name in the paper. We also state that there is no conflict of interest.
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Answers to Reviewer 1We would like to thank the Reviewer for his/her constructive comments. The manuscript has undergone changes to include data from new experiments. All concerns raised have been addressed and a detailed list of changes made is attached. We believe that the paper is significantly improved and hope that it is now acceptable for publication.
I have no major concerns regarding this study apart from a couple of considerations:1)The potential "translational" meaning of the observed findings could be more clearly addressed and detailed.The Reviewer raised an interesting aspect. It is now evident from an overwhelming amount of experimental and animal studies, that oxidative stress has a role in the etiology of hypertension. Unfortunately, data in patients are more varying and still no clear picture of this aspect has been drawn. ...