Apocynin alters redox signaling in conductance and resistance vessels of spontaneously hypertensive rats

Author(s)

Graton, Murilo E. ^{[1, 2]} ; Potje, Simone R. ^[3] ; Troiano, Jessica A. ^{[1, 2]} ; Vale, Gabriel T. ^[4] ; Perassa, Ligia A. ^{[1, 2]} ; Nakamune, Ana Claudia M. S. ^{[1, 2]} ; Tirapelli, Carlos R. ^[4] ; Bendhack, Lusiane M. ^[3] ; Antoniali, Cristina ^{[1, 2]}

Affiliation

^[1] Sao Paulo State Univ Unesp, Sch Dent, Dept Basic Sci, BR-16015050 Aracatuba, SP - Brazil

^[2] Sao Paulo State Univ UNESP, SBFis, Programa Posgrad Multictr Ciencias Fisiol, Aracatuba, SP - Brazil

^[3] Univ Sao Paulo, Fac Pharmaceut Sci Ribeirao Preto, Dept Chem & Phys, BR-14040903 Ribeirao Preto, SP - Brazil

^[4] Univ Sao Paulo, Coll Nursing Ribeirao Preto, Dept Psychiat Nursing & Human Sci, BR-14040902 Ribeirao Preto, SP - Brazil

• Document type: Journal article
• Source: Free Radical Biology and Medicine; v. 134, p. 53-63, APR 2019.
• Web of Science Citations: 1

Abstract

Chronic treatment with apocynin reduces blood pressure and prevents endothelial dysfunction development in spontaneously hypertensive rats (SHR). Mechanisms underlying apocynin effects on SHR remain unclear. Compared to diapocynin and other drugs, apocynin is a weak antioxidant, which suggests that its effects on SHR are associated with other mechanisms besides its antioxidant capacity. Angiotensin (Ang) II regulates NOX, the major reactive oxygen species (ROS) source in the cardiovascular system. We hypothesized that, by inhibiting NOX, apocynin could alter Ang II pressor and vasoconstrictor effects on SHR. We analyzed how Ang II affects blood pressure and vascular reactivity in aorta and mesenteric resistance arteries and evaluated plasma antioxidant capacity, NOX isoforms and subunits, NOS isoforms, AT(1) and AT(2) receptors expression, ROS production, and NOS activity in apocynin-treated SHR blood vessels (30 mg/Kg/day, p.o.). In SHR, apocynin reduced Ang II pressor effects, increased plasmatic antioxidant capacity, and blunted aortic and mesenteric NOX-dependent oxidants production and NOX2 and p47phox overexpression, which demonstrated that apocynin inhibits NOX in SHR blood vessels. Moreover, apocynin raised plasmatic and aortic nitrate/nitrite levels, maintained NOS activity and eNOS, p-eNOS, nNOS, iNOS, sGC-alpha, and sGC-beta expression in mesenteric bed, diminished AT(1) expression in aorta and mesenteric bed, and elevated AT(2) expression in SHR aorta. Apocynin increased Ang II vasoconstriction endothelial modulation in SHR resistance arteries. All these results showed that in vivo treatment with apocynin alters several mechanisms that reduce Ang II pressor and vasoconstrictor effects on SHR. Such apocynin effects involve other mechanisms besides vascular ROS modulation, which improves NO availability in SHR vascular cells. These integrated data could help us to understand the promising apocynin activity as an antihypertensive drug that acts differently from the drugs that are currently being used in the clinical setting. (AU)

• FAPESP's process: 16/22180-9 - Study of post-translational modification mechanisms that increase the bioavailability of nitric oxide in blood vessels of normotensive and spontaneously hypertensive rats SHR at the end of pregnancy.
• Grantee: Cristina Antoniali Silva
• Support Opportunities: Regular Research Grants