ic-87114 and Hypertension

1. The growth enzyme phosphatidylinositol 3-kinase (PI3K) was recently implicated in the mediation of arterial spontaneous tone, an event observed in arteries from hypertensive, but not normotensive, subjects that contributes to changes in total peripheral resistance in the hypertensive state. We have shown this occurrence in experimentally induced models of hypertension. However, because the majority of hypertension is genetically based, it is important to demonstrate a similar change in genetically hypertensive animals. 2. Aorta from spontaneously hypertensive rats (SHR; systolic blood pressure = 183 +/- 4 mmHg) and Wistar Kyoto (WKY) rats (115 +/- 2 mmHg) were isolated for the measurement of isometric contractile force. Aorta from SHR displayed small increases (approximately 5% maximum phenylephrine (PE)-induced contraction) in spontaneous tone, whereas aorta from WKY rats displayed none. The non-selective PI3K inhibitor LY294002 (20 micromol/L) and the selective inhibitor of the p110delta catalytic subunit of PI3K IC87114 (20 micromol/L) caused a fall of basal tone in SHR aorta (20 +/- 7 and 24 +/- 6% of the initial PE contraction, respectively), but did not alter tone in arteries from WKY rats. LY294002, but not IC87114, normalized the increased potency of noradrenaline (NA) observed in aorta from SHR (-log EC50 values for NA in the presence of vehicle in WKY rats and SHR 7.5 +/- 0.1 and 7.8 +/- 0.1, respectively (P < 0.05); -log EC(50) values for NA in the presence of LY294002 in WKY rats and SHR 7.0 +/- 0.1 and 7.0 +/- 0.1, respectively). 3. Biochemical expression of the p110 catalytic and p85 regulator subunits of PI3K in western analyses revealed no difference in expression of the regulatory p85alpha or p110alpha protein subunits between WKY rats and SHR; p110gamma was not detected. In contrast, p110delta expression was increased greater than 30% in aorta from SHR compared with WKY rats (827.6 +/- 88.5 vs 576.8 +/- 53.4 arbitrary densitometry units, respectively). Immunohistochemical analyses revealed expression of the p110delta isoform in the smooth muscle of arteries. 4. These data underscore the relevance of an enzyme historically classified as one committed to growth/anti-apoptosis in modifying contractility and supports involvement of PI3K in genetically based hypertension.

Topics: Adenine; Animals; Aorta; Blotting, Western; Chromones; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Hypertension; Immunohistochemistry; In Vitro Techniques; Male; Morpholines; Norepinephrine; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Quinazolines; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Time Factors; Up-Regulation; Vasoconstriction; Vasoconstrictor Agents

Increased expression of phosphoinositide 3-kinase (PI3-kinase) mediates elevated tone in the aorta from hypertensive deoxycorticosterone acetate (DOCA)-salt rats. In this article, we hypothesized that (1) alterations observed with respect to PI3-kinase observed in the aorta would also occur in mesenteric resistance arteries responsible for determining total peripheral resistance (TPR) and (2) p110delta activity was increased and localized to vascular smooth muscle cells (VSMCs), and was responsible for the increase in spontaneous tone in aortae from DOCA-salt rats. Mesenteric resistance arteries and aorta were isolated from DOCA-salt (190+/-3 mm Hg) and sham (121+/-2 mm Hg) rats. Myograph experiments revealed LY294002 (20 micromol/L), a PI3-kinase inhibitor, significantly decreased tone in mesenteric resistance arteries from DOCA-salt rats as compared with sham (-49+/-12 mg versus -10+/-7 mg). Western analyses of resistance artery protein homogenate revealed p85alpha and p110delta subunit protein, with significantly elevated levels of p110delta protein in the DOCA-salt compared with sham rats (0.30+/-0.07 versus 0.16+/-0.04% smooth muscle alpha-actin arbitrary units). Immunohistochemistry revealed p110delta-specific staining in VSMCs, with more intense staining in aortae from DOCA-salt rats. Compared with aortae from sham, p110delta-associated PI3-kinase activity was increased in DOCA-salt (158% of sham) and likely responsible for spontaneous tone because the p110delta specific inhibitor IC87114 decreased spontaneous tone in a concentration-dependent manner. Collectively, these data further implicate the p110delta isoform of PI3-kinase in arterial hyperresponsiveness in hypertension at the level of both large and small arteries.

Topics: Adenine; Animals; Aorta; Chromones; Class I Phosphatidylinositol 3-Kinases; Desoxycorticosterone; Disease Models, Animal; Enzyme Induction; Enzyme Inhibitors; Hypertension; Male; Mesenteric Arteries; Morpholines; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Phosphatidylinositol 3-Kinases; Phosphoinositide-3 Kinase Inhibitors; Protein Isoforms; Protein Subunits; Quinazolines; Rats; Rats, Sprague-Dawley; Sodium Chloride; Vascular Resistance