kb-r7943 and Hypertension

Topics: Aniline Compounds; Animals; Calcium Signaling; Cardiovascular Diseases; Humans; Hypertension; Kidney; Myocardial Reperfusion Injury; Phenyl Ethers; Reperfusion Injury; Sodium Chloride, Dietary; Sodium-Calcium Exchanger; Thiourea

Hypertension is the most common chronic disease, and is the leading risk factor for death caused by stroke, myocardial infarction, and end-stage renal failure. The critical importance of excess salt intake in the pathogenesis of hypertension is widely recognized. However, the molecular mechanisms underlying salt-sensitive hypertension remain obscure. Recent studies using selective inhibitors and genetically engineered mice provide compelling evidence that salt-sensitive hypertension is triggered by Ca2+ entry through Na+/Ca2+ exchanger type-1 (NCX1) in vascular smooth muscle. Intriguingly, endogenous Na+ pump inhibitors seem to be necessary for NCX1-mediated hypertension. These findings have enabled us to explain how high salt intake leads to hypertension, and further to describe the potential of vascular NCX1 as a new therapeutic or diagnostic target for salt-sensitive hypertension.

Topics: Aniline Compounds; Animals; Drug Design; Humans; Hypertension; Kidney; Mice; Muscle, Smooth, Vascular; Natriuresis; Phenyl Ethers; Sodium; Sodium Chloride, Dietary; Sodium-Calcium Exchanger; Sodium-Potassium-Exchanging ATPase; Thiourea

Subplasmalemmal ion fluxes have global effects on Ca(2+) signaling in vascular smooth muscle. Measuring cytoplasmic and mitochondrial [Ca(2+)]and [Na(+)], we previously showed that mitochondria buffer both subplasmalemmal cytosolic [Ca(2+)] and [Na(+)] in vascular smooth muscle cells. We have now directly measured sarcoplasmic reticulum [Ca(2+)] in aortic smooth muscle cells, revealing that mitochondrial Na(+)/Ca(2+) exchanger inhibition with CGP-37157 impairs sarcoplasmic reticulum Ca(2+) refilling during purinergic stimulation. By overexpressing hFis1 to remove mitochondria from the subplasmalemmal space, we show that the rate and extent of sarcoplasmic reticulum refilling is augmented by a subpopulation of peripheral mitochondria. In ATP-stimulated cells, hFis-1-mediated relocalization of mitochondria impaired the sarcoplasmic reticulum refilling process and reduced mitochondrial [Ca(2+)] elevations, despite increased cytosolic [Ca(2+)] elevations. Reversal of plasmalemmal Na(+)/Ca(2+) exchange was the primary Ca(2+) entry mechanism following ATP stimulation, based on the effects of KB-R7943. We propose that subplasmalemmal mitochondria ensure efficient sarcoplasmic reticulum refilling by cooperating with the plasmalemmal Na(+)/Ca(2+) exchanger to funnel Ca(2+) into the sarcoplasmic reticulum and minimize cytosolic [Ca(2+)] elevations that might otherwise contribute to hypertensive or proliferative vasculopathies.

Topics: Adenosine Triphosphate; Animals; Aorta; Calcium; Calcium Signaling; Cell Compartmentation; Cell Membrane; Clonazepam; Hypertension; Membrane Proteins; Mitochondria, Muscle; Mitochondrial Proteins; Muscle, Smooth, Vascular; Myocytes, Smooth Muscle; Rats; Recombinant Fusion Proteins; Sarcoplasmic Reticulum; Sodium; Sodium-Calcium Exchanger; Thiazepines; Thiourea

Compared to sympathetic nervous system, the role of parasympathetic innervation on tone development, especially under diseased conditions, of the pulmonary artery is relatively unknown. In this study, the contractile effect of acetylcholine and the type(s) of muscarinic (M) receptor involved in the pulmonary artery (1st intralobar branch; endothelium-denuded, under resting tension) of the normotensive Wistar-Kyoto (WKY) and age-matched (male, 22-26 weeks old) Spontaneously hypertensive rats (SHR) were investigated. Cumulative administration of acetylcholine (> or =0.1 microM) caused a concentration-dependent increase in tension (antagonised by p-fluoro-hexahydro-sila-difenidol and 4-diphenylacetoxy-N-methylpiperidine, both are selective muscarinic M(3) receptor antagonists) and the magnitude of maximum contraction (expressed as % of 50 mM [K(+)](o)-induced contraction) was markedly enhanced in the presence of neostigmine (10 microM, an anti-cholinesterase) (acetylcholine 30 microM, SHR: 72% vs. 35%; WKY: 32% vs. 20%). In SHR only, acetylcholine-elicited contraction was suppressed by 1-[beta-[3-(4-Methoxyphenyl)-propoxyl]-4-methoxyphenethyl]-1H-imidazole (SK&F 96365, 1 microM), amiloride (500 microM), ethyl-isopropyl-amiloride (EIPA, 10 microM), 2-[2-[4-(4-Nitrobenzyloxy)phenyl]ethyl]isothiourea (KB-R 7943, 5 microM), 2,4-dichlorobenzamil (10 microM), and an equal molar substitution of [Na(+)](o) (< or =30 mM) with choline or N-methyl-D-glucamine. In nominally [Ca(2+)](o)-free, EGTA (0.5 mM)-containing Krebs' solution, acetylcholine (> or =3 microM) only elicited a small contraction. In conclusion, muscarinic M(3) receptor activation is responsible for the pulmonary artery contraction induced by acetylcholine, with a greater magnitude observed in SHR. The exaggerated contraction in SHR is probably due to an influx of [Na(+)](o) through the Na(+)/H(+) exchanger and the store-operated channels (SOC) into smooth muscle cells. Elevation of cytosolic [Na(+)](i) subsequently leads to an influx of [Ca(2+)](o) through the reverse mode of the Na(+)/Ca(2+) exchanger seems to play a permissive role in mediating the exaggerated contractile response of acetylcholine recorded in the SHR.

Topics: Acetylcholine; Amiloride; Animals; Calcium; Cholinesterase Inhibitors; Dose-Response Relationship, Drug; Endothelium, Vascular; Enzyme Inhibitors; Female; Hypertension; Imidazoles; In Vitro Techniques; Indoles; Male; Maleimides; Muscarinic Agonists; Muscarinic Antagonists; Neostigmine; Protein Kinase C; Pulmonary Artery; Rats; Rats, Inbred SHR; Rats, Inbred WKY; Receptors, Muscarinic; Sodium; Sodium-Calcium Exchanger; Sodium-Hydrogen Exchangers; Sodium-Potassium-Exchanging ATPase; Species Specificity; Thiourea; Vasoconstriction; Vasodilator Agents