Masuo Ohashi

Effects of atorvastatin on inflammation and oxidative stress

Treatment with inhibitors of 3-hydroxyl-3-methylglutaryl coenzyme A reductase (statins) reduces the incidence of cardiovascular events, but it is unclear whether the beneficial effects are mediated solely by their lipid-lowering properties. We therefore investigated whether atorvastatin reduces inflammation and oxidative stress independently of its lipid-lowering effects. The subjects comprised 71 hyperlipidemic patients (64 ± 9 years old, mean ± SD) who were not receiving medical treatment. Serum lipid and C-reactive protein (CRP) levels, and urine 8-isoprostane level (an index of oxidative stress) were measured before and after 4 weeks of treatment with atorvastatin at 10 mg/day. In 38 patients, these biochemical variables and carotid intima-media thickness (IMT) were also measured after 6 months of treatment with atorvastatin. Atorvastatin markedly reduced CRP (from 0.69 ± 0.36 to 0.42 ± 0.20 and 0.35 ± 0.19 mg/l, median ± median absolute deviation, P < 0.0001), 8-isoprostane (from 225 ± 99 to 178 ± 75 and 179 ± 60 ng/g creatinine, P < 0.05), and low density-lipoprotein cholesterol (LDLC; from 165 ± 21 to 106 ± 18 and 112 ± 17 mg/dl, P < 0.0001) after 4 weeks and 6 months of treatment, respectively. However, the reductions in CRP and 8-isoprostane were not correlated with those of LDLC. After 6 months of treatment, IMT was significantly decreased compared with the baseline value (from 0.94 ± 0.26 to 0.90 ± 0.20 mm, P < 0.05), but this was not correlated with the reduction in LDLC. These results suggest that atorvastatin has beneficial effects on inflammation, oxidative stress, and the lipid profile in patients with hyperlipidemia. The extra-lipid effects are not attributable to the lipid-lowering effect of the statin, suggesting that the pleiotropic effects of atorvastatin are independent of its effects on the lipid profile.

Increased oxidative stress impairs endothelial modulation of contractions in arteries from spontaneously hypertensive rats

Objectives The endothelium modulates vascular contractions. We investigated the effects of oxidative stress on endothelial modulation of contractions in hypertension. Methods Changes in isometric tension of femoral arterial rings from spontaneously hypertensive (SHR) and Wistar–Kyoto (WKY) rats were recorded. Results The contractile response to norepinephrine of arteries with endothelium was greater in SHR than in WKY rats (P < 0.0001). Endothelium removal augmented the norepinephrine-induced contraction (P < 0.05). The augmentation was more pronounced in WKY than in SHR, which resulted in comparable contraction of arteries without endothelium in both strains. Nω-nitro-L-arginine methyl ester (100 μmol/l) mimicked the effect of endothelium removal. Production of nitric oxide (NO, assessed by measuring nitrite/nitrate concentrations) during the contraction was not different between SHR and WKY. Vitamin C suppressed the contraction of arteries with endothelium from SHR but not from WKY (P < 0.05). Diphenyleneiodonium and apocynin, inhibitors of nicotinamide adenine dinucleotide/nicotinamide adenine dinucleotide phosphate (NADH/NADPH) oxidase, attenuated the contraction of arteries with endothelium from SHR (P < 0.001) but not WKY, but did not affect contractions induced by serotonin. Superoxide generated by xanthine oxidase/hypoxanthine enhanced the norepinephrine-induced contraction of arteries with endothelium from WKY (P < 0.0001), and this effect was reversed by vitamin C. Conclusions In rat femoral arteries, NO released from the endothelium modulates vascular contraction. In SHR, production of superoxide by NADH/NADPH oxidase, which may be activated by norepinephrine, is enhanced, resulting in the inactivation of NO and impairment of endothelial modulation of vascular contractions. Vascular oxidative stress may contribute to the altered circulation in hypertension by impairing endothelial modulation of vascular contractions.

Acetylcholine-induced membrane potential changes in endothelial cells of rabbit aortic valve

Using a microelectrode technique, acetylcholine (ACh)‐induced membrane potential changes were characterized using various types of inhibitors of K+ and Cl− channels in rabbit aortic valve endothelial cells (RAVEC). ACh produced transient then sustained membrane hyperpolarizations. Withdrawal of ACh evoked a transient depolarization. High K+ blocked and low K+ potentiated the two ACh‐induced hyperpolarizations. Charybdotoxin (ChTX) attenuated the ACh‐induced transient and sustained hyperpolarizations; apamin inhibited only the sustained hyperpolarization. In the combined presence of ChTX and apamin, ACh produced a depolarization. In Ca2+‐free solution or in the presence of Co2+ or Ni2+, ACh produced a transient hyperpolarization followed by a depolarization. In BAPTA‐AM‐treated cells, ACh produced only a depolarization. A low concentration of A23187 attenuated the ACh‐induced transient, but not the sustained, hyperpolarization. In the presence of cyclopiazonic acid, the hyperpolarization induced by ACh was maintained after ACh removal; this maintained hyperpolarization was blocked by Co2+. Both NPPB and hypertonic solution inhibited the membrane depolarization seen after ACh washout. Bumetanide also attenuated this depolarization. It is concluded that in RAVEC, ACh produces a two‐component hyperpolarization followed by a depolarization. It is suggested that ACh‐induced Ca2+ release from the storage sites causes a transient hyperpolarization due to activation of ChTX‐sensitive K+ channels and that ACh‐activated Ca2+ influx causes a sustained hyperpolarization by activating both ChTX‐ and apamin‐sensitive K+ channels. Both volume‐sensitive Cl− channels and the Na+‐K+‐Cl− cotransporter probably contribute to the ACh‐induced depolarization.

Possible mechanisms underlying the midazolam-induced relaxation of the noradrenaline-contraction in rabbit mesenteric resistance artery

The mechanisms underlying the midazolam‐induced relaxation of the noradrenaline (NA)‐contraction were studied by measuring membrane potential, isometric force and intracellular concentration of Ca2+([Ca2+]i) in endothelium‐denuded muscle strips from the rabbit mesenteric resistance artery. The actions of midazolam were compared with those of nicardipine, an L‐type Ca2+‐channel blocker. Midazolam (30 and 100μm) did not modify either the resting membrane potential or the membrane depolarization induced by 10μm NA. NA (10μm) produced a phasic, followed by a tonic increase in both [Ca2+]i and force. Midazolam (10–100μm) did not modify the resting [Ca2+]i, but attenuated the NA‐induced phasic and tonic increases in [Ca2+]i and force, in a concentration‐dependent manner. In contrast, nicardipine (0.3μm) attenuated the NA‐induced tonic, but not phasic, increases in [Ca2+]i and force. In Ca2+‐free solution containing 2mm EGTA, NA (10μm) transiently increased [Ca2+]i and force. Midazolam (10–100μm), but not nicardipine (0.3μm), attenuated this NA‐induced increase in [Ca2+]i and force, in a concentration‐dependent manner. However, midazolam (10 and 30μm), had no effect on the increases in [Ca2+]i and force induced by 10mm caffeine. In ryanodine‐treated strips, which have functionally lost the NA‐sensitive Ca2+‐ storage sites, NA slowly increased [Ca2+]i and force. Nicardipine (0.3μm) did not modify the resting [Ca2+]i but partly attenuated the NA‐induced increases in [Ca2+]i and force. In the presence of nicardipine, midazolam (100μm) lowered the resting [Ca2+]i and further attenuated the remaining NA‐induced increases in [Ca2+]i and force. The [Ca2+]i‐force relationship was obtained in ryanodine‐treated strips by the application of ascending concentrations of Ca2+ (0.16–2.6mm) in Ca2+‐free solution containing 100mm K+. NA (10μm) shifted the [Ca2+]i‐force relationship to the left and enhanced the maximum Ca2+‐induced force. Under these conditions, whether in the presence or absence of 10μm NA, midazolam (10 and 30μm) attenuated the increases in [Ca2+]i and force induced by Ca2+ without changing the [Ca2+]i‐force relationship. It was concluded that, in smooth muscle of the rabbit mesenteric resistance artery, midazolam inhibits the NA‐induced contraction through its inhibitory action on NA‐induced Ca2+ mobilization. Midazolam attenuates NA‐induced Ca2+ influx via its inhibition of both nicardipine‐sensitive and ‐insensitive pathways. Furthermore, midazolam attenuates the NA‐induced release of Ca2+ from the storage sites. This effect contributes to the midazolam‐induced inhibition of the NA‐induced phasic contraction.

Inhibitory Effects of Propofol on Acetylcholine-induced, Endothelium-dependent Relaxation and Prostacyclin Synthesis in Rabbit Mesenteric Resistance Arteries

BACKGROUND Propofol (2,6-diisopropylphenol) modulates endothelium-dependent relaxation in some arterial preparations. The effect of propofol on endothelium-dependent, prostacyclin-mediated responses in mesenteric resistance arteries has not yet been clarified. METHODS The effect of propofol was examined on acetylcholine-induced membrane potential changes in the presence of N(G)-nitro-L-arginine (L-NOARG) in endothelium-intact rabbit mesenteric resistance arteries in vitro. The effects of propofol were also examined on the endothelium-dependent relaxation and prostacyclin synthesis that was induced by acetylcholine in the presence of L-NOARG and nicardipine. The effect of propofol on the relaxation induced by a prostacyclin analogue was examined in strips treated with L-NOARG and diclofenac. RESULTS Acetylcholine produced an initial and a slow membrane hyperpolarization. Propofol, 10 microM, and diclofenac each inhibited the acetylcholine-induced slow hyperpolarization, but not the initial hyperpolarization. Acetylcholine produced an endothelium-dependent relaxation that was significantly inhibited by propofol, 10 microM, and diclofenac. Propofol, 10 microM, greatly inhibited the acetylcholine-induced synthesis of prostacyclin, as did diclofenac. Propofol, 10 microM, had no effect on the relaxation induced by a prostacyclin analog. CONCLUSIONS In rabbit mesenteric resistance arteries, propofol inhibits the synthesis of prostacyclin and thus attenuates acetylcholine-induced, endothelium-dependent responses. Our results may help to explain why some actions seen with propofol in some preparations (e.g., vasoconstriction) are not seen after the endothelium is removed.

Brain natriuretic peptide detects cardiac abnormalities in mass screening

Background  Plasma brain natriuretic peptide (BNP) is elevated in asymptomatic patients with various cardiac abnormalities. We tested the hypothesis that measuring BNP is useful for detecting asymptomatic patients with cardiac abnormalities who are not identified by conventional health check‐up programmes.

Vasorelaxant effect of olprinone, an inhibitor of phosphodiesterase 3, on mesenteric small artery and vein of rabbits

The effects of olprinone, a cardiotonic agent that inhibits cyclic GMP (cGMP)-inhibited phosphodiesterase, was studied on isolated rabbit mesenteric small artery and vein. In the presence of indomethacin and propranolol, olprinone at concentrations of 10 nM to 10 microM and 1 microM to 100 microM relaxed norepinephrine-stimulated mesenteric artery and vein in a concentration-dependent manner, respectively. The relaxation was not endothelium-dependent in the artery. Removal of the endothelium, however, increased marginally the response of the vein to olprinone. Olprinone-induced relaxation was less pronounced in arteries contracted with high KCl solution + norepinephrine than in those contracted with norepinephrine alone. Nicardipine inhibited this attenuating effect of high KCl solution on the olprinone-induced relaxation. Olprinone (1 microM) enhanced the relaxation of artery and vein in response to a cAMP-increasing agent, 6-(3-dimethylaminopropionyl) forskolin (NKH477), but not to a cGMP- increasing agent, glyceryl trinitrate. Norepinephrine (10 microM) and caffeine (5 mM) elicited a transient, phasic contraction of the artery in Ca2+-free solution. Both olprinone and NKH477 attenuated more potently the norepinephrine-induced contraction than the caffeine-induced contraction. When norepinephrine (10 microM) and caffeine (5 mM) were successively applied in Ca2+-free solution, the contractile effect of caffeine was diminished compared to that in artery which had not been pretreated with norepinephrine. When the contraction in response to norepinephrine was partially attenuated by 1 microM olprinone, the following contraction evoked by caffeine was enlarged. It is concluded that olprinone relaxes the small artery more strongly than the vein via its direct action on smooth muscles. It is suggested that olprinone attenuates norepinephrine-induced contraction through inhibition of receptor-operated transmembrane Ca2+ influx and Ca2+ release from intracellular storage sites.

Crucial role of kidney function in resistance to antihypertensive therapy in patients with diabetes mellitus

Objectives Effective blood pressure (BP) control is difficult to achieve in diabetic patients. This study investigated factors that exacerbate resistance to antihypertensive medication in patients with diabetes. Methods Hypertensive patients with type 2 diabetes (n = 108, 67 ± 9 years) were subjected to a step-wise upward titration of medication (step 1, routine dose of angiotensin receptor blocker; step 2, routine doses of angiotensin receptor blocker and calcium channel blocker; step 3, step 1 + double dose of calcium channel blocker; step 4, double doses of angiotensin receptor blocker and calcium channel blocker; step 5, step 4 + routine dose of diuretic; step 6, step 5 + routine dose of β-blocker; step 7, step 6 + routine dose of α-blocker; step 8, step 6 + double dose of α-blocker) implemented with a target home BP of below 130/80 mmHg. The step number at which target BP was achieved was considered the amount of antihypertensive medications needed for BP control. Results All patients reached the target BP at step 4.0 ± 1.5. Multivariate regression analysis identified estimated glomerular filtration rate, but not measures of glycemic control, as an independent predictor of the number of drugs needed for BP control (P < 0.0001). Conclusion The number of antihypertensive medications needed for BP control in patients with diabetes mellitus is largely dependent on estimated glomerular filtration rate. Impaired kidney function could produce resistance to antihypertensive therapy in diabetic patients.

A Case of Reversible Dilated Cardiomyopathy after α-Interferon Therapy in a Patient with Renal Cell Carcinoma

A 47-year-old man with renal cell carcinoma underwent nephrectomy, and postoperative chemotherapy was performed with recombinant alpha-interferon. Five years later, he experienced dyspnea during physical exertion. An echocardiogram revealed dilatation and systolic dysfunction of the left ventricle, and thallium-201 myocardial scintigraphy showed diffuse heterogeneous perfusion. We diagnosed congestive heart failure because of cardiomyopathy induced by alpha-interferon therapy. Withdrawal of interferon therapy and the combination of an angiotensin-converting enzyme inhibitor, diuretics, and digitalis improved left ventricular systolic function. Furthermore, myocardial scintigraphy using [123I] beta-methyl-p-iodophenylpentadecanoic acid (123I-BMIPP) or [123 I]metaiodobenzylguanidine (123I-MIBG) revealed normal perfusion after the improvement of congestive heart failure. This is a rare case of interferon-induced cardiomyopathy that resulted in normal myocardial images in 123I-BMIPP and 123I-MIBG scintigrams after withdrawal of interferon therapy.

Doppler echocardiographic evaluation of latent pulmonary hypertension by passive leg raising.

Background The prevalence of chronic lung disease increases with advancing age. The purpose of this study was to detect latent pulmonary hypertension noninvasively in elderly patients with chronic lung disease.Methods The changes of flow-velocity by passive leg raising were assessed using pulsed Doppler echocardiography in the right ventricular outflow tract in 19 patients with chronic lung disease and 13 normal healthy subjects. Pulmonary artery pressure was measured simultaneously using a thermodilution cardiac output catheter.Results In patients with chronic lung disease examined at rest, we found pulmonary hypertension in seven, and none in 12. The normal pattern observed at rest changed to pulmonary hypertension pattern after leg raising in six out of the 12 patients. Pulmonary arterial catheterization confirmed the data obtained by pulsed Doppler echocardiography.Conclusions Some elderly patients with chronic lung disease have latent pulmonary hypertension which can be detected noninvasively by analyzing the changes of flow velocity profiles in the right ventricular outflow tract by passive leg raising.