Midoriko Higashi

Long-Term Inhibition of Rho-Kinase Suppresses Angiotensin II–Induced Cardiovascular Hypertrophy in Rats In Vivo Effect on Endothelial NAD(P)H Oxidase System

Abstract— Intracellular signaling pathway mediated by small GTPase Rho and its effector Rho-kinase plays an important role in regulation of vascular smooth muscle contraction and other cellular functions. We have recently demonstrated that Rho-kinase is substantially involved in angiotensin II–induced gene expressions and various cellular responses in vitro. However, it remains to be examined whether Rho-kinase is involved in the angiotensin II–induced cardiovascular hypertrophy in vivo and, if so, what mechanisms are involved. Long-term infusion of angiotensin II for 4 weeks caused hypertrophic changes of vascular smooth muscle and cardiomyocytes in rats. Both changes were significantly suppressed by concomitant oral treatment with fasudil, which is metabolized to a specific Rho-kinase inhibitor, hydroxyfasudil, after oral administration. Angiotensin II caused a perivascular accumulation of macrophages and Rho-kinase activation, both of which were also significantly suppressed by fasudil. Vascular NAD(P)H oxidase expression (nox1, nox4, gp91phox, and p22phox) and endothelial production of superoxide anions were markedly increased by angiotensin II, both of which were also significantly suppressed by fasudil. Thus, fasudil ameliorated the impaired endothelium-dependent relaxations caused by angiotensin II without affecting vasodilator function of vascular smooth muscle. These results provide evidence that Rho-kinase is substantially involved in the angiotensin II–induced cardiovascular hypertrophy in rats in vivo. The suppression of endothelial NAD(P)H oxidase upregulation and resultant superoxide production and the amelioration of endothelial vasodilator function may be involved in this process.

Long-Term Inhibition of Rho-Kinase Suppresses Left Ventricular Remodeling After Myocardial Infarction in Mice

Background—Rho-kinase has been implicated as an important regulator of inflammatory responses mediated by cytokines and chemokines. Because proinflammatory cytokines play a critical role in left ventricular (LV) remodeling after myocardial infarction (MI), we examined whether long-term blockade of Rho-kinase suppresses LV remodeling in a mouse model of MI in vivo. Methods and Results—Mice underwent ligation of the left coronary artery and were treated with a Rho-kinase inhibitor, fasudil (100 mg · kg−1 · d−1 in tap water), for 4 weeks, starting 1 day after the surgery. At 4 weeks, LV infarct size was histologically comparable between the 2 groups. LV cavity dilatation and dysfunction evaluated by echocardiography were significantly suppressed in the fasudil group (P <0.05, n=15 to 28). The beneficial effects of fasudil were accompanied by suppression of cardiomyocyte hypertrophy and interstitial fibrosis (both P <0.01, n=6). The expression of inflammatory cytokines, including transforming growth factor (TGF)-β2, TGF-β3, and macrophage migration inhibitory factor, was upregulated in the noninfarcted LV in the control group and was significantly suppressed in the fasudil group (both P <0.05, n=10 to 11). Rho-kinase activity as evaluated by the extent of phosphorylation of the ERM family, a substrate of Rho-kinase, was significantly increased in the noninfarcted LV in the control group and was significantly suppressed in the fasudil group (P <0.05, n=5). Conclusions—These results indicate that Rho-kinase is substantially involved in the pathogenesis of LV remodeling after MI associated with upregulation of proinflammatory cytokines, suggesting a therapeutic importance of the molecule for the prevention of post-MI heart failure.

Long-Term Treatment With a Specific Rho-Kinase Inhibitor Suppresses Cardiac Allograft Vasculopathy in Mice

Abstract— Cardiac allograft vasculopathy (CAV) continues to be a major cause of late graft failure after cardiac transplantation. We have demonstrated that Rho-kinase, an effector of the small GTPase Rho, plays an important role in the pathogenesis of arteriosclerosis. In this study, we examined whether the Rho-kinase–mediated pathway is also involved in the pathogenesis of CAV using a specific Rho-kinase inhibitor and a dominant-negative Rho-kinase. Hearts from AKR mice were heterotopically transplanted to C3H/He (allograft) or AKR mice (isograft), and the effects of long-term oral treatment with fasudil, which is metabolized to a specific Rho-kinase inhibitor hydroxyfasudil, on CAV were examined at 2 and 4 weeks after the transplantation. Coronary remodeling in the allografts characterized by intimal thickening and perivascular fibrosis was dose-dependently suppressed in the fasudil group compared with the control group (P <0.01, n=9 to 10). The inhibitory effects of hydroxyfasudil were mimicked by in vivo gene transfer of dominant-negative Rho-kinase (P <0.05, n=4). Among the proinflammatory cytokines examined, those of macrophage migration inhibitory factor, interferon-&ggr;, and transforming growth factor-&bgr;1 were upregulated in the control group and were dose-dependently inhibited in the fasudil group (P <0.01, n=5). Vascular inflammation in the allografts, as evidenced by accumulation of inflammatory cells (macrophages and T cells), was also significantly inhibited in the fasudil group (P <0.05, n=5 to 10). These results indicate that long-term treatment with fasudil suppresses CAV in mice, suggesting that Rho-kinase is an important therapeutic target for the prevention of CAV.

Inhibition of Renin-Angiotensin System Ameliorates Endothelial Dysfunction Associated With Aging in Rats

Objective—Endothelial vasodilator functions are progressively impaired with aging, which may account in part for the increased incidence of cardiovascular events in elderly people. We examined what treatment could ameliorate the endothelial dysfunction associated with aging in rats. Methods and Results—Aged (12-month-old) Wistar-Kyoto rats were treated with vehicle, temocapril, CS-866 (an angiotensin II type 1 receptor antagonist), cerivastatin, or hydralazine for 2 weeks. Endothelium-dependent relaxations (EDRs) of aortas from aged rats were markedly impaired compared with EDRs of aortas from young (3-month-old) rats. Indomethacin, NS-398 (a cyclooxygenase [COX]-2 inhibitor), and SQ-29548 (a thromboxane A2/prostaglandin H2 receptor antagonist) acutely restored EDRs in aged rats, suggesting an involvement of COX-2–derived vasoconstricting eicosanoids. Tiron, a superoxide scavenger, also partially improved EDRs, suggesting an involvement of superoxide. EDRs were significantly ameliorated in aged rats after long-term treatment with temocapril or CS-866 but not after treatment with cerivastatin or hydralazine. Indomethacin induced no further improvement of EDRs after treatment with temocapril or CS-866. COX-2 protein expression and superoxide production were increased in the aortas of aged rats and were also attenuated by treatment with temocapril or CS-866. Conclusions—These results demonstrate that long-term inhibition of the renin-angiotensin system ameliorates endothelial dysfunction associated with aging through the inhibition of the synthesis of COX-2–derived vasoconstricting factors and superoxide anions.

Effects of thermoregulatory vasoconstriction on pulse hemoglobin measurements using a co-oximeter in patients undergoing surgery

STUDY OBJECTIVE To validate intraoperative pulse hemoglobin (SpHb) measurements in anesthetized patients with large forearm temperature - fingertip temperature gradients. DESIGN prospective and observational study. SETTING Operating room of a university hospital. PATIENTS 28 patients undergoing surgery during general anesthesia, requiring arterial blood withdrawal. INTERVENTIONS Radial arterial blood pressure, forearm and fingertip skin surface temperatures, and SpHb were monitored. MEASUREMENTS Paired SpHb and arterial hemoglobin (Hb) measurements at different skin-surface temperature gradients. MAIN RESULTS A total of 175 paired SpHb and arterial Hb measurements were analyzed. The mean SpHb to arterial Hb differences in each group were 0.33 ± 1.41g/dL in the < 1°C group of the forearm temperature - fingertip temperature gradient, -0.31 ± 1.24g/dL in the 1 - 2°C group, - 0.59 ± 1.11g/dL in the 2 - 3°C group, and - 0.53 ± 0.87g/dL in the > 3°C group (P < 0.05). The percentage of nonmeasurable SpHb due to low perfusion state was 0% (0 of 115 paired measurements) in the < 1°C group, 6.7% (2 of 30 pairs) in the 1 - 2°C group, 16.7% (3 of 18 pairs) in the 2 - 3°C group, and 66.7% (8 of 12 pairs) in the > 3°C group. CONCLUSION SpHb measured at fingertip was significantly affected by the perfusion state, with lower perfusion associated with lower SpHb. Thermoregulatory vasoconstriction affects measurement of SpHb.

Diastolic dysfunction of the left ventricle is associated with pulmonary edema after renal transplantation

Post‐operative pulmonary complications are associated with high mortality and graft loss in renal transplantation recipients. Left ventricular diastolic dysfunction is not uncommon in patients with chronic renal failure, including those with preserved left ventricular systolic function. The purpose of this study was to determine the relationship between left ventricular diastolic dysfunction and incidence of post‐operative pulmonary edema in renal transplantation recipients with preserved left ventricular systolic function.

EFFECTS OF CARDIOPULMONARY BYPASS ON THE ACCURACY OF NON-INVASIVE HEMOGLOBIN MEASUREMENT BY PULSE CO-OXIMETRY

A non-invasive continuous measurement of hemoglobin (Hb) by pulse co-oximetry (SpHb) using Radical-7® (Masimo Corporation, CA, USA) is a newly developed method of measuring total Hb concentration. Previously, the accuracy of SpHb in clinical settings was reported (1). However, it has been also reported that SpHb has poor correlation with arterial Hb after cardiac surgery (2). Here we examined the accuracy of SpHb measured by New Radical-7®, which has new software version for measurement of total Hb, in cardiac surgery patients using cardiopulmonary bypass (CPB).