Yuichi Ono

Cyclin A/cdk2 Activation Is Involved in Hypoxia-Induced Apoptosis in Cardiomyocytes

Abstract— Cardiomyocytes are terminally differentiated cells characterized as withdrawal cell-cycle machinery, but nonetheless they are known to express cell-cycle regulators. Because many proteins related to the cell cycle induce apoptosis in proliferating cells, we examined the involvement of these proteins in the apoptosis pathway in cardiomyocytes. Primary rat cardiomyocytes were exposed to a severe hypoxic condition to induce apoptosis. The apoptosis rate of cardiomyocytes increased to ≈40% under 24 hours of hypoxia as evaluated by the TUNEL method. The cyclin A protein level assessed by immunoblot analysis accumulated in a time-dependent manner in cardiomyocytes, but there was no increase in nonmyocytes. Hypoxia increased the activity of cyclin A–associated kinase but not the activity of cyclin E–associated kinase, and the apoptosis was inhibited by infection of dominant-negative cdk2 adenovirus, suggesting that cyclin A and its associated kinase play significant roles in the apoptosis of cardiomyocytes. To investigate the cyclin A–mediated apoptosis, we infected cultured cells with cyclin A adenovirus. Apoptosis was induced in 63±12% of the infected cardiomyocytes in contrast to only 12±3% of the LacZ-infected control cells. In addition, the cells in the hypoxic condition showed an increase in caspase-3 activity and a subsequent decrease in p21cip1/waf1 protein, which is partly cleaved by caspase-3. These findings confirm that cyclin A–associated kinase mediates hypoxia-induced apoptosis in cardiomyocytes, and they also suggest that additional elements of the cell-cycle–dependent machinery participate in this mechanism.

Clinical Effectiveness of Tolvaptan in Patients With Acute Heart Failure and Renal Dysfunction

BACKGROUND More efficacious and/or safer decongestive therapy is clearly needed in acute heart failure (AHF) patients complicated by renal dysfunction. We tested the hypothesis that adding tolvaptan, an oral vasopressin-2 receptor antagonist, to conventional therapy with loop diuretics would be more effective treatment in this population. METHODS AND RESULTS A multicenter, open-label, randomized control trial was performed, and 217 AHF patients with renal dysfunction (estimated glomerular filtration rate 15-60 mL • min(-1) • 1.73 m(-2)) were randomized 1:1 to treatment with tolvaptan (n=108) or conventional treatment (n=109). The primary end point was 48-hour urine volume. The tolvaptan group showed more diuresis than the conventional treatment group (6464.4 vs 4999.2 mL; P <.001) despite significantly lower amounts of loop diuretic use (80 mg vs 120 mg; P <.001). Dyspnea relief was achieved significantly more frequently in the tolvaptan group at all time points within 48 hours except 6 hours after enrollment. The rate of worsening of renal function (≥0.3 mg/dL increase from baseline) was similar between the tolvaptan and conventional treatment groups (24.1% vs 27.8%, respectively; P =.642). CONCLUSIONS Adding tolvaptan to conventional treatment achieved more diuresis and relieved dyspnea symptoms in AHF patients with renal dysfunction. CLINICAL TRIAL REGISTRATION URL: http://www.umin.ac.jp/ctr/index/htm/ Unique identifier: UMIN000007109.

Prognostic impact of early treatment with tolvaptan in patients with acute heart failure and renal dysfunction.

BACKGROUND Renal dysfunction is a common comorbidity in acute heart failure (AHF) patients. The prognostic significance of early treatment with tolvaptan in AHF patients complicated with renal dysfunction has not been elucidated. METHODS Post hoc analysis was performed on a randomized clinical study for prespecified prognostic endpoints and prespecified subgroups. 217 AHF patients with renal dysfunction (eGFR 15 to 60mL/min/1.73m(2)) were randomized within 6h from hospitalization to either tolvaptan treatment for 2days or conventional treatment. The primary outcome was the combined endpoint of all-cause death and HF readmission. RESULTS During follow-up (636days, median) 99 patients experienced combined endpoint and 53 patients died. There was no significant difference in event-free survival rate for either the combined events (Log-rank: P=0.197) or all-cause death (Log-rank: P=0.894) between tolvaptan and conventional groups. In prespecified subgroup analysis, in patients whose BUN/creatinine ratio was above the median (>20), tolvaptan significantly reduced the risk of combined events (HR: 0.52, 95% CI: 0.30-0.91, P=0.021) with a significant interaction (P value for interaction=0.045). Likewise, in patients whose eGFR was 30mL/min/1.73m(2) or above, tolvaptan reduced the risk of combined events (HR: 0.54, 95% CI: 0.32-0.90, P=0.017) with a significant interaction (P value for interaction=0.015). CONCLUSION Short-term use of tolvaptan in acute-phase in AHF with renal dysfunction showed a neutral effect on prognosis. Patients with relatively preserved renal function and relatively high BUN/creatinine ratios are potentially favorable subgroups for treatment with tolvaptan.

Erratum: Corrigendum to “Clinical Effectiveness of Tolvaptan in Patients With Acute Heart Failure and Renal Dysfunction” (Journal of Cardiac Failure (2016) 22(6) (423–432)(S1071916416000671)(10.1016/j.cardfail.2016.02.007))

From the Department of Cardiology, Kameda Medical Center, Chiba, Japan; Department of Cardiology, Tokai University School of Medicine, Kanagawa, Japan; Department of Cardiology, Tomishiro Central Hospital, Okinawa, Japan; Department of Cardiology, Tokyo Metropolitan Hiroo Hospital, Tokyo, Japan; Department of Cardiology, Ome Municipal General Hospital, Tokyo, Japan; Department of Cardiology, Yokohama Minami Kyosai Hospital, Kanagawa, Japan; Department of Cardiovascular Medicine, Kobe City Medical Center General Hospital, Kobe, Japan; Department of Cardiology, Saitama Medical Center, Saitama Medical University, Kawagoe, Japan; Division of Cardiovascular Medicine, Toho University Ohashi Medical Center, Tokyo, Japan; Department of Cardiology, Hiratsuka Kyosai Hospital, Kanagawa, Japan; Department of Cardiology, Tokyo Yamate Medical Center, Tokyo, Japan; Department of Cardiology, Sakakibara Heart Institute of Okayama, Okayama, Japan; Department of Cardiology, National Disaster Medical Center, Tokyo, Japan; Department of Epidemiology, Harvard T. H. Chan School of Public Health, Boston, Massachusetts and Division of Cardiology, Hennepin County Medical Center and University of Minnesota, Minneapolis, Minnesota.

Overexpression of CDK inhibitor p16INK4A by adenovirus vector inhibits cardiac hypertrophy in vitro and in vivo

Cardiac hypertrophy is one of the serious complications which increase mortality due to cardiovascular diseases. However, only a partial reduction of cardiac hypertrophy has been successful using current drug therapy. We demonstrate here reduction of cardiac hypertrophy in vitro and in vivo using an adenovirus vector encoding cyclin-dependent kinase (cdk) inhibitor p16INK4a. Adenovirus-mediated overexpression of cdk inhibitor p16INK4a completely inhibited cardiac myocyte hypertrophy induced by endothelin (ET)-1, as evaluated by [3H]leucine incorporation into the cells and mRNA levels of skeletal alpha -actin (SK-A) or atrial natriuretic peptide (ANP) as well as by morphometric analyses. We then evaluated whether p16INK4a can suppress left-ventricular (LV) hypertrophy induced by aortic banding (AOB) in rats. Catheter-mediated gene transfer of AxCAp16 was performed according to the method reported by Hajjar et al. LV overload was produced by coarctation of the ascending aorta immediately after inoculation of the heart with adenovirus. Two weeks after the procedure, the left ventricular weight/body weight ratio (LVW/BW) increased in the AOB+LacZ group in comparison to that in controls. However, LVW/BW was identical in the AOB+p16 group and controls. Histologic analysis revealed that p16INK4a inhibited hypertrophy of cardiac myocytes. These results suggest that G1 cell cycle regulators may restrict cardiac hypertrophy, and offer a novel strategy for the gene therapy of cardiac hypertrophy.