LPL/AQP7/GPD2 promotes glycerol metabolism under hypoxia and prevents cardiac dysfunction during ischemia.

In the heart, fatty acid is a major energy substrate to fuel contraction under aerobic conditions. Ischemia downregulates fatty acid metabolism to adapt to the limited oxygen supply, making glucose the preferred substrate. However, the mechanism underlying the myocardial metabolic shift during ischemia remains unknown. Here, we show that lipoprotein lipase (LPL) expression in cardiomyocytes, a principal enzyme that converts triglycerides to free fatty acids and glycerol, increases during myocardial infarction (MI). Cardiomyocyte-specific LPL deficiency enhanced cardiac dysfunction and apoptosis following MI. Deficiency of aquaporin 7 (AQP7), a glycerol channel in cardiomyocytes, increased the myocardial infarct size and apoptosis in response to ischemia. Ischemic conditions activated glycerol-3-phosphate dehydrogenase 2 (GPD2), which converts glycerol-3-phosphate into dihydroxyacetone phosphate to facilitate adenosine triphosphate (ATP) synthesis from glycerol. Conversely, GPD2 deficiency exacerbated cardiac dysfunction after acute MI. Moreover, cardiomyocyte-specific LPL deficiency suppressed the effectiveness of peroxisome proliferator-activated receptor alpha (PPARα) agonist treatment for MI-induced cardiac dysfunction. These results suggest that LPL/AQP7/GPD2-mediated glycerol metabolism plays an important role in preventing myocardial ischemia-related damage.

Cardiomyocytes capture stem cell-derived, anti-apoptotic microRNA-214 via clathrin-mediated endocytosis in acute myocardial infarction.

Extracellular vesicles (EVs) have emerged as key mediators of intercellular communication that have the potential to improve cardiac function when used in cell-based therapy. However, the means by which cardiomyocytes respond to EVs remains unclear. Here, we sought to clarify the role of exosomes in improving cardiac function by investigating the effect of cardiomyocyte endocytosis of exosomes from mesenchymal stem cells on acute myocardial infarction (MI). Exposing cardiomyocytes to the culture supernatant of adipose-derived regenerative cells (ADRCs) prevented cardiomyocyte cell damage under hypoxia in vitro. In vivo, the injection of ADRCs into the heart simultaneous with coronary artery ligation decreased overall cardiac infarct area and prevented cardiac rupture after acute MI. Quantitative RT-PCR-based analysis of the expression of 35 known anti-apoptotic and secreted microRNAs (miRNAs) in ADRCs revealed that ADRCs express several of these miRNAs, among which miR-214 was the most abundant. Of note, miR-214 silencing in ADRCs significantly impaired the anti-apoptotic effects of the ADRC treatment on cardiomyocytes in vitro and in vivo To examine cardiomyocyte endocytosis of exosomes, we cultured the cardiomyocytes with ADRC-derived exosomes labeled with the fluorescent dye PKH67 and found that hypoxic culture conditions increased the levels of the labeled exosomes in cardiomyocytes. Chlorpromazine, an inhibitor of clathrin-mediated endocytosis, significantly suppressed the ADRC-induced decrease of hypoxia-damaged cardiomyocytes and also decreased hypoxia-induced cardiomyocyte capture of both labeled EVs and extracellular miR-214 secreted from ADRCs. Our results indicate that clathrin-mediated endocytosis in cardiomyocytes plays a critical role in their uptake of circulating, exosome-associated miRNAs that inhibit apoptosis.

Protein Kinase N Promotes Stress-Induced Cardiac Dysfunction Through Phosphorylation of Myocardin-Related Transcription Factor A and Disruption of Its Interaction With Actin.

BACKGROUND: Heart failure is a complex syndrome that results from structural or functional impairment of ventricular filling or blood ejection. Protein phosphorylation is a major and essential intracellular mechanism that mediates various cellular processes in cardiomyocytes in response to extracellular and intracellular signals. The RHOA-associated protein kinase (ROCK/Rho-kinase), an effector regulated by the small GTPase RHOA, causes pathological phosphorylation of proteins, resulting in cardiovascular diseases. RHOA also activates protein kinase N (PKN); however, the role of PKN in cardiovascular diseases remains unclear. METHODS: To explore the role of PKNs in heart failure, we generated tamoxifen-inducible, cardiomyocyte-specific PKN1- and PKN2-knockout mice by intercrossing the αMHC-CreERT2 line with Pkn1flox/flox and Pkn2flox/flox mice and applied a mouse model of transverse aortic constriction- and angiotensin II-induced heart failure. To identify a novel substrate of PKNs, we incubated GST-tagged myocardin-related transcription factor A (MRTFA) with recombinant GST-PKN-catalytic domain or GST-ROCK-catalytic domain in the presence of radiolabeled ATP and detected radioactive GST-MRTFA as phosphorylated MRTFA. RESULTS: We demonstrated that RHOA activates 2 members of the PKN family of proteins, PKN1 and PKN2, in cardiomyocytes of mice with cardiac dysfunction. Cardiomyocyte-specific deletion of the genes encoding Pkn1 and Pkn2 (cmc-PKN1/2 DKO) did not affect basal heart function but protected mice from pressure overload- and angiotensin II-induced cardiac dysfunction. Furthermore, we identified MRTFA as a novel substrate of PKN1 and PKN2 and found that MRTFA phosphorylation by PKN was considerably more effective than that by ROCK in vitro. We confirmed that endogenous MRTFA phosphorylation in the heart was induced by pressure overload- and angiotensin II-induced cardiac dysfunction in wild-type mice, whereas cmc-PKN1/2 DKO mice suppressed transverse aortic constriction- and angiotensin II-induced phosphorylation of MRTFA. Although RHOA-mediated actin polymerization accelerated MRTFA-induced gene transcription, PKN1 and PKN2 inhibited the interaction of MRTFA with globular actin by phosphorylating MRTFA, causing increased serum response factor-mediated expression of cardiac hypertrophy- and fibrosis-associated genes. CONCLUSIONS: Our results indicate that PKN1 and PKN2 activation causes cardiac dysfunction and is involved in the transition to heart failure, thus providing unique targets for therapeutic intervention for heart failure.

Measurement of Anti-Factor Xa Activity in Patients on Apixaban for Non-Valvular Atrial Fibrillation.

BACKGROUND: Chromogenic anti-factor Xa activity (AXA) assay is reported to be the most appropriate method to measure the pharmacodynamics of apixaban, but the distribution of AXA in non-valvular atrial fibrillation (NVAF) patients on apixaban therapy has not been fully elucidated. METHODS AND RESULTS: Steady-state trough and peak AXA were measured in 124 NVAF patients taking apixaban. In 25 patients, baseline, first peak, and trough AXA were also examined, and were 0.01±0.02 IU/ml, 0.83±0.43 IU/ml, and 0.34±0.17 IU/ml, respectively. First trough AXA was significantly lower than steady-state trough AXA, although it was significantly higher than baseline (P<0.0001). Similarly, first peak AXA was significantly lower than steady-state peak AXA (P<0.0001). In 124 patients, steady-state peak AXA was significantly higher in the 5-mg b.i.d. group than in the 2.5-mg b.i.d. group (2.05±0.73 IU/ml vs. 1.51±0.65 IU/ml, respectively; P<0.001), although there was no significant difference in trough AXA. Other than dose, age and serum creatinine were significantly related to both trough and peak AXA. CONCLUSIONS: The distribution of AXA in Japanese NVAF patients on apixaban therapy in daily clinical practice both in the acute and steady-state phase was measured. In patients taking apixaban, measurement of AXA clearly showed the pharmacodynamic profile of this drug.

Impact of HIF prolyl hydroxylase inhibitors in heart failure patients with renal anemia.

OBJECTIVE: Hypoxia-inducible factor prolyl hydroxylase (HIF-PH) inhibitors are a new class of anti-anemia agents. We retrospectively evaluated the safety and efficacy of HIF-PH inhibitors in patients with heart failure (HF) complicated by anemia associated with chronic kidney disase. HIF-PH inhibitor treatment was initiated in 32 patients with chronic HF complicated by renal anemia and were followed up for 3 months. RESULTS: Hematocrit and hemoglobin levels markedly improved 3 months after HIF-PH inhibitor treatment. However, levels of NT-proBNP, which is an indicator of HF, did not decrease considerably. Based on the rate of change in NT-proBNP, we divided the patients into "responder" and "non-responder" groups. The results showed that considerably more patients had a ferritin level of less than 100 ng/mL in the non-responder group at baseline. There were substantially more patients with TSAT of less than 20% in the non-responder group at 1 month after HIF-PH inhibitor treatment. The cut-off values to maximize the predictive power of ferritin level at baseline and TSAT value at 1 month after treatment were 41.8 ng/ml and 20.75. HIF-PH inhibitor treatment can be expected to be effective for improving both anemia and HF if ferritin≥41.8 ng/ml at baseline or TSAT≥20.75 at 1 month after treatment.

＜Editors' Choice＞ Very long-term clinical outcomes after percutaneous coronary intervention for complex vs non-complex lesions: 10-year outcomes following sirolimus-eluting stent implantation.

Few studies have reported the long-term outcomes (>10 years) following first-generation drug-eluting stent implantation. In this single-center retrospective study, we investigated the very long-term clinical outcomes after first-generation sirolimus-eluting stent (SES) implantation in patients with complex lesions. The study included 383 consecutive patients who underwent initial SES implantation between July 2004 and January 2006; 84 and 299 of these patients reported a history of percutaneous coronary intervention (PCI) for complex and noncomplex lesions, respectively. Complex PCI was defined as having at least one of the following features: left main trunk PCI, implantation of ≥3 stents, bifurcation lesions with implantation of 2 stents, total stent length >60 mm, or chronic total occlusion. The target lesion revascularization (TLR) rate was significantly higher in the complex PCI than in the noncomplex PCI group (29.4% vs 13.0%, P=0.001), and we observed a significant intergroup difference in the late TLR (>1 year) rates (21.6% vs 9.5%, P=0.008). Late TLR continued over 10 years at a rate of 2.4%/year in the complex PCI and 1.1%/year in the noncomplex PCI group. Cox regression analysis revealed that complex PCI was related to TLR both over 10 years (hazard ratio 2.29, P=0.003) and beyond 1 year (hazard ratio 2.32, P=0.01). Cardiac death was more common in the complex PCI than in the noncomplex PCI group, particularly 4 years after PCI (15.8% vs 7.5%, P=0.031). Sudden death was the major cause of cardiac death beyond 4 years in the complex PCI group. These data indicate that long-term careful follow-up is essential for patients implanted with SES, especially those treated for complex lesions.

Corticotropin releasing hormone receptor 2 antagonist, RQ-00490721, for the prevention of pressure overload-induced cardiac dysfunction.

BACKGROUND: G protein-coupled receptors (GPCRs) regulate the pathological and physiological functions of the heart. GPCR antagonists are widely used in the treatment of chronic heart failure. Despite therapeutic advances in the treatments for cardiovascular diseases, heart failure is a major clinical health problem, with significant mortality and morbidity. Corticotropin releasing hormone receptor 2 (CRHR2) is highly expressed in cardiomyocytes, and cardiomyocyte-specific deletion of the genes encoding CRHR2 suppresses pressure overload-induced cardiac dysfunction. This suggests that the negative modulation of CRHR2 may prevent the progression of heart failure. However, there are no systemic drugs against CRHR2. FINDINGS: We developed a novel, oral, small molecule antagonist of CRHR2, RQ-00490721, to investigate the inhibition of CRHR2 as a potential therapeutic approach for the treatment of heart failure. In vitro, RQ-00490721 decreased CRHR2 agonist-induced 3', 5'-cyclic adenosine monophosphate (cAMP) production. In vivo, RQ-00490721 showed sufficient oral absorption and better distribution to peripheral organs than to the central nervous system. Oral administration of RQ-00490721 inhibited the CRHR2 agonist-induced phosphorylation of cAMP-response element binding protein (CREB) in the heart, which regulates a transcription activator involved in heart failure. RQ-00490721 administration was not found to affect basal heart function in mice but protected them from pressure overload-induced cardiac dysfunction. INTERPRETATION: Our results suggest that RQ-00490721 is a promising agent for use in the treatment of chronic heart failure.

Isolated bilateral external iliac artery dissections with emotional stress.

We present a patient with isolated bilateral external iliac artery dissections associated with emotional stress. The diagnosis should be kept in mind in young, fit patients presenting lower back pain occurring subsequent to emotional stress.

Secondary Cardiac Lymphoma Presenting as Sick Sinus Syndrome and Atrial Fibrillation Which Required Leadless Pacemaker Implantation.

Cardiac involvement of malignant lymphoma is relatively common, although such a phenomenon has subclinical manifestations that are difficult to detect. We herein describe a patient with atrial fibrillation and sick sinus syndrome as the main symptoms. Computed tomography showed a mass in the right atrium extending into the superior vena cava (SVC). We implanted the patient with a leadless pacemaker. Transvenous biopsy revealed a diffuse large B-cell lymphoma. The patient was treated successfully with chemotherapy including rituximab. This case suggested that cardiac lymphoma may cause sick sinus syndrome, and leadless pacemaker implantation is a safe treatment option in patients with partial SVC obstruction.

Comparison of Anti-factor Xa Activity Among Three Different Factor Xa Inhibitors in Non-valvular Atrial Fibrillation Patients with Renal Impairment.

BACKGROUND: Factor-Xa inhibitors (FXaIs) are widely used for the treatment of non-valvular atrial fibrillation (NVAF). Although we have previously reported the distribution of the anti-factor Xa activity (AXA) values of three different FXaIs in NVAF patients, the differences in the distribution of AXA values among the different FXaIs in patients with renal impairment (RI) have not been fully elucidated. METHODS: Trough and peak AXA values were measured in 94 patients taking rivaroxaban, 124 patients taking apixaban, and 66 patients taking edoxaban. Of them, we identified 26 patients with moderate RI [creatinine clearance (CrCl) 30-49 mL/min] and 17 patients with severe RI (CrCl 15-29 mL/min) in the rivaroxaban cohort, 37 patients with moderate RI and 17 patients with severe RI in the apixaban cohort, and 21 patients with moderate RI and 9 patients with severe RI in the edoxaban cohort. AXA values were measured using chromogenic AXA assays. Both trough and peak AXA values were compared between patients with moderate RI and those with severe RI in each cohort, and differences in the peak-to-trough ratio among the different drugs were assessed. RESULTS: In the rivaroxaban cohort, the peak AXA value was significantly higher in patients with severe RI than in those with moderate RI. In the apixaban cohort, neither the trough nor peak AXA values significantly differed between patients with moderate RI and those with severe RI. In the edoxaban cohort, the trough AXA value was significantly higher in patients with severe RI than in those with moderate RI, and peak AXA tended to be higher in patients with severe RI. The peak-to-trough ratio of AXA values was significantly lower in patients taking apixaban than in those taking rivaroxaban and edoxaban. CONCLUSION: Among Japanese NVAF patients with RI, the peak or trough AXA values were higher in patients with severe RI than in those with moderate RI when taking rivaroxaban and edoxaban, whereas both the peak and trough AXA values were similar between patients with severe RI and those with moderate RI when taking apixaban. The peak-to-trough ratio of AXA values was the lowest in patients taking apixaban.

c-Maf expression in angioimmunoblastic T-cell lymphoma.

The oncogene c-Maf was recently found to be overexpressed in approximately 50% of multiple myeloma cases, and a role for c-Maf in promoting cyclin D2 expression has been postulated. We previously examined c-Maf expression in various T-cell lymphomas by reverse-transcription polymerase chain reaction and found extremely elevated c-Maf levels in angioimmunoblastic T-cell lymphoma (AILT). In this study, we examined T-cell lymphomas for c-Maf and cyclin expression immunohistochemically. Of 93 cases of T-cell lymphomas we investigated in the current study, c-Maf expression was seen in 23 out of 31 cases of AILT, 3 out of 11 of adult T-cell leukemia/lymphoma, 4 out of 19 of peripheral T-cell lymphoma, unspecified [PTCL(U)], and 0 out of 11 cases of mycosis fungoides, 0 out of 11 of anaplastic large cell lymphoma, and 1 out of 10 of extranodal NK/T-cell lymphoma, nasal type. Double immunostaining in AILT revealed that the majority of c-Maf-positive cells were also positive for CD43 (MT1), CD45RO (UCHL-1), and CD4 but were negative for CD20 (L26). Additionally, cyclins D1 and D2, which stimulate cell cycle progression, were overexpressed in a large number of the c-Maf-positive AILT samples. Quantitative reverse-transcription polymerase chain reaction analysis also showed that c-Maf was overexpressed in 8/31 cases of AILT, 0/19 cases of PTCL(U), 0/11 cases of anaplastic large cell lymphoma, 0/10 cases of extranodal NK/T-cell lymphoma, nasal type, and 2/8 cases of multiple myeloma, presenting significant difference between AILT and PTCL(U) (P=0.016, chi test). These findings strongly suggest that CD4-positive neoplastic T cells in AILT show c-Maf expression and provide new insight into the pathogenesis of AILT suggesting c-Maf to be a useful diagnostic marker for AILT.

Monitoring of anti-Xa activity and factors related to bleeding events: A study in Japanese patients with nonvalvular atrial fibrillation receiving rivaroxaban.

BACKGROUND: Anti-Xa activity (AXA) in patients with nonvalvular atrial fibrillation (NVAF) and relationship to bleeding events remains unclear. METHODS: We evaluated AXA in 94 patients at both trough and peak rivaroxaban concentrations. Rivaroxaban dosage was determined according to creatinine clearance (CrCl): 10 and 15mg once daily for patients with CrCl 15-49 and CrCl ≥50mL/min, respectively. AXA value distribution and its association with bleeding events were examined in enrolled subjects. RESULTS: The mean peak AXA level was significantly higher than the mean trough level (1.98±0.81 vs. 0.16±0.15IU/mL; p<0.001). The peak AXA level significantly differed among patients with CrCl 15-29, 30-49, 50-79, and ≥80mL/min (2.51±0.83, 1.72±0.76, 2.05±0.82, and 1.66±0.51IU/mL, respectively; p=0.004). Major and non-major clinically relevant bleeding events occurred in 22 patients (23.4% and 14.6% per year, respectively). The mean peak AXA level was significantly higher in patients who experienced bleeding events than in those who did not (2.40±0.70 vs. 1.84±0.80IU/mL; p=0.001). A Cox multivariate analysis showed that the peak AXA level was independently related to the incidence of major and non-major clinically relevant bleeding events (p=0.012). Cumulative bleeding rates were significantly higher in patients with high peak AXA levels (p<0.001). CONCLUSION: Peak AXA level was an independent predictor for bleeding events in Japanese NVAF patients receiving rivaroxaban.

Corticotropin releasing hormone receptor 2 exacerbates chronic cardiac dysfunction.

Heart failure occurs when the heart is unable to effectively pump blood and maintain tissue perfusion. Despite numerous therapeutic advancements over previous decades, the prognosis of patients with chronic heart failure remains poor, emphasizing the need to identify additional pathophysiological factors. Here, we show that corticotropin releasing hormone receptor 2 (Crhr2) is a G protein-coupled receptor highly expressed in cardiomyocytes and continuous infusion of the Crhr2 agonist, urocortin 2 (Ucn2), reduced left ventricular ejection fraction in mice. Moreover, plasma Ucn2 levels were 7.5-fold higher in patients with heart failure compared to those in healthy controls. Additionally, cardiomyocyte-specific deletion of Crhr2 protected mice from pressure overload-induced cardiac dysfunction. Mice treated with a Crhr2 antagonist lost maladaptive 3'-5'-cyclic adenosine monophosphate (cAMP)-dependent signaling and did not develop heart failure in response to overload. Collectively, our results indicate that constitutive Crhr2 activation causes cardiac dysfunction and suggests that Crhr2 blockade is a promising therapeutic strategy for patients with chronic heart failure.