MRP1-Dependent Extracellular Release of Glutathione Induces Cardiomyocyte Ferroptosis After Ischemia-Reperfusion.

BACKGROUND: The membrane components of cardiomyocytes are rich in polyunsaturated fatty acids, which are easily oxidized. Thus, an efficient glutathione-based lipid redox system is essential for maintaining cellular functions. However, the relationship between disruption of the redox system during ischemia-reperfusion (IR), oxidized lipid production, and consequent cell death (ferroptosis) remains unclear. We investigated the mechanisms underlying the disruption of the glutathione-mediated reduction system related to ferroptosis during IR and developed intervention strategies to suppress ferroptosis. METHODS: In vivo fluctuations of both intra- and extracellular metabolite levels during IR were explored via microdialysis and tissue metabolome analysis. Oxidized phosphatidylcholines were assessed using liquid chromatography high-resolution mass spectrometry. The areas at risk following IR were assessed using triphenyl-tetrazolium chloride/Evans blue stain. RESULTS: Metabolomic analysis combined with microdialysis revealed a significant release of glutathione from the ischemic region into extracellular spaces during ischemia and after reperfusion. The release of glutathione into extracellular spaces and a concomitant decrease in intracellular glutathione concentrations were also observed during anoxia-reperfusion in an in vitro cardiomyocyte model. This extracellular glutathione release was prevented by chemical inhibition or genetic suppression of glutathione transporters, mainly MRP1 (multidrug resistance protein 1). Treatment with MRP1 inhibitor reduced the intracellular reactive oxygen species levels and lipid peroxidation, thereby inhibiting cell death. Subsequent in vivo evaluation of endogenously oxidized phospholipids following IR demonstrated the involvement of ferroptosis, as levels of multiple oxidized phosphatidylcholines were significantly elevated in the ischemic region 12 hours after reperfusion. Inhibition of the MRP1 transporter also alleviated intracellular glutathione depletion in vivo and significantly reduced the generation of oxidized phosphatidylcholines. Administration of MRP1 inhibitors significantly attenuated infarct size after IR injury. CONCLUSIONS: Glutathione was released continuously during IR, primarily in an MRP1-dependent manner, and induced ferroptosis. Suppression of glutathione release attenuated ferroptosis and reduced myocardial infarct size following IR.

Predictors of Improvement in Exercise Tolerance After Balloon Pulmonary Angioplasty for Chronic Thromboembolic Pulmonary Hypertension.

Background Balloon pulmonary angioplasty (BPA) improves exercise tolerance and hemodynamic parameters in patients with chronic thromboembolic pulmonary hypertension. However, it is still unclear which patient characteristics contribute to the improvement in exercise tolerance after BPA in chronic thromboembolic pulmonary hypertension. Methods and Results We retrospectively analyzed 126 patients with chronic thromboembolic pulmonary hypertension (aged 63±14 years; female, 65%) who underwent BPA without concomitant programmed exercise rehabilitation at Keio University between November 2012 and April 2018. Hemodynamic data and 6-minute walk distance (6MWD), as a measure of exercise tolerance, were evaluated before and 1 year after BPA. The clinical characteristics that contributed to improvement in exercise tolerance were elucidated. The 6MWD significantly increased from 372.0 m (256.5-431.3) to 462.0 m (378.8-537.0) 1 year after BPA (P<0.001). The improvement rate in the 6MWD after BPA exhibited a good correlation with age, height, mean pulmonary artery pressure, and 6MWD at baseline (Spearman rank correlation coefficients=-0.28, 0.24, -0.40, and 0.44, respectively). Additional multivariable linear regression analysis revealed that young age, tall height, high mean pulmonary artery pressure, short 6MWD at baseline, and high lung capacity at baseline were significant predictors of the improvement in 6MWD by BPA (standardized partial regression coefficient -0.39, 0.22, 0.19, -0.62, and 0.25, P<0.001, 0.007, 0.011, <0.001, and <0.001, respectively). Conclusions BPA without concomitant programmed exercise rehabilitation significantly improves exercise tolerance. This was particularly true in young patients with high stature, high mean pulmonary artery pressure, short 6MWD, and lung capacity at the time of diagnosis.

Estimation of maximal lactate steady state using the sweat lactate sensor.

A simple, non-invasive algorithm for maximal lactate steady state (MLSS) assessment has not been developed. We examined whether MLSS can be estimated from the sweat lactate threshold (sLT) using a novel sweat lactate sensor for healthy adults, with consideration of their exercise habits. Fifteen adults representing diverse fitness levels were recruited. Participants with/without exercise habits were defined as trained/untrained, respectively. Constant-load testing for 30 min at 110%, 115%, 120%, and 125% of sLT intensity was performed to determine MLSS. The tissue oxygenation index (TOI) of the thigh was also monitored. MLSS was not fully estimated from sLT, with 110%, 115%, 120%, and 125% of sLT in one, four, three, and seven participants, respectively. The MLSS based on sLT was higher in the trained group as compared to the untrained group. A total of 80% of trained participants had an MLSS of 120% or higher, while 75% of untrained participants had an MLSS of 115% or lower based on sLT. Furthermore, compared to untrained participants, trained participants continued constant-load exercise even if their TOI decreased below the resting baseline (P < 0.01). MLSS was successfully estimated using sLT, with 120% or more in trained participants and 115% or less in untrained participants. This suggests that trained individuals can continue exercising despite decreases in oxygen saturation in lower extremity skeletal muscles.

Anaerobic threshold using sweat lactate sensor under hypoxia.

We aimed to investigate the reliability and validity of sweat lactate threshold (sLT) measurement based on the real-time monitoring of the transition in sweat lactate levels (sLA) under hypoxic exercise. In this cross-sectional study, 20 healthy participants who underwent exercise tests using respiratory gas analysis under hypoxia (fraction of inspired oxygen [FiO2], 15.4 ± 0.8%) in addition to normoxia (FiO2, 20.9%) were included; we simultaneously monitored sLA transition using a wearable lactate sensor. The initial significant elevation in sLA over the baseline was defined as sLT. Under hypoxia, real-time dynamic changes in sLA were successfully visualized, including a rapid, continual rise until volitionary exhaustion and a progressive reduction in the recovery phase. High intra- and inter-evaluator reliability was demonstrated for sLT's repeat determinations (0.782 [0.607-0.898] and 0.933 [0.841-0.973]) as intraclass correlation coefficients [95% confidence interval]. sLT correlated with ventilatory threshold (VT) (r = 0.70, p < 0.01). A strong agreement was found in the Bland-Altman plot (mean difference/mean average time: - 15.5/550.8 s) under hypoxia. Our wearable device enabled continuous and real-time lactate assessment in sweat under hypoxic conditions in healthy participants with high reliability and validity, providing additional information to detect anaerobic thresholds in hypoxic conditions.

Clinical usefulness of additional treatment with ezetimibe in patients with coronary artery disease on statin therapy. - From the viewpoint of cholesterol metabolism.-.

BACKGROUND: Ezetimibe-plus-statin therapy has been reported to provide greater reduction in low-density lipoprotein cholesterol (LDL-C) level than statin monotherapy. The aim of the present study was to evaluate the relationship between LDL-C lowering effect and baseline cholesterol absorption and synthesis markers in patients with coronary artery disease (CAD). METHODS AND RESULTS: A total of 171 patients with CAD whose LDL-C level was ≥ 100 mg/dl after treatment with atorvastatin (10mg/day) or rosuvastatin (2.5 mg/day) for 4 weeks were assigned to additionally receive ezetimibe (10mg/day) plus a statin or a double dose of statin for 12 weeks. The decreases in LDL-C (-30.0 ± 15.6 mg/dl vs. -19.2 ± 14.2 mg/dl) and the ratio of campesterol, an absorption marker, to total cholesterol levels (-1.35 ± 0.90 µg/mg vs. 0.33 ± 0.74 µg/mg) were greater in the ezetimibe-plus-statin group (P<0.05, respectively). The decrease in LDL-C level in the ezetimibe-plus-statin group was greatest in patients with baseline levels of higher absorption and lower synthesis markers and smallest in patients with baseline levels of lower absorption and higher synthesis markers (-34.3 ± 15.6 mg/dl vs. -21.5 ± 16.7 mg/dl, P<0.05). The decrease in LDL-C did not differ, irrespective of baseline levels of cholesterol absorption and synthesis markers, in the double-dose statin group, and was similar to that in patients with lower absorption and higher synthesis markers in the ezetimibe-plus-statin group. CONCLUSIONS: Ezetimibe-plus-statin therapy may be useful for lowering LDL-C level, irrespective of baseline levels of cholesterol absorption and synthesis markers.

Long-term effects of ezetimibe-plus-statin therapy on low-density lipoprotein cholesterol levels as compared with double-dose statin therapy in patients with coronary artery disease.

OBJECTIVE: To assess the mechanism of long-term LDL-C-lowering effect of ezetimibe-plus-statin. METHODS: Coronary artery disease patients whose LDL-C ≥ 70 mg/dL after treatment with atorvastatin 10 mg/day or rosuvastatin 2.5 mg/day were randomly assigned to receive ezetimibe 10 mg/day + statin (n = 78) or double-dose statin (n = 72) for 52 weeks. RESULTS: Greater LDL-C reduction was observed and maintained until 52 weeks in ezetimibe-plus-statin, while LDL-C levels re-increased after 12 weeks in double-dose statin. Although lathosterol/TC increased, campesterol/TC decreased more in ezetimibe-plus-statin. In contrast, lathosterol/TC unchanged and campesterol/TC increased, increasing campesterol/lathosterol ratio for 52 weeks in double-dose statin. Plasma PCSK9 levels were higher in double-dose statin than in ezetimibe-plus-statin at 12 weeks, but similar at 52 weeks. CONCLUSION: Although the difference in PCSK9 between 2 groups was transient, that in both campesterol and lathosterol persisted until 52 weeks. These results demonstrated simultaneous inhibition of cholesterol absorption and synthesis provides stable and greater decrease in LDL-C levels.

Current status of emergency care for ST-elevation myocardial infarction in an urban setting in Japan.

BACKGROUND: The door-to-balloon time (DTB) is an important predictor of the outcome for patients with ST-elevation myocardial infarction (STEMI). In Japan, percutaneous coronary intervention (PCI) can be performed at many hospitals, and the predominant strategy for reperfusion therapy is primary PCI. However, it remains unclear how rapidly reperfusion is achieved at these hospitals. METHODS AND RESULTS: The study group comprised 369 patients with STEMI who presented within 12 h of symptom onset to a tertiary emergency center (TEC) or at 11 community hospitals (CHs) in 2006 and underwent emergency coronary angiography. Median DTB was shorter in the TEC (63 vs 104 min, P<0.001), and the rate of DTB within 90 min was higher in the TEC (96% vs 39%, P<0.001). Lateral myocardial infarction, presentation during off-hours, and non-cardiologist as the first-contact physician were significantly associated with a prolonged DTB in CHs. There was a trend toward lower 30-day mortality from all causes in the TEC (2.0% vs 4.8%, P=0.08). Multiple logistic regression analysis demonstrated that prolonged DTB (>90 min) was an independent predictor of 30-day mortality (odds ratio 12.6; 95% confidence interval 1.85-86.2, P=0.01). CONCLUSIONS: Establishment of emergency cardiac care systems with the goal of DTB within 90 min is required in PCI-capable hospitals to improve clinical outcomes.

Cardiac tamponade due to rupture of coronary artery fistulas with a giant aneurysm containing a free floating ball thrombus: a case report.

A 76-year-old woman was admitted to our hospital with cardiac tamponade. Chest computed tomography revealed a large tumor adjacent to the pulmonary artery, the center of which was demonstrated as a high density area without contrast medium. Coronary angiography revealed a large aneurysm consisting of coronary artery fistulas. An afferent vessel connected tangentially to the surface of the aneurysm, so blood flowed around along the inner wall of the aneurysm. A filling defect was demonstrated in the center of the aneurysm that indicated a thrombus. The cause of cardiac tamponade was seemed to be bleeding of the coronary artery fistulas. Coil embolization was performed, but recanalization occurred. Therefore, ligature of the fistulas and aneurismal resection were performed using a cardiopulmonary bypass. A fresh floating thrombus was found in the aneurysm.