A threshold effect of COVID-19 risk on oil price returns.

Using U.S. data, we investigate how the COVID-19 pandemic influences oil price returns in an asset pricing framework. Unlike earlier studies, we consider a threshold model to allow for the possibility that COVID-19 risk may not play a role until it reaches a certain level. Based on WTI crude oil spot price data from January 2020 to December 2021, our findings show that oil returns significantly decline with the daily number of COVID-19 deaths but only if the daily death toll exceeds approximately 2100. In addition, a more severe COVID-19 pandemic can substantially increase the exposure of oil returns to various systematic risk factors, which has not been documented in previous literature.

Fibroblast inward-rectifier potassium current upregulation in profibrillatory atrial remodeling.

RATIONALE: Fibroblasts are involved in cardiac arrhythmogenesis and contribute to the atrial fibrillation substrate in congestive heart failure (CHF) by generating tissue fibrosis. Fibroblasts display robust ion currents, but their functional importance is poorly understood. OBJECTIVE: To characterize atrial fibroblast inward-rectifier K(+) current (IK1) remodeling in CHF and its effects on fibroblast properties. METHODS AND RESULTS: Freshly isolated left atrial fibroblasts were obtained from controls and dogs with CHF (ventricular tachypacing). Patch clamp was used to record resting membrane potential (RMP) and IK1. RMP was significantly increased by CHF (from -43.2±0.8 mV, control, to -55.5±0.9 mV). CHF upregulated IK1 (eg, at -90 mV from -1.1±0.2 to -2.7±0.5 pA/pF) and increased the expression of KCNJ2 mRNA (by 52%) and protein (by 80%). Ba(2+) (300 µmol/L) decreased the RMP and suppressed the RMP difference between controls and dogs with CHF. Store-operated Ca(2+) entry (Fura-2-acetoxymethyl ester) and fibroblast proliferation (flow cytometry) were enhanced by CHF. Lentivirus-mediated overexpression of KCNJ2 enhanced IK1 and hyperpolarized fibroblasts. Functional KCNJ2 suppression by lentivirus-mediated expression of a dominant negative KCNJ2 construct suppressed IK1 and depolarized RMP. Overexpression of KCNJ2 increased Ca(2+) entry and fibroblast proliferation, whereas the dominant negative KCNJ2 construct had opposite effects. Fibroblast hyperpolarization to mimic CHF effects on RMP enhanced the Ca(2+) entry. MicroRNA-26a, which targets KCNJ2, was downregulated in CHF fibroblasts. Knockdown of endogenous microRNA-26 to mimic CHF effects unregulated IK1. CONCLUSIONS: CHF upregulates fibroblast KCNJ2 expression and currents, thereby hyperpolarizing RMP, increasing Ca(2+) entry, and enhancing atrial fibroblast proliferation. These effects are likely mediated by microRNA-26a downregulation. Remodeling-induced fibroblast KCNJ2 expression changes may play a role in atrial fibrillation promoting fibroblast remodeling and structural/arrhythmic consequences.

Novel germline GJA5/connexin40 mutations associated with lone atrial fibrillation impair gap junctional intercellular communication.

Atrial fibrillation (AF) is the most common form of sustained cardiac arrhythmia worldwide. Here, we investigate the molecular and cellular mechanisms of lone AF-linked germline mutations in the connexin40 (Cx40) gene, GJA5. The entire coding region of GJA5 was sequenced in 68 unrelated patients with lone AF. A novel germline heterozygous missense mutation in Cx40 (p.I75F) was identified in one index patient. The mutation was also present in the proband's father with lone AF but was not found in the unaffected family members who were examined and 200 unrelated healthy control individuals. Electrophysiological studies revealed no electrical coupling of the cell pairs expressing the mutant alone and a significant reduction in gap junction coupling conductance when the mutant was coexpressed with wild-type (wt) Cx40 or Cx43. Interestingly, another lone AF-linked Cx40 mutant p.L229M did not show any apparent coupling defect when expressed alone or together with wt Cx40 but specifically reduced the gap junction coupling when coexpressed with wt Cx43. This study is the first to demonstrate that the germline familial mutations in Cx40 impair the gap junctions through different mechanisms, which may predispose the mutant carriers to AF.

Heterotypic connexin50/connexin50 mutant gap junction channels reveal interactions between two hemichannels during transjunctional voltage-dependent gating.

To investigate transjunctional voltage (Vj)-dependent gating mechanisms of connexin50 (Cx50) gap junction (GJ) channels and to elucidate the relative contribution of each hemichannel of a heterotypic GJ channel to Vj-dependent gating, we performed dual voltage-clamp recordings on heterotypic GJ channels formed by Cx50 and a mutant, Cx50N9R or a chimera, Cx50-Cx36N. Our results provide evidence that the two component hemichannels interact with each other during Vj-dependent gating. Cx50/Cx50N9R heterotypic GJ channels exhibited asymmetrical Vj-dependent gating which cannot be ascribed to the function of an individual hemichannel for a certain polarity of voltage; instead it can only be ascribed to the combined effects of both hemichannels. Single GJ channel open dwell-time analyses showed that homotypic Cx50 channels adopted short-lived and long-lived open states. Heterotypic combinations of Cx50/Cx50N9R gave rise to shorter mean dwell-times when Cx50-expressing cells received relatively positive Vj, and longer mean dwell-times when positive Vj was applied at the Cx50N9R side. In contrast, Cx50/Cx50-Cx36N heterotypic channels showed asymmetrical Vj-dependent gating, which appears to be caused by enhanced and reduced Vj-gating sensitivity of Cx50-Cx36N and Cx50 hemichannels, respectively. Unitary conductance of the main open state of both types of heterotypic GJ channel cannot be simply predicted by assuming a Vj redistribution across the two hemichannels arranged in series in heterotypic GJ channels. Our data also reveal reasons for the invisibility of fast Vj-gating transitions from open to substate in homotypic Cx50N9R and Cx50-Cx36N channels.

Orientin-induced cardioprotection against reperfusion is associated with attenuation of mitochondrial permeability transition.

In this study, we provide new evidence that orientin from bamboo leaves (Phyllostachys nigra) protect H9c2 cardiomyocytes against ischemia/reperfusion (I/R) injury through the mitochondrial apoptotic pathway. A previous work has identified that orientin could protect myocardium against ischemia/reperfusion injury. Mitochondria are both critical determinants of cardioprotection and crucial targets of cardioprotective signaling. Their role during reperfusion is conspicuously critical because the conditions promote apoptosis through the mitochondrial pathway and necrosis though irreversible damage to mitochondria, which is in association with mitochondrial permeability transition (MPT). After myocardial ischemia, opening of the mPTP is a critical determinant of cell death. The relationship of orientin and mPTP in mediating reperfusion-induced cardiomyocytes injury is still elusive. Here, our results indicate that the protective effect of orientin in H9c2 cells subjected to I/R injury is associated with depression of the mPTP opening, resultant mitochondrial dysfunction, and apoptosis. Further investigation of cellular mechanisms revealed that these effects were associated with inhibition of reactive oxygen species (ROS) generation, repolarization of mitochondrial membrane potential (Δψ(m)), suppression of mitochondrial cytochrome C release, enhancement of the Bcl-2 level, and inhibition of Bax and Smac/DIABLO levels. Furthermore, these beneficial effects of orientin were blocked by the phosphatidylinositol 3-kinase (PI3K) inhibitor wortmannin, and orientin could enhance Akt phosphorylation. In summary, we demonstrate that orientin protects H9c2 cardiomytocytes against I/R-induced apoptosis by modulating the mPTP opening, and this role of orientin may involve the PI3K/Akt signaling pathway.

Puerarin inhibits acid-sensing ion channels and protects against neuron death induced by acidosis.

Puerarin, the main isoflavone found in the root of the wild leguminous creeper Pueraria lobata (Willd.) Ohwi, is known to protect the brain from ischemia-induced injuries. However, its effect on acidosis, a byproduct of brain ischemia and one factor promoting cell death, remains unknown. The purpose of this study was to investigate the effects of puerarin on acid-sensing ion channels (ASICs), which are reported to be activated by extracellular acidosis. Using the MTT assay and Hoechst/PI staining, we showed that puerarin could prevent hippocampal cell death during extracellular low pH. Data from whole-cell patch clamp recordings demonstrated that puerarin decreased the amplitude of ASIC currents and accelerated the desensitization of ASICs. Puerarin also reduced the amplitude of homomeric ASIC1a channels in CHO cells expressing pECFP-ASIC1a. Collectively, our study demonstrated that puerarin prevented hippocampal cells from acidosis-induced death via ASIC blockage, providing a mechanical insight into the neuroprotective effects of puerarin during brain ischemia.

Clinical Features of Patients Infected with the 2019 Novel Coronavirus (COVID-19) in Shanghai, China.

BACKGROUND: Since mid-December 2019, a cluster of pneumonia-like diseases caused by a novel coronavirus, now designated COVID-19 by the WHO, emerged in Wuhan city and rapidly spread throughout China. Here we identify the clinical characteristics of COVID-19 in a cohort of patients in Shanghai. METHODS: Cases were confirmed by real-time RT-PCR and were analysed for demographic, clinical, laboratory and radiological features. RESULTS: Of 198 patients, the median duration from disease onset to hospital admission was 4 days. The mean age of the patients was 50.1 years, and 51.0% patients were male. The most common symptom was fever. Less than half of the patients presented with respiratory systems including cough, sputum production, itchy or sore throat, shortness of breath, and chest congestion. 5.6% patients had diarrhoea. On admission, T lymphocytes were decreased in 45.8% patients. Ground glass opacity was the most common radiological finding on chest computed tomography. 9.6% were admitted to the ICU because of the development of organ dysfunction. Compared with patients not treated in ICU, patients treated in the ICU were older, had longer waiting time to admission, fever over 38.5o C, dyspnoea, reduced T lymphocytes, elevated neutrophils and organ failure. CONCLUSIONS: In this single centre cohort of COVID-19 patients, the most common symptom was fever, and the most common laboratory abnormality was decreased blood T cell counts. Older age, male, fever over 38.5oC, symptoms of dyspnoea, and underlying comorbidity, were the risk factors most associated with severity of disease. KEY WORDS: 2019 novel coronavirus; acute respiratory infection; risk factors for disease severity.

B-type natriuretic peptide-induced cardioprotection against reperfusion is associated with attenuation of mitochondrial permeability transition.

B-type natriuretic peptide (BNP) is one peptide hormone released in response to myocyte stretch, whose functions play significant roles in health and disease. Its physiologic effects result in improved loading conditions and have led to the development of recombinant BNP as a therapeutic agent for heart failure. Previous work has identified that BNP protect myocardium against reperfusion injury through mitochondrial pathway. Mitochondria are both essential effectors of cardioprotection and primary targets of cardioprotective signaling. Their role during reperfusion is particularly critical because of the conditions that promote both apoptosis by the mitochondrial pathway and necrosis by irreversible damage to mitochondria in association with mitochondrial permeability transition pores (mPTP). After an episode of myocardial ischemia, opening of mPTP, at the onset of reperfusion, is a critical determinant of myocyte death. The relationship of BNP and mPTP in mediating reperfusion-induced cardiomyocytes injury is a novel investigative area. In this study, our results indicated that the beneficial effect of BNP in cultured cardiomyocytes subjected to reperfusion is associated with attenuation of mPTP opening, resultant mitochondrial dysfunction and apoptosis. Further investigation of underlying mechanisms revealed that these were associated with BNP-mediated repolarization of mitochondrial membrane potential (Deltapsi(m)), inhibition of reactive oxygen species (ROS) generation, improvement of Bcl-2 level, and inhibition of Bax and second mitochondria-derived activator of caspases/direct inhibitor of apoptosis protein-binding protein with a low isoelectric point (Smac/DIABLO) levels. In summary, we demonstrate that BNP exerts protective actions within reperfusion by inhibiting mPTP opening and these roles of BNP may involve phosphatidylinositol 3-kinase (PI3K) dependent pathway.

Protective effects of echinacoside, one of the phenylethanoid glycosides, on H(2)O(2)-induced cytotoxicity in PC12 cells.

We have investigated the protective effects of echinacoside (ECH), one of the phenylethanoid glycosides, on H(2)O(2)-induced cytotoxicity in the rat pheochromocytoma cell line (PC12 cells). Our data show that application of ECH to H(2)O(2)-injured PC12 cells (HIPCs) increased cell viability and decreased the apoptotic ratio. Flow cytometry (FCM) and laser scanning confocal microscopy (LSCM) analysis suggested that ECH exerted its inhibitory effects on the formation of reactive oxygen species (ROS) and the accumulation of intracellular free Ca(2+) ([Ca(2+)]i). In addition, ECH elevated the mitochondrial membrane potential (MMP) in HIPCs. Furthermore, Western blot analysis revealed that ECH prevented an H(2)O(2)-induced increase of the Bax/Bcl-2 ratio by down-regulating Bax protein expression and upregulating Bcl-2 protein expression. In summary, ECH showed significant neuroprotective effects on HIPCs through the mitochondrial apoptotic pathway, and could be a potential candidate for intervention in neurodegenerative diseases such as Alzheimer's and Parkinson's disease.

Role for nitric oxide in permeability of hippocampal neuronal hemichannels during oxygen glucose deprivation.

Increased hemichannel opening induced by oxygen glucose deprivation (OGD) was reported in the hippocampal pyramidal neuron. It was suggested that the pannexin1 hemichannel opening could mediate ionic flux dysregulation, anoxic depolarization, and energy-depleting efflux of glucose and ATP for ischemic neurons. However, the regulatory mechanisms of pannexin1 hemichannel opening have been poorly understood. Here we showed that excessive generation of nitric oxide (NO) during ischemia could induce the calcein leakage from neurons, which was markedly reduced by NO synthase inhibitor. The calcein leakage from neurons during OGD was also attenuated by the application of N-ethylmaleimide (NEM), an SH-alkylating agent, and dithiothreitol (DTT), a reducer of oxidized sulfhydryl groups. However, the soluble guanylyl cyclase (sGC) inhibitor had a minor effect on the calcein leakage during OGD. Furthermore, the elevated intracellular but not extracellular levels of glutathione could also inhibit the calcein leakage during OGD. Similar results were observed in metabolic inhibition (MI), which is another ischemic-like condition. Finally, immunocytochemical and immunoblotting analysis revealed that, after 1 hr of OGD stimulation, the distribution and expression of pannexin1 showed no significant difference compared with control. However, the pannexin1 mRNA expression was elevated after 1 hr of OGD and a sustained increase was maintained during reperfusion. These results implied that the reactive oxygen species (ROS), especially NO, might be involved in the enhanced pannexin1 hemichannel opening and that the S-nitrosylation but not the NO/cGMP pathway played a more important role in this event.

Atrial fibrillation-linked germline GJA5/connexin40 mutants showed an increased hemichannel function.

Mutations in GJA5 encoding the gap junction protein connexin40 (Cx40) have been linked to lone atrial fibrillation. Some of these mutants result in impaired gap junction function due to either abnormal connexin localization or impaired gap junction channels, which may play a role in promoting atrial fibrillation. However, the effects of the atrial fibrillation-linked Cx40 mutants on hemichannel function have not been studied. Here we investigated two atrial fibrillation-linked germline Cx40 mutants, V85I and L221I. These two mutants formed putative gap junction plaques at cell-cell interfaces, with similar gap junction coupling conductance as that of wild-type Cx40. Connexin deficient HeLa cells expressing either one of these two mutants displayed prominent propidium iodide-uptake distinct from cells expressing wild-type Cx40 or other atrial fibrillation-linked Cx40 mutants, I75F, L229M, and Q49X. Propidium iodide-uptake was sensitive to [Ca2+]o and the hemichannel blockers, carbenoxolone, flufenamic acid and mefloquine, but was not affected by the pannexin 1 channel blocking agent, probenecid, indicating that uptake is most likely mediated via connexin hemichannels. A gain-of-hemichannel function in these two atrial fibrillation-linked Cx40 mutants may provide a novel mechanism underlying the etiology of atrial fibrillation.

An atrial-fibrillation-linked connexin40 mutant is retained in the endoplasmic reticulum and impairs the function of atrial gap-junction channels.

Connexin40 (Cx40)-containing gap-junction channels are expressed in the atrial myocardium and provide a low-resistance passage for rapid impulse propagation. A germline mutation in the GJA5 gene, which encodes Cx40, resulting in a truncated Cx40 (Q49X) was identified in a large Chinese family with lone (idiopathic) atrial fibrillation (AF). This mutation co-segregated with seven AF probands in an autosomal-dominant way over generations. To test the hypothesis that this Cx40 mutant affects the distribution and function of atrial gap junctions, we studied the Q49X mutant in gap-junction-deficient HeLa and N2A cells. The Q49X mutant, unlike wild-type Cx40, was typically localized in the cytoplasm and failed to form gap-junction plaques at cell-cell interfaces. When the Q49X mutant was co-expressed with Cx40 or Cx43, the mutant substantially reduced the gap-junction plaque formation of Cx40 and Cx43. Electrophysiological studies revealed no electrical coupling of cell pairs expressing the mutant alone and a significant decrease in the coupling conductance when the mutant was co-expressed with Cx40 or Cx43. Further colocalization experiments with the organelle residential proteins indicate that Q49X was retained in the endoplasmic reticulum. These findings provide evidence that the Q49X mutant is capable of impairing gap-junction distribution and function of key atrial connexins, which might play a role in the predisposition to and onset of AF.

Suppression of nitric oxide implicated in the protective effect of echinacoside on H2O2-induced PC12 cell injury.

We investigated whether suppression of nitric oxide (NO) implicated in the protective effect of echinacoside (ECH), a phenylethanoid glycoside, on H2O2-induced injury to the rat pheochromocytoma cell line (PC12 cells). Data show that application of ECH to H2O2-injured PC12 cells (HIPCs) increased cell viability and decreased the necrotic ratio. Laser scanning confocal microscopic (LSCM) analysis suggested that ECH exerted an inhibitory effect on the formation of NO. In addition, RT-PCR analysis revealed that ECH down-regulated p65 and iNOS mRNA expressions in HIPCs. In summary, suppression of NO is related to the protective effect of ECH on HIPCs.

B-type natriuretic peptide protects cardiomyocytes at reperfusion via mitochondrial calcium uniporter.

B-type natriuretic peptide (BNP) is a regulatory autacoid in the mammalian myocardium, whose functions play significant roles in health and disease. Previous work has identified that BNP protect myocardium through mitochondrial pathway-dependent mechanism against ischemia-reperfusion (I/R) injury. Mitochondria are both essential effectors of cardioprotection and primary targets of cardioprotective signaling. In particular, mitochondrial channel are activated to act as the major determinants of cell life and death. Since the discovery of mitochondrial calcium uniporter (MCU), MCU has been its contribution to cardiomyocytes under specific physiological or pathological conditions. The role of mitochondria and MCU, in mediating reperfusion-induced heart injury is a novel investigative area. In addition, the relationship of BNP with MCU in cardiomyocytes undergoing reperfuison is unclear. In this study, we used cultured neonatal rat cardiomyocytes to investigate the effect of BNP on MCU during reperfusion, the well-characterized pathological process of heart diseases. Our results demonstrated that treatment with BNP protected cardiomyocytes from apoptosis against I/R injury. Further investigation of underlying mechanisms revealed that BNP could partly prevent opening of mitochondrial calcium uniporter during I/R. And these mechanisms were associated with BNP-attenuated dissipation of mitochondrial membrane potential (Deltapsi(m)), generation of reactive oxygen species (ROS). BNP also increased the level of anti-apoptotic Bcl-2 protein, decreased the expressions of pro-apoptotic Bax and Smac/DIABLO. In summary, we demonstrated that BNP exerts protective functions within reperfusion by blocking mitochondrial calcium uniporter. Our findings also suggested that phosphatidylinositol 3-kinase (PI3K) dependent pathway may be involved in the actions of BNP.

Manganese-induced apoptosis in rat myocytes.

Manganese can be toxic to the heart, causing dysfunction following long exposure. In our experiments, we examined the cytotoxicity of manganese in neonatal rat ventricular myocytes (NRVM) by MTT assays in vitro. Results showed that after incubation in the different concentrations of manganese for 24 h, apparent cytotoxicity was observed. At 500, 1000, and 1500 2 microM of manganese, the percentage of cell viability dropped to 82% +/- 6.13, 78% +/- 5.28, and 66% +/- 4.22, respectively. When cells were treated for 48 h, all concentrations tested exerted toxic effect; especially from 500 to 1500 microM the cell viability dropped from 67% +/- 4.84 to 37% +/- 3.25. Apoptosis in NRVM was then examined by flow cytometry. Results showed that the percentage of apoptotic cells treated with 500 microM of manganese for 24 h increased from 4% +/- 0.84 to 7% +/- 1.16. After 48 h of incubation, this percentage increased to 11% +/- 0.91. There was no significant difference between control groups (0 microM manganese) after 24 and 48 h incubation. The morphological changes of NRVM nuclei were visualized with the fluorescent DNA-binding dye Hoechst33342 after incubation in 500 microM of manganese for 48 h. Compared with normal nuclei, apoptotic nuclei showed the typical features of fragmentation and condensation. To investigate whether there are any apoptotic gene expression changes during apoptosis, we examined the expression level of Bcl-2, Bax, and P53 mRNAs after treatment with 500 microM of manganese for 48 h. The Bcl-2 mRNA expression decreased while the expression of Bax as well as P53 mRNAs increased. These results suggested that manganese cytotoxicity on NRVM could induce apoptosis in NRVM cells. The apoptosis process might involve, and be promoted by, the changes of the expression levels of P53, Bcl-2, and Bax proteins.