A pilot study on right ventricular longitudinal strain as a predictor of outcome in COVID-19 patients with evidence of cardiac involvement.

AIMS: The aim of this investigation was to evaluate echocardiographic parameters of cardiac function and in particular right ventricular (RV) function as a predictor of mortality in patients with coronavirus disease-2019 (COVID-19) pneumonia. METHODS AND RESULTS: This prospective observational study included 35 patients admitted to a UK district general hospital with COVID-19 and evidence of cardiac involvement, that is, raised Troponin I levels or clinical evidence of heart failure during the first wave of the COVID-19 pandemic (March-May 2020). All patients underwent echocardiography including speckle tracking for right ventricular longitudinal strain (RVLS) providing image quality was sufficient (30 out of 35 patients). Upon comparison of patients who survived COVID-19 with non-survivors, survivors had significantly smaller RVs (basal RV diameter 38.2 vs 43.5 mm P = .0295) with significantly better RV function (Tricuspid annular plane systolic excursion (TAPSE): 17.5 vs 15.3 mm P = .049; average RVLS: 24.3% vs 15.6%; P = .0018). Tricuspid regurgitation (TR) maximal velocity was higher in survivors (2.75 m/s vs 2.11 m/s; P = .0045) indicating that pressure overload was not the predominant driver of this effect and there was no significant difference in left ventricular (LV) ejection fraction. Kaplan-Meier and log-rank analysis of patients split into groups according to average RVLS above or below 20% revealed significantly increased 30-day mortality in patients with average RVLS under 20% (HR: 3.189; 95% CI: 1.297-12.91; P = .0195). CONCLUSION: This study confirms that RVLS is a potent and independent predictor of outcome in COVID-19 patients with evidence of cardiac involvement.

Foxp3+ T reg cells control psoriasiform inflammation by restraining an IFN-I-driven CD8+ T cell response.

Psoriasis is a complex inflammatory skin disease affecting ∼3% of the population worldwide. Although type I interferons (IFN-I) are thought to be involved in its pathogenesis, the details of this relationship remain elusive. Here we show that in a murine model of imiquimod-driven psoriatic skin inflammation, Foxp3+ regulatory T cells (T reg cells) control inflammation severity by restraining IFN-I. Depletion of T reg cells induces IFN-I and IFN-stimulated gene expression, and leads to accumulation of CD8+ T cells in lesional skin. Mononuclear phagocytes (MNPs) were the source of IFN-I, and their depletion reversed the effect of T reg cell depletion. Blockade of IFN-I signaling abolished CD8+ T cell infiltration and excess inflammation in the skin of T reg cell-depleted mice. Depletion of CD8+ T cells attenuated pathology, confirming their role as critical effector cells downstream of IFN-I. Our results describe an unexpected role for T reg cells in restraint of an MNP-IFN-I-driven CD8+ T cell response during psoriasiform skin inflammation. These findings highlight a pathway with potential relevance for the treatment of early-stage disease.

Mammalian γ2 AMPK regulates intrinsic heart rate.

AMPK is a conserved serine/threonine kinase whose activity maintains cellular energy homeostasis. Eukaryotic AMPK exists as αßγ complexes, whose regulatory γ subunit confers energy sensor function by binding adenine nucleotides. Humans bearing activating mutations in the γ2 subunit exhibit a phenotype including unexplained slowing of heart rate (bradycardia). Here, we show that γ2 AMPK activation downregulates fundamental sinoatrial cell pacemaker mechanisms to lower heart rate, including sarcolemmal hyperpolarization-activated current (I f) and ryanodine receptor-derived diastolic local subsarcolemmal Ca2+ release. In contrast, loss of γ2 AMPK induces a reciprocal phenotype of increased heart rate, and prevents the adaptive intrinsic bradycardia of endurance training. Our results reveal that in mammals, for which heart rate is a key determinant of cardiac energy demand, AMPK functions in an organ-specific manner to maintain cardiac energy homeostasis and determines cardiac physiological adaptation to exercise by modulating intrinsic sinoatrial cell behavior.

Mutation of Fnip1 is associated with B-cell deficiency, cardiomyopathy, and elevated AMPK activity.

Folliculin (FLCN) is a tumor-suppressor protein mutated in the Birt-Hogg-Dubé (BHD) syndrome, which associates with two paralogous proteins, folliculin-interacting protein (FNIP)1 and FNIP2, forming a complex that interacts with the AMP-activated protein kinase (AMPK). Although it is clear that this complex influences AMPK and other metabolic regulators, reports of its effects have been inconsistent. To address this issue, we created a recessive loss-of-function variant of Fnip1 Homozygous FNIP1 deficiency resulted in profound B-cell deficiency, partially restored by overexpression of the antiapoptotic protein BCL2, whereas heterozygous deficiency caused a loss of marginal zone B cells. FNIP1-deficient mice developed cardiomyopathy characterized by left ventricular hypertrophy and glycogen accumulation, with close parallels to mice and humans bearing gain-of-function mutations in the γ2 subunit of AMPK. Concordantly, γ2-specific AMPK activity was elevated in neonatal FNIP1-deficient myocardium, whereas AMPK-dependent unc-51-like autophagy activating kinase 1 (ULK1) phosphorylation and autophagy were increased in FNIP1-deficient B-cell progenitors. These data support a role for FNIP1 as a negative regulator of AMPK.

Chronic Activation of γ2 AMPK Induces Obesity and Reduces ß Cell Function.

Despite significant advances in our understanding of the biology determining systemic energy homeostasis, the treatment of obesity remains a medical challenge. Activation of AMP-activated protein kinase (AMPK) has been proposed as an attractive strategy for the treatment of obesity and its complications. AMPK is a conserved, ubiquitously expressed, heterotrimeric serine/threonine kinase whose short-term activation has multiple beneficial metabolic effects. Whether these translate into long-term benefits for obesity and its complications is unknown. Here, we observe that mice with chronic AMPK activation, resulting from mutation of the AMPK γ2 subunit, exhibit ghrelin signaling-dependent hyperphagia, obesity, and impaired pancreatic islet insulin secretion. Humans bearing the homologous mutation manifest a congruent phenotype. Our studies highlight that long-term AMPK activation throughout all tissues can have adverse metabolic consequences, with implications for pharmacological strategies seeking to chronically activate AMPK systemically to treat metabolic disease.

Resistance of Dynamin-related Protein 1 Oligomers to Disassembly Impairs Mitophagy, Resulting in Myocardial Inflammation and Heart Failure.

We have reported previously that a missense mutation in the mitochondrial fission gene Dynamin-related protein 1 (Drp1) underlies the Python mouse model of monogenic dilated cardiomyopathy. The aim of this study was to investigate the consequences of the C452F mutation on Drp1 protein function and to define the cellular sequelae leading to heart failure in the Python monogenic dilated cardiomyopathy model. We found that the C452F mutation increased Drp1 GTPase activity. The mutation also conferred resistance to oligomer disassembly by guanine nucleotides and high ionic strength solutions. In a mouse embryonic fibroblast model, Drp1 C452F cells exhibited abnormal mitochondrial morphology and defective mitophagy. Mitochondria in C452F mouse embryonic fibroblasts were depolarized and had reduced calcium uptake with impaired ATP production by oxidative phosphorylation. In the Python heart, we found a corresponding progressive decline in oxidative phosphorylation with age and activation of sterile inflammation. As a corollary, enhancing autophagy by exposure to a prolonged low-protein diet improved cardiac function in Python mice. In conclusion, failure of Drp1 disassembly impairs mitophagy, leading to a downstream cascade of mitochondrial depolarization, aberrant calcium handling, impaired ATP synthesis, and activation of sterile myocardial inflammation, resulting in heart failure.

Changes in the cardiac metabolome caused by perhexiline treatment in a mouse model of hypertrophic cardiomyopathy.

Energy depletion has been highlighted as an important contributor to the pathology of hypertrophic cardiomyopathy (HCM), a common inherited cardiac disease. Pharmacological reversal of energy depletion appears an attractive approach and the use of perhexiline has been proposed as it is thought to shift myocardial metabolism from fatty acid to glucose utilisation, increasing ATP production and myocardial efficiency. We used the Mybpc3-targeted knock-in mouse model of HCM to investigate changes in the cardiac metabolome following perhexiline treatment. Echocardiography indicated that perhexiline induced partial improvement of some, but not all hypertrophic parameters after six weeks. Non-targeted metabolomics, applying ultra-high performance liquid chromatography-mass spectrometry, described a phenotypic modification of the cardiac metabolome with 272 unique metabolites showing a statistically significant change (p < 0.05). Changes in fatty acids and acyl carnitines indicate altered fatty acid transport into mitochondria, implying reduction in fatty acid beta-oxidation. Increased glucose utilisation is indirectly implied through changes in the glycolytic, glycerol, pentose phosphate, tricarboxylic acid and pantothenate pathways. Depleted reduced glutathione and increased production of NADPH suggest reduction in oxidative stress. These data delineate the metabolic changes occurring during improvement of the HCM phenotype and indicate the requirements for further targeted interventions.

Repeat percutaneous coronary revascularization: indications and outcomes in a "real world" cohort.

OBJECTIVES: To investigate rates of and reasons for second and subsequent stent procedures in an unselected, "real-world" population. BACKGROUND: Repeat stenting is the primary difference reported in clinical trials of alternative revascularization strategies. The incidence, indication, and outcome for repeat stenting in contemporary practice outside the more selective populations of trials and registries has not been described. METHOD: All patients undergoing a first percutaneous coronary intervention (PCI) procedure with stenting from January 2001 to August 2009 (10,509) from a large UK tertiary referral and district general hospital were identified. Mortality and the incidence, timing, and indication for repeat revascularization in this population were investigated from patient records. RESULTS: Of 10,509 patients undergoing a first PCI and stent implant 23.5% underwent repeat angiography of which 11.2% required repeat PCI and 2% coronary artery bypass grafting (median follow-up of 3.8 years). A total of 1.3% went on to a third PCI. The commonest indication for repeat stenting was disease progression remote from the original stent (46%) and planned staged PCI (23%); 21% had a stent-related indication. Functional assessment before repeat stenting was used in one-third of stable patients. Mortality was 2.5% per annum. CONCLUSIONS: In contemporary practice, patients undergoing a first stenting procedure have a low subsequent mortality, and the substantial majority (86.4%) requires no further revascularization over a median 3.8 year follow-up. For those who do require repeat stenting, this is most commonly at a site remote from the first stent.

Signal integration and coincidence detection in the mitogen-activated protein kinase/extracellular signal-regulated kinase (ERK) cascade: concomitant activation of receptor tyrosine kinases and of LRP-1 leads to sustained ERK phosphorylation via down-regulation of dual specificity phosphatases (DUSP1 and -6).

Diverse stimuli can feed into the MAPK/ERK cascade; this includes receptor tyrosine kinases, G protein-coupled receptors, integrins, and scavenger receptors (LDL receptor-related protein (LRP)). Here, we investigated the consequence of concomitant occupancy of the receptor tyrosine kinases (by EGF, basic FGF, VEGF, etc.) and of LRP family members (by LDL or lactoferrin). The simultaneous stimulation of a receptor tyrosine kinase by its cognate ligand and of LRP-1 (by lactoferrin or LDL) resulted in sustained activation of ERK, which was redirected to the cytoplasm. Accordingly, elevated levels of active cytosolic ERK were translated into accelerated adhesion to vitronectin. The sustained ERK response was seen in several cell types, but it was absent in cells deficient in LRP-1 (but not in cells lacking the LDL receptor). This response was also contingent on the presence of urokinase (uPA) and its receptor (uPAR), because it was absent in uPA(-/-) and uPAR(-/-) fibroblasts. Combined stimulation of the EGF receptor and of LRP-1 delayed nuclear accumulation of phosphorylated ERK. This shift in favor of cytosolic accumulation of phospho-ERK was accounted for by enhanced proteasomal degradation of dual specificity phosphatases DUSP1 and DUSP6, which precluded dephosphorylation of cytosolic ERK. These observations demonstrate that the ERK cascade can act as a coincidence detector to decode the simultaneous engagement of a receptor tyrosine kinase and of LRP-1 and as a signal integrator that encodes this information in a spatially and temporally distinct biological signal. In addition, the findings provide an explanation of why chronic elevation of LRP-1 ligands (e.g. PAI-1) can predispose to cancer.