Innate Immune Signaling and Its Role in Metabolic and Cardiovascular Diseases.

The innate immune system is an evolutionarily conserved system that senses and defends against infection and irritation. Innate immune signaling is a complex cascade that quickly recognizes infectious threats through multiple germline-encoded cell surface or cytoplasmic receptors and transmits signals for the deployment of proper countermeasures through adaptors, kinases, and transcription factors, resulting in the production of cytokines. As the first response of the innate immune system to pathogenic signals, inflammatory responses must be rapid and specific to establish a physical barrier against the spread of infection and must subsequently be terminated once the pathogens have been cleared. Long-lasting and low-grade chronic inflammation is a distinguishing feature of type 2 diabetes and cardiovascular diseases, which are currently major public health problems. Cardiometabolic stress-induced inflammatory responses activate innate immune signaling, which directly contributes to the development of cardiometabolic diseases. Additionally, although the innate immune elements are highly conserved in higher-order jawed vertebrates, lower-grade jawless vertebrates lack several transcription factors and inflammatory cytokine genes downstream of the Toll-like receptors (TLRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) pathways, suggesting that innate immune signaling components may additionally function in an immune-independent way. Notably, recent studies from our group and others have revealed that innate immune signaling can function as a vital regulator of cardiometabolic homeostasis independent of its immune function. Therefore, further investigation of innate immune signaling in cardiometabolic systems may facilitate the discovery of new strategies to manage the initiation and progression of cardiometabolic disorders, leading to better treatments for these diseases. In this review, we summarize the current progress in innate immune signaling studies and the regulatory function of innate immunity in cardiometabolic diseases. Notably, we highlight the immune-independent effects of innate immune signaling components on the development of cardiometabolic disorders.

Association of Inpatient Use of Angiotensin-Converting Enzyme Inhibitors and Angiotensin II Receptor Blockers With Mortality Among Patients With Hypertension Hospitalized With COVID-19.

RATIONALE: Use of ACEIs (angiotensin-converting enzyme inhibitors) and ARBs (angiotensin II receptor blockers) is a major concern for clinicians treating coronavirus disease 2019 (COVID-19) in patients with hypertension. OBJECTIVE: To determine the association between in-hospital use of ACEI/ARB and all-cause mortality in patients with hypertension and hospitalized due to COVID-19. METHODS AND RESULTS: This retrospective, multi-center study included 1128 adult patients with hypertension diagnosed with COVID-19, including 188 taking ACEI/ARB (ACEI/ARB group; median age 64 [interquartile range, 55-68] years; 53.2% men) and 940 without using ACEI/ARB (non-ACEI/ARB group; median age 64 [interquartile range 57-69]; 53.5% men), who were admitted to 9 hospitals in Hubei Province, China from December 31, 2019 to February 20, 2020. In mixed-effect Cox model treating site as a random effect, after adjusting for age, gender, comorbidities, and in-hospital medications, the detected risk for all-cause mortality was lower in the ACEI/ARB group versus the non-ACEI/ARB group (adjusted hazard ratio, 0.42 [95% CI, 0.19-0.92]; P=0.03). In a propensity score-matched analysis followed by adjusting imbalanced variables in mixed-effect Cox model, the results consistently demonstrated lower risk of COVID-19 mortality in patients who received ACEI/ARB versus those who did not receive ACEI/ARB (adjusted hazard ratio, 0.37 [95% CI, 0.15-0.89]; P=0.03). Further subgroup propensity score-matched analysis indicated that, compared with use of other antihypertensive drugs, ACEI/ARB was also associated with decreased mortality (adjusted hazard ratio, 0.30 [95% CI, 0.12-0.70]; P=0.01) in patients with COVID-19 and coexisting hypertension. CONCLUSIONS: Among hospitalized patients with COVID-19 and coexisting hypertension, inpatient use of ACEI/ARB was associated with lower risk of all-cause mortality compared with ACEI/ARB nonusers. While study interpretation needs to consider the potential for residual confounders, it is unlikely that in-hospital use of ACEI/ARB was associated with an increased mortality risk.

COVID-19 and its Cardiac and Neurological Complications among Ontario Visible Minorities.

BACKGROUND: Due to lack of data on the epidemiology, cardiac, and neurological complications among Ontario visible minorities (Chinese and South Asians) affected by coronavirus disease (COVID-19), this population-based retrospective study was undertaken to study them systematically. METHODS: From January 1, 2020 to September 30, 2020 using the last name algorithm to identify Ontario Chinese and South Asians who were tested positive by PCR for COVID-19, their demographics, cardiac, and neurological complications including hospitalization and emergency visit rates were analyzed compared to the general population. RESULTS: Chinese (N = 1,186) with COVID-19 were found to be older (mean age 50.7 years) compared to the general population (N = 42,547) (mean age 47.6 years) (p < 0.001), while South Asians (N = 3,459) were younger (age of 42.1 years) (p < 0.001). The 30-day crude rate for cardiac complications among Chinese was 169/10,000 (p = 0.069), while for South Asians, it was 64/10,000 (p = 0.008) and, for the general population, it was 112/10,000. For neurological complications, the 30-day crude rate for Chinese was 160/10,000 (p < 0.001); South Asians was 40/10,000 (p = 0.526), and general population was 48/10,000. The 30-day all-cause mortality rate was significantly higher for Chinese at 8.1% vs 5.0% for the general population (p < 0.001), while it was lower in South Asians at 2.1% (p < 0.001). CONCLUSIONS: Chinese and South Asians in Ontario affected by COVID-19 during the first wave of the pandemic were found to have a significant difference in their demographics, cardiac, and neurological outcomes.

The Science Underlying COVID-19: Implications for the Cardiovascular System.

The coronavirus disease 2019 (COVID-19) pandemic has affected health and economy worldwide on an unprecedented scale. Patients have diverse clinical outcomes, but those with preexisting cardiovascular disease, hypertension, and related conditions incur disproportionately worse outcome. The high infectivity of severe acute respiratory syndrome coronavirus 2 is in part related to new mutations in the receptor binding domain, and acquisition of a furin cleavage site in the S-spike protein. The continued viral shedding in the asymptomatic and presymptomatic individuals enhances its community transmission. The virus uses the angiotensin converting enzyme 2 receptor for internalization, aided by transmembrane protease serine 2 protease. The tissue localization of the receptors correlates with COVID-19 presenting symptoms and organ dysfunction. Virus-induced angiotensin converting enzyme 2 downregulation may attenuate its function, diminish its anti-inflammatory role, and heighten angiotensin II effects in the predisposed patients. Lymphopenia occurs early and is prognostic, potentially associated with reduction of the CD4+ and some CD8+ T cells. This leads to imbalance of the innate/acquired immune response, delayed viral clearance, and hyperstimulated macrophages and neutrophils. Appropriate type I interferon pathway activation is critical for virus attenuation and balanced immune response. Persistent immune activation in predisposed patients, such as elderly adults and those with cardiovascular risk, can lead to hemophagocytosis-like syndrome, with uncontrolled amplification of cytokine production, leading to multiorgan failure and death. In addition to the airways and lungs, the cardiovascular system is often involved in COVID-19 early, reflected in the release of highly sensitive troponin and natriuretic peptides, which are all extremely prognostic, in particular, in those showing continued rise, along with cytokines such as interleukin-6. Inflammation in the vascular system can result in diffuse microangiopathy with thrombosis. Inflammation in the myocardium can result in myocarditis, heart failure, cardiac arrhythmias, acute coronary syndrome, rapid deterioration, and sudden death. Aggressive support based on early prognostic indicators with expectant management can potentially improve recovery. Appropriate treatment for heart failure, arrhythmias, acute coronary syndrome, and thrombosis remain important. Specific evidence-based treatment strategies for COVID-19 will emerge with ongoing global collaboration on multiple approaches being evaluated. To protect the wider population, antibody testing and effective vaccine will be needed to make COVID-19 history.

Innate Immune Nod1/RIP2 Signaling Is Essential for Cardiac Hypertrophy but Requires Mitochondrial Antiviral Signaling Protein for Signal Transductions and Energy Balance.

BACKGROUND: Cardiac hypertrophy is a key biological response to injurious stresses such as pressure overload and, when excessive, can lead to heart failure. Innate immune activation by danger signals, through intracellular pattern recognition receptors such as nucleotide-binding oligomerization domain 1 (Nod1) and its adaptor receptor-interacting protein 2 (RIP2), might play a major role in cardiac remodeling and progression to heart failure. We hypothesize that Nod1/RIP2 are major contributors to cardiac hypertrophy, but may not be sufficient to fully express the phenotype alone. METHODS: To elucidate the contribution of Nod1/RIP2 signaling to cardiac hypertrophy, we randomized Nod1-/-, RIP2-/-, or wild-type mice to transverse aortic constriction or sham operations. Cardiac hypertrophy, fibrosis, and cardiac function were examined in these mice. RESULTS: Nod1 and RIP2 proteins were upregulated in the heart after transverse aortic constriction, and this was paralleled by increased expression of mitochondrial proteins, including mitochondrial antiviral signaling protein (MAVS). Nod1-/- and RIP2-/- mice subjected to transverse aortic constriction exhibited better survival, improved cardiac function, and decreased cardiac hypertrophy. Downstream signal transduction pathways that regulate inflammation and fibrosis, including NF (nuclear factor) κB and MAPK (mitogen-activated protein kinase)-GATA4/p300, were reduced in both Nod1-/- and RIP2-/- mice after transverse aortic constriction compared with wild-type mice. Coimmunoprecipitation of extracted cardiac proteins and confocal immunofluorescence microscopy showed that Nod1/RIP2 interaction was robust and that this complex also included MAVS as an essential component. Suppression of MAVS expression attenuated the complex formation, NF κB signaling, and myocyte hypertrophy. Interrogation of mitochondrial function compared in the presence or ablation of MAVS revealed that MAVS serves to suppress mitochondrial energy output and mediate fission/fusion related dynamic changes. The latter is possibly linked to mitophagy during cardiomyocytes stress, which may provide an intriguing link between innate immune activation and mitochondrial energy balance under stress or injury conditions. CONCLUSIONS: We have identified that innate immune Nod1/RIP2 signaling is a major contributor to cardiac remodeling after stress. This process is critically joined by and regulated through the mitochondrial danger signal adapter MAVS. This novel complex coordinates remodeling, inflammatory response, and mitochondrial energy metabolism in stressed cardiomyocytes. Thus, Nod1/RIP2/MAVS signaling complex may represent an attractive new therapeutic approach toward heart failure.

Omics phenotyping in heart failure: the next frontier.

This state-of-the-art review aims to provide an up-to-date look at breakthrough omic technologies that are helping to unravel heart failure (HF) disease mechanisms and heterogeneity. Genomics, transcriptomics, proteomics, and metabolomics in HF are reviewed in depth. In addition, there is a thorough, expert discussion regarding the value of omics in identifying novel disease pathways, advancing understanding of disease mechanisms, differentiating HF phenotypes, yielding biomarkers for diagnosis or prognosis, or identifying new therapeutic targets in HF. The combination of multiple omics technologies may create a more comprehensive picture of the factors and physiology involved in HF than achieved by either one alone and provides a rich resource for predictive phenotype modelling. However, the successful translation of omics tools as solutions to clinical HF requires that the observations are robust and reproducible and can be validated across multiple independent populations to ensure confidence in clinical decision-making.

The Pathophysiologic Role of Gelsolin in Chronic Kidney Disease: Focus on Podocytes.

Chronic kidney disease (CKD) is normally related to proteinuria, a common finding in a compromised glomerular filtration barrier (GFB). GFB is a structure composed of glomerular endothelial cells, the basement membrane, and the podocytes. CKD with podocyte damage may be associated with actin cytoskeleton reorganization, resulting in podocyte effacement. Gelsolin plays a critical role in several diseases, including cardiovascular diseases and cancer. Our current study aimed to determine the connection between gelsolin and podocyte, and thus the mechanism underlying podocyte injury in CKD. Experiments were carried out on Drosophila to demonstrate whether gelsolin had a physiological role in maintaining podocyte. Furthermore, the survival rate of gelsolin-knocked down Drosophila larvae was extensively reduced after AgNO3 exposure. Secondly, the in vitro podocytes treated with puromycin aminonucleoside (PAN) enhanced the gelsolin protein expression, as well as small GTPase RhoA and Rac1, which also regulated actin dynamic expression incrementally with the PAN concentrations. Thirdly, we further demonstrated in vivo that GSN was highly expressed inside the glomeruli with mitochondrial dysfunction in a CKD mouse model. Our findings suggest that an excess of gelsolin may contribute to podocytes damage in glomeruli.

Myocarditis in the Setting of Cancer Therapeutics: Proposed Case Definitions for Emerging Clinical Syndromes in Cardio-Oncology

Recent developments in cancer therapeutics have improved outcomes but have also been associated with cardiovascular complications. Therapies harnessing the immune system have been associated with an immune-mediated myocardial injury described as myocarditis. Immune checkpoint inhibitors are one such therapy with an increasing number of case and cohort reports describing a clinical syndrome of immune checkpoint inhibitor­associated myocarditis. Although the full spectrum of immune checkpoint inhibitor­associated cardiovascular disease still needs to be fully defined, described cases of myocarditis range from syndromes with mild signs and symptoms to fatal events. These observations in the clinical setting stand in contrast to outcomes from randomized clinical trials in which myocarditis is a rare event that is investigator reported and lacking in a specific case definition. The complexities associated with diagnosis, as well as the heterogeneous clinical presentation of immune checkpoint inhibitor­associated myocarditis, have made ascertainment and identification of myocarditis with high specificity challenging in clinical trials and other data sets, limiting the ability to better understand the incidence, outcomes, and predictors of these rare events. Therefore, establishing a uniform definition of myocarditis for application in clinical trials of cancer immunotherapies will enable greater understanding of these events. We propose an operational definition of cancer therapy-associated myocarditis that may facilitate case ascertainment and report and therefore may enhance the understanding of the incidence, outcomes, and risk factors of this novel clinical syndrome.

Biomarker discovery in cardiac allograft vasculopathy using targeted aptamer proteomics.

Cardiac allograft vasculopathy (CAV) limits long-term survival after heart transplantation. Non-invasive evaluation is challenging, and currently, there is no validated biomarker for CAV diagnosis or prognostication. To identify potential candidate CAV biomarkers, we utilized the Slow Off-rate Modified Aptamer (SOMAscan) assay, which evaluates over 1000 serum proteins, including many relevant to biological pathways in CAV. We evaluated three heart transplant patient groups according to angiographic ISHLT CAV grade: CAV1-2 (mild-moderate CAV), CAV3 (severe CAV), and CAV0 (normal control). SOMAscan assays were performed and proteins quantitated. Comparisons of proteins between study groups were performed using one-way ANOVA (false discovery rate q-value < 0.10). Thirty-one patients (12 mild-moderate CAV, 9 severe CAV, 10 controls) were included: 81% male, median age 57 years and median 1.1 years post-transplant. Compared to controls, patients with mild-moderate CAV had similar characteristics, while patients with severe CAV had longer time from transplant and increased allosensitization. Statistical/bioinformatics analysis identified 14 novel biomarkers for CAV, including 4 specific for mild-moderate CAV. These proteins demonstrated important actions including apoptosis, inflammation, and platelet/coagulation activation. Upon preliminary receiver operating characteristics curve analysis, our protein biomarkers showed moderate-to-high discriminative ability for CAV (area under curve: 0.72 to 0.94). These candidate biomarkers are being validated in prospective studies.

Role of Biomarkers for the Prevention, Assessment, and Management of Heart Failure: A Scientific Statement From the American Heart Association.

BACKGROUND AND PURPOSE: Natriuretic peptides have led the way as a diagnostic and prognostic tool for the diagnosis and management of heart failure (HF). More recent evidence suggests that natriuretic peptides along with the next generation of biomarkers may provide added value to medical management, which could potentially lower risk of mortality and readmissions. The purpose of this scientific statement is to summarize the existing literature and to provide guidance for the utility of currently available biomarkers. METHODS: The writing group used systematic literature reviews, published translational and clinical studies, clinical practice guidelines, and expert opinion/statements to summarize existing evidence and to identify areas of inadequacy requiring future research. The panel reviewed the most relevant adult medical literature excluding routine laboratory tests using MEDLINE, EMBASE, and Web of Science through December 2016. The document is organized and classified according to the American Heart Association to provide specific suggestions, considerations, or contemporary clinical practice recommendations. RESULTS: A number of biomarkers associated with HF are well recognized, and measuring their concentrations in circulation can be a convenient and noninvasive approach to provide important information about disease severity and helps in the detection, diagnosis, prognosis, and management of HF. These include natriuretic peptides, soluble suppressor of tumorgenicity 2, highly sensitive troponin, galectin-3, midregional proadrenomedullin, cystatin-C, interleukin-6, procalcitonin, and others. There is a need to further evaluate existing and novel markers for guiding therapy and to summarize their data in a standardized format to improve communication among researchers and practitioners. CONCLUSIONS: HF is a complex syndrome involving diverse pathways and pathological processes that can manifest in circulation as biomarkers. A number of such biomarkers are now clinically available, and monitoring their concentrations in blood not only can provide the clinician information about the diagnosis and severity of HF but also can improve prognostication and treatment strategies.

Metformin increases degradation of phospholamban via autophagy in cardiomyocytes.

Phospholamban (PLN) is an effective inhibitor of the sarco(endo)plasmic reticulum Ca(2+) ATPase (SERCA). Here, we examined PLN stability and degradation in primary cultured mouse neonatal cardiomyocytes (CMNCs) and mouse hearts using immunoblotting, molecular imaging, and [(35)S]methionine pulse-chase experiments, together with lysosome (chloroquine and bafilomycin A1) and autophagic (3-methyladenine and Atg5 siRNA) antagonists. Inhibiting lysosomal and autophagic activities promoted endogenous PLN accumulation, whereas accelerating autophagy with metformin enhanced PLN degradation in CMNCs. This reduction in PLN levels was functionally correlated with an increased rate of SERCA2a activity, accounting for an inotropic effect of metformin. Metabolic labeling reaffirmed that metformin promoted wild-type and R9C PLN degradation. Immunofluorescence showed that PLN and the autophagy marker, microtubule light chain 3, became increasingly colocalized in response to chloroquine and bafilomycin treatments. Mechanistically, pentameric PLN was polyubiquitinylated at the K3 residue and this modification was required for p62-mediated selective autophagy trafficking. Consistently, attenuated autophagic flux in HECT domain and ankyrin repeat-containing E3 ubiquitin protein ligase 1-null mouse hearts was associated with increased PLN levels determined by immunoblots and immunofluorescence. Our study identifies a biological mechanism that traffics PLN to the lysosomes for degradation in mouse hearts.

Dynamic changes in myocardial matrix and relevance to disease: translational perspectives.

The cardiac extracellular matrix (ECM) provides the architectural scaffold to support efficient contraction and relaxation of cardiomyocytes. The elegant design of the ECM facilitates optimal force transduction, electric transmission, intercellular communication, and metabolic exchange within the myocardial microenvironment. In the setting of increased wall stress, injury, or disease, the ECM can undergo a series of dynamic changes that lead to favorable chamber remodeling and functional adaptation. Over time, sustained matrix remodeling can impair diastolic and systolic function caused by excess deposition of interstitial fibrous tissue. These pathological alterations in ECM structure/function are considered central to the evolution of adverse cardiac remodeling and the development of heart failure. This review discusses the complex dynamics of the cardiac ECM in the setting of myocardial infarction, pressure overload, and volume overload. We also summarize the current status of ECM biomarkers that may have clinical value in prognosticating cardiac disease progression in patients. Finally, we discuss the most current status of drugs under evaluation for use in cardiac fibrosis.

Innate immune interleukin-1 receptor-associated kinase 4 exacerbates viral myocarditis by reducing CCR5(+) CD11b(+) monocyte migration and impairing interferon production.

BACKGROUND: Viral myocarditis follows a fatal course in ≈30% of patients. Interleukin-1 receptor-associated kinase 4 (IRAK4), a major nodal signal transducer in innate immunity, can play a pivotal role in host inflammatory response. We sought to determine how IRAK4 modulates inflammation and outcome in a mouse model of viral myocarditis. METHODS AND RESULTS: Myocarditis was induced after intraperitoneal inoculation of coxsackievirus B3 into C57Bl/6 IRAK4-deficient mice and their littermate controls. Mortality and viral proliferation were markedly reduced in IRAK4(-/-) mice compared with their IRAK4(+/+) littermates. Disease resistance of IRAK4(-/-) mice paralleled increased amounts of protective heart-infiltrating CCR5(+) monocytes/macrophages and enhanced interferon-α and interferon-γ production 2 days after infection. Competitive bone marrow chimera demonstrated that intact IRAK4 function inhibited heart-specific migration of bone marrow-derived CCR5(+) cells. Mechanistically, lack of IRAK4 resulted in interferon regulatory factor 5 homodimerization via reduced melanoma differentiation-associated protein 5 degradation and enhanced Stat1 and Stat5 phosphorylation. Consequently, antiviral interferon-α and interferon-γ production, as well as CCR5(+) cell recruitment, increased, whereas the overall proinflammatory response was drastically reduced in the absence of IRAK4. CONCLUSIONS: Innate immunity signal transducer IRAK4 exacerbates viral myocarditis through inhibition of interferon production and reduced mobilization of protective CCR5(+) monocytes/macrophages to the heart. The combination of IRAK4 inhibitors and antiviral adjuvants may become an attractive therapeutic approach against viral myocarditis in the future.