HIV protease inhibitor-induced cardiac dysfunction and fibrosis is mediated by platelet-derived TGF-β1 and can be suppressed by exogenous carbon monoxide

The role and mechanism of heme oxygenase-1 in arrhythmias

The global incidence and prevalence of arrhythmias are continuously increasing. However, the precise mechanisms of underlying arrhythmogenesis and the optimal measures for effective treatment remain incompletely understood. The inducible form of heme oxygenase, known as heme oxygenase-1 (HO-1), is recognized as a potent antioxidant molecule capable of exerting anti-inflammatory and anti-apoptotic effects. Recent research indicates that HO-1 plays a role in preventing arrhythmias by mitigating cardiac remodeling, including electrical remodeling, ion remodeling, and structural remodeling. This review aimed to consolidate current knowledge regarding the involvement of HO-1 in arrhythmias and elucidate its underlying mechanisms of action.

HIV-Associated Cardiovascular Disease Pathogenesis: An Emerging Understanding Through Imaging and Immunology

Cardiac abnormalities were identified early in the epidemic of AIDS, predating the isolation and characterization of the etiologic agent, HIV. Several decades later, the causation and pathogenesis of cardiovascular disease (CVD) linked to HIV infection continue to be the focus of intense speculation. Before the widespread use of antiretroviral therapy, HIV-associated CVD was primarily characterized by HIV-associated cardiomyopathy linked to profound immunodeficiency. With increasing antiretroviral therapy use, viral load suppression, and establishment of immune competency, the effects of HIV on the cardiovascular system are more subtle. Yet, people living with HIV still face an increased incidence of cardiovascular pathology. Advances in cardiac imaging modalities and immunology have deepened our understanding of the pathogenesis of HIV-associated CVD. This review provides an overview of the pathogenesis of HIV-associated CVD integrating data from imaging and immunologic studies with particular relevance to the HIV population originating from high-endemic regions, such as sub-Saharan Africa. The review highlights key evidence gaps in the field and suggests future directions for research to better understand the complex HIV-CVD interactions.

Elucidating the Molecular Pathways and Therapeutic Interventions of Gaseous Mediators in the Context of Fibrosis

Fibrosis, a pathological alteration of the repair response, involves continuous organ damage, scar formation, and eventual functional failure in various chronic inflammatory disorders. Unfortunately, clinical practice offers limited treatment strategies, leading to high mortality rates in chronic diseases. As part of investigations into gaseous mediators, or gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H2S), numerous studies have confirmed their beneficial roles in attenuating fibrosis. Their therapeutic mechanisms, which involve inhibiting oxidative stress, inflammation, apoptosis, and proliferation, have been increasingly elucidated. Additionally, novel gasotransmitters like hydrogen (H2) and sulfur dioxide (SO2) have emerged as promising options for fibrosis treatment. In this review, we primarily demonstrate and summarize the protective and therapeutic effects of gaseous mediators in the process of fibrosis, with a focus on elucidating the underlying molecular mechanisms involved in combating fibrosis.

Myocardial fibrosis in right heart dysfunction

Cardiac fibrosis, associated with right heart dysfunction, results in significant morbidity and mortality. Stimulated by various cellular and humoral stimuli, cardiac fibroblasts, macrophages, CD4+ and CD8+ T cells, mast and endothelial cells promote fibrogenesis directly and indirectly by synthesizing numerous profibrotic factors. Several systems, including the transforming growth factor-beta and the renin-angiotensin system, produce type I and III collagen, fibronectin and α-smooth muscle actin, thus modifying the extracellular matrix. Although magnetic resonance imaging with gadolinium enhancement remains the gold standard, the use of circulating biomarkers represents an inexpensive and attractive means to facilitate detection and monitor cardiovascular fibrosis. This review explores the use of protein and nucleic acid (miRNAs) markers to better understand underlying pathophysiology as well as their role in the development of therapeutics to inhibit and potentially reverse cardiac fibrosis.

Factors influencing left ventricular diastolic dysfunction on echocardiography of people living with HIV in Kunming, China

BACKGROUND

The widespread use of antiretroviral therapy has prolonged the survival of people living with HIV (PLWH). Among these patients, co-existing cardiovascular diseases, particularly left ventricular diastolic dysfunction (LVDD), are receiving increasing attention.

METHODS

We recruited 386 patients in the PLWH group and 386 sex- and age (± 3 years)-matched individuals in the HIV-negative group, and used logistic regression to determine the risk factors of LVDD.

RESULTS

Compared to the HIV-negative group, PLWH had a significantly higher prevalence of smoking (p < .001), alcohol consumption (p < .001), hypertension (p = .002), diabetes (p = .020), and hyperlipidemia (p < .001) and a lower prevalence of body mass index (BMI) ≥ 24.0 kg/m2 (p < .001). The prevalence of LVDD on echocardiography was significantly higher in PLWH than in the HIV-negative group (25.9% vs 16.1%, p = .001). The multivariate analysis showed that non-youth (OR = 8.666; 95%CI = 4.310-17.459; p < .001), BMI ≥ 24.0 kg/m2 (OR = 1.992; 95% CI = 1.007-3.939; p = .048), hypertension (OR = 1.888; 95% CI = 1.044-3.415; p = .036), hyperlipidemia (OR = 1.911; 95% CI = 1.068-3.418; p = .029), and HIV infection (OR = 2.003; 95%CI = 1.341-2.992; p = .001) were risk factors for LVDD.

CONCLUSION

The rate of echocardiographic abnormalities was higher in PLWH. LVDD was associated with non-youth, BMI ≥ 24.0 kg/m2, hypertension, hyperlipidemia, and living with HIV.

The risk of new heart failure associated with protease inhibitor: Systematic scoping review

BACKGROUND

Protease inhibitors (PIs) have contributed to the long-term survival of persons with human immunodeficiency virus (PHIV). While there is a concern linking protease inhibitors to an increased risk of heart failure (HF), the evidence linking protease inhibitors and heart failure has been uncertain.

METHODS

Following the PRISMA Extension for Scoping Reviews, we searched MEDLINE and EMBASE for peer-reviewed articles using keywords including "protease inhibitor," "heart failure," and "human immunodeficiency virus" from their inception to December 21, 2022.

RESULTS

Five articles, including three observational studies and two randomized controlled trials, were included in the review. While protease inhibitors seem to be associated with atherosclerotic cardiovascular disease through their effects on metabolic markers, there is scarce evidence suggesting a direct association between protease inhibitors and heart failure. Although one study showed a possible correlation between protease inhibitor use and lower left ventricular ejection fraction and increased heart failure admission, the results were subject to confounders, and participants had poor medication adherence.

CONCLUSION

Although current data are conflicting, there could be an association between PIs and HF in PHIV. Future prospective studies are warranted to evaluate the incidence of heart failure stratified on the generation of PIs and with adjustment for other metabolic risk factors.

Carbon monoxide (CO) derived from the CO-releasing molecule CORM-2 reduces peritoneal adhesion formation in a rat model

BACKGROUND

Although low-dose carbon monoxide (CO) administration has been shown to have an anti-fibrotic effect in various fibrotic diseases, its effects on peritoneal adhesion (PA), one of the postoperative complications, are not elucidated. In this study, the effect of CO-releasing tricarbonyldichlororuthenium (II) dimer (CORM-2) administration on the formation of PA and the underlying factors of its potential effect were investigated.

METHODS AND RESULTS

After the induction of PA, rats were divided into four groups with 8 rats in each group. The rats received either (i) dimethyl sulfoxide:saline solution (1:10) as a vehicle, (ii) 2.5 mg/kg CORM-2, (iii) 5 mg/kg CORM-2, or (iv) inactive (i) CORM (iCORM) intragastrically every day for a duration of 7 days. PA was not induced in rats (n = 8) designated as sham controls. Gross, histological, immunohistochemical and quantitative real-time polymerase chain reaction analyses were performed to evaluate the effectiveness of CORM-2 administration. Gross analysis showed that CORM-2 administration reduced PA formation compared to rats treated with vehicle. Histological and immunohistochemical examinations showed that increased collagen deposition, myofibroblast accumulation, microvessel density, and M1 macrophage count in the peritoneal fibrosis area of vehicle-treated rats decreased following CORM-2 treatments. PCR analyses showed that CORM-2 treatments decreased hypoxia-induced Hif1a, profibrotic Tgfb1, ECM components Col1a1 and Col3a1, collagen degradation suppressor Timp1, fibrinolysis inhibitor Serpine1, and pro-inflammatory Tnf mRNA expressions, while increasing the M2 macrophage marker Arg1 mRNA expression.

CONCLUSIONS

These results suggested that CORM-2 administration reduces PA formation by affecting adhesiogenic processes such as pro-inflammatory response, fibrinolytic system, angiogenesis and fibrogenesis.

The loss of cardiac SIRT3 decreases metabolic flexibility and proteostasis in an age-dependent manner

SIRT3 is a longevity factor that acts as the primary deacetylase in mitochondria. Although ubiquitously expressed, previous global SIRT3 knockout studies have shown primarily a cardiac-specific phenotype. Here, we sought to determine how specifically knocking out SIRT3 in cardiomyocytes (SIRTcKO mice) temporally affects cardiac function and metabolism. Mice displayed an age-dependent increase in cardiac pathology, with 10-month-old mice exhibiting significant loss of systolic function, hypertrophy, and fibrosis. While mitochondrial function was maintained at 10 months, proteomics and metabolic phenotyping indicated SIRT3 hearts had increased reliance on glucose as an energy substrate. Additionally, there was a significant increase in branched-chain amino acids in SIRT3cKO hearts without concurrent increases in mTOR activity. Heavy water labeling experiments demonstrated that, by 3 months of age, there was an increase in protein synthesis that promoted hypertrophic growth with a potential loss of proteostasis in SIRT3cKO hearts. Cumulatively, these data show that the cardiomyocyte-specific loss of SIRT3 results in severe pathology with an accelerated aging phenotype.

Association between inflammatory biomarker profiles and cardiovascular risk in individuals with and without HIV

BACKGROUND

People with HIV have an increased risk for cardiovascular morbidity and mortality. Inflammation and immune activation may contribute to this excess risk.

METHODS

We assessed thirty-one biomarkers in a subset of POPPY participants and identified three distinct inflammatory profiles: 'gut/immune activation', 'neurovascular', and 'reference' (relatively low levels of inflammation). Ten-year cardiovascular disease (CVD) risk predictions were calculated using the QRISK, Framingham Risk Score (FRS) and the Data Collection on Adverse effects of anti-HIV Drugs (D:A:D) algorithms. The distributions of CVD risk scores across the different inflammatory profiles, stratified by HIV status, were compared using median quantile regression.

RESULTS

Of the 312 participants included [70% living with HIV, median (interquartile range; IQR) age 55 (51-60) years; 82% male; 91% white], 36, 130, and 146 were in the 'gut/immune activation', 'neurovascular', and 'reference' cluster, respectively. The median (IQR) QRISK scores were 9.3% (4.5-14.5) and 10.2% (5.5-16.9) for people with and without HV, respectively, with similar scores obtained with the FRS and D:A:D. We observed statistically significant differences between the distributions of scores in the three clusters among people with HV. In particular, median QRISK [5.8% (1.0-10.7) and 3.1% (0.3-5.8)] scores were higher, respectively, for those in the 'gut/immune activation' and 'neurovascular' clusters compared to those in the reference cluster.

CONCLUSIONS

People with HIV with increased gut/immune activation have a higher CVD risk compared to those with relatively low inflammation. Our findings highlight that clinically important inflammatory subgroups could be useful to differentiate risk and maximise prediction of CVD among people with HIV.

HIV-Related Myocardial Fibrosis: Inflammatory Hypothesis and Crucial Role of Immune Cells Dysregulation

Although the underlying mechanisms driving human immunodeficiency virus (HIV)-mediated cardiovascular diseases (CVD) onset and progression remain unclear, the role of chronic immune activation as a significant mediator is increasingly being highlighted. Chronic inflammation is a characteristic feature of CVD and considered a contributor to diastolic dysfunction, heart failure, and sudden cardiac death. This can trigger downstream effects that result in the increased release of pro-coagulant, pro-fibrotic, and pro-inflammatory cytokines. Subsequently, this can lead to an enhanced thrombotic state (by platelet activation), endothelial dysfunction, and myocardial fibrosis. Of note, recent studies have revealed that myocardial fibrosis is emerging as a mediator of HIV-related CVD. Together, such factors can eventually result in systolic and diastolic dysfunction, and an increased risk for CVD. In light of this, the current review article will focus on (a) the contributions of a chronic inflammatory state and persistent immune activation, and (b) the role of immune cells (mainly platelets) and cardiac fibrosis in terms of HIV-related CVD onset/progression. It is our opinion that such a focus may lead to the development of promising therapeutic targets for the treatment and management of CVD in HIV-positive patients.

Human immunodeficiency virus infection and risks of morbidity and death in adults with incident heart failure

AIMS

Human immunodeficiency virus (HIV) increases the risk of heart failure (HF), but whether it influences subsequent morbidity and mortality remains unclear.

METHODS AND RESULTS

We investigated the risks of hospitalization for HF, HF-related emergency department (ED) visits, and all-cause death in an observational cohort of incident HF patients with and without HIV using data from three large US integrated healthcare delivery systems. We estimated incidence rates and adjusted hazard ratios (aHRs) by HIV status at the time of HF diagnosis for subsequent outcomes. We identified 448 persons living with HIV (PLWH) and 3429 without HIV who developed HF from a frequency-matched source cohort of 38 868 PLWH and 386 586 without HIV. Mean age was 59.5 ± 11.3 years with 9.8% women and 31.8% Black, 13.1% Hispanic, and 2.2% Asian/Pacific Islander. Compared with persons without HIV, PLWH had similar adjusted rates of HF hospitalization [aHR 1.01, 95% confidence interval (CI): 0.81-1.26] and of HF-related ED visits [aHR 1.22 (95% CI: 0.99-1.50)], but higher adjusted rates of all-cause death [aHR 1.31 (95% CI: 1.08-1.58)]. Adjusted rates of HF-related morbidity and all-cause death were directionally consistent across a wide range of CD4 counts but most pronounced in the subset with a baseline CD4 count <200 or 200-499 cells/μL.

CONCLUSION

In a large, diverse cohort of adults with incident HF receiving care within integrated healthcare delivery systems, PLWH were at an independently higher risk of all-cause death but not HF hospitalizations or HF-related ED visits. Future studies investigating modifiable HIV-specific risk factors may facilitate more personalized care to optimize outcomes for PLWH and HF.

Gasotransmitters: Potential Therapeutic Molecules of Fibrotic Diseases

Fibrosis is defined as the pathological progress of excessive extracellular matrix (ECM), such as collagen, fibronectin, and elastin deposition, as the regenerative capacity of cells cannot satisfy the dynamic repair of chronic damage. The well-known features of tissue fibrosis are characterized as the presence of excessive activated and proliferated fibroblasts and the differentiation of fibroblasts into myofibroblasts, and epithelial cells undergo the epithelial-mesenchymal transition (EMT) to expand the number of fibroblasts and myofibroblasts thereby driving fibrogenesis. In terms of mechanism, during the process of fibrosis, the activations of the TGF-β signaling pathway, oxidative stress, cellular senescence, and inflammatory response play crucial roles in the activation and proliferation of fibroblasts to generate ECM. The deaths due to severe fibrosis account for almost half of the total deaths from various diseases, and few treatment strategies are available for the prevention of fibrosis as yet. Recently, numerous studies demonstrated that three well-defined bioactive gasotransmitters, including nitric oxide (NO), carbon monoxide (CO), and hydrogen sulfide (H₂S), generally exhibited anti-inflammatory, antioxidative, antiapoptotic, and antiproliferative properties. Besides these effects, a number of studies have reported that low-dose exogenous and endogenous gasotransmitters can delay and interfere with the occurrence and development of fibrotic diseases, including myocardial fibrosis, idiopathic pulmonary fibrosis, liver fibrosis, renal fibrosis, diabetic diaphragm fibrosis, and peritoneal fibrosis. Furthermore, in animal and clinical experiments, the inhalation of low-dose exogenous gas and intraperitoneal injection of gaseous donors, such as SNAP, CINOD, CORM, SAC, and NaHS, showed a significant therapeutic effect on the inhibition of fibrosis through modulating the TGF-β signaling pathway, attenuating oxidative stress and inflammatory response, and delaying the cellular senescence, while promoting the process of autophagy. In this review, we first demonstrate and summarize the therapeutic effects of gasotransmitters on diverse fibrotic diseases and highlight their molecular mechanisms in the process and development of fibrosis.

Application of carbon monoxide in kidney and heart transplantation: A novel pharmacological strategy for a broader use of suboptimal renal and cardiac grafts

Carbon monoxide (CO) was historically regarded solely as a poisonous gas that binds to hemoglobin and reduces oxygen-carrying capacity of blood at high concentrations. However, recent findings show that it is endogenously produced in mammalian cells as a by-product of heme degradation by heme oxygenase, and has received a significant attention as a medical gas that influences a myriad of physiological and pathological processes. At low physiological concentrations, CO exhibits several therapeutic properties including antioxidant, anti-inflammatory, anti-apoptotic, anti-fibrotic, anti-thrombotic, anti-proliferative and vasodilatory properties, making it a candidate molecule that could protect organs in various pathological conditions including cold ischemia-reperfusion injury (IRI) in kidney and heart transplantation. Cold IRI is a well-recognized and complicated cascade of interconnected pathological pathways that poses a significant barrier to successful outcomes after kidney and heart transplantation. A substantial body of preclinical evidence demonstrates that CO gas and CO-releasing molecules (CO-RMs) prevent cold IRI in renal and cardiac grafts through several molecular and cellular mechanisms. In this review, we discuss recent advances in research involving the use of CO as a novel pharmacological strategy to attenuate cold IRI in preclinical models of kidney and heart transplantation through its administration to the organ donor prior to organ procurement or delivery into organ preservation solution during cold storage and to the organ recipient during reperfusion and after transplantation. We also discuss the underlying molecular mechanisms of cyto- and organ protection by CO during transplantation, and suggest its clinical use in the near future to improve long-term transplantation outcomes.

Interactions of HIV and Antiretroviral Therapy With Neutrophils and Platelets

Neutrophils are important components of the innate immune system that mediate pathogen defense by multiple processes including phagocytosis, release of proteolytic enzymes, production of reactive oxygen species, and neutrophil extracellular trap formation. Abnormalities of neutrophil count and function have been described in the setting of HIV infection, with the majority of antiretroviral agents (ARVs), excluding zidovudine, having been reported to correct neutropenia. Questions still remain, however, about their impact on neutrophil function, particularly the possibility of persistent neutrophil activation, which could predispose people living with HIV to chronic inflammatory disorders, even in the presence of virally-suppressive treatment. In this context, the effects of protease inhibitors and integrase strand transfer inhibitors, in particular, on neutrophil function remain poorly understood and deserve further study. Besides mediating hemostatic functions, platelets are increasingly recognized as critical role players in the immune response against infection. In the setting of HIV, these cells have been found to harbor the virus, even in the presence of antiretroviral therapy (ART) potentially promoting viral dissemination. While HIV-infected individuals often present with thrombocytopenia, they have also been reported to have increased platelet activation, as measured by an upregulation of expression of CD62P (P-selectin), CD40 ligand, glycoprotein IV, and RANTES. Despite ART-mediated viral suppression, HIV-infected individuals reportedly have sustained platelet activation and dysfunction. This, in turn, contributes to persistent immune activation and an inflammatory vascular environment, seemingly involving neutrophil-platelet-endothelium interactions that increase the risk for development of comorbidities such as cardiovascular disease (CVD) that has become the leading cause of morbidity and mortality in HIV-infected individuals on treatment, clearly underscoring the importance of unraveling the possible etiologic roles of ARVs. In this context, abacavir and ritonavir-boosted lopinavir and darunavir have all been linked to an increased risk of CVD. This narrative review is therefore focused primarily on the role of neutrophils and platelets in HIV transmission and disease, as well as on the effect of HIV and the most common ARVs on the numbers and functions of these cells, including neutrophil-platelet-endothelial interactions.

Immune Dysregulation in Myocardial Fibrosis, Steatosis, and Heart Failure: Current Insights from HIV and the General Population

PURPOSE OF REVIEW

HIV is an independent risk factor for heart failure (HF). Cardiac imaging studies in people with HIV (PWH) have identified myocardial pathologies, namely fibrosis and steatosis, that likely contribute to the higher risk of HF. In this review, we survey existing epidemiological, clinical, and mechanistic literature to identify potential pathways that may contribute to the burden of myocardial fibrosis and steatosis among PWH.

RECENT FINDINGS

Multiple cohort studies over the past 20 years have demonstrated a roughly 2-fold higher risk of incident HF in PWH, as well as a disproportionate burden of myocardial fibrosis and steatosis in PWH without HF. Both myocardial fibrosis and steatosis are known contributors to HF in adults without HIV. Pathways involving the NLRP3 inflammasome, TGF-β1, and adipocyte dysfunction are known to play a crucial role in the development of myocardial fibrosis and steatosis. Upregulation of these pathways in HIV due to direct effects of viral proteins, persistent immune dysregulation, gut epithelial breakdown and dysbiosis, and toxicities from antiretroviral therapy may contribute to myocardial dysfunction in HIV. Understanding these pathways may lead to more precise diagnostic and therapeutic targets to curb HF in PWH. During the past three decades, observational and mechanistic studies have provided important insights into risk factors and pathways that may contribute to the increased HF risk in PWH. Future work is needed to characterize these pathways more precisely in mechanistic studies of PWH, with the goal of ultimately deriving valuable targets for prevention, early diagnosis, and treatment of HF in PWH.

HIV protease inhibitor ritonavir induces renal fibrosis and dysfunction: role of platelet-derived TGF-β1 and intervention via antioxidant pathways

OBJECTIVE

Chronic kidney disease (CKD) with tubular injury and fibrosis occurs in HIV infection treated with certain protease inhibitor-based antiretroviral therapies. The pathophysiology is unclear.

DESIGN

We hypothesized that fibrosis, mediated by platelet-derived transforming growth factor (TGF)-β1, underlies protease inhibitor-associated CKD. We induced this in mice exposed to the protease inhibitor ritonavir (RTV), and intervened with low-dose inhaled carbon monoxide (CO), activating erythroid 2-related factor (Nrf2)-associated antioxidant pathways.

METHODS

Wild-type C57BL/6 mice and mice deficient in platelet TGF-β1, were given RTV (10 mg/kg) or vehicle daily for 8 weeks. Select groups were exposed to CO (250 ppm) for 4 h after RTV or vehicle injection. Renal disorder, fibrosis, and TGF-β1-based and Nrf2-based signaling were examined by histology, immunofluorescence, and flow cytometry. Renal damage and dysfunction were assessed by KIM-1 and cystatin C ELISAs. Clinical correlations were sought among HIV-infected individuals.

RESULTS

RTV-induced glomerular and tubular injury, elevating urinary KIM-1 (P = 0.004). It enhanced TGF-β1-related signaling, accompanied by kidney fibrosis, macrophage polarization to an inflammatory phenotype, and renal dysfunction with cystatin C elevation (P = 0.008). Mice lacking TGF-β1 in platelets were partially protected from these abnormalities. CO inhibited RTV-induced fibrosis and macrophage polarization in association with upregulation of Nrf2 and heme oxygenase-1 (HO-1). Clinically, HIV infection correlated with elevated cystatin C levels in untreated women (n = 17) vs. age-matched controls (n = 19; P = 0.014). RTV-treated HIV+ women had further increases in cystatin C (n = 20; P = 0.05), with parallel elevation of HO-1.

CONCLUSION

Platelet TGF-β1 contributes to RTV-induced kidney fibrosis and dysfunction, which may be amenable to antioxidant interventions.

Non-ischemic dilated cardiomyopathy and cardiac fibrosis

Cardiac fibrosis is associated with non-ischemic dilated cardiomyopathy, increasing its morbidity and mortality. Cardiac fibroblast is the keystone of fibrogenesis, being activated by numerous cellular and humoral factors. Macrophages, CD4+ and CD8+ T cells, mast cells, and endothelial cells stimulate fibrogenesis directly by activating cardiac fibroblasts and indirectly by synthetizing various profibrotic molecules. The synthesis of type 1 and type 3 collagen, fibronectin, and α-smooth muscle actin is rendered by various mechanisms like transforming growth factor-beta/small mothers against decapentaplegic pathway, renin angiotensin system, and estrogens, which in turn alter the extracellular matrix. Investigating the underlying mechanisms will allow the development of diagnostic and prognostic tools and discover novel specific therapies. Serum biomarkers aid in the diagnosis and tracking of cardiac fibrosis progression. The diagnostic gold standard is cardiac magnetic resonance with gadolinium administration that allows quantification of cardiac fibrosis either by late gadolinium enhancement assessment or by T1 mapping. Therefore, the goal is to stop and even reverse cardiac fibrosis by developing specific therapies that directly target fibrogenesis, in addition to the drugs used to treat heart failure. Cardiac resynchronization therapy had shown to revert myocardial remodeling and to reduce cardiac fibrosis. The purpose of this review is to provide an overview of currently available data.

Prelamin A mediates myocardial inflammation in dilated and HIV-associated cardiomyopathies

Cardiomyopathies are complex heart muscle diseases that can be inherited or acquired. Dilated cardiomyopathy can result from mutations in LMNA, encoding the nuclear intermediate filament proteins lamin A/C. Some LMNA mutations lead to accumulation of the lamin A precursor, prelamin A, which is disease causing in a number of tissues, yet its impact upon the heart is unknown. Here, we discovered myocardial prelamin A accumulation occurred in a case of dilated cardiomyopathy, and we show that a potentially novel mouse model of cardiac-specific prelamin A accumulation exhibited a phenotype consistent with inflammatory cardiomyopathy, which we observed to be similar to HIV-associated cardiomyopathy, an acquired disease state. Numerous HIV protease therapies are known to inhibit ZMPSTE24, the enzyme responsible for prelamin A processing, and we confirmed that accumulation of prelamin A occurred in HIV+ patient cardiac biopsies. These findings (a) confirm a unifying pathological role for prelamin A common to genetic and acquired cardiomyopathies; (b) have implications for the management of HIV patients with cardiac disease, suggesting protease inhibitors should be replaced with alternative therapies (i.e., nonnucleoside reverse transcriptase inhibitors); and (c) suggest that targeting inflammation may be a useful treatment strategy for certain forms of inherited cardiomyopathy.

Inhibition of profibrotic microRNA-21 affects platelets and their releasate

Fibrosis is a major contributor to organ disease for which no specific therapy is available. MicroRNA-21 (miR-21) has been implicated in the fibrogenetic response, and inhibitors of miR-21 are currently undergoing clinical trials. Here, we explore how miR-21 inhibition may attenuate fibrosis using a proteomics approach. Transfection of miR-21 mimic or inhibitor in murine cardiac fibroblasts revealed limited effects on extracellular matrix (ECM) protein secretion. Similarly, miR-21–null mouse hearts showed an unaltered ECM composition. Thus, we searched for additional explanations as to how miR-21 might regulate fibrosis. In plasma samples from the community-based Bruneck Study, we found a marked correlation of miR-21 levels with several platelet-derived profibrotic factors, including TGF-β1. Pharmacological miR-21 inhibition with an antagomiR reduced the platelet release of TGF-β1 in mice. Mechanistically, Wiskott-Aldrich syndrome protein, a negative regulator of platelet TGF-β1 secretion, was identified as a direct target of miR-21. miR-21–null mice had lower platelet and leukocyte counts compared with littermate controls but higher megakaryocyte numbers in the bone marrow. Thus, to our knowledge this study reports a previously unrecognized effect of miR-21 inhibition on platelets. The effect of antagomiR-21 treatment on platelet TGF-β1 release, in particular, may contribute to the antifibrotic effects of miR-21 inhibitors.

MicroRNA-21 inhibition may convey its therapeutic benefits in fibrosis through its action in bone marrow cells rather than targeting fibroblasts directly.

Cardiac fibrosis: Cell biological mechanisms, molecular pathways and therapeutic opportunities

Cardiac fibrosis is a common pathophysiologic companion of most myocardial diseases, and is associated with systolic and diastolic dysfunction, arrhythmogenesis, and adverse outcome. Because the adult mammalian heart has negligible regenerative capacity, death of a large number of cardiomyocytes results in reparative fibrosis, a process that is critical for preservation of the structural integrity of the infarcted ventricle. On the other hand, pathophysiologic stimuli, such as pressure overload, volume overload, metabolic dysfunction, and aging may cause interstitial and perivascular fibrosis in the absence of infarction. Activated myofibroblasts are the main effector cells in cardiac fibrosis; their expansion following myocardial injury is primarily driven through activation of resident interstitial cell populations. Several other cell types, including cardiomyocytes, endothelial cells, pericytes, macrophages, lymphocytes and mast cells may contribute to the fibrotic process, by producing proteases that participate in matrix metabolism, by secreting fibrogenic mediators and matricellular proteins, or by exerting contact-dependent actions on fibroblast phenotype. The mechanisms of induction of fibrogenic signals are dependent on the type of primary myocardial injury. Activation of neurohumoral pathways stimulates fibroblasts both directly, and through effects on immune cell populations. Cytokines and growth factors, such as Tumor Necrosis Factor-α, Interleukin (IL)-1, IL-10, chemokines, members of the Transforming Growth Factor-β family, IL-11, and Platelet-Derived Growth Factors are secreted in the cardiac interstitium and play distinct roles in activating specific aspects of the fibrotic response. Secreted fibrogenic mediators and matricellular proteins bind to cell surface receptors in fibroblasts, such as cytokine receptors, integrins, syndecans and CD44, and transduce intracellular signaling cascades that regulate genes involved in synthesis, processing and metabolism of the extracellular matrix. Endogenous pathways involved in negative regulation of fibrosis are critical for cardiac repair and may protect the myocardium from excessive fibrogenic responses. Due to the reparative nature of many forms of cardiac fibrosis, targeting fibrotic remodeling following myocardial injury poses major challenges. Development of effective therapies will require careful dissection of the cell biological mechanisms, study of the functional consequences of fibrotic changes on the myocardium, and identification of heart failure patient subsets with overactive fibrotic responses.

Protease Inhibitors and Cardiovascular Outcomes in Patients With HIV and Heart Failure

BACKGROUND

Incident heart failure (HF) is increased in persons with human immunodeficiency virus (PHIV). Protease inhibitors (PIs) are associated with adverse cardiac remodeling and vascular events; however, there are no data on the use of PIs in PHIV with HF.

OBJECTIVES

This study sought to compare characteristics, cardiac structure, and outcomes in PHIV with HF who were receiving PI-based versus non-PI (NPI) therapy.

METHODS

This was a retrospective single-center study of all 394 antiretroviral therapy-treated PHIV who were hospitalized with HF in 2011, stratified by PI and NPI. The primary outcome was cardiovascular (CV) mortality, and the secondary outcome was 30-day HF readmission rate.

RESULTS

Of the 394 PHIV with HF (47% female, mean age 60 ± 9.5 years, CD4 count 292 ± 206 cells/mm3), 145 (37%) were prescribed a PI, whereas 249 (63%) were prescribed NPI regimens. All PI-based antiretroviral therapy contained boosted-dose ritonavir. PHIV who were receiving a PI had higher rates of hyperlipidemia, diabetes mellitus, and coronary artery disease (CAD); higher pulmonary artery systolic pressure (PASP); and lower left ventricular ejection fraction. In follow-up, PI use was associated with increased CV mortality (35% vs. 17%; p < 0.001) and 30-day HF readmission (68% vs. 34%; p < 0.001), effects seen in all HF types. Predictors of CV mortality included PI use, CAD, PASP, and immunosuppression. Overall, PIs were associated with a 2-fold increased risk of CV mortality.

CONCLUSIONS

PI-based regimens in PHIV with HF are associated with dyslipidemia, diabetes, CAD, a lower left ventricular ejection fraction, and a higher PASP. In follow-up, PHIV with HF who are receiving a PI have increased CV mortality and 30-day HF readmission.

HIV-associated cardiovascular disease: importance of platelet activation and cardiac fibrosis in the setting of specific antiretroviral therapies

HIV infection is a risk factor for cardiovascular disease (CVD). This risk is accentuated by certain combination antiretroviral therapies (cARTs), independent of their effects on lipid metabolism and insulin sensitivity. We sought to define potential mechanisms for this association through systematic review of clinical and preclinical studies of CVD in the setting of HIV/cART from the English language literature from 1989 to March 2018. We used PubMed, Web of Knowledge and Google Scholar, and conference abstracts for the years 2015-March 2018. We uncovered three themes: (1) a critical role for the HIV protease inhibitor (PI) ritonavir and certain other PI-based regimens. (2) The importance of platelet activation. Virtually all PIs, and one nucleoside reverse transcriptase inhibitor, abacavir, activate platelets, but a role for this phenomenon in clinical CVD risk may require additional postactivation processes, including: release of platelet transforming growth factor-β1; induction of oxidative stress with production of reactive oxygen species from vascular cells; suppression of extracellular matrix autophagy; and/or sustained proinflammatory signalling, leading to cardiac fibrosis and dysfunction. Cardiac fibrosis may underlie an apparent shift in the character of HIV-linked CVD over the past decade from primarily left ventricular systolic to diastolic dysfunction, possibly driven by cART. (3) Recognition of the need for novel interventions. Switching from cART regimens based on PIs to contemporary antiretroviral agents such as the integrase strand transfer inhibitors, which have not been linked to clinical CVD, may not mitigate CVD risk assumed under prior cART. In conclusion, attention to the effects of specific antiretroviral drugs on platelet activation and related profibrotic signalling pathways should help: guide selection of appropriate anti-HIV therapy; assist in evaluation of CVD risk related to novel antiretrovirals; and direct appropriate interventions.

Platelets in Immune Response to Virus and Immunopathology of Viral Infections

Platelets are essential effector cells in hemostasis. Aside from their role in coagulation, platelets are now recognized as major inflammatory cells with key roles in the innate and adaptive arms of the immune system. Activated platelets have key thromboinflammatory functions linking coagulation to immune responses in various infections, including in response to virus. Recent studies have revealed that platelets exhibit several pattern recognition receptors (PRR) including those from the toll-like receptor, NOD-like receptor, and C-type lectin receptor family and are first-line sentinels in detecting and responding to pathogens in the vasculature. Here, we review the main mechanisms of platelets interaction with viruses, including their ability to sustain viral infection and replication, their expression of specialized PRR, and activation of thromboinflammatory responses against viruses. Finally, we discuss the role of platelet-derived mediators and platelet interaction with vascular and immune cells in protective and pathophysiologic responses to dengue, influenza, and human immunodeficiency virus 1 infections.