Primary proteasome inhibition results in cardiac dysfunction

Thromboembolic risk of carfilzomib or bortezomib in combination with lenalidomide and dexamethasone for newly diagnosed multiple myeloma: A comparative systematic review and meta-analysis

Thrombosis represents a frequent and potentially severe complication in individuals diagnosed with multiple myeloma (MM). These events can be driven by both the disease as well as the therapies themselves. Overall, available evidence is inconclusive about the differential thrombogenicity of carfilzomib/lenalidomide/dexamethasone (KRd) and bortezomib/lenalidomide/dexamethasone (VRd). This meta-analysis compares the risk for venous thromboembolism (VTE; including deep venous thrombosis and pulmonary embolism) and arterial thromboembolism (ATE; including myocardial infarction and ischemic stroke) with KRd versus VRd as primary therapy for newly diagnosed MM (NDMM). Out of 510 studies identified after deduplication, one randomized controlled trial and five retrospective cohort studies were included. We analyzed 2304 patients (VRd: 1380; KRd: 924) for VTE events and 2179 patients (VRd: 1316; KRd: 863) for ATE events. Lower rates of VTE were observed in the VRd group when compared with the KRd group (6.16% vs. 8.87%; odds ratio [OR], 0.53; 95% confidence interval [CI], 0.32-0.88; p = .01). Both treatment groups exhibited minimal ATE incidence, with no significant difference between them (0.91% vs. 1.16%; OR, 1.01; 95% CI, 0.24-4.20; p = .99). In view of potential biases from retrospective studies, heterogeneity of baseline population characteristics, and limited access to patient-level data (e.g., VTE risk stratification and type of thromboprophylaxis regimen used) inherent to this meta-analysis, additional research is warranted to further validate our findings and refine strategies for thrombosis prevention in MM.

Transient Left Ventricular Dysfunction from Cardiomyopathies to Myocardial Viability: When and Why Cardiac Function Recovers

Transient left ventricular dysfunction (TLVD), a temporary condition marked by reversible impairment of ventricular function, remains an underdiagnosed yet significant contributor to morbidity and mortality in clinical practice. Unlike the well-explored atherosclerotic disease of the epicardial coronary arteries, the diverse etiologies of TLVD require greater attention for proper diagnosis and management. The spectrum of disorders associated with TLVD includes stress-induced cardiomyopathy, central nervous system injuries, histaminergic syndromes, various inflammatory diseases, pregnancy-related conditions, and genetically determined syndromes. Furthermore, myocardial infarction with non-obstructive coronary arteries (MINOCA) origins such as coronary artery spasm, coronary thromboembolism, and spontaneous coronary artery dissection (SCAD) may also manifest as TLVD, eventually showing recovery. This review highlights the range of ischemic and non-ischemic clinical situations that lead to TLVD, gathering conditions like Tako-Tsubo Syndrome (TTS), Kounis syndrome (KS), Myocarditis, Peripartum Cardiomyopathy (PPCM), and Tachycardia-induced cardiomyopathy (TIC). Differentiation amongst these causes is crucial, as they involve distinct clinical, instrumental, and genetic predictors that bode different outcomes and recovery potential for left ventricular function. The purpose of this review is to improve everyday clinical approaches to treating these diseases by providing an extensive survey of conditions linked with TLVD and the elements impacting prognosis and outcomes.

Novel insights into cardiovascular toxicity of cancer targeted and immune therapies: Beyond ischemia with non-obstructive coronary arteries (INOCA)

Novel immune and targeted therapies approved over the past 2 decades have resulted in dramatic improvements in cancer-specific outcomes for many cancer patients. However, many of these agents can induce cardiovascular toxicity in a subset of patients. The field of cardio-oncology was established based on observations that anti-neoplastic chemotherapies and mantle radiation can lead to premature cardiomyopathy in cancer survivors. While conventional chemotherapy, targeted therapy, and immune therapies can all result in cardiovascular adverse events, the mechanisms, timing, and incidence of these events are inherently different. Many of these effects converge upon the coronary microvasculature to involve, through endocardial endothelial cells, a more direct effect through close proximity to cardiomyocyte with cellular communication and signaling pathways. In this review, we will provide an overview of emerging paradigms in the field of Cardio-Oncology, particularly the role of the coronary microvasculature in mediating cardiovascular toxicity of important cancer targeted and immune therapies. As the number of cancer patients treated with novel immune and targeted therapies grows exponentially and subsequently the number of long-term cancer survivors dramatically increases, it is critical that cardiologists and cardiology researchers recognize the unique potential cardiovascular toxicities of these agents.

Genetic ablation of Lmp2 increases the susceptibility for impaired cardiac function

Proteasome degradation is an integral part of cellular growth and function. Proteasomal intervention may mitigate adverse myocardial remodeling, but is associated with the onset of heart failure. Previously, we have demonstrated that increasing abundance of cardiac Lmp2 and its incorporation into proteasome complexes is an endogenous mechanism for proteasome regulation during hypertrophic remodeling of the heart induced by chronic ß-adrenoreceptor stimulation. Here, we investigated whether Lmp2 is required for myocardial remodeling not driven by inflammation and show that Lmp2 is a tipping element for growth and function in the heart but not for proteasome insufficiency. While it has no apparent impact under unchallenged conditions, myocardial remodeling without Lmp2 exacerbates hypertrophy and restricts cardiac function. Under chronic ß-adrenoreceptor stimulation, as seen in the development of cardiovascular disease and the manifestation of heart failure, genetic ablation of Lmp2 in mice caused augmented concentric hypertrophy of the left ventricle. While the heart rate was similarly elevated as in wildtype, myocardial contractility was not maintained without Lmp2, and apparently uncoupled of the ß-adrenergic response. Normalized to the exacerbated myocardial mass, contractility was reduced by 41% of the pretreatment level, but would appear preserved at absolute level. The lack of Lmp2 interfered with elevated 26S proteasome activities during early cardiac remodeling reported previously, but did not cause bulk proteasome insufficiency, suggesting the Lmp2 containing proteasome subpopulation is required for a selected group of proteins to be degraded. In the myocardial interstitium, augmented collagen deposition suggested matrix stiffening in the absence of Lmp2. Indeed, echocardiography of left ventricular peak relaxation velocity (circumferential strain rate) was reduced in this treatment group. Overall, targeting Lmp2 in a condition mimicking chronic ß-adrenoreceptor stimulation exhibited the onset of heart failure. Anticancer therapy inhibiting proteasome activity, including Lmp2, is associated with adverse cardiac events, in particular heart failure. Sparing Lmp2 may be an avenue to reduce adverse cardiac events when chronic sympathetic nervous system activation cannot be excluded.

Heartbreaker: Detection and prevention of cardiotoxicity in hematological malignancies

Cancer survivors are at significant risk of cardiovascular (CV) morbidity and mortality; patients with hematologic malignancies have a higher rate of death due to heart failure compared to all other cancer subtypes. The majority of conventional hematologic cancer treatments is associated with increased risk of acute and long-term CV toxicity. The incidence of cancer therapy induced CV toxicity depends on the combination of patient characteristics and on the type, dose, and duration of the therapy. Early diagnosis of CV toxicity, appropriate referral, more specific cardiac monitoring follow-up and timely interventions in target patients can decrease the risk of CV adverse events, the interruption of oncological therapy, and improve the patient's prognosis. Herein, we summarize the CV effects of conventional treatments used in hematologic malignancies with a focus on definitions and incidence of the most common CV toxicities, guideline recommended early detection approaches, and preventive strategies before and during cancer treatments.

Small molecules as modulators of the proteostasis machinery: Implication in cardiovascular diseases

With the escalating prevalence of cardiovascular diseases, the substantial socioeconomic burden on healthcare systems is intensifying. Accumulating empirical evidence underscores the pivotal role of the proteostasis network in regulating cardiac homeostasis and function. Disruptions in proteostasis may contribute to the loss of protein function or the acquisition of toxic functions, which are intricately linked to the development of cardiovascular ailments such as atrial fibrillation, heart failure, atherosclerosis, and cardiac aging. It is widely acknowledged that the proteostasis network encompasses molecular chaperones, autophagy, and the ubiquitin proteasome system (UPS). Consequently, the proteostasis network emerges as an appealing target for therapeutic interventions in cardiovascular diseases. Numerous small molecules, acting as modulators of the proteostasis machinery, have exhibited therapeutic efficacy in managing cardiovascular diseases. This review centers on elucidating the role of the proteostasis network in various cardiovascular diseases and explores the potential of small molecules as therapeutic agents.

Cardiovascular Toxicity of Proteasome Inhibitors in Multiple Myeloma Therapy

The treatment for multiple myeloma has advanced significantly over the past few decades. Proteasome inhibitors have become the cornerstone of the treatment of multiple myeloma. However, proteasome inhibitors have shown cardiovascular complications such as hypertension, pulmonary hypertension, heart failure, arrhythmias, ischaemic heart disease and thromboembolism. Detection, monitoring and management of proteasome inhibitor-related cardiovascular toxicity are essential to improve clinical outcomes for patients. Proposed mechanisms of proteasome inhibitor-related cardiovascular toxicity are apoptosis, prolonged inhibition of the ubiquitin-proteasome system, accumulation of improperly folded proteins within cardiomyocytes and higher protein phosphatase 2A activity. To better understand the mechanisms underlying cardiotoxicity, further in vitro and in vivo experiments are required to investigate these hypotheses. Combined use of metformin or angiotensin II receptor blockers with the proteasome inhibitor, carfilzomib, showed an emerging role as a prophylactic therapy because they can preserve heart function in multiple myeloma patients. Metformin is expected to be an effective therapeutic intervention for the management of carfilzomib-induced cardiotoxicity. There has been evidence that three compounds, apremilast, rutin, and dexrazoxane, can reverse carfilzomib-induced cardiotoxicity in rats. The future transition from animal experiments to clinical trials is worth waiting for.

Label-free quantitative proteomics and stress responses in pigs-The case of short or long road transportation

Ethical livestock production is currently a major concern for consumers. In parallel, research has shown that transport duration is an important factor affecting animal welfare and has a negative impact on the final product quality and on the production cost. This study applied proteomics methods to the animal stress/welfare problem in pigs muscle-exudate with the aim to identify proteins indicative of molecular processes underpinning transport stress and to better characterise this species as a biomedical model. A broader perspective of the problem was obtained by applying label-free LC-MS to characterise the proteome response to transport stress (short or long road transportation) in pigs within the same genetic line. A total of 1,464 proteins were identified, following statistical analysis 66 proteins clearly separating pigs subject to short road transportation and pigs subject long road transportation. These proteins were mainly involved in cellular and metabolic processes. Catalase and stress-induced phosphoprotein-1 were further confirmed by Western blot as being involved in the process of self-protection of the cells in response to stress. This study provide an insight into the molecular processes that are involved in pig adaptability to transport stress and are a step-forward for the development of an objective evaluation method of stress in order to improve animal care and management in farm animals.

Cardiac mechanics in response to proteasome inhibition: a prospective study

AIM

Ubiquitin-Proteasome System (UPS) is of paramount importance regarding the function of the myocardial cell. Consistently, inhibition of this system has been found to affect myocardium in experimental models; yet, the clinical impact of UPS inhibition on cardiac function has not been comprehensively examined. Our aim was to gain insight into the effect of proteasome inhibition on myocardial mechanics in humans.

METHODS AND RESULTS

We prospectively evaluated 48 patients with multiple myeloma and an indication to receive carfilzomib, an irreversible proteasome inhibitor. All patients were initially evaluated and underwent echocardiography with speckle tracking analysis. Carfilzomib was administered according to Kd treatment protocol. Follow-up echocardiography was performed at the 3rd and 6th month. Proteasome activity (PrA) was measured in peripheral blood mononuclear cells.At 3 months after treatment, we observed early left ventricular (LV) segmental dysfunction and deterioration of left atrial (LA) remodelling, which was sustained and more pronounced than that observed in a cardiotoxicity control group. At 6 months, LV and right ventricular functions were additionally attenuated (P < 0.05 for all). These changes were independent of blood pressure, endothelial function, inflammation, and cardiac injury levels. Changes in PrA were associated with changes in global longitudinal strain (GLS), segmental LV strain, and LA markers (P < 0.05 for all). Finally, baseline GLS < -18% or LA strain rate > 1.71 were associated with null hypertension events.

CONCLUSION

Inhibition of the UPS induced global deterioration of cardiac function.

Molecular Mechanism of Pathogenesis and Treatment Strategies for AL Amyloidosis

In amyloid light-chain (AL) amyloidosis, small B-cell clones (mostly plasma cell clones) present in the bone marrow proliferate and secrete unstable monoclonal free light chains (FLCs), which form amyloid fibrils that deposit in the interstitial tissue, resulting in organ injury and dysfunction. AL amyloidosis progresses much faster than other types of amyloidosis, with a slight delay in diagnosis leading to a marked exacerbation of cardiomyopathy. In some cases, the resulting heart failure is so severe that chemotherapy cannot be administered, and death sometimes occurs within a few months. To date, many clinical studies have focused on therapeutics, especially chemotherapy, to treat this disease. Because it is necessary to promptly lower FLC, the causative protein of amyloid, to achieve a hematological response, various anticancer agents targeting neoplastic plasma cells are used for the treatment of this disease. In addition, many basic studies using human specimens to elucidate the pathophysiology of AL have been conducted. Gene mutations associated with AL, the characteristics of amyloidogenic LC, and the structural specificity of amyloid fibrils have been clarified. Regarding the mechanism of cellular and tissue damage, the mass effect due to amyloid deposition, as well as the toxicity of pre-fibrillar LC, is gradually being elucidated. This review outlines the pathogenesis and treatment strategies for AL amyloidosis with respect to its molecular mechanisms.

Cardiovascular-specific mortality among multiple myeloma patients: a population-based study

Introduction

Multiple myeloma (MM) survival has greatly improved in recent decades. MM is usually diagnosed at a median age of 66-70 years. MM patients do not necessarily die from primary cancer, so cardiovascular health may be a key factor threatening long-term survival. This study was designed to explore the cardiovascular disease mortality (CVM) trends in MM patients and compare them with those in the general population.

Methods

In total, 88,328 MM patients from the Surveillance, Epidemiology, and End Results (SEER) database (1975-2016) were included. Standardized mortality ratios (SMRs) were used to assess CVM risk.

Results

The CVM risk was significantly higher in MM patients than in the general population (SMR, 1.84 (95% CI, 1.78-1.89)). MM patients had the highest CVM SMR, at 2.62 (95% CI, 2.49-2.75), in the first year after diagnosis, and it decreased over the follow-up period. Over the study period, the incidence of CVM continued to decrease in MM patients diagnosed at age 65-74 (APC, -1.2% (95% CI, -1.9% to -0.4%)) and ⩾75 years (APC, -1.9% (95% CI, -2.6% to -1.2%)) but not younger. CVM was the second-most common cause of death in patients ⩾75 years. In only MM case analyses, male sex, Black race, older age at diagnosis, and earlier year of diagnosis were poor prognostic factors for heart-specific mortality.

Conclusion

The CVM risk in MM patients was significantly higher than that in the general population. To improve survival, cardiovascular health should receive attention upon diagnosis.

In Vivo Murine Models of Cardiotoxicity Due to Anticancer Drugs: Challenges and Opportunities for Clinical Translation

Modern therapeutic approaches have led to an improvement in the chances of surviving a diagnosis of cancer. However, this may come with side effects, with patients experiencing adverse cardiovascular events or exacerbation of underlying cardiovascular disease related to their cancer treatment. Rodent models of chemotherapy-induced cardiotoxicity are useful to define pathophysiological mechanisms of cardiac damage and to identify potential therapeutic targets. The key mechanisms involved in cardiotoxicity induced by specific different antineoplastic agents are summarized in this state-of-the-art review, as well as the rodent models of cardiotoxicity by different classes of anticancer drugs, along with the strategies tested for primary and secondary cardioprotection. Current approaches for early detection of cardiotoxicity in preclinical studies with a focus on the application of advanced imaging modalities and biomarker strategies are also discussed. Potential applications of cardiotoxicity modelling in rodents are illustrated in relation to the advancements of promising research topics of cardiotoxicity. Created with BioRender.com.

Mechanism and prevention strategy of a bidirectional relationship between heart failure and cancer (Review)

The relationship between cancer and heart failure has been extensively studied in the last decade. These studies have focused on describing heart injury caused by certain cancer treatments, including radiotherapy, chemotherapy and targeted therapy. Previous studies have demonstrated a higher incidence of cancer in patients with heart failure. Heart failure enhances an over-activation of the sympathetic nervous system and the renin-angiotensin-aldosterone system, and subsequently promotes cancer development. Other studies have found that heart failure and cancer both have a common pathological origin, flanked by chronic inflammation in certain organs. The present review aims to summarize and describe the recent discoveries, suggested mechanisms and relationships between heart failure and cancer. The current review provides more ideas on clinical prevention strategies according to the pathological mechanism involved.

Elucidating Carfilzomib's Induced Cardiotoxicity in an In Vivo Model of Aging: Prophylactic Potential of Metformin

Background: Carfilzomib is a first-line proteasome inhibitor indicated for relapsed/refractory multiple myeloma (MM), with its clinical use being hampered by cardiotoxic phenomena. We have previously established a translational model of carfilzomib cardiotoxicity in young adult mice, in which metformin emerged as a prophylactic therapy. Considering that MM is an elderly disease and that age is an independent risk factor for cardiotoxicity, herein, we sought to validate carfilzomib’s cardiotoxicity in an in vivo model of aging. Methods: Aged mice underwent the translational two- and four-dose protocols without and with metformin. Mice underwent echocardiography and were subsequently sacrificed for molecular analyses in the blood and cardiac tissue. Results: Carfilzomib decreased proteasomal activity both in PBMCs and myocardium in both protocols. Carfilzomib induced mild cardiotoxicity after two doses and more pronounced cardiomyopathy in the four-dose protocol, while metformin maintained cardiac function. Carfilzomib led to an increased Bip expression and decreased AMPKα phosphorylation, while metformin coadministration partially decreased Bip expression and induced AMPKα phosphorylation, leading to enhanced myocardial LC3B-dependent autophagy. Conclusion: Carfilzomib induced cardiotoxicity in aged mice, an effect significantly reversed by metformin. The latter possesses translational importance as it further supports the clinical use of metformin as a potent prophylactic therapy.

Mechanisms and Potential Treatment Options of Heart Failure in Patients With Multiple Myeloma

Multiple myeloma is a pathology of plasma cells, with one of the most common side effects of its treatment is heart failure. In addition, cardiac amyloidosis could cause heart failure by itself. Even though mechanisms of cardiac amyloidosis are known, and they involve lysosomal dysfunction, reactive oxygen species (ROS) accumulation, and infiltrative effect by fibrils, there is no specific agent that could protect from these effects. While the molecular mechanism of doxorubicin cardiotoxicity via topoisomerase II β is established, the only FDA-approved agent for treatment is dexrazoxane. Liposomal doxorubicin can potentially improve response and decrease the development of heart failure due to microscopic liposomes that can accumulate and penetrate only tumor vasculature. Supplements that enhance mitochondrial biogenesis are also shown to improve doxorubicin-induced cardiotoxicity. Other agents, such as JR-311, ICRF-193, and ursolic acid, could potentially become new treatment options. Proteasome inhibitors, novel agents, have significantly improved survival rates among multiple myeloma patients. They act on a proteasome system that is highly active in cardiomyocytes and activates various molecular cascades in malignant cells, as well as in the heart, through nuclear factor kappa B (NF-kB), endoplasmic reticulum (ER), calcineurin-nuclear factor of activated T-cells (NFAT), and adenosine monophosphate-activated protein kinase (AMPKa)/autophagy pathways. Metformin, apremilast, and rutin have shown positive results in animal studies and may become a promising therapy as cardioprotective agents. This article aims to highlight the main molecular mechanisms of heart failure among patients with multiple myeloma and potential treatment options to facilitate the development and research of new preventive strategies. Hence, this will have a positive impact on life expectancy in patients with multiple myeloma.

Ixazomib-associated cardiovascular adverse events in multiple myeloma: a systematic review and meta-analysis

Prolonged survival and expanded treatment options in myeloma patients have led to adverse events associated with treatment getting increased attention. This systematic review and meta-analysis aimed to determine the incidence of ixazomib-associated cardiovascular adverse events (CVAEs) and to compare the rates of ixazomib-associated CVAEs and related therapies. CVAEs were defined as heart failure, hypertension, ischemia, and arrhythmia. All-grade and high-grade CVAEs and study characteristics were recorded. A total of 266 potentially relevant articles were identified, and 246 were excluded after review. Twenty studies of 1715 patients with multiple myeloma were thus considered in this study. The estimated rates of all-grade and high-grade ixazomib associated CVAEs were 11.2 and 3.7%, respectively. Subgroup analysis showed that median age ≥65 years, none phase 1 trial and combination regimen were associated with higher rates of high-grade ixazomib associated CVAEs. Ixazomib was association with increased high-grade CVAEs risk (RR = 1.679, 95% CI: 1.078-2.615, P = 0.022). Ixazomib was associated with a significant rate of high-grade CVAEs. Future studies are needed to identify patients at high risk for high-grade CVAEs.

Cellular Protein Quality Control in Diabetic Cardiomyopathy: From Bench to Bedside

Heart failure is a serious comorbidity and the most common cause of mortality in diabetes patients. Diabetic cardiomyopathy (DCM) features impaired cellular structure and function, culminating in heart failure; however, there is a dearth of specific clinical therapy for treating DCM. Protein homeostasis is pivotal for the maintenance of cellular viability under physiological and pathological conditions, particularly in the irreplaceable cardiomyocytes; therefore, it is tightly regulated by a protein quality control (PQC) system. Three evolutionarily conserved molecular processes, the unfolded protein response (UPR), the ubiquitin-proteasome system (UPS), and autophagy, enhance protein turnover and preserve protein homeostasis by suppressing protein translation, degrading misfolded or unfolded proteins in cytosol or organelles, disposing of damaged and toxic proteins, recycling essential amino acids, and eliminating insoluble protein aggregates. In response to increased cellular protein demand under pathological insults, including the diabetic condition, a coordinated PQC system retains cardiac protein homeostasis and heart performance, on the contrary, inappropriate PQC function exaggerates cardiac proteotoxicity with subsequent heart dysfunction. Further investigation of the PQC mechanisms in diabetes propels a more comprehensive understanding of the molecular pathogenesis of DCM and opens new prospective treatment strategies for heart disease and heart failure in diabetes patients. In this review, the function and regulation of cardiac PQC machinery in diabetes mellitus, and the therapeutic potential for the diabetic heart are discussed.

Altered proteasome function in right ventricular hypertrophy

AIMS

In patients with pulmonary hypertension, right ventricular hypertrophy (RVH) is a detrimental condition that ultimately results in right heart failure and death. The ubiquitin proteasome system has been identified as a major protein degradation system to regulate cardiac remodelling in the left heart. Its role in right heart hypertrophy, however, is still ambiguous.

METHODS AND RESULTS

RVH was induced in mice by pulmonary artery banding (PAB). Both, expression and activity of the proteasome was found to be up-regulated in the hypertrophied right ventricle (RV) compared to healthy controls. Catalytic inhibition of the proteasome by the two proteasome inhibitors Bortezomib (BTZ) and ONX-0912 partially improved RVH both in preventive and therapeutic applications. Native gel analysis revealed that specifically the 26S proteasome complexes were activated in experimental RVH. Increased assembly of 26S proteasomes was accompanied by elevated expression of Rpn6, a rate-limiting subunit of 26S proteasome assembly, in hypertrophied cardiomyocytes of the right heart. Intriguingly, patients with RVH also showed increased expression of Rpn6 in hypertrophied cardiomyocytes of the RV as identified by immunohistochemical staining.

CONCLUSION

Our data demonstrate that alterations in expression and activity of proteasomal subunits play a critical role in the development of RVH. Moreover, this study provides an improved understanding on the selective activation of the 26S proteasome in RVH that might be driven by the rate-limiting subunit Rpn6. In RVH, Rpn6 therefore represents a more specific target to interfere with proteasome function than the commonly used catalytic proteasome inhibitors.

Non-Hematologic Toxicity of Bortezomib in Multiple Myeloma: The Neuromuscular and Cardiovascular Adverse Effects

Simple Summary

Multiple myeloma (MM) is a still uncurable tumor of mainly elderly patients originating from the terminally differentiated B cells. Introduction to the treatment of MM patients of a new class of drugs called proteasome inhibitors (bortezomib followed by carfilzomib and ixazomib) significantly improved disease control. Proteasome inhibitors interfere with the major mechanism of protein degradation in a cell leading to the severe imbalance in the protein turnover that is deadly to MM cells. Currently, these drugs are the mainstream of MM therapy but are also associated with an increased rate of the injuries to multiple organs and tissues. In this review, we summarize the current knowledge on the molecular mechanisms of the first-in-class proteasome inhibitor bortezomib-induced disturbances in the function of peripheral nerves and cardiac and skeletal muscle.

Abstract

The overall approach to the treatment of multiple myeloma (MM) has undergone several changes during the past decade. and proteasome inhibitors (PIs) including bortezomib, carfilzomib, and ixazomib have considerably improved the outcomes in affected patients. The first-in-class selective PI bortezomib has been initially approved for the refractory forms of the disease but has now become, in combination with other drugs, the backbone of the frontline therapy for newly diagnosed MM patients, as well as in the maintenance therapy and relapsed/refractory setting. Despite being among the most widely used and highly effective agents for MM, bortezomib can induce adverse events that potentially lead to early discontinuation of the therapy with negative effects on the quality of life and outcome of the patients. Although peripheral neuropathy and myelosuppression have been recognized as the most relevant bortezomib-related adverse effects, cardiac and skeletal muscle toxicities are relatively common in MM treated patients, but they have received much less attention. Here we review the neuromuscular and cardiovascular side effects of bortezomib. focusing on the molecular mechanisms underlying its toxicity. We also discuss our preliminary data on the effects of bortezomib on skeletal muscle tissue in mice receiving the drug.

Come Together: Protein Assemblies, Aggregates and the Sarcostat at the Heart of Cardiac Myocyte Homeostasis

Homeostasis in vertebrate systems is contingent on normal cardiac function. This, in turn, depends on intricate protein-based cellular machinery, both for contractile function, as well as, durability of cardiac myocytes. The cardiac small heat shock protein (csHsp) chaperone system, highlighted by αB-crystallin (CRYAB), a small heat shock protein (sHsp) that forms ∼3–5% of total cardiac mass, plays critical roles in maintaining proteostatic function via formation of self-assembled multimeric chaperones. In this work, we review these ancient proteins, from the evolutionarily preserved role of homologs in protists, fungi and invertebrate systems, as well as, the role of sHsps and chaperones in maintaining cardiac myocyte structure and function. We propose the concept of the “sarcostat” as a protein quality control mechanism in the sarcomere. The roles of the proteasomal and lysosomal proteostatic network, as well as, the roles of the aggresome, self-assembling protein complexes and protein aggregation are discussed in the context of cardiac myocyte homeostasis. Finally, we will review the potential for targeting the csHsp system as a novel therapeutic approach to prevent and treat cardiomyopathy and heart failure.

Pathophysiology and pathological remodelling associated with dilated cardiomyopathy in broiler chickens predisposed to heart pump failure

Broiler chickens selected for rapid growth are highly susceptible to dilated cardiomyopathy (DCM). In order to elucidate the pathophysiology of DCM, the present study examines the fundamental features of pathological remodelling associated with DCM in broiler chickens using light microscopy, transmission electron microscopy (TEM), and synchrotron Fourier Transform Infrared (FTIR) micro-spectroscopy. The morphological features and FTIR spectra of the left ventricular myocardium were compared among broiler chickens affected by DCM with clinical signs of heart pump failure, apparently normal fast-growing broiler chickens showing signs of subclinical DCM (high risk of heart failure), slow-growing broiler chickens (low risk of heart failure) and Leghorn chickens (resistant to heart failure, used here as physiological reference). The findings indicate that DCM and heart pump failure in fast-growing broiler chickens are a result of a complex metabolic syndrome involving multiple catabolic pathways. Our data indicate that a good deal of DCM pathophysiology in chickens selected for rapid growth is associated with conformational changes of cardiac proteins, and pathological changes indicative of accumulation of misfolded and aggregated proteins in the affected cardiomyocytes. From TEM image analysis it is evident that the affected cardiomyocytes demonstrate significant difficulty in the disposal of damaged proteins and maintenance of proteostasis, which leads to pathological remodelling of the heart and contractile dysfunction. It appears that the underlying causes of accumulation of damaged proteins are associated with dysregulated auto phagosome and proteasome systems, which, in susceptible individuals, create a milieu conducive for the development of DCM and heart failure. RESEARCH HIGHLIGHTS The light and electron microscopy image analyses revealed degenerative changes and protein aggregates in the cardiomyocytes of chickens affected by DCM. The analyses of FTIR spectra of the myocardium revealed that DCM and heart pump failure in broiler chickens are associated with conformational changes of myocardial proteins. The morphological changes in cardiomyocytes and conformational changes in myocardial proteins architecture are integral constituents of pathophysiology of DCM in fast-growing broiler chickens.

The proteasome activator REGγ accelerates cardiac hypertrophy by declining PP2Acα-SOD2 pathway

Pathological cardiac hypertrophy eventually leads to heart failure without adequate treatment. REGγ is emerging as 11S proteasome activator of 20S proteasome to promote the degradation of cellular proteins in a ubiquitin- and ATP-independent manner. Here, we found that REGγ was significantly upregulated in the transverse aortic constriction (TAC)-induced hypertrophic hearts and angiotensin II (Ang II)-treated cardiomyocytes. REGγ deficiency ameliorated pressure overload-induced cardiac hypertrophy were associated with inhibition of cardiac reactive oxygen species (ROS) accumulation and suppression of protein phosphatase 2A catalytic subunit α (PP2Acα) decay. Mechanistically, REGγ interacted with and targeted PP2Acα for degradation directly, thereby leading to increase of phosphorylation levels and nuclear export of Forkhead box protein O (FoxO) 3a and subsequent of SOD2 decline, ROS accumulation, and cardiac hypertrophy. Introducing exogenous PP2Acα or SOD2 to human cardiomyocytes significantly rescued the REGγ-mediated ROS accumulation of Ang II stimulation in vitro. Furthermore, treatment with superoxide dismutase mimetic, MnTBAP prevented cardiac ROS production and hypertrophy features that REGγ caused in vivo, thereby establishing a REGγ–PP2Acα–FoxO3a–SOD2 pathway in cardiac oxidative stress and hypertrophy, indicates modulating the REGγ-proteasome activity may be a potential therapeutic approach in cardiac hypertrophy-associated disorders.

The critical roles of protein quality control systems in the pathogenesis of heart failure

Heart failure is a refractory disease with a prevalence that has continuously increased around the world. Over the past decade, we have made remarkable progress in the treatment of heart failure, including drug therapies, device therapies, and regeneration therapies. However, as each of these heart failure therapies does not go much beyond symptomatic therapy, there is a compelling need to establish novel therapeutic strategies for heart failure in a fundamental way. As cardiomyocytes are terminally differentiated cells, protein quality control is critical for maintaining cellular homeostasis, optimal performance, and longevity. There are five evolutionarily conserved mechanisms for ensuring protein quality control in cells: the ubiquitin-proteasome system, autophagy, the unfolded protein response, SUMOylation, and NEDDylation. Recent research has clarified the molecular mechanism underlying how these processes degrade misfolded proteins and damaged organelles in cardiomyocytes. In addition, a growing body of evidence suggests that deviation from appropriate levels of protein quality control causes cellular dysfunction and death, which in turn leads to heart failure. We herein review recent advances in understanding the role of protein quality control systems in heart disease and discuss the therapeutic potential of modulating protein quality control systems in the human heart.

Ubiquitin and Ubiquitin-like proteins in cardiac disease and protection

Post-translational modification represents an important mechanism to regulate protein function in cardiac cells. Ubiquitin (Ub) and ubiquitin-like proteins (UBLs) are a family of protein modifiers that share a certain extent of sequence and structure similarity. Conjugation of Ub or UBLs to target proteins is dynamically regulated by a set of UBL-specific enzymes and modulates the physical and physiological properties of protein substrates. Ub and UBLs control a strikingly wide spectrum of cellular processes and not surprisingly are involved in the development of multiple human diseases including cardiac diseases. Further identification of novel UBL targets will expand our understanding of the functional diversity of UBL pathways in physiology and pathology. Here we review recent findings on the mechanisms, proteome and functions of a subset of UBLs and highlight their potential impacts on the development and progression of various forms of cardiac diseases.

In vitro and in vivo investigation of cardiotoxicity associated with anticancer proteasome inhibitors and their combination with anthracycline

Although proteasome inhibitors (PIs) are modern targeted anticancer drugs, they have been associated with a certain risk of cardiotoxicity and heart failure (HF). Recently, PIs have been combined with anthracyclines (ANTs) to further boost their anticancer efficacy. However, this raised concerns regarding cardiac safety, which were further supported by several in vitro studies on immature cardiomyocytes. In the present study, we investigated the toxicity of clinically used PIs alone (bortezomib (BTZ), carfilzomib (CFZ)) as well as their combinations with an ANT (daunorubicin (DAU)) in both neonatal and adult ventricular cardiomyocytes (NVCMs and AVCMs) and in a chronic rabbit model of DAU-induced HF. Using NVCMs, we found significant cytotoxicity of both PIs around their maximum plasma concentration (c_max) as well as significant augmentation of DAU cytotoxicity. In AVCMs, BTZ did not induce significant cytotoxicity in therapeutic concentrations, whereas the toxicity of CFZ was significant and more profound. Importantly, neither PI significantly augmented the cardiotoxicity of DAU despite even more profound proteasome-inhibitory activity in AVCMs compared with NVCMs. Furthermore, in young adult rabbits, no significant augmentation of chronic ANT cardiotoxicity was noted with respect to any functional, morphological, biochemical or molecular parameter under study, despite significant inhibition of myocardial proteasome activity. Our experimental data show that combination of PIs with ANTs is not accompanied by an exaggerated risk of cardiotoxicity and HF in young adult animal cardiomyocytes and hearts.

Cardiotoxicity of Carfilzomib in Two Japanese Patients with Relapsed Multiple Myeloma

Although multiple myeloma (MM) had been an incurable hematological malignancy with a poor prognosis, recent advances in novel anti-neoplastic agents, including carfilzomib (a proteasome inhibitor), have improved the prognosis. We herein report two cases of congestive heart failure in patients treated with carfilzomib. Although there are some reports on the cardiotoxicity of carfilzomib, to our knowledge, this is the first report on the cardiac involvement of carfilzomib in Japanese MM patients. We review the critical points from our two cases, with the aim of avoiding carfilzomib-associated heart failure in MM patients.

Bidirectional Relationship Between Cancer and Heart Failure: Old and New Issues in Cardio-oncology

The main focus of cardio-oncology has been the prevention and treatment of the cardiac toxicity of chemotherapy and radiotherapy. Furthermore, several targeted therapies have been associated with unexpected cardiotoxic side-effects. Recently, epidemiological studies reported a higher incidence of cancer in patients with heart failure (HF) compared with individuals without HF. On this basis, it has been proposed that HF might represent an oncogenic condition. This hypothesis is supported by preclinical studies demonstrating that hyperactivation of the sympathetic nervous system and renin-angiotensin-aldosterone system, which is a hallmark of HF, promotes cancer growth and dissemination. Another intriguing possibility is that the co-occurrence of HF and cancer is promoted by a common pathological milieu characterised by a state of chronic low-grade inflammation, which predisposes to both diseases. In this review, we provide an overview of the mechanisms underlying the bidirectional relationship between HF and cancer.

Cardiovascular adverse events in multiple myeloma patients

Multiple myeloma is a malignant disease, caused by an uncontrolled clonal proliferation of a specific group of white blood cells, the plasma cells. Clinical manifestations include bone pain due to osteolysis, hypercalcemia, anemia, and renal insufficiency. Proteasome inhibitors have substantially improved survival of patients suffering from multiple myeloma, providing an efficient treatment option mainly for relapsed and refractory multiple myeloma. Although constituting one substance class, bortezomib, carfilzomib, and ixazomib differ greatly regarding their non-hematologic side effects. This article reviews the clinical and preclinical data on approved proteasome inhibitors in an attempt to decipher the underlying pathomechanisms related to cardiovascular adverse events seen in clinical trials.

Emergence of Members of TRAF and DUB of Ubiquitin Proteasome System in the Regulation of Hypertrophic Cardiomyopathy

The ubiquitin proteasome system (UPS) plays an imperative role in many critical cellular processes, frequently by mediating the selective degradation of misfolded and damaged proteins and also by playing a non-degradative role especially important as in many signaling pathways. Over the last three decades, accumulated evidence indicated that UPS proteins are primal modulators of cell cycle progression, DNA replication, and repair, transcription, immune responses, and apoptosis. Comparatively, latest studies have demonstrated a substantial complexity by the UPS regulation in the heart. In addition, various UPS proteins especially ubiquitin ligases and proteasome have been identified to play a significant role in the cardiac development and dynamic physiology of cardiac pathologies such as ischemia/reperfusion injury, hypertrophy, and heart failure. However, our understanding of the contribution of UPS dysfunction in the plausible development of cardiac pathophysiology and the complete list of UPS proteins regulating these afflictions is still in infancy. The recent emergence of the roles of TNF receptor-associated factor (TRAFs) and deubiquitinating enzymes (DUBs) superfamily in hypertrophic cardiomyopathy has enhanced our knowledge. In this review, we have mainly compiled the TRAF superfamily of E3 ligases and few DUBs proteins with other well-documented E3 ligases such as MDM2, MuRF-1, Atrogin-I, and TRIM 32 that are specific to myocardial hypertrophy. In this review, we also aim to highlight their expression profile following physiological and pathological stimulation leading to the onset of hypertrophic phenotype in the heart that can serve as biomarkers and the opportunity for the development of novel therapies.

Untying the knot: protein quality control in inherited cardiomyopathies

Mutations in genes encoding sarcomeric proteins are the most important causes of inherited cardiomyopathies, which are a major cause of mortality and morbidity worldwide. Although genetic screening procedures for early disease detection have been improved significantly, treatment to prevent or delay mutation-induced cardiac disease onset is lacking. Recent findings indicate that loss of protein quality control (PQC) is a central factor in the disease pathology leading to derailment of cellular protein homeostasis. Loss of PQC includes impairment of heat shock proteins, the ubiquitin-proteasome system, and autophagy. This may result in accumulation of misfolded and aggregation-prone mutant proteins, loss of sarcomeric and cytoskeletal proteins, and, ultimately, loss of cardiac function. PQC derailment can be a direct effect of the mutation-induced activation, a compensatory mechanism due to mutation-induced cellular dysfunction or a consequence of the simultaneous occurrence of the mutation and a secondary hit. In this review, we discuss recent mechanistic findings on the role of proteostasis derailment in inherited cardiomyopathies, with special focus on sarcomeric gene mutations and possible therapeutic applications.

Cardiovascular complications of multiple myeloma in the elderly

INTRODUCTION

Multiple myeloma is a malignant neoplasm characterized by plasma cell proliferation in blood and bone marrow. Approximately two-thirds of the patients with multiple myeloma are >65 years at the time of diagnosis. Patients in this age group often have co-existing cardiovascular diseases. Areas covered: The presence of multiple myeloma adds to the malady by direct deposition of amyloid protein in the heart or via toxicity of chemotherapeutic agents. Cardiac contractile dysfunction, arrhythmias and thromboembolic disorders are the main issues in the management of elderly patients with multiple myeloma. Expert commentary: Assessment of cardiac risk and functional status requires careful evaluation by history, physical examination and imaging studies such as echocardiography and magnetic resonance imaging. The management of cardiovascular disorders in the presence of multiple myeloma is difficult and poses a challenge for the internist, the oncologist, and the cardiologist alike. This review is an overview of the problem of cardiovascular risk in and management of elderly patients with multiple myeloma.

Diminished stress resistance and defective adaptive homeostasis in age-related diseases

Adaptive homeostasis is defined as the transient expansion or contraction of the homeostatic range following exposure to subtoxic, non-damaging, signaling molecules or events, or the removal or cessation of such molecules or events (Mol. Aspects Med. (2016) 49, 1-7). Adaptive homeostasis allows us to transiently adapt (and then de-adapt) to fluctuating levels of internal and external stressors. The ability to cope with transient changes in internal and external environmental stress, however, diminishes with age. Declining adaptive homeostasis may make older people more susceptible to many diseases. Chronic oxidative stress and defective protein homeostasis (proteostasis) are two major factors associated with the etiology of age-related disorders. In the present paper, we review the contribution of impaired responses to oxidative stress and defective adaptive homeostasis in the development of age-associated diseases.

Beyond Anthracyclines: Preemptive Management of Cardiovascular Toxicity in the Era of Targeted Agents for Hematologic Malignancies

Advances in drug discovery have led to the use of effective targeted agents in the treatment of hematologic malignancies. Drugs such as proteasome inhibitors in multiple myeloma and tyrosine kinase inhibitors in chronic myeloid leukemia and non-Hodgkin lymphoma have changed the face of treatment of hematologic malignancies. There are several reports of cardiovascular adverse events related to these newer agents. Both "on-target" and "off-target" effects of these agents can cause organ-specific toxicity. The need for long-term administration for most of these agents requires continued monitoring of toxicity. Moreover, the patient population is older, often over 50 years of age, making them more susceptible to cardiovascular side effects. Additional factors such as prior exposure to anthracyclines often add to this toxicity. In light of their success and widespread use, it is important to recognize and manage the unique side effect profile of targeted agents used in hematologic malignancies. In this article, we review the current data for the incidence of cardiovascular side effects of targeted agents in hematologic malignancies and discuss a preemptive approach towards managing these toxicities.

Safety of ixazomib for the treatment of multiple myeloma

INTRODUCTION

Despite a major positive impact of proteasome inhibitors (PI), such as bortezomib and carfilzomib, on the survival of patients with multiple myeloma (MM) over the last few years, their use in clinical practice is limited by the development of drug resistance, significant side-effects or constraining administration schedules. Ixazomib is the first, and for now the only, oral PI, which was approved by the US Food and Drug Administration in 2015 and by the European Medicines Agency in 2016. Areas covered: In this review, we provide an overview of the preclinical and early-phase studies of ixazomib used as single-agent and in combination. Furthermore, we discuss the results of a recently published pivotal trial, which evaluated the safety profile and clinical benefit of the combination of ixazomib, lenalidomide and dexamethasone versus lenalidomide and dexamethasone alone in 722 patients with relapsed/refractory MM. Expert opinion: Ixazomib combines the comfort of oral administration, substantial clinical efficacy and a good safety profile with manageable side-effects, which mainly comprise low-grade hematological, digestive or cutaneous events, and the agent will therefore play an active part in long-term treatment strategies, both as single agent and as part of combination regimens. Ongoing phase III trials are currently defining its place in first-line, maintenance and relapse settings.

Cardiac events during treatment with proteasome inhibitor therapy for multiple myeloma

BACKGROUND

Proteasome inhibitors (PI) bortezomib and carfilzomib are cornerstone therapies for multiple myeloma. Higher incidence of cardiac adverse events (CAEs) has been reported in patients receiving carfilzomib. However, risk factors for cardiac toxicity remain unclear. Our objective was to evaluate the incidence of CAEs associated with PI and recognize risk factors for developing events.

METHODS

This was a descriptive analysis of 96 patients with multiple myeloma who received bortezomib (n = 44) or carfilzomib (n = 52). We compared the cumulative incidence of CAEs using a log rank test. Patient-related characteristics were assessed and multivariate analysis was used to identify risk factors for developing CAEs.

RESULTS

PI-related CAEs occurred in 21 (22%) patients. Bortezomib-associated CAEs occurred in 7 (16%) patients while carfilzomib-associated cardiac events occurred in 14 (27%) patients. The cumulative incidence of CAEs was not significantly different between agents. Events occurred after a median of 67.5 days on PI therapy. Heart failure was the most prevalent event type. More patients receiving carfilzomib were monitored by a cardiologist. By multivariate analysis, a history of prior cardiac events and longer duration of PI therapy were identified as independent risk factors for developing CAEs.

CONCLUSIONS

AEs were common in patients receiving PIs. Choice of PI did not impact the cumulative incidence of CAEs. Early involvement by a cardiologist in patients at high risk for CAEs may help to mitigate the frequency and severity of CAEs.

Spasmogenic Effects of the Proteasome Inhibitor Carfilzomib on Coronary Resistance, Vascular Tone and Reactivity

Background

Carfilzomib (CFZ) is a new proteasome inhibitor used for the treatment of multiple myeloma. Besides heart failure, angina and myocardial ischemia occurred following administration of CFZ, which is not contraindicated in patients with recent myocardial infarction/unstable angina excluded from the safety trials.

Aim of Study

To test the effects of CFZ (10^− 9 to 10^− 7 mol/L) on vascular tone and reactivity in the isolated rabbit heart and aorta.

Methods and Results

CFZ administered by bolus injection to the isolated heart increased coronary perfusion pressure (CPP) at all tested concentrations and mildly raised left ventricular pressure and heart rate, only at the highest concentration. Addition of CFZ directly into the organ bath increased the basal tone of isolated aortic strips with contraction plateau reached after 10 min. This spasmogenic effect doubled following ablation of the endothelium. Pretreatment with CFZ amplified the vasospastic action exerted by KCl, noradrenaline (NA) and angiotensin II (A) on aortic strips, and impaired vasodilation following administration of nitroglycerin (NTG) and nifedipine (NFP) on the contraction plateau induced by KCl, NA and A. Aortic strips pretreated with CFZ exhibited impaired relaxation, as compared to untreated strips, following administration of acetylcholine (Ach), an endothelium-dependent vasodilating agent, on the plateau of NA contraction (p < 0.05).

Conclusions

CFZ increased CPP, resting vasoconstricting tone and the spasmogenic effect of different agents. Preincubation with CFZ decreased the anti-spasmogenic activity of NTG and NFP, as well as reduced by over 50% the vasodilating effect of Ach, suggesting that CFZ can impair vasodilation via an endothelium dependent mechanism. Further studies are warranted to establish its clinical safety in patients with known CAD and prior history of coronary spasm.

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In the isolated aorta, carfilzomib increased basal tone and vasospastic action of KCl, noradrenaline and angiotensin II.

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In the isolated aorta, carfilzomib impaired the anti-spasmogenic activity of nitroglycerin, nifedipine and acetylcholine.

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In the isolated heart, carfilzomib increased coronary perfusion pressure, and mildly left ventricular pressure and heart rate.

Carfilzomib is a new chemotherapeutic agent used for the treatment of multiple myeloma. Our study shows that carfilzomib increases coronary perfusion pressure, resting vasoconstricting tone, and the spasmogenic effect of noradrenaline and angiotensin II, while it curbs the vasodilatory action of nitroglycerine and nifedipine. Our findings are relevant to human health as they warrant caution in the use of carfilzomib in elderly patients with cardiovascular risk factors and, even more importantly, in those with preexisting heart conditions, who are also eligible to receive carfilzomib, even though they were excluded from the safety trials, based on which carfilzomib use was approved.

Proteasome dysfunction in cardiomyopathies

The ubiquitin-proteasome system (UPS) plays a critical role in removing unwanted intracellular proteins and is involved in protein quality control, signalling and cell death. Because the heart is subject to continuous metabolic and mechanical stress, the proteasome plays a particularly important role in the heart, and proteasome dysfunction has been suggested as a causative factor in cardiac dysfunction. Proteasome impairment has been detected in cardiomyopathies, heart failure, myocardial ischaemia, and hypertrophy. Proteasome inhibition is also sufficient to cause cardiac dysfunction in healthy pigs, and patients using a proteasome inhibitor for cancer therapy have a higher incidence of heart failure. In this Topical Review we discuss the experimental data which suggest UPS dysfunction is a common feature of cardiomyopathies, with an emphasis on hypertrophic cardiomyopathy caused by sarcomeric mutations. We also propose potential mechanisms by which cardiomyopathy-causing mutations may lead to proteasome impairment, such as altered calcium handling and increased oxidative stress due to mitochondrial dysfunction.

First insight into the proteome landscape of the porcine short posterior ciliary arteries: Key signalling pathways maintaining physiologic functions

Short posterior ciliary arteries (sPCA) provide the major blood supply to the optic nerve head. Emerging evidence has linked structural and functional anomalies of sPCA to the pathogenesis of several ocular disorders that cause varying degrees of visual loss, particularly anterior ischaemic optic neuropathy and glaucoma. Although the functional relevance of this vascular bed is well-recognized, the proteome of sPCA remains uncharacterized. Since the porcine ocular system closely resembles that of the human's and is increasingly employed in translational ophthalmic research, this study characterized the proteome of porcine sPCA employing the mass spectrometry-based proteomics strategy. A total of 1742 proteins and 10527 peptides were identified in the porcine sPCA. The major biological processes involved in the maintenance of physiological functions of the sPCA included redox and metabolic processes, and cytoskeleton organization. These proteins were further clustered into diverse signalling pathways that regulate vasoactivity of sPCA, namely the tight junction, α- and β-adrenoceptor, 14-3-3, nitric oxide synthase and endothelin-1 -mediated signalling pathways. This study provides the first insight into the complex mechanisms dictating the vast protein repertoire in normal vascular physiology of the porcine sPCA. It is envisioned that our findings will serve as important benchmarks for future studies of sPCA.

Cardiac proteasome functional insufficiency plays a pathogenic role in diabetic cardiomyopathy

BACKGROUND

Diabetic cardiomyopathy is a major risk factor in diabetic patients but its pathogenesis remains poorly understood. The ubiquitin-proteasome system (UPS) facilitates protein quality control by degrading unnecessary and damaged proteins in eukaryotic cells, and dysfunction of UPS is implicated in various cardiac diseases. However, the overall functional status of the UPS and its pathophysiological role in diabetic cardiomyopathy have not been determined.

METHODS AND RESULTS

Type I diabetes was induced in wild-type and transgenic mice expressing a UPS functional reporter (GFPdgn) by injections of streptozotocin (STZ). STZ-induced diabetes progressively impaired cardiac UPS function as evidenced by the accumulation of GFPdgn proteins beginning two weeks after diabetes induction, and by a buildup of total and lysine (K) 48-linked polyubiquitinated proteins in the heart. To examine the functional role of the UPS in diabetic cardiomyopathy, cardiac overexpression of PA28α (PA28αOE) was used to enhance proteasome function in diabetic mouse hearts. PA28αOE diabetic mice displayed exhibited restoration of cardiac UPS function, as demonstrated by the diminished accumulation of GFPdgn and polyubiquitinated proteins. Moreover, PA28αOE diabetic mice exhibited reduced myocardial collagen deposition, decreased cardiomyocyte apoptosis, and improved cardiac systolic and diastolic function.

CONCLUSION

Impairment of cardiac UPS function is an early event in STZ-induced diabetes. Overexpression of PA28α attenuates diabetes-induced proteotoxic stress and cardiomyopathy, suggesting a potential therapeutic role for enhancement of cardiac proteasome function in this disorder.

Incidence and Risk of Cardiac Events in Patients With Previously Treated Multiple Myeloma Versus Matched Patients Without Multiple Myeloma: An Observational, Retrospective, Cohort Study

BACKGROUND

Multiple myeloma (MM) patients have age-, disease-, and treatment-related risk factors for cardiac events.

MATERIALS AND METHODS

We analyzed the 2006 to 2011 MarketScan database to determine whether the risk of cardiac events is greater in MM patients than in non-MM patients. Included were 1723 MM patients treated with corticosteroids and ≥ 3 drugs (bortezomib, immunomodulatory derivatives, and alkylating agents or anthracyclines). The index date (ID) was the date on which the 3-drug exposure criterion was met. Also included were 8615 age- and gender-matched non-MM patients (5:1). The distribution of non-MM patients' IDs matched that of the MM patients' IDs. Baseline was 6 months before the ID. The follow-up duration was from the ID to study end (ie, 2011 or end of enrollment or prescription drug coverage). Hazard ratios (HRs) and 95% confidence intervals (CIs) were adjusted for baseline variables when the univariate analyses showed a 10% difference.

RESULTS

The median duration of observation was 9 months (range, 0-60 months) for MM patients and 19 months (range, 0-66 months) for non-MM patients. The risk of any cardiac event (HR, 2.2; 95% CI, 1.9-2.5), dysrhythmia (HR, 4.1; 95% CI, 3.5-4.8), congestive heart failure (HR, 2.9; 95% CI, 2.2-3.7), cardiomyopathy (HR, 2.6; 95% CI, 1.8-3.8), and conduction disorders (HR, 1.7; 95% CI, 1.2-2.5) was significantly greater for MM than for non-MM patients. The incidence of hypertensive or arterial events and ischemic heart disease was similar between the 2 groups.

CONCLUSION

The present study provides the first known comparison of cardiac event risk in patients with MM versus age- and gender-matched patients without MM. The cardiac event risk was greater in MM patients with ≥ 3 previous drugs for any cardiac event, dysrhythmias, congestive heart failure, cardiomyopathy, and conduction disorders compared with patients without MM.

Sodium Sulfide Attenuates Ischemic-Induced Heart Failure by Enhancing Proteasomal Function in an Nrf2-Dependent Manner

BACKGROUND

Therapeutic strategies aimed at increasing hydrogen sulfide (H2S) levels exert cytoprotective effects in various models of cardiovascular injury. However, the underlying mechanism(s) responsible for this protection remain to be fully elucidated. Nuclear factor E2-related factor 2 (Nrf2) is a cellular target of H2S and facilitator of H2S-mediated cardioprotection after acute myocardial infarction. Here, we tested the hypothesis that Nrf2 mediates the cardioprotective effects of H2S therapy in the setting of heart failure.

METHODS AND RESULTS

Mice (12 weeks of age) deficient in Nrf2 (Nrf2 KO; C57BL/6J background) and wild-type littermates were subjected to ischemic-induced heart failure. Wild-type mice treated with H2S in the form of sodium sulfide (Na2S) displayed enhanced Nrf2 signaling, improved left ventricular function, and less cardiac hypertrophy after the induction of heart failure. In contrast, Na2S therapy failed to provide protection against heart failure in Nrf2 KO mice. Studies aimed at evaluating the underlying cardioprotective mechanisms found that Na2S increased the expression of proteasome subunits, resulting in an increased proteasome activity and a reduction in the accumulation of damaged proteins. In contrast, Na2S therapy failed to enhance the proteasome and failed to attenuate the accumulation of damaged proteins in Nrf2 KO mice. Additionally, Na2S failed to improve cardiac function when the proteasome was inhibited.

CONCLUSIONS

These findings indicate that Na2S therapy enhances proteasomal activity and function during the development of heart failure in an Nrf2-dependent manner and that this enhancement leads to attenuation in cardiac dysfunction.

Different effects of the nonsteroidal anti-inflammatory drugs meclofenamate sodium and naproxen sodium on proteasome activity in cardiac cells

The use of nonsteroidal anti-inflammatory drugs (NSAIDs) like meclofenamate sodium (MS), used to reduce pain, has been associated with an increased risk of cardiovascular disease (CVD). Naproxen (NAP), another NSAID, is not associated with increased risk of CVD. The molecular mechanism(s) by which NSAIDs induce CVD is unknown. We investigated the effects of MS and NAP on protein homeostasis and cardiotoxicity in rat cardiac H9c2 cells and murine neonatal cardiomyocytes. MS, but not NAP, significantly inhibited proteasome activity and reduced cardiac cell viability at pharmacological levels found in humans. Although proteasome subunit gene and protein expression were unaffected by NSAIDs, MS treated cell lysates showed higher 20S proteasome content, while purified proteasomes from MS treated cells had lower proteasome activity and higher levels of oxidized subunits than proteasomes from control cells. Addition of exogenous proteasome to MS treated cells improved cell viability. Both MS and NAP increased ROS production, but the rate of ROS production was greater in MS than in NAP treated cells. The ROS production is likely from mitochondria, as MS inhibited mitochondrial Complexes I and III, major sources of ROS, while NAP inhibited Complex I. MS also impaired mitochondrial membrane potential while NAP did not. Antioxidants were able to prevent the reduced cell viability caused by MS treatment. These results suggest that NSAIDs induce cardiotoxicity by a ROS dependent mechanism involving mitochondrial and proteasome dysfunction and may explain why some NSAIDs should not be given to patients for long periods.

Delineation of Molecular Pathways Involved in Cardiomyopathies Caused by Troponin T Mutations

Familial hypertrophic cardiomyopathy (FHC) is associated with mild to severe cardiac problems and is the leading cause of sudden death in young people and athletes. Although the genetic basis for FHC is well-established, the molecular mechanisms that ultimately lead to cardiac dysfunction are not well understood. To obtain important insights into the molecular mechanism(s) involved in FHC, hearts from two FHC troponin T models (Ile79Asn [I79N] and Arg278Cys [R278C]) were investigated using label-free proteomics and metabolomics. Mutations in troponin T are the third most common cause of FHC, and the I79N mutation is associated with a high risk of sudden cardiac death. Most FHC-causing mutations, including I79N, increase the Ca(2+) sensitivity of the myofilament; however, the R278C mutation does not alter Ca(2+) sensitivity and is associated with a better prognosis than most FHC mutations. Out of more than 1200 identified proteins, 53 and 76 proteins were differentially expressed in I79N and R278C hearts, respectively, when compared with wild-type hearts. Interestingly, more than 400 proteins were differentially expressed when the I79N and R278C hearts were directly compared. The three major pathways affected in I79N hearts relative to R278C and wild-type hearts were the ubiquitin-proteasome system, antioxidant systems, and energy production pathways. Further investigation of the proteasome system using Western blotting and activity assays showed that proteasome dysfunction occurs in I79N hearts. Metabolomic results corroborate the proteomic data and suggest the glycolytic, citric acid, and electron transport chain pathways are important pathways that are altered in I79N hearts relative to R278C or wild-type hearts. Our findings suggest that impaired energy production and protein degradation dysfunction are important mechanisms in FHCs associated with poor prognosis and that cardiac hypertrophy is not likely needed for a switch from fatty acid to glucose metabolism.

Priming the proteasome by protein kinase G: a novel cardioprotective mechanism of sildenafil

The proteasome mediates the degradation of most cellular proteins including misfolded proteins, pivotal to intracellular protein hemostasis. Proteasome functional insufficiency is implicated in a large subset of human failing hearts. Experimental studies have established proteasome functional insufficiency as a major pathogenic factor, rationalizing proteasome enhancement as a potentially new therapeutic strategy for congestive heart failure. Protein kinase G activation known to be cardioprotective was recently found to facilitate proteasomal degradation of misfolded proteins in cardiomyocytes; sildenafil was shown to activate myocardial protein kinase G, improve cardiac protein quality control and slow down the progression of cardiac proteinopathy in mice. This identifies the first clinically used drug that is capable of benign proteasome enhancement and unveils a potentially novel cardioprotective mechanism for sildenafil.

Metabolomic Quantitative Trait Loci (mQTL) Mapping Implicates the Ubiquitin Proteasome System in Cardiovascular Disease Pathogenesis

Levels of certain circulating short-chain dicarboxylacylcarnitine (SCDA), long-chain dicarboxylacylcarnitine (LCDA) and medium chain acylcarnitine (MCA) metabolites are heritable and predict cardiovascular disease (CVD) events. Little is known about the biological pathways that influence levels of most of these metabolites. Here, we analyzed genetics, epigenetics, and transcriptomics with metabolomics in samples from a large CVD cohort to identify novel genetic markers for CVD and to better understand the role of metabolites in CVD pathogenesis. Using genomewide association in the CATHGEN cohort (N = 1490), we observed associations of several metabolites with genetic loci. Our strongest findings were for SCDA metabolite levels with variants in genes that regulate components of endoplasmic reticulum (ER) stress (USP3, HERC1, STIM1, SEL1L, FBXO25, SUGT1) These findings were validated in a second cohort of CATHGEN subjects (N = 2022, combined p = 8.4x10^-6–2.3x10^-10). Importantly, variants in these genes independently predicted CVD events. Association of genomewide methylation profiles with SCDA metabolites identified two ER stress genes as differentially methylated (BRSK2 and HOOK2). Expression quantitative trait loci (eQTL) pathway analyses driven by gene variants and SCDA metabolites corroborated perturbations in ER stress and highlighted the ubiquitin proteasome system (UPS) arm. Moreover, culture of human kidney cells in the presence of levels of fatty acids found in individuals with cardiometabolic disease, induced accumulation of SCDA metabolites in parallel with increases in the ER stress marker BiP. Thus, our integrative strategy implicates the UPS arm of the ER stress pathway in CVD pathogenesis, and identifies novel genetic loci associated with CVD event risk.

Cardiovascular disease is a strongly heritable trait. Despite application of the latest genomic technologies, the genetic architecture of disease risk remains poorly defined, and mechanisms underlying this susceptibility are incompletely understood. In this study, we performed genome-wide mapping of heart disease-related metabolites measured in the blood as the genetic traits of interest (instead of the disease itself), in a large cohort of 3512 patients at risk of heart disease from the CATHGEN study. Our goal was to discover new cardiovascular disease genes and thereby mechanisms of disease pathogenesis by understanding the genes that regulate levels of these metabolites. These analyses identified novel genetic variants associated with metabolite levels and with cardiovascular disease itself. Importantly, by utilizing an unbiased systems-based approach integrating genetics, gene expression, epigenetics and metabolomics, we uncovered a novel pathway of heart disease pathogenesis, that of endoplasmic reticulum (ER) stress, represented by elevated levels of circulating short-chain dicarboxylacylcarnitine (SCDA) metabolites.