Atrophic cardiomyocyte signaling in hypertensive heart disease

Therapy-naïve malignancy causes cardiovascular disease: a state-of-the-art cardio-oncology perspective

Cardiovascular disease (CVD) and cancer are the leading causes of mortality worldwide. Although generally thought of as distinct diseases, the intersectional overlap between CVD and cancer is increasingly evident in both causal and mechanistic relationships. The field of cardio-oncology is largely focused on the cardiotoxic effects of cancer therapies (e.g., chemotherapy, radiation). Furthermore, the cumulative effects of cardiotoxic therapy exposure and the prevalence of CVD risk factors in patients with cancer lead to long-term morbidity and poor quality of life in this patient population, even when patients are cancer-free. Evidence from patients with cancer and animal models demonstrates that the presence of malignancy itself, independent of cardiotoxic therapy exposure or CVD risk factors, negatively impacts cardiac structure and function. As such, the primary focus of this review is the cardiac pathophysiological and molecular features of therapy-naïve cancer. We also summarize the strengths and limitations of preclinical cancer models for cardio-oncology research and discuss therapeutic strategies that have been tested experimentally for the treatment of cancer-induced cardiac atrophy and dysfunction. Finally, we explore an adjacent area of interest, called "reverse cardio-oncology," where the sequelae of heart failure augment cancer progression. Here, we emphasize the cross-disease communication between malignancy and the injured heart and discuss the importance of chronic low-grade inflammation and endocrine factors in the progression of both diseases.

Distinct Cardiac Connexin-43 Expression in Hypertrophied and Atrophied Myocardium May Impact the Vulnerability of the Heart to Malignant Arrhythmias. A Pilot Study

Our and other studies suggest that myocardial hypertrophy in response to hypertension and hyperthyroidism increases propensity of the heart to malignant arrhythmias, while these are rare in conditions of hypothyroidism or type-1 diabetes mellitus associated with myocardial atrophy. One of the crucial factors impacting the susceptibility of the heart to life-threatening arrhythmias is gap junction channel protein connexin-43 (Cx43), which ensure cell-to-cell coupling for electrical signal propagation. Therefore, we aimed to explore Cx43 protein abundance and its topology in hypertrophic and hypotrophic cardiac phenotype. Analysis were performed in left ventricular tissue of adult male spontaneously hypertensive rat (SHR), Wistar Kyoto rats treated for 8-weeks with L-thyroxine, methimazol or strepotozotocin to induce hyperthyroid, hypothyroid and type-1 diabetic status as well as non-treated animals. Results showed that comparing to healthy rats there was a decrease of total myocardial Cx43 and its variant phosphorylated at serine368 in SHR and hyperthyroid rats. Besides, enhanced localization of Cx43 was demonstrated on lateral sides of hypertrophied cardiomyocytes. In contrast, total Cx43 protein and its serine368 variant were increased in atrophied left ventricle of hypothyroid and type-1 diabetic rats. It was associated with less pronounced alterations in Cx43 topology. In parallel, the abundance of PKCepsilon, which phosphorylates Cx43 at serine368 that stabilize Cx43 function and distribution was reduced in hypertrophied heart while enhanced in atrophied once. Findings suggest that differences in the abundance of cardiac Cx43, its variant phosphorylated at serine368 and Cx43 topology may explain, in part, distinct propensity of hypertrophied and atrophied heart to malignant arrhythmias.

Does Myocardial Atrophy Represent Anti-Arrhythmic Phenotype?

This review focuses on cardiac atrophy resulting from mechanical or metabolic unloading due to various conditions, describing some mechanisms and discussing possible strategies or interventions to prevent, attenuate or reverse myocardial atrophy. An improved awareness of these conditions and an increased focus on the identification of mechanisms and therapeutic targets may facilitate the development of the effective treatment or reversion for cardiac atrophy. It appears that a decrement in the left ventricular mass itself may be the central component in cardiac deconditioning, which avoids the occurrence of life-threatening arrhythmias. The depressed myocardial contractility of atrophied myocardium along with the upregulation of electrical coupling protein, connexin43, the maintenance of its topology, and enhanced PKCƐ signalling may be involved in the anti-arrhythmic phenotype. Meanwhile, persistent myocardial atrophy accompanied by oxidative stress and inflammation, as well as extracellular matrix fibrosis, may lead to severe cardiac dysfunction, and heart failure. Data in the literature suggest that the prevention of heart failure via the attenuation or reversion of myocardial atrophy is possible, although this requires further research.

Preoperative myocardial expression of E3 ubiquitin ligases in aortic stenosis patients undergoing valve replacement and their association to postoperative hypertrophy

Currently, aortic valve replacement is the only treatment capable of relieving left ventricle pressure overload in patients with severe aortic stenosis. It aims to improve cardiac function and revert hypertrophy, by triggering myocardial reverse remodeling. Despite immediately relieving afterload, reverse remodeling turns out to be extremely variable. Among other factors, the extent of reverse remodeling may depend on how well ubiquitin-proteasome system tackle hypertrophy. Therefore, we assessed tagged ubiquitin and ubiquitin ligases in the left ventricle collected from patients undergoing valve replacement and tested their association to the degree of reverse remodeling. Patients were classified according to the regression of left ventricle mass (ΔLVM) and assigned to complete (ΔLVM≥15%) or incomplete (ΔLVM≤5%) reverse remodeling groups. No direct inter-group differences were observed. Nevertheless, correlation analysis supports a fundamental role of the ubiquitin-proteasome system during reverse remodeling. Indeed, total protein ubiquitination was associated to hypertrophic indexes such as interventricular septal thickness (r = 0.55, p = 0.03) and posterior wall thickness (r = 0.65, p = 0.009). No significant correlations were observed for Muscle Ring Finger 3. Surprisingly, though, higher levels of atrogin-1 were associated to postoperative interventricular septal thickness (r = 0.71, p = 0.005). In turn, Muscle Ring Finger 1 correlated negatively with this postoperative hypertrophy marker (r = -0.68, p = 0.005), suggesting a cardioprotective role during reverse remodeling. No significant correlations were found with left ventricle mass regression, although a trend for a negative association between the ligase Murine Double Minute 2 and mass regression (r = -0.44, p = 0.10) was found. Animal studies will be necessary to understand whether this ligase is protective or detrimental. Herein, we show, for the first time, an association between the preoperative myocardial levels of ubiquitin ligases and postoperative hypertrophy, highlighting the therapeutic potential of targeting ubiquitin ligases in incomplete reverse remodeling.

Depressed Myocardial Contractility: Can It Be Rescued?

Current dogma suggests patients with advanced systolic heart failure have an irreversible depression in myocardial contractility. Recent experience with improved ventricular function during continuous flow ventricular assist devices used as destination therapy would suggest otherwise. Herein, cellular and molecular signaling involved in reversing depressed myocardial contractility would be addressed. This includes cardiomyocyte thyroid hormone signaling responsible for the reexpression of fetal gene program that preserves cell efficiency (work and energy consumed) and the rescue of an endogenous population of atrophic myocytes bordering on microdomains of fibrosis to improve contractile mass.

Urinary congophilia in women with hypertensive disorders of pregnancy and preexisting proteinuria or hypertension

BACKGROUND

Congophilia indicates the presence of amyloid protein, which is an aggregate of misfolded proteins, that is implicated in the pathophysiologic condition of preeclampsia. Recently, urinary congophilia has been proposed as a test for the diagnosis and prediction of preeclampsia.

OBJECTIVES

The purpose of this study was to determine whether urine congophilia is present in a cohort of women with preeclampsia and in pregnant and nonpregnant women with renal disease.

STUDY DESIGN

With the use of a preeclampsia, chronic hypertension, renal disease, and systemic lupus erythematosus cohort, we analyzed urine samples from healthy pregnant control subjects (n = 31) and pregnant women with preeclampsia (n = 23), gestational hypertension (n = 10), chronic hypertension (n = 14), chronic kidney disease; n = 28), chronic kidney disease with superimposed preeclampsia (n = 5), and chronic hypertension and superimposed preeclampsia (n = 12). Samples from nonpregnant control subjects (n = 10) and nonpregnant women with either systemic lupus erythematosus with (n = 25) and without (n = 14) lupus nephritis were analyzed. For each sample, protein concentration was standardized before it was mixed with Congo Red, spotted to nitrocellulose membrane, and rinsed with methanol. The optical density of the residual Congo Red stain was determined; Congo red stain retention was calculated, and groups were compared with the use of the Mann-Whitney test or Kruskal-Wallis analysis of Variance test, as appropriate.

RESULTS

Congophilia was increased in urine from women with preeclampsia (median Congo red stain retention, 47%; interquartile range, 22-68%) compared with healthy pregnant control subjects (Congo red stain retention: 16%; interquartile range, 13-21%; P = .002), women with gestational hypertension (Congo red stain retention, 20%; interquartile range, 13-27%; P = .008), or women with chronic hypertension (Congo red stain retention, 17%; interquartile range, 12-28%; P = .01). There were no differences in Congo red retention between pregnant women with chronic hypertension and normal pregnant control subjects (Congo red stain retention, 17% [interquartile range, 12-28%] vs 16% [interquartile range, 13-21%], respectively; P = .72). Congophilia was present in pregnant women with chronic kidney disease (Congo red stain retention, 32%; interquartile range, 14-57%), being similar to values found in women with preeclampsia (P = .22) and for women with chronic kidney disease and superimposed preeclampsia (Congo red stain retention, 57%; [interquartile range, 29-71%; P = .18). Nonpregnant women with lupus nephritis had higher congophilia levels compared with nonpregnant female control subjects (Congo red stain retention, 38% [interquartile range, 17-73%] vs 9% [7-11%], respectively; P < .001) and nonpregnant women with systemic lupus erythematosus without nephritis (Congo red stain retention, 38% [interquartile range, 17-73%] vs 13% [interquartile range, 11-17%], respectively; P = .001). A significant positive correlation was observed between congophilia and protein:creatinine ratio (Spearman rank correlations, 0.702; 95% confidence interval, 0.618-0.770; P < .001).

CONCLUSION

This study confirms that women with preeclampsia and chronic kidney disease without preeclampsia have elevated urine congophilia levels compared with healthy pregnant women. Nonpregnant women with lupus nephritis also have elevated urine congophilia levels compared with healthy control subjects. An elevated Congo Red stain retention may not be able to differentiate between these conditions; further research is required to explore the use of congophilia in clinical practice.

Myofibroblast secretome and its auto-/paracrine signaling

Myofibroblasts (myoFb) are phenotypically transformed, contractile fibroblast-like cells expressing α-smooth muscle actin microfilaments. They are integral to collagen fibrillogenesis with scar tissue formation at sites of repair irrespective of the etiologic origins of injury or tissue involved. MyoFb can persist long after healing is complete, where their ongoing turnover of collagen accounts for a progressive structural remodeling of an organ (a.k.a. fibrosis, sclerosis or cirrhosis). Such persistent metabolic activity is derived from a secretome consisting of requisite components in the de novo generation of angiotensin (Ang) II. Autocrine and paracrine signaling induced by tissue AngII is expressed via AT1 receptor ligand binding to respectively promote: i) regulation of myoFb collagen synthesis via the fibrogenic cytokine TGF-β1-Smad pathway; and ii) dedifferentiation and protein degradation of atrophic myocytes immobilized and ensnared by fibrillar collagen at sites of scarring. Several cardioprotective strategies in the prevention of fibrosis and involving myofibroblasts are considered. They include: inducing myoFb apoptosis through inactivation of antiapoptotic proteins; AT1 receptor antagonist to interfere with auto-/paracrine myoFb signaling or to induce counterregulatory expression of ACE2; and attacking the AngII-AT1R-TGF-β1-Smad pathway by antibody or the use of triplex-forming oligonucleotides.

Small dedifferentiated cardiomyocytes bordering on microdomains of fibrosis: evidence for reverse remodeling with assisted recovery

With the perspective of functional myocardial regeneration, we investigated small cardiomyocytes bordering on microdomains of fibrosis, where they are dedifferentiated re-expressing fetal genes, and determined: (1) whether they are atrophied segments of the myofiber syncytium, (2) their redox state, (3) their anatomic relationship to activated myofibroblasts (myoFb), given their putative regulatory role in myocyte dedifferentiation and redifferentiation, (4) the relevance of proteolytic ligases of the ubiquitin-proteasome system as a mechanistic link to their size, and (5) whether they could be rescued from their dedifferentiated phenotype. Chronic aldosterone/salt treatment (ALDOST) was invoked, where hypertensive heart disease with attendant myocardial fibrosis creates the fibrillar collagen substrate for myocyte sequestration, with propensity for disuse atrophy, activated myoFb, and oxidative stress. To address phenotype rescue, 4 weeks of ALDOST was terminated followed by 4 weeks of neurohormonal withdrawal combined with a regimen of exogenous antioxidants, ZnSO4, and nebivolol (assisted recovery). Compared with controls, at 4 weeks of ALDOST, we found small myocytes to be: (1) sequestered by collagen fibrils emanating from microdomains of fibrosis and representing atrophic segments of the myofiber syncytia, (2) dedifferentiated re-expressing fetal genes (β-myosin heavy chain and atrial natriuretic peptide), (3) proximal to activated myoFb expressing α-smooth muscle actin microfilaments and angiotensin-converting enzyme, (4) expressing reactive oxygen species and nitric oxide with increased tissue 8-isoprostane, coupled to ventricular diastolic and systolic dysfunction, and (5) associated with upregulated redox-sensitive proteolytic ligases MuRF1 and atrogin-1. In a separate study, we did not find evidence of myocyte replication (BrdU labeling) or expression of stem cell antigen (c-Kit) at weeks 1-4 ALDOST. Assisted recovery caused complete disappearance of myoFb from sites of fibrosis with redifferentiation of these myocytes, loss of oxidative stress, and ubiquitin-proteasome system activation, with restoration of nitric oxide and improved ventricular function. Thus, small dedifferentiated myocytes bordering on microdomains of fibrosis can re-differentiate and represent a potential source of autologous cells for functional myocardial regeneration.