Cardiomyocyte-specific Bmal1 deletion in mice triggers diastolic dysfunction, extracellular matrix response, and impaired resolution of inflammation

Chronobiological Influence Over Cardiovascular Function: The Good, the Bad, and the Ugly

Essentially all biological processes fluctuate over the course of the day, observed at cellular (eg, transcription, translation, and signaling), organ (eg, contractility and metabolism), and whole-body (eg, physical activity and appetite) levels. It is, therefore, not surprising that both cardiovascular physiology (eg, heart rate and blood pressure) and pathophysiology (eg, onset of adverse cardiovascular events) oscillate during the 24-hour day. Chronobiological influence over biological processes involves a complex interaction of factors that are extrinsic (eg, neurohumoral factors) and intrinsic (eg, circadian clocks) to cells. Here, we focus on circadian governance of 6 fundamentally important processes: metabolism, signaling, electrophysiology, extracellular matrix, clotting, and inflammation. In each case, we discuss (1) the physiological significance for circadian regulation of these processes (ie, the good); (2) the pathological consequence of circadian governance impairment (ie, the bad); and (3) whether persistence/augmentation of circadian influences contribute to pathogenesis during distinct disease states (ie, the ugly). Finally, the translational impact of chronobiology on cardiovascular disease is highlighted.

The circadian clock is disrupted in mice with adenine-induced tubulointerstitial nephropathy

Chronic Kidney Disease (CKD) is increasing in incidence and has become a worldwide health problem. Sleep disorders are prevalent in patients with CKD raising the possibility that these patients have a disorganized circadian timing system. Here, we examined the effect of adenine-induced tubulointerstitial nephropathy on the circadian system in mice. Compared to controls, adenine-treated mice showed serum biochemistry evidence of CKD as well as increased kidney expression of inflammation and fibrosis markers. Mice with CKD exhibited fragmented sleep behavior and locomotor activity, with lower degrees of cage activity compared to mice without CKD. On a molecular level, mice with CKD exhibited low amplitude rhythms in their central circadian clock as measured by bioluminescence in slices of the suprachiasmatic nucleus of PERIOD 2::LUCIFERASE mice. Whole animal imaging indicated that adenine treated mice also exhibited dampened oscillations in intact kidney, liver, and submandibular gland. Consistently, dampened circadian oscillations were observed in several circadian clock genes and clock-controlled genes in the kidney of the mice with CKD. Finally, mice with a genetically disrupted circadian clock (Clock mutants) were treated with adenine and compared to wild type control mice. The treatment evoked worse kidney damage as indicated by higher deposition of gelatinases (matrix metalloproteinase-2 and 9) and adenine metabolites in the kidney. Adenine also caused non-dipping hypertension and lower heart rate. Thus, our data indicate that central and peripheral circadian clocks are disrupted in the adenine-treated mice, and suggest that the disruption of the circadian clock accelerates CKD progression.

Impact of Circadian Disruption on Cardiovascular Function and Disease

The circadian system, that is ubiquitous across species, generates ∼24 h rhythms in virtually all biological processes, and allows them to anticipate and adapt to the 24 h day/night cycle, thus ensuring optimal physiological function. Epidemiological studies show time-of-day variations in adverse cardiovascular (CV) events, and controlled laboratory studies demonstrate a circadian influence on key markers of CV function and risk. Furthermore, circadian misalignment, that is typically experienced by shift workers as well as by individuals who experience late eating, (social) jet lag, or circadian rhythm sleep-wake disturbances, increases CV risk factors. Therefore, understanding the mechanisms by which the circadian system regulates CV function, and which of these are affected by circadian disruption, may help to develop intervention strategies to mitigate CV risk.

Peripheral Circadian Oscillators

Circadian rhythms are ~24-hour cycles of physiology and behavior that are synchronized to environmental cycles, such as the light-dark cycle. During the 20th century, most research focused on establishing the fundamental properties of circadian rhythms and discovering circadian pacemakers that were believed to reside in the nervous system of animals. During this time, studies that suggested the existence of circadian oscillators in peripheral organs in mammals were largely dismissed. The discovery of a single-locus circadian pacemaker in the nervous system of several animals affirmed the single-oscillator model of the circadian system. However, the discovery of the genes that constituted the molecular timekeeping system provided the tools for demonstrating the existence of bona fide circadian oscillators in nearly every peripheral tissue in animals, including rodents, in the late 1990s and early 2000s. These studies led to our current understanding that the circadian system in animals is a hierarchical multi-oscillatory network, composed of master pacemaker(s) in the brain and oscillators in peripheral organs. Further studies showed that altering the temporal relationship between these oscillators by simulating jet-lag and metabolic challenges in rodents caused adverse physiological outcomes. Herein we review the studies that led to our current understanding of the function and pathology of the hierarchical multi-oscillator circadian system.

H. pylori infection induced BMAL1 expression and rhythm disorder aggravate gastric inflammation

BACKGROUND

Rhythm abnormalities are crucial for diverse diseases. However, their role in disease progression induced by Helicobacter pylori (H. pylori) remains elusive.

METHODS

H. pylori infection was used in in vivo and in vitro experiments to examine its effect on rhythmic genes. The GEO database was used to screen H. pylori affecting rhythm genes, and the effect of rhythm genes on inflammatory factors. Chromatin immunoprecipitation and dual luciferase assays were used to further find out the regulation between molecules. Animal models were used to confirm the relationship between rhythm genes and H. pylori-induced inflammation.

FINDINGS

BMAL1 disorders aggravate inflammation induced by H. pylori. Specifically, H. pylori induce BMAL1 expression in vitro and in vivo through transcriptional activation of LIN28A, breaking the circadian rhythm. Mechanistically, LIN28A binds to the promoter region of BMAL1 and directly activates its transcription under H. pylori infection. BMAL1 in turn functions as a transcription factor and enhances the expression of proinflammatory cytokine TNF-α, thereby promoting inflammation. Of note, BMAL1 dysfunction in the rhythm disorder animal model aggravates inflammatory response induced by H. pylori infection in vivo.

INTERPRETATION

These findings in this study imply the pathogenic relationship between BMAL1 and H. pylori. BMAL1 may serve as a potential diagnostic marker and therapeutic target for the early diagnosis and treatment of diseases related to H. pylori infection. FUND: National Natural Science Foundation of China.

Specialized Pro-resolving Mediators Directs Cardiac Healing and Repair with Activation of Inflammation and Resolution Program in Heart Failure

After myocardial infarction, splenic leukocytes direct biosynthesis of specialized pro-resolving mediators (SPMs) that are essential for the resolution of inflammation and tissue repair. In a laboratory environment, after coronary ligation of healthy risk free rodents (young adult mice) leukocytes biosynthesize SPMs with induced activity of lipoxygenases and cyclooxygenases, which facilitate cardiac repair. Activated monocytes/macrophages drive the biosynthesis of SPMs following experimental myocardial infarction in mice during the acute heart failure. In the presented review, we provided the recent updates on SPMs (resolvins, lipoxins and maresins) in cardiac repair that may serve as novel therapeutics for future heart failure therapy/management. We incorporated the underlying causes of non-resolving inflammation following cardiac injury if superimposed with obesity, hypertension, diabetes, disrupted circadian rhythm, co-medication (painkillers or oncological therapeutics), and/or aging that may delay or impair the biosynthesis of SPMs, intensifying pathological remodeling in heart failure.

Novel molecular therapeutic targets in cardiac fibrosis: a brief overview 1

Cardiac fibrosis, characterized by excessive accumulation of extracellular matrix, abolishes cardiac contractility, impairs cardiac function, and ultimately leads to heart failure. In recent years, significant evidence has emerged that supports the highly dynamic and responsive nature of the cardiac extracellular matrix. Although our knowledge of cardiac fibrosis has advanced tremendously over the past decade, there is still a lack of specific therapies owing to an incomplete understanding of the disease etiology and process. In this review, we attempt to highlight some of the recently investigated molecular determinants of ischemic and non-ischemic fibrotic remodeling of the myocardium that present as promising avenues for development of anti-fibrotic therapies.

Doxorubicin triggers splenic contraction and irreversible dysregulation of COX and LOX that alters the inflammation-resolution program in the myocardium

Doxorubicin (DOX) is a widely used drug for cancer treatment as a chemotherapeutic agent. However, the cellular and integrative mechanism of DOX-induced immunometabolism is unclear. Two-month-old male C57BL/6J mice were divided into high- and low-dose DOX-treated groups with a maintained saline control group. The first group was injected with a high dose of DOX (H-DOX; 15 mg·kg-1·wk-1), and the second group was injected with 7.5 mg·kg-1·wk-1 as a latent low dose of DOX (LL-DOX). H-DOX treatment led to complete mortality in 2 wk and 70% survival in the LL-DOX group compared with the saline control group. Therefore, an additional group of mice was injected with an acute high dose of DOX (AH-DOX) and euthanized at 24 h to compare with LL-DOX and saline control groups. The LL-DOX and AH-DOX groups showed obvious apoptosis and dysfunctional and structural changes in cardiac tissue. Splenic contraction was evident in AH-DOX- and LL-DOX-treated mice, indicating the systems-wide impact of DOX on integrative organs of the spleen, which is essential for cardiac homeostasis and repair. DOX dysregulated splenic-enriched immune-sensitive lipoxygenase and cyclooxygenase in the spleen and left ventricle compared with the saline control group. As a result, lipoxygenase-dependent D- and E-series resolvin precursors, such as 16HDoHE, 4HDoHE, and 12-HEPE, as well as cyclooxygenase-mediated PG species (PGD2, PGE2, and 6-keto-PG2α) were decreased in the left ventricle, suggestive of defective immunometabolism. Both AH-DOX and LL-DOX induced splenic contraction and expansion of red pulp with decreased CD169+ metallophilic macrophages. AH-DOX intoxicated macrophages in the spleen by depleting CD169+ cells in the acute setting and sustained the splenic macrophage loss in the chronic phase in the LL-DOX group. Thus, DOX triggers a vicious cycle of splenocardiac cachexia to facilitate defective immunometabolism and irreversible macrophage toxicity and thereby impaired the inflammation-resolution program. NEW & NOTEWORTHY Doxorubicin (DOX) triggered splenic mass loss and decreased CD169 with germinal center contraction in acute and chronic exposure. Cardiac toxicity of DOX is marked with dysregulation of immunometabolism and thereby impaired resolution of inflammation. DOX suppressed physiological levels of cytokines and chemokines with signs of splenocardiac cachexia.

Matrix metalloproteinase-12 as an endogenous resolution promoting factor following myocardial infarction

Following myocardial infarction (MI), timely resolution of inflammation promotes wound healing and scar formation while limiting excessive tissue damage. Resolution promoting factors (RPFs) are agents that blunt leukocyte trafficking and inflammation, promote necrotic and apoptotic cell clearance, and stimulate scar formation. Previously identified RPFs include mediators derived from lipids (resolvins, lipoxins, protectins, and maresins), proteins (glucocorticoids, annexin A1, galectin 1, and melanocortins), or gases (CO, H₂S, and NO). Matrix metalloproteinase-12 (MMP-12; macrophage elastase) has shown promising RPF qualities in a variety of disease states. We review here the evidence that MMP-12 may serve as a novel RPF with potential therapeutic efficacy in the setting of MI.

Role of double knockdown of tPA and MMP-9 on regulating the left ventricular function and remodeling followed by transverse aortic constriction-induced hypertrophic cardiomyopathy in mice

This study tested the hypothesis that extracellular matrix accumulation in tPA^-/-/MMP-9^-/- [double-knockout (DKO)] may be protective against left ventricular (LV) remodeling and dysfunction following transverse aortic constriction (TAC)-induced hypertrophic cardiomyopathy in mice. Wild-type C57BL/6 mice (n = 20) were equally categorized into sham-control (SC¹) and TAC¹. Similarly, DKO mice (n = 20) were equally divided into two groups (i.e., SC² and ATC²). By days 28/60 after TAC, LV ejection fraction (LVEF) was significantly higher in TAC² than TAC¹, whereas LV end-systolic/diastolic dimensions displayed an opposite pattern to LVEF between the two groups (all P < 0.05). By day 90, LVEF was significantly higher in SC groups than that in TAC¹ and TAC² without notable difference between the latter two groups, whereas LV end-systolic/diastolic dimensions, cardiomyocyte size and right-ventricular systolic pressure showed an opposite pattern compared with LVEF in all groups (all P < 0.01). Total heart weight was highest in TAC¹ and significantly higher in TAC² than those in the SC groups (P < 0.01). LV myocardial protein expressions of inflammation (TNF-α/NF-κβ), apoptosis (mitochondrial-Bax/cleaved caspase-3/PARP), oxidative stress (NOX-1/NOX-2/oxidized protein), fibrosis (Smad3/TGF-β), DNA/mitochondrial damage (γ-H2AX/cytosolic-cytochrome-C) and LV hypertrophy/pressure-overload (β-MHC/BNP) biomarkers were significantly increased in TAC² compared to TAC¹ and SC groups, and significantly increased in TAC¹ compared to SC groups (all P < 0.001). Histopathology demonstrated that the fibrotic/collagen-deposition areas and sarcomere length exhibited an identical pattern to inflammation among the four groups (all P < 0.0001). In conclusion, although tPA^-/-/MMP-9^-/- seemed to preserve cardiac function in an experimental setting of hypertrophic cardiomyopathy at an early stage, it failed to exert long-term protective effect.

Uremia increases QRS duration after β-adrenergic stimulation in mice

Chronic kidney disease (CKD) and uremia increase the risk of heart disease and sudden cardiac death. Coronary artery disease can only partly account for this. The remaining mechanistic links between CKD and sudden death are elusive, but may involve cardiac arrhythmias. For the present study, we hypothesized that a thorough electrophysiological study in mice with CKD would provide us valuable information that could aid in the identification of additional underlying causes of sudden cardiac death in patients with kidney disease. Partial (5/6) nephrectomy (NX) in mice induced mild CKD: plasma urea in NX was 24 ± 1 mmol/L (n = 23) versus 12 ± 1 mmol/L (n = 22) in sham-operated control mice (P < 0.05). Echocardiography did not identify structural or mechanical remodeling in NX mice. Baseline ECG parameters were comparable in conscious NX and control mice; however, the normal 24-h diurnal rhythm in QRS duration was lost in NX mice. Moreover, β-adrenergic stimulation (isoprenaline, 200 μg/kg intraperitoneally) prolonged QRS duration in conscious NX mice (from 12 ± 1 to 15 ± 2 msec, P < 0.05), but not in sham-operated controls (from 13 ± 1 to 13 ± 2 msec, P > 0.05). No spontaneous arrhythmias were observed in conscious NX mice, and intracardiac pacing in anesthetized mice showed a comparable arrhythmia vulnerability in NX and sham-operated mice. Isoprenaline (2 mg/kg intraperitoneally) changed the duration of the QRS complex from 11.2 ± 0.4 to 11.9 ± 0.5 (P = 0.06) in NX mice and from 10.7 ± 0.6 to 10.6 ± 0.6 (P = 0.50) in sham-operated mice. Ex vivo measurements of cardiac ventricular conduction velocity were comparable in NX and sham mice. Transcriptional activity of Scn5a, Gja1 and several profibrotic genes was similar in NX and sham mice. We conclude that proper kidney function is necessary to maintain diurnal variation in QRS duration and that sympathetic regulation of the QRS duration is altered in kidney disease.

Myocardial transcription factors in diastolic dysfunction: clues for model systems and disease

There are multiple intrinsic mechanisms for diastolic dysfunction ranging from molecular to structural derangements in ventricular myocardium. The molecular mechanisms regulating the progression from normal diastolic function to severe dysfunction still remain poorly understood. Recent studies suggest a potentially important role of core cardio-enriched transcription factors (TFs) in the control of cardiac diastolic function in health and disease through their ability to regulate the expression of target genes involved in the process of adaptive and maladaptive cardiac remodeling. The current relevant findings on the role of a variety of such TFs (TBX5, GATA-4/6, SRF, MYOCD, NRF2, and PITX2) in cardiac diastolic dysfunction and failure are updated, emphasizing their potential as promising targets for novel treatment strategies. In turn, the new animal models described here will be key tools in determining the underlying molecular mechanisms of disease. Since diastolic dysfunction is regulated by various TFs, which are also involved in cross talk with each other, there is a need for more in-depth research from a biomedical perspective in order to establish efficient therapeutic strategies.

Immune responsive resolvin D1 programs myocardial infarction-induced cardiorenal syndrome in heart failure

Resolvins are innate, immune responsive, bioactive mediators generated after myocardial infarction (MI) to resolve inflammation. The MI-induced bidirectional interaction between progressive left ventricle (LV) remodeling and kidney dysfunction is known to advance cardiorenal syndrome (CRS). Whether resolvins limit MI-induced cardiorenal inflammation is unclear. Thus, to define the role of exogenous resolvin D (RvD)-1 in post-MI CRS, we subjected 8- to 12-wk-old male C57BL/6 mice to coronary artery ligation. RvD1 was injected 3 h after MI. MI mice with no treatment served as MI controls (d 1 and 5). Mice with no surgery served as naive controls. In the injected mice, RvD1 promoted neutrophil (CD11b⁺/Ly6G⁺) egress from the infarcted LV, compared with the MI control group at d 5, indicative of neutrophil clearance and thereby resolved inflammation. Further, RvD1-injected mice showed higher reparative macrophages (F4/80⁺/Ly6C^low/CD206⁺) in the infarcted LV than did MI control mice at d 5 after MI. RvD1 suppressed the miRNA storm at d 1 and limited the MI-induced edematous milieu in a remote area of the LV compared with the MI control at d 5 after MI. Also, RvD1 preserved the nephrin expression that was diffuse in the glomerular membrane at d 5 and 28 in MI controls, indicating renal injury. RvD1 attenuated MI-induced renal inflammation, decreasing neutrophil gelatinase-associated lipocalin and proinflammatory cytokines and chemokines in the kidney compared with the MI control. In summary, RvD1 clears MI-induced inflammation by increasing resolving leukocytes and facilitates renoprotective mechanisms to limit CRS in acute and chronic heart failure.-Halade, G. V., Kain, V., Serhan, C. N. Immune responsive resolvin D1 programs myocardial infarction-induced cardiorenal syndrome in heart failure.

Impaired Production and Diurnal Regulation of Vascular RvDn-3 DPA Increase Systemic Inflammation and Cardiovascular Disease

RATIONALE

Diurnal mechanisms are central to regulating host responses. Recent studies uncovered a novel family of mediators termed as specialized proresolving mediators that terminate inflammation without interfering with the immune response.

OBJECTIVE

Herein, we investigated the diurnal regulation of specialized proresolving mediators in humans and their role in controlling peripheral blood leukocyte and platelet activation.

METHODS AND RESULTS

Using lipid mediator profiling and healthy volunteers, we found that plasma concentrations of n-3 docosapentaenoic acid-derived D-series resolvins (RvD_{n-3 DPA}) were regulated in a diurnal manner. The production and regulation of these mediators was markedly altered in patients at risk of myocardial infarct. These changes were associated with decreased 5-lipoxygenase expression and activity, as well as increased systemic adenosine concentrations. We also found a significant negative correlation between plasma RvD_{n-3 DPA} and markers of platelet, monocyte, and neutrophil activation, including CD63 and CD11b. Incubation of RvD_{n-3 DPA} with peripheral blood from healthy volunteers and patients with cardiovascular disease significantly and dose-dependently decreased platelet and leukocyte activation. Furthermore, administration of RvD5_{n-3 DPA} to ApoE^-/- (apolipoprotein E deficient) mice significantly reduced platelet-leukocyte aggregates, vascular thromboxane B₂ concentrations, and aortic lesions.

CONCLUSIONS

These results demonstrate that peripheral blood RvD_{n-3 DPA} are diurnally regulated in humans, and dysregulation in the production of these mediators may lead to cardiovascular disease.

Altered Circadian Timing System-Mediated Non-Dipping Pattern of Blood Pressure and Associated Cardiovascular Disorders in Metabolic and Kidney Diseases

The morning surge in blood pressure (BP) coincides with increased cardiovascular (CV) events. This strongly suggests that an altered circadian rhythm of BP plays a crucial role in the development of CV disease (CVD). A disrupted circadian rhythm of BP, such as the non-dipping type of hypertension (i.e., absence of nocturnal BP decline), is frequently observed in metabolic disorders and chronic kidney disease (CKD). The circadian timing system, controlled by the central clock in the suprachiasmatic nucleus of the hypothalamus and/or by peripheral clocks in the heart, vasculature, and kidneys, modulates the 24 h oscillation of BP. However, little information is available regarding the molecular and cellular mechanisms of an altered circadian timing system-mediated disrupted dipping pattern of BP in metabolic disorders and CKD that can lead to the development of CV events. A more thorough understanding of this pathogenesis could provide novel therapeutic strategies for the management of CVD. This short review will address our and others' recent findings on the molecular mechanisms that may affect the dipping pattern of BP in metabolic dysfunction and kidney disease and its association with CV disorders.

Obesity and Cardiometabolic Defects in Heart Failure Pathology

Obesity is a major global epidemic that sets the stage for diverse multiple pathologies, including cardiovascular disease. The obesity-related low-grade chronic inflamed milieu is more pronounced in aging and responsive to cardiac dysfunction in heart failure pathology. Metabolic dysregulation of obesity integrates with immune reservoir in spleen and kidney network. Therefore, an integrative systems biology approach is necessary to delay progressive cardiac alternations. The purpose of this comprehensive review is to largely discuss the impact of obesity on the cardiovascular pathobiology in the context of problems and challenges, with major emphasis on the diversified models, and to study cardiac remodeling in obesity. The information in this article is immensely helpful in teaching advanced undergraduate, graduate, and medical students about the advancement and impact of obesity on cardiovascular health. © 2017 American Physiological Society. Compr Physiol 7:1463-1477, 2017.

mRNA levels of circadian clock components Bmal1 and Per2 alter independently from dosing time-dependent efficacy of combination treatment with valsartan and amlodipine in spontaneously hypertensive rats

Chronopharmacological effects of antihypertensives play a role in the outcome of hypertension therapy. However, studies produce contradictory findings when combination of valsartan plus amlodipine (VA) is applied. Here, we hypothesized different efficacy of morning versus evening dosing of VA in spontaneously hypertensive rats (SHR) and the involvement of circadian clock genes Bmal1 and Per2. We tested the therapy outcome in short-term and also long-term settings. SHRs aged between 8 and 10 weeks were treated with 10 mg/kg of valsartan and 4 mg/kg of amlodipine, either in the morning or in the evening with treatment duration 1 or 6 weeks and compared with parallel placebo groups. After short-term treatment, only morning dosing resulted in significant blood pressure (BP) control (measured by tail-cuff method) when compared to placebo, while after long-term treatment, both dosing groups gained similar superior results in BP control against placebo. However, mRNA levels of Bmal1 and Per2 (measured by RT-PCR) exhibited an independent pattern, with similar alterations in left and right ventricle, kidney as well as in aorta predominantly in groups with evening dosing in both, short-term and also long-term settings. This was accompanied by increased cardiac mRNA expression of plasminogen activator inhibitor-1. In summary, morning dosing proved to be advantageous due to earlier onset of antihypertensive action; however, long-term treatment was demonstrated to be effective regardless of administration time. Our findings also suggest that combination of VA may serve as an independent modulator of circadian clock and might influence disease progression beyond the primary BP lowering effect.

Metabolic and Biochemical Stressors in Diabetic Cardiomyopathy

Diabetic cardiomyopathy (DCM) or diabetes-induced cardiac dysfunction is a direct consequence of uncontrolled metabolic syndrome and is widespread in US population and worldwide. Despite of the heterogeneous and distinct features of DCM, the clinical relevance of DCM is now becoming established. DCM progresses to pathological cardiac remodeling with the higher risk of heart attack and subsequent heart failure in diabetic patients. In this review, we emphasize lipid substrate quality and the phenotypic, metabolic, and biochemical stressors of DCM in the rodent and human pathophysiology. We discuss lipoxygenase signaling in the inflammatory pathway with multiple contributing and confounding factors leading to DCM. Additionally, emerging biochemical pathways are emphasized to make progress toward therapeutic advancement to treat DCM.

Cardiac extracellular matrix is associated with adverse outcome in patients with chronic heart failure

AIMS

Accumulation of extracellular matrix (ECM) is known to play a crucial role in the pathophysiology of heart failure (HF). However, its prognostic relevance is poorly investigated.

METHODS AND RESULTS

A total of 73 HF patients who underwent LV endomyocardial biopsy were enrolled in our study. ECM area was quantified by TissueFAXS and ImageJ software. Patients were followed-up at 6-month intervals. The study endpoint was defined as hospitalization for a cardiac reason and/or cardiac death. Furthermore, the influence of the ECM on invasively measured haemodynamic parameters was tested. During a median follow-up period of 9.0 months, 34 patients (46.6%) reached the combined endpoint. Median ECM area was 30.5%. Patients with ECM area ≥30.5% experienced significantly more events (67.6% vs. 25.0%, P < 0.001) in comparison with patients with an ECM area <30.5%. ECM area was independently associated with outcome in the total HF cohort [hazard ratio (HR) 1.041, 95% confidence interval (CI) 1.017-1.066, P = 0.001] as well as in HF patients with preserved (HR 1.079, 95% CI 1.001-1.163, P =0 .046) or reduced ejection fraction (HR 1.149, 95% CI 1.036-1.275, P = 0.009). Positive correlations were found between ECM area and LV end-diastolic pressure (P = 0.021, R = 0.303), pulmonary artery wedge pressure (P = 0.042, R = 0.249), mean pulmonary arterial pressure (P = 0.035, R = 0.258), as well as right atrial pressure (P = 0.003, R = 0.353).

CONCLUSION

ECM area within the LV myocardium correlates with left and right heart haemodynamics and is associated with clinical course in various non-ischaemic HF types.

Cardiomyocyte Circadian Oscillations Are Cell-Autonomous, Amplified by β-Adrenergic Signaling, and Synchronized in Cardiac Ventricle Tissue

Circadian clocks impact vital cardiac parameters such as blood pressure and heart rate, and adverse cardiac events such as myocardial infarction and sudden cardiac death. In mammals, the central circadian pacemaker, located in the suprachiasmatic nucleus of the hypothalamus, synchronizes cellular circadian clocks in the heart and many other tissues throughout the body. Cardiac ventricle explants maintain autonomous contractions and robust circadian oscillations of clock gene expression in culture. In the present study, we examined the relationship between intrinsic myocardial function and circadian rhythms in cultures from mouse heart. We cultured ventricular explants or dispersed cardiomyocytes from neonatal mice expressing a PER2::LUC bioluminescent reporter of circadian clock gene expression. We found that isoproterenol, a β-adrenoceptor agonist known to increase heart rate and contractility, also amplifies PER2 circadian rhythms in ventricular explants. We found robust, cell-autonomous PER2 circadian rhythms in dispersed cardiomyocytes. Single-cell rhythms were initially synchronized in ventricular explants but desynchronized in dispersed cells. In addition, we developed a method for long-term, simultaneous monitoring of clock gene expression, contraction rate, and basal intracellular Ca2+ level in cardiomyocytes using PER2::LUC in combination with GCaMP3, a genetically encoded fluorescent Ca2+ reporter. In contrast to robust PER2 circadian rhythms in cardiomyocytes, we detected no rhythms in contraction rate and only weak rhythms in basal Ca2+ level. In summary, we found that PER2 circadian rhythms of cardiomyocytes are cell-autonomous, amplified by adrenergic signaling, and synchronized by intercellular communication in ventricle explants, but we detected no robust circadian rhythms in contraction rate or basal Ca2+.

Low-Salt Diet and Circadian Dysfunction Synergize to Induce Angiotensin II-Dependent Hypertension in Mice

Blood pressure exhibits a robust circadian rhythm in health. In hypertension, sleep apnea, and even shift work, this balanced rhythm is perturbed via elevations in night-time blood pressure, inflicting silent damage to the vasculature and body organs. Herein, we examined the influence of circadian dysfunction during experimental hypertension in mice. Using radiotelemetry to measure ambulatory blood pressure and activity, the effects of angiotensin II administration were studied in wild-type (WT) and period isoform knockout (KO) mice (Per2-KO, Per2, 3-KO, and Per1, 2, 3-KO/Per triple KO [TKO] mice). On a normal diet, administration of angiotensin II caused nondipping blood pressure and exacerbated vascular hypertrophy in the Period isoform KO mice relative to WT mice. To study the endogenous effects of angiotensin II stimulation, we then administered a low-salt diet to the mice, which does stimulate endogenous angiotensin II in addition to lowering blood pressure. A low-salt diet decreased blood pressure in wild-type mice. In contrast, Period isoform KO mice lost their circadian rhythm in blood pressure on a low-salt diet, because of an increase in resting blood pressure, which was restorable to rhythmicity by the angiotensin receptor blocker losartan. Chronic administration of low salt caused vascular hypertrophy in Period isoform KO mice, which also exhibited increased renin levels and altered angiotensin 1 receptor expression. These data suggest that circadian clock genes may act to inhibit or control renin/angiotensin signaling. Moreover, circadian disorders such as sleep apnea and shift work may alter the homeostatic responses to sodium restriction to potentially influence nocturnal hypertension.

Altered myocardial metabolic adaptation to increased fatty acid availability in cardiomyocyte-specific CLOCK mutant mice

A mismatch between fatty acid availability and utilization leads to cellular/organ dysfunction during cardiometabolic disease states (e.g., obesity, diabetes mellitus). This can precipitate cardiac dysfunction. The heart adapts to increased fatty acid availability at transcriptional, translational, post-translational and metabolic levels, thereby attenuating cardiomyopathy development. We have previously reported that the cardiomyocyte circadian clock regulates transcriptional responsiveness of the heart to acute increases in fatty acid availability (e.g., short-term fasting). The purpose of the present study was to investigate whether the cardiomyocyte circadian clock plays a role in adaptation of the heart to chronic elevations in fatty acid availability. Fatty acid availability was increased in cardiomyocyte-specific CLOCK mutant (CCM) and wild-type (WT) littermate mice for 9weeks in time-of-day-independent (streptozotocin (STZ) induced diabetes) and dependent (high fat diet meal feeding) manners. Indices of myocardial metabolic adaptation (e.g., substrate reliance perturbations) to STZ-induced diabetes and high fat meal feeding were found to be dependent on genotype. Various transcriptional and post-translational mechanisms were investigated, revealing that Cte1 mRNA induction in the heart during STZ-induced diabetes is attenuated in CCM hearts. At the functional level, time-of-day-dependent high fat meal feeding tended to influence cardiac function to a greater extent in WT versus CCM mice. Collectively, these data suggest that CLOCK (a circadian clock component) is important for metabolic adaption of the heart to prolonged elevations in fatty acid availability. This article is part of a Special Issue entitled: Heart Lipid Metabolism edited by G.D. Lopaschuk.