Background: The nuclear receptor Rev-erbα/β, a key component of the circadian clock, emerges as a drug target for heart diseases, but the function of cardiac Rev-erb has not been studied in vivo. Circadian disruption is implicated in heart diseases, but it is unknown whether cardiac molecular clock dysfunction is associated with the progression of any naturally occurring human heart diseases. Obesity paradox refers to the seemingly protective role of obesity for heart failure, but the mechanism is unclear. Methods: We generated mouse lines with cardiac-specific Rev-erbα/β knockout (KO), characterized cardiac phenotype, conducted multi-omics (RNA-seq, ChIP-seq, proteomics, and metabolomics) analyses, and performed dietary and pharmacologic rescue experiments to assess the time-of-the-day effects. We compared the temporal pattern of cardiac clock gene expression with the cardiac dilation severity in failing human hearts. Results: KO mice display progressive dilated cardiomyopathy (DCM) and lethal heart failure. Inducible ablation of Rev-erbα/β in adult hearts causes similar phenotypes. Impaired fatty acid oxidation in the KO myocardium, particularly in the light cycle, precedes contractile dysfunctions with a reciprocal overreliance on carbohydrate utilization, particularly in the dark cycle. Increasing dietary lipids or sugars supply in the dark cycle does not affect cardiac dysfunctions in KO mice. However, obesity coupled with systemic insulin resistance paradoxically ameliorates cardiac dysfunctions in KO mice, associated with rescued expression of lipid oxidation genes only in the light cycle in phase with increased fatty acids availability from adipose lipolysis. Inhibition of glycolysis in the light cycle and lipid oxidation in the dark cycle, but not vice versa, ameliorates cardiac dysfunctions in KO mice. Altered temporal patterns of cardiac Rev-erb gene expression correlate with the cardiac dilation severity in human hearts with DCM. Conclusions: The study delineates temporal coordination between clock-mediated anticipation and nutrient-induced response in myocardial metabolism at multi-omics levels. The obesity paradox is attributable to increased cardiac lipids supply from adipose lipolysis in the fasting cycle due to systemic insulin resistance and adiposity. Cardiac molecular chronotypes may be involved in human DCM. Myocardial bioenergetics downstream of Rev-erb may be a chronotherapy target in treating heart failure and DCM.

Objective Bacterial endotoxin (lipopolysaccharide, LPS)-mediated sepsis involves dysregulated systemic inflammation, which injures the lung and other organs, often fatally. Vascular endothelial cells act as both targets and mediators of LPS-induced inflammatory responses. Dysfunction of endothelium results in increases of pro-inflammatory cytokine production and permeability leakage. Bone morphogenetic protein (BMP)-binding endothelial regulator (BMPER), an extracellular modulator of BMP signaling, has been identified as a vital component in chronic endothelial inflammatory responses and atherosclerosis. However, it is unclear whether BMPER also regulates inflammatory response in an acute setting such as sepsis. To address this question, we investigated the role of BMPER during LPS-induced acute lung injury. Approach and results Mice missing 1 allele of BMPER (BMPER+/− mice used in the place of BMPER−/− mice that die at birth) were used for LPS challenge. LPS-induced pulmonary inflammation and injury was reduced in BMPER+/− mice as shown by several measures, including survival rate, infiltration of inflammatory cells, edema and production of pro-inflammatory cytokines. Mechanistically, we have demonstrated that BMPER is required and sufficient for the activation of nuclear factor of activated T cells (NFAT) c1. This BMPER-induced NFAT activation is coordinated by multiple signaling pathways, including BMP-independent LRP1-ERK activation, calcineurin signaling and LRP1β-mediated nuclear factor-45 (NF45) nuclear export in response to BMPER treatment. Conclusions We conclude that BMPER plays a pivotal role in pulmonary inflammatory response, which provides new therapeutic options against sepsis shock. The new signaling pathway initiated by BMPER/LRP1 axis broadens our understanding about BMPER’s role in vascular homeostasis.

Protein kinase A (PKA) substrate phosphorylation is facilitated through its co-localization with its signaling partner by A-kinase anchoring proteins (AKAPs). mAKAP (muscle-selective AKAP) localizes PKA and its substrates such as phosphodiesterase-4D3 (PDE4D3), ryanodine receptor, and protein phosphatase 2A (PP2A) to the sarcoplasmic reticulum and perinuclear space. The genetic role of mAKAP, in modulating PKA/PDE4D3 molecular signaling during cardiac diseases, remains unclear. The purpose of this study was to examine the effects of naturally occurring mutations in human mAKAP on PKA and PDE4D3 signaling. We have recently identified potentially important human mAKAP coding non-synonymous polymorphisms located within or near key protein binding sites critical to β-adrenergic receptor signaling. Three mutations (P1400S, S2195F, and L717V) were cloned and transfected into a mammalian cell line for the purpose of comparing whether those substitutions disrupt mAKAP binding to PKA or PDE4D3. Immunoprecipitation study of mAKAP-P1400S, a mutation located in the mAKAP-PDE4D3 binding site, displayed a significant reduction in binding to PDE4D3, with no significant changes in PKA binding or PKA activity. Conversely, mAKAP-S2195F, a mutation located in mAKAP-PP2A binding site, showed significant increase in both binding propensity to PKA and PKA activity. Additionally, mAKAP-L717V, a mutation flanking the mAKAP-spectrin repeat domain, exhibited a significant increase in PKA binding compared to wild type, but there was no change in PKA activity. We also demonstrate specific binding of wild-type mAKAP to PDE4D3. Binding results were demonstrated using immunoprecipitation and confirmed with surface plasmon resonance (Biacore-2000); functional results were demonstrated using activity assays, Ca2+ measurements, and Western blot. Comparative analysis of the binding responses of mutations to mAKAP could provide important information about how these mutations modulate signaling.

Citation:McConnell BK, Singh S, Fan Q, Hernandez A, Portillo JP, Reiser PJ and Tikunova SB (2015) Knock-in mice harboring a Ca 2+ desensitizing mutation in cardiac troponin C develop early onset dilated cardiomyopathy. Front. Physiol. 6:242. doi: 10.3389/fphys.2015.00242 Knock-in mice harboring a Ca 2+ desensitizing mutation in cardiac troponin C develop early onset dilated cardiomyopathy The physiological consequences of aberrant Ca 2+ binding and exchange with cardiac myofilaments are not clearly understood. In order to examine the effect of decreasing Ca 2+ sensitivity of cTnC on cardiac function, we generated knock-in mice carrying a D73N mutation (not known to be associated with heart disease in human patients) in cTnC. The D73N mutation was engineered into the regulatory N-domain of cTnC in order to reduce Ca 2+ sensitivity of reconstituted thin filaments by increasing the rate of Ca 2+ dissociation. In addition, the D73N mutation drastically blunted the extent of Ca 2+ desensitization of reconstituted thin filaments induced by cTnI pseudo-phosphorylation. Compared to wild-type mice, heterozygous knock-in mice carrying the D73N mutation exhibited a substantially decreased Ca 2+ sensitivity of force development in skinned ventricular trabeculae. Kaplan-Meier survival analysis revealed that median survival time for knock-in mice was 12 weeks. Echocardiographic analysis revealed that knock-in mice exhibited increased left ventricular dimensions with thinner walls. Echocardiographic analysis also revealed that measures of systolic function, such as ejection fraction (EF) and fractional shortening (FS), were dramatically reduced in knock-in mice. In addition, knock-in mice displayed electrophysiological abnormalities, namely prolonged QRS and QT intervals. Furthermore, ventricular myocytes isolated from knock-in mice did not respond to β-adrenergic stimulation. Thus, knock-in mice developed pathological features similar to those observed in human patients with dilated cardiomyopathy (DCM). In conclusion, our results suggest that decreasing Ca 2+ sensitivity of the regulatory N-domain of cTnC is sufficient to trigger the development of DCM.