The vasculature in HFpEF vs HFrEF: differences in contractile protein expression produce distinct phenotypes

Aging related decreases in NM myosin expression and contractility in a resistance vessel

Introduction: Vasodilatation in response to NO is a fundamental response of the vasculature, and during aging, the vasculature is characterized by an increase in stiffness and decrease in sensitivity to NO mediated vasodilatation. Vascular tone is regulated by the activation of smooth muscle and nonmuscle (NM) myosin, which are regulated by the activities of myosin light chain kinase (MLCK) and MLC phosphatase. MLC phosphatase is a trimeric enzyme with a catalytic subunit, myosin targeting subunit (MYPT1) and 20 kDa subunit of unknown function. Alternative mRNA splicing produces LZ+/LZ- MYPT1 isoforms and the relative expression of LZ+/LZ- MYPT1 determines the sensitivity to NO mediated vasodilatation. This study tested the hypothesis that aging is associated with changes in LZ+ MYPT1 and NM myosin expression, which alter vascular reactivity. Methods: We determined MYPT1 and NM myosin expression, force and the sensitivity of both endothelial dependent and endothelial independent relaxation in tertiary mesenteric arteries of young (6mo) and elderly (24mo) Fischer344 rats. Results: The data demonstrate that aging is associated with a decrease in both the expression of NM myosin and force, but LZ+ MYPT expression and the sensitivity to both endothelial dependent and independent vasodilatation did not change. Further, smooth muscle cell hypertrophy increases the thickness of the medial layer of smooth muscle with aging. Discussion: The reduction of NM myosin may represent an aging associated compensatory mechanism to normalize the stiffness of resistance vessels in response to the increase in media thickness observed during aging.

Aging and Heart Failure with Preserved Ejection Fraction

Heart failure is a clinical syndrome characterized by the inability of the cardiovascular system to provide adequate cardiac output at normal filling pressures. This results in a clinical syndrome characterized by dyspnea, edema, and decreased exertional tolerance. Heart failure with preserved ejection fraction (HFpEF) is an increasingly common disease, and the incidence of HFpEF increases with age. There are a variety of factors which contribute to the development of HFpEF, including the presence of hypertension, diabetes, obesity, and other pro-inflammatory states. These comorbid conditions result in changes at the biochemical and cell signaling level which ultimately lead to a disease with a great deal of phenotypic heterogeneity. In general, the physiologic dysfunction of HFpEF is characterized by vascular stiffness, increased cardiac filling pressures, pulmonary hypertension, and impaired volume management. The normal and abnormal processes associated with aging serve as an accelerant in this process, resulting in the hypothesis that HFpEF represents a form of presbycardia. In this article, we aim to review the processes importance of aging in the development of HFpEF by examining the disease and its causes from the biochemical to physiologic level. © 2022 American Physiological Society. Compr Physiol 12: 1-10, 2022.

Epigenetic remodeling in heart failure with preserved ejection fraction

PURPOSE OF REVIEW

In this review, we critically address the role of epigenetic processing and its therapeutic modulation in heart failure with preserved ejection fraction (HFpEF).

RECENT FINDINGS

HFpEF associates with a poor prognosis and the identification of novel molecular targets and therapeutic approaches are in high demand. Emerging evidence indicates a key involvement of epigenetic signals in the regulation of transcriptional programs underpinning features of HFpEF. The growing understanding of chromatin dynamics has led to the development of selective epigenetic drugs able to reset transcriptional changes thus delaying or preventing the progression toward HFpEF. Epigenetic information in the setting of HFpEF can be employed to: (i) dissect novel epigenetic networks and chromatin marks contributing to HFpEF; (ii) unveil circulating and cell-specific epigenetic biomarkers; (iii) build predictive models by using computational epigenetics and deep machine learning; (iv) develop new chromatin modifying drugs for personalized management of HFpEF.

SUMMARY

Acquired epigenetic signatures during the lifetime can contribute to derail molecular pathways involved in HFpEF. A scrutiny investigation of the individual epigenetic landscape will offer opportunities to develop personalized epigenetic biomarkers and therapies to fight HFpEF in the decades to come.

Tissue-specific expression of myosin phosphatase subunits and isoforms in smooth muscle of mice and humans

Alternative splicing of exon24 (E24) of myosin phosphatase targeting subunit 1 (Mypt1) by setting sensitivity to nitric oxide (NO)/cGMP-mediated relaxation is a key determinant of smooth muscle function. Here we defined expression of myosin phosphatase (MP) subunits and isoforms by creation of new genetic mouse models, assay of human and mouse tissues, and query of public databases. A Mypt1-LacZ reporter mouse revealed that Mypt1 transcription is turned on early in development during smooth muscle differentiation. Mypt1 is not as tightly restricted in its expression as smooth muscle myosin heavy chain (Myh11) and its E6 splice variant. Mypt1 is enriched in mature smooth versus nonmuscle cells. The E24 splice variant and leucine zipper minus protein isoform that it encodes is enriched in phasic versus tonic smooth muscle. In the vascular system, E24 splicing increases as vessel size decreases. In the gastrointestinal system, E24 splicing is most predominant in smooth muscle of the small intestine. Tissue-specific expression of MP subunits and Mypt1 E24 splicing is conserved in humans, whereas a splice variant of the inhibitory subunit (CPI-17) is unique to humans. A Mypt1 E24 mini-gene splicing reporter mouse generated to define patterns of E24 splicing in smooth muscle cells (SMCs) dispersed throughout the organ systems was unsuccessful. In summary, expression of Mypt1 and splicing of E24 is part of the program of smooth muscle differentiation, is further enhanced in phasic smooth muscle, and is conserved in humans. Its low-level expression in nonmuscle cells may confound its measurement in tissue samples.

Reactive Oxygen Species Induced Pathways in Heart Failure Pathogenesis and Potential Therapeutic Strategies

With respect to structural and functional cardiac disorders, heart failure (HF) is divided into HF with reduced ejection fraction (HFrEF) and HF with preserved ejection fraction (HFpEF). Oxidative stress contributes to the development of both HFrEF and HFpEF. Identification of a broad spectrum of reactive oxygen species (ROS)-induced pathways in preclinical models has provided new insights about the importance of ROS in HFrEF and HFpEF development. While current treatment strategies mostly concern neuroendocrine inhibition, recent data on ROS-induced metabolic pathways in cardiomyocytes may offer additional treatment strategies and targets for both of the HF forms. The purpose of this article is to summarize the results achieved in the fields of: (1) ROS importance in HFrEF and HFpEF pathophysiology, and (2) treatments for inhibiting ROS-induced pathways in HFrEF and HFpEF patients. ROS-producing pathways in cardiomyocytes, ROS-activated pathways in different HF forms, and treatment options to inhibit their action are also discussed.

The Role of Systemic Microvascular Dysfunction in Heart Failure with Preserved Ejection Fraction

Heart failure with preserved ejection fraction (HFpEF) is a condition with increasing incidence, leading to a health care problem of epidemic proportions for which no curative treatments exist. Consequently, an urge exists to better understand the pathophysiology of HFpEF. Accumulating evidence suggests a key pathophysiological role for coronary microvascular dysfunction (MVD), with an underlying mechanism of low-grade pro-inflammatory state caused by systemic comorbidities. The systemic entity of comorbidities and inflammation in HFpEF imply that patients develop HFpEF due to systemic mechanisms causing coronary MVD, or systemic MVD. The absence or presence of peripheral MVD in HFpEF would reflect HFpEF being predominantly a cardiac or a systemic disease. Here, we will review the current state of the art of cardiac and systemic microvascular dysfunction in HFpEF (Graphical Abstract), resulting in future perspectives on new diagnostic modalities and therapeutic strategies.

Sexual dimorphism in cardiac remodeling: the molecular mechanisms ruled by sex hormones in the heart

Heart failure (HF) is growing in prevalence, due to an increase in aging and comorbidities. Heart failure with reduced ejection fraction (HFrEF) is more common in men, whereas heart failure with preserved ejection fraction (HFpEF) has a higher prevalence in women. However, the reasons for these epidemiological trends are not clear yet. Since HFpEF affects mostly postmenopausal women, sex hormones should play a pivotal role in HFpEF development. Furthermore, for HFpEF, contrary to HFrEF, effective therapeutic approaches are missing. Interestingly, studies evidenced that some therapies can have better results in women than in HFpEF men, emphasizing the necessity of understanding these observations at a molecular level. Thus, herein, we review the molecular mechanisms of estrogen and androgen actions in the heart in physiological conditions and explain how its dysregulation can lead to disease development. This clarification is essential in the road for an effective personalized management of HF, particularly HFpEF, towards the development of sex-specific therapeutic approaches.