Sacubitril Ameliorates Cardiac Fibrosis Through Inhibiting TRPM7 Channel

Endomyocardial fibrosis: recent advances and future therapeutic targets

Endomyocardial fibrosis, first described >75 years ago, is a cause of restrictive cardiomyopathy with an unclear aetiopathogenesis that is most commonly found in children and adolescents from tropical regions of Africa, Asia and South America. The epidemiological trends of this cardiomyopathy are difficult to ascertain. The characteristic hallmark of endomyocardial fibrosis is ventricular fibrosis that causes diastolic dysfunction and atrioventricular regurgitation. Although advances in medical treatment for heart failure and more tailored surgical techniques to treat the condition have increased survival, the outcomes in affected patients remain poor. A major focus of research is the identification of biomarkers of preclinical disease and new therapeutic targets. Collaborative multidisciplinary research and cross-learning from other fibrotic conditions should impart knowledge and help to improve the survival rates and the quality of life of patients with endomyocardial fibrosis.

Consequences of Amyloid-β Deficiency for the Liver

The hepatic content of amyloid beta (Aβ) decreases drastically in human and rodent cirrhosis highlighting the importance of understanding the consequences of Aβ deficiency in the liver. This is especially relevant in view of recent advances in anti-Aβ therapies for Alzheimer's disease (AD). Here, it is shown that partial hepatic loss of Aβ in transgenic AD mice immunized with Aβ antibody 3D6 and its absence in amyloid precursor protein (APP) knockout mice (APP-KO), as well as in human liver spheroids with APP knockdown upregulates classical hallmarks of fibrosis, smooth muscle alpha-actin, and collagen type I. Aβ absence in APP-KO and deficiency in immunized mice lead to strong activation of transforming growth factor-β (TGFβ), alpha secretases, NOTCH pathway, inflammation, decreased permeability of liver sinusoids, and epithelial-mesenchymal transition. Inversely, increased systemic and intrahepatic levels of Aβ42 in transgenic AD mice and neprilysin inhibitor LBQ657-treated wild-type mice protect the liver against carbon tetrachloride (CCl4)-induced injury. Transcriptomic analysis of CCl4-treated transgenic AD mouse livers uncovers the regulatory effects of Aβ42 on mitochondrial function, lipid metabolism, and its onco-suppressive effects accompanied by reduced synthesis of extracellular matrix proteins. Combined, these data reveal Aβ as an indispensable regulator of cell-cell interactions in healthy liver and a powerful protector against liver fibrosis.

TRPM7 mediates endoplasmic reticulum stress and ferroptosis in sepsis-induced myocardial injury

Transient receptor potential melastatin 7 (TRPM7), a non-selective cation channel, was significantly upregulated in the blood of patients with sepsis. This study focuses on the preliminary exploration of the probable regulatory mechanism of TRPM7 in sepsis-induced myocardial injury (SIMI). HL-1 cardiac muscle cell line was treated with lipopolysaccharide (LPS) to mimic SIMI in vitro, and TRPM7 level was assessed. The impacts of TRPM7 knockdown on cellular inflammation response, oxidative stress, apoptosis, endoplasmic reticulum (ER) stress, and ferroptosis were identified. In order to explore the mechanism, ER stress agonist tunicamycin (TM) or ferroptosis inducer erastin was applied to treat HL-1 cells. The influences of TM and erastin on the aforementioned aspects were evaluated. TRPM7 was elevated in response to LPS stimulation, and its knockdown reduced the secretion of inflammatory factors and oxidative stress degree. Moreover, TRPM7 knockdown significantly suppressed cell apoptosis, ER stress, and ferroptosis. TM and erastin reversed the functions of TRPM7 knockdown, indicating ER stress and ferroptosis mediated in the regulation of TRPM7. This research proposes the possibility of TRPM7 as a marker or target for SIMI, and provides theoretical support for follow-up research.

The impact of sacubitril/valsartan on outcome in patients suffering from heart failure with a concomitant diabetes mellitus

BACKGROUND

Guidelines classify sacubitril/valsartan as a significant part of medical treatment of heart failure with reduced ejection fraction (HFrEF). Data have shown that the HbA1c levels in patients with diabetes mellitus could be impacted by sacubitril/valsartan. A possible positive effect in diabetes patients treated with sacubitril/valsartan on outcome and echocardiography parameters is not well studied yet.

AIMS

The aim of the present study was to compare the impact of sacubitril/valsartan on life-threatening arrhythmias, atrial fibrillation, different echocardiography parameters and congestion rate in patients suffering from HFrEF according to the diagnosis diabetes mellitus or no diabetes mellitus.

METHODS AND RESULTS

Consecutive 240 patients with HFrEF from 2016 to 2020 were treated with sacubitril/valsartan and separated to concomitant diabetes mellitus (n = 87, median age 68 years interquartile range (IQR) [32-87]) or no diabetes mellitus (n = 153, median age 66 year IQR [34-89]). Different comorbidities and outcome data were evaluated over a follow-up period of 24 months. Arterial hypertension (87% vs. 64%; P < 0.01) and coronary artery disease (74% vs. 60%; P = 0.03) were more often documented in patients with diabetes mellitus compared with patients without diabetes mellitus. Over the follow-up of 24 months several changes were noted in both subgroups: Median left ventricular ejection fraction (EF) increased significantly in non-diabetes (27% IQR [3-44] at baseline to 35% IQR [13-64]; P < 0.001), but not in diabetic patients (29% IQR [10-65] at baseline to 30% IQR [13-55]; P = 0.11). Accordingly, NT-proBNP and troponin-I levels decreased significantly in non-diabetes patients (NT-brain natriuretic peptide [NT-proBNP] from median 1445 pg/mL IQR [12.6-74 676] to 491 pg/mL IQR [13-4571]; P < 0.001, troponin-I levels from 0.099 ng/mL IQR [0.009-138.69] to 0.023 ng/mL IQR [0.006-0.635]; P < 0.001), but not in diabetic patients (NT-proBNP from 1395 pg/mL IQR [100-29 924] to 885 pg/mL IQR [159-4331]; P = 0.06, troponin-I levels from 0.05 ng/mL IQR [0.013-103.0] to 0.020 ng/mL IQR [0.015-0.514]; P = 0.27). No significant change of laboratory parameters e. g. glomerular filtration rate, potassium level and creatinine levels were found in diabetes or non-diabetes patients. Comparing further echocardiography data, left atrial surface area, right atrial surface area, E/A ratio did not show a significant change either in the diabetes or non-diabetes group. However, the tricuspid annular plane systolic excursion was significantly increased in non-diabetes mellitus patients (from 17 mm IQR [3-31] to 18 mm [2.5-31]; P = 0.04), and not in diabetic s patients (17.5 mm IQR [8-30] to 18 mm IQR [14-31]; P = 0.70); the systolic pulmonary artery pressure remained unchanged in both groups. During follow-up, a similar rate of ventricular tachyarrhythmias was observed in both groups. The congestion rate decreased significantly in both groups, in diabetes patients (44.4% before sacubitril/valsartan and 13.5% after 24 months treatment; P = 0.0009) and in non-diabetic patients (28.4% before sacubitril/valsartan and 8.4% after 24 months treatment; P = 0.0004). The all-cause mortality rate was higher in patients with diabetes mellitus as compared with those without diabetes (25% vs. 8.1%; P < 0.01).

CONCLUSIONS

Sacubitril/valsartan reverses cardiac remodelling in non-diabetes patients. However, it reduces the congestion rate in diabetes and non-diabetes patients. The rates of ventricular tachyarrhythmias were similar in DM compared with non-DM over follow-up. The mortality rate remained to be over follow-up higher in diabetes patients compared with non-diabetes; however, it was lower compared with published data on diabetes and concomitant HFrEF not treated with sacubitril/valsartan.

The history and mystery of sacubitril/valsartan: From clinical trial to the real world

Heart failure is a serious threat to human health, with morbidity and mortality rates increasing despite the existence of multiple treatment options. Therefore, it is necessary to identify new therapeutic targets for this disease. Sacubitril/valsartan is a supramolecular sodium salt complex of the enkephalinase inhibitor prodrug sacubitril and the angiotensin receptor blocker valsartan. Its combined action increases endogenous natriuretic peptides while inhibiting the renin-angiotensin-aldosterone system and exerting cardioprotective effects. Clinical evidence suggests that sacubitril/valsartan is superior to conventional renin-angiotensin-aldosterone inhibitor therapy for patients with reduced ejection fraction heart failure who can tolerate angiotensin-converting enzyme inhibitors or angiotensin II receptor blockers. The therapy reduces the risk of heart failure hospitalization, cardiovascular mortality, and all-cause mortality and has a better safety and tolerability record. This review describes the potential pathophysiological mechanisms of cardiomyocyte injury amelioration by sacubitril/valsartan. We explore the protective effects of sacubitril/valsartan and outline the therapeutic value in patients with heart failure by summarizing the results of recent large clinical trials. Furthermore, a preliminary outlook shows that sacubitril/valsartan may be effective at treating other diseases, and provides some exploratory observations that lay the foundation for future studies on this drug.

Cardiovascular toxicity of tyrosine kinase inhibitors during cancer treatment: Potential involvement of TRPM7

Receptor tyrosine kinases (RTKs) are a class of membrane spanning cell-surface receptors that transmit extracellular signals through the membrane to trigger diverse intracellular signaling through tyrosine kinases (TKs), and play important role in cancer development. Therapeutic approaches targeting RTKs such as vascular endothelial growth factor receptor (VEGFR), epidermal growth factor receptor (EGFR), and platelet-derived growth factor receptor (PDGFR), and TKs, such as c-Src, ABL, JAK, are widely used to treat human cancers. Despite favorable benefits in cancer treatment that prolong survival, these tyrosine kinase inhibitors (TKIs) and monoclonal antibodies targeting RTKs are also accompanied by adverse effects, including cardiovascular toxicity. Mechanisms underlying TKI-induced cardiovascular toxicity remain unclear. The transient receptor potential melastatin-subfamily member 7 (TRPM7) is a ubiquitously expressed chanzyme consisting of a membrane-based ion channel and intracellular α-kinase. TRPM7 is a cation channel that regulates transmembrane Mg²⁺ and Ca²⁺ and is involved in a variety of (patho)physiological processes in the cardiovascular system, contributing to hypertension, cardiac fibrosis, inflammation, and atrial arrhythmias. Of importance, we and others demonstrated significant cross-talk between TRPM7, RTKs, and TK signaling in different cell types including vascular smooth muscle cells (VSMCs), which might be a link between TKIs and their cardiovascular effects. In this review, we summarize the implications of RTK inhibitors (RTKIs) and TKIs in cardiovascular toxicities during anti-cancer treatment, with a focus on the potential role of TRPM7/Mg²⁺ as a mediator of RTKI/TKI-induced cardiovascular toxicity. We also describe the important role of TRPM7 in cancer development and cardiovascular diseases, and the interaction between TRPM7 and RTKs, providing insights for possible mechanisms underlying cardiovascular disease in cancer patients treated with RTKI/TKIs.

Emerging role of transient receptor potential (TRP) ion channels in cardiac fibroblast pathophysiology

Cardiac fibroblasts make up a major proportion of non-excitable cells in the heart and contribute to the cardiac structural integrity and maintenance of the extracellular matrix. During myocardial injury, fibroblasts can be activated to trans-differentiate into myofibroblasts, which secrete extracellular matrix components as part of healing, but may also induce cardiac fibrosis and pathological cardiac structural and electrical remodeling. The mechanisms regulating such cellular processes still require clarification, but the identification of transient receptor potential (TRP) channels in cardiac fibroblasts could provide further insights into the fibroblast-related pathophysiology. TRP proteins belong to a diverse superfamily, with subgroups such as the canonical (TRPC), vanilloid (TRPV), melastatin (TRPM), ankyrin (TRPA), polycystin (TRPP), and mucolipin (TRPML). Several TRP proteins form non-selective channels that are permeable to cations like Na+ and Ca2+ and are activated by various chemical and physical stimuli. This review highlights the role of TRP channels in cardiac fibroblasts and the possible underlying signaling mechanisms. Changes in the expression or activity of TRPs such as TRPCs, TRPVs, TRPMs, and TRPA channels modulate cardiac fibroblasts and myofibroblasts, especially under pathological conditions. Such TRPs contribute to cardiac fibroblast proliferation and differentiation as well as to disease conditions such as cardiac fibrosis, atrial fibrillation, and fibroblast metal toxicity. Thus, TRP channels in fibroblasts represent potential drug targets in cardiac disease.

Emerging Antiarrhythmic Drugs for Atrial Fibrillation

Atrial fibrillation (AF), the most common cardiac arrhythmia worldwide, is driven by complex mechanisms that differ between subgroups of patients. This complexity is apparent from the different forms in which AF presents itself (post-operative, paroxysmal and persistent), each with heterogeneous patterns and variable progression. Our current understanding of the mechanisms responsible for initiation, maintenance and progression of the different forms of AF has increased significantly in recent years. Nevertheless, antiarrhythmic drugs for the management of AF have not been developed based on the underlying arrhythmia mechanisms and none of the currently used drugs were specifically developed to target AF. With the increased knowledge on the mechanisms underlying different forms of AF, new opportunities for developing more effective and safer AF therapies are emerging. In this review, we provide an overview of potential novel antiarrhythmic approaches based on the underlying mechanisms of AF, focusing both on the development of novel antiarrhythmic agents and on the possibility of repurposing already marketed drugs. In addition, we discuss the opportunity of targeting some of the key players involved in the underlying AF mechanisms, such as ryanodine receptor type-2 (RyR2) channels and atrial-selective K⁺-currents (I_K2P and I_SK) for antiarrhythmic therapy. In addition, we highlight the opportunities for targeting components of inflammatory signaling (e.g., the NLRP3-inflammasome) and upstream mechanisms targeting fibroblast function to prevent structural remodeling and progression of AF. Finally, we critically appraise emerging antiarrhythmic drug principles and future directions for antiarrhythmic drug development, as well as their potential for improving AF management.