Adriana Adameova

Mitochondrial DNA (mtDNA) is increasingly recognized as a damage-associated molecular pattern (DAMP) that signals mitochondrial injury and the consequent pro-death molecular signature. Such mtDNA release triggers programmed necrotic pathways, specifically necroptosis and pyroptosis, both of which are central to the pathogenesis of heart failure (HF). Mechanistically, mtDNA liberated from dysfunctional mitochondria engages cytosolic nucleic acid sensors and is associated with activation of necroptotic pathways via the Z-DNA binding protein 1 (ZBP1)-receptor-interacting protein kinase 3 (RIP3)-mixed lineage kinase domain-like pseudokinase (MLKL) axis. Similarly, it can stimulate cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling to promote the de novo synthesis of pro-necroptotic cytokines. Furthermore, mtDNA release has been shown to promote pyroptosis through nucleotide-binding domain, leucine-rich-containing family, pyrin domain-containing-3 (NLRP3), and/or absent in melanoma 2 (AIM2) inflammasomes, amplifying a proinflammatory environment. The article examines the mechanistic cross talk between these prodeath, proinflammatory pathways with a particular emphasis on how this mechanistic cross talk drives HF. Consequently, it highlights circulating mtDNA as a key biomarker for HF severity. Finally, it posits that mtDNA-targeted therapies, such as interventions preserving mitochondrial integrity and limiting mtDNA leakage and oxidation, and interventions inhibiting mtDNA-sensing pathways, may offer a viable strategy for novel therapeutic interventions in HF.

[This corrects the article DOI: 10.31083/j.rcm2306213.].

This study identifies necroptosis as a key pathomechanism in pressure overload-induced heart failure, with sex-dependent, prodeath molecular events. Novel findings indicate distinct pronecroptotic triggers: in males, necroptosis is driven by oxidative stress and mitochondrial DNA damage, whereas in females, a proinflammatory pathway involving tumor necrosis factor and compensatory mitochondrial biogenesis predominates. Pyroptosis and ferroptosis do not appear to be prominent. These sex-specific molecular necrosis-like divergences are important for developing personalized therapeutic strategies for heart failure.

Since cell dying in heart failure (HF) may vary based on the aetiology, we examined the main forms of regulated necrosis, such as necroptosis and pyroptosis, in the hearts damaged due to myocardial infarction (MI) or pressure overload. We also investigated the effects of a drug inhibiting RIP3, a proposed convergent point for both these necrosis-like cell death modes. In rat hearts, left ventricular function, remodelling, pro-cell death, and pro-inflammatory events were investigated, and the pharmacodynamic action of RIP3 inhibitor (GSK'872) was assessed. Regardless of the HF aetiology, the heart cells were dying due to necroptosis, albeit the upstream signals may be different. Pyroptosis was observed only in post-MI HF. The dysregulated miRNAs in post-MI hearts were accompanied by higher levels of a predicted target, HMGB1, its receptors (TLRs), as well as the exacerbation of inflammation likely originating from macrophages. The RIP3 inhibitor suppressed necroptosis, unlike pyroptosis, normalised the dysregulated miRNAs and tended to decrease collagen content and affect macrophage infiltration without affecting cardiac function or structure. The drug also mitigated the local heart inflammation and normalised the higher circulating HMGB1 in rats with post-MI HF. Elevated serum levels of HMGB1 were also detected in HF patients and positively correlated with C-reactive protein, highlighting pro-inflammatory axis. In conclusion, in MI-, but not pressure overload-induced HF, both necroptosis and pyroptosis operate and might underlie HF pathogenesis. The RIP3-targeting pharmacological intervention might protect the heart by preventing pro-death and pro-inflammatory mechanisms, however, additional strategies targeting multiple pro-death pathways may exhibit greater cardioprotection.

Background: Regulated forms of necrosis-like cell death (e.g., necroptosis) have been shown to contribute to cardiac ischemia/reperfusion (I/R) injury. However, pro-inflammatory necroptosis is unlikely to be involved during early reperfusion and little is known about the associated molecular changes. Thus, this study aimed to provide an in-depth protein screening with a particular focus on pro-pyroptotic and mitochondrial damage-related pathways. Methods: Langendorff-perfused rat hearts were subjected to 30-minute global ischemia followed by 10-minute reperfusion. Liquid chromatography coupled with mass spectrometry (LC-MS/MS) and immunoblotting techniques were used to study the complex cardiac proteome. In addition, calcium-induced mitochondrial swelling and lactate dehydrogenase (LDH) release were examined to assess mitochondrial stress and necrosis phenotype, respectively. Results: Approximately 160 proteins linked to cell death signaling, cellular metabolism, and post-translational modifications were significantly differentially expressed in I/R hearts compared to controls. Conventional proteins of pyroptosis, either of canonical or non-canonical signaling, were not affected during the short reperfusion. Notably, this type of I/R was associated with increased expression of p25 cleaved form of poly [ADP-ribose] polymerase 1 (PARP1 p25) and mature apoptosis-inducing factor (AIF), alongside nitrosative stress and mitochondrial swelling. Conversely, a receptor-interacting protein kinase 3 (RIP3) inhibitor (GSK′872, 250 nM) reversed mitochondrial swelling and plasma membrane rupture and mitigated the increase in the expression of PARP1 p25 and AIF. Conclusions: This study shows for the first time that necrosis-like injury during early I/R of the isolated heart is associated with mitochondrial events, rather than pro-inflammatory pyroptotic cell death. Furthermore, the inhibition of RIP3 mitigates this injury independent of targeting pro-inflammatory signaling.

Extensive work over the past 6 decades in the field of cardiovascular medicine has revealed that haemodynamic, hormonal, metabolic, cellular and molecular mechanisms of heart failure are not only complex but are also dependent upon the type and stage of heart disease. Although various agents such as b-adrenoreceptor blockers, angiotensin converting enzyme inhibitors, angiotensin II receptor antagonists and vasodilators are available for the treatment of heart failure, these interventions delay the progression of heart failure without reducing mortality and morbidity. In this article, literature on the pathophysiology of heart failure due to myocardial infarction and haemodynamic overload to identify molecular targets for future drug development is reviewed. Particularly, objective was to focus on the mechanisms of heart failure involving pathways for the generation of oxidative stress, myocardial inflammation and Ca2+-handling abnormalities. It is evident that elevated levels of plasma vasoactive hormones and growth factors as well as increased preload and afterload play critical roles in stimulating various signal transduction pathways for the occurrence of increased ventricular wall stress, cardiac remodelling and subsequent cardiac dysfunction. These alterations are associated with development of oxidative stress, myocardial inflammation, endothelial dysfunction, metabolic defects, intracellular Ca2+-handling abnormalities, apoptosis, fibrosis and changes in the extracellular matrix. In view of such pathogenic abnormalities in failing hearts, it is suggested these parameters may serve as excellent targets for drug development for the therapy of heart failure. In addition, there occurs activation of proteases and phospholipases as well as depression in cardiac gene expression for the induction of subcellular remodelling in failing hearts and thus interventions affecting these parameters may also be considered to exert beneficial effects in heart failure. There is also an urgent need to develop some existing and newer agents such as metabolic inhibitors, antioxidants and sodium-glucose cotransporter-2 inhibitors as well as gene and RNA based therapies for the treatment of heart failure.

Na⁺-K⁺ ATPase is an integral component of cardiac sarcolemma and consists of three major subunits, namely the α-subunit with three isoforms (α₁, α₂, and α₃), β-subunit with two isoforms (β₁ and β₂) and γ-subunit (phospholemman). This enzyme has been demonstrated to transport three Na and two K ions to generate a trans-membrane gradient, maintain cation homeostasis in cardiomyocytes and participate in regulating contractile force development. Na⁺-K⁺ ATPase serves as a receptor for both exogenous and endogenous cardiotonic glycosides and steroids, and a signal transducer for modifying myocardial metabolism as well as cellular survival and death. In addition, Na⁺-K⁺ ATPase is regulated by different hormones through the phosphorylation/dephosphorylation of phospholemman, which is tightly bound to this enzyme. The activity of Na⁺-K⁺ ATPase has been reported to be increased, unaltered and depressed in failing hearts depending upon the type and stage of heart failure as well as the association/disassociation of phospholemman and binding with endogenous cardiotonic steroids, namely endogenous ouabain and marinobufagenin. Increased Na⁺-K⁺ ATPase activity in association with a depressed level of intracellular Na⁺ in failing hearts is considered to decrease intracellular Ca²⁺ and serve as an adaptive mechanism for maintaining cardiac function. The slight to moderate depression of Na⁺-K⁺ ATPase by cardiac glycosides in association with an increased level of Na⁺ in cardiomyocytes is known to produce beneficial effects in failing hearts. On the other hand, markedly reduced Na⁺-K⁺ ATPase activity associated with an increased level of intracellular Na⁺ in failing hearts has been demonstrated to result in an intracellular Ca²⁺ overload, the occurrence of cardiac arrhythmias and depression in cardiac function during the development of heart failure. Furthermore, the status of Na⁺-K⁺ ATPase activity in heart failure is determined by changes in isoform subunits of the enzyme, the development of oxidative stress, intracellular Ca²⁺-overload, protease activation, the activity of inflammatory cytokines and sarcolemmal lipid composition. Evidence has been presented to show that marked alterations in myocardial cations cannot be explained exclusively on the basis of sarcolemma alterations, as other Ca²⁺ channels, cation transporters and exchangers may be involved in this event. A marked reduction in Na⁺-K⁺ ATPase activity due to a shift in its isoform subunits in association with intracellular Ca²⁺-overload, cardiac energy depletion, increased membrane permeability, Ca²⁺-handling abnormalities and damage to myocardial ultrastructure appear to be involved in the progression of heart failure.