Mitophagy in Cardiovascular Diseases

Cardiovascular diseases are one of the leading causes of death. Increasing evidence has shown that pharmacological or genetic targeting of mitochondria can ameliorate each stage of these pathologies, which are strongly associated with mitochondrial dysfunction. Removal of inefficient and dysfunctional mitochondria through the process of mitophagy has been reported to be essential for meeting the energetic requirements and maintaining the biochemical homeostasis of cells. This process is useful for counteracting the negative phenotypic changes that occur during cardiovascular diseases, and understanding the molecular players involved might be crucial for the development of potential therapies. Here, we summarize the current knowledge on mitophagy (and autophagy) mechanisms in the context of heart disease with an important focus on atherosclerosis, ischemic heart disease, cardiomyopathies, heart failure, hypertension, arrhythmia, congenital heart disease and peripheral vascular disease. We aim to provide a complete background on the mechanisms of action of this mitochondrial quality control process in cardiology and in cardiac surgery by also reviewing studies on the use of known compounds able to modulate mitophagy for cardioprotective purposes

The role of c subunit of F1FO-ATP synthase in mitochondrial permeability transition pore activity for the treatment of reperfusion injury after myocardial infarction

Mitochondrial permeability transition (MPT)-driven apoptosis is a type of programmed cell death during which the inner mitochondrial membrane (IMM) exhibits increased permeability with a consequent osmotic influx of solutes in the mitochondrial matrix. This event is mediated by the mitochondrial permeability transition pore complex (PTPC), a membrane multiprotein platform composed of pore-forming parts and modulators that contribute to its conformational state and, thus, to its mechanism of action. In two previous studies, we provided experimental evidence that the c subunit of F1FO ATP synthase plays a pivotal role in mitochondrial permeability transition pore (mPTP) activity and mPTP formation, demonstrating first, a strong correlation between the mPTP functional state and c subunit expression; and second, the multi-step nature of the mPTP opening by ATP synthase dimers disassembly and c-ring conformational arrangements. Recent cardiology research studies have reported a key role for mPTP opening in the progression of myocardial cell death secondary to reperfusion. Since up to 50% of the final infarct size is due to ischemia-reperfusion injury, targeting the PTPC could be a valuable adjunct in reducing infarct size. In this first project, we validated a new pharmacological approach as an adjunct to reperfusion in myocardial infarction (MI) treatment and described the discovery, optimization, and structure−activity relationship (SAR) studies of the first small-molecule mPTP opening inhibitors based on a 1,3,8-triazaspiro[4.5]decane scaffold that targets the c subunit of the F1FO ATP synthase complex. We identified three potential compounds with increased mPTP inhibitory activity at low concentrations, a specific localization to the mitochondrial compartment and beneficial effects in an ex vivo model of MI, they did not show off-target effects at the cellular and mitochondrial levels; moreover, the compounds preserved mitochondrial ATP content despite interacting with the ATP synthase complex. In vitro and pre-clinical models have demonstrated the deleterious effects of mitochondrial Permeability Transition Pore (mPTP) opening in the first few minutes upon reperfusion, becoming a key player in the acceleration of the injury process. According to this, targeting mPTP might be a valid adjuvant strategy to counteract the reperfusion damage. Hitherto, no evidences are present in a clinical scenario. Recent studies hypothesized that one of the pore-forming proteins of the mPTP is the FO ATP synthase c subunit. Its circulating levels had been found to be associated with surrogate endpoints of myocardial reperfusion in patients with ST-segment elevation myocardial infarction (STEMI). No data about genetic determinants in c subunit have ever been related to reperfusion injury in patients with MI. Overall in this project, the CROFT clinical study showed how mPTP activity measured in fibroblasts significantly correlate with that monitored in myocytes from the same patient, so in those conditions where cardiac biopsies are impossible to be taken, mPTP function in fibroblasts from STEMI patients may be predictive of the mPTP activity in myocytes. Moreover, for the first time we provided a proof of mPTP correlation to reperfusion injury developed upon MI in patients. In addition, a new polymorphism found in ATP5G1 gene encoding for c subunit in two STEMI patients was responsible for worsening reperfusion injury in vitro.Il processo di apoptosi provocata dalla transizione di permeabilità mitocondriale è un tipo di morte cellulare programmata durante il quale la membrana mitocondriale interna mostra un’aumentata permeabilità con un conseguente influsso osmotico di soluti nella matrice mitocondriale. Questo evento è mediato dal complesso proteico del poro mitocondriale di transizione della permeabilità, una piattaforma multiproteica di cui la composizione non è precisamente stabilita. In due studi precedenti, abbiamo dimostrato che la subunità c del complesso F1FO ATP sintasi ricopre un ruolo fondamentale nell’attività e nella formazione del poro mPTP, prima di tutto dimostrando una forte correlazione tra lo stato funzionale dell’mPTP e l’espressione della subunità c, in particolare tra la modalità a diversi passaggi con cui avviene l’apertura dell’mPTP data dal disassemblaggio dei dimeri di ATP sintasi e da riarrangiamenti conformazionali del c-ring. Studi recenti di cardiologia hanno riportato il ruolo chiave dell’apertura dell’mPTP nella progressione della morte delle cellule del miocardio in seguito a riperfusione, infatti più del 50% dell’area finale dell’infarto è dovuta al danno da ischemia e riperfusione. In questo progetto, abbiamo validato un nuovo approccio farmacologico tramite la scoperta, l’ottimizzazione e gli studi di relazione struttura-attività delle prime piccole molecole inibitrici dell’apertura dell’mPTP basate su uno 1,3,8-triazaspiro[4.5]decane scaffold che colpisce la subunità c. Abbiamo identificato tre potenziali composti che mostrano un’attività inibitoria dell’mPTP aumentata a dosi inferiori ai composti di riferimento, una migliore localizzazione nel compartimento mitocondriale e effetti positivi anche in un modello di MI ex vivo, inoltre non mostrano effetti collaterali né a livello cellulare né a livello mitocondriale preservando il contenuto mitocondriale di ATP nonostante la loro interazione diretta con il complesso dell’ATP sintasi. Sia modelli in vitro che preclinici hanno dimostrato l’effetto deleterio dell’apertura dell’mPTP nei primi minuti dopo la riperfusione, giocando un ruolo chiave nell’accelerazione del processo di danno tissutale, quindi colpire il mPTP può essere una valida strategia adiuvante per contrastare il danno da riperfusione. Studi recenti hanno ipotizzato che una delle proteine componenti il poro dell’mPTP è la subunità c della porzione FO dell’ATP sintasi. I suoi livelli circolanti sono stati associati con endpoints surrogati della riperfusione miocardica in pazienti con infarto miocardico con sopraslivellamento del tratto ST (STEMI). Non sono mai stati correlati dati sui determinanti genetici nella subunità c al danno da riperfusione in pazienti con infarto del miocardio. Complessivamente in questo studio clinico mostriamo come l’attività dell’mPTP misurata nei fibroblasti correla in modo significativo con quella monitorata nei cardiomiociti dello stesso paziente, in questo modo in quelle condizioni in cui le biopsie cardiache sono impossibili da ottenere, la funzione dell’mPTP nei fibroblasti di pazienti STEMI può essere predittiva dell’attività dell’mPTP nei cardiomiociti. Inoltre, per la prima volta abbiamo dimostrato una correlazione tra l’mPTP e il danno da riperfusione dopo infarto in pazienti. In aggiunta, un nuovo polimorfismo è stato trovato nel gene ATP5G1 che codifica per la subunità c in due pazienti STEMI ed è stato associato ad un peggioramento nel danno da riperfusione in vitro

Mitochondria-associated membranes (MAMs) and inflammation

The endoplasmic reticulum (ER) and mitochondria are tightly associated with very dynamic platforms termed mitochondria-associated membranes (MAMs). MAMs provide an excellent scaffold for crosstalk between the ER and mitochondria and play a pivotal role in different signaling pathways that allow rapid exchange of biological molecules to maintain cellular health. However, dysfunctions in the ER-mitochondria architecture are associated with pathological conditions and human diseases. Inflammation has emerged as one of the various pathways that MAMs control. Inflammasome components and other inflammatory factors promote the release of pro-inflammatory cytokines that sustain pathological conditions. In this review, we summarize the critical role of MAMs in initiating inflammation in the cellular defense against pathogenic infections and the association of MAMs with inflammation-mediated diseases

Intersection of mitochondrial fission and fusion machinery with apoptotic pathways: Role of Mcl-1

Mitochondria actively contribute to apoptotic cell death through mechanisms including the loss of integrity of the outer mitochondrial membrane, the release of intermembrane space proteins, such as cytochrome c, in the cytosol and the caspase cascade activation. This process is the result of careful cooperation not only among members of the Bcl-2 family but also dynamin-related proteins. These events are often accompanied by fission of the organelle, thus linking mitochondrial dynamics to apoptosis. Emerging evidences are suggesting a fine regulation of mitochondrial morphology by Bcl-2 family members and active participation of fission-fusion proteins in apoptosis. The debate whether in mitochondrial morphogenesis the role of Bcl-2 family members is functionally distinct from their role in apoptosis is still open and, above all, which morphological changes are associated with cell death sensitisation. This review will cover the findings on how the mitochondrial fission and fusion machinery may intersect apoptotic pathways focusing on recent advances on the key role played by Mcl-1

Regulation of endoplasmic reticulumâ\u80\u93mitochondria Ca2+transfer and its importance for anti-cancer therapies

Inter-organelle membrane contact sites are emerging as major sites for the regulation of intracellular Ca2+concentration and distribution. Here, extracellular stimuli operate on a wide array of channels, pumps, and ion exchangers to redistribute intracellular Ca2+among several compartments. The resulting highly defined spatial and temporal patterns of Ca2+movement can be used to elicit specific cellular responses, including cell proliferation, migration, or death. Plasma membrane (PM) also can directly contact mitochondria and endoplasmic reticulum (ER) through caveolae, small invaginations of the PM that ensure inter-organelle contacts, and can contribute to the regulation of numerous cellular functions through scaffolding proteins such as caveolins. PM and ER organize specialized junctions. Here, many components of the receptor-dependent Ca2+signals are clustered, including the ORAI1-stromal interaction molecule 1 complex. This complex constitutes a primary mechanism for Ca2+entry into non-excitable cells, modulated by intracellular Ca2+. Several contact sites between the ER and mitochondria, termed mitochondria-associated membranes, show a very complex and specialized structure and host a wide number of proteins that regulate Ca2+transfer. In this review, we summarize current knowledge of the particular action of several oncogenes and tumor suppressors at these specialized check points and analyze anti-cancer therapies that specifically target Ca2+flow at the inter-organelle contacts to alter the metabolism and fate of the cancer cell

The Complex Relationship between Hypoxia Signaling, Mitochondrial Dysfunction and Inflammation in Calcific Aortic Valve Disease: Insights from the Molecular Mechanisms to Therapeutic Approaches

Calcific aortic valve stenosis (CAVS) is among the most common causes of cardiovascular mortality in an aging population worldwide. The pathomechanisms of CAVS are such a complex and multifactorial process that researchers are still making progress to understand its physiopathology as well as the complex players involved in CAVS pathogenesis. Currently, there is no successful and effective treatment to prevent or slow down the disease. Surgical and transcatheter valve replacement represents the only option available for treating CAVS. Insufficient oxygen availability (hypoxia) has a critical role in the pathogenesis of almost all CVDs. This process is orchestrated by the hallmark transcription factor, hypoxia-inducible factor 1 alpha subunit (HIF-1α), which plays a pivotal role in regulating various target hypoxic genes and metabolic adaptations. Recent studies have shown a great deal of interest in understanding the contribution of HIF-1α in the pathogenesis of CAVS. However, it is deeply intertwined with other major contributors, including sustained inflammation and mitochondrial impairments, which are attributed primarily to CAVS. The present review aims to cover the latest understanding of the complex interplay effect of hypoxia signaling pathways, mitochondrial dysfunction, and inflammation in CAVS. We propose further hypotheses and interconnections on the complexity of these impacts in a perspective of better understanding the pathophysiology. These interplays will be examined considering recent studies that shall help us better dissect the molecular mechanism to enable the design and development of potential future therapeutic approaches that can prevent or slow down CAVS processes

Comprehensive Analysis of Mitochondrial Dynamics Alterations in Heart Diseases

The most common alterations affecting mitochondria, and associated with cardiac pathological conditions, implicate a long list of defects. They include impairments of the mitochondrial electron transport chain activity, which is a crucial element for energy formation, and that determines the depletion of ATP generation and supply to metabolic switches, enhanced ROS generation, inflammation, as well as the dysregulation of the intracellular calcium homeostasis. All these signatures significantly concur in the impairment of cardiac electrical characteristics, loss of myocyte contractility and cardiomyocyte damage found in cardiac diseases. Mitochondrial dynamics, one of the quality control mechanisms at the basis of mitochondrial fitness, also result in being dysregulated, but the use of this knowledge for translational and therapeutic purposes is still in its infancy. In this review we tried to understand why this is, by summarizing methods, current opinions and molecular details underlying mitochondrial dynamics in cardiac diseases

Calcium signaling from sarcoplasmic reticulum and mitochondria contact sites in acute myocardial infarction

: Acute myocardial infarction (AMI) is a serious condition that occurs when part of the heart is subjected to ischemia episodes, following partial or complete occlusion of the epicardial coronary arteries. The resulting damage to heart muscle cells have a significant impact on patient's health and quality of life. About that, recent research focused on the role of the sarcoplasmic reticulum (SR) and mitochondria in the physiopathology of AMI. Moreover, SR and mitochondria get in touch each other through multiple membrane contact sites giving rise to the subcellular region called mitochondria-associated membranes (MAMs). MAMs are essential for, but not limited to, bioenergetics and cell fate. Disruption of the architecture of these regions occurs during AMI although it is still unclear the cause-consequence connection and a complete overview of the pathological changes; for sure this concurs to further damage to heart muscle. The calcium ion (Ca2+) plays a pivotal role in the pathophysiology of AMI and its dynamic signaling between the SR and mitochondria holds significant importance. In this review, we tried to summarize and update the knowledge about the roles of these organelles in AMI from a Ca2+ signaling point of view. Accordingly, we also reported some possible cardioprotective targets which are directly or indirectly related at limiting the dysfunctions caused by the deregulation of the Ca2+ signaling

Comprehensive Analysis of Mitochondrial Dynamics Alterations in Heart Diseases

The most common alterations affecting mitochondria, and associated with cardiac pathological conditions, implicate a long list of defects. They include impairments of the mitochondrial electron transport chain activity, which is a crucial element for energy formation, and that determines the depletion of ATP generation and supply to metabolic switches, enhanced ROS generation, inflammation, as well as the dysregulation of the intracellular calcium homeostasis. All these signatures significantly concur in the impairment of cardiac electrical characteristics, loss of myocyte contractility and cardiomyocyte damage found in cardiac diseases. Mitochondrial dynamics, one of the quality control mechanisms at the basis of mitochondrial fitness, also result in being dysregulated, but the use of this knowledge for translational and therapeutic purposes is still in its infancy. In this review we tried to understand why this is, by summarizing methods, current opinions and molecular details underlying mitochondrial dynamics in cardiac diseases

Some Insights into the Regulation of Cardiac Physiology and Pathology by the Hippo Pathway

The heart is one of the most fascinating organs in living beings. It beats up to 100,000 times a day throughout the lifespan, without resting. The heart undergoes profound anatomical, biochemical, and functional changes during life, from hypoxemic fetal stages to a completely differentiated four-chambered cardiac muscle. In the middle, many biological events occur after and intersect with each other to regulate development, organ size, and, in some cases, regeneration. Several studies have defined the essential roles of the Hippo pathway in heart physiology through the regulation of apoptosis, autophagy, cell proliferation, and differentiation. This molecular route is composed of multiple components, some of which were recently discovered, and is highly interconnected with multiple known prosurvival pathways. The Hippo cascade is evolutionarily conserved among species, and in addition to its regulatory roles, it is involved in disease by drastically changing the heart phenotype and its function when its components are mutated, absent, or constitutively activated. In this review, we report some insights into the regulation of cardiac physiology and pathology by the Hippo pathway