Energy status determines the distinct biochemical and physiological behavior of interfibrillar and sub-sarcolemmal mitochondria

The multifaceted role of mitochondria in cardiac function: insights and approaches

Cardiovascular disease (CVD) remains a global economic burden even in the 21st century with 85% of deaths resulting from heart attacks. Despite efforts in reducing the risk factors, and enhancing pharmacotherapeutic strategies, challenges persist in early identification of disease progression and functional recovery of damaged hearts. Targeting mitochondrial dysfunction, a key player in the pathogenesis of CVD has been less successful due to its role in other coexisting diseases. Additionally, it is the only organelle with an agathokakological function that is a remedy and a poison for the cell. In this review, we describe the origins of cardiac mitochondria and the role of heteroplasmy and mitochondrial subpopulations namely the interfibrillar, subsarcolemmal, perinuclear, and intranuclear mitochondria in maintaining cardiac function and in disease-associated remodeling. The cumulative evidence of mitochondrial retrograde communication with the nucleus is addressed, highlighting the need to study the genotype-phenotype relationships of specific organelle functions with CVD by using approaches like genome-wide association study (GWAS). Finally, we discuss the practicality of computational methods combined with single-cell sequencing technologies to address the challenges of genetic screening in the identification of heteroplasmy and contributory genes towards CVD.

Mitochondrial transplantation: the advance to therapeutic application and molecular modulation

Mitochondrial transplantation provides a novel methodology for rescue of cell viability and cell function following ischemia-reperfusion injury and applications for other pathologies are expanding. In this review we present our methods and acquired data and evidence accumulated to support the use of mitochondrial transplantation.

Brain and Myocardial Mitochondria Follow Different Patterns of Dysfunction After Cardiac Arrest

ABSTRACT

Mitochondria is often considered as the common nexus of cardiac and cerebral dysfunction after cardiac arrest. Here, our goal was to determine whether the time course of cardiac and cerebral mitochondrial dysfunction is similar after shockable versus non-shockable cardiac arrest in rabbits. Anesthetized rabbits were submitted to 10 min of no-flow by ventricular fibrillation (VF group) or asphyxia (non-shockable group). They were euthanized at the end of the no-flow period or 30 min, 120 min, or 24 h after resuscitation for in vitro evaluation of oxygen consumption and calcium retention capacity. In the brain (cortex and hippocampus), moderate mitochondrial dysfunction was evidenced at the end of the no-flow period after both causes of cardiac arrest versus baseline. It partly recovered at 30 and 120 min after cardiac arrest, with lower calcium retention capacity and higher substrate-dependant oxygen consumption after VF versus non-shockable cardiac arrest. However, after 24 h of follow-up, mitochondrial dysfunction dramatically increased after both VF and non-shockable cardiac arrest, despite greater neurological dysfunction after the latter one. In the heart, mitochondrial dysfunction was also maximal after 24 h following resuscitation, with no significant difference among the causes of the cardiac arrest. During the earlier timing of evaluation, calcium retention capacity and ADP-dependant oxygen consumption were lower and higher, respectively, after non-shockable cardiac arrest versus VF. In conclusion, the kinetics of cardiac and cerebral mitochondrial dysfunction suggests that mitochondrial function does not play a major role in the early phase of the post-resuscitation process but is only involved in the longer pathophysiological events.

The Protective Effect of Anthocyanins Extracted from Aronia Melanocarpa Berry in Renal Ischemia-Reperfusion Injury in Mice

Background

Our previous research showed the antioxidant activity of anthocyanins extracted from Aronia melanocarpa of black chokeberry in vitro. Ischemia acute kidney injury is a significant risk in developing progressive and deterioration of renal function leading to clinic chronic kidney disease. There were many attempts to protect the kidney against this progression of renal damage. Current study was designed to examine the effect of pretreatment with three anthocyanins named cyanidin-3-arabinoside, cyanidin-3-glucodise, and cyaniding-3-galactoside against acute ischemia-reperfusion injury in mouse kidney.

Methods

Acute renal injury model was initiated by 30 min clamping bilateral renal pedicle and followed by 24-hour reperfusion in C57Bl/6J mice. Four groups of mice were orally pretreated in 50 mg/g/12 h for two weeks with cyanidin-3-arabinoside, cyanidin-3-glucodise, and cyaniding-3-galactoside and anthocyanins (three-cyanidin mixture), respectively, sham-control group and the renal injury-untreated groups only with saline.

Results

The model resulted in renal dysfunction with high serum creatinine, blood urea nitrogen, and changes in proinflammatory cytokines (TNF-ɑ, IL-1β, IL-6, and MCP-1), renal oxidative stress (SOD, GSH, and CAT), lipid peroxidation (TBARS and MDA), and apoptosis (caspase-9). Pretreatment of two weeks resulted in different extent amelioration of renal dysfunction and tubular damage and suppression of proinflammatory cytokines, oxidative stress, lipid peroxidation, and apoptosis, thus suggesting that cyanidins are potentially effective in acute renal ischemia by the decrease of inflammation, oxidative stress, and lipid peroxidation, as well as apoptosis.

Conclusion

the current study provided the first attempt to investigate the role of anthocyanins purified from Aronia melanocarpa berry in amelioration of acute renal failure via antioxidant and cytoprotective effects.

Diabetic cardiomyopathy attenuated the protective effect of ischaemic post-conditioning against ischaemia-reperfusion injury in the isolated rat heart model

The present study was designed to investigate the efficacy of post-conditioning (POC) in the diabetic heart with myopathy (DCM) against ischaemia-reperfusion (I/R) injury in an isolated rat heart model. Present work includes three groups of male Wistar rat viz., (i) normal, (ii) diabetes mellitus (DM) and (iii) DCM and each group was subdivided into normal perfusion, I/R, and POC. Isolated heart from the rats was analysed for tissue injury, contractile function, mitochondrial function, and oxidative stress. Results demonstrated that unlike in DM heart and normal heart, POC procedure failed to recover the DCM heart from I/R induced cardiac dysfunction (measured via cardiac hemodynamics and infarct size. POC was unsuccessful in preserving mitochondrial subsarcolemmal fraction during I/R when compared with DM and normal heart. To conclude, the development of myopathy in diabetic heart abolished the cardioprotective efficacy of POC and the underlying pathology was linked with the mitochondrial dysfunction.KEY MESSAGESEarly studies reported contradicting response of diabetic heart towards post-conditioning mediated cardioprotection.Deteriorated mitochondrial function underlines the failure of post-conditioning in DCM.Efficacy of cardioprotection depends on the varying pathology of different diabetes stages.

Mitochondrial dysfunction plays a key role in the abrogation of cardioprotection by sodium hydrosulfide post-conditioning in diabetic cardiomyopathy rat heart

Our previous study demonstrated that hydrogen sulfide post-conditioning (HPOC) renders cardioprotection against ischemia-reperfusion (I/R) injury in normal rat by preserving mitochondria. But its efficacy in ameliorating I/R in the diabetic heart with (DCM) or without cardiomyopathy (DM) is unclear and is the focus of the present study. Normal (N), diabetes mellitus (streptozotocin, 35 mg/kg; normal diet), and DCM (streptozotocin, 35 mg/kg; high-fat diet) rats were subjected to I/R (30 min global ischemia followed by 60 min reperfusion) in presence and absence of HPOC using ex vivo Langendorff perfusion system. At the end of heart perfusion, subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM) fractions from the tissue were isolated and measured for the ATP production, electron transport chain (ETC) enzyme activity, and membrane potential. The prominent I/R-associated injury in DCM rat was not subsequently attenuated by HPOC protocol unlike in the normal or diabetic rat heart (latter rat heart showed moderate protection) (HPOC recovery on infarct size: N 75% vs. DM 63% vs. DCM 48%). The baseline ATP content and subsequent ATP-producing capacity in DCM rat heart were low as compared with those in normal or DM rat heart, especially in SSM. HPOC protocol reversed the I/R-induced low mitochondrial ATP content and low ATP-producing capacity (both in non-energized and energized with glutamate/malate) significantly in normal and DM hearts, but not in DCM heart. Moreover in DCM, decreased activity of mitochondrial electron chain enzymes (complexes I, II, III, and IV) in SSM (26%, 88%, 57%, and 17%) and IFM (76%, 89%, 60%, and 13%) from sham control was maintained even after the conditioning of heart with hydrogen sulfide donor. Results altogether suggest that significantly higher levels of perturbing mitochondria in DCM rat heart underline the deteriorated cardiac recovery by HPOC.

Preconditioning the rat heart with sodium thiosulfate preserved the mitochondria in response to ischemia-reperfusion injury

Sodium thiosulfate preconditioning (SIPC) was recently reported to be cardioprotective due to its ability to inhibit caspase-3 activation, chelate calcium ions and scavenge free radicals. However, the rationale behind its ability to improve the contractility of isolated rat heart challenged with ischemia-reperfusion injury (IR) is not well understood. As mitochondrial preservation is implicated in cardioprotection against IR, the present study was conceived to identify whether the cardioprotective effects of SIPC is associated with mitochondrial preservation. Using the isolated Langendorff rat heart model, 1 mM sodium thiosulfate (STS) was used to precondition the rat heart before IR and was used to study its effect on cardiac mitochondria. The IR heart experienced a ventricular contractile dysfunction that was improved by SIPC. Upon assessing in-gel the ATP synthetic capacity of mitochondria from IR heart, there was a significant decline, while in SIPC it was well preserved close to sham. As a sustained flow of electrons through the ETC and well-integrated mitochondria are the prerequisites for ATP synthesis, SIPC improved the activities of ETC complex enzymes (I-IV), which was reflected from the preserved ultrastructure of the mitochondria as analyzed from electron-microscopy in the treated rat hearts. This observation was coherent with the elevated expression of PGC1α (20%), a critical regulator of ATP production, which increased the mitochondrial copy number as well in the STS treated heart compared to IR. In conclusion, mitochondria might be a critical target for SIPC mediated cardioprotection against IR.

Mitochondrial dysfunction: a key player in the pathogenesis of cardiovascular diseases linked to air pollution

Air pollution has become an environmental burden with regard to non-communicable diseases, particularly heart disease. It has been reported that air pollution can accelerate the development of heart failure and atrial fibrillation. Air pollutants encompass various particulate matters (PMs), which change the blood composition and heart rate and eventually leads to cardiac failure by triggering atherosclerotic plaque ruptures or by developing irreversible ischemia. A series of major epidemiological and observational studies have established the noxious effect of air pollutants on cardiovascular diseases (CVD), but the underlying molecular mechanisms of its susceptibility and the pathological disease events remain largely elusive and are predicted to be initiated in the cell organelle. The basis of this belief is that mitochondria are one of the major targets of environmental toxicants that can damage mitochondrial morphology, function and its DNA (manifested in non-communicable diseases). In this article, we review the literature related to air pollutants that adversely affect the progression of CVD and that target mitochondrial morphological and functional activities and how mitochondrial DNA (mtDNA) copy number variation, which reflects the airborne oxidant-induced cell damage, correlates with heart failure. We conclude that environmental health assessment should focus on the cellular/circulatory mitochondrial functional copy number status, which can predict the outcome of CVD.

Mitochondrial transplantation: From animal models to clinical use in humans

Mitochondrial transplantation is a novel therapeutic intervention to treat ischemia/reperfusion related disorders. The method for mitochondrial transplantation is simple and rapid and can be delivered to the end organ either by direct injection or vascular infusion. In this review, we provide mechanistic and histological studies in large animal models and present data to show clinical efficacy in human patients.

Vascular calcification abrogates the nicorandil mediated cardio-protection in ischemia reperfusion injury of rat heart

The present study was aimed to determine the efficacy of nicorandil in treating cardiac reperfusion injury with an underlying co-morbidity of vascular calcification (VC). Adenine diet was used to induce VC in Wistar rat and the heart was isolated to induce global ischemia reperfusion (IR) by Langendorff method, with and without the nicorandil (7.5mg/kg) pre-treatment and compared with those fed on normal diet. The adenine-treated rats displayed abnormal ECG changes and altered mitochondrial integrity compared to a normal rat heart. These hearts, when subjected to IR increased the infarct size, cardiac injury (measured by lactate dehydrogenase and creatine kinase activity in the coronary perfusate) and significantly altered the hemodynamics compared to the normal perfused heart. Nicorandil pretreatment in rat fed on normal diet enhanced the hemodynamics significantly (P<0.05) along with a substantial reduction in the mitochondrial dysfunction (measured by high ADP to oxygen consumption ratio, respiratory control ratio, enzyme activities and less swelling behavior) when subjected to IR. However, this cardio-protective effect of nicorandil was absent in rat heart with underlying calcification. Our results suggest that, the protective effect of nicorandil, a known mitochondrial ATP linked K⁺ channel opener, against myocardial reperfusion injury was confined to normal rat heart.

The renal mitochondrial dysfunction in patients with vascular calcification is prevented by sodium thiosulfate

PURPOSE

Vascular calcification (VC) is an impact of calcium accumulation in end-stage renal diseases, normally initiated in the mitochondria. Sodium thiosulfate (STS) is effective in rescuing mitochondrial function in the neurovascular complications associated with VC, but has limitation in protecting the cardiac mitochondria. However, the STS efficacy in restoring the renal mitochondrial function has not been studied, which is the primary focus of this study.

METHODS

Wistar rats (n = 6/group) were administered 0.75 % adenine in the diet for 28 days to induce renal failure. STS (400 mg/kg) was given in two regimens STS_Pre (preventive: along with adenine for 28 days) and STS_Cur (curative: 29th to 49th day). Renal failure was assessed by plasma and urinary markers. The effectiveness of treatment was assessed from oxidative stress, DNA damage, mitochondrial physiology and enzymology in the renal tissue.

RESULTS

0.75 % adenine diet caused renal medullary swelling, tubular interstitial nephropathy and impaired renal function (creatinine, urea, uric acid and ALP), which were recovered after STS treatment. The renal failure was due to oxidative stress as measured by elevated malondialdehyde (29 %) and lowered reduced glutathione (27 %) levels. STS reduced the lipid peroxidation and significantly (p < 0.05) elevated the antioxidant enzymes. Further, it improved renal mitochondrial respiratory capacity by maintaining the hyperpolarized membrane potential and restored the complex enzyme activities. Absence of renal DNA fragmentation supports the above findings.

CONCLUSION

STS protects the kidney by preserving renal mitochondria, in experimental adenine-induced vascular calcified rats. The efficacy was prominent when given after induction, i.e., in STS_Cur group.

Hydrogen sulfide post-conditioning preserves interfibrillar mitochondria of rat heart during ischemia reperfusion injury

Cardiac mitochondrial dysfunction is considered to be the main manifestation in the pathology of ischemia reperfusion injury, and by restoring its functional activity, hydrogen sulfide (H2S), a novel endogenous gaseotransmitter renders cardioprotection. Given that interfibrillar (IFM) and subsarcolemmal (SSM) mitochondria are the two main types in the heart, the present study investigates the specific H2S-mediated action on IFM and SSM during ischemic reperfusion in the Langendorff rat heart model. Rats were randomly divided into five groups, namely normal, ischemic control, reperfusion control (I/R), ischemic post-conditioning (POC), and H2S post-conditioning (POC_H2S). In reperfusion control, cardiac contractility decreased, and lactate dehydrogenase, creatine kinase, and infracted size increased compared to both normal and ischemic group. In hearts post-conditioned with H2S and the classical method improved cardiac mechanical function and decreased cardiac markers in the perfusate and infarct size significantly. Both POC and POC_H2S exerts its cardioprotective effect of preserving the IFM, as evident by significant improvement in electron transport chain enzyme activities and mitochondrial respiration. The in vitro action of H2S on IFM and SSM from normal and I/R rat heart supports H2S and mediates cardioprotection via IFM preservation. Our study indicates that IFM play an important role in POC_H2S mediated cardioprotection from reperfusion injury.

The Role of Oxidative Stress in Myocardial Ischemia and Reperfusion Injury and Remodeling: Revisited

Oxidative and reductive stress are dual dynamic phases experienced by the cells undergoing adaptation towards endogenous or exogenous noxious stimulus. The former arises due to the imbalance between the reactive oxygen species production and antioxidant defenses, while the latter is due to the aberrant increase in the reducing equivalents. Mitochondrial malfunction is the common denominator arising from the aberrant functioning of the rheostat that maintains the homeostasis between oxidative and reductive stress. Recent experimental evidences suggest that the maladaptation during oxidative stress could play a pivotal role in the pathophysiology of major cardiovascular diseases such as myocardial infraction, atherosclerosis, and diabetic cardiovascular complications. In this review we have discussed the role of oxidative and reductive stress pathways in the pathogenesis of myocardial ischemia/reperfusion injury and diabetic cardiomyopathy (DCM). Furthermore, we have provided impetus for the development of subcellular organelle targeted antioxidant drug therapy for thwarting the deterioration of the failing myocardium in the aforementioned cardiovascular conditions.

Sensitivity of Interfibrillar and Subsarcolemmal Mitochondria to Cobalt Chloride-induced Oxidative Stress and Hydrogen Sulfide Treatment

Oxidative stress plays a significant role not only in cardiovascular disease but also in non-communicable diseases, where it plays a significant role the mortality rate. Hydrogen sulfide, the biological gaseous signaling molecule that preserves mitochondria in its mode of action, is an effective cardioprotective drug. However, cardiac mitochondria comprise of two distinct populations, namely interfibrillar and subsarcolemmal mitochondria, which respond distinctly in cardiovascular disease. This study was designed to determine the direct impact of cobalt chloride-induced oxidative stress in isolated mitochondrial subpopulations with an intention to examine the efficacy of hydrogen sulfide in preserving interfibrillar and subsarcolemmal mitochondria functional activities when they were incubated as pretreated, co-treated and post-treated agent. Mitochondrial subpopulations were isolated from the heart of male Wistar rats and subjected to cobalt chloride treatment (500 μM) for 20 min, followed by incubation with 10 μM sodium hydrosulfide in three different ways (Pre, Co, and Post-cobalt chloride treatment). Mitochondrial oxidative stress was measured by the concentration of thiobarbituric acid reactive species, reduced glutathione and the activities of enzymes like superoxide dismutase, catalase and glutathione peroxidase. Mitochondrial membrane potential, swelling behavior and enzyme activities were measured to assess its function. The increased level of lipid peroxidation and the decreased level of reduced glutathione in cobalt chloride-induced group confirm the induction of oxidative stress and were more predominant in the subsarcolemmal mitochondria. Hydrogen sulfide treatment to interfibrillar and subsarcolemmal mitochondria preserved their functional activities, but the effect was prominent only with co-treated group. In conclusion, the present study demonstrated that subsarcolemmal mitochondria are more prone to oxidative stress and the co-treatment of the mitochondria with hydrogen sulfide preserved the enzyme activity in the in vitro conditions.

Hydrogen sulfide modulates sub-cellular susceptibility to oxidative stress induced by myocardial ischemic reperfusion injury

In this study, we compared the impact of H2S pre (HIPC) and post-conditioning (HPOC) on oxidative stress, the prime reason for myocardial ischemia reperfusion injury (I/R), in different compartments of the myocardium, such as the mitochondria beside its subpopulations (interfibrillar (IFM) and subsarcolemmal (SSM) mitochondria) and microsomal fractions in I/R injured rat heart. The results demonstrated that compared to I/R rat heart, HIPC and HPOC treated hearts shows reduced myocardial injury, enhanced antioxidant enzyme activities and reduced the level of TBARS in different cellular compartments. The extent of recovery (measured by TBARS and GSH levels) in subcellular fractions, were in the following descending order: microsome > SSM > IFM in both HIPC and HPOC. In summary, oxidative stress mediated mitochondrial dysfunction, one of the primary causes for I/R injury, was partly recovered by HIPC and HPOC treatment, with significant improvement in SSM fraction compared to the IFM.

Non-canonical roles for caveolin in regulation of membrane repair and mitochondria: implications for stress adaptation with age

Many different theories of ageing have been proposed but none has served the unifying purpose of defining a molecular target that can limit the structural and functional decline associated with age that ultimately leads to the demise of the organism. We propose that the search for a molecule with these unique properties must account for regulation of the signalling efficiency of multiple cellular functions that degrade with age due to a loss of a particular protein. We suggest caveolin as one such molecule that serves as a regulator of key processes in signal transduction. We define a particular distinction between cellular senescence and ageing and propose that caveolin plays a distinct role in each of these processes. Caveolin is traditionally thought of as a membrane-localized protein regulating signal transduction via membrane enrichment of specific signalling molecules. Ultimately we focus on two non-canonical roles for caveolin - membrane repair and regulation of mitochondrial function - which may be novel features of stress adaptation, especially in the setting of ageing. The end result of preserving membrane structure and mitochondrial function is maintenance of homeostatic signalling, preserving barrier function, and regulating energy production for cell survival and resilient ageing.

Subsarcolemmal and interfibrillar mitochondria display distinct superoxide production profiles

Cardiac subsarcolemmal mitochondria (SSM) and interfibrillar mitochondria (IFM) subpopulations display distinct biochemical, morphological, and functional characteristics. Moreover, they appear to be differently influenced during cardiac pathologies or toxic injuries. Although mitochondrial reactive oxygen species seem to play a critical role in cardiac function and diseases, limited information exists about the superoxide production characteristics of these mitochondrial subpopulations. In this work, using direct measurement of superoxide by electron paramagnetic resonance, we showed that differences in superoxide production profiles were present between cardiac IFM and SSM, in terms of intensity and major sites of superoxide generation. In SSM incubated with glutamate plus malate as substrates, the total observed superoxide levels were significantly higher than those observed with IFM, with an important contribution of the NADH-oxidizing site of complex I (site If) and the quinol-oxidizing site of complex III (site IIIQ0). In both IFM and SSM, succinate leads to similar rates of total superoxide levels with a substantial role for contribution of reverse electron transfer. Finally, using two spin probes with different membrane permeabilities, our data on complex III showed direct intra- and extra-mitochondrial superoxide release whereas complex I- and II-dependent superoxide were exclusively released inside the mitochondria, confirming previous studies. Feasibility of this approach to measure intra- and extra-mitochondrial superoxide levels and to characterize distinct superoxide production profiles of cardiac IFM and SSM has been demonstrated.