Mitochondrial Function in the Kidney and Heart, but Not the Brain, is Mainly Altered in an Experimental Model of Endotoxaemia

PANAXADIOL SAPONIN ALLEVIATES LPS-INDUCED CARDIOMYOPATHY SIMILAR TO DEXAMETHASONE VIA IMPROVING MITOCHONDRIAL QUALITY CONTROL

ABSTRACT

Septic cardiomyopathy is linked to a dysregulation in mitochondrial integrity and elevated mortality rates, for which an efficacious treatment remains elusive. PDS is a panaxadiol saponin extracted from ginseng stem and leaf. This study identified the protective effects of PDS and DEX in LPS-induced cardiomyopathy and explored the mechanism of them treating LPS-induced cardiomyopathy from the perspectives of mitochondrial quality control. DEX and PDS enhance antioxidant defense by degrading Keap1 to activate Nrf2; activate mitochondrial occurrence protein PGC-1α and fusion protein OPA1, Mfn1, and Mfn2 expression; and inhibit phosphorylation of mitochondrial fission protein Drp1, aiming to maintain normal structure and function of mitochondrial, thereby preserving oxidative phosphorylation capacity. In summary, our findings highlighted the protective efficacy of PDS and DEX in maintaining mitochondrial in LPS-induced cardiomyopathy, and mechanism improving mitochondrial quality control at least in part by promoting Nrf2 activation.

Obeticholic acid ameliorates sepsis-induced renal mitochondrial damage by inhibiting the NF-κb signaling pathway

Acute kidney injury (AKI), a common complication of sepsis, might be caused by overactivated inflammation, mitochondrial damage, and oxidative stress. However, the mechanisms underlying sepsis-induced AKI (SAKI) have not been fully elucidated, and there is a lack of effective therapies for AKI. To this end, this study aimed to investigate whether obeticholic acid (OCA) has a renoprotective effect on SAKI and to explore its mechanism of action. Through bioinformatics analysis, our study confirmed that the mitochondria might be a critical target for the treatment of SAKI. Thus, a septic rat model was established by cecal ligation puncture (CLP) surgery. Our results showed an evoked inflammatory response via the NF-κB signaling pathway and NLRP3 inflammasome activation in septic rats, which led to mitochondrial damage and oxidative stress. OCA, an Farnesoid X Receptor (FXR) agonist, has shown anti-inflammatory effects in numerous studies. However, the effects of OCA on SAKI remain unclear. In this study, we revealed that pretreatment with OCA can inhibit the inflammatory response by reducing the synthesis of proinflammatory factors (such as IL-1β and NLRP3) via blocking NF-κB and alleviating mitochondrial damage and oxidative stress in the septic rat model. Overall, this study provides insight into the excessive inflammation-induced SAKI caused by mitochondrial damage and evidence for the potential use of OCA in SAKI treatment.

Mitochondrial abnormalities in septic cardiomyopathy

Septic cardiomyopathy is a common complication in patients with sepsis, and is one of the indicators of poor prognosis. Its pathogenesis is complex, involving calcium ion imbalance in cardiomyocytes, nitric oxide (NO) synthesis disorder, mitochondrial abnormalities and immune inflammatory reaction, especially mitochondrial abnormalities. In this paper, the mechanism of mitochondrial abnormalities causing septic cardiomyopathy was discussed from the aspects of mitochondrial structure change, mitochondrial energy metabolism disorder, redox imbalance, mitochondrial calcium overload, mitochondrial biosynthesis and autophagy abnormalities.

Cardiomyocyte peroxisome proliferator-activated receptor α prevents septic cardiomyopathy via improving mitochondrial function

Clinically, cardiac dysfunction is a key component of sepsis-induced multi-organ failure. Mitochondria are essential for cardiomyocyte homeostasis, as disruption of mitochondrial dynamics enhances mitophagy and apoptosis. However, therapies targeted to improve mitochondrial function in septic patients have not been explored. Transcriptomic data analysis revealed that the peroxisome proliferator-activated receptor (PPAR) signaling pathway in the heart was the most significantly decreased in the cecal ligation puncture-treated mouse heart model, and PPARα was the most notably decreased among the three PPAR family members. Male Pparafl/fl (wild-type), cardiomyocyte-specific Ppara-deficient (PparaΔCM), and myeloid-specific Ppara-deficient (PparaΔMac) mice were injected intraperitoneally with lipopolysaccharide (LPS) to induce endotoxic cardiac dysfunction. PPARα signaling was decreased in LPS-treated wild-type mouse hearts. To determine the cell type in which PPARα signaling was suppressed, the cell type-specific Ppara-null mice were examined. Cardiomyocyte- but not myeloid-specific Ppara deficiency resulted in exacerbated LPS-induced cardiac dysfunction. Ppara disruption in cardiomyocytes augmented mitochondrial dysfunction, as revealed by damaged mitochondria, lowered ATP contents, decreased mitochondrial complex activities, and increased DRP1/MFN1 protein levels. RNA sequencing results further showed that cardiomyocyte Ppara deficiency potentiated the impairment of fatty acid metabolism in LPS-treated heart tissue. Disruption of mitochondrial dynamics resulted in increased mitophagy and mitochondrial-dependent apoptosis in Ppara△CM mice. Moreover, mitochondrial dysfunction caused an increase of reactive oxygen species, leading to increased IL-6/STAT3/NF-κB signaling. 3-Methyladenine (3-MA, an autophagosome formation inhibitor) alleviated cardiomyocyte Ppara disruption-induced mitochondrial dysfunction and cardiomyopathy. Finally, pre-treatment with the PPARα agonist WY14643 lowered mitochondrial dysfunction-induced cardiomyopathy in hearts from LPS-treated mice. Thus, cardiomyocyte but not myeloid PPARα protects against septic cardiomyopathy by improving fatty acid metabolism and mitochondrial dysfunction, thus highlighting that cardiomyocyte PPARα may be a therapeutic target for the treatment of cardiac disease.

Short-term Obesity Worsens Heart Inflammation and Disrupts Mitochondrial Biogenesis and Function in an Experimental Model of Endotoxemia

Cardiomyopathy is a well-known complication of sepsis that may deteriorate when accompanied by obesity. To test this hypothesis we fed C57black/6 male mice for 6 week with a high fat diet (60% energy) and submitted them to endotoxemic shock using E. coli LPS (10 mg/kg). Inflammatory markers (cytokines and adhesion molecules) were determined in plasma and heart tissue, as well as heart mitochondrial biogenesis and function. Obesity markedly shortened the survival rate of mouse after LPS injection and induced a persistent systemic inflammation since TNFα, IL-1β, IL-6 and resistin plasma levels were higher 24 h after LPS injection. Heart tissue inflammation was significantly higher in obese mice, as detected by elevated mRNA expression of pro-inflammatory cytokines (IL-1β, IL-6 and TNFα). Obese animals presented reduced maximum respiratory rate after LPS injection, however fatty acid oxidation increased in both groups. LPS decreased mitochondrial DNA content and mitochondria biogenesis factors, such as PGC1α and PGC1β, in both groups, while NRF1 expression was significantly stimulated in obese mice hearts. Mitochondrial fusion/fission balance was only altered by obesity, with no influence of endotoxemia. Obesity accelerated endotoxemia death rate due to higher systemic inflammation and decreased heart mitochondrial respiratory capacity.

Hypoxia-Inducible Factors and Burn-Associated Acute Kidney Injury-A New Paradigm?

O₂ deprivation induces stress in living cells linked to free-radical accumulation and oxidative stress (OS) development. Hypoxia is established when the overall oxygen pressure is less than 40 mmHg in cells or tissues. However, tissues and cells have different degrees of hypoxia. Hypoxia or low O₂ tension may be present in both physiological (during embryonic development) and pathological circumstances (ischemia, wound healing, and cancer). Meanwhile, the kidneys are major energy-consuming organs, being second only to the heart, with an increased mitochondrial content and O₂ consumption. Furthermore, hypoxia-inducible factors (HIFs) are the key players that orchestrate the mammalian response to hypoxia. HIFs adapt cells to low oxygen concentrations by regulating transcriptional programs involved in erythropoiesis, angiogenesis, and metabolism. On the other hand, one of the life-threatening complications of severe burns is acute kidney injury (AKI). The dreaded functional consequence of AKI is an acute decline in renal function. Taking all these aspects into consideration, the aim of this review is to describe the role and underline the importance of HIFs in the development of AKI in patients with severe burns, because kidney hypoxia is constant in the presence of severe burns, and HIFs are major players in the adaptative response of all tissues to hypoxia.

Intestinal Flora: A Potential New Regulator of Cardiovascular Disease

Although substantial progress has been made in reducing the burden of the disease by preventing the risk factors of cardiovascular disease (CVD), potential risk factors still exist and lead to its progression. In recent years, numerous studies have revealed that intestinal flora can interfere with the physiological processes of the host through changes in composition and function or related metabolites. Intestinal flora thus affects the occurrence and development of a variety of CVDs, including atherosclerosis, ischemic heart disease, and heart failure. Moreover, studies have found that interventions for intestinal flora and its metabolites provide new opportunities for CVD treatment. This article mainly discusses the interaction between the human intestinal flora and its metabolites, the occurrence and development of CVD, and the potential of intestinal flora as a new target for the diagnosis and treatment of CVD.

Protective Effects of Meldonium in Experimental Models of Cardiovascular Complications with a Potential Application in COVID-19

Right ventricular (RV) and left ventricular (LV) dysfunction is common in a significant number of hospitalized coronavirus disease 2019 (COVID-19) patients. This study was conducted to assess whether the improved mitochondrial bioenergetics by cardiometabolic drug meldonium can attenuate the development of ventricular dysfunction in experimental RV and LV dysfunction models, which resemble ventricular dysfunction in COVID-19 patients. Effects of meldonium were assessed in rats with pulmonary hypertension-induced RV failure and in mice with inflammation-induced LV dysfunction. Rats with RV failure showed decreased RV fractional area change (RVFAC) and hypertrophy. Treatment with meldonium attenuated the development of RV hypertrophy and increased RVFAC by 50%. Mice with inflammation-induced LV dysfunction had decreased LV ejection fraction (LVEF) by 30%. Treatment with meldonium prevented the decrease in LVEF. A decrease in the mitochondrial fatty acid oxidation with a concomitant increase in pyruvate metabolism was noted in the cardiac fibers of the rats and mice with RV and LV failure, respectively. Meldonium treatment in both models restored mitochondrial bioenergetics. The results show that meldonium treatment prevents the development of RV and LV systolic dysfunction by enhancing mitochondrial function in experimental models of ventricular dysfunction that resembles cardiovascular complications in COVID-19 patients.

Low cardiac content of long-chain acylcarnitines in TMLHE knockout mice prevents ischaemia-reperfusion-induced mitochondrial and cardiac damage

Increased tissue content of long-chain acylcarnitines may induce mitochondrial and cardiac damage by stimulating ROS production. N⁶-trimethyllysine dioxygenase (TMLD) is the first enzyme in the carnitine/acylcarnitine biosynthesis pathway. Inactivation of the TMLHE gene (TMLHE KO) in mice is expected to limit long-chain acylcarnitine synthesis and thus induce a cardio- and mitochondria-protective phenotype. TMLHE gene deletion in male mice lowered acylcarnitine concentrations in blood and cardiac tissues by up to 85% and decreased fatty acid oxidation by 30% but did not affect muscle and heart function in mice. Metabolome profile analysis revealed increased levels of polyunsaturated fatty acids (PUFAs) and a global shift in fatty acid content from saturated to unsaturated lipids. In the risk area of ischemic hearts in TMLHE KO mouse, the OXPHOS-dependent respiration rate and OXPHOS coupling efficiency were fully preserved. Additionally, the decreased long-chain acylcarnitine synthesis rate in TMLHE KO mice prevented ischaemia-reperfusion-induced ROS production in cardiac mitochondria. This was associated with a 39% smaller infarct size in the TMLHE KO mice. The arrest of the acylcarnitine biosynthesis pathway in TMLHE KO mice prevents ischaemia-reperfusion-induced damage in cardiac mitochondria and decreases infarct size. These results confirm that the decreased accumulation of ROS-increasing fatty acid metabolism intermediates prevents mitochondrial and cardiac damage during ischaemia-reperfusion.

IL-13 Alleviates Cardiomyocyte Apoptosis by Improving Fatty Acid Oxidation in Mitochondria

Sepsis-induced cardiac injury (SIC) is one of the most common complications in the intensive care unit (ICU) with high morbidity and mortality. Mitochondrial dysfunction is one of the main reasons for SIC, and Interleukin-13 (IL-13) is a master regulator of mitochondria biogenesis. The aim of the present study was to investigate the role of IL-13 in SIC and explore the underlying mechanism. It was found that reactive oxygen species (ROS) production and apoptosis were significantly increased in lipopolysaccharide (LPS)-stimulated primary cardiomyocytes, which was accompanied with obvious mitochondria dysfunction. The results of RNA-sequencing (RNA-seq), mitochondrial membrane potential, fatty acid uptake and oxidation rate suggested that treatment with IL-13 could restore the function and morphology of mitochondria, indicating that it played an important role in protecting septic cardiomyocytes. These findings demonstrated that IL-13 alleviated sepsis-induced cardiac inflammation and apoptosis by improving mitochondrial fatty acid uptake and oxidation, suggesting that IL-13 may prove to be a potential promising target for SIC treatment.

Inhibition of Fatty Acid Metabolism Increases EPA and DHA Levels and Protects against Myocardial Ischaemia-Reperfusion Injury in Zucker Rats

Long-chain ω-3 polyunsaturated fatty acids (PUFAs) are known to induce cardiometabolic benefits, but the metabolic pathways of their biosynthesis ensuring sufficient bioavailability require further investigation. Here, we show that a pharmacological decrease in overall fatty acid utilization promotes an increase in the levels of PUFAs and attenuates cardiometabolic disturbances in a Zucker rat metabolic syndrome model. Metabolome analysis showed that inhibition of fatty acid utilization by methyl-GBB increased the concentration of PUFAs but not the total fatty acid levels in plasma. Insulin sensitivity was improved, and the plasma insulin concentration was decreased. Overall, pharmacological modulation of fatty acid handling preserved cardiac glucose and pyruvate oxidation, protected mitochondrial functionality by decreasing long-chain acylcarnitine levels, and decreased myocardial infarct size twofold. Our work shows that partial pharmacological inhibition of fatty acid oxidation is a novel approach to selectively increase the levels of PUFAs and modulate lipid handling to prevent cardiometabolic disturbances.

Low-intensity exercise stimulates bioenergetics and increases fat oxidation in mitochondria of blood mononuclear cells from sedentary adults

AIM

Exercise training induces adaptations in muscle and other tissue mitochondrial metabolism, dynamics, and oxidative phosphorylation capacity. Mitochondrial fatty acid oxidation was shown to be pivotal for the anti-inflammatory status of immune cells. We hypothesize that exercise training can exert effects influence mitochondrial fatty acid metabolism in peripheral blood mononuclear cells (PBMCs). The aim was to investigate the effect of exercise on the fatty acid oxidation-dependent respiration in PBMCs.

DESIGN

Twelve fasted or fed volunteers first performed incremental-load exercise tests to exhaustion on a cycle ergometer to determine the optimal workload ensuring maximal health benefits in volunteers with a sedentary lifestyle. In addition, the same volunteers performed 60 min of low-intensity constant-load exercise.

RESULTS

In the incremental-load exercise, the maximal whole-body fat oxidation rate measured by indirect calorimetry was reached at the fasted state already at a 50 W workload. At the 75-175 W workloads, the contribution of fat oxidation significantly decreased to only 11%, the heart rate increased to 185 BPM, and the study participants reached exhaustion. These results show that low-intensity exercise (50W) is optimal for maximal whole-body fat utilization. After low-intensity exercise, the ROUTINE mitochondrial respiration, as well as fatty acid oxidation-dependent respiration in PBMCs at LEAK and OXPHOS states, were significantly increased by 31%, 65%, and 76%, respectively. In addition, during 60 min of low-intensity (50W) exercise, a 2-fold higher lipolysis rate was observed and 13.5 ± 0.9 g of fat was metabolized, which was 57% more than the amount of fat that was metabolized during the incremental-load exercise.

CONCLUSIONS

In individuals with a sedentary lifestyle participating in a bicycle ergometry exercise program, maximal lipolysis and whole-body fat oxidation rate is reached in a fasted state during low-intensity exercise. For the first time, it was demonstrated that low-intensity exercise improves bioenergetics and increases fatty acid oxidation in PBMCs and may contribute to the anti-inflammatory phenotype.

Capsaicin protects cardiomyocytes against lipopolysaccharide-induced damage via 14-3-3γ-mediated autophagy augmentation

Background: The myocardium is susceptible to lipopolysaccharide (LPS)-induced damage in sepsis, and cardiac dysfunction is a leading cause of mortality in patients with sepsis. The changes in cardiomyocyte autophagy in sepsis and the effects and mechanism of action of capsaicin (Cap) remain unclear.

Methods and Results: The potential pathway of 14-3-3γ-dependent autophagy and the effects and mechanisms of Cap were studied in LPS-induced injury to primary cultured neonatal rat cardiomyocytes. The results showed that cardiomyocyte viability decreased, lactate dehydrogenase and creatine kinase activities increased, 14-3-3γ expression was downregulated, and autophagy was inhibited after LPS challenge. Cap pretreatment augmented autophagy by upregulating 14-3-3γ expression and activating AMP-activated protein kinase (AMPK) and unc-51 like autophagy-activating kinase 1 (ULK1), suppressing mammalian target of rapamycin (mTOR), alleviating cardiac dysfunction and improving the inflammation response, whereas pAD/14-3-3γ-shRNA nullified the above effects. Cap pretreatment also decreased the levels of IL-1β, TNF-α, IL-6, and IL-10; suppressed intracellular oxidative stress; reduced the intracellular/mitochondrial reactive oxygen species (ROS); balanced GSH/GSSG; increased GSH-Px, catalase, and SOD activities; and decreased MDA contents. It also increased ATP content, activated complex Ⅰ and complex Ⅲ, stabilized the mitochondrial membrane potential, and decreased the mitochondrial permeability transition pore opening, thereby improving mitochondrial function.

Conclusion: Pretreatment with Cap can regulate autophagy by upregulating 14-3-3γ expression, inhibiting oxidative stress and inflammation, maintaining mitochondrial function, and protecting cardiomyocytes against LPS-induced injury.

SOFA Score, Hemodynamics and Body Temperature Allow Early Discrimination between Porcine Peritonitis-Induced Sepsis and Peritonitis-Induced Septic Shock

Porcine model of peritonitis-induced sepsis is a well-established clinically relevant model of human disease. Interindividual variability of the response often complicates the interpretation of findings. To better understand the biological basis of the disease variability, the progression of the disease was compared between animals with sepsis and septic shock. Peritonitis was induced by inoculation of autologous feces in fifteen anesthetized, mechanically ventilated and surgically instrumented pigs and continued for 24 h. Cardiovascular and biochemical parameters were collected at baseline (just before peritonitis induction), 12 h, 18 h and 24 h (end of the experiment) after induction of peritonitis. Analysis of multiple parameters revealed the earliest significant differences between sepsis and septic shock groups in the sequential organ failure assessment (SOFA) score, systemic vascular resistance, partial pressure of oxygen in mixed venous blood and body temperature. Other significant functional differences developed later in the course of the disease. The data indicate that SOFA score, hemodynamical parameters and body temperature discriminate early between sepsis and septic shock in a clinically relevant porcine model. Early pronounced alterations of these parameters may herald a progression of the disease toward irreversible septic shock.

Inhibition of CPT2 exacerbates cardiac dysfunction and inflammation in experimental endotoxaemia

The suppression of energy metabolism is one of cornerstones of cardiac dysfunction in sepsis/endotoxaemia. To investigate the role of fatty acid oxidation (FAO) in the progression of inflammation‐induced cardiac dysfunction, we compared the effects of FAO‐targeting compounds on mitochondrial and cardiac function in an experimental model of lipopolysaccharide (LPS)‐induced endotoxaemia. In LPS‐treated mice, endotoxaemia‐induced inflammation significantly decreased cardiac FAO and increased pyruvate metabolism, while cardiac mechanical function was decreased. AMP‐activated protein kinase activation by A769662 improved mitochondrial FAO without affecting cardiac function and inflammation‐related gene expression during endotoxaemia. Fatty acid synthase inhibition by C75 restored both cardiac and mitochondrial FAO; however, no effects on inflammation‐related gene expression and cardiac function were observed. In addition, the inhibition of carnitine palmitoyltransferase 2 (CPT2)‐dependent FAO by aminocarnitine resulted in the accumulation of FAO intermediates, long‐chain acylcarnitines, in the heart. As a result, cardiac pyruvate metabolism was inhibited, which further exacerbated inflammation‐induced cardiac dysfunction. In conclusion, although inhibition of CPT2‐dependent FAO is detrimental to cardiac function during endotoxaemia, present findings show that the restoration of cardiac FAO alone is not sufficient to recover cardiac function. Rescue of cardiac FAO should be combined with anti‐inflammatory therapy to ameliorate cardiac dysfunction in endotoxaemia.

Tumor susceptibility gene 101 ameliorates endotoxin-induced cardiac dysfunction by enhancing Parkin-mediated mitophagy

Cardiac mitochondrial damage and subsequent inflammation are hallmarks of endotoxin-induced myocardial depression. Activation of the Parkin/PTEN-induced kinase 1 (PINK1) pathway has been shown to promote autophagy of damaged mitochondria (mitophagy) and to protect from endotoxin-induced cardiac dysfunction. Tumor susceptibility gene 101 (TSG101) is a key member of the endosomal recycling complexes required for transport, which may affect autophagic flux. In this study, we investigated whether TSG101 regulates mitophagy and influences the outcomes of endotoxin-induced myocardial dysfunction. TSG101 transgenic and knockdown mice underwent endotoxin/lipopolysaccharide treatment (10 μg/g) and were assessed for survival, cardiac function, systemic/local inflammation, and activity of mitophagy mediators in the heart. Upon endotoxin challenge and compared with WT mice, TSG101 transgenic mice exhibited increased survival, preserved cardiac contractile function, reduced inflammation, and enhanced mitophagy activation in the heart. By contrast, TSG101 knockdown mice displayed opposite phenotypes during endotoxemia. Mechanistically, both coimmunoprecipitation assays and coimmunofluorescence staining revealed that TSG101 directly binds to Parkin in the cytosol of myocytes and facilitates translocation of Parkin from the cytosol to the mitochondria. Our results indicate that TSG101 elevation could protect against endotoxin-triggered myocardial injury by promoting Parkin-induced mitophagy.

Targeting of reactive isolevuglandins in mitochondrial dysfunction and inflammation

Inflammation is a major cause of morbidity and mortality in Western societies. Despite use of multiple drugs, both chronic and acute inflammation still represent major health burdens. Inflammation produces highly reactive dicarbonyl lipid peroxidation products such as isolevuglandins which covalently modify and cross-link proteins via lysine residues. Mitochondrial dysfunction has been associated with inflammation; however, its molecular mechanisms and pathophysiological role are still obscure. We hypothesized that inflammation-induced isolevuglandins contribute to mitochondrial dysfunction and mortality. To test this hypothesis, we have (a) investigated the mitochondrial dysfunction in response to synthetic 15-E2-isolevuglandin (IsoLG) and its adducts; (b) developed a new mitochondria-targeted scavenger of isolevuglandins by conjugating 2-hydroxybenzylamine to the lipophilic cation triphenylphosphonium, (4-(4-aminomethyl)-3-hydroxyphenoxy)butyl)-triphenylphosphonium (mito2HOBA); (c) tested if mito2HOBA protects from mitochondrial dysfunction and mortality using a lipopolysaccharide model of inflammation. Acute exposure to either IsoLG or IsoLG adducts with lysine, ethanolamine or phosphatidylethanolamine inhibits mitochondrial respiration and attenuates Complex I activity. Complex II function was much more resistant to IsoLG. We confirmed that mito2HOBA markedly accumulates in isolated mitochondria and it is highly reactive with IsoLGs. To test the role of mitochondrial IsoLGs, we studied the therapeutic potential of mito2HOBA in lipopolysaccharide mouse model of sepsis. Mito2HOBA supplementation in drinking water (0.1 g/L) to lipopolysaccharide treated mice increased survival by 3-fold, improved complex I-mediated respiration, and histopathological analyses supported mito2HOBA-mediated protection of renal cortex from cell injury. These data support the role of mitochondrial IsoLG in mitochondrial dysfunction and inflammation. We conclude that reducing mitochondrial IsoLGs may be a promising therapeutic target in inflammation and conditions associated with mitochondrial oxidative stress and dysfunction.