Cardiac disruption of SDHAF4-mediated mitochondrial complex II assembly promotes dilated cardiomyopathy

A mitochondria-targeted nanozyme with enhanced antioxidant activity to prevent acute liver injury by remodeling mitochondria respiratory chain

Developing nanomedicines with enhanced activity to scavenge reactive oxygen species (ROS) has emerged as a promising strategy for addressing ROS-associated diseases, such as drug-induced liver injury. However, designing nanozymes that not only remove ROS but also accelerate the repair of damaged liver cells remains challenging. Here, a two-pronged black phosphorus/Ceria nanozyme with mitochondria-targeting ability (TBP@CeO2) is designed. TBP@CeO2 nanozymes exhibit multienzyme activities and display significantly enhanced ROS scavenging capacity. They can effectively mitigate acetaminophen (APAP)-induced liver injury by scavenging excessive ROS and restoring mitochondrial complex II activity to promote energy-dependent liver cell repair. The in vitro experiments reveal that TBP@CeO2 nanozymes can effectively eliminate ROS and restore mitochondrial function, thereby decreasing the cytotoxicity on BRL 3A cells exposed to APAP/H2O2. The in vivo studies show that TBP@CeO2 nanozymes can improve the complex II activity and mitochondrial function in the liver, decreasing ROS and ensuring sufficient adenosine triphosphate (ATP) production, which helps protect the liver tissue against oxidative damage. This research introduces an innovative design strategy for nanozymes in the treatment of ROS-related diseases.

Knockout of the sulfide: quinone oxidoreductase SQR reduces growth of HCT116 tumor xenograft

Colorectal cancer (CRC) exhibits significant diversity and heterogeneity, posing a requirement for novel therapeutic targets. Polysulfides are associated with CRC progression and immune evasion, but the underlying mechanisms are not fully understood. Sulfide: quinone oxidoreductase (SQR), a mitochondrial flavoprotein, catalyzes hydrogen sulfide (H2S) oxidation and polysulfides production. Herein, we explored its role in CRC pathogenesis and its potential as a therapeutic target. Our findings revealed that SQR knockout disrupted polysulfides homeostasis, diminished mitochondrial function, impaired cell proliferation, and triggered early apoptosis in HCT116 CRC cells. Moreover, the SQR knockout led to markedly reduced tumor sizes in mice models of colon xenografts. Although the transcription of glycolytic genes remained largely unchanged, metabolomic analysis demonstrated a reprogramming of glycolysis at the fructose-1,6-bisphosphate degradation step, catalyzed by aldolase A (ALDOA). Both Western blot analysis and enzymatic assays confirmed the decrease in ALDOA levels and activity. In conclusion, the study establishes the critical role of SQR in mitochondrial function and metabolic regulation in CRC, with its knockout leading to metabolic reprogramming and diminished tumor growth in HCT116 tumor xenografts. These insights lay a foundation for the development of SQR-targeted therapies for CRC.

The proto-oncogenic miR-106a-363 cluster enhances adverse risk acute myeloid leukemia through mitochondrial activation

We investigated the clinical and functional role of the miR-106a-363 cluster in adult acute myeloid leukemia (AML). LAML miRNA-Seq TCGA analyses revealed that high expression of miR-106a-363 cluster members was associated with inferior survival, and miR-106a-5p and miR-20b-5p levels were significantly elevated in patients with adverse risk AML. Overexpression of the miR-106a-363 cluster and its individual members in a murine AML model significantly accelerated leukemogenesis. Proteomics analysis of leukemic bone marrow cells from these models emphasized the deregulation of proteins involved in intracellular transport, protein complex organization and mitochondrial function, driven predominantly by miR-106a-5p. These molecular alterations suggested mitochondrial activation as a potential mechanism for the observed increase in leukemogenicity. High-resolution respirometry and STED microscopy confirmed that miR-106a-5p enhances mitochondrial respiratory activity and increases mitochondrial volume. These findings demonstrate that the miR-106a-363 cluster, and particularly miR-106a-5p, contribute to AML progression through modulation of mitochondrial function and deregulation of mitochondria-coordinated pathways.

N7-methylguanosine tRNA modification promotes gastric cancer progression by activating SDHAF4-dependent mitochondrial oxidative phosphorylation

N7-methylguanosine (m7G) tRNA modification is closely implicated in tumor occurrence and development. However, the precise function and molecular mechanisms of m7G tRNA modification in gastric cancer (GC) remain unclear. In this study, we evaluated the expression and function of methyltransferase-like 1 (METTL1) and WD repeat domain 4 (WDR4) in GC and elucidated the mechanisms underlying the role of METTL1/WDR4-mediated m7G tRNA modifications in promoting GC progression. Upregulation of m7G methyltransferase complex proteins, METTL1 and WDR4, in GC tissues significantly correlates with poor patient prognosis. Functionally, METTL1 and WDR4 facilitate GC progression in vitro and in vivo. Mechanistically, METTL1 knockdown reduces the expression of m7G-modified tRNAs and attenuates the translation of oncogenes enriched in pathways associated with oxidative phosphorylation. Furthermore, METTL1 strengthens mitochondrial electron transport chain complex II (ETC II) activity by promoting succinate dehydrogenase assembly factor 4 (SDHAF4) translation, thereby accelerating GC metabolism and progression. Forced expression of SDHAF4 and chemical modulators of ETC II could reverse the effects of METTL1 on mouse GC. Collectively, our findings delineate the oncogenic role and molecular mechanisms of METTL1/WDR4-mediated m7G tRNA modifications in GC progression, suggesting METTL1/WDR4 and its downstream signaling axis as potential therapeutic targets for GC.

Exercise enhances cardiomyocyte mitochondrial homeostasis to alleviate left ventricular dysfunction in pressure overload induced remodelling

This study aims to explore how exercise enhances mitochondrial regulation and mitigates pathological cardiac hypertrophy. Rat groups were assigned as the control group (CN, n = 8), sham group (sham, n = 8), model group (SC, n = 16) and exercise group (SE, n = 20). A bioinformatics analysis was conducted to uncover the underlying mechanisms.H9C2 cells were divided into: the Ang II 0 h group (CON), Ang II 48 h group (Ang II), Ang II 48 h + sh-control group (sh-GFP + Ang II), Ang II 48 h + sh-ndufb10 group (sh-ndufb10 + Ang II), Ang II 48 h + overexpressedndufb10 control group (Ad-GFP + Ang II) and Ang II 48 h + over-expressedndufb10group (Ad-ndufb10 + Ang II). Mitochondrial function was measured. mRNA and protein expression were assessed by qPCR or western blot analysis respectively. In the SC group, a significant increase was observed in cardiomyocyte diameter, cardiac function, autophagy, and apoptosis. After 8 weeks of swimming exercise, there was a substantial reduction in cardiomyocyte diameter, an improvement in cardiac function, a mitigation of mitochondrial fission and autophagy. Ndufb10 was markedly enriched in oxidative phosphorylation and downregulated in the SC group, while it was upregulated in the SE group. In the sh-ndufb10 group, mitochondrial fusion was suppressed; fission and autophagy were further facilitated; mitochondrial membrane potential, mPTP, and ROS levels increased; and TUNEL positive nuclei and apoptosis-related proteins showed significant upregulation. Overexpression of ndufb10 reversed pathological hypertrophy, mitochondrial autophagy, mitochondrial dysfunction, and cardiomyocyte apoptosis in vitro. Swimming exercise improves mitochondrial abnormalities and reduces cardiomyocyte hypertrophy through regulation of the ndufb10 in left ventricular hypertrophy.

Identification of genes associated with longevity in dogs: 9 candidate genes described in Cavalier King Charles Spaniel

In the past years, dogs have served as a convenient natural model organism for longevity due to their similarity with humans concerning not only their environment but also the diseases and complications occurring in older age. Since many dog breeds have significantly shorter lifespan than their closely related breeds, identification of genes associated with longevity may help to elucidate its background and serve as a possible tool for selective breeding of long-living dogs. This genome-wide association study (GWAS) was undertaken to identify the candidate genes associated with longevity in Cavalier King Charles Spaniel individuals that have reached the age of more than 13 years. We described 15 SNPs localized in nine genes: B3GALNT1, NLRP1 like, PARP14, IQCJ-SCHIP1, COL9A1, COL19A1, SDHAF4, B3GAT2, and DIRC2 that are associated with longevity in purebred Cavalier King Charles Spaniels. These results are promising for future research and possible selective breeding of companion dogs with extended lifespan.

Acute Severe Hypoxia Decreases Mitochondrial Chain Complex II Respiration in Human Peripheral Blood Mononuclear Cells

Peripheral blood mononuclear cells' (PBMCs) mitochondrial respiration is impaired and likely involved in myocardial injury and heart failure pathophysiology, but its response to acute and severe hypoxia, often associated with such diseases, is largely unknown in humans. We therefore determined the effects of acute hypoxia on PBMC mitochondrial respiration and ROS production in healthy volunteers exposed to controlled oxygen reduction, achieving an inspired oxygen fraction of 10.5%. We also investigated potential relationships with gene expression of key biomarkers of hypoxia, succinate and inflammation, as hypoxia and inflammation share common mechanisms involved in cardiovascular disease. Unlike global mitochondrial respiration, hypoxemia with a spO2 ≤ 80% significantly reduced PBMC complex II respiration (from 6.5 ± 1.2 to 3.1 ± 0.5 pmol/s/106 cell, p = 0.04). Complex II activity correlated positively with spO2 (r = 0.63, p = 0.02) and inversely correlated with the succinate receptor SUCNR1 (r = -0.68), the alpha-subunit of the hypoxia-inducible factor (HIF-1α, r = -0.61), the chemokine ligand-9 (r = -0.68) and interferon-stimulated gene 15 (r = -0.75). In conclusion, severe hypoxia specifically impairs complex II respiration in association with succinate, inflammation and HIF-1α pathway interactions in human PBMCs. These results support further studies investigating whether modulation of complex II activity might modify the inflammatory and metabolic alterations observed in heart failure.

Genetic and Functional Changes in Mitochondria in the Pituitary Adenoma: The Pathogenesis and Its Therapy

Pituitary adenoma is a common neoplasm of the pituitary gland. Although most pituitary adenomas are benign, they can pose significant challenges in terms of their consequences and prognosis due to their tendency to invade surrounding tissues and their effects on hormone secretion. The management of pituitary adenomas typically involves surgery, medical therapy, and radiotherapy, each of which has its own limitations. Mitochondria play a crucial role in tumor development and progression by regulating various metabolic processes and signaling pathways within tumor cells and the tumor microenvironment. Multiple studies have indicated that mitochondrial dysfunction is implicated in human pituitary adenomas. Furthermore, several compounds with therapeutic effects on pituitary adenomas have been reported to target mitochondrial function. In this review, we summarize recent studies that highlight the involvement of mitochondrial homeostasis imbalance in the biology of pituitary adenomas. We conclude that mitochondria may represent a promising therapeutic target for the treatment of pituitary adenomas.

SDHAF2 facilitates mitochondrial respiration through stabilizing succinate dehydrogenase and cytochrome c oxidase assemblies

Succinate dehydrogenase (SDH) plays pivotal roles in maintaining cellular metabolism, modulating regulatory control over both the tricarboxylic acid cycle and oxidative phosphorylation to facilitate energy production within mitochondria. Given that SDH malfunction may serve as a hallmark triggering pseudo-hypoxia signaling and promoting tumorigenesis, elucidating the impact of SDH assembly defects on mitochondrial functions and cellular responses is of paramount importance. In this study, we aim to clarify the role of SDHAF2, one assembly factor of SDH, in mitochondrial respiratory activities. To achieve this, we utilize the CRISPR/Cas9 system to generate SDHAF2 knockout in HeLa cells and examine mitochondrial respiratory functions. Our findings demonstrate a substantial reduction in oxygen consumption rate in SDHAF2 knockout cells, akin to cells with inhibited SDH activity. In addition, in our in-gel activity assays reveal a significant decrease not only in SDH activity but also in cytochrome c oxidase (COX) activity in SDHAF2 knockout cells. The reduced COX activity is attributed to the assembly defect and remains independent of SDH inactivation or SDH complex disassembly. Together, our results indicate a critical role of SDHAF2 in regulating respiration by facilitating the assembly of COX.

Mitochondrial Reactive Oxygen Species Dysregulation in Heart Failure with Preserved Ejection Fraction: A Fraction of the Whole

Heart failure with preserved ejection fraction (HFpEF) is a multifarious syndrome, accounting for over half of heart failure (HF) patients receiving clinical treatment. The prevalence of HFpEF is rapidly increasing in the coming decades as the global population ages. It is becoming clearer that HFpEF has a lot of different causes, which makes it challenging to find effective treatments. Currently, there are no proven treatments for people with deteriorating HF or HFpEF. Although the pathophysiologic foundations of HFpEF are complex, excessive reactive oxygen species (ROS) generation and increased oxidative stress caused by mitochondrial dysfunction seem to play a critical role in the pathogenesis of HFpEF. Emerging evidence from animal models and human myocardial tissues from failed hearts shows that mitochondrial aberrations cause a marked increase in mitochondrial ROS (mtROS) production and oxidative stress. Furthermore, studies have reported that common HF medications like beta blockers, angiotensin receptor blockers, angiotensin-converting enzyme inhibitors, and mineralocorticoid receptor antagonists indirectly reduce the production of mtROS. Despite the harmful effects of ROS on cardiac remodeling, maintaining mitochondrial homeostasis and cardiac functions requires small amounts of ROS. In this review, we will provide an overview and discussion of the recent findings on mtROS production, its threshold for imbalance, and the subsequent dysfunction that leads to related cardiac and systemic phenotypes in the context of HFpEF. We will also focus on newly discovered cellular and molecular mechanisms underlying ROS dysregulation, current therapeutic options, and future perspectives for treating HFpEF by targeting mtROS and the associated signal molecules.

Differential expression of nuclear-derived mitochondrial succinate dehydrogenase genes in metabolically active buffalo tissues

BACKGROUND

Buffaloes are crucial to agriculture, yet mitochondrial biology in these animals is less studied compared to humans and laboratory animals. This research examines tissue-specific variations in mitochondrial succinate dehydrogenase (SDH) gene expression across buffalo kidneys, hearts, brains, and ovaries. Understanding these variations sheds light on mitochondrial energy metabolism and its impact on buffalo health and productivity, revealing insights into enzyme regulation and potential improvements in livestock management.

MATERIALS AND METHODS

RNA-seq data from buffalo kidney, heart, brain, and ovary tissues were reanalyzed to explore mitochondrial SDH gene expression. The expression of SDH subunits (SDHA, SDHB, SDHC, SDHD) and assembly factors (SDHAF1, SDHAF2, SDHAF3, SDHAF4) was assessed using a log2 fold-change threshold of + 1 for up-regulated and - 1 for down-regulated transcripts, with significance set at p < 0.05. Hierarchical clustering and differential expression analyses were performed to identify tissue-specific expression patterns and regulatory mechanisms, while Gene Ontology and KEGG pathway analyses were conducted to uncover functional attributes and pathway enrichments across different tissues.

RESULTS

Reanalysis of RNA-seq data from different tissues of healthy female buffaloes revealed distinct expression patterns for SDH subunits and assembly factors. While SDHA, SDHB, and SDHC showed variable expression across tissues, SDHAF2, SDHAF3, and SDHAF4 exhibited tissue-specific profiles. Significant up-regulation of SDHA, SDHB, and several assembly factors was observed in specific tissue comparisons, with fewer down-regulated transcripts. Gene ontology and KEGG pathway analyses linked the up-regulated transcripts to mitochondrial ATP synthesis and the respiratory electron transport chain. Notably, tissue-specific variations in mitochondrial function were particularly evident in the ovary.

CONCLUSION

This study identifies distinct SDH gene expression patterns in buffalo tissues, highlighting significant down-regulation of SDHA, SDHB, SDHC, and assembly factors in the ovary. These findings underscore the critical role of mitochondria in tissue-specific energy production and metabolic regulation, suggest potential metabolic adaptations, and emphasize the importance of mitochondrial complex II. The insights gained offer valuable implications for improving feed efficiency and guiding future research and therapies for energy metabolism disorders.

Valvular heart disease and cardiomyopathy in China: epidemiology and current treatments

The Annual Report on Cardiovascular Health and Diseases in China (2022) intricate landscape of cardiovascular health in China. In connection with the previous section, this ninth section of the report offers a comprehensive analysis of valvular heart disease and cardiomyopathy. Although rheumatic valve disease is still the main cause of valvular heart disease in China, with the aging of the population and the improvement of living standards, the prevalence of degenerative valvular heart disease is on the rise. Because many patients with valvular heart disease have only mild to moderate valve stenosis or insufficiency, and no symptoms, the detection rate in the population is low and late, resulting in many patients been in the severe late stage of disease at visit, increasing the difficulty of treatment and affecting effectiveness and prognosis. Therefore, we should strengthen the examination and screening of valvular heart disease in order to find and prevent it as early as possible. In addition, compared with other diseases, the treatment of valvular heart disease needs more and higher technical support (surgery, intervention, etc). However, not all hospitals can provide relevant technologies. At present, the treatment of valvular heart disease is still mainly concentrated in the provincial hospitals. It is necessary to carry out more professional training so that more doctors and hospitals can participate in the treatment of valvular heart disease. Cardiomyopathy is a group of myocardial diseases with abnormal myocardial structure and/or function, but couldn't be explained by hypertension, coronary atherosclerosis, valvular heart disease and congenital heart disease. It includes hypertrophic cardiomyopathy (HCM), dilated cardiomyopathy (DCM), arrhythmogenic cardiomyopathy (also known as arrhythmogenic right ventricular cardiomyopathy), restrictive cardiomyopathy (RCM) and undifferentiated cardiomyopathy.

Malonate given at reperfusion prevents post-myocardial infarction heart failure by decreasing ischemia/reperfusion injury

The mitochondrial metabolite succinate is a key driver of ischemia/reperfusion injury (IRI). Targeting succinate metabolism by inhibiting succinate dehydrogenase (SDH) upon reperfusion using malonate is an effective therapeutic strategy to achieve cardioprotection in the short term (< 24 h reperfusion) in mouse and pig in vivo myocardial infarction (MI) models. We aimed to assess whether inhibiting IRI with malonate given upon reperfusion could prevent post-MI heart failure (HF) assessed after 28 days. Male C57BL/6 J mice were subjected to 30 min left anterior coronary artery (LAD) occlusion, before reperfusion for 28 days. Malonate or without-malonate control was infused as a single dose upon reperfusion. Cardiac function was assessed by echocardiography and fibrosis by Masson's trichrome staining. Reperfusion without malonate significantly reduced ejection fraction (~ 47%), fractional shortening (~ 23%) and elevated collagen deposition 28 days post-MI. Malonate, administered as a single infusion (16 mg/kg/min for 10 min) upon reperfusion, gave a significant cardioprotective effect, with ejection fraction (~ 60%) and fractional shortening (~ 30%) preserved and less collagen deposition. Using an acidified malonate formulation, to enhance its uptake into cardiomyocytes via the monocarboxylate transporter 1, both 1.6 and 16 mg/kg/min 10 min infusion led to robust long-term cardioprotection with preserved ejection fraction (> 60%) and fractional shortening (~ 30%), as well as significantly less collagen deposition than control hearts. Malonate administration upon reperfusion prevents post-MI HF. Acidification of malonate enables lower doses of malonate to also achieve long-term cardioprotection post-MI. Therefore, the administration of acidified malonate upon reperfusion is a promising therapeutic strategy to prevent IRI and post-MI HF.

Cardiomyocyte-specific overexpression of FPN1 diminishes cardiac hypertrophy induced by chronic intermittent hypoxia

The significance of iron in myocardial mitochondria function cannot be underestimated, because deviations in iron levels within cardiomyocytes may have profound detrimental effects on cardiac function. In this study, we investigated the effects of ferroportin 1 (FPN1) on cardiac iron levels and pathological alterations in mice subjected to chronic intermittent hypoxia (CIH). The cTNT-FPN1 plasmid was administered via tail vein injection to induce the mouse with FPN1 overexpression in the cardiomyocytes. CIH was established by exposing the mice to cycles of 21%-5% FiO2 for 3 min, 8 h per day. Subsequently, the introduction of hepcidin resulted in a reduction in FPN1 expression, and H9C2 cells were used to establish an IH model to further elucidate the role of FPN1. First, FPN1 overexpression ameliorated CIH-induced cardiac dysfunction, myocardial hypertrophy, mitochondrial damage and apoptosis. Second, FPN1 overexpression attenuated ROS levels during CIH. In addition, FPN1 overexpression mitigated CIH-induced cardiac iron accumulation. Moreover, the administration of hepcidin resulted in a reduction in FPN1 levels, further accelerating the CIH-induced levels of ROS, LIP and apoptosis in H9C2 cells. These findings indicate that the overexpression of FPN1 in cardiomyocytes inhibits CIH-induced cardiac iron accumulation, subsequently reducing ROS levels and mitigating mitochondrial damage. Conversely, the administration of hepcidin suppressed FPN1 expression and worsened cardiomyocyte iron toxicity injury.

A self-reinforcing cycle hypothesis in heart failure pathogenesis

Heart failure is a progressive syndrome with high morbidity and mortality rates. Here, we suggest that chronic exposure of the heart to risk factors for heart failure damages heart mitochondria, thereby impairing energy production to levels that can suppress the heart's ability to pump blood and repair mitochondria (both energy-consuming processes). As damaged mitochondria accumulate, the heart becomes deprived of energy in a 'self-reinforcing cycle', which can persist after the heart is no longer chronically exposed to (or after antagonism of) the risk factors that initiated the cycle. Together with other previously described pathological mechanisms, this proposed cycle can help explain (1) why heart failure progresses, (2) why it can recur after cessation of treatment, and (3) why heart failure is often accompanied by dysfunction of multiple organs. Ideally, therapy of heart failure syndrome would be best attempted before the self-reinforcing cycle is triggered or designed to break the self-reinforcing cycle.

Metformin induction of heat shock factor 1 activation and the mitochondrial unfolded protein response alleviate cardiac remodeling in spontaneously hypertensive rats

Heart failure and cardiac remodeling are both characterized by mitochondrial dysfunction. Healthy mitochondria are required for adequate contractile activity and appropriate regulation of cell survival. In the mammalian heart, enhancement of the mitochondrial unfolded protein response (UPRmt) is cardioprotective under pressure overload conditions. We explored the UPRmt and the underlying regulatory mechanism in terms of hypertension-induced cardiac remodeling and the cardioprotective effect of metformin. Male spontaneously hypertensive rats and angiotensin II-treated neonatal rat cardiomyocytes were used to induce cardiac hypertrophy. The results showed that hypertension induced the formation of aberrant mitochondria, characterized by a reduced mtDNA/nDNA ratio and swelling, as well as lower levels of mitochondrial complexes I to V and inhibition of the expression of one protein subunit of each of complexes I to IV. Such changes eventually enlarged cardiomyocytes and increased cardiac fibrosis. Metformin treatment increased the mtDNA/nDNA ratio and regulated the UPRmt, as indicated by increased expression of activating transcription factor 5, Lon protease 1, and heat shock protein 60, and decreased expression of C/EBP homologous protein. Thus, metformin improved mitochondrial ultrastructure and function in spontaneously hypertensive rats. In vitro analyses revealed that metformin reduced the high levels of angiotensin II-induced mitochondrial reactive oxygen species in such animals and stimulated nuclear translocation of heat shock factor 1 (HSF1). Moreover, HSF1 small-interfering RNA reduced the metformin-mediated improvements in mitochondrial morphology and the UPRmt by suppressing hypertrophic signals and cardiomyocyte apoptosis. These results suggest that HSF1/UPRmt signaling contributes to the beneficial effects of metformin. Metformin-mediated targeting of mitochondrial protein homeostasis and modulation of HSF1 levels have potential therapeutic implications in terms of cardiac remodeling.

C4-HSL-mediated quorum sensing regulates nitrogen removal in activated sludge process at Low temperatures

The activated sludge process faces challenges in achieving adequate nitrification ability under low-temperature conditions. Therefore, we investigated the effects of different concentrations of exogenous N-butyryl-homoserine lactone (C4-HSL) on nitrogen removal in lab-scale sequencing batch reactors (SBRs) at 10 °C. The results revealed that both 10 and 100 μg/L of C4-HSL could improve NH4+-N removal efficiency by 26% and reduce the effluent TN concentration to below 15 mg/L. Analysis of extracellular polymeric substances (EPS) revealed that adding C4-HSL (especially 100 μg/L) reduced the protein-like substance content while increasing the humic and fulvic acid-like substance content in EPS. Protein-like substances could serve as carbon sources for denitrifiers, thus promoting denitrification. Moreover, exogenous C4-HSL increased the abundance of bacteria and genes associated with nitrification and denitrification. Further analysis of quorum sensing (QS) of microorganisms indicated that exogenous C4-HSL (especially 100 μg/L) promoted regulation, transportation, and decomposition functions in the QS process. Furthermore, CS, sdh, fum, and mdh gene expressions involved in the tricarboxylic acid (TCA) cycle were enhanced by 100 μg/L C4-HSL. Exogenous C4-HSL promoted microbial communication, microbial energy metabolism, and nitrogen metabolism, thereby improving the nitrogen removal efficiency of activated sludge systems at low temperatures. This study provides a feasible strategy for enhancing denitrogenation performance at low temperatures through exogenous C4-HSL.

The HIF-1/ BNIP3 pathway mediates mitophagy to inhibit the pyroptosis of fibroblast-like synoviocytes in rheumatoid arthritis

BACKGROUND

Synovial hypoxia, a critical pathological characteristic of rheumatoid arthritis (RA), significantly contributes to synovitis and synovial hyperplasia. In response to hypoxic conditions, fibroblast-like synoviocytes (FLS) undergo adaptive changes involving gene expression modulation, with hypoxia-inducible factors (HIF) playing a pivotal role. The regulation of BCL2/adenovirus e1B 19 kDa protein interacting protein 3 (BNIP3) and nucleotide-binding oligomerization segment-like receptor family 3 (NLRP3) expression has been demonstrated to be regulated by HIF-1. The objective of this study was to examine the molecular mechanism that contributes to the aberrant activation of FLS in response to hypoxia. Specifically, the interaction between BNIP3-mediated mitophagy and NLRP3-mediated pyroptosis was conjointly highlighted.

METHODS

The research methodology employed Western blot and immunohistochemistry techniques to identify the occurrence of mitophagy in synovial tissue affected by RA. Additionally, the levels of mitophagy under hypoxic conditions were assessed using Western blot, immunofluorescence, quantitative polymerase chain reaction (qPCR), and CUT&Tag assays. Pyroptosis was observed through electron microscopy, fluorescence microscopy, and Western blot analysis. Furthermore, the quantity of reactive oxygen species (ROS) was measured. The silencing of HIF-1α and BNIP3 was achieved through the transfection of short hairpin RNA (shRNA) into cells.

RESULTS

In the present study, a noteworthy increase in the expression of BNIP3 and LC3B was observed in the synovial tissue of patients with RA. Upon exposure to hypoxia, FLS of RA exhibited BNIP3-mediated mitophagy and NLRP3 inflammasome-mediated pyroptosis. It appears that hypoxia regulates the expression of BNIP3 and NLRP3 through the transcription factor HIF-1. Additionally, the activation of mitophagy has been observed to effectively inhibit hypoxia-induced pyroptosis by reducing the intracellular levels of ROS.

CONCLUSION

In summary, the activation of FLS in RA patients under hypoxic conditions involves both BNIP3-mediated mitophagy and NLRP3 inflammasome-mediated pyroptosis. Additionally, mitophagy can suppress hypoxia-induced FLS pyroptosis by eliminating ROS and inhibiting the HIF-1α/NLRP3 pathway.

Disordered-to-ordered transitions in assembly factors allow the complex II catalytic subunit to switch binding partners

Complex II (CII) activity controls phenomena that require crosstalk between metabolism and signaling, including neurodegeneration, cancer metabolism, immune activation, and ischemia-reperfusion injury. CII activity can be regulated at the level of assembly, a process that leverages metastable assembly intermediates. The nature of these intermediates and how CII subunits transfer between metastable complexes remains unclear. In this work, we identify metastable species containing the SDHA subunit and its assembly factors, and we assign a preferred temporal sequence of appearance of these species during CII assembly. Structures of two species show that the assembly factors undergo disordered-to-ordered transitions without the appearance of significant secondary structure. The findings identify that intrinsically disordered regions are critical in regulating CII assembly, an observation that has implications for the control of assembly in other biomolecular complexes.

Mitochondrial quality control in health and cardiovascular diseases

Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.

Succinate dehydrogenase is essential for epigenetic and metabolic homeostasis in hearts

A hallmark of heart failure is a metabolic switch away from fatty acids β-oxidation (FAO) to glycolysis. Here, we show that succinate dehydrogenase (SDH) is required for maintenance of myocardial homeostasis of FAO/glycolysis. Mice with cardiomyocyte-restricted deletion of subunit b or c of SDH developed a dilated cardiomyopathy and heart failure. Hypertrophied hearts displayed a decrease in FAO, while glucose uptake and glycolysis were augmented, which was reversed by enforcing FAO fuels via a high-fat diet, which also improved heart failure of mutant mice. SDH-deficient hearts exhibited an increase in genome-wide DNA methylation associated with accumulation of succinate, a metabolite known to inhibit DNA demethylases, resulting in changes of myocardial transcriptomic landscape. Succinate induced DNA hypermethylation and depressed the expression of FAO genes in myocardium, leading to imbalanced FAO/glycolysis. Inhibition of succinate by α-ketoglutarate restored transcriptional profiles and metabolic disorders in SDH-deficient cardiomyocytes. Thus, our findings reveal the essential role for SDH in metabolic remodeling of failing hearts, and highlight the potential of therapeutic strategies to prevent cardiac dysfunction in the setting of SDH deficiency.

Assembly of mitochondrial succinate dehydrogenase in human health and disease

Mitochondrial succinate dehydrogenase (SDH), also known as electron transport chain (ETC) Complex II, is the only enzyme complex engaged in both oxidative phosphorylation and the tricarboxylic acid (TCA) cycle. SDH has received increasing attention due to its crucial role in regulating mitochondrial metabolism and human health. Despite having the fewest subunits among the four ETC complexes, functional SDH is formed via a sequential and well-coordinated assembly of subunits. Along with the discovery of subunit-specific assembly factors, the dynamic involvement of the SDH assembly process in a broad range of diseases has been revealed. Recently, we reported that perturbation of SDH assembly in different tissues leads to interesting and distinct pathophysiological changes in mice, indicating a need to understand the intricate SDH assembly process in human health and diseases. Thus, in this review, we summarize recent findings on SDH pathogenesis with respect to disease and a focus on SDH assembly.

PET117 assembly factor stabilizes translation activator TACO1 thereby upregulates mitochondria-encoded cytochrome C oxidase 1 synthesis

Cytochrome c oxidase, also known as complex IV, facilitates the transfer of electrons from cytochrome c to molecular oxygen, resulting in the production of ATP. The assembly of complex IV is a tightly regulated and intricate process that entails the coordinated synthesis and integration of subunits encoded by the mitochondria and nucleus into a functional complex. Accurate regulation of translation is crucial for maintaining proper mitochondrial function, and defects in this process can lead to a wide range of mitochondrial disorders and diseases. However, the mechanisms governing mRNA translation by mitoribosomes in mammals remain largely unknown. In this study, we elucidate the critical role of PET117, a chaperone protein involved in complex IV assembly, in the regulation of mitochondria-encoded cytochrome c oxidase 1 (COX1) protein synthesis in human cells. Depletion of PET117 reduced mitochondrial oxygen consumption rate and impaired mitochondrial function. PET117 was found to interact with and stabilize translational activator of COX1 (TACO1) and prevent its ubiquitination. TACO1 overexpression rescued the inhibitory effects on mitochondria caused by PET117 deficiency. These findings provide evidence for a novel PET117-TACO1 axis in the regulation of mitochondrial protein expression, and revealed a previously unknown role of PET117 in human cells.

Mitochondria as intracellular signalling organelles. An update

Traditionally, mitochondria are known as "the powerhouse of the cell," responsible for energy (ATP) generation (by the electron transport chain, oxidative phosphorylation, the tricarboxylic acid cycle, and fatty acid ß-oxidation), and for the regulation of several metabolic processes, including redox homeostasis, calcium signalling, and cellular apoptosis. The extensive studies conducted in the last decades portray mitochondria as multifaceted signalling organelles that ultimately command cells' survival or death. Based on current knowledge, we'll outline the mitochondrial signalling to other intracellular compartments in homeostasis and pathology-related mitochondrial stress conditions here. The following topics are discussed: (i) oxidative stress and mtROS signalling in mitohormesis, (ii) mitochondrial Ca²⁺ signalling; (iii) the anterograde (nucleus-to-mitochondria) and retrograde (mitochondria-to-nucleus) signal transduction, (iv) the mtDNA role in immunity and inflammation, (v) the induction of mitophagy- and apoptosis - signalling cascades, (vi) the mitochondrial dysfunctions (mitochondriopathies) in cardiovascular, neurodegenerative, and malignant diseases. The novel insights into molecular mechanisms of mitochondria-mediated signalling can explain mitochondria adaptation to metabolic and environmental stresses to achieve cell survival.

A Mitochondrial Perspective on Noncommunicable Diseases

Mitochondria are the center of energy metabolism in eukaryotic cells and play a central role in the metabolism of living organisms. Mitochondrial diseases characterized by defects in oxidative phosphorylation are the most common congenital diseases. Meanwhile, mitochondrial dysfunction caused by secondary factors such as non-inherited genetic mutations can affect normal physiological functions of human cells, induce apoptosis, and lead to the development of various diseases. This paper reviewed several major factors and mechanisms that contribute to mitochondrial dysfunction and discussed the development of diseases closely related to mitochondrial dysfunction and drug treatment strategies discovered in recent years.

THADA, SDHAF4, and MACF1 Gene Polymorphisms and Placental Expression in Women with Gestational Diabetes

Gestational diabetes mellitus (GDM) is a metabolic disorder in pregnant women leading to various complications. Consequently, factors predisposing its development are being sought. Previous studies have shown that the pathogenesis of GDM is similar to that of type 2 diabetes, and it is therefore thought that the two diseases may have a common genetic basis. The aim of this study was to examine the associations between thyroid adenoma-associated (THADA) rs7578597 T>C, succinate dehydrogenase complex assembly factor 4 (SDHAF4) rs1048886 A>G, and microtubule-actin crosslinking factor 1 (MACF1) rs2296172 A>G gene polymorphisms and the risk of GDM development as well as selected clinical parameters in women with GDM. We also examined the expression of these genes in the placenta of women with and without GDM in association with clinical parameters. This case-control study included 272 pregnant women with GDM and 348 pregnant women with normal glucose tolerance. There were no statistically significant differences in the distribution of the THADA rs7578597 T>C, SDHAF4 rs1048886 A>G, and MACF1 rs2296172 A>G gene polymorphisms between pregnant control women and women with GDM. The associations between clinical parameters such as body mass before pregnancy, body mass at birth, body mass increase during pregnancy, BMI before pregnancy, BMI at birth, BMI increase during pregnancy, glycated hemoglobin (HbA1c), daily insulin requirement, childbirth time, and newborn body mass and APGAR score, and the THADA rs7578597 T>C, SDHAF4 rs1048886 A>G, and MACF1 rs2296172 A>G genotypes were statistically non-significant. We only observed lower values of body mass before pregnancy and body mass at birth in women with the SDHAF4 rs1048886 AG genotype in comparison with AA genotype carriers. There was no statistically significant difference in the expression of THADA, SDHAF4, and MACF1 genes in the placenta between women with GDM and healthy women. There were also no statistically significant correlations between THADA, SDHAF4, and MACF1 gene expression in the placenta and clinical parameters. The results of our study suggest that THADA rs7578597 T>C, SDHAF4 rs1048886 A>G, and MACF1 rs2296172 A>G gene polymorphisms are not significant factors associated with GDM onset. In addition, SDHAF4 rs1048886 A>G may be associated with body mass before pregnancy and body mass at birth in pregnant women.

M1 macrophage-derived extracellular vesicle containing tsRNA-5006c promotes osteogenic differentiation of aortic valve interstitial cells through regulating mitophagy

Background

Osteogenic differentiation of aortic valve interstitial cells (AVICs) plays a key role in the calcific aortic valve disease progression. Extracellular vesicles (EVs)-derived from M1-polarized macrophages (M1-EVs) orchestrated intercellular communication by delivering non-coding RNAs such as tRNA-derived small RNAs (tsRNAs) is crucial for cardiovascular disease. However, the role and mechanism of M1-EVs tsRNAs in osteogenic differentiation of AVICs remains largely unclear.

Methods

M1-EVs and PBS treated-RAW 264.7 cell-derived EVs (NC-EVs) were incubated with AVICs and subjected to small RNA sequencing. Candidate tsRNA in M1-EVs was silenced to explore their effects on AVIC osteogenic differentiation and mitophagy.

Results

DiI-labeled M1-EVs were internalized by AVICs, resulting in significantly increased calcium nodule formation and expression of osteogenesis-related genes in AVICs, including RUNX2, BMP2, osteopontin, and SPP1, compared with NC-EVs. Small RNA sequencing revealed that 17 tsRNAs were significantly up-regulated such as tsRNA-5006c, while 28 tsRNAs were significantly down-regulated in M1-EVs compared with NC-EVs. Intriguingly, tsRNA-5006c-deleted M1-EVs treatment significantly reduced calcium nodule formation and expression of osteogenesis-related genes in AVICs relative to control group. Moreover, target genes of tsRNA-5006c were mainly involved in autophagy-related signaling pathways, such as MAPK, Ras, Wnt, and Hippo signaling pathway. Hallmarks of mitophagy activation in AVICs including mitophagosome formation, TMRM fluorescence, expression of LC3-II, BINP3, and PGC1α, were significantly elevated in the M1-EVs group compared with NC-EVs group, whereas M1-EVs tsRNA-5006c inhibitor led to a significant reduction in these indicators.

Conclusion

M1-EVs carried tsRNA-5006c regulates AVIC osteogenic differentiation from the perspective of mitophagy, and we provide a new target for the prevention and treatment of aortic valve calcification.

Autophagy in striated muscle diseases

Impaired biomolecules and cellular organelles are gradually built up during the development and aging of organisms, and this deteriorating process is expedited under stress conditions. As a major lysosome-mediated catabolic process, autophagy has evolved to eradicate these damaged cellular components and recycle nutrients to restore cellular homeostasis and fitness. The autophagic activities are altered under various disease conditions such as ischemia-reperfusion cardiac injury, sarcopenia, and genetic myopathies, which impact multiple cellular processes related to cellular growth and survival in cardiac and skeletal muscles. Thus, autophagy has been the focus for therapeutic development to treat these muscle diseases. To develop the specific and effective interventions targeting autophagy, it is essential to understand the molecular mechanisms by which autophagy is altered in heart and skeletal muscle disorders. Herein, we summarize how autophagy alterations are linked to cardiac and skeletal muscle defects and how these alterations occur. We further discuss potential pharmacological and genetic interventions to regulate autophagy activities and their applications in cardiac and skeletal muscle diseases.