Phosphorylation in Novel Mitochondrial Creatine Kinase Tyrosine Residues Render Cardioprotection against Hypoxia/Reoxygenation Injury

NOR-1 Overexpression Elevates Myoglobin Expression via PERM1 and Enhances Mitochondrial Function and Endurance in Skeletal Muscles of Aged Mice

Skeletal muscle health and function deteriorate with age, ultimately leading to impaired mobility and disability. Exercise is among the most effective interventions to mitigate muscle dysfunction in aging and reverse deficits. However, low attrition and an impaired capacity to exercise may limit its utility in improving muscle function in aged persons. Therefore, it is crucial to advance our mechanistic understanding of the molecular transducers of exercise to identify new and innovative drug targets to improve muscle health. Transcriptomic profiling of the human response to exercise has revealed that the nuclear receptor NR4A3 (NOR-1) is among the most responsive genes to acute exercise. Previously, we observed that in vitro knockdown of NOR-1 alters metabolic signaling in C2C12 myotubes. Specifically, we found that expression of PERM1, CKMT2, myoglobin, and mTORC1 signaling were perturbed during the knockdown of NOR-1. Herein, we extend these findings and observe that a NOR-1-PERM1-myoglobin axis regulates myoglobin expression in vitro. Furthermore, we found that aging is associated with reduced skeletal muscle NOR-1 expression. Although it is well known that exercise improves aged muscle function, whether overexpression of the exercise-responsive gene NOR-1 can confer benefits and improve muscle function in an aged context has not been evaluated. We found that the overexpression of NOR-1 in aged muscle results in enhanced muscle endurance, mitochondrial respiration, and elevated expression of NOR-1 responsive genes that we previously identified in loss of function studies. However, we also observed that overexpression of NOR-1 did not improve maximal muscle torque production and resulted in a small but significant loss of muscle wet weight that was concomitant with elevated autophagy signaling. Our data suggest that NOR-1 expression may reduce muscle fatigability and that NOR-1 drives myoglobin expression in a PERM1-dependent manner.

Creatine kinase mitochondrial 2 promotes the growth and progression of colorectal cancer via enhancing Warburg effect through lactate dehydrogenase B

Background

Mitochondrial creatine kinase (MtCK) plays a pivotal role in cellular energy metabolism, exhibiting enhanced expression in various tumors, including colorectal cancer (CRC). Creatine kinase mitochondrial 2 (CKMT2) is a subtype of MtCK; however, its clinical significance, biological functions, and underlying molecular mechanisms in CRC remain elusive.

Methods

We employed immunohistochemical staining to discern the expression of CKMT2 in CRC and adjacent nontumor tissues of patients. The correlation between CKMT2 levels and clinical pathological factors was assessed. Additionally, we evaluated the association between CKMT2 and the prognosis of CRC patients using Kaplan-Meier survival curves and Cox regression analysis. Meanwhile, quantitative reverse transcription polymerase chain reaction (qRT-PCR) was used to detect the expression levels of CKMT2 in different CRC cell lines. Finally, we explored the biological functions and potential molecular mechanisms of CKMT2 in CRC cells through various techniques, including qRT-PCR, cell culture, cell transfection, western blot, Transwell chamber assays, flow cytometry, and co-immunoprecipitation.

Results

We found that CKMT2 was significantly overexpressed in CRC tissues compared with adjacent nontumor tissues. The expression of CKMT2 is correlated with pathological types, tumor size, distant metastasis, and survival in CRC patients. Importantly, CKMT2 emerged as an independent prognostic factor through Cox regression analysis. Experimental downregulation of CKMT2 expression in CRC cell lines inhibited the migration and promoted apoptosis of these cells. Furthermore, we identified a novel role for CKMT2 in promoting aerobic glycolysis in CRC cells through interaction with lactate dehydrogenase B (LDHB).

Conclusion

In this study, we found the elevated expression of CKMT2 in CRC, and it was a robust prognostic indicator in CRC patients. CKMT2 regulates glucose metabolism via amplifying the Warburg effect through interaction with LDHB, which promotes the growth and progression of CRC. These insights unveil a novel regulatory mechanism by which CKMT2 influences CRC and provide promising targets for future CRC therapeutic interventions.

Maintaining energy provision in the heart: the creatine kinase system in ischaemia-reperfusion injury and chronic heart failure

The non-stop provision of chemical energy is of critical importance to normal cardiac function, requiring the rapid turnover of ATP to power both relaxation and contraction. Central to this is the creatine kinase (CK) phosphagen system, which buffers local ATP levels to optimise the energy available from ATP hydrolysis, to stimulate energy production via the mitochondria and to smooth out mismatches between energy supply and demand. In this review, we discuss the changes that occur in high-energy phosphate metabolism (i.e., in ATP and phosphocreatine) during ischaemia and reperfusion, which represents an acute crisis of energy provision. Evidence is presented from preclinical models that augmentation of the CK system can reduce ischaemia-reperfusion injury and improve functional recovery. Energetic impairment is also a hallmark of chronic heart failure, in particular, down-regulation of the CK system and loss of adenine nucleotides, which may contribute to pathophysiology by limiting ATP supply. Herein, we discuss the evidence for this hypothesis based on preclinical studies and in patients using magnetic resonance spectroscopy. We conclude that the correlative evidence linking impaired energetics to cardiac dysfunction is compelling; however, causal evidence from loss-of-function models remains equivocal. Nevertheless, proof-of-principle studies suggest that augmentation of CK activity is a therapeutic target to improve cardiac function and remodelling in the failing heart. Further work is necessary to translate these findings to the clinic, in particular, a better understanding of the mechanisms by which the CK system is regulated in disease.

Cytosolic nucleic acid sensing and mitochondrial transcriptomic changes as early triggers of metabolic disease in db/db mice

Animal models of diabetes, such as db/db mice, are a useful tool for deciphering the genetic background of molecular changes at the initial stages of disease development. Our goal was to find early transcriptomic changes in three tissues involved in metabolism regulation in db/db mice: adipose tissue, muscle tissue and liver tissue. Nine animals (three per time point) were studied. Tissues were collected at 8, 12 and 16 weeks of age. Transcriptome-wide analysis was performed using mRNA-seq. Libraries were sequenced on NextSeq (Illumina). Differential expression (DE) analysis was performed with edgeR. The analysis of the gene expression profile shared by all three tissues revealed eight upregulated genes (Irf7, Sp100, Neb, Stat2, Oas2, Rtp4, H2-T24 and Oasl2) as early as between 8 and 12 weeks of age. The most pronounced differences were found in liver tissue: nine DE genes between 8 and 12 weeks of age (Irf7, Ly6a, Ly6g6d, H2-Dma, Pld4, Ly86, Fcer1g, Ly6e and Idi1) and five between 12 and 16 weeks of age (Irf7, Plac8, Ifi44, Xaf1 and Ly6a) (adj. p-value < 0.05). The mitochondrial transcriptomic profile also changed with time: we found two downregulated genes in mice between 8 and 12 weeks old (Ckmt2 and Cox6a2) and five DE genes between 12 and 16 weeks of age (Mavs, Tomm40L, Mtfp1, Ckmt2 and Cox6a2). The KEGG pathway analysis showed significant enrichment in pathways related to the autoimmune response and cytosolic DNA sensing. Our results suggest an important involvement of the immunological response, mainly cytosolic nucleic acid sensing, and mitochondrial signalling in the early stages of diabetes and obesity.

Proteomics as a Tool for the Study of Mitochondrial Proteome, Its Dysfunctionality and Pathological Consequences in Cardiovascular Diseases

The focus of this review is on the proteomic approaches applied to the study of the qualitative/quantitative changes in mitochondrial proteins that are related to impaired mitochondrial function and consequently different types of pathologies. Proteomic techniques developed in recent years have created a powerful tool for the characterization of both static and dynamic proteomes. They can detect protein-protein interactions and a broad repertoire of post-translation modifications that play pivotal roles in mitochondrial regulation, maintenance and proper function. Based on accumulated proteomic data, conclusions can be derived on how to proceed in disease prevention and treatment. In addition, this article will present an overview of the recently published proteomic papers that deal with the regulatory roles of post-translational modifications of mitochondrial proteins and specifically with cardiovascular diseases connected to mitochondrial dysfunction.

Proteomics Revealed That Mitochondrial Function Contributed to the Protective Effect of Herba Siegesbeckiae Against Cardiac Ischemia/Reperfusion Injury

Background

Myocardial ischemia/reperfusion (I/R) injury is the main obstacle to percutaneous coronary intervention, lacking effective therapeutic measures in a clinical setting. Herba Siegesbeckiae (HS) is a traditional herb with multiple pharmacological activities and evidence of cardiovascular protection. However, few data are available regarding the role of HS in cardiac I/R. This study aimed to explore the effect and underlying mechanism of HS aqueous extract on cardiac I/R injury.

Materials and Methods

Herba Siegesbeckiae aqueous extract was prepared and analyzed by UHPLC-MS/MS. After intragastric administration of HS once daily for 7 days, male Sprague-Dawley rats were subjected to 30 min occlusion of the left anterior descending coronary artery followed by 120 min reperfusion to elicit I/R. Various parameters like myocardial infarction and apoptosis, 12-lead ECG and hemodynamics, cardiac morphology and myocardial enzymes, quantitative proteomics, mitochondrial ultrastructure and electron transport chain (ETC) function, oxidative stress and antioxidation, and NLRP3 inflammasome and inflammation were evaluated.

Results

The chemical constituents of HS aqueous extract were mainly divided into flavonoids, diterpenoids, and organic acids. In vivo, HS aqueous extract notably alleviated myocardial I/R injury, as evidenced by a reduction in infarct size, apoptotic cells, and cardiac lesion enzymes; decline of ST-segment elevation; improvement of cardiac function; and preservation of morphology. Quantitative proteomics demonstrated that HS reversed the alteration in the expression of Adgb, Cbr1, Decr1, Eif5, Uchl5, Lmo7, Bdh1, Ckmt2, COX7A, and RT1-CE1 after I/R. In addition, HS preserved myocardial ultrastructure and restored the function of mitochondrial ETC complexes following exposure to I/R; HS significantly suppressed I/R-elicited increase of ROS, RNS, MDA, and 8-OHdG, restrained the acetylation of MnSOD, and recovered the activity of MnSOD; and HS reversed I/R-induced elevation of NLRP3 inflammasome and inhibited the release of inflammatory factors and pyroptosis.

Conclusion

Herba Siegesbeckiae aqueous extract ameliorated cardiac I/R injury, which is associated with mitigating oxidative stress, suppressing NLRP3 inflammasome, and restoring mitochondrial function by regulating the expression of Adgb, Cbr1, Decr1, Eif5, Uchl5, Lmo7, Bdh1, Ckmt2, COX7A, and RT1-CE1.

Quadruped Gait and Regulation of Apoptotic Factors in Tibiofemoral Joints following Intra-Articular rhPRG4 Injection in Prg4 Null Mice

Camptodactyly-arthropathy-coxa vara-pericarditis (CACP) syndrome leads to diarthrodial joint arthropathy and is caused by the absence of lubricin (proteoglycan 4—PRG4), a surface-active mucinous glycoprotein responsible for lubricating articular cartilage. In this study, mice lacking the orthologous gene Prg4 served as a model that recapitulates the destructive arthrosis that involves biofouling of cartilage by serum proteins in lieu of Prg4. This study hypothesized that Prg4-deficient mice would demonstrate a quadruped gait change and decreased markers of mitochondrial dyscrasia, following intra-articular injection of both hindlimbs with recombinant human PRG4 (rhPRG4). Prg4^−/− (N = 44) mice of both sexes were injected with rhPRG4 and gait alterations were studied at post-injection day 3 and 6, before joints were harvested for immunohistochemistry for caspase-3 activation. Increased stance and propulsion was shown at 3 days post-injection in male mice. There were significantly fewer caspase-3-positive chondrocytes in tibiofemoral cartilage from rhPRG4-injected mice. The mitochondrial gene Mt-tn, and myosin heavy (Myh7) and light chains (Myl2 and Myl3), known to play a cytoskeletal stabilizing role, were significantly upregulated in both sexes (RNA-Seq) following IA rhPRG4. Chondrocyte mitochondrial dyscrasias attributable to the arthrosis in CACP may be mitigated by IA rhPRG4. In a supporting in vitro crystal microbalance experiment, molecular fouling by albumin did not block the surface activity of rhPRG4.