NDUFA4L2 protects against ischaemia/reperfusion-induced cardiomyocyte apoptosis and mitochondrial dysfunction by inhibiting complex I

BDNF mimetic 7,8-dihydroxyflavone rescues rotenone-induced cytotoxicity in cardiomyocytes by ameliorating mitochondrial dysfunction

The relationship between mitochondrial dysfunction and cardiovascular disease pathogenesis is well recognized. 7,8-Dihydroxyflavone (7,8-DHF), a mimetic of brain-derived neurotrophic factor, inhibits mitochondrial impairments and improves cardiac function. However, the regulatory role of 7,8-DHF in the mitochondrial function of cardiomyocytes is not fully understood. To investigate the potential mito-protective effects of 7,8-DHF in cardiomyocytes, we treated H9c2 or HL-1 cells with the mitochondrial respiratory complex I inhibitor rotenone (Rot) as an in vitro model of mitochondrial dysfunction. We found that 7,8-DHF effectively eliminated various concentrations of Rot-induced cell death and reduced lactate dehydrogenase release. 7,8-DHF significantly improved mitochondrial membrane potential and inhibited mitochondrial reactive oxygen species. Moreover, 7,8-DHF decreased routine and leak respiration, restored protein levels of mitochondrial complex I-IV, and increased ATP production in Rot-treated H9c2 cells. The protective role of 7,8-DHF in Rot-induced damage was validated in HL-1 cells. Nuclear phosphorylation protein expression of signal transducer and activator of transcription 3 (STAT3) was significantly increased by 7,8-DHF. The present study suggests that 7,8-DHF rescues Rot-induced cytotoxicity by inhibiting mitochondrial dysfunction and promoting nuclear translocation of p-STAT3 in cardiomyocytes, thus nominating 7,8-DHF as a new pharmacological candidate agent against mitochondrial dysfunction in cardiac diseases.

Label-free quantitative SWATH-MS proteomic analysis of adult myocardial slices in vitro after biomimetic electromechanical stimulation

A special in vitro model maintained with ultrathin cardiac slices with a preserved architecture, multi-cellularity, and physiology of the heart tissue was used. In our experiments, we performed label-free quantitative SWATH-MS proteomic analysis of the adult myocardial slices in vitro after biomimetic electromechanical stimulation. Rat myocardial slices were stretched to sarcomere lengths (SL) within the physiological range of 1.8–2.2 μm. Electromechanically stimulated slices were compared with slices cultured without electromechanical stimulation (unloaded and nonstimulated-TW) on a liquid–air interface and with fresh myocardial slices (0 h-C). Quantitative (relative) proteomic analyses were performed using a label-free SWATH-MS technique on a high-resolution microLC-MS/MS TripleTOF 5600+ system (SCIEX). The acquired MS/MS spectra from the DDA LC–MS/MS analyses of the rat heart samples were searched against the UniProt Rattus norvegicus database (version of 15.05.2018) using the Paragon algorithm incorporated into ProteinPilot 4.5 (SCIEX) software. The highest number of differential proteins was observed in the TW group—121 when compared to the C group. In the 1.8 and 2.2 groups, 79 and 52 proteins present at a significantly different concentration from the control samples were found, respectively. A substantial fraction of these proteins were common for two or more comparisons, resulting in a list of 169 significant proteins for at least one of the comparisons. This study found the most prominent changes in the proteomic pattern related to mitochondrial respiration, energy metabolism, and muscle contraction in the slices that were stretched and fresh myocardial slices cultured without electromechanical stimulation.

Mitochondrial Ndufa4l2 Enhances Deposition of Lipids and Expression of Ca9 in the TRACK Model of Early Clear Cell Renal Cell Carcinoma

Mitochondrial dysfunction and aberrant glycolysis are hallmarks of human clear cell renal cell carcinoma (ccRCC). Whereas glycolysis is thoroughly studied, little is known about the mitochondrial contribution to the pathology of ccRCC. Mitochondrial Ndufa4l2 is predictive of poor survival of ccRCC patients, and in kidney cancer cell lines the protein supports proliferation and colony formation. Its role in ccRCC, however, remains enigmatic. We utilized our established ccRCC model, termed Transgenic Cancer of the Kidney (TRACK), to generate a novel genetically engineered mouse model in which dox-regulated expression of an shRNA decreases Ndufa4l2 levels specifically in the renal proximal tubules (PT). This targeted knockdown of Ndufa4l2 reduced the accumulation of neutral renal lipid and was associated with decreased levels of the ccRCC markers carbonic anhydrase 9 (CA9) and Enolase 1 (ENO1). These findings suggest a link between mitochondrial dysregulation (i.e. high levels of Ndufa4l2), lipid accumulation, and the expression of ccRCC markers ENO1 and CA9, and demonstrate that lipid accumulation and ccRCC development can potentially be attenuated by inhibiting Ndufa4l2.

The effect of sex on the mouse lens transcriptome

The transcriptome of mammalian tissues differs between males and females, and these differences can change across the lifespan, likely regulating known sexual dimorphisms in disease prevalence and severity. Cataract, the most prevalent disease of the ocular lens, occurs at similar rates in young individuals, but its incidence is elevated in older women compared to men of the same age. However, the influence of sex on the lens transcriptome was unknown. RNAseq based transcriptomic profiling of young adult C57BL/6J mouse lens epithelial and fiber cells revealed that few genes are differentially expressed between the sexes. In contrast, lens cells from aged (24 month old) male and female C57BL/6J mice differentially expressed many genes, including several whose expression is lens preferred. Like cataracts, posterior capsular opacification (PCO), a major sequela of cataract surgery, may also be more prevalent in women. Lens epithelial cells isolated from mouse eyes 24 h after lens fiber cell removal exhibited numerous transcriptomic differences between the sexes, including genes implicated in complement cascades and extracellular matrix regulation, and these differences are much more pronounced in aged mice than in young mice. These results provide an unbiased basis for future studies on how sex affects the lens response to aging, cataract development, and cataract surgery.

The aging mouse lens transcriptome

Age is a major risk factor for cataract (ARC). However, the influence of aging on the lens transcriptome is under studied. Lens epithelial (LEC) and fiber cells (LFC) were isolated from young (3 month old) and aged (24 month old) C57BL/6J mice, and the transcriptome elucidated via RNAseq. EdgeR estimated differential gene expression in pairwise contrasts, and Advaita's Ipathway guide and custom R scripts were used to evaluate the potential biological significance of differentially expressed genes (DEGs). This analysis revealed age-dependent decreases in lens differentiation marker expression in both LECs and LFCs, with gamma crystallin transcripts downregulating nearly 50 fold in aged LFCs. The expression of the transcription factors Hsf4 and Maf, which are known to activate lens fiber cell preferred genes, are downregulated, while FoxE3, which represses gamma crystallin expression, is upregulated in aged fibers. Aged LECs upregulate genes controlling the immune response, complement pathways, and cellular stress responses, including glutathione peroxidase 3 (Gpx3). Aged LFCs exhibit broad changes in the expression of genes regulating cell communication, and upregulate genes involved in antigen processing/presentation and cholesterol metabolism, while changes in the expression of mitochondrial respiratory chain genes are consistent with mitochondrial stress, including upregulation of NDufa4l2, which encodes an alternate electron transport chain protein. However, age did not profoundly affect the response of LECs to injury as both young and aged LECs upregulate inflammatory gene signatures at 24 h post injury to similar extents. These RNAseq profiles provide a rich data set that can be mined to understand the genetic regulation of lens aging and how this impinges on the pathophysiology of age related cataract.

PD-L1 induces macrophage polarization toward the M2 phenotype via Erk/Akt/mTOR

PD-L1 (programmed death-ligand 1) is the ligand of PD-1 (programmed cell death protein 1) and regulates inhibitory immune responses. It is well known that PD-L1 suppresses T cell function via binding to PD-1. However, little is known about the role of the PD-1/PD-L1 axis in macrophage polarization. According to previous studies, the function of the PD-1/PD-L1 axis in macrophage polarization is controversial, and the underlying mechanism has not been fully elucidated. Thus, we treated THP-1-derived macrophages with human PD-L1 Fc to determine the role of the PD-1/PD-L1 axis in macrophage polarization. To further explore the mechanism, we performed RNA sequencing and used specific inhibitors to identify the implicated signalling pathways. In this study, we found that PD-L1 induces the upregulation of CD206 expression, which is inhibited by nivolumab, LY294002, U0126, and rapamycin. Evaluation of differentially expressed genes (DEGs) and bioinformatics analysis indicated that PD-L1 also induces the upregulation of the expression of genes that maintain mitochondrial function and mediate metabolic switching. In addition, we did not detect PD-L1-induced CD86 alterations, indicating that PD-L1 treatment has no significant influence on M1 polarization. Taken together, these results suggest that PD-L1 binds to PD-1 and promotes M2 polarization accompanied by mitochondrial function enhancement and metabolic reprogramming via Erk/Akt/mTOR. This study elucidates the role of PD-L1 in macrophage polarization and verifies the underlying mechanisms for the first time. Considering that aberrantly upregulated PD-L1 expression contributes to a wide variety of diseases, targeting PD-L1-mediated macrophage polarization is a prospective therapeutic strategy for both neoplastic and nonneoplastic diseases.

NDUFA4L2 Regulated by HIF-1α Promotes Metastasis and Epithelial-Mesenchymal Transition of Osteosarcoma Cells Through Inhibiting ROS Production

Osteosarcoma (OS) accounts for a large proportion of the types of bone tumors that are newly diagnosed, and is a relatively common bone tumor. However, there are still no effective treatments for this affliction. One interesting avenue is related to the mitochondrial NDUFA4L2 protein, which is encoded by the nuclear gene and is known to be a critical mediator in the regulation of cell survival. Thus, in this study, we aimed to investigate the effect of NDUFA4L2 upon the metastasis and epithelial–mesenchymal transition of OS. We found that NDUFA4L2 protein expression was upregulated in hypoxic conditions. We also used 2-ME and DMOG, which are HIF-1α inhibitors and agonists, respectively, to assess the effects related to decreasing or increasing HIF-1α expression. 2-ME caused a significant decrease of NDUFA4L2 expression and DMOG had the opposite effect. It was obvious that down-regulation of NDUFA4L2 had a direct interaction with the apoptosis of OS cells. Western blotting, wound healing analyses, Transwell invasion assays, and colony formation assays all indicated and supported the conclusion that NDUFA4L2 promoted OS cell migration, invasion, proliferation, and the epithelial–mesenchymal transition. During experiments, we incidentally discovered that autophagy and the ROS inhibitor could be used to facilitate the rescuing of tumor cells whose NDUFA4L2 was knocked down. Our findings will help to further elucidate the dynamics underlying the mechanism of OS cells and have provided a novel therapeutic target for the treatment of OS.

Identification of mitochondrial function-associated lncRNAs in septic mice myocardium

The present study aimed to analyze long noncoding RNA (lncRNA) and messenger RNA (mRNA) expression profiles in septic mice heart and to identify potential lncRNAs and mRNAs that be responsible for cardiac mitochondrial dysfunction during sepsis. Mice were treated with 10 mg/kg of lipopolysaccharides to induce sepsis. LncRNAs and mRNAs expression were evaluated by using lncRNA and mRNA microarray or real-time polymerase chain reaction technique. LncRNA-mRNA coexpression network assay, Gene Ontology (GO) analysis, Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis were performed. The results showed that 1275 lncRNAs were differentially expressed in septic myocardium compared with those in the control group. A total of 2769 mRNAs were dysregulated in septic mice heart, most of which are mainly related to the process of inflammation, mitochondrial metabolism, oxidative stress, and apoptosis. Coexpression network analysis showed that 14 lncRNAs were highly correlated with 11 mitochondria-related differentially expressed mRNA. Among all lncRNAs and their cis-acting mRNAs, 41 lncRNAs-mRNA pairs (such as NONMMUG004378 and Apaf1 gene) were enriched in GO terms and KEGG pathways. In summary, we gained some specific lncRNAs and their potential target mRNAs that might be involved in mitochondrial dysfunction in septic myocardium. These findings provide a panoramic view of lncRNA and might allow developing new treatment strategies for sepsis.

Glutamine protects intestine against ischemia-reperfusion injury by alleviating endoplasmic reticulum stress induced apoptosis in rats

Purpose

Glutamine, as an essential part of enteral nutrition and parenteral nutrition agent, has been widely recognized to be a kind of important intestinal mucosa protectant in clinical practice and experimental research. However, the mechanisms of its protective effects are still not fully understand. Consequently, this study aimed to explore the potential mechanism of glutamine on ischemia-reperfusion (I/R) injury induced endoplasmic reticulum (ER) stress in intestine.

Methods

An experimental model of intestinal I/R in rats was established by 1 hour occlusion of the superior mesenteric artery followed by 3 hours of reperfusion. Morphologic changes of intestinal mucosa, apoptosis of epithelial cells, and expression of intestinal Grp78, Gadd153, Caspase-12, ATF4, PERK phosphorylation (P-PERK) and elF2αphosphorylation(P-elF2α) were determined.

Results

After I/R, the apoptotic index of intestinal mucosa epithelial cells observably increased with notable necrosis of intestinal mucosa, and the expressions of Grp78, Gadd153, Caspase-12, ATF4, P-PERK and P-elF2αall were increased. However, treatment with glutamine could significantly relieve intestinal I/R injury and apoptosis index. Moreover, glutamine could clearly up-regulate the expression of Grp78, restrain P-PERK and P-elF2α, and reduce ATF4, Gadd153 and Caspase-12 expressions.

Conclusion

Glutamine may be involved in alleviating ER stress induced intestinal mucosa cells apoptosis.

Mitochondrial complex I deficiency and cardiovascular diseases: current evidence and future directions

Compelling evidence demonstrates the emerging role of mitochondrial complex I deficiency in the onset and development of cardiovascular diseases (CVDs). In particular, defects in single subunits of mitochondrial complex I have been associated with cardiac hypertrophy, ischemia/reperfusion injury, as well as diabetic complications and stroke in pre-clinical studies. Moreover, data obtained in humans revealed that genes coding for complex I proteins were associated with different CVDs. In this review, we discuss recent experimental studies that underline the contributory role of mitochondrial complex I deficiency in the etiopathogenesis of several CVDs, with a particular focus on those involving loss of function models of mitochondrial complex I. We also discuss human studies and potential therapeutic strategies able to rescue mitochondrial function in CVDs.

Degradation of the mitochondrial complex I assembly factor TMEM126B under chronic hypoxia

Cell stress such as hypoxia elicits adaptive responses, also on the level of mitochondria, and in part is mediated by the hypoxia-inducible factor (HIF) 1α. Adaptation of mitochondria towards acute hypoxic conditions is reasonably well understood, while regulatory mechanisms, especially of respiratory chain assembly factors, under chronic hypoxia remains elusive. One of these assembly factors is transmembrane protein 126B (TMEM126B). This protein is part of the mitochondrial complex I assembly machinery. We identified changes in complex I abundance under chronic hypoxia, in association with impaired substrate-specific mitochondrial respiration. Complexome profiling of isolated mitochondria of the human leukemia monocytic cell line THP-1 revealed HIF-1α-dependent deficits in complex I assembly and mitochondrial complex I assembly complex (MCIA) abundance. Of all mitochondrial MCIA members, we proved a selective HIF-1-dependent decrease of TMEM126B under chronic hypoxia. Mechanistically, HIF-1α induces the E3-ubiquitin ligase F-box/WD repeat-containing protein 1A (β-TrCP1), which in turn facilitates the proteolytic degradation of TMEM126B. Attenuating a functional complex I assembly appears critical for cellular adaptation towards chronic hypoxia and is linked to destruction of the mitochondrial assembly factor TMEM126B.