Journal of Bioenergetics and Biomembranes最新文献

Accumulating studies have unraveled that dexmedetomidine (DEX) is neuroprotective against brain damage. However, it remains largely unknown about the mechanism involved in the neuroprotective effect of DEX. Therefore, this study explored whether DEX could affect mitophagy and pyroptosis in hypoxic-ischemic brain damage. We established a hippocampal neuron model of oxygen glucose-deprivation (OGD) and a rat model of cerebral ischemia/reperfusion (I/R) injury, which were then intervened with DEX and the autophagy inhibitor (3-MA). It was found that DEX intervention significantly increased neuron viability and mitophagy. Additionally, DEX intervention reversed increased oxidative stress and pyroptosis caused by OGD. DEX intervention further maintained the activation of the PINK1/Parkin pathway, while 3-MA treatment partly counteracted the protective effect of DEX on OGD-induced hippocampal neurons, suggesting that the inhibition of the PINK1/Parkin pathway reversed the function of DEX to increase cell viability and mitophagy and inhibit oxidative stress, pyroptosis, and apoptosis. Animal experiments also revealed that DEX intervention induced PINK1/Parkin pathway activation, reduced cerebral infarction and mitochondrial damage, promoted mitophagy, and inhibited pyroptosis, which was nullified by 3-MA treatment. Conclusively, DEX protects against pyroptosis and activates mitophagy in OGD/R-induced brain damage by activating the PINK1/Parkin pathway.

Background: Cataracts are a significant cause of vision loss, adversely affecting the quality of human life. Numerous studies have reported that lens epithelial cells (LECs) play a crucial role in age-related cataract (ARC). However, the roles of carboxypeptidase B 1 (CPB1) and transcription factor BTB and CNC homologue 2 (BACH2) in the pathogenesis of ARC remain unclear. In this study, we aim to explore the contributions of CPB1 and BACH2 to the development of ARC.

Methods: The Gene Expression Omnibus (GEO) was utilized to screen for differentially expressed genes. mRNA and protein levels were assessed using quantitative reverse transcription polymerase chain reaction (qRT-PCR) and western blot analysis. Flow cytometry was conducted to analyze apoptosis. The levels of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), and malondialdehyde (MDA) were measured using a commercial kit. Dual-luciferase reporter assays and chromatin immunoprecipitation (CHIP) were performed to investigate the interaction between CPB1 and BACH2. The methylation site of BACH2 was analyzed using the RNA-protein binding sites prediction suite and the sequence-based RNA adenosine methylation site predictor suite. Methylated RNA immunoprecipitation (Me-RIP) was employed to detect m6A modification level of BACH2.

Results: In ARC and H₂O₂-induced human lens epithelial cells (HLECs), CPB1, BACH2, and METTL3 were found to be up-regulated. Silencing CPB1 reduced apoptosis and MDA levels while enhancing the activities of SOD and GSH-PX in H₂O₂-induced HLECs. Additionally, CPB1 was shown to bind to BACH2, and knockdown of BACH2 attenuated apoptosis and oxidative stress in H₂O₂-induced HLECs by targeting CPB1. Notably, METTL3 promoted the BACH2 expression by enhancing CPB1 expression in H₂O₂-induced HLECs. Finally, silencing METTL3 inhibited apoptosis and oxidative stress in H₂O₂-induced HLECs by hampering BACH2 expression.

Conclusions: METTL3 facilitates apoptosis and oxidative stress in H₂O₂-induced HLECs by promoting the modification of BACH2 and CPB1 expression.

Glutamine is well recognized as critical to the growth of most cell types. Within mitochondria glutamine is converted to glutamate by glutaminase. Oxaloacetate and glutamate then react to form alpha-ketoglutarate (α-KG) and aspartate catalyzed by glutamic-oxaloacetic transaminase (GOT2) or directly converted to α-KG by glutamate dehydrogenase (GDH). We investigated the role of GOT2 in mediating glutamate metabolism and cell growth in undifferentiated C2C12 cells. CRISPR mediated GOT2 knockout (KO) impaired cell growth, partially overcome by higher concentrations of glutamine. Mitochondrial respiration did not differ between KO and wildtype (WT) cells. Metabolite profiling showed that GOT2KO decreased aspartate by about 50% in KO versus WT cells. In contrast, α-KG increased. Metabolites reflecting the pentose phosphate pathway were significantly increased in KO cells. Metabolic pathway analyses revealed alteration of the TCA cycle, the pentose phosphate pathway, and amino acid metabolism. Glutamine ¹³C-tracing revealed decreased generation of aspartate, increased ribulose phosphate and evidence for reductive carboxylation of α-KG to isocitrate in KO cells. GDH expression was detected in C2C12 cells but did not differ between WT and GOT2KO mitochondria. GDH is not or barely expressed in adult muscle, however, we observed clear expression in pre-weanling mice. Cytosolic glutamic-oxaloacetic transaminase, GOT1, expression did not differ between GOT2KO and WT cells. In summary, GOT2 is necessary for glutamate flux and generation of downstream metabolites needed for the growth of C2C12 myoblasts. Although respiration did not differ, lack of aspartate and other compounds needed for cell proliferation may have been major factors impairing growth.

Fibrillation of the amyloid beta (Aβ) peptide has often been associated with neurodegenerative pathologies such as Alzheimer's disease. In this study we examined the influence of several potential compositions of the lipid membrane on Aβ fibrillation by using liposomes as a basic model membrane. Firstly, it was revealed that Aβ fibrillation kinetics were enhanced and had the potential to occur at a faster rate on more fluid membranes compared to solid membranes. Next, the extent of fibril-related damage to membranes was examined with analysis of membrane polarity via the steady-state emission spectra of 6-dodecanoyl-2-dimethylaminonaphthalene (Laurdan). It was revealed that there was slight hydration behavior of the membrane during the lag phase (t_lag) of the kinetic process, possibly coinciding with Aβ monomer binding. However, as the fibrillation kinetic process continued the membrane gradually dehydrated. Hydration states of membranes during and after Aβ fibrillation processes were further examined via deconvolution analysis of the obtained Laurdan spectra. This allows a mapping of membrane hydration from the interior to exterior regions of the lipid membrane. Results revealed slight but definitive variations in deeper region membrane polarity during the time course of Aβ fibrillation, suggesting Aβ aggregation impacts not only the surface level aggregating region but also the inner regions of the membrane. These results can ultimately contribute to the future investigations of the nature of the membrane damage caused by Aβ aggregation.

The main therapeutic strategy for the treatment of patients with toxic liver failure is the elimination of the toxic agent in combination with the targeted mitigation of pathological processes that have been initiated due to the toxicant. In the current research we evaluated the strategy of metabolic supplementation to improve mitochondrial bioenergetics during acute liver intoxication. In our study, we have shown that acute CCl₄-induced intoxication negatively affects Complex I (in the presence of glutamate-malate as energy substrates) based respiration, generation of mitochondrial membrane potential (ΔΨ_m), mitochondrial NAD(P)H pool and NADH redox index, mitochondrial calcium retention capacity (CRC) and structure and functions of the liver. Boosting of mitochondrial bioenergetics through the complex II, using succinate as metabolic substrate in vitro, significantly improved mitochondrial respiration and generation of ΔΨ_m, but not mitochondrial CRC. Co-application of rotenone along with succinate, to prevent possible reverse electron flow, didn't show significant differences compared to the effects of succinate alone. Treatment of animals with acute liver failure, using a metabolic supplement containing succinate, inosine, methionine and nicotinamide improved Complex I based respiration, generation of ΔΨ_m, mitochondrial NAD(P)H pool and NADH redox index, mitochondrial CRC and slightly decreased the level of oxidative stress. These changes resulted in averting destructive and dystrophic changes in the structure of rat liver tissue caused by CCl₄ intoxication, concomitantly enhancing hepatic functionality. Thus, we propose that metabolic supplementation targeting complex II could serve as a potential adjunctive therapy in the management of acute liver intoxication.

To investigate the role of silent information regulator 6 (SIRT6) in regulating podocyte injury in diabetic nephropathy (DN) through autophagy mediated by Notch signaling pathway. A blank control group (group A), a diabetic nephropathy group (group B), and a Sirt6 intervention group (group C) were established. The group A cells were human normal glomerular podocyte cell lines (HGPCs) without any treatment. In group B, the cells were cultivated in glucose medium containing 30 mmol/L and a 10 µmol/L anti-LSirt6 antibody solution. Three sets of cells were tested for their capacity to proliferate via CCK8, for protein expression via Western blot, for associated mRNA expression levels via qPCR, and for cell migration and invasion ability via Transwell. The podocyte proliferation and migration activity in group B were reduced compared to group A, while these properties in group C were elevated compared to group B (DN). B Group is diabetes nephropathy. Compared with those in group B, the number of invading podocytes in group C were greater than those in group A, and the overall apoptosis rate in group C was lower than that in group B. The expression levels of apoptotic proteins in the podocytes in group C were greater than those in group B, and the bcl-2 level was lower than those in group B. The Notch1 and Jagged1 mRNA and protein levels in the podocytes in group B were greater than those in group A, whereas those in the podocytes in group C were lower than those in group B. Sirt6 can protect against podocyte autophagy injury in DN by regulating the Notch1 signaling pathway.

Cholestasis caused by impaired bile secretion in the liver is associated with the accumulation of primary bile acids (BA): cholic acid (CA) and chenodeoxycholic acid (CDCA) in the cells of this organ. The paper studies the uncoupling effect of the CA and CDCA on the succinate-fueled rat liver mitochondria under conditions of ΔpH to Δψ conversion by nigericin. It has been established that without nigericin, the dependence of the resting-state (state 4) respiration rate on the concentrations of these BA is nonlinear and is described by a parabolic equation. Under these conditions, the specific inhibitor of the ADP/ATP-antiporter - carboxyatractylate and the substrate of the aspartate/glutamate-antiporter - glutamate do not affect the state 4 respiration of mitochondria stimulated by these BA. It is suggested that without nigericin, the protonophore action of BA is due to the formation of a dimeric complex of their anion with the acid. In the presence of nigericin, the dependence of state 4 respiration rate on BA concentration is linear. Under these conditions, carboxyatractylate inhibits BA-stimulated respiration. Unlike the CDCA, the uncoupling action of CA is also suppressed by the substrates of the aspartate/glutamate-antiporter. The obtained results are considered as evidence that in the presence of nigericin, uncoupling action of CDCA is carried out primarily with the participation of ADP/ATP-antiporter. Both ADP/ATP-antiporter and aspartate/glutamate-antiporter are involved in the uncoupling action of CA. It is concluded that nigericin modifies the mechanism of the uncoupling action of BA in liver mitochondria by converting ΔpH to Δψ.

Lithium is used in the long-term treatment of bipolar disorder, exhibiting a beneficial effect on the neuronal cells. The concentration of lithium in the blood serum can vary and can easily approach a level that is related to cardiotoxic adverse effects. This is due to its narrow therapeutic index. In this study, we investigated the effect of higher than therapeutic dose of lithium. Rat cardiomyoblast cells were treated with 2 mM LiCl for 48 h, after which the mitochondrial parameters of the cells were analyzed. Lithium exposure reduced maximal respiratory capacity by diminishing reserve respiratory capacity (RRC), linked to a decrease in complex I (NADH dehydrogenase) activity and elevated superoxide radical levels. In addition, lithium treatment altered the composition of cellular membranes, including mitochondrial cardiolipin, a lipid essential for mitochondrial function. These findings suggest that impaired complex I activity, oxidative stress, and cardiolipin depletion collectively impair the ability of cells to meet high energy demands.

Bacillus licheniformis can use cyanide as a nitrogen source for its growth. However, it can also carry out aerobic respiration in the presence of this compound, a classic inhibitor of mammalian cytochrome c oxidase, indicating that B. licheniformis has a branched respiratory chain with various terminal oxidases. Here, we studied the modifications in the respiratory chain of B. licheniformis when cells were cultured in Nutrient Broth, an alkaline medium with ammonium, or an alkaline medium with cyanide. Then, we measured oxygen consumption in intact cells and membranes, enzyme activities, carried out 1D and 2D-BN-PAGE, followed by mass spectrometry analysis of BN-PAGE bands associated with NADH, NADPH, and succinate dehydrogenase activities. We found that cell growth was favored in a nutrient medium than in an alkaline medium with cyanide. In parallel, respiratory activity progressively decreased in cells cultured in the rich medium, alkaline medium with ammonium, and the lowest activity was in the cells growing in the alkaline medium with cyanide. B. licheniformis membranes contain NADH, NADPH, and succinate dehydrogenases, and the proteomic analysis detected the nitrate reductase and the bc, caa3, aa3, and bd complexes. The succinate dehydrogenase migrated with a molecular mass of 375 kDa, indicating its association with the nitrate reductase (115 kDa + 241 kDa, respectively). The NADH dehydrogenase of B. licheniformis forms aggregates of different molecular mass.

High IQ motif-containing GTPase activating protein 3 (IQGAP3) expression is considered to be associated with poor prognosis of colorectal cancer (CRC). However, its role in early-onset CRC (EOCRC) progress is unclear. The mRNA and protein levels of IQGAP3 and Parkin (PRKN) were examined by qRT-PCR and western blot. Cell proliferation, apoptosis and metastasis were determined by CCK8 assay, EdU assay, flow cytometry and transwell assay. ROS, MDA, GSH, Fe²⁺, ACSL4 and SLC7A11 levels were detected to assess cell ferroptosis. The interaction between PRKN and IQGAP3 was assessed by Co-IP assay and ubiquitination assay. Xenograft tumor models were constructed to explore the effect of PRKN and IQGAP3 on the tumorigenesis in vivo. IQGAP3 was upregulated, while PRKN was downregulated in EOCRC tissues and cells. IQGAP3 knockdown inhibited CRC cell proliferation, migration and invasion, while enhanced apoptosis and ferroptosis. PRKN ubiquitinated IQGAP3 to promote its degradation. PRKN overexpression suppressed CRC cell growth, metastasis and promoted ferroptosis, while these effects were reversed by upregulating IQGAP3. In animal study, upregulation of PRKN reduced CRC tumorigenesis by decreasing IQGAP3 expression in vivo. IQGAP3, ubiquitinated by PRKN, promoted EOCRC progression by enhancing cell proliferation, metastasis, repressing apoptosis and ferroptosis, which provided a novel target for EOCRC treatment.