Basal Respiration Rate Research Articles

Contribution of Organic Carbon, Moisture Content, Microbial Biomass-Carbon, and Basal Soil Respiration Affecting Microbial Population in Chronosequence Manganese Mine Spoil

The research was carried out to determine the potential effect of microbiota, organic carbon, percentage of moisture content, and microbial biomass concentration as an evaluator of variation in basal soil respiration rate. Relative distribution and composition of the microbial population were estimated from six different chronosequence manganese mine spoil (MBO0, MBO2, MBO4, MBO6, MBO8, MBO10) and forest soil (FS). The variation was seen in moisture content (6.494±0.210-11.535±0.072)%, organic carbon (0.126±0.001- 3.469± 0.099)%, MB-C (5.519±1.371- 646.969± 11.428) μg.g-1 of soil. A positive correlation was shown between OC with MB-C (r = 0.938; p< 0.01) and moisture content (MC) (r = 0.962; p< 0.01). Variation in the basal soil respiration (BSR) and microbial metabolic quotients (MMQ) was shown to range between 0.352 ± 0.007- 0.958 ±0.014μg CO2-C.g-1 and 6.5× 10-3 - 1.481×10-3 μg CO2-C.g-1 microbial-C.h-1 with BSR: OC from (2.793-0.276)% respectively. This result shows that there is a gradual increase in OC, MC, MB-C, and BSR across seven different sites due to progressive enhancement in soil fertility that leads to the initialization of succession. Stepwise multiple regression analysis further confirms the degree of variability added by microbial biomass C, moisture content, organic carbon, and microbial population on basal soil respiration in microbes. Principal component analysis enables the differentiation of seven different soil profiles into independent clusters based on cumulative variance given by physico-chemical and microbial attributes that indicate the level of degradation of land and act as an index to restore soil fertility.

PERM1 regulates mitochondrial energetics through O-GlcNAcylation in the heart

PERM1 was initially identified as a new downstream target of PGC-1α and ERRs that regulates mitochondrial bioenergetics in skeletal muscle. Subsequently, we and other groups demonstrated that PERM1 is also a positive regulator of mitochondrial bioenergetics in the heart. However, the exact mechanisms of regulatory functions of PERM1 remain poorly understood. O-GlcNAcylation is a post-translational modification of proteins that are regulated by two enzymes: O-GlcNAc transferase (OGT) that adds O-GlcNAc to proteins; O-GlcNAcase (OGA) that removes O-GlcNAc from proteins. O-GlcNAcylation is a powerful signaling mechanism mediating cellular responses to stressors and nutrient availability, which, among other targets, may influence cardiac metabolism. We hypothesized that PERM1 regulates mitochondrial energetics in cardiomyocytes through modulation of O-GlcNAcylation. We found that overexpression of PERM1 decreased the total levels of O-GlcNAcylated proteins, concomitant with decreased OGT and increased OGA expression levels. Luciferase gene reporter assay showed that PERM1 significantly decreases the promoter activity of Ogt without changing the promoter activity of Oga. The downregulation of OGT by PERM1 overexpression was mediated through its interaction with E2F1, a known transcription repressor of Ogt. A deliberate increase of O-GlcNAcylation through Oga silencing in cardiomyocytes decreased the basal and maximal mitochondrial respiration and ATP production rates, all of which were completely restored by PERM1 overexpression. Furthermore, excessive O-GlcNAcylation caused by the loss of PERM1 led to the increase of O-GlcNAcylated PGC-1α, a master regulator of mitochondrial bioenergetics, concurrent with the dissociation of PGC-1α from PPARα, a well-known transcription factor that regulates fatty acid β-oxidation. We conclude that PERM1 positively regulates mitochondrial energetics, in part, via suppressing O-GlcNAcylation in cardiac myocytes.

Olaparib promotes FABP4 expression and reduces antitumor effect in ovarian cancer cells with a BRCA1 mutation.

Olaparib (AZD2281) is used as a first-line maintenance treatment for patients with ovarian cancer (OC) with a breast cancer susceptibility gene (BRCA) mutation. Fatty acid binding protein 4 (FABP4) may serve an important role in cancer, but its role in olaparib-treated OC with a BRCA mutation requires further clarification. To explore the function of FABP4 and enhance the efficacy of AZD2281 in OC, cell counting kit-8, cell apoptosis, cell cycle, colony formation, cell transfection, western blotting, reverse transcription-quantitative polymerase chain reaction, chromatin immunoprecipitation, seahorse and reactive oxygen species assays were performed. In the present study, AZD2281 significantly promoted cell apoptosis, and inhibited cell cycle progression and colony formation in COV362 cells. In addition, AZD2281 significantly upregulated the levels of CCAAT enhancer binding protein α (CEBPα), peroxisome proliferator activated receptor γ (PPARγ) and FABP4. AZD2281 markedly promoted fold enrichment of CEBPα in the promoters of PPARγ and FABP4. Furthermore, FABP4 overexpression significantly decreased cell apoptosis and promoted cell cycle progression and colony formation. In contrast, FABP4 knockdown demonstrated the opposite effects. In addition, FABP4 significantly regulated levels of reactive oxygen species, adenosine triphosphate, aerobic glycolysis, basal respiration rate and fatty acid oxidation. The combination of AZD2281 with the FABP4 inhibitor BM S309403 further significantly increased cell apoptosis and decreased colony formation. In conclusion, the findings of the present study demonstrated that AZD2281 significantly enhanced FABP4 expression, leading to diminished antitumor efficacy in OC cells with a BRCA mutation by regulating CEBPα-PPARγ. Conversely, the combination of AZD2281 and FABP4 inhibitor BM S309403 demonstrated heightened antitumor effectiveness, presenting a promising therapeutic strategy for treating patients with OC with a BRCA mutation.

Respiratory bioenergetics is enhanced in human, but not bovine macrophages after exposure to M. bovis PPD: Exploratory insights into overall similar Cellular Metabolic Profiles.

The role of macrophage (MØ) cellular metabolism and reprogramming during TB infection is of great interest due to the influence of Mycobacterium spp. on MØ bioenergetics. Recent studies have shown that M. tuberculosis induces a TLR2-dependent shift towards aerobic glycolysis, comparable to the established LPS induced pro-inflammatory M1 MØ polarisation. Distinct differences in the metabolic profile of murine and human MØ indicates species-specific differences in bioenergetics. So far, studies examining the metabolic potential of bovine MØ are lacking, thus the basic bioenergetics of bovine and human MØ were explored in response to a variety of innate immune stimuli. Cellular energy metabolism kinetics were measured concurrently for both species on a Seahorse XFe96 platform to generate bioenergetic profiles for the response to the bona-fide TLR2 and TLR4 ligands, FSL-1 and LPS respectively. Despite previous reports of species-specific differences in TLR signalling and cytokine production between human and bovine MØ, we observed similar respiratory profiles for both species. Basal respiration remained constant between stimulated MØ and controls, whereas addition of TLR ligands induced increased glycolysis, as measured by the surrogate parameter ECAR. In contrast to MØ stimulation with M. tuberculosis PPD, another TLR2 ligand, M. bovis PPD treatment significantly enhanced basal respiration rates and glycolysis only in human MØ. Respiratory profiling further revealed significant elevation of ATP-linked OCR and maximal respiration suggesting a strong OXPHOS activation upon M. bovis PPD stimulation in human MØ. Our results provide an exploratory set of data elucidating the basic respiratory profile of bovine vs. human MØ that will not only lay the foundation for future studies to investigate host-tropism of the M. tuberculosis complex but may explain inflammatory differences observed for other zoonotic diseases.

PINK1-Mediated Mitochondrial Activity Confers Olaparib Resistance in Prostate Cancer Cells.

Olaparib, a PARP inhibitor, is a targeted therapy used in treating various cancers including castration-resistant prostate cancer (CRPC). Despite its efficacy, resistance to Olaparib remains a significant challenge. Understanding the molecular mechanisms underpinning this resistance is crucial for developing more effective treatment strategies. This study focuses on elucidating the role of mitochondrial alterations and the PINK1 gene in conferring Olaparib resistance in CRPC cells. We investigated the transcriptomic and functional differences in mitochondrial activity between Olaparib-resistant (2B-OlapR, LN-OlapR) and treatment naïve prostate cancer (PCa) cells (C4-2B, LNCaP) in both castration sentitive and resistant settings. Through RNA sequencing and Gene Set Enrichment Analysis (GSEA), we identified significant enrichment of mitochondrial and oxidative phosphorylation-related gene sets in Olaparib Resistant derived cell lines. Resistant lines exhibited enhanced mitochondrial functionality including increased basal and maximal respiration rates, as well as elevated ATP production and spare respiratory capacity compared to parental cells. Subsequent investigations revealed a substantial increase in mitochondrial mass and electron transport chain complex I activity in Olaparib-resistant cells. Furthermore, overexpression of the PINK1 gene was observed in resistant cells, which was correlated with resistance to Olaparib and poor clinical outcomes in prostate cancer patients. Inhibition of PINK1 expression significantly reduced mitochondrial function and mass, impaired cell growth, and decreased resistance to Olaparib. These findings suggest that PINK1 plays a crucial role in modulating mitochondrial dynamics that confer therapeutic resistance, highlighting its potential as a therapeutic target for overcoming Olaparib resistance in PCa.

Effect of long-term ethanol consumption and a high-fat diet on mitochondrial respiration in rat pancreatic acinar cells and hepatocytes

Chronic alcohol consumption may cause pancreatitis and alcohol-related liver diseases. Both adaptation and damage of liver mitochondria in animals on chronic ethanol and high-fat diets were demonstrated. It is currently not clear if ethanol or its metabolites such as fatty acid ethyl esters can cause mitochondrial damage to the pancreas. The present study aimed to evaluate the effect of chronic ethanol administration in combination with a high-fat diet on mitochondrial respiration in both pancreatic acinar cells and hepatocytes of rats. Wistar male rats on a high-fat diet (35% calories) were administered ethanol (6 g/kg body weight) by oral gavage for 14 days. Pancreatic acini cells and hepatocytes were isolated with collagenase digestion. The respiration of isolated cells was studied with a Clark electrode. Ethanol administration to rats kept on a high-fat diet was followed by a rapid loss of animal weight during the first 5 days of the experiment and diminished secretory response of pancreatic acini to acetylcholine, however, no changes in acinar cells ultrastructure, basal, oligomycin-insensitive or FCCP-uncoupled respiration were found. Meanwhile ethanol caused a significant (~40%) increase in basal and maximal FCCP-uncoupled respiration rate of isolated hepatocytes. In conclusion, chronic ethanol administration to rats on a high-fat diet does not cause mitochondrial damage in the pancreas, while mitochondria of the liver adapt to ethanol by increasing respiration rate. Keywords: ethanol, hepatocytes, high fat diet, mitochondrial respiration, pancreatic acinar cells

Вплив етанолу та циклоспорину А на дихання ізольованих гепатоцитів щурів

It is known that ethanol affects the oxidative processes in liver mitochondria, which can be one of the mechanisms of the development of the alcoholic liver disease. A well-known immunosuppressant cyclosporine A is also an inhibitor of mitochondrial permeabi­lity transition pore. However, the pharmacological interaction of ethanol and cyclosporin A is not sufficiently studied. The aim of the study was to investigate the effect of ethanol and cyclosporine A on the respiration rate of isolated rat hepatocytes. Five male Wistar rats were used in the study. Hepatocytes were isolated by perfusion with collagenase. Cell plasma membrane integrity was assessed with trypan blue staining (0.1 %). Intact cell number was 85.7±0.92 %. The rate of oxygen consumption was measured using a polarographic device based on a Clark electrode. Protonophore FCCP was used to study the uncoupled respiration. Cell respiration was studied in the presence of glucose, pyruvate or monomethylsuccinate in solution. Statistical analysis was performed with Origin Pro 2018 software. Significance of difference between groups was evaluated with analysis of variance test. After one hour incubation with ethanol (50 mM), the rate of basal respiration of hepatocytes oxidizing glucose increased by a meager 8 %. Similar result was obtained upon the presence of pyruvate in solution. Monomethylsuccinate, however, abolished the effect of ethanol on basal respiration. he but not uncoupled respiration of hepatocytes upon glucose or pyruvate oxidation. Ethanol did not affect the uncoupled respiration of hepatocytes in presence of glucose, pyruvate of monomethylsuccinate. Incubation with cyclocporin A did not cause any changes in cell oxygen consumption in all experiments. Cyclosporin A also did not modify the effects of ethanol on basal respiration of hepatocytes. Therefore, no pharmacological no interaction between ethanol and cyclosporin A was detected, which could be evidenced by the change of mitochondrial respiration of isolated hepatocytes.

The phenotypic spectrum of PTCD3 deficiency.

The PTCD3 gene product (protein PTCD3 or MRPS39) forms the entry channel of the mitochondrial small ribosomal subunit and binds to single-stranded mRNA. Here, we expand on the clinical manifestations of PTCD3 pathogenic variants by describing an early-onset patient with Leigh-like syndrome and two patients with milder form of disease, with combined oxidative phosphorylation deficiency. A 34-year-old male and his 33-year-old sister both have horizontal nystagmus, pronounced rough tremor, truncal ataxia, dysmetria, spasticity and hyperreflexia. The basal respiration rate decreased significantly for the male patient and his mother (p < 0.0001) compared to the controls. The whole genome sequencing analysis revealed two heterozygous variants in the PTCD3: c.1182T>A, p.(Tyr394Ter) and c.805C>T, p.(His269Tyr). Tyr394Ter variant ablates the C-terminal half of the protein, including a significant portion of the central fold. In silico modelling for the variant His269Tyr shows that the inclusion of the slightly larger tyrosine sidechain is well tolerated, with no significant change in either the position or the movement of the surrounding area. The third case is a 9-year-old boy, who has a global developmental delay, central hypotonia, hyperreflexia and abnormal MRI. PTCD3 pathogenic variant c.538+4A>G was identified by whole exome sequencing. To test the variant's effect on splicing, an RT-PCR experiment was performed, which revealed skipping of an out-of-frame exon 7.

Abstract 3042: Oxidized Phospholipids Inhibit Glycolysis In Cardiomyocytes And Decrease Oxidative Phosphorylation By Activating The Mitogen-activated Protein Kinase Pathway

Oxidized phospholipids (oxPLs) were shown to be key players in the progression of numerous cardiovascular diseases including myocardial infarction, atherosclerosis, or cardiac ischemia reperfusion injury. However, the oxidized phospholipid-induced signaling mechanisms causing cardiac dysfunction remain elusive. We tested the hypothesis that oxPLs impact metabolism in cardiomyocytes and explored the involved signaling pathways. In vitro, treatment of h9c2 cardiomyocytes with a mixture of oxidized phosphatidylcholines (oxPAPC) led to activation of a mitogen-activated protein kinase (MAPK) pathway, namely phosphorylation of extracellular signal-regulated kinase 1/2 (ERK 1/2). Moreover, oxPAPC induced the expression of regulatory enzymes associated with the pentose phosphate pathway (PPP), such as PGD, G6PD, TALDO1, as well as genes connected to Nrf2-dependent oxidative stress, like HMOX-1. Metabolically, oxPAPC significantly reduced basal respiration and maximal oxygen consumption rate, as well as glycolytic capacity in h9c2 cardiomyocytes, as measured using a Seahorse extracellular flux analyzer. Treatment with a MEK inhibitor (PD98059, 10μM) resulted in a partial rescue of basal respiration and maximal oxygen consumption rate after incubation with oxPAPC. On the other hand, p38 inhibition (SB203580, 10μM) resulted in a change of oxPAPC-induced gene expression of PPP regulatory enzymes and HMOX-1. Ongoing studies including RNA-sequencing and pathway analysis will further explicate the scope of oxPL-induced gene expression and the involved mechanisms. In vivo , AAV8-mediated expression of the oxPL-recognizing scFv-E06 in albumin cre mice that had been fed a high fat high sucrose diet for 12 weeks, resulted in decreased expression of genes associated with GO Terms “glutathione metabolism” compared to AAV-GFP expressing counterparts, in their hearts. In summary, our study provides evidence that oxPLs significantly influence cardiomyocyte metabolism towards a redox-regulatory phenotype accompanied by the inhibited glycolysis and the decrease in oxidative phosphorylation by activating MAPK pathways. Future experiments will elucidate the relationship between MAPK signaling induced by oxPLs and cardiac dysfunction.

HSP47 complements cholesterol synthesis-independent HMGCoA-reductase pathway-mediated fibroblast bioenergetics

Fibrosis, characterized by excessive extracellular matrix (ECM) components deposition, is a common pathological process underlying numerous chronic diseases. Differentiating fibroblasts into myofibroblasts leads to the deposition of fibrous proteins like collagen in the ECM. Heat shock protein 47 (HSP47) is a molecular chaperone protein that assists in the folding of collagen. Recent studies show that inhibition of cholesterol synthesis-independent HMGCoA-reductase pathway enzyme geranylgeranyl pyrophosphate synthase 1 (GGPS1) decreases fibroblast differentiation and its bioenergetics. However, the role of HSP47 in this pathway is unknown, although recent observations show that HSP47 is decreased when GGPS1 is inhibited. Hence, we tested the hypothesis that HSP47 promotes cellular respiration in myofibroblasts. Seahorse assays were performed on different fibroblasts/myofibroblasts repeatedly and the oxygen consumption rate (OCR) and extracellular acidification rate (ECAR) were measured in the presence and absence of HSP47 inhibitor (HY124817). Complex V of the electron transport chain was measured by immunoblotting ATP-5A. HY124817 tends to decrease the OCR, basal respiration rate, ATP-linked, and spare respiratory capacity. Co-incubation with HY124817 and digeranyl bisphosphonate (DGBP), an inhibitor of GGPS1, significantly (P = 0.043) inhibited further the ATP-linked OCR compared to the TGF group. Immunoblotting showed that Complex V did not change significantly across treatments. These results suggest that HSP47 is involved in fibroblast bioenergetics related to ATP-linked OCR in both differentiated myofibroblasts and normal fibroblasts. Inhibition of HSP47 complements the decrease in myofibroblast cellular respiration caused by the GGPS1 inhibition. This finding is novel in that HSP47 plays a role in fibroblast bioenergetics regulated by the cholesterol synthesis-independent HMGCoA-reductase pathway. Further research is necessary to identify what HSP47 targets and regulatory elements involved in this process. This would provide more insight into the mechanisms that underlie critical fibrosis conditions like myocardial fibrosis and potential therapeutics. This experience was supported by the Medical College of Wisconsin's Advancing Student Potential for Inclusion with Research Experiences (ASPIRE) program. The program is funded by a federal grant from the National Heart, Lung, and Blood Institute. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

BDE-99 stimulates generation of aberrant brown/beige adipocytes

Adipose tissue compromises one of the principal depots where brominated flame retardants (BFR) accumulate in vivo, yet whether BFR disturb thermogenic brown/beige adipocytes is still not referred to date. Herein, effects of BDE-99, a major congener of polybrominated diphenyl ethers (PBDEs) detected in humans, on brown/beige adipocytes were explored for the first time, aiming to provide new knowledge evaluating the obesogenic and metabolic disrupting effects of BFR. Our results firstly demonstrated that exposure to BDE-99 during the lineage commitment period significantly promoted C3H10T1/2 MSCs differentiating into brown/beige adipocytes, evidenced by the increase of brown/beige adipocyte marker UCP1, Cidea as well as mitochondrial membrane potential and basal respiration rate, which was similar to pharmacological PPARγ agonist rosiglitazone. Unexpectedly, the mitochondrial maximal respiration rate of BDE-99 stimulated brown/beige adipocytes was not synchronously enhanced and resulted in a significant reduction of mitochondrial spare respiration capacity (SRC) compared to control or rosiglitazone stimulated adipocytes, indicating a deficient energy-dissipating capacity of BDE-99 stimulated thermogenic adipocytes. Consistently with compromised mitochondrial SRC, lipidomic analysis further revealed that the lipids profile of mitochondria derived from BDE-99 stimulated brown/beige adipocytes were quite different from control or rosiglitazone stimulated cells. In detail, BDE-99 group contains more free fatty acid (FFA) and lyso-PE in mitochondria. In addition to energy metabolism, our results also demonstrated that BDE-99 stimulated brown/beige adipocytes were deficient in endocrine, which secreted more adverse adipokine named resistin, coinciding with comparable beneficial adipokine adiponectin compared with that of rosiglitazone. Taken together, our results showed for the first time that BDE-99 stimulated brown/beige adipocytes were aberrant in energy metabolism and endocrine, which strongly suggests that BDE-99 accumulated in human adipose tissue could interfere with brown/beige adipocytes to contribute to the occurrence of obesity and relevant metabolic disorders.

Relationship between Mitochondrial Oxphos Kinetics and Response to Induction Chemotherapy in Patients with Acute Myeloid Leukemia

Background: Acute myeloid leukemia (AML) is an aggressive hematologic malignancy carrying a poor prognosis. Relative to non-leukemic myeloid progenitors, AML cells present with elevations in mitochondrial metabolism driven by higher mitochondrial content. Despite having more mitochondria per cell, AML cells are inefficient at coupling respiration to ATP synthesis, indicative of intrinsic deficiencies in oxidative phosphorylation (OXPHOS) flux. The present study aimed to determine the relationship between mitochondrial OXPHOS kinetics and chemotherapy response in a clinical cohort of AML patients by comparing mitochondrial bioenergetic profiles between responders to induction chemotherapy with those who have persistent disease, and between adverse risk and intermediate risk AML. Methods: In this prospective study from January 2020 to February 2023, we collected bone marrow aspirate samples from patients with new diagnosis of AML on day 1 to evaluate the bioenergetic phenotype of the AML cells. We collected data on primary induction therapy, response to induction therapy, relapse, and other clinical features. We compared the bioenergetic phenotypes between the responders to primary induction chemotherapy and non-responders who had persistent disease post induction chemotherapy. We did the same comparison between patients with adverse risk and intermediate risk AML per European LeukemiaNet (ELN) 2022 risk stratification. Mitochondrial bioenergetic profiles were generated via high resolution respirometry using freshly isolated mononuclear cells from each patient's bone marrow aspirate. The Fisher exact test was used for categorical variables and the Wilcoxon Rank Sum for continuous variables. Results: In 18 AML patients included in the study, median age was 64 years (range 30-85 years), 67% (N=12) were male, 33% female, 61%(n=11) were Caucasian and 39%(n=7) were African Americans. Day 1 median blast count was 57% (range 20-92%). Initial induction therapy with cytarabine/daunorubicin (standard 7+3) with or without midostaurin (in patients with FLT3 mutations) was done in 12 (67%) patients and hypomethylating agent/venetoclax was used in 5 (28%) patients. One patient was managed with azacitidine only. Seven (39%) patients had persistent disease after induction and others responded to the initial induction. Relapsed disease after achieving remission with initial induction was seen in 8 (44%) patients. No patients had favorable risk cytogenetics/molecular findings, 10 had adverse risk AML and 9 had intermediate risk AML. TP53 mutation was observed in 4 patients, FLT3 mutation in 5 patients, IDH1 mutation in 4, and IDH2 mutation in 3 patients. The fraction of the respiratory network capable of performing OXPHOS (i.e., Fractional OXPHOS) was 0.426 in responders and 0.629 in non-responders (p=0.93). In responders, basal respiration in intact cells was non-significantly (p=0.54) lower ( JO2 9.838 pmol/s/million cells) compared to non-responders ( JO2 11.52 pmol/s/million cells). Adverse risk patients had lower fractional OXPHOS, and higher basal and maximal respiration rates as compared to intermediate risk AML patients (Table 1). Conclusion: While Fractional OXPHOS and basal respiration were lower in the patients who had remission after induction therapy, this difference was not statistically significant. We did not find a clinically significant correlation in the bioenergetic profile of AML cells; however, our study is limited by small sample size. Further research is warranted to investigate the role of OXPHOS kinetics in patients of AML that can translate into clinically meaningful outcomes.

EXTH-72. TARGETED INHIBITION OF THREE MAJOR PROLIFERATION PATHWAYS IN GLIOBLASTOMA INDUCES SENESCENCE THROUGH A MITOCHONDRIA-DEPENDENT MECHANISM

Abstract Glioblastoma (GBM) is a fatal brain tumor with a great unmet need for better therapies. Research on the genomic landscape of GBM has revealed that three major proliferation pathways — the PI3K-mTOR-AKT, the MAPK, and the CDK4/6-RB pathways — are overactive in the majority of GBM patients. Based on that knowledge we have developed a multi-target combination therapy (MTCT) by employing inhibitors of these three pathways. When these inhibitors are used in combination, lower, clinically more relevant concentrations of each drug are sufficient for target inhibition and proliferation arrest than with single agents. Excitingly, we find that MTCT not only shuts down proliferation but also causes permanent growth inhibition by the induction of senescence and the secretion of a senescence-associated secretory phenotype (SASP). MTCT-senescent cells have increased mitochondrial reactive oxygen species (mtROS). However, they do not acquire nuclear DNA damage but only local mitochondrial DNA damage. Addition of antioxidants that deplete mtROS resulted in senescence rescue both in terms of morphology and proliferation arrest. MTCT-senescent cells display an enhancement in total mitochondrial mass, mitochondrial DNA copy numbers, and the transcription of mitochondrial proteins. Despite this enhancement, the basal respiration rate of these cells is comparable to untreated cells, indicating an impaired maximal respiration capacity in MTCT-senescent cells. Concordantly, these cells display striking disturbances of their mitochondrial network. Intriguingly, depletion of functional mitochondria prevents the induction of mtROS and senescence by MTCT but not by classical senescence inducers such as ionizing radiation or high concentrations of CDK4/6 inhibitors. To conclude, MTCT induces senescence in GBM cells through a unique nuclear DNA damage-independent mechanism for which the mitochondria are essential.

Bile acids promote endothelial cell homeostasis via the regulation of cell metabolism and quiescence

Abstract Background Endothelial cell (EC) homeostasis is characterized by a quiescent and low-metabolic state. Obesity leads to EC dysfunction and CVD. We demonstrated that bariatric surgery improved obesity-induced EC dysfunction and increased fasting and post-prandial plasma levels of bile acids (BAs)(in particular, cholic acid (CA), chenodeoxycholic acid (CDCA) and deoxycholic acid (DCA)). BAs are emerging as metabolic signaling molecules in several tissues, but their effect on ECs has not been clearly established yet. Purpose We investigate the effect of BA on the maintenance of EC quiescence. Methods Human Aortic Endothelial Cells (HAECs) were treated for 24h with vehicle (0.1% DMSO), CA, CDCA and DCA (50uM each) in 2%FBS EGM-2 media. Percentage of apoptotic cells was assessed with AnnexinV/PI. Seahorse Mitostress test, Mitoplate and glucose uptake with 0.5µCi/ml of 14C-2-deoxy-D-glucose were used to evaluate changes of HAEC metabolism. Immunostaining for Ki67, Crystal Violet staining and scratch assay were performed to assess HAEC proliferation and migration. NO production and endothelial NO synthase (eNOS) activity were measured via DAF-2 probe and Western Blot, respectively. By qPCR genes involved in Notch pathway were evaluated. Mesoscale vascular injury panel, scratch assay, Ki67 immunostaining and glucose uptake were also performed in HAECs pre-treated with 50uM of BAs and stimulated with 0.5ng/mL TNF-α for 24h. Results HAECs treated with BAs increased NO production compared to vehicle and a reduction in both basal and maximal mitochondrial respiration and extracellular acidification rate was shown by Seahorse Mitostress test. Mitoplate assay displayed an overall reduction in the metabolic rate of HAECs treated with CA and DCA and a peculiar metabolic pattern in cells treated with CDCA. Reduction in glucose uptake was also observed after BA treatment, suggesting that BAs are able to decrease EC metabolism. Immunostaining for Ki67 and Crystal Violet highlighted that BAs reduced cell proliferation. The scratch assay also displayed a reduction in EC migration after BA treatment. BAs also reduced EC apoptosis, as significant differences in the percentage of AnnexinV/PI positive cells was observed in BA-treated cells compared to vehicle. qPCR showed increased expression of genes involved in Notch pathway promoting quiescence after BA treatment. Glucose uptake, scratch assay and Ki67 immunostaining performed in TNF-α stimulated HAECs suggested a BA-dependent endothelial protection in conditions of EC pro-inflammatory activation. We did not observed a reduction in pro-inflammatory biomarkers released in the supernatant of HAECs pre-treated with BA and stimulated with TNF-α. Conclusions Our results suggest that BAs may be involved in the maintenance of EC quiescence by regulating EC metabolism and gene expression profile. These findings highlight a potential role of BAs as endothelial-protective molecules.

Abstract 16374: Perm1 Regulates Mitochondrial Energetics Through O-Glcnacylation in Cardiomyocytes

O-GlcNAcylation is a post-translational modification of proteins that plays an important role in cellular homeostasis and stress responses. Two enzymes regulate O-GlcNAcylation: O-GlcNAc transferase (OGT) that adds O-GlcNAc to proteins; O-GlcNAcase (OGA) that removes O-GlcNAc from proteins. While O-GlcNAcylation is necessary to respond to ischemia/reperfusion injury, chronic activation of O-GlcNAcylation in the heart has adverse effects, and excessive O-GlcNAcylation leads to the development of heart failure. However, there is currently no therapy for heart failure that targets O-GlcNAcylation. Perm1 is a striated muscle-specific regulator of mitochondrial bioenergetics. We previously demonstrated that Perm1-knockout mice exhibit reduced cardiac function and myocardial energy reserve, in association with excessive O-GlcNAcylation and upregulation of OGT. Here, we hypothesized that Perm1 maintains mitochondrial energetics by suppressing O-GlcNAcylation. We found that adenovirus-mediated overexpression of Perm1 in cardiomyocytes significantly decreased O-GlcNAcylation (Figure 1A-B) and increased the basal and maximal respiration and ATP production rates as compared with control in Cell Mito Stress Test using a Seahorse 96x flux analyzer (orange vs. green, Figure 1C-D). Furthermore, the increased levels of O-GlcNAcylated proteins (215% of control, p&lt;0.05) via silencing OGA (si-OGA) in cardiomyocytes significantly decreased the basal and maximal respiration capacity and ATP production rates as compared with control (green vs. purple, Figure 1C-D), all which were completely rescued by Perm1 overexpression (blue, Figure 1C-D). These results suggest that Perm1 positively regulates mitochondrial energetics, in part, via suppressing O-GlcNAcylation and that Perm1 might be a new therapeutic target of heart failure that maintains mitochondrial function through preventing excessive O-GlcNAcylation under pathological stress.

P10.33.A TARGETED INHIBITION OF THREE MAJOR PROLIFERATION PATHWAYS IN GLIOBLASTOMA INDUCES SENESCENCE THROUGH A MITOCHONDRIA-DEPENDENT MECHANISM

Abstract BACKGROUND Glioblastoma (GBM) is a fatal brain tumor with a great unmet need for better therapies. Research on the genomic landscape of GBM has revealed that three major proliferation pathways — the PI3K-mTOR-AKT, the MAPK, and the CDK4/6-RB pathways — are overactive in the majority of GBM patients. Based on that knowledge we have developed a multi-target combination therapy (MTCT) by employing inhibitors of these three pathways. When these inhibitors are used in combination, lower, clinically more relevant concentrations of each drug are sufficient for target inhibition and proliferation arrest than with single agents.Excitingly, we find that MTCT not only shuts down proliferation but also causes permanent growth inhibition by the induction of senescence and the secretion of a senescence-associated secretory phenotype (SASP). MATERIAL AND METHODS Senescence is identified in a multimodal way, including morphological characterization, SASP production, beta-galactosidase activity, and colony outgrowth potential. RNAseq together with (phospho)proteomics are also applied to investigate the molecular mechanism in combination with techniques such as DNA damage assays, flow cytometry, western blot, metabolic assays, and fluorescence microscopy. RESULTS MTCT-senescent cells have increased mitochondrial reactive oxygen species (mtROS). However, they do not acquire nuclear DNA damage but only local mitochondrial DNA damage. Addition of antioxidants that deplete mtROS resulted in senescence rescue both in terms of morphology and proliferation arrest. MTCT-senescent cells display an enhancement in total mitochondrial mass, mitochondrial DNA copy numbers, and the transcription of mitochondrial proteins. Despite this enhancement, the basal respiration rate of these cells is comparable to untreated cells, indicating an impaired maximal respiration capacity in MTCT-senescent cells. Concordantly, these cells display striking disturbances of their mitochondrial network.Intriguingly, depletion of functional mitochondria prevents the induction of mtROS and senescence by MTCT but not by classical senescence inducers such as ionizing radiation or high concentrations of CDK4/6 inhibitors. CONCLUSION MTCT induces senescence in GBM cells through a unique nuclear DNA damage-independent mechanism for which the mitochondria are essential.

Uncoupled respiration stability of isolated pancreatic acini as a novel functional test for cell vitality

Background. Assessment of cell viability is crucial in cell studies. Testing plasma membrane integrity is a traditional approach of evaluating cell viability. Mitochondrial functional capacity closely correlates with plasma membrane integrity and overall cell health. This study aimed to investigate whether any aspect of mitochondrial adaptive capacity in isolated pancreatic acini is associated with the quality of isolated pancreatic acini preparations, as determined by the dye exclusion method. Materials and Methods. Experiments were carried out on male Wistar rats weig­hing 250–300 g. A suspension of isolated pancreatic acini was obtained using collagenase. The rate of oxygen consumption of rat isolated pancreatic acini was measured with Clark oxygen electrode. Basal respiration of isolated pancreatic acini was recorded for approximately 2 min. Afterwards, the mitochondrial adaptive capacity was examined using FCCP in concentrations from 0.5 to 2 μM. Uncoupled respiratory stability was calculated as a ratio of respiration rate at high and low FCCP concentrations. Plasma membrane integrity was assessed with trypan blue staining. A total of 74 preparations of isolated pancreatic acini were used in this study. Results. In all experiments, 92–99 % of pancreatic acinar cells exhibited negative trypan blue staining, indicating intact plasma membranes. The basal and maximal uncoupled respiration rates were not affected by the fraction of trypan-negative cells. However, acini preparations with &lt;less than 95 % plasma membrane integrity had significantly lower uncoupled respiration rates when exposed to a high concentration of FCCP (2 µM), indicating reduced stability of uncoupled respiration. Conclusions. Results of the study suggest that the stability of uncoupled respiration can serve as a novel metabolic functional test to complement the existing methods for assessing cell vitality.

Successional Changes in Vegetation Communities near Mine Pits

This study investigates demutational changes in plant communities of phosphorite mines between 2005 and 2021. A total of 23 plant species were initially found in the surveyed areas in 2005, while 68 species were identified in spring 2021. The plant communities were categorized into five different groups, with the older communities (No. I and II) exhibiting richer vegetation and greater diversity. Community No. III comprised various cereals, legumes, orchid plants, and mosses. Dominant species in community No. I included Betula pubescens, Carpinus betulus, Quercus robur, and Picea obovata, while community No. II featured Juniperus communis, Larix sibirica, Pinus sylvestris, and Abies sibirica. Erosion was observed in community No. V on slopes of different ages. The study also found changes in physicochemical indices, such as increased organic matter concentration and decreased pH value (4.9). The basal respiration rate of the pit soil was low (around 0.4 mg CO2/m2/h), and carbonate content ranged from 0.06 to 0.9%. This study presents novel data on the dynamics of species composition, plant community structure, and physicochemical soil parameters in human-altered habitats, thereby contributing to the expansion of our knowledge of vegetation recovery and evolution in such environments.

The structure of forest vegetation on industrial landfills of different ages

AbstractThe purpose of the research is to describe plant community formation on the quarry surfaces to determine a path for optimal revegetation. To achieve the goal, the studies determined soil pH, the content of skeletal fraction, basal respiration, and performed the acidimetric assessment of CO2. The research program aimed to investigate the peculiarities of plant communities' formation in areas with different degrees of revitalization and investigate the influence of soil cover on plant associations. Results showed that the average basal soil respiration rate on the quarry was extremely low (about 0.3 mg CO2/g of soil/h). The CO2 content in the carbonate ranged from 0.07% to 0.7%, with the higher figures observed in older Kuzbass rather than Mosbass and Sokolovsky quarries. An analysis of soil samples from three quarries revealed four plant groups at sites associated with the prevalence of specific fractions, such as gravel, sand, silt, and stony soil. Given that Kuzbass is the oldest open‐pit mine, forest vegetation species dominate here in the surveyed areas (&gt;40%), and this feature is typical of gravel soils. The dominant species present on the gravel substrate were downy birch (Betula pubescens), common hornbeam (Carpinus betulus), European oak (Quercus robur), Siberian spruce (Picea obovata), common juniper (Juniperus communis), Siberian larch (Larix sibirica), common pine (Pinus), and Siberian fir (Abies sibirica). Mosbass is also characterized by a diversity of similar species, though work on mineral mining there ended in 2009, more recently than in other sites. Stony and sandy soil fractions predominated in the Sokolovsky quarry, although other studied substrates were also present.

Stronger negative priming effect and lower basal respiration rates in nutrient-poor as compared to nutrient-rich forestry-drained peatland.

Land-use changes, e.g., forestry drainage, modify the characteristics of peatland soil and affect the peatland carbon (C) balance. Peat soil nutrient status, related mainly to the original peatland type, also has an impact on the C balance after drainage, as observed earlier at the ecosystem scale for two forestry-drained sites in Southern Finland. Here the aim was to compare the soil CO2 fluxes from the two sites, nutrient-poor and nutirent-rich forestry-drained peatlands, and study the effect of plant photosynthates on the decomposition of peat C. Therefore, the respiration rates and priming effect (PE) of peat soils with variable nutrient status were examined in the laboratory. Half of the samples were labelled with 13 C-glucose to study the effect of fresh C addition on the soil decomposition. The 13 CO2 -samples were analysed with isotope ratio mass spectrometry. A two-pool mixing model was applied to separate the soil- and sugar-derived respirations and to determine the PE. The nutrient-rich peat soil respired generally more than the nutrient-poor peat. A negative PE was observed in both peat soils, suggesting that the addition of fresh C did not increase the soil decomposition, but on the contrary decreased it. The negative PE was significantly more pronounced in nutrient-poor peat soil than in the nutrient-rich peat treatments, suggesting that the higher nutrient availability suppresses the negative PE. These results imply that microbes prefer utilizing fresh C instead of old C in the short term and that the peat decomposition is suppressed in the presence of fresh C inputs from vegetation at forestry-drained peatlands. These effects are even stronger in peat soils with less nutrients available. Ecosystem scale and soil process models could be improved with the help of these results.