Mitochondrial Electron Transport Chain Research Articles

Aging, ROS, and cellular senescence: a trilogy in the progression of liver fibrosis.

Ageing is an inevitable and multifaceted biological process that impacts a wide range of cellular and molecular mechanisms, leading to the development of various diseases, such as liver fibrosis. Liver fibrosis progresses to cirrhosis, which is an advanced form due to high amounts of extracellular matrix and restoration of normal liver structure with failure to repair damaged tissue and cells, marking the end of liver function and total liver failure, ultimately death. The most important factors are reactive oxygen species (ROS) and cellular senescence. Oxidative stress is defined as an impairment by ROS, which are by-products of the mitochondrial electron transport chain and other key molecular pathways that induce cell damage and can activate cellular senescence pathways. Cellular senescence is characterized by pro-inflammatory cytokines, growth factors, and proteases secreted by senescent cells, collectively known as the senescence-associated secretory phenotype (SASP). The presence of senescent cells, which disrupt tissue architecture and function and increase senescent cell production in liver tissues, contributes to fibrogenesis. Hepatic stellate cells (HSCs) are activated in response to chronic liver injury, oxidative stress, and senescence signals that drive excessive production and deposition of extracellular matrix. This review article aims to provide a comprehensive overview of the pathogenic role of ROS and cellular senescence in the aging liver and their contribution to fibrosis.

Abstract 4117594: Fetal Synthetic Glucocorticoid (sGC) Exposure Results in Later Life Cardiac Dysfunction and Ventricular Remodeling in Male Baboon Offspring

The “theory of developmental origins of health and disease” posits that stress in critical developmental periods will program life-course health and may affect cardiovascular (CV) health. Mothers at risk for premature delivery receive synthetic glucocorticoids (sGC) to enhance fetal lung maturation and manage fetal respiratory distress, but sGC exposure is linked to long-term CV dysfunction in offspring. Four groups of male baboons were studied: sGC exposed in utero at middle age (sGC-MA, 13.8±0.2Y), older sGC exposed in utero (sGC-O, 17.1±0.4Y), middle age unexposed (CTR-MA, 13.5±0.6Y), and older, unexposed baboons (CTR-O, 17.4±0.4Y). Gated, breath-hold, cine cardiac magnetic resonance imaging was performed at 3 Tesla (Siemens TIM Trio) to assess left ventricular (LV) function and myocardial strain, analyzed using cvi42® software. Mitochondrial electron transport chain (ETC) complex activity was analyzed using LV tissue from sGC-O and CTR-O euthanized baboons. Protein quantification was used to measure mitochondrial function and RNA-seq assessed differential gene expression and gene ontology (GO) enrichment. Unpaired t-tests were used. Data are reported as mean ± SD. Stroke volume and ejection fraction were similar in the elderly groups (4 sGC-O, 8 CTR-O). However, higher end-systolic and end-diastolic sphericity indexes (SI) and shorter LV axis lengths indicated remodeling. Also, global longitudinal and radial strains were reduced (both p<0.04) in sGC-O vs. CTR-O. Reduced LV cardiac output (p=0.005) was found in 5 sGC-MA animals vs 4 sGC-O animals, but not in 5 CTR-MA vs 8 CTR-O. In sGC-MA vs sGC-O, but not CTR-MA vs CTR-O, significant increases in SI (p=0.001), radial strain (p=0.02), and longitudinal (p=0.03) strain were found, but LV axis length (p=0.03) was reduced. LV mitochondrial analysis in 4 sGC-O vs 4 CTR-O myocardial samples revealed 33.5% less ETC activity (p=0.002) and 19.8% less complex I expression (p=0.048) in sGC. LV RNA-seq identified 63 upregulated and 20 downregulated genes in the sGC-O samples. GO pathway enrichment included changes in heart contraction, wounding responses, and leukocyte regulation pathways. These findings indicate that fetal sGC exposure developmentally programs offspring with LV remodeling and long-term cardiac and gene expression changes in male baboons, the closest available experimental nonhuman primate species to man. Future studies on females will probe sexual dimorphism in developmental programming.

Mitochondrial AOX1a and an H2O2 feed-forward signalling loop regulate flooding tolerance in rice.

Flooding is a widespread natural disaster that causes tremendous yield losses of global food production. Rice is the only cereal capable of growing in aquatic environments. Direct seeding by which seedlings grow underwater is an important cultivation method for reducing rice production cost. Hypoxic germination tolerance and root growth in waterlogged soil are key traits for rice adaptability to flooded environments. Alternative oxidase (AOX) is a non-ATP-producing terminal oxidase in the plant mitochondrial electron transport chain, but its role in hypoxia tolerance had been unclear. We have discovered that AOX1a is necessary and sufficient to promote germination/coleoptile elongation and root development in rice under flooding/hypoxia. Hypoxia enhances endogenous H2O2 accumulation, and H2O2 in turn activates an ensemble of regulatory genes including AOX1a to facilitate the conversion of deleterious reactive oxygen species to H2O2 in rice under hypoxia. We show that AOX1a and H2O2 act interdependently to coordinate three key downstream events, that is, glycolysis/fermentation for minimal ATP production, root aerenchyma development and lateral root emergence under hypoxia. Moreover, we reveal that ectopic AOX1a expression promotes vigorous root and plant growth, and increases grain yield under regular irrigation conditions. Our discoveries provide new insights into a unique sensor-second messenger pair in which AOX1a acts as the sensor perceiving low oxygen tension, while H2O2 accumulation serves as the second messenger triggering downstream root development in rice against hypoxia stress. This work also reveals AOX1a genetic manipulation and H2O2 pretreatment as potential targets for improving flooding tolerance in rice and other crops.

Abstract 4123630: MRPL44 Plays an Important Role in Cardiac Hypertrophy and Function

Background: Mitochondrial ribosomal large subunit 44 (MRPL44) knockout mice were embryonic lethal, for which mutations are known to cause mitochondrial infantile cardiomyopathy and hypertrophic cardiomyopathy. However, it remains unknown how MRPL44 contributes to cardiac function and hypertrophy. Aims: Our aim is to investigate the effect of MRPL44 haploinsufficiency in mice. Methods: MRPL44 haploinsufficient (MRPL44 +/- ) mice were generated. Mineralocorticoid receptor-associated hypertension mice were induced in MRPL44 +/- and wild-type (WT, MRPL44 +/+ ) mice with subcutaneous infusion of aldosterone(Aldo) and 8% NaCl food for 4 weeks after uninephrectomy. Systolic blood pressure was measured by tail cuffs every week. WB, qPCR, cardiac echo, and histological examinations were performed. RNA sequencing analysis, electron microscopy examinations and mitochondrial activity assay were performed to find differences between MRPL44 +/- and MRPL44 +/+ mice. Results: MRPL44 haploinsufficient mice spontaneously developed left ventricular hypertrophy. Heart rate, blood pressure, and cardiac systolic function were normal in MRPL44 haploinsufficient mice. MRPL44 was decreased about to 70% in MRPL44 haploinsufficient mice and mitochondrial arrangement were impaired in electron microscopic analysis. After Aldo treatment, blood pressure elevation were similar, however, MRPL44 haploinsufficient mice developed left ventricular systolic dysfunction and dilation compared with MRPL44 +/+ mice. WB showed mitochondrial electron transport chain protein complex IV expression was significantly decreased. Furthermore, mitochondrial activity assay showed MRPL44 haploinsufficient mice had a significant reduction in complex IV activity, whereas complex I and II activity were similar to MRPL44 +/+ mice. RNA sequencing analysis showed the significant changes in the expression of ribosomal subunits coded by nucleus in addition to mitochondrial ribosomal subunits. These results indicate MRPL44 plays an important role in the cardiac function of mitochondrial electron transport chain protein complexes via the expression of ribosomal protein subunits coded by both nucleus and mitochondria. Conclusion: MRPL44 haploinsufficient mice spontaneously develop left ventricular hypertrophy and shows systolic dysfunction after aldosterone treatment accompanied with oxidative phosphorylation enzyme dysfunction.

Inhibition of VDAC1 oligomerization blocks cysteine deprivation-induced ferroptosis via mitochondrial ROS suppression

Ferroptosis, a regulated form of cell death dependent on reactive oxygen species (ROS), is characterized by iron accumulation and lethal lipid peroxidation. Mitochondria serve as the primary source of ROS and thus play a crucial role in ferroptosis initiation and execution. This study highlights the role of mitochondrial ROS and the significance of voltage-dependent anion channel 1 (VDAC1) oligomerization in ferroptosis induced by cysteine deprivation or ferroptosis-inducer RSL3. Our results demonstrate that the mitochondria-targeted antioxidants MitoQ and MitoT effectively block ferroptosis induction and that dysfunction of complex III of the mitochondrial electron transport chain contributes to ferroptosis induction. Pharmacological inhibitors that target VDAC1 oligomerization have emerged as potent suppressors of ferroptosis that reduce mitochondrial ROS production. These findings underscore the critical involvement of mitochondrial ROS production via complex III of the electron transport chain and the essential role of VDAC1 oligomerization in ferroptosis induced by cysteine deprivation or RSL3. This study deepens our understanding of the intricate molecular networks governing ferroptosis and provides insights into the development of novel therapeutic strategies targeting dysregulated cell death pathways.

TAp73 regulates mitochondrial dynamics and multiciliated cell homeostasis through an OPA1 axis

Dysregulated mitochondrial fusion and fission has been implicated in the pathogenesis of numerous diseases. We have identified a novel function of the p53 family protein TAp73 in regulating mitochondrial dynamics. TAp73 regulates the expression of Optic Atrophy 1 (OPA1), a protein responsible for controlling mitochondrial fusion, cristae biogenesis and electron transport chain function. Disruption of this axis results in a fragmented mitochondrial network and an impaired capacity for energy production via oxidative phosphorylation. Owing to the role of OPA1 in modulating cytochrome c release, TAp73−/− cells display an increased sensitivity to apoptotic cell death, e.g., via BH3-mimetics. We additionally show that the TAp73/OPA1 axis has functional relevance in the upper airway, where TAp73 expression is essential for multiciliated cell differentiation and function. Consistently, ciliated epithelial cells of Trp73−/− (global p73 knock-out) mice display decreased expression of OPA1 and perturbations of the mitochondrial network, which may drive multiciliated cell loss. In support of this, Trp73 and OPA1 gene expression is decreased in chronic obstructive pulmonary disease (COPD) patients, a disease characterised by alterations in mitochondrial dynamics. We therefore highlight a potential mechanism involving the loss of p73 in COPD pathogenesis. Our findings also add to the growing body of evidence for growth-promoting roles of TAp73 isoforms.

Evaluation of the Detrimental Impact of Low-Intensity Laser Radiation on the Characteristics of Sperm Movement, Motion, and DNA Damage

It is generally accepted that low-level laser therapy promotes cellular energy production and increases the synthesis of ATP by triggering the mitochondrial electron transport chain's photosensitive cytochrome c oxidase complex. Nevertheless, this investigation aimed to examine the possible adverse impact on sperm function and DNA integrity of low-intensity laser radiation with a wavelength of 980 nm. Following standard analysis, forty semen samples were collected and categorized as either asthenospermic, oligospermic, or normospermic. The remaining semen was subjected to standard semen analysis, and the aliquots were divided into treatment and control groups. A continuous-wave 980 nm laser with an output power of 100 mW and an energy density of 10 J/cm2 was applied to the treated samples for 30 s. Divided samples underwent incubation at 37oC, and semen analysis was used to assess aliquots at 30 s and 2 h intervals. Following the incubation time, each sample was frozen in 250 mL at -80oC until DNA fragmentation was examined using flow cytometry. Thirty minutes after treatment, there was a noticeable increase in sperm movement; the rise was largest in oligospermic and asthenospermic samples (88%) while samples of normal sperm displayed the least increment (7.5%). There was no discernible increase in DNA damage in the treatment samples compared to the control samples. The treatment samples had 21.8% and the control samples had 25.3% of the DNA fragmentation index. The dynamics of sperm motion were noticeably altered. Short-term exposure to low-level laser radiation appeared to improve the motion and movement of treated sperm, and after 2 h, there was no increase in DNA damage. Asthenospermia and mitochondrial dysfunction may be related in some circumstances. To fully understand the ramifications of these results for possible medicinal applications, more research is needed. Our research's conclusions suggest that low-level laser stimulation is a useful and safe technique for identifying viable immotile spermatozoa in a particular sample. It may also cause these spermatozoa to move about, which could have positive therapeutic effects.

Short-Term Exposure to 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine Induces Colonic Energy Metabolism Disorders in Rats.

2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP) is one of the most abundant heterocyclic aromatic amines generated in thermally processed meat products, and the toxicities of its short-term exposure in the intestines remain unclear. This study aimed to elucidate the short-term PhIP toxicity in colons through administering PhIP orally to rats for 4 weeks. The results indicated that short-term PhIP exposure induced colonic oxidative stress, a significant decrease of serum triglyceride, and a disrupted colonic gene expression pattern associated with mitochondrial electron transport chain and energy metabolism. Thirteen energy metabolites, including lactate and d-erythrose-4-phosphate, showed significant changes under short-term PhIP effects. Energy metabolism pathway analysis revealed that PhIP-induced colonic energy metabolism disorders are characterized by inhibited glycolysis and enhanced tricarboxylic acid cycle. Further investigation found that PhIP altered the energy metabolic phenotype of colon epithelial cells to increase aerobic respiration. In summary, our study provides new insights into the colon toxicity induced by a short-term PhIP exposure.

Mid-late gestation leptin infusion induces placental mitochondrial and endoplasmic reticulum unfolded protein responses in a mouse model of preeclampsia

IntroductionPreeclamptic patients, both lean and obese, present with elevated leptin levels which are associated with the development of maternal endothelial dysfunction and adverse fetal outcomes, such as growth restriction, leading to low birth weight. Recent studies in pregnant mice demonstrate that mid-late gestation leptin infusion induces clinical characteristics of preeclampsia, including elevated maternal blood pressure, maternal endothelial dysfunction and fetal growth restriction. However, whether leptin triggers placental stress responses that contribute to adverse fetal outcomes as in preeclampsia is unknown. MethodsIn the current study we measured the expression of proteins involved in the endoplasmic reticulum (UPRer) and mitochondrial (UPRmt) unfolded protein responses in placentas of wild-type sham normal pregnant and leptin-infused preeclamptic mice. ResultsThe data show that mid-late gestation leptin infusion induced activation of indices of placental UPRer and UPRmt, while reducing placental repair mechanisms to UPRmt in preeclamptic mice. Mid-late gestation infusion with leptin upregulated markers of placental oxidative stress, reduced the placental expression levels of mitochondrial electron transport chain complexes I and II and increased the expression of placental endothelin-1 (ET-1) in preeclamptic mice. The leptin-induced activation of several placental UPRmt markers as well as ET-1 levels correlated with fetal growth restriction and impaired maternal endothelial function in preeclamptic mice. DiscussionCollectively, these data indicate that elevated levels of leptin in mid-late pregnancy in mice promote placental stress responses, akin to those in pregnant women with preeclampsia.

Mitochondrial Bioenergetics Deficiency in cisd-1 Mutants is Linked to AMPK-Mediated Lipid Metabolism

BackgroundCISD-1 is a mitochondrial iron-sulfate [2Fe-2S] protein known to be associated with various human diseases, including cancer and diabetes. Previously, we demonstrated that CISD-1 deficiency in worms lowers glucose and ATP levels. In this study, we further explored how worms compensate for lower ATP levels by analyzing changes in cytoplasmic and mitochondrial iron content, AMPK activities, and total lipid profiles. Materials and MethodsExpression levels of CISD-1 and CISD-1::GFP fusion proteins in wild-type worms (N2), cisd-1-deletion mutants (tm4993 and syb923) and GFP insertion transgenic worms (PHX953 and SJL40) were examined by western blot. Fluorescence microscopy analyzed CISD-1::GFP pattern in PHX953 embryos and adults, and lipid droplet sizes in N2, cisd-1, aak-2 and aak-2;cisd-1 worms. Total and mitochondrial iron content, electron transport complex profiles, and AMPK activity were investigated in tm4993 and syb923 mutants. mRNA levels of mitochondrial β-oxidation genes, acs-2, cpt-5, and ech-1, were quantified by RT-qPCR in various genetic worm strains. Lipidomic analyses were performed in N2 and cisd-1(tm4993) worms. ResultsDefects in cisd-1 lead to an imbalance in iron transport and cause proton leak, resulting in lower ATP production by interrupting the mitochondrial electron transport chain. We identified a signaling pathway that links ATP deficiency-induced AMPK (AMP activated protein kinase) activation to the expression of genes that facilitate lipolysis via β-oxidation. ConclusionOur data provide a functional coordination between CISD-1 and AMPK constitutes a mitochondrial bioenergetics quality control mechanism that provides compensatory energy resources.

Biogenesis of Cytochromes c and c1 in the Electron Transport Chain of Malaria Parasites.

Plasmodium malaria parasites retain an essential mitochondrional electron transport chain (ETC) that is critical for growth within humans and mosquitoes and is a key antimalarial drug target. ETC function requires cytochromes c and c1, which are unusual among heme proteins due to their covalent binding to heme via conserved CXXCH sequence motifs. Heme attachment to these proteins in most eukaryotes requires the mitochondrial enzyme holocytochrome c synthase (HCCS) that binds heme and the apo cytochrome to facilitate the biogenesis of the mature cytochrome c or c1. Although humans encode a single bifunctional HCCS that attaches heme to both proteins, Plasmodium parasites are like yeast and encode two separate HCCS homologues thought to be specific for heme attachment to cyt c (HCCS) or cyt c1 (HCC1S). To test the function and specificity of Plasmodium falciparum HCCS and HCC1S, we used CRISPR/Cas9 to tag both genes for conditional expression. HCC1S knockdown selectively impaired cyt c1 biogenesis and caused lethal ETC dysfunction that was not reversed by the overexpression of HCCS. Knockdown of HCCS caused a more modest growth defect but strongly sensitized parasites to mitochondrial depolarization by proguanil, revealing key defects in ETC function. These results and prior heterologous studies in Escherichia coli of cyt c hemylation by P. falciparum HCCS and HCC1S strongly suggest that both homologues are essential for mitochondrial ETC function and have distinct specificities for the biogenesis of cyt c and c1, respectively, in parasites. This study lays a foundation to develop novel strategies to selectively block ETC function in malaria parasites.

Molecular basis for thermogenesis and volatile production in the titan arum.

The titan arum (Amorphophallus titanum), commonly known as the corpse flower, produces the largest unbranched inflorescence in the world. Its rare blooms last only a few days and are notable both for their burst of thermogenic activity and for the odor of rotting flesh by which they attract pollinators. Studies on the titan arum can therefor lend insight into the mechanisms underlying thermogenesis as well as the production of sulfur-based volatiles, about which little is known in plants. Here, we made use of transcriptome and metabolite analyses to uncover underlying mechanisms that enable thermogenesis and volatile production in the titan arum. The ability to perform thermogenesis correlated with the expression of genes involved in bypass steps for the mitochondrial electron transport chain, in particular alternative oxidase expression, and through our analysis is placed within the context of sugar transport and metabolism. The major odorants produced by the titan arum are dimethyl disulfide and dimethyl trisulfide, and we identified pathways for sulfur transport and metabolism that culminate in the production of methionine, which our analysis identifies as the amino acid substrate for production of these odorants. Putrescine, derived from arginine, was identified as an additional and previously unrecognized component of the titan arum's odor. Levels of free methionine and putrescine were rapidly depleted during thermogenesis, consistent with roles in production of the titan arum's odor. Models for how tissues of the titan arum contribute to thermogenesis and volatile production are proposed.

MRPL44 haploinsufficient mouse spontaneously develops hypertrophic cardiomyopathy and shows systolic dysfunction after aldosterone treatment

Abstract Introduction It has been recently reported there are big differences in pathophysiological and molecular phenotypes in mouse and human hypertrophic cardiomyopathy. These differences are observed all in terms of myocyte redox, mitochondrial number and respiration, mitochondrial reactive oxygen species generation and Ca2+ handling. Therefore we should search for molecules to be able to induce similar phenotype and molecular signaling both in mice and human. Mitochondrial ribosomal large subunit 44 (MRPL44) knockout mice were embryonic lethal, for which mutations are known to cause mitochondrial infantile cardiomyopathy and hypertrophic cardiomyopathy. Purpose Our purpose is to investigate the effect of MRPL44 haploinsufficiency in mice. Methods MRPL44 haploinsufficient (MRPL44+/-) mice were generated. Mineralocorticoid receptor-associated hypertension mice were induced in MRPL44+/- and wild-type (WT, MRPL44+/+) mice with subcutaneous infusion of aldosterone(Aldo) and 8% NaCl food for 4 weeks after uninephrectomy. Systolic blood pressure was measured by tail cuffs every week. WB, qPCR, cardiac echo, and histological examinations were performed. RNA sequencing analysis, electron microscopy examinations and mitochondrial activity assay were performed to find differences between MRPL44+/- and MRPL44+/+ mice. Results MRPL44 haploinsufficient mice spontaneously developed left ventricular hypertrophy in 6 weeks old. Heart rate, blood pressure, and cardiac systolic function were normal in MRPL44 haploinsufficient mice. MRPL44 was decreased about to 70% in MRPL44 haploinsufficient mice and mitochondrial arrangement were impaired in electron microscopic analysis. After Aldo treatment, blood pressure elevation were similar, however, MRPL44 haploinsufficient mice developed left ventricular systolic dysfunction and dilation compared with MRPL44+/+ mice. WB showed mitochondrial electron transport chain protein complex IV expression was significantly decreased. Furthermore, mitochondrial activity assay showed MRPL44 haploinsufficient mice had a significant reduction in complex IV activity, whereas complex I and II activity were similar to MRPL44+/+ mice. RNA sequencing analysis showed the significant changes in the expression of ribosomal subunits coded by nucleus in addition to mitochondrial ribosomal subunits. These results indicate MRPL44 plays an important role in the cardiac function of mitochondrial electron transport chain protein complexes via the expression of ribosomal protein subunits coded by both nucleus and mitochondria. Conclusions MRPL44 haploinsufficient mice spontaneously develop left ventricular hypertrophy and shows systolic dysfunction after aldosterone treatment accompanied with oxidative phosphorylation enzyme dysfunction.

Ferroptosis Inhibition Combats Metabolic Derangements and Improves Cardiac Function in Pulmonary Artery Banded Pigs.

Right heart failure (RHF) is a leading cause of mortality in multiple cardiovascular diseases and preclinical and human data suggest impaired metabolism is a significant contributor to right-sided cardiac dysfunction. Ferroptosis is a nonapopotic form of cell death driven by impaired metabolism. Rodent data suggests ferroptosis inhibition can restore mitochondrial electron transport chain function and enhance cardiac contractility in left heart failure models, but the effects of ferroptosis inhibition in translational large animal models of RHF are unknown. Here, we showed ferrostatin-1 mediated ferroptosis antagonism improve right heart structure and function in pulmonary artery banded pigs. Molecularly, ferrostatin-1 restored mitochondrial cristae structure and combatted downregulation of electron transport chain proteins. Metabolomics and lipidomics analyses revealed ferrostatin-1 improved fatty acid metabolism. Thus, these translational data suggest ferroptosis may be a therapeutic target for RHF.

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.

Bioengineered Extracellular Vesicles Delivering siMDM2 Sensitize Oxaliplatin Therapy Efficacy in Colorectal Cancer.

Oxaliplatin (OXA) is the first-line drug for the treatment of colorectal cancer (CRC), and susceptibility to drug resistance affects patient prognosis. However, the exact underlying mechanisms remain unclear. Platinum-acquired resistance in CRC is a continuous transition process; though, current research has mainly focused on the end state of drug resistance, and the early events of drug resistance have been ignored. In this study, single-cell transcriptome sequencing is combined with a dynamic network biomarker (DNB), and found that the functional inhibition of the mitochondrial electron transport chain complex I occur early in the development of attained resistance to OXA in CRC cells, as evidenced by a decrease in the levels of subunit proteins, primarily NDUFB8. Specifically, the mouse double minute 2 homologue (MDM2) mediates the ubiquitination and degradation of NDUFB8, reducing intracellular reactive oxygen species (ROS) generation under chemotherapeutic stress, consequently contributing to drug resistance. Based on this, the study constructs engineered extracellular vesicles carrying siMDM2 by electroporation and validates the application of EV-siMDM2 to improve the efficacy of OXA-based chemotherapy by inhibiting the MDM2/NDUFB8/ROS signaling axis in patient-derived xenograft (PDX) and hepatic and pulmonary metastasis mouse models, thus providing new ideas and an experimental basis for the platinum-resistant treatment of CRC.

Olduvai domain expression downregulates mitochondrial pathways: implications for human brain evolution and neoteny.

Encoded by the NBPF gene family, Olduvai (formerly DUF1220) protein domains have undergone the largest human lineage-specific copy number expansion of any coding region in the genome. Olduvai copy number shows a linear relationship with several brain size-related measures and cortical neuron number among primates and with normal and disease-associated (micro- and macrocephaly) variation in brain size in human populations. While Olduvai domains have been shown to promote proliferation of neural stem cells, the mechanism underlying such effects has remained unclear. Here, we investigate the function of Olduvai by transcriptome and proteome analyses of cells overexpressing NBPF1 , a gene encoding 7 Olduvai domains. Our results from both RNAseq and mass spectrometry approaches suggest a potential downregulation of mitochondria. In our proteomics study, a Gene Ontology (GO) enrichment analysis for the downregulated proteins revealed a striking overrepresentation of the biological process related to the mitochondrial electron transport chain ( p value: 1.81e-11) and identified deregulation of the NADH dehydrogenase activity ( p value: 2.43e-11) as the primary molecular function. We verify the reduction of apparent mitochondria via live-cell imaging experiments. Given these and previous Olduvai findings, we suggest that the Olduvai-mediated, dosage-dependent reduction in available energy via mitochondrial downregulation may have resulted in a developmental slowdown such that the neurogenic window among primates, and most extremely in humans, was expanded over a greater time interval, allowing for production of greater numbers of neurons and a larger brain. We further suggest that such a slowdown may extend to other developmental processes that also exhibit neotenic features.

Extremely Low-Frequency Electromagnetic Field (ELF-EMF) Increases Mitochondrial Electron Transport Chain Activities and Ameliorates Depressive Behaviors in Mice.

Compromised mitochondrial electron transport chain (ETC) activities are associated with depression in humans and rodents. However, the effects of the enhancement of mitochondrial ETC activities on depression remain elusive. We recently reported that an extremely low-frequency electromagnetic field (ELF-EMF) of as low as 10 μT induced hormetic activation of mitochondrial ETC complexes in human/mouse cultured cells and mouse livers. Chronic social defeat stress (CSDS) for 10 consecutive days caused behavioral defects mimicking depression in mice, and using an ELF-EMF for two to six weeks ameliorated them. CSDS variably decreased the mitochondrial ETC proteins in the prefrontal cortex (PFC) in 10 days, which were increased by an ELF-EMF in six weeks. CSDS had no effect on the mitochondrial oxygen consumption rate in the PFC in 10 days, but using an ELF-EMF for six weeks enhanced it. CSDS inactivated SOD2 by enhancing its acetylation and increased lipid peroxidation in the PFC. In contrast, the ELF-EMF activated the Sirt3-FoxO3a-SOD2 pathway and suppressed lipid peroxidation. Furthermore, CSDS increased markers for mitophagy, which was suppressed by the ELF-EMF in six weeks. The ELF-EMF exerted beneficial hormetic effects on mitochondrial energy production, mitochondrial antioxidation, and mitochondrial dynamics in a mouse model of depression. We envisage that an ELF-EMF is a promising therapeutic option for depression.

The translation initiation factor eIF2α regulates lipid homeostasis and metabolic aging.

Aging is usually accompanied by excessive body fat gain, leading to increased susceptibility to comorbidities. This study aimed to explore an unexpected function for the eukaryotic initiation factor-2α (eIF2α) during aging. Reducing the eIF2α dose led to a reconfiguration of the metabolic equilibrium, promoting catabolism, facilitating lipolysis, and decreasing body fat accumulation while maintaining healthy glucose and lipid metabolism during aging. Specifically, eIF2α enhanced the expression of distinct messenger RNAs encoding mitochondrial electron transport chain proteins at the translation level. The mitochondrial respiration increased in eIF2α heterozygotes, even during aging. Deceleration of translation was demonstrated as a conserved mechanism for promoting longevity across various species. Our findings demonstrated that the restriction of translation by reducing eIF2α expression could fend off multiple tissue damage and improve metabolic homeostasis during aging. Hence, eIF2α was a crucial target for benefiting mammalian aging achieving delayed mammalian aging.

Sex and organ specific proteomic responses to vitamin C deficiency in the brain, heart, liver, and spleen of Gulo-/- mice.

Recent advances in mass spectrometry have indicated that the water-soluble antioxidant vitamin C differentially modulates the abundance of various proteins in the hepatic tissue of female and male mice. In this study, we performed LC-MS/MS to identify and quantify proteins that correlate with serum vitamin C concentrations in the whole brain, heart, liver, and spleen tissues in mice deficient for the enzyme L-Gulonolactone oxidase required for vitamin C synthesis in mammals. This work shows for the first time that various biological processes affected by a vitamin C deficiency are not only sex specific dependent but also tissue specific dependent even though many proteins have been identified and quantified in more than three organs. For example, the abundance of several complex III subunits of the mitochondrial electron transport chain correlated positively with the levels of serum vitamin C only in the liver and not in the other tissues examined in this study even though such proteins were identified in all the organs analyzed. Western blot analyses on the Uqcrc1 and Uqcrfs1 complex III subunits validated the mass spectrometry results. Interestingly, the ferritin subunits represented the few quantified protein complexes that correlated positively with serum vitamin C in all the organs examined. Concomitantly, serum ferritin light chain 1 was inversely correlated with vitamin C levels in the serum. Thus, our study provides an initial comprehensive atlas of proteins significantly correlating with vitamin C in four organs in mice that will be a useful resource to the scientific community.