Altered Mitochondrial Dynamics Research Articles

Propionic acid induces alterations in mitochondrial morphology and dynamics in SH-SY5Y cells

Propionic acid (PPA) is used to study the role of mitochondrial dysfunction in neurodevelopmental conditions like autism spectrum disorders. PPA is known to disrupt mitochondrial biogenesis, metabolism, and turnover. However, the effect of PPA on mitochondrial dynamics, fission, and fusion remains challenging to study due to the complex temporal nature of these mechanisms. Here, we use complementary quantitative visualization techniques to examine how PPA influences mitochondrial ultrastructure, morphology, and dynamics in neuronal-like SH-SY5Y cells. PPA (5 mM) induced a significant decrease in mitochondrial area (p < 0.01), Feret's diameter and perimeter (p < 0.05), and in area2 (p < 0.01). Mitochondrial event localiser analysis demonstrated a significant increase in fission and fusion events (p < 0.05) that preserved mitochondrial network integrity under stress. Moreover, mRNA expression of cMYC (p < 0.0001), NRF1 (p < 0.01), TFAM (p < 0.05), STOML2 (p < 0.0001), and OPA1 (p < 0.01) was significantly decreased. This illustrates a remodeling of mitochondrial morphology, biogenesis, and dynamics to preserve function under stress. Our data provide new insights into the influence of PPA on mitochondrial dynamics and highlight the utility of visualization techniques to study the complex regulatory mechanisms involved in the mitochondrial stress response.

Mitochondrial Dysfunction in Repeat Expansion Diseases.

Repeat expansion diseases are a group of neuromuscular and neurodegenerative disorders characterized by expansions of several successive repeated DNA sequences. Currently, more than 50 repeat expansion diseases have been described. These disorders involve diverse pathogenic mechanisms, including loss-of-function mechanisms, toxicity associated with repeat RNA, or repeat-associated non-ATG (RAN) products, resulting in impairments of cellular processes and damaged organelles. Mitochondria, double membrane organelles, play a crucial role in cell energy production, metabolic processes, calcium regulation, redox balance, and apoptosis regulation. Its dysfunction has been implicated in the pathogenesis of repeat expansion diseases. In this review, we provide an overview of the signaling pathways or proteins involved in mitochondrial functioning described in these disorders. The focus of this review will be on the analysis of published data related to three representative repeat expansion diseases: Huntington's disease, C9orf72-frontotemporal dementia/amyotrophic lateral sclerosis, and myotonic dystrophy type 1. We will discuss the common effects observed in all three repeat expansion disorders and their differences. Additionally, we will address the current gaps in knowledge and propose possible new lines of research. Importantly, this group of disorders exhibit alterations in mitochondrial dynamics and biogenesis, with specific proteins involved in these processes having been identified. Understanding the underlying mechanisms of mitochondrial alterations in these disorders can potentially lead to the development of neuroprotective strategies.

Abstract P3175: Mitochondrial Fission And Extracellular Mitochondria Mediate Cardiac Dysfunction In Obesity Induced Cardiomyopathy

Background: Recent studies have demonstrated that dysregulation of mitochondrial dynamics, including excessive mitochondrial fission, lead to extracellular release of damaged mitochondria (exMito) as an alternate mechanism for mitochondrial quality control. However, the exact role of this mechanism on obesity cardiomyopathy (OCM) has not been explored. This project aims to determine if Drp1/Fis1 dependent excessive mitochondrial fission mediates the release of damaged mitochondria and propagate cardiomyocyte injury in OCM. Methods: H9c2 cardiomyoblast were treated with 200 μM palmitate (PA) to induce lipotoxicity. C57BL6/J mice were subjected to a high-fat diet (HFD) for 12 weeks to induce OCM. Changes in cardiac Drp1 activity, mitochondrial morphology, bioenergetics and contractile function was evaluated. Simultaneously, exMito were collected and characterized from supernatant and plasma. Using peptide P110 co-treatment , we determined the impact of pharmacologic inhibition of Drp1/Fis1 dependent mitochondrial fission on cardiac mitochondrial function as well as the quality and quantity of exMito. Results: H9c2 cells treated with PA demonstrated excessive mitochondrial fission, increased oxidative stress and decreased ATP level. The excessive mitochondrial fission seen following PA treatment was associated with the release of damaged exMito. The exMito isolated from PA treated cells were noted to mediate cytotoxicity to healthy H9c2s independent of PA. P110 treatment was protective against PA mediated mitochondrial damage, represented by improved bioenergetic profile, increased ATP and lower oxidative stress. P110 treatment also lowered the release of damaged mitochondria from PA treated H9c2s. Similarly, treatment of HFD mice with P110, improved mitochondrial function and glucose utilization, exMito release and subsequently improved cardiomyocyte contractile function. Conclusion: Lipotoxicity induced mitochondrial fission, disrupted mitochondrial function leading to release of exMito. P110 limited lipotoxicity mediated alterations in mitochondrial dynamics, mitochondrial function and exMito, and then improved cardiac function. Therefore, pathologic fission and exMito may play a critical role in OCM.

Abstract P3206: Sex-specific Differences In Proteasome Activity And Mitochondrial Function In Mouse Hearts Lacking Natriuretic Peptide Receptor A

Objective: Atrial natriuretic peptide (ANP) is a cardiac hormone that plays an important role in cardiovascular function and energy metabolism by signaling through natriuretic peptide receptor A (NPRA). Genetic ablation of NPRA in mice resulted in hypertension, cardiac hypertrophy, and fibrosis. The cardiovascular phenotypes were reported to be more severe in male NPRA-knockout (KO) mice. It is known that reductions in proteasomal activities can lead to mitochondrial dysfunction. Similarly, an imbalance between mitochondrial fission and fusion events can impair mitochondrial function. We hypothesized that alterations in proteasomal function and mitochondrial dynamics might form the basis for phenotype differences reported for NPRA-KO mice. Method/Results: Non-invasive echocardiography, RT-QPCR, Western blotting, and proteasomal assays were performed to evaluate cardiac functions. Preliminary results revealed significant decreases in the activities of two proteasome subunits (β1 and β5) in male and female NPRA-KO hearts compared to sex-matched wild-type (WT) hearts. Notably, the percent-activity reductions were much higher in male NPRA-KO hearts. Western blotting analysis revealed that the expression levels of mitochondrial fusion proteins (Mfn1, Mfn2, and Opa1) were significantly increased in both male and female NPRA-KO hearts compared to WT controls. However, the expression of fission proteins (Drp1 &amp; MFF) was significantly increased only in male NPRA-KO hearts. Consistent with a more imbalance in mitochondrial dynamics in male NPRA-KO hearts, the expression levels of enzymes that promote fatty acid oxidation (ECHS1 and phospho-PDH) were unfavorably altered in male but not in female NPRA-KO hearts compared to controls. In addition, various echocardiographic and electrocardiographic parameters related to the cardiac function such as cardiac output, diastolic volume, left ventricular wall thickness, QRS duration, and stroke volume, were altered significantly more in male than in female NPRA-KO hearts. Conclusion: Our findings suggest that more pronounced sex-specific alterations in proteasome/mitochondrial functions in male NPRA-KO hearts can lead to changes in cardiac metabolism and a severe disease phenotype.

N-3 PUFA-Enriched Diet Preserves Skeletal Muscle Mitochondrial Function and Redox State and Prevents Muscle Mass Loss in Mice with Chronic Heart Failure.

Rationale and Methods: Skeletal muscle derangements, potentially including mitochondrial dysfunction with altered mitochondrial dynamics and high reactive oxygen species (ROS) generation, may lead to protein catabolism and muscle wasting, resulting in low exercise capacity and reduced survival in chronic heart failure (CHF). We hypothesized that 8-week n-3-PUFA isocaloric partial dietary replacement (Fat = 5.5% total cal; EPA + DHA = 27% total fat) normalizes gastrocnemius muscle (GM) mitochondrial dynamics regulators, mitochondrial and tissue pro-oxidative changes, and catabolic derangements, resulting in preserved GM mass in rodent CHF [Myocardial infarction (MI)-induced CHF by coronary artery ligation, left-ventricular ejection fraction <50%]. Results: Compared to control animals (Sham), CHF had a higher GM mitochondrial fission-fusion protein ratio, with low ATP and high ROS production, pro-inflammatory changes, and low insulin signalling. n-3-PUFA normalized all mitochondrial derangements and the pro-oxidative state (oxidized to total glutathione ratio), associated with normalized GM cytokine profile, and enhanced muscle-anabolic insulin signalling and prevention of CHF-induced GM weight loss (all p < 0.05 vs. CHF and p = NS vs. S). Conclusions:n-3-PUFA isocaloric partial dietary replacement for 8 weeks normalizes CHF-induced derangements of muscle mitochondrial dynamics regulators, ROS production and function. n-3-PUFA mitochondrial effects result in preserved skeletal muscle mass, with potential to improve major patient outcomes in clinical settings.

Growth hormone remodels the 3D-structure of the mitochondria of inflammatory macrophages and promotes metabolic reprogramming.

Macrophages are a heterogeneous population of innate immune cells that support tissue homeostasis through their involvement in tissue development and repair, and pathogen defense. Emerging data reveal that metabolism may control macrophage polarization and function and, conversely, phenotypic polarization may drive metabolic reprogramming. Here we use biochemical analysis, correlative cryogenic fluorescence microscopy and cryo-focused ion-beam scanning electron microscopy. We demonstrate that growth hormone (GH) reprograms inflammatory GM-CSF-primed monocyte-derived macrophages (GM-MØ) by functioning as a metabolic modulator. We found that exogenous treatment of GM-MØ with recombinant human GH reduced glycolysis and lactate production to levels similar to those found in anti-inflammatory M-MØ. Moreover, GH treatment of GM-MØ augmented mitochondrial volume and altered mitochondrial dynamics, including the remodeling of the inner membrane to increase the density of cristae. Our data demonstrate that GH likely serves a modulatory role in the metabolism of inflammatory macrophages and suggest that metabolic reprogramming of macrophages should be considered as a new target to intervene in inflammatory diseases.

Abnormal expression of fission and fusion genes and the morphology of mitochondria in eutopic and ectopic endometrium

Mitochondria play a pivotal role in physiological and metabolic function of the cell. Mitochondrial dynamics orchestrate mitochondrial function and morphology, involving fission and fusion as well as ultrastructural remodeling. Mounting evidence unravels the close link between mitochondria and endometriosis. However, how mitochondrial architecture changes through fission and fusion in eutopic and ectopic tissues of women with ovarian endometriosis remains unknown. We detected the expression of fission and fusion genes and the morphology of mitochondria in eutopic and ectopic endometrium in ovarian endometriosis. The results showed that the expression of DRP1 and LCLAT1 was upregulated in eutopic endometrial stromal cells (ESCs), and the expression of DRP1, OPA1, MFN1, MFN2, and LCLAT1 was significantly downregulated in ectopic ESCs, and reduced number of mitochondria, wider cristae width and narrower cristae junction width was observed, but there was no difference in cell survival rate. The altered mitochondrial dynamics and morphology might, respectively, provide an advantage for migration and adhesion in eutopic ESCs and be the adaptive response in ectopic endometrial cells to survive under hypoxic and oxidative stress environment.

Aging and oocyte competence: A molecular cell perspective.

Follicular microenvironment is paramount in the acquisition of oocyte competence, which is dependent on two interconnected and interdependent processes: nuclear and cytoplasmic maturation. Extensive research conducted in human and model systems has provided evidence that those processes are disturbed with female aging. In fact, advanced maternal age (AMA) is associated with a lower chance of pregnancy and live birth, explained by the age-related decline in oocyte quality/competence. This decline has largely been attributed to mitochondria, essential for oocyte maturation, fertilization, and embryo development; with mitochondrial dysfunction leading to oxidative stress, responsible for nuclear and mitochondrial damage, suboptimal intracellular energy levels, calcium disturbance, and meiotic spindle alterations, that may result in oocyte aneuploidy. Nuclear-related mechanisms that justify increased oocyte aneuploidy include deoxyribonucleic acid (DNA) damage, loss of chromosomal cohesion, spindle assembly checkpoint dysfunction, meiotic recombination errors, and telomere attrition. On the other hand, age-dependent cytoplasmic maturation failure is related to mitochondrial dysfunction, altered mitochondrial biogenesis, altered mitochondrial morphology, distribution, activity, and dynamics, dysmorphic smooth endoplasmic reticulum and calcium disturbance, and alterations in the cytoskeleton. Furthermore, reproductive somatic cells also experience the effects of aging, including mitochondrial dysfunction and DNA damage, compromising the crosstalk between granulosa/cumulus cells and oocytes, also affected by a loss of gap junctions. Old oocytes seem therefore to mature in an altered microenvironment, with changes in metabolites, ribonucleic acid (RNA), proteins, and lipids. Overall, understanding the mechanisms implicated in the loss of oocyte quality will allow the establishment of emerging biomarkers and potential therapeutic anti-aging strategies. This article is categorized under: Reproductive System Diseases > Molecular and Cellular Physiology.

BET Protein Inhibitor JQ1 Modulates Mitochondrial Dysfunction and Oxidative Stress Induced by Chronic Kidney Disease.

Among the mechanisms involved in the progression of kidney disease, mitochondrial dysfunction has special relevance. Epigenetic drugs such as inhibitors of extra-terminal domain proteins (iBET) have shown beneficial effects in experimental kidney disease, mainly by inhibiting proliferative and inflammatory responses. The impact of iBET on mitochondrial damage was explored in in vitro studies in renal cells stimulated with TGF-β1 and in vivo in murine unilateral ureteral obstruction (UUO) model of progressive kidney damage. In vitro, JQ1 pretreatment prevented the TGF-β1-induced downregulation of components of the oxidative phosphorylation chain (OXPHOS), such as cytochrome C and CV-ATP5a in human proximal tubular cells. In addition, JQ1 also prevented the altered mitochondrial dynamics by avoiding the increase in the DRP-1 fission factor. In UUO model, renal gene expression levels of cytochrome C and CV-ATP5a as well as protein levels of cytochrome C were reduced These changes were prevented by JQ1 administration. In addition, JQ1 decreased protein levels of the DRP1 fission protein and increased the OPA-1 fusion protein, restoring mitochondrial dynamics. Mitochondria also participate in the maintenance of redox balance. JQ1 restored the gene expression of antioxidant proteins, such as Catalase and Heme oxygenase 1 in TGF-β1-stimulated human proximal tubular cells and in murine obstructed kidneys. Indeed, in tubular cells, JQ1 decreased ROS production induced by stimulation with TGF-β1, as evaluated by MitoSOXTM. iBETs, such as JQ1, improve mitochondrial dynamics, functionality, and oxidative stress in kidney disease.

Perturbation of mitochondrial dynamics links to the aggravation of periodontitis by diabetes

ABSTRACT Diabetes and periodontitis are prevalent diseases that considerably impact global economy and diabetes is a major risk factor of periodontitis. Mitochondrial dynamic alterations are involved in many diseases including diabetes and this study aims to evaluate their relevance with diabetes aggravated periodontitis. Sixty mice are randomly divided into 4 groups: control, periodontitis, diabetes and diabetic periodontitis. Periodontitis severity is evaluated by alveolar bone loss, inflammation and oxidative stress status. Mitochondrial structural and functional defects are evaluated by the mitochondrial fission/fusion events, mitochondrial reactive oxygen species (ROS) accumulation, complex activities and adenosine triphosphate (ATP) production. Advanced glycation end product (AGE) and Porphyromonas gingivalis are closely related to periodontitis occurrence and development. Human gingival fibroblast cells (HGF-1) are used to investigate the AGE role and lipopolysaccharide (LPS) from Porphyromonas gingivalis (P-LPS) in aggravating diabetic periodontitis by mitochondrial dynamic and function alterations. In vivo, diabetic mice with periodontitis show severe bone loss, increased inflammation and oxidative stress accumulation. Among mice with periodontitis, diabetic mice show worse mitochondrial dynamic perturbations than lean mice, along with fusion protein levels inducing more mitochondrial fission in gingival tissue. In vitro, AGEs and P-LPS co-treatment causes severe.

The Muscle Stem Cell Mediates Remodeling of Skeletal Muscle Mitochondrial Networks

Skeletal muscle regeneration is an energy-demanding biological process that relies on mitochondria to generate ATP. While interfibrillar mitochondrial networks in healthy skeletal muscle fibers exhibit an organized architecture segregated into columns along the Z-line of the myofiber, regenerating fibers demonstrate altered mitochondrial networks that span several sarcomeres. Although it’s been established that skeletal muscle regeneration parallels altered mitochondrial dynamics and biogenesis, the cells that mediate the remodeling of mitochondrial networks have not been thoroughly investigated. Because muscle stem cells (MuSCs) play a critical role in muscle regeneration, we explored the relationship between MuSCs and mitochondria in regenerating muscle fibers. In order to induce muscle regeneration, we employed the hindlimb ischemia mouse model of peripheral artery disease (PAD) and the mdx mouse model of Duchenne’s muscular dystrophy (DMD). Furthermore, transgenic reporter mice such as Pax7-tdTomato, H2B-EGFP, and mitoDendra2 were used mark MuSCs, track nuclei, and label mitochondria, respectively. Fluorescently-labelled MuSCs were also transplanted into BaCl2-injured muscle to elucidate their behavior and interactions throughout muscle regeneration. Immunofluorescence, single fiber staining, and biochemical assays from harvested muscles were performed for data analysis. Following injury, there was a dramatic increase in the number of endogenous MuSCs 7 days post-injury compared to contralateral control while there was a significant increase in fusion of the accreted MuSCs into the myofiber at days 14 and 28. Interestingly, all fused myofibers at days 14 and 28 were regenerating, demarcated by central nucleation, suggesting that fusion of the MuSC is critical for myofiber regeneration. To determine the origin of the centrally located myonuclei, primary MuSCs from H2B-EGFP reporter mice were isolated and transplanted into injured muscle. For myofibers in which the transplanted MuSCs fused into, centrally located myonuclei were GFP+, implying that these myonuclei were derived from MuSCs. Surprisingly, regenerating muscle fibers isolated from the mitoDendra2 mouse model exhibited high densities of mitochondrial content adjacent to the centrally located myonuclei. In order to test whether MuSCs are responsible for producing these central myonuclei near mitochondria, primary MuSCs isolated from mitoDendra2 reporter mice were transplanted into mdx mice and fused myofibers indeed exhibited high Dendra2+ mitochondrial density between central nuclei as well as a restoration of the mitochondrial network. Finally, we also observed a change in myogenic potential and mitochondrial respiration after transplanting MuSCs that have been preconditioned to enhance mitochondrial biogenesis. Overall, these data indicate that following skeletal muscle injury, MuSC-derived myonuclei synthesize new mitochondria to generat This work was supported by the National Institute of Health under award number (R01AG072309, R21AR072287), Department of Defense under award number W81XWH-20-1-0336, and Regenerative Engineering and Medicine Grant. This is the full abstract presented at the American Physiology Summit 2023 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.

Alteration in mitochondrial dynamics promotes the proinflammatory response of microglia and is involved in cerebellar dysfunction of young and aged mice following LPS exposure

Cerebellar dysfunction is implicated in impaired motor coordination and balance, thus disturbing the dynamics of sensorimotor integration. Neuroinflammation and aging could be prominent contributors to cerebellar aberration. Additionally, changes in mitochondrial dynamics may precede microglia activation in several chronic neurodegenerative diseases; however, the underlying mechanism remains largely unknown. Here using LPS (1 mg/kg i.p. for four consecutive days) stimulation in both young (3 months old) and aged (12 months old) mice, followed by molecular analysis on the 21st day, we have explored the correlation between aging and mitochondrial dynamic alteration in the backdrop of chronic neuroinflammation. Following LPS stimulation, we observed microglia activation and subsequent elevation in proinflammatory cytokines (M1; TNF-α, IFN-γ) with NLRP3 activation and a concomitant reduction in the expression of anti-inflammatory markers (M2; YM1, TGF-β1) in the cerebellar tissue of aged mice compared with the young LPS and aged controls. Remarkably, senescence (p21, p27, p53) and epigenetic (HDAC2) markers were found upregulated in the cerebellum tissue of the aged LPS group, suggesting their crucial role in LPS-induced cerebellar deficit. Further, we demonstrated alteration in the antagonistic forces of mitochondrial fusion and fission with increased expression of the mitochondrial fission-related gene [FIS1] and decreased fusion-related genes [MFN1 and MFN2]. We noted increased mtDNA copy number, microglia activation, and inflammatory response of IL1-β and IFN-γ post-chronic neuroinflammation in aged LPS group. Our results suggest that the crosstalk between mitochondrial dynamics and altered microglial activation paradigm in chronic neuroinflammatory conditions may be the key to understanding the cerebellar molecular mechanism.

Chronodisruption and Loss of Melatonin Rhythm, Associated with Alterations in Daily Motor Activity and Mitochondrial Dynamics in Parkinsonian Zebrafish, Are Corrected by Melatonin Treatment.

Beyond sleep/wake, clock genes regulate the daily rhythms of melatonin production, motor activity, innate immunity, and mitochondrial dynamics, among others. All these rhythms are affected in Parkinson's disease (PD), suggesting that chronodisruption may be an early stage of the disease. The aim of this study was to evaluate the connection between clock genes and these rhythms in PD, and whether melatonin administration reestablished the normal clock function. Parkinsonism was induced with 600 μM MPTP (N-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) in 24-120 h post fertilization (hpf) zebrafish embryos and melatonin was administered at a dose of 1 μM. Day-night melatonin rhythm disappeared in MPTP-treated embryos, which showed an advance in the activity phase in parallel with changes in the rhythm of clock genes. An alteration in the fission-to-fusion mitochondrial dynamics was also detected in parkinsonian embryos, increasing the former and leading to apoptosis. Melatonin administration to MPTP-treated embryos fully restored the circadian system, including the rhythms of clock genes, motor activity, melatonin rhythm, and mitochondrial dynamics, and decreasing apoptosis. Because clock-controlled rhythms such as sleep/wake alterations are early events in PD, the data here reported may point to chronodisruption as one initial pathophysiological event of the disease.

Mitochondrial Dysfunction in CD4+ T Effector Memory RA+ Cells.

Human ageing is accompanied by poor responses to infection and decreased vaccine efficacy. While the causes of this can be attributed to defects in the immune system that increase with age, it is unknown whether mitochondrial dysfunction may also contribute to these phenomena. This study aims to assess mitochondrial dysfunction in CD4+ terminal effector memory T cells re-expressing CD45RA (TEMRA) cells and other CD4+ memory T cell subtypes, which are increased in number in the elderly population, with respect to how their metabolic responses to stimulation are altered compared to CD4+ naïve T cells. In this study, we show that CD4+ TEMRA cells exhibit altered mitochondrial dynamics compared to CD4+ naïve cells and CD4+ central and effector memory cells, with a 25% reduction in OPA1 expression. CD4+ TEMRA and memory cells show increased upregulation of Glucose transporter 1 following stimulation and higher levels of mitochondrial mass compared to CD4+ naïve T cells. Additionally, TEMRA cells exhibit a decrease in mitochondrial membrane potential compared to other CD4+ memory cell subsets by up to 50%. By comparing young to aged individuals, more significant mitochondria mass and lower membrane potential were observed in CD4+ TEMRA of young individuals. In conclusion, we suggest that CD4+ TEMRA cells may be impaired with respect to their metabolic response to stimulation, possibly contributing to impaired responses to infection and vaccination.

Abstract 4831: Mitochondrial plasticity enables metabolic reprogramming and metastatic latency

Abstract Introduction: Metastatic relapses are common in epidermal growth factor receptor 2 (HER2) amplified breast cancer patients considered disease-free after primary diagnosis and treatment. Stem-like disseminated tumor cells with specialized metastatic traits adapt and survive as latent metastases in distal organs by overcoming oxidative stress, nutrient limitation, microenvironmental and immune defenses. These latent subclinical metastatic cells are responsible for late recurrences. Understanding the traits and vulnerabilities of these cells is critical for developing strategies to prevent metastatic relapse. Method: Here, we employed mouse models and patient samples along with RNA sequencing, Steady-state metabolite analysis, Lipid profiling, C13-isotope tracing, C12-BODIPY pulse chase, Lentiviral shRNA Knockdown, Transmission electron microscopy etc. to investigate how disseminated latent metastatic cells meet their cellular energetic demands and initiate overt metastasis in the lipid-rich brain microenvironment. Result: The ability to utilize available nutrients in distal organs and rewire metabolism is critical for survival of disseminated tumor cells. We report that latent metastatic cells in the brain uptake, store, and utilize fatty acids secreted by tumor-associated reactive astrocytes to meet their cellular energetic needs. Fatty acid oxidation (FAO) and dynamin-related protein 1(DRP1) driven punctate mitochondria enabled utilization of fatty acids and promote survival of latent cells by maintaining cellular bioenergetics and redox homeostasis. Attenuating fatty acid oxidation by genetic and pharmacological inhibition disrupted mitochondrial dynamics and limits metastatic incidence. Likewise, depleting DRP1 altered mitochondrial dynamics that results in reduced FAO, increased reactive oxygen species and attenuated metastatic latency and relapse in HER2+ breast cancer brain metastatic models. Furthermore, comparison with patient-matched primary tumor and brain metastasis identified increased pDRP1 expression in brain metastatic lesions. Moreover, pharmacological inhibition of DRP1 reduced brain metastatic burden in these preclinical models. Conclusion: Despite significant advances in targeted therapies, HER2+ breast cancer patients often develop brain metastasis and their prevention and management remain an unmet need. Our findings in latent HER2+ breast cancer brain metastatic models demonstrate mitochondrial plasticity and altered fatty acid metabolism are key determinants of metastatic adaptation to the brain and establish DRP1 as a promising therapeutic target for treating brain metastasis. Key Words: Breast Cancer Brain Metastasis, Mitochondrial Plasticity, DRP1, Metastatic Latency, Redox Homeostasis. Citation Format: Pravat Kumar Parida, Srinivas Malladi. Mitochondrial plasticity enables metabolic reprogramming and metastatic latency. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4831.

The Role of Bacteria-Mitochondria Communication in the Activation of Neuronal Innate Immunity: Implications to Parkinson's Disease.

Mitochondria play a key role in regulating host metabolism, immunity and cellular homeostasis. Remarkably, these organelles are proposed to have evolved from an endosymbiotic association between an alphaproteobacterium and a primitive eukaryotic host cell or an archaeon. This crucial event determined that human cell mitochondria share some features with bacteria, namely cardiolipin, N-formyl peptides, mtDNA and transcription factor A, that can act as mitochondrial-derived damage-associated molecular patterns (DAMPs). The impact of extracellular bacteria on the host act largely through the modulation of mitochondrial activities, and often mitochondria are themselves immunogenic organelles that can trigger protective mechanisms through DAMPs mobilization. In this work, we demonstrate that mesencephalic neurons exposed to an environmental alphaproteobacterium activate innate immunity through toll-like receptor 4 and Nod-like receptor 3. Moreover, we show that mesencephalic neurons increase the expression and aggregation of alpha-synuclein that interacts with mitochondria, leading to their dysfunction. Mitochondrial dynamic alterations also affect mitophagy which favors a positive feedback loop on innate immunity signaling. Our results help to elucidate how bacteria and neuronal mitochondria interact and trigger neuronal damage and neuroinflammation and allow us to discuss the role of bacterial-derived pathogen-associated molecular patterns (PAMPs) in Parkinson's disease etiology.

CD38-Induced Metabolic Dysfunction Primes Multiple Myeloma Cells for NAD+-Lowering Agents

Cancer cells fuel growth and energy demands by increasing their NAD+ biosynthesis dependency, which therefore represents an exploitable vulnerability for anti-cancer strategies. CD38 is a NAD+-degrading enzyme that has become crucial for anti-MM therapies since anti-CD38 monoclonal antibodies represent the backbone for treatment of newly diagnosed and relapsed multiple myeloma patients. Nevertheless, further steps are needed to enable a full exploitation of these strategies, including deeper insights of the mechanisms by which CD38 promotes tumorigenesis and its metabolic additions that could be selectively targeted by therapeutic strategies. Here, we present evidence that CD38 upregulation produces a pervasive intracellular-NAD+ depletion, which impairs mitochondrial fitness and enhances oxidative stress; as result, genetic or pharmacologic approaches that aim to modify CD38 surface-level prime MM cells to NAD+-lowering agents. The molecular mechanism underlying this event is an alteration in mitochondrial dynamics, which decreases mitochondria efficiency and triggers energetic remodeling. Overall, we found that CD38 handling represents an innovative strategy to improve the outcomes of NAD+-lowering agents and provides the rationale for testing these very promising agents in clinical studies involving MM patients.

Early Mitochondrial Defects in the 5xFAD Mouse Model of Alzheimer's Disease.

Mitochondrial (MT) dysfunction is a hallmark of Alzheimer's disease (AD). Amyloid-β protein precursor and amyloid-β peptides localize to MT and lead to MT dysfunction in familial forms of AD. This dysfunction may trigger subsequent types of pathology. To identify the MT phenotypes that occur early in order to help understand the cascade of AD pathophysiology. The 5xFAD mouse model was used to explore the time course of MT pathologies in both sexes. Protein biomarkers for MT dynamics were measured biochemically and MT function was measured using oxygen consumption and ATP assays. We discovered progressive alterations in mitochondrial dynamics (biogenesis, fission, fusion, and mitophagy) and function (O2 consumption, ATP generation, and Ca2+ import) in the hippocampus of 5xFAD mice in both sexes as early as 2 months of age. Thus, mitochondrial dynamics and function become altered at young ages, consistent with an early role for mitochondria in the AD pathological cascade. Our study offers the baseline information required to understand the hierarchical relationship between the multiple pathologies that develop in this mouse model and provides early biomarkers for MT dysfunction. This will aid in dissecting the temporal cascade of pathologies, understanding sex-specific differences, and in testing the efficacy of putative mitochondrial therapeutics.

Iron and mitochondria in the susceptibility, pathogenesis and progression of COPD.

Chronic obstructive pulmonary disease (COPD) is a debilitating lung disease characterised by airflow limitation, chronic bronchitis, emphysema and airway remodelling. Cigarette smoke is considered the primary risk factor for the development of COPD; however, genetic factors, host responses and infection also play an important role. Accumulating evidence highlights a role for iron dyshomeostasis and cellular iron accumulation in the lung as a key contributing factor in the development and pathogenesis of COPD. Recent studies have also shown that mitochondria, the central players in cellular iron utilisation, are dysfunctional in respiratory cells in individuals with COPD, with alterations in mitochondrial bioenergetics and dynamics driving disease progression. Understanding the molecular mechanisms underlying the dysfunction of mitochondria and cellular iron metabolism in the lung may unveil potential novel investigational avenues and therapeutic targets to aid in the treatment of COPD.

High Concentration Hydrogen Mitigates Sepsis-Induced Acute Lung Injury in Mice by Alleviating Mitochondrial Fission and Dysfunction.

Background: Multiple organ failure (MOF) is the main cause of early death in septic shock. Lungs are among the organs that are affected in MOF, resulting in acute lung injury. A large number of inflammatory factors and stress injury in sepsis can lead to alterations in mitochondrial dynamics. Numerous studies have confirmed that hydrogen can alleviate sepsis in the animal model. The purpose of this experiment was to explore the therapeutic effect of high concentration (67%) hydrogen on acute lung injury in septic mice and its mechanism. Methods: The moderate and severe septic models were prepared by cecal ligation and puncture. Hydrogen with different concentrations was inhaled for one hour at 1 h and 6 h after the corresponding surgery. The arterial blood gas of mice during hydrogen inhalation was monitored in real time, and the 7-day survival rate of mice with sepsis was recorded. The pathological changes of lung tissues and functions of livers and kidneys were measured. The changes of oxidation products, antioxidant enzymes and pro-inflammatory cytokines in lungs and serums were detected. Mitochondrial function was measured. Results: The inhalation of 2% or 67% hydrogen improves the 7-day survival rate and reduces acute lung injury as well as liver and kidney injury in sepsis. The therapeutic effect of 67% hydrogen inhalation on sepsis was related to increasing antioxidant enzyme activity, reducing oxidation products and pro-inflammatory cytokines in lungs and serums. Compared with the Sham group, mitochondrial dysfunction was alleviated in hydrogen groups. Conclusions: Hydrogen inhalation by high or low concentration can both significantly improve sepsis; however, a high concentration demonstrates a better protective effect. High concentration hydrogen inhalation can significantly improve the mitochondrial dynamic balance and reduce the lung injury in septic mice.