Mitofusin 1 and optic atrophy 1 shift metabolism to mitochondrial respiration during aging

Role of Mitofusin 1 in mediating reactive oxygen species in alveolar macrophages during Streptococcuspneumoniae

Alveolar macrophages (AM) are key effectors of the immune response and are essential for host responses to S. pneumoniae. Mitochondria are highly dynamic organelles whose function aids in regulating the cell cycle, innate immunity, autophagy, redox signaling, calcium homeostasis, and mitochondrial quality control in AM. In response to cellular stress, mitochondria can engage in stress-induced mitochondrial hyperfusion (SIMH). The current study aimed to investigate the role of Mfn1 on mitochondrial control of reactive oxygen species (ROS) in AMs and the role of Mfn1 deficiency on immune responses to S. pneumoniae. Compared to Mfn1FloxCre- controls, there were distinct histological differences in lung tissue collected from Mfn1Floxed; CreLysM mice, with less injury and inflammation observed in mice with Mfn1 deficient myeloid cells. There was a significant decrease in lipid peroxidation and ROS production in Mfn1 deficient AM that was associated with increased superoxide dismutase (SOD) and antioxidant activity. Our findings demonstrate that Mfn1 deficiency in myeloid cells decreased inflammation and lung tissue injury during S. pneumoniae infection.

Physiological skin oxygen levels: An important criterion for skin cell functionality and therapeutic approaches

The skin is made up of different layers with various gradients, which maintain a complex microenvironment, particularly in terms of oxygen levels. However, all types of skin cells are cultured in conventional incubators that do not reproduce physiological oxygen levels. Instead, they are cultured at atmospheric oxygen levels, a condition that is far removed from physiology and may lead to the generation of free radicals known to induce skin ageing. This review aims to summarize the current literature on the effect of physiological oxygen levels on skin cells, highlight the shortcomings of current in vitro models, and demonstrate the importance of respecting skin oxygen levels. We begin by clarifying the terminology used about oxygen levels and describe the specific distribution of oxygen in the skin. We review and discuss how skin cells adapt their oxygen consumption and metabolism to oxygen levels environment, as well as the changes that are induced, particularly, their redox state, life cycle and functions. We examine the effects of oxygen on both simple culture models and more complex reconstructed skin models. Finally, we present the implications of oxygen modulation for a more therapeutic approach.

Mitochondrial Structure and Function in Human Heart Failure

Despite clinical and scientific advancements, heart failure is the major cause of morbidity and mortality worldwide. Both mitochondrial dysfunction and inflammation contribute to the development and progression of heart failure. Although inflammation is crucial to reparative healing following acute cardiomyocyte injury, chronic inflammation damages the heart, impairs function, and decreases cardiac output. Mitochondria, which comprise one third of cardiomyocyte volume, may prove a potential therapeutic target for heart failure. Known primarily for energy production, mitochondria are also involved in other processes including calcium homeostasis and the regulation of cellular apoptosis. Mitochondrial function is closely related to morphology, which alters through mitochondrial dynamics, thus ensuring that the energy needs of the cell are met. However, in heart failure, changes in substrate use lead to mitochondrial dysfunction and impaired myocyte function. This review discusses mitochondrial and cristae dynamics, including the role of the mitochondria contact site and cristae organizing system complex in mitochondrial ultrastructure changes. Additionally, this review covers the role of mitochondria-endoplasmic reticulum contact sites, mitochondrial communication via nanotunnels, and altered metabolite production during heart failure. We highlight these often-neglected factors and promising clinical mitochondrial targets for heart failure.

Systems genetics analysis of human body fat distribution genes identifies adipocyte processes

Excess abdominal fat is a sexually dimorphic risk factor for cardio-metabolic disease and is approximated by the waist-to-hip ratio adjusted for body mass index (WHRadjBMI). Whereas this trait is highly heritable, few causal genes are known. We aimed to identify novel drivers of WHRadjBMI using systems genetics. We used two independent cohorts of adipose tissue gene expression and constructed sex- and depot-specific Bayesian networks to model gene-gene interactions from 8,492 genes. Using key driver analysis, we identified genes that, in silico and putatively in vitro, regulate many others. 51-119 key drivers in each network were replicated in both cohorts. In other cell types, 23 of these genes are found in crucial adipocyte pathways: Wnt signaling or mitochondrial function. We overexpressed or down-regulated seven key driver genes in human subcutaneous pre-adipocytes. Key driver genes ANAPC2 and RSPO1 inhibited adipogenesis, whereas PSME3 increased adipogenesis. RSPO1 increased Wnt signaling activity. In differentiated adipocytes, MIGA1 and UBR1 down-regulation led to mitochondrial dysfunction. These five genes regulate adipocyte function, and we hypothesize that they regulate fat distribution.

Identification of key mitochondria-related genes and their relevance to the immune system linking Parkinson's disease and primary Sjögren's syndrome through integrated bioinformatics analyses

BACKGROUND

Mitochondria are the metabolic hubs of cells, regulating energy production and antigen presentation, which are essential for activation, proliferation, and function of immune cells. Recent evidence indicates that mitochondrial antigen presentation may have an impact on diseases such as Parkinson's disease (PD) and autoimmune diseases. However, there is limited knowledge about the mechanisms that regulate the presentation of mitochondrial antigens in these diseases.

METHODS

In the current study, RNA sequencing was performed on labial minor salivary gland (LSG) from 25 patients with primary Sjögren's syndrome (pSS) and 14 non-pSS aged controls. Additionally, we obtained gene expression omnibus datasets associated with PD patients from NCBI Gene Expression Omnibus (GEO) databases. Single-sample Gene Set Enrichment Analysis (ssGSEA), ESTIMATE and Spearman correlations were conducted to explore the association between mitochondrial related genes and the immune system. Furthermore, we applied weighted Gene Co-expression Network Analysis (WGCNA) to identify hub mitochondria-related genes and investigate the correlated networks in both diseases. Single cell transcriptome analysis, immunohistochemical (IHC) staining and quantitative real-time PCR (qRT-PCR) were used to verify the activation of the hub mitochondria-related pathway. Pearson correlations and the CIBERSORT algorithms were employed to further reveal the correlation between hub mitochondria-related pathways and immune infiltration.

RESULTS

The transcriptome analysis revealed the presence of overlapping mitochondria-related genes and mitochondrial DNA damage in patients with pSS and PD. Reactive oxygen species (ROS), the senescence marker p53, and the inflammatory markers CD45 and Bcl-2 were found to be regionally distributed in LSGs of pSS patients. WGCNA analysis identified the STING pathway as the central mitochondria-related pathway closely associated with the immune system. Single cell analysis, IHC staining, and qRT-PCR confirmed the activation of the STING pathway. Subsequent, bioinformatic analysis revealed the proportion of infiltrating immune cells in the STING-high and STING-low groups of pSS and PD. Furthermore, the study demonstrated the association of the STING pathway with innate and adaptive immune cells, as well as functional cells, in the immune microenvironment of PD and pSS.

CONCLUSION

Our study uncovered a central pathway that connects mitochondrial dysfunction and the immune microenvironment in PD and pSS, potentially offering valuable insights into therapeutic targets for these conditions.

Deciphering mitochondrial dysfunction: Pathophysiological mechanisms in vascular cognitive impairment

Vascular cognitive impairment (VCI) encompasses a range of cognitive deficits arising from vascular pathology. The pathophysiological mechanisms underlying VCI remain incompletely understood; however, chronic cerebral hypoperfusion (CCH) is widely acknowledged as a principal pathological contributor. Mitochondria, crucial for cellular energy production and intracellular signaling, can lead to numerous neurological impairments when dysfunctional. Recent evidence indicates that mitochondrial dysfunction-marked by oxidative stress, disturbed calcium homeostasis, compromised mitophagy, and anomalies in mitochondrial dynamics-plays a pivotal role in VCI pathogenesis. This review offers a detailed examination of the latest insights into mitochondrial dysfunction within the VCI context, focusing on both the origins and consequences of compromised mitochondrial health. It aims to lay a robust scientific groundwork for guiding the development and refinement of mitochondrial-targeted interventions for VCI.

Downregulation of Mitochondrial Fusion Protein Expression Affords Protection from Canonical Necroptosis in H9c2 Cardiomyoblasts

Necroptosis, a form of necrosis, and alterations in mitochondrial dynamics, a coordinated process of mitochondrial fission and fusion, have been implicated in the pathogenesis of cardiovascular diseases. This study aimed to determine the role of mitochondrial morphology in canonical necroptosis induced by a combination of TNFα and zVAD (TNF/zVAD) in H9c2 cells, rat cardiomyoblasts. Time-course analyses of mitochondrial morphology showed that mitochondria were initially shortened after the addition of TNF/zVAD and then their length was restored, and the proportion of cells with elongated mitochondria at 12 h was larger in TNF/zVAD-treated cells than in non-treated cells (16.3 ± 0.9% vs. 8.0 ± 1.2%). The knockdown of dynamin-related protein 1 (Drp1) and fission 1, fission promoters, and treatment with Mdivi-1, a Drp-1 inhibitor, had no effect on TNF/zVAD-induced necroptosis. In contrast, TNF/zVAD-induced necroptosis was attenuated by the knockdown of mitofusin 1/2 (Mfn1/2) and optic atrophy-1 (Opa1), proteins that are indispensable for mitochondrial fusion, and the attenuation of necroptosis was not canceled by treatment with Mdivi-1. The expression of TGFβ-activated kinase (TAK1), a negative regulator of RIP1 activity, was upregulated and the TNF/zVAD-induced RIP1-Ser166 phosphorylation, an index of RIP1 activity, was mitigated by the knockdown of Mfn1/2 or Opa1. Pharmacological TAK1 inhibition attenuated the protection afforded by Mfn1/2 and Opa1 knockdown. In conclusion, the inhibition of mitochondrial fusion increases TAK1 expression, leading to the attenuation of canonical necroptosis through the suppression of RIP1 activity.

An integral role of mitochondrial function in the pathophysiology of preeclampsia

Preeclampsia (PE) is associated with high maternal and perinatal morbidity and mortality. The development of effective treatment strategies remains a major challenge due to the limited understanding of the pathogenesis. In this review, we summarize the current understanding of PE research, focusing on the molecular basis of mitochondrial function in normal and PE placentas, and discuss perspectives on future research directions. Mitochondria integrate numerous physiological processes such as energy production, cellular redox homeostasis, mitochondrial dynamics, and mitophagy, a selective autophagic clearance of damaged or dysfunctional mitochondria. Normal placental mitochondria have evolved innovative survival strategies to cope with uncertain environments (e.g., hypoxia and nutrient starvation). Cytotrophoblasts, extravillous trophoblast cells, and syncytiotrophoblasts all have distinct mitochondrial morphology and function. Recent advances in molecular studies on the spatial and temporal changes in normal mitochondrial function are providing valuable insight into PE pathogenesis. In PE placentas, hypoxia-mediated mitochondrial fission may induce activation of mitophagy machinery, leading to increased mitochondrial fragmentation and placental tissue damage over time. Repair mechanisms in mitochondrial function restore placental function, but disruption of compensatory mechanisms can induce apoptotic death of trophoblast cells. Additionally, molecular markers associated with repair or compensatory mechanisms that may influence the development and progression of PE are beginning to be identified. However, contradictory results have been obtained regarding some of the molecules that control mitochondrial biogenesis, dynamics, and mitophagy in PE placentas. In conclusion, understanding how the mitochondrial morphology and function influence cell fate decisions of trophoblast cells is an important issue in normal as well as pathological placentation biology. Research focusing on mitochondrial function will become increasingly important for elucidating the pathogenesis and effective treatment strategies of PE.

BNIP3 as a new tool to promote healthy brain aging

The article "Neuronal induction of BNIP3-mediated mitophagy slows systemic aging in Drosophila" reveals BCL2-interacting protein 3 as a therapeutic target to counteract brain aging and prolong overall organismal health with age. In this spotlight, we consider the roles of BNIP3, a mitochondrial outer membrane protein, in the adult nervous system, including its induction of mitophagy and prevention of dysfunctional mitochondria in the aged brain. Implications for other tissue types to reduce the burden of aging are further considered.

Metabolic characterization of human sperm cells using the Seahorse metabolic flux analyzer

BACKGROUND

The concerning trend on male infertility global prevalence, together with the unexplainable causes in half of those cases, highlights that there are still aspects of this disease to be understood and solved. To address this issue, one should not only be aware of the limitations of the implemented diagnostic tools, but also understand the sperm cell in depth, structurally, biochemically, molecularly in order to develop reliable and ready-to-be new/improved diagnostic tools. In this sense, the sperm cells metabolism, highly related to its functionality, seems to be a promising aspect to explore. Though there is much information on the human sperm metabolism, there is still a lack of a quick integrated and comprehensive analysis that may be introduced with the potential to reveal innovative clinically relevant information.

OBJECTIVES

Find metabolic details on human sperm that can be accessed easily, in real time and using few cells, relying on the bivalent potential of the Seahorse flux analyzer (SFA).

RESULTS

We have obtained standard records on human sperm cells' oxygen consumption rate (OCR) and extracellular acidification rate (ECAR), that together with the metabolic metrics provided information on sperm cells' oxidative and glycolytic metabolism. Furthermore, a metabolic interindividual variation was observed.

DISCUSSION AND CONCLUSION

Although the comparison with other species or cell types is not linear and warrant further studies, the metabolic profile of human sperm cells seems to be similar to that of other species. Altogether our results corroborate the value of SFA for metabolic human sperm cell analysis, warranting new studies, and anticipating several applications in the male infertility field.

FOXO1 reduces STAT3 activation and causes impaired mitochondrial quality control in diabetic cardiomyopathy

AIMS

To investigate the role of FOXO1 in STAT3 activation and mitochondrial quality control in the diabetic heart.

METHODS

Type 1 diabetes mellitus (T1DM) was induced in rats by a single intraperitoneal injection of 60 mg · kg-1 streptozotocin (STZ), while type 2 diabetes mellitus (T2DM) was induced in rats with a high-fat diet through intraperitoneal injection of 35 mg · kg-1 STZ. Primary neonatal mouse cardiomyocytes and H9c2 cells were exposed to low glucose (5.5 mM) or high glucose (HG; 30 mM) with or without treatment with the FOXO1 inhibitor AS1842856 (1 μM) for 24 hours. In addition, the diabetic db/db mice (aged 8 weeks) and sex- and age-matched non-diabetic db/+ mice were treated with vehicle or AS1842856 by oral gavage for 15 days at a dose of 5 mg · kg-1  · d-1 .

RESULTS

Rats with T1DM or T2DM had excessive cardiac FOXO1 activation, accompanied by decreased STAT3 activation. Immunofluorescence and immunoprecipitation analysis showed colocalization and association of FOXO1 and STAT3 under basal conditions in isolated cardiomyocytes. Selective inhibition of FOXO1 activation by AS1842856 or FOXO1 siRNA transfection improved STAT3 activation, mitophagy and mitochondrial fusion, and decreased mitochondrial fission in isolated cardiomyocytes exposed to HG. Transfection with STAT3 siRNA further reduced mitophagy, mitochondrial fusion and increased mitochondrial fission in HG-treated cardiomyocytes. AS1842856 alleviated cardiac dysfunction, pathological damage and improved STAT3 activation, mitophagy and mitochondrial dynamics in diabetic db/db mice. Additionally, AS1842856 improved mitochondrial function indicated by increased mitochondrial membrane potential and adenosine triphosphate production and decreased mitochondrial reactive oxygen species production in isolated cardiomyocytes exposed to HG.

CONCLUSIONS

Excessive FOXO1 activation during diabetes reduces STAT3 activation, with subsequent impairment of mitochondrial quality, ultimately promoting the development of diabetic cardiomyopathy.

Vutiglabridin Alleviates Cellular Senescence with Metabolic Regulation and Circadian Clock in Human Dermal Fibroblasts

The process of cellular senescence, which is characterized by stable cell cycle arrest, is strongly associated with dysfunctional cellular metabolism and circadian rhythmicity, both of which are reported to result from and also be causal to cellular senescence. As a result, modifying any of them-senescence, metabolism, or the circadian clock-may affect all three simultaneously. Obesity accelerates aging by disrupting the homeostasis of reactive oxygen species (ROS) via an increased mitochondrial burden of fatty acid oxidation. As a result, if senescence, metabolism, and circadian rhythm are all linked, anti-obesity treatments may improve metabolic regulation while also alleviating senescence and circadian rhythm. Vutiglabridin is a small molecule in clinical trials that improves obesity by enhancing mitochondrial function. We found that chronic treatment of senescent primary human dermal fibroblasts (HDFs) with vutiglabridin alleviates all investigated markers of cellular senescence (SA-β-gal, CDKN1A, CDKN2A) and dysfunctional cellular circadian rhythm (BMAL1) while remarkably preventing the alterations of mitochondrial function and structure that occur during the process of cellular senescence. Our results demonstrate the significant senescence-alleviating effects of vutiglabridin, specifically with the restoration of cellular circadian rhythmicity and metabolic regulation. These data support the potential development of vutiglabridin against aging-associated diseases and corroborate the intricate link between cellular senescence, metabolism, and the circadian clock.

Hexavalent-Chromium-Induced Disruption of Mitochondrial Dynamics and Apoptosis in the Liver via the AMPK-PGC-1α Pathway in Ducks

Hexavalent chromium (Cr(VI)) is a hazardous substance that poses significant risks to environmental ecosystems and animal organisms. However, the specific consequences of Cr(VI) exposure in terms of liver damage remain incompletely understood. This study aims to elucidate the mechanism by which Cr(VI) disrupts mitochondrial dynamics, leading to hepatic injury in ducks. Forty-eight healthy 8-day-old ducks were divided into four groups and subjected to diets containing varying doses of Cr(VI) (0, 9.28, 46.4, and 232 mg/kg) for 49 days. Our results demonstrated that Cr(VI) exposure resulted in disarranged liver lobular vacuolation, along with increasing the serum levels of ALT, AST, and AKP in a dose-dependent manner, which indicated liver damage. Furthermore, Cr(VI) exposure induced oxidative stress by reducing the activities of T-SOD, SOD, GSH-Px, GSH, and CAT, while increasing the contents of MDA and H2O2. Moreover, Cr(VI) exposure downregulated the activities of CS and MDH, resulting in energy disturbance, as evidenced by the reduced AMPK/p-AMPK ratio and PGC-1α protein expression. Additionally, Cr(VI) exposure disrupted mitochondrial dynamics through decreased expression of OPA1, Mfn1, and Mfn2 and increased expression of Drp-1, Fis1, and MFF proteins. This disruption ultimately triggered mitochondria-mediated apoptosis, as evidenced by elevated levels of caspase-3, Cyt C, and Bax, along with decreased expression of Bcl-2 and the Bcl-2/Bax ratio, at both the protein and mRNA levels. In summary, this study highlights that Cr(VI) exposure induces oxidative stress, inhibits the AMPK-PGC-1α pathway, disrupts mitochondrial dynamics, and triggers liver cell apoptosis in ducks.

Systems genetics analysis of human body fat distribution genes identifies Wnt signaling and mitochondrial activity in adipocytes

BACKGROUND

Excess fat in the abdomen is a sexually dimorphic risk factor for cardio-metabolic disease. The relative storage between abdominal and lower-body subcutaneous adipose tissue depots is approximated by the waist-to-hip ratio adjusted for body mass index (WHRadjBMI). Genome-wide association studies (GWAS) identified 346 loci near 495 genes associated with WHRadjBMI. Most of these genes have unknown roles in fat distribution, but many are expressed and putatively act in adipose tissue. We aimed to identify novel sex- and depot-specific drivers of WHRadjBMI using a systems genetics approach.

METHODS

We used two independent cohorts of adipose tissue gene expression with 362 - 444 males and 147 - 219 females, primarily of European ancestry. We constructed sex- and depot- specific Bayesian networks to model the gene-gene interactions from 8,492 adipose tissue genes. Key driver analysis identified genes that, in silico and putatively in vitro, regulate many others, including the 495 WHRadjBMI GWAS genes. Key driver gene function was determined by perturbing their expression in human subcutaneous pre-adipocytes using lenti-virus or siRNA.

RESULTS

51 - 119 key drivers in each network were replicated in both cohorts. We used single-cell expression data to select replicated key drivers expressed in adipocyte precursors and mature adipocytes, prioritized genes which have not been previously studied in adipose tissue, and used public human and mouse data to nominate 53 novel key driver genes (10 - 21 from each network) that may regulate fat distribution by altering adipocyte function. In other cell types, 23 of these genes are found in crucial adipocyte pathways: Wnt signaling or mitochondrial function. We selected seven genes whose expression is highly correlated with WHRadjBMI to further study their effects on adipogenesis/Wnt signaling (ANAPC2, PSME3, RSPO1, TYRO3) or mitochondrial function (C1QTNF3, MIGA1, PSME3, UBR1).Adipogenesis was inhibited in cells overexpressing ANAPC2 and RSPO1 compared to controls. RSPO1 results are consistent with a positive correlation between gene expression in the subcutaneous depot and WHRadjBMI, therefore lower relative storage in the subcutaneous depot. RSPO1 inhibited adipogenesis by increasing β-catenin activation and Wnt-related transcription, thus repressing PPARG and CEBPA. PSME3 overexpression led to more adipogenesis than controls. In differentiated adipocytes, MIGA1 and UBR1 downregulation led to mitochondrial dysfunction, with lower oxygen consumption than controls; MIGA1 knockdown also lowered UCP1 expression.

SUMMARY

ANAPC2, MIGA1, PSME3, RSPO1, and UBR1 affect adipocyte function and may drive body fat distribution.

Senomorphic effect of diphenyleneiodonium through AMPK/MFF/DRP1 mediated mitochondrial fission

With an aging population and the numerous health impacts associated with old age, the identification of anti-aging drugs has become an important new research direction. Although mitochondria have been recognized to affect aging, anti-aging drugs specifically targeting the mitochondria are less well characterized. In this study, diphenyleneiodonium (DPI) was identified as a potential senomorphic drug that functions by promoting mitochondrial fission. DPI significantly reduced the number of senescence-associated β-galactosidase (SA-β-gal) positive cells and increased the number of proliferating Ki-67 positive cells in BrdU or irradiation stress-induced senescent NIH3T3 cells or IMR90 cells and mouse embryonic fibroblasts (MEFs) replicative senescent cells. Cell cycle arrest genes and senescence-associated secretory phenotype (SASP) factors were downregulated with DPI treatment. In addition, the oxygen consumption rate (OCR) of mitochondrial respiration showed that DPI significantly reduced senescence-associated hyper OCR. Mechanistically, DPI promoted mitochondrial fission by enhancing AMPK/MFF phosphorylation and DRP1 mitochondrial translocation. Inhibition of DRP1 by Mdivi-1 abolished DPI-induced mitochondrial fission and the anti-senescence phenotype. Importantly, Eighty-eight-week-old mice treated with DPI had significantly reduced numbers of SA-β-gal positive cells and reduced expression of cell cycle arrest genes and SASP factors in their livers and kidneys. Pathological and functional assays showed DPI treatment not only reduced liver fibrosis and immune cell infiltration but also improved aged-related physical impairments in aged mice. Taken together, our study identified a potential anti-aging compound that exerts its effects through modulation of mitochondrial morphology.

Using mass spectrometry imaging to visualize age-related subcellular disruption

Metabolic homeostasis balances the production and consumption of energetic molecules to maintain active, healthy cells. Cellular stress, which disrupts metabolism and leads to the loss of cellular homeostasis, is important in age-related diseases. We focus here on the role of organelle dysfunction in age-related diseases, including the roles of energy deficiencies, mitochondrial dysfunction, endoplasmic reticulum (ER) stress, changes in metabolic flux in aging (e.g., Ca2+ and nicotinamide adenine dinucleotide), and alterations in the endoplasmic reticulum-mitochondria contact sites that regulate the trafficking of metabolites. Tools for single-cell resolution of metabolite pools and metabolic flux in animal models of aging and age-related diseases are urgently needed. High-resolution mass spectrometry imaging (MSI) provides a revolutionary approach for capturing the metabolic states of individual cells and cellular interactions without the dissociation of tissues. mass spectrometry imaging can be a powerful tool to elucidate the role of stress-induced cellular dysfunction in aging.

CPNE1 regulates myogenesis through the PERK-eIF2α pathway mediated by endoplasmic reticulum stress

Sarcopenia is characterized by a progressive reduction in muscle mass or muscle physiological function associated with aging, but the relevant molecular mechanisms are not clear. Here, we identify the role of the myogenesis modifier CPNE1 in sarcopenia. CPNE1 is upregulated in aged skeletal muscles and young skeletal muscle satellite cells with palmitate-induced atrophy. The overexpression of CPNE1 hinders proliferation and differentiation and increases muscle atrophy characteristics in young skeletal muscle-derived satellite cells. In addition, CPNE1 overexpression disrupts the balance of mitochondrial fusion and division and causes endoplasmic reticulum stress. We found that the effects of CPNE1 on mitochondrial function are dependent on the PERK/eIF2α/ATF4 pathway. The overexpression of CPNE1 in young muscles alters membrane lipid composition, reduces skeletal muscle fibrosis regeneration, and exercise capacity in mice. These effects were reversed by PERK inhibitor GSK2606414. Moreover, immunoprecipitation indicates that CPNE1 overexpression greatly increased the acetylation of PERK. Therefore, CPNE1 is an important modifier that drives mitochondrial homeostasis to regulate myogenic cell proliferation and differentiation via the PERK-eIF2α pathway, which could be a valuable target for age-related sarcopenia.

Minoxidil Regulates Aging-Like Phenotypes in Rat Cortical Astrocytes In Vitro

Mainly due to the slanted focus on the mechanism and regulation of neuronal aging, research on astrocyte aging and its modulation during brain aging is scarce. In this study, we established aged astrocyte culture model by long-term culturing. Cellular senescence was confirmed through SA-β-gal staining as well as through the examination of morphological, molecular, and functional markers. RNA sequencing and functional analysis of astrocytes were performed to further investigate the detailed characteristics of the aged astrocyte model. Along with aged phenotypes, decreased astrocytic proliferation, migration, mitochondrial energetic function and support for neuronal survival and differentiation has been observed in aged astrocytes. In addition, increased expression of cytokines and chemokine-related factors including plasminogen activator inhibitor -1 (PAI-1) was observed in aged astrocytes. Using the RNA sequencing results, we searched potential drugs that can normalize the dysregulated gene expression pattern observed in long-term cultured aged astrocytes. Among several candidates, minoxidil, a pyrimidine-derived anti-hypertensive and anti-pattern hair loss drug, normalized the increased number of SA-β-gal positive cells and nuclear size in aged astrocytes. In addition, minoxidil restored up-regulated activity of PAI-1 and increased mitochondrial superoxide production in aged astrocytes. We concluded that long term culture of astrocytes can be used as a reliable model for the study of astrocyte senescence and minoxidil can be a plausible candidate for the regulation of brain aging.

IKCa channels control breast cancer metabolism including AMPK-driven autophagy

Ca²⁺-activated K⁺ channels of intermediate conductance (IK) are frequently overexpressed in breast cancer (BC) cells, while IK channel depletion reduces BC cell proliferation and tumorigenesis. This raises the question, of whether and mechanistically how IK activity interferes with the metabolic activity and energy consumption rates, which are fundamental for rapidly growing cells. Using BC cells obtained from MMTV-PyMT tumor-bearing mice, we show that both, glycolysis and mitochondrial ATP-production are reduced in cells derived from IK-deficient breast tumors. Loss of IK altered the sub-/cellular K⁺- and Ca²⁺- homeostasis and mitochondrial membrane potential, ultimately resulting in reduced ATP-production and metabolic activity. Consequently, we find that BC cells lacking IK upregulate AMP-activated protein kinase activity to induce autophagy compensating the glycolytic and mitochondrial energy shortage. Our results emphasize that IK by modulating cellular Ca²⁺- and K⁺-dynamics contributes to the remodeling of metabolic pathways in cancer. Thus, targeting IK channel might disturb the metabolic activity of BC cells and reduce malignancy.

APOL1 variant-expressing endothelial cells exhibit autophagic dysfunction and mitochondrial stress

Polymorphisms in the Apolipoprotein L1 (APOL1) gene are common in ancestrally African populations, and associate with kidney injury and cardiovascular disease. These risk variants (RV) provide an advantage in resisting Trypanosoma brucei, the causal agent of African trypanosomiasis, and are largely absent from non-African genomes. Clinical associations between the APOL1 high risk genotype (HRG) and disease are stronger in those with comorbid infectious or immune disease. To understand the interaction between cytokine exposure and APOL1 cytotoxicity, we established human umbilical vein endothelial cell (HUVEC) cultures representing each APOL1 genotype. Untreated HUVECs were compared to IFNɣ-exposed; and APOL1 expression, mitochondrial function, lysosome integrity, and autophagic flux were measured. IFNɣ increased median APOL1 expression across all genotypes 22.1 (8.3 to 29.8) fold (p=0.02). Compared to zero risk variant-carrying HUVECs (0RV), HUVECs carrying 2 risk variant copies (2RV) showed both depressed baseline and maximum mitochondrial oxygen consumption (p<0.01), and impaired mitochondrial networking on MitoTracker assays. These cells also demonstrated a contracted lysosomal compartment, and an accumulation of autophagosomes suggesting a defect in autophagic flux. Upon blocking autophagy with non-selective lysosome inhibitor, hydroxychloroquine, autophagosome accumulation between 0RV HUVECs and untreated 2RV HUVECs was similar, implicating lysosomal dysfunction in the HRG-associated autophagy defect. Compared to 0RV and 2RV HUVECs, HUVECs carrying 1 risk variant copy (1RV) demonstrated intermediate mitochondrial respiration and autophagic flux phenotypes, which were exacerbated with IFNɣ exposure. Taken together, our data reveal that IFNɣ induces APOL1 expression, and that each additional RV associates with mitochondrial dysfunction and autophagy inhibition. IFNɣ amplifies this phenotype even in 1RV HUVECs, representing the first description of APOL1 pathobiology in variant heterozygous cell cultures.

Carnosol Reduced Pathogenic Protein Aggregation and Cognitive Impairment in Neurodegenerative Diseases Models via Improving Proteostasis and Ameliorating Mitochondrial Disorders

Neurodegenerative diseases (NDs) such as Alzheimer's disease, Parkinson's disease, and Huntington's disease are incurable diseases with progressive loss of neural function and require urgent development of effective treatments. Carnosol (CL) reportedly has a pharmacological effect in the prevention of dementia. Nevertheless, the mechanisms of CL's neuroprotection are not entirely clear. The present study aimed to investigate the effects and mechanisms of CL-mediated neuroprotection through Caenorhabditis elegans models. First, CL restored ND protein homeostasis via inhibiting the IIS pathway, regulating MAPK signaling, and simultaneously activating molecular chaperone, thus inhibiting amyloid peptide (Aβ), polyglutamine (polyQ), and α-synuclein (α-syn) deposition and reducing protein disruption-mediated behavioral and cognitive impairments as well as neuronal damages. Furthermore, CL could repair mitochondrial structural damage via improving the mitochondrial membrane protein function and mitochondrial structural homeostasis and improve mitochondrial functional defects via increasing adenosine triphosphate contents, mitochondrial membrane potential, and reactive oxygen species levels, suggesting that CL could improve the ubiquitous mitochondrial defects in NDs. More importantly, we found that CL activated mitochondrial kinetic homeostasis related genes to improve the mitochondrial homeostasis and dysfunction in NDs. Meanwhile, CL up-regulated unc-17, cho-1, and cha-1 genes to alleviate Aβ-mediated cholinergic neurological disorders and activated Notch signaling and the Wnt pathway to diminish polyQ- and α-syn-induced ASH neurons as well as dopaminergic neuron damages. Overall, our study clarified the beneficial anti-ND neuroprotective effects of CL in different aspects and provided new insights into developing CL into products with preventive and therapeutic effects on NDs.

Cellular Bioenergetics: Experimental Evidence for Alcohol-induced Adaptations

At-risk alcohol use is associated with multisystemic effects and end-organ injury, and significantly contributes to global health burden. Several alcohol-mediated mechanisms have been identified, with bioenergetic maladaptation gaining credence as an underlying pathophysiological mechanism contributing to cellular injury. This evidence-based review focuses on the current knowledge of alcohol-induced bioenergetic adaptations in metabolically active tissues: liver, cardiac and skeletal muscle, pancreas, and brain. Alcohol metabolism itself significantly interferes with bioenergetic pathways in tissues, particularly the liver. Alcohol decreases states of respiration in the electron transport chain, and activity and expression of respiratory complexes, with a net effect to decrease ATP content. In addition, alcohol dysregulates major metabolic pathways, including glycolysis, the tricarboxylic acid cycle, and fatty acid oxidation. These bioenergetic alterations are influenced by alcohol-mediated changes in mitochondrial morphology, biogenesis, and dynamics. The review highlights similarities and differences in bioenergetic adaptations according to tissue type, pattern of (acute vs. chronic) alcohol use, and energy substrate availability. The compromised bioenergetics synergizes with other critical pathophysiological mechanisms, including increased oxidative stress and accelerates cellular dysfunction, promoting senescence, programmed cell death, and end-organ injury.

Oxidative stress-mediated mitochondrial fission promotes hepatic stellate cell activation via stimulating oxidative phosphorylation

Previous studies have demonstrated dysregulated mitochondrial dynamics in fibrotic livers and hepatocytes. Little is currently known about how mitochondrial dynamics are involved, nor is it clear how mitochondrial dynamics participate in hepatic stellate cell (HSC) activation. In the present study, we investigated the role of mitochondrial dynamics in HSC activation and the underlying mechanisms. We verified that mitochondrial fission was enhanced in human and mouse fibrotic livers and active HSCs. Moreover, increased mitochondrial fission driven by fis1 overexpression could promote HSC activation. Inhibiting mitochondrial fission using mitochondrial fission inhibitor-1 (Mdivi-1) could inhibit activation and induce apoptosis of active HSCs, indicating that increased mitochondrial fission is essential for HSC activation. Mdivi-1 treatment also induced apoptosis in active HSCs in vivo and thus ameliorated CCl₄-induced liver fibrosis. We also found that oxidative phosphorylation (OxPhos) was increased in active HSCs, and OxPhos inhibitors inhibited activation and induced apoptosis in active HSCs. Moreover, increasing mitochondrial fission upregulated OxPhos, while inhibiting mitochondrial fission downregulated OxPhos, suggesting that mitochondrial fission stimulates OxPhos during HSC activation. Next, we found that inhibition of oxidative stress using mitoquinone mesylate (mitoQ) and Tempol inhibited mitochondrial fission and OxPhos and induced apoptosis in active HSCs, suggesting that oxidative stress contributes to excessive mitochondrial fission during HSC activation. In conclusion, our study revealed that oxidative stress contributes to enhanced mitochondrial fission, which triggers OxPhos during HSC activation. Importantly, inhibiting mitochondrial fission has huge prospects for alleviating liver fibrosis by eliminating active HSCs.

Impact of MnTBAP and Baricitinib Treatment on Hutchinson–Gilford Progeria Fibroblasts

Hutchinson–Gilford progeria syndrome (HGPS) is a rare premature aging disease. It is caused by a mutation in the LMNA gene, which results in a 50-amino-acid truncation of prelamin A. The resultant truncated prelamin A (progerin) lacks the cleavage site for the zinc-metallopeptidase ZMPSTE24. Progerin is permanently farnesylated, carboxymethylated, and strongly anchored to the nuclear envelope. This leads to abnormalities, such as altered nuclear shape, mitochondrial dysfunction, and inflammation. HGPS patients display symptoms of physiological aging, including atherosclerosis, alopecia, lipodystrophy, and arthritis. Currently, no cure for HGPS exists. Here we focus on a drug combination consisting of the superoxide dismutase mimetic MnTBAP and JAK1/2 inhibitor baricitinib (Bar) to restore phenotypic alterations in HGPS fibroblasts. Treating HGPS fibroblasts with the MnTBAP/Bar combination improved mitochondrial functions and sustained Bar’s positive effects on reducing progerin and pro-inflammatory factor levels. Collectively, MnTBAP/Bar combination treatment ameliorates the aberrant phenotype of HGPS fibroblasts and is a potential treatment strategy for patients with HGPS.

Mitochondrial Elongation and OPA1 Play Crucial Roles during the Stemness Acquisition Process in Pancreatic Ductal Adenocarcinoma

Simple Summary

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal neoplasia and the currently used treatments are not effective in a wide range of patients. Presently, the evidence points out that cancer stem cells (CSCs) are key players during tumor development, metastasis, chemoresistance, and tumor relapse. The study of the metabolism of CSCs, specifically the mitochondrial alterations, could pave the way to the discovery of new therapeutical targets. In this study, we show that during progressive de-differentiation, pancreatic CSCs undergo changes in mitochondrial mass, dynamics, and function. Interestingly, the silencing of OPA1, a protein involved in mitochondrial fusion, significantly inhibits the formation of CSCs. These results reveal new insight into mitochondria and stemness acquisition that could be useful for the design of novel potential therapies in PDAC.

Abstract

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer with an overall 5-year survival rate of less than 9%. The high aggressiveness of PDAC is linked to the presence of a subpopulation of cancer cells with a greater tumorigenic capacity, generically called cancer stem cells (CSCs). CSCs present a heterogeneous metabolic profile that might be supported by an adaptation of mitochondrial function; however, the role of this organelle in the development and maintenance of CSCs remains controversial. To determine the role of mitochondria in CSCs over longer periods, which may reflect more accurately their quiescent state, we studied the mitochondrial physiology in CSCs at short-, medium-, and long-term culture periods. We found that CSCs show a significant increase in mitochondrial mass, more mitochondrial fusion, and higher mRNA expression of genes involved in mitochondrial biogenesis than parental cells. These changes are accompanied by a regulation of the activities of OXPHOS complexes II and IV. Furthermore, the protein OPA1, which is involved in mitochondrial dynamics, is overexpressed in CSCs and modulates the tumorsphere formation. Our findings indicate that CSCs undergo mitochondrial remodeling during the stemness acquisition process, which could be exploited as a promising therapeutic target against pancreatic CSCs.

Mitochondrial fusion regulates proliferation and differentiation in the type II neuroblast lineage in Drosophila

Optimal mitochondrial function determined by mitochondrial dynamics, morphology and activity is coupled to stem cell differentiation and organism development. However, the mechanisms of interaction of signaling pathways with mitochondrial morphology and activity are not completely understood. We assessed the role of mitochondrial fusion and fission in the differentiation of neural stem cells called neuroblasts (NB) in the Drosophila brain. Depleting mitochondrial inner membrane fusion protein Opa1 and mitochondrial outer membrane fusion protein Marf in the Drosophila type II NB lineage led to mitochondrial fragmentation and loss of activity. Opa1 and Marf depletion did not affect the numbers of type II NBs but led to a decrease in differentiated progeny. Opa1 depletion decreased the mature intermediate precursor cells (INPs), ganglion mother cells (GMCs) and neurons by the decreased proliferation of the type II NBs and mature INPs. Marf depletion led to a decrease in neurons by a depletion of proliferation of GMCs. On the contrary, loss of mitochondrial fission protein Drp1 led to mitochondrial clustering but did not show defects in differentiation. Depletion of Drp1 along with Opa1 or Marf also led to mitochondrial clustering and suppressed the loss of mitochondrial activity and defects in proliferation and differentiation in the type II NB lineage. Opa1 depletion led to decreased Notch signaling in the type II NB lineage. Further, Notch signaling depletion via the canonical pathway showed mitochondrial fragmentation and loss of differentiation similar to Opa1 depletion. An increase in Notch signaling showed mitochondrial clustering similar to Drp1 mutants. Further, Drp1 mutant overexpression combined with Notch depletion showed mitochondrial fusion and drove differentiation in the lineage, suggesting that fused mitochondria can influence differentiation in the type II NB lineage. Our results implicate crosstalk between proliferation, Notch signaling, mitochondrial activity and fusion as an essential step in differentiation in the type II NB lineage.

Mitochondrial morphology and function are coupled to stem cell differentiation and organism development. It is of interest to examine the mechanisms of interaction of mitochondrial dynamics with signaling pathways during stem cell differentiation. We have assessed the role of mitochondrial fusion and fission in the differentiation of neural stem cells called neuroblasts (NB) in the Drosophila brain. Depleting mitochondrial fusion proteins Opa1 and Marf led to mitochondrial fragmentation, loss of mitochondrial activity and proliferation, thereby causing a decrease in the numbers of differentiated cells in each type II NB lineage. Mutants in mitochondrial fission protein Drp1 led to mitochondrial fusion but did not cause any differentiation defects. Decreased Notch signaling by the canonical pathway led to mitochondrial fragmentation and a decrease in differentiated cells in each type II NB lineage. Expression of Drp1 mutants in type II NB lineages depleted of Opa1 and Marf suppressed their proliferation and differentiation defects. Expression of Drp1 mutant in type II NB lineages depleted of Notch also led to a rescue of differentiated progeny in each lineage. Our results implicate crosstalk between Notch signaling, mitochondrial activity and fusion as important steps for proliferation and differentiation in the type II NB lineage.

Studies on Regulation of Global Protein Profile and Cellular Bioenergetics of Differentiating SH-SY5Y Cells

The SH-SY5Y cells differentiated by sequential exposure of retinoic acid (RA) and brain-derived neurotrophic growth factor (BDNF) are a well-employed cellular model for studying the mechanistic aspects of neural development and neurodegeneration. Earlier studies from our lab have identified dramatic upregulation (77 miRNAs) and downregulation (17 miRNAs) of miRNAs in SH-SY5Y cells differentiated with successive exposure of RA + BDNF and demonstrated the essential role of increased levels of P53 proteins in coping with the differentiation-induced changes in protein levels. In continuation to our earlier studies, we have performed unbiased LC-MS/MS global protein profiling of naïve and differentiated SH-SY5Y cells and analyzed the identified proteins in reference to miRNAs identified in our earlier studies to identify the cellular events regulated by both identified miRNAs and proteins. Analysis of LC-MS/MS data has shown a significant increase and decrease in levels of 215 and 163 proteins, respectively, in differentiated SH-SY5Y cells. Integrative analysis of miRNA identified in our previous studies and protein identified in the present study is carried out to discover novel miRNA-protein regulatory modules to elucidate miRNA-protein regulatory relationships of differentiating neurons. In silico network analysis of miRNAs and proteins deregulated upon SH-SY5Y differentiation identified cell cycle, synapse formation, axonogenesis, differentiation, neuron projection, and neurotransmission, as the topmost involved pathways. Further, measuring mitochondrial dynamics and cellular bioenergetics using qPCR and Seahorse XFp Flux Analyzer, respectively, showed that differentiated cells possess increased mitochondrial dynamics and OCR relative to undifferentiated cells. In summary, our studies have identified a novel set of proteins deregulated during neuronal differentiation and establish the role of miRNAs identified in earlier studies in the regulation of proteins identified by LC-MS/MS-based global profiling of differentiating neurons, which will help in future studies related to neural development and neurodegeneration.

Cellular senescence links mitochondria-ER contacts and aging

Membrane contact sites emerged in the last decade as key players in the integration, regulation and transmission of many signals within cells, with critical impact in multiple pathophysiological contexts. Numerous studies accordingly point to a role for mitochondria-endoplasmic reticulum contacts (MERCs) in modulating aging. Nonetheless, the driving cellular mechanisms behind this role remain unclear. Recent evidence unravelled that MERCs regulate cellular senescence, a state of permanent proliferation arrest associated with a pro-inflammatory secretome, which could mediate MERC impact on aging. Here we discuss this idea in light of recent advances supporting an interplay between MERCs, cellular senescence and aging.

Myocardial Ischemia-Reperfusion Injury: Therapeutics from a Mitochondria-Centric Perspective

Coronary arterial disease is the most common cardiovascular disease. Myocardial ischemia-reperfusion injury caused by the initial interruption of organ blood flow and subsequent restoration of organ blood flow is an important clinical problem with various cardiac reperfusion strategies after acute myocardial infarction. Even though blood flow recovery is necessary for oxygen and nutrient supply, reperfusion causes pathological sequelae that lead to the aggravation of ischemic injury. At present, although it is known that injury will occur after reperfusion, clinical treatment always focuses on immediate recanalization. Mitochondrial fusion, fission, biogenesis, autophagy, and their intricate interaction constitute an effective mitochondrial quality control system. The mitochondrial quality control system plays an important role in maintaining cell homeostasis and cell survival. The removal of damaged, aging, and dysfunctional mitochondria is mediated by mitochondrial autophagy. With the help of appropriate changes in mitochondrial dynamics, new mitochondria are produced through mitochondrial biogenesis to meet the energy needs of cells. Mitochondrial dysfunction and the resulting oxidative stress have been associated with the pathogenesis of ischemia/reperfusion (I/R) injury, which play a crucial role in the pathophysiological process of myocardial injury. This review aimed at elucidating the mitochondrial quality control system and establishing the possibility of using mitochondria as a potential therapeutic target in the treatment of I/R injuries.

Mitochondrial fusion mediated by mitofusin 1 regulates macrophage mycobactericidal activity by enhancing autophagy

Mitochondria as a highly dynamic organelle continuously changes morphology and position during its life cycle. Mitochondrial dynamics including fission and fusion play a critical role in maintaining functional mitochondria for ATP production, which is directly linked to host defense against Mtb infection. However, how macrophages regulate mitochondrial dynamics during Mycobacterium tuberculosis (Mtb) infection remains elusive. In this study, we found that Mtb infection induced mitochondrial fusion through enhancing the expression of mitofusin 1 (MFN1), which resulted in increased ATP production. Silencing MFN1 inhibited mitochondrial fusion and subsequently reduced ATP production, which, in turn, severely impaired macrophages mycobactericidal activity by inhibiting autophagy. Impairment of mycobactericidal activity and autophagy was replicated using oligomycin, an inhibitor of ATP synthase. In summary, our study revealed MFN1-mediated mitochondrial fusion is essential for macrophages mycobactericidal activity through the regulation of ATP dependent autophagy. MFN1-mediated metabolism pathway might be targets for development of host direct therapy (HDT) strategy against TB.

Metformin Protects against Radiation-Induced Acute Effects by Limiting Senescence of Bronchial-Epithelial Cells

Radiation-induced damage to normal lung parenchyma remains a dose-limiting factor in thorax-associated radiotherapy (RT). Severe early and late complications with lungs can increase the risk of morbidity in cancer patients after RT. Herein, senescence of lung epithelial cells following RT-induced cellular stress, or more precisely the respective altered secretory profile, the senescence-associated secretory phenotype (SASP), was suggested as a central process for the initiation and progression of pneumonitis and pulmonary fibrosis. We previously reported that abrogation of certain aspects of the secretome of senescent lung cells, in particular, signaling inhibition of the SASP-factor Ccl2/Mcp1 mediated radioprotection especially by limiting endothelial dysfunction. Here, we investigated the therapeutic potential of a combined metformin treatment to protect normal lung tissue from RT-induced senescence and associated lung injury using a preclinical mouse model of radiation-induced pneumopathy. Metformin treatment efficiently limited RT-induced senescence and SASP expression levels, thereby limiting vascular dysfunctions, namely increased vascular permeability associated with increased extravasation of circulating immune and tumor cells early after irradiation (acute effects). Complementary in vitro studies using normal lung epithelial cell lines confirmed the senescence-limiting effect of metformin following RT finally resulting in radioprotection, while fostering RT-induced cellular stress of cultured malignant epithelial cells accounting for radiosensitization. The radioprotective action of metformin for normal lung tissue without simultaneous protection or preferable radiosensitization of tumor tissue might increase tumor control probabilities and survival because higher radiation doses could be used.

Aclonifen causes developmental abnormalities in zebrafish embryos through mitochondrial dysfunction and oxidative stress

The herbicide aclonifen is commonly used in agriculture. Aclonifen is toxic to experimental animals, causing developmental abnormalities, decreased energy production for survival, and impaired organogenesis. However, no studies have reported the functional defects and toxicity caused by aclonifen in embryonic development. We hypothesized that the mechanism underlying the toxicity of several herbicides in various organisms involves mitochondrial dysfunction, which subsequently promotes genotoxicity, cytotoxicity, and acute organotoxicity. In the present study, we demonstrated that mitochondrial dysfunction during development results in decreased body length, delayed yolk sac absorption, malformed spinal cord, disrupted brain and eye formation, and the activation of apoptosis in zebrafish embryos. Aclonifen induced oxidative stress by elevating the level of reactive oxygen species, causing mitochondrial damage. Likewise, impaired embryonic vascularization can promote cardiovascular disorders. In this study, we characterized the toxicity of aclonifen in a non-target organism. These findings increase our understanding of the toxicological effects of herbicides in unexpected environments.

Mitofusin-2: A New Mediator of Pathological Cell Proliferation

Cell proliferation is an important cellular process for physiological tissue homeostasis and remodeling. The mechanisms of cell proliferation in response to pathological stresses are not fully understood. Mitochondria are highly dynamic organelles whose shape, number, and biological functions are modulated by mitochondrial dynamics, including fusion and fission. Mitofusin-2 (Mfn-2) is an essential GTPase-related mitochondrial dynamics protein for maintaining mitochondrial network and bioenergetics. A growing body of evidence indicates that Mfn-2 has a potential role in regulating cell proliferation in various cell types. Here we review these new functions of Mfn-2, highlighting its crucial role in several signaling pathways during the process of pathological cell proliferation. We conclude that Mfn-2 could be a new mediator of pathological cell proliferation and a potential therapeutic target.

N-alkyl triphenylvinylpyridinium conjugated dihydroartemisinin perturbs mitochondrial functions resulting in enhanced cancer versus normal cell toxicity

Dihydroartemisinin (DHA) is an FDA-approved antimalarial drug that has been repurposed for cancer therapy because of its preferential antiproliferative effects on cancer versus normal cells. Mitochondria represent an attractive target for cancer therapy based on their regulatory role in proliferation and cell death. This study investigates whether DHA conjugated to innately fluorescent N-alkyl triphenylvinylpyridinium (TPVP) perturbs mitochondrial functions resulting in a differential toxicity of cancer versus normal cells. TPVP-DHA treatments resulted in a dose-dependent toxicity of human melanoma and pancreatic cancer cells, whereas normal human fibroblasts were resistant to this treatment. TPVP-DHA treatments resulted in a G₁-delay of the cancer cell cycle, which was also associated with a significant inhibition of the mTOR-metabolic and ERK1/2-proliferative signaling pathways. TPVP-DHA treatments perturbed mitochondrial functions, which correlated with increases in mitochondrial fission. In summary, TPVP mediated mitochondrial targeting of DHA enhanced cancer cell toxicity by perturbing mitochondrial functions and morphology.

Bioenergetic analysis of aged-phenotype skin in a rare syndromic cutis laxa

BACKGROUND

Skin aging is an inevitable phenomenon characterized by wrinkled skin and loss of elasticity. To date, several studies have been performed on skin aging to discover the underlying mechanisms and improve efficient preventive strategies and anti-aging therapeutics.

AIMS

Here, we aimed to investigate the modifications of oxidative phosphorylation and glycolysis which are the critical determinants of aging in aged-phenotype skin.

METHODS

Due to the complexity of the skin aging process, we performed bioenergetic measurements on aged-phenotype fibroblasts from an inherited cutis laxa syndrome which remarkably presents clinical features of normal aged skin. Bioenergetic analysis was performed on cutis laxa samples (n = 3) and healthy samples (n = 3) using Seahorse XFe24 Analyzer. We also compared the sensitivity of cultured aged-phenotype fibroblasts to normal cells in glucose withdrawal.

RESULTS

Our results show a significant increase in oxidative phosphorylation parameters but not glycolysis in the patient fibroblast cells implying increased energy demand and preferential dependence on mitochondrial respiration in those cells. Interestingly, we found the patient cells demonstrate hypersensitivity to glucose starvation, supporting their enhanced energy consumption.

CONCLUSIONS

In summary, our work suggested increased energy demand and higher oxidative phosphorylation in aged-phenotype cells which can be considered in anti-skin aging therapeutic design.

MFN2 contributes to metabolic disorders and inflammation in the aging of rat chondrocytes and osteoarthritis

OBJECTIVE

Metabolic disorders and inflammation of chondrocytes are major pathological changes in aging cells and osteoarthritis (OA). Recent studies demonstrated age-related mitochondrial dysfunction may be a key contributing factor in the development of OA. Mitofusin 2 (MFN2) is a key regulator of mitochondrial fusion, cell metabolism, autophagy and apoptosis. This study was performed to ascertain whether MFN2 was involved in the aging of chondrocytes and OA.

METHODS

Metabolic measurements were taken in rat chondrocytes between different ages (3-week, 5-month, 12-month). MFN2 activity was detected in both human and rat chondrocytes during aging and OA. Then, knockdown of MFN2 with small interfering RNA (siRNA) was performed to confirm whether MFN2 contributes to metabolic changes. Lentiviruses were used to establish MFN2-overexpression/knockdown OA models both in vivo and in vitro to confirm whether MFN2 contributes to OA progress. Further, regulatory mechanism of MFN2 was assessed and interaction between MFN2 and PARKIN was performed.

RESULTS

A metabolic shift to mitochondrial respiration was confirmed in rat chondrocytes during aging. MFN2 expression was elevated in both human and rat chondrocytes during aging and OA. Knockdown of MFN2 with siRNA reversed the age-related metabolic changes in rat chondrocytes. Overexpression of MFN2 exacerbated inflammation and OA progress, while knockdown of MFN2 ameliorated inflammation and OA progress. Further, MFN2 could be ubiquitinated by PARKIN, declined PARKIN expression during aging and OA might result in elevated MFN2 expression.

CONCLUSIONS

Elevated MFN2 contributes to metabolic changes and inflammation during aging of rat chondrocytes and osteoarthritis.

Interplay of mitochondrial fission-fusion with cell cycle regulation: Possible impacts on stem cell and organismal aging

Declining mitochondrial function and homeostasis is a hallmark of aging. It is appreciated that the role of mitochondria is much more complex than generating reactive oxygen species to cause aging-related tissue damage. More recent literature describes that the ability of mitochondria to undergo fission or fusion events with each other impacts aging processes. A dynamic balance of mitochondrial fission and fusion events is required to sustain critical cellular functions including cell cycle. Specifically, cell cycle regulators modulate molecular activities of the mitochondrial fission (and fusion) machinery towards regulating cell cycle progression. In this review, we discus literature leading to our understanding on how shifts in the dynamic balance of mitochondrial fission and fusion can modulate progression through, exit from, and re-entry to the cell cycle or in undergoing senescence. Importantly, core regulators of mitochondrial fission or fusion are emerging as crucial stem cell regulators. We discuss the implication of such regulation in stem cells in the context of aging, given that aberrations in adult stem cells promote aging. We also propose a few hypotheses that may provide direction for further understanding about the roles of mitochondrial fission-fusion dynamics in aging biology.

UGCG overexpression leads to increased glycolysis and increased oxidative phosphorylation of breast cancer cells

The only enzyme in the glycosphingolipid (GSL) metabolic pathway, which produces glucosylceramide (GlcCer) de novo is UDP-glucose ceramide glucosyltransferase (UGCG). UGCG is linked to pro-cancerous processes such as multidrug resistance development and increased proliferation in several cancer types. Previously, we showed an UGCG-dependent glutamine metabolism adaption to nutrient-poor environment of breast cancer cells. This adaption includes reinforced oxidative stress response and fueling the tricarboxylic acid (TCA) cycle by increased glutamine oxidation. In the current study, we investigated glycolytic and oxidative metabolic phenotypes following UGCG overexpression (OE). UGCG overexpressing MCF-7 cells underwent a metabolic shift from quiescent/aerobic to energetic metabolism by increasing both glycolysis and oxidative glucose metabolism. The energetic metabolic phenotype was not associated with increased mitochondrial mass, however, markers of mitochondrial turnover were increased. UGCG OE altered sphingolipid composition of the endoplasmic reticulum (ER)/mitochondria fractions that may contribute to increased mitochondrial turnover and increased cell metabolism. Our data indicate that GSL are closely connected to cell energy metabolism and this finding might contribute to development of novel therapeutic strategies for cancer treatment.

Arachidonate 12-lipoxygenase and 12-hydroxyeicosatetraenoic acid contribute to stromal aging-induced progression of pancreatic cancer

The incidence of pancreatic cancer increases with age, suggesting that chronological aging is a significant risk factor for this disease. Fibroblasts are the major nonmalignant cell type in the stroma of human pancreatic ductal adenocarcinoma (PDAC). In this study, we investigated whether the chronological aging of normal human fibroblasts (NHFs), a previously underappreciated area in pancreatic cancer research, influences the progression and therapeutic outcomes of PDAC. Results from experiments with murine xenografts and 2D and 3D co-cultures of NHFs and PDAC cells revealed that older NHFs stimulate proliferation of and confer resistance to radiation therapy of PDAC. MS-based metabolite analysis indicated that older NHFs have significantly increased arachidonic acid 12-lipoxygenase (ALOX12) expression and elevated levels of its mitogenic metabolite, 12-(S)-hydroxy-5,8,10,14-eicosatetraenoic acid (12-(S)-HETE) compared with their younger counterparts. In co-cultures with older rather than with younger NHFs, PDAC cells exhibited increases in mitogen-activated protein kinase signaling and cellular metabolism, as well as a lower oxidation state that correlated with their enhanced proliferation and resistance to radiation therapy. Expression of ALOX12 was found to be significantly lower in PDAC cell lines and tumor biopsies, suggesting that PDAC cells rely on a stromal supply of mitogens for their proliferative needs. Pharmacological (hydroxytyrosol) and molecular (siRNA) interventions of ALOX12 in older NHFs suppressed their ability to stimulate proliferation of PDAC cells. We conclude that chronological aging of NHFs contributes to PDAC progression and that ALOX12 and 12-(S)-HETE may be potential stromal targets for interventions that seek to halt progression and improve therapy outcomes.

Mitochondrial Bioenergetics and Dynamics in Secretion Processes

Secretion is an energy consuming process that plays a relevant role in cell communication and adaptation to the environment. Among others, endocrine cells producing hormones, immune cells producing cytokines or antibodies, neurons releasing neurotransmitters at synapsis, and more recently acknowledged, senescent cells synthesizing and secreting multiple cytokines, growth factors and proteases, require energy to successfully accomplish the different stages of the secretion process. Calcium ions (Ca²⁺) act as second messengers regulating secretion in many of these cases. In this setting, mitochondria appear as key players providing ATP by oxidative phosphorylation, buffering Ca²⁺ concentrations and acting as structural platforms. These tasks also require the concerted actions of the mitochondrial dynamics machinery. These proteins mediate mitochondrial fusion and fission, and are also required for transport and tethering of mitochondria to cellular organelles where the different steps of the secretion process take place. Herein we present a brief overview of mitochondrial energy metabolism, mitochondrial dynamics, and the different steps of the secretion processes, along with evidence of the interaction between these pathways. We also analyze the role of mitochondria in secretion by different cell types in physiological and pathological settings.

Mitophagy, Mitochondrial Dynamics, and Homeostasis in Cardiovascular Aging

Biological aging is an inevitable and independent risk factor for a wide array of chronic diseases including cardiovascular and metabolic diseases. Ample evidence has established a pivotal role for interrupted mitochondrial homeostasis in the onset and development of aging-related cardiovascular anomalies. A number of culprit factors have been suggested in aging-associated mitochondrial anomalies including oxidative stress, lipid toxicity, telomere shortening, metabolic disturbance, and DNA damage, with recent findings revealing a likely role for compromised mitochondrial dynamics and mitochondrial quality control machinery such as autophagy. Mitochondria undergo consistent fusion and fission, which are crucial for mitochondrial homeostasis and energy adaptation. Autophagy, in particular, mitochondria-selective autophagy, namely, mitophagy, refers to a highly conservative cellular process to degrade and clear long-lived or damaged cellular organelles including mitochondria, the function of which gradually deteriorates with increased age. Mitochondrial homeostasis could be achieved through a cascade of independent but closely related processes including fusion, fission, mitophagy, and mitochondrial biogenesis. With improved health care and increased human longevity, the ever-rising aging society has imposed a high cardiovascular disease prevalence. It is thus imperative to understand the role of mitochondrial homeostasis in the regulation of lifespan and healthspan. Targeting mitochondrial homeostasis should offer promising novel therapeutic strategies against aging-related complications, particularly cardiovascular diseases.

Nutritional preconditioning induced by astragaloside Ⅳ on isolated hearts and cardiomyocytes against myocardial ischemia injury via improving Bcl-2-mediated mitochondrial function

Ischemic preconditioning and pharmacological preconditioning are common strategies to prevent lethal myocardial injury, especially nutritional preconditioning (NPC). In this study, we investigated the effects of astragaloside IV (Ast), as an NPC agent, on myocardium suffered anoxia/reoxygenation (A/R) injury. Rats received 5 mg/kg Ast daily for 3 weeks by intragastric administration. Then, hearts were harvested and underwent A/R treatment using a Langendorff apparatus. Ast- pretreatment significantly promoted functional recovery of the myocardium, reduced infarct size, and oxidative stress, and decreased the apoptotic index. Similar findings were demonstrated in H9c2 cardiomyocytes that were pretreated with Ast for 24 h. Moreover, Ast-pretreatment significantly upregulated Bcl-2 expression, especially in mitochondria. The effects of Ast treatment against A/R injury were also reflected by increased antioxidant potential, inhibited reactive oxygen species (ROS) burst, increased oxygen consumption rate, maintained mitochondrial membrane potential (MMP), inhibited mitochondrial permeability transition pore (mPTP) opening, and prevented apoptosis. Selective inhibition of Bcl-2 by ABT-737 decreased myocardial injury protection of Ast. Ast-pretreatment resulted in NPC- related effects against A/R, and mitochondria may be the target of a cascade of events elicited by upregulating Bcl-2 expression, promoting translocation of Bcl-2 into mitochondria, maintaining MMP, inhibiting ROS bursts, thereby leading to recovery of mitochondrial respiration, preventing mPTP opening, decreasing cytochrome C release, preventing apoptosis, and ultimately alleviating myocardial injury.

Relationships Between Ion Channels, Mitochondrial Functions and Inflammation in Human Aging

Aging is often associated with a loss of function. We believe aging to be more an adaptation to the various, and often continuous, stressors encountered during life in order to maintain overall functionality of the systems. The maladaptation of a system during aging may increase the susceptibility to diseases. There are basic cellular functions that may influence and/or are influenced by aging. Mitochondrial function is amongst these. Their presence in almost all cell types makes of these valuable targets for interventions to slow down or even reserve signs of aging. In this review, the role of mitochondria and essential physiological regulators of mitochondria and cellular functions, ion channels, will be discussed in the context of human aging. The origins of inflamm-aging, associated with poor clinical outcomes, will be linked to mitochondria and ion channel biology.

The Effects of APOE4 on Mitochondrial Dynamics and Proteins in vivo

This study examined the effects of apolipoprotein E4 (APOE4), the most prevalent genetic risk factor for Alzheimer's disease (AD), on proteins involved in mitochondrial dynamics and autophagy, in the hippocampus of targeted replacement mice. Immunohistochemical measurements revealed that the levels of the mitochondrial fusion-mediating protein, MFN1, were higher, whereas those of corresponding fission-regulating protein, DRP-1, were lower in the hippocampus of ApoE4 mice than in the corresponding ApoE3 mice, indicating that APOE4 is associated with increased mitochondrial fusion and decreased fission. A similar ApoE4-driven decrease in DRP-1 was also observed in AD brains. The levels of the mitochondrial proteins COX1 and Tom40, were higher in the ApoE4 mice, which is consistent with the increased fusion. Measurements of the levels of cleaved PINK1 and parkin, which mark and target mitochondria for mitophagic degradation, revealed lower levels of cleaved PINK1, suggesting reduced mitochondrial membrane potential, and higher levels of parkin in the hippocampus of ApoE4 compared with the ApoE3 mice, indicating altered mitophagy. The levels of the ubiquitin-binding scaffold protein, p62/SQSTM1, which directs selected cargo to the autophagosomes, were also higher in the ApoE4 mice. These findings suggest that APOE4 is associated with enhanced mitochondrial fusion and decreased fission. Additionally, the results indicate that mitophagy/autophagy is reduced in ApoE4 mice, resulting in higher levels of proteins such as parkin and p62, which are normally degraded during this process. Taken together, these results suggest a novel mechanism that may underlie the pathological effects of APOE4 and indicate that use of APOE4 genotyping could pave the way for identification of novel APOE4-related therapeutic targets.

Ipragliflozin improves mitochondrial abnormalities in renal tubules induced by a high-fat diet

AIMS/INTRODUCTION

Complete mechanisms of renoprotective effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors have not been elucidated yet. Mitochondrial biogenesis is regulated by membrane GTPases, such as optic atrophy factor 1 and mitofusion 2. Here, we investigated whether SGLT2 inhibition in mice fed with a high-fat diet (HFD) improved mitochondrial morphology and restored mitochondrial biogenesis-related molecules.

MATERIALS AND METHODS

Mice were fed a control diet or HFD with or without ipragliflozin treatment. After 16 weeks, the kidneys were taken out and utilized for the analysis.

RESULTS

HFD-fed mice treated with ipragliflozin showed increased caloric intake and ate more food than the control HFD-fed mice. Body and kidney weights, and blood glucose levels were not altered by ipragliflozin treatment in HFD-fed mice. Histological analysis showed that, compared with control mice, HFD-fed mice displayed tubular vacuolation, dilatation and epithelial cell detachment; ipragliflozin ameliorated these alterations. Furthermore, ultrastructural analysis showed that the tubule mitochondria of HFD-fed mice exhibited significant damage. Again, ipragliflozin reversed the damage to a normal state, and restored optic atrophy factor 1 and mitofusion 2 levels in HFD-fed mice. Increased urine 8-hydroxydeoxyguanosine levels in HFD-fed mice were suppressed by ipragliflozin as well. In vitro experiments using HK-2 cells revealed that either high glucose or high palmitate suppressed optic atrophy factor 1 and mitofusion 2 levels. Suppression of SGLT2 by a specific small interfering ribonucleic acid or ipragliflozin restored these GTPase levels to their normal values.

CONCLUSIONS

SGLT2 inhibition might act directly on tubular cells and protect kidney tubular cells from mitochondrial damage by metabolic insults regardless of blood glucose levels or improvement in bodyweight reduction.

Spontaneous DNA damage to the nuclear genome promotes senescence, redox imbalance and aging

Accumulation of senescent cells over time contributes to aging and age-related diseases. However, what drives senescence in vivo is not clear. Here we used a genetic approach to determine if spontaneous nuclear DNA damage is sufficient to initiate senescence in mammals. Ercc1-/∆ mice with reduced expression of ERCC1-XPF endonuclease have impaired capacity to repair the nuclear genome. Ercc1-/∆ mice accumulated spontaneous, oxidative DNA damage more rapidly than wild-type (WT) mice. As a consequence, senescent cells accumulated more rapidly in Ercc1-/∆ mice compared to repair-competent animals. However, the levels of DNA damage and senescent cells in Ercc1-/∆ mice never exceeded that observed in old WT mice. Surprisingly, levels of reactive oxygen species (ROS) were increased in tissues of Ercc1-/∆ mice to an extent identical to naturally-aged WT mice. Increased enzymatic production of ROS and decreased antioxidants contributed to the elevation in oxidative stress in both Ercc1-/∆ and aged WT mice. Chronic treatment of Ercc1-/∆ mice with the mitochondrial-targeted radical scavenger XJB-5-131 attenuated oxidative DNA damage, senescence and age-related pathology. Our findings indicate that nuclear genotoxic stress arises, at least in part, due to mitochondrial-derived ROS, and this spontaneous DNA damage is sufficient to drive increased levels of ROS, cellular senescence, and the consequent age-related physiological decline.

Targeting Mitochondria to Counteract Age-Related Cellular Dysfunction

Senescence is related to the loss of cellular homeostasis and functions, which leads to a progressive decline in physiological ability and to aging-associated diseases. Since mitochondria are essential to energy supply, cell differentiation, cell cycle control, intracellular signaling and Ca²⁺ sequestration, fine-tuning mitochondrial activity appropriately, is a tightrope walk during aging. For instance, the mitochondrial oxidative phosphorylation (OXPHOS) ensures a supply of adenosine triphosphate (ATP), but is also the main source of potentially harmful levels of reactive oxygen species (ROS). Moreover, mitochondrial function is strongly linked to mitochondrial Ca²⁺ homeostasis and mitochondrial shape, which undergo various alterations during aging. Since mitochondria play such a critical role in an organism’s process of aging, they also offer promising targets for manipulation of senescent cellular functions. Accordingly, interventions delaying the onset of age-associated disorders involve the manipulation of mitochondrial function, including caloric restriction (CR) or exercise, as well as drugs, such as metformin, aspirin, and polyphenols. In this review, we discuss mitochondria’s role in and impact on cellular aging and their potential to serve as a target for therapeutic interventions against age-related cellular dysfunction.

OPA1: How much do we know to approach therapy?

OPA1 is a GTPase that controls several functions, such as mitochondrial dynamics and energetics, mtDNA maintenance and cristae integrity. In the last years, there have been described other cellular pathways and mechanisms involving OPA1 directly or through its interaction. All this new information, by implementing our knowledge on OPA1 is instrumental to elucidating the pathogenic mechanisms of OPA1 mutations. Indeed, these are associated with dominant optic atrophy (DOA), one of the most common inherited optic neuropathies, and with an increasing number of heterogeneous neurodegenerative disorders. In this review, we overview all recent findings on OPA1 protein functions, on its dysfunction and related clinical phenotypes, focusing on the current therapeutic options and future perspectives to treat DOA and the other associated neurological disorders due to OPA1 mutations.

Eight human OPA1 isoforms, long and short: What are they for?

OPA1 is a dynamin-related GTPase that controls mitochondrial dynamics, cristae integrity, energetics and mtDNA maintenance. The exceptional complexity of this protein is determined by the presence, in humans, of eight different isoforms that, in turn, are proteolytically cleaved into combinations of membrane-anchored long forms and soluble short forms. Recent advances highlight how each OPA1 isoform is able to fulfill "essential" mitochondrial functions, whereas only some variants carry out "specialized" features. Long forms determine fusion, long or short forms alone build cristae, whereas long and short forms together tune mitochondrial morphology. These findings offer novel challenging therapeutic potential to gene therapy.