Mitochondrial Homeostasis and Cellular Senescence

Toxicity mechanism of acrolein on energy metabolism disorder and apoptosis in human ovarian granulosa cells

Acrolein (ACR), an unsaturated, highly reactive aldehyde, is a widespread environmental toxin. ACR exerts permanent and irreversible side effects on ovarian functions. Granulosa cells play a crucial role in supporting ovarian function. Thus, in this study, we investigated the toxicity effects of granulosa cells induced by ACR. Following treatment with varying ACR concentrations (0, 12.5, 25, 50, and 100 μM), we observed that ACR exposure induced reactive oxygen species accumulation, mitochondrial energy metabolism disorder, and apoptosis in KGN cells (a human ovarian granulosa cell line) in a dose-dependent manner. In addition, mitochondrial biogenesis in KGN cells displayed biphasic changes after ACR exposure, with activation at a low ACR dose (12.5 μM), but inhibition at higher ACR doses (≥50 μM). SIRT1/PGC-1α-mediated mitochondrial biogenesis is crucial for maintaining intracellular mitochondrial homeostasis and cellular function. The inhibition/activation of the SIRT1/PGC-1α pathway in KGN cells validated its role in ACR-induced damage. The results indicated that the inhibition of the SIRT1/PGC-1α pathway aggravated ACR-induced cell damage, whereas its activation partially counteracted ACR-induced cell damage. This study attempted to uncover a novel mechanism of ACR-induced ovarian toxicity so as to provide an effective treatment option for safeguarding female reproductive health from the adverse effects of ACR.

Lycopene alleviates Deoxynivalenol-induced toxicity in Porcine intestinal epithelial cells by mediating mitochondrial function

Deoxynivalenol (DON) is widely found in food and feed, posing a threat to human and animal health. Lycopene (Lyc) is a natural plant extracts with significant antioxidant properties. This study was conducted to investigate the protective effects of Lyc on IPEC-J2 cells upon DON exposure. The detection of cell viability and trypan blue staining showed that Lyc alleviated cell damage and decreased cell apoptotic rate induced by DON. The analysis of reactive oxygen species (ROS) level and antioxidant parameter measurements showed that Lyc significantly down-regulated the content of ROS and restored antioxidant enzyme activity. Furthermore, mitochondrial membrane potential (ΔΨm) detection, mitochondrial DNA copy number (mtDNAcn) assay and adenosine triphosphate (ATP) concentration detection showed Lyc improved mitochondrial function after DON exposure. The results of transcriptome analysis, ROS detection and CCK8 assay suggested that Lyc may activated the oxidative phosphorylation (OXPHOS) to improve mitochondrial function. Conclusively, our results suggested that Lyc alleviated DON-induced oxidative stress by improving mitochondrial function through OXPHOS signaling pathway.

Mutant NOTCH3ECD Triggers Defects in Mitochondrial Function and Mitophagy in CADASIL Cell Models

Background

Cerebral autosomal-dominant arteriopathy with subcortical infarction and leukoencephalopathy (CADASIL) is an inherited small-vessel disease that affects the white matter of the brain. Recent studies have confirmed that the deposition of NOTCH3ECD is the main pathological basis of CADASIL; however, whether different mutations present the same pathological characteristics remains to be further studied. Some studies have found that mitochondrial dysfunction is related to CADASIL; however, the specific effects of NOTCH3ECD on mitochondrial remain to be determined.

Objective

We aimed to explore the role of mitochondrial dysfunction in CADASIL.

Methods

We established transgenic human embryonic kidney-293T cell models (involving alterations in cysteine and non-cysteine residues) via lentiviral transfection. Mitochondrial function and structure were assessed using flow cytometry and transmission electron microscopy, respectively. Mitophagy was assessed using western blotting and immunofluorescence.

Results

We demonstrated that NOTCH3ECD deposition affects mitochondrial morphology and function, and that its protein levels are significantly correlated with mitochondrial quality and can directly bind to mitochondria. Moreover, NOTCH3ECD deposition promoted the induction of autophagy and mitophagy. However, these processes were impaired, leading to abnormal mitochondrial accumulation.

Conclusions

This study revealed a common pathological feature of NOTCH3ECD deposition caused by different NOTCH3 mutations and provided new insights into the role of NOTCH3ECD in mitochondrial dysfunction and mitophagy.

S100A9 as a Key Myocardial Injury Factor Interacting with ATP5 Exacerbates Mitochondrial Dysfunction and Oxidative Stress in Sepsis-Induced Cardiomyopathy

Purpose

Sepsis-induced cardiomyopathy (SICM) is a prevalent cardiac dysfunction caused by sepsis. Mitochondrial dysfunction is a crucial pathogenic factor associated with adverse cardiovascular adverse events; however, research on SICM remains insufficient.

Methods

To investigate the factors contributing to the pathological progression of SICM, we performed a comprehensive analysis of transcriptomic data from the GEO database using bioinformatics and machine learning techniques. CRISPR-Cas9 S100A9 knockout mice and primary cardiomyocytes were exposed to lipopolysaccharide to simulate SICM. Transcriptome analysis and mass spectrometry of primary cardiomyocytes were used to determine the potential pathogenic mechanisms of S100A9. The mitochondrial ultrastructure and mitochondrial membrane potential (MMP) were detected using transmission electron microscopy and flow cytometry, respectively. Pink1/Parkin and Drp1 proteins were detected using Western blotting to evaluate mitochondrial autophagy and division. The mtDNA and mRNA levels of mitochondrial transcription factors and synthases were evaluated using real-time polymerase chain reaction.

Results

Bioinformatics analysis identified 12 common differentially expressed genes, including SERPINA3N, LCN2, MS4A6D, LRG1, OSMR, SOCS3, FCGR2b, S100A9, S100A8, CASP4, ABCA8A, and NFKBIZ. Significant S100A9 upregulation was closely associated with myocardial injury exacerbation and cardiac function deterioration. GSEA revealed that myocardial contractile function, oxidative stress, and mitochondrial function were significantly affected by S100A9. Knocking out S100A9 alleviates the inflammatory response and mitochondrial dysfunction. The interaction of S100A9 with ATP5 enhanced mitochondrial division and autophagy, inhibited MMP and ATP synthesis, and induced oxidative stress, which are related to the Nlrp3-Nfkb-Caspase1 and Drp1-Pink1-Parkin signaling pathways. The expression of mitochondrial transcription factors (TFAM and TFBM) and ATP synthetases (ATP6 and ATP8, as well as COX1, COX2, and COX3) was further suppressed by S100A9 in SICM. Targeted S100A9 inhibition by paquinimod partially reversed myocardial mitochondrial dysfunction and oxidative stress.

Conclusion

The interaction of S100A9 with ATP5 exacerbates myocardial damage in sepsis by inducing mitochondrial dysfunction and oxidative stress.

Multifunctional scaffolds for bone repair following age-related biological decline: Promising prospects for smart biomaterial-driven technologies

The repair of large bone defects due to trauma, disease, and infection can be exceptionally challenging in the elderly. Despite best clinical practice, bone regeneration within contemporary, surgically implanted synthetic scaffolds is often problematic, inconsistent, and insufficient where additional osteobiological support is required to restore bone. Emergent smart multifunctional biomaterials may drive important and dynamic cellular crosstalk that directly targets, signals, stimulates, and promotes an innate bone repair response following age-related biological decline and when in the presence of disease or infection. However, their role remains largely undetermined. By highlighting their mechanism/s and mode/s of action, this review spotlights smart technologies that favorably align in their conceivable ability to directly target and enhance bone repair and thus are highly promising for future discovery for use in the elderly. The four degrees of interactive scaffold smartness are presented, with a focus on bioactive, bioresponsive, and the yet-to-be-developed autonomous scaffold activity. Further, cell- and biomolecular-assisted approaches were excluded, allowing for contemporary examination of the capabilities, demands, vision, and future requisites of next-generation biomaterial-induced technologies only. Data strongly supports that smart scaffolds hold significant promise in the promotion of bone repair in patients with a reduced osteobiological response. Importantly, many techniques have yet to be tested in preclinical models of aging. Thus, greater clarity on their proficiency to counteract the many unresolved challenges within the scope of aging bone is highly warranted and is arguably the next frontier in the field. This review demonstrates that the use of multifunctional smart synthetic scaffolds with an engineered strategy to circumvent the biological insufficiencies associated with aging bone is a viable route for achieving next-generation therapeutic success in the elderly population.

Targeting mitochondria for ovarian aging: new insights into mechanisms and therapeutic potential

Ovarian aging is a complex process characterized by a decline in oocyte quantity and quality, directly impacting fertility and overall well-being. Recent researches have identified mitochondria as pivotal players in the aging of ovaries, influencing various hallmarks and pathways governing this intricate process. In this review, we discuss the multifaceted role of mitochondria in determining ovarian fate, and outline the pivotal mechanisms through which mitochondria contribute to ovarian aging. Specifically, we emphasize the potential of targeting mitochondrial dysfunction through innovative therapeutic approaches, including antioxidants, metabolic improvement, biogenesis promotion, mitophagy enhancement, mitochondrial transfer, and traditional Chinese medicine. These strategies hold promise as effective means to mitigate age-related fertility decline and preserve ovarian health. Drawing insights from advanced researches in the field, this review provides a deeper understanding of the intricate interplay between mitochondrial function and ovarian aging, offering valuable perspectives for the development of novel therapeutic interventions aimed at preserving fertility and enhancing overall reproductive health.

Kidney Aging and Chronic Kidney Disease

The process of aging inevitably leads to an increase in age-related comorbidities, including chronic kidney disease (CKD). In many aspects, CKD can be considered a state of accelerated and premature aging. Aging kidney and CKD have numerous common characteristic features, ranging from pathological presentation and clinical manifestation to underlying mechanisms. The shared mechanisms underlying the process of kidney aging and the development of CKD include the increase in cellular senescence, the decrease in autophagy, mitochondrial dysfunction, and the alterations of epigenetic regulation, suggesting the existence of potential therapeutic targets that are applicable to both conditions. In this review, we provide a comprehensive overview of the common characteristics between aging kidney and CKD, encompassing morphological changes, functional alterations, and recent advancements in understanding the underlying mechanisms. Moreover, we discuss potential therapeutic strategies for targeting senescent cells in both the aging process and CKD.

The miR-30-5p/TIA-1 axis directs cellular senescence by regulating mitochondrial dynamics

Senescent cells exhibit a diverse spectrum of changes in their morphology, proliferative capacity, senescence-associated secretory phenotype (SASP) production, and mitochondrial homeostasis. These cells often manifest with elongated mitochondria, a hallmark of cellular senescence. However, the precise regulatory mechanisms orchestrating this phenomenon remain predominantly unexplored. In this study, we provide compelling evidence for decreases in TIA-1, a pivotal regulator of mitochondrial dynamics, in models of both replicative senescence and ionizing radiation (IR)-induced senescence. The downregulation of TIA-1 was determined to trigger mitochondrial elongation and enhance the expression of senescence-associated β-galactosidase, a marker of cellular senescence, in human foreskin fibroblast HS27 cells and human keratinocyte HaCaT cells. Conversely, the overexpression of TIA-1 mitigated IR-induced cellular senescence. Notably, we identified the miR-30-5p family as a novel factor regulating TIA-1 expression. Augmented expression of the miR-30-5p family was responsible for driving mitochondrial elongation and promoting cellular senescence in response to IR. Taken together, our findings underscore the significance of the miR-30-5p/TIA-1 axis in governing mitochondrial dynamics and cellular senescence.

Molecular and cellular consequences of mitochondrial DNA double-stranded breaks

Mitochondria are subcellular organelles essential for life. Beyond their role in producing energy, mitochondria govern various physiological mechanisms, encompassing energy generation, metabolic processes, apoptotic events, and immune responses. Mitochondria also contain genetic material that is susceptible to various forms of damage. Mitochondrial double-stranded breaks (DSB) are toxic lesions that the nucleus repairs promptly. Nevertheless, the significance of DSB repair in mammalian mitochondria is controversial. This review presents an updated view of the available research on the consequences of mitochondrial DNA DSB from the molecular to the cellular level. We discuss the crucial function of mitochondrial DNA damage in regulating processes such as senescence, integrated stress response, and innate immunity. Lastly, we discuss the potential role of mitochondrial DNA DSB in mediating the cellular consequences of ionizing radiations, the standard of care in treating solid tumors.

Combined Endurance and Resistance Exercise Mitigates Age-Associated Cardiac Dysfunction

Aging is associated with a decline in cardiac function. Exercise has been shown to effectively reduce the risks of cardiovascular diseases. Here whether a combination of endurance and resistance exercises can improve cardiac function in aged mice during late life is investigated. Through transcriptome analysis, several signaling pathways activated in the hearts of 22-month-old mice after combined exercise, including cardiac muscle contraction, mitophagy, and longevity regulation are identified. Combined exercise training mitigated age-associated pathological cardiac hypertrophy, reduced oxidative stress, cardiac senescence, and enhanced cardiac function. Upstream stimulatory factor 2 (Usf2) is upregulated in the aged mouse hearts with combined exercise compared to sedentary mice. In the human cardiomyocytes senescent model, overexpression of Usf2 led to anti-senescence effects, while knockdown of Usf2 exacerbated cellular senescence. The results suggest that a combination of endurance and resistance exercises, such as swimming and resistance running, can mitigate age-related pathological cardiac remodeling and cardiac dysfunction in late life. These cardioprotective effects are likely due to the activation of Usf2 and its anti-senescence effect. Therefore, Usf2 can potentially be a novel therapeutic target for mitigating age-related cardiac dysfunction.

Roles of O-GlcNAcylation in Mitochondrial Homeostasis and Cardiovascular Diseases

Protein posttranslational modifications are important factors that mediate the fine regulation of signaling molecules. O-linked β-N-acetylglucosamine-modification (O-GlcNAcylation) is a monosaccharide modification on N-acetylglucosamine linked to the hydroxyl terminus of serine and threonine of proteins. O-GlcNAcylation is responsive to cellular stress as a reversible and posttranslational modification of nuclear, mitochondrial and cytoplasmic proteins. Mitochondrial proteins are the main targets of O-GlcNAcylation and O-GlcNAcylation is a key regulator of mitochondrial homeostasis by directly regulating the mitochondrial proteome or protein activity and function. Disruption of O-GlcNAcylation is closely related to mitochondrial dysfunction. More importantly, the O-GlcNAcylation of cardiac proteins has been proven to be protective or harmful to cardiac function. Mitochondrial homeostasis is crucial for cardiac contractile function and myocardial cell metabolism, and the imbalance of mitochondrial homeostasis plays a crucial role in the pathogenesis of cardiovascular diseases (CVDs). In this review, we will focus on the interactions between protein O-GlcNAcylation and mitochondrial homeostasis and provide insights on the role of mitochondrial protein O-GlcNAcylation in CVDs.

Mitochondrial Dysfunction in Chronic Obstructive Pulmonary Disease: Unraveling the Molecular Nexus

Chronic obstructive pulmonary disease (COPD) is a prevalent and debilitating respiratory disorder characterized by persistent airflow limitation and chronic inflammation. In recent years, the role of mitochondrial dysfunction in COPD pathogenesis has emerged as a focal point of investigation. This review endeavors to unravel the molecular nexus between mitochondrial dysfunction and COPD, delving into the intricate interplay of oxidative stress, bioenergetic impairment, mitochondrial genetics, and downstream cellular consequences. Oxidative stress, a consequence of mitochondrial dysfunction, is explored as a driving force behind inflammation, exacerbating the intricate cascade of events leading to COPD progression. Bioenergetic impairment sheds light on the systemic consequences of mitochondrial dysfunction, impacting cellular functions and contributing to the overall energy imbalance observed in COPD patients. This review navigates through the genetic landscape, elucidating the role of mitochondrial DNA mutations, variations, and haplogroups in COPD susceptibility and severity. Cellular consequences, including apoptosis, autophagy, and cellular senescence, are examined, providing insights into the intricate mechanisms by which mitochondrial dysfunction influences COPD pathology. Therapeutic implications, spanning antioxidant strategies, mitochondria-targeted compounds, and lifestyle modifications, are discussed in the context of translational research. Important future directions include identifying novel biomarkers, advancing mitochondria-targeted therapies, and embracing patient-centric approaches to redefine COPD management. This abstract provides a comprehensive overview of our review, offering a roadmap for understanding and addressing the molecular nexus between mitochondrial dysfunction and COPD, with potential implications for precision medicine and improved patient outcomes.

Targeting shared pathways in tauopathies and age-related macular degeneration: implications for novel therapies

The intricate parallels in structure and function between the human retina and the central nervous system designate the retina as a prospective avenue for understanding brain-related processes. This review extensively explores the shared physiopathological mechanisms connecting age-related macular degeneration (AMD) and proteinopathies, with a specific focus on tauopathies. The pivotal involvement of oxidative stress and cellular senescence emerges as key drivers of pathogenesis in both conditions. Uncovering these shared elements not only has the potential to enhance our understanding of intricate neurodegenerative diseases but also sets the stage for pioneering therapeutic approaches in AMD.

Formoterol Acting via β2-Adrenoreceptor Restores Mitochondrial Dysfunction Caused by Parkinson's Disease-Related UQCRC1 Mutation and Improves Mitochondrial Homeostasis Including Dynamic and Transport

Formoterol, a β2-adrenergic receptor (β2AR) agonist, shows promise in various diseases, but its effectiveness in Parkinson's disease (PD) is debated, with unclear regulation of mitochondrial homeostasis. This study employed a cell model featuring mitochondrial ubiquinol-cytochrome c reductase core protein 1 (UQCRC1) variants associated with familial parkinsonism, demonstrating mitochondrial dysfunction and dynamic imbalance, exploring the therapeutic effects and underlying mechanisms of formoterol. Results revealed that 24-h formoterol treatment enhanced cell proliferation, viability, and neuroprotection against oxidative stress. Mitochondrial function, encompassing DNA copy number, repatriation, and complex III-linked respiration, was comprehensively restored, along with the dynamic rebalance of fusion/fission events. Formoterol reduced extensive hypertubulation, in contrast to mitophagy, by significantly upregulating protein Drp-1, in contrast to fusion protein Mfn2, mitophagy-related protein Parkin. The upstream mechanism involved the restoration of ERK signaling and the inhibition of Akt overactivity, contingent on the activation of β2-adrenergic receptors. Formoterol additionally aided in segregating healthy mitochondria for distribution and transport, therefore normalizing mitochondrial arrangement in mutant cells. This study provides preliminary evidence that formoterol offers neuroprotection, acting as a mitochondrial dynamic balance regulator, making it a promising therapeutic candidate for PD.

Phosphatidate phosphatase Lipin1 involves in diabetic encephalopathy pathogenesis via regulating synaptic mitochondrial dynamics

Diabetic encephalopathy (DE) is a common central nervous system complication of diabetes mellitus without effective therapy currently. Recent studies have highlighted synaptic mitochondrial damages as a possible pathological basis for DE, but the underlying mechanisms remain unclear. Our previous work has revealed that phosphatidate phosphatase Lipin1, a critical enzyme involved with phospholipid synthesis, is closely related to the pathogenesis of DE. Here, we demonstrate that Lipin1 is significantly down-regulated in rat hippocampus of DE. Knock-down of Lipin1 within hippocampus of normal rats induces dysregulation of homeostasis in synaptic mitochondrial dynamics with an increase of mitochondrial fission and a decrease of fusion, then causes synaptic mitochondrial dysfunction, synaptic plasticity deficits as well as cognitive impairments, similar to that observed in response to chronic hyperglycemia exposure. In contrast, an up-regulation of Lipin1 within hippocampus in the DE model ameliorates this cascade of dysfunction. We also find that the effect of Lipin1 that regulating mitochondrial dynamics results from maintaining appropriate phospholipid components in the mitochondrial membrane. In conclusion, alterations in hippocampal Lipin1 contribute to hippocampal synaptic mitochondrial dysfunction and cognitive deficits observed in DE. Targeting Lipin1 might be a potential therapeutic strategy for the clinical treatment of DE.

Defining Mitochondrial Cristae Morphology Changes Induced by Aging in Brown Adipose Tissue

Mitochondria are required for energy production and even give brown adipose tissue (BAT) its characteristic color due to their high iron content and abundance. The physiological function and bioenergetic capacity of mitochondria are connected to the structure, folding, and organization of its inner-membrane cristae. During the aging process, mitochondrial dysfunction is observed, and the regulatory balance of mitochondrial dynamics is often disrupted, leading to increased mitochondrial fragmentation in aging cells. Therefore, it is hypothesized that significant morphological changes in BAT mitochondria and cristae will be present with aging. A quantitative 3D electron microscopy approach is developed to map cristae network organization in mouse BAT to test this hypothesis. Using this methodology, the 3D morphology of mitochondrial cristae is investigated in adult (3-month) and aged (2-year) murine BAT tissue via serial block face-scanning electron microscopy (SBF-SEM) and 3D reconstruction software for manual segmentation, analysis, and quantification. Upon investigation, an increase is found in mitochondrial volume, surface area, and complexity and decreased sphericity in aged BAT, alongside significant decreases in cristae volume, area, perimeter, and score. Overall, these data define the nature of the mitochondrial structure in murine BAT across aging.

Mitophagy induction improves salivary gland stem/progenitor cell function by reducing senescence after irradiation

BACKGROUND AND PURPOSE

Patients undergoing radiotherapy for head and neck cancer often experience a decline in their quality of life due to the co-irradiation of salivary glands. Radiation-induced cellular senescence is a key factor contributing to salivary gland dysfunction. Interestingly, mitochondrial dysfunction and cellular senescence have been reported to be strongly interconnected and thus implicated in several aging-related diseases. This study aims to investigate the role of mitochondrial dysfunction in senescence induction in salivary gland stem/progenitor cells after irradiation.

MATERIALS AND METHODS

A dose of 7 Gy photons was used to irradiate mouse salivary gland organoids. Senescent markers and mitochondrial function were assessed using rt-qPCR, western blot analysis, SA-β-Gal staining and flow cytometry analysis. Mitochondrial dynamics-related proteins were detected by western blot analysis while Mdivi-1 and MFI8 were used to modulate the mitochondrial fission process. To induce mitophagy, organoids were treated with Urolithin A and PMI and subsequently stem/progenitor cell self-renewal capacity was assessed as organoid forming efficiency.

RESULTS

Irradiation led to increased senescence and accumulation of dysfunctional mitochondria. This was accompanied by a strong downregulation of mitochondrial fission-related proteins and mitophagy-related genes. After irradiation, treatment with the mitophagy inducer Urolithin A attenuated the senescent phenotype and improved organoid growth and stem/progenitor cell self-renewal capacity.

CONCLUSION

This study shows the important interplay between senescence and mitochondrial dysfunction after irradiation. Importantly, activation of mitophagy improved salivary gland stem/progenitor cell function thereby providing a novel therapeutic strategy to restore the regenerative capacity of salivary glands following irradiation.

Senescent adipocytes and type 2 diabetes - current knowledge and perspective concepts

Among civilization diseases, the number of individuals suffering from type 2 diabetes (T2DM) is expected to increase to more than a billion in less than 20 years, which is associated with, e.g., populational aging, poor diet, sedentary lifestyle, genetic predispositions, and immunological factors. T2DM affects many organs and is characterized by insulin resistance, high glucose levels, and adipocyte dysfunction, which are related to senescence. Although this type of cellular aging has beneficial biological functions, it can also act unfavorable since senescent adipocytes resist apoptosis, enhance cytokine secretion, downregulate cell identity genes, and acquire the senescence-associated secretory phenotype that renders a more oxidative environment. Opposing T2DM is possible via a wide variety of senotherapies, including senolytics and senomorphics; nevertheless, further research is advised to expand therapeutic possibilities and benefits. Consequences that ought to be deeply researched include secretory phenotype, chronic inflammation, increasing insulin resistance, as well as impairment of adipogenesis and functioning of adipocyte cells. Herein, despite reviewing T2DM and fat tissue senescence, we summarized the latest adipocyte-related anti-diabetes solutions and suggested further research directions.

Skin Barrier Function: The Interplay of Physical, Chemical, and Immunologic Properties

An intact barrier function of the skin is important in maintaining skin health. The regulation of the skin barrier depends on a multitude of molecular and immunological signaling pathways. By examining the regulation of a healthy skin barrier, including maintenance of the acid mantle and appropriate levels of ceramides, dermatologists can better formulate solutions to address issues that are related to a disrupted skin barrier. Conversely, by understanding specific skin barrier disruptions that are associated with specific conditions, such as atopic dermatitis or psoriasis, the development of new compounds could target signaling pathways to provide more effective relief for patients. We aim to review key factors mediating skin barrier regulation and inflammation, including skin acidity, interleukins, nuclear factor kappa B, and sirtuin 3. Furthermore, we will discuss current and emerging treatment options for skin barrier conditions.

Consequences of Aging on Bone

With the aging of the global population, the incidence of musculoskeletal diseases has been increasing, seriously affecting people's health. As people age, the microenvironment within skeleton favors bone resorption and inhibits bone formation, accompanied by bone marrow fat accumulation and multiple cellular senescence. Specifically, skeletal stem/stromal cells (SSCs) during aging tend to undergo adipogenesis rather than osteogenesis. Meanwhile, osteoblasts, as well as osteocytes, showed increased apoptosis, decreased quantity, and multiple functional limitations including impaired mechanical sensing, intercellular modulation, and exosome secretion. Also, the bone resorption function of macrophage-lineage cells (including osteoclasts and preosteoclasts) was significantly enhanced, as well as impaired vascularization and innervation. In this study, we systematically reviewed the effect of aging on bone and the within microenvironment (including skeletal cells as well as their intracellular structure variations, vascular structures, innervation, marrow fat distribution, and lymphatic system) caused by aging, and mechanisms of osteoimmune regulation of the bone environment in the aging state, and the causal relationship with multiple musculoskeletal diseases in addition with their potential therapeutic strategy.

Mitochondrial dynamics and metabolism across skin cells: implications for skin homeostasis and aging

Aging of human skin is a complex process leading to a decline in homeostasis and regenerative potential of this tissue. Mitochondria are important cell organelles that have a crucial role in several cellular mechanisms such as energy production and free radical maintenance. However, mitochondrial metabolism as well as processes of mitochondrial dynamics, biogenesis, and degradation varies considerably among the different types of cells that populate the skin. Disturbed mitochondrial function is known to promote aging and inflammation of the skin, leading to impairment of physiological skin function and the onset of skin pathologies. In this review, we discuss the essential role of mitochondria in different skin cell types and how impairment of mitochondrial morphology, physiology, and metabolism in each of these cellular compartments of the skin contributes to the process of skin aging.

Human ovarian aging is characterized by oxidative damage and mitochondrial dysfunction

STUDY QUESTION

Are human ovarian aging and the age-related female fertility decline caused by oxidative stress and mitochondrial dysfunction in oocytes?

SUMMARY ANSWER

We found oxidative damage in oocytes of advanced maternal age, even at the primordial follicle stage, and confirmed mitochondrial dysfunction in such oocytes, which likely resulted in the use of alternative energy sources.

WHAT IS KNOWN ALREADY

Signs of reactive oxygen species-induced damage and mitochondrial dysfunction have been observed in maturing follicles, and even in early stages of embryogenesis. However, although recent evidence indicates that also primordial follicles have metabolically active mitochondria, it is still often assumed that these follicles avoid oxidative phosphorylation to prevent oxidative damage in dictyate arrested oocytes. Data on the influence of ovarian aging on oocyte metabolism and mitochondrial function are still limited.

STUDY DESIGN, SIZE, DURATION

A set of 39 formalin-fixed and paraffin-embedded ovarian tissue biopsies were divided into different age groups and used for immunofluorescence analysis of oxidative phosphorylation activity and oxidative damage to proteins, lipids, and DNA. Additionally, 150 immature oocytes (90 germinal vesicle oocytes and 60 metaphase I oocytes) and 15 cumulus cell samples were divided into different age groups and used for targeted metabolomics and lipidomics analysis.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Ovarian tissues used for immunofluorescence microscopy were collected through PALGA, the nationwide network, and registry of histo- and cytopathology in The Netherlands. Comprehensive metabolomics and lipidomics were performed by liquid-liquid extraction and full-scan mass spectrometry, using oocytes and cumulus cells of women undergoing ICSI treatment based on male or tubal factor infertility, or fertility preservation for non-medical reasons.

MAIN RESULTS AND THE ROLE OF CHANCE

Immunofluorescence imaging on human ovarian tissue indicated oxidative damage by protein and lipid (per)oxidation already at the primordial follicle stage. Metabolomics and lipidomics analysis of oocytes and cumulus cells in advanced maternal-age groups demonstrated a shift in the glutathione-to-oxiglutathione ratio and depletion of phospholipids. Age-related changes in polar metabolites suggested a decrease in mitochondrial function, as demonstrated by NAD+, purine, and pyrimidine depletion, while glycolysis substrates and glutamine accumulated, with age. Oocytes from women of advanced maternal age appeared to use alternative energy sources like glycolysis and the adenosine salvage pathway, and possibly ATP which showed increased production in cumulus cells.

LIMITATIONS, REASONS FOR CAUTION

The immature oocytes used in this study were all subjected to ovarian stimulation with high doses of follicle-stimulating hormones, which might have concealed some age-related differences.

WIDER IMPLICATIONS OF THE FINDINGS

Further studies on how to improve mitochondrial function, or lower oxidative damage, in oocytes from women of advanced maternal age, for instance by supplementation of NAD+ precursors to promote mitochondrial biogenesis, are warranted. In addition, supplementing the embryo medium of advanced maternal-age embryos with such compounds could be a treatment option worth exploring.

STUDY FUNDING/COMPETING INTEREST(S)

The study was funded by the Amsterdam UMC. The authors declare to have no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Aging, oxidative stress and degenerative diseases: mechanisms, complications and emerging therapeutic strategies

Aging accompanied by several age-related complications, is a multifaceted inevitable biological progression involving various genetic, environmental, and lifestyle factors. The major factor in this process is oxidative stress, caused by an abundance of reactive oxygen species (ROS) generated in the mitochondria and endoplasmic reticulum (ER). ROS and RNS pose a threat by disrupting signaling mechanisms and causing oxidative damage to cellular components. This oxidative stress affects both the ER and mitochondria, causing proteopathies (abnormal protein aggregation), initiation of unfolded protein response, mitochondrial dysfunction, abnormal cellular senescence, ultimately leading to inflammaging (chronic inflammation associated with aging) and, in rare cases, metastasis. RONS during oxidative stress dysregulate multiple metabolic pathways like NF-κB, MAPK, Nrf-2/Keap-1/ARE and PI3K/Akt which may lead to inappropriate cell death through apoptosis and necrosis. Inflammaging contributes to the development of inflammatory and degenerative diseases such as neurodegenerative diseases, diabetes, cardiovascular disease, chronic kidney disease, and retinopathy. The body's antioxidant systems, sirtuins, autophagy, apoptosis, and biogenesis play a role in maintaining homeostasis, but they have limitations and cannot achieve an ideal state of balance. Certain interventions, such as calorie restriction, intermittent fasting, dietary habits, and regular exercise, have shown beneficial effects in counteracting the aging process. In addition, interventions like senotherapy (targeting senescent cells) and sirtuin-activating compounds (STACs) enhance autophagy and apoptosis for efficient removal of damaged oxidative products and organelles. Further, STACs enhance biogenesis for the regeneration of required organelles to maintain homeostasis. This review article explores the various aspects of oxidative damage, the associated complications, and potential strategies to mitigate these effects.

Cancer cells reprogram to metastatic state through the acquisition of platelet mitochondria

Metastasis is the major cause of cancer deaths, and cancer cells evolve to adapt to various tumor microenvironments, which hinders the treatment of tumor metastasis. Platelets play critical roles in tumor development, especially during metastasis. Here, we elucidate the role of platelet mitochondria in tumor metastasis. Cancer cells are reprogrammed to a metastatic state through the acquisition of platelet mitochondria via the PINK1/Parkin-Mfn2 pathway. Furthermore, platelet mitochondria regulate the GSH/GSSG ratio and reactive oxygen species (ROS) in cancer cells to promote lung metastasis of osteosarcoma. Impairing platelet mitochondrial function has proven to be an efficient approach to impair metastasis, providing a direction for osteosarcoma therapy. Our findings demonstrate mitochondrial transfer between platelets and cancer cells and suggest a role for platelet mitochondria in tumor metastasis.

Senescent Cells: Dual Implications on the Retinal Vascular System

Cellular senescence, a state of permanent cell cycle arrest in response to endogenous and exogenous stimuli, triggers a series of gradual alterations in structure, metabolism, and function, as well as inflammatory gene expression that nurtures a low-grade proinflammatory milieu in human tissue. A growing body of evidence indicates an accumulation of senescent neurons and blood vessels in response to stress and aging in the retina. Prolonged accumulation of senescent cells and long-term activation of stress signaling responses may lead to multiple chronic diseases, tissue dysfunction, and age-related pathologies by exposing neighboring cells to the heightened pathological senescence-associated secretory phenotype (SASP). However, the ultimate impacts of cellular senescence on the retinal vasculopathies and retinal vascular development remain ill-defined. In this review, we first summarize the molecular players and fundamental mechanisms driving cellular senescence, as well as the beneficial implications of senescent cells in driving vital physiological processes such as embryogenesis, wound healing, and tissue regeneration. Then, the dual implications of senescent cells on the growth, hemostasis, and remodeling of retinal blood vessels are described to document how senescent cells contribute to both retinal vascular development and the severity of proliferative retinopathies. Finally, we discuss the two main senotherapeutic strategies-senolytics and senomorphics-that are being considered to safely interfere with the detrimental effects of cellular senescence.

Application of mesenchymal stem cells for anti-senescence and clinical challenges

Senescence is a hot topic nowadays, which shows the accumulation of senescent cells and inflammatory factors, leading to the occurrence of various senescence-related diseases. Although some methods have been identified to partly delay senescence, such as strengthening exercise, restricting diet, and some drugs, these only slow down the process of senescence and cannot fundamentally delay or even reverse senescence. Stem cell-based therapy is expected to be a potential effective way to alleviate or cure senescence-related disorders in the coming future. Mesenchymal stromal cells (MSCs) are the most widely used cell type in treating various diseases due to their potentials of self-replication and multidirectional differentiation, paracrine action, and immunoregulatory effects. Some biological characteristics of MSCs can be well targeted at the pathological features of aging. Therefore, MSC-based therapy is also a promising strategy to combat senescence-related diseases. Here we review the recent progresses of MSC-based therapies in the research of age-related diseases and the challenges in clinical application, proving further insight and reference for broad application prospects of MSCs in effectively combating senesce in the future.

Noninvasive morpho-molecular imaging reveals early therapy-induced senescence in human cancer cells

Anticancer therapy screening in vitro identifies additional treatments and improves clinical outcomes. Systematically, although most tested cells respond to cues with apoptosis, an appreciable portion enters a senescent state, a critical condition potentially driving tumor resistance and relapse. Conventional screening protocols would strongly benefit from prompt identification and monitoring of therapy-induced senescent (TIS) cells in their native form. We combined complementary all-optical, label-free, and quantitative microscopy techniques, based on coherent Raman scattering, multiphoton absorption, and interferometry, to explore the early onset and progression of this phenotype, which has been understudied in unperturbed conditions. We identified TIS manifestations as early as 24 hours following treatment, consisting of substantial mitochondrial rearrangement and increase of volume and dry mass, followed by accumulation of lipid vesicles starting at 72 hours. This work holds the potential to affect anticancer treatment research, by offering a label-free, rapid, and accurate method to identify initial TIS in tumor cells.

Urban aerosol particulate matter promotes mitochondrial oxidative stress-induced cellular senescence in human retinal pigment epithelial ARPE-19 cells

Environmental exposure to urban particulate matter (UPM) is a serious health concern worldwide. Although several studies have linked UPM to ocular diseases, no study has reported effects of UPM exposure on senescence in retinal cells. Therefore, this study aimed to investigate the effects of UPM on senescence and regulatory signaling in human retinal pigment epithelial ARPE-19 cells. Our study demonstrated that UPM significantly promoted senescence, with increased senescence-associated β-galactosidase activity. Moreover, both mRNA and protein levels of senescence markers (p16 and p21) and the senescence-associated secretory phenotype, including IL-1β, matrix metalloproteinase-1, and -3 were upregulated. Notably, UPM increased mitochondrial reactive oxygen species-dependent nuclear factor-kappa B (NF-κB) activation during senescence. In contrast, use of NF-κB inhibitor Bay 11-7082 reduced the level of senescence markers. Taken together, our results provide the first in vitro preliminary evidence that UPM induces senescence by promoting mitochondrial oxidative stress-mediated NF-κB activation in ARPE-19 cells.

Reducing oxidative protein folding alleviates senescence by minimizing ER-to-nucleus H2 O2 release

Oxidative protein folding occurs in the endoplasmic reticulum (ER) to generate disulfide bonds, and the by-product is hydrogen peroxide (H2 O2 ). However, the relationship between oxidative protein folding and senescence remains uncharacterized. Here, we find that the protein disulfide isomerase (PDI), a key oxidoreductase that catalyzes oxidative protein folding, accumulated in aged human mesenchymal stem cells (hMSCs) and deletion of PDI alleviated hMSCs senescence. Mechanistically, knocking out PDI slows the rate of oxidative protein folding and decreases the leakage of ER-derived H2 O2 into the nucleus, thereby decreasing the expression of SERPINE1, which was identified as a key driver of cell senescence. Furthermore, we show that depletion of PDI alleviated senescence in various cell models of aging. Our findings reveal a previously unrecognized role of oxidative protein folding in promoting cell aging, providing a potential target for aging and aging-related disease intervention.

Defining Mitochondrial Cristae Morphology Changes Induced by Aging in Brown Adipose Tissue

Mitochondria are required for energy production and even give brown adipose tissue (BAT) its characteristic color due to their high iron content and abundance. The physiological function and bioenergetic capacity of mitochondria are connected to the structure, folding, and organization of its inner-membrane cristae. During the aging process, mitochondrial dysfunction is observed, and the regulatory balance of mitochondrial dynamics is often disrupted, leading to increased mitochondrial fragmentation in aging cells. Therefore, we hypothesized that significant morphological changes in BAT mitochondria and cristae would be present with aging. We developed a quantitative three-dimensional (3D) electron microscopy approach to map cristae network organization in mouse BAT to test this hypothesis. Using this methodology, we investigated the 3D morphology of mitochondrial cristae in adult (3-month) and aged (2-year) murine BAT tissue via serial block face-scanning electron microscopy (SBF-SEM) and 3D reconstruction software for manual segmentation, analysis, and quantification. Upon investigation, we found increases in mitochondrial volume, surface area, and complexity and decreased sphericity in aged BAT, alongside significant decreases in cristae volume, area, perimeter, and score. Overall, these data define the nature of the mitochondrial structure in murine BAT across aging.

Abstract Figure

Ultraviolet Radiation-Induced Mitochondrial Disturbances Are Attenuated by Metabolites of Melatonin in Human Epidermal Keratinocytes

Melatonin (N-acetyl-5-methoxytryptamine) is recognized as an effective antioxidant produced by the pineal gland, brain and peripheral organs, which also has anti-inflammatory, immunomodulatory, and anti-tumour capacities. Melatonin has been reported as a substance that counteracts ultraviolet radiation B (UVB)-induced intracellular disturbances. Nevertheless, the mechanistic actions of related molecules including its kynurenic derivatives (N1-acetyl-N2-formyl-5-methoxykynurenine (AFMK)), its indolic derivatives (6-hydroxymelatonin (6(OH)MEL) and 5-methoxytryptamine (5-MT)) and its precursor N-acetylserotonin (NAS) are only poorly understood. Herein, we treated human epidermal keratinocytes with UVB and assessed the protective effect of the studied substances in terms of the maintenance of mitochondrial function or their radical scavenging capacity. Our results show that UVB caused the significant elevation of catalase (CAT) and superoxide dismutase (Mn-SOD), the dissipation of mitochondrial transmembrane potential (mtΔΨ), a reduction in ATP synthesis, and the enhanced release of cytochrome c into cytosol, leading subsequently to UVB-mediated activation of the caspases and apoptosis (appearance of sub-G1 population). Our findings, combined with data reported so far, indicate the counteracting and beneficial actions of melatonin and its molecular derivatives against these deleterious changes within mitochondria. Therefore, they define a path to the development of novel strategies delaying mitochondrial aging and promoting the well-being of human skin.

Mitochondrial quality control in lung diseases: current research and future directions

Lung diseases are a major global health problem, affecting millions of people worldwide. Recent research has highlighted the critical role that mitochondrial quality control plays in respiratory-related diseases, including chronic obstructive pulmonary disease (COPD), lung cancer, and idiopathic pulmonary fibrosis (IPF). In this review, we summarize recent findings on the involvement of mitochondrial quality control in these diseases and discuss potential therapeutic strategies. Mitochondria are essential organelles for energy production and other cellular processes, and their dysfunction is associated with various diseases. The quality control of mitochondria involves a complex system of pathways, including mitophagy, mitochondrial biogenesis, fusion/fission dynamics, and regulation of gene expression. In COPD and lung cancer, mitochondrial quality control is often involved in disease development by influencing oxidative stress and apoptosis. In IPF, it appears to be involved in the disease process by participating in the cellular senescence process. Mitochondrial quality control is a promising target for therapeutic interventions in lung diseases. However, there are conflicting reports on different pathological processes, such as the role of mitochondrial autophagy in lung cancer, which pose difficulties in the study of targeted mitochondrial quality control drugs. Additionally, there seems to be a delicate balance between the mitochondrial quality control processes in the physiological state. Emerging evidence suggests that molecules such as PTEN-induced putative kinase 1 (PINK1), parkin RBR E3 ubiquitin protein ligase (PRKN), dynamin-related protein 1 (DRP1), and peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α), as well as the signaling pathways they affect, play an important role in respiratory-related diseases. Targeting these molecules and pathways could contribute to the development of effective treatments for lung diseases. In conclusion, the involvement of mitochondrial quality control in lung diseases presents a promising new avenue for disease treatment. Further research is needed to better understand the complex mechanisms involved in the pathogenesis of respiratory diseases and to develop targeted therapies that could improve clinical outcomes.

Dysregulated cellular redox status during hyperammonemia causes mitochondrial dysfunction and senescence by inhibiting sirtuin-mediated deacetylation

Perturbed metabolism of ammonia, an endogenous cytotoxin, causes mitochondrial dysfunction, reduced NAD+ /NADH (redox) ratio, and postmitotic senescence. Sirtuins are NAD+ -dependent deacetylases that delay senescence. In multiomics analyses, NAD metabolism and sirtuin pathways are enriched during hyperammonemia. Consistently, NAD+ -dependent Sirtuin3 (Sirt3) expression and deacetylase activity were decreased, and protein acetylation was increased in human and murine skeletal muscle/myotubes. Global acetylomics and subcellular fractions from myotubes showed hyperammonemia-induced hyperacetylation of cellular signaling and mitochondrial proteins. We dissected the mechanisms and consequences of hyperammonemia-induced NAD metabolism by complementary genetic and chemical approaches. Hyperammonemia inhibited electron transport chain components, specifically complex I that oxidizes NADH to NAD+ , that resulted in lower redox ratio. Ammonia also caused mitochondrial oxidative dysfunction, lower mitochondrial NAD+ -sensor Sirt3, protein hyperacetylation, and postmitotic senescence. Mitochondrial-targeted Lactobacillus brevis NADH oxidase (MitoLbNOX), but not NAD+ precursor nicotinamide riboside, reversed ammonia-induced oxidative dysfunction, electron transport chain supercomplex disassembly, lower ATP and NAD+ content, protein hyperacetylation, Sirt3 dysfunction and postmitotic senescence in myotubes. Even though Sirt3 overexpression reversed ammonia-induced hyperacetylation, lower redox status or mitochondrial oxidative dysfunction were not reversed. These data show that acetylation is a consequence of, but is not the mechanism of, lower redox status or oxidative dysfunction during hyperammonemia. Targeting NADH oxidation is a potential approach to reverse and potentially prevent ammonia-induced postmitotic senescence in skeletal muscle. Since dysregulated ammonia metabolism occurs with aging, and NAD+ biosynthesis is reduced in sarcopenia, our studies provide a biochemical basis for cellular senescence and have relevance in multiple tissues.

Mitigating Oxidative Stress in Perinatal Cells: A Critical Step toward an Optimal Therapeutic Use in Regenerative Medicine

Oxidative stress (OS) occurs when the production of reactive oxygen species (ROS) is not balanced by the body's antioxidant defense system. OS can profoundly affect cellular health and function. ROS can have a profound negative impact on cells that undergo a predestined and time-regulated process of proliferation or differentiation, such as perinatal stem cells. Due to the large-scale employment of these immunotolerant stem cells in regenerative medicine, it is important to reduce OS to prevent them from losing function and increase their application in the regenerative medicine field. This goal can be achieved through a variety of strategies, such as the use of antioxidants and other compounds that can indirectly modulate the antioxidant defense system by enhancing cellular stress response pathways, including autophagy and mitochondrial function, thereby reducing ROS levels. This review aims to summarize information regarding OS mechanisms in perinatal stem cells and possible strategies for reducing their deleterious effects.

Parkinson's Disease: A Tale of Many Players

In 2020, more than 9 million patients suffering from Parkinson's disease (PD) were reported worldwide, and studies predict that the burden of this disease will grow substantially in industrial countries. In the last decade, there has been a better understanding of this neurodegenerative disorder, clinically characterized by motor disturbances, impaired balance, coordination, memory difficulties, and behavioral changes. Various preclinical investigations and studies on human postmortem brains suggest that local oxidative stress and inflammation promote misfolding and aggregation of alpha-synuclein within Lewy bodies and cause nerve cell damage. Parallel to these investigations, the familial contribution to the disease became evident from studies on genome-wide association in which specific genetic defects were linked to neuritic alpha-synuclein pathology. As for treatment, currently available pharmacological and surgical interventions may improve the quality of life but do not stop the progress of neurodegeneration. However, numerous preclinical studies have provided insights into the pathogenesis of PD. Their results provide a solid base for clinical trials and further developments. In this review, we discuss the pathogenesis, the prospects, and challenges of synolytic therapy, CRISPR, gene editing, and gene- and cell-based therapy. We also throw light on the recent observation that targeted physiotherapy may help improve the gait and other motor impairments.

Epigenetic Mechanisms of Aging and Aging-Associated Diseases

Aging is an inevitable outcome of life, characterized by a progressive decline in tissue and organ function. At a molecular level, it is marked by the gradual alterations of biomolecules. Indeed, important changes are observed on the DNA, as well as at a protein level, that are influenced by both genetic and environmental parameters. These molecular changes directly contribute to the development or progression of several human pathologies, including cancer, diabetes, osteoporosis, neurodegenerative disorders and others aging-related diseases. Additionally, they increase the risk of mortality. Therefore, deciphering the hallmarks of aging represents a possibility for identifying potential druggable targets to attenuate the aging process, and then the age-related comorbidities. Given the link between aging, genetic, and epigenetic alterations, and given the reversible nature of epigenetic mechanisms, the precisely understanding of these factors may provide a potential therapeutic approach for age-related decline and disease. In this review, we center on epigenetic regulatory mechanisms and their aging-associated changes, highlighting their inferences in age-associated diseases.

Mitochondrion: A bridge linking aging and degenerative diseases

Aging is a natural process, characterized by progressive loss of physiological integrity, impaired function, and increased vulnerability to death. For centuries, people have been trying hard to understand the process of aging and find effective ways to delay it. However, limited breakthroughs have been made in anti-aging area. Since the hallmarks of aging were summarized in 2013, increasing studies focus on the role of mitochondrial dysfunction in aging and aging-related degenerative diseases, such as neurodegenerative diseases, osteoarthritis, metabolic diseases, and cardiovascular diseases. Accumulating evidence indicates that restoring mitochondrial function and biogenesis exerts beneficial effects in extending lifespan and promoting healthy aging. In this paper, we provide an overview of mitochondrial changes during aging and summarize the advanced studies in mitochondrial therapies for the treatment of degenerative diseases. Current challenges and future perspectives are proposed to provide novel and promising directions for future research.

Yeast Chromatin Mutants Reveal Altered mtDNA Copy Number and Impaired Mitochondrial Membrane Potential

Mitochondria are multifunctional, dynamic organelles important for stress response, cell longevity, ageing and death. Although the mitochondrion has its genome, nuclear-encoded proteins are essential in regulating mitochondria biogenesis, morphology, dynamics and function. Moreover, chromatin structure and epigenetic mechanisms govern the accessibility to DNA and control gene transcription, indirectly influencing nucleo-mitochondrial communications. Thus, they exert crucial functions in maintaining proper chromatin structure, cell morphology, gene expression, stress resistance and ageing. Here, we present our studies on the mtDNA copy number in Saccharomyces cerevisiae chromatin mutants and investigate the mitochondrial membrane potential throughout their lifespan. The mutants are arp4 (with a point mutation in the ARP4 gene, coding for actin-related protein 4-Arp4p), hho1Δ (lacking the HHO1 gene, coding for the linker histone H1), and the double mutant arp4 hho1Δ cells with the two mutations. Our findings showed that the three chromatin mutants acquired strain-specific changes in the mtDNA copy number. Furthermore, we detected the disrupted mitochondrial membrane potential in their chronological lifespan. In addition, the expression of nuclear genes responsible for regulating mitochondria biogenesis and turnover was changed. The most pronounced were the alterations found in the double mutant arp4 hho1Δ strain, which appeared as the only petite colony-forming mutant, unable to grow on respiratory substrates and with partial depletion of the mitochondrial genome. The results suggest that in the studied chromatin mutants, hho1Δ, arp4 and arp4 hho1Δ, the nucleus-mitochondria communication was disrupted, leading to impaired mitochondrial function and premature ageing phenotype in these mutants, especially in the double mutant.

Investigation of the cell structure and organelles during autolytic PCD of Antirrhinum majus "Legend White" petals

One of the classes of the plant developmental programmed cell death (PCD) is vacuolar cell death or autolysis. The results of the transmission electron microscope (TEM) studies indicated that this type of PCD occurs during the petal senescence of Antirrhinum majus "Legend White" flowers. The major hallmarks of the process related to the ultrastructure of the cells involved chloroplast degradation, vacuolation, chromatin condensation, cell wall swelling, degradation of Golgi apparatus, protoplasmic shrinkage, degradation of the endoplasmic reticulum, nuclear fragmentation, rupture of tonoplast, and plasma membrane. Macroautophagy and microautophagy processes were also clearly observed during vacuole formation. As in yeasts, in the present study, Golgi apparatus became autophagosome-like structures during degradation that had autophagy activity and then disappeared. Our results revealed a type of selective microautophagy, piecemeal microautophagy of the nucleus (PMN), in nuclear degradation during PCD of petals that has not previously been reported in plants. Moreover, vesicular structures, such as paramural and multilamellar bodies, were observed in some stages.

RhoA rescues cardiac senescence by regulating Parkin-mediated mitophagy

Heart failure is one of the leading causes of death worldwide. RhoA, a small GTPase, governs actin dynamics in various tissue and cell types, including cardiomyocytes; however, its involvement in cardiac function has not been fully elucidated. Here, we generated cardiomyocyte-specific RhoA conditional knockout (cKO) mice, which demonstrated a significantly shorter lifespan with left ventricular dilation and severely impaired ejection fraction. We found that the cardiac tissues of the cKO mice exhibited structural disorganization with fibrosis and also exhibited enhanced senescence compared with control mice. In addition, we show that cardiomyocyte mitochondria were structurally abnormal in the aged cKO hearts. Clearance of damaged mitochondria by mitophagy was remarkably inhibited in both cKO cardiomyocytes and RhoA-knockdown HL-1 cultured cardiomyocytes. In RhoA-depleted cardiomyocytes, we reveal that the expression of Parkin, an E3 ubiquitin ligase that plays a crucial role in mitophagy, was reduced, and expression of N-Myc, a negative regulator of Parkin, was increased. We further reveal that the RhoA-Rho kinase axis induced N-Myc phosphorylation, which led to N-Myc degradation and Parkin upregulation. Re-expression of Parkin in RhoA-depleted cardiomyocytes restored mitophagy, reduced mitochondrial damage, attenuated cardiomyocyte senescence, and rescued cardiac function both in vitro and in vivo. Finally, we found that patients with idiopathic dilated cardiomyopathy without causal mutations for dilated cardiomyopathy showed reduced cardiac expression of RhoA and Parkin. These results suggest that RhoA promotes Parkin-mediated mitophagy as an indispensable mechanism contributing to cardioprotection in the aging heart.

Sirt3 activates autophagy to prevent DOX-induced senescence by inactivating PI3K/AKT/mTOR pathway in A549 cells

Sirtuin 3 (Sirt3), a mitochondrial deacetylase, regulates mitochondrial redox homeostasis and autophagy and is involved in physiological and pathological processes such as aging, cellular metabolism, and tumorigenesis. We here investigate how Sirt3 regulates doxorubicin (DOX)-induced senescence in lung cancer A549 cells. Sirt3 greatly reduced DOX-induced upregulation of senescence marker proteins p53, p16, p21 and SA-β-Gal activity as well as ROS levels. Notably, Sirt3 reversed DOX-induced autophagic flux blockage, as shown by increased p62 degradation and LC3II/LC3I ratio. Importantly, the autophagy inhibitors 3-methyladenine (3-MA) and chloroquine (CQ) partially abolished the antioxidant stress and antiaging effects of Sirt3, while the autophagy activator rapamycin (Rap) potentiated these effects of Sirt3, demonstrating that autophagy mediates the anti-aging effects of Sirt3. Additionally, Sirt3 inhibited the DOX-induced activation of the phosphatidylinositol-3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) signaling pathway, which in turn activated autophagy. The PI3K inhibitor LY294002 promoted the antioxidant stress and antiaging effects of Sirt3, while the AKT activator SC-79 reversed these effects of Sirt3. Taken together, Sirt3 counteracts DOX-induced senescence by improving autophagic flux.

H2S contributed from CSE during cellular senescence suppresses inflammation and nitrosative stress

Aging involves the time-dependent deterioration of physiological functions attributed to various intracellular and extracellular factors. Cellular senescence is akin to aging and involves alteration in redox homeostasis. This is primarily marked by increased reactive oxygen/nitrogen species (ROS/RNS), inflammatory gene expression, and senescence-associated beta-galactosidase activity, all hallmarks of aging. It is proposed that gasotransmitters which include hydrogen sulfide (H₂S), carbon monoxide (CO), and nitric oxide (NO), may affect redox homeostasis during senescence. H₂S has been independently shown to induce DNA damage and suppress oxidative stress. While an increase in NO levels during aging is well established, the role of H₂S has remained controversial. To understand the role of H₂S during aging, we evaluated H₂S homeostasis in non-senescent and senescent cells, using a combination of direct measurements with a fluorescent reporter dye (WSP-5) and protein sulfhydration analysis. The free intracellular H₂S and total protein sulfhydration levels are high during senescence, concomitant to cystathionine gamma-lyase (CSE) expression induction. Using lentiviral shRNA-mediated expression knockdown, we identified that H₂S contributed by CSE alters global gene expression, which regulates key inflammatory processes during cellular senescence. We propose that H₂S decreases inflammation during cellular senescence by reducing phosphorylation of IκBα and the p65 subunit of nuclear factor kappa B (NF-κB). H₂S was also found to reduce NO levels, a significant source of nitrosative stress during cellular senescence. Overall, we establish H₂S as a key gasotransmitter molecule that regulates inflammatory phenotype and nitrosative stress during cellular senescence.

Aging and Bone Metabolism

Changes in bone architecture and metabolism with aging increase the likelihood of osteoporosis and fracture. Age-onset osteoporosis is multifactorial, with contributory extrinsic and intrinsic factors including certain medical problems, specific prescription drugs, estrogen loss, secondary hyperparathyroidism, microenvironmental and cellular alterations in bone tissue, and mechanical unloading or immobilization. At the histological level, there are changes in trabecular and cortical bone as well as marrow cellularity, lineage switching of mesenchymal stem cells to an adipogenic fate, inadequate transduction of signals during skeletal loading, and predisposition toward senescent cell accumulation with production of a senescence-associated secretory phenotype. Cumulatively, these changes result in bone remodeling abnormalities that over time cause net bone loss typically seen in older adults. Age-related osteoporosis is a geriatric syndrome due to the multiple etiologies that converge upon the skeleton to produce the ultimate phenotypic changes that manifest as bone fragility. Bone tissue is dynamic but with tendencies toward poor osteoblastic bone formation and relative osteoclastic bone resorption with aging. Interactions with other aging physiologic systems, such as muscle, may also confer detrimental effects on the aging skeleton. Conversely, individuals who maintain their BMD experience a lower risk of fractures, disability, and mortality, suggesting that this phenotype may be a marker of successful aging. © 2023 American Physiological Society. Compr Physiol 13:4355-4386, 2023.

Molecular Mechanisms of Neuroinflammation in Aging and Alzheimer's Disease Progression

Aging is the most prominent risk factor for late-onset Alzheimer's disease. Aging associates with a chronic inflammatory state both in the periphery and in the central nervous system, the evidence thereof and the mechanisms leading to chronic neuroinflammation being discussed. Nonetheless, neuroinflammation is significantly enhanced by the accumulation of amyloid beta and accelerates the progression of Alzheimer's disease through various pathways discussed in the present review. Decades of clinical trials targeting the 2 abnormal proteins in Alzheimer's disease, amyloid beta and tau, led to many failures. As such, targeting neuroinflammation via different strategies could prove a valuable therapeutic strategy, although much research is still needed to identify the appropriate time window. Active research focusing on identifying early biomarkers could help translating these novel strategies from bench to bedside.

Anti-Aging Effects of Anthocyanin Extracts of Sambucus canadensis Caused by Targeting Mitochondrial-Induced Oxidative Stress

Anthocyanin is a natural antioxidant agent extracted from the fruits of Sambucus canadensis, which has been considered to have potential anti-aging effects. Cell senescence is the primary cause of aging and related diseases. Recently, research on the development of compounds for eliminating senescent cells or damaged organs have shown prospects. The compounds which promote the clearing of senescent cells are called "senolytics". Though anthocyanin is considered to have potential anti-aging effects owing to its anti-inflammatory and antioxidant activities, the mechanism of the elimination of senescent cells remains unclear. In this study, we prepared anthocyanins extracted from the fruits of Sambucus canadensis and evaluated their anti-aging effects in vivo and in vitro. We found that anthocyanin could significantly reduce cell senescence and aging of the lens by inhibiting the activity of the PI3K/AKT/mTOR signaling pathway, consequently promoting the apoptosis of senescent cells, increasing the autophagic and mitophagic flux, and enhancing the renewal of mitochondria and the cell to maintain cellular homeostasis, leading to attenuating aging. Therefore, our study provided a basis for anthocyanin to be used as new "senolytics" in anti-aging.

Mitochondrial Aging and Senolytic Natural Products with Protective Potential

Living organisms do not disregard the laws of thermodynamics and must therefore consume energy for their survival. In this way, cellular energy exchanges, which aim above all at the production of ATP, a fundamental molecule used by the cell for its metabolisms, favor the formation of waste products that, if not properly disposed of, can contribute to cellular aging and damage. Numerous genes have been linked to aging, with some favoring it (gerontogenes) and others blocking it (longevity pathways). Animal model studies have shown that calorie restriction (CR) may promote longevity pathways, but given the difficult application of CR in humans, research is investigating the use of CR-mimetic substances capable of producing the same effect. These include some phytonutrients such as oleuropein, hydroxytyrosol, epigallo-catechin-gallate, fisetin, quercetin, and curcumin and minerals such as magnesium and selenium. Some of them also have senolytic effects, which promote the apoptosis of defective cells that accumulate over the years (senescent cells) and disrupt normal metabolism. In this article, we review the properties of these natural elements that can promote a longer and healthier life.

The role of vitamin D on redox regulation and cellular senescence

Vitamin D is considered an essential micronutrient for human health that is metabolized into a multifunctional secosteroid hormone. We can synthesize it in the skin through ultraviolet B (UVB) rays or acquire it from the diet. Its deficiency is a major global health problem that affects all ages and ethnic groups. Furthermore, dysregulation of vitamin D homeostasis has been associated with premature aging, driven by various cellular processes, including oxidative stress and cellular senescence. Various studies have shown that vitamin D can attenuate oxidative stress and delay cellular senescence, mainly by inducing the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and Klotho and improving mitochondrial homeostasis, proposing this vitamin as an excellent candidate for delaying aging. However, the mechanisms around these processes are not yet fully explored. Therefore, in this review, the effects of vitamin D on redox regulation and cellular senescence are discussed to propose new lines of research and clinical applications of vitamin D in the context of age-related diseases.

Combined physical exercise reverses the reduced expression of Bmal1 in the liver of aged mice

Aging can modify the morphology and function of the liver, such as generating a decrease in the mitochondria content, autophagy, and cell senescence. Although exercise training has several beneficial effects on hepatic metabolism, its actions on autophagy processes, mitochondrial function, and cellular senescence need to be more widely explored. The present study verified the effects of aging and exercise on hepatic circadian markers, autophagy, and mitochondria activity in 24-month-old mice with a combined exercise training protocol. In addition, we used public datasets from human livers in several conditions and BMAL1 knockout mice. C57BL/6 mice were distributed into Control (CT, young, 6-month-old mice), sedentary old (Old Sed, sedentary, 24-month-old mice), and exercised old (Old Ex, 24-month-old mice submitted to a combined exercise training protocol). The exercise training protocol consisted of three days of endurance exercise - treadmill running, and two days of resistance exercise - climbing a ladder, for three weeks. At the end of the protocol, the liver was removed and prepared for histological analysis, reverse transcription-quantitative polymerase chain reaction (RT-qPCR), immunoblotting technique, and oxygen consumption. Heatmaps were built using a human dataset and Bmal1 knockout samples. In summary, the Old Sed had reduced strength, coordination, and balance, as well as a decrease in Bmal1 expression and the presence of degenerated liver cells. Still, this group upregulated the transcription factors related to mitochondrial biogenesis. The Old Ex group had increased strength, coordination, and balance, improved glucose sensitivity, as well as restored Bmal1 expression and the mitochondrial transcription factors. The human datasets indicated that mitochondrial markers and autophagy strongly correlate with specific liver diseases but not aging. We can speculate that mitochondrial and autophagy molecular markers alterations may depend on long-term training.

Targeting Multiple Homeostasis-Maintaining Systems by Ionophore Nigericin Is a Novel Approach for Senolysis

Within the present study we proposed a novel approach for senolysis based on the simultaneous disturbance of the several homeostasis-maintaining systems in senescent cells including intracellular ionic balance, energy production and intracellular utilization of damaged products. Of note, we could not induce senolysis by applying ouabain, amiloride, valinomycin or NH₄Cl-compounds that modify each of these systems solely. However, we found that ionophore nigericin can disturb plasma membrane potential, intracellular pH, mitochondrial membrane potential and autophagy at once. By affecting all of the tested homeostasis-maintaining systems, nigericin induced senolytic action towards stromal and epithelial senescent cells of different origins. Moreover, the senolytic effect of nigericin was independent of the senescence-inducing stimuli. We uncovered that K⁺ efflux caused by nigericin initiated pyroptosis in senescent cells. According to our data, the higher sensitivity of senescent cells compared to the control ones towards nigericin-induced death was partially mediated by the lower intracellular K⁺ content in senescent cells and by their predisposition towards pyroptosis. Finally, we proposed an interval dosing strategy to minimize the negative effects of nigericin on the control cells and to achieve maximal senolytic effect. Hence, our data suggest ionophore nigericin as a new senotherapeutic compound for testing against age-related diseases.

Vascular dysfunction in COVID-19 patients: update on SARS-CoV-2 infection of endothelial cells and the role of long non-coding RNAs

Although COVID-19 is primarily a respiratory disease, it may affect also the cardiovascular system. COVID-19 patients with cardiovascular disorder (CVD) develop a more severe disease course with a significantly higher mortality rate than non-CVD patients. A common denominator of CVD is the dysfunction of endothelial cells (ECs), increased vascular permeability, endothelial-to-mesenchymal transition, coagulation, and inflammation. It has been assumed that clinical complications in COVID-19 patients suffering from CVD are caused by SARS-CoV-2 infection of ECs through the angiotensin-converting enzyme 2 (ACE2) receptor and the cellular transmembrane protease serine 2 (TMPRSS2) and the consequent dysfunction of the infected vascular cells. Meanwhile, other factors associated with SARS-CoV-2 entry into the host cells have been described, including disintegrin and metalloproteinase domain-containing protein 17 (ADAM17), the C-type lectin CD209L or heparan sulfate proteoglycans (HSPG). Here, we discuss the current data about the putative entry of SARS-CoV-2 into endothelial and smooth muscle cells. Furthermore, we highlight the potential role of long non-coding RNAs (lncRNAs) affecting vascular permeability in CVD, a process that might exacerbate disease in COVID-19 patients.