The mitochondrial genome in aging and senescence

Autophagy and Senescence: The Molecular Mechanisms and Implications in Liver Diseases

The liver is the primary organ accountable for complex physiological functions, including lipid metabolism, toxic chemical degradation, bile acid synthesis, and glucose metabolism. Liver function homeostasis is essential for the stability of bodily functions and is involved in the complex regulation of the balance between cell proliferation and cell death. Cell proliferation-halting mechanisms, including autophagy and senescence, are implicated in the development of several liver diseases, such as cholestasis, viral hepatitis, nonalcoholic fatty liver disease, liver fibrosis, and hepatocellular carcinoma. Among various cell death mechanisms, autophagy is a highly conserved and self-degradative cellular process that recycles damaged organelles, cellular debris, and proteins. This process also provides the substrate for further metabolism. A defect in the autophagy machinery can lead to premature diseases, accelerated aging, inflammatory state, tumorigenesis, and cellular senescence. Senescence, another cell death type, is an active player in eliminating premalignant cells. At the same time, senescent cells can affect the function of neighboring cells by secreting the senescence-associated secretory phenotype and induce paracrine senescence. Autophagy can promote and delay cellular senescence under different contexts. This review decodes the roles of autophagy and senescence in multiple liver diseases to achieve a better understanding of the regulatory mechanisms and implications of autophagy and senescence in various liver diseases.

Mitochondria pleiotropism in stem cell senescence: Mechanisms and therapeutic approaches

Aging is a complex biological process characterized by a progressive decline in cellular and tissue function, ultimately leading to organismal aging. Stem cells, with their regenerative potential, play a crucial role in maintaining tissue homeostasis and repair throughout an organism's lifespan. Mitochondria, the powerhouses of the cell, have emerged as key players in the aging process, impacting stem cell function and contributing to age-related tissue dysfunction. Here are discuss the mechanisms through which mitochondria influence stem cell fate decisions, including energy production, metabolic regulation, ROS signalling, and epigenetic modifications. Therefore, this review highlights the role of mitochondria in driving stem cell senescence and the subsequent impact on tissue function, leading to overall organismal aging and age-related diseases. Finally, we explore potential anti-aging therapies targeting mitochondrial health and discuss their implications for promoting healthy aging. This comprehensive review sheds light on the critical interplay between mitochondrial function, stem cell senescence, and organismal aging, offering insights into potential strategies for attenuating age-related decline and promoting healthy longevity.

Mitochondria as central hubs in synaptic modulation

Mitochondria are present in the pre- and post-synaptic regions, providing the energy required for the activity of these very specialized neuronal compartments. Biogenesis of synaptic mitochondria takes place in the cell body, and these organelles are then transported to the synapse by motor proteins that carry their cargo along microtubule tracks. The transport of mitochondria along neurites is a highly regulated process, being modulated by the pattern of neuronal activity and by extracellular cues that interact with surface receptors. These signals act by controlling the distribution of mitochondria and by regulating their activity. Therefore, mitochondria activity at the synapse allows the integration of different signals and the organelles are important players in the response to synaptic stimulation. Herein we review the available evidence regarding the regulation of mitochondrial dynamics by neuronal activity and by neuromodulators, and how these changes in the activity of mitochondria affect synaptic communication.

Insights into the Global Transcriptome Response of Lentinula edodes Mycelia during Aging

The spawn of Lentinula edodes and other basidiomycete fungi tend to age with long-term culture. This causes heavy yield losses if aging spawn is used for propagation. In this study, we cultivated dikaryotic L. edodes mycelia in plates for 60 days to produce intrinsic aging phenotypes. We found that intracellular reactive oxygen species levels increased in contrast to mitochondrial depolarization and also observed greater DNA fragmentation with longer culture time. Transcriptome analysis of mycelia at different growth stages revealed pronounced expression differences between short- and long-term cultures. In particular, "phenylalanine, tyrosine, and tryptophan biosynthesis", "mitophagy and autophagy", "MAPK signaling pathway", and "ABC transporter" were among the enriched terms in the mycelial aging process. Weighted correlation network analysis identified LeAtg8, LeHog1, LePbs2, and LemTOR as key genes during aging. Western blotting confirmed that LeATG8 and phosphorylated LeHOG1 protein levels were significantly upregulated in aging mycelia. Our combined analytical approach provides insights into the mechanisms that regulate mycelial aging, indicating that autophagy/mitophagy plays a major role in counteracting the effects of age on mycelial growth development.

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.

Helicobacter pylori-positive chronic atrophic gastritis and cellular senescence

BACKGROUND

Chronic atrophic gastritis (CAG) is a pathological stage in the Correa's cascade, whereby Helicobacter pylori (H. pylori) infection is the primary cause. Cellular senescence is an inducing factor for cancer occurrence and cellular senescence is an obvious phenomenon in gastric mucosal tissues of H. pylori-positive CAG patients.

METHODS

In this review, we collated the information on cellular senescence and H. pylori-positive CAG.

RESULTS

At present, only a few studies have observed the effect of cellular senescence on precancerous lesions. In combination with the latest research, this review has collated the information on cellular senescence and H. pylori-positive CAG from four aspects- telomere shortening, DNA methylation, increased reacive oxygen species (ROS) production, and failure of autophagy.

CONCLUSION

This is expected to be helpful for exploring the relevant mechanisms underlying inflammatory cancerous transformation and formulating appropriate treatment strategies.

Role of angiotensin II in aging

Aging is an inevitable progressive decline in physiological organ function that increases the chance of disease and death. The renin-angiotensin system (RAS) is involved in the regulation of vasoconstriction, fluid homeostasis, cell growth, fibrosis, inflammation, and oxidative stress. In recent years, unprecedented advancement has been made in the RAS study, particularly with the observation that angiotensin II (Ang II), the central product of the RAS, plays a significant role in aging and chronic disease burden with aging. Binding to its receptors (Ang II type 1 receptor - AT1R in particular), Ang II acts as a mediator in the aging process by increasing free radical production and, consequently, mitochondrial dysfunction and telomere attrition. In this review, we examine the physiological function of the RAS and reactive oxygen species (ROS) sources in detail, highlighting how Ang II amplifies or drives mitochondrial dysfunction and telomere attrition underlying each hallmark of aging and contributes to the development of aging and age-linked diseases. Accordingly, the Ang II/AT1R pathway opens a new preventive and therapeutic direction for delaying aging and reducing the incidence of age-related diseases in the future.

Occupational exposure to pesticides and its association with telomere length - A systematic review and meta-analysis

BACKGROUND

Telomere length is a common biomarker for the cumulative effect of environmental factors on aging-related diseases, therefore an association has been hypothesized between occupational exposure to pesticides and shorter telomere length.

OBJECTIVE

This study is a systematic review and meta-analysis aiming to examine the association between telomere length and occupational exposure to pesticides.

METHODS

We systematically searched in SciELO, PubMed, Scopus, Embase, Cochrane, Lilacs, Science Direct, and Web of Science databases for all observational studies containing measurements of telomere length on groups occupationally exposed to pesticides. Data were synthesized through qualitative synthesis and meta-analysis. We estimated the associations between exposed and non-exposed groups by using the natural log of the response ratio (lnRR). Heterogeneity was quantified using the Cochran Q test and I² statistics.

RESULTS

Six studies were included in the qualitative synthesis and meta-analysis, with a total of 480 participants exposed to pesticides. The time of exposure evaluated 391 participants that had a range of 5 to >30 years of occupational exposure. Most studies presented shorter telomere length in the occupationally exposed group. From the six studies included in the meta-analysis, three presented telomere length measurement as a single copy gene (T/S), and three presented telomere length measurement as base pairs (bp). The statistical analysis pooled estimates (log ratio of means) of the telomere length in both measurements (T/S and bp) showed a shortening of telomere length in the exposed group when compared with the non-exposed (control) group. Two of six studies reported longer telomere length in the group exposed to pesticides.

DISCUSSION

Our findings suggest an association between occupational exposure to pesticides and shorter telomere length. However, we found a small number of studies to include in our meta-analysis, being required more high-quality studies to strengthen our findings and conclusions.

Multi-Ingredient Supplement Supports Mitochondrial Health through Interleukin-15 Signaling in Older Adult Human Dermal Fibroblasts

The macroscopic and microscopic deterioration of human skin with age is, in part, attributed to a functional decline in mitochondrial health. We previously demonstrated that exercise attenuated age-associated changes within the skin through enhanced mitochondrial health via IL-15 signaling, an exercise-induced cytokine whose presence increases in circulation following physical activity. The purpose of this investigation was to determine if these mitochondrial-enhancing effects could be mimicked with the provision of a novel multi-ingredient supplement (MIS). Cultured human fibroblasts isolated from older, sedentary women were treated with control media (CON) or CON supplemented with the following active ingredients to create the MIS: coenzyme Q10, alpha lipoic acid, resveratrol, curcumin, zinc, lutein, astaxanthin, copper, biotin, and vitamins C, D, and E. Outcomes were determined following 24 or 72 h of treatment. MIS provision to dermal fibroblasts significantly increased the mRNA abundance of mitochondrial biogenesis activators and downstream IL-15 signaling pathways, and proteins for oxidative phosphorylation subunits and antioxidant defenses. These findings were co-temporal with lower cellular senescence and cytotoxicity following MIS treatment. In summary, MIS supplementation led to exercise-mimetic effects on human dermal fibroblasts and their mitochondria by reproducing the molecular and biochemical effects downstream of IL-15 activation.

Relationship between oxidative stress and lifespan in Daphnia pulex

Macromolecular damage leading to cell, tissue and ultimately organ dysfunction is a major contributor to aging. Intracellular reactive oxygen species (ROS) resulting from normal metabolism cause most damage to macromolecules and the mitochondria play a central role in this process as they are the principle source of ROS. The relationship between naturally occurring variations in the mitochondrial (MT) genomes leading to correspondingly less or more ROS and macromolecular damage that changes the rate of aging associated organismal decline remains relatively unexplored. MT complex I, a component of the electron transport chain (ETC), is a key source of ROS and the NADH dehydrogenase subunit 5 (ND5) is a highly conserved core protein of the subunits that constitute the backbone of complex I. Using Daphnia as a model organism, we explored if the naturally occurring sequence variations in ND5 correlate with a short or long lifespan. Our results indicate that the short-lived clones have ND5 variants that correlate with reduced complex I activity, increased oxidative damage, and heightened expression of ROS scavenger enzymes. Daphnia offers a unique opportunity to investigate the association between inherited variations in components of complex I and ROS generation which affects the rate of aging and lifespan.

The overexpression of Tipe2 in CRC cells suppresses survival while endogenous Tipe2 accelerates AOM/DSS induced-tumor initiation

Aging is a natural and progressive process characterized by an increased frequency of age-related diseases such as cancer. But its mechanism is unclear. TNFAIP8L2 (Tipe2) is an important negative regulator for homeostasis through inhibiting TLR and TCR signaling. Our work reveals that Tipe2 might have dual function by regulating senescence. One side, the overexpression of Tipe2 in CRC cells could induce typical senescent phenotype, especially exposure to oxidative stress. Tipe2 inhibits telomerase activity by regulating c-Myc and c-Est-2 binding to the hTERT promotor. Interestingly, Tipe2 KO mice treated with D-Gal showed a less serious inverse of CD4:CD8 ratio, a lower percentage of Treg compared to WT. Besides, Tipe2 KO mice were more tolerant to the initiation of AOM/DSS-induced CRC, accompanied by a lower level of Treg within IEL. Therefore, specific antibodies against CD25 effectively ameliorate tumorigenesis. These data suggest strongly that the overexpressed Tipe2 suppresses tumor cells proliferation and survival, but endogenous Tipe2 promotes the initiation of tumorigenesis when exposure to dangerous environment such as AOM/DSS-related inflammation.

Redd1 knockdown prevents doxorubicin-induced cardiac senescence

Regulated in development and DNA damage response-1 (Redd1) is a stress-response gene that is transcriptionally induced by diverse stressful stimuli to influence cellular growth and survival. Although evidence suggests that aging may drive Redd1 expression in skeletal muscles, the expression patterns and functions of Redd1 in senescent cardiomyocytes remain unspecified. To address this issue, in vitro and in vivo models of cardiomyocyte senescence were established by administration of doxorubicin (Dox). Redd1 overexpression and knockdown was achieved in cultured H9c2 cardiomyocytes and mouse tissues using, respectively, lentivirals and adeno-associated virus 9 (AAV9) vectors. In the hearts of both aged (24 months old) and Dox-treated mice, as well as in Dox-exposed H9c2 cardiomyocytes, high Redd1 expression accompanied the increase in both cellular senescence markers (p16INK4a and p21) and pro-inflammatory cytokine expression indicative of a stress-associated secretory phenotype (SASP). Notably, Redd1 overexpression accentuated, whereas Redd1 silencing markedly attenuated, Dox-induced cardiomyocyte senescence features both in vitro and in vivo. Notably, AAV9-shRNA-mediated Redd1 silencing significantly alleviated Dox-induced cardiac dysfunction. Moreover, through pharmacological inhibition, immunofluorescence, and western blotting, signaling pathway analyses indicated that Redd1 promotes cardiomyocyte senescence as a downstream effector of p38 MAPK to promote NF-kB signaling via p65 phosphorylation and nuclear translocation.

Donor and Recipient Age-Mismatches: The Potential of Transferring Senescence

In transplantation, donor and recipients frequently differ in age. Senescent cells accumulate in donor organs with aging and have the potential to promote senescence in adjacent cells when transferred into recipient animals. Characteristically, senescent cells secrete a myriad of pro-inflammatory, soluble molecules as part of their distinct secretory phenotype that have been shown to drive senescence and age-related co-morbidities. Preliminary own data show that the transplantation of old organs limits the physical reserve of recipient animals. Here, we review how organ age may affect transplant recipients and discuss the potential of accelerated aging.

Pathologically phosphorylated tau at S396/404 (PHF-1) is accumulated inside of hippocampal synaptic mitochondria of aged Wild-type mice

Brain aging is a natural process characterized by cognitive decline and memory loss. This impairment is related to mitochondrial dysfunction and has recently been linked to the accumulation of abnormal proteins in the hippocampus. Age-related mitochondrial dysfunction could be induced by modified forms of tau. Here, we demonstrated that phosphorylated tau at Ser 396/404 sites, epitope known as PHF-1, is increased in the hippocampus of aged mice at the same time that oxidative damage and mitochondrial dysfunction are observed. Most importantly, we showed that tau PHF-1 is located in hippocampal mitochondria and accumulates in the mitochondria of old mice. Finally, since two mitochondrial populations were found in neurons, we evaluated tau PHF-1 levels in both non-synaptic and synaptic mitochondria. Interestingly, our results revealed that tau PHF-1 accumulates primarily in synaptic mitochondria during aging, and immunogold electron microscopy and Proteinase K protection assays demonstrated that tau PHF-1 is located inside mitochondria. These results demonstrated the presence of phosphorylated tau at PHF-1 commonly related to tauopathy, inside the mitochondria from the hippocampus of healthy aged mice for the first time. Thus, this study strongly suggests that synaptic mitochondria could be damaged by tau PHF-1 accumulation inside this organelle, which in turn could result in synaptic mitochondrial dysfunction, contributing to synaptic failure and memory loss at an advanced age.

Skin Immunomodulation during Regeneration: Emerging New Targets

Adipose-Derived Stem Cells (ADSC) are present within the hypodermis and are also expected to play a pivotal role in wound healing, immunomodulation, and rejuvenation activities. They orchestrate, through their exosome, the mechanisms associated to cell differentiation, proliferation, and cell migration by upregulating genes implicated in different functions including skin barrier, immunomodulation, cell proliferation, and epidermal regeneration. ADSCs directly interact with their microenvironment and specifically the immune cells, including macrophages and T and B cells, resulting in differential inflammatory and anti-inflammatory mechanisms impacting, in return, ADSCs microenvironment and thus skin function. These useful features of ADSCs are involved in tissue repair, where the required cell proliferation, angiogenesis, and anti-inflammatory responses should occur rapidly in damaged sites. Different pathways involved have been reported such as Growth Differentiation Factor-11 (GDF11), Tumor Growth Factor (TGF)-β, Metalloproteinase (MMP), microRNA, and inflammatory cytokines that might serve as specific biomarkers of their immunomodulating capacity. In this review, we try to highlight ADSCs’ network and explore the potential indicators of their immunomodulatory effect in skin regeneration and aging. Assessment of these biomarkers might be useful and should be considered when designing new clinical therapies using ADSCs or their specific exosomes focusing on their immunomodulation activity.

Chronic Nucleoside Reverse Transcriptase Inhibitors Disrupt Mitochondrial Homeostasis and Promote Premature Endothelial Senescence

Combination antiretroviral therapy (cART) has improved the life expectancy of HIV patients, thus increasing the number of people living with HIV (PLWH). However, cardiovascular diseases (CVD) are now one of the most prevalent causes of death among PLWH. Nucleoside reverse transcriptase inhibitors (NRTIs) are the backbone of cART, and the emtricitabine (FTC) and tenofovir disoproxil fumarate (TDF) coformulation is commonly used. In prior studies, acute NRTI treatment-induced endothelial dysfunction, increased reactive oxygen species production, and mitophagic activity, suggesting that mitochondrial dysfunction may be critical to NRTI-induced endothelial dysfunction. Mitochondrial dysfunction plays a causal role in endothelial senescence, whereas premature endothelial senescence can promote the development of CVD. We hypothesize that for chronic NRTI treatment, a disruption in mitochondrial homeostasis leads to premature endothelial senescence and predisposes PLWH to CVD. We used human aortic endothelial cells (HAEC) and HIV-1 transgenic (Tg26) mice to test the interrelationship between mitochondrial and vascular dysfunction after chronic NRTI treatment in vitro and in vivo. Mitochondrial DNA copy number was decreased in late-passage HAEC treated with NRTIs, and senescence-associated β-galactosidase accumulation was elevated. In late-passage HAEC, NRTIs decreased the activity of Parkin-mediated mitophagy. In Tg26 mice treated with FTC, plasma nitrite levels were decreased. Endothelium-dependent vasodilation in NRTI-treated Tg26 mice was also reduced. Our work suggests that long-term use of NRTI may disrupt mitochondrial homeostasis, induce premature endothelial senescence, and impair vascular function.

Its written all over your face: The molecular and physiological consequences of aging skin

Perhaps the most recognizable consequences of tissue aging are manifested in the skin. Hair graying and loss, telltale wrinkles, and age spots are indicative of physiological aging symptoms, many of which are analogous to processes in other tissues as well with less visible outcomes. While the study of skin aging has been conducted for decades, more recent work has illuminated many of the fundamental molecular and physiological causes of aging in the skin. Recent technological advances have allowed for the detection and quantification of a variety of physiological triggers that lead to aging in the skin and molecular methods have begun to determine the etiology of these phenotypic features. This review will attempt to summarize recent work in this area and provide some speculation about the next wave of studies.

Molecular changes in glaucomatous trabecular meshwork. Correlations with retinal ganglion cell death and novel strategies for neuroprotection

Glaucoma is a chronic neurodegenerative disease characterized by retinal ganglion cell loss. Although significant advances in ophthalmologic knowledge and practice have been made, some glaucoma mechanisms are not yet understood, therefore, up to now there is no effective treatment able to ensure healing. Indeed, either pharmacological or surgical approaches to this disease aim in lowering intraocular pressure, which is considered the only modifiable risk factor. However, it is well known that several factors and metabolites are equally (if not more) involved in glaucoma. Oxidative stress, for instance, plays a pivotal role in both glaucoma onset and progression because it is responsible for the trabecular meshwork cell damage and, consequently, for intraocular pressure increase as well as for glaucomatous damage cascade. This review at first shows accurately the molecular-derived dysfunctions in antioxidant system and in mitochondria homeostasis which due to both oxidative stress and aging, lead to a chronic inflammation state, the trabecular meshwork damage as well as the glaucoma neurodegeneration. Therefore, the main molecular events triggered by oxidative stress up to the proapoptotic signals that promote the ganglion cell death have been highlighted. The second part of this review, instead, describes some of neuroprotective agents such as polyphenols or polyunsaturated fatty acids as possible therapeutic source against the propagation of glaucomatous damage.

Endothelial mitochondrial senescence accelerates cardiovascular disease in antiretroviral-receiving HIV patients

Combination antiretroviral therapy (cART) has been hugely successful in reducing the mortality associated with human immunodeficiency virus (HIV) infection, resulting in a growing population of people living with HIV (PLWH). Since PLWH now have a longer life expectancy, chronic comorbidities have become the focus of the clinical management of HIV. For example, cardiovascular complications are now one of the most prevalent causes of death in PLWH. Numerous epidemiological studies show that antiretroviral treatment increases cardiovascular disease (CVD) risk and early onset of CVD in PLWH. Nucleoside reverse transcriptase inhibitors (NRTIs) are the backbone of cART, and two NRTIs are typically used in combination with one drug from another drug class, e.g., a fusion inhibitor. NRTIs are known to induce mitochondrial dysfunction, contributing to toxicity in numerous tissues, such as myopathy, lipoatrophy, neuropathy, and nephropathy. In in vitro studies, short-term NRTI treatment induces an endothelial dysfunction with an increased reactive oxygen species (ROS) production; long-term NRTI treatment decreases cell replication capacity, while increasing mtROS production and senescent cell accumulation. These findings suggest that a mitochondrial oxidative stress is involved in the pathogenesis of NRTI-induced endothelial dysfunction and premature senescence. Mitochondrial dysfunction, defined by a compromised mitochondrial quality control via biogenesis and mitophagy, has a causal role in premature endothelial senescence and can potentially initiate early cardiovascular disease (CVD) development in PLWH. In this review, we explore the hypothesis and present literature supporting that long-term NRTI treatment induces vascular dysfunction by interfering with endothelial mitochondrial homeostasis and provoking mitochondrial genomic instability, resulting in premature endothelial senescence.

Tortuous Paths of Insulin Signaling and Mitochondria in Alzheimer's Disease

Due to the exponential growth of aging population worldwide, neurodegenerative diseases became a major public health concern. Among them, Alzheimer's disease (AD) prevails as the most common in the elderly, rendering it a research priority. After several decades considering the brain as an insulin-insensitive organ, recent advances proved a central role for this hormone in learning and memory processes and showed that AD shares a high number of features with systemic conditions characterized by insulin resistance. Mitochondrial dysfunction has also been widely demonstrated to play a major role in AD development supporting the idea that this neurodegenerative disease is characterized by a pronounced metabolic dysregulation. This chapter is intended to discuss evidence demonstrating the key role of insulin signaling and mitochondrial anomalies in AD.

Mitochondrial regulation of cardiac aging

Aging is associated with progressive decline in cardiac structure and function. Accumulating evidence in model organisms and humans links cardiac aging to mitochondrial regulation, encompassing a complex interplay of mitochondrial morphology, mitochondrial ROS, mitochondrial DNA mutations, mitochondrial unfolded protein response, nicotinamide adenine dinucleotide levels and sirtuins, as well as mitophagy. This review summarizes the recent discoveries on the mitochondrial regulation of cardiac aging and the possible molecular mechanisms underlying the anti-aging effects, as well as the potential interventions that alleviate aging-related cardiac diseases and attenuate cardiac aging via the regulation of mitochondria.

Evaluating the Remote Control of Programmed Cell Death, with or without a Compensatory Cell Proliferation

Organisms and their different component levels, whether organelle, cellular or other, come by birth and go by death, and the deaths are often balanced by new births. Evolution on the one hand has built demise program(s) in cells of organisms but on the other hand has established external controls on the program(s). For instance, evolution has established death program(s) in animal cells so that the cells can, when it is needed, commit apoptosis or senescent death (SD) in physiological situations and stress-induced cell death (SICD) in pathological situations. However, these programmed cell deaths are not predominantly regulated by the cells that do the dying but, instead, are controlled externally and remotely by the cells' superior(s), i.e. their host tissue or organ or even the animal's body. Currently, it is still unclear whether a cell has only one death program or has several programs respectively controlling SD, apoptosis and SICD. In animals, apoptosis exterminates, in a physiological manner, healthy but no-longer needed cells to avoid cell redundancy, whereas suicidal SD and SICD, like homicidal necrosis, terminate ill but useful cells, which may be followed by regeneration of the live cells and by scar formation to heal the damaged organ or tissue. Therefore, “who dies” clearly differentiates apoptosis from SD, SICD and necrosis. In animals, apoptosis can occur only in those cell types that retain a lifelong ability of proliferation and never occurs in those cell types that can no longer replicate in adulthood. In cancer cells, SICD is strengthened, apoptosis is dramatically weakened while SD has been lost. Most published studies professed to be about apoptosis are actually about SICD, which has four basic and well-articulated pathways involving caspases or involving pathological alterations in the mitochondria, endoplasmic reticula, or lysosomes.

Role of lncRNAs in aging and age-related diseases

Aging is progressive physiological degeneration and consequently declined function, which is linked to senescence on both cellular and organ levels. Accumulating studies indicate that long noncoding RNAs (lncRNAs) play important roles in cellular senescence at all levels-transcriptional, post-transcriptional, translational, and post-translational. Understanding the molecular mechanism of lncRNAs underlying senescence could facilitate interpretation and intervention of aging and age-related diseases. In this review, we describe categories of known and novel lncRNAs that have been involved in the progression of senescence. We also identify the lncRNAs implicated in diseases arising from age-driven degeneration or dysfunction in some representative organs and systems (brains, liver, muscle, cardiovascular system, bone pancreatic islets, and immune system). Improved comprehension of lncRNAs in the aging process on all levels, from cell to organismal, may provide new insights into the amelioration of age-related pathologies and prolonged healthspan.

Mitochondria and Reactive Oxygen Species in Aging and Age-Related Diseases

Aging has been linked to several degenerative processes that, through the accumulation of molecular and cellular damage, can progressively lead to cell dysfunction and organ failure. Human aging is linked with a higher risk for individuals to develop cancer, neurodegenerative, cardiovascular, and metabolic disorders. The understanding of the molecular basis of aging and associated diseases has been one major challenge of scientific research over the last decades. Mitochondria, the center of oxidative metabolism and principal site of reactive oxygen species (ROS) production, are crucial both in health and in pathogenesis of many diseases. Redox signaling is important for the modulation of cell functions and several studies indicate a dual role for ROS in cell physiology. In fact, high concentrations of ROS are pathogenic and can cause severe damage to cell and organelle membranes, DNA, and proteins. On the other hand, moderate amounts of ROS are essential for the maintenance of several biological processes, including gene expression. In this review, we provide an update regarding the key roles of ROS-mitochondria cross talk in different fundamental physiological or pathological situations accompanying aging and highlighting that mitochondrial ROS may be a decisive target in clinical practice.

Brain Mitochondria, Aging, and Parkinson's Disease

This paper reconsiders the role of mitochondria in aging and in Parkinson’s Disease (PD). The most important risk factor for PD is aging. Alterations in mitochondrial activity are typical of aging. Mitochondrial aging is characterized by decreased oxidative phosphorylation, proteasome activity decrease, altered autophagy, and mitochondrial dysfunction. Beyond declined oxidative phosphorylation, mitochondrial dysfunction consists of a decline of beta-oxidation as well as of the Krebs cycle. Not inherited mitochondrial DNA (mtDNA) mutations are acquired over time and parallel the decrease in oxidative phosphorylation. Many of these mitochondrial alterations are also found in the PD brain specifically in the substantia nigra (SN). mtDNA deletions and development of respiratory chain deficiency in SN neurons of aged individuals as well as of individuals with PD converge towards a shared pathway, which leads to neuronal dysfunction and death. Finally, several nuclear genes that are mutated in hereditary PD are usually implicated in mitochondrial functioning to a various extent and their mutation may cause mitochondrial impairment. In conclusion, a tight link exists between mitochondria, aging, and PD.

Punicalagin induces senescent growth arrest in human papillary thyroid carcinoma BCPAP cells via NF-κB signaling pathway

Papillary thyroid carcinoma (PTC) is the most common endocrine carcinoma. Our previous study revealed that punicalagin (PUN), an active component from pomegranate, triggered autophagic cell death and DNA damage response (DDR) in papillary thyroid carcinoma BCPAP cells. But the detailed anti-cancer mechanisms of punicalagin against PTC still remained to be further explored. DDR activation is a proven cause of cellular senescence, which mediates anti-tumor processes under certain circumstances. In this study, we reported that punicalagin treatment generated a senescent phenotype of BCPAP cells characterized as altered morphology, increased cell granularity and senescence-associated β-galactosidase (SA-β-Gal) staining. Senescence induced by punicalagin treatment was further confirmed by cell cycle arrest and upregulation of cyclin-dependent kinase inhibitor p21. Meanwhile, the senescence-associated secretory phenotype (SASP) included high levels of inflammatory cytokines, principally IL-6 and IL-1β. Furthermore, punicalagin exposure caused the phosphorylation and subsequent degradation of IκBα as well as the nuclear translocation of p65, suggesting the activation of NF-κB signaling pathway. Inhibition of NF-κB by pyrrolidine dithiocarbamate (PDTC), a selective inhibitor of NF-κB, partially reversed the cellular senescent phenotype induced by punicalagin in BCPAP cells as evidenced by the decreased fraction of SA-β-Gal staining positive cells and blockage of SASP generation. These results collectively showed that punicalagin treatment induced senescent growth arrest and SASP via triggering NF-κB activation. These observations elucidated novel anti-cancer mechanisms of punicalagin and might provide new potential prospects for PTC therapy.

Spermidine ameliorates the neuronal aging by improving the mitochondrial function in vitro

Changes in mitochondrial structure and function are the initial factors of cell aging. Spermidine has an antiaging effect, but its effect on neuronal aging and mitochondrial mechanisms is unclear. In this study, mouse neuroblastoma (N2a) cells were treated with d‑galactose (d‑Gal) to establish cell aging to investigate the antiaging effect and mechanisms of spermidine. Changes in the cell cycle and β-galactosidase activity were analyzed to evaluate the extent of cell aging. Stabilities of mitochondrial mRNA and mitochondrial membrane potential (MMP) were evaluated in the process of cell aging under different treatments. The mitochondrial function was also evaluated using the Seahorse Metabolic Analysis System combined with ATP production. The unfolded protein response (UPR) of the N2a cells was analyzed under different treatments. Results showed that spermidine pretreatment could delay the cell aging and could maintain the mitochondrial stability during d‑Gal treatment. Spermidine increased the proportion of cells in the S phase and maintained the MMP. The oxygen utilization and ATP production in the N2a cells were reduced by d‑Gal treatment but were partially rescued by the spermidine pretreatment. Spermidine ameliorated the N2a cell aging by promoting the autophagy and inhibiting the apoptosis except the UPR. These results showed that spermidine could ameliorate the N2a cell aging by maintaining the mitochondrial mRNA transcription, MMP and oxygen utilization during the d‑Gal treatment.

miR-21 suppression prevents cardiac alterations induced by d-galactose and doxorubicin

d-galactose (d-gal)-induced cardiac alterations and Doxorubicin (Dox)-induced cardiomyocyte senescence are commonly used models to study cardiac aging. Accumulating evidence has suggested that microRNAs (miRNAs, miRs) are critically involved in the regulation of cellular and organismal aging and age-related diseases. However, little has been revealed about the roles of miRNAs in cardiac alterations induced by d-gal and Dox. In this study, we used miRNA arrays to investigate the dysregulated miRNAs in heart samples from 15month-old versus 2month-old male C57BL/6 mice and further validated them in d-gal-induced pseudo-aging mouse model and Dox-induced cardiomyocyte senescence in vitro model. We confirmed a significant increase of miR-21 in all these models by quantitative reverse transcription polymerase chain reactions. We further demonstrated that miR-21 was able to promote Dox-induced cardiomyocyte senescence whereas suppression of miR-21 could prevent that, as determined by percentage of β-gal-positive cells and gene markers of aging. Phosphatase and tensin homolog (PTEN) was identified as a target gene of miR-21, mediating its effect in increasing cardiomyocyte senescence. Finally, we found that miR-21 knockout mice were resistant to d-gal-induced alterations in aging-markers and cardiac function. Collectively, this study provides direct evidence that inhibition of miR-21 is protective against d-gal-induced cardiac alterations and Dox-induced cardiomyocyte senescence via targeting PTEN. Inhibition of miR-21 might be a novel strategy to combat cardiac aging.

Ageing and latent CMV infection impact on maturation, differentiation and exhaustion profiles of T-cell receptor gammadelta T-cells

Ageing is a broad cellular process, largely affecting the immune system, especially T-lymphocytes. Additionally to immunosenescence alone, cytomegalovirus (CMV) infection is thought to have major impacts on T-cell subset composition and exhaustion. These impacts have been studied extensively in TCRαβ+ T-cells, with reduction in naive, increase in effector (memory) subsets and shifts in CD4/CD8-ratios, in conjunction with morbidity and mortality in elderly. Effects of both ageing and CMV on the TCRγδ+ T-cell compartment remain largely elusive. In the current study we investigated Vγ- and Vδ-usage, maturation, differentiation and exhaustion marker profiles of both CD4 and CD8 double-negative (DN) and CD8+TCRγδ+ T-cells in 157 individuals, age range 20–95. We observed a progressive decrease in absolute numbers of total TCRγδ+ T-cells in blood, affecting the predominant Vγ9/Vδ2 population. Aged TCRγδ+ T-cells appeared to shift from naive to more (late-stage) effector phenotypes, which appeared more prominent in case of persistent CMV infections. In addition, we found effects of both ageing and CMV on the absolute counts of exhausted TCRγδ+ T-cells. Collectively, our data show a clear impact of ageing and CMV persistence on DN and CD8+TCRγδ+ T-cells, similar to what has been reported in CD8+TCRαβ+ T-cells, indicating that they undergo similar ageing processes.

Protective proteins and telomere length in placentas from patients with pre-eclampsia in the last trimester of gestation

INTRODUCTION

Visfatin/nicotinamide phosphoribosyltransferase (Nampt), an enzyme involved in energy metabolism and sirtuins, SIRT1 and SIRT3, which are NAD-dependent deacetylases, are critical for cellular function. All three either regulate or are regulated by intracellular NAD+ levels and therefore available cellular energy, important for placental cell survival and successful pregnancy. This study investigates whether these protective proteins are involved in the placental pathophysiology of pre-eclampsia (PE) and if they are associated with 8-oxo-deoxyguanosine (8OHdG), a marker of oxidative damage or with placental telomere length.

METHODS

Maternal blood and placental samples were collected from 31 patients with PE and 30 controls between 31 and 40 weeks gestation. Quantitative immunohistochemistry was performed on placental specimens for visfatin/Nampt, SIRT1, SIRT3, and nuclear 8OHdG. Plasma visfatin was measured by ELISA and telomere length by Southern blot analysis of telomere restriction fragments.

RESULTS

Visfatin/Nampt and SIRT1 in syncytiotrophoblast decreased in PE compared to controls (p < 0.0001, p = 0.004 respectively). SIRT3 decreased in PE most significantly at preterm (p = 0.002). 8OHdG was only significantly lower in preterm controls compared to term controls (p = 0.01) and correlated with SIRT1 in all samples (r = 0.27). Telomere length was not different in PE and controls.

DISCUSSION

Decreased visfatin/Nampt, SIRT1 and SIRT3 in syncytiotrophoblast in PE suggests a lack of placental reserve in metabolic energy efficiency, increased inflammation, and lower resistance to environmental stressors. However, there was little effect on nuclear function, or evidence of genomic DNA damage, which would lead to cellular senescence and death.

ROS, Cell Senescence, and Novel Molecular Mechanisms in Aging and Age-Related Diseases

The aging process worsens the human body functions at multiple levels, thus causing its gradual decrease to resist stress, damage, and disease. Besides changes in gene expression and metabolic control, the aging rate has been associated with the production of high levels of Reactive Oxygen Species (ROS) and/or Reactive Nitrosative Species (RNS). Specific increases of ROS level have been demonstrated as potentially critical for induction and maintenance of cell senescence process. Causal connection between ROS, aging, age-related pathologies, and cell senescence is studied intensely. Senescent cells have been proposed as a target for interventions to delay the aging and its related diseases or to improve the diseases treatment. Therapeutic interventions towards senescent cells might allow restoring the health and curing the diseases that share basal processes, rather than curing each disease in separate and symptomatic way. Here, we review observations on ROS ability of inducing cell senescence through novel mechanisms that underpin aging processes. Particular emphasis is addressed to the novel mechanisms of ROS involvement in epigenetic regulation of cell senescence and aging, with the aim to individuate specific pathways, which might promote healthy lifespan and improve aging.

Methylation profiling by bisulfite sequencing analysis of the mtDNA Non-Coding Region in replicative and senescent Endothelial Cells

The regulation and function of Mitochondrial DNA (mtDNA) cytosine methylation (5 mC) are largely unexplored. Mitochondria, Endothelial Cell (EC) senescence, and cardiovascular dysfunction are closely related. We extensively investigated the mtDNA Non-Coding Region (NCR) methylation pattern and its variations in EC replicative senescence. We observed previously undescribed 5 mC clusters and a biased distribution of 5 mC among DNA sites and throughout the NCR. The methylation pattern in senescent EC showed non-random variations, including the hypo-methylation of mtDNA replication regulatory sites. Additional experiments opened to a possible role for 5 mC in D-loop formation, rather than in mitochondrial gene expression.

[Ageing: a matter of heart?]

Ageing is considered as a major risk factor for the development of chronic diseases. Among these, heart failure seems to be particularly important for both triggering and accelerating pathological ageing. In the present review, we give a general overview of the most relevant results concerning the mechanism of normal and premature senescence of cardiomyocytes and cardiac stromal cells. In particular, we will address the role of telomere dysfunction, DNA damage response, impairment of mitochondrial function, miRNAs and secretome of senescent cells in cardiac ageing and failure.

Isolation of Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High Throughput Microplate Respiratory Measurements

Dysfunctional skeletal muscle mitochondria play a role in altered metabolism observed with aging, obesity and Type II diabetes. Mitochondrial respirometric assays from isolated mitochondrial preparations allow for the assessment of mitochondrial function, as well as determination of the mechanism(s) of action of drugs and proteins that modulate metabolism. Current isolation procedures often require large quantities of tissue to yield high quality mitochondria necessary for respirometric assays. The methods presented herein describe how high quality purified mitochondria (~ 450 µg) can be isolated from minimal quantities (~75-100 mg) of mouse skeletal muscle for use in high throughput respiratory measurements. We determined that our isolation method yields 92.5± 2.0% intact mitochondria by measuring citrate synthase activity spectrophotometrically. In addition, Western blot analysis in isolated mitochondria resulted in the faint expression of the cytosolic protein, GAPDH, and the robust expression of the mitochondrial protein, COXIV. The absence of a prominent GAPDH band in the isolated mitochondria is indicative of little contamination from non-mitochondrial sources during the isolation procedure. Most importantly, the measurement of O2 consumption rate with micro-plate based technology and determining the respiratory control ratio (RCR) for coupled respirometric assays shows highly coupled (RCR; >6 for all assays) and functional mitochondria. In conclusion, the addition of a separate mincing step and significantly reducing motor driven homogenization speed of a previously reported method has allowed the isolation of high quality and purified mitochondria from smaller quantities of mouse skeletal muscle that results in highly coupled mitochondria that respire with high function during microplate based respirometirc assays.

Using Isolated Mitochondria from Minimal Quantities of Mouse Skeletal Muscle for High throughput Microplate Respiratory Measurements

Skeletal muscle mitochondria play a specific role in many disease pathologies. As such, the measurement of oxygen consumption as an indicator of mitochondrial function in this tissue has become more prevalent. Although many technologies and assays exist that measure mitochondrial respiratory pathways in a variety of cells, tissue and species, there is currently a void in the literature in regards to the compilation of these assays using isolated mitochondria from mouse skeletal muscle for use in microplate based technologies. Importantly, the use of microplate based respirometric assays is growing among mitochondrial biologists as it allows for high throughput measurements using minimal quantities of isolated mitochondria. Therefore, a collection of microplate based respirometric assays were developed that are able to assess mechanistic changes/adaptations in oxygen consumption in a commonly used animal model. The methods presented herein provide step-by-step instructions to perform these assays with an optimal amount of mitochondrial protein and reagents, and high precision as evidenced by the minimal variance across the dynamic range of each assay.

Neuroretinal Degeneration in HIV Patients Without Opportunistic Ocular Infections in the cART Era

Subtle structural and functional retinal abnormalities, termed 'HIV-associated Neuroretinal Disorder (HIV-NRD)', have been reported in HIV patients receiving combination antiretroviral therapy (cART), without infectious retinitis or any apparent fundus abnormalities otherwise. In this review, we provide an overview of studies investigating HIV-NRD in HIV patients without opportunistic ocular infections in the cART era, and try to elucidate underlying mechanisms and associated risk factors. Most studies focused on patients with severe immune-deficiency and demonstrated that patients with nadir CD4 counts<100 cells/μL are most at risk for neuroretinal damage, with a thinner retinal nerve fiber layer, subtle loss of color vision and/or contrast sensitivity, visual field deficits, and subnormal electrophysiological responses. In contrast, alterations in retinal vascular calibers and retinal blood flow were not associated with nadir CD4 counts, but instead with detectable viremia, suggesting a role for (chronic) inflammation in microvascular damage. Although the alterations in visual function are subtle, they can lead to difficulties in activities, such as reading or driving, thereby affecting quality of life. Since HIV has become a chronic disease, its long-term effects with respect to visual function loss become more important, as is recently emphasized by a longitudinal study, reporting that AIDS patients with HIV-NRD have higher risks of developing bilateral visual impairment and even blindness than patients without HIV-NRD. The question remains whether patients with high (>350 cells/μL) nadir CD4 counts and well-suppressed HIV infection on cART remain at risk for HIV-NRD, as this group constitutes a growing part of the aging HIV-infected population.

Biomolecular bases of the senescence process and cancer. A new approach to oncological treatment linked to ageing

Human ageing is associated with a gradual decline in the physiological functions of the body at multiple levels and it is a key risk factor for many diseases, including cancer. Ageing process is intimately related to widespread cellular senescence, characterised by an irreversible loss of proliferative capacity and altered functioning associated with telomere attrition, accumulation of DNA damage and compromised mitochondrial and metabolic function. Tumour and senescent cells may be generated in response to the same stimuli, where either cellular senescence or transformation would constitute two opposite outcomes of the same degenerative process. This paper aims to review the state of knowledge on the biomolecular relationship between cellular senescence, ageing and cancer. Importantly, many of the cell signalling pathways that are found to be altered during both cellular senescence and tumourigenesis are regulated through shared epigenetic mechanisms and, therefore, they are potentially reversible. MicroRNAs are emerging as pivotal players linking ageing and cancer. These small RNA molecules have generated great interest from the point of view of future clinical therapy for cancer because successful experimental results have been obtained in animal models. Micro-RNA therapies for cancer are already being tested in clinical phase trials. These findings have potential importance in cancer treatment in aged people although further research-based knowledge is needed to convert them into an effective molecular therapies for cancer linked to ageing.

The Interplay Between Respiratory Supercomplexes and ROS in Aging

SIGNIFICANCE

The molecular mechanism of aging is still vigorously debated, although a general consensus exists that mitochondria are significantly involved in this process. However, the previously postulated role of mitochondrial-derived reactive oxygen species (ROS) as the damaging agents inducing functional loss in aging has fallen out of favor in the recent past. In this review, we critically examine the role of ROS in aging in the light of recent advances on the relationship between mitochondrial structure and function.

RECENT ADVANCES

The functional mitochondrial respiratory chain is now recognized as a reflection of the dynamic association of respiratory complexes in the form of supercomplexes (SCs). Besides providing kinetic advantage (channeling), SCs control ROS generation by the respiratory chain, thus providing a means to regulate ROS levels in the cell. Depending on their concentration, these ROS are either physiological signals essential for the life of the cell or toxic species that damage cell structure and functions.

CRITICAL ISSUES

We propose that under physiological conditions the dynamic nature of SCs reversibly controls the generation of ROS as signals involved in mitochondrial-nuclear communication. During aging, there is a progressive loss of control of ROS generation so that their production is irreversibly enhanced, inducing a vicious circle in which signaling is altered and structural damage takes place.

FUTURE DIRECTIONS

A better understanding on the forces affecting SC association would allow the manipulation of ROS generation, directing these species to their physiological signaling role.

Age-related decrease in mtDNA content as a consequence of mtDNA 4977 bp deletion

As one of the most frequent somatic mutations accumulated during aging in human mitochondrial DNA, the 4977 bp deletion has intrigued scientific interest in recent years. Although many studies have shown a significant increase in the amount of 4977 bp deletion, the findings with respect to an age-dependent escalate of ΔmtDNA4977 bp in blood are still disputatious. Therefore, we investigated the presence of common deletion and mtDNA deletion level in whole blood samples of 100 old individuals (60-90 years). We detected the accumulation of common deletion in 46 old individuals. Consequently, there was statistically significant difference between the aged and young individuals in mitochondrial content (p = 0.01) and deletion levels ranged from 2% to 17% of the total mtDNA (mean: 10% ± 0.02%). We conclude that common deletion has decreased the mtDNA content; however, it is not clearly detectable in the blood as one of the fast replicating tissues comparing with tissues with low mitotic activity.

Bax modulates neuronal survival while p53 is unaltered after Cytochrome C induced oxidative stress in the adult olfactory bulb in vivo

Background

The granule and periglomerular cells of the olfactory bulb migrate from the sub-ventricular zone (SVZ) as progenitor cell forming the neuronal stream of the rostral olfactory bulb. These cells are characterized by their ability to divide while expressing adult proteins; a phenomenon attributed to the prolonged cell cycle and the regulatory activities of proteins which modulates apoptosis and proliferation in the developing nervous system. Of interest are the proteins concerned with tumor suppression (p53) and cell cycle exit (Bax) and how they regulate survivability of these neurons in the adult system after an induced oxidative stress.

Purpose

This study sets to investigate the interplay between p53 and Bax in the adult olfactory bulb (periglomerular and granule cell layer), and how these proteins determine proliferation and neuronal survival after Cytochrome C induced-oxidative stress. Also, we demonstrate the effect of the induced-stress threshold on such regulation in vivo.

Methods

Adult Wistar rats were segregated into three groups. 10 and 20 mg/Kg BW of potassium cyanide (KCN) was administered to the treatment groups for 15 days while the control received normal saline for the same duration. The olfactory bulb was dissected and processed for general histology and immunohistochemistry of p53/Bax in the periglomerular and granule cell layers. Total (Histology) and immunopositive (p53 and Bax) cell count was done using Image J. Subsequently, we determined the analysis of variance with significance set at *P<0.05.

Results

We observed an increase in cell count for the 10 mg/KgBW treatment; this was characterized by a significant decrease in Bax expression and no change in p53 expression when this treatment group was compared to the control. However, no change was observed in the total cell count for 20 mg/Kg BW treatment for the same duration of exposure. Interestingly, there was also no significant change in Bax and p53 for this treatment when compared with the control.

Conclusion

Although p53 plays an important role in development of the olfactory bulb neurons, our findings suggests it has little contribution in neuronal cell viability and proliferation in the adult olfactory bulb. No significant change in p53 was observed irrespective of treatment dose and cell count while Bax expression was reduced at 10 mg/Kg BW treatment and was associated with an increased cell count. We conclude that regulation of survival of neurons in the adult olfactory bulb, following induced-oxidative stress was more dependent of the expression of Bax and the threshold of the induced stress rather than p53 expression.

Impaired dynamics and function of mitochondria caused by mtDNA toxicity leads to heart failure

Cardiac mitochondrial dysfunction has been implicated in heart failure of diverse etiologies. Generalized mitochondrial disease also leads to cardiomyopathy with various clinical manifestations. Impaired mitochondrial homeostasis may over time, such as in the aging heart, lead to cardiac dysfunction. Mitochondrial DNA (mtDNA), close to the electron transport chain and unprotected by histones, may be a primary pathogenetic site, but this is not known. Here, we test the hypothesis that cumulative damage of cardiomyocyte mtDNA leads to cardiomyopathy and heart failure. Transgenic mice with Tet-on inducible, cardiomyocyte-specific expression of a mutant uracil-DNA glycosylase 1 (mutUNG1) were generated. The mutUNG1 is known to remove thymine in addition to uracil from the mitochondrial genome, generating apyrimidinic sites, which obstruct mtDNA function. Following induction of mutUNG1 in cardiac myocytes by administering doxycycline, the mice developed hypertrophic cardiomyopathy, leading to congestive heart failure and premature death after ∼2 mo. The heart showed reduced mtDNA replication, severely diminished mtDNA transcription, and suppressed mitochondrial respiration with increased Pgc-1α, mitochondrial mass, and antioxidative defense enzymes, and finally failing mitochondrial fission/fusion dynamics and deteriorating myocardial contractility as the mechanism of heart failure. The approach provides a model with induced cardiac-restricted mtDNA damage for investigation of mtDNA-based heart disease.

Parkinson's disease as a result of aging

It is generally considered that Parkinson's disease is induced by specific agents that degenerate a clearly defined population of dopaminergic neurons. Data commented in this review suggest that this assumption is not as clear as is often thought and that aging may be critical for Parkinson's disease. Neurons degenerating in Parkinson's disease also degenerate in normal aging, and the different agents involved in the etiology of this illness are also involved in aging. Senescence is a wider phenomenon affecting cells all over the body, whereas Parkinson's disease seems to be restricted to certain brain centers and cell populations. However, reviewed data suggest that Parkinson's disease may be a local expression of aging on cell populations which, by their characteristics (high number of synaptic terminals and mitochondria, unmyelinated axons, etc.), are highly vulnerable to the agents promoting aging. The development of new knowledge about Parkinson's disease could be accelerated if the research on aging and Parkinson's disease were planned together, and the perspective provided by gerontology gains relevance in this field.

Vascular biology of ageing-Implications in hypertension

Ageing is associated with functional, structural and mechanical changes in arteries that closely resemble the vascular alterations in hypertension. Characteristic features of large and small arteries that occur with ageing and during the development of hypertension include endothelial dysfunction, vascular remodelling, inflammation, calcification and increased stiffness. Arterial changes in young hypertensive patients mimic those in old normotensive individuals. Hypertension accelerates and augments age-related vascular remodelling and dysfunction, and ageing may impact on the severity of vascular damage in hypertension, indicating close interactions between biological ageing and blood pressure elevation. Molecular and cellular mechanisms underlying vascular alterations in ageing and hypertension are common and include aberrant signal transduction, oxidative stress and activation of pro-inflammatory and pro-fibrotic transcription factors. Strategies to suppress age-associated vascular changes could ameliorate vascular damage associated with hypertension. An overview on the vascular biology of ageing and hypertension is presented and novel molecular mechanisms contributing to these processes are discussed. The complex interaction between biological ageing and blood pressure elevation on the vasculature is highlighted. This article is part of a Special Issue entitled: CV Ageing.

The mitochondrial lncRNA ASncmtRNA-2 is induced in aging and replicative senescence in Endothelial Cells

Age-associated cardiovascular diseases are at least partially ascribable to vascular cell senescence. Replicative senescence (RS) and stress-induced premature senescence (SIPS) are provoked respectively by endogenous (telomere erosion) and exogenous (H2O2, UV) stimuli resulting in cell cycle arrest in G1 and G2 phases. In both scenarios, mitochondria-derived ROS are important players in senescence initiation. We aimed to define whether a mtDNA-transcribed long-non-coding-RNA (lncRNA), ASncmtRNA-2, has a role in vascular aging and senescence. Aortas of old mice, characterized by increased senescence, showed an increment in ASncmtRNA-2 expression. In vitro analysis of Endothelial Cells (EC) and Vascular Smooth Muscle Cells (VSMC) established that ASncmtRNA-2 is induced in EC, but not in VSMC, during RS. Surprisingly, ASncmtRNA-2 is not upregulated in two different EC SIPS scenarios, treated with H2O2 and UV. The p16 gene displayed similar ASncmtRNA-2 expression patterns, suggesting a possible co-regulation of the two genes. Interestingly, the expression of two miRNAs, hsa-miR-4485 and hsa-miR-1973, with perfect homology to the double strand region of ASncmtRNA-2 and originating at least in part from a mitochondrial transcript, was induced in RS, opening to the possibility that this lncRNA functions as a non-canonical precursor of these miRNAs. Cell cycle analysis of EC transiently over-expressing ASncmtRNA-2 revealed an accumulation of EC in the G2/M phase, but not in the G1 phase. We propose that ASncmtRNA-2 in EC might be involved in the RS establishment by participating in the cell cycle arrest in G2/M phase, possibly through the production of hsa-miR-4485 and hsa-miR-1973. This article is part of a Special Issue entitled: Mitochondria.