Stress-induced Senescence Research Articles

Oxidative stress-induced senescence mediates inflammatory and fibrotic phenotypes in fibroblasts from systemic sclerosis patients.

SSc is an autoimmune connective tissue disorder characterized by inflammation and fibrosis. Although constitutive activation of fibroblasts is proposed to be responsible for the fibrotic and inflammatory features of the disease, the underlying mechanism remains elusive, and effective therapeutic targets are still lacking. The aim of this study was to evaluate the role of oxidative stress-induced senescence and its contribution to the pro-fibrotic and pro-inflammatory phenotypes of fibroblasts from SSc patients. Dermal fibroblasts were isolated from SSc (n = 13) and healthy (n = 10) donors. Fibroblasts' intracellular and mitochondrial reactive oxygen species (ROS) were determined by flow cytometry. Mitochondrial function was measured by Seahorse XF24 analyser. Fibrotic and inflammatory gene expressions were assessed by qPCR and key pro-inflammatory components of the fibroblasts' secretome (IL-6 and IL-8) were quantified by ELISA. Compared with healthy fibroblasts, SSc fibroblasts displayed higher levels of both intracellular and mitochondrial ROS. Oxidative stress in SSc fibroblasts induced the expression of fibrotic genes and activated the TGF-β-activated kinase 1 (TAK1)-IκB kinase β (IKKβ)-IFN regulatory factor 5 (IRF5) inflammatory signalling cascade. These cellular responses paralleled the presence of a DNA damage response, a senescence-associated secretory phenotype and a fibrotic response. Treatment of SSc fibroblasts with ROS scavengers reduced their pro-inflammatory secretome production and fibrotic gene expression. Oxidative stress-induced cellular senescence in SSc fibroblasts underlies their pro-inflammatory and pro-fibrotic phenotypes. Targeting redox imbalance of SSc fibroblasts enhances their in vitro functions and could be of relevance for SSc therapy.

Transcriptome-wide characterization of the WRKY family genes in Lonicera macranthoides and the role of LmWRKY16 in plant senescence.

Lonicera macranthoides is an important woody plant with high medicinal values widely cultivated in southern China. WRKY, one of the largest transcription factor families, participates in plant development, senescence, and stress responses. However, a comprehensive study of the WRKY family in L. macranthoides hasn't been reported previously. To establish an extensive overview of the WRKY family in L. macranthoides and identify senescence-responsive members of LmWRKYs. RNA-Seq and phylogenetic analysis were employed to identify the LmWRKYs and their evolutionary relationships. Quantitative real-time (qRT-PCR) and transgenic technology was utilized to investigate the roles of LmWRKYs in response to developmental-, cold-, and ethylene-induced senescence. A total of 61 LmWRKY genes with a highly conserved motif WRKYGQK were identified. Phylogenetic analysis of LmWRKYs together with their orthologs from Arabidopsis classified them into three groups, with the number of 15, 39, and 7, respectively. 17 LmWRKYs were identified to be differentially expressed between young and aging leaves by RNA-Seq. Further qRT-PCR analysis showed 15 and 5 LmWRKY genes were significantly induced responding to tissue senescence in leaves and stems, respectively. What's more, five LmWRKYs, including LmWRKY4, LmWRKY5, LmWRKY6, LmWRKY11, and LmWRKY16 were dramatically upregulated under cold and ethylene treatment in both leaves and stems, indicating their involvements commonly in developmental- and stress-induced senescence. In addition, function analysis revealed LmWRKY16, a homolog of AtWRKY75, can accelerate plant senescence, as evidenced by leaf yellowing during reproductive growth in LmWRKY16-overexpressing tobaccos. The results lay the foundation for molecular characterization of LmWRKYs in plant senescence.

Induction of Stress-Induced Renal Cellular Senescence In Vitro: Impact of Mouse Strain Genetic Diversity.

Cellular senescence, a stress-induced state of irreversible cell cycle arrest, is associated with organ dysfunction and age-related disease. While immortalized cell lines bypass key pathways of senescence, important mechanisms of cellular senescence can be studied in primary cells. Primary tubular epithelial cells (PTEC) derived from mouse kidney are highly susceptible to develop cellular senescence, providing a valuable tool for studying such mechanisms. Here, we tested whether genetic differences between mouse inbred strains have an impact on the development of stress-induced cellular senescence in cultured PTEC. Kidneys from 129S1, B6, NOD, NZO, CAST, and WSB mice were used to isolate PTEC. Cells were monitored for expression of typical senescence markers (SA-β-galactosidase, γ-H2AX+/Ki67−, expression levels of CDKN2A, lamin B1, IL-1a/b, IL-6, G/M-CSF, IFN-g, and KC) at 3 and 10 days after pro-senescent gamma irradiation. Clear differences were found between PTEC from different strains with the highest senescence values for PTEC from WSB mice and the lowest for PTEC from 129S1 mice. PTEC from B6 mice, the most commonly used inbred strain in senescence research, had a senescence score lower than PTEC from WSB and CAST mice but higher than PTEC from NZO and 129S1 mice. These data provide new information regarding the influence of genetic diversity and help explain heterogeneity in existing data. The observed differences should be considered when designing new experiments and will be the basis for further investigation with the goal of identifying candidate loci driving pro- or anti-senescent pathways.

Cascade of Inflammatory, Fibrotic Processes, and Stress-Induced Senescence in Chronic GVHD-Related Dry Eye Disease.

Ocular graft-versus-host disease (GVHD) is a major complication after allogeneic hematopoietic stem cell transplantation. Ocular GVHD affects recipients’ visual function and quality of life. Recent advanced research in this area has gradually attracted attention from a wide range of physicians and ophthalmologists. This review highlights the mechanism of immune processes and the molecular mechanism, including several inflammation cascades, pathogenic fibrosis, and stress-induced senescence related to ocular GVHD, in basic spectrum topics in this area. How the disease develops and what kinds of cells participate in ocular GVHD are discussed. Although the classical immune process is a main pathological pathway in this disease, senescence-associated changes in immune cells and stem cells may also drive this disease. The DNA damage response, p16/p21, and the expression of markers associated with the senescence-associated secretory phenotype (SASP) are seen in ocular tissue in GVHD. Macrophages, T cells, and mesenchymal cells from donors or recipients that increasingly infiltrate the ocular surface serve as the source of increased secretion of IL-6, which is a major SASP driver. Agents capable of reversing the changes, including senolytic reagents or those that can suppress the SASP seen in GVHD, provide new potential targets for the treatment of GVHD. Creating innovative therapies for ocular GVHD is necessary to treat this intractable ocular disease.

Outcomes of Deferoxamine Action on H2O2-Induced Growth Inhibition and Senescence Progression of Human Endometrial Stem Cells.

Mesenchymal stem cells (MSCs) are broadly applied in regenerative therapy to replace cells that are lost or impaired during disease. The low survival rate of MSCs after transplantation is one of the major limitations heavily influencing the success of the therapy. Unfavorable microenvironments with inflammation and oxidative stress in the damaged regions contribute to MSCs loss. Most of the strategies developed to overcome this obstacle are aimed to prevent stress-induced apoptosis, with little attention paid to senescence—another common stress reaction of MSCs. Here, we proposed the strategy to prevent oxidative stress-induced senescence of human endometrial stem cells (hMESCs) based on deferoxamine (DFO) application. DFO prevented DNA damage and stress-induced senescence of hMESCs, as evidenced by reduced levels of reactive oxygen species, lipofuscin, cyclin D1, decreased SA-β-Gal activity, and improved mitochondrial function. Additionally, DFO caused accumulation of HIF-1α, which may contribute to the survival of H2O2-treated cells. Importantly, cells that escaped senescence due to DFO preconditioning preserved all the properties of the initial hMESCs. Therefore, once protecting cells from oxidative damage, DFO did not alter further hMESCs functioning. The data obtained may become the important prerequisite for development of a new strategy in regenerative therapy based on MSCs preconditioning using DFO.

Contrasting roles of GmNAC065 and GmNAC085 in natural senescence, plant development, multiple stresses and cell death responses

NACs are plant-specific transcription factors involved in controlling plant development, stress responses, and senescence. As senescence-associated genes (SAGs), NACs integrate age- and stress-dependent pathways that converge to programmed cell death (PCD). In Arabidopsis, NAC-SAGs belong to well-characterized regulatory networks, poorly understood in soybean. Here, we interrogated the soybean genome and provided a comprehensive analysis of senescence-associated Glycine max (Gm) NACs. To functionally examine GmNAC-SAGs, we selected GmNAC065, a putative ortholog of Arabidopsis ANAC083/VNI2 SAG, and the cell death-promoting GmNAC085, an ANAC072 SAG putative ortholog, for analyses. Expression analysis of GmNAC065 and GmNAC085 in soybean demonstrated (i) these cell death-promoting GmNACs display contrasting expression changes during age- and stress-induced senescence; (ii) they are co-expressed with functionally different gene sets involved in stress and PCD, and (iii) are differentially induced by PCD inducers. Furthermore, we demonstrated GmNAC065 expression delays senescence in Arabidopsis, a phenotype associated with enhanced oxidative performance under multiple stresses, higher chlorophyll, carotenoid and sugar contents, and lower stress-induced PCD compared to wild-type. In contrast, GmNAC085 accelerated stress-induced senescence, causing enhanced chlorophyll loss, ROS accumulation and cell death, decreased antioxidative system expression and activity. Accordingly, GmNAC065 and GmNAC085 targeted functionally contrasting sets of downstream AtSAGs, further indicating that GmNAC85 and GmNAC065 regulators function inversely in developmental and environmental PCD.

RABL6A Regulates Schwann Cell Senescence in an RB1-Dependent Manner.

Schwann cells are normally quiescent, myelinating glia cells of the peripheral nervous system. Their aberrant proliferation and transformation underlie the development of benign tumors (neurofibromas) as well as deadly malignant peripheral nerve sheath tumors (MPNSTs). We discovered a new driver of MPNSTs, an oncogenic GTPase named RABL6A, that functions in part by inhibiting the RB1 tumor suppressor. RB1 is a key mediator of cellular senescence, a permanent withdrawal from the cell cycle that protects against cell immortalization and transformation. Based on the RABL6A-RB1 link in MPNSTs, we explored the hypothesis that RABL6A promotes Schwann cell proliferation and abrogates their senescence by inhibiting RB1. Using sequentially passaged normal human Schwann cells (NHSCs), we found that the induction of replicative senescence was associated with reduced expression of endogenous RABL6A. Silencing RABL6A in low passage NHSCs caused premature stress-induced senescence, which was largely rescued by co-depletion of RB1. Consistent with those findings, Rabl6-deficient MEFs displayed impaired proliferation and accelerated senescence compared to wildtype MEFs. These results demonstrate that RABL6A is required for maintenance of proper Schwann cell proliferation and imply that aberrantly high RABL6A expression may facilitate malignant transformation.

Cellular senescence as a driver of cognitive decline triggered by chronic unpredictable stress

When an individual is under stress, the undesired effect on the brain often exceeds expectations. Additionally, when stress persists for a long time, it can trigger serious health problems, particularly depression. Recent studies have revealed that depressed patients have a higher rate of brain aging than healthy subjects and that depression increases dementia risk later in life. However, it remains unknown which factors are involved in brain aging triggered by chronic stress. The most critical change during brain aging is the decline in cognitive function. In addition, cellular senescence is a stable state of cell cycle arrest that occurs because of damage and/or stress and is considered a sign of aging. We used the chronic unpredictable stress (CUS) model to mimic stressful life situations and found that, compared with nonstressed control mice, CUS-treated C57BL/6 mice exhibited depression-like behaviors and cognitive decline. Additionally, the protein expression of the senescence marker p16INK4a was increased in the hippocampus, and senescence-associated β-galactosidase (SA-β-gal)-positive cells were found in the hippocampal dentate gyrus (DG) in CUS-treated mice. Furthermore, the levels of SA-β-gal or p16INK4a were strongly correlated with the severity of memory impairment in CUS-treated mice, whereas clearing senescent cells using the pharmacological senolytic cocktail dasatinib plus quercetin (D + Q) alleviated CUS-induced cognitive deficits, suggesting that targeting senescent cells may be a promising candidate approach to study chronic stress-induced cognitive decline. Our findings open new avenues for stress-related research and provide new insight into the association of chronic stress-induced cellular senescence with cognitive deficits.

Melatonin treatment delays postharvest senescence and maintains the organoleptic quality of ‘Newhall’ navel orange (Citrus sinensis (L.) Osbeck) by inhibiting respiration and enhancing antioxidant capacity

Melatonin can improve postharvest quality and strengthen resistance to oxidative stress-induced senescence of many horticultural products, however, the effects of melatonin on storage quality and physiological senescence of citrus fruit are still unclear. The objective of this study was to determine the effect of 200 μmol•L−1 melatonin on the organoleptic quality and antioxidant system of ‘Newhall’ navel orange stored under ambient conditions for 84 days post-harvest. Melatonin caused a significant decrease in respiration rate and weight loss rate, and increased in fruit firmness, total soluble solids, soluble sugar content, titratable acidity and Citrus Color Index (CCI) indicating inhibition of fruit quality deterioration. Melatonin treatment impeded the accumulation of hydrogen peroxide and malondialdehyde, suggesting an inhibition of reactive oxygen species (ROS) burst and oxidative damage. In addition, the application of melatonin enhanced ROS scavenging capacity by increasing the activity and expressions of catalase, superoxide dismutase, ascorbate peroxidase, glutathione reductase and by promoting the accumulation of ascorbate, reduced glutathione and total phenol. Moreover, the PCA (principal component analysis) demonstrated melatonin delayed postharvest senescence of orange fruit is associated with inhibition of postharvest respiration and stimulation of oxidant-defense system.

PTH Protects Osteocytes From Oxidative Stress and Cellular Senescence

Age-induced osteoporosis is characterized by a progressive decline in bone formation and increase in bone resorption with uncoupled activities of osteoblasts and osteoclasts. Parathyroid hormone (PTH) is used in the clinic to treat osteoporosis due to its anabolic actions on bone via binding to the PTH receptor (PPR). The receptor is highly expressed in cells of the osteoblastic lineage, including osteocytes. Osteocytes are the most abundant cells in bone and serve as a key regulator of bone remodeling. Despite the significant role of PPR signaling in skeletal homeostasis, its function in osteocytes during aging remains unclear. We have gathered preliminary data demonstrating that mice lacking PPR predominantly in osteocytes (Dmp1-PPRKO) have marked age-induced bone loss due to increased bone resorption and suppressed bone formation. These mice, with aging, develop characteristics of skeletal senescence: a decrease in osteoprogenitors and an increase in bone marrow adiposity and p16Ink4a/Cdkn2a expression in bone. Since senescence of cells in the bone microenvironment has been reported as a cause of age-induced bone loss, we hypothesized that PPR signaling protects osteocytes from senescence. To test this hypothesis, we generated osteocytes (Ocy454-12H), in which the PPR expression was ablated using CRISPR/Cas9 technique. Ocy454-12H-PPRKO and Ocy454-12H-PPRCtrl cells were treated with PTH followed by an exposure to hydrogen peroxide (H2O2). High levels of intracellular reactive oxygen species (ROS), including H2O2, promote protein and DNA oxidation, resulting in cell death and senescence. PTH treatment significantly suppressed the increase in H2O2-induced cell death, measured by resazurin-based assays, in PPRCtrl but not in PPRKO cells. We analyzed intracellular ROS levels using a fluorescent probe and found that PTH treatment significantly suppressed the increase in ROS upon H2O2 exposure, suggesting an antioxidant function of PTH in osteocytes. To further investigate if PTH prevents osteocytes from oxidative stress-induced senescence, we examined senescence-associated β-galactosidase (SA β-gal) activity in cells that were treated with PTH followed by an exposure to low doses of H2O2. Compared to untreated and PPRKO groups, treatment with PTH significantly decreased the number of SA β-gal positive cells, demonstrating that PPR signaling protects osteocytes, and possibly other osteoblastic cells, from H2O2-induced cellular senescence. PTH treatment reduced mRNA expression of p21/Cdkn1a. Taken together these results demonstrate that PPR signaling is important to protect osteocytes from cellular senescence.

Lithium inhibits oxidative stress-induced neuronal senescence through miR-34a.

Neuronal senescence, triggered by telomere shortening, oncogene activation, DNA damage, or oxidative stress, has been associated with neurodegenerative diseases' pathogenesis. Therefore, preventing neuronal senescence could be a novel treatment strategy for neurodegenerative diseases. Lithium (Li), the first-line treatment against bipolar disorder, has been shown to have neuroprotective effects in clinical, pre-clinical, and in vitro studies. Li can protect cells from senescence, and its effect on neuronal senescence was investigated in our study. Furthermore, we also investigated the effects of Li on the senescence-associated miR-34a/Sirt1/p53 pathway. In this study, hydrogen peroxide was used as an inducer for the "stress-induced premature senescence" model. In the senescence model, we have assessed Li's effects on senescence by analyzing β-galactosidase activity, Sudan Black B, and senescence-associated heterochromatin foci (SAHF) stainings, and on cell cycle arrest by BrdU staining. Furthermore, expression levels of senescence and cell cycle arrest-related proteins (p53, p21, p16INK4a, and SIRT1) by western blotting. Finally, the effects of Li on senescence-associated miR-34a levels were measured by quantitative PCR. We show via Sudan Black B staining, β-Gal activity assay, and by detecting SAHF, Li protects against senescence in neuronal cells. Then, Li's effect on signaling has also been determined on pathways involved in senescence and cell cycle arrest. Moreover, we have observed that Li has a modulatory effect on miR-34a expression. Therefore, we posit that Li suppresses senescence in neuronal cells and that this effect is mediated through miR-34a/Sirt1/p53 axis.

Senescence‐Associated Secretory Phenotype (SASP) factors down‐regulate glutamate transporter expression in human brainstem astrocytes through a paracrine fashion

Glia-neuron crosstalk in the brainstem is emerging as a critical player in the regulation of sympathetic nerve activity (SNA). Specifically, astrocytes modulate SNA by tightly regulating synaptic glutamate levels through transporter mediated re-uptake mechanisms. Pro-inflammatory mediators like TNFα have been shown to negatively affect glutamate transporter expression in astrocytes. Previous studies from our laboratory have provided evidence for oxidative stress-induced senescence and their secretory phenotype (SASP), a potential source of inflammation, in human brainstem astrocytes. Hence, in the present study we hypothesize that inflammatory mediators in SASP factors down-regulate glutamate re-uptake transporter expression in a paracrine manner. To test our hypothesis, we induced senescence in cultured human brainstem astrocytes with hydrogen peroxide (H2O2) treatment at a dose of 300 μM for 2 hours. Senescence induction was confirmed through PCR expression for senescence markers and SA-beta-gal staining 7 days after H2O2 treatment. Conditioned media collected from the senescent and control astrocytes were used to assess the paracrine effect of SASP factors on astrocytic glutamate transporter expression. Following 36 hours of treatment with conditioned media from senescent astrocytes, we observed a significant down-regulation of two of the major astrocytic glutamate re-uptake transporters, EAAT1 (GLAST-1) and EAAT2 (GLT-1) in human brainstem astrocytes. This suggests that soluble SASP factors in the secretome of senescent cells can alter the function of glutamate transporters in the astrocytes through a paracrine action. Increased activity of glutamatergic neurons in the rostral ventrolateral medulla due to reduced glutamate re-uptake at the synapse may be a possible glial mechanism underlying enhanced sympathoexcitation in obesity.

Current Understanding of Leaf Senescence in Rice.

Leaf senescence, which is the last developmental phase of plant growth, is controlled by multiple genetic and environmental factors. Leaf yellowing is a visual indicator of senescence due to the loss of the green pigment chlorophyll. During senescence, the methodical disassembly of macromolecules occurs, facilitating nutrient recycling and translocation from the sink to the source organs, which is critical for plant fitness and productivity. Leaf senescence is a complex and tightly regulated process, with coordinated actions of multiple pathways, responding to a sophisticated integration of leaf age and various environmental signals. Many studies have been carried out to understand the leaf senescence-associated molecular mechanisms including the chlorophyll breakdown, phytohormonal and transcriptional regulation, interaction with environmental signals, and associated metabolic changes. The metabolic reprogramming and nutrient recycling occurring during leaf senescence highlight the fundamental role of this developmental stage for the nutrient economy at the whole plant level. The strong impact of the senescence-associated nutrient remobilization on cereal productivity and grain quality is of interest in many breeding programs. This review summarizes our current knowledge in rice on (i) the actors of chlorophyll degradation, (ii) the identification of stay-green genotypes, (iii) the identification of transcription factors involved in the regulation of leaf senescence, (iv) the roles of leaf-senescence-associated nitrogen enzymes on plant performance, and (v) stress-induced senescence. Compiling the different advances obtained on rice leaf senescence will provide a framework for future rice breeding strategies to improve grain yield.

664 Pro-energetics creatine and nicotinamide prevent stress-induced senescence in human dermal fibroblasts

Senescence is the process by which cells irreversibly avoid dividing without undergoing cell death and enter a state of irreversible growth arrest. Fibroblast senescence associated with aging is known to contribute to the increased incidence of non-melanoma skin cancer in the aged population. To that end, agents that can inhibit fibroblast senescence could be protective. Senescence can be induced by various cellular stressors such as DNA damage, oncogenic activation and oxidative stress. Hydrogen peroxide (H2O2), ultraviolet light, tert-butyl hydroperoxide, and hyperoxia are pro-oxidative stressors which are used experimentally to induce premature senescence.

Paricalcitol inhibits oxidative stress-induced cell senescence of the bile duct epithelium dependent on modulating Sirt1 pathway in cholestatic mice

BackgroundClinical studies indicate that vitamin D receptor (VDR) expression is reduced in primary biliary cirrhosis patient livers. However, the mechanism by which activated VDR effect cholestatic liver injury remains unclear. MethodsMice were injected intraperitoneally with the VDR agonist paricalcitol or a vehicle 3 days prior to bile duct ligation (BDL) and for 5 or 28 days after surgery. The analyses of liver morphology and necrotic areas were based on H&E staining. Serum biochemical indicators of liver damage were analyzed by commercial kits. The mechanisms of paricalcitol on cholestatic liver injury were determined by Western blot analysis. ResultsParicalcitol ameliorated the BDL-induced liver damage in mice. Paricalcitol increased the proliferation of BECs to promote the repair of the bile duct. Paricalcitol also reduced the BDL-induced oxidative stress level in the mice. Mechanistic analysis revealed that paricalcitol decreased the number of SA-β-gal-positive cells and downregulated the expression of p53, p21 and p16 proteins which was associated with reducing oxidative stress. Additionally, paricalcitol exerted the inhibitory effect of cell senescence was through reducing DNA damage and promoting DNA repair. Interesting, we found that paricalcitol prevented the downregulation of oxidative stress-induced Sirt1 expression in the BDL mice and t-BHP-induced BECs models. Moreover, paricalcitol suppressed cell senescence through a Sirt1-dependent pathway. These results were confirmed by antioxidant ALCAR and the Sirt1 inhibitor EX-527. ConclusionParicalcitol alleviated cholestatic liver injury through promoting the repair of damaged bile ducts and reducing oxidative stress-induced cell senescence of the bile duct via modulating Sirt1 pathway.

PHYTOCHROME INTERACTING FACTORS PIF4 and PIF5 promote heat stress induced leaf senescence in Arabidopsis.

Leaf senescence can be triggered by multiple abiotic stresses including darkness, nutrient limitation, salinity, and drought. Recently, heatwaves have been occurring more frequently, and they dramatically affect plant growth and development. However, the underlying molecular networks of heat stress-induced leaf senescence remain largely uncharacterized. Here we showed that PHYTOCHROME INTERACTING FACTOR 4 (PIF4) and PIF5 proteins could efficiently promote heat stress-induced leaf senescence in Arabidopsis. Transcriptomic profiling analysis revealed that PIF4 and PIF5 are likely to function through multiple biological processes including hormone signaling pathways. Further, we characterized NAC019, SAG113, and IAA29 as direct transcriptional targets of PIF4 and PIF5. The transcription of NAC019, SAG113, and IAA29 changes significantly in daytime after heat treatment. In addition, we demonstrated that PIF4 and PIF5 proteins were accumulated during the recovery after heat treatment. Moreover, we showed that heat stress-induced leaf senescence is gated by the circadian clock, and plants might be more actively responsive to heat stress-induced senescence during the day. Taken together, our findings proposed important roles for PIF4 and PIF5 in mediating heat stress-induced leaf senescence, which may help to fully illustrate the molecular network of heat stress-induced leaf senescence in higher plants and facilitate the generation of heat stress-tolerant crops.

Breast cancer type 1 and neurodegeneration: consequences of deficient DNA repair.

Numerous cellular processes, including toxic protein aggregation and oxidative stress, have been studied extensively as potential mechanisms underlying neurodegeneration. However, limited therapeutic efficacy targeting these processes has prompted other mechanisms to be explored. Previous research has emphasized a link between cellular senescence and neurodegeneration, where senescence induced by excess DNA damage and deficient DNA repair results in structural and functional changes that ultimately contribute to brain dysfunction and increased vulnerability for neurodegeneration. Specific DNA repair proteins, such as breast cancer type 1, have been associated with both stress-induced senescence and neurodegenerative diseases, however, specific mechanisms remain unclear. Therefore, this review explores DNA damage-induced senescence in the brain as a driver of neurodegeneration, with particular focus on breast cancer type 1, and its potential contribution to sex-specific differences associated with neurodegenerative disease.

A Compendium on Hypertension: New Advances and Future Impact.

A Compendium on Hypertension: New Advances and Future Impact.

Vascular Stress Signaling in Hypertension.

Cells respond to stress by activating a variety of defense signaling pathways, including cell survival and cell death pathways. Although cell survival signaling helps the cell to recover from acute insults, cell death or senescence pathways induced by chronic insults can lead to unresolved pathologies. Arterial hypertension results from chronic physiological maladaptation against various stressors represented by abnormal circulating or local neurohormonal factors, mechanical stress, intracellular accumulation of toxic molecules, and dysfunctional organelles. Hypertension and aging share common mechanisms that mediate or prolong chronic cell stress, such as endoplasmic reticulum stress and accumulation of protein aggregates, oxidative stress, metabolic mitochondrial stress, DNA damage, stress-induced senescence, and proinflammatory processes. This review discusses common adaptive signaling mechanisms against these stresses including unfolded protein responses, antioxidant response element signaling, autophagy, mitophagy, and mitochondrial fission/fusion, STING (signaling effector stimulator of interferon genes)-mediated responses, and activation of pattern recognition receptors. The main molecular mechanisms by which the vasculature copes with hypertensive and aging stressors are presented and recent advancements in stress-adaptive signaling mechanisms as well as potential therapeutic targets are discussed.

Skeletal Aging and Osteoporosis: Mechanisms and Therapeutics.

Bone is a dynamic organ maintained by tightly regulated mechanisms. With old age, bone homeostasis, which is maintained by an intricate balance between bone formation and bone resorption, undergoes deregulation. Oxidative stress-induced DNA damage, cellular apoptosis, and cellular senescence are all responsible for this tissue dysfunction and the imbalance in the bone homeostasis. These cellular mechanisms have become a target for therapeutics to treat age-related osteoporosis. Genetic mouse models have shown the importance of senescent cell clearance in alleviating age-related osteoporosis. Furthermore, we and others have shown that targeting cellular senescence pharmacologically was an effective tool to alleviate age- and radiation-induced osteoporosis. Senescent cells also have an altered secretome known as the senescence associated secretory phenotype (SASP), which may have autocrine, paracrine, or endocrine function. The current review discusses the current and potential pathways which lead to a senescence profile in an aged skeleton and how bone homeostasis is affected during age-related osteoporosis. The review has also discussed existing therapeutics for the treatment of osteoporosis and rationalizes for novel therapeutic options based on cellular senescence and the SASP as an underlying pathogenesis of an aging bone.