Induction of oxidative stress causes functional alterations in mouse urothelium via a TRPM8‐mediated mechanism: implications for aging

The incidence of bladder conditions such as overactive bladder syndrome and its associated urinary incontinence is highly prevalent in the elderly. However, the mechanisms underlying these disorders are unclear. Studies suggest that the urothelium forms a ‘sensory network’ with the underlying innervation, alterations in which, could compromise bladder function. As the accumulation of reactive oxygen species can cause functional alterations with age, the aim of this study was to investigate whether oxidative stress alters urothelial sensory signalling and whether the mechanism underlying the effect of oxidative stress on the urothelium plays a role in aging. Five‐month‐old(young) and 24‐month‐old (aged) mice were used. H₂O₂, used to induce oxidative stress, resulted in an increase in bladder afferent nerve activity and urothelial intracellular calcium in preparations from young mice. These functional changes were concurrent with upregulation of TRPM8 in the urothelium. Moreover, application of a TRPM8 antagonist significantly attenuated the H₂O₂‐induced calcium responses. Interestingly, an upregulation of TRPM8 was also found in the urothelium from aged mice, where high oxidative stress levels were observed, together with a greater calcium response to the TRPM8 agonist WS12. Furthermore, these calcium responses were attenuated by pretreatment with the antioxidant N‐acetyl‐cysteine. This study shows that oxidative stress affects urothelial function involving a TRPM8‐mediated mechanism and these effects may have important implications for aging. These data provide an insight into the possible mechanisms by which oxidative stress causes physiological alterations in the bladder, which may also occur in other organs susceptible to aging.     

Reprogramming to a pluripotent state modifies mesenchymal stem cell resistance to oxidative stress

Properties of induced pluripotent stem cells (iPSC) have been extensively studied since their first derivation in 2006. However, the modification in reactive oxygen species (ROS) production and detoxification caused by reprogramming still needs to be further elucidated. The objective of this study was to compare the response of iPSC generated from menstrual blood–derived mesenchymal stem cells (mb‐iPSC), embryonic stem cells (H9) and adult menstrual blood–derived mesenchymal stem cells (mbMSC) to ROS exposure and investigate the effects of reprogramming on cellular oxidative stress (OS). mbMSC were extremely resistant to ROS exposure, however, mb‐iPSC were 10‐fold less resistant to H₂O₂, which was very similar to embryonic stem cell sensitivity. Extracellular production of ROS was also similar in mb‐iPSC and H9 and almost threefold lower than in mbMSC. Furthermore, intracellular amounts of ROS were higher in mb‐iPSC and H9 when compared with mbMSC. As the ability to metabolize ROS is related to antioxidant enzymes, we analysed enzyme activities in these cell types. Catalase and superoxide dismutase activities were reduced in mb‐iPSC and H9 when compared with mbMSC. Finally, cell adhesion under OS conditions was impaired in mb‐iPSC when compared with mbMSC, albeit similar to H9. Thus, reprogramming leads to profound modifications in extracellular ROS production accompanied by loss of the ability to handle OS.     

Antioxidant N-acetyl-L-cysteine inhibits erythropoietin-induced differentiation of erythroid progenitors derived from mouse fetal liver

To determine the role of reactive oxygen species in erythroid differentiation, we investigated the effects of an antioxidant, N-acetyl-L-cysteine (NAC), on the differentiation of erythroid progenitors derived from mouse fetal liver. In response to erythropoietin (Epo), erythroid progenitors undergo differentiation in vitro and express erythroid-specific genes such as betamajor-globin, Alas2, MafK, p45, Eklf, and Gata1. Expression of these genes was decreased in the presence of NAC, whereas the expression of c-myb, which is downregulated during erythroid differentiation, remained constant. Moreover, NAC treatment inhibited an increase in the number of cells expressing high levels of erythroid-specific antigen TER119. Treatment with another antioxidant, pyrrolidine dithiocarbamate, also caused the attenuation of TER119 expression. These results suggest that reactive oxygen species are involved in Epo-mediated erythroid differentiation.     

Inflammatory exposure drives long-lived impairment of hematopoietic stem cell self-renewal activity and accelerated aging

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Free radical processes in aging, neurodegenerative diseases and other pathological states

Literature data on the role of oxidative stress in aging have been summarized. There are certain links between parameters of free radical processes (intensity of generation of reactive oxygen species in mitochondria, oxidative modification of mitochondrial DNA, activity of desaturases, involved into biosynthesis of polyunsaturated C₂₀ and C₂₂ fatty acids) with life span. The review highlights the role of oxidative stress as on of pathogenic factors of numerous diseases including various neurodegenerative disorders. Special attention is paid to oxidative modification of proteins as one of early and reliable markers of tissue injury in free radical pathology. Oxidative destruction of proteins plays a major role in etiology of such neurodegenerative diseases as Alzheimer’s and Parkinson’s diseases. Oxidative stress and the stress related protein aggregation are considered as the pathogenic link in the development of familiar amyotrophic lateral sclerosis. Oxidative modification of proteins is associated with the development of cataract. The age-and pathology-related increases in the content of oxidized proteins in tissues is assessed as an early and specific parameter of oxidative stress.     

Vitamin C alleviates aging defects in a stem cell model for Werner syndrome

Werner syndrome (WS) is a premature aging disorder that mainly affects tissues derived from mesoderm. We have recently developed a novel human WS model using WRN-deficient human mesenchymal stem cells (MSCs). This model recapitulates many phenotypic features of WS. Based on a screen of a number of chemicals, here we found that Vitamin C exerts most efficient rescue for many features in premature aging as shown in WRN-deficient MSCs, including cell growth arrest, increased reactive oxygen species levels, telomere attrition, excessive secretion of inflammatory factors, as well as disorganization of nuclear lamina and heterochromatin. Moreover, Vitamin C restores in vivo viability of MSCs in a mouse model. RNA sequencing analysis indicates that Vitamin C alters the expression of a series of genes involved in chromatin condensation, cell cycle regulation, DNA replication, and DNA damage repair pathways in WRNdeficient MSCs. Our results identify Vitamin C as a rejuvenating factor for WS MSCs, which holds the potential of being applied as a novel type of treatment of WS.     

Managing odds in stem cells: insights into the role of mitochondrial antioxidant enzyme MnSOD

Reactive oxygen species (ROS) have been poised at a straddled state of being beneficiary as well detrimental depending on its threshold levels. Maintaining the homeostasis of ROS is imperative for normal cellular physiology, wherein physiological concentrations of ROS are involved in cell signaling and elevated ROS contribute to the development of various diseases. Superoxide dismutases (SODs), enzymes involved in dismutation of superoxide anion to hydrogen peroxide, arrive as a first line of defense when there is perturbation in the homeostasis of ROS. As mitochondria are the main site of superoxide production, among SODs, mitochondrial manganese SOD (MnSOD) is the primary antioxidant enzyme that protects cells from ROS. Most importantly, knockout of MnSOD leads to postnatal lethality and tissue-specific conditional knockout in brain resulted in death of mice, conclusively portraying the essential role of MnSOD in development. Although MnSOD has been extensively discussed with the purview of tumor biology and aging, understanding the crucial role of MnSOD in stem cell physiology is still at its infant stage. Ever increasing progress in stem cell research has recently unveiled the essential role of MnSOD in self-renewal and differentiation of stem cells. In this review, we will conglomerate the current aspects by which MnSOD can contribute to embryonic stem cells’ and adult stem cells’ functions and interpret the necessity of understanding MnSOD for further stem cell mediated applications.     

Hsf1 promotes hematopoietic stem cell fitness and proteostasis in response to ex vivo culture stress and aging

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Seasonal changes in antioxidant level of scots pine (Pinus sylvestris L.) needles exposed to industrial pollution. I. ascorbate and thiol content

Current and previous year needles from three 16 years-old populations of Scots pine (Pinus sylvestris L.) trees were seasonally collected at the three experimental areas: Luboń- close to the phosphate fertiliser factory, Głogów — close to the copper foundry and Kórnik — control site. Głogów is the most polluted site, where at 1998 monthly mean daily concentrations of different pollutants were: SO₂ - 17 μg·m⁻³, NO_x - 12 μg·m⁻³ and dust containing heavy metals as Cu, Pb, Cd - 29 μg·m⁻³. Trees growing in Luboń were influenced for many years by high concentration of SO₂ and fluor compounds. A few years ago emissions were markedly reduced, but low pH of soil and high concentration of aluminium ions still influence the growth of trees. Seasonal changes of ascorbate and thiol content were observed in each needle class and population, with the maximum in the winter and minimum in the summer. In needles from trees growing on polluted sites higher level of ascorbic acid and thiols comparing to control site was observed. Significant differences appeared in each population of Scots pine growing under higher pollution stress in the Głogów site. In needles from trees growing in Luboń significant differences in ascorbic acid and thiols content were evidently less numerous. Needles from polluted sites in some seasons contained significantly more malondialdehyde (MDA) and those was more frequent in Głogów than in Luboń. The results indicated that in the Głogów site trees are more influenced by pollution stress than in Luboń and the defense reaction measured as an increase of the antioxidant level is more evident.     

Production of reactive species and modulation of antioxidant network in response to heat shock: a critical balance for cell fate

Exposure to adverse temperature conditions is a common stress factor for plants. In order to cope with heat stress, plants activate several defence mechanisms responsible for the control of reactive oxygen species (ROS) and redox homeostasis. Specific heat shocks (HSs) are also able to activate programmed cell death (PCD). In this paper, the alteration of several oxidative markers and ROS scavenging enzymes were studied after subjecting cells to two different HSs. Our results suggest that, under moderate HS, the redox homeostasis is mainly guaranteed by an increase in glutathione (GSH) content and in the ascorbate peroxidase (APX) and catalase (CAT) activities. These two enzymes undergo different regulatory mechanisms. On the other hand, the HS-induced PCD determines an increase in the activity of the enzymes recycling the ascorbate- and GSH-oxidized forms and a reduction of APX; whereas, CAT decreases only after a transient rise of its activity, which occurs in spite of the decrease of its gene expression. These results suggest that the enzyme-dependent ROS scavenging is enhanced under moderate HS and suppressed under HS-induced PCD. Moreover, the APX suppression occurring very early during PCD, could represent a hallmark of cells that have activated a suicide programme.     

Senolytic treatment reduces oxidative protein stress in an aging male murine model of post-traumatic osteoarthritis

Senolytic drugs are designed to selectively clear senescent cells (SnCs) that accumulate with injury or aging. In a mouse model of osteoarthritis (OA), senolysis yields a pro-regenerative response, but the therapeutic benefit is reduced in aged mice. Increased oxidative stress is a hallmark of advanced age. Therefore, here we investigate whether senolytic treatment differentially affects joint oxidative load in young and aged animals. We find that senolysis by a p53/MDM2 interaction inhibitor, UBX0101, reduces protein oxidative modification in the aged arthritic knee joint. Mass spectrometry coupled with protein interaction network analysis and biophysical stability prediction of extracted joint proteins revealed divergent responses to senolysis between young and aged animals, broadly suggesting that knee regeneration and cellular stress programs are contrarily poised to respond as a function of age. These opposing responses include differing signatures of protein-by-protein oxidative modification and abundance change, disparate quantitative trends in modified protein network centrality, and contrasting patterns of oxidation-induced folding free energy perturbation between young and old. We develop a composite sensitivity score to identify specific key proteins in the proteomes of aged osteoarthritic joints, thereby nominating prospective therapeutic targets to complement senolytics.     

Cellular aging leads to functional heterogeneity of hematopoietic stem cells: a modeling perspective

Hematopoietic stem cells (HSCs) are the source for the life-long supply of functional cells in peripheral blood while they simultaneously maintain their own reserve pool. However, there is accumulating evidence that HSCs are themselves subject to quantitative and qualitative exhaustion. Although several processes linked to mitotic activity can potentially account for the observed aging phenomena (e.g., DNA damage, telomere shortening, epigenetic modification), a precise understanding of HSC exhaustion is still missing. It is particularly unclear how individual aging processes on the single-cell level translate on the phenotypic level of the overall tissue and whether there is a functional implication of an age-structured HSC population. We address these issues by applying a novel mathematical model of HSC organization in which division-specific, cumulative alterations of stem cell quality determine the phenotypic and functional appearance of the overall cell population. Adapting the model to a number of basic experimental findings, we quantify the level of additional heterogeneity that is introduced by a population of individually aging cells. Based on this model, we are able to conclude that division-dependent processes of cellular aging explain a wide range of phenomena on HSC exhaustion and that HSC aging needs to be considered as a highly heterogeneous process. We furthermore report that functional heterogeneity between young and old HSCs appears closely similar to the phenomena described for long- and short-term repopulating cells. We speculate whether differential, division-coupled stem cell aging introduces an intra-animal variability that also accounts for heterogeneity with respect to the repopulation ability of HSCs.     

内源性神经干细胞与脑老化的治疗

近十几年研究发现成年人脑神经元可以再生,使人们重新认识老年脑神经细胞的可塑性,它为脑损伤的修复带来新的希望。最新研究表明,神经再生可被调控,是一种新的修复机制。这使得利用内源性神经干细胞治疗老龄相关的神经退行性疾病成为可能。     

Restoration of peroxisomal catalase import in a model of human cellular aging

Peroxisomes play an important role in human cellular metabolism by housing enzymes involved in a number of essential biochemical pathways. Many of these enzymes are oxidases that transfer hydrogen atoms to molecular oxygen forming hydrogen peroxide. The organelle also contains catalase, which readily decomposes the hydrogen peroxide, a potentially damaging oxidant. Previous work has demonstrated that aging compromises peroxisomal protein import with catalase being particularly affected. The resultant imbalance in the relative ratio of oxidases to catalase was seen as a potential contributor to cellular oxidative stress and aging. Here we report that altering the peroxisomal targeting signal of catalase to the more effective serine-lysine-leucine (SKL) sequence results in a catalase molecule that more strongly interacts with its receptor and is more efficiently imported in both in vitro and in vivo assays. Furthermore, catalase-SKL monomers expressed in cells interact with endogenous catalase subunits resulting in altered trafficking of the latter molecules. A dramatic reduction in cellular hydrogen peroxide levels accompanies this increased peroxisomal import of catalase. Finally, we show that catalase-SKL stably expressed in cells by retroviral-mediated transduction repolarizes mitochondria and reduces the number of senescent cells in a population. These results demonstrate the utility of a catalase-SKL therapy for the restoration of a normal oxidative state in aging cells.     

TpMRK regulates cell division of Tetrahymena in response to oxidative stress

TpMRK was identified as a stress‐responsive mitogen activated protein kinase (MAPK)‐related kinase and has been shown to play a critical role in the stress signalling in Tetrahymena cells. Here, we found that the mRNA expression of TpMRK was correlated with cell division of Tetrahymena with decreased expression occurring in cells prior to entering synchronous cell division induced by heat treatment. Notably, cell division was delayed with a lower division index of 40% after exposure to hydrogen peroxide while 85% of cells underwent cell division synchronously at 75 min after heat treatment without the oxidative exposure. Furthermore, inactivation of TpMRK signalling by p38 MAPK inhibitor SB203580 or MEK inhibitor PD 98059 partially derepressed cell division induced by hydrogen peroxide. Our data suggest that oxidative stimuli might cause aberration of synchronous cell division of Tetrahymena through activating the TpMRK cascade. Copyright © 2009 John Wiley & Sons, Ltd.     

New strategy of bone marrow mesenchymal stem cells against oxidative stress injury via Nrf2 pathway: oxidative stress preconditioning

Clinically, bone marrow mesenchymal stem cells (BMSCs) have been used in treatment of many diseases, but the local oxidative stress (OS) of lesion severely limits the survival of BMSCs, which reduces the efficacy of BMSCs transplantation. Therefore, enhancing the anti-OS stress ability of BMSCs is a key breakthrough point. Preconditioning is a common protective mechanism for cells or body. Here, the aim of this study was to investigate the effects of OS preconditioning on the anti-OS ability of BMSCs and its mechanism. Fortunately, OS preconditioning can increase the expression of superoxide dismutase, catalase, NQO1, and heme oxygenase 1 through the nuclear factor erythroid 2-related factor 2 pathway, thereby decreased the intracellular reactive oxygen species (ROS) levels, relieved the damage of ROS to mitochondria, DNA and cell membrane, enhanced the anti-OS ability of BMSCs, and promoted the survival of BMSCs under OS.