Aging is associated with increased regulatory T‐cell function

Regulatory T‐cell (Treg, CD4⁺CD25⁺) dysfunction is suspected to play a key role in immune senescence and contributes to increased susceptibility to diseases with age by suppressing T‐cell responses. FoxP3 is a master regulator of Treg function, and its expression is under control of several epigenetically labile promoters and enhancers. Demethylation of CpG sites within these regions is associated with increased FoxP3 expression and development of a suppressive phenotype. We examined differences in FoxP3 expression between young (3–4 months) and aged (18–20 months) C57BL/6 mice. DNA from CD4⁺ T cells is hypomethylated in aged mice, which also exhibit increased Treg numbers and FoxP3 expression. Additionally, Treg from aged mice also have greater ability to suppress effector T‐cell (Teff) proliferation in vitro than Tregs from young mice. Tregs from aged mice exhibit greater redox remodeling–mediated suppression of Teff proliferation during coculture with DCs by decreasing extracellular cysteine availability to a greater extent than Tregs from young mice, creating an adverse environment for Teff proliferation. Tregs from aged mice produce higher IL‐10 levels and suppress CD86 expression on DCs more strongly than Tregs from young mice, suggesting decreased T‐cell activity. Taken together, these results reveal a potential mechanism of higher Treg‐mediated activity that may contribute to increased immune suppression with age.     

Large-Scale Clonal Analysis Resolves Aging of the Mouse Hematopoietic Stem Cell Compartment

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Aging affects the in vivo regenerative potential of human mesoangioblasts

Sarcopenia is the age‐related loss of muscle mass, strength, and function. Although the role of human satellite cells (SCs) as adult skeletal muscle stem cells has been deeply investigated, little is known about the impact of aging on muscle interstitial stem cells. Here, we isolated the non‐SC CD56^– fraction from human muscle biopsies of young and elderly subjects. The elderly interstitial cell population contained a higher number of CD15⁺ and PDGFRα⁺ cells when compared to young samples. In addition, we found that the CD56^–/ALP⁺ cells were well represented as a multipotent stem cell population inside the CD56^– fraction. CD56^–/ALP⁺/CD15^– cells were clonogenic, and since they were myogenic and expressed NG2, α‐SMA and PDGFRβ can be considered mesoangioblasts (MABs). Interestingly, elderly MABs displayed a dramatic impairment in the myogenic differentiation ability in vitro and when transplanted in dystrophic immunodeficient Sgcb‐null Rag2‐null γc‐null mice. In addition, elderly MABs proliferated less, but yet retained other multilineage capabilities. Overall, our results indicate that aging negatively impacted on the regenerative potential of MABs and this should be carefully considered for potential therapeutic applications of MABs.     

Antimonial resistance in Leishmania donovani is associated with increased in vivo parasite burden

Leishmania donovani is an intracellular protozoan parasite that causes visceral leishmaniasis (VL). Antimonials (SSG) have long been the first-line treatment against VL, but have now been replaced by miltefosine (MIL) in the Indian subcontinent due to the emergence of SSG-resistance. Our previous study hypothesised that SSG-resistant L. donovani might have increased in vivo survival skills which could affect the efficacy of other treatments such as MIL. The present study attempts to validate these hypotheses. Fourteen strains derived from Nepalese clinical isolates with documented SSG-susceptibility were infected in BALB/c mice to study their survival capacity in drug free conditions (non-treated mice) and in MIL-treated mice. SSG-resistant parasites caused a significant higher in vivo parasite load compared to SSG-sensitive parasites. However, this did not seem to affect the strains' response to MIL-treatment since parasites from both phenotypes responded equally well to in vivo MIL exposure. We conclude that there is a positive association between SSG-resistance and in vivo survival skills in our sample of L. donovani strains which could suggest a higher virulence of SSG-R strains compared to SSG-S strains. These greater in vivo survival skills of SSG-R parasites do not seem to directly affect their susceptibility to MIL. However, it cannot be excluded that repeated MIL exposure will elicit different adaptations in these SSG-R parasites with superior survival skills compared to the SSG-S parasites. Our results therefore highlight the need to closely monitor drug efficacy in the field, especially in the context of the Kala-azar elimination programme ongoing in the Indian subcontinent.     

The extreme longevity of Arctica islandica is associated with increased peroxidation resistance in mitochondrial membranes

The deleterious reactive carbonyls released upon oxidation of polyunsaturated fatty acids in biological membranes are believed to foster cellular aging. Comparative studies in mammals and birds have shown that the susceptibility to peroxidation of membrane lipids peroxidation index (PI) is negatively correlated with longevity. Long‐living marine molluscs are increasingly studied as longevity models, and the presence of different types of lipids in the membranes of these organisms raises questions on the existence of a PI–longevity relationship. We address this question by comparing the longest living metazoan species, the mud clam Arctica islandica (maximum reported longevity = 507 year) to four other sympatric bivalve molluscs greatly differing in longevity (28, 37, 92, and 106 year). We contrasted the acyl and alkenyl chain composition of phospholipids from the mitochondrial membranes of these species. The analysis was reproduced in parallel for a mix of other cell membranes to investigate whether a different PI–longevity relationship would be found. The mitochondrial membrane PI was found to have an exponential decrease with increasing longevity among species and is significantly lower for A. islandica. The PI of other cell membranes showed a linear decrease with increasing longevity among species and was also significantly lower for A. islandica. These results clearly demonstrate that the PI also decreases with increasing longevity in marine bivalves and that it decreases faster in the mitochondrial membrane than in other membranes in general. Furthermore, the particularly low PI values for A. islandica can partly explain this species’ extreme longevity.     

Dysregulated autophagy in the RPE is associated with increased susceptibility to oxidative stress and AMD

Autophagic dysregulation has been suggested in a broad range of neurodegenerative diseases including age-related macular degeneration (AMD). To test whether the autophagy pathway plays a critical role to protect retinal pigmented epithelial (RPE) cells against oxidative stress, we exposed ARPE-19 and primary cultured human RPE cells to both acute (3 and 24 h) and chronic (14 d) oxidative stress and monitored autophagy by western blot, PCR, and autophagosome counts in the presence or absence of autophagy modulators. Acute oxidative stress led to a marked increase in autophagy in the RPE, whereas autophagy was reduced under chronic oxidative stress. Upregulation of autophagy by rapamycin decreased oxidative stress-induced generation of reactive oxygen species (ROS), whereas inhibition of autophagy by 3-methyladenine (3-MA) or by knockdown of ATG7 or BECN1 increased ROS generation, exacerbated oxidative stress-induced reduction of mitochondrial activity, reduced cell viability, and increased lipofuscin. Examination of control human donor specimens and mice demonstrated an age-related increase in autophagosome numbers and expression of autophagy proteins. However, autophagy proteins, autophagosomes, and autophagy flux were significantly reduced in tissue from human donor AMD eyes and 2 animal models of AMD. In conclusion, our data confirm that autophagy plays an important role in protection of the RPE against oxidative stress and lipofuscin accumulation and that impairment of autophagy is likely to exacerbate oxidative stress and contribute to the pathogenesis of AMD.     

Dysregulated autophagy in the RPE is associated with increased susceptibility to oxidative stress and AMD

Autophagic dysregulation has been suggested in a broad range of neurodegenerative diseases including age-related macular degeneration (AMD). To test whether the autophagy pathway plays a critical role to protect retinal pigmented epithelial (RPE) cells against oxidative stress, we exposed ARPE-19 and primary cultured human RPE cells to both acute (3 and 24 h) and chronic (14 d) oxidative stress and monitored autophagy by western blot, PCR, and autophagosome counts in the presence or absence of autophagy modulators. Acute oxidative stress led to a marked increase in autophagy in the RPE, whereas autophagy was reduced under chronic oxidative stress. Upregulation of autophagy by rapamycin decreased oxidative stress-induced generation of reactive oxygen species (ROS), whereas inhibition of autophagy by 3-methyladenine (3-MA) or by knockdown of ATG7 or BECN1 increased ROS generation, exacerbated oxidative stress-induced reduction of mitochondrial activity, reduced cell viability, and increased lipofuscin. Examination of control human donor specimens and mice demonstrated an age-related increase in autophagosome numbers and expression of autophagy proteins. However, autophagy proteins, autophagosomes, and autophagy flux were significantly reduced in tissue from human donor AMD eyes and 2 animal models of AMD. In conclusion, our data confirm that autophagy plays an important role in protection of the RPE against oxidative stress and lipofuscin accumulation and that impairment of autophagy is likely to exacerbate oxidative stress and contribute to the pathogenesis of AMD.     

Tenascin gene expression in rat liver and in rat liver cells In vivo and in vitro studies

Tenascin is a major glycoprotein constituent of the extracellular matrix with a strong affinity to fibronectin; its distribution is believed to be temporarily and spatially limited. Tenascin gene expression is increased during wound healing processes. As repair mechanisms in chronic liver diseases resemble wound healing we studied tenascin gene expression in rat liver and in isolated rat liver cells. In normal rat liver a tenascin specific antiserum stains sinusoidal cells with fiber-like prolongations, which at the same time are desmin-positive (ITO-cells). In the CCl₄-acutely-damaged liver a strong tenascin staining is detected in cells located among the mononuclear cells of the inflammatory infiltrates in the areas of necrosis and in cells of the sinusoids. In CG⁴-chronically-damaged liver a strong tenascin staining is demonstrable in the connective tissue septa. In both cases, many of the tenascin-positive cells can be identified as desmin-positive by means of the double-staining fluorescence technique. The wall of larger vessels is always tensacin-negative. The staining pattern obtained with a fibronectin-specific antiserum is somewhat comparable with that of tenascin but the vessel wall was positive. Hepatocytes, Kupffer cells, ITO-cells and endothelial cells were isolated from rat liver and studied for their capacity to express the tenascin gene. Biosynthetically labeled tenascin was immunoprecipated from supernatants and cell lysates obtained from cultured ITO-cells and to a much lesser extent from intracellular lysates obtained from endothelial cells; its synthesis in ITO-cells increased during the time in culture. Tenascin was also identified immuno-cytochemically in increasing amount in ITO-cells in culture. We conclude that ITO-cells may play a major role in tenascin synthesis during liver fibrogenesis. Some of these results were presented at the Annual Meeting of the American Association Study of the Liver, Chicago, USA, 1990. G.R. holds a Hermann and Lilly Schilling professorship     

Aging is associated with elevated muscle triglyceride content and increased insulin-stimulated fatty acid uptake

The purpose of the present study was to examine the utilization of fatty acids (FA) and muscle substrates by skeletal muscle in young, middle-aged, and old adult rats under hyperglycemic and hyperinsulinemic conditions. Male Fischer 344 x Brown Norway rats aged 5, 15, or 24 mo underwent hindlimb perfusion with a medium of 20 mM glucose, 1 mM palmitate, 1,000 microU/ml insulin, [1-14C]palmitate, and [3-3H]glucose. Glucose uptake and palmitate delivery were similar among age groups. Palmitate uptake and oxidation as well as muscle protein concentration of fatty acid translocase (FAT/CD36) and plasma membrane fatty acid-binding protein (FABPPM) were significantly increased (P < or = 0.05) in 24- vs. 5- and 15-mo-old animals. Compared with 5- and 15-mo-old animals, pre- and postperfusion muscle triglyceride (TG) levels were significantly (P < 0.05) elevated 72-145% in red and 112-129% in white muscles of 24-mo-old animals. Palmitate uptake was associated with total preperfusion TG concentration (r2 = 0.27, P < 0.05) and total TG synthesis rate (r2 = 0.68, P < 0.05). These results indicate that, under insulin-stimulated conditions, FA uptake is significantly increased in old animals, which is associated with increased rates of TG synthesis and may contribute to the accumulation of TG in muscle of old animals.     

Aging is associated with increased FGF21 levels but unaltered FGF21 responsiveness in adipose tissue

Fibroblast growth factor 21 (FGF21) has been proposed to be an antiaging hormone on the basis of experimental studies in rodent models. However, circulating FGF21 levels are increased with aging in rodents and humans. Moreover, despite the metabolic health‐promoting effects of FGF21, the levels of this hormone are increased under conditions such as obesity and diabetes, an apparent incongruity that has been attributed to altered tissue responsiveness to FGF21. Here, we investigated serum FGF21 levels and expression of genes encoding components of the FGF21‐response molecular machinery in adipose tissue from healthy elderly individuals (≥70 years old) and young controls. Serum FGF21 levels were increased in elderly individuals and were positively correlated with insulinemia and HOMA‐IR, indices of mildly deteriorated glucose homeostasis. Levels of β‐Klotho, the coreceptor required for cellular responsiveness to FGF21, were increased in subcutaneous adipose tissue from elderly individuals relative to those from young controls, whereas FGF receptor‐1 levels were unaltered. Moreover, total ERK1/2 protein levels were decreased in elderly individuals in association with an increase in the ERK1/2 phosphorylation ratio relative to young controls. Adipose explants from aged and young mice respond similarly to FGF21 “ex vivo”. Thus, in contrast to what is observed in obesity and diabetes, high levels of FGF21 in healthy aging are not associated with repressed FGF21‐responsiveness machinery in adipose tissue. The lack of evidence for impaired FGF21 responsiveness in adipose tissue establishes a distinction between alterations in the FGF21 endocrine system in aging and chronic metabolic pathologies.     

Aging is associated with chronic innate immune activation and dysregulation of monocyte phenotype and function

Chronic inflammation in older individuals is thought to contribute to inflammatory, age‐related diseases. Human monocytes are comprised of three subsets (classical, intermediate and nonclassical subsets), and despite being critical regulators of inflammation, the effect of age on the functionality of monocyte subsets remains to be fully defined. In a cross‐sectional study involving 91 healthy male (aged 20–84 years, median 52.4) and 55 female (aged 20–82 years, median 48.3) individuals, we found age was associated with an increased proportion of intermediate and nonclassical monocytes (P = 0.002 and 0.04, respectively) and altered phenotype of specific monocyte subsets (e.g. increased expression of CD11b and decreased expression of CD38, CD62L and CD115). Plasma levels of the innate immune activation markers CXCL10, neopterin (P < 0.001 for both) and sCD163 (P = 0.003) were significantly increased with age. Whilst similar age‐related changes were observed in both sexes, monocytes from women were phenotypically different to men [e.g. lower proportion of nonclassical monocytes (P = 0.002) and higher CD115 and CD62L but lower CD38 expression] and women exhibited higher levels of CXCL10 (P = 0.012) and sCD163 (P < 0.001) but lower sCD14 levels (P < 0.001). Monocytes from older individuals exhibit impaired phagocytosis (P < 0.05) but contain shortened telomeres (P < 0.001) and significantly higher intracellular levels of TNF both at baseline and following TLR4 stimulation (P < 0.05 for both), suggesting a dysregulation of monocyte function in the aged. These data show that aging is associated with chronic innate immune activation and significant changes in monocyte function, which may have implications for the development of age‐related diseases.     

Rosiglitazone is not associated with an increased risk of bladder cancer

BackgroundWhether rosiglitazone may increase bladder cancer risk has not been extensively investigated.MethodsThe reimbursement databases of all Taiwanese diabetic patients under oral anti-diabetic agents or insulin from 1996 to 2009 were retrieved from the National Health Insurance. An entry date was set at 1 January 2006 and a total of 885,236 patients with type 2 diabetes were followed up for bladder cancer incidence till end of 2009. Incidences for ever-users, never-users and subgroups of rosiglitazone exposure (using tertile cutoffs of time since starting rosiglitazone, duration of therapy and cumulative dose) were calculated and hazard ratios estimated by Cox regression.ResultsThere were 102,926 ever-users and 782,310 never-users, respective numbers of incident bladder cancer 356 (0.35%) and 2753 (0.35%), and respective incidence 98.3 and 101.6 per 100,000 person-years. The overall hazard ratios (95% confidence intervals) did not show significant association in unadjusted model [0.969 (0.867, 1.082)] and models adjusted for age and sex [0.983 (0.880, 1.098)] or all covariates [0.980 (0.870, 1.104)]. Neither the P values for the hazard ratios for the different categories of the dose–responsive parameters, nor their P-trends were significant.ConclusionsRosiglitazone does not increase the risk of bladder cancer.     

Age-dependent vulnerability to experimental acute pancreatitis is associated with increased systemic inflammation and thrombosis

The severity and mortality rates of acute pancreatitis (AP) are significantly elevated in the elderly population. However, due to a lack of appropriate animal models, the underlying mechanisms for this age‐dependent vulnerability remain largely unknown. The purpose of this study was to characterize a murine model of AP, which displays age‐associated severity, and to use this model to identify pathophysiologies that are distinctive of the aged with AP. AP was induced in young (4–5 months), middle‐aged (12–13 months), and aged (23–25 months) C57BL/6 mice by repeated injection of caerulein, a homologue of the gastrointestinal hormone cholecystokinin. Approximately 10% of aged mice died during AP, while young and middle‐aged mice showed no mortality. Although both young and aged mice exhibited early signs of edema and inflammation in the pancreas, kidney, and lung, young mice showed signs of recovery within 24 h, while aged mice exhibited increasingly severe tissue damage and cell death. There was a significant age‐dependent increase in pancreatic neutrophil activation and systemic inflammation as assessed by pancreatic myeloperoxidase and plasma interleukin‐6 (IL‐6) concentration, respectively. Importantly, aged but not young mice with AP showed significantly elevated thrombosis in the lung and kidney as well as a marked increase in plasma concentration of plasminogen activator inhibitor‐1 (PAI‐1), a primary inhibitor of the fibrinolytic system. These results demonstrate that aging is associated with increased severity of AP characterized by augmented and prolonged pancreatic inflammation and the presence of multiple extra‐pancreatic sequelae including thrombosis.     

Aging of mouse eggs in vivo and in vitro

Morphological and cytochemical (acid phosphatase) changes associated with mouse ova and cumulus cells aged within the oviducts (in vivo) or in culture (in vitro; 1–24 hours postovulation) have been investigated. Structural alterations of cumulus cells were apparent immediately after ovulation and included nuclear pycnosis and cytoplasmic vacuolization. Nevertheless, approximately 30% of the cumulus masses examined contained cells that plated out when cultured and remained viable for up t o three days in vitro. From 12 t o 24 hours postovulation almost all cumulus cells of specimens aged in vivo showed signs of degeneration. Disruption of the meiotic spindle and an increase in acid phosphatase positive organelles were characteristic of in vivo and in vitro aging ova. The percentage of fragmented eggs obtained from super-ovulated (5 IU PMS followed by 5 IU HCG) mice approximately one and 24 hours postovulation was not significantly different. Eggs obtained from superovulated animals and aged in vitro for 24 hours yielded significantly more fragmented ova. Fragmented eggs were not obtained from cycling females on the morning of estrus. When such eggs were cultured in vitro for 24 hours the percent fragmentation was significantly lower than that for aged eggs obtained from super-ovulated mice. These results indicate that 1) similar morphological alterations occur among cumulus cells and eggs aged either in vitro or in vivo, 2) ova from superovulated mice do not constitute a homogeneous population and 3) the method of superovulation employed in this study induces the ovulation of a relatively large group of eggs that are susceptible to fragmentation when cultured in vitro.     

Responsiveness of dentate neurons generated throughout adult life is associated with resilience to cognitive aging

During aging, some individuals are resilient to the decline of cognitive functions whereas others are vulnerable. These inter‐individual differences in memory abilities have been associated with differences in the rate of hippocampal neurogenesis measured in elderlies. Whether the maintenance of the functionality of neurons generated throughout adult life is linked to resilience to cognitive aging remains completely unexplored. Using the immediate early gene Zif268, we analyzed the activation of dentate granule neurons born in adult (3‐month‐old), middle‐aged (12‐month‐old), or senescent (18‐month‐old) rats (n = 96) in response to learning when animals reached 21 months of age. The activation of neurons born during the developmental period was also examined. We show that adult‐born neurons can survive up to 19 months and that neurons generated 4, 10, or 19 months before learning, but not developmentally born neurons, are activated in senescent rats with good learning abilities. In contrast, aged rats with bad learning abilities do not exhibit activity‐dependent regulation of newborn cells, whatever their birthdate. In conclusion, we propose that resilience to cognitive aging is associated with responsiveness of neurons born during adult life. These data add to our current knowledge by showing that the aging of memory abilities stems not only from the number but also from the responsiveness of adult‐born neurons.     

Rosetting is associated with increased Plasmodium falciparum in vivo multiplication rate in the Saimiri sciureus monkey

Severe Plasmodium falciparum malaria in African children is associated with high peripheral parasite densities and high rate of rosette-forming parasites. To explore the relationship between rosette formation and parasite density in vivo, we compared the multiplication rate of a rosette-forming variant (varO) of the Palo Alto line with a sibling non-rosetting variant (varR) in splenectomized Saimiri monkeys. The multiplication rate of varO parasites was 1.5-fold higher than that of the varR variant. This indicates that rosetting is indeed associated with high parasite multiplication efficiency in vivo and, as such, may contribute to the high parasite densities observed in severe malaria.     

ADAM8 expression is associated with increased invasiveness and reduced patient survival in pancreatic cancer

ADAM8 belongs to a family of transmembrane proteins implicated in cell-cell interactions, proteolysis of membrane proteins, and various aspects of carcinogenesis. In the present study, we aimed to evaluate the expression and function of ADAM8 in pancreatic cancer. ADAM8 mRNA levels were analysed by quantitative RT-PCR and correlated to patient survival. Immunohistochemistry was performed to localize ADAM8 in pancreatic tis-sues. Silencing of ADAM8 expression was carried out by transfection with specific siRNA oligonucleotides. Cell growth and invasion assays were used to assess the functional consequences of ADAM8 silencing. SELDI-TOF-MS was performed to detect the proteolytic activity of ADAM8 in pancreatic cancer cells. ADAM8 mRNA was significantly overexpressed in pancreatic ductal adenocarcinoma (PDAC) compared with normal pancreatic tissues (5.3-fold increase; P= 0.0008), and high ADAM8 mRNA and protein expression levels correlated with reduced survival time of PDAC patients (P= 0.048 and P= 0.065, respectively). Silencing of ADAM8 expression did not significantly influence pancreatic cancer cell growth but suppressed invasiveness. In addition, decreased proteolytic activity was measured in cell culture supernatants following silencing of ADAM8. In conclusion, ADAM8 is overexpressed in PDAC, influences cancer cell invasiveness and correlates with reduced survival, suggesting that ADAM8 might be a potential target in pancreatic cancer therapy.     

Evidence for clonal attenuation of growth potential in hela cells

Summary The growth of primary clones and serial subclones of HeLa cells and of diploid human fibroblast-like cells were compared both in the presence and absence of feeder layers; the latter had no significant effects upon the results. Clones and subclones of both cell types displayed great heterogeneity in growth rates, typically with a bimodality of growth distributions. Serial passages of clones selected on the basis of superior rates of proliferation showed attentuation of growth potentials; the extent of such attentuations was much less in the case of HeLa cells, suggesting at least one possible basis for the differences in long-term growth potential between these two classes of cell lines. This research was supported by Grants AG 00257 and AG 00592 from NIH. Dr. Martinez was supported by Postdoctoral Fellowship AG/HD 02765 from NIH.