Browsing by Subject "Aging"

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Aging impairs regulatory T cells to affect the mouse model of late-onset multiple sclerosis
(2022-08) Wang, Weikan; Su, Dong-Ming; Berg, Rance E.; Bunnell, Bruce A.; Yang, Shaohua; Jones, Harlan P.; Zode, Gulab S.
Although multiple sclerosis (MS) primarily onsets in young adults, it can also develop in the elderly, which is termed late-onset (aged) MS. CD4+ Foxp3 + regulatory T (Treg) cells play an ameliorative role in severity of MS or its animal model experimental autoimmune encephalomyelitis (EAE), and the aged immune system accumulates peripheral Treg (pTreg) cells. However, late-onset MS in the aged patients presents a more progressive disease course. We investigated why the accumulated pTreg cells fail to ameliorate the MS severity in the aged individuals by using an aged EAE mouse model to recapitulate late-onset MS in patients. We observed that the onset of EAE is delayed in aged mice, but disease severity is increased compared to young EAE mice. We found that the distribution of Treg cells in aged EAE mice exhibited an increased proportion of polyclonal (pan-) pTreg cells and a decreased proportion of antigen specific-pTreg cells in the periphery, but decreased proportions of both pan- and antigen specificTreg cells in the central nervous system (CNS). Transiently inhibiting Foxp3 or depleting pTreg cells partially corrected Treg distribution and restored the balance of effector T cells (Teff) and Treg cells in the aged inflamed CNS, thereby ameliorating the disease in the aged EAE mice. Furthermore, in the aged inflamed CNS, CNS-Treg cells exhibited a high plasticity and T effector (CNS-Teff) cells presented a great clonal expansion, disrupting the Treg/Teff balance. These results provide evidence and mechanism that accumulated aged pTreg cells play a detrimental role in neuronal inflammation of aged MS.
AMP-Activated Protein Kinase (AMPK) signaling regulates the age-related decline of hippocampal neurogenesis
(2018-05) Wang, Brian S.; Jin, Kunlin; Hodge, Lisa M.; Singh, Meharvan; Sumien, Nathalie; Yang, Shaohua
Aging is the progressive decline of physiological function and increased vulnerability to disease and death. By the year 2050, 2 billion people will be over the age of 60. Accompanying this, the incidence of age-associated neurological diseases is expected to rise. Thus, there is an urgent need to find therapies to promote healthy brain aging. The finding that neurogenesis continues into adulthood allows us to target endogenous neurogenesis as a potential therapeutic. However, the number of stem cells can decrease by about 80% in the aged brain and is a main cause for the decrease in brain function. The reasons for the age-related decline in neurogenesis can be due to intrinsic factors such as cell metabolism, which have been studied but its role in neurogenesis remains largely unexplored. Interestingly, neural stem cells (NSCs) possess metabolically different characteristics from their differentiated progeny, suggesting the need for a shift in cellular metabolism to accommodate the requirements for neurogenesis. In the process of the metabolic shift, the AMP-activated protein kinase (AMPK) plays a pivotal role for controlling stem cell proliferation and differentiation as a cell's master metabolic regulator. Additionally, AMPK has been reported to control the functions of signaling pathways that regulate the aging process, which suggests its potential involvement in the age-related decline of neurogenesis. Therefore, we hypothesize that inhibition of AMPK signaling activation (phosphorylation) in the old brain will cause a concomitant increase in hippocampal neurogenesis. Our specific aim is to establish whether AMPK signaling plays a critical role in the age-related decline of hippocampal neurogenesis. Our objectives for this aim are to (i) determine the expression pattern of AMPK in the subgranular and subventricular zones of young-adult and old mice using immunohistochemistry and Western blotting; and (ii) examine the impact of loss or gain of AMPK activation on hippocampal neurogenesis in young-adult and old mice using pharmacological agents Compound C (AMPK inhibitor) and 5-Aminoimidazole-4-carboxamide ribonucleotide (AICAR, AMPK activator). Our results show that (i) AMPK subunit isoforms are differentially expressed in the neurogenic regions – most are localized to the cytoplasm in the subgranular zone (SGZ) with the exception of α2 and β1, while most isoforms are found in the nucleus in the subventricular zone (SVZ) except α1; (ii) AMPK signaling activation was significantly increased in the SGZ and SVZ; and (iii) short-term but not long-term pharmacological inhibition of AMPK signaling could partially rescue hippocampal neurogenesis in the old brain. Taken together, these results indicate that AMPK is a critical mediator in the regulation of downstream processes for the age-related decline in hippocampal neurogenesis.
ATROPHIED THYMUS-GENERATED TH17 CELL INVOLVEMENT IN AUTOIMMUNITY IN THE ELDERLY
(2013-04-12) Shaw, Jennifer
Purpose: Aging induced thymic involution is proposed to be related to an increased incidence of autoimmune disorders because one of roles of a functional thymus is to generate central immune tolerance to prevent autoimmunity. Th17 cells have been shown to play a role in autoimmunity and can be generated in the thymus. Therefore, it can be questioned whether self-reactive Th17 clones can be generated in the aged atrophied thymus and become involved in the process of autoimmune development in the elderly once being induced under certain circumstances. Methods: We used conditional FoxN1 knockout (FC) mice, which possess an atrophied thymus, mimicing aged mice when injected with tamoxifen. The control mice with the normal thymus are termed FF. We used a cell sorting approach to isolate CD4 single positive thymocytes and naive CD4 positive spleen T cells. Sorted cells were cultured in conditions to induce Th17 differentiation. Flow cytometry was used to analyze cell populations. We used Rag gene knockout mice as hosts to receive Th17 cell infusion for observation of autoimmune phenotypes by histochemistry. Results: 1. The percentage of induced Th17 thymocytes is higher in FC mice compared to FF mice, but without induction there is no difference in FC and FF two groups. This indicates that when given a stimulus such as infection the atrophied thymus may produce a higher percentage of auto-reactive Th17 cells compared to a normal thymus. 2. The percentage of induced Th17 splenocytes and non-induced Th17 splenocytes shows no difference between FC and FF mice. However, there is greater inflammation and cell infiltration in the organs (such as the colon and lung) in the Rag-/- mice infused with FC Th17 compared to that infused with FF Th17. The result shows that although the percentage of Th17 cells from an atrophied thymus is not affected in the periphery, they may have higher auto-reactive activity compared to a normal thymus. Conclusions: The atrophied thymus may be defective in the generation of central immune tolerance and therefore allow auto-reactive Th17 cells to survive and leave the thymus.
Blood Inflammatory Exosomes with Age Prime Microglia through Complement Signaling for Negative Stroke Outcomes
(2020-05) Zhang, Hongxia; Jin, Kunlin; Forster, Michael J.; Yang, Shaohua; Shi, Xiangrong; Cunningham, J. Thomas
The systemic inflammatory milieu plays an important role in the age-related decline of functional integrity, but its contribution to age-related disease (e.g., stroke) remains largely unknown. Here, we found that activated complement molecules (C1q, C3a, C3b) in serum exosomes increased with age, whereas CD46, a C3b/C4b-inactivating factor, was higher in serum exosomes from young rats. These serum inflammatory exosomes passed the blood-brain barrier and primed the microglial response that led to exacerbation of synaptic loss and motor deficits after ischemic stroke via microglial C3a receptor (C3aR). When aged rats were exposed to serum exosomes from young rats, microglia-mediated synaptic loss was reduced and motor deficits after stroke were improved. Administration of C3aR inhibitor or microglial depletion attenuated synaptic loss associated with the treatment of serum exosome from aged rats, in parallel with improved post-stroke outcome. Our data suggest that peripheral circulating old exosomes act as inflammatory mediators and influence ischemic stroke outcome through a complement-microglia axis.
EFFECT OF ANTIOXIDANTS SUPPLEMENTATION AND MODERATE EXERCISE ON MOTOR FUNCTION IN YOUNG AND OLD MICE
(2014-03) Sidhu, Akram; Vann, Philip; Wong, Jessica; Sumien, Nathalie
The present study provided an assessment of the effect of exercise and/or vitamins on anxiety, coordinated running and motor function in young and old mice. Our data indicate that the effect of exercise and antioxidant supplementation may vary depending the age of the subject. Furthermore, there seem to be an increase their beneficial outcomes on motor function, when exercise is combined with antioxidant supplementation. Purpose (a): Aging is associated with a decline in psychomotor functioning and ability to learn new motor learning skills. Interventions such as exercise and antioxidants supplementation when investigated independently seem to have a beneficial impact on motor function in both human and animal subjects. A large number of health conscious individuals often combine exercise with vitamin supplementation, anticipating a synergistic effect maximizing their performance. Recent studies have also indicated a potential for an antagonistic action of the antioxidants on the beneficial effects of exercise. To date, it has not been well established what the nature of the interaction between antioxidant supplementation and exercise is in terms of functional outcomes and whether age will influence the outcomes. This study investigated the effects of moderate exercise and antioxidant supplementation on the motor performance of young and old mice. Methods (b): Separate groups of young (4 months), and old (20 months) male C57BL/6J mice were placed under one of the following treatments: Sedentary/control diet (SedCon), Sedentary/antioxidant-rich diet (vitamin E (128 IU/kg/d of body weight) and vitamin C (189 mg/kg/d of body weight); SedEC); Exercise/control diet (ExCon); Exercise/antioxidant-rich diet (ExEC). After 8 weeks of pre-treatment, the mice underwent a series of behavioral tests while remaining on their respective condition (elevated plus maze, spontaneous activity; coordinated running, wire suspension, and bridge walking). Results (c): Our preliminary data suggested that the time spent in the closed arms was increased in all treated mice compared to controls, and that the increase seemed more evident in the young mice. The latency to fall from a rotating rod seemed to be increased in the ExEC young and old mice when compared to all the other groups. The ExCon group had higher latency to fall while the other treatment groups seemed to have lower latencies when compared to SedCon within the young group. In the old group, only the ExEC group had higher latencies that the SedCon group while the others did not seem to differ. Latencies to fall from the bridge were increased in young groups where mice exercised (ExCon and ExEC), while they were decreased in SedEC and ExCon old mice compared to controls. Conclusions (d): Our data indicated that exercise and antioxidant supplementation can affect motor performance of young and old mice. Though preliminary, there seemed to be a differential effect dependent on the age of the mice. Lastly, there seem to be some type of interaction between antioxidant supplementation and exercise that may increase their beneficial outcomes.
EFFECTS OF SHORT-TERM PHYTOESTROGEN SUPPLEMENTATION ON THE BEHAVIOR OF MALE AND FEMALE MICE
(2013-04-12) Sidhu, Akram
Purpose: Plant-derived, non-steroidal compounds called phytoestrogens have been widely used as substitutes for estrogen in anticipation of estrogen-like therapeutic effects without producing the side effects associated with estrogen therapy. Human and animal data are still controversial regarding the beneficial effects of such compounds and whether they are differential based on the gender/sex of the subjects. This study investigated the effects of short-term phytoestrogen intake on the age-associated behavioral changes in the young, middle and old mice of both sex. Methods: Separate groups of young (6 months), middle (12 months) and old (24 months) male and female C57BL/6J mice were placed on either a phytoestrogen-free (PF) diet (N=15-17) or a phytoestrogen-rich (PR) diet containing (350-650 mg/kg phytoestrogens (N=16-19) for a period of 16 weeks. After 5 weeks on the diets, the mice were subjected to a series of behavioral tests to measure spontaneous activity (locomotor activity), anxiety (elevated plus maze, EPM), and cognitive function (water maze and active avoidance test). Results: PR mice exhibited increased spontaneous activity when compared to the PF mice, regardless of sex and especially in their rearing activity. In the EPM task, female mice spent less time in the open arms when compared to their males counterpart. At 24 months, PR male mice spent less time in open arms than their age-matched controls. In the water maze, PR mice performed worse than the PF mice which was particularly noticeable in the old mice, however there was no effect of the diet in the males. No major effects of diets were found in the active avoidance paradigm. Conclusions: Overall, short-term supplementation with phytoestrogens did not seem to affect anxiety levels or cognitive, though it may adversely impact spatial learning and memory in female mice, especially of old age.
Neurobehavioral and biochemical consequences of chronic, low-dose methamphetamine exposure in male and female mice
(2022-08) Davis, Delaney L.; Sumien, Nathalie; Huang, Ren-Qi; Gatch, Michael B.; Phillips, Nicole R.; Schreihofer, Derek A.; Ma, Rong
Although prescription psychostimulants are effective in reducing attention deficit hyperactivity disorder (ADHD) symptomology, misuse of these drugs can pose serious risks such as potential abuse, dependence, and/or neurotoxicity. Of particular concern is that young adults have the highest prevalence of prescription stimulant misuse, with almost 10% of college students admitting to using amphetamine (e.g. Adderall) or methylphenidate (e.g. Ritalin) products. Despite these drugs being widely used for therapeutic and recreational use, the long-term effects of prescription stimulants have not been systematically evaluated in controlled clinical trials. Therefore, it is critical to conduct this research because young adults may be a vulnerable, at-risk population to the potential adverse consequences of long-term amphetamine use. This dissertation research evaluates the biochemical and behavioral consequences of chronic exposure of the prototypical psychostimulant, methamphetamine (METH), in a rodent model. It is hypothesized that repeated doses of METH, within the therapeutic dosing range used in a clinical setting, will induce neurotoxicity through the interplay of biological mechanisms of oxidative stress, glutamate excitotoxicity, neuroinflammation and epigenetic alterations and increase susceptibility to addiction that will be exacerbated by aging processes. Overall, the body of results showed short-term alterations in brain biochemistry and behavioral function, that do not necessarily persist past 5 months after METH treatment. In conclusion, this dissertation highlights the importance of long-term studies in addressing prescription stimulant misuse in an adult population to better understand the safety of these widely used and prescribed psychostimulants.
Novel pharmacotherapy: NNI-362, an allosteric p70S6 kinase stimulator, reverses cognitive and neural regenerative deficits in models of aging and disease
(BioMed Central Ltd., 2021-01-13) Sumien, Nathalie; Wells, Matthew S.; Sidhu, Akram; Wong, Jessica M.; Forster, Michael J.; Zheng, Qiao-Xi; Kelleher-Andersson, Judith A.
Aging is known to slow the neurogenic capacity of the hippocampus, one of only two mammalian adult neurogenic niches. The reduction of adult-born neurons with age may initiate cognitive decline progression which is exacerbated in chronic neurodegenerative disorders, e.g., Alzheimer's disease (AD). With physiologic neurogenesis diminished, but still viable in aging, non-invasive therapeutic modulation of this neuron regeneration process remains possible. The discovery of truly novel neuron regenerative therapies could be identified through phenotypic screening of small molecules that promote adult-born neurons from human neural progenitor cells (hNPCs). By identifying neuron-generating therapeutics and potentially novel mechanism of actions, therapeutic benefit could be confirmed through in vivo proof-of-concept studies. The key aging and longevity mTOR/p70S6 kinase axis, a commonly targeted pathway, is substrate for potential selective kinase modulators to promote new hippocampal neurons from NPCs. The highly regulated downstream substrate of mTOR, p70S6 kinase, directly controls pleiotropic cellular activities, including translation and cell growth. Stimulating this kinase, selectively in an adult neurogenic niche, should promote NPC proliferation, and cell growth and survival in the hippocampus. Studies of kinase profiling and immunocytochemistry of human progenitor neurogenesis suggest that the novel small molecule NNI-362 stimulates p70S6 kinase phosphorylation, which, in turn, promotes proliferation and differentiation of NPCs to neurons. NNI-362 promoted the associative reversal of age- and disease-related cognitive deficits in aged mice and Down syndrome-modeled mice. This oral, allosteric modulator may ultimately be beneficial for age-related neurodegenerative disorders involving hippocampal-dependent cognitive impairment, specifically AD, by promoting endogenous hippocampal regeneration.
PERICYTE AND CAPILLARY MAY DECLINE DEPENDING ON THE AGING PROCESS IN MICE
(2022-05) Omoba, Oluwaseun E.; Jin, Kunlin; Rickards, Caroline A.; Mathis, Keisa W.
Purpose. In this study, we explore the effects of aging on pericytes and capillaries using mice. Pericytes are important components of the neurovascular unit and function as contractile cells around the walls of capillaries. They play many important roles in the brain, such as blood vessel formation, cerebral brain blood flow, maintenance of the blood-brain barrier, and regulation of immune cell entry into the CNS. Dysfunction of pericytes contribute to a wide range of illnesses that result in cognitive impairments such as cerebrovascular disease, stroke, Alzheimer's disease (AD), and other neurological disorders. Aging has been studied and shown to be an established risk for vascular dysfunction that affects the integrity of the neurovascular unit. Furthermore, studies have shown significant reductions in pericyte density during age-related disorders, but these studies are few. Most nutrients in the brain are supplied by capillaries, and because pericytes are embedded on capillaries, studying their patterns and effects may lead to a better understanding of the pathophysiology and preliminary triggers of age-related disorders. In this study, we explore whether both pericyte and capillary numbers are affected in the adult brain of mice as they age. Methods. All experiments were performed on young (3 month old; n=3) and old (20-23 month old; n=3) C57BL/6 male mice. To identify pericytes and capillaries for quantification, immunohistochemistry and immunofluorescence were used. Pericytes were stained using the biomarker PDGFrβ and capillaries were stained using Lectin. CA1, CA2, CA3, and DG sites were chosen for quantification in the hippocampus, and layers I-VI in the somatosensory cortex of each mouse. Confocal imaging was used to study and quantify the population of PDGFrβ and lectin-positive cells. T-tests were performed to compare the number of pericytes in the hippocampus and somatosensory cortex of the two groups of mice (young and old). Results. Old mice exhibited significantly lower capillary (via lectin) and pericyte (via PDGFrβ) numbers than young mice (p < 0.0001) in the hippocampus. There was no significant reduction in the number of pericyte (p = 0.1448) and capillary (p = 0.0967) in the somatosensory cortex. Pericytes that expressed PDGFrβ were only classified as such when colocalized to capillaries. To record the number of pericytes embedded on capillaries, the number of PDGFrβ + Lectin that expressed a "bump-on-a-log" morphology was also quantified and showed a significant reduction in the hippocampus (p < 0.0001) and somatosensory cortex (p = 0.0110) with age. Conclusion. Since cerebrovascular dysfunction plays a vital role in the development of cognitive impairment disorders, understanding the aging patterns of neurovasculature cells such as pericytes may aid in the early prevention of age-related illnesses.
RBAP48 AS A POTENTIAL MEMORY GENE
(2014-03) Manheim, Jessica; Rybalchenko, Nataliya; Singh, Meharvan
Aging individuals tend to experience cognitive decline, which provide an opportunity to investigate why some individuals age successfully while others do not. Our study investigates RbAp48, a gene related to cognitive function, to determine if the expression of this “memory gene” declines with age. Our data suggests that RbAp48 does decrease with age, and future studies will test whether steroid hormones, which have known influences on cognitive function, play a role in regulating RbAp48 gene expression. Purpose (a): With aging, there is a tendency for humans to experience cognitive decline. These variations in cognitive functioning provide an opportunity to investigate the reasons why some individuals age successfully versus those that do not. In a comprehensive analysis of gene regulation in the normal aging processes, it was recently shown that the histone binding protein, RbAp48, is implicated in age-related memory loss. Given the suggested role of RbAp48 in cognitive function, we sought to determine if, in animal models of aging currently being used in our laboratory, RbAp48 declines with age. Methods (b): We evaluated the expression of RbAp48 in the hippocampus of female C57Bl/6 mice that were 7.5 months and 25.5 months of age, representing young adult and old mice. RbAp48 mRNA was assessed using reverse transcriptase (rt) conversion of RNA to cDNA, followed by real time polymerase chain reaction (PCR). In parallel, the levels of GAPDH, a “housekeeping” gene, was measured to take into consideration variation in starting material. Differences in expression of RbAp48 were based on the delta-delta CT methodology published by Livak and Schmittgen (2001). Statistical evaluation of differences between experimental groups was determined using a two-tailed t-test. Results (c): Our data revealed an approximate 21% reduction in the levels of RbAp48 mRNA in the 25.5 month mice, compared to the 7.5 month mice. While not statistically significant (n=3, p=0.0791), we anticipate that these data warrant further analysis and expansion of our sample size to more reliably ascertain differences as a function of chronological age. Conclusions (d): These studies suggest that the expression of RbAp48, a presumptive “memory gene”, declines with age. Our future studies will determine if the steroid hormones, estrogen and progesterone, which have known influences on cognitive function, regulate the expression of RbAp48.
REELIN SIGNAL TRANSDUCTION PATHWAY IN APOE3 AND APOE4 TRANSGENIC MICE
(2013-04-12) Dugal, Maricelie
Purpose: The ɛ4 allele of apolipoprotein E (APOE) has been associated with increased risk for the development of late-onset, familial and sporadic Alzheimer's disease (AD). The mechanisms underlying the increase risk of AD development conferred by the ɛ4 allele remains unclear. Reelin and its associated signal transduction pathway are involved in developmental processes, and more specifically, in regulating neuronal migration and cortical lamination in the embryotic brain. Recently, it has been determined that reelin is present in the adult brain throughout the neocortex and hippocampus suggesting a potential role in synaptic plasticity. Furthermore, studies have shown that disruption of the reelin pathway led to decreased memory, impaired long-term potentiation (LTP), and affected dendritic spine morphology. This preliminary study investigated the role of the reelin pathway as a potential mechanism underlying the functional declines associated with APOE polymorphism. Methods: Separate groups of young (7 months) male and female mice expressing human apolipoprotein E4 or E3 in glial cells) were subjected to a series of behavioral tests to measure spontaneous activity, reflexes (walking initiation, alley turn, and negative geotaxis), motor function (wire suspension, bridge walking, coordinated running), and cognitive function (spatial water maze, active avoidance). Brain regions were dissected to determine the levels of reelin and other contributors of its pathway such as dab1, fyn, AMPA and NR2A via western blot analyses. Results: ApoE3 mice took longer latencies to fall in bridge walking, wire suspension, and coordinated running tasks than their ApoE4 counterparts, most notably in males. In the active avoidance task, ApoE3 female mice took fewer trials to reach criterion in session 3 over their ApoE4 counterparts. Western blot analyses will reveal whether reelin may underlie the differences in brain function between genotype and sex. Conclusions: Our results indicate that there may be functional differences between sex as well as ApoE polymorphism. Western blot analyses will reveal whether reelin, dab1, fyn, AMPA and NR2A may underlie the differences in brain function between genotype and sex.
Strategies & mechanisms to reduce locomotor impairment in aging & Parkinson's disease
(2021-05) Kasanga, Ella A.; Salvatore, Michael; Sumien, Nathalie; Luedtke, Robert R.; Bugnariu, Nicoleta L.; Goulopoulou, Styliani
The maintenance of physical function throughout the lifespan is a hallmark of successful aging. However, vulnerability to motor impairment during aging is evident in a substantial fraction of those reaching their seventh to ninth decade of life. Aging-related Parkinsonism is a major source of aging-related motor impairment and manifests similarly to Parkinson's disease (PD). Such disability is associated with a loss of independent living, frailty and mortality. Aging is a major risk factor for these two conditions and with the expected exponential increase in the aging population, their prevalence will also increase. Thus, there is the need to identify interventions which can attenuate this motor impairment, and elucidate the mechanisms mediating their protective benefits. Both pharmacological and non-pharmacological interventions, including exercise, have been proposed to ameliorate motor impairment in this target population. However, most of these interventions are instituted in preclinical models before motor function decline is evident. Also, in the quest to elucidate the underlying neurobiological mechanisms, most studies investigate the role of striatal dopamine (DA) regulation which is presumed to be paramount for the initiation or maintenance of locomotor activities. However, many studies do not report a corresponding increase in striatal DA regulation despite improved motor function. This dissertation research, therefore, evaluates interventions designed to prevent further motor decline in both aging and PD rat models after the onset of motor decline. It is hypothesized that improvement in motor function from the implemented interventions: caloric restriction, treadmill exercise and a pharmacological therapy-ceftriaxone, may not be dependent on only increased striatal, but also nigral, dopaminergic transmission. From several angles of intervention to mitigate motor decline in the models used, it is clear that motor function preservation or recovery can occur if interventions are initiated at a time-point when motor decline is already evident. The body of results show that preservation of motor function is not associated with preservation or restoration of striatal tyrosine hydroxylase expression, the rate-limiting enzyme in the synthesis of DA. Taken together, this dissertation delineates the efficacy of select interventions to attenuate motor decline and identifies key mechanistic targets for possible translation in this vulnerable population.
TESTOSTERONE REPLACEMENT THERAPY: ONE SIZE FITS ALL?
(2014-03) Nazarali, Rizwan; Cunningham, Rebecca
Testosterone replacement therapy (TRT) has been used to improve libido and overall well-being in men. Recently, there has been a rise in off-label TRT to treat diminished libido in women. Current studies from our laboratory have shown that testosterone is linked with cognition and memory in aging men. However, the relationship is murkier when associating cognitive impairment with testosterone in aging women. A key component of aging is oxidative stress (OS). Previous studies by our laboratory have shown that OS and the male sex hormone, testosterone, have a significant impact on neuronal viability, and subsequently cognition. An analysis of plasma biomarker proteins for OS (homocysteine) and testosterone was conducted on 177 Mexican-American women, 185 Caucasian women, 117 Mexican-American men, and 116 Caucasian men with a mean age of 72 from the Texas Alzheimer’s Research and Care Consortium (TARCC) to determine their role on memory and cognitive impairment. Participants were stratified according to their OS status (Low OS 12 mol/L of homocysteine). Participants were diagnosed as cognitively intact, mild cognitive impairment, or Alzheimer’s disease. Our results show that OS was significantly higher in men relative to women. Under a low oxidative stress environment, testosterone did not have a significant impact on memory or cognitive impairment, regardless of ethnicity or gender. However, in a high OS environment, testosterone significantly improved memory function and decreased cognitive impairment in Mexican-American men. Further, testosterone had a negative impact in Caucasian men, in which testosterone increased cognitive impairment. Testosterone had no effect on memory or cognitive impairment in women, irrespective of ethnicity. Collectively, the data support the hypotheses that: 1) testosterone mediates cognitive impairment in Caucasian men with high OS, 2) TRT therapy may be a viable option for Mexican-American men and, 3) testosterone does not alter memory or cognitive impairment in women. Therefore, the use of TRT should be tailored to an individual with respect to ethnicity and gender. Purpose (a): Testosterone replacement therapy (TRT) has been used to improve libido and overall well-being in men. Recently, there has been a rise in off-label TRT to treat diminished libido in women. Current studies from our laboratory have shown that testosterone is linked with cognition and memory in aging men. However, the relationship is murkier when associating cognitive impairment with testosterone in aging women. A key component of aging is oxidative stress (OS). Previous studies by our laboratory have shown that OS and the male sex hormone, testosterone, have a significant impact on neuronal viability, and subsequently cognition. Methods (b): An analysis of plasma biomarker proteins for OS (homocysteine) and testosterone was conducted on 177 Mexican-American women, 185 Caucasian women, 117 Mexican-American men, and 116 Caucasian men with a mean age of 72 from the Texas Alzheimer’s Research and Care Consortium (TARCC) to determine their role on memory and cognitive impairment. Participants were stratified according to their OS status (Low OS < 12 mol/L and High OS >12 mol/L of homocysteine). Participants were diagnosed as cognitively intact, mild cognitive impairment, or Alzheimer’s disease. Results (c): Our results show that OS was significantly higher in men relative to women. Under a low oxidative stress environment, testosterone did not have a significant impact on memory or cognitive impairment, regardless of ethnicity or gender. However, in a high OS environment, testosterone significantly improved memory function and decreased cognitive impairment in Mexican-American men. Furthermore, testosterone had a negative impact in Caucasian men, in which testosterone increased cognitive impairment. Testosterone had no effect on memory or cognitive impairment in women, irrespective of ethnicity. Conclusions (d): Collectively, the data support the hypotheses that: 1) testosterone mediates cognitive impairment in Caucasian men with high OS, 2) TRT therapy may be a viable option for Mexican-American men and, 3) testosterone does not alter memory or cognitive impairment in women. Therefore, the use of TRT should be tailored to an individual with respect to ethnicity and gender.
Testosterone Replacement Therapy: Role in Modulating Oxidative Stress within the Entorhinal Cortex
(2021-05) Tajani, Ammaar H.; Cunningham, Rebecca L.; Jones, Harlan P.; Romero, Steven A.
Sleep apnea affects approximately a quarter of all Americans. The effects of sleep apnea involve a decrease in testosterone levels, along with an increased rate of hypertension, stroke, and coronary heart disease. Chronic Intermittent Hypoxia (CIH) has also been shown to increase aging and negatively affect cognitive function, as seen with increased oxidative stress within the Entorhinal Cortex. However, it is unknown if Testosterone Replacement Therapy (TRT) can ameliorate the impact of CIH on the entorhinal cortex, which could have significant therapeutic impacts on sleep apnea related cognitive impairment. We hypothesized that TRT would mitigate protein levels of oxidative stress and inflammation, as measured by COX2, GFAP, and Calpain enzymatic activity. Banked brain tissue from young (3 month) F344/BN F1 hybrid male rats were used. Rats were separated into three treatment groups: gonadally intact, gonadectomized (GDX), and GDX with TRT. Then rats were either exposed to room air (normoxic conditions) or CIH for 8 days. Our results showed that neither TRT nor CIH impacted inflammation and oxidative stress related proteins in the entorhinal cortex. However, rats that were exposed to isoflurane anesthesia (GDX and GDX+TRT) showed neuroinflammation. Cognitive impairment has been associated with isoflurane related surgeries. However, the mechanism is unknown, though based on the data inflammation may be involved in isoflurane induced cognitive impairment in surgical patients.
THE EFFECTS OF ANDROGENS ON CASPASE-1 MEDIATED SIGNALING IN OXIDATIVE STRESSED DOPAMINE NEURONS
(2014-03) Holmes, Shaletha S.; Su, Chang; Singh, Meharvan; Cunningham, Rebecca
Parkinson’s disease (PD), a neurodegenerative disorder characterized by oxidative stress and the loss of dopamine neurons in the midbrain, affects the aging population. In fact, males have a higher risk for PD than females. While the mechanisms remain elusive, one possibility may be that androgens, such as testosterone, play a potential role. Our studies suggest that androgens can increase the expression of Caspase-1, an enzyme whose activity increases with oxidative stress and can result in mitochondrial collapse, ubiquitination, alpha-synuclein–positive lewy body accumulation, inflammation and apoptosis. Therefore, we hypothesize that in oxidative stress conditions, androgens suppress KLF4, a negative regulator of caspase-1, resulting in the increase of Caspase-1 to promote toxic protein accumulation, inflammation, and apoptotic neuronal cell death. This study is related to the role of testosterone in high levels of oxidative stress associated with aging. Purpose (a): Oxidative stress and an extensive loss of dopamine neurons in the nigrostriatal pathway are hallmarks of Parkinson’s disease (PD), a neurodegenerative disorder affecting millions of people. Males have a higher risk for PD than females. While the mechanisms remain elusive, one possibility may be that androgens, such as testosterone, play a potential role. Our studies suggest that androgens can increase the expression of Caspase-1, an enzyme whose activity increases with oxidative stress and can result in mitochondrial collapse, ubiquitination, alpha-synuclein–positive lewy body accumulation, inflammation and apoptosis. We hypothesize that in oxidative stress conditions, androgens suppress KLF4, a negative regulator of caspase-1, resulting in overexpression of Caspase-1 leading to toxic protein accumulation, inflammation, and apoptosis. Methods (b): We exposed a dopaminergic cell line (N27 cells) to a sublethal concentration of the pro-oxidant, tert-butyl hydrogen peroxide (H2O2) for 24 hrs and assessed cell viability in the presence or absence of testosterone. Results (c): Physiologically relevant concentrations of testosterone (0, 1, 10, 100 nM) failed to compromise cell viability in non-oxidatively stressed cells1. In contrast, testosterone did promote cell death in the H2O2 pre-treated cells. In H202 treated cells, testosterone increased caspase-1 expression and activation, as evidenced by an increase in cleaved caspase-1. In addition, KLF4 expression was decreased by testosterone in H2O2 treated cells. The role of KLF4 as a negative regulator of caspase-1 was confirmed in experiments showing that siRNA-mediated knockdown of KLF4 increased caspase-1 levels in H2O2 treated cells. Testosterone increased H202 mediated expression of COX2 signaling, a protein associated with inflammation. Also, testosterone decreased H2O2-induced ubiquitin expression resulting in the accumulation of toxic proteins. Further, testosterone increased H202 induced in apoptosis. Conclusions (d): Overall, these results indicate that androgens such as testosterone exert negative effects under oxidative stress conditions through the suppression of KLF4 and activation of caspase-1 signaling pathways leading to cell death. Thus, supporting a role for androgens for the gender bias observed in PD.
The Influence of Aging and Glycation on Protein-Thiol Mixed Disulfides in the Eye Lens
(1994-06-01) Dickerson Jr., Jaime E.; McConathy, Walter J.; Yorio, Thomas; Lou, Marjorie
Jaime E. Dickerson, Jr., The Influence of Aging and Glycation on Protein-Thiol Mixed Disulfides in the Eye Lens. Doctor of Philosophy (Biomedical Sciences), June, 1994, 163 pp., 9 tables, 28 illustrations, bibliography, 116 titles. The human lens is continually growing. As new cells are formed they differentiate into fiber cells which have no organelles, no protein synthesis or turnover. Lens protein aging involves formation of very large aggregations and insoluble complexes. These are held together through disulfide linkages. Reduced gluthathione (GSH) is present in high concentrations. The oxidized form, (GSSG), (5% of the total) can form mixed disulfides with proteins. This can destabilize the protein conformation. Accumulation of mixed disulfides may increase the potential for further modification. The participation of a PSSG (protein/gluthathione mixed disulfide) in the formation of a protein-protein disulfide becomes increasingly likely. The purpose of this work is to document PSSG and protein-cysteine mixed disulfide (PSSC) accumulation in human lenses (through eight decades), and to identify a third mixed disulfide discovered in this research. The free thiol molecules GSH and cysteine were also quantitated for normal and cataractous lenses. Glycation may alter conformation similar to mixed disulfides and potentiate mixed or protein-protein disulfide formation. This model was evaluated two ways. First, purified alpha crystalline was incubated with ascorbate and conformational changes were evaluated with CD spectroscopy. Second, rat lenses were cultured under high sugar conditions to determine if the resulting glycation influenced the level of mixed disulfides. Conversely, the effect of prior mixed disulfide formation on the extent of glycation in another purified crystalline, gamma, was evaluated. The results indicate: GSH declines in the lens with age, cysteine exists in the lens albeit at relatively low levels, PSSG shows a triphasic pattern of accumulation, PSSC accumulated linearly with increasing age, the existence of a third mixed disulfide species, gamma glutamylcysteine mixed disulfide, detected in old or cataractous lenses, has been confirmed, glycation by ascorbic acid alters α- crystalline secondary structure, the influence of glycation is minimal on mixed disulfide formation, mixed disulfide formation affects glycation of gamma crystalline.
VIGOROUS PHYSICAL ACTIVITY ASSOCIATED WITH HIGHER SCORES ON THE MMSE IN AN OLDER HISPANIC MEXICAN AMERICAN POPULATION: A HEALTH & AGING BRAIN AMONG LATINO ELDERS (HABLE) STUDY
(2014-03) Schwarzkopf, Heinz; Edwards, Melissa; Johnson, Leigh A.
Background: Physical activity has been shown to delay the onset and effects of cognitive decline, dementia and Alzheimer’s disease in the elderly. Few studies have evaluated the effects of physical activity among Hispanic Mexican Americans, a minority segment of the population, which has been shown to be less active when compared to non-Hispanic Whites. This study serves to evaluate the relationship between physical activity and cognition among Hispanic Mexican American, adults and elders Methods: Preliminary data was analyzed on 19 Hispanic Mexican Americans enrolled in the Health and Aging Brain Study among Latino Elders (HABLE), a recently developed community-based study of factors related to aging. The International Physical Activity Questionnaire (IPAQ) was utilized to assess physical activity and global cognitive functioning was evaluated with the Mini Mental Status Exam (MMSE). Separate linear regressions were conducted to analyze the relationship between hours spent engaging in either vigorous, moderate, or walking forms of physical activity and global cognitive functioning. Covariates included age, gender, education and language of test administration. Results: The results indicated that level of physical activity among Hispanic Mexican Americans differentially impacted cognitive functioning. Among those in the sample who engaged in vigorous activity, there was a significant relationship on global cognition such that increased hours of vigorous activity was positively related to global cognition (p=0.04). There was no significant association found between hours of moderate (p=0.74) or walking (p=0.70) physical activity and cognition. Conclusions: This study demonstrated the impact of level of physical activity on cognitive functioning among Hispanic Mexican Americans. . Vigorous physical activity was significantly related to better cognition among Hispanic Mexican Americans and more research is needed to further explore this relationship.