Age and organ dependent spontaneous generation of nuclear 8-hydroxydeoxyguanosine in male Fischer 344 rats

Long-term suboptimal dietary trace element supply does not affect trace element homeostasis in murine cerebellum

The ageing process is associated with alterations of systemic trace element (TE) homeostasis increasing the risk, e.g. neurodegenerative diseases. Here, the impact of long-term modulation of dietary intake of copper, iron, selenium, and zinc was investigated in murine cerebellum. Four- and 40-wk-old mice of both sexes were supplied with different amounts of those TEs for 26 wk. In an adequate supply group, TE concentrations were in accordance with recommendations for laboratory mice while suboptimally supplied animals received only limited amounts of copper, iron, selenium, and zinc. An additional age-adjusted group was fed selenium and zinc in amounts exceeding recommendations. Cerebellar TE concentrations were measured by inductively coupled plasma-tandem mass spectrometry. Furthermore, the expression of genes involved in TE transport, DNA damage response, and DNA repair as well as selected markers of genomic stability [8-oxoguanine, incision efficiency toward 8-oxoguanine, 5-hydroxyuracil, and apurinic/apyrimidinic sites and global DNA (hydroxy)methylation] were analysed. Ageing resulted in a mild increase of iron and copper concentrations in the cerebellum, which was most pronounced in the suboptimally supplied groups. Thus, TE changes in the cerebellum were predominantly driven by age and less by nutritional intervention. Interestingly, deviation from adequate TE supply resulted in higher manganese concentrations of female mice even though the manganese supply itself was not modulated. Parameters of genomic stability were neither affected by age, sex, nor diet. Overall, this study revealed that suboptimal dietary TE supply does not substantially affect TE homeostasis in the murine cerebellum.

Potential role of inducible nitric oxide synthase (iNOS) activity in testicular dysfunction following co-administration of alcohol and combination antiretroviral therapy (cART) in diabetic rats: an immunohistochemistry study

Diabetes, alcohol abuse, and combination antiretroviral therapy (cART) use have been reported to cause multi-organ complications via induction of oxidative stress and inflammation. Moreover, these are the most common factors implicated in male reproductive dysfunctions. This study evaluated testicular oxidative stress, inflammation, apoptosis, and germ cell proliferation in diabetic rats receiving alcohol or cART and their combination. Thirty adult male Sprague Dawley rats were divided into five groups, each consisting of six rats; control, diabetic only (DM), diabetic treated with alcohol (DM + A), diabetic treated with cART (DM + cART), and diabetic treated with both alcohol and cART (DM + A + cART). After 90 days of treatment, the rats were terminated, and the testes were extracted and processed for immunohistochemistry analysis for oxidative stress, inflammatory cytokines, apoptosis, and cell proliferation marker. In comparison to the control, oxidative stress markers, inducible nitric oxide synthase (iNOS), malondialdehyde (MDA), and 8-hydroxydeoxyguanosine (8-OHDG) increased significantly in all treated groups. Expression of testicular proinflammatory cytokines, interleukin-1β, and tumor necrosis factor-α was upregulated in all treated groups, but interleukin-6 was upregulated in DM, DM + cART, and DM + A + cART treated groups and was downregulated in the DM + A treated group. All treated animal groups showed an upregulation of apoptotic marker (caspase 3) and a downregulation of proliferation marker (Ki-67). However, Ki-67 staining intensity significantly increased in treated animals compared to the control. These findings suggest that diabetes, alcohol abuse, cART use, and their combination via iNOS activity upregulation can induce inflammation and oxidative stress in testicular tissue, stimulating germ cell apoptosis and proliferation inhibition leading to failure of spermatogenesis.

Mechanistic aspects of ameliorative effects of Eicosapentanoic acid ethyl ester on methotrexate-evoked testiculopathy in rats

Disrupted spermatogenesis and testicular injury are among the devastating outcomes of methotrexate. A major contributor to methotrexate-induced testiculopathy is oxidative damage which triggers apoptosis and altered autophagy responses. Eicosapentaenoic acid ethyl ester (EPA-E) is an antihyperlipidemic derivative of omega-3 fatty acids that exhibited affinity to peroxisome proliferator-activated receptor-γ (PPAR-γ) that possesses both antioxidant and autophagy modulating properties. This is an exploratory study aiming at assessing the effectiveness of EPA-E to alleviate testicular damage induced by methotrexate. The specific exploratory hypothesis of this experiment is: EPA-E administration for 1 week to methotrexate-treated rats reduces testicular damage compared to control rats. As a secondary outcome, we were interested in identifying the implicated mechanism that mediates the action of EPA-E. In adult male Wistar rats, testiculopathy was achieved by a single methotrexate injection (20 mg/kg, ip). Rats received vehicle, EPA-E (0.3 g/kg/day, po) alone or with selective PPAR-γ antagonist (bisphenol A diglycidyl ether, BADGE) at 30 mg/kg/day, ip for 1 week. EPA-E recuperated methotrexate-attenuated serum total testosterone while reduced testicular inflammation and oxidative stress, restoring superoxide dismutase (SOD) while reducing malondialdehyde (MDA) and 8-hydroxy-2'-deoxyguanosine (8-OHdG). Methotrexate-induced testicular apoptosis (caspase-3 and p53) was suppressed upon EPA-E treatment. Besides, EPA-E curbed methotrexate-induced abnormal autophagy by downregulating LC3A/B and beclin-1. Interestingly, BADGE-coadministration reversed EPA-E beneficial actions. Collectively, our findings suggest PPAR-γ role in EPA-E-mediated mitigation of methotrexate-evoked testiculopathy via suppression of oxidative stress, apoptosis, as well as abnormal autophagy. Furthermore, EPA-E could be used as a preventive therapy for some testiculopathies mediated by oxidative stress.

Choroid Plexus Aquaporins in CSF Homeostasis and the Glymphatic System: Their Relevance for Alzheimer's Disease

The glymphatic system, a fluid-clearance pathway involved in brain waste clearance, is known to be impaired in neurological disorders, including Alzheimer's disease (AD). For this reason, it is important to understand the specific mechanisms and factors controlling glymphatic function. This pathway enables the flow of cerebrospinal fluid (CSF) into the brain and subsequently the brain interstitium, supported by aquaporins (AQPs). Continuous CSF transport through the brain parenchyma is critical for the effective transport and drainage of waste solutes, such as toxic proteins, through the glymphatic system. However, a balance between CSF production and secretion from the choroid plexus, through AQP regulation, is also needed. Thus, any condition that affects CSF homeostasis will also interfere with effective waste removal through the clearance glymphatic pathway and the subsequent processes of neurodegeneration. In this review, we highlight the role of AQPs in the choroid plexus in the modulation of CSF homeostasis and, consequently, the glymphatic clearance pathway, with a special focus on AD.

Choroid plexus function in neurological homeostasis and disorders: The awakening of the circadian clocks and orexins

As research regarding the role of circadian rhythms, sleep, and the orexinergic system in neurodegenerative diseases is growing, it is surprising that the choroid plexus (CP) remains underappreciated in this realm. Despite its extensive role in the regulation of circadian rhythms and orexinergic signalling, as well as acting as the primary conduit between cerebrospinal fluid (CSF) and the circulatory system, providing a mechanism by which toxic waste molecules can be removed from the brain, the CP has been largely unexplored in neurodegeneration. In this review, we explore the role of the CP in maintaining brain homeostasis and circadian rhythms, regulating CSF dynamics, and how these functions change across the lifespan, from development to senescence. In addition, we examine the relationship between the CP, orexinergic signalling, and the glymphatic system, highlighting gaps in the literature and areas that require immediate exploration. Finally, we assess current knowledge, including possible therapeutic strategies, regarding the role of the CP in neurological disorders, such as traumatic brain injury, migraine, Alzheimer's disease, and multiple sclerosis.

Alzheimer’s Amyloid-β Accelerates Human Neuronal Cell Senescence Which Could Be Rescued by Sirtuin-1 and Aspirin

Cellular senescence is a major biological process related to aging. Neuronal cell senescence contributes to the pathogenesis of many aging-related neurodegenerative diseases including Alzheimer’s disease (AD). In this study, we showed that amyloid-β₄₂ oligomers (Aβ), one of the core pathological players of AD, significantly upregulated the expression of senescence markers, p21, plasminogen activator inhibitor-1 (PAI-1), and SA-β-gal (senescence-associated β-galactosidase) in multiple human neuronal cells, including SK-N-SH cells, SH-SY5Y cells, and neural stem cell (NSC)-derived neuronal cells. Moreover, it was consistently observed among the cells that Aβ promoted senescence-associated DNA damage as the levels of 8-OHdG staining, histone variant H2AX phosphorylation (γ-H2AX), and genomic DNA lesion increased. Mechanism study revealed that the exposure of Aβ markedly suppressed the expression of sirtuin-1 (SIRT1), a critical regulator of aging, and the exogenous expression of SIRT1 alleviated Aβ-induced cell senescence phenotypes. To our surprise, a widely used cardiovascular drug aspirin considerably rescued Aβ-induced cellular senescence at least partially through its regulation of SIRT1. In conclusion, our findings clearly demonstrate that exposure of Aβ alone is sufficient to accelerate the senescence of human neuronal cells through the downregulation of SIRT1.

The dynamic changes of Nrf2 mediated oxidative stress, DNA damage and base excision repair in testis of rats during aging

Accumulation of oxidative stress, DNA damage and impaired DNA repair appear to play critical roles in the decline of testicular function with aging. However, when those factors begin to lose control in testis during aging has not yet been well understood. This study was designed to assess the changes of oxidative stress and DNA damage status, and DNA repair capacity in testis during aging. Thus, male Sprague-Dawley rats at 3, 9, 15 and 24 months of age were used to delineate the dynamic changes in testicular weight and index, testosterone concentration, testicular histology, Nrf2-mediated oxidative stress, DNA damage, DNA repair and apoptosis. Results showed that testicular weight and index, testosterone concentration and spermatid number progressively declined from 9 to 24 months of age. Similarly, seminiferous tubule diameters and seminiferous epithelium heights gradually diminished with aging. Nrf2-mediated antioxidant defense ability was significantly impaired in testis with increasing age including decreased the activity of SOD and the expression levels of Nrf2, HO-1 and NQO-1, and increased the contents of MDA. In addition, DNA damage including DNA single-strand breaks (SSBs) and DNA double-strand breaks (DSBs) also progressively increased accompanied by increased levels of 8-hydroxydeoxyguanosine (8-OHdG) and γ-H2AX, and activated ATM/Chk2 and ATR/Chk1 pathway. Consistent with the results of Nrf2 pathway, the expression levels of APE1, OGG1 and XRCC1 involved in base excision DNA repair (BER) pathway increased from 3 to 9 months of age, and then gradually decreased after 9 months of age. Finally, TUNEL and Western blot results further confirmed germ cell apoptosis progressively increased from 3 to 24 months of age as evidenced by decreased ratio of Bcl-2/Bax and levels of Bcl-2 expression, and increased Bax expression levels. Taken together, our results suggest that downregulation of antioxidant ability mediated by Nrf2 pathway and impairment of BER capacity might correlate with increased DNA damage, and then induce declining testicular function during aging after adult.

Reproductive Effects of Nicotinamide on Testicular Function and Structure in Old Male Rats: Oxidative, Apoptotic, Hormonal, and Morphological Analyses

Aging is a natural process in which morphological and functional abnormalities in living organisms increase irreversibly. Nicotinamide (NAM) acts both as a precursor of many metabolites and as a cofactor of many enzymes involved in cell energy metabolism, homeostasis of redox balance, and regulation of signaling pathways. In this study, we investigated the effects of NAM treatment on morphological and biochemical changes in testis of old rats. The rats were treated with 200, 400, and 800 mg/kg NAM doses as a gavage for 1 month. As a result, we determined the dose-dependent therapeutic effects of NAM on testicular tissues of aged rats. We found that NAM treatment decreased total oxidant status (TOS), caspase 3 (CASP3) and cytochrome c (CYC) levels and increased total antioxidant status (TAS), follicle-stimulating hormone (FSH), luteinizing hormone (LH), and testosterone levels (P<0.05). NAM treatment significantly reduced the age-related histopathological parameters such as cellular loss, necrotic tissue, interstitial edema, tubular damage, and vascular congestion in aged rat testicular tissue compared to the control group. Moreover, based on histomorphological analysis, we detected that NAM treatment resulted in a dose-dependent improvement in testicular tissue damage of old rats. Consequently, the results showed that the reproductive decline caused by aging could be ameliorated with NAM treatment.

Genome-Wide Screen of the Hippocampus in Aged Rats Identifies Mitochondria, Metabolism and Aging Processes Implicated in Sevoflurane Anesthesia

Previous studies have shown multiple mechanisms and pathophysiological changes after anesthesia, and genome-wide studies have been implemented in the studies of brain aging and neurodegenerative diseases. However, the genome-wide gene expression patterns and modulation networks after general anesthesia remains to be elucidated. Therefore, whole transcriptome microarray analysis was used to explore the coding gene expression patterns in the hippocampus of aged rats after sevoflurane anesthesia. Six hundred and thirty one upregulated and 183 downregulated genes were screened out, then 44 enriched terms of biological process, 16 of molecular function and 18 of the cellular components were identified by Gene Ontology (GO) and KEGG analysis. Among them, oxidative stress, metabolism, aging, and neurodegeneration were the most enriched biological processes and changed functions. Thus, involved genes of these processes were selected for qPCR verification and a good consistency was confirmed. The potential signaling pathways were further constructed including mitochondrion and oxidative stress-related Hifs-Prkcd-Akt-Nfe2l2-Sod1 signaling, multiple metabolism signaling (Scd2, Scap-Hmgcs2, Aldh18a1-Glul and Igf1r), as well as aging and neurodegeneration related signaling (Spidr-Ercc4-Cdkn1a-Pmaip1 and Map1lc3b). These results provide potential therapeutic gene targets for brain function modulation and memory formation process after inhaled anesthesia in the elderly, which could be valuable for preventing postoperative brain disorders and diseases, such as perioperative neurocognitive disorders (PND), from the genetic level in the future.

Redox Signaling in Neurotransmission and Cognition During Aging

SIGNIFICANCE

Oxidative stress increases in the brain with aging and neurodegenerative diseases. Previous work emphasized irreversible oxidative damage in relation to cognitive impairment. This research has evolved to consider a continuum of alterations, from redox signaling to oxidative damage, which provides a basis for understanding the onset and progression of cognitive impairment. This review provides an update on research linking redox signaling to altered function of neural circuits involved in information processing and memory. Recent Advances: Starting in middle age, redox signaling triggers changes in nervous system physiology described as senescent physiology. Hippocampal senescent physiology involves decreased cell excitability, altered synaptic plasticity, and decreased synaptic transmission. Recent studies indicate N-methyl-d-aspartate and ryanodine receptors and Ca²⁺ signaling molecules as molecular substrates of redox-mediated senescent physiology.

CRITICAL ISSUES

We review redox homeostasis mechanisms and consider the chemical character of reactive oxygen and nitrogen species and their role in regulating different transmitter systems. In this regard, senescent physiology may represent the co-opting of pathways normally responsible for feedback regulation of synaptic transmission. Furthermore, differences across transmitter systems may underlie differential vulnerability of brain regions and neuronal circuits to aging and disease.

FUTURE DIRECTIONS

It will be important to identify the intrinsic mechanisms for the shift in oxidative/reductive processes. Intrinsic mechanism will depend on the transmitter system, oxidative stressors, and expression/activity of antioxidant enzymes. In addition, it will be important to identify how intrinsic processes interact with other aging factors, including changes in inflammatory or hormonal signals. Antioxid. Redox Signal. 28, 1724-1745.

GIT2-A keystone in ageing and age-related disease

Since its discovery, G protein-coupled receptor kinase-interacting protein 2, GIT2, and its family member, GIT1, have received considerable interest concerning their potential key roles in regulating multiple inter-connected physiological and pathophysiological processes. GIT2 was first identified as a multifunctional protein that is recruited to G protein-coupled receptors (GPCRs) during the process of receptor internalization. Recent findings have demonstrated that perhaps one of the most important effects of GIT2 in physiology concerns its role in controlling multiple aspects of the complex ageing process. Ageing can be considered the most prevalent pathophysiological condition in humans, affecting all tissue systems and acting as a driving force for many common and intractable disorders. The ageing process involves a complex interplay among various deleterious activities that profoundly disrupt the body's ability to cope with damage, thus increasing susceptibility to pathophysiologies such as neurodegeneration, central obesity, osteoporosis, type 2 diabetes mellitus and atherosclerosis. The biological systems that control ageing appear to function as a series of interconnected complex networks. The inter-communication among multiple lower-complexity signaling systems within the global ageing networks is likely coordinated internally by keystones or hubs, which regulate responses to dynamic molecular events through protein-protein interactions with multiple distinct partners. Multiple lines of research have suggested that GIT2 may act as one of these network coordinators in the ageing process. Identifying and targeting keystones, such as GIT2, is thus an important approach in our understanding of, and eventual ability to, medically ameliorate or interdict age-related progressive cellular and tissue damage.

DNA Damage, DNA Repair, Aging, and Neurodegeneration

Aging in mammals is accompanied by a progressive atrophy of tissues and organs, and stochastic damage accumulation to the macromolecules DNA, RNA, proteins, and lipids. The sequence of the human genome represents our genetic blueprint, and accumulating evidence suggests that loss of genomic maintenance may causally contribute to aging. Distinct evidence for a role of imperfect DNA repair in aging is that several premature aging syndromes have underlying genetic DNA repair defects. Accumulation of DNA damage may be particularly prevalent in the central nervous system owing to the low DNA repair capacity in postmitotic brain tissue. It is generally believed that the cumulative effects of the deleterious changes that occur in aging, mostly after the reproductive phase, contribute to species-specific rates of aging. In addition to nuclear DNA damage contributions to aging, there is also abundant evidence for a causative link between mitochondrial DNA damage and the major phenotypes associated with aging. Understanding the mechanistic basis for the association of DNA damage and DNA repair with aging and age-related diseases, such as neurodegeneration, would give insight into contravening age-related diseases and promoting a healthy life span.

CUX2 protein functions as an accessory factor in the repair of oxidative DNA damage

CUX1 and CUX2 proteins are characterized by the presence of three highly similar regions called Cut repeats 1, 2, and 3. Although CUX1 is ubiquitously expressed, CUX2 plays an important role in the specification of neuronal cells and continues to be expressed in postmitotic neurons. Cut repeats from the CUX1 protein were recently shown to stimulate 8-oxoguanine DNA glycosylase 1 (OGG1), an enzyme that removes oxidized purines from DNA and introduces a single strand break through its apurinic/apyrimidinic lyase activity to initiate base excision repair. Here, we investigated whether CUX2 plays a similar role in the repair of oxidative DNA damage. Cux2 knockdown in embryonic cortical neurons increased levels of oxidative DNA damage. In vitro, Cut repeats from CUX2 increased the binding of OGG1 to 7,8-dihydro-8-oxoguanine-containing DNA and stimulated both the glycosylase and apurinic/apyrimidinic lyase activities of OGG1. Genetic inactivation in mouse embryo fibroblasts or CUX2 knockdown in HCC38 cells delayed DNA repair and increased DNA damage. Conversely, ectopic expression of Cut repeats from CUX2 accelerated DNA repair and reduced levels of oxidative DNA damage. These results demonstrate that CUX2 functions as an accessory factor that stimulates the repair of oxidative DNA damage. Neurons produce a high level of reactive oxygen species because of their dependence on aerobic oxidation of glucose as their source of energy. Our results suggest that the persistent expression of CUX2 in postmitotic neurons contributes to the maintenance of genome integrity through its stimulation of oxidative DNA damage repair.

Mapping NAD(+) metabolism in the brain of ageing Wistar rats: potential targets for influencing brain senescence

Over the last decade, the importance of NAD(+) has expanded beyond its role as an essential cofactor for energy metabolism. NAD(+) has emerged as a major signalling molecule that serves as the sole substrate for several enzymatic reactions including the DNA repair enzyme, poly(ADP-ribose) polymerase (PARP), NAD-dependent protein deacetylases or CD38, and transcriptional factors by a new class of histone deacetylases known as sirtuins. NAD(+) levels are regulated by the metabolic status and cellular stress caused by oxidative stress and DNA damage. Since a detailed study of NAD(+) metabolism in the healthy ageing mammalian brain is nascent, we examined the effect of ageing on intracellular NAD(+) metabolism in different brain regions in female Wistar rats in young (3 months), middle aged (12 months) and older adults (24 months). Our results are the first to show a significant decline in intracellular NAD(+) levels and NAD:NADH ratio with ageing in the CNS, occurring in parallel to an increase in lipid peroxidation and protein oxidation (o- and m-tyrosine) and a decline in total antioxidant capacity. Hyperphosphorylation of H2AX levels was also observed together with increased PARP-1 and PARP-2 expression, and CD38 activity, concomitantly with reduced NAD(+) and ATP levels and SIRT1 function in the cortex, brainstem, hippocampus and cerebellum. Reduced activity of mitochondrial complex I-IV and impaired maximum mitochondrial respiration rate were also observed in the ageing rat brain. Among the multiple physiological pathways associated with NAD(+) catabolism, our discovery of CD38 as the major regulator of cellular NAD(+) levels in rat neurons indicates that CD38 is a promising therapeutic target for the treatment of age-related neurodegenerative diseases.

Differences in the activities of resveratrol and ascorbic acid in protection of ethanol-induced oxidative DNA damage in human peripheral lymphocytes

Previous studies have shown that ethanol induces oxidative DNA damage in human peripheral lymphocytes. In the present study, protective effect of resveratrol and ascorbic acid on ethanol-induced oxidative DNA damage in human peripheral lymphocytes in vitro were comparatively investigated. Pretreatments with resveratrol at 5, 25, and 50μM, which were in the concentration range of in vitro research, significantly inhibited ethanol-induced oxidative DNA damage in 24h, whereas ascorbic acid showed such DNA protective activity only in 1h. Further study showed that both compounds could directly scavenge hydroxyl radical produced during ethanol metabolism. Resveratrol significantly inhibited ethanol metabolism by regulating alcohol dehydrogenase 1B (ADH1B) and acetaldehyde dehydrogenase 2 (ALDH2) mRNA expressions. Moreover, resveratrol also activated the base excision repair (BER) system in mRNA and protein levels in DNA auto-repair process. However, ascorbic acid showed no effect on ethanol metabolic pathway and BER system. Thus, the present study provided the first evidence that even though both resveratrol and ascorbic acid are anti-oxidants, they possessed differential mechanisms of action in protection against ethanol-induced oxidative DNA damage in human peripheral lymphocytes.

DNA repair deficiency in neurodegeneration

Deficiency in repair of nuclear and mitochondrial DNA damage has been linked to several neurodegenerative disorders. Many recent experimental results indicate that the post-mitotic neurons are particularly prone to accumulation of unrepaired DNA lesions potentially leading to progressive neurodegeneration. Nucleotide excision repair is the cellular pathway responsible for removing helix-distorting DNA damage and deficiency in such repair is found in a number of diseases with neurodegenerative phenotypes, including Xeroderma Pigmentosum and Cockayne syndrome. The main pathway for repairing oxidative base lesions is base excision repair, and such repair is crucial for neurons given their high rates of oxygen metabolism. Mismatch repair corrects base mispairs generated during replication and evidence indicates that oxidative DNA damage can cause this pathway to expand trinucleotide repeats, thereby causing Huntington's disease. Single-strand breaks are common DNA lesions and are associated with the neurodegenerative diseases, ataxia-oculomotor apraxia-1 and spinocerebellar ataxia with axonal neuropathy-1. DNA double-strand breaks are toxic lesions and two main pathways exist for their repair: homologous recombination and non-homologous end-joining. Ataxia telangiectasia and related disorders with defects in these pathways illustrate that such defects can lead to early childhood neurodegeneration. Aging is a risk factor for neurodegeneration and accumulation of oxidative mitochondrial DNA damage may be linked with the age-associated neurodegenerative disorders Alzheimer's disease, Parkinson's disease and amyotrophic lateral sclerosis. Mutation in the WRN protein leads to the premature aging disease Werner syndrome, a disorder that features neurodegeneration. In this article we review the evidence linking deficiencies in the DNA repair pathways with neurodegeneration.

Age related changes in NAD+ metabolism oxidative stress and Sirt1 activity in wistar rats

The cofactor nicotinamide adenine dinucleotide (NAD+) has emerged as a key regulator of metabolism, stress resistance and longevity. Apart from its role as an important redox carrier, NAD+ also serves as the sole substrate for NAD-dependent enzymes, including poly(ADP-ribose) polymerase (PARP), an important DNA nick sensor, and NAD-dependent histone deacetylases, Sirtuins which play an important role in a wide variety of processes, including senescence, apoptosis, differentiation, and aging. We examined the effect of aging on intracellular NAD+ metabolism in the whole heart, lung, liver and kidney of female wistar rats. Our results are the first to show a significant decline in intracellular NAD+ levels and NAD:NADH ratio in all organs by middle age (i.e.12 months) compared to young (i.e. 3 month old) rats. These changes in [NAD(H)] occurred in parallel with an increase in lipid peroxidation and protein carbonyls (o- and m- tyrosine) formation and decline in total antioxidant capacity in these organs. An age dependent increase in DNA damage (phosphorylated H2AX) was also observed in these same organs. Decreased Sirt1 activity and increased acetylated p53 were observed in organ tissues in parallel with the drop in NAD+ and moderate over-expression of Sirt1 protein. Reduced mitochondrial activity of complex I-IV was also observed in aging animals, impacting both redox status and ATP production. The strong positive correlation observed between DNA damage associated NAD+ depletion and Sirt1 activity suggests that adequate NAD+ concentrations may be an important longevity assurance factor.

Antegrade flow and peripheral resistance determine the level of endogenous arteriogenesis in patients with superficial femoral artery occlusion

OBJECTIVES

Occlusion in a limb artery leads to impaired blood supply and ischaemia. Collateral artery growth (arteriogenesis) is one of the most effective natural response mechanisms to compensate this pathologic situation. However, it is unknown if clinically important features, like poor run-off, have an impact on compensatory vessel growth.

METHODS

Study population of this retrospective study consisted of 70 patients who suffered from lower limb ischaemia and underwent bypass surgery because of an occlusion of the superficial femoral artery. Clinical data were collected and pre- and postoperative angiograms were reviewed. Number of collateral vessels bypassing the occluded segment was counted. Features of inflow and outflow vessels were recorded.

RESULTS

The mean number of collaterals was 13 + or - 0.5 per patient. In univariate analysis, short daily walking distance, chronic critical leg ischaemia, low ankle brachial index, low number of patent calf arteries and stenosed inflow arteries predicted low number of collateral arteries. In the multivariate analysis, only the quality of inflow and the number of patent calf vessels demonstrated an independent association (P < 0.05) with the number of collaterals.

CONCLUSIONS

Ankle-brachial index, grade of symptoms and daily walking capacity could be used to predict collateral density. Importantly, a good antegrade flow and peripheral runoff seem to have a significant effect on collateral density, implying an impact on the activation of arteriogenesis.

Relationship between levels of oxidative DNA damage, lipid peroxidation and mitochondrial membrane potential in young and old F344 rats

The extent of in vivo oxidative damage has been known to be cumulative over the period of the life of mammals. Our hypothesis is that there should be a positive correlation between the levels of 8-hydroxy-2'-deoxyguanosine (8OHdG) and 8-iso-prostaglandin F(2alpha) (8-iso-PGF(2alpha)) in major rat tissues. We also investigated whether increased level of oxidative stress causes a decrease in the mitochondrial membrane potential of peripheral lymphocytes of old rats using the MitoTracker Red fluorochrome. Our results show positive correlations between 8OHdG and 8-iso-PGF(2alpha) for liver, brain and kidney measured by HPLC-UV-ECD (electrochemical detector) and EIA methods, respectively. However, heart tissues show a negative correlation. The mitochondrial membrane potential of old rat lymphocytes records significant decrease compared with the young lymphocytes. Based on our results, we conclude that in ageing studies, specific tissues need to be examined in order to measure the localised DNA damage and lipid peroxidation as different tissues display different extent of oxidative damage. We believe this approach of using combined markers is useful to verify the true efficacy of health intervention studies in animals and humans. In addition, the isoprostane assay can be further developed looking at lipid peroxidation as a potential marker in ageing studies.

Immunolocalization of 8-OHdG and OGG1 in pancreatic islets of streptozotocin-induced diabetic rats

This study examined whether oxidative DNA damage and its repair system contribute to the occurrence of diabetes in an experimental rat model. The changed morphological findings of the 8-hydroxydeoxyguanosine (8-OHdG) and 8-oxoG-DNA glycosylase (OGG1) were examined in the pancreatic islets in streptozotocin-induced diabetic rats (60 mg/kg, i.p.). The patterns of immunolocalization were mainly observed in the periphery of the normal pancreatic islet: 8-OHdG in the nucleus and OGG1 in the cytoplasm. The altered immunolocalization of 8-OHdG and OGG1 were greatest in the first hours after streptozotocin injection, and then declined in parallel with the morphological observations of pancreatic beta cell destruction. These results suggested that increased oxidative DNA damage might play a role as the inducer of diabetes and that OGG1 may not successfully mediate DNA repair in streptozotocin-induced diabetic rat pancreas.

Possible carcinogenic risks of copper gluconate and their prevention by co-administered green tea catechins evaluated by a rat medium-term multi-organ carcinogenicity bioassay protocol

Carcinogenic risks of copper gluconate, green tea catechins and their combined exposure were evaluated using a rat medium-term multi-organ carcinogenicity bioassay protocol. Male BrlHan:WIST@Jcl (GALAS) rats were given N-nitrosodiethylamine (DEN), N-methylnitrosourea (MNU), 1,2-dimethylhydrazine (DMH), N-butyl-N-(4-hydroxybutyl)nitrosamine (BBN) and 2,2'-dihydroxy-di-n-propylnitrosamine (DHPN) for a total multiple initiation period of 4 weeks (DMBDD treatment). Rats were then given a diet containing copper gluconate at a concentration of 0, 10, 300, 3000 or 6000 ppm with or without a co-administration of catechins starting 1 week later by admixing in the drinking water at a concentration of 5000 ppm. All survivors were sacrificed at the end of week 29. Number of putatively preneoplastic, glutathione S-transferase placental form-positive, liver lesions significantly increased by copper gluconate of 300 ppm or greater. In addition, both incidence and grade of hyperplasia in the forestomach significantly increased by copper gluconate of 6000 ppm. Catechins, exerting no effects by themselves, inhibited these effects of copper gluconate. The present results indicate that copper gluconate may possess carcinogenic risks for the liver and forestomach at its high dose level, and that co-administered green tea catechins may exert preventive effects.

DNA repair, mitochondria, and neurodegeneration

Accumulation of nuclear and mitochondrial DNA damage is thought to be particularly deleterious in post-mitotic cells, which cannot be replaced through cell division. Recent experimental evidence demonstrates the importance of DNA damage responses for neuronal survival. Here, we summarize current literature on DNA damage responses in the mammalian CNS in aging and neurodegeneration. Base excision repair (BER) is the main pathway for the removal of small DNA base modifications, such as alkylation, deamination and oxidation, which are generated as by-products of normal metabolism and accumulate with age in various experimental models. Using neuronal cell cultures, human brain tissue and animal models, we and others have shown an active BER pathway functioning in the brain, both in the mitochondrial and nuclear compartments. Mitochondrial DNA repair may play a more essential role in neuronal cells because these cells depend largely on intact mitochondrial function for energy metabolism. We have characterized several BER enzymes in mammalian mitochondria and have shown that BER activities change with age in mitochondria from different brain regions. Together, the results reviewed here advocate that mitochondrial DNA damage response plays an important role in aging and in the pathogenesis of neurodegenerative diseases.

NADH hyperoxidation correlates with enhanced susceptibility of aged rats to hypoxia

Aging increases mitochondrial dysfunction and susceptibility to hypoxia. Previous reports have indicated an association between post-hypoxic hyperoxidation of intra-mitochondrial enzymes and delayed neuronal injury. Therefore we investigated the relationship between NADH fluorescence and neuronal function during and after hypoxia across the lifespan. Hippocampal slices were prepared from adult (1 to >22 months) F344 rats. NADH fluorescence, extracellular voltage and tissue PO(2) were recorded from the CA1 region during hypoxia (95% N(2)) of various lengths following onset of hypoxic spreading depression (hsd). Slices from younger rats recovered evoked neuronal responses to a greater degree and exhibited less hyperoxidation after a hypoxic episode, than slices from older rats. However, the use of Ca(2+) free-media in slices from >22 month old rats improved recovery and delayed NADH hyperoxidation (2.5 min hypoxia after hsd). Post-hypoxic decrease of NADH fluorescence (hyperoxidation) was age dependent and correlated with decreased neuronal recovery. Slices exposed to repeated hypoxic episodes yielded data suggesting depletion of the NAD(+) pool, which may have contributed to the deterioration of neuronal function.

Differential attenuation of oxidative/nitrosative injuries in early prostatic neoplastic lesions in TRAMP mice by dietary antioxidants

BACKGROUND

Dietary antioxidants with yet unproven efficacies in averting prostate cancer (PCa) are widely used in the United States as preventives. Experimental evidence establishing a causal relationship between oxidative and nitrosative stress (OS/NS) and PCa development and showing its modulation by dietary antioxidants would help justify their usage.

METHODS

The TRAMP (Transgenic Adenocarcinoma of the Mouse Prostate) mouse model was used to demonstrate the OS/NS-associated damage, as evident by 8-hydroxy-2'-deoxyguanosine (8-OHdG), 4-hydroxynonenal (4-HNE)-protein-adducts and nitrotyrosine (Ntyr), in prostatic premalignant lesions, and to evaluate the antioxidant efficacy of various dietary supplements [natural antioxidant (NAO) from spinach extracts, (-) epigallocatechin-3-gallate (EGCG), or N-acetylcystein (NAC)] during the early PCa development.

RESULT

We show, for the first time, that oxidative/nitrosative damages of genomic DNA and cellular proteins were discretely localized in premalignant lesions, but not in adjacent morphologically normal epithelia, of TRAMP prostates; these injuries were absent in age-matched nontransgenic littermates. The extent of OS/NS-related injuries correlated well with the tempo of development and prevalence of premalignant lesions in various prostatic lobes and exhibited a clear trend of increase from 12 to 20 weeks of age. Treatment of TRAMP mice with various antioxidants as dietary supplements resulted in differential alleviation of OS/NS-related prostatic injuries. The antioxidant potencies of the dietary supplements did not fully correlate with their documented antiPCa actions, suggest that they may exert additional "nonantioxidant," antitumor effects in this model.

CONCLUSIONS

Our data indicate that in TRAMP mice, OS/NS injuries are likely involved in early prostatic tumorigenesis and can be modulated by various antioxidants.

Oxidative DNA damage from potassium bromate exposure in Long-Evans rats is not enhanced by a mixture of drinking water disinfection by-products

Public drinking water treated with chemical disinfectants contains a complex mixture of disinfection by-products (DBPs) for which the relative toxicity of the mixtures needs to be characterized to accurately assess risk. Potassium bromate (KBrO(3)) is a by-product from ozonation of high-bromide surface water for production of drinking water and is a rodent carcinogen that produces thyroid, mesothelial, and renal tumors. The proposed mechanism of KBrO(3) renal carcinogenesis involves the formation of 8-oxoguanine (8-oxoG), a promutagenic base lesion in DNA typically removed through base excision repair (BER). In this study, male Long-Evans rats were exposed via drinking water to carcinogenic concentrations of KBrO(3) (0.4 g/L), 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (0.07 g/L), chloroform (1.8 g/L), bromodichloromethane (0.7 g/L), or a mixture of all these chemicals at the same concentrations for 3 weeks. Half of one kidney was processed for microscopic examination, and the remaining kidney was frozen for isolation of genomic DNA. Levels of 8-oxoG were measured using HPLC with electrochemical detection in DNA samples incubated with formamidopyrimidine-DNA glycosylase. Aldehydic lesions (e.g. abasic sites) in DNA samples were quantitated using an aldehyde-reactive probe slot-blot assay. Treatment with KBrO(3) produced a measurable increase of 8-oxoG in the kidney, and this effect was greater than that produced by treatment with the DBP mixture. No other single chemical treatment caused measurable increases of 8-oxoG. The mixture effect on the amount of 8-oxoG observed in this study suggests an interaction between chemicals that reduced the generation of oxidative DNA damage. No increases in abasic sites were observed with treatment, but a decrease was apparent in the rats treated with the DBP mixture. These data are consistent with previous studies where chronic exposure to this chemical mixture in drinking water resulted in a less than additive carcinogenic response in Tsc2 mutant Long-Evans rats.

The Choroid Plexus‐Cerebrospinal Fluid System: From Development to Aging

The function of the cerebrospinal fluid (CSF) and the tissue that secretes it, the choroid plexus (CP), has traditionally been thought of as both providing physical protection to the brain through buoyancy and facilitating the removal of brain metabolites through the bulk drainage of CSF. More recent studies suggest, however, that the CP-CSF system plays a much more active role in the development, homeostasis, and repair of the central nervous system (CNS). The highly specialized choroidal tissue synthesizes trophic and angiogenic factors, chemorepellents, and carrier proteins, and is strategically positioned within the ventricular cavities to supply the CNS with these biologically active substances. Through polarized transport systems and receptor-mediated transcytosis across the choroidal epithelium, the CP, a part of the blood-CSF barrier (BCSFB), controls the entry of nutrients, such as amino acids and nucleosides, and peptide hormones, such as leptin and prolactin, from the periphery into the brain. The CP also plays an important role in the clearance of toxins and drugs. During CNS development, CP-derived growth factors, such as members of the transforming growth factor-beta superfamily and retinoic acid, play an important role in controlling the patterning of neuronal differentiation in various brain regions. In the adult CNS, the CP appears to be critically involved in neuronal repair processes and the restoration of the brain microenvironment after traumatic and ischemic brain injury. Furthermore, recent studies suggest that the CP acts as a nursery for neuronal and astrocytic progenitor cells. The advancement of our knowledge of the neuroprotective capabilities of the CP may therefore facilitate the development of novel therapies for ischemic stroke and traumatic brain injury. In the later stages of life, the CP-CSF axis shows a decline in all aspects of its function, including CSF secretion and protein synthesis, which may in themselves increase the risk for development of late-life diseases, such as normal pressure hydrocephalus and Alzheimer's disease. The understanding of the mechanisms that underlie the dysfunction of the CP-CSF system in the elderly may help discover the treatments needed to reverse the negative effects of aging that lead to global CNS failure.

Suppressive effects on delayed type hypersensitivity by fasting and dietary restriction in ICR mice

Dietary restriction improves declining physiologic functions, prevents or lessens the severity of neoplasms and autoimmune diseases, and attenuates various inflammatory reactions. In the present study, we compared the effect on allergic dermatitis from repeated short-term fasting (every 3 days), and from moderate dietary restriction receiving 60% of the amount of food consumed by an ad libitum feeding group. In addition, we attempted to verify the involvement of corticosteroids and oxidative stress during nutritional deprivation. The overall food intake in mice undergoing moderate dietary restriction was less than that in mice undergoing repeated fasting. Nonetheless, moderate dietary restriction and repeated fasting showed similar suppressive effects on dermatitis. Furthermore, both the restricted-diet and fasted mice showed less oxidative stress than the mice fed ad libitum. In RU486 (a glucocorticoid receptor antagonist)-injected mice, no suppressive effect of fasting on dermatitis was seen. In conclusion, repeated fasting and moderate dietary restriction suppressed dermatitis in similar ways. Hypercorticism and reduced oxidative stress is associated with the suppression of dermatitis.

Androgenic regulation of oxidative stress in the rat prostate: involvement of NAD(P)H oxidases and antioxidant defense machinery during prostatic involution and regrowth

Little is known about the roles of androgens in the regulation of redox state in the prostate, a cellular process believed to profoundly influence normal and aberrant prostate functions. We demonstrate that castration induced discrete oxidative stress (OS) in the acinar epithelium of rat ventral prostate (VP), as evident from marked increases in 8-hydroxy-2'-deoxy-guanosine and 4-hydroxynonenal protein adducts in the regressing epithelium. Testosterone replacement partially reduced OS in VP epithelia of castrates, but the level remained higher than in intact rats. Quantification of steady-state mRNA levels of 14 genes involved in the anabolism and catabolism of reactive oxygen species (ROS) showed that castration resulted in dramatic increases of three ROS-generating NAD(P)H oxidases (Noxs) including Nox1, gp91(phox), and Nox4, significant reductions of key ROS-detoxifying enzymes (superoxide dismutase 2, glutathione peroxidase 1, thioredoxin, and peroxiredoxin 5), and unchanged levels of catalase, glutathione reductase, gamma-glutamyl transpeptidase, and glutathione synthetase. Testosterone replacement in castrated rats partially reduced expression of Noxs but restored expression of superoxide dismutase 2, glutathione peroxidase 1, thioredoxin, and peroxiredoxin 5 to complete normalcy and induced a compensatory increase in expression of catalase, glutathione reductase, gamma-glutamyl transpeptidase, and glutathione synthetase in the regenerating VP. Expression of superoxide dismutase 1, glutathione S-transferase-pi, and glucose-6-phosphate dehydrogenase was unaffected by castration and testosterone replacement. These findings indicate androgen-deprivation induces OS in the rat VP through elevation of ROS anabolism and diminution of antioxidant detoxification. Androgen replacement partially reduces OS in rat VP to precastration levels. Expression of Noxs remained high amid a broad-based recovery of antioxidant defense mechanism(s). These data might have implications on the use of androgen blockade for prostate cancer prevention and androgen therapy for andropause treatment in elderly men.

Effect of diet on cancer development: is oxidative DNA damage a biomarker?

Free radicals and other reactive species are generated in vivo and many of them can cause oxidative damage to DNA. Although there are methodological uncertainties about accurate quantitation of oxidative DNA damage, the levels of such damage that escape immediate repair and persist in DNA appear to be in the range that could contribute significantly to mutation rates in vivo. The observation that diets rich in fruits and vegetables can decrease both oxidative DNA damage and cancer incidence is consistent with this. By contrast, agents increasing oxidative DNA damage usually increase risk of cancer development. Such agents include cigarette smoke, several other carcinogens, and chronic inflammation. Rheumatoid arthritis and diabetes are accompanied by increased oxidative DNA damage but the pattern of increased cancer risk seems unusual. Other uncertainties are the location of oxidative DNA damage within the genome and the variation in rate and level of oxidative damage between different body tissues. In well-nourished human volunteers, fruits and vegetables have been shown to decrease oxidative DNA damage in several studies, but data from short-term human intervention studies suggest that the protective agents are not vitamin C, vitamin E, beta-carotene, or flavonoids.

Radiation-induced kidney injury: a role for chronic oxidative stress?

Kidney irradiation clearly leads to a progressive reduction in function associated with concomitant glomerulosclerosis and/or tubulointerstitial fibrosis. However, the particular cell types, mediators and/or mechanisms involved in the development and progression of radiation nephropathy remain ill defined. Angiotensin II (Ang II) plays a major pathogenic role; administration of Ang II blockers markedly abrogates the severity of radiation nephropathy in experimental models. Both ionizing radiation and Ang II signal via generation of reactive oxygen species (ROS). Thus, we hypothesized that localized kidney irradiation might lead to a chronic oxidative stress. In view of the difficulty in measuring ROS in vivo we adopted an indirect immunohistochemical approach in which we used a monoclonal antibody specific for 8-hydroxy-2'-deoxyguanosine (8-OHdG), one of the most commonly used markers of DNA oxidation. The right kidney of 7-8 week-old male Sprague-Dawley rats was removed. Five to 6 weeks later the remaining hypertrophied kidney was irradiated with single doses of 0-20.0 Gy X-rays. Groups of rats, three per dose, were killed at 4, 8, 16 and 24 weeks post-irradiation, their kidneys fixed, and sections stained with the 8-OHdG-specific antibody N45.1. For quantitation of glomerular DNA oxidation with the N45.1 antibody stained sections, 50 glomeruli/animal were counted. The presence of any intensely stained nuclei within the glomerular tuft was scored as positive. Quantitation of tubular DNA oxidation employed a 10 x 10 point ocular grid. Sections were examined at 400 magnification; 250 tubular profiles were counted. All tubules with any nuclear staining were scored as positive.Sham-irradiated kidneys showed little evidence of DNA oxidation over the experimental period. In contrast, localized kidney irradiation led to a marked, dose-independent increase in glomerular and tubular cell nuclear DNA oxidation. This increase was evident at the first time point studied, i.e. 4 weeks after irradiation, and persisted for up to 24 weeks postirradiation. DNA oxidation in the irradiated kidney was only seen in apparently viable glomerular and tubular cells. Thus, while from 16 to 24 weeks post-irradiation structural alterations had progressed to glomerular sclerosis and tubular atrophy, positive staining for 8-OHdG was not observed in severely atrophic tubules. Similarly, fewer positive staining cells were noted in glomeruli undergoing sclerosis, while none were seen in totally sclerotic glomeruli. These data support the hypothesis that renal irradiation is associated with a chronic and persistent oxidative stress.

Age-dependent expression of 8-hydroxy-2'-deoxyguanosine in human pituitary gland

A major oxidative product, 8-hydroxy-2'-deoxyguanosine (8-OHdG) is involved in ageing, carcinogenesis, and different diseases. The expression of 8-OHdG in the human pituitary gland was investigated immunohistochemically using specimens from individuals aged 19-88 years. 8-OHdG was localized at the nuclei of the anterior lobar parenchymal cells of the pituitary gland. The number of cells positive for 8-OHdG were counted, and the ratio of the positive cells to the total parenchymal cells was evaluated. The ratios increased in accordance with the ages of the individuals examined. Statistically, there was a significant correlation between the ages in years and the 8-OHdG positive ratios in the anterior lobar parenchymal cells (r = 0.757, p < 0.01). These findings indicate an age-dependent accumulation of 8-OHdG in the pituitary gland, which may also be related to the ageing of neuroendocrine systems as well.

Does oxidative damage to DNA increase with age?

The levels of 8-oxo-2-deoxyguanosine (oxo8dG) in DNA isolated from tissues of rodents (male F344 rats, male B6D2F1 mice, male C57BL/6 mice, and female C57BL/6 mice) of various ages were measured using sodium iodide to prevent oxidative damage to DNA during DNA isolation. Oxo8dG was measured in nuclear DNA (nDNA) isolated from liver, heart, brain, kidney, skeletal muscle, and spleen and in mitochondrial DNA (mtDNA) isolated from liver. We observed a significant increase in oxo8dG levels in nDNA with age in all tissues and strains of rodents studied. The age-related increase in oxo8dG in nDNA from old mice was shown not to the result of the tissue's reduced ability to remove the oxo8dG lesion. Rather, the increase in oxo8dG levels appears to arise from an age-related increase in the sensitivity of these tissues to oxidative stress. We also observed an age-related increase in oxo8dG in mtDNA isolated from the livers of the rats and mice. Dietary restriction, which is known to retard aging and increase the lifespan of rodents, was shown to significantly reduce the age-related accumulation of oxo8dG levels in nDNA in all tissues of male B6D23F1 mice and in most tissues of male F344 rats. Our study also showed that dietary restriction prevented the age-related increase in oxo8dG levels in mtDNA isolated from the livers of both rats and mice.

Levels of 8-hydroxy-2'-deoxyguanosine in cellular DNA from 12 tissues of young and old Sprague-Dawley rats

The age dependent increase of 8-hydroxy-2'-deoxyguanosine (8-OH-dG) reported in DNA of organs of old rats appears to vary with the strain, age and sex of the animals used for the investigation. Here we report on 8-OH-dG concentrations in the cellular DNA of 12 tissues of male Sprague-Dawley rats aged 5 or 30 months and kept under standard conditions throughout their lives until being killed. DNA from frozen organs was isolated using a Qiagen DNA purification kit. Following digestion (nuclease P1, alkaline nuclease) hydrolysed DNA was applied onto a HPLC column; native nucleosides were monitored at 254 nm and 8-OH-dG by electrochemical detection. 8-OH-dG levels in organs of young rats ranged between 10 and 90 micromol/mol deoxyguanosine (dG). Highest levels (micromol 8-OH-dG /mol dG) were detected in the oesophagus (90), muscle (61), brain (65), liver (59), spleen (57), and testicles (63). 8-OH-dG in DNA from kidney, lung, heart, small and large intestine ranged between 28 and 38 micromol/mol dG. Lowest amounts were found in the glandular stomach (10). DNA of old rats generally contained higher 8-OH-dG levels with significant increases in liver (186%) and kidney (372%); other organs showed no significant decreases (spleen, brain, testicles) or increases up to 69% (heart). These findings are discussed in the context with previously published data on 8-OH-dG levels in organs from young and old rats.

Ageing choroid plexus-cerebrospinal fluid system

The impact of ageing on the choroid plexus (CP)-CSF circulatory system has largely been un-investigated, or has been of interest only in relation to neurological disease. This paper reviews the evidence for age-related changes to the CP-CSF system and compares changes with disease states where appropriate. The changes discussed include reduced ion transport capabilities, evidence for oxidative stress, altered hormone interactions, decreased CSF secretion rates in animal models and the contradictory nature of human data, reduced clearance of protein from CSF, and slower fluid turnover. The potential impacts of these changes are highlighted, including the possibility of reduced resistance to stress insults and slow clearance of toxic compounds from CSF with specific reference to amyloid peptide. Other impacts may include the reduced ability of CSF to act as a circulating medium for hormone and growth factors to reach their brain targets, and reduced homeostasis of CSF nutrients (amino acids, vitamins), which might influence brain interstitial fluid homeostasis.