Aging-related changes in the nigral angiotensin system enhances proinflammatory and pro-oxidative markers and 6-OHDA-induced dopaminergic degeneration

An age-related proinflammatory, pro-oxidant state in the nigra may increase the vulnerability of dopaminergic neurons to additional damage. Angiotensin II, via type 1 (AT1) receptors, is one of the most important known inflammation and oxidative stress inducers. However, it is not known if there are age-related changes in the nigral angiotensin system. In aged rats, we observed increased activation of the nicotinamide adenine dinucleotide phosphate-oxidase (NADPH oxidase) complex and increased levels of the proinflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α, which indicate pro-oxidative, proinflammatory state in the nigra. We also observed enhanced 6-hydroxydopamine (6-OHDA)-induced dopaminergic cell death in aged rats. This is associated with increased expression of AT1 receptors and decreased expression of AT2 receptors in aged rats, and is reduced by treatment with the AT1 antagonist candesartan. The present results indicate that brain angiotensin is involved in changes that may increase the risk of Parkinson's disease with aging. Furthermore, the results suggest that manipulation of the brain angiotensin system may constitute an effective neuroprotective strategy against aging-related risk of dopaminergic degeneration.     

老年大鼠肾脏微分离肾小球、肾小管及动脉血管紧张素Ⅱ受体的表达

目的: 观察老年大鼠肾脏不同部位不同亚型的血管紧张素Ⅱ受体(ATR)基因表达的改变。方法: 取3月龄及24月龄雄性Wistar大鼠肾脏,行Western印迹杂交及Northern 印迹杂交检测肾皮质AT₁R的蛋白及基因表达,行冰冻切片(厚5 μm),通过激光切割、弹射微分离系统分离肾小球、肾小管及动脉,提取RNA,利用RT-PCR方法观察AT_1aR mRNA、AT_1bR mRNA及AT₂R mRNA的表达。结果: 24月龄大鼠肾脏的AT₁R在蛋白水平及基因水平均低于3月龄大鼠。应用自动激光微分离技术成功分离了大鼠肾脏的肾小球、肾小管及小动脉。24月龄大鼠肾小球AT_1aR mRNA的表达与3月龄大鼠比较无明显差异,在肾小管表达低于3月龄大鼠,动脉表达高于3月龄大鼠;AT_1bR mRNA在肾小球、肾小管表达均低于3月龄大鼠,在动脉的表达高于3月龄大鼠;AT₂R mRNA的表达在肾小管明显高于3月龄大鼠,在肾小球及动脉的表达无明显差异。结论: 老年大鼠的肾小球、肾小管及肾内动脉各型血管紧张素受体的改变不同,有可能在肾脏增龄性改变中起重要作用。     

Pathophysiology of neurodegenerative diseases: An interplay among axonal transport failure,oxidative stress,and inflammation?

Neurodegenerative diseases (NDs) are heterogeneous neurological disorders characterized by a progressive loss of selected neuronal populations. A significant risk factor for most NDs is aging. Considering the constant increase in life expectancy, NDs represent a global public health burden. Axonal transport (AT) is a central cellular process underlying the generation and maintenance of neuronal architecture and connectivity. Deficits in AT appear to be a common thread for most, if not all, NDs. Neuroinflammation has been notoriously difficult to define in relation to NDs. Inflammation is a complex multifactorial process in the CNS, which varies depending on the disease stage. Several lines of evidence suggest that AT defect, axonopathy and neuroinflammation are tightly interlaced. However, whether these impairments play a causative role in NDs or are merely a downstream effect of neuronal degeneration remains unsettled. We still lack reliable information on the temporal relationship between these pathogenic mechanisms, although several findings suggest that they may occur early during ND pathophysiology. This article will review the latest evidence emerging on whether the interplay between AT perturbations and some aspects of CNS inflammation can participate in ND etiology, analyze their potential as therapeutic targets, and the urge to identify early surrogate biomarkers.     

Calcium dysregulation and neuroinflammation: Discrete and integrated mechanisms for age-related synaptic dysfunction

Some of the best biomarkers of age-related cognitive decline are closely linked to synaptic function and plasticity. This review highlights several age-related synaptic alterations as they relate to Ca²⁺ dyshomeostasis, through elevation of intracellular Ca²⁺, and neuroinflammation, through production of pro-inflammatory cytokines including interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α). Though distinct in many ways, Ca²⁺ and neuroinflammatory signaling mechanisms exhibit extensive cross-talk and bidirectional interactions. For instance, cytokine production in glial cells is strongly dependent on the Ca²⁺ dependent protein phosphatase calcineurin, which shows elevated activity in animal models of aging and disease. In turn, pro-inflammatory cytokines, such as TNF, can augment the expression/activity of L-type voltage sensitive Ca²⁺ channels in neurons, leading to Ca²⁺ dysregulation, hyperactive calcineurin activity, and synaptic depression. Thus, in addition to discussing unique contributions of Ca²⁺ dyshomeostasis and neuroinflammation, this review emphasizes how these processes interact to hasten age-related synaptic changes.     

Psychomotor performance in the senescent rodent: reduction of deficits via striatal dopamine receptor up-regulation

JOSEPH, J. A., R. T. BARTUS, D. CLODY, D. MORGAN, C. FINCH, B. BEER AND S. SESACK. Psychomotor performance in the senescent rodent: Reduction of deficits via striatal dopamine receptor up-regulation. NEUROBIOL AGING 4(4) 313–319, 1983.—In order to determine the relationship between striatal dopamine (DA) receptor density and psychomotor performance in senescent animals, two experiments were carried out. In the first, the age-related motor deficits were characterized using a battery of four psychomotor tests (rod walking, wire hanging, inclined screen, plank walking). These tests were administered to three gro groups of male Fischer rats (mature, 6–8 months; middle aged, 12–18 months; and senescent, 25 months) and performance measured. Age-related differences were observed on all the tasks, with the oldest animals showing the poorest performance. These animals were then used in a second experiment in which one-half of the group of animals from each age was administered 1.86 mg/kg/day of haloperidol for 14 days (via surgically implanted Alza Minipumps). Control groups of animals from each age were given pumps which contained only the vehicle (HCl diluted with distilled water, pH = 2.9). Following the 14 day drug administration, the pumps were surgically removed and 3 days later all the groups were retested on the psychomotor tests. Stereotypy (to 0.5 mg/kg of apomorphine, sniffing, licking, grooming and cage crossings) was also re-examined. Results show that haloperidol-treated animals from all three age groups display greater response times (i.e., better performance) than vehicle-treated animals on the battery of four motor tests and, the haloperidol-treated old animals exhibit more sniffing and grooming than the vehicle-treated old animals. Parallel increases in [³H]spiperone binding seen in all haloperidol-treated groups suggest a relationship between increases in the density of striatal DA receptors and improvement in motor performance.     

Psychomotor performance in the senescent rodent: reduction of deficits via striatal dopamine receptor up-regulation

JOSEPH, J. A., R. T. BARTUS, D. CLODY, D. MORGAN, C. FINCH, B. BEER AND S. SESACK. Psychomotor performance in the senescent rodent: Reduction of deficits via striatal dopamine receptor up-regulation. NEUROBIOL AGING 4(4) 313–319, 1983.—In order to determine the relationship between striatal dopamine (DA) receptor density and psychomotor performance in senescent animals, two experiments were carried out. In the first, the age-related motor deficits were characterized using a battery of four psychomotor tests (rod walking, wire hanging, inclined screen, plank walking). These tests were administered to three gro groups of male Fischer rats (mature, 6–8 months; middle aged, 12–18 months; and senescent, 25 months) and performance measured. Age-related differences were observed on all the tasks, with the oldest animals showing the poorest performance. These animals were then used in a second experiment in which one-half of the group of animals from each age was administered 1.86 mg/kg/day of haloperidol for 14 days (via surgically implanted Alza Minipumps). Control groups of animals from each age were given pumps which contained only the vehicle (HCl diluted with distilled water, pH = 2.9). Following the 14 day drug administration, the pumps were surgically removed and 3 days later all the groups were retested on the psychomotor tests. Stereotypy (to 0.5 mg/kg of apomorphine, sniffing, licking, grooming and cage crossings) was also re-examined. Results show that haloperidol-treated animals from all three age groups display greater response times (i.e., better performance) than vehicle-treated animals on the battery of four motor tests and, the haloperidol-treated old animals exhibit more sniffing and grooming than the vehicle-treated old animals. Parallel increases in [³H]spiperone binding seen in all haloperidol-treated groups suggest a relationship between increases in the density of striatal DA receptors and improvement in motor performance.     

Apelin-13对高尿酸诱导的脂肪细胞氧化应激的作用

目的:探讨apelin-13对高尿酸诱导的3T3-L1脂肪细胞氧化应激的作用及其机制。方法:3T3-L1脂肪细胞予以10 mg/dL尿酸刺激,部分细胞予以1μmol/L apelin-13预处理,以100μmol/L H₂O₂刺激的细胞为阳性对照。48 h后,流式细胞术检测活性氧族(ROS)含量,生化试剂盒检测细胞及培养液上清抗氧化酶[超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH-Px)和过氧化氢酶(CAT)]和促氧化酶NADPH氧化酶(NOX)的活性以及丙二醛(MDA)含量,real-time PCR法检测细胞局部肾素-血管紧张素系统(RAS)各组份血管紧张素原(AGT)、血管紧张素转化酶I(ACE1)、血管紧张素II 1型受体(AT1R)和AT2R及血管紧张素II 1型受体相关蛋(APJ)的mRNA表达水平,ELISA法检测细胞及培养液中血管紧张素II(AngⅡ)浓度。结果:10 mg/dL的尿酸明显降低3T3-L1脂肪细胞SOD、GSH-Px和CAT的活性,升高NOX的活性,增加MDA的含量,细胞内ROS的含量相应升高;apel...     

Dl-3-n-butylphthalide, a natural antioxidant, protects dopamine neurons in rotenone models for Parkinson's disease

In the absence of a cure for Parkinson's disease, development of preventive medications for this devastating disease is particularly encouraged. Dl-3-n-butylphthalide (NBP), an established natural antioxidant for clinical stroke treatment in China, can reportedly reduce beta-amyloid-induced neuronal toxicity in cultured neuronal cells, and attenuate neurodegenerative changes in aged rats. However, whether or not NBP confers neuroprotection in parkinsonian models is still unknown. In this study, we investigated the effects of NBP in rotenone models for Parkinson's diseases. In a cellular model, pretreatment with NBP enhanced cell viability by decreasing nuclear fragmentation, retaining mitochondrial membrane potential, and preventing reactive oxygen species (ROS) from generation. In a rodent model, 2-week treatment with NBP was able to ameliorate apomorphine-evoked rotations by 48% and rescue dopaminergic (DA) neurons by 30% and striatal DA terminal by 49%. Furthermore, NBP upregulated the vesicular monoamine transporter 2 gene expression in vitro and in vivo. Together, NBP protects DA neurons likely by reducing oxidative stress, offering an alternative neuroprotective medication for Parkinson's disease.     

New advances on glial activation in health and disease

In addition to being the support cells of the central nervous system (CNS), astrocytes are now recognized as active players in the regulation of synaptic function, neural repair, and CNS immunity. Astrocytes are among the most structurally complex cells in the brain, and activation of these cells has been shown in a wide spectrum of CNS injuries and diseases. Over the past decade, research has begun to elucidate the role of astrocyte activation and changes in astrocyte morphology in the progression of neural pathologies, which has led to glial-specific interventions for drug development. Future therapies for CNS infection, injury, and neurodegenerative disease are now aimed at targeting astrocyte responses to such insults including astrocyte activation, astrogliosis and other morphological changes, and innate and adaptive immune responses.     

Melatonin attenuates the decrement of dendritic protein MAP-2 immuno-staining in the hippocampal CA1 and CA3 fields of the aging male rat

Neuronal death during brain aging results, at least in part, from the disruption of synaptic connectivity caused by oxidative stress. Synaptic elimination might be caused by increased instability of the neuronal processes. In vitro evidence shows that melatonin increases MAP-2 expression, a protein that improves the stability of the dendritic cytoskeleton, opening the possibility that melatonin could prevent synaptic elimination by increasing dendritic stability. One way to begin exploring this issue in vivo is to evaluate whether long-term melatonin treatment changes the intensity of MAP-2 immuno-staining in areas commonly afflicted by aging that are rich in dendritic processes. Accordingly, we evaluated the effects of administering melatonin for 6 or 12 months on the intensity of MAP-2 immuno-staining in the strata oriens and lucidum of the hippocampal CA1 and CA3 fields of aging male rats, through semi-quantitative densitometry. Melatonin treated rats showed a relative increment in the intensity of MAP-2 immuno-staining in both regions after 6 or 12 months of treatment, as compared with age matched control rats. Although melatonin untreated and treated rats showed a decrease of MAP-2 immuno-staining in the hippocampus with increasing age, such decrement was less pronounced following melatonin treatment. These findings were confirmed by qualitative Western blot analyses. The melatonin effect seems specific because MAP-2 staining in the primary somatosensory cortex was not affected by the treatment. Thus, chronic melatonin administration increases MAP-2 immuno-staining and attenuates its decay in the adult aging hippocampus. These results are compatible with the idea that melatonin could improve dendritic stability and thus diminish synaptic elimination in the aging brain.     

体外反搏对心肌缺血犬RAS的影响及与血流动力学的关系

目的:探讨心肌缺血与体外反搏(ECP)时犬局部肾素-血管紧张素系统(RAS)和血流动力学的改变以及它们之间的关系。方法:采用冠状动脉结扎法复制犬急性心肌缺血模型,检测缺血及外加反搏时缺血心肌、主动脉、肾脏、肺等局部肾素活性、血管紧张素Ⅱ(AngⅡ)水平和血管紧张素转换酶(ACE)活性,用八导生理记录仪记录血流动力学,分析它们之间的关系。结果:缺血能激活缺血区心肌、主动脉处肾素、ACE和AngⅡ,除缺血区心肌肾素外,ECP抑制缺血区心肌与主动脉处三者。缺血还能激活对循环RAS影响较大的肾脏与肺RAS,反搏对其有一定抑制作用。缺血与反搏时的血流动力学改变和心血管局部AngⅡ水平有关。结论:体外反搏治疗心肌缺血时,局部RAS和血流动力学状态的改变呈相关关系,即体外反搏对血流动力学的改善作用和能抑制局部RAS有关,这可能是它对缺血心肌起保护作用的机制之一。     

Caloric restriction alleviates abnormal locomotor activity and dopamine levels in the brain of the methionine sulfoxide reductase A knockout mouse

Oxidative stress is associated with the aging process, a risk factor for neurodegenerative diseases, and decreased by reduced energy intake. Oxidative modifications can affect protein function; the sulfur-containing amino acids, including methionine, are particularly susceptible to oxidation. A methionine sulfoxide can be enzymatically reduced by the methionine sulfoxide reductase (Msr) system. Previously, we have shown that MsrA^−/− mice exhibit altered locomotor activity and brain dopamine levels as function of age. Previous studies have demonstrated that a caloric restriction enhances antioxidant defense and reduces the action of reactive oxygen species. Here we examine locomotor behavior and dopamine levels of MsrA^−/− mice after caloric restriction starting at eight months of age and ending at 17 months. The MsrA^−/− mice did not have any significant difference in spontaneous distance traveled when compared to controls at 17 months of age. In contrast, our previous report showed decreased locomotor activity in the MsrA^−/− mice at 12 months of age and older when fed ad-libitum. After completion of the caloric restriction diet, dopamine levels were comparable to control mice. This differs from the abnormal dopamine levels previously observed in MsrA^−/− mice fed ad-libitum. Thus, caloric restriction had a neutralization effect on MsrA ablation. In summary, it is suggested that caloric restriction alleviates abnormal locomotor activity and dopamine levels in the brain of the methionine sulfoxide reductase A knockout mouse.     

Cerebral hypoxia-ischemia and middle cerebral artery occlusion induce expression of the cannabinoid CB2 receptor in the brain

Until recently the cannabinoid CB2 receptor was believed to be absent from the central nervous system. In this study we have identified CB2 expressing cells that appear in the rat brain following stroke and hypoxic-ischemia. At 3 days following surgery CB2-positive macrophages, deriving from resident microglia and/or invading monocytes appear on the lesioned side of the brain. By day 7, a mixed population of CB2-positive cells is present. Microglia-derived macrophages are the key cells in the first stages of brain inflammation, and a pivotal step in the neurodegeneration that follows the acute stage of injury. Thus, CB2 may be important in the brain during injury, and in inflammatory neurodegenerative disorders. The presence of CB2-positive cells in the brain following stroke may provide a novel strategy for cannabinoid-mediated intervention into stroke induced neurodegeneration without the psychoactive effects of CB1 receptor stimulation.     

Nrf2 signaling and redox homeostasis in the aging heart: A potential target to prevent cardiovascular diseases?

Aging process is often accompanied with a high incidence of cardiovascular diseases (CVD) due to the synergistic effects of age-related changes in heart morphology/function and prolonged exposure to injurious effects of CVD risk factors. Oxidative stress, considered a hallmark of aging, is also an important feature in pathologies that predispose to CVD development, like hypertension, diabetes and obesity. Approaches directed to prevent the occurrence of CVD during aging have been explored both in experimental models and in controlled clinical trials, in order to improve health span, reduce hospitalizations and increase life quality during elderly. In this review we discuss oxidative stress role as a main risk factor that relates CVD with aging. As well as interventions that aim to reduce oxidative stress by supplementing with exogenous antioxidants. In particular, strategies of improving the endogenous antioxidant defenses through activating the nuclear factor related-2 factor (Nrf2) pathway; one of the best studied molecules in cellular redox homeostasis and a master regulator of the antioxidant and phase II detoxification response.     

Mechanisms of endothelial dysfunction in obesity-associated hypertension

Obesity is strongly associated with high blood pressure, dyslipidemia, and type 2 diabetes. These conditions synergistically increase the risk of cardiovascular events. A number of central and peripheral abnormalities can explain the development or maintenance of high blood pressure in obesity. Of great interest is endothelial dysfunction, considered to be a primary risk factor in the development of hypertension. Additional mechanisms also related to endothelial dysfunction have been proposed to mediate the development of hypertension in obese individuals. These include: increase in both peripheral vasoconstriction and renal tubular sodium reabsorption, increased sympathetic activity and overactivation of both the renin-angiotensin system and the endocannabinoid system and insulin resistance. The discovery of new mechanisms regulating metabolic and vascular function and a better understanding of how vascular function can be influenced by these systems would facilitate the development of new therapies for treatment of obesity-associated hypertension.     

Olfactory dysfunction in aging and neurodegenerative diseases

Alterations in olfactory functions are proposed to be early biomarkers for neurodegeneration. Many neurodegenerative diseases are age-related, including two of the most common, Parkinson’s disease (PD) and Alzheimer’s disease (AD). The establishment of biomarkers that promote early risk identification is critical for the implementation of early treatment to postpone or avert pathological development. Olfactory dysfunction (OD) is seen in 90% of early-stage PD patients and 85% of patients with early-stage AD, which makes it an attractive biomarker for early diagnosis of these diseases. Here, we systematically review widely applied smelling tests available for humans as well as olfaction assessments performed in some animal models and the relationships between OD and normal aging, PD, AD, and other conditions. The utility of OD as a biomarker for neurodegenerative disease diagnosis and future research directions are also discussed.     

Local bone interaction between renin-angiotensin system and kallikrein-kinin system in diabetic rat

Objective: This study was performed to investigate bone deteriorations and the involvement of skeletal renin-angiotensin system (RAS) and kallikrein-kinin system (KKS) of male rat in response to the hyperglycemia. Methods: The biomarkers in serum and urine were measured by ELISA kit, and tibias were taken for the measurement on gene, protein expression and histological analysis, feumrs were taken for the measurement on biomechanical parameters and micro-CT. Results: The DM1 showed the decreased level of osteocalcin, testosterone and FGF-23, and the increased level of serum CTX as compared to those of vehicle group. The H&E staining showed remarkable bone deteriorations, including increased disconnections and separation of trabecular bone among growth plate and joint cartilage in DM1 group. Biomechanically, the maximum load, maximum stress, and strain parameter of DM1 group was significantly lower than control group. Type 1 diabetic mice displayed bone loss shown the reduction of bone volume/total volume, trabecular number, trabecular thickness and bone mineral density. The STZ injection significantly up-regulated mRNA expression of AT1R, AGT, renin, renin-receptor, and ACE, and the expression of AT2R, B1R and B2R were down-regulated in tibia of rat in hyperglycemia group. The protein expression of renin, ACE and Ang II were significantly up-regulated, and AT2R, B1R and B2R were down-regulated in DM1 group. Conclusions: The treatment of hyperglycemia was detrimental to bone as compared to the vehicle group, and the underlying mechanism was mediated, at least partially, through down-regulation of KSS activity and up-regulation of RAS activity in local bone.     

The oxidatively induced DNA lesions 8,5'-cyclo-2'-deoxyadenosine and 8-hydroxy-2'-deoxyadenosine are strongly resistant to acid-induced hydrolysis of the glycosidic bond

The 8,5'-cyclopurine-2'-deoxynucleosides (cPu) are unique oxidatively induced DNA lesions in that they are specifically repaired by NER. In the absence of NER, a possible mechanism for cPu removal is spontaneous glycosidic bond hydrolysis followed by enzymic processing. Such a mechanism could be significant if the glycosidic bond in cPu were substantially destabilized, as shown for other DNA lesions. Therefore, we investigated the stability of the glycosidic bond in a cPu, (5'S)-8,5'-cyclo-2'-deoxyadenosine (S-cdA) against acid hydrolysis. For comparison, we also studied 8-hydroxy-2'-deoxyadenosine (8-OH-dA). We found that the glycosidic bond in S-cdA is approximately 40-fold more resistant to glycosidic bond hydrolysis compared to dA. Interestingly, under the same conditions, the glycosidic bond in 8-OH-dA was even more stable than in S-cdA. These studies effectively rule out any mechanism for the removal of S-cdA or 8-OH-dA from DNA that requires spontaneous glycosidic bond hydrolysis, and further support the proposed role of cPu in the neurodegeneration observed in xeroderma pigmentosum patients who lack NER. Of broader significance, since NER does not function in non-transcribed DNA sequences of terminally differentiated cells, including neurons, cPu are expected to accumulate in such sequences even in individuals with normal NER, which could be important in the ageing process.     

Decline in striatal dopamine D1 and D2 receptor activation in aged F344 rats

Aging differentially affects receptor function. In the present electrophysiological study we compared neuronal responsiveness to locally applied dopamine D₁ and D₂ receptor agonist in the striatum of female Fischer 344 rats aged 3 and 26–27 months. In a subgroup of the old rats, the nigrostriatal dopamine bundle was destroyed unilaterally with 6-hydroxydopamine (6-OHDA) to assess receptor plasticity in response to denervation. Spontaneous firing rate of striatal neurons was higher in aged compared to young rats. Higher doses of the D₁ agonist SKF 38393 or the D₂ agonist quinpirole were required to elicit a 50% change in firing rate in aged compared to young rats. No difference with SKF 38393 or quinpirole was detected between 6-OHDA denervated and control (nonlesioned) striatum in aged rats. Supersensitivity to D₂ agonists has been reported following 6-OHDA lesions in young rats. These observations suggest that D₂ receptors in aged rat striatum might not be as plastic as in younger rats.     

The adversities of aging

The aging process is evolutionarily conserved and subject to quantitative modification by both genetic and environmental factors. Fundamental mechanisms of aging result in progressive deficits in the function of cells and organs, often leading to diseases that ultimately kill the organism such as cancers, cardiovascular disease and neurodegenerative disorders. Oxidative stress and damage to all of the major classes of molecules in cells are involved in aging and age-related diseases. The widely pursued approach of targeting disease-specific processes to develop therapeutic interventions has not had a major impact on healthspan. A more productive approach would be to target the fundamental mechanisms of aging throughout adult life so as to extend healthspan. Caloric restriction and regular exercise are two such approaches.