Biomarkers of oxidative stress in vascular dementia patients

Blood-based biomarkers of cerebral small vessel disease

Age-associated cerebral small vessel disease (CSVD) represents a clinically heterogenous condition, arising from diverse microvascular mechanisms. These lead to chronic cerebrovascular dysfunction and carry a substantial risk of subsequent stroke and vascular cognitive impairment in aging populations. Owing to advances in neuroimaging, in vivo visualization of cerebral vasculature abnormities and detection of CSVD, including lacunes, microinfarcts, microbleeds and white matter lesions, is now possible, but remains a resource-, skills- and time-intensive approach. As a result, there has been a recent proliferation of blood-based biomarker studies for CSVD aimed at developing accessible screening tools for early detection and risk stratification. However, a good understanding of the pathophysiological processes underpinning CSVD is needed to identify and assess clinically useful biomarkers. Here, we provide an overview of processes associated with CSVD pathogenesis, including endothelial injury and dysfunction, neuroinflammation, oxidative stress, perivascular neuronal damage as well as cardiovascular dysfunction. Then, we review clinical studies of the key biomolecules involved in the aforementioned processes. Lastly, we outline future trends and directions for CSVD biomarker discovery and clinical validation.

Chronic cerebral hypoperfusion: a critical feature in unravelling the etiology of vascular cognitive impairment

Vascular cognitive impairment (VCI) describes a wide spectrum of cognitive deficits related to cerebrovascular diseases. Although the loss of blood flow to cortical regions critically involved in cognitive processes must feature as the main driver of VCI, the underlying mechanisms and interactions with related disease processes remain to be fully elucidated. Recent clinical studies of cerebral blood flow measurements have supported the role of chronic cerebral hypoperfusion (CCH) as a major driver of the vascular pathology and clinical manifestations of VCI. Here we review the pathophysiological mechanisms as well as neuropathological changes of CCH. Potential interventional strategies for VCI are also reviewed. A deeper understanding of how CCH can lead to accumulation of VCI-associated pathology could potentially pave the way for early detection and development of disease-modifying therapies, thus allowing preventive interventions instead of symptomatic treatments.

Keap1 as Target of Genistein on Nrf2 Signaling Pathway Antagonizing Aβ induced Oxidative Damage of Cerebrovascular Endothelial Cells

BACKGROUND

β-amyloid peptides (Aβ) induced oxidative damage contributes to the pathogenesis of neurodegenerative diseases and cerebrovascular system is more vulnerable to oxidative stress. Our earlier study showed a clue that Genistein (Gen) might activate Nf-E2 related factor 2 (Nrf2) pathway to protect cerebrovascular cells from oxidative damage induced by Aβ, but the specific mechanisms and regulation targets are unclear.

OBJECTIVE

In this study, the anti-oxidative effects and the possible targets of Gen on regulating Nrf2 pathway in bEnd.3 cells were investigated. Cells were divided into control, Aβ25-35, Gen and Gen+Aβ25-35 groups.

METHODS

Cell viability, levels of malondialdehyde (MDA), Superoxide Dismutase (SOD) activity and nitrotyrosine were evaluated. Moreover, mRNA and/or protein expressions of Nrf2 and kelch-like ECH-associated protein 1 (Keap1) were measured. Then we transfected Keap1 over-expressed plasmid into bEnd.3 cells and measured the protein expressions of Nrf2 pathway related factors. Data showed that Gen could inhibit the over-production of MDA and nitrotyrosine and activate SOD activity. Besides we got the phenomenon that Gen could up-regulate the mRNA and protein expressions of Nrf2 and down-regulate Keap1 protein expression, the Keap1 over-expressed plasmid study indicated that the up-regulation of Nrf2 protein expression induced by pretreatment of Gen could be blocked by the transfection of Keap1 over-expressed plasmid, and the same results also occurred in Nrf2 downstream factors.

CONCLUSION

Gen could alleviate the cerebrovascular cells oxidative damage induced by Aβ25-35 through regulating Nrf2 pathway, and Keap1 might be one of the targets of Gen on activating Nrf2 pathway.

Marinoid J, a phenylglycoside from Avicennia marina fruit, ameliorates cognitive impairment in rat vascular dementia: a quantitative iTRAQ proteomic study

CONTEXT

Fruit of Avicennia marina (Forsk.) Vierh. (Acanthaceae) is used as a Chinese herb. Studies have found that it contains marinoid J, a novel phenylethanoid glycoside (PG) compound, but its neuroprotective functions are largely unknown.

OBJECTIVE

This study evaluated the effects of marinoid J on vascular dementia (VD) and determined its potential mechanisms of action.

MATERIALS AND METHODS

The VD model was established by the ligation of the bilateral common carotid artery in Sprague-Dawley rats, who received daily intragastrically administration of saline, marinoid J (125 or 500 mg/kg body weight/d), or oxiracetam (250 mg/kg body weight/d) for 14 days (20 rats in each group). The Morris water maze (MWM) was used to evaluate cognitive performance. The hippocampus was subjected to histological and proteomic analyses.

RESULTS

Marinoid J shortened the escape latency of VD rats (31.07 ± 3.74 s, p < 0.05). It also decreased malondialdehyde (MDA) (27.53%) and nitric oxide (NO) (20.41%) while increasing superoxide dismutase (SOD) (11.26%) and glutathione peroxidase (GSH-Px) (20.38%) content in hippocampus tissues. Proteomic analysis revealed 45 differentially expressed proteins (DEPs) in marinoid J-treated VD rats, which included angiotensin-converting enzyme (ACE), keratin 18 (KRT18), cluster of differentiation 34 (CD34), and synaptotagmin II (SYT2).

CONCLUSIONS

Marinoid J played a role in protecting hippocampal neurons by regulating a set of proteins that influence oxidative stress and apoptosis, this effect may thereby alleviate the symptoms of VD rats. Thus, pharmacological manipulation of marinoid J may offer a novel opportunity for VD treatment.

Regulatory microRNAs and vascular cognitive impairment and dementia

Vascular cognitive impairment and dementia (VCID) is defined as a progressive dementia disease related to cerebrovascular injury and often occurs in aged populations. Despite decades of research, effective treatment for VCID is still absent. The pathological processes of VCID are mediated by the molecular mechanisms that are partly modulated at the post-transcriptional level. As small endogenous non-coding RNAs, microRNAs (miRs) can regulate target gene expression through post-transcriptional gene silencing. miRs have been reported to play an important role in the pathology of VCID and have recently been suggested as potential novel pharmacological targets for the development of new diagnosis and treatment strategies in VCID. In this review, we summarize the current understanding of VCID, the possible role of miRs in the regulation of VCID and attempt to envision future therapeutic strategies. Since manipulation of miR levels by either pharmacological or genetic approaches has shown therapeutic effects in experimental VCID models, we also emphasize the potential therapeutic value of miRs in clinical settings.

Vascular Cognitive Impairment: Information from Animal Models on the Pathogenic Mechanisms of Cognitive Deficits

Vascular cognitive impairment (VCI) is the second most common cause of cognitive deficit after Alzheimer's disease. Since VCI patients represent an important target population for prevention, an ongoing effort has been made to elucidate the pathogenesis of this disorder. In this review, we summarize the information from animal models on the molecular changes that occur in the brain during a cerebral vascular insult and ultimately lead to cognitive deficits in VCI. Animal models cannot effectively represent the complex clinical picture of VCI in humans. Nonetheless, they allow some understanding of the important molecular mechanisms leading to cognitive deficits. VCI may be caused by various mechanisms and metabolic pathways. The pathological mechanisms, in terms of cognitive deficits, may span from oxidative stress to vascular clearance of toxic waste products (such as amyloid beta) and from neuroinflammation to impaired function of microglia, astrocytes, pericytes, and endothelial cells. Impaired production of elements of the immune response, such as cytokines, and vascular factors, such as insulin-like growth factor 1 (IGF-1), may also affect cognitive functions. No single event could be seen as being the unique cause of cognitive deficits in VCI. These events are interconnected, and may produce cascade effects resulting in cognitive impairment.

CZ-7, a new derivative of Claulansine F, ameliorates 2VO-induced vascular dementia in rats through a Nrf2-mediated antioxidant responses

Vascular dementia (VD) results from accumulated damage in the vascular system, which is characterized by progressive impairments in memory and cognition and is second only to Alzheimer's disease (AD) in prevalence among all types of dementia. In contrast to AD, there is no FDA-approved treatment for VD owing to its multiple etiologies. In this study, we investigated whether CZ-7, a new derivative of Claulansine F (Clau F) with verified neuroprotective activity in vitro, could ameliorate the cognitive impairment of rats with permanent occlusion of bilateral common carotid arteries (2VO) and its potential mechanisms of action. The 2VO rats were orally administered CZ-7 (10, 20, 40 mg/kg) from day 27 to day 53 post-surgery. Morris water maze tests conducted at day 48-51 revealed that CZ-7 administration significantly reduced the escape latency in 2VO rats. After the rats were sacrificed on day 53, morphological studies using Nissl and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining showed that administration of CZ-7 markedly attenuated the pathological changes in CA1-CA3 area of the hippocampus, including neuronal cell loss, nuclear shrinkage, and dark staining of neurons, and significantly decreased the chronic cerebral hypoperfusion-induced cell loss. Klüver-Barrera staining study revealed that CZ-7 administration significantly improved the white matter lesions. 8-OHdG and reactive oxygen species (ROS) immunofluorescent analyses showed that CZ-7 administration significantly decreased oxidative stress in CA1-CA3 area of the hippocampus. Finally, we found that the CZ-7-improved oxidative stress might be mediated via the Nrf2 pathway, evidenced by the double immunofluorescent staining of Nrf2 and the elevation of expression levels of oxidative stress proteins HO-1 and NQO1. In conclusion, CZ-7 has therapeutic potential for VD by alleviating oxidative stress injury through Nrf2-mediated antioxidant responses.

Naomaitai Ameliorated Brain Damage in Rats with Vascular Dementia by PI3K/PDK1/AKT Signaling Pathway

Background/Aims

Naomaitai can improve blood perfusion and ameliorate the damage in the paraventricular white matter. This study was focused on observing the neuroprotective effect of Naomaitai on the vascular dementia of rat and exploring the action mechanism of PI3K/PDK1/AKT signaling pathway.

Methods

A vascular dementia model of rats was established by permanent, bilateral common carotid artery occlusion. Rats' behavior was tested by Neurological deficit score and the Morris water maze. The pathology and apoptosis were detected through HE staining and TUNEL assay. Myelin sheath loss and nerve fiber damage were detected by LFB staining. Inflammatory factors, oxidative stress, and brain damage markers were detected through ELISA. The expression of apoptosis-related proteins and PI3K/PDK1/AKT signaling pathway related proteins were measured by western blot. The expressions of PI3K, PDK1, AKT, and MBP in paraventricular white matter cells were detected by immunofluorescence.

Results

Naomaitai treatment decreased neurological function score in rats with vascular dementia, ameliorated paraventricular white matter damage caused by long-term hypoxia, and hypoperfusion reduced the brain injury markers S-100β and NSE contents, suppressed inflammatory reaction and oxidative stress, reduced IL-1β, IL-6, TNF-α, and MDA contents, and remarkably increased IL-10 and SOD contents. TUNEL and western blot assay showed that Naomaitai treatment decreased neuronal cell apoptosis, increased Bcl-2 expression, and reduced caspase-3 and Bax expression. Furthermore, we found Naomaitai inhibited PI3K and PDK1 expression and activated phosphorylated AKT protein in rats with vascular dementia. However, the protective effect of Naomatai in rats with vascular dementia was inhibited, and expression of PI3K signaling pathway-related proteins was blocked after administration of PI3K inhibitor.

Conclusion

Naomaitai can ameliorate brain damage in rats with vascular dementia, inhibit neuronal apoptosis, and have anti-inflammatory and antioxidative stress effects, which may be regulated by the PI3K/PDK1/AKT signaling pathway.

Oxidative damage to DNA in independent-living elderly persons and their correlations with sociodemographic, anthropometric, and functional parameters

Abstract Objective: To evaluate the correlations between oxidative DNA damage among elderly persons aged between 60 and 79 years and sociodemographic, anthropometric and functional parameters. Method: The present study has a descriptive, quantitative and cross-sectional design. A group of 195 independent-living elderly persons of both genders underwent blood collection and the subsequent measurement of serum concentrations of 8-OHdG, a residue generated by the attack of reactive oxygen species to DNA. The same subjects also underwent evaluation for body mass index (BMI), body fat percentage, the Short Physical Performance Battery (SPPB), and the education level of the participants was analyzed. Statistical analysis was performed using the Spearman correlation test, adopting a 5% significance level. Result: Higher fat percentage and BMI are directly correlated with higher concentrations of 8-OHdG, while SPPB and education were inversely correlated with the concentration of this molecule in the sample. Conclusion: These results suggest factors such as lifestyle and educational level influenced oxidative DNA damage in these elderly persons and had an impact on their functional capacity.

Uric acid is associated with vascular dementia in Chinese population

OBJECTIVE

Mounting evidence suggests that oxidative stress is involved in the pathogenesis of vascular dementia (VD). Uric acid (UA) has long been implicated as a critical cause of cardiovascular disease. Nevertheless, UA was also expected to play an important role in antioxidant and neuroprotection recently. We hypothesized that UA may have a protective role against VD. The aim of this study was to investigate the link between serum UA and cognitive dysfunction in VD.

MATERIALS AND METHODS

There were altogether 127 VD subjects and 81 nondemented controls enrolled in our study. Serum UA, demographic, and clinical characteristics were recorded at baseline, and all participants underwent Mini-Mental State Examination (MMSE) at the beginning of the trial.

RESULTS

The VD group showed lower MMSE scores and serum UA levels than nondemented controls and there was significant statistical difference between the two groups (p < .05). Demographic and clinical characteristics such as age, gender, education, body mass index (BMI), total cholesterol (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL), low-density lipoprotein cholesterol (LDL), blood urea nitrogen (BUN), and serum creatinine (Scr) did not differ dramatically between groups (p > .05). In VD subjects, there was a positive correlation between serum UA and MMSE scores (r = .32, p < .05), and this correlation was independent of demographic and clinical characteristics (β = .272, p < .05).

CONCLUSIONS

VD subjects have dramatically lower serum UA levels in comparison to nondemented controls. Lower serum UA levels are linked to cognitive dysfunction and could serve as a potential predictor for VD.

8-Hydroxy-2-Deoxyguanosine Levels and Cardiovascular Disease: A Systematic Review and Meta-Analysis of the Literature

SIGNIFICANCE

8-Hydroxy-2-deoxyguanosine (8-OHdG) is generated after the repair of ROS-mediated DNA damages and, thus, is one of the most widely recognized biomarkers of oxidative damage of DNA because guanosine is the most oxidized among the DNA nucleobases. In several pathological conditions, high urinary levels of oxidized DNA-derived metabolites have been reported (e.g., cancer, atherosclerosis, hypertension, and diabetes).

RECENT ADVANCES

Even if published studies have shown that DNA damage is significantly associated with the development of atherosclerosis, the exact role of this damage in the onset and progression of this pathology is not fully understood, and the association of oxidative damage to DNA with cardiovascular disease (CVD) still needs to be more extensively investigated. We performed a meta-analysis of the literature to investigate the association among 8-OHdG levels and CVD.

CRITICAL ISSUES

Fourteen studies (810 CVD patients and 1106 controls) were included in the analysis. We found that CVD patients showed higher 8-OHdG levels than controls (SMD: 1.04, 95%CI: 0.61, 1.47, p < 0.001, I(2) = 94%, p < 0.001). The difference was confirmed both in studies in which 8-OHdG levels were assessed in urine (MD: 4.43, 95%CI: 1.71, 7.15, p = 0.001) and in blood samples (MD: 1.42, 95%CI: 0.64, 2.21, p = 0.0004). Meta-regression models showed that age, hypertension, and male gender significantly impacted on the difference in 8-OHdG levels among CVD patients and controls.

FUTURE DIRECTIONS

8-OHdG levels are higher in patients with CVD than in controls. However, larger prospective studies are needed to test 8-OHdG as a predictor of CVD.

NADPH oxidase 1, a novel molecular source of ROS in hippocampal neuronal death in vascular dementia

AIMS

Chronic cerebral hypoperfusion (CCH) is a common pathological factor that contributes to neurodegenerative diseases such as vascular dementia (VaD). Although oxidative stress has been strongly implicated in the pathogenesis of VaD, the molecular mechanism underlying the selective vulnerability of hippocampal neurons to oxidative damage remains unknown. We assessed whether the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (Nox) complex, a specialized superoxide generation system, plays a role in VaD by permanent ligation of bilateral common carotid arteries in rats.

RESULTS

Male Wistar rats (10 weeks of age) were subjected to bilateral occlusion of the common carotid arteries (two-vessel occlusion [2VO]). Nox1 expression gradually increased in hippocampal neurons, starting at 1 week after 2VO and for approximately 15 weeks after 2VO. The levels of superoxide, DNA oxidation, and neuronal death in the CA1 subfield of the hippocampus, as well as consequential cognitive impairment, were increased in 2VO rats. Both inhibition of Nox by apocynin, a putative Nox inhibitor, and adeno-associated virus-mediated Nox1 knockdown significantly reduced 2VO-induced reactive oxygen species generation, oxidative DNA damage, hippocampal neuronal degeneration, and cognitive impairment.

INNOVATION AND CONCLUSION

We provided evidence that neuronal Nox1 is activated in the hippocampus under CCH, causing oxidative stress and consequential hippocampal neuronal death and cognitive impairment. This evidence implies that Nox1-mediated oxidative stress plays an important role in neuronal cell death and cognitive dysfunction in VaD. Nox1 may serve as a potential therapeutic target for VaD.

Acupuncture mechanism and redox equilibrium

Oxidative stress participates in the pathological process of various diseases. Acupuncture is a component of the health care system in China that can be traced back for at least 3000 years. Recently, increased evidences indicate that acupuncture stimulation could reduce oxidative damage in organisms under pathological state, but the exact mechanism remains unclear. This review focuses on the emerging links between acupuncture and redox modulation in various disorders, such as vascular dementia, Parkinson's disease, and hypertension, ranging from redox system, antioxidant system, anti-inflammatory system, and nervous system to signaling pathway. Although the molecular and cellular pathways studies of acupuncture effect on oxidative stress are preliminary, they represent an important step forward in the research of acupuncture antioxidative effect.

Cognitive change in donepezil treated patients with vascular or mixed dementia

BACKGROUND

vascular dementia (VaD) and mixed Alzheimer's disease (AD/VaD) are common. How best to monitor treatment is not clear. Our objective was to compare responsiveness and construct validity of change scores, following donepezil treatment, of the standardized Mini-Mental State Examination (sMMSE) and other measures potentially usable in primary care.

METHODS

A six-month, outcome measurement study. The Disability Assessment for Dementia (DAD), CLOX-1 and 2, Phonetic Fluency, a short Neuropsychiatric Inventory, (the NPI-Q), Clinical Global Impression (CGI) and the SymptomGuide™ (SG) were measured. Construct validity was tested by correlating change scores, and responsiveness by calculating standardized response means (SRMs).

RESULTS

Of 148 treated patients, 116 completed. The mean sMMSE increased by 0.7 (95% Confidence Interval (CI) = -0.005, 1.41; p=0.06; SRM= 0.15). There was no statistically significant difference in the DAD. The NPI-Q (-1.4; 95% CI = -2.08, -0.72; p<0.01; SRM=0.24), CLOX-1 (0.9; 95% CI = 0.19, 1.61; p<0.01; SRM=0.21), CLOX-2 (0.9; 95% CI = 0.17, 1.63; p=0.03; SRM=0.26), Phonetic Fluency (0.9; 95% CI = 0.19, 1.61; p=0.02; SRM=0.21) and SG (0.35; 95% CI = 0.20,0.51; p<0.01; SRM=0.28) each detected significant improvement. The CGI suggested improvement in 74 completers (64%) - mostly "minimal" (44/116, 38%) - while 21/116 (18%) were worse. Change scores at 24 weeks were at best modestly correlated with each other (range -0.22 to 0.30).

DISCUSSION

Different measures showed different responsiveness, in a setting in which the mean treatment effect seems to have been small, but clinically detectable. Patient-centered and executive function measures might be useful in vascular and mixed dementia.

Can urinary excretion rate of 8-isoprostrane and malonaldehyde predict postoperative cognitive dysfunction in aging?

Oxidative stress has been associated with mild cognitive impairment (MCI) and Alzheimer's disease (AD). However, little is known about oxidative stress in postoperative cognitive dysfunction (POCD) in aging. The aim of this study was to investigate urinary excretion rate of 8-isoprostane:creatinine (U8-isoPG:Cr) and malonaldehyde:creatinine (UMDA:Cr) to predict short-term POCD in elderly patients undergoing general and orthopedic surgery. 72 patients aged above 65 years were enrolled in this prospective observational study. Each patient underwent cognitive testing to determine POCD performed by an investigator before surgery and 1 week after surgery. Morning urine was collected at baseline, 1, 2, and 7 days postoperatively. U8-isoPG was performed using enzymelinked immunosorbent assay (ELISA), and UMDA levels were measured by chemiluminescence detection. Creatinine levels were also analyzed if differences in the oxidative biomarkers were observed in the urine creatinine concentration. (1). Of 72 patients who completed cognitive testing, postoperative cognitive dysfunction was detected in 29.2 % (n = 21) of patients in 7 days. (2) U8-isoPG:Cr levels in 7 days postoperatively were significantly higher in POCD patients compared with the non-POCD group (p = 0.01). When measuring change from baseline, U8-isoPG:Cr levels were higher than that of control groups (p = 0.01). (3) UMDA:Cr levels were significantly elevated in 1 and 2 days postoperatively in both groups (p < 0.05). U8-isoPG:Cr level seems to be a valuable marker to detect lipid peroxidation early in POCD patients. However, it will also be important to take into account or reduce potential confounders to improve the identification of changes in the status of oxidative stress as a marker for POCD.

Ac-cel, a novel antioxidant, protects against hydrogen peroxide-induced injury in PC12 cells via attenuation of mitochondrial dysfunction

Oxidative stress has been implicated in pathophysiology of many neurodegenerative diseases (ND) and increased oxidative stress is closely associated with mitochondrial dysfunction. As a result, looking for potent antioxidants, especially those targeting mitochondria, has become an attractive strategy in ND therapy. In this study, we explored protective effects and potential mechanism of Ac-cel, a novel compound, against hydrogen peroxide (H(2)O(2))-induced injury in PC12 cells. Pretreatment of PC12 cells with Ac-cel prior to 24 h of H(2)O(2) exposure markedly attenuated cytotoxicity induced by H(2)O(2) as evidenced by morphological changes and 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Ac-cel also exhibited potent antiapoptotic effect demonstrated by results of annexin V and PI staining. The above beneficial effects of Ac-cel were accompanied by improved mitochondrial function, reduced caspase-3 cleavage as well as upregulated ratio of Bcl-2/Bax protein expression. Moreover, Ac-cel pretreatment markedly reversed intracellular reactive oxygen species (ROS) accumulation following 30 min of H(2)O(2) exposure in PC12 cells. Further, subcellular investigation indicated that Ac-cel significantly reduced production of mitochondrial ROS in isolated rat cortical mitochondria. Taken together, the present study, for the first time, reports that Ac-cel pretreatment inhibits H(2)O(2)-stimulated early accumulation of intracellular ROS possibly via reducing mitochondrial ROS production directly and leads to subsequent preservation of mitochondrial function. These results indicate that Ac-cel is a potential drug candidate for treatment of oxidative stress-associated ND.