Current Neurovascular Research - Volume 11, Issue 2, 2014

Chronic cerebral hypoperfusion (CCH) is a risk factor for the development of vascular dementia (VaD). CCH participates in a negative role in cognitive impairments. Transient receptor potential vanilloid subtype 1 (TRPV1) participates in cognition, ischemic damage and neuroprotection. Selective norepinephrine transporter (NET) inhibitors have a role in cognitive dysfunction and oxidative stress. The role of TRPV1 and NET in CCH induced VaD is still unknown. The present study has been structured to investigate the role of vanillin; a selective agonist of TRPV1 as well as atomoxetine; a selective NET inhibitor in CCH induced VaD in mice. Permanent bilateral common carotid arteries ligation or two vessel occlusion (2VO) technique was used to induce a stage of chronic cerebral hypoperfusion in mice. 2VO animals have shown significant impairment of locomotion (Actophotometer), motor coordination (Rota rod), learning and memory (Morris water maze). 2VO animals have shown significant reduction in brain catalase, glutathione, and superoxide dismutase, with significant increase in brain infarct size (TTC staining), malondialdehyde and acetyl cholinesterase-AChE activity. Whereas, administration of vanillin as well as atomoxetine has significantly attenuated 2VO induced impaired locomotion, motor coordination, learning and memory, brain damage, brain oxidative stress and higher AChE activity. It may be concluded that 2VO induced CCH has elicited VaD, which was attenuated by vanillin and atomoxetine. Thus, modulators of vanilloid receptors and norepinephrine transporter may be explored further for their benefits in CCH induced VaD.

Salvianolate has been reported to possess protective properties. However, its specific mechanisms have yet to be identified. Our study aimed to identify the molecular mechanism of antioxidative stress function of salvianolate on rat ischemia and reperfusion brain tissues. Rats were randomly distributed into three experimental groups: sham, model and intervention . All animal neurobehavioral tests were performed at the end of 72-h reperfusion per Longa’s method, and rats with a score of 0 (no neurological deficit) or 4 (severe neurological deficit with impaired consciousness) were excluded. Brain slices were obtained after 72 h of reperfusion and stained with triphenyltetrazolium chloride. Western blot analysis and quantitative real-time polymerase chain reaction (qRT–PCR) were used to determine levels of GOLPH3, Akt/p-Akt, and mTOR/p-mTOR expressions in ischemic cortex. Salvianolate (18mg/kg intraperitoneal injection) significantly decreased the neurological deficit scores of rats in groups of 72 h I/R and reduced the number of TUNELpositive cells in the cerebral cortex when given at onset and at 24 and 48 h after reperfusion, leading to decreased cerebral infarction in rats after ischemia/reperfusion injury. Results of Western blot and qRT-PCR showed that salvianolate could significantly upregulate the expression of Golgi phosphoprotein-3 as well as the phosphorylation of Akt and mTOR. Above findings indicate that salvianolate exerts potent and long-term neuroprotective effects in the model of cerebral I/R, and Golgi phosphoprotein-3 and its downstream activation of Akt/mTOR signaling pathway may provide a new insight for the antioxidative effect of salvianolate.

Parkinson’s disease (PD) is associated with higher risk of cognitive impairment that may lead to memory loss, confusion, and decreased attention span. In this study, we have investigated the effect of GW0742, a PPAR-β/δ agonist in rat model of cognitive impairment associated with PD. Bilateral intranigral administration of 1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine (MPTP) (100 μg/1 μl/side) produced significant cognitive dysfunctions. PPAR-β/δ agonist GW0742 at a dose of 30 and 100 μg/kg showed significant improvement in cognitive impairments caused by MPTP in rat model of PD as evident from passive avoidance and Morris water maze test. MPTP-induced massive oxidative damage and DNA fragmentation was ameliorated by GW0742 treatment as observed after MDA and GSH estimation and TUNEL assay. Tyrosine hydroxylase positive neurons were decreased by 25% of normal control in MPTP group and GW0742 treatment restored tyrosine hydroxylase levels showing neuroprotective nature. Further, we performed physiologically based pharmacokinetic (PBPK) modeling study using GastroPlus to characterize the kinetics of GW0742 in the brain. The predicted amounts of GW0742 in brain suggest that it has the ability to cross the blood brain barrier. This study implicates the involvement of PPAR-β/δ in PD induced cognitive impairment.

There is considerable interest in defining the molecular pathways involved in seizure-induced neuronal death. Necrotic, apoptotic and anti-apoptotic signalling pathways are activated after status epilepticus (SE). Analyses of apoptosis and necrosis have been merely reported, however conditions of autophagic cell death with hallmarks of type 2 programmed cell death-morphology are relatively few. Autophagy is a highly regulated cellular mechanism for the bulk degradation of cytoplasmic contents which is involved in a variety of physiological and pathological conditions associated with neurological diseases. Our goal was to examine whether autophagy is implicated in the cell death machinery after SE. For this purpose, we used lithium-pilocarpine model of SE in 14-day-old rats and examined the dynamics in the expression of autophagic markers in the hippocampus in controls and in animals subjected to SE at 6, 24, and 48h after the insult. Protein levels of central components of the autophagic machinery were dramatically affected by SE with, however, altered dynamics, compared to controls. Levels of LC3, phospho-mTOR/mTOR, BAG3 and Hsp70 were significantly increased, whereas Beclin 1 levels remained unchanged after SE. The dynamics in the expression of Atg3, Atg5, Atg7, Atg14 and LAMP1 were slightly altered. The amount of SQSTM1/p62 underwent a dramatic and highly significant breakdown 48 h after the induction of SE. These results demonstrate for the first time that SE in the immature brain results in significant alterations of autophagy dynamics. There is a growing interest in the role of autophagy in neurodegeneration, and an emerging consensus that autophagy represents a double-edged sword, acting either as a prosurvival mechanism, or as part of a cell death pathway.

Enlarged perivascular spaces (EPVS) are a feature of cerebral small vessel disease (cSVD) and have been related to cSVD severity. A higher number of EPVS were related to decreased cognition in healthy elderly, but this has never been investigated in patients at high risk of cSVD. We included 189 patients with a high risk of cSVD (hypertensive patients and lacunar stroke patients). Patients underwent brain MRI and extensive neuropsychological assessment. EPVS were rated in the basal ganglia (BG) and centrum semiovale (CSO). Correlation analyses between EPVS and cognitive domains were adjusted for white matter lesions (WMLs), age, sex and symptomatic stroke. Negative correlations were found between EPVS in the BG and all cognitive domains, independent of WMLs. After correction for age, results remained significant for information processing speed (IPS) only. No independent correlation was found between EPVS in the CSO and cognition. We demonstrated that more BG EPVS were associated with a decrease in IPS, independent of age and WMLs. This emphasizes that specifically EPVS in the BG are associated with cSVD, and with cSVD-related decreases in cognition.

Dyslipidemia is one of the pathognomonic elements of athero-genesis, as well as cerebro- and cardio-vascular disease (CCVD). Hemostatic factors are also involved in athero-sclerosis and ischemic changes, however their relationship with disrupted lipid homeostasis is not well characterized. The aim of this study was to determine the coagulation state of dyslipidemic patients and to evaluate their association with CCVD risk factors. Biochemical and hematological parameters, as well as neuro-psychiatric profile of 109 dyslipidemic subjects and 107 normo-lipidic healthy volunteers were assessed. Serum bio-marker levels and cognitive performance generally did not differ in the groups, but prothrombin fragment 1+2 (F1+2) and D-dimer concentrations were markedly higher among women. Hyper-coagulability was not associated with dyslipidemia, but was correlated with the female gender, which might pose an increased thromboembolic risk in asymptomatic women.

In humans the mechanism governing the internal jugular vein (IJV) valve opening and closure is still unclear. M-mode is used in echo-cardiology for the heart valves assessment. Sometimes it was performed also in deep peripheral veins and in vena cava assessment, but never in the IJV valve. Aim of the present study is to investigate the IJV valves physiology in healthy volunteers, by means of both B and M-mode ultrasound. Eighty-three (83) healthy volunteers (35 Male, 48 Female, 25.7±6.7 y.o.), for a total of 166 IJVs, were enrolled. The entire cohort underwent IJVs high-resolution B and M-mode evaluation, in standardized postural and respiratory conditions. Presence, motility, and number of cusps, as well as their opening and closure mechanism have been assessed. Bilateral valve absence occurred in 13/83 (16%), whereas at least a one side absence was recorded in 38/83 (46% of the cohort) (p<0.0356). Valve leaflets were always mobile and respectively bi-cusps in 34%, or mono-cusp in 27%. The latter was significantly more frequent on the left side (35%) than on the right side (19%) (p<0.0013). In supine, M-mode valve opening was synchronous with the cardiac cycle. To the contrary, in an upright position, the valve remained always open and saddled to the wall, independently from the cardiac cycle. In healthy subjects, the IJV valve leaflets are always mobile, but the significant rate of mono and bilateral absence could suggest a progressive phylogenetic importance loss of such apparatus. M-mode ultrasound enhances the characterization of IJV valve, for this reason it should be taken into consideration to routinely add it to the cerebral venous return investigation.

Repeated electroconvulsive therapy (rECT) is widely applied in the treatment of refractory depression. Among the side effects of rECT, memory impairment is noticeable and needs effective protection. In this study, by employing a recognized repeated electroconvulsive shock (rECS) rat model, we found that rECS induced the significant spatial memory retention deficits with the simultaneous decreases in long-term potential (LTP), enhanced excitable postsynaptic potentials (EPSP), population spike (PS) and input/output curve in perforant pathway-dentate gyrus (PP-DG), but had no obvious neuron loss or dentritic spine loss in the brain by Nissle or Golgi stainings. Furthermore, the increased synaptic proteins of NR2A/B, PSD93, PSD95, the immediate early gene c-Fos and CREB protein were detected in hippocampus of rECS rats. rECS was also found to cause enhanced axon reorganization in DG region of hippocampus by Timm staining. Intraperitoneal injection of phenylbutyric acid (PBA), an aromatic short chain fatty acid acting as a molecule chaperon, could prevent rats from the rECS-induced memory deficits and synaptic potential enhancement by decreasing the levels of the abnormally increased memory-associated proteins and enhanced axon reorganization in hippocampus. Our data suggested that PBA might be potentially used to attenuate the rECS-induced memory impairment.

Cognitive abilities depend primarily on cerebrovascular health and aging. In this work, we examine the pathogenic mechanisms of brain dysfunction linked to vascular risk factors, insulin signaling and cerebrovascular damage and explore how these mechanisms interfere with neurodegeneration. Although Abeta hypothesis prevails in the ethiology of Alzheimer's Disease (AD), it has become increasingly evident that disturbances in cerebral glucose metabolism is an invariant pathophysiological feature of AD and may provide an ubiquituos mechanism underlying the pathogenesis of AD. Currently, it is difficult to identify efficient therapeutic approach for brain protection and recovery, especially because we do not fully understand the underlying neurobiological processes, the nature of the pathophysiological mechanisms and the links between these two categories. Endogenous neurobiological processes, such as “brain reserves”, neurotrophicity, neuroplasticity and neurogenesis, are central to protection and recovery and represent the background of endogenous defense activity (EDA). The historical concept of neuroprotection being the suppression of pathophysiological processes by a single mechanism or molecule may have been effective in clinical practice, but is now obsolete and indicates a failure of the reductionist approach to neuroprotection in the clinical setting. Pharmacological intervention should address modulation not suppression. The more pathophysiological processes are modulated, the better the chances are for therapeutic success in brain protection and recovery. Therefore, drugs with pleiotropic neuroprotective mechanisms of action are the best candidates for acute neuroprotection.

On a global basis, at least 15 million individuals suffer some form of a stroke every year. Of these individuals, approximately 800,000 of these cerebrovascular events occur in the United States (US) alone. The incidence of stroke in the US has declined from the third leading cause of death to the fourth, a result that can be attributed to multiple factors that include improved vascular disease management, reduced tobacco use, and more rapid time to treatment in patients that are clinically appropriate to receive recombinant tissue plasminogen activator. However, treatment strategies for the majority of stroke patients are extremely limited and represent a critical void for care. A number of new therapeutic considerations for stroke are under consideration, but it is the mammalian target of rapamycin (mTOR) that is receiving intense focus as a potential new target for cerebrovascular disease. As part of the phosphoinositide 3-kinase (PI 3-K) and protein kinase B (Akt) cascade, mTOR is an essential component of mTOR Complex 1 (mTORC1) and mTOR Complex 2 (mTORC2) to govern cell death involving apoptosis, autophagy, and necroptosis, cellular metabolism, and gene transcription. Vital for the consideration of new therapeutic strategies for stroke is the ability to understand how the intricate and complex pathways of mTOR signaling sometimes lead to disparate clinical outcomes.