Liang Chao Wang

Population based study on patients with traumatic brain injury suggests increased risk of dementia

Objective The relationship between traumatic brain injury (TBI) and the risk of dementia remains controversial. This population based study was designed to estimate and compare the risk of dementia in TBI and non-TBI individuals during the 5 year period after TBI. Methods This study was a retrospective cohort study. Data were obtained from the Longitudinal Health Insurance Database 2000. We included 44 925 patients receiving ambulatory or hospital care and 224 625 non-TBI patients; patients were matched for sex, age and year of index use of healthcare. Patients <15 years of age and those admitted to the intensive care unit were excluded. Each individual was studied for 5 years to identify the subsequent development of dementia. Data were analysed by Cox proportional hazard regression. Results During the 5 year follow-up period, 1196 TBI (2.66%) and 224 625 non-TBI patients (1.53%) patients developed dementia. During the 5 year follow-up period, TBI was independently associated with a 1.68 (range 1.57–1.80) times greater risk of dementia after adjusting for sociodemographic characteristics and selected comorbidities. Conclusions The findings of this study suggest an increased risk of dementia among individuals with TBI. We suggest the need for more intensive medical monitoring and health education in individuals with TBI.

Attenuating inflammation but stimulating both angiogenesis and neurogenesis using hyperbaric oxygen in rats with traumatic brain injury.

BACKGROUND: Inflammation, angiogenesis, neurogenesis, and gliosis are involved in traumatic brain injury (TBI). Several studies provide evidence supporting the neuroprotective effect of hyperbaric oxygen (HBO2) therapy in TBI. The aim of this study was to ascertain whether inflammation, angiogenesis, neurogenesis, and gliosis during TBI are affected by HBO2 therapy. METHODS: Rats were randomly divided into three groups: TBI + NBA (normobaric air: 21% O2 at 1 absolute atmospheres), TBI + HBO2, and Sham operation + NBA. TBI + HBO2 rats received 100% O2 at 2.0 absolute atmospheres for 1 hr/d for three consecutive days. Behavioral tests and biochemical and histologic evaluations were done 4 days after TBI onset. RESULTS: TBI + NBA rats displayed: (1) motor and cognitive dysfunction; (2) cerebral infarction and apoptosis; (3) activated inflammation (evidenced by increased brain myeloperoxidase activity and higher serum levels of tumor necrosis factor-&agr;); (4) neuronal loss (evidenced by fewer NeuN-positive cells); and (5) gliosis (evidenced by more glial fibrillary protein-positive cells). In TBI + HBO2 rats, HBO2 therapy significantly reduced TBI-induced motor and cognitive dysfunction, cerebral infarction and apoptosis, activated inflammation, neuronal loss, and gliosis. In addition, HBO2 therapy stimulated angiogenesis (evidenced by more bromodeoxyuridine-positive endothelial and vascular endothelial growth factor-positive cells), neurogenesis (evidenced by more bromodeoxyuridine-NeuN double-positive and glial cells-derived neurotrophic factor-positive cells), and overproduction of interleukin-10 (an anti-inflammatory cytokine). CONCLUSIONS: Collectively, these results suggest that HBO2 therapy may improve outcomes of TBI in rats by inhibiting activated inflammation and gliosis while stimulating both angiogenesis and neurogenesis in the early stage.

Long Course Hyperbaric Oxygen Stimulates Neurogenesis and Attenuates Inflammation after Ischemic Stroke

Several studies have provided evidence with regard to the neuroprotection benefits of hyperbaric oxygen (HBO) therapy in cases of stroke, and HBO also promotes bone marrow stem cells (BMSCs) proliferation and mobilization. This study investigates the influence of HBO therapy on the migration of BMSCs, neurogenesis, gliosis, and inflammation after stroke. Rats that sustained transient middle cerebral artery occlusion (MCAO) were treated with HBO three weeks or two days. The results were examined using a behavior test (modified neurological severity score, mNSS) and immunostaining to evaluate the effects of HBO therapy on migration of BMSCs, neurogenesis, and gliosis, and expression of neurotrophic factors was also evaluated. There was a lower mNSS score in the three-week HBO group when compared with the two-day HBO group. Mobilization of BMSCs to an ischemic area was more improved in long course HBO treatments, suggesting the duration of therapy is crucial for promoting the homing of BMSCs to ischemic brain by HBO therapies. HBO also can stimulate expression of trophic factors and improve neurogenesis and gliosis. These effects may help in neuronal repair after ischemic stroke, and increasing the course of HBO therapy might enhance therapeutic effects on ischemic stroke.

Magnesium sulfate and nimesulide have synergistic effects on rescuing brain damage after transient focal ischemia.

Magnesium sulfate and nimesulide are commonly used drugs with reported neuroprotective effects. Their combination as stroke treatment has the potential benefits of decreasing individual drug dosage and fewer adverse effects. This study evaluated their synergistic effects and compared a low-dose combination with individual drug alone and placebo. Sprague-Dawley rats underwent 90 min of focal ischemia with intraluminal suture occlusion of the middle cerebral artery followed by reperfusion. The rats were randomly assigned to receive one of the following treatments: placebo, magnesium sulfate (MgSO₄; 45 mg/kg) intravenously immediately after the induction of middle cerebral artery occlusion, nimesulide (6 mg/kg) intraperitoneally before reperfusion, and combined therapy. Three days after the ischemia-reperfusion insult, therapeutic outcome was assessed by 2,3,5-triphenyltetrazolium chloride staining and a 28-point neurological severity scoring system. Cyclooxygenase-2, prostaglandin E₂, myeloperoxidase, and caspase-3 expression after treatment were evaluated using Western blot analyses and immunohistochemical staining, followed by immunoreactive cell analysis using tissue cytometry. Only the combination treatment group showed a significant decrease in infarction volume (10.93±6.54% versus 26.43±7.08%, p<0.01), and neurological severity score (p<0.05). Low-dose MgSO₄ or nimesulide showed no significant neuroprotection. There was also significant suppression of cyclooxygenase-2, prostaglandin E₂, myeloperoxidase, and caspase-3 expression in the combination treatment group, suggesting that the combination of the two drugs improved the neuroprotective effects of each individual drug. MgSO₄ and nimesulide have synergistic effects on ischemia-reperfusion insults. Their combination helps decrease drug dosage and adverse effects. Combined treatment strategies may help to combat stroke-induced brain damage in the future.

Memantine Alleviates Brain Injury and Neurobehavioral Deficits after Experimental Subarachnoid Hemorrhage

Subarachnoid hemorrhage (SAH) causes brain injury via glutamate excitotoxicity, which leads to an excessive Ca2+ influx and this starts an apoptotic cascade. Memantine has been proven to reduce brain injury in several types of brain insults. This study investigated the neuro-protective potential of memantine after SAH and explored the underlying mechanisms. An endovascular perforation rat model of SAH was used and Sprague–Dawley rats were randomized into sham surgery, SAH + vehicle, and SAH + memantine groups. The effects of memantine on SAH were evaluated by assessing the neuro-behavioral functions, blood–brain barrier (BBB) permeability and neuronal cell preservation. The mechanisms of action of memantine, with its N-methyl-d-aspartate (NMDA) antagonistic characteristics on nitric oxide synthase (NOS) expression and peroxynitrite formation, were also investigated. The apoptotic cascade after SAH was suppressed by memantine. Neuronal NOS (nNOS) expression, peroxynitrite formation, and subsequent oxidative/nitrosative stress were also reduced. Memantine effectively preserved BBB integrity, rescued neuronal injury, and improved neurological outcome in experimental SAH. Memantine has neuro-protective potential in experimental SAH and may help combat SAH-induced brain damage in the future.

Stroke suggests increased risk of dementia

BACKGROUND Stroke is a major cause of disability in the elderly and considerably increases the risk of dementia, which is another important source of disability. This population-based study aimed to examine the risk of dementia in patients with stroke compared with non-stroke cases with similar comorbidities. METHODS Using the Taiwan National Health Insurance databank covering the period 2001-2007, this retrospective cohort study evaluated the risk of dementia in 10,884 patients with first stroke who had no history of dementia. In this study, we performed a 1:5 case-control matched analysis, in which cases were matched to controls based on their estimated propensity scores, which were estimated with demographics and associated risk factors. This approach reduced selection bias. Cox proportional hazards regression analysis was then used to estimate the risk of dementia in stroke patients. RESULTS During the 5-year follow-up period, 1,487 (13.74%) stroke and 1,402 (2.59%) non-stroke patients suffered dementia. Stroke was independently associated with a 6.09 (95% confidence interval [CI], 5.66 to 6.55) times greater risk of dementia 5 years after stroke. Older age was associated with a higher incidence of dementia after stroke. Each stroke type had different impacts on the occurrence of dementia. The hazard ratio of dementia among hemorrhagic stroke patients was much higher than those of ischemic stroke and controls. CONCLUSION The findings of this study suggest that stroke confers an increased risk of dementia, especially in the elderly and in patients with hemorrhagic stroke. We advocate the need for close observation and enhanced health education programs to benefit patients with stroke.

Memantine Attenuates Delayed Vasospasm after Experimental Subarachnoid Hemorrhage via Modulating Endothelial Nitric Oxide Synthase.

Delayed cerebral vasospasm is an important pathological feature of subarachnoid hemorrhage (SAH). The cause of vasospasm is multifactorial. Impairs nitric oxide availability and endothelial nitric oxide synthase (eNOS) dysfunction has been reported to underlie vasospasm. Memantine, a low-affinity uncompetitive N-methyl-d-aspartate (NMDA) blocker has been proven to reduce early brain injury after SAH. This study investigated the effect of memantine on attenuation of vasospasm and restoring eNOS functionality. Male Sprague-Dawley rats weighing 350–450 g were randomly divided into three weight-matched groups, sham surgery, SAH + vehicle, and SAH + memantine groups. The effects of memantine on SAH were evaluated by assessing the severity of vasospasm and the expression of eNOS. Memantine effectively ameliorated cerebral vasospasm by restoring eNOS functionality. Memantine can prevent vasospasm in experimental SAH. Treatment strategies may help combat SAH-induced vasospasm in the future.

Increased risk of dementia in patients with non-apnea sleep disorder

BACKGROUND Sleep disorders other than sleep apnea (non-apnea sleep disorder, NSD), esp. insomnia and excessive daytime sleepiness, has been reported to induce higher risk of cognitive decline and dementia in previous longitudinal follow-up studies. However, large-scale nationwide populationbased study may further confirm the association between NSD and dementia. METHODS It was a nationwide population-based retrospective study. We used data from Taiwans National Health Insurance Research Database (NHIRD) between January 2000 and December 2011. The NSD cohort comprised 92,079 patients aged over 20 years with no preexisting dementia. The comparison cohort was propensity-score matched 1:1 with 92079 controls. Incident dementia cases were identified to the end of 2011. The NSD cohort to non-NSD cohort adjusted hazard ratios (aHRs) of dementia were assessed using multivariable Cox proportional hazards regression analysis. RESULTS Incidence of dementia was 4.19 and 2.95 per 1,000 person-years in the NSD and non-NSD cohorts, respectively, with an aHR of 1.46 (95% CI=1.38-1.54; p<0.0001). Risk of dementia was higher in both gender and whole age subgroup, with slightly higher in men (aHR: 1.48, 95% CI=1.35-1.62, p<0.0001) and in the younger population (aHR: 2.79, 95% CI=1.63-4.78, p<0.0001). Dementia was most likely to occur in the first year of follow-up (aHR: 1.73, 95% CI=1.49-2.02; p<0.0001), but dementia risk remained high 5 years after NSD diagnosis compared to controls (aHR: 1.44, 95% CI=1.32-1.57; p<0.0001). CONCLUSION NSD may be an early indicator of decline in cognitive functioning and onset of dementia in the short-term period. It also carries a higher risk for dementia in the long run. Patients with NSD should require close monitoring for cognitive decline.

G-CSF-mobilized Bone Marrow Mesenchymal Stem Cells Replenish Neural Lineages in Alzheimer’s Disease Mice via CXCR4/SDF-1 Chemotaxis

Recent studies reported granulocyte colony-stimulating factor (G-CSF) treatment can improve the cognitive function of Alzheimer’s disease (AD) mice, and the mobilized hematopoietic stem cells (HSCs) or bone marrow mesenchymal stem cells (BM-MSCs) are proposed to be involved in this recovery effect. However, the exact role of mobilized HSC/BM-MSC in G-CSF-based therapeutic effects is still unknown. Here, we report that C-X-C chemokine receptor type 4 (CXCR4)/stromal cell-derived factor 1 (SDF-1) chemotaxis was a key mediator in G-CSF-based therapeutic effects, which was involved in the recruitment of repair-competent cells. Furthermore, we found both mobilized HSCs and BM-MSCs were able to infiltrate into the brain, but only BM-MSCs replenished the neural lineage cells and contributed to neurogenesis in the brains of AD mice. Together, our data show that mobilized BM-MSCs are involved in the replenishment of neural lineages following G-CSF treatment via CXCR4/SDF-1 chemotaxis and further support the potential use of BM-MSCs for further autogenically therapeutic applications.

Newly Diagnosed Dementia and Increased Risk of Hemorrhagic Stroke: A Nationwide Population-based Study

BACKGROUND This retrospective cohort study was designed to assess whether there is an association between newly diagnosed dementia and the risk of stroke. METHODS From Taiwans National Health Insurance Research Database of reimbursement claims, we identified 2811 patients with newly diagnosed dementia and 14,055 randomly selected, age-matched patients without dementia. A Cox proportional hazards model was constructed to calculate the development of stroke, including ischemic stroke, and intracerebral, or subarachnoid hemorrhage. RESULTS During the 3-year follow-up period, 339 patients with dementia (12.06%) and 691 patients without dementia (4.92%) developed stroke. The adjusted HRs of developing stroke among newly diagnosed dementia patients were 2.33-times (range, 2.05-2.66), and the incidence of hemorrhagic stroke was higher than that of other stroke types. Patients who had Alzheimers disease were at the highest risk of hemorrhagic stroke. CONCLUSION Individuals with dementia, especially Alzheimers disease, are at greater risk of developing stroke, especially in intracerebral and subarachnoid hemorrhage than patients without dementia. Early mental screening programs and health education should be initiated for dementia patients.