Effects of cyclooxygenase (COX) inhibition on memory impairment and hippocampal damage in the early period of cerebral hypoperfusion in rats

Time-dependent dual mode of action of COX-2 inhibition on mouse serum corticosterone levels

To elucidate the effect of cyclooxygenase-2 (COX-2) inhibition on corticosterone release, mice were divided into a group receiving NS398, a selective COX-2 inhibitor at a dose of 3 mg/kg for seven days, and a group receiving NS398 for fourteen days. After this time, the mice were sacrificed, and blood serum was collected. An ELISA protocol was used to analyze serum corticosterone levels. Short-term COX-2 inhibition increased corticosterone levels, while long-term inhibition lowered them. The exact schedule of experiments was repeated after the lipopolysaccharide (LPS) Escherichia coli challenge in mice to check the influence of stress stimuli on the tested parameters. In this case, we observed increases in corticosterone levels, significant in a seven-day pattern. These results indicate that corticosterone levels are regulated through a COX-2-dependent mechanism in mice.

Small molecules targeting cyclooxygenase/prostanoid cascade in experimental brain ischemia: Do they translate?

Acute brain ischemia accounts for most of stroke cases and constitutes a leading cause of deaths among adults and permanent disabilities in survivors. Currently, the intravenous thrombolysis is the only available medication for ischemic stroke; mechanical thrombectomy is an emerging alternative treatment for occlusion of large arteries and has shown some promise in selected subsets of patients. However, the overall narrow treatment window and potential risks largely limit the patient eligibility. New druggable targets are needed to innovate the treatment of brain ischemia. As the rate-limiting enzyme in the biosyntheses of prostanoids, cyclooxygenase (COX), particularly the inducible isoform COX-2, has long been implicated in mechanisms of acute stroke-induced brain injury and inflammation. However, the notion of therapeutically targeting COX has been diminished over the past two decades due to significant complications of the cardiovascular and cerebrovascular systems caused by long-term use of COX-2 inhibitor drugs. New treatment strategies targeting the downstream prostanoid signaling receptors regulating the deleterious effects of COX cascade have been proposed. As such, a large number of selective small molecules that negatively or positively modulate these important inflammatory regulators have been evaluated for neuroprotection and other beneficial effects in various animal models of brain ischemia. These timely preclinical studies, though not yet led to clinical innovation, provided new insights into the regulation of inflammatory reactions in the ischemic brain and could guide drug discovery efforts aiming for novel adjunctive strategies, along with current reperfusion therapy, to treat acute brain ischemia with higher specificity and longer therapeutic window.

Role of HMGB1 in an Animal Model of Vascular Cognitive Impairment Induced by Chronic Cerebral Hypoperfusion

The pathophysiology of vascular cognitive impairment (VCI) is associated with chronic cerebral hypoperfusion (CCH). Increased high-mobility group box protein 1 (HMGB1), a nonhistone protein involved in injury and inflammation, has been established in the acute phase of CCH. However, the role of HMGB1 in the chronic phase of CCH remains unclear. We developed a novel animal model of CCH with a modified bilateral common carotid artery occlusion (BCCAO) in C57BL/6 mice. Cerebral blood flow (CBF) reduction, the expression of HMGB1 and its proinflammatory cytokines (tumor necrosis factor-alpha [TNF-α], interleukin [IL]-1β, and IL-6), and brain pathology were assessed. Furthermore, we evaluated the effect of HMGB1 suppression through bilateral intrahippocampus injection with the CRISPR/Cas9 knockout plasmid. Three months after CCH induction, CBF decreased to 30–50% with significant cognitive decline in BCCAO mice. The 7T-aMRI showed hippocampal atrophy, but amyloid positron imaging tomography showed nonsignificant amyloid-beta accumulation. Increased levels of HMGB1, TNF-α, IL-1β, and IL-6 were observed 3 months after BCCAO. HMGB1 suppression with CRISPR/Cas9 knockout plasmid restored TNF-α, IL-1β, and IL-6 and attenuated hippocampal atrophy and cognitive decline. We believe that HMGB1 plays a pivotal role in CCH-induced VCI pathophysiology and can be a potential therapeutic target of VCI.

NS398, a cyclooxygenase-2 inhibitor, reverses memory performance disrupted by imipramine in C57Bl/6J mice

Imipramine has been widely used as an antidepressant in the clinic over the years. Unfortunately, it produces a detrimental effect on memory. At the same time, COX-2 inhibitors engagement in the mechanisms of memory formation, and synapse plastic changes has been well documented. Our previous studies have demonstrated the contribution of cyclooxygenase-2 (COX-2) inhibition to the parameters of the mGluR5 pathway in memory formation. Because chronic administration of imipramine has been shown to affect mGluR5, the purpose of this study was to verify the hypothesis of COX-2 pathway engagement in disrupting effects of imipramine. Imipramine is currently used as a reference compound, and therefore it seems important to decipher and understand mood-related pathways, as well as cognitive changes activated during its use. This study covers the examination of spatial, and motor parameters. To this end, C57Bl/6J mice received imipramine, and NS398 (a COX-2 inhibitor) alone, or in combination for 7 or 14 days. We performed the modified Barnes maze (MBM), modified rotarod (MR) tests, and electrophysiological studies. The harmful effect of imipramine on MBM learning was improved by NS398 use. The same modulatory role of the COX-2 inhibitor in procedural learning in the MR test was found. In conclusion, our data show the involvement of the COX-2 pathway in changes in the long-term memory, and procedural memory of C57Bl/6J mice after chronic imipramine treatment.

Amidated and Ibuprofen-Conjugated Kyotorphins Promote Neuronal Rescue and Memory Recovery in Cerebral Hypoperfusion Dementia Model

Chronic brain ischemia is a prominent risk factor for neurological dysfunction and progression for dementias, including Alzheimer’s disease (AD). In rats, permanent bilateral common carotid artery occlusion (2VO) causes a progressive neurodegeneration in the hippocampus, learning deficits and memory loss as it occurs in AD. Kyotorphin (KTP) is an endogenous antinociceptive dipeptide whose role as neuromodulator/neuroprotector has been suggested. Recently, we designed two analgesic KTP-derivatives, KTP-amide (KTP–NH₂) and KTP–NH₂ linked to ibuprofen (IbKTP–NH₂) to improve KTP brain targeting. This study investigated the effects of KTP-derivatives on cognitive/behavioral functions (motor/spatial memory/nociception) and hippocampal pathology of female rats in chronic cerebral hypoperfusion (2VO-rat model). 2VO-animals were treated with KTP–NH₂ or IbKTP–NH₂ for 7 days at weeks 2 and 5 post-surgery. After behavioral testing (week 6), coronal sections of hippocampus were H&E-stained or immunolabeled for the cellular markers GFAP (astrocytes) and NFL (neurons). Our findings show that KTP-derivatives, mainly IbKTP–NH₂, enhanced cognitive impairment of 2VO-animals and prevented neuronal damage in hippocampal CA1 subfield, suggesting their potential usefulness for the treatment of dementia.

Chronic treatment with resveratrol, a natural polyphenol found in grapes, alleviates oxidative stress and apoptotic cell death in ovariectomized female rats subjected to chronic cerebral hypoperfusion

OBJECTIVES

Resveratrol appears to have neuroprotective potential in various animal models of brain disorders including cerebral ischemia and neurodegenerative diseases. Chronic cerebral hypoperfusion is a well-known pathological condition contributing to the neurodegenerative diseases such as vascular dementia. Purpose of the present study is to evaluate the possible therapeutic potential of resveratrol in a model of vascular dementia of ovariectomized female rats. Assessment of the potential was based on the determination of brain oxidative status, caspase-3 level, glial fibrillary acidic protein (GFAP), and neuronal damage on hippocampus and cerebral cortex.

METHODS

For creating the model of chronic cerebral hypoperfusion, ovariectomized female Wistar rats were subjected to the modified two vessel occlusion method, with the right common carotid artery being occluded first and the left one a week later.

RESULTS

At the 15th day following the ligation, neuronal damage was accompanied by the increased immunoreactivities of both GFAP and caspase-3, and significant neurodegeneration was evident in the hippocampus and cortex, all of which were significantly alleviated with resveratrol treatment (10 mg/kg). Biochemical analysis revealed that the resveratrol treatment decreased lipid peroxidation and restored reduced glutathione level as well.

DISCUSSION

The collected data of the present study suggest that the administration of resveratrol may provide a remarkable therapeutic benefit for vascular dementia, which is most likely related to the prevention of both apoptotic cell death and oxidative stress. We believe that therapeutic efficacy of resveratrol deserves to be tested for potential clinical application in postmenopausal elderly women suffering from vascular dementia.

Protective effect of Daming capsule against chronic cerebral ischemia

Background

Accumulating evidence has shown that chronic cerebral ischemia (CCI) is one of the major causes of vascular dementia (VD) characterized by dysregulated cholesterol homeostasis and lipoprotein disturbances. Positive value of lipid-lowering agents has been widely evaluated for the treatment of VD. In the present study, we investigated whether Daming capsule (DMC) protected against CCI-induced VD and its possible mechanisms of action. DMC is a multi-herbal formula composed of Rheum palmatum L., Cassia obtusifolia L., Salvia miltiorrhiza, and Panax ginseng C.A., which has been used to treat hyperlipidemia for years in China.

Methods

A network pharmacology method was established to reveal whether DMC contained any chemical constituent targeting CCI-related proteins. Furthermore, the potential anti-CCI effects of DMC (100 mg/kg or 200 mg/kg) administered for 30 days were investigated in vivo on rats that were subjected to permanent bilateral occlusion of the carotid arteries (2-VO). Spatial learning and memory abilities were evaluated using a Morris water maze (MWM) and morphological changes of cerebral cortex and hippocampus were assessed using hematoxylin and eosin staining. Moreover, the lipid peroxidation levels and antioxidative capabilities were measured using biochemical analysis.

Results

Our network pharmacology analysis revealed the existence of multiple CCI-related chemical-target interactions in DMC, suggesting a potential protective effect. An in vivo experiment verified that 200 mg/kg DMC improved cognitive deficits of 2-VO rats in the MWM test and attenuated pathological alterations in both the cerebral cortex and the hippocampus. Biochemical assays indicated that DMC decreased malondialdehyde levels and CCI-elevated superoxide dismutase activities, but increased the activities of glutathione peroxidase and catalase.

Conclusions

Our findings suggested that DMC protected against cognitive dysfunction and nerve injuries caused by CCI, which is most likely related to its antioxidant actions.

Animal models of vascular dementia: translational potential at the present time and in 2050

ABSTRACT: Vascular dementia is a heterogeneous syndrome, and includes subcortical ischemic vascular dementia. For translational research, subcortical ischemic vascular dementia is an appropriate target since this is the most prevalent subtype and exhibits relatively uniform clinical and neuropathological changes. These changes consist of hypertensive arteriolar changes, lacunar infarctions, hypertensive hemorrhage and white matter lesions. Among various species, rodents are most frequently used, but their small volume of white matter may impede analysis of white matter lesions. Primate models have a larger volume, but the degree of white matter lesions is inconsistent. Animal models should accommodate the effect of aging and comorbidities, and in the case of primate models, low accessibility should be overcome by repeated and quantitative examinations using modern neuroimaging techniques and functional measures, especially for memory and motor function. There is no model that replicates all features of subcortical ischemic vascular dementia and, therefore, rodent and primate models should be selected appropriately for translational research.

n-Butanol soluble fraction of the water extract of Chinese toon fruit ameliorated focal brain ischemic insult in rats via inhibition of oxidative stress and inflammation

AIM OF THE STUDY

Toona sinensis Roem. (Meliaceae; Toona sinensis; Chinese toon) is a type of arbor that is widely distributed in Asia. The fruits of Toona sinensis Roem has been traditionally recognized for treatment of cerebrovascular diseases. To evaluate the potential clinical use of the fruits of Toona sinensis Roem, we determined the dose dependence of the neuroprotective efficacy in a focal cerebral ischemic reperfusion model of rats and explored the underlying mechanisms.

MATERIALS AND METHODS

Rats were subjected to occlusion of the middle cerebral artery (MCAO) by a nylon filament and treated with different doses (20mg/kg and 30 mg/kg) of n-butanol soluble fraction of the water extract of Chinese toon fruit or the vehicle for 1 week before induction of ischemia, s.i.d..

RESULTS

n-Butanol soluble fraction of the water extract of Chinese toon fruit reduced in a dose-dependent manner the ischemia-induced cerebral infarct and edema volume and attenuated neurological deficits observed at 6h point after ischemia. n-Butanol soluble fraction of the water extract of Chinese toon fruit reduced the levels of nitrate, nitrite, lipid peroxidation, cyclooxygenase-1, thromboxane in post-ischemic brain. n-Butanol soluble fraction of the water extract of Chinese toon fruit adjusted the elevation of the activity of glutathione peroxidase and superoxide dismutase in ischemic brain.

CONCLUSIONS

The present study was the first evidence of effectiveness of n-butanol soluble fraction of the water extract of Chinese toon fruit in the rat stroke models, as it reduced infarct volume, inhibited the oxidative stress and inflammation.

Ligustilide alleviates brain damage and improves cognitive function in rats of chronic cerebral hypoperfusion

ETHNOPHARMACOLOGICAL RELEVANCE

Ligustilide (LIG), a main lipophilic component of Danggui (Chinese Angelica root, Radix Angelica sinensis) which is a popular used herb to treat menstrual disorders in traditional chinese medicine, has been reported to possess some neuroprotective effects on permanent focal ischemia and transient forebrain ischemia.

AIM OF THE STUDY

Based on previous work, we intended to investigate the protective effects of LIG on parietal cortex and hippocampus of rats in chronic cerebral hypoperfusion model.

MATERIALS AND METHODS

Chronic cerebral hypoperfusion was induced by permanent, bilateral common carotid artery's occlusion (2VO). The rats were treated with LIG (80mg/kg, by oral) from the eighth day after surgery for seven consecutive days. Their spatial learning and memory abilities were assessed using the Morris water maze. After six days for maze test, rats were sacrificed. Coronal sections in cortex and hippocampus were stained with cresyl violet or labeled with NeuN (Neuronal Nuclei), MAP-2 (Microtubule-Associated Protein-2), Caspase-3 and GFAP (Glial Fibrillary Acidic Protein) antibodies.

RESULTS

LIG treatment for seven days decreased escape latency and swimming distance of 2VO rats from the third day in maze tests, and increased percent time in the target quadrant. LIG prevented neuronal loss, dendrites damage and neuronal apoptosis in both parietal cortex and hippocampus of 2VO rats; and it also inhibited astrocytic activation and proliferation stimulated by hypoperfusion.

CONCLUSIONS

These results demonstrate that LIG show obvious neuroprotective potential for treating chronic cerebral hypoperfusion injury, which may be attributed to its anti-apoptosis of neuron and anti-proliferation of astrocyte both in cortex and in hippocampus of 2VO rats. We suggest that LIG can be developed as an effective drugs for the prevention of vascular dementia (VD).

Brain damage in preterm newborns and maternal medication: the ELGAN Study

OBJECTIVE

We sought to evaluate the association between maternal medication use during pregnancy and cerebral white matter damage and cerebral palsy (CP) among very preterm infants.

STUDY DESIGN

This analysis of data from the Extremely Low Gestational Age Newborns (ELGAN) Study included 877 infants born <28 weeks' gestation. Mothers were interviewed, charts were reviewed, placentas were cultured and assessed histologically, and children were evaluated at 24 months corrected age. A diagnostic algorithm classified neurologic findings as quadriparetic CP, diparetic CP, hemiparetic CP, or no CP.

RESULTS

After adjustment for the potential confounding of disorders for which medications might have been indicated, the risk of quadriparetic CP remained elevated among the infants of mothers who consumed aspirin (odds ratio [OR], 3.0; 95% confidence interval [CI], 1.3-6.9) and nonsteroidal antiinflammatory drugs (NSAIDs) (OR, 2.4; 95% CI, 1.04-5.8). The risk of diparetic CP was also associated with maternal consumption of an NSAID, but only if the consumption was not approved by a physician (OR, 3.5; 95% CI 1.1-11.0).

CONCLUSION

The possibility that aspirin and NSAID use in pregnancy could lead to perinatal brain damage cannot be excluded.

Changes in oxidative metabolism and memory and learning in an cerebral hypoperfusion model in rats

INTRODUCTION

Chronic hypoperfusion in rats produces memory and learning impairments due to permanent occlusion of commun carotid arteries (POCCA). Molecular mechanisms leading to behavioural disorders have been poorly studied. For this reason, the aim of the present study was to characterise oxidative metabolism disorders and their implications in memory and learning impairments.

METHODS

Superoxide dismutase (SOD) and catalase (CAT) activities were determined in cortex, hippocampus and striatum homogenates at 24 hours and at 22 days after the lesion. Haematoxylin-eosin staining and glial fibrillary acidic protein (GFAP) immunoreactivity were performed on coronal sections. Behavioural impairments were explored using the Morris water maze (MWM). Escape latencies were determined in all behavioural studies.

RESULTS

The lesion induced a significant increase (P<.01) in CAT activity in the cortex at 24 hours, while SOD activity was significantly higher (P<.01) in the cortex and hippocampus at 22 days. An intense vacuolization was observed in the cortex and striatum as a result of the lesion. A neuronal loss in the striatum and hippocampus was observed. The glial reaction increased in the cortex and striatum. Visual alterations were observed in the lesion group with the lowest evolution time (P<.001). Escape latencies, corresponding to MWM schemes for long-term and short-term memory evaluation increased significantly (P<.05) in both groups of lesioned animals.

CONCLUSION

It was concluded that changes in SOD and CAT activities indicate a possible implication of oxidative imbalance in the pathology associated with chronic cerebral hypoperfusion. In addition, the POCCA model in rats is useful for understanding mechanisms by which cerebral hypoperfusion produces memory and learning impairments.

Bilateral common carotid artery ligation transiently changes brain lipid metabolism in rats

Brain lipid metabolism was studied in rats following permanent bilateral common carotid artery ligation (BCCL), a model for chronic cerebral hypoperfusion. Unesterified (free) fatty acids (uFA) and acyl-CoA concentrations were measured 6 h, 24 h, and 7 days after BCCL or sham surgery, in high energy-microwaved brain. In BCCL compared to sham rats, cytosolic phospholipase A(2) (cPLA(2)) immunoreactivity in piriform cortex, and concentrations of total uFA and arachidonoyl-CoA, an intermediate for arachidonic acid reincorporation into phospholipids, were increased only at 6 h. At 24 h, immunoreactivity for secretory phospholipase A(2) (sPLA(2)), which may regulate blood flow, was increased near cortical and hippocampal blood vessels. BCCL did not affect levels of brain IB(4)+ microglia, glial fibrillary acidic protein (GFAP)+ astrocytes, cyclooxygenase-2 (COX-2) immunoreactivity at any time, but increased cPLA(2) immunoreactivity in one region at 6 h. Thus, BCCL affected brain lipid metabolism transiently, likely because of compensatory sPLA(2)-mediated vasodilation, without producing evidence of neuroinflammation.

Parecoxib mitigates spatial memory impairment induced by sevoflurane anesthesia in aged rats

BACKGROUND

Inflammation in brain plays a critical role in the pathogenesis of cognitive impairment. Anti-inflammatory therapy may thus constitute a novel approach for associated cognitive dysfunction. The present study investigated the effects of parecoxib in the prevention of cognitive impairments induced by sevoflurane in aged rats.

METHODS

Sixty-six aged rats were divided randomly into three groups: control group (n = 22, sham anesthesia), sevoflurane group (n = 22, received 2% sevoflurane for 5 h) and parecoxib group (n = 22, received intraperitoneal injections of 10 mg/kg parecoxib and then exposed to 2% sevoflurane for 5 h). Spatial learning performance was tested by Morris water maze. The expression of cyclooxygenase-2 protein and ultrastructure of synapse in hippocampus were measured.

RESULTS

Sevoflurane anesthesia impaired the spatial learning and memory in aged rats. Compared with sevoflurane group, parecoxib group showed shorter escape latency and more number of crossings over the previous platform area. Furthermore, parecoxib treatment also significantly prevented the synaptic changes induced by sevoflurane.

CONCLUSION

Parecoxib mitigates spatial memory impairment induced by sevoflurane anesthesia in aged rats. The synaptic morphometry change may be one of the mechanisms involved in learning and memory deficit.

Effects of chronic guanosine treatment on hippocampal damage and cognitive impairment of rats submitted to chronic cerebral hypoperfusion

Chronic cerebral hypoperfusion contributes to a cognitive decline related to brain disorders. Its experimental model in rats is a permanent bilateral common carotid artery occlusion (2VO). Overstimulation of the glutamatergic system excitotoxicity due to brain energetic disturbance in 2VO animals seems to play a pivotal role as a mechanism of cerebral damage. The nucleoside guanosine (GUO) exerts extracellular effects including antagonism of glutamatergic activity. Accordingly, our group demonstrated several neuroprotective effects of GUO against glutamatergic excitotoxicity. Therefore, in this study, we evaluated a chronic GUO treatment effects in rats submitted to 2VO. We evaluated the animals performance in the Morris water maze and hippocampal damage by neurons and astrocytes immunohistochemistry. In addition, we investigated the cerebrospinal fluid (CSF) brain derived neurotrophic factor (BDNF) and serum S100B levels. Additionally, the purine CSF and plasma levels were determined. GUO treatment did not prevent the cognitive impairment promoted by 2VO. However, none of the 2VO animals treated with GUO showed differences in the hippocampal regions compared to control, while 20% of 2VO rats not treated with GUO presented loss of pyramidal neurons and increased glial labeling cells in CA1 hippocampal region. In addition, we did not observe differences in CSF BDNF nor serum S100B levels among the groups. Of note, both the 2VO surgery and GUO treatment changed the purine CSF and plasma profile. In conclusion, GUO treatment did not prevent the cognitive impairment observed in 2VO animals, but our data suggest that GUO could be neuroprotective against hippocampal damage induced by 2VO.

Chronic brain hypoperfusion causes early glial activation and neuronal death, and subsequent long-term memory impairment

Reduction of cerebral blood flow is an important risk factor for dementia states and other brain dysfunctions. In present study, the effects of permanent occlusion of common carotid arteries (2VO), a well established experimental model of brain ischemia, on memory function were investigated, as assessed by reference and working spatial memory protocols and the object recognition task; cell damage to the hippocampus, as measured through changes in immunoreactivity for GFAP and the neuronal marker NeuN was also studied. The working hypothesis is that metabolic impairment following hypoperfusion will affect neuron and glial function and result in functional damage. Adult male Wistar rats were submitted to the modified 2VO method, with the right common carotid artery being occluded first and the left one week later, and tested seven days, three and six months after the ischemic event. A significant cognitive deficit was found in both reference and working spatial memory, as well as in the object recognition task, three and six months after surgery. Neuronal death and reactive astrogliosis were already present at 7 days and continued for up to 3 months after the occlusion; interestingly, there was no significant reduction in hippocampal volume. Present data suggests that cognitive impairment caused by brain hypoperfusion is long - lasting and persists beyond the time point of recovery from glial activation and neuronal loss.

Dynamics of dystroglycan complex proteins and laminin changes due to angiogenesis in rat cerebral hypoperfusion

Permanent bilateral carotid occlusion is a well known cerebral hypoperfusion model in rats. The aim of our study was to investigate the different stages of vascular reaction by detecting changes in the extracellular martix proteins and to examine their relationship to angiogenesis after occlusion. Experiments were performed on adult male rats. Brain samples were investigated from day 1 to day 30 post-surgery. Immunohistochemical analysis was performed on the whole hippocampus and on the adjacent cortex in order to investigate extracellular martix proteins, such as the markers of dystroglycan complex (β-dystroglycan, α-dystrobrevin and utrophin) and a marker of basal lamina (laminin). The levels of the proteins were estimated by western blot analysis. Vascular density as well as blood-brain barrier permeability were studied on brain slices from the same regions. Our results showed altered laminin and β-dystroglycan immunoreactivity beginning 2 days after the onset of occlusion followed by an increased utrophin immunoreactivity without blood-brain barrier disruption 5 days later. By day 30 of hypoperfusion, when increased vascular density was detected, all changes returned to baseline levels. Western blot analysis showed significant differences in β-dystroglycan and utrophin expression. Our results indicate that the different stages of neovascularisation resulting from cerebral hypoperfusion can be well defined by the markers laminin, β-dystroglycan, and utrophin and that these markers are more likely to correlate with glio-vascular decoupling than does altered blood-brain barrier function.

The modified 2VO ischemia protocol causes cognitive impairment similar to that induced by the standard method, but with a better survival rate

Permanent bilateral occlusion of the common carotid arteries (2VO) in the rat has been established as a valid experimental model to investigate the effects of chronic cerebral hypoperfusion on cognitive function and neurodegenerative processes. Our aim was to compare the cognitive and morphological outcomes following the standard 2VO procedure, in which there is concomitant artery ligation, with those of a modified protocol, with a 1-week interval between artery occlusions to avoid an abrupt reduction of cerebral blood flow, as assessed by animal performance in the water maze and damage extension to the hippocampus and striatum. Male Wistar rats (N = 47) aged 3 months were subjected to chronic hypoperfusion by permanent bilateral ligation of the common carotid arteries using either the standard or the modified protocol, with the right carotid being the first to be occluded. Three months after the surgical procedure, rat performance in the water maze was assessed to investigate long-term effects on spatial learning and memory and their brains were processed in order to estimate hippocampal volume and striatal area. Both groups of hypoperfused rats showed deficits in reference (F(₈,₁₇₂) = 7.0951, P < 0.00001) and working spatial memory [2nd (F(₂,₄₄) = 7.6884, P < 0.001), 3rd (F(₂,₄₄) = 21.481, P < 0.00001) and 4th trials (F(₂,₄₄) = 28.620, P < 0.0001)]; however, no evidence of tissue atrophy was found in the brain structures studied. Despite similar behavioral and morphological outcomes, the rats submitted to the modified protocol showed a significant increase in survival rate, during the 3 months of the experiment (P < 0.02).

Expression of enzymes involved in the prostanoid metabolism by cortical astrocytes after LPS-induced inflammation

Neuroinflammatory processes are a common epiphenomenon for a number of neurological and neurodegenerative diseases. Besides microglia, astrocytes are implicated in brain inflammation in response to harmful stimuli and pathological processes. Bacterial endotoxins can induce the synthesis and release of proinflammatory mediators, i.e., cytokines and chemokines, by astroglia. In this study, we have investigated the effect of lipopolysaccharide (LPS) treatment on the expression of enzymes of prostanoid synthesis and degradation in cultured mouse cortical astrocytes using an Affymetrix Gene Chip array, quantitative reverse transcriptase polymerase chain reaction (RT-PCR), and an enzyme-immunosorbent assay. LPS treatment induced an upregulation of enzymes responsible for prostaglandin E2 synthesis, a downregulation of enzymes that catalyzes prostaglandin E2 (PGE2) degradation and production of proinflammatory leukotrienes. Changes in enzyme expression were accompanied by a highly significant increase in extracellular PGE2. Our data demonstrate that astrocytes are directly involved in the complex regulation of proinflammatory prostanoids in the CNS under pathological processes, thus being of potential interest as targets for therapeutical interventions. Further studies are required to unravel the different roles and interactions between astroglia and other cells of the brain-intrinsic innate immune system during inflammation.