Effects of gemfibrozil on outcome after permanent middle cerebral artery occlusion in mice

Neuroprotective effects of gemfibrozil in neurological disorders: Focus on inflammation and molecular mechanisms

BACKGROUND

Gemfibrozil (Gem) is a drug that has been shown to activate PPAR-α, a nuclear receptor that plays a key role in regulating lipid metabolism. Gem is used to lower the levels of triglycerides and reduce the risk of coronary heart disease in patients. Experimental studies in vitro and in vivo have shown that Gem can prevent or slow the progression of neurological disorders (NDs), including cerebral ischemia (CI), Alzheimer's disease (AD), Parkinson's disease (PD), and multiple sclerosis (MS). Neuroinflammation is known to play a significant role in these disorders.

METHOD

The literature review for this study was conducted by searching Scopus, Science Direct, PubMed, and Google Scholar databases.

RESULT

The results of this study show that Gem has neuroprotective effects through several cellular and molecular mechanisms such as: (1) Gem has the ability to upregulate pro-survival factors (PGC-1α and TFAM), promoting the survival and function of mitochondria in the brain, (2) Gem strongly inhibits the activation of NF-κB, AP-1, and C/EBPβ in cytokine-stimulated astroglial cells, which are known to increase the expression of iNOS and the production of NO in response to proinflammatory cytokines, (3) Gem protects dopamine neurons in the MPTP mouse model of PD by increasing the expression of PPARα, which in turn stimulates the production of GDNF in astrocytes, (4) Gem reduces amyloid plaque pathology, reduces the activity of glial cells, and improves memory, (5) Gem increases myelin genes expression (MBP and CNPase) via PPAR-β, and (6) Gem increases hippocampal BDNF to counteract depression.

CONCLUSION

According to the study, Gem was investigated for its potential therapeutic effect in NDs. Further research is needed to fully understand the therapeutic potential of Gem in NDs.

Oxyberberine protects middle cerebral artery occlusion triggered cerebral injury through TLR4/NLRP3 pathway in rats

Cerebral ischemia is a life-threatening health concern that leads to severe neurological complications and fatalities worldwide. Although timely intervention with clot-removing agents curtails serious post-stroke neurological dysfunctions, no effective neuroprotective intervention is available for addressing post-recanalization neuroinflammation. Herein, for the first time we studied the effect of oxyberberine (OBB), a derivative of berberine, on transient middle cerebral artery occlusion (MCAO)-generated neurological consequences in Sprague-Dawley rats. The MCAO-operated rats exhibited significant somatosensory and sensorimotor dysfunctions in adhesive removal, foot fault, paw whisker, and rotarod assays at 1 and 3 days post-surgery. These MCAO-generated neurological deficits were prevented in OBB-treated (50 and 100 mg/kg) rats, and also coincided with a smaller infarct area (in 2,3,5-triphenyl tetrazolium chloride staining) and decreased neuronal death (in cresyl violet staining) in the ipsilateral hemisphere of these animals. The immunostaining of neuronal nuclear protein (NeuN) and glial-fibrillary acidic protein (GFAP) also echoes the neuroprotective nature of OBB. The increased expression of neuroinflammatory and blood-brain barrier tight junction proteins like toll-like receptor 4 (TLR4), TRAF-6, nuclear factor kappa B (NF-κB), pNF-κB, nNOS, ASC, and IKBα in the ipsilateral part of MCAO-operated rats were restored to normal following OBB treatment. We also observed the decline in plasma levels/mRNA transcription of TNF-α, IL-1β, NLRP3, IL-6, and matrix metalloproteinase-9 and increased expression of occludin and claudin in OBB-treated rats. These outcomes imply that OBB may prevent the MCAO-induced neurological consequences and neuroinflammation by interfering with TLR4 and NLRP3 signaling in rats.

Integrating network pharmacology and bioinformatics to explore and experimentally verify the regulatory effect of Buyang Huanwu decoction on glycolysis and angiogenesis after cerebral infarction

ETHNOPHARMACOLOGICAL RELEVANCE

Promoting the recovery of cerebral blood circulation after cerebral infarction (CI) is an important intervention. Buyang Huanwu decoction (BHD) is a classic prescription for treating CI that promotes angiogenesis. Cytoplasmic glycolysis ischaemic-region cells after CI may be highly activated to maintain metabolic activity under hypoxia. From the perspective of long-term maintenance of glycolytic metabolism in the ischaemic area after CI, it may be beneficial to promote angiogenesis and maintain glial cell activation and neuronal survival. In this context, the regulatory relationship of lncRNAs and miRNAs with mRNAs is worthy of attention. Mining the competitive binding relationships among RNAs will aid in the screening of key gene targets post-CI. In this study, network pharmacology and bioinformatics were used to construct a ceRNA network, screen key targets, and explore the effect of glycolysis on angiogenesis during BHD-mediated CI regulation.

AIM OF THE STUDY

This study aimed to explore the effect of BHD on angiogenesis after glycolysis regulation in CI.

MATERIALS AND METHODS

According to the 21 active BHD ingredients we identified by our research team, we conducted network pharmacology. BHD targets that can regulate glycolysis and angiogenesis after CI were screened from the GeneCards, CTD and OMIM databases. We retrieved CI-related datasets from the GEO database and screened for differentially expressed lncRNAs and miRNAs. LncRNA‒miRNA-mRNA/TF targeting relationships were screened and organized with the miRcode, miRDB, TargetScan, miRWalk, and TransmiR v2.0 databases. Cytoscape was used to construct an lncRNA‒miRNA-mRNA/TF ceRNA network. Through BioGPS, key mRNAs/TFs in the network were screened for enrichment analysis. Animal experiments were then conducted to validate some key mRNAs/TFs and enriched signalling pathways.

RESULTS

PFKFB3 and other genes may help regulate glycolysis and angiogenesis through AMPK and other signalling pathways. The anti-CI effect of BHD may involve maintaining activation of genes such as AMPK and PFKFB3 in the ischaemic cortex, maintaining moderate glycolysis levels in brain tissue, and promoting angiogenesis.

CONCLUSION

BHD can regulate glycolysis and promote angiogenesis after CI through multiple pathways and targets, in which AMPK signalling pathway activation may be important.

TREM2 regulates microglial lipid droplet formation and represses post-ischemic brain injury

Triggering receptor expressed on myeloid cells 2 (TREM2) is a transmembrane receptor protein predominantly expressed in microglia within the central nervous system (CNS). TREM2 regulates multiple microglial functions, including lipid metabolism, immune reaction, inflammation, and microglial phagocytosis. Recent studies have found that TREM2 is highly expressed in activated microglia after ischemic stroke. However, the role of TREM2 in the pathologic response after stroke remains unclear. Herein, TREM2-deficient microglia exhibit an impaired phagocytosis rate and cholesteryl ester (CE) accumulation, leading to lipid droplet formation and upregulation of Perilipin-2 (PLIN2) expression after hypoxia. Knockdown of TREM2 results in increased lipid synthesis (PLIN2, SOAT1) and decreased cholesterol clearance and lipid hydrolysis (LIPA, ApoE, ABCA1, NECH1, and NPC2), further impacting microglial phenotypes. In these lipid droplet-rich microglia, the TGF-β1/Smad2/3 signaling pathway is downregulated, driving microglia towards a pro-inflammatory phenotype. Meanwhile, in a neuron-microglia co-culture system under hypoxic conditions, we found that microglia lost their protective effect against neuronal injury and apoptosis when TREM2 was knocked down. Under in vivo conditions, TREM2 knockdown mice express lower TGF-β1 expression levels and a lower number of anti-inflammatory M2 phenotype microglia, resulting in increased cerebral infarct size, exacerbated neuronal apoptosis, and aggravated neuronal impairment. Our work suggests that TREM2 attenuates stroke-induced neuroinflammation by modulating the TGF-β1/Smad2/3 signaling pathway. TREM2 may play a direct role in the regulation of inflammation and also exert an influence on the post-ischemic inflammation and the stroke pathology progression via regulation of lipid metabolism processes. Thus, underscoring the therapeutic potential of TREM2 agonists in ischemic stroke and making TREM2 an attractive new clinical target for the treatment of ischemic stroke and other inflammation-related diseases.

Gemfibrozil Improves Microcirculatory Oxygenation of Colon and Liver without Affecting Mitochondrial Function in a Model of Abdominal Sepsis in Rats

Recent studies observed, despite an anti-hyperlipidaemic effect, a positive impact of fibrates on septic conditions. This study evaluates the effects of gemfibrozil on microcirculatory variables, mitochondrial function, and lipid peroxidation levels with regard to its potential role as an indicator for oxidative stress in the colon and liver under control and septic conditions and dependencies on PPARα-mediated mechanisms of action. With the approval of the local ethics committee, 120 Wistar rats were randomly divided into 12 groups. Sham and septic animals were treated with a vehicle, gemfibrozil (30 and 100 mg/kg BW), GW 6471 (1 mg/kg BW, PPARα inhibitor), or a combination of both drugs. Sepsis was induced via the colon ascendens stent peritonitis (CASP) model. Then, 24 h post sham or CASP surgery, a re-laparotomy was performed. Measures of vital parameters (heart rate (HR), mean arterial pressure (MAP), and microcirculation (µHbO2)) were recorded for 90 min. Mitochondrial respirometry and assessment of lipid peroxidation via a malondialdehyde (MDA) assay were performed on colon and liver tissues. In the untreated sham animals, microcirculation remained stable, while pre-treatment with gemfibrozil showed significant decreases in the microcirculatory oxygenation of the colon. In the CASP animals, µHbO2 levels in the colon and the liver were significantly decreased 90 min after laparotomy. Pre-treatment with gemfibrozil prevented the microcirculatory aberrations in both organs. Gemfibrozil did not affect mitochondrial function and lipid peroxidation levels in the sham or CASP animals. Gemfibrozil treatment influences microcirculation depending on the underlying condition. Gemfibrozil prevents sepsis-induced microcirculatory aberrances in the colon and liver PPARα-independently. In non-septic animals, gemfibrozil impairs the microcirculatory variables in the colon without affecting those in the liver.

Laser Speckle Flowmetry for the Prognostic Estimation Study of Permanent Focal Ischemia in Mice

The distal middle cerebral artery occlusion (dMCAO) model that mainly targets the cortex and causes low mortality is developed for the study of permanent focal ischemia, and it is highly appropriate for the study in the aged population. The two most common methods used to establish dMCAO models are dMCAO alone and dMCAO plus ipsilateral common carotid artery occlusion (CCAO). Up to now, studies on the prognosis of the two types of dMCAO models and the accuracy of cerebral blood flow (CBF) in predicting prognosis have not yet been reported. In the present study, we established permanent focal ischemia models in two groups of aged mice by dMCAO alone or by dMCAO plus ipsilateral common carotid artery occlusion (CCAO). CBF was evaluated by laser speckle flowmetry (LSF) before and after surgery. Cerebral infarction was assessed by TTC staining at day 2 after surgery and MAP2 staining at day 21 after surgery. In addition, behavioral outcomes were evaluated using the modified Garcia scoring system, adhesive removal test, and foot-fault test. Our results showed that compared with those in the dMCAO alone group, the mice in the dMCAO plus CCAO group had a larger cerebral infarct size and more severe neurological deficits. According to the results of the correlation analysis, the area of the ischemic core region on CBF imaging in the dMCAO group was helpful in predicting the infarct volume. In addition, the total CBF of the ischemic area in the dMCAO plus CCAO group showed a significant correlation with Garcia scores 3 days after surgery, but there was no significant correlation of CBF imaging with the foot-fault test 7 days after surgery. These results suggest that the total CBF of the ischemic area might be helpful to predict the severity of neurological damage at the acute stage.

Gemfibrozil, a lipid-lowering drug, reduces anxiety, enhances memory, and improves brain oxidative stress in d-galactose-induced aging mice

Gemfibrozil (GFZ) is a lipid-lowering drug with several other effects, such as antioxidant and anti-inflammatory activities. In the current study, chronic d-galactose treatment (d-gal, 150 mg/kg/day; i.p., 6 weeks) induced a model of accelerated aging in male mice and was used to study the behavioral, anti-oxidative, and neuroprotective effects of GFZ (100 mg/kg/day; p.o.). Anxiety-like behaviors were assessed using the elevated plus-maze while working memory was measured by spontaneous alternation in a Y-maze. Brain oxidative stress was determined by measuring malondialdehyde (MDA) levels, superoxide dismutase (SOD), and glutathione peroxidase (GPx) activities. Neuropathological evaluation of the brain with hematoxylin-eosin and Masson's trichrome staining was also performed. The results demonstrated that the anxious-like phenotype and the cognitive impairments observed in d-gal-treated mice could be prevented in those animals coadministered with GFZ. Besides, the decrease in SOD and GPx antioxidant enzymatic activities and increase of MDA levels were also prevented in the brains of d-gal plus GFZ treated mice. Preliminary hematoxylin-eosin staining also suggested neuroprotective effects of GFZ. The results of Masson's trichrome staining showed no evidence of fibrosis in brain sections of different experimental groups. The current data provide novel insights into GFZ in the d-galactose-induced aging mouse model that open promising future research lines to determine inflammatory mediators and cell signaling underlying these effects.

Gemfibrozil attenuates doxorubicin induced toxicity in renal tissues of male rats by reducing the oxidative insult and inflammation

Nephrotoxicity is a significant side effect of doxorubicin (DXN) treatment. We investigated the protective effect of gemfibrozil (GEM) co-administration with DXN on DXN induced nephrotoxicity. We divided 28 male Wistar rats into four groups of seven. Group 1 received normal saline for 2 weeks. Group 2 received 15 mg/kg DXN for 2 weeks. Group 3 received DXN + GEM for 2 weeks. Group 4 received GEM for 2 weeks. On day 15 of the experiment, blood samples were collected, animals were sacrificed and kidneys were excised for biochemical and histological evaluation. We measured serum creatinine, blood urine nitrogen, renal malondialdehyde, nitric oxide, glutathione, superoxide dismutase, glutathione peroxidase, catalase, tumor necrosis factor-α and interleukin-1β. GEM administration mitigated DXN induced nephrotoxicity. GEM co-administered with DXN attenuated the inflammatory and oxidative responses associated with DXN induced nephrotoxicity.

Wallerian degeneration in experimental focal cortical ischemia

Wallerian degeneration (WaD), commonly secondary to cerebral infarction, is the descending damage of fiber tracts with their accompanying myelin sheaths. However, whether this sequential injury can occur in non-ischemic corpus callosum (CC) and striatum in focal cortical ischemic model has not been fully demonstrated. The present study aimed to elucidate detailed histopathologic changes in CC and striatum after acute focal cortical infarction induced by permanent distal middle cerebral artery occlusion (dMCAO) in Sprague-Dawley rat. We found that myelin integrity, myelin-related proteins, MBP and MAG, and NF200-marked neurofilaments were all compromised in non-ischemic white matter regions, bilateral CC and ipsilateral striatum, along with cortical ischemia (all P < 0.05). Electron microscopy showed wide gaps between myelin sheath layers or between axon and myelin, with an abnormal folding of myelin sheath, and enlarged fluid-filled areas. APP accumulations were noted at 24 h post-dMCAO in those non-ischemic regions, and the deposition prolonged until 14 days after cortical ischemia (all P < 0.05). Moreover, in these areas, microglia and astrocytes were robustly and persistently activated in different patterns. No substantial changes were observed in contralateral striatum. In conclusion, our results suggest that WaD may be involved in non-ischemic CC and striatum after focal cortical infarction, accompanied by APP aggregation and neuroglia initiation forming the glial scar.

Protective Effect of Gemfibrozil on Hepatotoxicity Induced by Acetaminophen in Mice: the Importance of Oxidative Stress Suppression

Purpose: Gemfibrozil (GEM) apart from agonist activity at peroxisome proliferator-activated receptor-alpha (PPAR-α) has antioxidant and anti-inflammatory properties. Accordingly, the present study was designed to investigate the protective effect of GEM on acute liver toxicity induced by acetaminophen (APAP) in mice.

Methods: In this study, mice divided in seven groups include, control group, APAP group, GEM group, three APAP groups pretreated with GEM at the doses of 25, 50 and 100 mg/kg respectively and APAP group pretreated with N-Acetyl cysteine. GEM, NAC or vehicle were administered for 10 days. In last day, GEM and NAC were gavaged 1 h before and 1 h after APAP injection. Twenty four hours after APAP, mice were sacrificed. Serum parameters include alanine aminotransferase (ALT), aspartate aminotransferase (AST) and liver tissue markers including catalase enzyme activity, reactive oxygen species (ROS), malondialdehyde and reduced glutathione (GSH) levels determined and histopathological parameters measured.

Results: GEM led to significant decrease in serum ALT and AST activities and increase in catalase activity and hepatic GSH level and reduces malondialdehyde and ROS levels in the liver tissue. In confirmation, histopathological findings revealed that GEM decrease degeneration, vacuolation and necrosis of hepatocytes and infiltration of inflammatory cells.

Conclusion: Present data demonstrated that GEM has antioxidant properties and can protect the liver from APAP toxicity, just in the same pathway that toxicity occurs by toxic ROS and that GEM may be an alternative therapeutic agent to NAC in APAP toxicity.

Gemfibrozil has antidepressant effects in mice: Involvement of the hippocampal brain-derived neurotrophic factor system

Major depressive disorder has become one of the most serious neuropsychiatric disorders worldwide. However, currently available antidepressants used in clinical practice are ineffective for a substantial proportion of patients and always have side effects. Besides being a lipid-regulating agent, gemfibrozil is an agonist of peroxisome proliferator-activated receptor-α (PPAR-α). We investigated the antidepressant effects of gemfibrozil on C57BL/6J mice using the forced swim test (FST) and tail suspension test (TST), as well as the chronic unpredictable mild stress (CUMS) model of depression. The changes in brain-derived neurotrophic factor (BDNF) signaling cascade in the brain after CUMS and gemfibrozil treatment were further assessed. Pharmacological inhibitors and lentivirus-expressed short hairpin RNA (shRNA) were also used to clarify the antidepressant mechanisms of gemfibrozil. Gemfibrozil exhibited significant antidepressant actions in the FST and TST without affecting the locomotor activity of mice. Chronic gemfibrozil administration fully reversed CUMS-induced depressive-like behaviors in the FST, TST and sucrose preference test. Gemfibrozil treatment also restored CUMS-induced inhibition of the hippocampal BDNF signaling pathway. Blocking PPAR-α and BDNF but not the serotonergic system abolished the antidepressant effects of gemfibrozil on mice. Gemfibrozil produced antidepressant effects in mice by promoting the hippocampal BDNF system.

The Positive Regulation of eNOS Signaling by PPAR Agonists in Cardiovascular Diseases

Increasing evidence shows that activation of peroxisome proliferator-activated receptors (PPARs) plays an essential role in the regulation of vascular endothelial function through a range of mechanisms, including non-metabolic. Among these, the PPAR-mediated activation of endothelial nitric oxide synthase (eNOS) appears to be of considerable importance. The regulated and sustained bioavailability of nitric oxide (NO) in the endothelium is essential to avoid the development of cardiovascular diseases such as hypertension or atherosclerosis. Therefore, a deeper understanding of the different effects of specific PPAR ligands on NO bioavailability could be useful in the development of novel or multi-targeted PPAR agonists. In this review, we report the most meaningful and up-to-date in vitro and in vivo studies of the regulation of NO production performed by different PPAR agonists. Insights into the molecular mechanisms of PPAR-mediated eNOS activation are also provided. Although findings from animal studies in which the activation of PPARα, PPARβ/δ, or PPARγ have provided clear vasoprotective effects have been promising, several benefits from PPAR agonists are offset by unwanted outcomes. Therefore, new insights could be useful in the development of tissue-targeted PPAR agonists with more tolerable side effects to improve treatment options for cardiovascular diseases.

Deletion of the WNK3-SPAK kinase complex in mice improves radiographic and clinical outcomes in malignant cerebral edema after ischemic stroke

The WNK-SPAK kinase signaling pathway controls renal NaCl reabsorption and systemic blood pressure by regulating ion transporters and channels. A WNK3-SPAK complex is highly expressed in brain, but its function in this organ remains unclear. Here, we investigated the role of this kinase complex in brain edema and white matter injury after ischemic stroke. Wild-type, WNK3 knockout, and SPAK heterozygous or knockout mice underwent transient middle cerebral artery occlusion. One cohort of mice underwent magnetic resonance imaging. Ex-vivo brains three days post-ischemia were imaged by slice-selective spin-echo diffusion tensor imaging magnetic resonance imaging, after which the same brain tissues were subjected to immunofluorescence staining. A second cohort of mice underwent neurological deficit analysis up to 14 days post-transient middle cerebral artery occlusion. Relative to wild-type mice, WNK3 knockout, SPAK heterozygous, and SPAK knockout mice each exhibited a >50% reduction in infarct size and associated cerebral edema, significantly less demyelination, and improved neurological outcomes. We conclude that WNK3-SPAK signaling regulates brain swelling, gray matter injury, and demyelination after ischemic stroke, and that WNK3-SPAK inhibition has therapeutic potential for treating malignant cerebral edema in the setting of middle cerebral artery stroke.

Icariin attenuates cerebral ischemia-reperfusion injury through inhibition of inflammatory response mediated by NF-κB, PPARα and PPARγ in rats

Icariin (ICA), an active flavonoid extracted from Chinese medicinal herb Epimedii, has been reported to exhibit many pharmacological effects including alleviating brain injury. However, little is known about the protection of ICA on ischemic stroke. Hence, this study was designed to investigate the neuroprotective effect of ICA and explore its underlying mechanisms on ischemic stroke induced by cerebral ischemia-reperfusion (I/R) injury in rats. The animals were pretreated with ICA at doses of 10, 30mg/kg twice per day for 3 consecutive days followed by cerebral I/R injury induced by middle cerebral artery occlusion (MCAO) for 2h and reperfusion for 24h. Neurological function and infarct volume were observed at 24h after reperfusion, the protein expression levels of interleukin-1β (IL-1β), transforming growth factor-β1 (TGF-β1), PPARα and PPARγ, inhibitory κB-α (IκB-α) degradation and nuclear factor κB (NF-κB) p65 phosphorylation were detected by Western blot, respectively. It was found that pretreatment with ICA could decrease neurological deficit score, diminish the infarct volume, and reduce the protein levels of IL-1β and TGF-β1. Moreover, ICA suppressed IκB-α degradation and NF-κB activation induced by I/R. Furthermore, the present study also showed that ICA up-regulated PPARα and PPARγ protein levels. These findings suggest that ICA has neuroprotective effect on ischemic stroke in rats through inhibition of inflammatory responses mediated by NF-κB and PPARα and PPARγ.

White matter injury and microglia/macrophage polarization are strongly linked with age-related long-term deficits in neurological function after stroke

Most of the successes in experimental models of stroke have not translated well to the clinic. One potential reason for this failure is that stroke mainly afflicts the elderly and the majority of experimental stroke studies rely on data gathered from young adult animals. Therefore, in the present study we established a reliable, reproducible model of stroke with low mortality in aged (18month) male mice and contrasted their pathophysiological changes with those in young (2month) animals. To this end, mice were subjected to permanent tandem occlusion of the left distal middle cerebral artery (dMCAO) with ipsilateral common carotid artery occlusion (CCAO). Cerebral blood flow (CBF) was evaluated repeatedly during and after stroke. Reduction of CBF was more dramatic and sustained in aged mice. Aged mice exhibited more severe long-term sensorimotor deficits, as manifested by deterioration of performance in the Rotarod and hanging wire tests up to 35d after stroke. Aged mice also exhibited significantly worse long-term cognitive deficits after stroke, as measured by the Morris water maze test. Consistent with these behavioral observations, brain infarct size and neuronal tissue loss after dMCAO were significantly larger in aged mice at 2d and 14d, respectively. The young versus aged difference in neuronal tissue loss, however, did not persist until 35d after dMCAO. In contrast to the transient difference in neuronal tissue loss, we found significant and long lasting deterioration of white matter in aged animals, as revealed by the loss of myelin basic protein (MBP) staining in the striatum at 35d after dMCAO. We further examined the expression of M1 (CD16/CD32) and M2 (CD206) markers in Iba-1(+) microglia by double immunofluorescent staining. In both young and aged mice, the expression of M2 markers peaked around 7d after stroke whereas the expression of M1 markers peaked around 14d after stroke, suggesting a progressive M2-to-M1 phenotype shift in both groups. However, aged mice exhibited significantly reduced M2 polarization compared to young adults. Remarkably, we discovered a strong positive correlation between favorable neurological outcomes after dMCAO and MBP levels or the number of M2 microglia/macrophages. In conclusion, our studies suggest that the distal MCAO stroke model consistently results in ischemic brain injury with long-term behavioral deficits, and is therefore suitable for the evaluation of long-term stroke outcomes. Furthermore, aged mice exhibit deterioration of functional outcomes after stroke and this deterioration is linked to white matter damage and reductions in M2 microglia/macrophage polarization.

Factors secreted by endothelial progenitor cells enhance neurorepair responses after cerebral ischemia in mice

Cell therapy with endothelial progenitor cells (EPCs) has emerged as a promising strategy to regenerate the brain after stroke. Here, we aimed to investigate if treatment with EPCs or their secreted factors could potentiate angiogenesis and neurogenesis after permanent focal cerebral ischemia in a mouse model of ischemic stroke. BALB/C male mice were subjected to distal occlusion of the middle cerebral artery, and EPCs, cell-free conditioned media (CM) obtained from EPCs, or vehicle media were administered one day after ischemia. Magnetic resonance imaging (MRI) was performed at baseline to confirm that the lesions were similar between groups. Immunohistochemical and histological evaluation of the brain was performed to evaluate angio-neurogenesis and neurological outcome at two weeks. CM contained growth factors, such as VEGF, FGF-b and PDGF-bb. A significant increase in capillary density was noted in the peri-infarct areas of EPC- and CM-treated animals. Bielschowsky's staining revealed a significant increase in axonal rewiring in EPC-treated animals compared with shams, but not in CM-treated mice, in close proximity with DCX-positive migrating neuroblasts. At the functional level, post-ischemia forelimb strength was significantly improved in animals receiving EPCs or CM, but not in those receiving vehicle media. In conclusion, we demonstrate for the first time that the administration of EPC-secreted factors could become a safe and effective cell-free option to be considered in future therapeutic strategies for stroke.

PPARα is involved in the multitargeted effects of a pretreatment with atorvastatin in experimental stroke

There is now substantial data in the literature showing that statins can protect against cerebral ischemia. This neuroprotective potency is related to their pleiotropic effects that modulate various pathways implicated in the pathophysiology of stroke. It has been demonstrated that statins exert anti-inflammatory and vasculoprotective effects, thus contributing to a reduction in infarct size. The underlying mechanisms are still incompletely known. As a cross-talk between statins and the nuclear receptor PPARα has been described, we hypothesized that this cross-talk is necessary to neuroprotection in stroke. We studied the effects of a 14-day preventive atorvastatin treatment (10 mg/kg/day) on C57Bl6 wild-type and PPARα-KO mice submitted to experimental stroke. PPARα was involved in the atorvastatin-induced neuroprotective effect, as confirmed by the measurement of infarct volumes. We also evidenced that the anti-inflammatory action of atorvastatin is mediated, at least partly, by PPARα. The decrease in IL-6 plasmatic levels was PPARα dependent. The cerebral expression of the adhesion molecules ICAM-1 and vascular cell adhesion molecule was reduced by the atorvastatin treatment, and this effect was PPARα dependent in the cortex but not in the striatum of treated animals. Atorvastatin also diminished the cerebral expression of iNOS in the cortex, but had no effect in the striatum of treated mice, whatever the PPARα status. At the vascular level, we found that the atorvastatin-related endothelial nitric oxide synthase upregulation was regulated by PPARα in the aorta, while there was no effect in the brain. We demonstrate here that PPARα is a key mediator of the multitargeted neuroprotective effects of statins in stroke.

Gemfibrozil pretreatment affecting antioxidant defense system and inflammatory, but not Nrf-2 signaling pathways resulted in female neuroprotection and male neurotoxicity in the rat models of global cerebral ischemia-reperfusion

Two important pathophysiological mechanisms involved during cerebral ischemia are oxidative stress and inflammation. In pathological conditions such as brain ischemia the ability of free radicals production is greater than that of elimination by endogenous antioxidative systems, so brain is highly injured due to oxidation and neuroinflammation. Fibrates as peroxisome proliferator-activated receptor (PPAR)-α ligands, are reported to have antioxidant and anti-inflammatory actions. In this study, gemfibrozil, a fibrate is investigated for its therapeutic potential against global cerebral ischemia-reperfusion (I/R) injury of male and female rats. This study particularly has focused on inflammatory and antioxidant signaling pathways, such as nuclear factor erythroid-related factor (Nrf)-2, as well as the activity of some endogenous antioxidant agents. It was found that pretreatment of animals with gemfibrozil prior to I/R resulted in a sexually dimorphic outcome. Within females it proved to be protective, modulating inflammatory factors and inducing antioxidant defense system including superoxide dismutase (SOD), catalase, as well as glutathione level. However, Nrf-2 signaling pathway was not affected. It also decreased malondialdehyde level as an index of lipid peroxidation. In contrast, gemfibrozil pretreatment was toxic to males, enhancing the expression of inflammatory factors such as tumor necrosis factor-α, nuclear factor-κB, and cyclooxygenase-2, and decreasing Nrf-2 expression and SOD activity, leading to hippocampal neurodegeneration. Considering that gemfibrozil is a commonly used anti-hyperlipidemic agent in clinic, undoubtedly more investigations are crucial to exactly unravel its sex-dependent neuroprotective/neurodegenerative potential.

Assessing post-stroke behavior in mouse models of focal ischemia

Experimental treatment strategies and neuroprotective drugs that showed therapeutic promise in animal models of stroke have failed to produce beneficial effects in human stroke patients. The difficulty in translating preclinical findings to humans represents a major challenge in cerebrovascular research. The reasons behind this translational road block might be explained by a number of factors, including poor quality control in various stages of the research process, the validity of experimental stroke models, and differences in drug administration and pharmacokinetics. Another major difference between animal studies and clinical trials is the choice of end point or outcome measures. Here, we discuss the necessity of poststroke behavioral testing to bridge the gap between clinical and experimental end points. We review established sensory-motor tests for outcome determination after focal ischemia based on the published literature as well as our own personal experience. Selected tests are described in more detail and good laboratory practice standards for behavioral testing are discussed. This review is intended for stroke researchers planning to use behavioral testing in mice.

Distal occlusion of the middle cerebral artery in mice: are we ready to assess long-term functional outcome?

Rodent animal models of stroke are widely used with brain ischemia inducible by various occlusion methods. Permanent or transient occlusion of the distal portion of the middle cerebral artery (MCAO) offers a reproducible model with low mortality rates, and it is the most likely model of choice for mid- and long-term studies to assess neurorepair or long-term effects of neuroprotective drugs. Therefore, a measurable and stable neurological assessment would be required to evaluate sensorimotor and cognitive deficits at short and long terms as suggested by the Stroke Therapy Academic Industry Roundtable preclinical recommendations. We review the usefulness of different tests used to measure functional outcome after distal MCAO in mice and further sustain these data with our own multilaboratories' experience. Results show that several tests were suitable to detect neurological deterioration at short term. Grip strength and latency to move have shown some usefulness at long term, with important differences between strains, while less clear are the data for the corner test. Important strain differences in terms of infarct volume are also reported in this study. Statistical power analysis and sample size calculation of our data confirmed the value of grip strength and latency to move tests but suggest that larger sample size would be required. In conclusion, there are no robust data supporting the use of a specific behavior test to assess long-term functional outcome after distal MCAO in mice. This is an important limitation since translational basic research should provide data to help further clinical trial evaluation. New multicenter studies with larger sample size and specific mouse strains are needed to confirm the validity of tests, such as the corner, latency to move or grip strength.

Expression Pattern of Peroxisome Proliferator-Activated Receptors in Rat Hippocampus following Cerebral Ischemia and Reperfusion Injury

The present study was designed to investigate the pattern of time-dependent expression of peroxisome proliferator-activated receptors (PPARα, β, and γ) after global cerebral ischemia and reperfusion (I/R) damage in the rat hippocampus. Male Sprague Dawley (SD) rats were subjected to global cerebral I/R. The rat hippocampi were isolated to detect the expression of PPARs mRNA and protein levels at 30 min–30 d after I/R by RT-PCR and Western blot analysis, respectively. The expression levels of PPARs mRNA and protein in the rat hippocampus significantly increased and peaked at 24 h for PPARα and γ (at 48 h for PPARβ) after I/R, then gradually decreased, and finally approached control levels on d 30. The present results suggest that global cerebral I/R can cause obvious increases of hippocampal PPARs mRNA and protein expression within 15 d after I/R. These findings may help to guide the experimental and clinical therapeutic use of PPARs agonists against brain injury.

The Influence of Stroke Risk Factors and Comorbidities on Assessment of Stroke Therapies in Humans and Animals

The main driving force behind the assessment of novel pharmacological agents in animal models of stroke is to deliver new drugs to treat the human disease rather than to increase knowledge of stroke pathophysiology. There are numerous animal models of the ischaemic process and it appears that the same processes operate in humans. Yet, despite these similarities, the drugs that appear effective in animal models have not worked in clinical trials. To date, tissue plasminogen activator is the only drug that has been successfully used at the bedside in hyperacute stroke management. Several reasons have been put forth to explain this, but the failure to consider comorbidities and risk factors common in older people is an important one. In this article, we review the impact of the risk factors most studied in animal models of acute stroke and highlight the parallels with human stroke, and, where possible, their influence on evaluation of therapeutic strategies.

Effects of chronic systemic treatment with peroxisome proliferator-activated receptor α activators on neuroinflammation induced by intracerebral injection of lipopolysaccharide in adult mice

We examined whether chronic systemic treatment with agonists for peroxisome proliferator-activated receptor α (PPARα) influences neuroinflammation induced by lipopolysaccharide (LPS) injection into the somatosensory cortex in adult mice. Mice were pretreated with Wy-14643 or fenofibrate, both at 30 mg/kg, for 7 days. These treatment protocols increased the amount of PPARα mRNA and active form of PPARα protein in the brain. LPS injection reduced the PPARα mRNA level in the brain. On the contrary, TNFα, IL-1β, IL-6, iNOS, COX-2, ICAM-1, VCAM-1, and PECAM-1 were elevated at 6h after LPS. Wy-14643 and fenofibrate inhibited the elevations of TNFα, IL-1β, IL-6, COX-2, ICAM-1, and VCAM-1. Wy-14643, but not fenofibrate, also attenuated the iNOS elevation. At 3 days after LPS, Wy-14643 and fenofibrate showed similar inhibitions in these molecules. LPS injection also elevated IL-6 protein levels in the brain and serum at 6h, which was inhibited by fenofibrate. Histological analyses showed that Wy-14643 and fenofibrate profoundly attenuated microglia/macrophage activation, neutrophil recruitment, and neuronal injury at 3 days after LPS. These findings suggest that activation of PPARα attenuates neuroinflammation in the adult mouse brain, implicating that PPARα may be a potential therapeutic target for CNS diseases in which neuroinflammation plays a substantial role.

Chronic treatment with fibrates elevates superoxide dismutase in adult mouse brain microvessels

Fibrates are activators of peroxisome proliferator-activated receptor (PPAR) α. Pretreatment with fibrates has been shown to protect brain against ischemia in mice. We hypothesized that fibrates elevate superoxide dismutase (SOD) levels in the brain microvessels (BMVs). BMVs were isolated from male C57BL/6 and PPARα null mice that had been treated with fenofibrate or gemfibrozil for 7 days. To examine the effect of discontinuation of fenofibrate, another animal group treated with fenofibrate was examined on post-discontinuation day 3 (D-3). To examine whether SOD elevations attenuate oxidative stress in the ischemic brain, separate animals treated with fenofibrate for 7 days were subjected to 60 minutes of focal ischemia on post-discontinuation day 0 (D-0) or D-3. Fenofibrate (30 mg/kg) increased mRNA levels of all three isoforms of SOD and activity level in BMV on D-0, but these effects were not detected on D-3. The elevations were not detected in PPARα null mice. SOD levels were also elevated by gemfibrozil (30 mg/kg). Fenofibrate significantly reduced superoxide production and protein oxidation in the ischemic brain at 30 minutes after reperfusion. Fenofibrate reduced infarct size measured at 24 hours after reperfusion on D-0; however, the infarct reduction was not seen when ischemia was induced on D-3. These findings suggest that fibrates elevate SOD in BMV through PPARα, which contributes to the infarct reduction, at least in part. Further studies are needed to establish the link between the SOD elevations and the brain protection by fibrates against ischemia.

Fenofibrate improves cerebral blood flow after middle cerebral artery occlusion in mice

Fibrates, one group of peroxisome proliferator-activated receptor (PPAR) activators, are lipid lowering drugs. Fibrates have been shown to attenuate brain tissue injury after focal cerebral ischemia. In this study, we investigated the impact of fenofibrate on cerebral blood flow (CBF) in male wild type and PPARalpha-null mice. Animals were treated for 7 days with fenofibrate and subjected to 2 h of filamentous middle cerebral artery occlusion and reperfusion under isoflurane anesthesia. Cortical surface CBF was measured by laser speckle imaging. Regional CBF (rCBF) in nonischemic animals was measured by (14)C-iodoantipyrine autoradiography. Fenofibrate did not affect rCBF and mean arterial blood pressure in nonischemic animals. In ischemic animals, laser speckle imaging showed delayed expansions of ischemic area, which was attenuated by fenofibrate. Fenofibrate also enhanced CBF recovery after reperfusion. However, such effects of fenofibrate on CBF in the ischemic brain were not observed in PPARalpha-null mice. These findings show that fenofibrate improves CBF in the ischemic hemisphere. Moreover, fenofibrate requires PPARalpha expression for the cerebrovascular protective effects in the ischemic brain.