Abstract Background and purpose Claudin-5 plays a crucial role in maintaining blood-brain barrier (BBB) integrity through endothelial tight junction formation. Alternative splicing of claudin-5 within the microvascular endothelium may modulate BBB structural and functional dynamics, thereby affecting neuronal damage and recovery after ischemic stroke. The aim of this study was to investigate temporal and hemisphere-specific changes in claudin-5 isoform expression after ischemic stroke and to evaluate their correlation with BBB dysfunction and neurological outcomes. Methods Male Wistar rats underwent thromboembolic stroke. Claudin-5 isoform expression was assessed at 3, 6, and 24 h post-stroke onset, with additional groups receiving recombinant tissue plasminogen activator (rt-PA) at 4 h post-stroke. Brain edema, infarct volume, hemorrhage, and cerebral blood flow were evaluated using 9.4T MRI. Ipsilateral and contralateral cerebrovascular claudin-5 expression was quantified via western blotting while neurological function was assessed by 28-point neuroscore. RNA sequencing analysis was performed to identify novel splice variants. In addition, molecular dynamics simulations of AlphaFold-predicted claudin-5 isoform 1 and 2 tetramers embedded in lipid bilayers were performed to quantify steric–electrostatic barrier properties and ion permeability. Results A time-dependent increase in claudin-5 isoform 1 (35 kDa) expression levels in the ipsilateral cerebrovasculature at 6 h was observed. Isoform 2 (25 kDa) and fragment (10 kDa) isoforms of claudin-5 remained unchanged. Treatment with rt-PA maintained the elevated levels of isoform 1 claudin-5 protein expression within the ipsilateral hemisphere. Increased isoform 1 expression correlated with edema, hemorrhage, and worsened neurological function at 24 h post-stroke onset. RNA sequencing revealed novel CLDN5 splice isoforms in post-stroke rat brain tissue resembling known human CLDN5 isoforms. Computational modeling suggested that isoform 1 forms a wide but electrostatically exclusionary pore with strong anion selectivity, whereas isoform 2 permits markedly greater cation permeability. These isoform-specific barrier properties are consistent with the in vivo association of isoform 1 upregulation with BBB dysfunction after stroke. Conclusion These findings demonstrate that ischemic stroke induces temporal, hemisphere-specific alterations in claudin-5 isoform expression that correlate with BBB dysfunction and poor neurological outcomes. The combination of RNA sequencing and molecular dynamics simulations indicates that alternative splice variants of claudin-5 confer distinct structural and permeability profiles, representing a previously unrecognized mechanism of endothelial tight junction dysfunction in stroke. These results highlight claudin-5 isoform expression as both a novel biologically relevant and a potential therapeutic target for preserving BBB integrity following cerebral ischemia.

Introduction Ambient air pollution, especially fine particulate matter 2.5 (PM2.5) has emerged as a critical environmental risk factor for cerebrovascular diseases, contributing to an estimated 7.9 million premature deaths annually. PM2.5 induces cellular toxicity and is hypothesized to disrupt the blood-brain barrier (BBB), a pathological hallmark in cerebrovascular diseases such as ischemic stroke. Despite epidemiological evidence linking PM2.5 to increased stroke incidence, its underlying cellular mechanism driving this association is poorly understood. It remains unclear how environmentally relevant pollution concentrations affects brain endothelial function or influence stroke-related biomarkers such as the lectin-like oxLDL receptor 1 (LOX-1). Method Primary adult male human brain microvascular endothelial cells (HBMEC) were exposed to PM2.5 (5, 15, 75, or 300 μg/m3) collected from an urban environment in southern Sweden, or control. Thereafter, exposed to normoxia (21% O2) or hypoxia (1% O2) and glucose deprivation, followed by reperfusion as a model for ischemic stroke. Cell viability, oxidative stress, inflammation, BBB integrity (claudin-5, ZO-1) and LOX-1 protein expression were assessed. Results PM2.5 exposure induced cellular dysfunction, oxidative stress and inflammation starting at 75 μg/m3 PM2.5. Notably, decreased claudin-5 and ZO-1 protein levels and increased LOX-1 expression at concentrations as low as 15 μg/m3 PM2.5, levels commonly encountered in urban environments globally. The cellular effects of PM2.5 closely resembled those induced by ischemic-like injury. Conclusion These findings demonstrate dose-dependent detrimental effects of PM2.5 on HBMEC. The results suggest that ambient urban PM2.5 may act as a predisposing factor for cerebrovascular disease onset, by causing endothelial and barrier dysregulation. ### Competing Interest Statement The authors have declared no competing interest. Swedish Research Council Thure Carlssons Foundation AFA, 160226

Axonal injuries commonly contribute to poor functional outcomes following traumatic brain injury (TBI). To assess cerebral blood flow (CBF) and energy metabolic disturbances in a TBI model of widespread axonal injury, we exposed 105 adult mice to the central (midline) fluid percussion injury (cFPI) diffuse TBI model, or sham injury, and used 9.4 T magnetic resonance (MR) arterial spin labeling (ASL), cortical and hippocampal mitochondrial respiration, and hippocampal MR spectroscopy at 1- and 7-days post-injury (dpi). Widespread, bilateral CBF reductions were observed at day 1 dpi, changes that were normalized by 7 dpi. However, cortical and hippocampal mitochondrial respiration and reactive oxygen species (ROS) production was not significantly altered at 1 and 7 dpi. Moreover, hippocampal volumes, evaluated by MRI, were not altered by cFPI, and by immunohistochemistry only a few apoptotic hippocampal cells were observed. By MRS, evidence of delayed (7 dpi) membrane disruption (phosphocholine and glycerophosphocholine) and glutamate/glutamine increase were observed. While widespread traumatic axonal pathology associated with functional impairments is observed in this TBI model, early CBF alterations were transient and did not translate into significant energy metabolic disturbances. Instead, the delayed hippocampal metabolite changes observed by MRS may contribute to the functional impairment observed in this diffuse TBI model.

Laminins are basement membrane components that regulate a plethora of biological processes. Despite decades of research, the exact roles of laminins in different tissues and in organogenesis remain to be elucidated. Here, we investigated the function of laminin γ1 chain in heart, lung and other tissues by generating a mouse that lacks laminin γ1 in cells expressing SM22α (Tagln) (LMγ1 flox/SM22α Cre mouse, referred to as LMγ1KO). Laminin γ1 deletion led to basement membrane disruption around cardiomyocytes, smooth muscle cells, alveolar cells and skeletal muscle. This, in turn, led to perinatal death of conditional LMγ1KO mice. Synchrotron-based imaging revealed developmental heart abnormalities: ventricular and atrioventricular septal defects. Lung tissue from embryos and newborns showed impaired alveolization and this defect was not reversed ex vivo. We also created adult inducible laminin γ1 knockout mice (iLMγ1KO) with targeted knockdown in all tissues, and they exhibited decreased contractility of smooth muscle in colonic and arterial tissue. Finally, both LMγ1KO neonates and iLMγ1KO adults displayed severe dystrophic features in skeletal muscle. In summary, our study reveals novel roles for laminin γ1 chain and basement membranes in heart, lung, skeletal and smooth muscle. Compromising basement membranes around various cell types expressing SM22α during embryonic development did not impair early organogenesis of lung, heart and skeletal muscle, but rather disturbed late developmental events in these tissues. Our results could help to understand clinical implications for patients with laminin α2 chain mutations (muscular dystrophy) and laminin α4 mutations (cardiomyopathy), but also for patients with congenital heart disease and lung diseases.

Exposure to airborne particulate matter 2.5 (particle size 3; 12, 24, or 36h) or vehicle, then exposed to normoxia (21% O2) or ischemic-like injury, hypoxia plus glucose deprivation (HGD; 1% O2), for 3h. HBMEC barrier function was assessed via trans-endothelial electrical resistance (TEER). HBMEC levels or expression of barrier markers (claudin-5, occludin, ZO-1), adhesion molecules (ICAM-1 and PECAM-1), inflammatory proteins (iNOS, COX-2, LOX-1, TNF-α, IL-1β), and autophagic protein (Beclin-1) were examined using qRT-PCR, in cell western, and standard immunoblotting. Ischemia-like injury as well as PM2.5 decreased HBMEC barrier function. PM2.5 also induced a concomitant temporal and dose dependent decrease in claudin-5 and increase in iNOS as well as TNF-α levels. Additionally, PM2.5 increased protein levels of beclin-1 and LOX-1 like that of HGD alone; however, combination of PM2.5 and HGD decreased levels of beclin-1. HGD alone or in combination with PM2.5 decreased levels of PECAM-1, but PM2.5 alone did not alter PECAM-1. PM2.5 in the presence or absence of HGD induced differential alteration in claudin-5 isoform protein levels. Intriguingly, PM2.5 decreased claudin-5 mRNA levels like that observed in HBMECs exposed to HGD alone. PM2.5 plus HGD significantly increased mRNA levels of both ICAM-1 and IL-1β. In conclusion, PM2.5 mediated inflammatory and vascular pathogenesis involves a potential complex intracellular molecular framework associated with the brain endothelium which is compounded by ischemic like injury. These findings have revealed detrimental effects of PM2.5 on the brain vascular endothelium which will help to identify targets in the endothelium to restore or preserve cerebrovascular homeostasis. University of Arizona Valley Research Partnership Grant VRP37 P2 (RJG), American Heart Association 19AIREA34480018 (RJG), UA VRP Grant VRP55 P1a (TSW). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Elevated plasma levels of oxidized low-density lipoprotein (oxLDL) are a risk factor and key component that accelerates and worsens cardiovascular disease fueling inflammation, plaque buildup and vascular damage. OxLDL can elicit its detrimental action via lectin-like oxLDL receptor 1 (LOX-1). In this study, we determined whether oxLDL, via LOX-1, alters aortic vascular reactivity and determined if sex and age differences exist. Thoracic aortic endothelium-intact or -denuded ring segments were isolated from 7 to 12 months old intact C57BL/6J female and male mice and pre-incubated with oxLDL ex vivo (50ug/dL; 2 h). Using wire myography, cumulative concentration-response curves to phenylephrine (PE) were generated to determine contractile responses. From these curves, the EC50 was determined and used to contract rings to assess acetylcholine (ACh) dependent relaxation. Calculated aortic stiffness and remodeling were also assessed. BI-0115 (10 μM; selective LOX-1 inhibitor) was used to determine LOX-1 dependence. We observed differential sex, age, endothelial cell, and LOX-1 dependent alterations to the efficacy of PE-induced contractile responses and ACh-mediated vasorelaxation in thoracic aortic rings following oxLDL exposure. Additionally, we observed a distinct sex and age effect on thoracic aortic stiffness following exposure to oxLDL. There was also a sex effect on calculated vessel diameter, as well as an age effect on oxLDL-mediated aortic remodeling that was LOX-1 dependent. Thus, LOX-1 inhibition and the resulting attenuation of oxLDL/endothelial-mediated alterations in aortic function suggests that there are differential sex differences in the role of oxLDL/LOX-1 in the thoracic aorta of middle-aged male and female mice. NEW and NOTEWORTHY. We investigated the effects of oxLDL via the LOX-1 receptor on murine thoracic aortic vasoreactivity, stiffness, and remodeling across age and sex. Acute exposure to oxLDL led to altered vasoreactivity, endothelial dysfunction, and changes in aortic stiffness and remodeling. These effects were in-part age, sex, endothelial, and LOX-1 dependent. This study reveals potential complex interactions in oxLDL/LOX-1-mediated vascular responses that could serve as potential therapeutic intervention for vascular diseases such as atherosclerosis and stroke.

BACKGROUND:Acute ischemic stroke triggers endothelial activation that disrupts vascular integrity and increases hemorrhagic transformation leading to worsened stroke outcomes. rt-PA (recombinant tissue-type plasminogen activator) is an effective treatment; however, its use is limited due to a restricted time window and hemorrhagic transformation risk, which in part may involve activation of MMPs (matrix metalloproteinases) mediated through LOX-1 (lectin-like oxLDL [oxidized low-density lipoprotein] receptor 1). This study's overall aim was to evaluate the therapeutic potential of novel MMP-9 (matrix metalloproteinase 9) ± LOX-1 inhibitors in combination with rt-PA to improve stroke outcomes.METHODS:A rat thromboembolic stroke model was utilized to investigate the impact of rt-PA delivered 4 hours poststroke onset as well as selective MMP-9 (JNJ0966) ±LOX-1 (BI-0115) inhibitors given before rt-PA administration. Infarct size, perfusion, and hemorrhagic transformation were evaluated by 9.4-T magnetic resonance imaging, vascular and parenchymal MMP-9 activity via zymography, and neurological function was assessed using sensorimotor function testing. Human brain microvascular endothelial cells were exposed to hypoxia plus glucose deprivation/reperfusion (hypoxia plus glucose deprivation 3 hours/R 24 hours) and treated with ±tPA and ±MMP-9 ±LOX-1 inhibitors. Barrier function was assessed via transendothelial electrical resistance, MMP-9 activity was determined with zymography, and LOX-1 and barrier gene expression/levels were measured using qRT-PCR (quantitative reverse transcription PCR) and Western blot.RESULTS:Stroke and subsequent rt-PA treatment increased edema, hemorrhage, MMP-9 activity, LOX-1 expression, and worsened neurological outcomes. LOX-1 inhibition improved neurological function, reduced edema, and improved endothelial barrier integrity. Elevated MMP-9 activity correlated with increased edema, infarct volume, and decreased neurological function. MMP-9 inhibition reduced MMP-9 activity and LOX-1 expression. In human brain microvascular endothelial cells, LOX-1/MMP-9 inhibition differentially attenuated MMP-9 levels, inflammation, and activation following hypoxia plus glucose deprivation/R.CONCLUSIONS:Our findings indicate that LOX-1 inhibition and ± MMP-9 inhibition attenuate negative aspects of ischemic stroke with rt-PA therapy, thus resulting in improved neurological function. While no synergistic effect was observed with simultaneous LOX-1 and MMP-9 inhibition, a distinct interaction is evident.

Ambient airborne particles with an aerodynamic diameter of <2.5 µm (PM2.5), which contain particles from combustion processes, are linked to increased risks for cardiovascular and respiratory diseases. In this experimental study, the short-term and long-term physiologic consequences of PM2.5 inhalation were investigated with the focus on inflammatory parameters and vascular tonus. PM2.5 collected from urban environments in southern Sweden were aerosolized with a nebulizer and delivered to male Sprague Dawley rats. The rats were divided into two treatment groups (n=8 in each): short-term exposed (8 h with an estimated lung exposure rate of 90 μg PM2.5/h); and long-term exposed (3 h/day, 5 days/week, for 8 weeks, with an estimated lung exposure rate of 30 μg PM2.5/h). A group of non-particle-exposed control animals (n=8) was run in parallel with each test group. The results showed that short-term exposure increased the numbers of lymphocytes in the bronchoalveolar lavage fluids. Long-term exposure led to impaired substance P-induced relaxation and increased endothelin-1-induced contraction of the coronary arteries. The contractile response was found to be mediated by endothelin receptor A. Long-term exposure led to increased interleukin-6 levels in brain tissues, as compared to the controls. In summary, this explorative study reveals that exposure to aerosolized, ambient PM2.5 leads to impaired coronary artery function and neuroinflammation. Further investigations into the impacts on health effects of short-term and long-term exposures to urban air pollution are warranted.

Cerebellar dysfunction is commonly observed following traumatic brain injury (TBI). While direct impact to the cerebellum by TBI is rare, cerebellar pathology may be caused by indirect injury via cortico-cerebellar pathways. To address the hypothesis that degeneration of Purkinje cells (PCs), which constitute the sole output from the cerebellum, is linked to long-range axonal injury and demyelination, we used the central fluid percussion injury (cFPI) model of widespread traumatic axonal injury in mice. Compared to controls, TBI resulted in early PC loss accompanied by alterations in the size of pinceau synapses and levels of non-phosphorylated neurofilament in PCs. A combination of vDISCO tissue clearing technique and immunohistochemistry for vesicular glutamate transporter type 2 show that diffuse TBI decreased mossy and climbing fiber synapses on PCs. At 2 days post-injury, numerous axonal varicosities were found in the cerebellum supported by fractional anisotropy measurements using 9.4 T MRI. The disruption and demyelination of the cortico-cerebellar circuits was associated with poor performance of brain-injured mice in the beam-walk test. Despite a lack of direct input from the injury site to the cerebellum, these findings argue for novel long-range mechanisms causing Purkinje cell injury that likely contribute to cerebellar dysfunction after TBI.

Some degree of spontaneous recovery is usually observed after stroke. Experimental studies have provided information about molecular mechanisms underlying this recovery. However, the majority of pre-clinical stroke studies are performed in male rodents, and females are not well studied. This is a clear discrepancy when considering the clinical situation. Thus, it is important to include females in the evaluation of recovery mechanisms for future therapeutic strategies. This study aimed to evaluate spontaneous recovery and molecular mechanisms involved in the recovery phase two weeks after stroke in female rats. Transient middle cerebral artery occlusion was induced in female Wistar rats using a filament model. Neurological functions were assessed up to day 14 after stroke. Protein expression of interleukin 10 (IL-10), transforming growth factor (TGF)-β, neuronal specific nuclei protein (NeuN), nestin, tyrosine-protein kinase receptor Tie-2, extracellular signal-regulated kinase (ERK) 1/2, and Akt were evaluated in the peri-infarct and ischemic core compared to contralateral side of the brain at day 14 by western blot. Expression of TGF-β in middle cerebral arteries was evaluated by immunohistochemistry. Spontaneous recovery after stroke was observed from day 2 to day 14 and was accompanied by a significantly higher expression of nestin, p-Akt, p-ERK1/2 and TGF-β in ischemic regions compared to contralateral side at day 14. In addition, a significantly higher expression of TGF-β was observed in occluded versus non-occluded middle cerebral arteries. The expression of Tie-2 and IL-10 did not differ between the ischemic and contralateral sides. Spontaneous recovery after ischemic stroke in female rats was coincided by a difference observed in the expression of molecular markers. The alteration of these markers might be of importance to address future therapeutic strategies.

Abstract Air pollution and exposure to fine airborne particles with aerodynamic diameter <2.5 μm (PM2.5) negatively impacts human health. Airways constitute a primary route of exposure but PM2.5‐contaminated food, drinks as well as mucociliary and hepatobiliary clearance all constitute potential entry points into the intestine. This study evaluated intestinal histopathological and inflammatory changes as well as enteric neuronal numbers after short‐ or long‐term exposure to urban PM2.5. Using a nebulizer, male rats were exposed to a mist with a concentration of 5.3mg PM2.5/m3 for 8 h (short term) or 1.8 mg PM2.5/m3 for 3 h/day, 5 days/week for 8 weeks (long‐term) with controls run in parallel. Samples were taken from three regions of the small intestine as well as the colon. Results showed that short‐term exposure to PM2.5 induces mucosal lesions and reduces IL1β levels in the small intestine but not colon. No significant changes were observed after long‐term exposure, suggesting the presence of intestinal adaptation to environmental stressors in the PM2.5. To our knowledge, this is the first study to systematically characterize regional effects along the intestine.

Ischemia, both in the form of focal thromboembolic stroke and following subarachnoid hemorrhage (SAH), causes upregulation of vasoconstrictive receptor systems within the cerebral vasculature. Descriptions regarding changes in purinergic signaling following ischemia are lacking, especially when the importance of purinergic signaling in regulating vascular tone is taken into consideration. This prompted us to evaluate changes in P2Y(6) -mediated vasomotor reactivity in two different stroke models in rat. We used wire myography to measure changes in cerebral vasoreactivity to the P2Y(6) agonist UDP-beta-S following either experimental SAH or transient middle cerebral artery occlusion. Changes in receptor localization or receptor expression were evaluated using immunohistochemistry and quantitative flow cytometry. Transient middle cerebral artery occlusion caused an increase in Emax when compared to sham (233.6 [206.1-258.5]% vs. 161.1 [147.1-242.6]%, p = 0.0365). No such change was seen following SAH. Both stroke models were associated with increased levels of P2Y(6) receptor expression in the vascular smooth muscle cells (90.94 [86.99-99.15]% and 93.79 [89.9696.39]% vs. 80.31 [70.80-80.86]%, p = 0.021) and p = 0.039 respectively. There was no change in receptor localization in either of the stroke models. Based on these findings, we conclude that focal ischemic stroke increases vascular sensitivity to UDP-beta-S by upregulating P2Y(6) receptors on vascular smooth muscle cells while experimental SAH did not induce changes in vasoreactivity in spite of increased P2Y(6) receptor expression.

The neurovascular niche is crucial for constant blood supply and blood-brain barrier (BBB) function and is altered in a number of different neurological conditions, making this an intensely active field of research. Brain vasculature is unique for its tight association of endothelial cells with astrocytic endfeet processes. Separation of the vascular compartment by centrifugation-based methods confirmed enrichment of astrocytic endfeet processes, making it possible to study the entire vascular niche with such methods. Several centrifugation-based separation protocols are found in the literature; however, with some constraints which limit their applicability and the scope of the studies. Here, we describe and validate a protocol for physically separating the neurovascular niche from the parenchyma, which is optimized for smaller tissue quantities. Using endothelial, neuronal, and astrocyte markers, we show that quantitative Western blot-based target detection can be performed of both the vessel-enriched and parenchymal fractions using as little as a single mouse brain hemisphere. Validation of our protocol in rodent stroke models by detecting changes in tight junction protein expression, serum albumin signals and astrocyte activation, i.e., increased glial fibrillary acidic protein expression, between the ipsilateral and the lesion-free contralateral hemisphere demonstrates this protocol as a new way of detecting BBB breakdown and astrogliosis, respectively.

The loss of vascular integrity at the level of the blood brain barrier leads to a vicious cascade of secondary injuries following acute ischemic stroke (AIS). Elevated MMP-9 activity within the cerebral vasculature has been implicated with severe degradation of the vascular basement membrane leading to abnormal cerebrovascular permeability and detrimental stroke outcome. Sphingosine-1-phosphate receptor (S1PR) modulation improves stroke outcome in AIS patients, however the influence of selective S1PR1ligands, such as ozanimod, on brain endothelial health and MMP-9 activity following AIS has not been investigated. Thus, the aim of this study was to determine the impact of acute ischemic injury on MMP-9 activity in both the rat and the human cerebrovasculature as well as the vascular specific role of ozanimod on human endothelial health and MMP-9 activity. Using an in vivo thromboembolic stroke model, cerebral vessels were isolated from male Wistar rats that underwent a right middle cerebral artery (MCA) thrombin injection. Sham-operated animals underwent the same surgical procedure; however, nothing was injected. Vascular MMP-9 enzymatic activity of was evaluated at 3, 6 and 24h post injury using zymography. Using an in vitro ischemic injury model (HGD; hypoxia plus glucose deprivation), male human brain microvascular endothelial cells (HBMECs; P7) were treated with ozanimod (0.5nM) or vehicle (DMSO) and then exposed to normoxia (21% O2) or HGD (1% O2). In some experiments, W146 (a selective antagonist), verified S1PR1 dependence. Morphology and vacuole formations were assessed using crystal violet staining. Enzymatic activity of MMP-9 was evaluated via zymography and the extracellular H2O2 concentration, inducer of MMP-9 activity, was measured using a colorimetric assay. Following in vivo thromboembolic occlusion, ipsilateral MMP-9 activity increased at 6h post injury and returned to baseline when compared to sham. In comparison to the contralateral side, thromboembolic occlusion induced a time dependent modulation of ipsilateral MMP-9 activity compared to the contralateral side with the highest activity peaking at 6h. In our in vitro HBMEC stroke model, MMP-9 enzymatic activity was increased following 3h HGD exposure, and this response was attenuated by ozanimod. Concomitantly, during HGD, H2O2 production, a partial inducer of MMP-9 activity, was increased in a time dependent manner when compared to normoxic controls. Furthermore, HGD induced an increase in HBMEC vacuole formations and a decrease in cell viability at 3h. Loss of cell viability was rescued with ozanimod. In conclusion, increased MMP-9 activity, in part due to H2O2, is an acute response to ischemic injury in the cerebrovasculature. Specifically, ozanimod's ability to attenuate endothelial MMP-9 activity may play an important beneficial role in mitigating blood brain barrier integrity loss following an acute ischemic injury.

In acute ischemic stroke, the only FDA-approved drug; recombinant tissue plasminogen activator (rt-PA) is limited by restricted time-window due to an enhanced risk of hemorrhagic transformation which is thought to be caused by metalloproteinase (MMP). In experimental stroke inhibitors of the mitogen–activated protein kinase kinase extracellular signal–regulated kinase kinase (MEK) 1/2 pathways reduce the MMPs. This study evaluated whether a MEK1/2 inhibitor in combination with rt-PA can prevent the detrimental effects of delayed rt-PA therapy in stroke. Thromboembolic stroke was induced in C57 black/6J mice and the MEK1/2 inhibitor U0126 was administrated 3.5 h and rt-PA 4 h post stroke-onset. Treatment with rt-PA demonstrated enhanced MMP-9 protein levels and hemorrhagic transformation which was prevented when U0126 was given in conjunction with rt-PA. By blocking the MMP-9 with U0126 the safety of rt-PA administration was improved and demonstrates a promising adjuvant strategy to reduce the harmful effects of delayed rt-PA treatment in acute ischemic stroke.

Background Women account for 60% of all stroke deaths and are more often permanently disabled than men, despite their higher observed stroke incidence. Considering the clinical population affected by stroke, an obvious drawback is that many pre-clinical and clinical studies only investigate young males. To improve therapeutic translation from bench to bedside, we believe that it is advantageous to include both sexes in experimental models of stroke. The aims of this study were to identify early cerebral vascular responses to ischemic stroke in females, compare the differential gene expression patterns with those seen in males, and identify potential new therapeutic targets. Results Transient middle cerebral artery occlusion (tMCAO) was used to induce stroke in both female and male rats, the middle cerebral arteries (MCAs) were isolated 3 h post reperfusion and RNA was extracted. Affymetrix whole transcriptome expression profiling was performed on female ( n = 12) MCAs to reveal differentially expressed genes. In total, 1076 genes had an increased expression and 879 genes a decreased expression in the occluded MCAs as compared with the control MCAs from female rats. An enrichment of genes related to apoptosis, regulation of transcription, protein autophosphorylation, inflammation, oxidative stress, and tissue repair and recovery were seen in the occluded MCA . The high expression genes chosen for qPCR verification ( Adamts4 , Olr1 , JunB , Fosl1 , Serpine1 , S1pr3 , Ccl2 and Socs3 ) were all shown to be upregulated in the same manner in both females and males after tMCAO ( p < 0.05; n = 23). When comparing the differentially expressed genes in female MCAs (occluded and non-occluded) with our previous findings in males after tMCAO, a total of 297 genes overlapped (all groups had 32 genes in common). Conclusions The cascades of processes initiated in the vasculature following reperfusion are complex. Dynamic gene expression alterations were observed in the occluded MCAs, and to a less pronounced degree in the non-occluded MCAs. Dysregulation of inflammation and blood-brain barrier breakdown are possible pharmacological targets. The sample of genes (< 1% of the differentially expressed genes) validated for this microarray did not reveal any sex differences. However, sex differences might be observed for other gene targets.

The recent clinical trial (DAWN) suggests that recanalization treatment may be beneficial up to 24 h after stroke onset, thus re-opening avenues for development of new therapeutic strategies. Unfortunately, there is a continuous failure of drugs in clinical trials and one of the major reasons proposed for this translational roadblock is the animal models. Therefore, the purpose of this study was to validate a new thromboembolic stroke rat model that mimics the human pathology, and that can be used for evaluating new strategies to save the brain in conditions compatible with recanalization. Stroke was induced by injection of thrombin into the middle cerebral artery. Recombinant tissue-type plasminogen activator (rt-PA) or saline was administrated at 1 h/4 h after stroke onset, and outcome was evaluated after 24 h. Induced ischemia resulted in reproducible cortical brain injuries causing a decrease in neurological function 24 h after stroke onset. Early rt-PA treatment resulted in recanalization, reduced infarct size and improved neurological functions, while late rt-PA treatment showed no beneficial effects and caused hemorrhagic transformation in 25% of the rats. This validated and established model's resemblance to human ischemic stroke and high translational potential, makes it an important tool in the development of new therapeutic strategies for stroke.

Stroke is one of the leading causes of mortality and morbidity worldwide, and few therapeutic treatments have shown beneficial effect clinically. One reason for this could be the lack of risk factors incorporated into the preclinical stroke research. We have previously demonstrated phenotypic receptor changes to be one of the injurious mechanisms occurring after stroke but mostly in healthy rats. The aim of this study was to investigate if hypertension has an effect on vasoconstrictive receptor responses to endothelin 1, sarafotoxin 6c and angiotensin II after stroke by inducing transient middle cerebral artery occlusion in spontaneously hypertensive rats and Wistar-Kyoto rats using the wire-myograph. We demonstrated an increased contractile response to endothelin 1 and extracellular potassium as well as an increased carbachol-induced dilator response in the middle cerebral arteries from hypertensive rats after stroke. This study demonstrates the importance of including risk factors in experimental stroke research.