Brain Ischemia Suppresses Immunity in the Periphery and Brain via Different Neurogenic Innervations.

Brain ischemia inhibits immune function systemically, with resulting infectious complications. Whether in stroke different immune alterations occur in brain and periphery and whether analogous mechanisms operate in these compartments remains unclear. Here we show that in patients with ischemic stroke and in mice subjected to middle cerebral artery occlusion, natural killer (NK) cells display remarkably distinct temporal and transcriptome profiles in the brain as compared to the periphery. The activation of catecholaminergic and hypothalamic-pituitary-adrenal axis leads to splenic atrophy and contraction of NK cell numbers in the periphery through a modulated expression of SOCS3, whereas cholinergic innervation-mediated suppression of NK cell responses in the brain involves RUNX3. Importantly, pharmacological or genetic ablation of innervation preserved NK cell function and restrained post-stroke infection. Thus, brain ischemia compromises NK cell-mediated immune defenses through mechanisms that differ in the brain versus the periphery, and targeted inhibition of neurogenic innervation limits post-stroke infection.

LOX-1 and MMP-9 Inhibition Attenuates the Detrimental Effects of Delayed rt-PA Therapy and Improves Outcomes After Acute Ischemic 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.

Ozanimod differentially preserves human cerebrovascular endothelial barrier proteins and attenuates matrix metalloproteinase-9 activity following in vitro acute ischemic injury.

Endothelial integrity is critical in mitigating a vicious cascade of secondary injuries following acute ischemic stroke (AIS). Matrix metalloproteinase-9 (MMP-9), a contributor to endothelial integrity loss, is elevated during stroke and is associated with worsened stroke outcome. We investigated the FDA-approved selective sphingosine-1-phosphate receptor 1 (S1PR1) ligand, ozanimod, on the regulation/activity of MMP-9 as well as endothelial barrier components [platelet endothelial cell adhesion molecule 1 (PECAM-1), claudin-5, and zonula occludens 1 (ZO-1)] in human brain microvascular endothelial cells (HBMECs) following hypoxia plus glucose deprivation (HGD). We previously reported that S1PR1 activation improves HBMEC integrity; however, mechanisms underlying S1PR1 involvement in endothelial cell barrier integrity have not been clearly elucidated. We hypothesized that ozanimod would attenuate an HGD-induced increase in MMP-9 activity that would concomitantly attenuate the loss of integral barrier components. Male HBMECs were treated with ozanimod or vehicle and exposed to 3 h of normoxia (21% O2) or HGD (1% O2). Immunoblotting, zymography, qRT-PCR, and immunocytochemical labeling techniques assessed processes related to MMP-9 and barrier markers. We observed that HGD acutely increased MMP-9 activity and reduced claudin-5 and PECAM-1 levels, and ozanimod attenuated these responses. In situ analysis, via PROSPER, suggested that attenuation of MMP-9 activity may be a primary factor in maintaining these integral barrier proteins. We also observed that HGD increased intracellular mechanisms associated with augmented MMP-9 activation; however, ozanimod had no effect on these select factors. Thus, we conclude that ozanimod has the potential to attenuate HGD-mediated decreases in HBMEC integrity in part by decreasing MMP-9 activity as well as preserving barrier properties.NEW & NOTEWORTHY We have identified a potential novel mechanism by which ozanimod, a selective sphingosine-1-phosphate receptor 1 (S1PR1) agonist, attenuates hypoxia plus glucose deprivation (HGD)-induced matrix metalloproteinase-9 (MMP-9) activity and disruptions in integral human brain endothelial cell barrier proteins. Our results suggest that ischemic-like injury elicits increased MMP-9 activity and alterations of barrier integrity proteins in human brain microvascular endothelial cells (HBMECs) and that ozanimod via S1PR1 attenuates these HGD-induced responses, adding to its therapeutic potential in cerebrovascular protection during the acute phase of ischemic stroke.

Ozanimod, an S1PR1 ligand, attenuates hypoxia plus glucose deprivation-induced autophagic flux and phenotypic switching in human brain VSM cells.

Vascular smooth muscle (VSM) cell phenotypic expression and autophagic state are dynamic responses to stress. Vascular pathologies, such as hypoxemia and ischemic injury, induce a synthetic VSM phenotype and autophagic flux resulting in a loss of vascular integrity and VSM cell death respectfully. Both clinical pilot and experimental stroke studies demonstrate that sphingosine-1-phosphate receptor (S1PR) modulation improves stroke outcome; however, specific mechanisms associated with a beneficial outcome at the level of the cerebrovasculature have not been clearly elucidated. We hypothesized that ozanimod, a selective S1PR type 1 ligand, will attenuate VSM synthetic phenotypic expression and autophagic flux in primary human brain VSM cells following acute hypoxia plus glucose deprivation (HGD; in vitro ischemic-like injury) exposure. Cells were treated with ozanimod and exposed to normoxia or HGD. Crystal violet staining, standard immunoblotting, and immunocytochemical labeling techniques assessed cellular morphology, vacuolization, phenotype, and autophagic state. We observed that HGD temporally decreased VSM cell viability and concomitantly increased vacuolization, both of which ozanimod reversed. HGD induced a simultaneous elevation and reduction in levels of pro- and antiautophagic proteins respectfully, and ozanimod attenuated this response. Protein levels of VSM phenotypic biomarkers, smoothelin and SM22, were decreased following HGD. Furthermore, we observed an HGD-induced epithelioid and synthetic morphological appearance accompanied by disorganized cytoskeletal filaments, which was rescued by ozanimod. Thus, we conclude that ozanimod, a selective S1PR1 ligand, protects against acute HGD-induced phenotypic switching and promotes cell survival, in part, by attenuating HGD-induced autophagic flux thus improving vascular patency in response to acute ischemia-like injury.

The selective sphingosine 1-phosphate receptor 1 modulator RP101075 improves microvascular circulation after cerebrovascular thrombosis.

Sphingosine-1-phosphate receptor (S1PR) modulators provide protection in preclinical and clinical studies for ischemic stroke, but the influences of S1PR modulation on microvascular thrombosis remain poorly understood. This study investigates the impact of a selective S1PR1 modulator RP101075 on microvascular circulation in a mouse model of laser-induced thrombosis. The flow velocity of cortical arterioles in mice was measured in vivo under 2-photon laser scanning microscopy. Thrombosis was induced in cortical arterioles by laser irritation. At 30 min after laser-induced thrombosis, mice were treated with either RP101075 or vehicle. RP101075 did not alter the flow velocity of cortical arterioles under physiologic conditions. Laser-induced thrombosis led to a pronounced reduction of flow velocity in cortical arterioles that persisted for ≥90 min. The reduction of flow velocity in cortical arterioles following thrombosis was significantly attenuated following RP101075 treatment. RP101075 did not significantly affect coagulation time, bleeding time, heart rate, and blood pressure. In addition, RP101075 treatment reduced thrombus volume, which was accompanied by a reduction of leukocyte content in the thrombus. Our findings demonstrate that the selective S1PR1 modulator RP101075 improves microvascular circulation after thrombosis, implying a component of improved microvascular circulation to the benefit of S1PR modulation in cerebral ischemia.-Li, H., Zhou, X., Li, Y., Ma, X., Gonzales, R. J., Qiu, S., Shi, F.-D., Liu, Q. The selective sphingosine 1-phosphate receptor 1 modulator RP101075 improves microvascular circulation after cerebrovascular thrombosis.

Fingolimod enhances the efficacy of delayed alteplase administration in acute ischemic stroke by promoting anterograde reperfusion and retrograde collateral flow.

OBJECTIVE: The present study was undertaken to determine the efficacy of coadministration of fingolimod with alteplase in acute ischemic stroke patients in a delayed time window. METHODS: This was a prospective, randomized, open-label, blinded endpoint clinical trial, enrolling patients with internal carotid artery or middle cerebral artery proximal occlusion within 4.5 to 6 hours from symptom onset. Patients were randomly assigned to receive alteplase alone or alteplase with fingolimod. All patients underwent pretreatment and 24-hour noncontrast computed tomography (CT)/perfusion CT/CT angiography. The coprimary endpoints were the decrease of National Institutes of Health Stroke Scale scores over 24 hours and the favorable shift of modified Rankin Scale score (mRS) distribution at day 90. Exploratory outcomes included vessel recanalization, anterograde reperfusion, and retrograde reperfusion of collateral flow. RESULTS: Each treatment group included 23 patients. Compared with alteplase alone, patients receiving fingolimod plus alteplase exhibited better early clinical improvement at 24 hours and a favorable shift of mRS distribution at day 90. In addition, patients who received fingolimod and alteplase exhibited a greater reduction in the perfusion lesion accompanied by suppressed infarct growth by 24 hours. Fingolimod in conjunction with alteplase significantly improved anterograde reperfusion of downstream territory and prevented the failure of retrograde reperfusion from collateral circulation. INTERPRETATION: Fingolimod may enhance the efficacy of alteplase administration in the 4.5- to 6-hour time window in patients with a proximal cerebral arterial occlusion and salvageable penumbral tissue by promoting both anterograde reperfusion and retrograde collateral flow. These findings are instructive for the design of future trials of recanalization therapies in extended time windows. Ann Neurol 2018;84:725-736.

Activation of JAK/STAT3 restores NK-cell function and improves immune defense after brain ischemia.

Stroke-induced immune suppression predisposes the host to infections and can contribute to high morbidity and mortality in stroke patients. Because ischemic stroke has a profound effect on the systemic immune response, which may explain the increased susceptibility of stroke patients to infection, an urgent need persists for a better understanding of mechanisms associated with immune suppression; new and effective treatments for stroke can then be identified. NK cells play a key role in early host defense against pathogens by killing infected cells and/or producing cytokines such as IFN-γ. Because the phenotype and function of peripheral NK cells have been widely investigated in ischemic stroke, nCounter Inflammation Gene Array Analysis was used to build immune-related gene profiles of NK cells to comprehensively analyze the molecular signature of NK cells after ischemic brain injury. We observed distinct gene expression profiles reflecting different splenic NK-cell phenotypes and functional properties across the time course of transient middle cerebral artery occlusion (MCAO). Based on gene expression and pathway-network analysis, lower expression levels of signal transducer and activator of transcription-3 (STAT3) were observed in animals with MCAO compared with sham control animals. Genetic activation of STAT3 through the introduction of STAT3 clustered regularly interspaced short palindromic repeats (CRISPR) plasmid prevented the loss of NK-cell-derived IFN-γ production after MCAO, together with reduced bacterial burden and mortality. Our data suggest that brain ischemia impairs NK-cell-mediated immune defense in the periphery, at least in part through the JAK-STAT3 pathway, which can be readdressed by modulating STAT3 activation status.-Jin, W.-N., Ducruet, A. F., Liu, Q., Shi, S. X.-Y., Waters, M., Zou, M., Sheth, K. N., Gonzales, R., Shi, F.-D. Activation of JAK/STAT3 restores NK-cell function and improves immune defense after brain ischemia.

Palmitate induces glycosylation of cyclooxygenase-2 in primary human vascular smooth muscle cells.

Vascular basal cyclooxygenase-2 (COX-2) expression and activity can be induced by endotoxin, hypoxia, or ischemia. During vascular pathologies such as atherosclerosis, increases in COX-2 activity result in prostanoid production, a contributor to the development and progression of vascular inflammation leading to unstable atherosclerotic plaques and increased risk for thrombotic events. Recent studies demonstrate that select free fatty acids, such as palmitate, can act as proinflammatory mediators. However, the effect of palmitate on COX-2 expression and activity, and its impact on the development and progression of vascular inflammation, are not well elucidated. We investigated the effect of palmitate on COX-2 expression and function in human vascular smooth muscle cells. Cells were treated with palmitate, COX-2 protein levels were assessed using Western analysis, and activity was assessed via ELISA. We observed that palmitate dose-dependently increased COX-2 levels and specifically enhanced band intensity of the COX-2 74 kDa band (slowest migrating band). This response was attenuated by N-linked glycosylation inhibition, suggesting that palmitate impacts expression of the fully activated glycoform of COX-2. Palmitate-induced increases in COX-2 levels correlated with an increase in prostaglandin E2 production that was also attenuated by a glycosylation inhibitor. Additionally, palmitate altered cell morphology and increased cell density which were reversed by selective COX-2 inhibition. Thus, we conclude that palmitate acts on COX-2 by two separate mechanisms of action in human vascular smooth muscle. It elicits dose-dependent increases in COX-2 protein expression and modulates regulation of COX-2 activity via modification of posttranslational glycosylation.

Brain Ischemia Induces Diversified Neuroantigen-Specific T-Cell Responses That Exacerbate Brain Injury.

BACKGROUND AND PURPOSE: Autoimmune responses can occur when antigens from the central nervous system are presented to lymphocytes in the periphery or central nervous system in several neurological diseases. However, whether autoimmune responses emerge after brain ischemia and their impact on clinical outcomes remains controversial. We hypothesized that brain ischemia facilitates the genesis of autoimmunity and aggravates ischemic brain injury. METHODS: Using a mouse strain that harbors a transgenic T-cell receptor to a central nervous system antigen, MOG35-55 (myelin oligodendrocyte glycoprotein) epitope (2D2), we determined the anatomic location and involvement of antigen-presenting cells in the development of T-cell reactivity after brain ischemia and how T-cell reactivity impacts stroke outcome. Transient middle cerebral artery occlusion and photothrombotic stroke models were used in this study. We also quantified the presence and status of T cells from brain slices of ischemic patients. RESULTS: By coupling transfer of labeled MOG35-55-specific (2D2) T cells with tetramer tracking, we show an expansion in reactivity of 2D2 T cells to MOG91-108 and MOG103-125 in transient middle cerebral artery occlusion and photothrombotic stroke models. This reactivity and T-cell activation first occur locally in the brain after ischemia. Also, microglia act as antigen-presenting cells that effectively present MOG antigens, and depletion of microglia ablates expansion of 2D2 reactive T cells. Notably, the adoptive transfer of neuroantigen-experienced 2D2 T cells exacerbates Th1/Th17 responses and brain injury. Finally, T-cell activation and MOG-specific T cells are present in the brain of patients with ischemic stroke. CONCLUSIONS: Our findings suggest that brain ischemia activates and diversifies T-cell responses locally, which exacerbates ischemic brain injury.

A translocator protein 18 kDa agonist protects against cerebral ischemia/reperfusion injury.

BACKGROUND: Cerebral ischemia is a leading cause of death and disability with limited treatment options. Although inflammatory and immune responses participate in ischemic brain injury, the molecular regulators of neuroinflammation after ischemia remain to be defined. Translocator protein 18 kDa (TSPO) mainly localized to the mitochondrial outer membrane is predominantly expressed in glia within the central nervous system during inflammatory conditions. This study investigated the effect of a TSPO agonist, etifoxine, on neuroinflammation and brain injury after ischemia/reperfusion. METHODS: We used a mouse model of middle cerebral artery occlusion (MCAO) to examine the therapeutic potential and mechanisms of neuroprotection by etifoxine. RESULTS: TSPO was upregulated in Iba1+ or CD11b+CD45int cells from mice subjected to MCAO and reperfusion. Etifoxine significantly attenuated neurodeficits and infarct volume after MCAO and reperfusion. The attenuation was pronounced in mice subjected to 30, 60, or 90 min MCAO. Etifoxine reduced production of pro-inflammatory factors in the ischemic brain. In addition, etifoxine treatment led to decreased expression of interleukin-1ß, interleukin-6, tumor necrosis factor-α, and inducible nitric oxide synthase by microglia. Notably, the benefit of etifoxine against brain infarction was ablated in mice depleted of microglia using a colony-stimulating factor 1 receptor inhibitor. CONCLUSIONS: These findings indicate that the TSPO agonist, etifoxine, reduces neuroinflammation and brain injury after ischemia/reperfusion. The therapeutic potential of targeting TSPO requires further investigations in ischemic stroke.

Androgens and the cerebrovasculature: modulation of vascular function during normal and pathophysiological conditions.

Sex steroids are commonly known for their contribution to phenotypic as well as biological reproductive sex differences mediated through classical regulation of neuroendocrine loops. However, sex steroids also have considerable impact on physiological function of non-reproductive tissues including the cerebrovasculature. Preclinical studies have shown that endogenous and exogenous administration of sex steroids significantly influences both cerebrovascular tone and brain function under normal conditions and following a pathological insult (e.g., middle cerebral artery occlusion). However, the precise mechanism(s) of how sex steroids modulate vasomotor responses and/or neurological outcomes in vivo is difficult to define since evidence based on both clinical and experimental studies has been shown to be dependent upon several variables including dose, duration of administration, presence of underlying pathologies, species, and sex. While progesterone, testosterone (TEST), and dihydrotestosterone (DHT) have all been investigated for their impact on the cerebral circulation, the effects of 17ß-estradiol (E2) have been best characterized. Since recent reviews have highlighted studies reporting the actions of E2 on cerebral vascular function and health, only key points are included in this review. Conversely, less is known about the effect of androgens on the blood vessel wall, particularly in the cerebral circulation. The few studies that do address a role for androgen's modulation of cerebrovascular function under normal and pathophysiological conditions provide confounding evidence for either beneficial or detrimental effects. Therefore, the focus of this review is to highlight mechanisms associated with TEST, DHT, and its recently recognized androgen metabolite (3ß-diol) on cerebrovascular function during healthy and diseased states.

The influence of acute resistance exercise on cyclooxygenase-1 and -2 activity and protein levels in human skeletal muscle.

This study evaluated the activity and content of cyclooxygenase (COX)-1 and -2 in response to acute resistance exercise (RE) in human skeletal muscle. Previous work suggests that COX-1, but not COX-2, is the primary COX isoform elevated with resistance exercise in human skeletal muscle. COX activity, however, has not been assessed after resistance exercise in humans. It was hypothesized that RE would increase COX-1 but not COX-2 activity. Muscle biopsies were taken from the vastus lateralis of nine young men (25 ± 1 yr) at baseline (preexercise), 4, and 24 h after a single bout of knee extensor RE (three sets of 10 repetitions at 70% of maximum). Tissue lysate was assayed for COX-1 and COX-2 activity. COX-1 and COX-2 protein levels were measured via Western blot analysis. COX-1 activity increased at 4 h (P < 0.05) compared with preexercise, but returned to baseline at 24 h (PRE: 60 ± 10, 4 h: 106 ± 22, 24 h: 72 ± 8 nmol PGH2·g total protein(-1)·min(-1)). COX-2 activity was elevated at 4 and 24 h after RE (P < 0.05, PRE: 51 ± 7, 4 h: 100 ± 19, 24 h: 98 ± 14 nmol PGH2·g total protein(-1)·min(-1)). The protein level of COX-1 was not altered (P > 0.05) with acute RE. In contrast, COX-2 protein levels were nearly 3-fold greater (P > 0.05) at 4 h and 5-fold greater (P = 0.06) at 24 h, compared with preexercise. In conclusion, COX-1 activity increases transiently with exercise independent of COX-1 protein levels. In contrast, both COX-2 activity and protein levels were elevated with exercise, and this elevation persisted to at least 24 h after RE.

Chronic Cognitive and Cerebrovascular Function after Mild Traumatic Brain Injury in Rats.

Severe traumatic brain injury (TBI) results in cognitive dysfunction in part due to vascular perturbations. In contrast, the long-term vasculo-cognitive pathophysiology of mild TBI (mTBI) remains unknown. We evaluated mTBI effects on chronic cognitive and cerebrovascular function and assessed their interrelationships. Sprague-Dawley rats received midline fluid percussion injury (n = 20) or sham (n = 21). Cognitive function was assessed (3- and 6-month novel object recognition [NOR], novel object location [NOL], and temporal order object recognition [TOR]). Six-month cerebral blood flow (CBF) and cerebral blood volume (CBV) using contrast magnetic resonance imaging (MRI) and ex vivo circle of Willis artery endothelial and smooth muscle-dependent function were measured. mTBI rats showed significantly impaired NOR, with similar trends (non-significant) in NOL/TOR. Regional CBF and CBV were similar in sham and mTBI. NOR correlated with CBF in lateral hippocampus, medial hippocampus, and primary somatosensory barrel cortex, whereas it inversely correlated with arterial smooth muscle-dependent dilation. Six-month baseline endothelial and smooth muscle-dependent arterial function were similar among mTBI and sham, but post-angiotensin 2 stimulation, mTBI showed no change in smooth muscle-dependent dilation from baseline response, unlike the reduction in sham. mTBI led to chronic cognitive dysfunction and altered angiotensin 2-stimulated smooth muscle-dependent vasoreactivity. The findings of persistent pathophysiological consequences of mTBI in this animal model add to the broader understanding of chronic pathophysiological sequelae in human mild TBI.

Dihydrotestosterone attenuates hypoxia inducible factor-1α and cyclooxygenase-2 in cerebral arteries during hypoxia or hypoxia with glucose deprivation.

Dihydrotestosterone (DHT) attenuates cytokine-induced cyclooxygenase-2 (COX-2) in coronary vascular smooth muscle. Since hypoxia inducible factor-1α (HIF-1α) activation can lead to COX-2 production, this study determined the influence of DHT on HIF-1α and COX-2 following hypoxia or hypoxia with glucose deprivation (HGD) in the cerebral vasculature. COX-2 and HIF-1α levels were assessed via Western blot, and HIF-1α activation was indirectly measured via a DNA binding assay. Experiments were performed using cerebral arteries isolated from castrated male rats treated in vivo with placebo or DHT (18 days) followed by hypoxic exposure ex vivo (1% O(2)), cerebral arteries isolated from castrated male rats treated ex vivo with vehicle or DHT (10 or 100 nM; 18 h) and then exposed to hypoxia ex vivo (1% O(2)), or primary human brain vascular smooth muscle cells treated with DHT (10 nM; 6 h) or vehicle then exposed to hypoxia or HGD. Under normoxic conditions, DHT increased COX-2 (cells 51%; arteries ex vivo 31%; arteries in vivo 161%) but had no effect on HIF-1α. Following hypoxia or HGD, HIF-1α and COX-2 levels were increased; this response was blunted by DHT (cells HGD: -47% COX-2, -34% HIF-1α; cells hypoxia: -29% COX-2, -54% HIF-1α; arteries ex vivo: -37% COX-2; arteries in vivo: -35% COX-2) and not reversed by androgen receptor blockade. Hypoxia-induced HIF-1α DNA-binding was also attenuated by DHT (arteries ex vivo and in vivo: -55%). These results demonstrate that upregulation of COX-2 and HIF-1α in response to hypoxia is suppressed by DHT via an androgen receptor-independent mechanism.

Dihydrotestosterone alters cyclooxygenase-2 levels in human coronary artery smooth muscle cells.

Both protective and nonprotective effects of androgens on the cardiovascular system have been reported. Our previous studies show that the potent androgen receptor (AR) agonist dihydrotestosterone (DHT) increases levels of the vascular inflammatory mediator cyclooxygenase (COX)-2 in rodent cerebral arteries independent of an inflammatory stimulus. Little is known about the effects of androgens on inflammation in human vascular tissues. Therefore, we tested the hypothesis that DHT alters COX-2 levels in the absence and presence of induced inflammation in primary human coronary artery smooth muscle cells (HCASMC). Furthermore, we tested the ancillary hypothesis that DHT's effects on COX-2 levels are AR-dependent. Cells were treated with DHT (10 nM) or vehicle for 6 h in the presence or absence of LPS or IL-1beta. Similar to previous observations in rodent arteries, in HCASMC, DHT alone increased COX-2 levels compared with vehicle. This effect of DHT was attenuated in the presence of the AR antagonist bicalutamide. Conversely, in the presence of LPS or IL-1beta, increases in COX-2 were attenuated by cotreatment with DHT. Bicalutamide did not affect this response, suggesting that DHT-induced decreases in COX-2 levels occur independent of AR stimulation. Thus we conclude that DHT differentially influences COX-2 levels under physiological and pathophysiological conditions in HCASMC. This effect of DHT on COX-2 involves AR-dependent and- independent mechanisms, depending on the physiological state of the cell.

Targeted role for sphingosine-1-phosphate receptor 1 in cerebrovascular integrity and inflammation during acute ischemic stroke.

Endothelial sphingosine-1-phosphate receptors are emerging as relevant therapeutic targets during acute ischemic stroke (AIS). Physiologically, the cerebrovascular endothelium plays a vital role in maintaining barrier integrity and cerebrovascular homeostasis. During a cerebral ischemic event, products from parenchymal cell death are released and trigger vascular endothelial dysfunction and vascular inflammation leading to barrier integrity disruption. Endothelial dysfunction, inflammation, and a breach in barrier property play a significant role in contributing to a vicious cycle which promotes brain edema formation and exacerbates neuronal injury post stroke. Data from experimental stroke models and clinical trials suggest that selective sphingosine-1-phosphate receptor type 1 (S1PR1) modulation improves endothelial health and function and, as a result, contributes to improved neurological outcome post ischemic injury. This review highlights the impact of sphingosine-1-phosphate (S1P)/S1PR1 signaling involved in blood brain barrier (BBB) integrity and cerebrovascular inflammation following AIS. We focus on the beneficial actions of S1PR1 signaling during ischemic injury including barrier protection to lessen brain edema formation and reduction in the development and progression of vascular inflammation by attenuating endothelial cell activation resulting in reduced neurovascular inflammation. Potential gaps and future directions related to the role of S1PR during AIS are also discussed.

Chronic doxorubicin administration impacts satellite cell and capillary abundance in a muscle-specific manner.

Anthracycline chemotherapies are effective at reducing disease recurrence and mortality in cancer patients. However, these drugs also contribute to skeletal muscle wasting and dysfunction. The purpose of this study was to assess the impact of chronic doxorubicin (DOX) administration on satellite cell and capillary densities in different skeletal muscles. We hypothesized that DOX would reduce satellite cell and capillary densities of the soleus (SOL) and extensor digitorum longus (EDL) muscles, along with muscle fiber size. Ovariectomized female Sprague-Dawley rats were randomized to receive three bi-weekly intraperitoneal injections of DOX (4 mg∙kg-1 ; cumulative dose 12 mg∙kg-1 ) or vehicle (VEH; saline). Animals were euthanized 5d following the last injection and the SOL and EDL were dissected and prepared for immunohistochemical and RT-qPCR analyses. Relative to VEH, CSA of the SOL and EDL fibers were 26% and 33% smaller, respectively, in DOX (P < 0.05). In the SOL, satellite cell and capillary densities were 39% and 35% lower, respectively, in DOX (P < 0.05), whereas in the EDL satellite cell and capillary densities were unaffected by DOX administration (P > 0.05). Proliferating satellite cells were unaffected by DOX in the SOL (P > 0.05). In the SOL, MYF5 mRNA expression was increased in DOX (P < 0.05), while in the EDL MGF mRNA expression was reduced in DOX (P < 0.05). Chronic DOX administration is associated with reduced fiber size in the SOL and EDL; however, DOX appeared to reduce satellite cell and capillary densities only in the SOL. These findings highlight that therapeutic targets to protect skeletal muscle from DOX may vary across muscles.

Androgenic/estrogenic balance in the male rat cerebral circulation: metabolic enzymes and sex steroid receptors.

Tissues from males can be regulated by a balance of androgenic and estrogenic effects because of local metabolism of testosterone and expression of relevant steroid hormone receptors. As a critical first step to understanding sex hormone influences in the cerebral circulation of males, we investigated the presence of enzymes that metabolize testosterone to active products and their respective receptors. We found that cerebral blood vessels from male rats express 5alpha-reductase type 2 and aromatase, enzymes responsible for conversion of testosterone into dihydrotestosterone (DHT) and 17beta-estradiol, respectively. Protein levels of these enzymes, however, were not modulated by long-term in vivo hormone treatment. We also showed the presence of receptors for both androgens (AR) and estrogens (ER) from male cerebral vessels. Western blot analysis showed bands corresponding to the full-length AR (110 kDa) and ERalpha (66 kDa). Long-term in vivo treatment of orchiectomized rats with testosterone or DHT, but not estrogen, increased AR levels in cerebral vessels. In contrast, ERalpha protein levels were increased after in vivo treatment with estrogen but not testosterone. Fluorescent immunostaining revealed ERalpha, AR, and 5alpha-reductase type 2 in both the endothelial and smooth muscle layers of cerebral arteries, whereas aromatase staining was solely localized to the endothelium. Thus, cerebral vessels from males are target tissues for both androgens and estrogen. Furthermore, local metabolism of testosterone might balance opposing androgenic and estrogenic influences on cerebrovascular as well as brain function in males.

Depletion of microglia exacerbates postischemic inflammation and brain injury.

Brain ischemia elicits microglial activation and microglia survival depend on signaling through colony-stimulating factor 1 receptor (CSF1R). Although depletion of microglia has been linked to worse stroke outcomes, it remains unclear to what extent and by what mechanisms activated microglia influence ischemia-induced inflammation and injury in the brain. Using a mouse model of transient focal cerebral ischemia and reperfusion, we demonstrated that depletion of microglia via administration of the dual CSF1R/c-Kit inhibitor PLX3397 exacerbates neurodeficits and brain infarction. Depletion of microglia augmented the production of inflammatory mediators, leukocyte infiltration, and cell death during brain ischemia. Of note, microglial depletion-induced exacerbation of stroke severity did not solely depend on lymphocytes and monocytes. Importantly, depletion of microglia dramatically augmented the production of inflammatory mediators by astrocytes after brain ischemia . In vitro studies reveal that microglia restricted ischemia-induced astrocyte response and provided neuroprotective effects. Our findings suggest that neuroprotective effects of microglia may result, in part, from its inhibitory action on astrocyte response after ischemia.

Exercise Protects Skeletal Muscle during Chronic Doxorubicin Administration.

PURPOSE: This study aimed to assess the ability for exercise training performed before and during biweekly doxorubicin (DOX) administration to attenuate adverse effects of DOX on skeletal muscle. We hypothesized that DOX treatment would increase REDD1, impair mammalian target of rapamycin (mTOR) signaling, and reduce muscle fiber size, and that exercise training would attenuate these responses. METHODS: Eight-week-old ovariectomized female Sprague-Dawley rats were randomized to one of four treatments: exercise + DOX (Ex-Dox), Ex + vehicle (Ex-Veh), sedentary + DOX (Sed-Dox), and Sed + Veh (Sed-Veh). DOX (4 mg·kg) or vehicle (saline) intraperitoneal injections were performed biweekly for a total of three injections (cumulative dose, 12 mg·kg). Ex animals performed interval exercise (4 × 4 min, 85%-90% V˙O2peak) 5 d·wk starting 1 wk before the first injection and continued throughout study duration. Animals were euthanized ~5 d after the last injection, during which the soleus muscle was dissected and prepared for immunoblot and immunohistochemical analyses. RESULTS: REDD1 mRNA and protein were increased only in Sed-Dox (P < 0.05). The phosphorylation of mTOR and 4E-BP1 and MHC I and MHC IIa fiber size were lower in Sed-Dox versus Sed-Veh (P < 0.05). By contrast, REDD1 mRNA and protein, mTOR, 4E-BP1, and MHC I fiber size were not different between Ex-Dox and Ex-Veh (P > 0.05). LC3BI was higher, and the LC3BII/I ratio was lower in Sed-Dox versus Sed-Veh (P < 0.05) but not between Ex-Dox and Ex-Veh (P > 0.05). CONCLUSION: These data suggest that DOX may inhibit mTORC1 activity and reduce MHCI and MHCIIa fiber size, potentially through elevated REDD1, and that exercise may provide a therapeutic strategy to preserve skeletal muscle size during chronic DOX treatment.