Sphingosine-1-phosphate receptor 3 signaling is a critical modulator of stroke outcome

Stroke is a leading cause of long-term disability worldwide. Its highly complex pathogenesis is characterized by a deleterious cycle of vascular dysfunction and inflammation. Recently, the bioactive phospholipid sphingosine-1-phosphate (S1P), has gained increasing attention in cardiovascular diseases due to its involvement in both vascular function and immune cell responses. Altered S1P levels have been reported in several cardiovascular and inflammation-associated diseases, including stroke. S1P signals via five ubiquitously expressed S1P receptors, S1Pr1-5. Previous in vitro studies revealed alterations of S1Pr3 signaling under inflammatory conditions. During vascular adaptation to disease models of middle cerebral artery occlusion (MCAo), we determined the expression pattern of S1Pr3 in brain tissue with qPCR and western blot. Transient MCAo in endothelial- and astrocyte-specific RiboTag transgenic mice allowed us to determine changes in S1P signaling through immunoprecipitation of translating mRNAs from both cell types. For modulation of S1Pr3 signaling, we used S1Pr3-/- mice or pharmacological S1Pr3 inhibition administered 4 and 8 hours after permanent MCAo. Stroke outcome was determined by infarct size evaluation, neuroscore, and assessment of cerebral blood flow (CBF) using magnetic resonance imaging. S1Pr3 expression was significantly increased 1 day and 3 days post-ischemia in the ipsilateral hemisphere of WT mice on the gene and protein level. Mice lacking S1Pr3 revealed improved neurological function and reduced ischemic lesion during the acute phase after experimental stroke. Using vessel-parenchyma fractionation of brain tissue, we detected the majority of S1Pr3 associated with cerebral vessels. RiboTag analysis unveiled an augmentation of astrocyte- but not endothelial-specific S1Pr3 expression 1 day and 3 days post-stroke. RiboTag results were further confirmed using in situ hybridization colocalization of Gfap and Sox9, astrocytic markers and S1Pr3 in the ischemic hemisphere. Single administration of an S1Pr3 antagonist 4 hours after permanent MCAo led to significant CBF improvements in the ipsilateral hemisphere 1 day post-stroke that persisted up to 3 days. Consequently, infarct size was significantly reduced in mice treated with S1Pr3 antagonist. However, later administration at 8 hours post-stroke did not improve CBF or reduced infarct size. In conclusion, our findings point to an important involvement of the S1P/S1Pr3 signaling axis during stroke, and a potential contribution of astrocytes-specific S1Pr3 signaling during the acute phase post-stroke. Modulating S1Pr3-mediated vascular responses may emerge as a viable target to improving stroke outcome

Not all lectins are equally suitable for labeling rodent vasculature

The vascular system is vital for all tissues and the interest in its visualization spans many fields. A number of different plant-derived lectins are used for detection of vasculature; however, studies performing direct comparison of the labeling efficacy of different lectins and techniques are lacking. In this study, we compared the labeling efficacy of three lectins: Griffonia simplicifolia isolectin B4 (IB4); wheat germ agglutinin (WGA), and Lycopersicon esculentum agglutinin (LEA). The LEA lectin was identified as being far superior to the IB4 and WGA lectins in histological labeling of blood vessels in brain sections. A similar signal-to-noise ratio was achieved with high concentrations of the WGA lectin injected during intracardial perfusion. Lectins were also suitable for labeling vasculature in other tissues, including spinal cord, dura mater, heart, skeletal muscle, kidney, and liver tissues. In uninjured tissues, the LEA lectin was as accurate as the Tie2–eGFP reporter mice and GLUT-1 immunohistochemistry for labeling the cerebral vasculature, validating its specificity and sensitivity. However, in pathological situations, e.g., in stroke, the sensitivity of the LEA lectin decreases dramatically, limiting its applicability in such studies. This work can be used for selecting the type of lectin and labeling method for various tissues

Simvastatin therapy attenuates memory deficits that associate with brain monocyte infiltration in chronic hypercholesterolemia

Abstract Evidence associates cardiovascular risk factors with unfavorable systemic and neuro-inflammation and cognitive decline in the elderly. Cardiovascular therapeutics (e.g., statins and anti-hypertensives) possess immune-modulatory functions in parallel to their cholesterol- or blood pressure (BP)-lowering properties. How their ability to modify immune responses affects cognitive function is unknown. Here, we examined the effect of chronic hypercholesterolemia on inflammation and memory function in Apolipoprotein E (ApoE) knockout mice and normocholesterolemic wild-type mice. Chronic hypercholesterolemia that was accompanied by moderate blood pressure elevations associated with apparent immune system activation characterized by increases in circulating pro-inflammatory Ly6Chi monocytes in ApoE-/- mice. The persistent low-grade immune activation that is associated with chronic hypercholesterolemia facilitates the infiltration of pro-inflammatory Ly6Chi monocytes into the brain of aged ApoE-/- but not wild-type mice, and links to memory dysfunction. Therapeutic cholesterol-lowering through simvastatin reduced systemic and neuro-inflammation, and the occurrence of memory deficits in aged ApoE-/- mice with chronic hypercholesterolemia. BP-lowering therapy alone (i.e., hydralazine) attenuated some neuro-inflammatory signatures but not the occurrence of memory deficits. Our study suggests a link between chronic hypercholesterolemia, myeloid cell activation and neuro-inflammation with memory impairment and encourages cholesterol-lowering therapy as safe strategy to control hypercholesterolemia-associated memory decline during ageing

Fenofibrate Decreases Hepatic P-Glycoprotein in a Rat Model of Hereditary Hypertriglyceridemia

P-glycoprotein (P-gp) is a membrane-bound transporter encoded by Mdr1a/Abcb1a and Mdr1b/Abcb1b genes in rodents involved in the efflux of cytotoxic chemicals and metabolites from cells. Modulation of its activity influences P-gp-mediated drug delivery and drug-drug interaction (DDI). In the current study, we tested the effects of fenofibrate on P-gp mRNA and protein content in non-obese model of metabolic syndrome. Males hereditary hypertriglyceridemic rats (HHTg) were fed standard laboratory diet (STD) (Controls) supplemented with micronized fenofibrate in lower (25 mg/kg b. wt./day) or in higher (100 mg/kg b. wt./day) dose for 4 weeks. Liver was used for the subsequent mRNA and protein content analysis. Fenofibrate in lower dose decreased hepatic Mdr1a by 75% and Mdr1b by 85%, while fenofibrate in higher dose decreased Mdr1a by 90% and Mdr1b by 92%. P-gp protein content in the liver was decreased by 74% in rat treated with fenofibrate at lower dose and by 88% in rats using fenofibrate at higher dose. These findings demonstrate for the first time that fenofibrate decreases both mRNA and protein amount of P-gp and suggest that fenofibrate could affect bioavailability and interaction of drugs used to treat dyslipidemia-induced metabolic disorders

The emerging alliance of sphingosine-1-phosphate signaling and immune cells: from basic mechanisms to implications in hypertension.

The immune system plays a considerable role in hypertension. In particular, T-lymphocytes are recognized as important players in its pathogenesis. Despite substantial experimental efforts, the molecular mechanisms underlying the nature of T-cell activation contributing to an onset of hypertension or disease perpetuation are still elusive. Amongst other cell types, lymphocytes express distinct profiles of GPCRs for sphingosine-1-phosphate (S1P) – a bioactive phospholipid that is involved in many critical cell processes and most importantly majorly regulates T-cell development, lymphocyte recirculation, tissue-homing patterns and chemotactic responses. Recent findings have revealed a key role for S1P chemotaxis and T-cell mobilization for the onset of experimental hypertension, and elevated circulating S1P levels have been linked to several inflammation-associated diseases including hypertension in patients. In this article, we review the recent progress towards understanding how S1P and its receptors regulate immune cell trafficking and function and its potential relevance for the pathophysiology of hypertension. Linked Articles: This article is part of a themed section on Immune Targets in Hypertension

Improving cerebrovascular function to increase neuronal recovery in neurodegeneration associated to cardiovascular disease

Mounting evidence indicates that the presence of cardiovascular disease (CVD) and risk factors elevates the incidence of cognitive impairment (CI) and dementia. CVD and associated decline in cardiovascular function can impair cerebral blood flow (CBF) regulation, leading to the disruption of oxygen and nutrient supply in the brain where limited intracellular energy storage capacity critically depends on CBF to sustain proper neuronal functioning. During hypertension and acute as well as chronic CVD, cerebral hypoperfusion and impaired cerebrovascular function are often associated with neurodegeneration and can lead to CI and dementia. Currently, all forms of neurodegeneration associated to CVD lack effective treatments, which highlights the need to better understand specific mechanisms linking cerebrovascular dysfunction and CBF deficits to neurodegeneration. In this review, we discuss vascular targets that have already shown attenuation of neurodegeneration or CI associated to hypertension, heart failure (HF) and stroke by improving cerebrovascular function or CBF deficits