Biology subjects

Anrather, J.

Publications and source records attributed to Anrather, J..

3 recordsLinked to original sources

bioRxiv2018

Exacerbation of blood brain barrier dysfunction and brain injury after aneurysmal subarachnoid hemorrhage in endothelial specific S1PR1 knock out mice.

Blood brain barrier (BBB) dysfunction upon ischemia and hypoxia has been implicated in the exacerbation of neuronal injury in stroke. Despite the therapeutic potential of the cerebrovascular endothelium, the limited understanding of the endothelial signaling pathways governing BBB function restricts progress towards developing novel therapeutic approaches specifically targeting the endothelium. Sphingosine-1-phosphate (S1P) is a potent modulator of endothelial function via its receptors (S1PR). Recent human and mouse studies indicate that vasoprotective endothelial S1P signaling via S1PR1 may be impaired in cardiovascular and inflammatory diseases. Herein, we investigated the expression of S1PR1 in the mouse and human cerebrovascular endothelium and the role of endothelial-specific S1PR1 signaling in brain injury in a mouse model of aneurysmal subarachnoid hemorrhage (SAH), the most devastating type of stroke. We found that S1PR1 is the most abundant S1PR transcript in the mouse brain and in mouse and human brain endothelial cells (20-100 mRNA copies per cell). S1PR1 transcripts were significantly enriched (~6 fold) in mouse cortical microvessels compared to total brain. Using the S1PR1-eGFP knock in mouse, we found that S1PR1-eGFP is abundantly expressed in the cerebrovascular endothelium in the mouse brain. A similar pattern of expression was observed in human brain samples. Endothelial specific deletion of S1PR1 in adult mice (S1pr1 flox/floxxCdh5-CreERT2, referred to as S1pr1iECKO), resulted in exacerbation of brain edema, neuronal injury and worsened neurological outcomes upon SAH compared to S1pr1 flox/flox littermates. No differences in the subarachnoid blood, hemostasis or cerebral blood flow changes during and after SAH were found between groups. Mechanistically, S1pr1iECKO exhibited aggravated BBB dysfunction and increased phosphorylation of myosin light chain (MLC) in isolated cortical microvessels, a downstream effector of the Rho-ROCK pathway implicated in endothelial inflammation and barrier dysfunction. Taken together, our data indicate that S1PR1 is an endogenous protective signaling pathway in the endothelium, critical to maintain BBB function and to mitigate neuronal injury in pathological conditions. Thus, the therapeutic and diagnostic potential of the endothelial sphingosine-1-phosphate pathway in stroke deserves further study.

neuroscience↗

bioRxiv2018

Endogenous protection from ischemic brain injury by preconditioned monocytes

Exposure to low dose lipopolysaccharide prior to cerebral ischemia is neuroprotective in stroke models, a phenomenon termed preconditioning. While it is well established that lipopolysaccharide-preconditioning induces central and peripheral immune responses, the cellular mechanisms modulating ischemic injury remain unclear. Here, we investigated the role of immune cells in the brain protection afforded by preconditioning and we tested whether monocytes may be reprogrammed by ex vivo lipopolysaccharide exposure thus modulating the inflammatory injury after cerebral ischemia in male mice. We found that systemic injection of low-dose lipopolysaccharide induces a distinct subclass of CD115+Ly6Chi monocytes that protect the brain after transient middle cerebral artery occlusion in mice. Remarkably, adoptive transfer of monocytes isolated from preconditioned mice into naive mice 7 hours after transient middle cerebral artery occlusion reduced brain injury. Gene expression and functional studies showed that IL-10, iNOS and CCR2 in monocytes are essential for the neuroprotection. This protective activity was elicited even if mouse or human monocytes were exposed ex vivo to lipopolysaccharide and then injected into male mice after stroke. Cell tracking studies showed that protective monocytes are mobilized from the spleen and reach brain and meninges, wherein they suppressed post-ischemic inflammation and neutrophils influx into the brain parenchyma. Our findings unveil a previously unrecognized subpopulation of splenic monocytes capable to protect the brain with an extended therapeutic window, and provide the rationale for cell therapies based on the delivery of autologous or allogeneic protective monocytes into patients with ischemic stroke.\n\nSignificance StatementInflammation is a key component of the pathophysiology of the brain in stroke, a leading cause of death and disability with limited therapeutic options. Here, we investigate endogenous mechanisms of protection against cerebral ischemia. Using LPS preconditioning as an approach to induce ischemic tolerance in mice, we found the generation of neuroprotective monocytes within the spleen from where they traffic to the brain and meninges suppressing post-ischemic inflammation. Importantly, systemic LPS preconditioning can be mimicked by adoptive transfer of in vitro-preconditioned mouse or human monocytes at translational relevant time points after stroke. This model of neuroprotection may facilitate clinical efforts to increase the efficacy of bone marrow mononuclear cell treatments in acute neurological diseases such as cerebral ischemia.

neuroscience↗

bioRxiv2018

A master regulatory network restoring brain glutamate homeostasis is coordinately activated in stroke

Post-transcriptional regulation by miRNAs is essential for complex molecular responses to physiological insult and disease. Although many disease-associated miRNAs are known, their global targets and culminating network effects on pathophysiology remain poorly understood. We applied AGO CLIP to systematically elucidate altered miRNA-target interactions in brain following ischemia/reperfusion (I/R) injury. Among 1,190 identified, most prominent was the cumulative loss of target regulation by miR-29 family members. Integration of translational and time-course RNA profiles revealed a dynamic mode of miR-29 target de-regulation, led by acute translational activation and later increase in RNA levels, allowing rapid proteomic changes to take effect. These functional regulatory events rely on canonical and non-canonical miR-29 binding and engage glutamate reuptake signals to control local glutamate levels. These results uncover a miRNA target network that acts acutely to maintain brain homeostasis after ischemic stroke.

neuroscience↗