ABSTRACT
Sphingosine 1-phosphate (S1P) is a bioactive sphingolipid which modulates vascular integrity through its receptors, S1P1-S1P5. Notably, S1P2 has been shown to mediate the disruption of cerebrovascular integrity in vitro and in vivo. However, the mechanism underlying this process has not been fully elucidated. We evaluated the role of S1P2 in blood-brain barrier (BBB) disruption induced by lipopolysaccharide (LPS)-mediated systemic inflammation and found that BBB disruption and neutrophil infiltration were significantly attenuated in S1pr2-/- mice relative to S1pr2+/- littermates. This is concomitant with attenuation of LPS-induced transcriptional activation of IL-6 and downregulation of occludin. Furthermore, S1pr2-/- mice had significantly reduced expression of genes essential for neutrophil infiltration: Sele, Cxcl1, and Cxcl2. Conversely, pharmacological agonism of S1P2 induced transcriptional activation of E-selectin in vitro and in vivo. Although S1P2 does not appear to be required for activation of microglia, stimulation of microglial cells with the S1P2 potentiated the response of endothelial cells to LPS. These results demonstrate that S1P2 promotes LPS-induced neutrophil extravasation by inducing expression of endothelial adhesion molecule gene, Sele, and potentiating microglial inflammation of endothelial cells. It is likely that S1P2 is a mediator of cerebrovascular inflammation and represents a potential therapeutic target for neurodegenerative disease such as vascular cognitive impairment.
Subject(s)
Blood-Brain Barrier/metabolism , Leukocytes/metabolism , Neurodegenerative Diseases/metabolism , Sphingosine-1-Phosphate Receptors/deficiency , Animals , Blood-Brain Barrier/drug effects , Blood-Brain Barrier/pathology , Brain/drug effects , Brain/metabolism , Brain/pathology , Cell Line , Leukocytes/drug effects , Lipopolysaccharides/toxicity , Male , Mice , Mice, 129 Strain , Mice, Inbred C57BL , Mice, Knockout , Neurodegenerative Diseases/chemically induced , Neurodegenerative Diseases/pathology , Sphingosine-1-Phosphate Receptors/geneticsABSTRACT
Regeneration of skeletal muscle after volumetric injury is thought to be impaired by a dysregulated immune microenvironment that hinders endogenous repair mechanisms. Such defects result in fatty infiltration, tissue scarring, chronic inflammation, and debilitating functional deficits. Here, we evaluated the key cellular processes driving dysregulation in the injury niche through localized modulation of sphingosine-1-phosphate (S1P) receptor signaling. We employ dimensionality reduction and pseudotime analysis on single cell cytometry data to reveal heterogeneous immune cell subsets infiltrating preclinical muscle defects due to S1P receptor inhibition. We show that global knockout of S1P receptor 3 (S1PR3) is marked by an increase of muscle stem cells within injured tissue, a reduction in classically activated relative to alternatively activated macrophages, and increased bridging of regenerating myofibers across the defect. We found that local S1PR3 antagonism via nanofiber delivery of VPC01091 replicated key features of pseudotime immune cell recruitment dynamics and enhanced regeneration characteristic of global S1PR3 knockout. Our results indicate that local S1P receptor modulation may provide an effective immunotherapy for promoting a proreparative environment leading to improved regeneration following muscle injury.
Subject(s)
Cyclopentanes/therapeutic use , Immunotherapy/methods , Muscle, Skeletal/injuries , Regeneration/drug effects , Sphingosine-1-Phosphate Receptors/physiology , Animals , Cyclopentanes/pharmacology , Drug Liberation , Flow Cytometry , Leukopenia/genetics , Male , Mice , Mice, Inbred C57BL , Mice, Knockout , Microscopy, Atomic Force , Muscle, Skeletal/immunology , Muscle, Skeletal/metabolism , Muscle, Skeletal/pathology , Myeloid Cells/immunology , Nanofibers , Organ Size , Quadriceps Muscle/immunology , Quadriceps Muscle/injuries , Quadriceps Muscle/metabolism , Quadriceps Muscle/pathology , Signal Transduction/drug effects , Sphingosine-1-Phosphate Receptors/deficiency , Sphingosine-1-Phosphate Receptors/genetics , T-Lymphocyte Subsets/immunology , Tissue ScaffoldsABSTRACT
Tumor immunosuppression is a limiting factor for successful cancer therapy. The lipid sphingosine-1-phosphate (S1P), which signals through 5 distinct G protein-coupled receptors (S1PR1-5), has emerged as an important regulator of carcinogenesis. However, the utility of targeting S1P in tumors is hindered by S1P's impact on immune cell trafficking. Here, we report that ablation of the immune cell-specific receptor S1PR4, which plays a minor role in immune cell trafficking, delayed tumor development and improved therapy success in murine models of mammary and colitis-associated colorectal cancer through increased CD8+ T cell abundance. Transcriptome analysis revealed that S1PR4 affected proliferation and survival of CD8+ T cells in a cell-intrinsic manner via the expression of Pik3ap1 and Lta4h. Accordingly, PIK3AP1 expression was connected to increased CD8+ T cell proliferation and clinical parameters in human breast and colon cancer. Our data indicate a so-far-unappreciated tumor-promoting role of S1P by restricting CD8+ T cell expansion via S1PR4.
