CD8 T Cell-Initiated Vascular Endothelial Growth Factor Expression Promotes Central Nervous System Vascular Permeability under Neuroinflammatory Conditions

Abstract

Dysregulation of the blood-brain barrier (BBB) is a hallmark feature of numerous neurologic disorders as diverse as multiple sclerosis, stroke, epilepsy, viral hemorrhagic fevers, cerebral malaria, and acute hemorrhagic leukoencephalitis. CD8 T cells are one immune cell type that have been implicated in promoting vascular permeability in these conditions. Our laboratory has created a murine model of CD8 T cell-mediated CNS vascular permeability using a variation of the Theiler’s murine encephalomyelitis virus system traditionally used to study multiple sclerosis. Previously, we demonstrated that CD8 T cells have the capacity to initiate astrocyte activation, cerebral endothelial cell tight junction protein alterations and CNS vascular permeability through a perforin-dependent process. To address the downstream mechanism by which CD8 T cells promote BBB dysregulation, in this study, we assess the role of vascular endothelial growth factor (VEGF) expression in this model. We demonstrate that neuronal expression of VEGF is significantly upregulated prior to, and coinciding with, CNS vascular permeability. Phosphorylation of fetal liver kinase-1 is significantly increased early in this process indicating activation of this receptor. Specific inhibition of neuropilin-1 significantly reduced CNS vascular permeability and fetal liver kinase-1 activation, and preserved levels of the cerebral endothelial cell tight junction protein occludin. Our data demonstrate that CD8 T cells initiate neuronal expression of VEGF in the CNS under neuroinflammatory conditions, and that VEGF may be a viable therapeutic target in neurologic disease characterized by inflammation-induced BBB disruption.

Experimental Model Systems to Define Mechanisms of Immune-Mediated Blood Brain Barrier Disruption in Acute Disseminated Encephalomyelitis (ADEM) and Acute Hemorrhagic Leukoencephalitis (AHLE)

“…Through analysis of FITC-albumin leakage into the brain, it was found that inhibition of neuropilin-1 with high doses of ATWLPPR VEGF inhibitor resulted in decreased CNS vascular permeability when compared to mice treated with PBS or scrambled RAPTLWP peptide. Furthermore, there was no significant difference between mice treated with VEGF inhibitor and mice treated with mock E7 peptide (Suidan et al, 2010). As previously reported using the PIFS model, degradation of the tight junction protein occludin occurs prior to CNS vascular permeability .…”

Improved Treatment Efficacy of Antiangiogenic Therapy when Combined with Picornavirus Vaccination in the GL261 Glioma Model

“…The effects of VEGF in gliomas have been shown to be enhanced by hypoxia, tumor cell expression of the cytokine, and hematopoietic derived factors [4,5,57]. More recently, CD8+ and CD4+ T cells have been demonstrated to promote VEGF upregulation in the CNS under neuroinflammatory conditions [35,36]. While enhanced VEGF expression in our model is apparent, the source of this increase requires further investigation.…”

“…Additionally, detailed characterizations of the effector functions of infiltrating immune cells, including alterations to cytotoxic function and immunosuppressive capacity, are underway. Furthermore, reciprocal studies will investigate altered angiogenic responses following enhancement of antitumor responses, as immune cells have also been shown to modulate VEGF expression and angiogenesis [35,36].…”

“…Immune cell infiltration of human GBM is extensive, with monocytes/macrophages representing the largest cellular fraction and growing evidence of CD8+ T cell involvement [33,34]. Both CD8+ and CD4+ T-cell responses have been shown to drive VEGF upregulation in the CNS under neuroinflammatory conditions, which could contribute to angiogenesis and tumor progression [35,36]. Alternatively, tumor antigen-specific cytotoxic CD8+ T cells and T helper 1/17 CD4+ T cells have been shown to contribute to antitumor immunity, hindering tumor outgrowth [34,[37][38][39].…”

Krüppel-like factor KLF10 regulates transforming growth factor receptor II expression and TGF-β signaling in CD8+ T lymphocytes

“…Splenocytes were stained for the expression of cell surface TGF-␤RII and viral Ag-tetramers and analyzed by flow cytometry. D b :VP2121-130 and D b :GARC tetramers were made as previously described (19). In additional experiments, splenocytes were stimulated in vitro with viral peptides or control antigen and analyzed for the expression of IFN-␥ by intracellular staining among viral-specific CD8 ϩ T cells.…”