Traumatic brain injury increases TGF beta RII expression on endothelial cells.

Transforming growth factor beta (TGFbeta) modulates a variety of growth related functions following traumatic injury. The cellular response to TGFbeta is predominantly mediated through TGFbeta receptor I (TGFbetaRI) and receptor II (TGFbetaRII) on the cell surface and SMAD proteins intracellularly. We investigated the expression of TGFbeta receptors in the acute and chronic phases of a traumatic cerebral injury (TCI) by immunohistochemistry and in cultures of murine brain microvascular endothelial (EN) cells using cytofluorimetry. Here, we report that TGFbetaRII expression significantly increases on brain endothelial cells in the chronic phase of TCI. SMAD3 and SMAD4 protein expression were also upregulated suggesting the activation of TGFbeta receptor intracellular signaling. When TGFbetaRI and TGFbetaRII expression was studied in in vitro cultures of murine brain microvessel EN cells, TGFbetaRII showed increased expression on proliferating cells that are incorporating BrdU. These data show a differential expression of TGFbetaRI and TGFbetaRII on brain microvessel EN cells in the acute and chronic phases of TCI that might be associated with EN proliferation following injury.

A small population of vasculitogenic T cells expands and has skewed T cell receptor usage after culture with syngeneic smooth muscle cells.

Adoptive transfer of lymphocytes co-cultured with syngeneic smooth muscle (SM) cells to healthy recipient mice results in vasculitic lesions predominantly in post-capillary venules. The present study focuses on the mechanisms by which the disease-inducing CD4(+) T cells are generated in co-culture of lymphocytes with SM cells. Microvascular SM cells provide survival signals to both CD4(+) and CD8(+) naïve syngeneic T cells and can activate only a limited range of CD4(+) T lymphocytes in culture. Additionally, approximately 0.4% of the original CD4(+) T cells divide at least twice in co-culture with SM cells. Survival of CD4(+) T cells in co-culture is dependent on a TCR mediated process, since transgenic CD4 (+)cells with a unique specificity for a non-murine peptide do not survive in culture with SM. Analysis of TCR Vbeta shows no superantigen activation of T cells following co-culture with SM cells. Spectratype analysis of TCR Vbeta Jbeta segment usage reveals a skewage in the TCR repertoire of T cells co-cultured with SM, and also of T cells from vasculitic lung. These results are consistent with a specific immune response of pathogenic T cells against one or more activating antigenic determinants of the microvascular SM cells, in contrast to non-specific cytokine activation.

Activated/effector CD4+ T cells exacerbate acute damage in the central nervous system following traumatic injury.

CD4(+) helper T cells (Th) have been demonstrated to participate in the chronic phase of traumatic injury repair in the central nervous system (CNS). Here, we show that CD4(+) T cells can also contribute to the severity of the acute phase of CNS traumatic injury. We compared the area of tissue damage and the level of cellular apoptosis in aseptic cerebral injury (ACI) sites of C57BL/6 wild type and RAG1(-/-) immunodeficient mice. We demonstrate that ACI is attenuated in RAG1(-/-) mice compared to C57BL/6 animals. Adoptive transfer of CD4(+)CD62L(low)CD44(high) activated/effector T cells 24 h prior to ACI into RAG1(-/-) mice resulted in a significantly enhanced acute ACI that was comparable to ACI in the C57BL/6 animals. Adoptive transfer of CD4(+)CD62L(high)CD44(low) naive/non-activated T cells did not increase ACI in the brains of RAG1(-/-) mice. T cell inhibitory agents, cyclosporin A (CsA) and FK506, significantly decreased ACI-induced acute damage in C57BL/6 mice. These results suggest a previously undescribed role for activated/effector CD4(+) T cells in exacerbating ACI-induced acute damage in the CNS and raise a novel possibility for acute treatment of sterile traumatic brain injury.