Biomedical subjects

K Biernacki

Publications and source records attributed to K Biernacki.

5 recordsLinked to original sources

PubMed2001

T lymphocytes conditioned with Interferon beta induce membrane and soluble VCAM on human brain endothelial cells.

Vascular cell adhesion molecule (VCAM)-1 plays a critical role in mediating inflammatory cell adhesion and migration. Factors regulating the expression of membrane (m)VCAM and its cleaved counterpart soluble (s)VCAM are poorly understood. We previously demonstrated that serum sVCAM levels are increased in multiple sclerosis (MS) patients treated with interferon beta 1b (IFNbeta1b), which correlated with a reduction in gadolinium enhancing lesions on magnetic resonance imaging. However, subsequent studies have shown that IFNbeta does not directly induce VCAM expression on endothelial cells. We demonstrate here that co-culture with IFNbeta-conditioned T cells induces mVCAM on human brain endothelial cells (HBEC). Further, rapid shedding of sVCAM occurs, which mirrors the response after in vivo IFNbeta treatment. The VCAM induction is mediated partially through tumor necrosis factor (TNF)alpha and can be abrogated by sTNF receptor. VCAM could also be induced on astroglioma lines using IFNbeta-conditioned T cells, which suggests the effect is not specific for HBEC. Kinetic studies demonstrated an increase in the sVCAM to mVCAM ratio over time, which may contribute to the ultimate therapeutic effect of IFNbeta in patients. These data have important implications for understanding the events occurring at the blood brain barrier in vivo, and for determining the mechanism of action of IFNbeta in MS.

Adult↗

PubMed2001

Glial cell influence on the human blood-brain barrier.

The blood-brain barrier (BBB) is a specialized structure of the central nervous system (CNS) that restricts immune cell migration and soluble molecule diffusion from the systemic compartment into the CNS. Astrocytes and microglia are resident cells of the CNS that contribute to the formation of the BBB. In this article, we consider the influence of these glial cells on the immune regulatory functions of the microvascular endothelium, with special emphasis on the human BBB. A series of in vitro studies demonstrate that soluble factors produced by glial cells, under basal culture conditions, help restrict development of inflammation within the CNS. These soluble factor effects include upregulating expression of molecules including HT7, UEA-1 lectin-binding sites, and angiotensin receptors that help define the phenotype of endothelial cells. These factors also induce tight junction formation between brain endothelial cells, contributing to the restricted permeability of the BBB. In contrast, these factors have little effect on expression of molecules by ECs that either promote lymphocyte migration, such as chemokines and adhesion molecules or molecules that are required for competent antigen presentation, such as MHC and co-stimulatory molecules. Glial cells that become activated in response to signals derived from the immune system or generated within the CNS, produce an array of inflammatory molecules that increase permeability and promote lymphocyte trafficking and persistence. These observations emphasize the bidirectional nature of neural-immune interactions; this dynamic system should be amenable to therapeutic interventions.

Animals↗

PubMed2001

Regulation of Th1 and Th2 lymphocyte migration by human adult brain endothelial cells.

Endothelial cells of the blood-brain barrier (BBB) have the ability to regulate and restrict the passage of cells and molecules from the periphery to the CNS. We have used an in vitro assay of lymphocyte migration across monolayers of human adult brain endothelial cells (HBEC) as a model of lymphocyte migration across the BBB. We found that human allogeneic or MBP-reactive Th2-polarized lymphocytes migrate more avidly than Th1-polarized lymphocytes. Migration of Th2 but not Th1 cells across brain endothelium was inhibited by antibodies directed at MCP-1, a chemokine produced by HBECs. We could detect CCR2, a chemokine receptor that recognizes MCP-1 on Th2 but not Th1 lymphocytes. ICAM-1 and VCAM-1 molecules were expressed on the surface of HBECs under basal conditions and were upregulated by Th1 but not Th2 cell-derived supernatants. Migration of both lymphocyte subsets was dependent on LFA-1/ICAM-1 interactions. Blocking VLA-4/VCAM-1 binding did not influence actual trans-endothelial migration. These results suggest that HBECs composing the BBB favor the migration of Th2 cells. We postulate that this selectivity may help prevent activated Th1 lymphocytes, the putative CNS autoimmune disease initiating cells, from reaching the CNS parenchyma and favor entry of Th2 cells, a putative means to induce bystander suppression in the CNS.

Adult↗

PubMed2000

Kinin B1 receptor expression and function on human brain endothelial cells.

The kinin B1 receptor is an inducible receptor expressed in response to inflammatory mediators. We sought to determine whether kinin B1 receptor can be expressed on human brain endothelial cells (HBECs) in vitro and whether signaling via this receptor can regulate permeability and chemokine production properties of these cells. Multiplex RT-PCR amplification and western blot techniques were used to evaluate B1 receptor expression by HBECs. Although B1 receptor mRNA and protein could not be detected on resting HBECs, interferon-gamma induced a dose- and time-dependent up-regulation of B1 receptor mRNA and protein on HBECs. Stimulation of interferon-gamma-treated HBECs with the selective B1 agonist R-838 (Sar [D-Phe8] des Arg9-BK) induced a dose- and time-dependent increase in the production of inositol 3,4,5 tri-phosphate and nitric oxide. Permeability of the HBECs monolayer, as measured by BSA diffusion, was significantly increased by application of the B1 agonist. This biological effect of R-838 could be prevented by R-715, a B1 receptor antagonist and by L-NAME, a nitric oxide synthase blocker. R-838 also inhibited interleukin-8 release from HBECs. We demonstrate that B1 receptors can be up regulated on the surface of HBECs by molecules released during inflammatory response and that signaling via this receptor can regulate BBB permeability and chemokine production in vitro.

Adult↗

PubMed2000

B7 expression and antigen presentation by human brain endothelial cells: requirement for proinflammatory cytokines.

Interaction between systemic immune cells with cells of the blood-brain barrier is a central step in development of CNS-directed immune responses. Endothelial cells are the first cells of the blood-brain barrier encountered by migrating lymphocytes. To investigate the antigen-presenting capacity of human adult brain endothelial cells (HBECs), we used HBECs derived from surgically resected temporal lobe tissue, cocultured with allogeneic peripheral blood derived CD4+ T lymphocytes. HBECs in response to IFN-gamma, but not under basal culture conditions, expressed HLA-DR, B7.1 and B7.2 antigens. Despite such up-regulation, these IFN-gamma-treated HBECs, in contrast to human microglia and PB monocytes, did not sustain allogeneic CD4+ cell proliferation, supported only low levels of IL-2 and IFN-gamma production, and did not stimulate IL-2 receptor expression. CD4+ T cell proliferation and increased IL-2 receptor expression could be obtained by addition of IL-2. Our data suggests that, although HBECs cannot alone support T cell proliferation and cytokine production, HBECs acting in concert with cytokines derived from a proinflammatory environment could support such a response.

Adult↗