IL-11 Activates Human Endothelial Cells to Resist Immune-Mediated Injury

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Persistent E-selectin expression on human dermal microvascular endothelial cells (HDMEC), believed to mediate skin-specific T cell homing, results from a slow rate of surface protein internalization after cytokine induction. Following transduction of unactivated HDMEC with E-selectin cDNA, the rate of internalization was largely independent of increasing levels of surface protein expression, leading to prolonged t1/2 values of over 4 h, comparable to that observed following cytokine induction. In HUVEC, the rate of internalization increased with surface expression level, leading to an essentially constant t1/2 of under 2 h. Thus, the internalization process rather than cytokine responsiveness or E-selectin structure underlies the difference in endothelial cell behavior. Mutational analysis of the cytoplasmic region demonstrated a role for a di-leucine-type motif involving I588 and L589 but not for a putative tyrosine-type motif. Control of E-selectin surface expression appears to be phosphoserine dependent, since alanine but not aspartic acid substitution for S581 slows E-selectin internalization.

Section: Immunoassaysmentioning

confidence: 99%

Cutting Edge: Internalization of Transduced E-Selectin by Cultured Human Endothelial Cells: Comparison of Dermal Microvascular and Umbilical Vein Cells and Identification of a Phosphoserine-Type Di-leucine Motif

Kluger

Shiao

Bothwell

et al. 2002

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“…Fibroblast growth factor (3), platelet-derived growth factor, RANKL/ TNF-related activation-induced cytokine (4), angiopoietin-1 (5), TNF-␣, and IL-1 (6) all use PI3K and Akt, although IL-11 requires MAPK/ERK1 (7). Additionally, IL-4 and IL-13, which are known to promote cell survival through inhibition of apoptosis in various cell types, were found to protect human EC from apoptosis, in association with up-regulation of A1 and A20 expression (8).…”

Section: Ascular Endothelial Cells (Ec)mentioning

confidence: 99%

IL-4 and IL-13 Induce Protection of Porcine Endothelial Cells from Killing by Human Complement and from Apoptosis through Activation of a Phosphatidylinositide 3-Kinase/Akt Pathway

Grehan

Levay‐Young

Fogelson

et al. 2005

Vascular endothelial cells (EC) perform critical functions that require a balance of cell survival and cell death. EC death by apoptosis and EC activation and injury by the membrane attack complex of complement are important mechanisms in atherosclerosis and organ graft rejection. Although the effects of various cytokines on EC apoptosis have been studied, little is known about their effects on complement-mediated EC injury. Therefore, we studied the abilities of various cytokines to induce protection of porcine aortic EC against apoptosis and killing by human complement, a model of pig-to-human xenotransplantation. We found that porcine EC incubated with IL-4 or IL-13, but not with IL-10 or IL-11, became protected from killing by complement and apoptosis induced by TNF-α plus cycloheximide. Maximal protection required 10 ng/ml IL-4 or IL-13, developed progressively from 12 to 72 h of incubation, and lasted 48–72 h after cytokine removal. Protection from complement was not associated with reduced complement activation, C9 binding, or changes in CD59 expression. Inhibition of PI3K prevented development of protection; however, inhibition of p38 MAPK or p42/44 MAPK had no effect. IL-4 and IL-13 induced rapid phosphorylation of Akt. Although protection was inhibited by an Akt inhibitor and a dominant negative Akt mutant transduced into EC, it was induced by transduction of EC with the constitutively active Akt variant, myristylated Akt. We conclude that IL-4 and IL-13 can induce protection of porcine EC against killing by apoptosis and human complement through activation of the PI3K/Akt signaling pathway.

“…Importantly, this mechanism does not restore EC as CTL targets to the same level as BLC. Lack of activating costimulators (36) or production of inhibitory cytokines (37,38) might further contribute to the immune privilege of vascular endothelium. However, it has been shown in previous work that different cells process and present the same peptide source proteins in quantitatively different ways (39).…”

Section: Discussionmentioning

confidence: 99%

Two Preferentially Expressed Proteins Protect Vascular Endothelial Cells from an Attack by Peptide-Specific CTL

Thommen

Keller

Kapoor

et al. 2012

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Vascular endothelial cells (EC) are an exposed tissue with intimate contact with circulating Ag-specific CTL. Experimental in vitro and clinical data suggested that endothelial cells present a different repertoire of MHC class I-restricted peptides compared with syngeneic leukocytes or epithelial cells. This endothelial-specific peptide repertoire might protect EC from CTL-mediated cell death. The HLA-A*02-restricted peptide profile of human EC and syngeneic B lymphoblastoid cells was biochemically analyzed and compared. For EC selective peptides, source protein expression, peptide binding affinity, and peptide–HLA-A*02 turnover were measured. The significance of abundant peptide presentation for target cell recognition by immunodominant CTL was tested by small interfering RNA treatment of EC to knock down the source proteins. High amounts of two peptides, PTRF56–64 and CD59106–114, were consistently detected in EC. This predominance of two endothelial peptides was explained by cell type-specific source protein expression that compensated for poor HLA-A*02 binding affinity and short half-live of peptide/HLA-A*02 complexes. Knocking down the source proteins containing the abundant endothelial peptide motifs led to a nearly 100-fold increase of surface expression of SMCY311–319, an immunodominant minor histocompatibility Ag, as detected by cytotoxicity assays using SMCY311–319-specific CTL. We conclude that EC express and present preferentially two distinct HLA-A*02-restricted peptides at extraordinary high levels. These abundant self-peptides may protect EC from CTL-mediated lysis by competing for HLA-A*02 binding sites with immunodominant scarcely expressed antigenic peptides.