IL-22 and IL-20 are key mediators of the epidermal alterations in psoriasis while IL-17 and IFN-gamma are not.

Psoriasis is a common chronic skin disease with a largely unknown pathogenesis. We demonstrate here that transgenic over-expression of interleukin (IL)-22 in mice resulted in neonatal mortality and psoriasis-like skin alterations including acanthosis and hypogranularity. This cutaneous phenotype may be caused by the direct influence of IL-22 on keratinocytes, since this cytokine did not affect skin fibroblasts, endothelial cells, melanocytes, or adipocytes. The comparison of cytokines with hypothesized roles in psoriasis pathogenesis determined that neither interferon (IFN)-gamma nor IL-17, but only IL-22 and, with lower potency, IL-20 caused psoriasis-like morphological changes in a three-dimensional human epidermis model. These changes were associated with inhibited keratinocyte terminal differentiation and with STAT3 upregulation. The IL-22 effect on differentiation-regulating genes was STAT3-dependent. In contrast to IL-22 and IL-20, IFN-gamma and IL-17 strongly induced T-cell and neutrophilic granulocyte-attracting chemokines, respectively. Tumor necrosis factor-alpha potently induced diverse chemokines and additionally enhanced the expression of IL-22 receptor pathway elements and amplified some IL-22 effects. This study suggests that different cytokines are players in the psoriasis pathogenesis although only the IL-10 family members IL-22 and IL-20 directly cause the characteristic epidermal alterations.

GLEPP1/protein-tyrosine phosphatase phi inhibitors block chemotaxis in vitro and in vivo and improve murine ulcerative colitis.

We describe novel, cell-permeable, and bioavailable salicylic acid derivatives that are potent and selective inhibitors of GLEPP1/protein-tyrosine phosphatase . Two previously described GLEPP1 substrates, paxillin and Syk, are both required for cytoskeletal rearrangement and cellular motility of leukocytes in chemotaxis. We show here that GLEPP1 inhibitors prevent dephosphorylation of Syk1 and paxillin in resting cells and block primary human monocyte and mouse bone marrow-derived macrophage chemotaxis in a gradient of monocyte chemotactic protein-1. In mice, the GLEPP1 inhibitors also reduce thioglycolate-induced peritoneal chemotaxis of neutrophils, lymphocytes, and macrophages. In murine disease models, the GLEPP1 inhibitors significantly reduce severity of contact hypersensitivity, a model for allergic dermatitis, and dextran sulfate sodium-induced ulcerative colitis, a model for inflammatory bowel disease. Taken together, our data provide confirmation that GLEPP1 plays an important role in controlling chemotaxis of multiple types of leukocytes and that pharmacological inhibition of this phosphatase may have therapeutic use.

LPS differentially regulates adhesion and transendothelial migration of human monocytes under static and flow conditions.

One of the key components of the innate immune response is the recognition of microbial products such as LPS by Toll-like receptors on monocytes and neutrophils. We show here that short-term stimulation of primary human monocytes with LPS led to an increase in adhesion of monocytes to endothelial cells and a dramatic decrease in transendothelial migration under static conditions. In contrast, under normal physiological flow, monocyte adhesion and migration across a human umbilical vein endothelial cell monolayer appeared to be unaffected by LPS treatment. LPS stimulation of monocytes activated beta(1) and beta(2) integrins, but did not increase their surface expression levels. During septic shock, reduction in blood flow as a result of vasodilation and vascular permeability leads to adhesion and accumulation of LPS-stimulated circulating monocytes onto the blood vessel walls. The different findings of monocyte migration under static and flow conditions in our study may offer one explanation for this phenomenon. The rapid engagement of LPS-activated monocytes preventing transendothelial migration could represent a novel mechanism of bacterial exclusion from the vasculature. This occurs during the early stages of sepsis, and in turn may modulate the severity of the pathophysiology.

Protein therapeutics--lessons learned and a view of the future.

Protein therapeutics represent a rapidly growing proportion of marketed drugs and have an undisputed place alongside chemistry-based oral therapies; indeed, for certain indications they are the only effective therapy. Therapeutic proteins can be mined from diverse sources to target interactions that are not accessible to small molecules, and can be engineered to have optimal pharmacological properties. Nevertheless, the development of such therapeutics is hampered by several issues, such as cost of production, patient compliance, immunogenicity and reticence of reimbursement agencies to pay for their use in chronic treatment. Herein we review some of these issues in detail. The application of technological advancements will address some of these issues and enable the development of a growing number of biological therapies that will continue to improve patient quality of life for decades to come.

Haemangiomas are formed by cells expressing high levels of alphavbeta3 integrin and lacking acetylated LDL uptake.

Haemangiomas are benign tumours occurring in up to 12% of Caucasians, particularly in infancy and childhood. In the present study, two variant cell lines were isolated from murine endothelioma cells. One variant, named t.End.1V(high), represented 16.9% of the parental cell population and was selected by virtue of high expression levels of integrin alphavbeta3 and reduced capacity to endocytose acetylated low-density lipoproteins (Ac-LDLs). A second variant, named t.End.1V(low), represented 38.8% of the parental endothelioma cell line, expressed low levels of alphavbeta3 integrin, and was able to endocytose Ac-LDL. These phenotypic modifications were stable and correlated with specific morphological and functional properties of the two variant cell lines. While the t.End.1V(high) cells induced the formation of large haemangiomas when injected subcutaneously into mice, the t.End.1V(low) cells formed haemangiocytomas. When compared with t.End.1V(low) cells, the t.End.1V(high) cells showed increased migratory capacity, lacked an inflammatory response, and formed cord-like structures in fibrin gels. In contrast, the t.End.1V(low) cells organized into cysts with a lumen in fibrin gels. They rarely formed blood-filled haemangiomas in vivo and recruited host smooth muscle cells, a phenomenon typical for vessel wall maturation of resting cells. These data suggest that Ac-LDL uptake and the level of alphavbeta3 integrin expression are linked to the ability of endothelial cells to form large haemangiomas in vivo.

The alpha v beta 3 integrin as a tumor homing ligand for lymphocytes.

Despite the presence of tumor-specific effector cells in the circulation of cancer patients, the immune response of the majority of these patients is not sufficient to prevent the growth and spread of their tumors. That tumor cells can be killed in vitro by tumor-reactive cytotoxic T cells is testimony to the fact that the tumors are not inherently resistant to T cell killing, but rather that there is a failure in immune recognition and effector cell activation. Many reasons for this failure of the body's defense system have been suggested, including the inability of tumor-reactive lymphocytes to migrate to tumor tissue. Here we designed a strategy to improve homing of primary lymphocytes into vascularized tumors. As a homing molecule we selected the integrin alpha v beta 3 since it is expressed by angiogenic vascular endothelium in tumors. To promote lymphocyte adhesion to alpha v beta 3 we "painted" primary lymphocytes with a recombinant, glycosylphosphatidylinositol-linked high-affinity ligand for alpha v beta 3. These painted lymphocytes specifically bound to alpha v beta 3 in vitro and homed to vascularized, solid tumors in vivo. This novel strategy may provide a significant advance in anti-tumor treatment such as adoptive immune therapy.

Forging the endothelium during inflammation: pushing at a half-open door?

During an inflammatory response, changes in the adhesive properties of the endothelium occur that enable normally non-adherent blood-borne leukocytes to adhere and subsequently to traverse the endothelium through small gaps at inter-cellular junctions. This review concentrates on the role played by inter-endothelial adhesion molecules during transmigration and the way in which their expression may be regulated during inflammation. We show that the final "open" signals that lead to the formation of clefts between adjacent endothelial cells may be derived from inflamed tissue underlying the endothelium and from activated leukocytes.

Junctional adhesion molecules and interendothelial junctions.

Similar to epithelia, endothelial cells are linked to each other via intercellular junctional complexes including gap junctions, adherens junctions and tight junctions. While polarized epithelial cells show a high degree of spatial sorting of junctional complexes, endothelia organize their junctions randomly. For this reason the nature of endothelial contacts may be highly adaptable to the need of permeability and leukocyte transmigration. For instance, high endothelial venules (HEVs) in lymphoid organs, where lymphocytes continuously exit the bloodstream, generally show more leaky contacts than brain with its impermeable blood-brain barrier. We recently identified an Ig superfamily molecule named JAM-2 which is specifically expressed in junctions of lymphatic endothelial cells and HEVs. We showed that JAM-2 belongs to the novel CTX molecular family and we now cloned the human equivalent of JAM-2. The presence of JAM-2 at sites of constitutive lymphocyte circulation argues for a role of this molecule in facilitating transmigration. This is supported by the increased transmigration in vitro across endothelial cells overexpressing JAM-2 at intercellular contacts.

Junctional adhesion molecule-2 (JAM-2) promotes lymphocyte transendothelial migration.

The molecular mechanisms underlying lymphocyte extravasation remain poorly characterized. We have recently identified junctional adhesion molecule-2 (JAM-2), and have shown that antibodies to JAM-2 stain high endothelial venules (HEVs) within lymph nodes and Peyer patches of adult mice. Here we show that mouse lymphocytes migrate in greater numbers across monolayers of endothelioma cells transfected with JAM-2. The significance of these findings to an understanding of both normal and pathologic lymphocyte extravasation prompted us to clone the human homologue of JAM-2. We herein demonstrate that an anti-JAM-2 antibody, or a soluble JAM-2 molecule, blocks the transmigration of primary human peripheral blood leukocytes across human umbilical vein endothelial cells expressing endogenous JAM-2. Furthermore, we show that JAM-2 is expressed on HEVs in human tonsil and on a subset of human leukocytes, suggesting that JAM-2 plays a central role in the regulation of transendothelial migration.

Role of interendothelial adhesion molecules in the control of vascular functions.

The function of endothelium is the lining of the vessel wall and the control of vascular permeability, homeostasis and leukocyte emigration from the blood into the surrounding tissue. Different adhesion molecules expressed in a coordinated and regulated way control this function. In this review, we discuss adhesion molecules involved in endothelial junctions and their involvement in leukocyte transendothelial migration. Passage of the leukocyte across the endothelium appears to require delocalization of certain vascular adhesion molecules whereas other molecules interact directly with leukocyte ligands. Understanding of the function of vascular adhesion molecules is further complicated as they transduce signals to the endothelium and interact with the cytoskeleton and adaptor proteins.