The Selectins and their Ligands

Serum adhesion molecule levels as prognostic markers in patients with early systemic sclerosis: a multicentre, prospective, observational study

Objective

To assess the utility of circulating adhesion molecule levels as a prognostic indicator of disease progression in systemic sclerosis (SSc) patients with early onset disease.

Methods

Ninety-two Japanese patients with early onset SSc presenting with diffuse skin sclerosis and/or interstitial lung disease were registered in a multicentre, observational study. Concentrations of intercellular adhesion molecule (ICAM) −1, E-selectin, L-selectin, and P-selectin in serum samples from all patients were measured by enzyme-linked immunosorbent asssay (ELISA). In 39 patients, adhesion molecule levels were measured each year for four years. The ability of baseline adhesion molecule levels to predict subsequent progression and severity in clinical and laboratory features were evaluated statistically.

Results

At their first visit, serum levels of ICAM-1, E-selection, P-selectin were significantly elevated and serum L-selectin levels were significantly reduced in patients with SSc compared with healthy controls. Overall, serum ICAM-1 levels at each time point were significantly inversely associated with the %vital capacity (VC) of the same time and subsequent years by univariate analysis. The initial serum ICAM-1 levels were significantly inversely associated with the %VC at the fourth year by multiple regression analysis. The initial serum P-selectin levels were significantly associated with the health assessment questionnaire disability index (HAQ-DI) at the fourth year by multiple regression analysis. Initial adhesion molecule levels were not significantly associated with other clinical features including skin thickness score. Baseline adhesion molecule levels were not significantly associated with subsequent rate of change of clinical parameters.

Conclusion

In patients with SSc, serum levels of ICAM-1 and P-selectin may serve as prognostic indicators of respiratory dysfunction and physical disability, respectively. Further longitudinal studies of larger populations are needed to confirm these findings.

Increased circulating soluble vascular adhesion protein-1 levels in systemic sclerosis: association with lower frequency and severity of interstitial lung disease

AIM

To determine circulating soluble vascular adhesion protein-1 (sVAP-1) levels and their clinical associations in patients with systemic sclerosis (SSc).

METHOD

Serum VAP-1 levels were examined by enzyme-linked immunosorbent assay in 71 SSc patients, 13 systemic lupus erythematosus patients and 50 healthy individuals.

RESULTS

Serum sVAP-1 levels were significantly elevated in SSc patients (617.2 ± 338.7 ng/mL) compared with healthy individuals (320.2 ± 144.2 ng/mL; P < 0.001) and patients with systemic lupus erythematosus (329.0 ± 176.1 ng/mL; P < 0.001). Among SSc patients, there were no differences in serum sVAP-1 levels between those with limited cutaneous SSc and those with diffuse cutaneous SSc. SSc patients with raised sVAP-1 levels had interstitial lung disease and decreased percent vital capacity less often than those with normal sVAP-1 levels. sVAP-1 levels were positively correlated with percent vital capacity in patients with SSc.

CONCLUSION

Serum sVAP-1 levels were increased in patients with SSc, and associated with a lower frequency and severity of interstitial lung disease in SSc, suggesting that sVAP-1 plays a role in the pathogenesis of interstitial lung disease in SSc.

Exogenous application of hydrogen sulfide donor attenuates inflammatory reactions through the L-selectin-involved pathway in the cutaneous reverse passive Arthus reaction

H2S has been highlighted recently as an endogenous, gaseous signaling molecule, especially in inflammations. The deposition of IC induces an acute inflammatory response with tissue injury. To assess the roles of H2S in the IC-induced diseases, the cutaneous, reverse passive Arthus reaction was conducted using NaHS as a H2S donor. Furthermore, we conducted similar experiments using selectin(-/-) mice to determine the involvement of selectin molecules in the H2S-mediated pathway. Exogenous application of NaHS dramatically attenuated inflammatory reactions in WT mice associated with Arthus reaction. Namely, mRNA expressions of TNF-α, IFN-γ, and neutrophil numbers were reduced significantly in the lesional skins of NaHS-treated WT mice relative to untreated ones. NaHS treatment significantly reduced these three parameters in the lesional skins of E- and P-selectin(-/-) mice but not in those of L-selectin(-/-) mice. Quite similar results were obtained in the blocking study using WT mice injected with mAb to E-, P-, and L-selectin. Our results indicated that the exogenous application of NaHS attenuates inflammatory responses in reverse passive Arthus reaction through a L-selectin-involved pathway but not through E- or P-selectin pathways.

The roles of P- and E-selectins and P-selectin glycoprotein ligand-1 in primary and metastatic mouse melanomas

BACKGROUND

Malignant melanoma is often accompanied by a host response of inflammatory cell infiltration that is highly regulated by multiple adhesion molecules.

OBJECTIVE

To evaluate the role of adhesion molecules, including P-selectin glycoprotein ligand-1 (PSGL-1), P-selectin, and E-selectin.

METHODS

Subcutaneous primary growth and metastasis to the lung of B16 melanoma cells were examined in mice lacking PSGL-1, P-selectin, or E-selectin.

RESULTS

Primary subcutaneous growth of B16 melanoma was augmented by loss of PSGL-1, P-selectin, or E-selectin, while pulmonary metastasis was reduced by the loss of E-selectin. The enhancement of subcutaneous tumor growth was associated with a reduced accumulation of natural killer cells, CD4(+) T cells and CD8(+) T cells, while the attenuation of pulmonary metastasis was related to the numbers of CD8(+) T cells. The expressions of transforming growth factor (TGF)-β and interleukin (IL)-6 were correlated with primary subcutaneous growth; TGF-β, IL-6, and interferon-γ were related to number of metastatic lung nodules. Cytotoxicity against melanoma cells in splenocytes and in tumor-draining lymph node cells were not defective by the absence of adhesion molecules, suggesting that the enhancement of tumor growth and metastasis caused by the loss of selectins results from an impaired migration of effector cells into the tissue.

CONCLUSIONS

The results indicate the complexity of anti-tumor responses mediated by adhesion molecules in primary subcutaneous tumors and pulmonary metastasis of murine experimental melanoma.

Temporal effects in porcine skin following bromine vapor exposure

Bromine is an industrial chemical that causes severe cutaneous burns. When selecting or developing effective treatments for bromine burns, it is important to understand the molecular mechanisms of tissue damage and wound healing. This study investigated the effect of cutaneous bromine vapor exposure on gene expression using a weanling swine burn model by microarray analysis. Ventral abdominal sites were exposed to a mean calculated bromine vapor concentration of 0.51 g/L for 7 or 17 min. At 6 h, 48 h, and 7 days post-exposure, total RNA from skin samples was isolated, processed, and analyzed with Affymetrix GeneChip® Porcine Genome Arrays (N = 3 per experimental group). Differences in gene expression were observed with respect to exposure duration and sampling time. Ingenuity Pathways Analysis (IPA) revealed four common biological functions (cancer, cellular movement, cell-to-cell signaling and interaction, and tissue development) among the top ten functions of each experimental group, while canonical pathway analysis revealed 9 genes (ARG2, CCR1, HMOX1, ATF2, IL-8, TIMP1, ESR1, HSPAIL, and SELE) that were commonly shared among four significantly altered signaling pathways. Among these, the transcripts encoding HMOX1 and ESR1 were identified using IPA as common potential therapeutic targets for Phase II/III clinical trial or FDA-approved drugs. The present study describes the transcriptional responses to cutaneous bromine vapor exposure identifying molecular networks and genes that could serve as targets for developing therapeutics for bromine-induced skin injury.

Cell adhesion molecules regulate fibrotic process via Th1/Th2/Th17 cell balance in a bleomycin-induced scleroderma model

Mice s.c. injected with bleomycin, an experimental model for human systemic sclerosis, develop skin and lung fibrosis, which is mediated by inflammatory cell infiltration. This process is highly regulated by multiple adhesion molecules and does not require Ag sensitization. To assess the role of adhesion molecules in this pathogenetic process, bleomycin-induced fibrosis was examined in mice lacking adhesion molecules. L-selectin and/or ICAM-1 deficiency inhibited skin and lung fibrosis with decreased Th2 and Th17 cytokines and increased Th1 cytokines. In contrast, P-selectin deficiency, E-selectin deficiency with or without P-selectin blockade, or P-selectin glycoprotein ligand 1 (PSGL-1) deficiency augmented the fibrosis in parallel with increased Th2 and Th17 cytokines and decreased Th1 cytokines. Furthermore, loss of L-selectin and/or ICAM-1 reduced Th2 and Th17 cell numbers in bronchoalveolar lavage fluid, whereas loss of P-selectin, E-selectin, or PSGL-1 reduced Th1 cell numbers. Moreover, Th1 cells exhibited higher PSGL-1 expression and lower expression of LFA-1, a ligand for ICAM-1, whereas Th2 and Th17 cells showed higher LFA-1 and lower PSGL-1 expression. This study suggests that L-selectin and ICAM-1 regulate Th2 and Th17 cell accumulation into the skin and lung, leading to the development of fibrosis, and that P-selectin, E-selectin, and PSGL-1 regulate Th1 cell infiltration, resulting in the inhibition of fibrosis.

Platelets control leukocyte recruitment in a murine model of cutaneous arthus reaction

Platelets have been shown to be important in inflammation, but their role in the cutaneous Arthus reaction remains unclear. To assess the role of platelets in this pathogenetic process, the cutaneous Arthus reaction was examined in wild-type mice and mice lacking E-selectin, P-selectin, or P-selectin glycoprotein ligand-1 (PSGL-1) with or without platelet depletion by busulfan, a bone marrow precursor cell-specific toxin. Edema and hemorrhage induced by immune complex challenge significantly decreased in busulfan-treated wild-type mice compared with untreated mice. Busulfan treatment did not affect edema and hemorrhage in P-selectin- or PSGL-1-deficient mice, suggesting that the effect by busulfan is dependent on P-selectin and PSGL-1 expression. The inhibited edema and hemorrhage paralleled reduced infiltration of neutrophils and mast cells and reduced levels of circulating platelets. Increased cutaneous production of interleukin-6, tumor necrosis factor-alpha, and platelet-derived chemokines during Arthus reaction was inhibited in busulfan-treated wild-type mice relative to untreated mice, which paralleled the reduction in cutaneous inflammation. Flow cytometric analysis showed that immune complex challenge generated blood platelet-leukocyte aggregates that decreased by busulfan treatment. In thrombocytopenic mice, the cutaneous inflammation after immune complex challenge was restored by platelet infusion. These results suggest that platelets induce leukocyte recruitment into skin by forming platelet-leukocyte aggregates and secreting chemokines at inflamed sites, mainly through the interaction of P-selectin on platelets with PSGL-1 on leukocytes.

Low zone tolerance requires ICAM-1 expression to limit contact hypersensitivity elicitation

Painting subsensitizing doses of contact sensitizers on skin (low-dose tolerization) induces antigen (Ag)-specific tolerance, known as low zone tolerance (LZT), which has been experimentally demonstrated by the inhibition of contact hypersensitivity (CHS). Although LZT resulted from the inhibition of the sensitization phase, the effects on the effector/elicitation phase remain unknown. L-selectin and ICAM-1 regulate leukocyte influx into inflamed tissues during the elicitation phase of CHS. LZT was investigated in mice lacking either L-selectin or ICAM-1 to evaluate the roles these leukocyte receptors play in LZT during the elicitation phase. Low-dose tolerization effectively suppressed CHS in wild-type and L-selectin-deficient mice, but not in ICAM-1-deficient mice. Low-dose-tolerized ICAM-1-deficient splenocytes effectively suppressed the elicitation phase in naive wild-type recipients. Sensitized ICAM-1-deficient splenocytes showed normal proliferative responses to the sensitizing Ag and generated normal CHS in wild-type recipients. Thus, ICAM-1 deficiency did not affect sensitization. LZT was associated with a lack of ICAM-1 upregulation after elicitation, suggesting a potentially mechanistic role for ICAM-1. The blockade of IL-10, a possible mediator of LZT, produced by hapten-specific suppressor cells, abrogated LZT and restored ICAM-1 upregulation. These results indicate that low-dose tolerization controls CHS by abrogating ICAM-1 upregulation during the elicitation phase.

Cell adhesion molecules, the extracellular matrix and oral squamous carcinoma

Carcinomas are characterized by invasion of malignant cells into the underlying connective tissue and migration of malignant cells to form metastases at distant sites. These processes require alterations in cell-cell and cell-extracellular matrix interactions. As cell adhesion molecules play a role in cell-cell and cell-extracellular matrix adhesion and interactions they are involved in the process of tumour invasion and metastases. In epithelial tissues, receptors of the integrin family mediate adhesion to the adjacent matrix whereas cadherins largely mediate intercellular adhesion. These and other cell adhesion molecules such as intercellular adhesion molecule-1, CD44, dystroglycans and selectins, are involved and undergo changes in carcinomas, which provide possible targets for anti-cancer drug treatments. In the extracellular matrix that is associated with tumours, laminin 5, oncofetal fibronectin and tenascin C appear. The degree of expression of some of these moieties indicates prognosis in oral cancer and offer targets for antibody-directed radiotherapy. Metalloproteases which degrade the extracellular matrix are increased in carcinomas, and their activity is necessary for tumour angiogenesis and consequent invasion and metastases. Metalloprotease inhibitors have begun to produce decreases in mortality in clinical trials. This report provides a brief overview of our current understanding of cell adhesion molecules, the extracellular matrix, tumour invasion and metastasis.

Phase-dependent roles of E-selectin during chronic contact hypersensitivity responses

Chronic contact hypersensitivity (CH) models induced by repeated hapten exposure exhibit chronic dermatitis and immunological abnormalities resembling atopic dermatitis. To assess the contribution of endothelial selectins (P- and E-selectins) to cutaneous chronic inflammation, chronic CH responses were assessed in mice lacking P- or E-selectin. Elicitation with oxazolone on the ears of P-selectin(-/-) mice 7 days after the sensitization induced a typical delayed-type hypersensitivity response similar to that found in wild-type mice. By contrast, a significant increase in ear swelling was observed in E-selectin(-/-) mice 36 to 48 hours after first elicitation. E-selectin(-/-) mice showed augmented P-selectin up-regulation, and administration of anti-P-selectin monoclonal antibody significantly inhibited the enhanced ear response, suggesting that the enhanced ear-swelling response in E-selectin(-/-) mice resulted from compensatory increase in P-selectin expression. In the late phase of chronic CH, acceleration of ear swelling was significantly reduced in both E- and P-selectin(-/-) mice relative to wild-type littermates. Thus, the loss of P- or E-selectin suppressed inflammatory responses during the chronic phase of the chronic models, whereas early-phase inflammatory responses were exacerbated by E-selectin blockade. Collectively, P- and E-selectins cooperatively regulate CH response, although their roles may be different depending on the phase of the reaction.

Endothelial selectins regulate skin wound healing in cooperation with L-selectin and ICAM-1

Skin wound healing is mediated by inflammatory cell infiltration that is highly regulated by various adhesion molecules. Mice lacking intercellular adhesion molecule-1 (ICAM-1) delayed skin wound healing and mice lacking both L-selectin and ICAM-1 (L-selectin/ICAM-1(-/-)) show more delayed wound healing. Deficiency of both endothelial selectins (E-selectin or P-selectin) also delays wound healing. However, the relative contribution and interaction of selectins and ICAM-1 to the wound healing remain unknown. To clarify them, repair of excisional wounds was examined in L-selectin/ICAM-1(-/-) mice, wild-type mice with both E- and P-selectin blockade, and L-selectin/ICAM-1(-/-) mice with both E- and P-selectin blockade. Wild-type mice with both E- and P-selectin blockade showed delayed wound healing that was comparable with that in L-selectin/ICAM-1(-/-) mice. Combined E- and P-selectin blockade in L-selectin/ICAM-1(-/-) mice resulted in more significant delay. Mice lacking or blocked for adhesion molecules also showed suppressed keratinocyte migration, angiogenesis, granulation tissue formation, leukocyte infiltration, and cytokine expression, including transforming growth factor-beta and interleukin-6. Application of basic fibroblast growth factor (bFGF) but not platelet-derived growth factor to the wounds significantly improved wound healing in L-selectin/ICAM-1(-/-) mice with both E- and P-selectin blockade. bFGF significantly increased the leukocyte infiltration and subsequent fibrogenic cytokine production, as well as keratinocyte migration, angiogenesis, and collagen synthesis despite the loss of four kinds of adhesion molecules. These results indicate that skin wound healing is regulated cooperatively by all selectins and ICAM-1 and may provide critical information for the therapy of skin wounds.

Intercellular adhesion molecule-1 and vascular cell adhesion molecule-1 cooperatively contribute to the cutaneous Arthus reaction

Immune complex (IC)-induced inflammation is mediated by inflammatory cell infiltration, a process that is highly regulated by expression of multiple adhesion molecules. The roles and interactions of ICAM-1 and VCAM-1, the major regulators of leukocyte firm adhesion, were examined in the cutaneous reverse-passive Arthus reaction using ICAM-1-deficient (ICAM-1-/-) mice and blocking mAb against VCAM-1. Within 8 h, IC challenge of wild-type mice induced edema, hemorrhage, interstitial accumulation of neutrophils and mast cells, as well as production of TNF-alpha and IL-6. All of these inflammatory parameters were reduced significantly in ICAM-1-/- mice. The blockade of VCAM-1 in wild-type mice did not affect any inflammatory parameters. In contrast, ICAM-1-/- mice treated with anti-VCAM-1 mAb had significantly reduced edema, hemorrhage, and neutrophil infiltration. Furthermore, VCAM-1 blockade in ICAM-1-/- mice suppressed cutaneous TNF-alpha and IL-6 production. Thus, VCAM-1 plays a complementary role to ICAM-1 in the cutaneous Arthus reaction by regulating leukocyte accumulation and proinflammatory cytokine production.

Characteristics of two CD75-related cell-surface expressed antigens of human lymphocytes

The structure of cell surface carbohydrates expressed on human leukocytes is dependent on the cell's developmental stage, differentiation, and activation. Although modification of oligosaccharide side chains by sialylation is quite common, antigenic determinants on lymphocytes associated with the presence of sialoglycans are still incompletely defined. In the study presented here, monoclonal antibodies (mAbs) were used to characterize two novel but related cell surface carbohydrate antigens. One antigen, denominated as B8, is largely masked by sialyl residues on most lymphocytes, while it is detectable on the majority of B cells. Treatment with sialidase resulted in the exposure of B8 on the surface of blood cells including lymphocytes. Although the second carbohydrate antigen, C1, was sialidase-sensitive, its molecular properties and cellular distribution place it in close vicinity to B8. B8(+) as well as C1(+) lymphocytes were found predominantly in the mantle zone of secondary follicles of tonsillar tissue. These findings raised the possibility that B8 and C1 are closely related to a category of carbohydrate antigens previously classified as CDw76 (recently assigned to CD75s). MAbs directed against B8 or C1 precipitated 34, 37, 43, and 200kDa glycoproteins from tonsillar lymphocytes, indicating that identical cell surface proteins are associated with both antigens. In contrast to B8, however, the expression of C1 was increased on lymphocytes upon activation. Together the results suggest that CD75-related epitopes are distinct molecular entities which may be exposed on glycoproteins and are differently expressed on lymphocytes.

E- and P-selectins synergistically inhibit bleomycin-induced pulmonary fibrosis

The development of bleomycin-induced lung injury, which is a model of pulmonary fibrosis, results from inflammatory cell infiltration, a process highly regulated by the expression of multiple adhesion molecules. Therefore, bleomycin-induced lung fibrosis was examined in E-selectin-/- mice, P-selectin-/- mice, and E-selectin-/- mice treated with anti-P-selectin monoclonal antibody (mAb) in comparison of wild-type mice. E-selectin-/- mice treated with anti-P-selectin mAb exhibited augmented lung fibrosis histologically, increased lung collagen deposition, and increased mortality compared to wild-type mice. Furthermore, lung interferon-gamma mRNA expression decreased in E-selectin-/- mice treated with anti-P-selectin mAb relative to wild-type mice, while tumor necrosis factor-alpha and interleukin-6 mRNA expression increased in these mice. Similar changes were observed in E-selectin-/- mice, albeit to a lesser extent than those treated with anti-P-selectin mAb. Remarkably, flow cytometric analysis revealed that the frequency of interferon-gamma-producing natural killer T (NKT) cells in the bronchoalveolar lavage was decreased in E-selectin-/- mice and E-selectin-/- mice treated with anti-P-selectin mAb compared with wild-type mice. Moreover, the majority of NKT cells expressed high levels of CXCR3, suggesting that NKT cell infiltration is also dependent on CXCR3 expression. These results suggest that E- and P-selectins synergistically inhibit lung fibrosis by promoting the recruitment of NKT cells.

Decreased expression levels of CD22 and L-selectin on peripheral blood B lymphocytes from patients with bullous pemphigoid

Bullous pemphigoid (BP), an autoimmune subepidermal-blistering disease of the elderly, is caused by antibodies against BP antigens at the epidermal basement membrane zone (BMZ). CD22 is a B lymphocyte specific response regulator, which is down-regulated after B-cell activation. Old CD22-deficient mice produce class-switched autoantibodies. To assess the role of CD22 in the pathogenesis of BP, we examined CD22 expression on B cells from BP patients and correlated its expression with clinical parameters. B cell expression of CD22 was 20% lower in BP patients when compared to healthy control subjects. In addition, B cells from BP patients showed decreased expression of L-selectin, which is an indicator of leukocyte activation, and CD22 expression levels were correlated with L-selectin expression. These results suggest that the decreased CD22 expression may be associated with the activation of B cells in BP. CD22 expression levels in BP patients did not correlate with the levels of anti-epidermal BMZ antibodies, and old CD22-deficient mice did not develop the anti-epidermal BMZ antibody. These results suggest that a decrease in CD22 expression may not be associated with BP-specific antibody production.

Regulation of local and metastatic host-mediated anti-tumour mechanisms by L-selectin and intercellular adhesion molecule-1

Malignant melanoma is often accompanied by a host response of inflammatory cell infiltration that is highly regulated by multiple adhesion molecules. To assess the role of adhesion molecules, including L-selectin and intercellular adhesion molecule-1 (ICAM-1), in this process, subcutaneous primary growth and metastasis to the lung of B16 melanoma cells not expressing L-selectin, ICAM-1 or their ligands were examined in mice lacking L-selectin, ICAM-1 or both. Primary subcutaneous growth of B16 melanoma was augmented by loss of L-selectin, ICAM-1 or both, while pulmonary metastasis was enhanced by the loss of L-selectin or combined loss of L-selectin and ICAM-1. In both situations, the combined loss of L-selectin and ICAM-1 exhibited the greatest effect. This enhancement was associated generally with a reduced accumulation of natural killer (NK) cells, CD4+ T cells and CD8+ T cells and also with a diminished release of interferon (IFN)-gamma and tumour necrosis factor (TNF)-alpha but not interleukin (IL)-6. Cytotoxicity against melanoma was not defective by the absence of ICAM-1, L-selectin or both, suggesting that the enhancement of tumour growth and metastasis caused by the loss of adhesion molecules results from an impaired migration of effector cells into the tissue rather than from a suppression of the cytotoxic response. The results indicate that L-selectin and ICAM-1 contribute co-operatively to the anti-tumour reaction by regulating lymphocyte infiltration to the tumour.

Clinical significance of serum levels of soluble intercellular adhesion molecule-1 and soluble L-selectin in malignant melanoma

Although several molecules have been evaluated as tumor markers of malignant melanoma (MM) progression, there are few available markers sensitive enough to detect recurrence or metastasis. The objective of the present study was to determine clinical significance of serum soluble adhesion molecules in the monitoring of progression in patients with MM. Serum levels of soluble L-selectin (sL-selectin), sE-selectin, sP-selectin, and soluble intercellular adhesion molecule-1 (sICAM-1) were determined by ELISA in 57 MM patients. In a retrospective longitudinal study, nine serum samples from two MM patients were analyzed during a follow-up period of 4.0 and 4.3 years, respectively. Serum sICAM-1 levels in MM patients were significantly higher than those in healthy controls and tended to be elevated as the disease stage progressed. In contrast, serum sL-selectin levels were significantly lower in MM patients compared to healthy controls and tended to decrease as the disease stage progressed. There was no significant difference in serum sE-selectin and sP-selectin levels between MM patients and normal control. In a longitudinal study, increased sICAM-1 and decreased sL-selectin levels were generally associated with the progression of MM. These results suggest that monitoring both sICAM-1 and sL-selectin is available to evaluate the progression of MM.

P-selectin glycoprotein ligand-1 is required for the development of cutaneous vasculitis induced by immune complex deposition

Immune complex (IC)-induced tissue injury is mediated by inflammatory cell infiltration that is highly regulated by various adhesion molecules. To assess the contribution of P-selectin glycoprotein ligand-1 (PSGL-1) and selectins in the pathogenetic process, the cutaneous reverse-passive Arthus reaction was examined in mice treated with monoclonal antibodies (mAb) to PSGL-1 or P- and/or E-selectin. Edema and hemorrhage were significantly reduced in mice treated with anti-P-selectin mAb compared with control mice while they were not inhibited in mice treated with anti-E-selectin mAb. It is remarkable that blocking PSGL-1 by mAb resulted in significant, further reduction in edema and hemorrhage compared with blocking anti-P- or anti-E-selectin. However, blockade of E- and P-selectins exhibited more significant reduction relative to PSGL-1 blockade. The inhibited edema and hemorrhage paralleled reduced infiltration of neutrophils and mast cells. Reduced infiltration of neutrophils and mast cells was observed in the peritoneal Arthus reaction and was associated with the decreased production of tumor necrosis factor alpha and interleukin-6. The results of this study indicate that PSGL-1 contributes to the Arthus reaction mainly as a ligand of P-selectin and partly as a ligand of E- and/or L-selectin by regulating neutrophil and mast-cell recruitment and that PSGL-1 would be a therapeutic target for human IC-mediated diseases.

Ultraviolet light exposure suppresses contact hypersensitivity by abrogating endothelial intercellular adhesion molecule-1 up-regulation at the elicitation site

Hapten sensitization through UV-exposed skin induces systemic immune suppression, which is experimentally demonstrated by inhibition of contact hypersensitivity (CHS). Although this UV-induced effect has been shown to be mediated by inhibition of the afferent phase of the CHS, the UV effects on the efferent (elicitation) phase remain unknown. In this study, UV effects on endothelial ICAM-1 expression at elicitation sites were first examined. Mice were sensitized by hapten application onto UV-exposed back skin, and ears were challenged 5 days later. ICAM-1 up-regulation at nonirradiated elicitation sites following hapten challenge was eliminated by UV exposure on sensitization sites distant from elicitation sites. To assess whether loss of the ICAM-1 up-regulation at elicitation sites contributed to UV-induced immunosuppression, we examined CHS responses in UV-exposed ICAM-1-deficient (ICAM-1(-/-)) mice that genetically lacked the ICAM-1 up-regulation. ICAM-1(-/-) mice exhibited reduced CHS responses without UV exposure, but UV exposure did not further reduce CHS responses in ICAM-1(-/-) mice. Furthermore, ICAM-1 deficiency did not affect the afferent limb, because ICAM-1(-/-) mice had normal generation of hapten-specific suppressor and effector T cells. This UV-induced immunosuppression was associated with a lack of TNF-alpha production after Ag challenge at elicitation sites. Local TNF-alpha injection before elicitation abrogated the UV-induced CHS inhibition with increased endothelial ICAM-1 expression. TNF-alpha production at elicitation sites was down-regulated by IL-10, a possible mediator produced by hapten-specific suppressor T cells that are generated by UV exposure. These results indicate that UV exposure inhibits CHS by abrogating up-regulation of endothelial ICAM-1 expression after Ag challenge at elicitation sites.

Relative contributions of selectins and intercellular adhesion molecule-1 to tissue injury induced by immune complex deposition

Immune complex-induced tissue injury is mediated by inflammatory cell infiltration that is highly regulated by multiple adhesion molecules. To assess the relative contribution of adhesion molecules, including selectins and ICAM-1, in this pathogenetic process, the cutaneous passive Arthus reaction was examined in mice lacking E-selectin, P-selectin, or both L-selectin and ICAM-1 with anti-P- or E-selectin mAbs. Edema and hemorrhage were significantly reduced in P-selectin(-/-) mice compared with wild-type mice while they were not inhibited in E-selectin(-/-) mice. Combined E- and P-selectin blockade resulted in more significant reduction relative to L-selectin/ICAM-1(-/-) as well as P-selectin(-/-) mice. Remarkably, both E- and P-selectin blockade in L-selectin/ICAM-1(-/-) mice completely abrogated edema and hemorrhage. The inhibited edema and hemorrhage paralleled reduced infiltration of neutrophils and mast cells that expressed significant levels of P-selectin glycoprotein ligand-1. Similarly reduced infiltration of neutrophils and mast cells was observed in the peritoneal Arthus reaction and was associated partly with the decreased production of tumor necrosis factor-alpha and interleukin-6. The results of this study indicate that both endothelial selectins contribute predominantly to the Arthus reaction by regulating mast cell and neutrophil infiltration and that the full development of the Arthus reaction is mediated cooperatively by all selectins and ICAM-1.

L-selectin or ICAM-1 deficiency reduces an immediate-type hypersensitivity response by preventing mast cell recruitment in repeated elicitation of contact hypersensitivity

Repeated Ag exposure results in a shift in the time course of contact hypersensitivity (CH) from a typical delayed-type to an immediate-type response followed by a late phase reaction. Chronic CH responses are clinically relevant to human skin allergic diseases, such as atopic dermatitis, that are usually caused by repeated stimulation with environmental Ags. Chronic inflammatory responses result in part from infiltrating leukocytes. To determine the role of leukocyte adhesion molecules in chronic inflammation, chronic CH responses were assessed in mice lacking L-selectin, ICAM-1, or both adhesion molecules. Following repeated hapten sensitization for 24 days at 2-day intervals, wild-type littermates developed an immediate-type response at 30 min after elicitation, followed by a late phase reaction. By contrast, loss of ICAM-1, L-selectin, or both, eliminated the immediate-type response and inhibited the late phase reaction. Similar results were obtained when wild-type littermates repeatedly exposed to hapten for 22 days were treated with mAbs to L-selectin and/or ICAM-1 before the elicitation on day 24. The lack of an immediate-type response on day 24 paralleled a lack of mast cell accumulation after 30 min of elicitation and decreased serum IgE production. Repeated Ag exposure in wild-type littermates resulted in increased levels of serum L-selectin, a finding also observed in atopic dermatitis patients. The current study demonstrates that L-selectin and ICAM-1 cooperatively regulate the induction of the immediate-type response by mediating mast cell accumulation into inflammatory sites and suggests that L-selectin and ICAM-1 are potential therapeutic targets for regulating human allergic reactions.

Intercellular adhesion molecule-1 and L-selectin regulate bleomycin-induced lung fibrosis

The development of bleomycin-induced lung injury, a model of pulmonary fibrosis, results from inflammatory cell infiltration, a process highly regulated by the expression of multiple adhesion molecules. At present, the identity and role of the adhesion molecules involved in the fibrotic process are unknown. Therefore, bleomycin-induced pulmonary fibrosis was examined in mice lacking L-selectin (L-selectin(-/-)) expression, intercellular adhesion molecule-1 (ICAM-1) expression, or both. After 16 days of intratracheal bleomycin challenge, collagen deposition was inhibited in both L-selectin(-/-) and ICAM-1(-/-) mice when compared with wild-type littermates. Interestingly, collagen deposition was virtually eliminated in L-selectin/ICAM-1(-/-) mice relative to either the L-selectin(-/-) or ICAM-1(-/-) mice. Decreased pulmonary fibrosis was associated with reduced accumulation of leukocytes, including neutrophils and lymphocytes. Decreased mRNA expression of proinflammatory cytokines and transforming growth factor (TGF)-beta1 paralleled the inhibition of collagen deposition. The present study indicates that L-selectin and ICAM-1 play a critical role in pulmonary fibrosis by mediating the accumulation of leukocytes, which regulate the production of proinflammatory cytokines and TGF-beta1. This suggests that these adhesion molecules are potential therapeutic targets for inhibiting human pulmonary fibrosis.

The cutaneous reverse Arthus reaction requires intercellular adhesion molecule 1 and L-selectin expression

The deposition of immune complexes (IC) induces an acute inflammatory response with tissue injury. IC-induced inflammation is mediated by inflammatory cell infiltration, a process highly regulated by expression of multiple adhesion molecules. To assess the role of L-selectin and ICAM-1 in this pathogenetic process, the cutaneous reverse passive Arthus reaction was examined in mice lacking L-selectin (L-selectin(-/-)), ICAM-1 (ICAM-1(-/-)), or both (L-selectin/ICAM-1(-/-)). Edema and hemorrhage, which peaked 4 and 8 h after IC challenge, respectively, were significantly reduced in L-selectin(-/-), ICAM-1(-/-), and L-selectin/ICAM-1(-/-) mice compared with wild-type littermates. In general, edema and hemorrhage were more significantly inhibited in ICAM-1(-/-) mice than in L-selectin(-/-) mice, but were most significantly reduced in L-selectin/ICAM-1(-/-) mice compared with ICAM-1(-/-) or L-selectin(-/-) mice. Decreased edema and hemorrhage correlated with reduced neutrophil and mast cell infiltration in all adhesion molecule-deficient mice, but leukocyte infiltration was most affected in L-selectin/ICAM-1(-/-) mice. Reduced neutrophil and mast cell infiltration was also observed for all mutant mice in the peritoneal Arthus reaction. Furthermore, cutaneous TNF-alpha production was inhibited in each deficient mouse, which paralleled the reductions in cutaneous inflammation. These results indicate that ICAM-1 and L-selectin cooperatively contribute to the cutaneous Arthus reaction by regulating neutrophil and mast cell recruitment and suggest that ICAM-1 and L-selectin are therapeutic targets for human IC-mediated disease.

Elevated serum levels of soluble L-selectin in patients with systemic sclerosis declined after intravenous injection of lipo-prostaglandin E1

To determine whether serum soluble L-selectin (sL-selectin) levels are elevated in patients with systemic sclerosis (SSc) and whether serum sL-selectin levels change after treatment with lipo-prostaglandin E1 (lipo-PGE1), serum sL-selectin levels were examined by ELISA in patients with SSc (n=24), psoriasis vulgaris (n=22), and contact dermatitis (n=9), as well as normal control subjects (n=26). In five patients with SSc, serum sL-selectin levels were examined before and after intravenous injections of lipo-PGE1. Serum sL-selectin levels were significantly increased in patients with SSc (P<0.01) than those in normal control subjects. The elevated serum sL-selectin levels in patients with SSc significantly decreased 1 day (P<0.05), 7 days (P<0.05) and 14 days (P<0.05) after starting the treatment with lipo-PGE1. These results suggest that L-selectin may be involved in the disease process in SSc, and lipo-PGE1 may alter some inflammatory events in SSc.

Decreased expression levels of L-selectin on subsets of leucocytes and increased serum L-selectin in severe psoriasis

L-selectin is a leucocyte adhesion molecule involved in leucocyte interactions with vascular endothelial cells. Following leucocyte activation L-selectin is endoproteolytically released from the cell surface. To assess whether psoriasis vulgaris results in systemic leucocyte activation, we examined expression levels of L-selectin on subsets of peripheral blood leucocytes from patients with psoriasis (n = 25) and normal control subjects. Serum levels of soluble L-selectin were quantified by ELISA in patients with psoriasis (n = 75), pustulosis palmaris et plantaris, and contact dermatitis, as well as normal control subjects. Psoriasis severity was evaluated by psoriasis area and severity index (PASI). L-selectin expression levels on CD4+ T cells, B cells, monocytes, and neutrophils from patients with severe-type psoriasis (PASI > or = 15) was significantly decreased compared with leucocytes from normal control subjects. Furthermore, L-selectin expression on CD4+ T cells showed good inverse correlation with PASI scores. Monocyte L-selectin expression was restored when the skin lesions of psoriasis were remitted. The frequencies of L-selectin+ CD4+ T cells or L-selectin+ CD8+ T cells from patients with psoriasis were almost normal. Serum L-selectin levels in patients with severe-type psoriasis were significantly higher than those in normal control subjects. These results suggest that subsets of leucocytes may be activated in psoriasis, and that L-selectin expression levels on some leucocyte subsets, especially CD4+ T cells, tend to correlate with disease severity of psoriasis.

L-Selectin Ligands Expressed by Human Leukocytes Are HECA-452 Antibody-Defined Carbohydrate Epitopes Preferentially Displayed by P-Selectin Glycoprotein Ligand-1

Leukocytes express L-selectin ligands critical for leukocyte-leukocyte interactions at sites of inflammation. The predominant leukocyte L-selectin ligand is P-selectin glycoprotein ligand-1 (PSGL-1), which displays appropriate sialyl Lewis x (sLex)-like carbohydrate determinants for L-selectin recognition. Among the sLex-like determinants expressed by human leukocytes is a unique carbohydrate epitope defined by the HECA-452 mAb. The HECA-452 Ag is a critical component of L-selectin ligands expressed by vascular endothelial cells. However, HECA-452 Ag expression on human leukocyte L-selectin ligands has not been assessed. In this study, the HECA-452 mAb blocked 88–99% of neutrophil rolling on, or attachment to, adherent cells expressing L-selectin in multiple experimental systems. A function-blocking anti-PSGL-1 mAb also inhibited L-selectin binding to neutrophils by 89–98%. In addition, the HECA-452 and anti-PSGL-1 mAbs blocked the majority of P-selectin binding to neutrophils. Western blot analysis revealed that PSGL-1 immunoprecipitated from neutrophils displayed HECA-452 mAb-reactive determinants and that PSGL-1 was the predominant scaffold for HECA-452 Ag display. Leukocyte L-selectin ligands also contained sulfated determinants since culturing ligand-bearing cells with NaClO3 abrogated L-selectin binding. Consistent with this, human neutrophils expressed mRNA encoding five different sulfotransferases associated with the generation of selectin ligands: CHST1, CHST2, CHST3, TPST1, and HEC-GlcNAc6ST. Therefore, the HECA-452-defined carbohydrate determinant displayed on PSGL-1 represented the predominant L-selectin and P-selectin ligand expressed by neutrophils.