Intercellular adhesion molecule 1 and selectin l play crucial roles in ulcerative colitis.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease that primarily affects the mucosal layer of the colon (large intestine). However, the relationship between Intercellular Adhesion Molecule-1 (ICAM1), SELL and UC is unclear. The UC datasets, GSE87466 and GSE36807, were downloaded from the gene expression omnibus database. The R package limma was utilized to identify differentially expressed genes (DEGs). Weighted gene co-expression network analysis was conducted. The construction and analysis of protein-protein interaction network, functional enrichment analysis, gene set enrichment analysis, and comparative toxicogenomics database analysis were performed. TargetScan was employed to screen miRNAs regulating central DEGs. Western blot (WB) was used to verify. A total of 2118 DEGs were identified in our study. Gene ontology analysis indicated their enrichment primarily in immune system processes, cellular responses to chemical stimuli, responses to organic substances, responses to external stimuli, and immune responses. Kyoto Encyclopedia of Genes and Genomes analysis revealed that the target cells were mainly enriched in chemokine signaling pathways and TNF signaling pathways. Gene set enrichment analysis enrichment analysis showed significant enrichment in chemokine signaling pathways and cell adhesion molecules. In the Metascape enrichment project, gene ontology terms included regulation of cell activation and positive regulation of immune response. Through the construction and analysis of a protein-protein interaction network, we identified 11 core genes (ICAM1, SELL, CD44, CD40, CCR7, CXCL8, CD19, CCL4, CD274, IL7R, IL1B). We found that the core genes (ICAM1, SELL) were highly expressed in UC samples and lowly expressed in normal samples, suggesting their potential regulatory roles in UC. These core genes were associated with lymphoproliferative disorders, inflammation and necrosis. WB results confirmed the high expression of ICAM1 and SELL in UC. ICAM1 and SELL are highly expressed in UC, and the higher the ICAM1 and SELL genes, the worse the prognosis.

Role of Hydrogen Sulfide, Substance P and Adhesion Molecules in Acute Pancreatitis.

Inflammation is a natural response to tissue injury. Uncontrolled inflammatory response leads to inflammatory disease. Acute pancreatitis is one of the main reasons for hospitalization amongst gastrointestinal disorders worldwide. It has been demonstrated that endogenous hydrogen sulfide (H2S), a gasotransmitter and substance P, a neuropeptide, are involved in the inflammatory process in acute pancreatitis. Cell adhesion molecules (CAM) are key players in inflammatory disease. Immunoglobulin (Ig) gene superfamily, selectins, and integrins are involved at different steps of leukocyte migration from blood to the site of injury. When the endothelial cells get activated, the CAMs are upregulated which leads to them interacting with leukocytes. This review summarizes our current understanding of the roles H2S, substance P and adhesion molecules play in acute pancreatitis.

A Sialylated-Bortezomib Prodrug Strategy Based on a Highly Expressed Selectin Target for the Treatment of Leukemia or Solid Tumors.

PURPOSE: This study aimed to explore the potential of sialic acid - related selectin targeting strategy in the treatment of leukemia and some solid tumors. We expected it could "actively" bind tumor cells and kill them, reducing non-specific toxicity to normal cells. METHODS: BOR-SA prodrug was synthesized by reacting an ortho-dihydroxy group in SA with a boronic acid group in BOR. Two kinds of leukemia cells (RAW264.7 and HL60 cells), one solid sarcoma cell model (S180 cells) and their corresponding normal cells (monocytes (MO), neutrophil (NE) and fibroblast (L929)) were selected for the in vitro cell experiments (cytotoxicity, cellular uptake, cell cycle and apoptosis experiments). The S180 tumor-bearing Kunming mice model was established for anti-tumor pharmacodynamic experiments. RESULTS: In vitro cell assay results showed that uptake of BOR-SA by HL60 and S180 cells were increased compared with the control group. BOR-SA induced a lower IC50, higher ratio of apoptosis and cell cycle arrest of tumor cells. In vivo anti-S180 tumor pharmacodynamics experiments showed that mice in the BOR-SA group had higher tumor inhibition rate, higher body weight and lower immune organ toxicity compared with the control group. CONCLUSIONS: sialic acid-mediated selectin targeting strategy may have great potential in the treatment of related tumors.

Immune imbalance of global gene expression, and cytokine, chemokine and selectin levels in the brains of offspring with social deficits via maternal immune activation.

The murine maternal immune activation (MIA) offspring model enables longitudinal studies to explore aberrant social behaviors similar to those observed in humans. High levels of cytokines, chemokines and cell adhesion molecules (CAM) have been found in the plasma and/or brains of psychiatric patients. We hypothesized that upregulation of the systemic or brain immune response has an augmenting effect by potentially increasing the interplay between the neuronal and immune systems during the growth of the MIA offspring. In this study, a C57BL/6j MIA female offspring model exhibiting social deficits was established. The expression of fetal interferon (IFN)-stimulated (gbp3, irgm1, ifi44), adolescent immunodevelopmental transcription factor (eg, r2, tfap2b), hormone (pomc, hcrt), adult selectin (sell, selp) and neuroligin (nlgn2) genes was altered. Systemic upregulation of endogenous IL-10 occurred at the adult stage, while both IL-1ß and IL-6 were increased and persisted in the sera throughout the growth of the MIA offspring. The cerebral IL-6 levels were endogenously upregulated, but both MCP-1 (macrophage inflammatory protein-1) and L-selectin levels were downregulated at the adolescent and/or adult stages. However, the MIA offspring were susceptible to lipopolysaccharide (LPS) stimulation. After reinjecting the MIA offspring with LPS in adulthood, a variety of sera and cerebral cytokines, chemokines and CAMs were increased. Particularly, both MCP-1 and L-selectin showed relatively high expression in the brain compared with the expression levels in phosphate-buffered saline (PBS)-treated offspring injected with LPS. Potentially, MCP-1 was attracted to the L-selectin-mediated immune cells due to augmentation of the immune response following stimulation in MIA female offspring.

Genome-Wide Association Study in African Americans with Acute Respiratory Distress Syndrome Identifies the Selectin P Ligand Gene as a Risk Factor.

RATIONALE: Genetic factors are involved in acute respiratory distress syndrome (ARDS) susceptibility. Identification of novel candidate genes associated with increased risk and severity will improve our understanding of ARDS pathophysiology and enhance efforts to develop novel preventive and therapeutic approaches. OBJECTIVES: To identify genetic susceptibility targets for ARDS. METHODS: A genome-wide association study was performed on 232 African American patients with ARDS and 162 at-risk control subjects. The Identify Candidate Causal SNPs and Pathways platform was used to infer the association of known gene sets with the top prioritized intragenic SNPs. Preclinical validation of SELPLG (selectin P ligand gene) was performed using mouse models of LPS- and ventilator-induced lung injury. Exonic variation within SELPLG distinguishing patients with ARDS from sepsis control subjects was confirmed in an independent cohort. MEASUREMENTS AND MAIN RESULTS: Pathway prioritization analysis identified a nonsynonymous coding SNP (rs2228315) within SELPLG, encoding P-selectin glycoprotein ligand 1, to be associated with increased susceptibility. In an independent cohort, two exonic SELPLG SNPs were significantly associated with ARDS susceptibility. Additional support for SELPLG as an ARDS candidate gene was derived from preclinical ARDS models where SELPLG gene expression in lung tissues was significantly increased in both ventilator-induced (twofold increase) and LPS-induced (5.7-fold increase) murine lung injury models compared with controls. Furthermore, Selplg-/- mice exhibited significantly reduced LPS-induced inflammatory lung injury compared with wild-type C57/B6 mice. Finally, an antibody that neutralizes P-selectin glycoprotein ligand 1 significantly attenuated LPS-induced lung inflammation. CONCLUSIONS: These findings identify SELPLG as a novel ARDS susceptibility gene among individuals of European and African descent.

Lack of functional selectin-ligand interactions enhances innate immune resistance to systemic Listeria monocytogenes infection.

Selectin-ligand interactions are important for leukocyte homing and functionality. The roles of selectin-ligand interactions in modulating immunity to intracellular infections are not completely understood. Mice lacking the expression of fucosyltransferase-IV and -VII (Fucosyltransferase-IV and -VII double knockout, FtDKO) exhibit deficient functionality of selectin-ligand interactions. We addressed the kinetics of infection and immunity to Listeria monocytogenes (LM), an intracellular pathogen, in FtDKO mice. These mice exhibited enhanced ability to clear infection and increased survival to a lethal dose of LM infection relative to wild-type (WT) C57BL/6J controls. This was associated with increased levels of neutrophils, monocytes, and dendritic cells (DCs) in the blood and/or infected organs. Adoptive transfer of bone marrow (BM) cells from FtDKO mice to WT mice resulted in enhanced neutrophil numbers and improved clearance of LM bacteria in recipients. In vivo depletion of myeloid innate immune cells, particularly neutrophils, monocytes, macrophages, and DCs, using anti-Ly-6G (RB6-8C5) monoclonal antibody, reduced the ability of FtDKO mice to curtail LM infection. Nevertheless, depletion using anti-Ly-6G (1A8) known to exclusively deplete neutrophils did not abrogate increased resistance of FtDKO mice to LM infection, suggesting a role for other myeloid innate immune cells in this model. Examination of BM hematopoietic progenitors through flow cytometry and cell culture colony-forming unit assay showed increased frequencies of granulocyte-macrophage progenitors in FtDKO relative to WT mice, Overall, our results indicate that functional selectin ligand deficiency enhances innate immune-mediated resistance to systemic LM infection despite defective leukocyte migration and lymphocyte homing.

Polymorphisms in the selectin gene cluster are associated with fertility and survival time in a population of Holstein Friesian cows.

Selectins are adhesion molecules, which mediate attachment between leucocytes and endothelium. They aid extravasation of leucocytes from blood into inflamed tissue during the mammary gland's response to infection. Selectins are also involved in attachment of the conceptus to the endometrium and subsequent placental development. Poor fertility and udder health are major causes for culling dairy cows. The three identified bovine selectin genes SELP, SELL and SELE are located in a gene cluster. SELP is the most polymorphic of these genes. Several SNP in SELP and SELE are associated with human vascular disease, while SELP SNP rs6127 has been associated with recurrent pregnancy loss in women. This study describes the results of a gene association study for SNP in SELP (n = 5), SELL (n = 2) and SELE (n = 1) with fertility, milk production and longevity traits in a population of 337 Holstein Friesian dairy cows. Blood samples for PCR-RFLP were collected at 6 months of age and animals were monitored until either culling or 2,340 days from birth. Three SNP in SELPEx4-6 formed a haplotype block containing a Glu/Ala substitution at rs42312260. This region was associated with poor fertility and reduced survival times. SELPEx8 (rs378218397) coded for a Val475Met variant locus in the linking region between consensus repeats 4 and 5, which may influence glycosylation. The synonymous SNP rs110045112 in SELEEx14 deviated from Hardy Weinberg equilibrium. For both this SNP and rs378218397 there were too few AA homozygotes present in the population and AG heterozygotes had significantly worse fertility than GG homozygotes. Small changes in milk production associated with some SNP could not account for the reduced fertility and only SELPEx6 showed any association with somatic cell count. These results suggest that polymorphisms in SELP and SELE are associated with the likelihood of successful pregnancy, potentially through compromised implantation and placental development.

Endothelial cell activation in central nervous system inflammation.

Leukocyte migration across the endothelial barrier plays an essential role in CNS inflammation. The migration process requires complex endothelial adhesion molecules concentrated at the junctions of endothelial cells. Recent findings suggest that cerebral endothelial cells play an active role in the pathogenesis of CNS inflammatory diseases. This review describes our current understanding of the effects of various inflammatory mediators of leukocyte migration on cerebral endothelial cells, the mechanisms underlying the leukocyte-endothelial cell interactions, and the crosstalk between endothelial cells and glial cells or platelets. These emerging mechanisms may provide new therapeutic strategies for a variety of CNS inflammatory diseases.

Role of selectins and their ligands in human implantation stage.

Selectins are a family of calcium-dependent, type I transmembrane, carbohydrate-binding glycoproteins. Selectins and their ligands are not only involved in physiological processes such as leukocyte homing and pathological processes such as cancer, but also play an essential role in the human implantation. L-selectin and its ligands participate in the adhesion of the blastocyst to the endometrium at the maternal-fetal interface. P-selectin and E-selectin are involved in immune recognition of maternal decidua to the embedded embryo as well as trophoblast migration within decidual spiral arterioles. Moreover, altered expression of selectins and their ligands are found to be associated with some abnormal pregnancies and infertilities. This review focuses on the current progress of research on the role of selectins and their ligands in the human implantation process.

Zooming in on selectins in cancer.

Selectins are involved in leukocyte and cancer cell trafficking, which can be targeted with drugs and nanoparticles (Shamay et al., this issue).

Regulation of tissue infiltration by neutrophils: role of integrin α3ß1 and other factors.

PURPOSE OF REVIEW: Neutrophils have traditionally been viewed in the context of acute infection and inflammation forming the first line of defense against invading pathogens. Neutrophil trafficking to the site of inflammation requires adhesion and transmigration through blood vessels, which is orchestrated by adhesion molecules, such as ß2 and ß1-integrins, chemokines, and cytokines. The review focuses on recent advances in understanding the regulators of neutrophil recruitment during inflammation in both acute and chronic settings. RECENT FINDINGS: Recent findings suggest that besides the established pathways of selectin or chemokine-mediated integrin activation, signaling by distinct Toll-like receptors (TLRs) (especially TLR2, TLR4, and TLR5) can activate integrin-dependent neutrophil adhesion. Moreover, the integrin α3ß1 has been vitally implicated as a new player in neutrophil recruitment and TLR-mediated responses in septic inflammation. Furthermore, several endogenous inhibitory mechanisms of leukocyte recruitment have been identified, including the secreted molecules Del-1, PTX3, and GDF-15, which block distinct steps of the leukocyte adhesion cascade, as well as novel regulatory signaling pathways, involving the protein kinase AKT1 and IFN-λ2/IL-28A. SUMMARY: The leukocyte adhesion cascade is a tightly regulated process, subjected to both positive and negative regulators. Dysregulation of this process and hence neutrophil recruitment can lead to the development of inflammatory and autoimmune diseases.

The neutrophil function and lymphocyte profile of milk from bovine mammary glands infected with Streptococcus dysgalactiae.

Streptococcus dysgalactiae is a bacterium that accounts for a notable proportion of both clinical and subclinical intramammary infections (IMIs). Thus, the present study explores the function of milk neutrophils and the lymphocyte profile in mammary glands naturally infected with Streptococcus dysgalactiae. Here, we used 32 culture-negative control quarters from eight clinically healthy dairy cows with low somatic cell counts and 13 S. dysgalactiae-infected quarters from six dairy cows. Using flow cytometry, we evaluated the percentage of milk monocytes/macrophages and neutrophils, expression of CD62L, CD11b and CD44 by milk neutrophils, the levels of intracellular reactive oxygen species (ROS) production and phagocytosis of Staphylococcus aureus by milk neutrophils, and neutrophil viability. Furthermore, the percentages of B cell (CD21(+)) and T lymphocyte subsets (CD3(+)/CD4(+)/CD8(-); CD3(+)/CD8(+)/CD4(-); and CD3(+)/CD8(-)/CD4(-)), and the expression of CD25 by T milk lymphocytes (CD3(+)) and T CD4(+) milk cells were also assessed by flow cytometry using monoclonal antibodies. The present study showed a higher SCC and percentage of milk neutrophils, and a decrease in the percentage of milk monocytes/macrophages from S. dysgalactiae-infected quarters when compared to uninfected ones. We also observed a higher expression of CD11b by milk neutrophils and a tendency toward a decrease in neutrophil apoptosis rate in S. dysgalactiae-infected quarters. In addition, the S. dysgalactiae-infected quarters had higher percentages of milk T cells (CD3(+)) and their subset CD3(+)CD8(+)CD4(-) cells. Overall, the present study provided new insights into S. dysgalactiae IMIs, including distinct lymphocyte profiles, and a tendency toward an inhibition of apoptosis in milk neutrophils.

Differential Features of AIRE-Induced and AIRE-Independent Promiscuous Gene Expression in Thymic Epithelial Cells.

Establishment of self-tolerance in the thymus depends on promiscuous expression of tissue-restricted Ags (TRA) by thymic epithelial cells (TEC). This promiscuous gene expression (pGE) is regulated in part by the autoimmune regulator (AIRE). To evaluate the commonalities and discrepancies between AIRE-dependent and -independent pGE, we analyzed the transcriptome of the three main TEC subsets in wild-type and Aire knockout mice. We found that the impact of AIRE-dependent pGE is not limited to generation of TRA. AIRE decreases, via non-cell autonomous mechanisms, the expression of genes coding for positive regulators of cell proliferation, and it thereby reduces the number of cortical TEC. In mature medullary TEC, AIRE-driven pGE upregulates non-TRA coding genes that enhance cell-cell interactions (e.g., claudins, integrins, and selectins) and are probably of prime relevance to tolerance induction. We also found that AIRE-dependent and -independent TRA present several distinctive features. In particular, relative to AIRE-induced TRA, AIRE-independent TRA are more numerous and show greater splicing complexity. Furthermore, we report that AIRE-dependent versus -independent TRA project nonredundant representations of peripheral tissues in the thymus.

Role of siglecs and related glycan-binding proteins in immune responses and immunoregulation.

Virtually all cells and extracellular material are heavily decorated by various glycans, yet our understanding of the structure and function of these moieties lags behind the understanding of nucleic acids, lipids, and proteins. Recent years have seen a tremendous acceleration of knowledge in the field of glycobiology, revealing many intricacies and functional contributions that were previously poorly appreciated or even unrecognized. This review highlights several topics relevant to glycoimmunology in which mammalian and pathogen-derived glycans displayed on glycoproteins and other scaffolds are recognized by specific glycan-binding proteins (GBPs), leading to a variety of proinflammatory and anti-inflammatory cellular responses. The focus for this review is mainly on 2 families of GBPs, sialic acid-binding immunoglobulin-like lectins (siglecs) and selectins, that are involved in multiple steps of the immune response, including distinguishing pathogens from self, cell trafficking to sites of inflammation, fine-tuning of immune responses leading to activation or tolerance, and regulation of cell survival. Importantly for the clinician, accelerated rates of discovery in the field of glycoimmunology are being translated into innovative medical approaches that harness the interaction of glycans and GBPs to the benefit of the host and might soon lead to novel diagnostics and therapeutics.

Social defeat promotes a reactive endothelium in a brain region-dependent manner with increased expression of key adhesion molecules, selectins and chemokines associated with the recruitment of myeloid cells to the brain.

Repeated social defeat (RSD) in mice causes myeloid cell trafficking to the brain that contributes to the development of prolonged anxiety-like behavior. Myeloid cell recruitment following RSD occurs in regions where neuronal and microglia activation is observed. Thus, we hypothesized that crosstalk between neurons, microglia, and endothelial cells contributes to brain myeloid cell trafficking via chemokine signaling and vascular adhesion molecules. Here we show that social defeat caused an exposure- and brain region-dependent increase in several key adhesion molecules and chemokines involved in the recruitment of myeloid cells. For example, RSD induced distinct patterns of adhesion molecule expression that may explain brain region-dependent myeloid cell trafficking. VCAM-1 and ICAM-1 mRNA expression were increased in an exposure-dependent manner. Furthermore, RSD-induced VCAM-1 and ICAM-1 protein expression were localized to the vasculature of brain regions implicated in fear and anxiety responses, which spatially corresponded to previously reported patterns of myeloid cell trafficking. Next, mRNA expression of additional adhesion molecules (E- and P-selectin, PECAM-1) and chemokines (CXCL1, CXCL2, CXCL12, CCL2) were determined in the brain. Social defeat induced an exposure-dependent increase in mRNA levels of E-selectin, CXCL1, and CXCL2 that increased with additional days of social defeat. While CXCL12 was unaffected by RSD, CCL2 expression was increased by six days of social defeat. Last, comparison between enriched CD11b(+) cells (microglia/macrophages) and enriched GLAST-1(+)/CD11b(-) cells (astrocytes) revealed RSD increased mRNA expression of IL-1ß, CCL2, and CXCL2 in microglia/macrophages but not in astrocytes. Collectively, these data indicate that key mediators of leukocyte recruitment were increased in the brain vasculature following RSD in an exposure- and brain region-dependent manner.

Expression of selectins and P-selectin glycoprotein ligand-1 in dogs with lymphocytic-plasmacytic enteritis.

Lymphocytic-plasmacytic enteritis (LPE) is the most common form of inflammatory bowel disease (IBD) affecting the canine small intestine; however, the molecular pathogenesis of this disease remains unclear. Although selectins and their ligands play a critical role as cell adhesion molecules during inflammation, there is very little information about their involvement in canine LPE. The aim of this study was to evaluate transcript expression of selectins (E-, L-, and P- selectin) and P-selectin glycoprotein ligand-1 (PSGL-1) in the duodenal mucosa of 21 dogs with LPE and 10 healthy laboratory beagles. Duodenal expression of E-selectin, L-selectin, P-selectin, and PSGL-1 was quantified by real-time reverse-transcription PCR. Correlations between clinical severity, histopathological grade, selectins, and PSGL-1 were analyzed by Spearman's rank test. Transcript expression of duodenal E- and P-selectins and PSGL-1 was higher in dogs with LPE than in healthy laboratory beagles; however, there was no difference in L-selectin expression. Positive correlations between E- and L-selectin and between L- and P-selectin were observed in the duodenum of LPE dogs. The selectins and ligand may recruit circulating inflammatory cells into the lesion. These findings improve our understanding of the inflammatory cascade of canine LPE.

Expression and function of endothelial selectins during human development.

Leucocyte trafficking is vital for the immune defence. In adults, early tethering and rolling interactions between leucocytes and endothelial cells are mediated by P-, E- and L-selectins and their ligands. In contrast, the role of selectins in migration of mononuclear cells during fetal development in humans remains unknown. We studied the functions of endothelial E- and P-selectins and their counter-receptors during human ontogeny. Immunohistochemical stainings showed that P-selectin is expressed in megakaryocytes and endothelial cells starting from gestational weeks 7 and 11, respectively. Endothelial E-selectin appeared latest, at week 32. Real-time imaging using in vitro flow chamber assays showed that cord blood mononuclear leucocytes used E-, P- and L-selectin and PSGL-1 to roll on and adhere to endothelium under physiological shear stress. These data show that selectins are synthesized and functional before birth in humans and have the potential to mediate the emigration of mononuclear cells and inflammatory responses.

[Endothelial cell adhesion molecules].

The review presents current data concerning the functional role of endothelial cell adhesion molecules belonging to different structural families: integrins, selectins, cadherins, and the immunoglobulin super-family. In this manuscript the regulatory mechanisms and factors of adhesion molecules expression and distribution on the surface of endothelial cells are discussed. The data presented reveal the importance of adhesion molecules in the regulation of structural and functional state of endothelial cells in normal conditions and in pathology. Particular attention is paid to the importance of these molecules in the processes of physiological and pathological angiogenesis, regulation of permeability of the endothelial barrier and cell transmigration.

The Drosophila selectin furrowed mediates intercellular planar cell polarity interactions via frizzled stabilization.

Establishment of planar cell polarity (PCP) in a tissue requires coordination of directional signals from cell to cell. It is thought that this is mediated by the core PCP factors, which include cell-adhesion molecules. Here, we demonstrate that furrowed, the Drosophila selectin, is required for PCP generation. Disruption of PCP in furrowed-deficient flies results from a primary defect in Fz levels and cell adhesion. Furrowed localizes at or near apical junctions, largely colocalizing with Frizzled and Flamingo (Fmi). It physically interacts with and stabilizes Frizzled, and it mediates intercellular Frizzled-Van Gogh (Vang)/Strabismus interactions, similarly to Fmi. Furrowed does so through a homophilic cell-adhesion role that is distinct from its known carbohydrate-binding function described during vertebrate blood-cell/endothelial cell interactions. Importantly, the carbohydrate function is dispensable for PCP establishment. In vivo studies suggest that Furrowed functions partially redundantly with Fmi, mediating intercellular Frizzled-Vang interactions between neighboring cells.

Endothelial cells recruit macrophages and contribute to a fibrotic milieu in bleomycin lung injury.

Systemic sclerosis (SSc) is a systemic autoimmune disease that causes inflammation, vasculopathy, and fibrosis of the skin and internal organs. One of the most severe complications of SSc involves the development of pulmonary fibrosis. Endothelial cell injury precedes the development of fibrosis, and is believed to be an initiating event. Therefore, we aimed to characterize the role of endothelial cells in the progression of pulmonary fibrosis, using a well-established bleomycin (BLM) model of pulmonary fibrosis. Endothelial cells were isolated by cell sorting, and the analysis of gene expression was performed with quantitative RT-PCR. Endothelial injury was induced between the first and second week, as shown by the elevated expression of the vascular injury markers matrix metallopeptidase-12 and von Willebrand factor. After injury, endothelial activation was indicated by the up-regulation of selectins, CCL chemokines, and inflammatory mediators, including complement anaphylatoxin receptors (C3aR and C5aR), oncostatin M, and leukemia inhibitory factor. The endothelial cell overexpression of fibrotic mediators, including connective tissue growth factor, plasminogen activator inhibitor-1, osteopontin, fibronectin, and fibroblast specific protein-1, was observed in the second and fourth weeks. This study suggests that endothelial cells actively contribute to the disease process via multiple mechanisms, including the recruitment of inflammatory cells and the establishment of a profibrotic environment during the development of BLM-induced pulmonary fibrosis.