Therapeutic targeting of endothelial ligands for L-selectin (PNAd) in a sheep model of asthma

Nanotargeted Delivery of Immune Therapeutics in Type 1 Diabetes

Immune therapeutics holds great promise in the treatment of type 1 diabetes (T1D). Nonetheless, their progress is hampered by limited efficacy, equipoise, or issues of safety. To address this, a novel and specific nanodelivery platform for T1D that targets high endothelial venules (HEVs) presented in the pancreatic lymph nodes (PLNs) and pancreas is developed. Data indicate that the pancreata of nonobese diabetic (NOD) mice and patients with T1D are unique in their expression of newly formed HEVs. Anti-CD3 mAb is encapsulated in poly(lactic-co-glycolic acid)-poly(ethylene glycol) nanoparticles (NPs), the surfaces of which are conjugated with MECA79 mAb that recognizes HEVs. Targeted delivery of these NPs improves accumulation of anti-CD3 mAb in both the PLNs and pancreata of NOD mice. Treatment of hyperglycemic NOD mice with MECA79-anti-CD3-NPs results in significant reversal of T1D compared to those that are untreated, treated with empty NPs, or provided free anti-CD3. This effect is associated with a significant reduction of T effector cell populations in the PLNs and a decreased production of pro-inflammatory cytokine in the mice treated with MECA79-anti-CD3-NPs. In summary, HEV-targeted therapeutics may be used as a means by which immune therapeutics can be delivered to PLNs and pancreata to suppress autoimmune diabetes effectively.

Delivery of costimulatory blockade to lymph nodes promotes transplant acceptance in mice

The lymph node (LN) is the primary site of alloimmunity activation and regulation during transplantation. Here, we investigated how fibroblastic reticular cells (FRCs) facilitate the tolerance induced by anti-CD40L in a murine model of heart transplantation. We found that both the absence of LNs and FRC depletion abrogated the effect of anti-CD40L in prolonging murine heart allograft survival. Depletion of FRCs impaired homing of T cells across the high endothelial venules (HEVs) and promoted formation of alloreactive T cells in the LNs in heart-transplanted mice treated with anti-CD40L. Single-cell RNA sequencing of the LNs showed that anti-CD40L promotes a Madcam1+ FRC subset. FRCs also promoted the formation of regulatory T cells (Tregs) in vitro. Nanoparticles (NPs) containing anti-CD40L were selectively delivered to the LNs by coating them with MECA-79, which binds to peripheral node addressin (PNAd) glycoproteins expressed exclusively by HEVs. Treatment with these MECA-79-anti-CD40L-NPs markedly delayed the onset of heart allograft rejection and increased the presence of Tregs. Finally, combined MECA-79-anti-CD40L-NPs and rapamycin treatment resulted in markedly longer allograft survival than soluble anti-CD40L and rapamycin. These data demonstrate that FRCs are critical to facilitating costimulatory blockade. LN-targeted nanodelivery of anti-CD40L could effectively promote heart allograft acceptance.

The Percentage of PNAd-Expressing Vessels is Correlated with Disease Severity in Eosinophilic Chronic Rhinosinusitis

BACKGROUND

Eosinophilic chronic rhinosinusitis (ECRS) is a chronic inflammatory condition of the paranasal sinuses characterized by intractable nasal polyps with prominent eosinophil infiltration. These eosinophils are presumably recruited from peripheral blood via vessels expressing peripheral lymph node addressin (PNAd), a set of glycoproteins decorated with 6-sulfo sialyl Lewis x (sLe^x) glycans that serve as L-selectin ligands. Based on the severity classification algorithm proposed by the Japanese Epidemiological Survey of Refractory Eosinophilic Chronic Rhinosinusitis (JESREC) study group, ECRS is divided into mild, moderate and severe groups; however, as yet there are few reports comparing the clinicopathological differences among these groups.

OBJECTIVE

Our goal was to elucidate clinicopathological differences among the three different severities of ECRS with special reference to eosinophils and PNAd-expressing vessels.

METHODS

We performed quantitative immunohistochemical analysis of PNAd-expressing vessels using surgical specimens of nasal polyps from patients exhibiting varying severity of ECRS (n = 35) and from individuals with non-ECRS (n = 10). To this end, we immunostained tissue sections with anti-PNAd and anti-CD34 monoclonal antibodies, and then determined the number of vessels immunolabeled with each antibody.

RESULTS

The number of eosinophils infiltrating nasal polyps was correlated with ECRS severity. We also found that the PNAd + /CD34 + vessel ratio, namely, the percentage of PNAd-expressing vessels among all vessels, was positively correlated not only with ECRS severity but also with the number of eosinophils infiltrating nasal polyps formed in ECRS.

CONCLUSION

These results strongly suggest that PNAd-expressing vessels play at least a partial role in eosinophil recruitment to nasal polyps and consequent severity of ECRS.

High endothelial venules as potential gateways for therapeutics

High endothelial venules (HEVs) are specialized blood vessels that support the migration of lymphocytes from the bloodstream into lymph nodes (LNs). They are also formed ectopically in mammalian organs affected by chronic inflammation and cancer. The recent arrival of immunotherapy at the forefront of many cancer treatment regimens could boost a crucial role for HEVs as gateways for the treatment of cancer. In this review, we describe the microanatomical and biochemical characteristics of HEVs, mechanisms of formation of newly made HEVs, immunotherapies potentially dependent on HEV-mediated T cell homing to tumors, and finally, how HEV-targeted therapies might be used as a complementary approach to potentially shape the therapeutic landscape for the treatment of cancer and immune-mediated diseases.

Complementary Role of GlcNAc6ST2 and GlcNAc6ST3 in Synthesis of CL40-Reactive Sialylated and Sulfated Glycans in the Mouse Pleural Mesothelium

Sialyl 6-sulfo Lewis X (6-sulfo sLe^X) and its derivative sialyl 6-sulfo N-acetyllactosamine (LacNAc) are sialylated and sulfated glycans of sialomucins found in the high endothelial venules (HEVs) of secondary lymphoid organs. A component of 6-sulfo sLe^X present in the core 1-extended O-linked glycans detected by the MECA-79 antibody was previously shown to exist in the lymphoid aggregate vasculature and bronchial mucosa of allergic and asthmatic lungs. The components of 6-sulfo sLe^X in pulmonary tissues under physiological conditions remain to be analyzed. The CL40 antibody recognizes 6-sulfo sLe^X and sialyl 6-sulfo LacNAc in O-linked and N-linked glycans, with absolute requirements for both GlcNAc-6-sulfation and sialylation. Immunostaining of normal mouse lungs with CL40 was performed and analyzed. The contribution of GlcNAc-6-O-sulfotransferases (GlcNAc6STs) to the synthesis of the CL40 epitope in the lungs was also elucidated. Here, we show that the expression of the CL40 epitope was specifically detected in the mesothelin-positive mesothelium of the pulmonary pleura. Moreover, GlcNAc6ST2 (encoded by Chst4) and GlcNAc6ST3 (encoded by Chst5), but not GlcNAc6ST1 (encoded by Chst2) or GlcNAc6ST4 (encoded by Chst7), are required for the synthesis of CL40-positive glycans in the lung mesothelium. Furthermore, neither GlcNAc6ST2 nor GlcNAc6ST3 is sufficient for in vivo expression of the CL40 epitope in the lung mesothelium, as demonstrated by GlcNAc6ST1/3/4 triple-knock-out and GlcNAc6ST1/2/4 triple-knock-out mice. These results indicate that CL40-positive sialylated and sulfated glycans are abundant in the pleural mesothelium and are synthesized complementarily by GlcNAc6ST2 and GlcNAc6ST3, under physiological conditions in mice.

Vascular Endothelial Cells: Heterogeneity and Targeting Approaches

Forming the inner layer of the vascular system, endothelial cells (ECs) facilitate a multitude of crucial physiological processes throughout the body. Vascular ECs enable the vessel wall passage of nutrients and diffusion of oxygen from the blood into adjacent cellular structures. ECs regulate vascular tone and blood coagulation as well as adhesion and transmigration of circulating cells. The multitude of EC functions is reflected by tremendous cellular diversity. Vascular ECs can form extremely tight barriers, thereby restricting the passage of xenobiotics or immune cell invasion, whereas, in other organ systems, the endothelial layer is fenestrated (e.g., glomeruli in the kidney), or discontinuous (e.g., liver sinusoids) and less dense to allow for rapid molecular exchange. ECs not only differ between organs or vascular systems, they also change along the vascular tree and specialized subpopulations of ECs can be found within the capillaries of a single organ. Molecular tools that enable selective vascular targeting are helpful to experimentally dissect the role of distinct EC populations, to improve molecular imaging and pave the way for novel treatment options for vascular diseases. This review provides an overview of endothelial diversity and highlights the most successful methods for selective targeting of distinct EC subpopulations.

Therapeutic Effects of an Anti-sialyl Lewis X Antibody in a Murine Model of Allergic Asthma

Asthma is an allergic disease that causes severe infiltration of leukocytes into the lungs. Leukocyte infiltration is mediated by the binding of sialyl Lewis X (sLex) glycans present on the leukocytes to E-and P-selectins present on the endothelial cells at the sites of inflammation. Here, we found that mouse eosinophils express sLex glycans, and their infiltration into the lungs and proliferation in the bone marrow were significantly suppressed by an anti-sLex monoclonal antibody (mAb) F2 in a murine model of ovalbumin-induced asthma. The percentage of eosinophils in the bronchoalveolar lavage fluid and bone marrow and serum IgE levels decreased significantly in the F2-administered mice. Levels of T helper type 2 (Th2) cytokines and chemokines, involved in IgE class switching and eosinophil proliferation and recruitment, were also decreased in the F2-administered mice. An ex vivo cell rolling assay revealed that sLex glycans mediate the rolling of mouse eosinophils on P-selectin-expressing cells. These results indicate that the mAb F2 exerts therapeutic effects in a murine model of allergen-induced asthma, suggesting that sLex carbohydrate antigen could serve as a novel therapeutic target for allergic asthma.

High endothelial venules (HEVs) in immunity, inflammation and cancer

High endothelial venules (HEVs) are specialized blood vessels mediating lymphocyte trafficking to lymph nodes (LNs) and other secondary lymphoid organs. By supporting high levels of lymphocyte extravasation from the blood, HEVs play an essential role in lymphocyte recirculation and immune surveillance for foreign invaders (bacterial and viral infections) and alterations in the body’s own cells (neoantigens in cancer). The HEV network expands during inflammation in immune-stimulated LNs and is profoundly remodeled in metastatic and tumor-draining LNs. HEV-like blood vessels expressing high levels of the HEV-specific sulfated MECA-79 antigens are induced in non-lymphoid tissues at sites of chronic inflammation in many human inflammatory and allergic diseases, including rheumatoid arthritis, Crohn’s disease, allergic rhinitis and asthma. Such vessels are believed to contribute to the amplification and maintenance of chronic inflammation. MECA-79⁺ tumor-associated HEVs (TA-HEVs) are frequently found in human tumors in CD3⁺ T cell-rich areas or CD20⁺ B-cell rich tertiary lymphoid structures (TLSs). TA-HEVs have been proposed to play important roles in lymphocyte entry into tumors, a process essential for successful antitumor immunity and lymphocyte-mediated cancer immunotherapy with immune checkpoint inhibitors, vaccines or adoptive T cell therapy. In this review, we highlight the phenotype and function of HEVs in homeostatic, inflamed and tumor-draining lymph nodes, and those of HEV-like blood vessels in chronic inflammatory diseases. Furthermore, we discuss the role and regulation of TA-HEVs in human cancer and mouse tumor models.

Selectins-The Two Dr. Jekyll and Mr. Hyde Faces of Adhesion Molecules-A Review

Selectins belong to a group of adhesion molecules that fulfill an essential role in immune and inflammatory responses and tissue healing. Selectins are glycoproteins that decode the information carried by glycan structures, and non-covalent interactions of selectins with these glycan structures mediate biological processes. The sialylated and fucosylated tetrasaccharide sLe^x is an essential glycan recognized by selectins. Several glycosyltransferases are responsible for the biosynthesis of the sLe^x tetrasaccharide. Selectins are involved in a sequence of interactions of circulated leukocytes with endothelial cells in the blood called the adhesion cascade. Recently, it has become evident that cancer cells utilize a similar adhesion cascade to promote metastases. However, like Dr. Jekyll and Mr. Hyde’s two faces, selectins also contribute to tissue destruction during some infections and inflammatory diseases. The most prominent function of selectins is associated with the initial stage of the leukocyte adhesion cascade, in which selectin binding enables tethering and rolling. The first adhesive event occurs through specific non-covalent interactions between selectins and their ligands, with glycans functioning as an interface between leukocytes or cancer cells and the endothelium. Targeting these interactions remains a principal strategy aimed at developing new therapies for the treatment of immune and inflammatory disorders and cancer. In this review, we will survey the significant contributions to and the current status of the understanding of the structure of selectins and the role of selectins in various biological processes. The potential of selectins and their ligands as therapeutic targets in chronic and acute inflammatory diseases and cancer will also be discussed. We will emphasize the structural characteristic of selectins and the catalytic mechanisms of glycosyltransferases involved in the biosynthesis of glycan recognition determinants. Furthermore, recent achievements in the synthesis of selectin inhibitors will be reviewed with a focus on the various strategies used for the development of glycosyltransferase inhibitors, including substrate analog inhibitors and transition state analog inhibitors, which are based on knowledge of the catalytic mechanism.

Development of Mucosal PNAd+ and MAdCAM-1+ Venules during Disease Course in Ulcerative Colitis

PNAd and MAdCAM-1 addressins on venules are of importance in T-cell homing and potential therapeutic targets in ulcerative colitis (UC). Normally, PNAd⁺ high endothelial venules (HEVs) are only present in lymphoid organs, whereas small numbers of MAdCAM-1⁺ venules can be seen in non-lymphoid tissue. We aimed to study their presence in the intestinal mucosa of UC patients at diagnosis and during follow-up, and their correlation with disease activity. Colonic biopsy specimens of 378 UC patients were analyzed by immunohistochemistry for CD3, CD20, ERG, MECA-79 (PNAd) and MECA-376 (MAdCAM-1) and compared to healthy controls (HC). The proportion of PNAd⁺HEVs in UC at diagnosis was 4.9% (IQR 2.0%-8.3%), while none were detected in HC. During follow-up, PNAd⁺HEVs completely disappeared in remission (n = 93), whereas the proportion in active disease was similar to baseline (n = 285, p = 0.39). The proportion of MAdCAM-1⁺venules in UC at baseline was 5.8% (IQR 2.6-10.0). During follow-up, the proportion in remission was comparable to diagnosis, but upregulated (7.5% (IQR 4.4-10.9), p = 0.001) in active disease. In conclusion, PNAd⁺HEVs appear in UC during active inflammation which could thus serve as a marker for disease activity, whereas MAdCAM-1⁺venules remain present after inflammation is resolved and increase after subsequent flares, reflecting chronicity and potentially serving as a therapeutic target.

Induction of peripheral lymph node addressin in human nasal mucosa with eosinophilic chronic rhinosinusitis

Eosinophilic chronic rhinosinusitis (ECRS) is characterised by formation of nasal polyps with prominent eosinophilic infiltration; however, how eosinophils are recruited in this pathological setting remains unclear. In the present study, we carried out quantitative immunohistochemical analysis of nasal polyps associated with ECRS (n=30) and non-ECRS (n=30) to evaluate expression of an L-selectin ligand peripheral lymph node addressin (PNAd) on vascular endothelial cells. We found that PNAd was induced primarily on the luminal surface of venular vessels present in nasal mucosa in both ECRS and non-ECRS, while the number of PNAd-expressing vessels in ECRS significantly exceeded that seen in non-ECRS. Moreover, the number of eosinophils attached to the luminal surface of PNAd-expressing vessels in ECRS was significantly greater than that in non-ECRS, while the number of neutrophils and lymphocytes attached did not differ significantly between conditions. Furthermore, eosinophils, which express cell surface L-selectin, adhered to PNAd-expressing Chinese hamster ovary (CHO) cells in a calcium-dependent manner, and that adhesion was significantly inhibited by pretreatment of eosinophils with DREG-56, an anti-human L-selectin monoclonal antibody. These findings combined suggest that interaction between L-selectin and PNAd plays at least a partial role in eosinophil recruitment in human nasal mucosa with ECRS.

Role of MAdCAM-1-Expressing High Endothelial Venule-Like Vessels in Colitis Induced in Mice Lacking Sulfotransferases Catalyzing L-Selectin Ligand Biosynthesis

Ulcerative colitis (UC) is a chronic inflammatory disease histologically characterized by diffuse mononuclear cell infiltrates in colonic mucosa. These inflammatory cells are considered to be recruited via high endothelial venule (HEV)-like vessels displaying mucosal addressin cell adhesion molecule 1 (MAdCAM-1), the ligand for α4β7 integrin, and/or peripheral lymph node addressin (PNAd), an L-selectin ligand. 6- O-sulfation of N-acetylglucosamine in the carbohydrate moiety of PNAd is catalyzed exclusively by N-acetylglucosamine-6- O-sulfotransferase 1 (GlcNAc6ST-1) and GlcNAc6ST-2. To determine the role of 6- O-sulfation of N-acetylglucosamine on HEV-like vessels in UC, we used a chronic dextran sulfate sodium-induced colitis model using mice deficient in both GlcNAc6ST-1 and GlcNAc6ST-2. We found that more inflammatory cells, with expression of tumor necrosis factor α, were infiltrated in double knockout mouse colitis compared with that in wild-type mice. Moreover, the number of MAdCAM-1-positive vessels was increased in double knockout mouse colitis, and these vessels were bound by E-selectin•IgM chimeras that bind to unsulfated sialyl Lewis X (sLeX). These findings suggest that interactions between MAdCAM-1 and α4β7 integrin and/or unsulfated sLeX and L-selectin may become a dominant mechanism for inflammatory cell recruitment in the absence of 6-sulfo sLeX and contribute to more severe colitis phenotypes seen in double knockout mice.

Trafficking receptor signatures define blood plasmablasts responding to tissue-specific immune challenge

Antibody-secreting cells are generated in regional lymphoid tissues and traffic as plasmablasts (PBs) via lymph and blood to target sites for local immunity. We used multiparameter flow cytometry to define PB trafficking programs (TPs, combinations of adhesion molecules and chemoattractant receptors) and their imprinting in patients in response to localized infection or immune insults. TPs enriched after infection or autoimmune inflammation of mucosae correlate with sites of immune response or symptoms, with different TPs imprinted during small intestinal, colon, throat, and upper respiratory immune challenge. PBs induced after intramuscular or intradermal influenza vaccination, including flu-specific antibody-secreting cells, display TPs characterized by the lack of mucosal homing receptors. PBs of healthy donors display diverse mucosa-associated TPs, consistent with homeostatic immune activity. Identification of TP signatures of PBs may facilitate noninvasive monitoring of organ-specific immune responses.

Lymphangiogenesis is a feature of acute GVHD, and VEGFR-3 inhibition protects against experimental GVHD

Lymph vessels play a crucial role in immune reactions in health and disease. In oncology the inhibition of lymphangiogenesis is an established therapeutic concept for reducing metastatic spreading of tumor cells. During allogeneic tissue transplantation, the inhibition of lymphangiogenesis has been successfully used to attenuate graft rejection. Despite its critical importance for tumor growth, alloimmune responses, and inflammation, the role of lymphangiogenesis has not been investigated during allogeneic hematopoietic stem cell transplantation (allo-HSCT). We found that acute graft-versus-host disease (aGVHD) is associated with lymphangiogenesis in murine allo-HSCT models as well as in patient intestinal biopsies. Inhibition of aGVHD-associated lymphangiogenesis by monoclonal antibodies against vascular endothelial growth factor receptor 3 (VEGFR-3) ameliorated aGVHD and improved survival in murine models. The administration of anti-VEGFR-3 antibodies did not interfere with hematopoietic engraftment and improved immune reconstitution in allo-HSCT recipients with aGVHD. Anti-VEGFR-3 therapy had no significant impact on growth of malignant lymphoma after allo-HSCT. We conclude that aGVHD is associated with lymphangiogenesis in intestinal lesions and in lymph nodes. Our data show that anti-VEGFR-3 treatment ameliorates lethal aGVHD and identifies the lymphatic vasculature as a novel therapeutic target in the setting of allo-HSCT.

Soluble L-Selectin as an Independent Biomarker of Bronchial Asthma

BACKGROUND

We sought to determine the association of plasma level of soluble L-selectin (sL-selectin) and F206L polymorphism of L-selectin with asthma.

METHODS

A total of 90 asthmatic patients and 90 sex- and age-matched healthy controls were enrolled. The plasma level of sL-selectin was measured by enzyme-linked immunosorbent assay (ELISA) method. An amplification refractory mutation system polymerase chain reaction was performed to detect F206L polymorphism of L-selectin.

RESULTS

The mean plasma levels of sL-selectin was significantly higher in the patients with asthma than the controls (2113 ± 466 vs. 1664 ± 322 ng/ml, P = 0.001). Logistic regression analysis after adjustment for age, sex, and body mass index demonstrated that plasma levels of sL-selectin are an independent biomarkers for asthma (odds ratio [OR], 1.86; 95% confidence interval [95% CI], 1.42-2.24). The area under the receiver operating characteristic (ROC) curve for sL-selectin was 0.792, 95% CI (0.732-0.862), P = 0.0001. Individuals with the minor homozygote of F206L polymorphism of L-selectin demonstrated a higher level of sL-selectin than the major homozygous (2319 ± 732 vs. 1917 ± 453 ng/ml, P = 0.02). No association was found between F206L polymorphism of L-selectin with asthma.

CONCLUSION

Our study suggests that plasma level of sL-selectin is an independent biomarker for asthma.

Ectopic expression of MECA-79 as a novel prognostic indicator in gastric cancer

The aim of this study was to clarify the clinical implications of a unique carbohydrate determinant, MECA-79, in gastric cancer specimens and cells. Immunohistochemical analysis showed that 62 of 225 (27.6%) cases were defined as positive for MECA-79. MECA-79 expression was correlated with depth of invasion, venous invasion, TNM stage, and distant metastasis. In survival analyses, patients with MECA-79 expression had worse prognosis by the log-rank test. Multivariate analysis of the Cox proportional hazard model showed that MECA-79 expression was an independent factor of a worse cancer-specific survival. Among 11 gastric cancer cells, MECA-79 was observed in only MKN7 cells, which also expressed GlcNAc6ST-2 transcript. A knockdown of GlcNAc6ST-2 in MKN7 cells showed a markedly reduced expression of MECA-79, suggesting that GlcNAc-sulfation of MECA-79 is mainly synthesized by GlcNAc6ST-2. Furthermore, real-time RT-PCR analysis revealed that GlcNAc6ST-2 was significantly increased in cancer tissues compared with paired normal mucosa. In conclusion, the expression of MECA-79 could be a useful marker for the prognosis of gastric cancer. Our results might also provide novel perspectives on the biology of MECA-79 and GlcNAc6ST-2 in cancer progression and metastasis.

Functional contributions of N- and O-glycans to L-selectin ligands in murine and human lymphoid organs

L-selectin initiates lymphocyte interactions with high endothelial venules (HEVs) of lymphoid organs through binding to ligands with specific glycosylation modifications. 6-Sulfo sLe(x), a sulfated carbohydrate determinant for L-selectin, is carried on core 2 and extended core 1 O-glycans of HEV-expressed glycoproteins. The MECA-79 monoclonal antibody recognizes sulfated extended core 1 O-glycans and partially blocks lymphocyte-HEV interactions in lymphoid organs. Recent evidence has identified the contribution of 6-sulfo sLe(x) carried on N-glycans to lymphocyte homing in mice. Here, we characterize CL40, a novel IgG monoclonal antibody. CL40 equaled or surpassed MECA-79 as a histochemical staining reagent for HEVs and HEV-like vessels in mouse and human. Using synthetic carbohydrates, we found that CL40 bound to 6-sulfo sLe(x) structures, on both core 2 and extended core 1 structures, with an absolute dependency on 6-O-sulfation. Using transfected CHO cells and gene-targeted mice, we observed that CL40 bound its epitope on both N-glycans and O-glycans. Consistent with its broader glycan-binding, CL40 was superior to MECA-79 in blocking lymphocyte-HEV interactions in both wild-type mice and mice deficient in forming O-glycans. This superiority was more marked in human, as CL40 completely blocked lymphocyte binding to tonsillar HEVs, whereas MECA-79 inhibited only 60%. These findings extend the evidence for the importance of N-glycans in lymphocyte homing in mouse and indicate that this dependency also applies to human lymphoid organs.

The contribution of L-selectin to airway hyperresponsiveness in chronic allergic airways disease

L-selectin is a cell adhesion molecule, which mediates leukocyte rolling on bronchopulmonary endothelium. Previous studies in a murine model of allergic airways disease have shown that L-selectin plays a role in the regulation of airway hyperresponsiveness in asthma via mechanisms independent of inflammation. Airway remodeling has been shown to modulate airway hyperresponsiveness independently of inflammation.

L-selectin: role in regulating homeostasis and cutaneous inflammation

The maintenance of immune surveillance and the generation of normal immune responses are dependent on leukocyte migration to appropriate lymphoid and non-lymphoid tissues. The process of leukocyte migration occurs through complex and highly regulated interactions between the circulating leukocytes and the vascular endothelium. Multiple families of adhesion molecules as well as specific chemoattractants and their cognate receptors function to stabilize these interactions and induce migration into the tissue. L-selectin is a key adhesion molecule that regulates both the migration of leukocytes at sites of inflammation and the recirculation of lymphocytes between blood and lymphoid tissues. L-selectin-mediated lymphocyte recirculation is required for maintaining the appropriate tissue distribution of lymphocyte subpopulations including naïve and effector subsets such as regulatory T cells. In addition, L-selectin-mediated entry into peripheral lymph nodes is required for optimal induction of lymphocyte homeostatic proliferation during lymphopenia. Importantly, L-selectin has been shown to have both adhesive and signaling functions during leukocyte migration. Specifically, L-selectin is highly efficient at capturing free-flowing leukocytes from the blood and supporting subsequent fast rolling interactions along the vascular endothelium. During rolling, synergistic interactions between L-selectin and integrin functions slow leukocyte rolling velocities allowing for chemoattractant-induced activation and eventual firm adhesion of the leukocyte to the vascular endothelium. Engagement of L-selectin by ligand generates transmembrane signals leading to activation of intracellular signaling pathways, increased integrin binding affinity, and enhanced chemotaxis. L-selectin has also been shown to mediate leukocyte recruitment during chronic inflammatory and autoimmune diseases and thus is a potential therapeutic target for drug development.

Dual inhibition of cathepsin G and chymase is effective in animal models of pulmonary inflammation

RATIONALE

Mast cells and neutrophils are key contributors to the pathophysiological inflammatory processes that underpin asthma and chronic obstructive pulmonary disease, partly through the release of noxious serine proteases, including cathepsin G (Cat G) and chymase. From this standpoint, a dual inhibitor of neutrophil Cat G and mast cell chymase could protect against these disease-related inflammatory responses.

OBJECTIVES

We examined the antiinflammatory pharmacology of RWJ-355871, a dual inhibitor of Cat G and chymase, in animal models of inflammation that evince pathophysiological pathways relevant to asthma and chronic obstructive pulmonary disease to determine the therapeutic potential of this compound.

METHODS

In an ovalbumin (OVA)-sensitized rat model, RWJ-355871 was administered to block the mast-cell-mediated increase in paw volume caused by OVA injection. In a sheep asthma model, antigen-induced airway responses were assessed with and without aerosol treatment with RWJ-355871. In a murine tobacco-smoke model of airway inflammation, the effect of RWJ-355871 on smoke-induced neutrophilia was determined.

MEASUREMENTS AND MAIN RESULTS

Intravenous treatment of OVA-sensitized rats with RWJ-355871 provided dose-dependent reduction in the increase in rat paw volume. In allergic sheep, aerosol pretreatment with RWJ-355871 showed dose-dependent inhibition of the antigen-induced early response, late response, and post-antigen-induced airway hyperreponsiveness. In tobacco-smoke-exposed mice, nebulized RWJ-355871 significantly reduced the smoke-induced neutrophilia from the levels observed in untreated mice.

CONCLUSIONS

The preclinical antiinflammatory effects of RWJ-355871 in these animal models of inflammation indicate that this dual inhibitor may have therapeutic utility for treating airway inflammatory diseases involving mechanisms that depend on Cat G and/or chymase.

Role of sulfated O-glycans expressed by high endothelial venule-like vessels in pathogenesis of chronic inflammatory gastrointestinal diseases

Lymphocyte homing is mediated by a cascade of adhesive interactions between circulating lymphocytes and specialized endothelial cells comprising high endothelial venules (HEVs). Sulfated O-glycans expressed on HEVs, collectively called peripheral lymph node addressin (PNAd), interact with L-selectin expressed on lymphocytes, contributing to the initial step of the lymphocyte homing. In chronic inflammatory states, PNAd is induced on HEV-like vessels but absent in non-lymphoid tissues under normal conditions. Such HEV-like vessels have been observed in various chronic inflammatory diseases including rheumatoid arthritis, lymphocytic thyroiditis, Helicobacter pylori-associated chronic gastritis, and inflammatory bowel disease (IBD), and implicated in lymphocyte recruitment in those diseases. In H. pylori-associated chronic gastritis, PNAd-expressing HEV-like vessels are induced, and the progression of chronic inflammation is highly correlated with appearance of these vessels. Furthermore, eradication of H. pylori by antibiotics resulted in disappearance of PNAd. These results indicate that inhibition of PNAd formation could have therapeutic effect by attenuating lymphocyte recruitment. In ulcerative colitis (UC), PNAd-expressing HEV-like vessels are induced, preferentially in the active phase, and T cells, particularly CD4(+) T cells, are closely associated with these vessels, suggesting that T cell recruitment via PNAd-expressing HEV-like vessels plays at least a partial role in UC pathogenesis. Additionally, N-acetylglucosamine-6-O-sulfotransferase 1 (GlcNAc6ST-1) is suggested to be a candidate to regulate PNAd induction on HEV-like vessels in UC. These results provide a potential therapeutic strategy to treat UC by blocking T cell adhesion to PNAd-expressing HEV-like vessels. Inhibition or down-regulation of GlcNAc6ST-1 may be an alternative.

A prostaglandin D2 receptor antagonist modifies experimental asthma in sheep

BACKGROUND

Prostaglandin (PG) D(2) is the major cylooxygenase metabolite released by mast cells upon allergen stimulation, and elicits responses through either the prostanoid DP1 receptor and/or the chemoattractant receptor homologous molecule expressed on T-helper type 2 (Th2) cells (CRTH2/DP2). Experimental evidence suggests that stimulation of one or both these receptors contributes to asthma pathophysiology.

OBJECTIVE

The aim of this study was to test the hypothesis that the prostanoid DP1 receptor contributes to asthma pathophysiology by determining the efficacy of an orally active antagonist for this receptor, S-5751, on allergen-induced bronchoconstriction, airway hyperresponsiveness (AHR) and cellular inflammation in the sheep model of asthma.

METHODS

PGD(2)-induced cyclic adenosine monophosphate (cAMP) production in platelet-rich plasma was used to establish the in vitro efficacy of S-5751. In vivo, sheep naturally allergic to Ascaris suum were challenged with an aerosolized antigen with and without S-5751 treatment (given 4 days before and for 6 days after the challenge).

RESULTS

S-5751 inhibited PGD(2)-induced cAMP production in platelet-rich plasma with an IC(50) value of 0.12 microm. S-5751 at 30 mg/kg, but not at 3 mg/kg, reduced the early bronchoconstriction and inhibited the late bronchoconstriction. AHR and inflammatory cell infiltration in bronchoalveolar lavage fluid at days 1 and 7 were also inhibited with the 30 mg/kg dose. The responses observed with S-5751 at 30 mg/kg were comparable with those with montelukast treatment (0.15 mg/kg, twice a day, intravenous); however, S-5751 did not block inhaled leukotrieneD(4)-induced broncoconstriction.

CONCLUSION

Prostanoid DP1 receptor inhibition may represent an alternative target for asthma therapy.

Conditional gene targeting in mouse high endothelial venules

High endothelial venules (HEVs) are specialized blood vessels of secondary lymphoid organs composed of endothelial cells with a characteristic cuboidal morphology. Lymphocytes selectively adhere to and migrate across HEVs to initiate immune responses. In this study, we established a novel transgenic mouse line expressing Cre recombinase under the transcriptional control of the gene encoding HEV-expressed sulfotransferase, N-acetylglucosamine-6-O-sulfotransferase 2 (GlcNAc6ST-2), using bacterial artificial chromosome recombineering. Crossing these transgenic mice with the ROSA26 reporter strain, which expresses lacZ following Cre-mediated recombination, and staining the resulting progeny with 5-bromo-4-chloro-5-indolyl-beta-D-galactoside indicated that Cre recombinase was specifically expressed in mAb MECA79-reactive HEVs in secondary lymphoid organs but not in any other blood vessels of the transgenic mice. The expression of Cre recombinase correlated with a developmental switch, from immature, mAb MECA367-reactive HEVs to mature, mAb MECA79-reactive HEVs in neonatal lymph nodes. In addition to the HEVs, Cre recombinase was also strongly expressed in the colonic villi, which recapitulated the intrinsic expression of GlcNAc6ST-2 as confirmed in GlcNAc6ST-2(GFP/GFP) knock-in mice and by RT-PCR. Furthermore, treatment with an antimicrobial agent revealed that the colonic expression of Cre recombinase in the transgenic mice was regulated by commensal bacteria in the colon. In addition, Cre recombinase was expressed in a small subset of cells in the brain, testis, stomach, small intestine, and lung. In view of the restricted expression of Cre recombinase, this transgenic mouse line should be useful for elucidating tissue-specific gene functions using the Cre/loxP system.

The N-glycolyl form of mouse sialyl Lewis X is recognized by selectins but not by HECA-452 and FH6 antibodies that were raised against human cells

E-, P- and L-selectins critically function in lymphocyte recirculation and recruiting leukocytes to inflammatory sites. MECA-79 antibody inhibits L-selectin-mediated lymphocyte adhesion in several species and does not require sialic acid in its epitope. Many other antibodies, however, recognize human selectin ligands expressing N-acetylneuraminic acid but not mouse selectin ligands expressing N-glycolylneuraminic acid, suggesting that difference in sialic acid in sialyl Lewis X leads to differential reactivity. We found that HECA-452 and FH6 monoclonal antibodies bind Chinese hamster ovary (CHO) cells expressing N-acetylneuraminyl Lewis X oligosaccharide but not its N-glycolyl form. Moreover, synthetic N-acetylneuraminyl Lewis X oligosaccharide but not its N-glycolyl oligosaccharide inhibited HECA-452 and FH6 binding. By contrast, E-, P- and L-selectin bound to CHO cells regardless of whether they express N-acetyl or N-glycolyl form of sialyl Lewis X, showing that selectins have a broader recognition capacity than HECA-452 and FH-6 anti-sialyl Lewis x antibodies.

Cell adhesion antagonists: therapeutic potential in asthma and chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) and asthma are inflammatory diseases of the lung where a hallmark feature is excessive leukocyte infiltration that leads to tissue injury. Cell adhesion molecules (e.g. selectins and integrins) play a key role in cell trafficking, and in the lung they regulate leukocyte extravasation, migration within the interstitium, cellular activation, and tissue retention. All selectin family members (including L-selectin, P-selectin, and E-selectin) and many of the beta1 and beta2 integrins appear to be important therapeutic targets, as numerous animal studies have demonstrated essential roles for these cell adhesion molecules in lung inflammation. Not surprisingly, these families of adhesion molecules have been under intense investigation by the pharmaceutical industry for the development of novel therapeutics. Integrins are validated drug targets, as drugs that antagonize integrin alphaIIbbeta3 (e.g. abciximab), integrin alphaLbeta2 (efalizumab), and integrin alpha4beta1 (natalizumab) are currently US FDA-approved for acute coronary syndromes, psoriasis, and multiple sclerosis, respectively. However, none has been approved for indications related to asthma or COPD. Here, we provide an overview of roles played by selectins and integrins in lung inflammation. We also describe recent clinical results (both failures and successes) in developing adhesion molecule antagonists, with specific emphasis on those targets that may have potential benefit in asthma and COPD. Early clinical trials using selectin and integrin antagonists have met with limited success. However, recent positive phase II clinical trials with a small-molecule selectin antagonist (bimosiamose) and a small-molecule integrin alpha4beta1 antagonist (valategrast [R411]), have generated enthusiastic anticipation that novel strategies to treat asthma and COPD may be forthcoming.

Modeling of asthma, COPD and cystic fibrosis in sheep

Sheep naturally allergic to Ascaris suum antigen have been used to study the pathophysiology of asthma and more recently allergic rhinitis, chronic obstructive pulmonary disease (COPD) and cystic fibrosis. The utility of the model as it relates to the study of these diseases is discussed.

IL-6 and IL-8 increase the expression of glycosyltransferases and sulfotransferases involved in the biosynthesis of sialylated and/or sulfated Lewisx epitopes in the human bronchial mucosa

Bronchial mucins from patients suffering from CF (cystic fibrosis) exhibit glycosylation alterations, especially increased amounts of the sialyl-Lewisx (NeuAcα2-3Galβ1-4[Fucα1-3]GlcNAc-R) and 6-sulfo-sialyl-Lewisx (NeuAcα2-3Galβ1-4[Fucα1-3][SO3H-6]GlcNAc-R) terminal structures. These epitopes are preferential receptors for Pseudomonas aeruginosa, the bacteria responsible for the chronicity of airway infection and involved in the morbidity and early death of CF patients. However, these glycosylation changes cannot be directly linked to defects in CFTR (CF transmembrane conductance regulator) gene expression since cells that secrete airway mucins express no or very low amounts of the protein. Several studies have shown that inflammation may affect glycosylation and sulfation of various glycoproteins, including mucins. In the present study, we show that incubation of macroscopically healthy fragments of human bronchial mucosa with IL-6 (interleukin-6) or IL-8 results in a significant increase in the expression of α1,3/4-fucosyltransferases [FUT11 (fucosyltransferase 11 gene) and FUT3], α2-6- and α2,3-sialyltransferases [ST3GAL6 (α2,3-sialyltransferase 6 gene) and ST6GAL2 (α2,6-sialyltransferase 2 gene)] and GlcNAc-6-O-sulfotransferases [CHST4 (carbohydrate sulfotransferase 4 gene) and CHST6] mRNA. In parallel, the amounts of sialyl-Lewisx and 6-sulfo-sialyl-Lewisx epitopes at the periphery of high-molecular-mass proteins, including MUC4, were also increased. In conclusion, our results indicate that IL-6 and -8 may contribute to the increased levels of sialyl-Lewisx and 6-sulfo-sialyl-Lewisx epitopes on human airway mucins from patients with CF.

Standardization of diagnostic criteria for eosinophilic chronic rhinosinusitis in the Oestrus ovis infected sheep model

BACKGROUND

The sheep is an established model for endoscopic surgical procedures, as well as for postsurgical healing. Standardization of the presence and the degree of eosinophilia within this model still has not been done. This study was undertaken to show the eosinophilic response secondary to Oestrus ovis parasitic infestation within the nasal cavity to standardize the sheep model of chronic rhinosinusitis (CRS) and to set diagnostic criteria for CRS in sheep.

METHODS

Nasal mucosal secretions were obtained from sheep naturally infested with O. ovis and showed signs of CRS and from sheep treated with ivermectin to prevent the infestation. Full thickness mucosal biopsy specimens from the lateral nasal wall were obtained also from these sheep. After histological fixing and staining, the degree of eosinophilia in the mucous secretion smears and in the epithelial layer of the lateral nasal wall was quantified using a light microscope.

RESULTS

The average number of eosinophils in the mucous secretions and in the nasal wall epithelium was significantly higher in the sheep that showed signs of rhinosinusitis and had visible O. ovis larvae compared with control sheep (p = 0.003 and p = 0.05, respectively).

CONCLUSION

Based on the average numbers of eosinophils observed the diagnostic criterion for CRS in sheep is two eosinophils per high-power field averaged over three fields of secreted mucous smears or an average of at least one eosinophil per high-power field of nasal wall epithelial biopsy specimens.

Preferential induction of peripheral lymph node addressin on high endothelial venule-like vessels in the active phase of ulcerative colitis

OBJECTIVES

In the colonic mucosa with ulcerative colitis (UC), it has been suggested that L-selectin-peripheral lymph node addressin (PNAd) interaction plays a role in lymphocyte recruitment, which requires PNAd induction on high endothelial venule (HEV)-like vessels. The present study was undertaken to elucidate how these HEV-like vessels participate in the pathogenesis of UC and also to determine whether the presence of such vessels is correlated with clinical outcomes.

METHODS

Biopsy specimens composed of active (N = 32) and remission (N = 12) phases of UC were subjected to immunohistochemistry for CD34, MECA-79, and HECA-452, and the immunostained sections were quantitatively analyzed. An in vitro binding assay with L-selectin*IgM chimeric protein was carried out to determine whether PNAd on HEV-like vessels formed in UC functions as an L-selectin ligand. RT-PCR was carried out to determine which enzyme is upregulated for PNAd biosynthesis on HEV-like vessels induced in the active phase of UC. Triple immunostaining for MECA-79 together with CD3 and CD20/CD79alpha, CD4 and CD8, or CXCR3 and ST2L was carried out to determine which lymphocyte population closely associates with these vessels.

RESULTS

PNAd-expressing HEV-like vessels were preferentially induced in the active phase of UC with increased transcription of the gene encoding N-acetylglucosamine-6-O-sulfotransferase (GlcNAc6ST)-1, which directs expression of the MECA-79 epitope. Moreover, T cells, particularly CD4(+) T cells, were more closely associated with these HEV-like vessels than B cells.

CONCLUSIONS

T-cell recruitment via PNAd-expressing HEV-like vessels induced by expression of GlcNAc6ST-1 may play a role in UC pathogenesis.

Critical functions of N-glycans in L-selectin-mediated lymphocyte homing and recruitment

Lymphocyte homing is mediated by specific interaction between L-selectin on lymphocytes and the carbohydrate ligand 6-sulfo sialyl Lewis X on high endothelial venules. Here we generated mice lacking both core 1 extension and core 2 branching enzymes to assess the functions of O-glycan-borne L-selectin ligands in vivo. Mutant mice maintained robust lymphocyte homing, yet they lacked O-glycan L-selectin ligands. Biochemical analyses identified a class of N-glycans bearing the 6-sulfo sialyl Lewis X L-selectin ligand in high endothelial venules. These N-glycans supported the binding of L-selectin to high endothelial venules in vitro and contributed in vivo to O-glycan-independent lymphocyte homing in wild-type and mutant mice. Our results demonstrate the critical function of N-glycan-linked 6-sulfo sialyl Lewis X in L-selectin-dependent lymphocyte homing and recruitment.

A distinctive set of genes is upregulated during the inflammation-carcinoma sequence in mouse stomach infected by Helicobacter felis

Helicobacter pylori infects over half the population worldwide and is a leading cause of chronic gastritis and gastric cancer. However, the mechanism by which this organism induces inflammation and carcinogenesis is not fully understood. In the present study we used insulin-gastrin (INS-GAS) transgenic mice that fully develop gastric adenocarcinoma after infection of H. pylori-related Helicobacter felis. Histological examination revealed that more than half of those mice developed invasive adenocarcinoma after 8 months of infection. These carcinomas were stained by NCC-ST-439 and HECA-452 that recognize 6-sulfated and non-sulfated sialyl Lewis X. Lymphocytic infiltration predominantly to submucosa was observed in most H. felis-infected mice, and this was associated with the formation of peripheral lymph node addressin (PNAd) on high endothelial venule (HEV)-like vessels detected by MECA-79. Time-course analysis of gene expression by using gene microarray revealed upregulation of several inflammation-associated genes including chemokines, adhesion molecules, surfactant protein D (SP-D), and CD74 in the infected stomach. Immunohistochemical analysis demonstrated that SP-D is expressed in hyperplasia and adenocarcinoma whereas CD74 is expressed in adenocarcinoma in situ and invasive carcinoma. These results as a whole indicate that H. felis induces HEV-like vessels and inflammation-associated chemokines and chemokine receptors, followed by adenocarcinoma formation.

Sulfated L-selectin ligands as a therapeutic target in chronic inflammation

The homing of lymphocytes to peripheral lymph nodes is initiated by an adhesive interaction between L-selectin on lymphocytes and peripheral node addressin (PNAd), a set of sialomucins displayed on high endothelial venules (HEVs) of lymph nodes. The monoclonal antibody MECA-79 reacts with the PNAd sialomucins by recognizing an N-acetylglucosamine (GlcNAc)-6-sulfated oligosaccharide, which overlaps with sialyl 6-sulfo Lewis X, the L-selectin recognition determinant. Two HEV-expressed sulfotransferases, GlcNAc6ST-1 and GlcNAc6ST-2, are essential for the expression of the MECA-79 epitope and L-selectin ligand activity on lymph-node HEVs. PNAd, as defined by MECA-79 staining, is also expressed on activated blood vessels at several sites of chronic inflammation. Recent evidence indicates that the same two sulfotransferases underlie the formation of functional PNAd at these sites. Experiments in a sheep model of asthma demonstrate that a chronic inflammatory disease can be ameliorated by targeting PNAd.

Efficacy of IL-13 neutralization in a sheep model of experimental asthma

IL-13 contributes to airway hyperresponsiveness, mucus secretion, inflammation, and fibrosis, suggesting that it plays a central role in asthma pathogenesis. Neutralization of IL-13 with sIL-13Ralpha2-Fc (sIL-13R) reduces allergen-induced airway responses in rodent models of respiratory disease, but its efficacy in a large animal model has not been previously reported. In this study, we determined whether two different strategies for IL-13 neutralization modified experimental asthma in sheep. Sheep with natural airway hypersensitivity to Ascaris suum antigen were treated intravenously either with sIL-13R, a strong antagonist of sheep IL-13 bioactivity in vitro, or with IMA-638 (IgG1, kappa), a humanized antibody to human IL-13. Higher doses of IMA-638 were used because, although it is a potent antagonist of human IL-13, this antibody has 20 to 30 times lower binding and neutralization activity against sheep IL-13. Control animals received human IgG of irrelevant specificity. Sheep were treated 24 h before inhalation challenge with nebulized A. suum. The effects on antigen-induced early and late bronchial responses, and antigen-induced hyperresponsiveness, were assessed. Both sIL-13R and IMA-638 provided dose-dependent inhibition of the antigen-induced late responses and airway hyperresponsiveness. The highest dose of IMA-638 also reduced the early phase response. These findings suggest that IL-13 contributes to allergen-induced airway responses in this sheep model of asthma, and that neutralization of IL-13 is an effective strategy for blocking these A. suum-induced effects.

Selectins and glycosyltransferases in leukocyte rolling in vivo

Leukocyte rolling is an important step for the successful recruitment of leukocytes into tissue and occurs predominantly in inflamed microvessels and in high endothelial venules of secondary lymphoid organs. Leukocyte rolling is mediated by a group of C-type lectins, termed selectins. Three different selectins have been identified - P-, E- and L-selectin - which recognize and bind to crucial carbohydrate determinants on selectin ligands. Among selectin ligands, P-selectin glycoprotein ligand-1 is the main inflammatory selectin ligand, showing binding to all three selectins under in vivo conditions. Functional relevant selectin ligands expressed on high endothelial venules of lymphoid tissue are less clearly defined at the protein level. However, high endothelial venule-expressed selectin ligands were instrumental in uncovering the crucial role of post-translational modifications for selectin ligand activity. Several glycosyltransferases, such as core 2 beta1,6-N-acetylglucosaminyltransferase-I, beta1,4-galactosyltransferases, alpha1,3-fucosyltransferases and alpha2,3-sialyltransferases have been described to participate in the synthesis of core 2 decorated O-glycan structures carrying the tetrasaccharide sialyl Lewis X, a carbohydrate determinant on selectin ligands with binding activity to all three selectins. In addition, modifications, such as carbohydrate or tyrosine sulfation, were also found to contribute to the synthesis of functional selectin ligands.

Whole-body periodic acceleration modifies experimental asthma in sheep

RATIONALE

Nitric oxide is released from vascular endothelium in response to increased pulsatile shear stress. Nitric oxide inhibits mast cell activation and is antiinflammatory and therefore might be protective in asthma.

OBJECTIVES

We determined if a noninvasive motion platform that imparts periodic sinusoidal inertial forces to the whole body along the spinal axis (pGz) causing release of endothelial nitric oxide modulates experimental asthma in sheep.

METHODS

Allergic sheep were untreated (control) or were treated with pGz alone or after receiving intravenously the nitric oxide synthase inhibitor N(w)-nitro-L-arginine methyl ester (L-NAME) before aerosol challenge with Ascaris suum, and the effect on antigen-induced airway responses was determined. Bronchoalveolar lavage cells obtained 6 h after antigen challenge were analyzed for nuclear factor-kappaB (NF-kappaB) activity in the respective groups.

RESULTS

pGz treatment for 1 h before antigen challenge reduced the early airway response and blocked the late airway response but did not prevent the antigen-induced airway hyperresponsiveness 24 h after challenge. Administration of L-NAME before pGz completely reversed this protection, whereas L-NAME alone did not affect the antigen-induced responses. NF-kappaB activity was 1.9- and 1.8-fold higher in the control and L-NAME + pGz groups, respectively, compared with pGz-treated animals. Extending the pGz treatment to twice daily for 3 d and then 1 h before antigen challenge blocked the early and late airway responses, the 24-h airway hyperresponsiveness, and the airway inflammatory cell response.

CONCLUSION

Whole-body pGz modulates allergen-induced airway responses in allergic sheep.

Induction of PNAd and N-acetylglucosamine 6-O-sulfotransferases 1 and 2 in mouse collagen-induced arthritis

BACKGROUND

Leukocyte recruitment across blood vessels is fundamental to immune surveillance and inflammation. Lymphocyte homing to peripheral lymph nodes is mediated by the adhesion molecule, L-selectin, which binds to sulfated carbohydrate ligands on high endothelial venules (HEV). These glycoprotein ligands are collectively known as peripheral node addressin (PNAd), as defined by the function-blocking monoclonal antibody known as MECA-79. The sulfation of these ligands depends on the action of two HEV-expressed N-acetylglucosamine 6-O-sulfotransferases: GlcNAc6ST-2 and to a lesser degree GlcNAc6ST-1. Induction of PNAd has also been shown to occur in a number of human inflammatory diseases including rheumatoid arthritis (RA).

RESULTS

In order to identify an animal model suitable for investigating the role of PNAd in chronic inflammation, we examined the expression of PNAd as well as GlcNAc6ST-1 and -2 in collagen-induced arthritis in mice. Here we show that PNAd is expressed in the vasculature of arthritic synovium in mice immunized with collagen but not in the normal synovium of control animals. This de novo expression of PNAd correlates strongly with induction of transcripts for both GlcNAc6ST-1 and GlcNAc6ST-2, as well as the expression of GlcNAc6ST-2 protein.

CONCLUSION

Our results demonstrate that PNAd and the sulfotransferases GlcNAc6ST-1 and 2 are induced in mouse collagen-induced arthritis and suggest that PNAd antagonists or inhibitors of the enzymes may have therapeutic benefit in this widely-used mouse model of RA.

Lymphocyte migration studies

For maintenance of immunity and tolerance, the organs and tissues of the organism are connected by migrating lymphoid cells. Understanding lymphocyte migration is essential for many disorders and diseases-- especially in the mucosa-lined organs. Detailed analyses of migrating lymphocytes have been performed in many species, especially in laboratory animals. However, important experiments in lymphocyte migration have been carried out in large animals, for example sheep, cattle and pigs. These species allow experimental procedures like in situ-organ labelling, lymphocyte retransfusion studies or lymph vessel cannulations. Such studies have made an important contribution to the understanding of the overall principles of lymphocyte migration especially in the mucosal immune system. Major results on the specific migration of naïve and memory T cells through lymphoid organs, the re-distribution of gamma/delta T cells in the intestinal immune system and the emigration of newly produced B cells from the ileal Peyer's patches have been obtained in large animals. Since there are growing numbers of markers for large animals, and molecular biology methods are available in these species, experiments in large animals will be an essential tool for the understanding of lymphocyte migration especially in mucosal organs.

Roles of Sulfated Glycans in Lymphocyte Homing

Lymphocyte homing is mediated by a specific interaction between the lymphocyte homing receptor L-selectin and its sulfated glycoprotein ligands, which are expressed on high endothelial venules (HEV) in the lymph nodes. To examine the significance of the sulfation of L-selectin ligands, our group has generated gene-targeted mice deficient in both N-acetylglucosamine-6-O-sulfotransferase (GlcNAc6ST)-1 and GlcNAc6ST-2. The mutant mice show approximately 75% less lymphocyte homing to the peripheral lymph nodes than normal, indicating that GlcNAc6ST-1 and GlcNAc6ST-2 play a major role in the biosynthesis of L-selectin ligand in HEV. In agreement with this interpretation, an oligosaccharide analysis indicated that 6-sulfo sialyl Lewis X, a major L-selectin ligand sulfated glycan, is almost completely abrogated in the double-deficient mice. Lymphocyte homing into the parenchyma of lymph nodes is mediated by a series of interactions: rolling, activation by chemokines, integrin-mediated adhesion, and transmigration. During the rolling interaction, which is mediated by L-selectin and sulfated glycans, lymphocytes receive activation signals from chemokines presented on the surface of HEV by heparan sulfate, a sulfated glycosaminoglycan, which leads to the activation of lymphocyte beta2 integrin. Sulfated glycans are thus involved in both the rolling and the chemokine-induced activation steps between lymphocytes and HEV. In this article, recent findings on the roles of sulfated glycans in both of these lymphocyte-homing steps will be reviewed. The possible application of sulfated glycans for the prevention of inflammatory disorders will also be discussed.

A major class of L-selectin ligands is eliminated in mice deficient in two sulfotransferases expressed in high endothelial venules

The interaction of L-selectin on lymphocytes with sulfated ligands on high endothelial venules leads to rolling and is critical for recruitment of lymphocytes into peripheral lymph nodes. Peripheral node addressin represents a class of L-selectin ligands recognized by the function-blocking monoclonal antibody MECA-79. Its epitope overlaps with sialyl 6-sulfo Lewis X, an L-selectin recognition determinant. Here, mice lacking two N-acetylglucosamine-6-O-sulfotransferases (GlcNAc6ST-1 and GlcNAc6ST-2) demonstrated elimination of both peripheral node addressin and sialyl 6-sulfo Lewis X in high endothelial venules, considerably reduced lymphocyte homing to peripheral lymph nodes and reduced sticking of lymphocytes along high endothelial venules. Our results establish an essential function for the sulfotransferases in L-selectin ligand synthesis and may have relevance for therapy of inflammatory diseases.

N-acetylglucosamine-6-O-sulfotransferases 1 and 2 cooperatively control lymphocyte homing through L-selectin ligand biosynthesis in high endothelial venules

Lymphocyte homing is mediated by specific interactions between L-selectin on lymphocytes and sulfated carbohydrates restricted to high endothelial venules in lymph nodes. Here we generated mice deficient in both N-acetylglucosamine-6-O-sulfotransferase 1 (GlcNAc6ST-1) and GlcNAc6ST-2 and found that mutant mice had approximately 75% less homing of lymphocytes to the peripheral lymph nodes than did wild-type mice. Consequently, these mice had lower contact hypersensitivity responses than those of wild-type mice. Carbohydrate structural analysis showed that 6-sulfo sialyl Lewis X, a dominant ligand for L-selectin, was almost completely absent from the high endothelial venules of these mutant mice, whereas the amount of unsulfated sialyl Lewis X was much greater. These results demonstrate the essential function of GlcNAc6ST-1 and GlcNAc6ST-2 in L-selectin ligand biosynthesis in high endothelial venules and their importance in immune surveillance.

A HEV-restricted sulfotransferase is expressed in rheumatoid arthritis synovium and is induced by lymphotoxin-alpha/beta and TNF-alpha in cultured endothelial cells

BACKGROUND

The recruitment of lymphocytes to secondary lymphoid organs relies on interactions of circulating cells with high endothelial venules (HEV). HEV are exclusive to these organs under physiological conditions, but they can develop in chronically-inflamed tissues. The interaction of L-selectin on lymphocytes with sulfated glycoprotein ligands on HEV results in lymphocyte rolling, which represents the initial step in lymphocyte homing. HEV expression of GlcNAc6ST-2 (also known as HEC-GlcNAc6ST, GST-3, LSST or CHST4), an HEV-restricted sulfotransferase, is essential for the elaboration of L-selectin functional ligands as well as a critical epitope recognized by MECA-79 mAb.

RESULTS

We examined the expression of GlcNAc6ST-2 in relationship to the MECA-79 epitope in rheumatoid arthritis (RA) synovial vessels. Expression of GlcNAc6ST-2 was specific to RA synovial tissues as compared to osteoarthritis synovial tissues and localized to endothelial cells of HEV-like vessels and small flat-walled vessels. Double MECA-79 and GlcNAc6ST-2 staining showed colocalization of the MECA-79 epitope and GlcNAc6ST-2. We further found that both TNF-alpha and lymphotoxin-alphabeta induced GlcNAc6ST-2 mRNA and protein in cultured human umbilical vein endothelial cells.

CONCLUSION

These observations demonstrate that GlcNAc6ST-2 is induced in RA vessels and provide potential cytokine pathways for its induction. GlcNAc6ST-2 is a novel marker of activated vessels within RA ectopic lymphoid aggregates. This enzyme represents a potential therapeutic target for RA.