VCAM-1 contributes to rapid eosinophil accumulation induced by the chemoattractants PAF and LTB4: evidence for basal expression of functional VCAM-1 in rat skin

Inhibiting Th1/2 cells influences hepatic capillarization by adjusting sinusoidal endothelial fenestrae through Rho-ROCK-myosin pathway

CD4⁺ T cells are considered to be vital in chronic liver diseases, but their exact roles in hepatic capillarization, the typical characteristic of liver fibrosis, are poorly understood. This study aimed to assess the roles of typical subtype of CD4⁺ T cells, named T helper 1 (Th1) and Th2 cells in liver fibrosis. Taking advantage of well established fibrotic rat model, we conducted in vitro and in vivo experiments to explore the interactions between liver sinusoidal endothelial cells (LSECs) and Th1/2 cells; meanwhile we evaluated the degree of hepatic capillarization when inhibiting these interactions with inhibitory antibodies. Our results showed that prohibiting interactions between Th2 cells and LSECs caused the restoration of fenestrae, increased cytokine level of Th1 cells and reduction of hepatic capillarization; inhibiting the interaction between Th1 cells and LSECs produced the opposite effects. Moreover, increased Rho and myosin light chain phosphorylation were observed when Th1 cells were inhibited with the corresponding inhibitory antibody; Th2 cell inhibition yielded the opposite results. This study indicated that Th1/2 cells steer the capillarization process in different directions and this effect is probably mediated by the Rho-Rho kinase (ROCK)-myosin signaling pathway.

Diagnosis and management of eosinophilic asthma: a US perspective

Eosinophilic asthma is now recognized as an important subphenotype of asthma based on the pattern of inflammatory cellular infiltrate in the airway. Eosinophilic asthma can be associated with increased asthma severity, atopy, late-onset disease, and steroid refractoriness. Induced sputum cell count is the gold standard for identifying eosinophilic inflammation in asthma although several noninvasive biomarkers, including fractional exhaled nitric oxide and periostin, are emerging as potential surrogates. As novel therapies and biologic agents become increasingly available, there is an increased need for specific phenotype-directed treatment strategies. Greater recognition and understanding of the unique immunopathology of this asthma phenotype has important implications for management of the disease and the potential to improve patient outcomes. The present review provides a summary of the clinical features, pathogenesis, diagnosis, and management of eosinophilic asthma.

Leukotriene B4 mediates gammadelta T lymphocyte migration in response to diverse stimuli

Herein, we investigated the involvement of the 5-LO-derived lipid mediator LTB(4) in gammadelta T cell migration. When injected into the i.pl. space of C57BL/6 mice, LTB(4) triggered gammadelta T lymphocyte mobilization in vivo, a phenomenon also observed in in vitro chemotaxis assays. The i.pl. injection of Escherichia coli endotoxin (LPS) triggered increased levels of LTB(4) in pleural cavities. The in vivo inhibition of LTB(4) biosynthesis by the 5-LO inhibitor zileuton or the FLAP inhibitor MK886 attenuated LPS-induced gammadelta T cell accumulation into pleural cavities. Accordingly, 5-LO KO mice failed to recruit gammadelta T cells into the inflammatory site after i.pl. LPS. Antagonists of the high-affinity LTB(4) receptor BLT1, CP105,696, and LY292476 also attenuated LPS-induced gammadelta T cell accumulation in pleural cavities as well as in vitro chemotaxis toward pleural washes obtained from LPS-simulated mice. LTB(4)/BLT1 also accounted for gammadelta T cell migration induced by i.pl. administration of Mycobacterium bovis BCG or antigen in sensitized mice. BLT1 was expressed on naïve, resident as well as LPS-recruited gammadelta T cells. Isolated gammadelta T cells were found to undergo F-actin cytoskeleton reorganization when incubated with LTB(4) in vitro, confirming that gammadelta T lymphocytes can respond directly to LTB(4). In addition to its direct effect on gammadelta T cells, LTB(4) triggered their accumulation indirectly, via modulation of CCL2 production in mouse pleural cavities. These data show that gammadelta T cell migration into the pleural cavity of mice during diverse inflammatory responses is dependent on LTB(4)/BLT1.

Blockade of airway inflammation and hyperresponsiveness by inhibition of BLT2, a low-affinity leukotriene B4 receptor

BLT2 is a low-affinity receptor for leukotriene B(4) (LTB(4)), a potent lipid mediator of inflammation generated from arachidonic acid via the 5-lipoxygenase pathway. Unlike BLT1, a high-affinity receptor for LTB(4), no clear physiological function has yet been identified for BLT2, especially with regard to the pathogenesis of asthma. The aim of this study was to investigate whether BLT2 plays a role in the pathogenesis of asthma. A murine model of allergic asthma was used to evaluate the role of BLT2 in ovalbumin-induced airway inflammation and airway hyperresponsiveness. The levels of BLT2 mRNA and its ligand, LTB(4), in the lung airway were highly elevated after ovalbumin challenge, and down-regulation of BLT2 with antisense BLT2 oligonucleotides markedly attenuated airway inflammation and airway hyperresponsiveness. Further analysis, aimed at identifying mediators downstream of BLT2, revealed that BLT2 activation led to elevation of reactive oxygen species and subsequent activation of NF-kappaB, thus inducing the expression of vascular cell adhesion molecule-1, which is known to be involved in eosinophil infiltration into the lung airway. Together, our results suggest that BLT2 plays a pivotal, mediatory role in the pathogenesis of asthma, acting through a "reactive oxygen species-NF-kappaB"-linked inflammatory signaling pathway.

The VCAM-1 gene that encodes the vascular cell adhesion molecule is a target of the Sry-related high mobility group box gene, Sox18

VCAM-1 (vascular cell adhesion molecule-1) and Sox18 are involved in vascular development. VCAM-1 is an important adhesion molecule that is expressed on endothelial cells and has a critical role in endothelial activation, inflammation, lymphatic pathophysiology, and atherogenesis. The Sry-related high mobility group box factor Sox18 has previously been implicated in endothelial pathologies. Mutations in human and mouse Sox18 leads to hypotrichosis and lymphedema. Furthermore, both Sox18 and VCAM-1 have very similar spatio-temporal patterns of expression, which is suggestive of cross-talk. We use biochemical techniques, cell culture systems, and the ragged opossum (RaOP) mouse model with a naturally occurring mutation in Sox18 to demonstrate that VCAM-1 is an important target of Sox18. Transfection, site-specific mutagenesis, and gel shift analyses demonstrated that Sox18 directly targeted and trans-activated VCAM-1 expression. Importantly, the naturally occurring Sox18 mutant attenuates the expression and activation of VCAM-1 in vitro. Furthermore, in vivo quantitation of VCAM-1 mRNA levels in wild type and RaOP mice demonstrates that RaOP animals show a dramatic and significant reduction in VCAM-1 mRNA expression in lung, skin, and skeletal muscle. Our observation that the VCAM-1 gene is an important target of SOX18 provides the first molecular insights into the vascular abnormalities in the mouse mutant ragged and the human hypotrichosis-lymphedema-telangiectasia disorder.

Expression of cell surface adhesion molecules by peripheral blood eosinophils during Trichostrongylus colubriformis infection in sheep

The effect of infection of sheep with the gastrointestinal nematode parasite Trichostrongylus colubriformis on expression of adhesion molecules CD11a, CD11b, CD11c, CD18, CD44, CD49d and CD62L by peripheral blood eosinophils was examined by flow cytometry. Initially, to establish the sensitivity of adhesion molecules to inflammatory signals, eosinophil-rich exudates were elicited in non-lactating mammary glands of immune sheep by infusion of 50 microg of soluble antigen extract from T. colubriformis third stage larvae. Eosinophils comprised 40.8% of mammary leucocytes and 4.5% of peripheral blood leucocytes. In comparison with blood, the percentage of eosinophils expressing CD18 increased and the percentage expressing CD62L decreased in exudates and the mean fluorescent intensity, an indicator of receptor number per cell, for CD11a and CD49d also decreased on exudate eosinophils. Peripheral blood eosinophils were examined over 8 weeks during trickle infection of immune sheep with infective or irradiated third stage larvae of T. colubriformis. During the last 3 weeks of infection, CD11a staining decreased in infected sheep and CD44 staining decreased in sheep receiving either infective or irradiated larvae. Other surface markers did not change. The results indicate that systemic changes in expression of adhesion molecules by eosinophils occur during T. colubriformis infection in sheep.

alpha(4) integrin-dependent eosinophil recruitment in allergic but not non-allergic inflammation

1. Although anti-alpha(4) integrin mAbs reduce eosinophil accumulation in several models of allergic inflammation, it is not clear whether this occurs via a direct action to block eosinophil alpha(4) integrins or indirectly on another cell type. The role of alpha(4) integrins on the accumulation of (111)In-labelled eosinophils in allergic and non-allergic inflammation in guinea-pig skin was therefore investigated. 2. Intradermal injection of antigen in sensitized skin sites induced accumulation of (111)In-eosinophils that was reduced up to 70% by two anti-alpha(4) integrin mAbs. In contrast, accumulation of (111)In-eosinophils to intradermal chemoattractants was unaffected by the same mAbs. 3. Accumulation of (111)In-eosinophils in allergic and non-allergic conditions was partly inhibited by a low dose of an anti-beta(2) integrin mAb. In combination with anti-alpha(4) integrin mAb, responses were not further reduced suggesting that these adhesion pathways are not additive or synergic. 4. Pretreating skin sites with antiserum or contaminating LPS did not reveal an alpha(4) integrin dependent pathway for chemoattractant-induced (111)In-eosinophil accumulation. These data suggest that alpha(4) integrins are involved in the response to antigen in sensitized skin sites. 5. Pretreating (111)In-eosinophil with alpha(4) integrin mAb blocked their adhesion to fibronectin in vitro but did not inhibit their accumulation in allergic inflammation suggesting that the blocking effect in vivo was eosinophil independent. 6. These data support the concept that targeting alpha(4) integrins on cells other than eosinophils could control eosinophil accumulation and have therapeutic potential in allergic diseases such as asthma and atopic dermatitis.