Generation and characterization of a novel adhesion function blocking monoclonal antibody recognizing both rat and mouse E-selectin

IL-17A potentiates TNFα-induced secretion from human endothelial cells and alters barrier functions controlling neutrophils rights of passage

Interleukin-17A (IL-17A) is an important pro-inflammatory cytokine that regulates leukocyte mobilization and recruitment. To better understand how IL-17A controls leukocyte trafficking across capillaries in the peripheral blood circulation, we used primary human dermal microvascular endothelial cells (HDMEC) to investigate their secretory potential and barrier function when activated with IL-17A and TNFα. Activation by TNFα and IL-17A causes phosphorylation of p38 as well as IκBα whereby NFκB subsequently becomes phosphorylated, a mechanism that initiates transcription of adhesion molecules such as E-selectin. Members of the neutrophil-specific GRO-family chemokines were significantly up-regulated upon IL-17A stimulation on the mRNA and protein level, whereas all tested non-neutrophil-specific chemokines remained unchanged in comparison. Moreover, a striking synergistic effect in the induction of granulocyte colony-stimulating factors (G-CSF) was elicited when IL-17A was used in combination with TNFα, and IL-17A was able to significantly augment the levels of TNFα-induced E-selectin and ICAM-1. In accordance with this observation, IL-17A was able to markedly increase TNFα-induced neutrophil adherence to HDMEC monolayers in an in vitro adhesion assay. Using a trans-well migration assay with an HDMEC monolayer as a barrier, we here show that pre-stimulating the endothelial cells with TNFα and IL-17A together enhances the rate of neutrophil transmigration compared to TNFα or IL-17A alone. These results show that IL-17A and TNFα act in cooperation to facilitate neutrophil migration across the endothelial cell barrier. In addition, the synergistic actions of IL-17A with TNFα to secrete G-CSF appear to be important for mobilizing neutrophils from the bone marrow to the blood stream.

Differing requirements for CCR4, E-selectin, and α4β1 for the migration of memory CD4 and activated T cells to dermal inflammation

CCR4 on T cells is suggested to mediate skin homing in mice. Our objective was to determine the interaction of CCR4, E-selectin ligand (ESL), and α(4)β(1) on memory and activated T cells in recruitment to dermal inflammation. mAbs to rat CCR4 were developed. CCR4 was on 5-21% of memory CD4 cells, and 20% were also ESL(+). Anti-TCR-activated CD4 and CD8 cells were 40-55% CCR4(+), and ∼75% of both CCR4(+) and CCR4(-) cells were ESL(+). CCR4(+) memory CD4 cells migrated 4- to 7-fold more to dermal inflammation induced by IFN-γ, TNF, TLR agonists, and delayed-type hypersensitivity than CCR4(-) cells. CCR4(+) activated CD4 cells migrated only 5-50% more than CCR4(-) cells to these sites. E-selectin blockade inhibited ∼60% of CCR4(+) activated CD4 cell migration but was less effective on memory cells where α(4)β(1) was more important. Anti-α(4)β(1) also inhibited CCR4(-) activated CD4 cells more than CCR4(+) cells. Anti-E-selectin reduced activated CD8 more than CD4 cell migration. These findings modify our understanding of CCR4, ESL, α(4)β(1), and dermal tropism. There is no strict relationship between CCR4 and ESL for skin homing of CD4 cells, because the activation state and inflammatory stimulus are critical determinants. Dermal homing memory CD4 cells express CCR4 and depend more on α(4)β(1) than ESL. Activated CD4 cells do not require CCR4, but CCR4(+) cells are more dependent on ESL than on α(4)β(1), and CCR4(-) cells preferentially use α(4)β(1). The differentiation from activated to memory CD4 cells increases the dependence on CCR4 for skin homing and decreases the requirement for ESL.

Efficacy of an inhibitor of adhesion molecule expression (GI270384X) in the treatment of experimental colitis

Modulation of adhesion molecule expression or function is regarded as a promising therapy for inflammatory conditions. This study evaluates the effects of an inhibitor of adhesion molecule expression (GI270384X) in two experimental models of colitis. Colitis of different severity was induced in C57BL/6J mice by administering 1, 2, or 3% dextran sulfate sodium (DSS). GI270384X (3, 10, or 25 mg.kg(-1).day(-1)) was administered as pretreatment or started 3 days after colitis induction. In IL-10-deficient mice, the highest dose was given for 2 wk. The clinical course of colitis, pathological changes, serum inflammatory biomarkers, expression of adhesion molecules, and leukocyte-endothelial cell interactions in colonic venules were measured in mice treated with vehicle or with active drug. In the most severe forms of colitis (2% and 3% DSS and IL-10-deficient mice), the magnitude of colonic inflammation was not modified by treatment with GI270384X. In a less severe form of colitis (1% DSS), GI270384X treatment dose dependently ameliorated the clinical signs of colitis, colonic pathological changes, and serum levels of biomarkers (IL-6 and serum amyloid A). Administration of 25 mg.kg(-1).day(-1) GI270384X abrogated upregulation of ICAM-1 in the inflamed colon but had no effect on VCAM-1 or E-selectin expression. This was associated with a significant reduction in number of rolling and firmly adherent leukocytes in colonic venules. These results indicate that GI270384X is effective in the treatment of experimental colitis of moderate severity. Reduced adhesion molecule expression and leukocyte recruitment to the inflamed intestine contribute to this beneficial effect.

Roflumilast inhibits leukocyte-endothelial cell interactions, expression of adhesion molecules and microvascular permeability

BACKGROUND AND PURPOSE

The present study addressed the effects of the investigational PDE4 inhibitor roflumilast on leukocyte-endothelial cell interactions and endothelial permeability in vivo and in vitro.

EXPERIMENTAL APPROACH

In vivo, intravital video-microscopy was used to determine effects of roflumilast p.o. on leukocyte-endothelial cell interactions and microvascular permeability in rat mesenteric venules. In vitro, the effects of roflumilast N-oxide, the active metabolite of roflumilast in humans, and other PDE4 inhibitors on neutrophil adhesion to tumour necrosis factor alpha (TNFalpha)-activated human umbilical vein endothelial cells (HUVEC), E-selectin expression and thrombin-induced endothelial permeability was evaluated. Flow cytometry was used to determine the effect of roflumilast on N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced CD11b upregulation on human neutrophils.

KEY RESULTS

In vivo, roflumilast, given 1 h before lipopolysaccharide (LPS), dose-dependently reduced leukocyte-endothelial cell interactions in rat mesenteric postcapillary venules. It also diminished histamine-induced microvascular permeability. Immunohistochemical analyses revealed that roflumilast prevented LPS-induced endothelial P- and E-selectin expression. In vitro, roflumilast N-oxide concentration-dependently suppressed neutrophil adhesion to TNFalpha-activated HUVEC and CD11b expression on fMLP-stimulated neutrophils. It also reduced TNFalpha-induced E-selectin expression on HUVEC, when PDE3 activity was blocked. HUVEC permeability elicited by thrombin was concentration-dependently suppressed by roflumilast N-oxide. While roflumilast N-oxide was as potent as roflumilast at inhibiting stimulated endothelial cell and neutrophil functions, both compounds were significantly more potent than the structurally unrelated PDE4 inhibitors, rolipram or cilomilast.

CONCLUSIONS AND IMPLICATIONS

These findings further support earlier observations on the inhibition of inflammatory cell influx and protein extravasation by roflumilast in vivo.

Complete repair of dystrophic skeletal muscle by mesoangioblasts with enhanced migration ability

Efficient delivery of cells to target tissues is a major problem in cell therapy. We report that enhancing delivery of mesoangioblasts leads to a complete reconstitution of downstream skeletal muscles in a mouse model of severe muscular dystrophy (α-sarcoglycan ko). Mesoangioblasts, vessel-associated stem cells, were exposed to several cytokines, among which stromal- derived factor (SDF) 1 or tumor necrosis factor (TNF) α were the most potent in enhancing transmigration in vitro and migration into dystrophic muscle in vivo. Transient expression of α4 integrins or L-selectin also increased several fold migration both in vitro and in vivo. Therefore, combined pretreatment with SDF-1 or TNF-α and expression of α4 integrin leads to massive colonization (>50%) followed by reconstitution of >80% of α-sarcoglycan–expressing fibers, with a fivefold increase in efficiency in comparison with control cells. This study defines the requirements for efficient engraftment of mesoangioblasts and offers a new potent tool to optimize future cell therapy protocols for muscular dystrophies.

Basic fibroblast growth factor (bFGF, FGF-2) potentiates leukocyte recruitment to inflammation by enhancing endothelial adhesion molecule expression

Basic fibroblast growth factor (bFGF, FGF-2) is a potent angiogenic factor and endothelial cell mitogen. Although bFGF levels are increased in chronically inflamed tissue, its role in inflammation is unclear. We investigated the effect of bFGF on acute dermal inflammation and the recruitment of monocytes, T cells, and neutrophils. Leukocyte recruitment to inflamed sites was quantified with radiolabeled leukocytes. Intradermal injection of bFGF in rats did not induce leukocyte recruitment or inflammation. However, the recruitment of leukocytes to inflammation induced by tumor necrosis factor-alpha, interferon-gamma, C5a, or a delayed hypersensitivity reaction was enhanced by bFGF by 55 to 132% (P < 0.05). Either acute or prolonged bFGF treatment of dermal sites had this effect. The potentiating effect of bFGF on leukocyte recruitment was also seen in joints. There was no associated modulation of vascular permeability, blood flow, or angiogenesis in the sites by bFGF. However, the expression of the endothelial cell adhesion molecules (CAMs) for leukocytes, P-selectin, E-selectin, and ICAM-1, was significantly up-regulated in the inflamed tissue by bFGF, as quantified by radiolabeled anti-CAM antibody binding in vivo. Thus, although not directly proinflammatory, bFGF synergistically potentiates inflammatory mediator-induced leukocyte recruitment, at least in part, by enhancing CAM up-regulation on endothelium.

Analysis of leukocyte rolling in vivo and in vitro

Leukocyte rolling is an important step for the successful recruitment of leukocytes from blood to tissues mediated by a specialized group of glycoproteins termed selectins. Because of the dynamic process of leukocyte rolling, binding of selectins to their respective counter-receptors (selectin ligands) needs to fulfill three major requirements: (1) rapid bond formation, (2) high tensile strength, and (3) fast dissociation rates. These criteria are perfectly met by selectins, which interact with specific carbohydrate determinants on selectin ligands. This chapter describes the theoretical background, technical requirements, and analytical tools needed to quantitatively assess leukocyte rolling in vivo and in vitro. For the in vivo setting, intravital microscopy allows the observation and recording of leukocyte rolling under different physiological and pathological conditions in almost every organ. Real-time and off-line analysis tools help to assess geometric, hemodynamic, and rolling parameters. Under in vitro conditions, flow chamber assays such as parallel plate flow chamber systems have been the mainstay to study interactions between leukocytes and adhesion molecules under flow. In this setting, adhesion molecules are immobilized on plastic, in a lipid monolayer, or presented on cultured endothelial cells on the chamber surface. Microflow chambers are available for studying leukocyte adhesion in the context of whole blood and without blood cell isolation. The microscopic observation of leukocyte rolling in different in vivo and in vitro settings has significantly contributed to our understanding of the molecular mechanisms responsible for the stepwise extravasation of leukocytes into inflamed tissues.

L-NAME induces direct arteriolar leukocyte adhesion, which is mainly mediated by angiotensin-II

OBJECTIVE

Acute inhibition (1 h) of nitric oxide synthase (NOS) with L-NAME causes leukocyte recruitment in the rat mesenteric postcapillary venules that is angiotensin-II (Ang-II) dependent. Since 4-h exposure to Ang-II provokes arteriolar leukocyte adhesion, this study was designed to investigate whether subacute (4-h) NOS inhibition also causes this effect.

METHODS

Rats were intraperitoneally injected with saline, L-NAME, or 1H-[1,2,4]-oxidazolol-[4,3-a]-quinoxalin-1-one (ODQ). Leukocyte accumulation in the mesenteric microcirculation was examined 4 h later via intravital microscopy. Some groups were pretreated with losartan, an AT(1) Ang-II receptor antagonist.

RESULTS

At 4-h, L-NAME caused a significant increase in arteriolar leukocyte adhesion and leukocyte-endothelial cell interactions in postcapillary venules. Mononuclear cells were the predominant leukocytes attached to the arteriolar endothelium. Administration of losartan inhibited L-NAME-induced arteriolar leukocyte adhesion by 90%. L-NAME provoked increased expression of P-selectin, E-selectin, ICAM-1, and VCAM-1 in arterial endothelium, which was attenuated by losartan pretreatment. Inhibition of guanylyl cyclase with ODQ mimicked the effects exerted by L-NAME and losartan also reduced these effects.

CONCLUSIONS

NOS inhibition for 4-h results in the attachment of leukocytes to the arterial endothelium, a critical event in disease states such as hypertension and atherosclerosis, which could be prevented by the administration of AT(1)Ang-II receptor antagonists.

Radiation-induced up-regulation of adhesion molecules in brain microvasculature and their modulation by dexamethasone

Little is known about the time course and magnitude of the up-regulation of endothelial cell adhesion molecules (ECAMs) in irradiated brain vasculature and the mechanisms by which dexamethasone modulates this up-regulation. We used antibody-conjugated microspheres and a rat closed cranial window model to determine the time course of functional up-regulation of radiation (20 Gy)-induced ICAM1, E-selectin and P-selectin in the pial vasculature of the rat brain and to determine the relationship between suppression of inflammation by dexamethasone and the expression of these ECAMs. The results indicate that ICAM1, E-selectin and P-selectin were up-regulated to a functional level in the microvasculature with distinct time-course patterns. The number of adherent anti-E-selectin and anti-P-selectin microspheres was 5- 12 times greater than that of IgG microspheres 3-6 h postirradiation, and their expression returned to normal at 48 h. The number of adherent anti-ICAM1 microspheres was five and nine times greater than that of IgG at 24 and 48 h, respectively, and returned to baseline by 7 days. Dexamethasone significantly reduced the number of adhering leukocytes and the number of adhering anti-ICAM1, anti-E-selectin and anti-P-selectin microspheres to background levels. Our findings partially identify a key sequence in radiation-induced inflammatory response and provide a potential means to limit radiation-induced inflammatory responses and their potential side effects in the brain.

Erythromycin exerts in vivo anti-inflammatory activity downregulating cell adhesion molecule expression

1. Macrolides have long been used as anti-bacterial agents; however, there is some evidence that may exert anti-inflammatory activity. Therefore, erythromycin was used to characterize the mechanisms involved in their in vivo anti-inflammatory activity. 2. Erythromycin pretreatment (30 mg kg(-1) day(-1) for 1 week) reduced the lipopolysaccharide (LPS; intratracheal, 0.4 mg kg(-1))-induced increase in neutrophil count and elastase activity in the bronchoalveolar lavage fluid (BALF) and lung tissue myeloperoxidase activity, but failed to decrease tumor necrosis factor-alpha and macrophage-inflammatory protein-2 augmented levels in BALF. Erythromycin pretreatment also prevented lung P-selectin, E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) mRNA upregulation in response to airway challenge with LPS. 3. Mesentery superfusion with LPS (1 mug ml(-1)) induced a significant increase in leukocyte-endothelial cell interactions at 60 min. Erythromycin pretreatment abolished the increases in these parameters. 4. LPS exposure of the mesentery for 4 h caused a significant increase in leukocyte rolling flux, adhesion and emigration, which were inhibited by erythromycin by 100, 93 and 95%, respectively. 5. Immunohistochemical analysis showed that LPS exposure of the mesentery for 4 h caused a significant enhancement in P-selectin, E-selectin, ICAM-1 and VCAM-1 expression that was downregulated by erythromycin pretreatment. 6. Flow cytometry analysis indicated that erythromycin pretreatment inhibited LPS-induced CD11b augmented expression in rat neutrophils. 7. In conclusion, erythromycin inhibits leukocyte recruitment in the lung and this effect appears mediated through downregulation of CAM expression. Therefore, macrolides may be useful in the control of neutrophilic pulmonary diseases.

A down-regulatable E-selectin ligand is functionally important for PSGL-1-independent leukocyte-endothelial cell interactions

P-selectin glycoprotein-1 (PSGL-1) supports P-selectin-dependent rolling in vivo and in vitro. However, controversy exists regarding the importance of PSGL-1-dependent and -independent E-selectin rolling. Using antibodies against PSGL-1 and PSGL-1(-/-) mice, we demonstrated abolition of P-selectin-dependent rolling but only partial inhibition of E-selectin-mediated rolling in the cremaster microcirculation following local administration of tumor necrosis factor alpha (TNF-alpha). In vitro studies demonstrated that binding of recombinant mouse E-selectin chimera to PSGL-1(-/-) neutrophils was dramatically decreased in mice treated systemically but not locally with TNF-alpha. Further, PSGL-1 blockade abolished E-selectin-dependent rolling in wild-type mice following systemic TNF-alpha administration but not local TNF-alpha administration. Together, these data support an E-selectin ligand present on PSGL-1(-/-) neutrophils that is down-regulatable upon systemic but not local activation. To determine whether the PSGL-1-independent E-selectin ligand was physiologically important, we used a P- and E-selectin-dependent cutaneous contact hypersensitivity model. Binding studies showed no E-selectin ligand down-regulation in this model. The few cells that rolled on E-selectin ligand following PSGL-1 antibody administration or in PSGL-1 deficiency were sufficient to induce profound contact hypersensitivity. In conclusion, E-selectin mediates PSGL-1-dependent and independent rolling and the latter can be down-regulated by systemic activation and can replace PSGL-1 to support the development of inflammation.

Direct evidence of leukocyte adhesion in arterioles by angiotensin II

Although leukocytes adhere in arteries in various vascular diseases, to date no endogenous proinflammatory molecule has been identified to initiate leukocyte adhesion in the arterial vasculature. This study was undertaken to assess angiotensin II (Ang II)-induced leukocyte adhesion in arterioles in vivo. Rats received intraperitoneal injections of Ang II; 4 hours later, leukocyte recruitment in mesenteric microcirculation was examined using intravital microscopy. Ang II (1 nM) produced significant arteriolar leukocyte adhesion of mononuclear cells. Using function-blocking monoclonal antibodies (mAbs) against different rat cell adhesion molecules (CAMs), we discovered that this effect was dependent on P-selectin and β2-integrin. In postcapillary venules, Ang II also induced leukocyte infiltration, which was reduced by P-selectin and by β2- and α4-integrin blockade. Interestingly, neutrophils were the primary cells recruited in venules. Although β2-integrin expression in peripheral leukocytes of Ang II-treated animals was not altered, it was increased in peritoneal cells. Immunohistochemical studies revealed increased P-selectin, E-selectin, intercellular cell adhesion molecule-1 (ICAM-1), and vascular cell adhesion molecule-1 (VCAM-1) expression in response to Ang II in arterioles and venules. These findings provide the first evidence that Ang II causes leukocyte adhesion to the arterial endothelium in vivo at physiologically relevant doses. Therefore, Ang II may be a key molecule in cardiovascular diseases in which leukocyte adhesion to the arteries is a characteristic feature. (Blood. 2004;104:402-408)

Identification of a putative pathway for the muscle homing of stem cells in a muscular dystrophy model

Attempts to repair muscle damage in Duchenne muscular dystrophy (DMD) by transplanting skeletal myoblasts directly into muscles are faced with the problem of the limited migration of these cells in the muscles. The delivery of myogenic stem cells to the sites of muscle lesions via the systemic circulation is a potential alternative approach to treat this disease. Muscle-derived stem cells (MDSCs) were obtained by a MACS(R) multisort method. Clones of MDSCs, which were Sca-1+/CD34-/L-selectin+, were found to adhere firmly to the endothelium of mdx dystrophic muscles after i.v. or i.m. injections. The subpopulation of Sca-1+/CD34- MDSCs expressing L-selectin was called homing MDSCs (HMDSCs). Treatment of HMDSCs with antibodies against L-selectin prevented adhesion to the muscle endothelium. Importantly, we found that vascular endothelium from striate muscle of young mdx mice expresses mucosal addressin cell adhesion molecule-1 (MAdCAM-1), a ligand for L-selectin. Our results showed for the first time that the expression of the adhesion molecule L-selectin is important for muscle homing of MDSCs. This discovery will aid in the improvement of a potential therapy for muscular dystrophy based on the systemic delivery of MDSCs.

Heterogeneity of endothelial cells from different organ sites in T-cell subset recruitment

Chemokines and adhesion molecules play a critical role in the recruitment of leukocytes into specific organ sites. Little is known, however, regarding the repertoire of chemokines and adhesion molecules expressed within different vascular beds. In this study, we compare adhesion molecule expression, chemokine induction, and T-cell subset-endothelial interactions under defined flow conditions on resting and tumor necrosis factor (TNF)-alpha-activated murine lung endothelial cells (MLECs) and heart endothelial cells (MHECs). Our study revealed that only MHECs exhibited high constitutive VCAM-1 expression. Exposure to TNF-alpha up-regulated adhesion molecule expression and chemokine production in both MLECs and MHECs. However, high levels of Regulated on Activation Normal T cell Expressed And Secreted (RANTES) expression were detected only in TNF-alpha-activated MHECs. TNF-alpha-stimulated MLECs and MHECs both supported T-helper cell interactions under defined flow conditions. Most T cells instantaneously arrested on MHECs but exhibited a rolling phenotype on MLECs. Blocking studies revealed that T-cell arrest on MHECs was mediated by constitutive VCAM-1 and TNF-alpha-induced RANTES. These findings are consistent with the hypothesis that functional heterogeneity of endothelial cells from different sites exists and some of it is retained in vitro. Furthermore, these results provide an insight into the molecular mechanisms that may mediate T-helper cell recruitment to these organs.

Leukocyte-endothelial cell interactions are enhanced in dermal postcapillary venules of MRL/fas(lpr) (lupus-prone) mice: roles of P- and E-selectin

MRL/fas(lpr) mice are affected by a systemic autoimmune disease that results in widespread leukocytic infiltration of the vasculature, including in the skin. The molecular pathways responsible for this leukocyte recruitment are poorly understood. Therefore, the aim of these experiments was to examine the mechanisms of leukocyte trafficking in the dermal microvasculature of MRL/fas(lpr) mice. Intravital microscopy was used to examine leukocyte rolling and adhesion in dermal postcapillary venules of MRL/fas(lpr) mice at 8, 12, and 16 wk of age. When compared with age-matched BALB/c and MRL(+/+) (nondiseased) mice, leukocyte rolling and adhesion in MRL/fas(lpr) mice were significantly enhanced at 12 wk of age, and remained elevated at 16 wk of age. At 8 and 12 wk, leukocyte rolling in all three strains was almost entirely inhibited by an anti-P-selectin mAb. In contrast, at 16 wk some (approximately 10%) leukocyte rolling persisted following P-selectin blockade. This residual rolling was predominantly inhibitable with an anti-E-selectin mAb; however, treatment with anti-E-selectin mAb alone had a minimal effect. P-selectin-deficient MRL/fas(lpr) mice also displayed leukocyte rolling that was significantly lower than in wild-type MRL/fas(lpr) mice. However, in these mice, leukocyte adhesion remained at the elevated levels observed in wild-type MRL/fas(lpr) mice. This adhesion was eliminated by chronic treatment with anti-E-selectin mAb. These findings indicate that leukocyte-endothelial cell interactions are enhanced in the dermal microvasculature of MRL/fas(lpr) mice above the age of 12 wk. Furthermore, the data suggest that the endothelial selectins share overlapping roles in mediating this enhanced leukocyte recruitment.

Leukocyte recruitment in colon cancer: role of cell adhesion molecules, nitric oxide, and transforming growth factor beta1

BACKGROUND & AIMS

A deficient leukocyte recruitment has been suggested in tumor vasculature, but little is known about the underlying molecular mechanism. To characterize leukocyte-endothelium interaction in experimental colon cancer, quantify the main endothelial cell adhesion molecules (CAMs), and evaluate the effect of tumor-derived products.

METHODS

Leukocyte recruitment was assessed by intravital videomicroscopy in mice bearing HT29-derived tumors. Endothelial CAMs were measured using the dual-radiolabeled antibody technique. The role of molecules mediating leukocyte rolling (P-, E-, and L-selectin) or adhesion (intercellular adhesion molecule 1 [ICAM-1] and vascular cell adhesion molecule 1 [VCAM-1]) carcinoembryonic antigen (CEA), and transforming growth factor (TGF) beta1 was assessed through immunoblockade, whereas participation of nitric oxide (NO) and cyclooxygenase (COX) metabolites were evaluated by means of nonselective and selective inhibition.

RESULTS

Basal and lipopolysaccharide-stimulated leukocyte rolling and adhesion were markedly reduced in tumor vasculature. ICAM-1 immunoblockade prevented leukocyte adhesion in both tumor and nontumor microvessels. Neither baseline nor LPS-induced endothelial ICAM-1, P-, and E-selectin expression in tumors were reduced with respect to nontumor vasculature. Although VCAM-1 expression was reduced in tumor endothelium, immunoneutralization of VCAM-1 failed to reverse LPS-induced leukocyte recruitment in this setting. CEA immunoblockade and COX inhibition did not modify the deficient leukocyte rolling. Nonselective NO inhibition partially reversed the defective adhesion response in tumor microvessels. Finally, TGF-beta1 immunoblockade partially and selectively restored impaired leukocyte rolling and adhesion in tumor microvessels.

CONCLUSIONS

Impaired leukocyte recruitment in tumor vasculature cannot be attributed to a depressed expression of the main CAMs. Selective restoration after NO inhibition and TGF-beta1 immunoblockade suggests involvement of both molecules in this phenomenon.

Rolipram inhibits leukocyte-endothelial cell interactions in vivo through P- and E-selectin downregulation

1. Rolipram, a selective phosphodiesterase (PDE) type 4 inhibitor, was used to characterize leukocyte recruitment mechanisms in models of acute and subacute inflammation. Intravital microscopy within the rat mesenteric microcirculation was employed. 2. Mesentery superfusion with PAF (0.1 microM) induced a significant increase in leukocyte rolling flux, adhesion and emigration at 60 min. Rolipram pretreatment, markedly inhibited these parameters by 100, 95 and 95% respectively. 3. Similar effects were observed when the mesentery was superfused with LPS (1 microg ml(-1)) for the same time period and these leukocyte parameters were nearly abrogated by rolipram pretreatment. 4. LPS exposure of the mesentery for 4 h caused a greater increase in leukocyte rolling flux, adhesion and emigration which were inhibited by rolipram administration by 51, 71 and 81% respectively. 5. Immunohistochemistry revealed a significant increase in P-selectin expression after 60 min superfusion with PAF which was attenuated by rolipram. 6. LPS exposure of the mesentery for 4 h caused a significant increase in P- and E-selectin, intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expression. Rolipram pretreatment down-regulated both P- and E-selectin expression but had no effect on ICAM-1 and VCAM-1 expression. 7. Significant increases in plasma cyclic AMP levels were detected at 4.5 h after rolipram administration. 8. In conclusion, we have demonstrated that rolipram is a potent in vivo inhibitor of leukocyte-endothelial cell interactions. The effects observed are mediated through endothelial P- and E-selectin downregulation. Therefore, selective PDE-4 inhibitors may be useful in the control of different inflammatory disorders.

The role of E-selectin, P-selectin, and very late activation antigen-4 in T lymphocyte migration to dermal inflammation

T lymphocyte infiltration into inflamed tissues is thought to involve lymphocyte rolling on vascular endothelial cells. Because both selectin and alpha(4) integrin adhesion molecules can mediate leukocyte rolling, the contribution of these receptors to lymphocyte migration to inflammation was examined. The recruitment of (111)In-labeled spleen T cells to intradermal sites injected with IFN-gamma, TNF-alpha, LPS, poly inosine-cytosine, and Con A was measured in the rat, and the effect of blocking mAbs to E-selectin, P-selectin, very late activation Ag-4 (VLA-4), and LFA-1 was determined on this T cell migration in vivo. Anti-E-selectin and anti-P-selectin mAbs each inhibited 10-40 and 20-48%, respectively, of the T lymphocyte migration to the inflammatory sites, depending on the stimulus. Blocking VLA-4 inhibited 50% of the migration to all of the lesions except Con A. Treatment with both anti-VLA-4 and anti-E-selectin mAbs inhibited up to 85% of the lymphocyte accumulation, while P-selectin and VLA-4 blockade in combination was not more effective than VLA-4 blockade alone in TNF-alpha, IFN-gamma, LPS, and poly inosine-cytosine lesions. Inhibiting E-selectin, P-selectin, and VLA-4 together nearly abolished lymphocyte migration to all inflammatory sites. Anti-LFA-1 mAb strongly inhibited lymphocyte accumulation by itself, and this inhibition was not significantly further reduced by E- or P-selectin blockade. Thus, T cell migration to dermal inflammation is dependent on E-selectin, P-selectin, and VLA-4, likely because these three receptors are required for rolling of memory T lymphocytes, but VLA-4 and E-selectin are especially important for lymphocyte infiltration in these tissues.

Molecular mechanisms involved in lymphocyte recruitment in inflamed brain microvessels: critical roles for P-selectin glycoprotein ligand-1 and heterotrimeric G(i)-linked receptors

Lymphocyte recruitment into the brain is a critical event in the pathogenesis of multiple sclerosis and experimental autoimmune encephalomyelitis. We developed a novel intravital microscopy model to directly analyze through the skull the interactions between lymphocytes and the endothelium in cerebral venules of mice. No adhesive interactions were observed between lymphocytes and the nonactivated endothelium in the cerebral microcirculation. When brain venules were activated by pretreating mice with TNF-alpha or LPS, proteolipid protein 139-151 autoreactive T lymphocytes rolled and arrested; notably, only a few peripheral lymph node cells rolled and firmly adhered. Abs anti-P-selectin glycoprotein ligand-1 and anti-E- and P-selectin blocked tethering and rolling of autoreactive lymphocytes, suggesting that P-selectin glycoprotein ligand-1/endothelial selectins are critical in the recruitment of lymphocytes in inflamed brain venules. E- and P-selectin were expressed on cerebral vessels upon in vivo activation and had a patchy distribution during the preclinical phase of active and passive experimental autoimmune encephalomyelitis. LFA-1/ICAM-1 and alpha(4) integrins/VCAM-1 supported rolling, but were not relevant to rolling velocity. Firm arrest was mainly mediated by LFA-1 and ICAM-1. Pretreatment of autoreactive lymphocytes with pertussis toxin blocked integrin-dependent arrest, implicating a requirement for G(i) protein-dependent signaling in vessels from nonlymphoid districts. In conclusion, our data unveils the molecular mechanisms controlling the recruitment of autoreactive lymphocytes in inflamed cerebral vessels and suggest new insights into the pathogenesis of autoimmune inflammatory diseases of the CNS.

Small molecule selectin ligand inhibition improves outcome in ischemic acute renal failure

BACKGROUND

The pathophysiologic and potential therapeutic role of selectins in renal ischemia-reperfusion injury (IRI) is not fully understood, due in part to redundancy in the roles of individual selectins. We hypothesized that blockade of ligands for all three selectins using a novel small molecule (TBC-1269) would improve the course of renal IRI by overcoming redundancy issues. This was investigated in a rat model of renal IRI.

METHODS

Rats were treated with TBC-1269 either during or post-IRI. The effects of TBC-1269 were investigated in two models of renal IRI: moderate IRI (30 minutes bilateral renal artery clamping) and severe IRI (45 minutes clamping). The combination of anti-E- and anti-P-selectin antibodies also was investigated in rats subjected to moderate IRI. Renal function, histological injury and mortality were assessed.

RESULTS

Rats treated with TBC-1269 during moderate IRI showed significantly reduced serum creatinine (SCr) and tubular necrosis post-ischemia compared to control animals. By contrast, delayed treatment (post-IRI) did not show a reduction in SCr. In rats with severe IRI, TBC-1269 treatment during IRI significantly reduced mortality at 48 hours post-ischemia. Rats with moderate IRI and treated with the combination of anti-E- and anti-P-selectin antibodies showed significantly reduced SCr compared to control rats at 24 hours post-ischemia.

CONCLUSIONS

Small molecule selectin ligand inhibition provides a novel and effective approach to attenuate ischemic acute renal failure. Timing of treatment is crucial to success.

Recruitment of neutrophils across the blood-brain barrier: the role of E- and P-selectins

The adult central nervous system parenchyma is resistant to inflammation, but in juvenile rats the injection of inflammatory mediators, interleukin-1 beta for example, gives rise to extensive neutrophil recruitment and neutrophil-dependent blood-brain barrier breakdown. The factors that confer this resistant phenotype are unknown. In this study, the authors demonstrate that E- and P-selectin expression is increased to a similar extent in adult and juvenile brain after the intracerebral injection of IL-1 beta. Thus, the refractory nature of the brain parenchyma cannot be attributed to an absence of selectin expression. However, in injuries where the resistant characteristic of the brain parenchyma is compromised, and neutrophil recruitment occurs, selectin blockade may be an advantage. The authors investigated the contribution that selectins make to neutrophil recruitment during acute inflammation in the brain. The authors examined neutrophil recruitment by immunohistochemistry on brain sections of juvenile rats killed four hours after the intracerebral injection of IL-1 beta and the intravenous injection of neutralizing anti-selectin monoclonal antibodies (mAb). The administration of the P-selectin blocking mAb inhibited neutrophil recruitment by 85% compared with controls. Surprisingly, E-selectin blockade had no effect on neutrophil recruitment to the brain parenchyma. Thus, P-selectin appears to play a pivotal role in mediating neutrophil recruitment to the brain parenchyma during acute inflammation.

E-selectin, but not P-selectin, is required for development of adjuvant-induced arthritis in the rat

OBJECTIVE

To determine the role of the endothelial cell adhesion molecules E- and P-selectin in the development and severity of adjuvant-induced arthritis (AIA) in the rat.

METHODS

Lewis rats were immunized subcutaneously with Mycobacterium butyricum (Mb), and blocking monoclonal antibodies (mAb) to rat E- and P-selectin were administered. Clinical score, radiolabeled (51Cr and 111In) blood polymorphonuclear leukocyte (PMN) and monocyte migration to joints, and histologic features were monitored.

RESULTS

When mAb treatment was started on day 5 postimmunization with Mb (preclinical stage), development of AIA was significantly (P < 0.01) inhibited by mAb to E- but not to P-selectin (mean score on day 14 control 10.2, anti-E 2.8, anti-P 9.1). This was associated with markedly decreased migration (by 66-94%) of PMN and monocytes to arthritic joints and diminished cartilage degradation. When treatment was delayed until animals showed signs of arthritis (day 10 postimmunization), only a marginal and variable effect was observed as compared with blockade during the preclinical (day 5) stage. E-selectin blockade on day 5 and day 7 postimmunization resulted in inhibition of antigen-dependent T cell-mediated inflammation, since it decreased T cell migration to sites of dermal-delayed hypersensitivity induced by Mb without affecting migration to concanavalin A or cytokines. The proliferative response of T cells to Mb in vitro was not altered.

CONCLUSION

E-selectin plays an important role early in the development of AIA. This adhesion molecule may contribute to the migration of antigen-reactive T cells to peripheral tissues, including the joints where T cells initiate the arthritis.

The beta2, alpha4, alpha5 integrins and selectins mediate chemotactic factor and endotoxin-enhanced neutrophil sequestration in the lung

Intravascular chemotactic factor activation of neutrophils (polymorphonuclear leukocytes; PMNLs), associated with actin polymerization resulting in PMNL stiffening, induces rapid and transient sequestration in the pulmonary vasculature and lung dysfunction. Recent studies have proposed that this sequestration is mediated by physical lodging of PMNLs because of loss of deformability. To examine the contribution of cell adhesion molecules in this process, we used blocking monoclonal antibodies (mAbs) to rat selectins and integrins in a model of PMNL margination (reflected by acute blood neutropenia) induced by N-formyl-met-leu-phe (FMLP) chemotactic factor infusion in normal or lipopolysaccharide (LPS)-primed rats. Blood PMNL levels dropped by 70% within 1 minute and for the duration of FMLP infusion (20 minutes) in normal or by 90% in LPS-primed rats. Pretreatment with mAbs to beta2(WT.3), VLA-4(TA-2 F(ab)(2)), and VLA-5 (HMalpha5 F(ab)(2)) in combination inhibited the decrease by 50% and to a greater degree than beta2 blockade alone (35% inhibition). F(ab)(2) mAbs to L-(HRL-3), P-(RMP-1), plus E-(RME-1) selectins had no effect but they potentiated inhibition by anti-beta2 + anti-VLA-4 + anti-VLA5 mAb treatment (69% inhibition, P < 0.05). Similar results were observed in the first 6 minutes in LPS-primed rats with complete inhibition of sequestration thereafter by combined selectin and integrin blockade. These results indicate that besides PMNL stiffening because of actin polymerization, both selectins and integrins substantially contribute to activated PMNL sequestration in the lung.

Role of P-selectin in radiation-induced intestinal inflammatory damage

The aims of our study were to characterize the dose- and time-dependent changes in endothelial P-selectin expression and the role of this adhesion molecule as a mediator of radiation-induced inflammation. For that purpose, endothelial P-selectin expression was measured by the radiolabeled antibody technique in control and irradiated mice at 2, 6, and 24 hr following abdominal irradiation with 4 or 10 Gy; leukocyte endothelial cell interactions were assessed using intravital microscopy in intestinal venules following irradiation at the aforementioned doses and times in C57BL/6 and P-selectin-deficient mice. In wild-type mice, radiation induced a time- and dose-dependent up-regulation of P-selectin and a significant increase in the flux of rolling leukocytes 2 hr after irradiation. Irradiation induced a significant increase in leukocyte adhesion that was dose-dependent. Following irradiation, P-selectin-deficient mice did not show any increase in leukocyte rolling but did demonstrate a response in leukocyte adhesion similar to that of the wild-type mice. Radiation-induced dose-dependent histological inflammatory damage that did not differ between P-selectin-deficient and wild-type mice. We conclude that P-selectin is up-regulated following irradiation and is a key molecular determinant of leukocyte rolling but not leukocyte adhesion in this inflammatory condition. Therefore, isolated neutralization of this adhesion molecule is not an effective means for preventing radiation-induced inflammation.

The alpha 4 beta 1 (very late antigen (VLA)-4, CD49d/CD29) and alpha 5 beta 1 (VLA-5, CD49e/CD29) integrins mediate beta 2 (CD11/CD18) integrin-independent neutrophil recruitment to endotoxin-induced lung inflammation

The beta(2) integrin cell adhesion molecules (CAM) mediate polymorphonuclear leukocyte (PMNL) emigration in most inflamed tissues, but, in the lung, other yet to be identified CAMs appear to be involved. In Lewis rats, the intratracheal injection of Escherichia coli-LPS induced acute (6-h) PMNL accumulation in the lung parenchyma (280 x 10(6) by myeloperoxidase assay; PBS control = 35 x 10(6)) and bronchoalveolar lavage fluid (BALF = 27 x 10(6); PBS = 0.1 x 10(6)). Parenchymal accumulation was not inhibited by a blocking Ab to beta(2) integrins and only minimally inhibited (20.5%; p < 0.05) in BALF. We examined the role of alpha(4)beta(1) and alpha(5)beta(1) integrins and of selectins in this PMNL recruitment. Treatment with mAbs to alpha(4)beta(1) or alpha(5)beta(1), even in combination, had no effect on PMNL accumulation induced by intratracheal LPS. However, anti-alpha(4) combined with anti-beta(2) mAbs inhibited PMNL recruitment to the parenchyma by 56% (p < 0.001) and to BALF by 58% (p < 0.01). The addition of anti-alpha(5) mAb to beta(2) plus alpha(4) blockade inhibited PMNL accumulation further (by 79%; p < 0.05). In contrast, blockade of L-, P-, and E-selectins in combination or together with beta(2), alpha(4), and alpha(5) integrins had no effect. LPS-induced BALF protein accumulation was not inhibited by treatment with anti-beta(2) plus alpha(4) mAbs, but was prevented when alpha(5)beta(1) was also blocked. Thus, while selectins appear to play no role, alpha(4)beta(1) and alpha(5)beta(1) function as major alternate CAMs to the beta(2) integrins in mediating PMNL migration to lung and to pulmonary vascular and epithelial permeability.

Differential role of selectins in experimental colitis

BACKGROUND AND AIMS

The role of selectins in experimental colitis remains unknown. The aims of this study were to characterize the time-course expression of selectins in trinitrobenzene sulfonic acid (TNBS)-induced colitis, the functional role of selectins in colonic leukocyte-endothelial cell interactions, and the therapeutic usefulness of selectin blockade in this model.

METHODS

Control and TNBS-induced colitic rats were studied. Expression of P- and E-selectin was assessed by the radiolabeled antibody technique, and L-selectin by flow cytometry. Leukocyte-endothelial cell interactions were studied in colonic venules by using intravital microscopy under basal conditions and after P-, E-, or L-selectin immunoblockade. Additional groups of animals were treated with anti-P-selectin antibody, a nonbinding antibody, or dexamethasone, for 7 days.

RESULTS

P-selectin and E-selectin expression were markedly up-regulated in colitic rats. Increased leukocyte rolling was abrogated by anti-P-selectin, but only attenuated by anti-E- or anti-L-selectin antibodies. Only pretreatment with anti-P- selectin decreased leukocyte adhesion. Animals chronically treated with dexamethasone, but not with anti- P-selectin, had significantly lower macroscopic and histologic damage scores, colon weight, and myeloperoxidase (MPO) activity than those treated with nonbinding antibody.

CONCLUSIONS

P-selectin plays a key role on leukocyte rolling and its blockade attenuates leukocyte adhesion in TNBS-induced colitis. However, treatment with an anti-P-selectin antibody does not significantly improve colitis.

Differential upregulation of cellular adhesion molecules at the sites of oxidative stress in experimental acute pancreatitis

BACKGROUND

Severe acute pancreatitis (AP)(2) is associated with exaggerated leukocyte adherence and activation. Endothelial cellular adhesion molecules (CAMs) can be induced by cytokines, but also directly by oxygen free radicals (OFRs), mediated by nuclear factor kappa-B (NF-kappa B). We investigated the behavior of inducible CAMs in relation to pancreatic oxidative stress. Our novel modification of cerium capture histochemistry (reaction of OFRs with cerium produces laser reflective Ce perhydroxide precipitates) combined with reflectance confocal laser scanning microscopy (CLSM) allows the histological codemonstration of in vivo OFR production and immunolabeled CAMs, or NF-kappa B.

METHODS

Taurocholate AP was induced in rats; sham operated and normal animals served as controls. To achieve in situ, in vivo reaction of cerium with OFRs, animals were perfused with CeCl(3) solution at different time points (1, 2, 8, 24 h) and then sacrificed. E-selectin, P-selectin, ICAM-1, VCAM, and NF-kappa B p65 were labeled by immunofluorescence (IF) on frozen sections of cerium perfused pancreata. IF and Ce perhydroxide reflectance were simultaneously detected by CLSM. Pancreatic gene expression of the same CAMs was quantified by competitive RT-PCR (MIMIC internal control).

RESULTS

Control pancreata showed negligible reflectance and minimal CAM expression. Early (1, 2 h) AP samples were characterized by intense, heterogeneous acinar OFR production, strong P-selectin, and increasing ICAM expression, with nuclear translocation of p65, histologically all colocalizing with the areas of acinar oxidative stress. Adherent polymorphonuclear leukocytes (PMNs) displayed weak OFR formation. Later (8, 24 h), a slowly declining P-selectin, but persisting ICAM-1 expression, was paralleled by widespread adherence of PMNs producing surprisingly large amounts of OFRs. VCAM and E-selectin showed a mild increase at 24 h. CAM gene activation was in good correlation with the protein expression.

CONCLUSIONS

The early acinar oxidative stress is colocalized with NF-kappa B activation, preferential P-selectin, and ICAM upregulation in this AP model. Subsequently, adherent, activated PMNs become the major source of OFRs, thereby contributing to tissue damage.

Heme oxygenase modulates selectin expression in different regional vascular beds

Heme oxygenase (HO) catalyzes the degradation of heme to biliverdin, iron, and CO. The inducible isoform (HO-1) has been implicated as a modulator of the inflammatory response. HO-1 activity can be induced by hemin and inhibited with zinc protoporphyrin IX (ZnPP). Using these reagents, we assessed the possibility that HO-1 modulates the inflammatory response by altering the expression of endothelial cell adhesion molecules. Endotoxin (lipopolysaccharide, LPS)-induced expression of P- and E-selectin expression was quantified in different vascular beds of the rat using the dual radiolabeled monoclonal antibody technique. Pretreatment with hemin attenuated, whereas ZnPP treatment exacerbated, the increased selectin expression normally elicited by LPS. Biliverdin, at an equimolar dosage, was as effective as hemin in attenuating LPS-induced selectin expression in the lung, kidneys, liver, and intestines. These findings indicate that the anti-inflammatory properties of HO-1 may be related to an inhibitory action of P- and E-selectin expression in the vasculature. Biliverdin (or its metabolite, bilirubin), rather than CO, may account for this action of HO-1 on endothelial cell adhesion molecule expression.

The role of alpha(4) and LFA-1 integrins in selectin-independent monocyte and neutrophil migration to joints of rats with adjuvant arthritis

Monocytes and neutrophils are chronically recruited to joints in rheumatoid arthritis. In the joints of rats with adjuvant arthritis, this is mediated, in part, by selectin-dependent and selectin-independent mechanisms. To define the selectin-independent mechanisms, (51)Cr-labeled blood monocytes, (111)In-labeled neutrophils and function blocking mAb to the selectins and integrins were utilized. Integrins contributed to the selectin-independent monocyte migration to arthritic joints with 58-70% inhibition of this recruitment by anti-alpha(4) or anti-LFA-1 mAb, relative to selectin blockade alone. alpha(4) plus P-selectin blockade was as effective as combined blockade of alpha(4), P-, E- and L-selectin, mediating approximately 83% of the overall monocyte migration to the joints. In contrast, LFA-1 was the predominant selectin-independent mechanism for neutrophil recruitment to the joints. LFA-1 together with P-selectin had essential roles in the talar joint. In dermal inflammation in the arthritic rats, LFA-1 accounted for most (69%) of the selectin-independent monocyte migration to the chemoattractant C5a(desArg) (zymosan-activated serum), whereas LFA-1 and Mac-1 both contributed to selectin-independent neutrophil recruitment to C5a(desArg). alpha(4) integrin and P-selectin in concert mediated monocyte recruitment to lipopolysaccharide and IFN-gamma lesions (81%). Thus: (1) either alpha(4) or LFA-1 can mediate monocyte migration to arthritic joints in the absence of selectin function and alpha(4) together with P-selectin is particularly important; (2) LFA-1 is the predominant mechanism of selectin-independent migration of neutrophils to inflamed joints; and (3) in arthritic rats, selectin-independent migration of monocytes and neutrophils to dermal inflammation is mediated by alpha(4) or LFA-1 or both LFA-1 and Mac-1, depending on the leukocyte type, and inflammatory stimulus.

The role of selectins in VLA-4 and CD18-independent neutrophil migration to joints of rats with adjuvant arthritis

Neutrophil migration from blood into inflamed tissues is mediated by adhesion molecules on neutrophils and on vascular endothelium. It was previously shown that the integrins VLA-4 and CD11/CD18 in combination mediate 70-80% of neutrophil recruitment to arthritic joints of rats. To investigate if the remaining recruitment involves the selectins, the effect of adhesion-blocking monoclonal antibodies (mAb) to each of the selectins (E-, P and L-), in combination with mAb to VLA-4 and CD18, on the migration of radiolabeled neutrophils to joints of rats with adjuvant arthritis was examined. Blocking P-selectin inhibited neutrophil accumulation in hindlimb joints by 40% whereas mAb to P- and E-selectin together inhibited the accumulation in all joints by 60% relative to anti-VLA-4 plus anti-CD18 treatment alone. Overall there was 90% inhibition relative to arthritic controls. Blocking E- or L-selectin alone or together had no effect. Our results demonstrate that P-selectin in particular and in concert with E-selectin are required for the VLA-4- and CD18-independent migration of neutrophils to sites of chronic arthritis in the rat.

Endogenous interleukin-10 regulates hemodynamic parameters, leukocyte-endothelial cell interactions, and microvascular permeability during endotoxemia

The objective of this study was to determine whether endogenous IL-10 is capable of regulating hemodynamic parameters, leukocyte recruitment, and microvascular permeability in response to endotoxin. Intravital microscopy was used to examine hemodynamic parameters, leukocyte rolling and adhesion, and microvascular permeability in cremasteric postcapillary venules in wild-type mice and in IL-10-deficient (IL-10(-/-)) mice exposed to lipopolysaccharide (LPS). Doses of LPS (3 or 30 microg/kg, IV), which did not reduce blood pressure and minimally altered microvascular hemodynamic factors in wild-type mice, caused significant reductions in these parameters in IL-10(-/-) mice, demonstrating at least a 10-fold increased sensitivity in IL-10(-/-) mice to LPS-induced hemodynamic alterations. Furthermore, in response to LPS (30 microg/kg, IV), leukocyte rolling, adhesion, and fluorescein isothiocyanate-albumin extravasation were increased in the IL-10(-/-) mice. Antibody blockade experiments showed that in both types of mice, leukocyte rolling was mediated by E-selectin and P-selectin. Leukocyte accumulation into other tissues, such as lung, also was enhanced greatly in IL-10(-/-) mice. This was specific to endotoxin, because acute chemotactic stimuli including N-formyl-methionyl-leucyl-phenylalanine elicited similar responses in IL-10(-/-) and wild-type mice. These results suggest that endogenous IL-10 may be a homeostatic regulator of hemodynamic parameters, leukocyte-endothelial cell interactions, and microvascular dysfunction in response to endotoxin and provide potential mechanisms to explain the protective effect of IL-10 against LPS-induced mortality.

Role of E- and P-selectin in migration of monocytes and polymorphonuclear leucocytes to cytokine and chemoattractant-induced cutaneous inflammation in the rat

The contribution of E- and P-selectin in the rat to the migration of polymorphonuclear leucocytes (PMNL) and monocytes to acute dermal inflammation induced by a chemoattractant (C5ades Arg) or endothelial cell activating agents [lipopolysaccharide, tumour necrosis factor-alpha (TNF-alpha), alpha-thrombin and interferon-gamma] administered intradermally was investigated. Migration was quantitated using radiolabelled blood PMNL and monocytes and new, function-blocking monoclonal antibodies (mAbs) to rat E- and P-selectin were employed. Monocyte migration to inflamed skin was partially inhibited (40-75%) by P-selectin mAb with all stimuli tested, but not by anti-E-selectin. PMNL migration in response to all stimuli was also inhibited (50-75%) by blocking P-selectin, but in contrast to monocytes, PMNL accumulation was partially inhibited by mAb to E-selectin in alpha-thrombin and TNF-alpha lesions. When P-selectin was blocked by mAb, mAb to E-selectin significantly inhibited further (by 70-90%) both PMNL and monocyte accumulation in all lesions, indicating that both P- and E-selectin contribute to the migration of these leucocytes. Blocking L-selectin in addition to P- and E-selectin, had no effect on the remaining migration. Thus, optimal PMNL and monocyte migration to chemotactic factor- and cytokine-induced skin inflammation is P-selectin dependent. E-selectin becomes important, in most conditions used here, when P-selectin mediated recruitment is not operative. A selectin independent pathway likely mediates up to 20% of PMNL and monocyte migration to acute inflammation, at least in skin.