Search

Two key characteristics of the inflammatory response are the recruitment of leukocytes to inflamed tissue as well as changes in vessel permeability. We explored the relationship between these two processes using intravital confocal microscopy in cremasters of anesthetized (65 mg/kg Nembutal ip) mice. We provide direct evidence that intercellular adhesion molecule-1 (ICAM-1) links leukocyte-endothelial cell interactions and changes in solute permeability ([P.sub.s]). Importantly, we show that arterioles, not just venules, respond to proinflammatory stimuli, thus contributing to microvascular exchange. We identified two independent, ICAM-1-mediated pathways regulating [P.sub.s]. Under control conditions in wild-type (WT) mice, there is a constitutive PKC-dependent pathway ([P.sub.s] = 1.0 [+ or -] 0.10 and 2.2 [+ or -] 0.46 x [10.sup.-6] cm/s in arterioles and venules, respectively), which was significantly reduced in ICAM-1 knockout (KO) mice ([P.sub.s] = 0.54 [+ or -] 0.07 and 0.77 [+ or -] 0.11 x [10.sub.-6] cm/s). The PKC inhibitor hisindolylmaleimid 1 (1 [micro]mol/l in 0.01% DMSO) decreased [P.sub.s] in WT mice to levels similar to those in ICAM-1 KO mice. Likewise, a PKC activator (phorbol-12-myristate-acetate; 1 [micro]mol/l in 0.01% DMSO) successfully restored [P.sub.s] in ICAM-1 KO vessels to be not different from that of the WT controls. On the other hand, during TNF-[alpha]-induced inflammation, [P.sub.s] in WT mice was significantly increased (2-fold in venules and 2.5-fold in arterioles) in a Src-dependent and PKC-independent manner. The blockade of Src (PP2; 2 [micro]mol/l in 0.01% DMSO) but not PKC significantly reduced the TNF-[alpha]-dependent increase in [P.sub.s]. We conclude that ICAM-1 plays an essential role in the regulation of [P.sub.s] in microvessels and that there are two separate (constitutive and inducible) signaling pathways that regulate permeability under normal and inflamed conditions. adhesion molecules; microvascular exchange

Cell adhesion, mediated by specific receptor-ligand interactions, plays an important role in biological processes such as tumor metastasis and inflammatory cascade. For example, interactions between [[beta].sub.2]-integrin (lymphocyte function-associated antigen-1 and/or Mac-l) on polymorphonuclear neutrophils (PMNs) and ICAM-1 on melanoma cells initiate the bindings of melanoma cells to PMNs within the tumor microenvironment in blood flow, which in turn activate PMN-melanoma cell aggregation in a near-wall region of the vascular endothelium, therefore enhancing subsequent extravasation of melanoma cells in the microcirculations. Kinetics of integrin-ligand bindings in a shear flow is the determinant of such a process, which has not been well understood. In the present study, interactions of PMNs with WM9 melanoma cells were investigated to quantify the kinetics of [[beta].sub.2]-integrin and ICAM-1 bindings using a cone-plate viscometer that generates a linear shear flow combined with a two-color flow cytometry technique. Aggregation fractions exhibited a transition phase where it first increased before 60 s and then decreased with shear durations. Melanoma-PMN aggregation was also found to be inversely correlated with the shear rate. A previously developed probabilistic model was modified to predict the time dependence of aggregation fractions at different shear rates and medium viscosities. Kinetic parameters of [[beta].sub.2]-integrin and ICAM-1 bindings were obtained by individual or global fittings, which were comparable to respectively published values. These findings provide new quantitative understanding of the biophysical basis of leukocyte-tumor cell interactions mediated by specific receptor-ligand interactions under shear flow conditions. heterotypic cell aggregation; adhesion molecule; leukocyte; tumor cell; reverse rate; binding affinity; probabilistic model; polymorpho-nuclear neutrophils; intercellular adhesion molecule-1

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 x [kg.sup.-1] x [day.sup.-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 leukocyteendothelial 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 x [kg.sup.-1] x [day.sup.-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. endothelium; ICAM-1; leukocyte

Byline: Helena Yusuf-Makagiansar (1), Irwan T. Makagiansar (1), Teruna J. Siahaan (1) Keywords: leukocyte infiltration; T-lymphocytes; adhesion molecules; apoptosis; LFA-1-peptide Abstract: Tissue inflammation is characterized by aggravated leukocyte infiltration into the sites of inflammation. The mechanism requires the interactions of leukocyte adhesion-molecules and their ligands in the inflamed tissues. In this study, we demonstrate that a cyclic peptide cLAB.L [cyclo1, 12-PenITDGEATDSGC], derived from the 'inserted' or I-domain of LFA-1 is able to inhibit the adherence of T-lymphocytes to the epithelial cell monolayers. This inhibition has been thought to involve the disruption of LFA-1/ICAM-1 interaction. The heterotypic adhesion of phorbol ester-activated Molt-3 cells and IFN-I3-induced Caco-2 monolayers was inhibited upon treatment of the monolayers with monoclonal antibodies (MAbs) to adhesion molecules or with cLAB.L peptide. The adhesion can be inhibited by MAbs to ICAM-1, ICAM-2, and VCAM-1, and cLAB.L peptide in a concentration-dependent manner. However, none of the individual uses of these molecules led to a total inhibition. The inhibitory activity of cLAB.L is greatly reduced by low temperature and the absence of cell activation. Treatment of cLAB.L peptide may trigger an early event of apoptosis on activated but not on non-activated Molt-3 cells no indication of peptide-induced apoptosis was found on Caco-2 cells. Taken together, data from this work suggest that cLAB.L may have applications to direct cell-targeted delivery during tissue inflammation. Author Affiliation: (1) Department of Pharmaceutical Chemistry, Simons Research Laboratories, The University of Kansas, 2095 Constant Avenue, Lawrence, Kansas, 66047 Article History: Registration Date: 17/10/2004