Biomedical subjects

Azucena Salas

Publications and source records attributed to Azucena Salas.

18 recordsLinked to original sources

PubMed2006

Importance of force linkage in mechanochemistry of adhesion receptors.

The alpha subunit-inserted (I) domain of integrin alphaLbeta2 [lymphocyte function-associated antigen-1 (LFA-1)] binds to intercellular adhesion molecule-1 (ICAM-1). The C- and N-termini of the alpha I domain are near one another on the "lower" face, opposite the metal ion-dependent adhesion site (MIDAS) on the "upper face". In conversion to the open alpha I domain conformation, a 7 A downward, axial displacement of C-terminal helix alpha7 is allosterically linked to rearrangement of the MIDAS into its high-affinity conformation. Here, we test the hypothesis that when an applied force is appropriately linked to conformational change, the conformational change can stabilize adhesive interactions that resist the applied force. Integrin alpha I domains were anchored to the cell surface through their C- or N-termini using type I or II transmembrane domains, respectively. C-terminal but not N-terminal anchorage robustly supported cell rolling on ICAM-1 substrates in shear flow. In contrast, when the alphaL I domain was mutationally stabilized in the open conformation with a disulfide bond, it mediated comparable levels of firm adhesion with type I and type II membrane anchors. To exclude other effects as the source of differential adhesion, these results were replicated using alpha I domains conjugated through the N- or C-terminus to polystyrene microspheres. Our results demonstrate a mechanical feedback system for regulating the strength of an adhesive bond. A review of crystal structures of integrin alpha and beta subunit I domains and selectins in high- and low-affinity conformations demonstrates a common mechanochemical design in which biologically applied tensile force stabilizes the more extended, high-affinity conformation.

Cell Adhesion↗

PubMed2006

A small molecule agonist of an integrin, alphaLbeta2.

The binding of integrin alpha(L)beta(2) to its ligand intercellular adhesion molecule-1 is required for immune responses and leukocyte trafficking. Small molecule antagonists of alpha(L)beta(2) are under intense investigation as potential anti-inflammatory drugs. We describe for the first time a small molecule integrin agonist. A previously described alpha/beta I allosteric inhibitor, compound 4, functions as an agonist of alpha(L)beta(2) in Ca(2+) and Mg(2+)and as an antagonist in Mn(2+). We have characterized the mechanism of activation and its competitive and noncompetitive inhibition by different compounds. Although it stimulates ligand binding, compound 4 nonetheless inhibits lymphocyte transendothelial migration. Agonism by compound 4 results in accumulation of alpha(L)beta(2) in the uropod, extreme uropod elongation, and defective de-adhesion. Small molecule integrin agonists open up novel therapeutic possibilities.

Allosteric Regulation↗

PubMed2006

AL-57, a ligand-mimetic antibody to integrin LFA-1, reveals chemokine-induced affinity up-regulation in lymphocytes.

Affinity of integrin lymphocyte function-associated antigen 1 (LFA-1) is enhanced by conformational changes from the low-affinity closed form to the high-affinity (HA) open form of the ligand-binding inserted (I) domain as shown by work with purified I domains. However, affinity up-regulation of LFA-1 on the cell surface by physiological agonists such as chemokines has yet to be demonstrated by monovalent reagents. We characterize a mAb, AL-57 (activated LFA-1 clone 57), that has been developed by phage display that selectively targets the HA open conformation of the LFA-1 I domain. AL-57 discriminates among low-affinity, intermediate-affinity, and HA states of LFA-1. Furthermore, AL-57 functions as a ligand mimetic that binds only upon activation and requires Mg2+ for binding. Compared with the natural ligand intercellular adhesion molecule-1, AL-57 shows a tighter binding to the open I domain and a 250-fold slower off rate. Monovalent Fab AL-57 demonstrates affinity increases on a subset (approximately 10%) of lymphocyte cell surface LFA-1 molecules upon stimulation with CXCL-12 (CXC chemokine ligand 12). Affinity up-regulation correlates with global conformational changes of LFA-1 to the extended form. Affinity increase stimulated by CXCL-12 is transient and peaks 2 to 5 min after stimulation.

Amino Acid Sequence↗

PubMed2006

Identification and characterization of a human monoclonal antagonistic antibody AL-57 that preferentially binds the high-affinity form of lymphocyte function-associated antigen-1.

LFA-1 (alpha(L)beta(2)) mediates cell-cell and cell-extracellular matrix adhesions essential for immune and inflammatory responses. One critical mechanism regulating LFA-1 activity is the conformational change of the ligand-binding alpha(L) I domain from low-affinity (LA), closed form, to the high-affinity (HA), open form. Most known integrin antagonists bind both forms. Antagonists specific for the HA alpha(L) I domain have not been described. Here, we report the identification and characterization of a human antibody AL-57, which binds to the alpha(L) I domain in a HA but not LA conformation. AL-57 was discovered by selection from a human Fab-displaying library using a locked-open HA I domain as target. AL-57 Fab-phage bound HA I domain-expressing K562 cells (HA cells) in a Mg(2+)-dependent manner. AL-57 IgG also bound HA cells and PBMCs, activated by Mg(2+)/EGTA, PMA, or DTT. The binding profile of AL-57 IgG on PBMCs was the same as that of ICAM-1, the main ligand of LFA-1. In contrast, an anti-alpha(L) murine mAb MHM24 did not distinguish between the HA and LA forms. Moreover, AL-57 IgG blocked ICAM-1 binding to HA cells with a potency greater than MHM24. It also inhibited ICAM-1 binding to PBMCs, blocked adhesion of HA cells to keratinocytes, and inhibited PHA-induced lymphocyte proliferation with potencies comparable with MHM24. These results indicate that specifically targeting the HA I domain is sufficient to inhibit LFA-1-mediated, adhesive functions. AL-57 represents a therapeutic candidate for treatment of inflammatory and autoimmune diseases.

Antibodies, Monoclonal↗

PubMed2006

Transition from rolling to firm adhesion can be mimicked by extension of integrin alphaLbeta2 in an intermediate affinity state.

AlphaLbeta2 affinity for intercellular adhesion molecule-1 (ICAM-1) is regulated by the conformation of the alphaL I domain, which is in turn controlled by the conformation and orientation of other adjacent domains. Additionally, overall integrin conformation (bent versus straightened) influences the orientation of the I domain and access to its ligands, influencing adhesive efficiency. The open or high affinity I domain conformation supports strong adhesion, whereas the closed, low affinity conformation mediates weak interactions or rolling. We have previously suggested that alphaLbeta2 can also exist on the cell surface in an intermediate affinity state. Here we have studied the adhesive properties of integrin alphaLbeta2 containing mutant I domains with intermediate affinities for ICAM-1. In an overall bent conformation, the intermediate affinity state of alphaLbeta2 is hardly detected by conventional adhesion assays, but robust adhesion is seen when an extended conformation is induced by a small molecule alpha/beta I allosteric antagonist. Intermediate affinity alphaLbeta2 supports more stable rolling than wild-type alphaLbeta2 under shear conditions. Moreover, antagonist-induced extension transforms rolling adhesion into firm adhesion in a manner reminiscent of chemokine activation of integrin alphaLbeta2. These findings suggest the relevance of intermediate affinity states of alphaLbeta2 to the transition between inactive and active states and demonstrate the importance of both I domain affinity and overall integrin conformation for cell adhesion.

Allosteric Site↗

PubMed2005

Microsomal triglyceride transfer protein lipidation and control of CD1d on antigen-presenting cells.

Microsomal triglyceride transfer protein (MTP), an endoplasmic reticulum (ER) chaperone that loads lipids onto apolipoprotein B, also regulates CD1d presentation of glycolipid antigens in the liver and intestine. We show MTP RNA and protein in antigen-presenting cells (APCs) by reverse transcription-polymerase chain reaction and by immunoblotting of mouse liver mononuclear cells and mouse and human B cell lines. Functional MTP, demonstrated by specific triglyceride transfer activity, is present in both mouse splenocytes and a CD1d-positive mouse NKT hybridoma. In a novel in vitro transfer assay, purified MTP directly transfers phospholipids, but not triglycerides, to recombinant CD1d. Chemical inhibition of MTP lipid transfer does not affect major histocompatibility complex class II presentation of ovalbumin, but considerably reduces CD1d-mediated presentation of alpha-galactosylceramide (alpha-galcer) and endogenous antigens in mouse splenic and bone marrow-derived dendritic cells (DCs), as well as in human APC lines and monocyte-derived DCs. Silencing MTP expression in the human monocyte line U937 affects CD1d function, as shown by diminished presentation of alpha-galcer. We propose that MTP acts upstream of the saposins and functions as an ER chaperone by loading endogenous lipids onto nascent CD1d. Furthermore, our studies suggest that a small molecule inhibitor could be used to modulate the activity of NKT cells.

Animals↗

PubMed2004

The primacy of affinity over clustering in regulation of adhesiveness of the integrin {alpha}L{beta}2.

Dynamic regulation of integrin adhesiveness is required for immune cell-cell interactions and leukocyte migration. Here, we investigate the relationship between cell adhesion and integrin microclustering as measured by fluorescence resonance energy transfer, and macroclustering as measured by high resolution fluorescence microscopy. Stimuli that activate adhesion through leukocyte function-associated molecule-1 (LFA-1) failed to alter clustering of LFA-1 in the absence of ligand. Binding of monomeric intercellular adhesion molecule-1 (ICAM-1) induced profound changes in the conformation of LFA-1 but did not alter clustering, whereas binding of ICAM-1 oligomers induced significant microclustering. Increased diffusivity in the membrane by cytoskeleton-disrupting agents was sufficient to drive adhesion in the absence of affinity modulation and was associated with a greater accumulation of LFA-1 to the zone of adhesion, but redistribution did not precede cell adhesion. Disruption of conformational communication within the extracellular domain of LFA-1 blocked adhesion stimulated by affinity-modulating agents, but not adhesion stimulated by cytoskeleton-disrupting agents. Thus, LFA-1 clustering does not precede ligand binding, and instead functions in adhesion strengthening after binding to multivalent ligands.

Binding, Competitive↗

PubMed2004

The binding sites for competitive antagonistic, allosteric antagonistic, and agonistic antibodies to the I domain of integrin LFA-1.

We explore the binding sites for mAbs to the alpha I domain of the integrin alphaLbeta2 that can competitively inhibit, allosterically inhibit, or activate binding to the ligand ICAM-1. Ten mAbs, some of them clinically important, were mapped to species-specific residues. The results are interpreted with independent structures of the alphaL I domain determined in seven different crystal lattices and in solution, and which are present in three conformational states that differ in affinity for ligand. Six mAbs bind to adjacent regions of the beta1-alpha1 and alpha3-alpha4 loops, which show only small (mean, 0.8 angstroms; maximum, 1.8 angstroms) displacements among the eight I domain structures. Proximity to the ligand binding site and to noncontacting portions of the ICAM-1 molecule explains competitive inhibition by these mAbs. Three mAbs bind to a segment of seven residues in the beta5-alpha6 loop and alpha6 helix, in similar proximity to the ligand binding site, but on the side opposite from the beta1-alpha1/alpha3-alpha4 epitopes, and far from noncontacting portions of ICAM-1. These residues show large displacements among the eight structures in response to lattice contacts (mean, 3.6 angstroms; maximum, 9.4 angstroms), and movement of a buried Phe in the beta5-alpha6 loop is partially correlated with affinity change at the ligand binding site. Together with a lack of proximity to noncontacting portions of ICAM-1, these observations explain variation among this group of mAbs, which can either act as competitive or allosteric antagonists. One agonistic mAb binds distant from the ligand binding site of the I domain, to residues that show little movement (mean, 0.5 angstroms; maximum, 1.0 angstroms). Agonism by this mAb is thus likely to result from altering the orientation of the I domain with respect to other domains within an intact integrin alphaLbeta2 heterodimer.

Allosteric Site↗

PubMed2004

CD1d function is regulated by microsomal triglyceride transfer protein.

CD1d is a major histocompatibility complex (MHC) class I-related molecule that functions in glycolipid antigen presentation to distinct subsets of T cells that express natural killer receptors and an invariant T-cell receptor-alpha chain (invariant NKT cells). The acquisition of glycolipid antigens by CD1d occurs, in part, in endosomes through the function of resident lipid transfer proteins, namely saposins. Here we show that microsomal triglyceride transfer protein (MTP), a protein that resides in the endoplasmic reticulum of hepatocytes and intestinal epithelial cells (IECs) and is essential for lipidation of apolipoprotein B, associates with CD1d in hepatocytes. Hepatocytes from animals in which Mttp (the gene encoding MTP) has been conditionally deleted, and IECs in which Mttp gene products have been silenced, are unable to activate invariant NKT cells. Conditional deletion of the Mttp gene in hepatocytes is associated with a redistribution of CD1d expression, and Mttp-deleted mice are resistant to immunopathologies associated with invariant NKT cell-mediated hepatitis and colitis. These studies indicate that the CD1d-regulating function of MTP in the endoplasmic reticulum is complementary to that of the saposins in endosomes in vivo.

Abetalipoproteinemia↗

PubMed2004

Intersubunit signal transmission in integrins by a receptor-like interaction with a pull spring.

The function of some multidomain proteins is regulated by interdomain communication. We use second-site suppressor cysteine mutations to test a hypothesis on how the inserted (I)-like domain in the integrin beta-subunit regulates ligand binding by the neighboring I domain in the integrin alpha-subunit [Huth, J. R., Olejniczak, E. T., Mendoza, R., Liang, H., Harris, E. A., et al. (2000) Proc. Natl. Acad. Sci. USA 97, 5231-5236; and Alonso, J. L., Essafi, M., Xiong, J. P., Stehle, T. & Arnaout, M. A. (2002) Curr. Biol. 12, R340-R342]. The hypothesis is that an interaction between the beta I-like metal ion-dependent adhesion site (MIDAS) and an intrinsic ligand in the linker following the alpha I domain, Glu-310, exerts a pull that activates the alpha I domain. Individual mutation of alpha(L) linker residue Glu-310 or beta(2) MIDAS residues Ala-210 or Tyr-115 to cysteine abolishes I domain activation, whereas the double mutation of alpha(L)-E310C with either beta(2)-A210C or beta(2)-Y115C forms a disulfide bond that constitutively activates ligand binding. The disulfide-bonded mutant is resistant to small molecule antagonists that bind to the beta I-like domain near its interface with the alpha I domain and inhibit communication between these domains but remains susceptible to small molecule antagonists that bind underneath the I domain alpha 7-helix and certain allosteric antagonistic antibodies. Thus, the alpha 7-helix and its linker are better modeled as a pull spring than a bell rope. The results suggest that alpha(L) residue Glu-310, which is universally conserved in all I domain-containing integrins, functions as an intrinsic ligand for the beta I-like domain, and that when integrins are activated, the beta I-like MIDAS binds to Glu-310, pulls the spring, and thereby activates the alpha I domain.

Animals↗

PubMed2004

Rolling adhesion through an extended conformation of integrin alphaLbeta2 and relation to alpha I and beta I-like domain interaction.

In vivo, beta(2) integrins and particularly alpha(L)beta(2) (LFA-1) robustly support firm adhesion of leukocytes, but can also cooperate with other molecules in supporting rolling adhesion. Strikingly, a small molecule alpha/beta I-like allosteric antagonist, XVA143, inhibits LFA-1-dependent firm adhesion, while at the same time it enhances adhesion in shear flow and rolling both in vitro and in vivo. XVA143 appears to induce the extended conformation of integrins as shown by increased activation epitope exposure. Fab to the beta(2) I-like domain converts firm adhesion to rolling adhesion, but does not enhance adhesion. Residue alpha(L)-Glu-310 in the linker following the I domain is critical for communication to the beta(2) I-like domain, rolling, integrin extension, and activation by Mn(2+) of firm adhesion. The results demonstrate the importance of integrin extension in rolling, and suggest that rolling and firm adhesion are mediated by extended conformations of alpha(L)beta(2) that differ in the affinity of the alpha(L) I domain for ICAM-1.

Animals↗

PubMed2003

Endothelial cells proactively form microvilli-like membrane projections upon intercellular adhesion molecule 1 engagement of leukocyte LFA-1.

Specific leukocyte/endothelial interactions are critical for immunity and inflammation, yet the molecular details of this interaction interface remain poorly understood. Thus, we investigated, with confocal microscopy, the distribution dynamics of the central adhesion molecules ICAM-1 and LFA-1 in this context. Monolayers of activated HUVECs stained with fluorescent anti-ICAM-1 Fabs or Chinese hamster ovary-K1 cells expressing ICAM-1-green fluorescent protein were allowed to bind LFA-1-bearing monocytes, neutrophils, or K562 LFA-1 transfectants. ICAM-1 was rapidly relocalized to newly formed microvilli-like membrane projections in response to binding LFA-1 on leukocytes. These ICAM-1-enriched projections encircled the leukocytes extending up their sides and clustered LFA-1 underneath into linear tracks. Projections formed independently of VCAM-1/very late Ag 4 interactions, shear, and proactive contributions from the LFA-1-bearing cells. In the ICAM-1-bearing endothelial cells, projections were enriched in actin but not microtubules, required intracellular calcium, and intact microfilament and microtubule cytoskeletons and were independent of Rho/Rho kinase signaling. Disruption of these projections with cytochalasin D, colchicine, or BAPTA-AM had no affect on firm adhesion. These data show that in response to LFA-1 engagement the endothelium proactively forms an ICAM-1-enriched cup-like structure that surrounds adherent leukocytes but is not important for firm adhesion. This finding leaves open a possible role in leukocyte transendothelial migration, which would be consistent with the geometry and kinetics of formation of the cup-like structure.

Actin Cytoskeleton↗

PubMed2003

Bistable regulation of integrin adhesiveness by a bipolar metal ion cluster.

Integrin alpha(4)beta(7) mediates rolling adhesion in Ca(2+) and Ca(2+) + Mg(2+), and firm adhesion in Mg(2+) and Mn(2+), mimicking the two key steps in leukocyte accumulation in inflamed vasculature. We mutated an interlinked linear array of three divalent cation-binding sites present in integrin beta-subunit I-like domains. The middle, metal ion-dependent adhesion site (MIDAS) is required for both rolling and firm adhesion. One polar site, that adjacent to MIDAS (ADMIDAS), is required for rolling because its mutation results in firm adhesion. The other polar site, the ligand-induced metal binding site (LIMBS), is required for firm adhesion because its mutation results in rolling. The LIMBS mediates the positive regulatory effects of low Ca(2+) concentrations, whereas the ADMIDAS mediates the negative regulatory effects of higher Ca(2+) concentrations, which are competed by Mn(2+). The bipolar sites thus stabilize two alternative phases of adhesion.

Amino Acid Sequence↗

PubMed2003

Small molecule integrin antagonists that bind to the beta2 subunit I-like domain and activate signals in one direction and block them in the other.

Leukocyte integrins contain an inserted (I) domain in their alpha subunits and an I-like domain in their beta(2) subunit, which directly bind ligand and regulate ligand binding, respectively. We describe a novel mechanistic class of integrin inhibitors that bind to the metal ion-dependent adhesion site of the beta(2) I-like domain and prevent its interaction with and activation of the alpha(L) I domain. The inhibitors do not bind to the alpha(L) I domain but stabilize alpha/beta subunit association and can show selectivity for alpha(L)beta(2) compared to alpha(M)beta(2). The inhibitors reveal a crucial intersection for relaying conformational signals within integrin extracellular domains. While blocking signals in one direction to the I domain, the antagonists induce the active conformation of the I-like domain and stalk domains, and thus transmit conformational signals in the other direction toward the transmembrane domains.

Allosteric Regulation↗

PubMed2002

Stabilizing the integrin alpha M inserted domain in alternative conformations with a range of engineered disulfide bonds.

Conformational movement of the C-terminal alpha7 helix in the integrin inserted (I) domain, a major ligand-binding domain that adopts an alpha/beta Rossmann fold, has been proposed to allosterically regulate ligand-binding activity. Disulfide bonds were engineered here to reversibly lock the position of the alpha7 helix in one of two alternative conformations seen in crystal structures, termed open and closed. Our results show that pairs of residues with Cbeta atoms farther apart than optimal for disulfide bond stereochemistry can be successfully replaced by cysteine, suggesting that backbone movement accommodates disulfide formation. We also find more success with substituting partially exposed than buried residues. Disulfides stabilizing the open conformation resulted in constitutively active alphaMbeta2 heterodimers and isolated alphaM inserted domains, which were reverted to an inactive form by dithiothreitol reduction. By contrast, a disulfide stabilizing the closed conformation resulted in inactive alphaMbeta2 that was resistant to activation but became activatable after dithiothreitol treatment.

Dimerization↗

PubMed2002

Transition from rolling to firm adhesion is regulated by the conformation of the I domain of the integrin lymphocyte function-associated antigen-1.

The integrin lymphocyte function-associated antigen-1 (alpha(L)beta(2)), which is known for its ability to mediate firm adhesion and migration, can also contribute to tethering and rolling in shear flow. The alpha(L) I domain can be mutationally locked with disulfide bonds into two distinct conformations, open and closed, which have high and low affinity for the ligand intercellular adhesion molecule 1 (ICAM-1), respectively. The wild type I domain exists primarily in the lower energy closed conformation. We have measured for the first time the effect of conformational change on adhesive behavior in shear flow. We show that wild type and locked open I domains, expressed in alpha(L)beta(2) heterodimers or as isolated domains on the cell surface, mediate rolling adhesion and firm adhesion, respectively. alpha(L)beta(2) is thus poised for the conversion of rolling to firm adhesion upon integrin activation in vivo. Isolated I domains are surprisingly more effective than alpha(L)beta(2) in interactions in shear flow, which may in part be a consequence of the presence of alpha(L)beta(2) in a bent conformation. Furthermore, the force exerted on the C-terminal alpha-helix appears to stabilize the open conformation of the wild type isolated I domain and contribute to its robustness in supporting rolling. An allosteric small molecule antagonist of alpha(L)beta(2) inhibits both rolling adhesion and firm adhesion, which has important implications for its mode of action in vivo.

Actins↗

PubMed2002

Nitric oxide supplementation ameliorates dextran sulfate sodium-induced colitis in mice.

Nitric oxide (NO) synthesis is up-regulated in inflammatory bowel disease. However, its role in the pathophysiology of this condition is controversial. The aims of this study were to assess whether nitric oxide administration ameliorates experimental colitis and to determine the possible mechanisms underlying its effects on intestinal inflammation. For this purpose, the NO donor diethylamine NONOate (DETA/NO; 0.01, 0.1, 1, 5, or 10 mg/kg/day), or the DETA moiety, was administered daily to mice with dextran sulfate sodium-induced colitis. Daily body weight and colonic pathologic alterations at Day 10 were determined. Leukocyte endothelial cell interactions in colonic venules were assessed with intravital microscopy, and expression of endothelial cell adhesion molecules was determined using radiolabeled antibodies. IL-12 and IFN-gamma production were measured in intestinal tissue. Colitis induced a significant loss of body weight, reduction of colon length, and increase in colon weight and myeloperoxidase activity. Administration of 1 mg/kg/day DETA/NO significantly attenuated these pathologic changes. The marked increase in leukocyte rolling and adhesion in colonic venules of colitic mice were significantly reduced by administration of 1 mg/kg/day DETA/NO. Development of colitis was associated with a marked increase in endothelial expression of intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and P-selectin. Supplementation with NO significantly attenuated the up-regulation of endothelial intercellular adhesion molecule-1 and P-selectin, but not vascular cell adhesion molecule-1, in colonic tissue. NO abrogated the increase in IL-12 and IFN-gamma mRNA expression in the colon of colitic mice. The DETA moiety alone did not have any effect on any of the parameters studied. In conclusion, exogenous NO supplementation significantly ameliorates dextran sulfate sodium-induced colitis. This effect is related to a reduction in leukocyte recruitment and proinflammatory cytokine production.

Animals↗

PubMed2002

The role of P-selectin in experimental colitis as determined by antibody immunoblockade and genetically deficient mice.

We assessed the effects of genetic ablation of the P-selectin gene in comparison with functional immunoblockade of P-selectin on leukocyte recruitment and the course of disease in dextran sulfate sodium-induced colitis in mice. Compared with control antibody-treated wild-type (WT) mice, WT mice treated with anti-P-selectin antibody and P-selectin(-/-) mice had significantly decreased leukocyte rolling and adhesion in colonic venules and reduced clinical and pathological colitis scores. These reductions were more pronounced in anti-P-selectin-treated than in P-selectin(-/-) mice. In colonic endothelium, up-regulation of ICAM-1 was similar in WT and P-selectin(-/-) mice, but VCAM-1 up-regulation was significantly higher in the latter group. Lung leukocyte infiltration and VCAM-1 expression were increased only in P-selectin(-/-) colitic mice. Mortality was observed only in P-selectin(-/-) mice. Therefore, ablation of P-selectin function ameliorates colitis, but this protection is attenuated in P-selectin(-/-) mice, probably due to compensatory mechanisms that involve up-regulation of other adhesion molecules such as VCAM-1.

Animals↗