Biomedical subjects

Gabriele Weitz-Schmidt

Publications and source records attributed to Gabriele Weitz-Schmidt.

14 recordsLinked to original sources

PubMed2006

Statins inhibit lymphocyte homing to peripheral lymph nodes.

Lymphocyte homing to peripheral lymph nodes is governed by adhesion molecules, including lymphocyte function-associated antigen 1 (LFA-1). Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors and exert anti-inflammatory effects, e.g. inhibition of LFA-1. It is still not known whether statin compounds are capable of inhibiting lymphocyte homing in vivo. We used a cervical lymph node preparation to study the effects of simvastatin on lymphocyte adhesion to high endothelial venules (HEVs) by means of intravital fluorescence microscopy (IVM). IVM revealed that firm adhesion of lymphocytes to HEV endothelium critically depends on the adhesive function of LFA-1. The number of firmly adherent lymphocytes was reduced by 58% in LFA-1-deficient mice (P < 0.05 versus wild-type controls). As in mutant mice, acute treatment with simvastatin (i.p. injection at 2 hr prior to IVM) inhibited the firm adhesion of lymphocytes to HEV endothelium of wild-type animals by 63% (P < 0.05 versus vehicle-treated wild-type controls). In addition, acute treatment with the synthetic statin-derivate LFA878 also reduced firm lymphocyte adhesion in HEVs by 63% (P > 0.05 versus placebo-treated controls). Histological analysis after a 10-day treatment with simvastatin showed reduced cellularity of cervical lymph nodes, as indicated by a reduction of the relative area of haematoxylin-stained cell nuclei in cervical lymph node cross-sections from 94 +/- 0% in vehicle-treated controls to 77 +/- 3% in simvastatin-treated mice (P < 0.05). We conclude that statin compounds are capable of inhibiting lymphocyte homing to murine peripheral lymph nodes in vivo. This may have novel implications for the treatment of adaptive immune responses, e.g. transplant rejection.

Animals↗

PubMed2006

Hypothesis: the antitumor activities of statins may be mediated by IL-18.

Statins, which inhibit 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase, are thought to reduce the risk of cancer through the inhibition of Ras farnesylation and serum lipid level. A pleiotropic proinflammatory cytokine, interleukin-18 (IL-18), is reported to exhibit significant antitumor activities through the activation of cytotoxic T lymphocytes and natural killer cells and the inhibition of angiogenesis. Previously, we found that pravastatin, fluvastatin, and simvastatin induced the production of IL-18 in human monocytes. The addition of mevalonate abolished the IL-18 production induced by pravastatin, fluvastatin, and simvastatin, indicating that the IL-18 production might be a result of the inhibition of HMG-CoA reductase. We present a new hypothesis that the production of IL-18 might play roles in the action of statins on cancer.

Humans↗

PubMed2005

1,4-Diazepane-2,5-diones as novel inhibitors of LFA-1.

1,4-Diazepane-2,5-diones (2) are found to be a new class of potent LFA-1 inhibitors. The synthesis, structure, and biological evaluation of these 1,4-diazepine-2,5-diones and related derivatives are described.

Heterocyclic Compounds, 4 or More Rings↗

PubMed2004

Differential effect of LFA703, pravastatin, and fluvastatin on production of IL-18 and expression of ICAM-1 and CD40 in human monocytes.

A novel, proinflammatory cytokine, interleukin (IL)-18 production was detected in the medium of human monocytes treated with 3-hydroxy-3-methylglutaryl coenzyme-A (HMG-CoA) reductase inhibitors, pravastatin, and fluvastatin (0.1 and 1 muM) but not with the statin-derived lymphocyte function-associated antigen-1 (LFA-1) inhibitor LFA703, which did not inhibit HMG-CoA reductase. Pravastatin and fluvastatin also induced the production of IL-18, tumor necrosis factor alpha (TNF-alpha) and interferon-gamma (IFN-gamma) in human peripheral blood mononuclear cells (PBMC) in contrast to LFA703. IL-18 production by PBMC is located upstream of the cytokine cascade activated by these statins. The IL-18-induced cytokine production was demonstrated to be dependent on adhesion molecule expression on monocytes. In the absence and presence of lower concentrations (0.1 and 1 ng/ml) of IL-18, pravastatin and fluvastatin inhibited the expression of intercellular adhesion molecule (ICAM)-1 and induced the expression of CD40, whereas LFA703 had no effect. In the presence of higher concentrations (5, 10, and 100 ng/ml) of IL-18, pravastatin, fluvastatin, and LFA703 similarly inhibited the expression of ICAM-1 and CD40 as well as the production of IL-12, TNF-alpha, and IFN-gamma in PBMC. The effects of pravastatin and fluvastatin but not LFA703 were abolished by the addition of mevalonate, indicating the involvement of HMG-CoA reductase in the action of pravastatin and fluvastatin. Thus, the effects of LFA703 were distinct from those of pravastatin and fluvastatin in the presence of lower concentrations of IL-18. It was concluded that LFA703 has the inhibitory effect on an IL-18-initiated immune response without any activation on monocytes.

Antibodies, Monoclonal↗

PubMed2004

Improved lymphocyte function-associated antigen-1 (LFA-1) inhibition by statin derivatives: molecular basis determined by x-ray analysis and monitoring of LFA-1 conformational changes in vitro and ex vivo.

The integrin lymphocyte function-associated antigen-1 (LFA-1) (alphaLbeta2; CD11a/CD18) plays an important role in leukocyte migration and T cell activation. LFA-1 is inhibited by the cholesterol-lowering drug lovastatin, which binds to an allosteric site of the alphaL I domain termed the lovastatin site (L-site). Here we report for the first time the x-ray structures of the LFA-1 I domain complexed with derivatives of lovastatin optimized for LFA-1 inhibition. This analysis identified two new subpockets within the L-site occupied by chemical groups of the statin derivatives but not by lovastatin itself. Occupancy of these L-site subpockets led to distinct conformational changes in LFA-1, which were detectable by an epitope-monitoring assay. We utilized this assay to demonstrate improved LFA-1 inhibition in human blood in vitro and in blood samples from treated animals ex vivo. Moreover, we demonstrate that the novel lovastatin-derived LFA-1 inhibitor LFA878 exhibits potent anti-inflammatory effects in carrageenan-induced rat paw edema. In summary, the findings reported here extend the understanding of LFA-1 inhibition at the molecular level, allow for the identification and design of LFA-1 inhibitors of further enhanced potency, and support the expectation that LFA-1 inhibitors binding to the L-site will be of therapeutic value in treating inflammatory diseases.

Animals↗

PubMed2004

Statin-derived 1,3-oxazinan-2-ones as submicromolar inhibitors of LFA-1/ICAM-1 interaction: stabilization of the metabolically labile vanillyl side chain.

Modification of the vanillyl substituent on a potent, semisynthetic lymphocyte function-associated antigen (LFA)-1/intercellular adhesion molecule (ICAM)-1 binding inhibitor of the statin family resulted in metabolically more stable analogues that displayed submicromolar inhibitory activity in vitro and considerable anti-inflammatory activity in vivo. The benzodioxole derivative 2b emerged with the best overall profile.

Animals↗

PubMed2004

Lymphocyte function antigen-1 mediates leukocyte adhesion and subsequent liver damage in endotoxemic mice.

1. Sepsis is associated with leukocyte activation and recruitment in the liver. We investigated the role of lymphocyte function antigen-1 (LFA-1) in endotoxin-induced leukocyte-endothelium interactions, microvascular perfusion failure, hepatocellular injury and apoptosis in the liver by use of gene-targeted mice, blocking antibodies and a synthetic inhibitor of LFA-1 (LFA703). For this purpose, mice were challenged with lipopolysaccharide (LPS)+D-galactosamine (Gal), and intravital microscopy of the liver microcirculation was conducted 6 h later. 2. The number of firmly adherent leukocytes in response to LPS/Gal was reduced by 48% in LFA-1-deficient mice. Moreover, endotoxin-induced increases of apoptosis and enzyme markers of hepatocellular injury were decreased by 64 and 69-90%, respectively, in LFA-1-deficient mice. Furthermore, sinusoidal perfusion was improved in endotoxemic mice lacking LFA-1. 3. A similar protective pattern was observed in endotoxemic mice pretreated with an antibody against LFA-1. Thus, immunoneutralization of LFA-1 reduced endotoxin-induced leukocyte adhesion by 55%, liver enzymes by 64-66% and apoptosis by 42%, in addition to the preservation of microvascular perfusion. 4. Administration of a novel statin-derived inhibitor of LFA-1, LFA703, significantly decreased leukocyte adhesion (more than 56%) and the subsequent liver injury in endotoxemic mice. 5. Thus, this study demonstrates a pivotal role of LFA-1 in supporting leukocyte adhesion in the liver. Moreover, interference with LFA-1-mediated leukocyte adhesion protects against endotoxemic liver damage, and may constitute a potential therapeutic strategy in sepsis.

Animals↗

PubMed2004

Pharmacodynamics in the development of new immunosuppressive drugs.

Over the past 10-20 years a number of immunosuppressive drugs, such as cyclosporine A, tacrolimus, sirolimus, or mycophenolate mofetil have been approved for clinical use and have been highly successful in preventing or delaying graft rejection. Nevertheless, there is an incessant need for better and safer drugs to improve short-term and long-term outcomes following transplantation. A number of low-molecular-weight molecules that interfere with immune cell functions are in development. These include molecules that inhibit the janus protein tyrosine kinase JAK3, compounds that alter lymphocyte trafficking (the sphingosine-1-phosphate receptor antagonist FTY720), and new malononitrilamides (FK778). All seem to show promising therapeutic potential. Among the biologic agents, there are high expectations for antibodies or recombinant chimeric molecules targeting costimulatory surface molecules or pathways involved in the migration of immune cells. The list of such targets includes the ligand pairs CD28:B7, CD154:CD40, LFA-1:ICAM-1, ICOS:B7RP-1, and VLA-4:VCAM-1. However, the clinical development of drugs for transplantation has proved to be difficult, complex, and time consuming. Therefore, newly emerging drug candidates will also demand better methods for monitoring their efficacy as well as their side effects in vivo. Pharmacokinetics (PK) and pharmacodynamics (PD) are complementary approaches used to select drugs on the basis of their in vivo efficacy as well as safety. Whereas PK monitors the handling of the drug by the body, PD focuses on the biologic effect of the drug on its target. Therefore, PD studies of in vivo efficacy are useful for clinical decisions to determine the optimal dose and type of immunosuppressant. At the preclinical stage, PD is aimed at accelerating the selection of lead compounds via PD-controlled trials in animals. Moreover, PD can help to discover new mechanisms of action for a drug or a drug candidate. However, its full potential has not been used, mainly because of laborious and time-consuming methodology. This review focuses on established and novel PD/PK approaches to assess immunosuppressive compounds in the context of new evolving drugs or drug combinations.

Animals↗

PubMed2003

A statin-based inhibitor of lymphocyte function antigen-1 protects against ischemia/reperfusion-induced leukocyte adhesion in the colon.

1. Statins are mainly used to control hypercholesterolemia; however, recent studies have also ascribed anti-inflammatory effects to the statins. LFA703 is a novel statin-derived compound, which potently inhibits lymphocyte function antigen-1 (LFA-1, CD11a/CD18) but does not affect HMG-CoA reductase activity. 2. The objective of this study was to examine the anti-inflammatory mechanisms of LFA703 in ischemia/reperfusion (I/R)-induced leukocyte-endothelium interactions in the colon. For this purpose, the superior mesenteric artery was occluded for 30 min and leukocyte responses were analyzed in colonic venules after 120 min of reperfusion in mice using inverted intravital fluorescence microscopy. 3. First, the inhibitory mechanisms of LFA703 on leukocyte adhesion were investigated in vitro using a mouse CD4+8+ thymocyte cell line. Immunoneutralization of LFA-1 and ICAM-1 abolished leukocyte adhesion, whereas inhibition of VLA-4 had no effect in this in vitro assay. Indeed, it was found that LFA703 dose-dependently reduced LFA-1-dependent leukocyte adhesion to mouse endothelial cells in vitro with an IC50 of 3.2 microm. 4. I/R caused an increase in leukocyte rolling and adhesion in colonic venules. Immunoneutralization of LFA-1 significantly reduced I/R-induced leukocyte adhesion by 89% in colonic venules. In contrast, I/R-provoked leukocyte rolling was insensitive to inhibition of LFA-1 function. 5. Administration of 30 mg kg-1 of LFA703 decreased reperfusion-induced leukocyte adhesion by more than 91%, while the level of leukocyte rolling was unchanged, suggesting that LFA703 effectively blocked LFA-1-dependent firm adhesion of leukocyte in the colon. However, LFA703 did not decrease the expression of LFA-1 on circulating leukocytes. 6. This study demonstrates that LFA-1 is indeed a critical adhesion molecule in mediating postischemic leukocyte adhesion in the colon. Moreover, this is the first study showing that a statin-based synthetic compound has the capacity to abolish LFA-1-dependent leukocyte adhesion in I/R. These novel findings may have great implications in the clinical treatment of conditions associated with I/R-induced tissue injury, such as organ transplantation, trauma and major surgery.

Animals↗

PubMed2003

1,4-Diazepane-2-ones as novel inhibitors of LFA-1.

The design, synthesis, and biological evaluation of 1,4-diazepane-2-ones as novel LFA-1 antagonists from a scaffold-based combinatorial library are described. Initial optimization of the library lead has resulted in high-affinity antagonists of the LFA-1/ICAM-1 interaction, such as compounds 18d and 18e with IC(50) values of 110 and 70 nM, respectively.

Cell-Free System↗

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↗

PubMed2003

Lymphocyte function-associated antigen-1 blockade by statins: molecular basis and biological relevance.

Lymphocyte function-associated antigen-1 (LFA-1) belongs to the integrin family and plays an important role in leukocyte trafficking and in T-cell activation. Random screening of chemical libraries identified the 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor lovastatin as an inhibitor of the LFA-1/intercellular adhesion molecule (ICAM)-1 interaction. The effect of lovastatin on LFA-1 was found to be unrelated to the inhibition of HMG-CoA reductase and to be mediated by lovastatin binding to a novel allosteric site within LFA-1. The biological relevance of LFA-1 inhibition by statins with respect to the overall benefit of this drug class is reviewed. The implications of the statin effect on LFA-1 for future drug design and therapy are discussed.

Adjuvants, Immunologic↗

PubMed2002

Small molecule inhibitors induce conformational changes in the I domain and the I-like domain of lymphocyte function-associated antigen-1. Molecular insights into integrin inhibition.

The beta(2) integrin lymphocyte function-associated antigen-1 (LFA-1) is a conformationally flexible alpha/beta heterodimeric receptor, which is expressed on the surface of all leukocytes. LFA-1 mediates cell adhesion crucial for normal immune and inflammatory responses. Intracellular signals or cations are required to convert LFA-1 from a nonligand binding to a ligand binding state. Here we investigated the effect of small molecule inhibitors on LFA-1 by monitoring the binding of monoclonal antibodies mapped to different receptor domains. The inhibitors were found to not only induce epitope changes in the I domain of the alpha(L) chain but also in the I-like domain of the beta(2) chain depending on the individual chemical structure of the inhibitor and its binding site. For the first time, we provide strong evidence that the I-like domain represents a target for allosteric LFA-1 inhibition similar to the well established regulatory L-site on the I domain of LFA-1. Moreover, the antibody binding patterns observed in the presence of the various inhibitors establish a conformational interaction between the LFA-1 I domain and the I-like domain in the native receptor that is formed upon activation. Differentially targeting the binding sites of the inhibitors, the L-site and the I-like domain, may open new avenues for highly specific therapeutic intervention in diseases where integrins play a pathophysiological role.

Allosteric Site↗

PubMed2002

Statins as anti-inflammatory agents.

The beneficial effects of 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors (statins) in cardiovascular disease have generally been attributed to their cholesterol-lowering property. However, an increasing number of in vitro and in vivo studies indicate that statins have direct anti-inflammatory effects that are not mediated by their hypocholesterolemic activity. In this article, the HMG-CoA-reductase-dependent and -independent mechanisms by which statins might affect leukocyte adhesion and migration to sites of inflammation are reviewed and the implications for the design of new statin-derived drugs are discussed.

Animals↗