Biomedical subjects

Lars Karlsson

Publications and source records attributed to Lars Karlsson.

31 records · Page 2Linked to original sources

PubMed2004

A potent and selective histamine H4 receptor antagonist with anti-inflammatory properties.

Histamine mediates its physiological function through binding to four known histamine receptors. Here, we describe the first selective antagonist of the histamine H4 receptor, the newest member of the histamine receptor family, and provide evidence that such antagonists have anti-inflammatory activity in vivo. 1-[(5-chloro-1H-indol-2-yl)carbonyl]-4-methylpiperazine (JNJ 7777120) has a K(i) of 4.5 nM versus the human receptor and a pA(2) of 8.1. It is equipotent against the human, mouse, and rat receptors. It exhibits at least 1000-fold selectivity over H1, H2, or H3 receptors and has no cross-reactivity against 50 other targets. This compound has an oral bioavailability of approximately 30% in rats and 100% in dogs, with a half-life of approximately 3 h in both species. JNJ 7777120 blocks histamine-induced chemotaxis and calcium influx in mouse bone marrow-derived mast cells. In addition, it can block the histamine-induced migration of tracheal mast cells from the connective tissue toward the epithelium in mice. JNJ 7777120 significantly blocks neutrophil infiltration in a mouse zymosan-induced peritonitis model. This model is reported to be mast cell-dependent, which suggests that the compound effect may be mediated by mast cells. These results indicate that the histamine H4 receptor plays a role in the inflammatory process. Selective H4 receptor antagonists like JNJ 7777120 may have the potential to be useful in treating inflammation in humans.

Animals↗

PubMed2004

Histamine H4 receptor mediates eosinophil chemotaxis with cell shape change and adhesion molecule upregulation.

1. During mast cell degranulation, histamine is released in large quantities. Human eosinophils were found to express histamine H(4) but not H(3) receptors. The possible effects of histamine on eosinophils and the receptor mediating these effects were investigated in our studies. 2. Histamine (0.01-30 microm) induced a rapid and transient cell shape change in human eosinophils, but had no effects on neutrophils. The maximal shape change was at 0.3 microm histamine with EC(50) at 19 nm. After 60 min incubation with 1 microm histamine, eosinophils were desensitized and were refractory to shape change response upon histamine restimulation. Histamine (0.01-1 microm) also enhanced the eosinophil shape change induced by other chemokines. 3. Histamine-induced eosinophil shape change was mediated by the H(4) receptor. This effect was completely inhibited by H(4) receptor-specific antagonist JNJ 7777120 (IC(50) 0.3 microm) and H(3)/H(4) receptor antagonist thioperamide (IC(50) 1.4 microm), but not by selective H(1), H(2) or H(3) receptor antagonists. H(4) receptor agonists imetit (EC(50) 25 nm) and clobenpropit (EC(50) 72 nm) could mimic histamine effect in inducing eosinophil shape change. 4. Histamine (0.01-100 microm) induced upregulation of adhesion molecules CD11b/CD18 (Mac-1) and CD54 (ICAM-1) on eosinophils. This effect was mediated by the H(4) receptor and could be blocked by H(4) receptor antagonists JNJ 7777120 and thioperamide. 5. Histamine (0.01-10 microm) induced eosinophil chemotaxis with an EC(50) of 83 nm. This effect was mediated by the H(4) receptor and could be blocked by H(4) receptor antagonists JNJ 7777120 (IC(50) 86 nm) and thioperamide (IC(50) 519 nm). Histamine (0.5 microm) also enhanced the eosinophil shape change induced by other chemokines. 6. In conclusion, we have demonstrated a new mechanism of eosinophil recruitment driven by mast cells via the release of histamine. Using specific histamine receptor ligands, we have provided a definitive proof that the H(4) receptor mediates eosinophil chemotaxis, cell shape change and upregulation of adhesion molecules. The effect of H(4) receptor antagonists in blocking eosinophil infiltration could be valuable for the treatment of allergic diseases. The histamine-induced shape change and upregulation of adhesion molecules on eosinophils can serve as biomarkers for clinical studies of H(4) receptor antagonists.

Cell Adhesion Molecules↗

PubMed2004

Histamine H4 receptor antagonists: the new antihistamines?

Antihistamines (histamine H1 receptor antagonists) are a mainstay treatment for atopic allergy, yet they are only partially effective in relieving the symptoms of the disease. They also have very limited value for the treatment of asthma, despite the well-characterized bronchoconstrictory effects of histamine. The recent discovery of a fourth histamine receptor (H4), and the realization that it is exclusively expressed on hematopoietic cell types that are most implicated in the development and symptomatology of allergy and asthma, suggests that pharmacological targeting of the H4 receptor, either alone or in combination with H1 receptor antagonists, may prove useful for treating both allergy and asthma. Here we review the known biology associated with the H4 receptor, as well the effects of a highly selective H1 receptor antagonist.

Animals↗

PubMed2003

Identification of a potent and selective noncovalent cathepsin S inhibitor.

Cathepsin S is considered crucial for normal presentation of major histocompatibility complex (MHC) class II-restricted antigens by antigen presenting cells to CD4+ T cells. It is a key enzyme for the degradation of the class II-associated invariant chain, a process that is required for effective antigen loading of class II molecules. Here, we report a selective, orally available, high-affinity cathepsin S inhibitor, 1-[3-[4-(6-Chloro-2,3-dihydro-3-methyl-2-oxo-1H-benzimidazol-1-yl)-1-piperidinyl]propyl]-4,5,6,7-tetrahydro-5-(methylsulfonyl)-3-[4-(trifluoromethyl)phenyl]-1H-pyrazolo[4,3-c]pyridine. (JNJ 10329670), that represents a novel class of immunosuppressive compounds. JNJ 10329670 is a highly potent (Ki of approximately 30 nM), nonpeptidic, noncovalent inhibitor of human cathepsin S, but it is much less active against the mouse, dog, monkey, and bovine enzymes. The compound is inactive against other proteases, including the closely related cathepsins L, F, and K. This selectivity makes JNJ 10329670 an excellent tool for exploring the role of cathepsin S in human systems. Treatment of human B cell lines and primary human dendritic cells with JNJ 10329670 resulted in the accumulation of the p10 fragment of the invariant chain (IC50 of approximately 1 microM). In contrast, inhibition of invariant chain proteolysis was much less effective in a human monocytic cell line, suggesting that other enzymes may degrade the invariant chain in this cell type. JNJ 10329670 was shown to block the proteolysis of the invariant chain in vivo by using immunocompromised mice injected with human peripheral blood mononuclear cells (PBMCs). Furthermore, this inhibitor blocks the presentation of tetanus toxoid and giant ragweed by human PBMCs. The properties of JNJ 10329670 make it a candidate for immunosuppressive therapy of allergies and autoimmune diseases.

Animals↗

PubMed2003

The first potent and selective non-imidazole human histamine H4 receptor antagonists.

Following the discovery of the human histamine H4 receptor, a high throughput screen of our corporate compound collection identified compound 6 as a potential lead. Investigation of the SAR resulted in the discovery of novel compounds 10e and 10l, which are the first potent and selective histamine H4 receptor antagonists to be described.

Animals↗

PubMed2003

Analysis of H2-O influence on antigen presentation by B cells.

HLA-DM (DM; in mouse H2-DM) promotes the exchange of MHC class II-associated peptides, resulting in the accumulation of stable MHC class II-peptide complexes. In naive (but not germinal center) B cells, a large part of DM is tightly associated with HLA-DO (DO; in mouse H2-O), but the functional consequence of this association for Ag presentation is debated. Here, we have extended previous studies by examining the presentation of multiple epitopes after Ag internalization by fluid phase endocytosis or receptor-mediated uptake by membrane Ig (mIg) receptors. We find that the effects of H2-O are more complex than previously appreciated; thus, while only minor influences on Ag presentation could be detected after fluid phase uptake, many epitopes were substantially affected after mIg-mediated uptake. Unexpectedly, the presentation of different epitopes was found to be enhanced, diminished, or unaffected in the absence of H2-O, depending on the specificity of the mIg used for Ag internalization. Interestingly, epitopes from the same Ag did not necessarily show the same H2-O dependency. This finding suggests that H2-O may control the repertoire of peptides presented by B cells depending on the mIg-Ag interaction. The absence of DO/H2-O from germinal center B cells suggests that this control may be released during B cell maturation.

Animals↗

PubMed2003

Catalytic activity of ADAM8, ADAM15, and MDC-L (ADAM28) on synthetic peptide substrates and in ectodomain cleavage of CD23.

The ADAM family of disintegrin metalloproteases plays important roles in "ectodomain shedding," the process by which biologically active, soluble forms of cytokines, growth factors, and their receptors are released from membrane-bound precursors. Whereas ADAM8, ADAM15, and MDC-L (ADAM28) are expressed in specific cell types and tissues, their in vivo functions and substrates are not known. By screening a library of synthetic peptides as potential substrates, we show that soluble recombinant forms of these enzymes have similar proteolytic substrate specificity, clearly distinct from that of ADAM17 (TNFalpha-converting enzyme). A number of tumor necrosis factor (TNF) family proteins and CD23 were screened as potential substrates for ectodomain cleavage. We found that ADAM8, ADAM15, and MDC-L, but not ADAM17, catalyzed ectodomain shedding of CD23, the low affinity IgE receptor. ADAM8-dependent, soluble CD23 release required proteolytically active ADAM8, and a physical association of ADAM8 was observed with the membrane-bound form of CD23. The ADAM8-dependent release of sCD23 and the endogenous release from B cell lines could be similarly inhibited by a hydroxamic acid, metalloprotease inhibitor compound. We conclude that ADAM8 could contribute to ectodomain shedding of CD23 and may thus be a potential target for therapeutic intervention in allergy and inflammation.

ADAM Proteins↗

PubMed2003

H2-O influence on antigen presentation in H2-E-expressing mice.

MHC class II molecules sample peptides generated in the endosomal/lysosomal system for cell surface presentation to CD4+ T cells. Peptide loading requires the endosomal/lysosomal resident HLA-DM (DM; H2-DM, mouse), but in B cells, DM is tightly associated with HLA-DO (DO; H2-O, mouse). We have previously shown that H2-O differentially modulates the processing and presentation of different antigenic epitopes on H2-Ab molecules. Using H2-Ead-transgenic mice, we here show that presentation of different epitopes by H2-Ed/b molecules is similarly influenced by H2-O after membrane immunoglobulin-mediated uptake of antigen. In addition, B cells from H2-Ead-transgenic mice (which co-express H2-Ab and H2-Ed/b molecules) show an altered pattern of presentation of H2-Ab-restricted epitopes. In H2-Ead-transgenic, H2-O-deficient mice, further changes in the peptide repertoire were observed. Thus, H2-Ed/b expression influences the epitopes presented by H2-Ab, and this effect is further altered by expression of H2-O.

Animals↗

PubMed2003

An application of a muscle model to study electromyographic signals.

A simulation program for research and teaching electromyography (EMG) has been developed. It has a great number of parameters that may be optionally changed in simulations of normal and diseased muscle. The simulator is user-friendly and fast and can actually be run without much help from the manual. It is easy to introduce new motor units (MU), to change MU and individual muscle fibre parameters, to insert an EMG electrode and to change its position. The model allows simulation of the most common pathological situations. The resulting signals are displayed in a conventional form. The generated EMG signals obtained with the three electrodes that have been used so far are reasonably similar to the signals obtained in real recordings. A few shortcomings in simulating, e.g. end plate zone and abnormal volume conduction characteristics do not seem to influence the principal results. The simulator can, therefore, be used in teaching and even for research.

Electromyography↗

PubMed2003

Cloning, expression, purification, and activity of dog (Canis familiaris) and monkey (Saimiri boliviensis) cathepsin S.

Cathepsin S is the key protease responsible for the removal of the invariant chain from MHC class II molecules and, as such, has attracted much attention as a target for developing immunosuppressive drugs. To help in testing candidate compounds, the monkey (Saimiri boliviensis) and dog (Canis familiaris) cathepsin S cDNAs have been cloned. The monkey cDNA sequence encodes a 330 amino acid protein with 95% homology to human cathepsin S. The dog cDNA sequence encodes a 331 amino acid protein with 91% homology to human cathepsin S. The amino acid differences do not have a major effect on the hydrolysis of the substrate Z-VVR-AMC, but may affect the substrate specificity. As for human and bovine cathepsin S, activity against Z-VVR-AMC extends into the neutral pH range. These parameters are important for understanding the role of cathepsin S in different species and for testing inhibitors in animal models of autoimmunity.

Amino Acid Sequence↗

PubMed2002

Regulated expression of human histocompatibility leukocyte antigen (HLA)-DO during antigen-dependent and antigen-independent phases of B cell development.

Human histocompatibility leukocyte antigen (HLA)-DO, a lysosomal resident major histocompatibility complex class II molecule expressed in B cells, has previously been shown to be a negative regulator of HLA-DM peptide loading function. We analyze the expression of DO in human peripheral blood, lymph node, tonsil, and bone marrow to determine if DO expression is modulated in the physiological setting. B cells, but not monocytes or monocyte-derived dendritic cells, are observed to express this protein. Preclearing experiments demonstrate that approximately 50% of HLA-DM is bound to DO in peripheral blood B cells. HLA-DM and HLA-DR expression is demonstrated early in B cell development, beginning at the pro-B stage in adult human bone marrow. In contrast, DO expression is initiated only after B cell development is complete. In all situations, there is a striking correlation between intracellular DO expression and cell surface class II-associated invariant chain peptide expression, which suggests that DO substantially inhibits DM function in primary human B cells. We report that the expression of DO is markedly downmodulated in human germinal center B cells. Modulation of DO expression may provide a mechanism to regulate peptide loading activity and antigen presentation by B cells during the development of humoral immune responses.

Adult↗

PubMed2002

Development and validation of a capillary electrophoresis method for ximelagatran assay and related substance determination in drug substance and tablets.

The advantages of simplicity, selectivity, versatility and ease of use of free solution capillary electrophoresis (CE) present an orthogonal and complementary separation technique to the established methods of liquid chromatography (LC) for pharmaceutical analysis. This work presents the development and performance of a suitable CE method for ximelagatran (formerly H 376/95) assay and related substance determination in both drug substance and tablets. The method employed was a low pH phosphate buffer, to which acetonitrile and hydroxypropyl-beta-cyclodextrin were added, in order to facilitate the separation of ximelagatran and its related substances. An applied field of 350 V/cm was used and all compounds were resolved in approximately 20 min. Benzamidine hydrochloride was used as an internal standard in quantification. The data indicate that the performance of the validated method offers equivalent and complementary information, in terms of selectivity, sensitivity, accuracy, linearity and precision, to that of an established gradient LC method employed for similar purposes. Robustness of the method was investigated by experimental design and evaluated using multivariate calculations.

Anticoagulants↗

PubMedDate not supplied

A family with abdominal aortic aneurysms.

This investigation focused on 7 siblings to 2 brothers with abdominal aortic aneurysm (AAA), with respect to AAA, Chlamydia pneumoniae (CP) serology, serum cholesterol, and smoking habits. Five male and 4 female siblings were included. All siblings underwent ultrasonography, and surgical specimens from the aorta were prepared for immunohistochemical (IHC) analysis. Blood was obtained from all living siblings and serum cholesterol level was analyzed. Serologic analysis was done by microimmunofluorescence (MIF). Smoking habits were recorded. In addition to the 2 known siblings with AAA, 2 other brothers with AAA were found. Four of 8 siblings had IgG 1/512 or greater and 7 of 8 had IgA 1/64 or greater. Two of 3 were positive for CP in IHC obtained from aortic specimens. Two of 8 had hypercholesterolemia; 7 of 9 were smokers. C. pneumoniae as well as smoking seems to be important in the pathogenesis of AAA in this small cohort; however, larger patient cohorts are needed.

Aged↗