IκB kinase inhibition as a potential treatment of osteoarthritis - results of a clinical proof-of-concept study.

OBJECTIVE: This publication summarizes the clinical development of the compound SAR113945, an IκB kinase inhibitor injected intra-articularly in a slow-release formulation to treat patients with symptomatic osteoarthritis (OA) of the knee. RESULTS: In vitro experiments demonstrated a specific inhibition of the IκB kinase complex. Profiling of SAR113945 on kinases, enzymes and ion channels supported the initiation of a clinical development. Cellular assay systems also revealed an inhibition in the synthesis of interleukin 1ß, tumor necrosis factor α (TNFα) and the prostaglandin E2 (PGE2). In vivo studies demonstrated positive effects of SAR113945 on thermal and mechanical hyperalgesia and even showed superiority in comparison with triamcinolone. Pharmacokinetic measurements showed a sustained release of dissolved SAR113945 locally supporting a comparably high exposure in the knee joint combined with a low systemic exposure. Three phase 1 studies with a dose-escalating design confirmed safety and tolerability of SAR113945. In those studies SAR113945 showed a positive trend on the WOMAC scores. The proof-of-concept or phase 2a study failed to show any effect in the overall group of recruited study participants for the primary endpoint, the WOMAC pain subscore at day 56, but showed a statistically significant difference in a subgroup of patients who had presented with effusion at baseline. CONCLUSION: Inhibiting the NFκB signaling pathway is an attractive method to treat patients with signs and symptoms of OA. The preclinical work and the results of the phase 1 studies appeared promising for a full clinical development, however, the proof-of-concept study failed to show efficacy in a larger patient sample size.

IL-1beta, but not BMP-7 leads to a dramatic change in the gene expression pattern of human adult articular chondrocytes--portraying the gene expression pattern in two donors.

Anabolic and catabolic cytokines and growth factors such as BMP-7 and IL-1beta play a central role in controlling the balance between degradation and repair of normal and (osteo)arthritic articular cartilage matrix. In this report, we investigated the response of articular chondrocytes to these factors IL-1beta and BMP-7 in terms of changes in gene expression levels. Large scale analysis was performed on primary human adult articular chondrocytes isolated from two human, independent donors cultured in alginate beads (non-stimulated and stimulated with IL-1beta and BMP-7 for 48 h) using Affymetrix gene chips (oligo-arrays). Biostatistical and bioinformatic evaluation of gene expression pattern was performed using the Resolver software (Rosetta). Part of the results were confirmed using real-time PCR. IL-1beta modulated significantly 909 out of 3459 genes detectable, whereas BMP-7 influenced only 36 out of 3440. BMP-7 induced mainly anabolic activation of chondrocytes including classical target genes such as collagen type II and aggrecan, while IL-1beta, both, significantly modulated the gene expression levels of numerous genes; namely, IL-1beta down-regulated the expression of anabolic genes and induced catabolic genes and mediators. Our data indicate that BMP-7 has only a limited effect on differentiated cells, whereas IL-1beta causes a dramatic change in gene expression pattern, i.e. induced or repressed much more genes. This presumably reflects the fact that BMP-7 signaling is effected via one pathway only (i.e. Smad-pathway) whereas IL-1beta is able to signal via a broad variety of intracellular signaling cascades involving the JNK, p38, NFkB and Erk pathways and even influencing BMP signaling.

Comparison of the chondrosarcoma cell line SW1353 with primary human adult articular chondrocytes with regard to their gene expression profile and reactivity to IL-1beta.

OBJECTIVE: In this study, the human chondrosarcoma cell line SW1353 was investigated by gene expression analysis in order to validate it as an in vitro model for primary human (adult articular) chondrocytes (PHCs). METHODS: PHCs and SW1353 cells were cultured as high density monolayer cultures with and without 1ng/ml interleukin-1beta (IL-1beta). RNA was isolated and assayed using a custom-made oligonucleotide microarray representing 312 chondrocyte-relevant genes. The expression levels of selected genes were confirmed by real-time polymerase chain reaction and the gene expression profiles of the two cell types, both with and without IL-1beta treatment, were compared. RESULTS: Overall, gene expression profiling showed only very limited similarities between SW1353 cells and PHCs at the transcriptional level. Similarities were predominantly seen with respect to catabolic effects after IL-1beta treatment. In both cell systems matrix metalloproteinase-1 (MMP-1), MMP-3 and MMP-13 were strongly induced by IL-1beta, without significant induction of MMP-2. IL-6 was also found to be up-regulated by IL-1beta in both cellular models. On the other hand, intercellular mediators such as leukemia inhibitory factor (LIF) and bone morphogenetic protein-2 (BMP-2) were not induced by IL-1beta in SW1353 cells, but significantly up-regulated in PHCs. Bioinformatical analysis identified nuclear factor kappa-B (NFkappaB) as a common transcriptional regulator of IL-1beta induced genes in both SW1353 cells and PHCs, whereas other transcription factors were only found to be relevant for individual cell systems. CONCLUSION: Our data characterize SW1353 cells as a cell line with only a very limited potential to mimic PHCs, though SW1353 cells can be of value to study the induction of protease expression within cells, a phenomenon also seen in chondrocytes.

Molecular phenotyping of HCS-2/8 cells as an in vitro model of human chondrocytes.

OBJECTIVE: Cultures of primary articular chondrocytes for studying chondrocyte biology are notoriously difficult to handle. One alternative is the use of chondrocytic cell lines. Because the HCS-2/8 cells are the most widely used cell line in cartilage research, we investigated the molecular phenotype of these cells by mRNA-expression profiling. DESIGN: Monolayers of HCS-2/8 cells were cultured to sub-confluence, confluence and over-confluence; primary human chondrocytes were grown in monolayer culture and alginate-bead cultures and several other chondrocytic cell lines were cultured as monolayers. RNA was isolated and analyzed by cDNA array profiling using Affymetrix GeneChips (U95A/U95Av2) and quantitative PCR. RESULTS: Important similarities, but also remarkable differences between the HCS-2/8 cells and adult human articular chondrocytes were detected: Aggrecan and several cartilage typical collagens as well as SOX9 transcripts were strongly expressed in HCS-2/8 cells, whereas HCS-2/8 cells expressed hardly any chondrocyte-typical cartilage matrix degrading enzymes. Of all culturing conditions, clustering analysis showed that HCS-2/8 cultured at confluence are most closely related to primary chondrocytes. CONCLUSION: Our study confirms how careful one needs to be in choosing in vitro model systems for investigating effects of interest. The major issue of chondrocyte cell lines appears to be that they mainly proliferate and show less expression of genes of matrix synthesis and turnover. A successful approach will have to select suitable chondrocyte cell lines and to validate findings obtained using primary chondrocytes. This allows to establish a reproducible in vitro model showing the property of interest and subsequently to relate back the obtained results to the physiologic situation.

A developmentally regulated aconitase related to iron-regulatory protein-1 is localized in the cytoplasm and in the mitochondrion of Trypanosoma brucei.

Mitochondrial energy metabolism and Krebs cycle activities are developmentally regulated in the life cycle of the protozoan parasite Trypanosoma brucei. Here we report cloning of a T. brucei aconitase gene that is closely related to mammalian iron-regulatory protein 1 (IRP-1) and plant aconitases. Kinetic analysis of purified recombinant TbACO expressed in Escherichia coli resulted in a K(m) (isocitrate) of 3 +/- 0.4 mM, similar to aconitases of other organisms. This was unexpected since an arginine conserved in the aconitase protein family and crucial for substrate positioning in the catalytic center and for activity of pig mitochondrial aconitase (Zheng, L., Kennedy, M. C., Beinert, H., and Zalkin, H. (1992) J. Biol. Chem. 267, 7895-7903) is substituted by leucine in the TbACO sequence. Expression of the 98-kDa TbACO was shown to be lowest in the slender bloodstream stage of the parasite, 8-fold elevated in the stumpy stage, and increased a further 4-fold in the procyclic stage. The differential expression of TbACO protein contrasted with only minor changes in TbACO mRNA, indicating translational or post-translational mechanisms of regulation. Whereas animal cells express two distinct compartmentalized aconitases, mitochondrial aconitase and cytoplasmic aconitase/IRP-1, TbACO accounts for total aconitase activity in trypanosomes. By cell fractionation and immunofluorescence microscopy, we show that native as well as a transfected epitope-tagged TbACO localizes in both the mitochondrion (30%) and in the cytoplasm (70%). Together with phylogenetic reconstructions of the aconitase family, this suggests that animal IRPs have evolved from a multicompartmentalized ancestral aconitase. The possible functions of a cytoplasmic aconitase in trypanosomes are discussed.

An in vitro-differentiated human cell line as a model system to study the interaction of Neisseria gonorrhoeae with phagocytic cells.

The extreme host specificity of pathogenic neisseriae limits investigations aimed at the analysis of bacterial-host interactions almost completely to the use of in vitro models. Although permanent epithelial and endothelial cell lines are already indispensable tools with respect to initial infection processes, studies concerning the interaction of neisseriae with phagocytic cells have been confined to primary human blood cells. We investigated the use of human leukemia-derived monocytic and myelomonocytic cell lines that can be differentiated in vitro towards phagocytic cells by a panel of chemical and biological reagents including cytokines, vitamin analogs, and antileukemia drugs. Whereas tumor necrosis factor alpha, gamma interferon, bufalin, or granulocyte-macrophage colony-stimulating factor only marginally increased the ability of monocytic MonoMac-6 and myelomonocytic JOSK-M cells to interact with the bacteria, retinoic acid and vitamin D3 treatment for 2 to 4 days led to highly phagocytic cells that internalized gonococci in an Opa protein-specific manner. This is comparable to the phagocytosis by primary monocytes from human blood, where more than 80% of cells are infected with intracellular bacteria. The increased phagocytic activity of JOSK-M cells following in vitro differentiation was paralleled by enhanced oxidative burst capacity. Whereas undifferentiated cells responded to neither phorbol 12-myristate 13-acetate nor other known soluble and particulate stimuli, cells incubated with retinoic acid and bufalin showed the same pattern and the same intensity of oxidative burst activity in response to Neisseria gonorrhoeae as primary cells: Opa-expressing gonococci elicited an oxidative burst, whereas Opa- gonococci did not. The surface expression of major histocompatibility complex (MHC) class II molecules was only slightly changed after retinoic acid treatment. Also, phagocytosis of gonococci had no influence on MHC class II surface expression. Taken together, our results demonstrate that in vitro-differentiated human myelomonocytic JOSK-M cells provide a suitable model for the study of a variety of aspects of the gonococcal interaction with phagocytes.