Targeting tumor necrosis factor-alpha in inflammatory bowel disease: why, how, and when?

Identification of heme oxygenase-1 stimulators by a convenient ELISA-based bilirubin quantification assay

The upregulation of heme oxygenase-1 (HO-1) has proven to be a useful tool for fighting inflammation. In order to identify new HO-1 inducers, an efficient screening method was developed which can provide new lead structures for drug research. We designed a simple ELISA-based HO-1 enzyme activity assay, which allows for the screening of 12 compounds in parallel in the setting of a 96-well plate. The well-established murine macrophage cell line RAW264.7 is used and only about 26µg of protein from whole cell lysates is needed for the analysis of HO-1 activity. The quantification of HO-1 activity is based on an indirect ELISA using the specific anti-bilirubin antibody 24G7 to quantify directly bilirubin in the whole cell lysate, applying a horseradish peroxidase-tagged antibody together with ortho-phenylenediamine and H2O2 for detection. The bilirubin is produced on the action of HO enzymes by converting their substrate heme to biliverdin and additional recombinant biliverdin reductase together with NADPH at pH 7.4 in buffer. This sensitive assay allows for the detection of 0.57-82pmol bilirubin per sample in whole cell lysates. Twenty-three small molecules, mainly natural products with an α,β-unsaturated carbonyl unit such as polyphenols, including flavonoids and chalcones, terpenes, an isothiocyanate, and the drug oltipraz were tested at typically 6 or 24h incubation with RAW264.7 cells. The activity of known HO-1 inducers was confirmed, while the chalcones cardamonin, flavokawain A, calythropsin, 2',3,4'-trihydroxy-4-methoxychalcone (THMC), and 2',4'-dihydroxy-3,4-dimethoxychalcone (DHDMC) were identified as new potent HO-1 inducers. The highest inductive power after 6h incubation was found at 10µM for DHDMC (6.1-fold), carnosol (3.9-fold), butein (3.1-fold), THMC (2.9-fold), and zerumbone (2.5-fold). Moreover, the time dependence of HO-1 protein production for DHDMC was compared to its enzyme activity, which was further evaluated in the presence of lipopolysaccharide and the specific HO-1 inhibitor tin protoporphyrin IX. Taken together, we developed a convenient and highly sensitive ELISA-based HO-1 enzyme activity assay, allowing the identification and characterization of molecules potentially useful for the treatment of inflammatory and autoimmune diseases.

A pilot study of leukocytapheresis efficacy with 1.5 liter blood processing volume in patients with ulcerative colitis

Standard leukocytapheresis (LCAP) protocols recommend the processing of a 3 L blood volume. In this study, we evaluated the clinical effects of LCAP with 1.5 L of blood processing (1.5L-LCAP) in patients with active ulcerative colitis (UC). Ten patients with moderate to severe UC were enrolled. Their clinical and endoscopic responses, the kinetics of the peripheral blood counts and cytokine responses were evaluated. Clinical and endoscopic effects were assessed using the clinical activity index described by Rachmilewitz, and by Matts' endoscopic classification, respectively. The 1.5L-LCAP induced clinical remission in 8 out of 10 patients (80%). Endoscopic improvement was noted in 6 out of 7 patients (85.7%). Prednisolone (PSL) was used in 8 patients; the PSL dose could be reduced in 6 patients, and weaning was possible in one patient. Adverse effects were not observed during 1.5L-LCAP therapy. During the 1.5L-LCAP session, the leukocyte count reached the minimum at 1.0 L of blood processing, but promptly increased after completion of the session, and reached a maximum after 30 min. Interleukin (IL)-1beta-induced IL-8 and IL-6 secretion by peripheral blood mononuclear cells were both significantly reduced by 1.5L-LCAP therapy. 1.5L-LCAP was clinically effective for active UC patients. Cellular responses induced by 1.5L-LCAP were similar to those induced by a standard LCAP session.

TNFalpha kinoid vaccination-induced neutralizing antibodies to TNFalpha protect mice from autologous TNFalpha-driven chronic and acute inflammation

The proinflammatory cytokine TNFalpha is a potent mediator of septic shock and a therapeutic target for chronic inflammatory pathologies including rheumatoid arthritis and Crohn's disease. As an alternative to anti-human TNFalpha (hTNFalpha) mAbs and other hTNFalpha blocker approved drugs, we developed an active anti-hTNFalpha immunotherapy, based on a vaccine comprised of a keyhole limpet hemocyanin-hTNFalpha heterocomplex immunogen (hTNFalpha kinoid) adjuvanted in incomplete Freund's adjuvant. In mice transgenic for hTNFalpha (TTg mice), hTNFalpha kinoid vaccination elicited high titers of Abs that neutralized hTNFalpha bioactivities but did not result in a cellular response to hTNFalpha. The vaccine was safe and effective in two experimental models. Kinoid-immunized but not control TTg mice resisted hTNFalpha-driven shock in one model and were prevented from spontaneous arthritis, inflammatory synovitis, and articular destruction in a second model. These data demonstrate an anti-cytokine induction of autoimmune protection against both acute and chronic hTNFalpha exposure. They show that active vaccination against a human cytokine can be achieved, and that the immune response can be effective and safe.

Suppression of inflammatory cytokine secretion by granulocyte/monocyte adsorptive apheresis in active ulcerative colitis

To elucidate the molecular mechanisms involved in the therapeutic effects of granulocyte/monocyte adsorption apheresis, changes were investigated in the cytokine responses of peripheral blood mononuclear cells (PBMC) before and after granulocyte/monocyte adsorptive apheresis in ulcerative colitis (UC) patients. Four patients with active UC were enrolled. All patients responded to granulocyte/monocyte adsorptive apheresis. A total of 20 sessions of four patients were analyzed. Peripheral blood mononuclear cells were isolated from peripheral venous blood within 5 min before and after each session of granulocyte/monocyte adsorptive apheresis. The cells were stimulated with interleukin (IL)-1beta and tumor necrosis factor (TNF)-alpha for 24 h, and the secreted IL-8 and IL-6 levels were determined by enzyme-linked immunosorbent assay (ELISA). IL-1beta-induced IL-8 and IL-6 secretion was significantly decreased after granulocyte/monocyte adsorptive apheresis. TNF-alpha-induced IL-8 secretion was also significantly decreased after apheresis, but there was no significant difference in TNF-alpha-induced IL-6 secretion (P = 0.052). In conclusion, granulocyte/monocyte adsorptive apheresis down-regulates the IL-1beta- and TNF-alpha-induced inflammatory responses in PBMC. The induction of hyporesponsiveness to pro-inflammatory cytokines may be an important factor mediating the clinical effects of granulocyte/macrophage adsorptive apheresis in UC patients.

On the genetic involvement of apoptosis-related genes in Crohn's disease as revealed by an extended association screen using 245 markers: no evidence for new predisposing factors

Crohn's disease (CD) presents as an inflammatory barrier disease with characteristic destructive processes in the intestinal wall. Although the pathomechanisms of CD are still not exactly understood, there is evidence that, in addition to e.g. bacterial colonisation, genetic predisposition contributes to the development of CD. In order to search for predisposing genetic factors we scrutinised 245 microsatellite markers in a population-based linkage mapping study. These microsatellites cover gene loci the encoded protein of which take part in the regulation of apoptosis and (innate) immune processes. Respective loci contribute to the activation/suppression of apoptosis, are involved in signal transduction and cell cycle regulators or they belong to the tumor necrosis factor superfamily, caspase related genes or the BCL2 family. Furthermore, several cytokines as well as chemokines were included. The approach is based on three steps: analyzing pooled DNAs of patients and controls, verification of significantly differing microsatellite markers by genotyping individual DNA samples and, finally, additional reinvestigation of the respective gene in the region covered by the associated microsatellite by analysing single-nucleotide polymorphisms (SNPs). Using this step-wise process we were unable to demonstrate evidence for genetic predisposition of the chosen apoptosis- and immunity-related genes with respect to susceptibility for CD.

Anti-TNF therapy: Where have we got to in 2005?

The blockade of TNF has had significant impact on the therapy of a number of chronic autoimmune diseases. In this chapter we review the concepts leading up to this therapy in rheumatoid arthritis (RA), how it spreads into other autoimmune diseases, and how greater understanding of its use has led to augmented therapeutic benefit. There are still many limitations, but the prospects for the future are intriguing.