Regional variation in gene expression in the healthy colon is dysregulated in ulcerative colitis

OBJECTIVE

To investigate differential intestinal gene expression in patients with ulcerative colitis and in controls.

DESIGN

Genome-wide expression study (41,058 expression sequence tags, 215 biopsies).

SETTING

Western General Hospital, Edinburgh, UK, and Genentech, San Francisco, USA.

PATIENTS

67 patients with ulcerative colitis and 31 control subjects (23 normal subjects and 8 patients with inflamed non-inflammatory bowel disease biopsies).

INTERVENTIONS

Paired endoscopic biopsies were taken from 5 specific anatomical locations for RNA extraction and histology. The Agilent microarray platform was used and confirmation of results was undertaken by real time polymerase chain reaction and immunohistochemistry.

RESULTS

In healthy control biopsies, cluster analysis showed differences in gene expression between the right and left colon. (chi(2) = 25.1, p<0.0001). Developmental genes, homeobox protein A13 (HOXA13), (p = 2.3x10(-16)), HOXB13 (p<1x10(-45)), glioma-associated oncogene 1 (GLI1) (p = 4.0x10(-24)), and GLI3 (p = 2.1x10(-28)) primarily drove this separation. When all ulcerative colitis biopsies and control biopsies were compared, 143 sequences had a fold change of >1.5 in the ulcerative colitis biopsies (0.01>p>10(-45)) and 54 sequences had a fold change of <-1.5 (0.01>p>10(-20)). Differentially upregulated genes in ulcerative colitis included serum amyloid A1 (SAA1) (p<10(-45)) the alpha defensins 5 and 6 (DEFA5 and 6) (p = 0.00003 and p = 6.95x10(-7), respectively), matrix metalloproteinase 3 (MMP3) (p = 5.6x10(-10)) and MMP7 (p = 2.3x10(-7)). Increased DEFA5 and 6 expression was further characterised to Paneth cell metaplasia by immunohistochemistry and in situ hybridisation. Sub-analysis of the inflammatory bowel disease 2 (IBD2) and IBD5 loci, and the ATP-binding cassette (ABC) transporter genes revealed a number of differentially regulated genes in the ulcerative colitis biopsies.

CONCLUSIONS

Key findings are the expression gradient in the healthy adult colon and the involvement of novel gene families, as well as established candidate genes in the pathogenesis of ulcerative colitis.

A His19 to Ala mutant of melanoma growth-stimulating activity is a partial antagonist of the CXCR2 receptor

Melanoma growth stimulating activity (MGSA) and IL-8 are related chemokines that are potent chemoattractants and activators of neutrophils both in vitro and in vivo. Increasing evidence suggests that these molecules play an important role in inflammation; thus, antagonists of their action could be useful therapeutically as antiinflammatory agents. We have generated an MGSA mutant, H19A, that shows a dissociation between receptor binding and biologic activity. The biologic activity of the H19A mutant is between 133-fold and 282-fold less potent than that of wild-type MGSA measured by three independent assays of neutrophil function, i.e., elastase release chemotaxis and the up-regulation of CD18. In addition, pretreatment of cells with the H19A mutant inhibited the ability of MGSA to induce elastase release and chemotaxis and to increase intracellular calcium. However, competition binding studies in cells transfected with the CXCR2 receptor and in neutrophils demonstrate that the receptor affinity of the H19A mutant is only 13-fold less than that of wild-type MGSA. These studies suggest that the mutant MGSA is defective in activating signaling through the receptor and indicate that binding to the receptor is not sufficient to activate a biologic response. The dissociation between receptor binding and activation for this mutant suggests that it should be possible to design antagonists of MGSA that may be of clinical utility.

Chemokine binding and activities mediated by the mouse IL-8 receptor

In humans and rabbits two similar IL-8R mediate the chemotaxis and activation of neutrophils induced by alpha chemokines. We present data to suggest that there is only one such IL-8R gene in mice. We then use mice with a targeted deletion of this gene to characterize alpha chemokine ligands that signal via the mouse IL-8R. These experiments show that mouse macrophage inflammatory protein 2 binds the receptor with high affinity (Kd = approximately 1.5 nM) and potently activates both an intracellular Ca2+ flux and a chemotactic response, events absent in neutrophils from receptor-deleted mice. Mouse KC is approximately 10-fold less potent. These results show that macrophage inflammatory protein 2 and KC potently activate mouse neutrophils via a unique IL-8R, and these proteins may function as the major proinflammatory alpha chemokines in mice.

Chemokine binding and activities mediated by the mouse IL-8 receptor

In humans and rabbits two similar IL-8R mediate the chemotaxis and activation of neutrophils induced by alpha chemokines. We present data to suggest that there is only one such IL-8R gene in mice. We then use mice with a targeted deletion of this gene to characterize alpha chemokine ligands that signal via the mouse IL-8R. These experiments show that mouse macrophage inflammatory protein 2 binds the receptor with high affinity (Kd = approximately 1.5 nM) and potently activates both an intracellular Ca2+ flux and a chemotactic response, events absent in neutrophils from receptor-deleted mice. Mouse KC is approximately 10-fold less potent. These results show that macrophage inflammatory protein 2 and KC potently activate mouse neutrophils via a unique IL-8R, and these proteins may function as the major proinflammatory alpha chemokines in mice.

Oxidation of thiol drugs and biochemicals by the lactoperoxidase/hydrogen peroxide system

The thiol moiety is prone to oxidative free radical formation, which may be important in mediating the toxicity of some thiol-containing compounds. The oxidation of the compounds cysteine, cysteamine, N-acetylcysteine, glutathione, penicillamine, and captopril were studied using ESR and oxygen uptake techniques. Lactoperoxidase, with hydrogen peroxide to provide oxidizing equivalents, was used to initiate the oxidation. The reaction appears to be strongly peroxide dependent, with either exogenous H2O2 or thiol-derived peroxide driving the reaction.

Recombinant tumor necrosis factor causes activation of human granulocytes

We have tested the hypothesis that tumor necrosis factor (TNF), by binding to and activating granulocytes, may contribute to the pathogenesis of gram-negative sepsis and the adult respiratory distress syndrome (ARDS). Buffy coat granulocytes incubated with as little as 0.5 ng/mL of recombinant TNF (rTNF) showed a dose-related increase in nitroblue tetrazolium dye reduction, in granulocyte polarization, in superoxide anion release, and in visually apparent aggregation. Purified lipopolysaccharide (1 microgram/mL) caused polymorphonuclear (PMN) aggregation and activation that was neutralized by polymyxin B. The release of superoxide was augmented by preincubation of the PMNs with gamma-interferon. The effect of TNF was neutralized by TNF-specific murine monoclonal antibodies but not by polymyxin B. Scatchard analysis of 125I-rTNF binding to granulocytes revealed about 1,200 receptors per cell with a Kd of 4.9 X 10(-10) mol/L. These results suggest that the release of TNF by mononuclear phagocytes contributes to granulocyte activation and aggregation during inflammation.