Non-steroidal anti-inflammatory drugs inhibit Helicobacter pylori-induced human neutrophil reactive oxygen metabolite production in vitro

BACKGROUND

Helicobacter pylori infection is associated with increased production of gastric mucosal reactive oxygen metabolites which have been implicated in mucosal damage and carcinogenesis. In vitro, neutrophils produce reactive oxygen metabolites following activation by H. pylori. Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit neutrophil activation by several factors, e.g. N-formyl-methionyl-leucyl-phenyalanine (f-MLP).

AIM

To examine the effect of NSAIDs on H. pylori-induced reactive oxygen metabolite production by human peripheral blood neutrophils.

METHODS

Neutrophils were stimulated by H. pylori (NCTC 11637) water extract or f-MLP in the presence or absence of NSAIDs. Reactive oxygen metabolite activity was measured by luminol-enhanced chemiluminescence.

RESULTS

H. pylori water extract stimulated a sevenfold increase in chemiluminescence which was inhibited dose-dependently by diclofenac. All six NSAIDs studied (at 10-4 M) significantly inhibited H. pylori-and f-MLP-stimulated neutrophil reactive oxygen metabolite production. Meclofenamic acid and diclofenac had the greatest inhibitory effects on both H. pylori and f-MLP-stimulated neutrophil reactive oxygen metabolite production. The inhibitory effects of other NSAIDs varied with the activation stimulus. NSAIDs did not quench reactive oxygen metabolites generated in a cell-free xanthine:xanthine oxidase assay.

CONCLUSION

Several NSAIDs attenuate H. pylori-induced neutrophil reactive oxygen metabolites production in vitro. This may be relevant to a potential chemopreventative role in gastric cancer and to a possible lack of synergy between H. pylori and NSAID use regarding peptic ulceration.

High-affinity binding sites for gastrin-releasing peptide on human colorectal cancer tissue but not uninvolved mucosa

Human colorectal cancer tissue and matched uninvolved mucosa from 21 patients were examined by radioligand displacement for the presence of binding sites for bombesin-like peptides. Five cancers, but no uninvolved mucosa, expressed high-affinity, low-capacity bombesin binding sites (Kd = 6.53 nM, Bmax = 58.6 fmol mg-1 protein) of the gastrin-releasing peptide (GRP)-preferring subtype (IC50 4.8 nM). Bombesin-like peptides may have a role in the pathogenesis of colorectal cancer, and bombesin receptor antagonists may be of value in the treatment of receptor-positive tumours.

High affinity binding sites for gastrin releasing peptide on human gastric cancer and Ménétrier's mucosa

The bombesin-like peptides gastrin releasing peptide (GRP) and neuromedin B are found in the submucosal and myenteric plexuses of the human gastrointestinal tract. These peptides are potent mitogens to Swiss 3T3 fibroblasts and are important autocrine growth factors in human small cell lung cancer cells. We have recently described the presence of receptors for the bombesin-like peptide, GRP, on the human gastric cancer cell line St42. In this study, we examined fresh resected gastric cancer and uninvolved mucosa from 23 patients for the presence of binding sites to the bombesin-like peptides. Thirteen of 23 gastric cancers expressed high affinity binding sites for bombesin (mean Kd = 3.42 nM; mean Bmax = 40.5 pmol/mg protein), of which 12 were subsequently characterized and found to be of the GRP-preferring subtype. One of 23 mucosal samples specifically bound bombesin and was the only sample from a patient with Ménétrier's disease, a disorder of mucosal growth known to be premalignant. The early gastric cancer from this patient also possessed high affinity binding sites for GRP. This is the first description of binding sites to bombesin-like peptides on human gastric cancer and Ménétrier's mucosa. The role of bombesin/GRP antagonists in the treatment of gastric cancer warrants investigation.