Chamomile infusions inhibit two proteases involved in gastric inflammation: elastase and metalloprotease-9

Chamomile (Chamomilla recutita L., Asteraceae Family) is traditionally used as an herbal remedy for the treatment of gastrointestinal inflammatory diseases and is commercially available in sachets containing either the dried flower-heads (capitula) or sifted flowers. Matrix metalloproteases (MMPs) and neutrophil elastase (NE) are proteases involved in gastric inflammation, and contribute to the degradation of gastric mucosa and to the Helicobacter pylori colonization. This study was undertaken to investigate whether the anti-inflammatory effect of chamomile infusion at gastric level could be ascribed to the inhibition of MMP-9 and elastase. LC-ESI-MS/MS analysis of flavonoids present in CFI and SFI showed different profiles as regards the concentration of apigenin-7-glu, and luteolin-7-glu. MMP-9 secretion and expression were evaluated in human gastric adenocarcinoma cells (AGS) stimulated by 200 nM PMA; NE activity was measured using a chromogenic substrate. The assays were conducted in the presence of chamomile infusions derived from capitula (CFI) and sifted (SFI) flowers (100-1500 µg/ml). Individual flavonoids occurring in both types of infusions were tested as well at 10 µM. The activity and secretion of MMP-9 was determined by zymography and human elastase activity by spectrophotometric assay. MMP-9 promoter activity was investigated in cells transiently transfected with a plasmid containing the luciferase reporter gene under the control of the MMP-9 promoter. Both types of infusion inhibited the enzymatic activity (-63% and -43% at 1500 μg/ml, for CFI and SFI respectively), the secretion of MMP-9 (IC50 404 and 348 μg/ml for CFI and SFI respectively), as well as the promoter activity (-50% at 1500 μg/ml). Both CFI and SFI reduced the NF-kB driven transcription in a concentration-dependent manner. Notably, the concentration at which the effect was observed is comparable to that affecting the MMP-9 promoter activity. CFI and SFI inhibited elastase activity in a concentration-dependent manner (IC50s of 369 and 537 μg/ml for CFI and SFI, respectively). All the tested flavonoid-7-glycosides (apigenin, luteolin, patuletin and hyperoside) are active at same extent against the targets under study; therefore their contribution to the overall in vitro effect depends on the concentration of each in the infusion. In conclusion, the present study provides some experimental evidence that MMP-9 and elastase inhibition could represent a mechanism for the anti-inflammatory activity of chamomile infusion at the gastric level. Other mechanisms, however, may also be concurrent.