Basophils Infiltrate Human Gastric Mucosa at Sites of Helicobacter pylori Infection, and Exhibit Chemotaxis in Response to H. pylori-derived Peptide Hp(2–20)

Abstract

Basophils, which are normally confined to the circulation, can migrate to sites of allergic inflammation. Using the specific mAb, BB1, we detected basophil infiltration of the gastric mucosa of Helicobacter pylori-infected patients affected by moderate and severe gastritis. Basophils were not found in H. pylori-free individuals or in subjects with mild gastritis. The H. pylori-derived peptide, Hp(2–20), was a potent basophil chemoattractant in vitro, whereas the control peptide, Hp1, was ineffective. Basophils from peripheral blood of healthy volunteers expressed mRNA for the formyl peptide receptors, N-formyl-peptide receptor (FPR), FPR-like (FPRL)1, and FPRL2. Preincubation of basophils with FMLP or Hp(2–20) caused complete desensitization to a subsequent challenge with homologous stimulus. Incubation of basophils with a low concentration of FMLP, which binds with high affinity to FPR, but not to FPRL1 or FPRL2, did not affect the chemotactic response to Hp(2–20). In contrast, a high concentration of FMLP, which binds to FPRL1 and FPRL2, reduced the chemotactic response to Hp(2–20). The FPR antagonist, cyclosporin H, prevented chemotaxis induced by FMLP, but not by Hp(2–20). Hp(2–20) could be responsible, at least in part, for basophil infiltration of the gastric mucosa of H. pylori-infected patients presumably through the interaction with FPRL1 and FPRL2.

Urokinase Induces Basophil Chemotaxis through a Urokinase Receptor Epitope That Is an Endogenous Ligand for Formyl Peptide Receptor-Like 1 and -Like 2

“…Interestingly, uPA and uPAR 84 -95 do not share sequence homologies with any of the other agonists. Human monocytes and basophils express FPRL2, and Hp 2-20 exerts its chemotactic effect by activating this receptor subtype (27,57). Our results are compatible with the hypothesis that FPRL2 is involved in the chemotactic activity induced by urokinase in basophils.…”

“…Our results are compatible with the hypothesis that uPA-dependent chemotaxis is mediated by the exposure of a chemotactic urokinase receptor epitope that is an endogenous agonist for FPRL2 on human basophils. Finally, the results described in this study may have practical implications in disorders such as allergic diseases and certain bacterial infections in which basophils infiltrating the sites of inflammation play a prominent role (57,(65)(66)(67). In fact, it is conceivable that agents acting on uPAR-mediated chemotaxis (i.e., by blocking the chemotactic epitope) may be used to modify the basophildriven inflammatory reactions.…”

“…Until recently, FPRL2 was considered an orphan receptor despite its sequence homology with the other two formyl receptors, FPR and FPRL1 (19). Betten et al (27) and our group (57) have demonstrated that the Hp 2-20 induces monocyte and basophil chemotaxis, respectively, through the activation of FPRL2. Therefore, other endogenous or exogenous ligands may exist, making FPRL2 a promiscuous receptor like FPRL1.…”

Helicobacter pylori Hp(2–20) Promotes Migration and Proliferation of Gastric Epithelial Cells by Interacting with Formyl Peptide Receptors In Vitro and Accelerates Gastric Mucosal Healing In Vivo

“…The primers for GAPDH were 5Ј-GCC AAAGGGTCATCATCTC (sense) and 3Ј-GTAGAGGCAGGGA TGATGTTC (antisense). PCR products, together with a DNA ladder as a size standard, were separated on a 1% agarose gel, stained with ethidium bromide, and visualized with the image analysis system ChemiDoc XRS (Bio-Rad) (11,17).…”

“…Therefore, this study was designed: (1) to assess whether gastric epithelial cell lines express FPRs; (2) to investigate whether Hp (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) stimulates cell migration and proliferation and VEGF expression and release in gastric epithelial cell lines; (3) to investigate the role of FPRs in any such effect(s); and (4) to evaluate whether Hp (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20) accelerates healing in a rat model of indomethacin-induced gastric mucosal damage.…”