Chemoattractant cross-desensitization of the human neutrophil IL-8 receptor involves receptor internalization and differential receptor subtype regulation.
Human neutrophils undergo rapid homologous receptor desensitization following repeated stimulation with chemoattractants such as IL-8, C5a, and FMLP. It has also been demonstrated that cross-desensitization among these chemoattractant receptors occurs. We investigated the mechanisms underlying the cross-desensitization of responses to IL-8 induced by pretreatment with FMLP or C5a. In [125I]-labeled IL-8 binding studies we found that the cross-desensitization induced by FMLP or C5a was associated with a subsequent reduction in IL-8 binding to neutrophils. There was no recovery of [125I]-labeled IL-8 binding on removal of the C5a or FMLP pretreatment. FACS analysis using mAbs specific for the two IL-8R subtypes showed differential regulation of IL-8R A and IL-8R B cell surface expression after chemoattractant pretreatment. Homologous desensitization by IL-8 resulted in internalization of IL-8R A and IL-8R B, but only IL-8R A was completely re-expressed after removal of agonist. FMLP stimulation led to a substantial loss of IL-8R B from the cell surface, whereas C5a stimulation induced only a partial loss. In both cases there was no re-expression of IL-8R B on removal of the chemoattractant stimulation. C5a and FMLP did not affect IL-8R A expression. Calcium mobilization studies using melanoma growth stimulatory activity and IL-8 suggest that a sustained loss of IL-8R B may play a part in maintaining FMLP-induced IL-8R cross-desensitization. Chemoattractant-induced cross-desensitization of neutrophils may be of importance in regulating neutrophil accumulation during the inflammatory response in vivo.
Sabroe
I
I
Applied Pharmacology, National Heart and Lung Institute, Imperial College of Science, Technology, and Medicine, London, United Kingdom.
Williams
T J
TJ
Hébert
C A
CA
Collins
P D
PD
D015703:Antigens, CD / Q000145:classification / Q000378:metabolism*; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002630:Chemotactic Factors / Q000494:pharmacology*; D015936:Complement C5a / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D004705:Endocytosis; D006801:Humans; D016209:Interleukin-8 / Q000378:metabolism* / Q000494:pharmacology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000502:physiology*; D018123:Receptors, Interleukin / Q000145:classification / Q000378:metabolism*; D023062:Receptors, Interleukin-8A
D015703:Antigens, CD; D002630:Chemotactic Factors; D016209:Interleukin-8; D018123:Receptors, Interleukin; D023062:Receptors, Interleukin-8A; D009240:N-Formylmethionine Leucyl-Phenylalanine; D015936:Complement C5a; D002118:Calcium