Impaired neutrophil chemotaxis in sepsis associates with GRK expression and inhibition of actin assembly and tyrosine phosphorylation.
The deregulation of inflammatory response during sepsis seems to reflect the overproduction of mediators, which suppress leukocyte functions. We investigated the intracellular mechanisms underlying the inability of neutrophils from severe septic patients to migrate toward chemoattractants. Patients with sepsis (52) and 15 volunteers were prospectively enrolled. Patients presented increased circulating levels of tumor necrosis factor-alpha, interferon-gamma, interleukin (IL)-8, and IL-10. Patients showed reduced neutrophil chemotaxis to formyl-methionyl-leucyl-phenylalanine (FMLP), leukotriene B4 (LTB4) or IL-8. No difference in the transcription or expression of the IL-8 receptor, CXCR1, was detected in neutrophils from controls and patients. However, septic neutrophils failed to increase tyrosine phosphorylation and actin polymerization in response to IL-8 or LTB4. In contrast, septic neutrophils, similar to controls, showed phagocytic activity that induced actin polymerization and augmented phosphotyrosine content. Treatment of control neutrophils with cytokines and lipopolysaccharide (LPS) to mimic endogenous septic environment inhibited actin polymerization and tyrosine phosphorylation in response to IL-8 or LTB4. High expression of G protein-coupled receptor kinase 2 (GRK2) and GRK5 was detected in septic neutrophils and control cells treated with cytokines plus LPS. Data suggest that endogenous mediators produced during sepsis might continually activate circulating neutrophils, leading to GRK activation, which may induce neutrophil desensitization to chemoattractants.
Arraes
Sandra Mara A
SM
Department of Pharmacology, Faculty of Medicine of Ribeirão Preto, University of São Paulo, Avenida Bandeirantes, 3900, Ribeirão Preto, São Paulo, Brazil 14049-900.
Freitas
Marta S
MS
da Silva
Simone V
SV
de Paula Neto
Heitor A
HA
Alves-Filho
Jose Carlos
JC
Auxiliadora Martins
Maria
M
Basile-Filho
Anibal
A
Tavares-Murta
Beatriz M
BM
Barja-Fidalgo
Christina
C
Cunha
Fernando Q
FQ
D000199:Actins / Q000096:biosynthesis*; D002465:Cell Movement; D002634:Chemotaxis, Leukocyte / Q000502:physiology*; D016207:Cytokines / Q000494:pharmacology; D017931:DNA Primers; D054769:G-Protein-Coupled Receptor Kinase 2; D054774:G-Protein-Coupled Receptor Kinase 5; D006801:Humans; D008070:Lipopolysaccharides / Q000494:pharmacology; D009240:N-Formylmethionine Leucyl-Phenylalanine / Q000494:pharmacology; D009504:Neutrophils / Q000187:drug effects / Q000502:physiology*; D019000:Phosphotyrosine / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D023062:Receptors, Interleukin-8A / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018805:Sepsis / Q000097:blood*; D051552:beta-Adrenergic Receptor Kinases / Q000235:genetics*
D000199:Actins; D016207:Cytokines; D017931:DNA Primers; D008070:Lipopolysaccharides; D023062:Receptors, Interleukin-8A; D019000:Phosphotyrosine; D009240:N-Formylmethionine Leucyl-Phenylalanine; D017346:Protein Serine-Threonine Kinases; C496567:GRK2 protein, human; D051552:beta-Adrenergic Receptor Kinases; D054769:G-Protein-Coupled Receptor Kinase 2; D054774:G-Protein-Coupled Receptor Kinase 5; C517898:GRK5 protein, human