Submitted May 22, 2006
Accepted June 24, 2006
Impaired neutrophil chemotaxis in sepsis associates with
GRK expression and inhibition of actin assembly and
tyrosine phosphorylation
Sandra Mara A Arraes, Marta S Freitas, Simone V da Silva, Heitor A de Paula Neto, Jose Carlos Alves-Filho, Maria A Martins, Anibal Basile-Filho, Beatriz M Tavares-Murta, Christina Barja-Fidalgo, and Fernando Q Cunha*
University of Sao Paulo, Brazil
Universidade do Estado do Rio de Janeiro, Brazil
Federal University of Triangulo Mineiro, Brazil
* Corresponding author; email: fdqcunha{at}fmrp.usp.br.
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 towards
chemoattractants. Fifty-two septic patients and 15
volunteers were prospectively enrolled. Patients presented
increased circulating levels of tumor necrosis
factor-
, interferon-
, interleukin (IL)-8
and IL-10. Patients showed reduced neutrophil chemotaxis
to formyl-methionyl-leucyl-phenylalanine (FMLP),
leukotriene (LT)B4 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 augment in
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 (GRK)2 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.
