Neutrophil apoptosis: a marker of disease severity in sepsis and sepsis-induced acute respiratory distress syndrome.
BACKGROUND
Apoptosis of neutrophils (polymorphonuclear neutrophils [PMNs]) may limit inflammatory injury in sepsis and acute respiratory distress syndrome (ARDS), but the relationship between the severity of sepsis and extent of PMN apoptosis and the effect of superimposed ARDS is unknown. The objective of this study was to correlate neutrophil apoptosis with the severity of sepsis and sepsis-induced ARDS.


METHODS
A prospective cohort study was conducted in intensive care units of three tertiary hospitals in Porto Alegre, southern Brazil. Fifty-seven patients with sepsis (uncomplicated sepsis, septic shock, and sepsis-induced ARDS) and 64 controls were enrolled. Venous peripheral blood was collected from patients with sepsis within 24 hours of diagnosis. All surgical groups, including controls, had their blood drawn 24 hours after surgery. Control patients on mechanical ventilation had blood collected within 24 hours of initiation of mechanical ventilation. Healthy controls were blood donors. Neutrophils were isolated, and incubated ex vivo, and apoptosis was determined by light microscopy on cytospun preparations. The differences among groups were assessed by analysis of variance with Tukeys.


RESULTS
In medical patients, the mean percentage of neutrophil apoptosis (+/- standard error of the mean [SEM]) was lower in sepsis-induced ARDS (28% +/- 3.3%; n = 9) when compared with uncomplicated sepsis (57% +/- 3.2%; n = 8; p < 0.001), mechanical ventilation without infection, sepsis, or ARDS (53% +/- 3.0%; n = 11; p < 0.001) and healthy controls (69% +/- 1.1%; n = 33; p < 0.001) but did not differ from septic shock (38% +/- 3.7%; n = 12; p = 0.13). In surgical patients with sepsis, the percentage of neutrophil apoptosis was lower for all groups when compared with surgical controls (52% +/- 3.6%; n = 11; p < 0.001).


CONCLUSIONS
In medical patients with sepsis, neutrophil apoptosis is inversely proportional to the severity of sepsis and thus may be a marker of the severity of sepsis in this population.
Fialkow
Léa
L
Department of Internal Medicine, Faculty of Medicine, Federal University of Rio Grande do Sul, Porto Alegre, Rio Grande do Sul, 90035-003, Brazil. lfialkow@terra.com.br
Fochesatto Filho
Luciano
L
Bozzetti
Mary C
MC
Milani
Adriana R
AR
Rodrigues Filho
Edison M
EM
Ladniuk
Roberta M
RM
Pierozan
Paula
P
de Moura
Rafaela M
RM
Prolla
João C
JC
Vachon
Eric
E
Downey
Gregory P
GP
D000328:Adult; D017209:Apoptosis; D015415:Biomarkers; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009504:Neutrophils; D011446:Prospective Studies; D012128:Respiratory Distress Syndrome / Q000097:blood* / Q000209:etiology*; D018805:Sepsis / Q000097:blood* / Q000150:complications*; D012720:Severity of Illness Index
D015415:Biomarkers