Hypertonic saline enhances host response to bacterial challenge by augmenting receptor-independent neutrophil intracellular superoxide formation.
OBJECTIVE
This study sought to determine whether hypertonic saline (HTS) infusion modulates the host response to bacterial challenge.


METHODS
Sepsis was induced in 30 Balb-C mice by intraperitoneal injection of Escherichia coli (5 x 107 organisms per animal). In 10 mice, resuscitation was performed at 0 and 24 hours with a 4 mL/kg bolus of HTS (7.5% NaCl), 10 animals received 4 mL/kg of normal saline (0.9% NaCl), and the remaining animals received 30 mL/kg of normal saline. Samples of blood, spleen, and lung were cultured at 8 and 36 hours. Polymorphonucleocytes were incubated in isotonic or hypertonic medium before culture with E. coli. Phagocytosis was assessed by flow cytometry, whereas intracellular bacterial killing was measured after inhibition of phagocytosis with cytochalasin B. Intracellular formation of free radicals was assessed by the molecular probe CM-H(2)DCFDA. Mitogen-activated protein (MAP) kinase p38 and ERK-1 phosphorylation, and nuclear factor kappa B (NFkappaB) activation were determined. Data are represented as means (SEM), and an analysis of variance test was performed to gauge statistical significance.


RESULTS
Significantly reduced bacterial culture was observed in the animals resuscitated with HTS when compared with their NS counterparts, in blood (51.8 +/- 4.3 vs. 82.0 +/- 3.3 and 78.4 +/- 4.8, P = 0.005), lung (40.0 +/- 4.1 vs. 93.2 +/- 2.1 and 80.9 +/- 4.7, P = 0.002), and spleen (56.4 +/- 3.8 vs. 85.4 +/- 4.2 and 90.1 +/- 5.9, P = 0.05). Intracellular killing of bacteria increased markedly (P = 0.026) and superoxide generation was enhanced upon exposure to HTS (775.78 +/- 23.6 vs. 696.57 +/- 42.2, P = 0.017) despite inhibition of MAP kinase and NFkappaB activation.


CONCLUSIONS
HTS significantly enhances intracellular killing of bacteria while attenuating receptor-mediated activation of proinflammatory cascades.
Shields
Conor J
CJ
Department of Academic Surgery, Cork University Hospital and National University of Ireland, Cork, Ireland.
O'Sullivan
Adrian W
AW
Wang
Jiang H
JH
Winter
Desmond C
DC
Kirwan
William O
WO
Redmond
H Paul
HP
D000704:Analysis of Variance; D000818:Animals; D003196:Computer Graphics; D004195:Disease Models, Animal; D004789:Enzyme Activation; D004927:Escherichia coli Infections / Q000628:therapy*; D006801:Humans; D008297:Male; D051379:Mice; D008807:Mice, Inbred BALB C; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D016328:NF-kappa B / Q000378:metabolism; D009504:Neutrophils / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects; D011897:Random Allocation; D012462:Saline Solution, Hypertonic / Q000627:therapeutic use*; D013481:Superoxides / Q000378:metabolism*; D016019:Survival Analysis
D016328:NF-kappa B; D012462:Saline Solution, Hypertonic; D013481:Superoxides; D020929:Mitogen-Activated Protein Kinase Kinases