Cm. Carpati et al., DIPHOSPHORYL LIPID-A FROM RHODOPSEUDOMONAS-SPHAEROIDES INDUCES TOLERANCE TO ENDOTOXIC-SHOCK IN THE RAT, Critical care medicine, 21(5), 1993, pp. 753-758
Objectives: To examine the hemodynamic effects of diphosphoryl lipid A
from Rhodopseudomonas sphaeroides and to examine the ability of this
substance to induce tolerance to endotoxic shock. Design: Randomized,
prospective, controlled study comparing the hemodynamic actions of R.
sphaeroides diphosphoryl lipid A to those effects of lipopolysaccharid
e from Salmonella minnesota, followed by a prospective, randomized, co
ntrolled study comparing pretreatment with R. sphaeroides diphosphoryl
lipid A and phosphate-buffered saline in the induction of tolerance t
o endotoxic shock. Setting. Laboratory of the Section of Critical Care
Medicine at a University Hospital. Subjects: Male Sprague-Dawley rats
. Interventions: Eight rats were randomized to receive intravenous R.
sphaeroides diphosphoryl lipid A, 0.5 mg/100 g body weight or S. minne
sota lipopolysaccharide, 0.5 mg/100 g body weight. Ten rats were then
randomized to receive R. sphaeroides diphosphoryl lipid A, 0.5 mg/100
g body weight, or phosphate-buffered saline intravenously 48 hrs befor
e receiving S. minnesota lipopolysaccharide, 5 mg/100 g body weight, b
y intravenous infusion. Measurements and Main Results: Cardiac index w
as significantly decreased from baseline in rats treated with lipopoly
saccharide; there was no significant change in the R. sphaeroides diph
osphoryl lipid A group. Peak circulating tumor necrosis factor (TNF) c
oncentrations in the lipopolysaccharide-treated rats were higher than
in R. sphaeroides diphosphoryl lipid A-treated rats (3.1 +/- 1.0 vs. 1
.5 /- 0.4 ng/mL). R. sphaeroides diphosphoryl lipid A significantly at
tenuated lipopolysaccharide-induced changes in mean arterial pressure
and cardiac index. At baseline, there was no significant difference in
serum TNF concentrations between rats pretreated with R. sphaeroides
diphosphoryl lipid A and those rats pretreated with phosphate-buffered
saline. TNF levels peaked at 1 hr post-lipopolysaccharide infusion at
4.3 +/- 0.6 ng/mL in the phosphate-buffered saline group and at 2.0 /- 0.5 ng/mL in the R. sphaeroides diphosphoryl lipid A group (p < .02
). Four of five rats pretreated with R. sphaeroides diphosphoryl lipid
A survived endotoxic shock, whereas none of the phosphate-buffered sa
line-pretreated rats survived (p = .05). Conclusions: These observatio
ns are consistent with previous reports of the limited toxic effects o
f R. sphaeroides diphosphoryl lipid A and suggest that this molecule r
etains the ability to induce tolerance to endotoxic shock.