title: Acute on chronic exposure to endotoxin in preterm fetal sheep.
abstract: Acute, high-dose exposure to endotoxin lipopolysaccharide (LPS) in preterm fetal sheep can trigger periventricular white matter lesions (PVL), in association with severe hypotension/hypoxemia and significant mortality. Intriguingly, however, chronic or repeated exposure to LPS can induce tachyphylaxis. We therefore tested the hypothesis that progressive, acute on chronic fetal infection would be associated with white matter injury with little fetal mortality. Chronically instrumented preterm (0.7 gestational age) fetal sheep were exposed to a continuous low-dose LPS infusion (100 ng over 24 h, followed by 250 ng/24 h for 96 h) or saline. Boluses of 1 μg LPS or saline were given at 48, 72, and 96 h; sheep were killed at day 10. Six of 11 fetal sheep exposed to saline infusion + LPS boluses died 4-7 h after the first bolus. In contrast, there was no fetal mortality after saline infusions alone (n = 9), low-dose LPS infusion + saline boluses (n = 5), or low-dose LPS + LPS boluses (n = 9). Low-dose LPS infusion + LPS boluses was associated with greater microglial induction than low-dose LPS + saline boluses but a similar area of periventricular white matter inflammation. One fetus developed severe focal white matter necrosis after LPS infusion + boluses. The acute cardiovascular compromise associated with high-dose, acute exposure to LPS is markedly attenuated by previous low-dose infusions, with limited apparent exacerbation of periventricular white matter injury compared with low-dose infusion alone.
authors.affiliation: Department of Physiology, the University of Auckland, New Zealand.
authors.forename: Sam
authors.initials: S
authors.lastname: Mathai
authors.forename: Lindsea C
authors.initials: LC
authors.lastname: Booth
authors.forename: Joanne O
authors.initials: JO
authors.lastname: Davidson
authors.forename: Paul P
authors.initials: PP
authors.lastname: Drury
authors.forename: Mhoyra
authors.initials: M
authors.lastname: Fraser
authors.forename: Ellen C
authors.initials: EC
authors.lastname: Jensen
authors.forename: Sherly
authors.initials: S
authors.lastname: George
authors.forename: Andrew
authors.initials: A
authors.lastname: Naylor
authors.forename: Alistair J
authors.initials: AJ
authors.lastname: Gunn
authors.forename: Laura
authors.initials: L
authors.lastname: Bennet
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D001921:Brain / Q000187:drug effects* / Q000503:physiopathology*; D004305:Dose-Response Relationship, Drug; D004731:Endotoxins / Q000633:toxicity*; D005260:Female; D008297:Male; D009413:Nerve Fibers, Myelinated / Q000187:drug effects*; D011247:Pregnancy; D047928:Premature Birth; D011297:Prenatal Exposure Delayed Effects / Q000139:chemically induced* / Q000503:physiopathology*; D012756:Sheep; D015996:Survival Rate; D023382:Toxicity Tests, Acute; D036401:Toxicity Tests, Chronic
chemical_list: D004731:Endotoxins