Ascending Lipopolysaccharide-Induced Intrauterine Inflammation in Near-Term Rabbits Leading to Newborn Neurobehavioral Deficits

Abstract

Background: Chorioamnionitis from ascending bacterial infection through the endocervix is a potential risk factor for cerebral palsy. Tetrahydrobiopterin, an essential cofactor for nitric oxide synthase (NOS) and amino acid hydroxylases, when augmented in the fetal brain, prevents some of the cerebral palsy-like deficits in a rabbit hypoxia-ischemia model. Objectives: To study the effect of lipopolysaccharide (LPS)-induced intrauterine inflammation in preterm gestation on motor deficits in the newborn, and whether biosynthesis of tetrahydrobiopterin or inflammatory mediators is affected in the fetal brain. Methods: Pregnant rabbits at 28 days gestation (89% term) were administered either saline or LPS into both endocervical openings. One group underwent spontaneous delivery, and neurobehavioral tests were performed at postnatal day (P) 1 and P11, with some kits being sacrificed at P1 for histological analysis. Another group underwent Cesarean section 24 h after LPS administration. Gene sequences for rabbit biosynthetic enzymes of tetra­hydrobiopterin pathways were determined and analyzed in addition to cytokines, using quantitative real-time polymerase chain reaction. Results: Exposure to 200 μg/kg/mL LPS caused a locomotion deficit and mild hypertonia at P1. By P11, most animals turned into normal-appearing kits. There was no difference in neuronal cell death in the caudate between hypertonic and nonhypertonic kits at P1 (n = 3–5 in each group). Fetal brain GTP cyclohydrolase I was increased, whereas sepiapterin reductase and 6-pyruvoyltetrahydropterin synthase were decreased, 24 h after LPS administration. Neuronal NOS was also increased. Regardless of the position in the uterus or the brain region, expression of TNF-α and TGF-β was decreased, whereas that of IL-1β, IL-6, and IL-8 was increased (n = 3–4 in each group). Conclusions: This is the first study using an ascending LPS-induced intrauterine inflammation model in rabbits, showing mostly transient hypertonia and mainly locomotor deficits in the kits. Not all proinflammatory cytokines are increased in the fetal brain following LPS administration. Changes in key tetrahydro­biopterin biosynthetic enzymes possibly indicate different effects of the inflammatory insult.

Immunobiology of Cervix Ripening

“…In addition, concerns about the usefulness of the intrauterine administration of LPS as a model for ascending infection-induced preterm birth in women were raised by a compelling study that found systemic, but not intravaginal treatment induce preterm birth in mice (141). Except for introduction of LPS into the endocervix (144), which breaches the luminal epithelial immune interface, there is consistent evidence for systemic inflammatory drive of preterm birth. By example, the importance of myeloid-derived immune cells and activities for cervix remodeling was emphasized in a recent study in mice that used antibody treatment to suppress the cytokine granulocyte-macrophage colony stimulating factor (GM-CSF) and block LPS-induced preterm birth (145).…”

Neuronal vulnerability to fetal hypoxia-reoxygenation injury and motor deficit development relies on regional brain tetrahydrobiopterin levels

“…cDNA sequencing was performed using a 96-capillary automated DNA sequencer (Applied Biosystems 3730XL) and confirmed by alignment with the predicted sequences at GenBank. The rabbit gene sequence and GenBank ID has recently been published [11].…”

“…Total RNA was purified from the cortex, cerebellum, and thalamus using the PureLink RNA Mini Kit (Life Technologies, Grand Island, NY) as done previously [11]. Samples were chosen in pairs of either high or low tetrahydrobiopterin levels.…”

Microbiota Signals during the Neonatal Period Forge Life-Long Immune Responses

“…In spite of this, the fetus can mount an inflammatory response. For example, intrauterine immune activation by LPS augments IL-1β, IL-6 and IL-8 while reducing TNF-α and TGF-β in the fetal brain [ 140 ]. Similarly, intestinal NF-κB function, as well as expression of NF-κB, IL-1β and TNF-α, augment in newborns that receive Escherichia coli solution or E. coli -fermented formula [ 141 ].…”