No abstract

Epidemiological studies show a markedly increased risk of cerebral palsy following the combined exposure of infection and birth asphyxia. However, the underlying mechanisms of this increased vulnerability remain unclear. We have examined the effects of a low dose of bacterial endotoxin on hypoxic--ischaemic injury in the immature brain of rats. Bacterial endotoxin (lipopolysaccharide 0.3 mg/kg) was administered to 7-day-old rats 4 h prior to unilateral hypoxia--ischaemia and the neurological outcome was determined 3 days later. Rectal temperature and cerebral blood flow was measured during the study and the expression of CD14 and toll-like receptor-4 mRNA in the brain was examined. We found that a low dose of endotoxin dramatically sensitizes the immature brain to injury and induces cerebral infarction in response to short periods of hypoxia--ischaemia that by themselves caused no or little injury. This effect could not be explained by a reduction in cerebral blood flow or hyperthermia. In association with the sensitization of injury we found an altered expression of CD14 mRNA and toll-like receptor-4 mRNA in the brain. These results suggest that the innate immune system may be involved in the vulnerability of the immature brain following the combination of infection and hypoxia--ischaemia.

Data indicate that bacterial products in combination with other antenatal or postnatal exposures increase the risk of perinatal brain injury. We have previously shown that administration of lipopolysaccharide (LPS) 4 h before hypoxia-ischemia (HI) increases brain injury in 7-d-old rats. The mechanisms behind such sensitization are unclear, but contrasts against a preconditioning effect of LPS given 1-3 d before ischemia in adult animals. To investigate how the effects of LPS depend on the time interval between administration and HI in the developing brain, we evaluated the effect of varying time interval (2-72 h) between LPS and HI, the duration of HI (20 or 50 min), and age of the rat pups (postnatal d 4 or 7). Outcome was assessed by brain injury scoring of specific regions. We found that LPS reduced brain injury (by 78%) when administered 24 h before 50 min of HI. However, when LPS was administered 6 h before either 20 or 50 min of HI, brain injury was increased by 2026% and 137%, respectively. Even LPS given 72 h before HI increased injury, both when LPS was administered at postnatal d 4 (by 446%) and 7 (by 77%). In conclusion, LPS enhanced vulnerability in the developing brain both in the acute (4 -6 h) and the chronic (72 h) phase after administration, whereas an intermediate interval between LPS and HI had the opposite effect. The long-term sensitizing effect of LPS has not been previously described. (Pediatr Res 58: 112-116, 2005) Abbreviations DAB, 3,3-diaminobenzidine HI, hypoxia-ischemia LPS, lipopolysaccharide MAP-2, microtubule-associated protein-2 MCAO, middle cerebral artery occlusion NF-B, nuclear factor-kappaB PND, postnatal day TGF-␤1, transforming growth factor-␤1 TNF-␣, tumor necrosis factor-␣ The etiology of newborn encephalopathy is complex and many causal pathways have been suggested to operate antenatally and to interact with intrapartal and postnatal factors (1,2). Antenatal infection has been identified as one cause of encephalopathy and cerebral palsy (1,3,4), acting alone or in combination with other events such as potentially asphyxiating conditions during birth (5).We previously showed that the combination of a low-dose LPS and a sub-threshold period of HI results in increased brain damage in 7-d-old rats, implicating that bacterial products sensitize the immature brain (6). We also detected an increase in CD14 mRNA in the neonatal brain, suggesting activation of the innate immune system. Recently, we explored the effect of peripheral LPS on global gene expression in the immature CNS (unpublished observations). Multiple genes were regulated in a sequential manner with specific patterns of expression at different time points after LPS, suggesting that CNS vulnerability may depend on the time interval between LPS and the subsequent insult. Indeed, previous studies in the adult setting show that a single dose of LPS before permanent MCAO reduced brain injury when LPS was injected 2-4 d before MCAO (7,8). Furthermore, it is well recognized that the neurodevelopmental stage is important ...

To improve the understanding of the molecular mechanisms whereby lipopolysaccharide (LPS) affects the immature brain, global gene expression following LPS exposure was investigated in neonatal rats. Brains (n = 5/time point) were sampled 2, 6, and 72 h after LPS and compared with age-matched controls. The mRNA from each brain was analyzed separately on Affymextrix GeneChip Rat Expression Set 230. The number of genes regulated after LPS were 847 at 2 h, 1564 at 6 h, and 1546 genes at 72 h. Gene ontology analysis demonstrated that, at both 2 and 6 h after LPS, genes associated with protein metabolism, response to external stimuli and stress (immune and inflammatory response, chemotaxis) and cell death were overrepresented. At 72 h, the most strongly regulated genes belonged to secretion of neurotransmitters, transport, synaptic transmission, cell migration, and neurogenesis. Several pathways associated with cell death/survival were identified (caspase-tumor necrosis factor alpha [TNF-alpha]-, p53-, and Akt/phosphatidylinositol-3-kinase (PI3 K)-dependent mechanisms). Caspase-3 activity increased and phosphorylation of Akt decreased 8 h after peripheral LPS exposure. These results show a complex cerebral response to peripheral LPS exposure. In addition to the inflammatory response, a significant number of cell death-associated genes were identified, which may contribute to increased vulnerability of the immature brain to hypoxia-ischemia (HI) following LPS exposure.

This study indicates that VSC and LSC are two equally effective surgical procedures to correct vaginal vault prolapse, but the LSC technique requires a longer operating time.