Stress induced changes in HO-1 expression alter immune adaptation to pregnancy in mice

Abstract

PROBLEM: The inducible enzyme Heme oxygenase 1 (HO-1) plays a regulatory role in a number of inflammatory processes. It catabolizes the degradation of heme and acts as an anti-oxidant and cytoprotectant through its products biliverdin, carbon monoxide and free iron. In the placenta, HO-1 is highly expressed and assumed to act pregnancyprotective, but its function throughout pregnancy is not well understood. Our objective was to examine if alteration of HO-1 expression, e.g. upon stress challenges during late murine pregnancyor inHO-1mutantmiceaffect fetal development and maternal immune adaptation. METHODS: DBA/2J-mated BALB/c females were exposed to 24hour sound stress on gestation days (gd) 12.5 and 14.5. On gd 16.5 placental tissue and uterusdraining lymph nodes (LN) were collected, fetal weight was documented. Placental HO-1 expression was analyzed by immunohistochemistry and quantitative reverse transcription polymerase chain reaction. HO-1+/-BALB/c mice were syngeneically mated. On gd 16.5 tissue was collected and fetal HO-1 genotype and weight was recorded. Placental tissue sections were stained for Masson’s trichrome to study placental function. Phenotype and frequency of maternal immune cells harvested from uterus-draining LN were identified by flow cytometry. For statistical analyses, continuous outcomes were checked for normal distribution. If data was normally distributed, one-way analyses of variance were carried out. For not normally distributed data, Mann-Whitney U-tests were used. Level of significance was set at a p-value of 0.05. RESULTS: Stress challenge lowered HO-1 tissue expression at the feto-maternal interface and significantly decreased HO-1 expression largely in Tand dendritic cells among maternal leucocytes from LN. Further, the frequency of CD8+ T cells was increased and inversely correlated with a reduced expression of CD122 in stressed dams compared to controls. Stress challenges led to a reduced fetal weight, especially in females offspring. Similarly, an increased frequency of CD8+ T cells and a reduction of CD122+ could be detected on HO-1+/dams, compared to wild type (wt) controls. Lower fetal weight was observed in heterozygote offspring, compared to wt fetuses of the same litter. Placental size was slightly decreased in + offspring when compared to wt, while the labyrinth/junctional zone ratio was increased. munology 94 (2012) 5–130