Interleukin-10 attenuates experimental fetal growth restriction and demise.

Premature labor, fetal demise, and fetal growth restriction are accompanied by indices of inflammation or infection of the uteroplacental unit. To understand whether these events are causally related, we established an animal model of fetal demise and growth restriction and evaluated the potential utility of the anti-inflammatory cytokine interleukin-10 (IL-10). We administered low-dose endotoxin (lipopolysaccharide, or LPS, 100 microg/kg, i.p.) to third trimester rats (gestational days 14-20). Control rats received normal saline. A third group received IL-10 (100 microg/kg; s.c.) concomitantly with LPS for 7 prenatal days. Cytokine gene expression (IL-10 and TNF-alpha) was evaluated by RT-PCR and tissue levels (TNF-alpha) were determined by ELISA. Apoptosis was evaluated by TdT-mediated dUTP nick end labeling immunohistochemistry, and nitric oxide (NO) levels were quantified by microelectrode electrochemical detection in explants in culture media. LPS exposure resulted in 43% fetal demise and reduced the size of the surviving fetuses. Placental weight was not altered by LPS. IL-10 attenuated the LPS-induced fetal death rate (to 22%) and growth restriction (P<0.05). In normal rats, IL-10 did not affect fetus size or the incidence of resorptions, although placental size was marginally smaller. Increased uterine TNF-alpha content and NO release and apoptosis of uterine epithelia and muscularis were hallmarks of the LPS model. All were normalized by IL-10. IL-10 may represent a new therapeutic option for the treatment of a variety of perinatal complications. Benefit may result from the suppression of TNF-alpha- and NO-mediated cell death.

Fetal growth retardation in rats may result from apoptosis: role of peroxynitrite.

Administration of the nitric oxide synthase (NOS) inhibitor NG-nitro-L-arginine methyl ester (L-NAME) results in fetal growth retardation. This study was designed to further examine the influence of NO on fetal growth, specifically, the potential role of inducible NOS and to evaluate the possibility that apoptosis contributed to uteroplacental dysfunction. L-NAME administration caused a paradoxical increase in NO synthesis determined by direct detection of NO by electrochemistry, nitrite accumulation, and cGMP levels, indicating that a lack of NO was not the cause of the fetal growth retardation. Additionally, supplemental L-arginine or NO donors failed to reverse the effects of L-NAME on fetal and placental size. Administration of low dose endotoxin (30 micrograms/kg IP daily for 6 d) also caused significant reductions in fetal and placental size and increased NO synthesis comparable to that seen with L-NAME. Inducible NOS was constitutively expressed in the pregnant uterus (smooth muscle and epithelia) and placenta (sinusoids and macrophages) but was absent in the nonpregnant state as determined by RT-PCR and immunohistochemistry. Neither L-NAME nor endotoxin modified the expression of iNOS. In situ evidence for apoptosis (DNA fragmentation) was minimal to absent in control pregnant rats, but markedly evident in the placenta (decidua) and uterus of rats treated with L-NAME or endotoxin. Immunohistochemical evidence for nitrotyrosine, a marker for peroxynitrite formation, was absent in control rats but colocalized with apoptosis in the L-NAME and LPS groups. We conclude that L-NAME-induced fetal growth retardation is not due to a lack of NO, but as for endotoxin, results from a net reduction in cellular proliferation due to the induction of apoptosis, possibly in response to peroxynitrite formation.

Nitric oxide synthase inhibition decreases tolerance to hyperoxia in newborn rats.

We evaluated the effects of sustained perinatal inhibition of NO synthase (NOS) on hyperoxia induced lung injury in newborn rats. N(G)-nitro-Larginine-methyl-ester (L-NAME) or untreated water was administered to pregnant rats for the final 7 days of gestation and during lactation; followed by postnatal exposure to hyperoxia (>95% O(2)) or room air. The survival rate of L-NAME treated pups when placed in > 95% O(2) at birth was significantly lower than controls from day 4 (L-NAME, 87%; control pups, 100%, p < 0.05) to 14 (L-NAME, 0%; control pups, 53%, p < 0.05). Foetal pulmonary artery vasoconstriction was induced by L-NAME with a decrease in internal diameter from 0.88 +/- 0.03 mm to 0.64 +/- 0.01 mm in control vs. L-NAME groups (p < 0.05), respectively. We conclude that perinatal NOS inhibition results in pulmonary artery vasoconstriction and a decreased tolerance to hyperoxia induced lung injury in newborn rats.