Heightened maternal inflammation is linked to placental oxidative and nitrosative stress associated with fetal growth restriction in the rat

Deficient trophoblast invasion and spiral artery remodeling are associated with pregnancy complications such as pre-eclampsia (PE) and fetal growth restriction (FGR). Using a model in which pregnant Wistar rats are given daily, low-dose, injections of bacterial lipopolysaccharide (LPS; 10 – 40 µg/kg) on gestational days (GD) 13.5 – 16.5, our group has shown that abnormal maternal inflammation is causally linked to shallow trophoblast invasion, deficient spiral artery remodeling, and altered utero-placental hemodynamics leading to FGR/PE; these alterations were shown to be mediated by TNF-a. The present research evaluated certain consequences of decreased placental perfusion; this was accomplished by examining placental alterations indicative of decreased placental perfusion. Additionally, the role of glyceryl trinitrate (GTN) was determined as a potential therapeutic to prevent the consequences of decreased placental perfusion. Results indicated that dams experiencing heightened maternal inflammation showed significantly greater expression of hypoxia-inducible factor-1a (HIF-1a) and nitrotyrosine, both of which are markers of decreased perfusion and oxidative/nitrosative stress. Contrary to expectations, inflammation did not appear to affect nitric oxide (NO) bioavailability, as revealed by a lack of change in placental or plasma levels of cyclic guanosine monophosphate (cGMP). However, continuous transdermal administration of GTN (25 µg/hr) on GD 12.5 – 16.5 prevented the accumulation of HIF-1a and nitrotyrosine in placentas from LPS-treated rats. These results support the concept that maternal inflammation contributes to placental hypoxia and oxidative/nitrosative stress. Additionally, they indicate that GTN has potential applications in the treatment and/or prevention of pregnancy complications associated with abnormal maternal inflammation.

The role of Schizosaccharomyces pombe Cdc2 phosphorylation sites on Cdc25 in mitotic timing

Cell size control and mitotic timing in Schizosaccharomyces pombe is coupled to the environment through several signal transduction pathways that include stress response, checkpoint and nutritional status impinging on Cdc25 tyrosine phosphatase and Wee1 tyrosine kinase. These in turn regulate Cdc2 (Cdk1) activity and through a double feedback loop, further activates Cdc25 on 12 possible phosphorylation sites as well as inhibiting Wee1. Phosphomutants of the T89 Cdc2 phosphorylation site on Cdc25, one with a glutamate substitution (T89E) which is known to phosphomimetically activate proteins and an alanine substitution (T89A), which is known to block phosphorylation, exhibit a small steady-state cell size (semi-wee phenotype), a known hallmark for aberrant mitotic control. To determine whether the T89 phosphorylation site plays an integral role in mitotic timing, the phosphomutants were subjected to nitrogen shifts to analyze their transient response in the context of nutritional control. Results for both up and downshifts were replicated for the T89E phosphomutant, however, for the T89A phosphomutant, only a nutritional downshift has been completed so far. We found that the steady-state cell size of both phosphomutants was significantly smaller than the wild-type and in the context of nutritional control. Furthermore, the constitutively activated T89E phosphomutant exhibits residual mitotic entry, whereas the wild-type undergoes a complete mitotic suppression with mitotic recovery also occurring earlier than the wild-type. In response to downshifts, both phosphomutants exhibited an identical response to the wild-type. Further characterization of the other Cdc2 phosphorylation sites on Cdc25 are required before conclusions can be drawn, however T89 remains a strong candidate for being important in activating Cdc25.