Tumor necrosis factor α induces a model of preeclampsia in pregnant baboons (Papio hamadryas).

Preeclampsia is a common disease of pregnancy characterised by maternal hypertension and proteinuria. Abnormal placentation in early pregnancy and abnormal cytokine and anti-angiogenic factor expression are thought to contribute to the clinical syndrome of endothelial dysfunction evident in the second half of gestation. The mechanisms underlying both the placental pathology and its translation to the maternal clinical syndrome are not fully understood. A model of preeclampsia manifest by clinically evident endothelial dysfunction (increased blood pressure and proteinuria) was induced by administration of low-dose TNF-α for 2weeks at mid-gestation in pregnant baboons (Papio hamadryas). Blood pressure was monitored continuously and remotely by intra-arterial radiotelemetry. Following TNF-α infusion, there was an increase in systolic and diastolic blood pressure and development of proteinuria in pregnant treated animals, but not in pregnant saline controls nor in non-pregnant TNF-α treated animals. The treated pregnant animals also developed elevated plasma soluble FMS-like tyrosine kinase-1 (sFLT-1) and increased placental mRNA expression of sFLT-1 and soluble endoglin (sEng). These results clearly demonstrate that the cytokine TNF-α can induce the clinical and biochemical features of human preeclampsia. The results identify a link between cytokines, placental dysfunction and endothelial dysfunction resulting in a loss of maternal blood pressure control.

Effect of hypoxia and exogenous IL-10 on the pro-inflammatory cytokine TNF-alpha and the anti-angiogenic molecule soluble Flt-1 in placental villous explants.

INTRODUCTION: The placenta plays a pivotal role in the pathophysiology of preeclampsia. Insufficient trophoblast invasion within the placenta can cause focal regions of ischaemia/hypoxia that, in turn, may stimulate the production of inflammatory cytokines. These cytokines are thought to cause endothelial cell activation and dysfunction, resulting in the clinical signs of preeclampsia. In addition to insufficient trophoblast invasion, the presence of inadequate maternal vasculature remodelling by trophoblasts also leads to changes in angiogenesis that may result from variations in the inflammatory cytokine profile. AIMS: This study examined changes in the protein levels of IL-10 (immunoregulatory), TNF-alpha (pro-inflammatory) and sFlt-1 (anti-angiogenic) in normal term placentas under different oxygen tensions. The second aim was to determine if the link between varying levels of the cytokine, IL-10, and the expression/release of TNF-alpha was oxygen dependent, and whether there was a concurrent change in sFlt-1. METHODS: Normal term placentas (n=6) were cultured at three different oxygen tensions (2%, 8% or 21%) in the presence or absence of exogenous IL-10. Protein (TNF-alpha and sFlt-1) secretion was measured using commercial ELISA kits, and qRT-PCR was used to examine gene expression. RESULTS: Placental IL-10 release was significantly reduced at 2% oxygen when compared to 8% (p=0.045) and 21% (p=0.013). Expression of TNF-alpha and sFlt-1 was not significantly different. Exogenous IL-10 significantly reduced TNF-alpha protein levels only when explants were cultured in 2% oxygen (p=0.05). Soluble Flt-1 protein secretion was unaffected by the addition of IL-10 at any of the oxygen tensions tested. CONCLUSION: TNF-alpha release can be inhibited in vitro by IL-10 under hypoxic conditions. However, IL-10 has no affect on sFlt-1 in term placentas, suggesting that these molecules act either via different pathways, or if linked, may be so at different stages of placental development.

Placental Growth Factor Reduces Blood Pressure in a Uteroplacental Ischemia Model of Preeclampsia in Nonhuman Primates.

An imbalance in the angiogenesis axis during pregnancy manifests as clinical preeclampsia because of endothelial dysfunction. Circulating soluble fms-like tyrosine kinase 1 (sFLT-1) increases and placental growth factor (PlGF) reduces before and during disease. We investigated the clinical and biochemical effects of replenishing the reduced circulating PlGF with recombinant human PlGF (rhPlGF) and thus restoring the angiogenic balance. Hypertensive proteinuria was induced in a nonhuman primate (Papio hamadryas) by uterine artery ligation at 136 days gestation (of a 182-day pregnancy). Two weeks after uteroplacental ischemia, rhPlGF (rhPlGF, n=3) or normal saline (control, n=4) was administered by subcutaneous injection (100 µg/kg per day) for 5 days. Blood pressure was monitored by intra-arterial radiotelemetry and sFLT-1 and PlGF by ELISA. Uteroplacental ischemia resulted in experimental preeclampsia evidenced by increased blood pressure, proteinuria, and endotheliosis on renal biopsy and elevated sFLT-1. PlGF significantly reduced after uteroplacental ischemia. rhPlGF reduced systolic blood pressure in the treated group (-5.2±0.8 mm Hg; from 132.6±6.6 mm Hg to 124.1±7.6 mm Hg) compared with an increase in systolic blood pressure in controls (6.5±3 mm Hg; from 131.3±1.5 mm Hg to 138.6±1.5 mm Hg). Proteinuria reduced in the treated group (-72.7±55.7 mg/mmol) but increased in the control group. Circulating levels of total sFLT-1 were not affected by the administration of PlGF; however, a reduction in placental sFLT-1 mRNA expression was demonstrated. There was no significant difference between the weights or lengths of the neonates in the rhPlGF or control group; however, this study was not designed to assess fetal safety or outcomes. Increasing circulating PlGF by the administration of rhPlGF improves clinical parameters in a primate animal model of experimental preeclampsia.

Yeast diversity sampling on the San Juan Islands reveals no evidence for the spread of the Vancouver Island Cryptococcus gattii outbreak to this locale.

Biological diversity has been estimated for various phyla of life, such as insects and mammals, but in the microbe world is has been difficult to determine species richness and abundance. Here we describe a study of species diversity of fungi with a yeast-like colony morphology from the San Juan Islands, a group of islands that lies southeast of Vancouver Island, Canada. Our sampling revealed that the San Juan archipelago biosphere contains a diverse range of such fungi predominantly belonging to the Basidiomycota, particularly of the order Tremellales. One member of this group, Cryptococcus gattii, is the etiological agent of a current and ongoing outbreak of cryptococcosis on nearby Vancouver Island. Our sampling did not, however, reveal this species. While the lack of recovery of C. gattii does not preclude its presence on the San Juan Islands, our results suggest that the Strait of Juan de Fuca may be serving as a geographical barrier to restrict the dispersal of this primary human fungal pathogen into the United States.