PLACENTAL CYTOKINES AND PATHOGENESIS OF PREECLAMPSIA

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Inadequate trophoblast invasion and physiologic remodelling of spiral arteries initiate focal placental ischemia and hypoxia in preeclampsia. Placental hypoxia has been implicated in the production of "toxic" factor(s) by the placenta which circulate causing maternal disease allegedly by compromising vascular endothelial function. Trophoblasts and other placental cells normally produce a variety of cytokines, which are potentially deleterious to the vascular endothelium. We recently discovered that trophoblasts and other placental cells also express erythropoietin (EPO), which is the prototype molecule for transcriptional regulation by hypoxia. This finding suggests a new and logical approach to narrowing the search for the "toxic" factor(s) produced in the placenta by hypoxia during preeclampsia, that have remained elusive for years. That is, identification of DNA sequences homologous to the hypoxic responsive-enhancer element of EPO within the genes encoding various cytokines may provide a possible link between placental hypoxia and overproduction of these potentially deleterious factors in preeclampsia. Indeed, our preliminary experiments show that hypoxia stimulates production of TNF-alpha and IL-1beta by placental villous explants, and plasma TNF-alpha is elevated in preeclampsia. An overall goal of this grant proposal is to investigate whether cytokines are overproduced by the placenta in response to hypoxia contributing to increased plasma levels, and thus, endothelial activation and dysfunction in preeclampsia. Although compelling, the evidence suggesting endothelial activation and dysfunction in the disease is mainly circumstantial. Therefore, another goal is to provide direct evidence for endothelial activation by investigating the expression of products of cellular activation (consistent with cytokine stimulation) on the endothelium of blood vessels in skin biopsies, as well as in branches of inferior epigastric arteries and veins. Five Hypotheses and Specific Aims, listed under Specific Aims in the Research Plan, test various aspects of the pathogenesis of preeclampsia as proposed in the following general schema. Of note, the etiology of the disease presumably related to deficient trophoblast invasion is not addressed by this proposal. DEFICIENT TROPHOBLAST INVASION OF SPIRAL ARTERIES------>FOCAL PLACENTAL HYPOXIA AIM4> OVERPRODUCTION OF PLACENTAL CYTOKINES AIM 2 >ELEVATED PLASMA CYTOKINES AIMS 1 & 3 >ENDOTHELIAL ACTIVATION AND DYSFUNCTION AIM5 >DISEASE MANIFESTATIONS