OR07-4 Preterm Birth and Transgenerational Epigenetic Programming of Hypertension in Mice

Introduction: Prematurity, a worldwide health issue, is often associated with renal tubular immaturity leading to major salt loss, whose mechanisms remain poorly understood. Moreover, these premature infants are prone to develop early hypertension in adulthood. Objective: To study ontogenesis of renal mineralocorticoid and glucocorticoid signaling pathways in preterm mice, and to evaluate their contribution to neonatal adaptation and to the emergence of hypertension in adulthood. Materials and Methods: We have developed a murine model of prematurity induced by intra-peritoneal injection of O111/B4 lipopolysaccharides (LPS) at 18 days of gestation in Swiss CD1 mice. Offspring of injected mice, when LPS did not trigger preterm birth, were used as a control to exclude intrinsic LPS effects. Pups were sacrificed at various developmental stages (D0, D7 and M6). Blood pressure and heart rate were measured in males at M6 and their plasma steroid profiles were measured using LC-MSMS. Renal mRNA and protein expression of major players of corticosteroid signaling pathways were examined using RT-qPCR and western-blot analyses. Second (F2) and third (F3) generations, established by mating prematurely born adult females with wild type males, were also analyzed. We performed Methylation DNA Immunoprecipitation-qPCR to study the methylation status of candidate corticosteroid target genes that were differentially expressed between the 2 populations. Results: As anticipated, preterm newborn mice presented with maladaptation, high neonatal mortality (35%), and a lower birth weight compared to controls (1.29±0.21 vs 1.46±0.15g, P=0.0027). Former preterm males developed hypertension at M6 (123.1±1.43 vs 114.5±0.79mmHg, P<0.0001). We found a robust activation of renal corticosteroid target gene transcription at birth in preterm mice (αENaC (+45%), Sgk1 (+132%), Gilz (+85%)), which was not related to modified expression of the mineralocorticoid receptor (MR) and glucocorticoid receptor (GR). Interestingly, a significant increased blood pressure was found in the F2 and F3 males, descendants of the preterm group, concomitantly with increased renal Gilz mRNA expression, despite similar MR or GR expression, and plasma aldosterone or corticosterone levels. Gilz promoter methylation was reduced in preterm offspring with a negative correlation between methylation and expression (P=0.008), highly suggestive of an epigenetic Gilz regulation. Conclusion: We provide first evidence for alterations of the renal corticosteroid signaling pathways induced by prematurity, with a trans-generational transmission of blood pressure dysregulation, associated with epigenetic Gilz regulation. This study should allow better understanding of prematurity-related defects, leading hopefully to better management of premature infants from birth to adulthood.