Physiological and biochemical determinants of hypertension and renal dysfunction in a preclinical model of sleep apnea and estrogen loss - PROJECT SUMMARY/ABSTRACT In this proposal we seek to identify the physiological and biochemical mechanisms by which sleep apnea (SA), may contribute to hypertension (HTN) and kidney dysfunction. We hypothesize that chronic intermittent hypoxia (CIH) causes reductions in renal blood flow (RBF) and tissue oxygen levels (PO2) secondary to increased renal sympathetic nerve activity (RSNA) in males. Crucially, these reductions in RBF lead to downregulation of the shear stress-sensitive transcription factor KLF2 in renal endothelial cells. KLF2 controls expression of genes related to endothelin-1, antioxidant enzymes, eNOS, inflammation, and fibrosis in the kidney. We propose the loss of KLF2 and dysregulation of its downstream targets leads to sodium retention, HTN, and renal damage. In females we hypothesize that circulating estrogen plays a protective role, and that estrogen loss (via ovariectomy, OVX) will result in a similar cardio-renal phenotype to males in our experimental model of SA. To test this hypothesis we will expose male, female, and OVX female rats to CIH and measure arterial pressure (BP, tail cuff and telemetry), RBF, glomerular filtration rate (GFR), sodium excretion, PO2, expression of renal KLF2 and important downstream targets (ET-1, NRF2, eNOS, TGFβ) as well as biomarkers of renal injury (NGAL, IL-18, KIM-1, creatinine, fibrosis). Biochemical pathways will be assessed using standard laboratory techniques (ELISA, qRT-PCR, western blot, Masson’s Trichrome). Aim I of the proposed studies will determine the relationship between RSNA-mediated reductions in RBF and biochemical changes that occur in the kidney after CIH. We will measure of ET-1, ADMA and BH4, NGAL, KIM-1, creatinine various cytokines (using a multiplex array), and collagen content and expression of KLF2, eNOS, NRF2, pro-inflammatory cytokines, nitrotyrosine, and TGFβ in the kidneys of male and female rats (intact and OVX) with and without renal denervation. Aim II will explore the effectiveness of the g-protein coupled estrogen receptor agonist G1 to prevent downregulation of KLF2 in the kidney associated with CIH exposure. Using the techniques described for AIM I, these studies will determine the relative effectiveness of G1 in attenuating these adverse consequences. These studies will determine if CIH per se contributes to persistent disruption of renal hemodynamic regulation and oxygen homeostasis and will explore the role of sex steroid hormones in this process. Finally, the studies outlined in this proposal will have a positive impact on the institutional research environment at Des Moines University Medicine and Health Sciences by providing crucial resources for the research training of medical students and supporting the growth of DMU’s biomedical research enterprise.
