Abstract 19149: Estrogen Reverses Remodeling of the Molecular Correlates of IKslow Expression and Caveolins Associated with Right Ventricular Failure
Introduction: Recently we discovered that estrogen (E2) can rescue severe pulmonary hypertension (PH) by restoring lung and heart function. However, exact molecular mechanisms of this rescue are not clear. PH is associated with right ventricular failure (RVF) and increased incidence of arrhythmias. Thus, we explored if regulation of IKslow expression, one of the major repolarizing currents in rodent hearts, by E2 is one of the mechanisms contributing to improved heart function. As caveolins (CAV) are known to associate with molecular correlates of IKslow and defects in CAV have been shown to cause PH, we also examined regulation of CAV in E2 rescue of PH.
Methods: ph with rvf was induced in rats by s.c. monocrotaline (mct, 60 mg/kg, n=13). after 21 days, one group received e2 (n=6) for 10 days. saline treated rats were control (ctrl, n=6). at day 31, a period of increased sudden death, the rats were sacrificed. rt pcr, western blot and confocal microscopy were performed in rv (n=10). p<0.05 was considered significant. values are mean±se.
results: RT PCR of the molecular correlates of IKslow, Kv1.5 and Kv2.1 revealed that only Kv1.5 transcripts were downregulated ∼2 fold in RVF. Kv 1.5 protein was also reduced ∼8 fold in RVF (0.12±0.03 in MCT vs. 1±0.18 in CTRL, p<0.05) and E2 partially restored Kv1.5 protein (0.46±0.06, p<0.05 vs. MCT). KCNE2, an ancillary K channel subunit, has been shown to associate with Kv1.5 in murine heart. There was a significant reduction in KCNE-2 protein ∼3 fold in MCT (0.3±0.1 in MCT vs. 1±0.1 in CTRL, p<0.05) that was reversed by E2 (0.9±0.05, p<0.05 vs. MCT). Both CAV-3 (0.22±0.1 in MCT vs. 1±0.05 in CTRL, p<0.05) and CAV-1 (0.026±0.008 in MCT vs. 1±0.3 in CTRL, p<0.05) proteins were downregulated in MCT by ∼5 and ∼40 fold respectively and their protein levels were restored to levels comparable to CTRL by E2 (CAV-3 0.8±0.1, CAV-1 0.74±0.24, p<0.05 vs. MCT). Confocal microscopy revealed that Kv1.5, KCNE2 and Cav-3 were all distributed at surface and t-tubules in CTRL. These proteins almost disappeared from the surface and t-tubules and Kv1.5 was mainly distributed at intercalated disks in RVF. E2 was able to restore the subcellular distribution of KV1.5, KCNE2 and CAV3 to CTRL.
Conclusions: E2 reverses remodeling of K-channels and Caveolins associated with RVF.
- © 2010 by American Heart Association, Inc.