Novel Role of Big Potassium Channels (BK) Activation in Ameliorating Uremic Cardiomyopathy in Chronic Kidney Disease (CKD) Mouse Model Restricted; Files Only
Bian, Shuyang (Spring 2024)
Published
Abstract
Background: Uremic cardiomyopathy and renal fibrosis contribute to chronic kidney disease (CKD)-induced morbidity and mortality. We previously reported that activation of BK channels in renal tubal epithelial cells prevent renal fibrosis in CKD mouse models. Thus, we hypothesized that upregulation of the BK channels would suppress cardiac fibrosis in CKD.
Methods: CKD mice were induced by 5/6 nephrectomy. To upregulate the cardiac and renal BK channel activity, BMS-191011 (10 mg/kg BW), a general BK channel opener or activator, was given by IP injection every day for 6-8 weeks. Single channel recordings were used to analyze the activation of BK channels. Blood pressure was measured by non-invasive photoplethysmography using the tail-cuff method. Echocardiogram was used to detect heart function. Cultured H9C2 cardiac myoblasts were used to detect the impact of NS1916 (20mM), another BK opener, on fibrosis markers and oxidative stress. The mRNA expression of BK in heart was assayed by qPCR. The Hydrogen peroxide (H2O2) was tested by Amplex Red Hydrogen Peroxide Kit. DHE (Dihydroethidium) was assayed to detect superoxide. Superoxide Dismutase (SOD), a downregulator of oxidative enzyme, was measured using colorimetric activity kit.
Results: The expression of BK mRNA and protein was decreased, and cardiac fibrosis was increased in the heart of CKD mice. Single channel recordings showed that human uremic serum (USer) reduced BK channel activity in cardiomyocytes. Activation of BK channel by BSM-191011 decreased the CKD-induced increase in systolic and diastolic blood pressure. Echocardiograms showed that increased left ventricular (LV) end-diastolic dimension in the 5/6Nx mice was reduced after BK opener treatment. Ejection fraction (EF) also improved. Fibronectin and vimentin expression were significantly increased in CKD heart, conversely, but BMS treatment reduced the amount of both proteins. In cultured cardiac myoblasts, USer and TGF-β increased fibronectin and collagen I in a dose-dependent manner. BK openers reduced USer and TGF-induced upregulation of both proteins in H9C2 cells. The USer also significantly increased H2O2 and superoxide production in cultured H9C2 cells. Activation of BK channel significantly abolished this upregulation. In addition, while the USer and TGF-β decrease SOD production, NS1916 blocked this decline in a dose dependent manner.
Conclusions: Activation of BK channels in CKD animals attenuates cardiac fibrosis. The mechanism involves a reduction of uremia-invoked oxidative stress. This study may provide new approaches to develop therapeutic strategies for treating uremic cardiomyopathy in CKD.
Table of Contents
I. INTRODUCTION 2
II. ORGANISMS AND MATERIALS 11
III. METHODS USED 13
IV. RESULTS 21
IN VIVO EXPERIMENTS RESULTS 21
IN VITRO EXPERIMENTS RESULTS USING CARDIOMYOCYTES (H9C2) 29
INDOXYL SULFATE AND MACROPHAGE INTERPLAY 32
TGF-Β AND BK ACTIVATOR 37
V. DISCUSSION, LIMITATIONS, AND FUTURE PLANS 39
APPENDIX. 48
FUNDING 51
BIBLIOGRAPHY 52
About this Honors Thesis
| School | |
|---|---|
| Department | |
| Degree | |
| Submission | |
| Language |
|
| Research Field | |
| Stichwort | |
| Committee Chair / Thesis Advisor | |
| Committee Members |
Primary PDF
| Thumbnail | Title | Date Uploaded | Actions |
|---|---|---|---|
|
|
File download under embargo until 24 May 2026 | 2024-04-29 20:51:31 -0400 | File download under embargo until 24 May 2026 |
Supplemental Files
| Thumbnail | Title | Date Uploaded | Actions |
|---|