Abstract: TH-PO307
Cadmium Attenuates Tonicity Responsive Gene Expression in Kidney Cells via RNA Polymerase II Pausing
Session Information
- Fluid, Electrolyte, and Acid-Base Disorders: Basic
November 03, 2022 | Location: Exhibit Hall, Orange County Convention Center‚ West Building
Abstract Time: 10:00 AM - 12:00 PM
Category: Fluid‚ Electrolyte‚ and Acid-Base Disorders
- 1001 Fluid‚ Electrolyte‚ and Acid-Base Disorders: Basic
Authors
- Zhao, Amy Y., National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
- Kamuche, Princes, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
- Delker, Don, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
- Watts, Jason A., National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina, United States
Background
The kidney is a target organ for many environmental exposures, such as the heavy metal cadmium. Cadmium is taken up by renal epithelial cells, where it accumulates, leading to acute and chronic renal injury. While cadmium is a known nephrotoxin, the transcriptional regulatory mechanisms preceding cadmium-induced renal injury remain largely unexplored. Previously, we identified RNA polymerase II (RNA Pol II) pausing as a mediator of the osmotic stress response. Here, we investigate the transcriptional response to environmental stress and identify cadmium as a modifier of RNA Pol II pausing regulation.
Methods
Cultured renal proximal tubule cells (RPTEC/TERT1) and inner medullary collecting duct cells (IMCD) were exposed to hypertonic salt and cadmium chloride. Changes in transcription were monitored by measuring RNA Pol II gene occupancy, and gene expression was measured by qPCR and RNA-seq.
Results
We began by characterizing the expression of PAX2 and PAX8. These transcription factors are induced in response to hypertonic stress and acute kidney injury, and they are regulated by RNA Pol II pausing. In collecting duct and proximal tubule cells, hypertonic stress led to dose-dependent induction of PAX2/8, whereas cadmium treatment resulted in dose-dependent PAX2/8 repression in both cell types. When combined with hypertonic stress, cadmium treatment abrogated the induction of PAX2/8. We extended these results by RNA-seq and identified over 600 genes where cadmium exposure resulted in attenuated gene activation following hypertonic stress. To determine how cadmium mediates this effect, we performed chromatin immunoprecipitation and found that RNA Pol II is recruited to gene promoters following hypertonic stress, but its release into productive elongation is impaired in the presence of cadmium.
Conclusion
Cadmium exposure attenuates tonicity responsive gene expression through stabilization of paused RNA Pol II. This effect on transcription regulation represents a new aspect of cadmium nephrotoxicity, where blocking induction of genes that allow adaptation to hypertonic stress leads to greater cellular injury. These results have implications for renal conditions associated with environmental exposures, such as chronic kidney disease of unknown etiology.
Funding
- Other NIH Support