Rapamycin inhibition of mTORC1 reverses lithium-induced proliferation of renal collecting duct cells

Yang Gao, Melissa J. Romero-Aleshire, Qi Cai, Theodore J. Price, Heddwen L. Brooks

Research output: Contribution to journalArticle

14 Scopus citations

Abstract

Nephrogenic diabetes insipidus (NDI) is the most common renal side effect in patients undergoing lithium therapy for bipolar affective disorders. Approximately 2 million US patients take lithium of whom ~50% will have altered renal function and develop NDI (2, 37). Lithium-induced NDI is a defect in the urinary concentrating mechanism. Lithium therapy also leads to proliferation and abundant renal cysts (microcysts), commonly in the collecting ducts of the cortico-medullary region. The mTOR pathway integrates nutrient and mitogen signals to control cell proliferation and cell growth (size) via the mTOR Complex 1 (mTORC1). To address our hypothesis that mTOR activation may be responsible for lithium-induced proliferation of collecting ducts, we fed mice lithium chronically and assessed mTORC1 signaling in the renal medulla. We demonstrate that mTOR signaling is activated in the renal collecting ducts of lithium-treated mice; lithium increased the phosphorylation of rS6 (Ser240/Ser244), p-TSC2 (Thr1462), and p-mTOR (Ser2448). Consistent with our hypothesis, treatment with rapamycin, an allosteric inhibitor of mTOR, reversed lithium-induced proliferation of medullary collecting duct cells and reduced levels of p-rS6 and p-mTOR. Medullary levels of p-GSK3β were increased in the renal medullas of lithium-treated mice and remained elevated following rapamycin treatment. However, mTOR inhibition did not improve lithium-induced NDI and did not restore the expression of collecting duct proteins aquaporin-2 or UT-A1.

Original languageEnglish (US)
Pages (from-to)F1201-F1208
JournalAmerican Journal of Physiology - Renal Physiology
Volume305
Issue number8
DOIs
StatePublished - Oct 15 2013

Keywords

  • Aquaporin-2
  • Collecting ducts
  • GSK3ß
  • Urea transporter

ASJC Scopus subject areas

  • Physiology
  • Urology

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