Cyclooxygenase-2-dependent phosphorylation of the pro-apoptotic protein Bad inhibits tonicity-induced apoptosis in renal medullary cells

Kidney Int. 2011 Nov;80(9):938-945. doi: 10.1038/ki.2011.199. Epub 2011 Jun 29.

Abstract

During antidiuresis, cell survival in the renal medulla requires cyclooxygenase-2 (COX-2) activity. We have recently found that prostaglandin E2 (PGE2) promotes cell survival by phosphorylation and, hence, inactivation of the pro-apoptotic protein Bad during hypertonic stress in Madin-Darby canine kidney (MDCK) cells in vitro. Here we determine the role of COX-2-derived PGE(2) on phosphorylation of Bad and medullary apoptosis in vivo using COX-2-deficient mice. Both wild-type and COX-2-knockout mice constitutively expressed Bad in tubular epithelial cells of the renal medulla. Dehydration caused a robust increase in papillary COX-2 expression, PGE2 excretion, and Bad phosphorylation in wild-type, but not in the knockout mice. The abundance of cleaved caspase-3, a marker of apoptosis, was significantly higher in papillary homogenates, especially in tubular epithelial cells of the knockout mice. Knockdown of Bad in MDCK cells decreased tonicity-induced caspase-3 activation. Furthermore, the addition of PGE2 to cells with knockdown of Bad had no effect on caspase-3 activation; however, PGE2 caused phosphorylation of Bad and substantially improved cell survival in mock-transfected cells. Thus, tonicity-induced COX-2 expression and PGE2 synthesis in the renal medulla entails phosphorylation and inactivation of the pro-apoptotic protein Bad, thereby counteracting apoptosis in renal medullary epithelial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Apoptosis* / drug effects
  • Caspase 3 / metabolism
  • Cell Line
  • Cyclooxygenase 2 / deficiency
  • Cyclooxygenase 2 / genetics
  • Cyclooxygenase 2 / metabolism*
  • Cyclooxygenase 2 Inhibitors / pharmacology
  • Dehydration / enzymology
  • Dehydration / pathology
  • Dinoprostone / metabolism
  • Disease Models, Animal
  • Dogs
  • Epithelial Cells / drug effects
  • Epithelial Cells / enzymology*
  • Epithelial Cells / pathology
  • Kidney Medulla / drug effects
  • Kidney Medulla / enzymology*
  • Kidney Medulla / pathology
  • Mice
  • Mice, 129 Strain
  • Mice, Inbred C57BL
  • Mice, Knockout
  • Osmotic Pressure
  • Phosphorylation
  • RNA Interference
  • Saline Solution, Hypertonic
  • bcl-Associated Death Protein / metabolism*

Substances

  • Bad protein, mouse
  • Cyclooxygenase 2 Inhibitors
  • Saline Solution, Hypertonic
  • bcl-Associated Death Protein
  • Ptgs2 protein, mouse
  • Cyclooxygenase 2
  • Casp3 protein, mouse
  • Caspase 3
  • Dinoprostone