Insulin is a potent survival factor in mesangial cells: role of the PI3-kinase/Akt pathway

Kidney Int. 2002 Apr;61(4):1312-21. doi: 10.1046/j.1523-1755.2002.00257.x.

Abstract

Background: Elucidating the mechanisms of apoptosis is important for understanding the molecular mechanisms underlying glomerular disease. The phosphatidylinositol 3 kinase (PI3-kinase)/Akt pathway is essential for survival signaling in non-renal cells. However, little is known about the anti-apoptotic effect of insulin and the role of the PI3-kinase/Akt pathway in mesangial cells (MC) apoptosis.

Methods: Apoptosis was induced in wild type, p27Kip1 (p27) -/- and p21Cip1/Waf1 (p21) -/- mouse MC by survival factor withdrawal, actinomycin D, ultraviolet (UV)-B irradiation and cycloheximide in the presence or absence of insulin (1 micromol/L) or insulin-like growth factor-I (IGF-I; 100 ng/mL). The activation and levels of Akt, extracellular signal regulated kinase (ERK) and specific cell cycle proteins were determined by Western blot analysis.

Results: Insulin and IGF-I inhibited wild-type MC apoptosis induced by survival factor withdrawal, actinomycin D, ultraviolet-B irradiation and cycloheximide and in p27 -/- MC when apoptosis was induced by survival factor withdrawal. Akt was activated by insulin and IGF-I during apoptosis. Blocking PI3-kinase with LY294002 reduced Akt activation and abrogated the anti-apoptotic effect of insulin. ERK was activated during apoptosis and blocking ERK activation with U0126 or PD98059 partially rescued MC from apoptosis. Moreover, insulin also suppressed ERK activation during apoptosis. Our results also showed that the CDK-inhibitor p21 was increased by insulin and that p21 up-regulation was PI3-kinase/Akt pathway dependent. Furthermore, p21 -/- MC apoptosis induced by survival factor withdrawal was not rescued by insulin in contrast to the wild-type and p27 -/- MC. These data suggest that p21 may have a critical role in the anti-apoptotic effect of insulin.

Conclusions: Insulin is a potent survival factor for MC in response to a number of different apoptotic triggers, and this effect is mediated through the PI3-kinase/Akt pathway. Moreover, ERK and p21 may be involved in anti-apoptotic effect of insulin in MC.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Apoptosis / drug effects
  • Apoptosis / physiology
  • Cell Cycle Proteins / genetics
  • Cell Cycle Proteins / physiology
  • Cell Survival / physiology
  • Cells, Cultured
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclin-Dependent Kinase Inhibitor p27
  • Cyclins / genetics
  • Cyclins / physiology
  • Enzyme Activation / drug effects
  • Enzyme Activation / physiology
  • Enzyme Inhibitors / metabolism
  • Glomerular Mesangium / cytology
  • Glomerular Mesangium / drug effects
  • Glomerular Mesangium / physiology*
  • Insulin / pharmacology
  • Insulin / physiology*
  • Insulin-Like Growth Factor I / pharmacology
  • Mice
  • Mice, Knockout / genetics
  • Mitogen-Activated Protein Kinases / metabolism
  • Phosphatidylinositol 3-Kinases / physiology*
  • Protein-Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / physiology*
  • Proto-Oncogene Proteins c-akt
  • Tumor Suppressor Proteins / genetics
  • Tumor Suppressor Proteins / physiology

Substances

  • Cdkn1a protein, mouse
  • Cdkn1b protein, mouse
  • Cell Cycle Proteins
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • Enzyme Inhibitors
  • Insulin
  • Proto-Oncogene Proteins
  • Tumor Suppressor Proteins
  • Cyclin-Dependent Kinase Inhibitor p27
  • Insulin-Like Growth Factor I
  • Phosphatidylinositol 3-Kinases
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt
  • Mitogen-Activated Protein Kinases