PI3K inhibitors reverse the suppressive actions of insulin on CPY2E1 expression by activating stress-response pathways in primary rat hepatocytes

Jaspreet S. Sidhu, Fei Liu, Sean M. Boyle, Curtis J. Omiecinski

Research output: Contribution to journalArticle

27 Citations (Scopus)

Abstract

Insulin-associated signaling pathways are critical in the regulation of hepatic physiology. Recent inhibitor-based studies have implicated a mechanistic role for phosphatidylinositol 3′ kinase (PI3K) in the insulin-mediated suppression of CYP2E1 mRNA levels in hepatocytes. We investigated the dose dependence for this response and for the effects of insulin and extracellular matrix on PI3K signaling and CYP2E1 mRNA expression levels using a highly defined rat primary hepatocyte culture system. The PI3K inhibitors wortmannin and LY294002 stimulated stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) and p38 mitogen-activated protein kinase (MAPK) phosphorylation in a rapid and concentration-dependent manner that paralleled the inhibition of protein kinase B (PKB) phosphorylation. Although PI3K inhibitors reversed the suppressive effects of insulin on CYP2E1 expression, these effects only occurred at concentrations well in excess of those required to achieve complete inhibition of PKB phosphorylation. These same concentrations produced cytotoxic responses as evidenced by perturbed cellular morphology and elevated release of lactate dehydrogenase. Wortmannin-mediated activation of the SAPK/JNK and p38 MAPK pathways also resulted in the mobilization of activator protein-1 complex to the nuclear compartment. We conclude that the suppression of CYP2E1 mRNA expression by insulin is not directly associated with PI3K-dependent pathway activation, but rather is linked to a cytotoxic response stemming from acute challenge with PI3K inhibitors.

Original languageEnglish (US)
Pages (from-to)1138-1146
Number of pages9
JournalMolecular pharmacology
Volume59
Issue number5
DOIs
StatePublished - Jan 1 2001

Fingerprint

Phosphatidylinositol 3-Kinase
Hepatocytes
Cytochrome P-450 CYP2E1
Insulin
Proto-Oncogene Proteins c-akt
JNK Mitogen-Activated Protein Kinases
Phosphorylation
p38 Mitogen-Activated Protein Kinases
Heat-Shock Proteins
Protein Kinases
Messenger RNA
2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one
Critical Pathways
Transcription Factor AP-1
L-Lactate Dehydrogenase
Extracellular Matrix
Liver

All Science Journal Classification (ASJC) codes

  • Molecular Medicine
  • Pharmacology

Cite this

Sidhu, Jaspreet S. ; Liu, Fei ; Boyle, Sean M. ; Omiecinski, Curtis J. / PI3K inhibitors reverse the suppressive actions of insulin on CPY2E1 expression by activating stress-response pathways in primary rat hepatocytes. In: Molecular pharmacology. 2001 ; Vol. 59, No. 5. pp. 1138-1146.
@article{dd4a81f1efbd4d4388a637a65dfff74b,
title = "PI3K inhibitors reverse the suppressive actions of insulin on CPY2E1 expression by activating stress-response pathways in primary rat hepatocytes",
abstract = "Insulin-associated signaling pathways are critical in the regulation of hepatic physiology. Recent inhibitor-based studies have implicated a mechanistic role for phosphatidylinositol 3′ kinase (PI3K) in the insulin-mediated suppression of CYP2E1 mRNA levels in hepatocytes. We investigated the dose dependence for this response and for the effects of insulin and extracellular matrix on PI3K signaling and CYP2E1 mRNA expression levels using a highly defined rat primary hepatocyte culture system. The PI3K inhibitors wortmannin and LY294002 stimulated stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) and p38 mitogen-activated protein kinase (MAPK) phosphorylation in a rapid and concentration-dependent manner that paralleled the inhibition of protein kinase B (PKB) phosphorylation. Although PI3K inhibitors reversed the suppressive effects of insulin on CYP2E1 expression, these effects only occurred at concentrations well in excess of those required to achieve complete inhibition of PKB phosphorylation. These same concentrations produced cytotoxic responses as evidenced by perturbed cellular morphology and elevated release of lactate dehydrogenase. Wortmannin-mediated activation of the SAPK/JNK and p38 MAPK pathways also resulted in the mobilization of activator protein-1 complex to the nuclear compartment. We conclude that the suppression of CYP2E1 mRNA expression by insulin is not directly associated with PI3K-dependent pathway activation, but rather is linked to a cytotoxic response stemming from acute challenge with PI3K inhibitors.",
author = "Sidhu, {Jaspreet S.} and Fei Liu and Boyle, {Sean M.} and Omiecinski, {Curtis J.}",
year = "2001",
month = "1",
day = "1",
doi = "10.1124/mol.59.5.1138",
language = "English (US)",
volume = "59",
pages = "1138--1146",
journal = "Molecular Pharmacology",
issn = "0026-895X",
publisher = "American Society for Pharmacology and Experimental Therapeutics",
number = "5",

}

PI3K inhibitors reverse the suppressive actions of insulin on CPY2E1 expression by activating stress-response pathways in primary rat hepatocytes. / Sidhu, Jaspreet S.; Liu, Fei; Boyle, Sean M.; Omiecinski, Curtis J.

In: Molecular pharmacology, Vol. 59, No. 5, 01.01.2001, p. 1138-1146.

Research output: Contribution to journalArticle

TY - JOUR

T1 - PI3K inhibitors reverse the suppressive actions of insulin on CPY2E1 expression by activating stress-response pathways in primary rat hepatocytes

AU - Sidhu, Jaspreet S.

AU - Liu, Fei

AU - Boyle, Sean M.

AU - Omiecinski, Curtis J.

PY - 2001/1/1

Y1 - 2001/1/1

N2 - Insulin-associated signaling pathways are critical in the regulation of hepatic physiology. Recent inhibitor-based studies have implicated a mechanistic role for phosphatidylinositol 3′ kinase (PI3K) in the insulin-mediated suppression of CYP2E1 mRNA levels in hepatocytes. We investigated the dose dependence for this response and for the effects of insulin and extracellular matrix on PI3K signaling and CYP2E1 mRNA expression levels using a highly defined rat primary hepatocyte culture system. The PI3K inhibitors wortmannin and LY294002 stimulated stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) and p38 mitogen-activated protein kinase (MAPK) phosphorylation in a rapid and concentration-dependent manner that paralleled the inhibition of protein kinase B (PKB) phosphorylation. Although PI3K inhibitors reversed the suppressive effects of insulin on CYP2E1 expression, these effects only occurred at concentrations well in excess of those required to achieve complete inhibition of PKB phosphorylation. These same concentrations produced cytotoxic responses as evidenced by perturbed cellular morphology and elevated release of lactate dehydrogenase. Wortmannin-mediated activation of the SAPK/JNK and p38 MAPK pathways also resulted in the mobilization of activator protein-1 complex to the nuclear compartment. We conclude that the suppression of CYP2E1 mRNA expression by insulin is not directly associated with PI3K-dependent pathway activation, but rather is linked to a cytotoxic response stemming from acute challenge with PI3K inhibitors.

AB - Insulin-associated signaling pathways are critical in the regulation of hepatic physiology. Recent inhibitor-based studies have implicated a mechanistic role for phosphatidylinositol 3′ kinase (PI3K) in the insulin-mediated suppression of CYP2E1 mRNA levels in hepatocytes. We investigated the dose dependence for this response and for the effects of insulin and extracellular matrix on PI3K signaling and CYP2E1 mRNA expression levels using a highly defined rat primary hepatocyte culture system. The PI3K inhibitors wortmannin and LY294002 stimulated stress-activated protein kinase/c-Jun NH2-terminal kinase (SAPK/JNK) and p38 mitogen-activated protein kinase (MAPK) phosphorylation in a rapid and concentration-dependent manner that paralleled the inhibition of protein kinase B (PKB) phosphorylation. Although PI3K inhibitors reversed the suppressive effects of insulin on CYP2E1 expression, these effects only occurred at concentrations well in excess of those required to achieve complete inhibition of PKB phosphorylation. These same concentrations produced cytotoxic responses as evidenced by perturbed cellular morphology and elevated release of lactate dehydrogenase. Wortmannin-mediated activation of the SAPK/JNK and p38 MAPK pathways also resulted in the mobilization of activator protein-1 complex to the nuclear compartment. We conclude that the suppression of CYP2E1 mRNA expression by insulin is not directly associated with PI3K-dependent pathway activation, but rather is linked to a cytotoxic response stemming from acute challenge with PI3K inhibitors.

UR - http://www.scopus.com/inward/record.url?scp=0035040202&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0035040202&partnerID=8YFLogxK

U2 - 10.1124/mol.59.5.1138

DO - 10.1124/mol.59.5.1138

M3 - Article

C2 - 11306697

AN - SCOPUS:0035040202

VL - 59

SP - 1138

EP - 1146

JO - Molecular Pharmacology

JF - Molecular Pharmacology

SN - 0026-895X

IS - 5

ER -