TY - JOUR
T1 - N-(methylamino)isobutyric acid inhibits proliferation of CFSC-2C hepatic stellate cells
AU - Freeman, T. L.
AU - Thiele, Geoffrey Milton
AU - Klassen, Lynell Warren
AU - Klassen, B. T.
AU - Mailliard, Mark E
N1 - Funding Information:
The contribution of T.M. Donohue (Ph.D.) and D.J. Tuma (Ph.D.) are acknowledged for help with the protein degradation study and for excellent guidance during the development of this work, respectively. The Omaha Veterans Medical Center and the University of Nebraska Medical Center are acknowledged for supporting this research by contribution of both funds and space.
PY - 2004/7/15
Y1 - 2004/7/15
N2 - Activation of hepatic stellate cells (HSCs) involves the induction of ECM protein synthesis and rapid cell proliferation. Thus, agents that interfere with either process could potentially mitigate the development of liver disease by reducing the synthesis of proteins associated with fibrosis or by reducing the number of activated HSC. Previously, we described that the non-metabolizable amino acid analog N-(methylamino)isobutyric acid (MeAIB) reduced hepatic collagen content of rats in a model of CCl4-induced liver injury, and in vitro studies using CFSC-2G cells indicated that MeAIB directly reduced collagen synthesis. However, the MeAIB-mediated reduction of hepatic collagen, in vivo, following liver injury was associated with a decrease in hepatic α-smooth muscle actin (α-SMA) which suggested that MeAIB also inhibited the activation of HSCs. Because HSC activation is inseparable from proliferation, the purpose of this study was to examine the effect of MeAIB treatment on the proliferation of HSCs in an in vitro model utilizing CFSC-2G cell cultures. In these studies, MeAIB effectively inhibited the proliferation of CFSC-2G cells by interfering with the progression of the cells through the G1-phase of the cell cycle which delayed entry into S-phase. MeAIB prevented the phosphorylation of p70S6 kinase (p70S6K) at Thr389 and reduced the phosphorylation at Thr421/Ser424. Because p70S6K is required for G 1-cell cycle progression and is known to be regulated by nutrient availability, this correlates well with MeAIB interfering with the proliferation of CFSC-2G HSCs. In addition, the rate of protein synthesis was reduced by MeAIB treatment following mitogenic stimulation, which agrees with a p70S6K-mediated reduction in translation. These data are consistent with MeAIB inhibiting the proliferation of CFSC-2G cells by altering the mitogen activated pathway(s) leading to phosphorylation of p70S6K by a yet to be described mechanism.
AB - Activation of hepatic stellate cells (HSCs) involves the induction of ECM protein synthesis and rapid cell proliferation. Thus, agents that interfere with either process could potentially mitigate the development of liver disease by reducing the synthesis of proteins associated with fibrosis or by reducing the number of activated HSC. Previously, we described that the non-metabolizable amino acid analog N-(methylamino)isobutyric acid (MeAIB) reduced hepatic collagen content of rats in a model of CCl4-induced liver injury, and in vitro studies using CFSC-2G cells indicated that MeAIB directly reduced collagen synthesis. However, the MeAIB-mediated reduction of hepatic collagen, in vivo, following liver injury was associated with a decrease in hepatic α-smooth muscle actin (α-SMA) which suggested that MeAIB also inhibited the activation of HSCs. Because HSC activation is inseparable from proliferation, the purpose of this study was to examine the effect of MeAIB treatment on the proliferation of HSCs in an in vitro model utilizing CFSC-2G cell cultures. In these studies, MeAIB effectively inhibited the proliferation of CFSC-2G cells by interfering with the progression of the cells through the G1-phase of the cell cycle which delayed entry into S-phase. MeAIB prevented the phosphorylation of p70S6 kinase (p70S6K) at Thr389 and reduced the phosphorylation at Thr421/Ser424. Because p70S6K is required for G 1-cell cycle progression and is known to be regulated by nutrient availability, this correlates well with MeAIB interfering with the proliferation of CFSC-2G HSCs. In addition, the rate of protein synthesis was reduced by MeAIB treatment following mitogenic stimulation, which agrees with a p70S6K-mediated reduction in translation. These data are consistent with MeAIB inhibiting the proliferation of CFSC-2G cells by altering the mitogen activated pathway(s) leading to phosphorylation of p70S6K by a yet to be described mechanism.
KW - ALLN
KW - ECM
KW - MAPK
KW - MeAIB
KW - N-(methylamino)isobutyric acid
KW - N-acetyl-leu-leu-norleu-al
KW - N-boc-ile-glu-(O-t-butyl)-ala-leucinal
KW - PSI
KW - extracellular matrix
KW - mitogen activated protein kinase
KW - p70S6 kinase
KW - p70S6K
KW - α-SMA
KW - α-smooth muscle actin
UR - http://www.scopus.com/inward/record.url?scp=2942602937&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=2942602937&partnerID=8YFLogxK
U2 - 10.1016/j.bcp.2004.03.012
DO - 10.1016/j.bcp.2004.03.012
M3 - Article
C2 - 15193994
AN - SCOPUS:2942602937
SN - 0006-2952
VL - 68
SP - 223
EP - 230
JO - Biochemical Pharmacology
JF - Biochemical Pharmacology
IS - 2
ER -