TY - JOUR
T1 - Mechanical stretch down-regulates expression of the Smad6 gene in cultured rat mesangial cells
AU - Hayashi, Yoshimitsu
AU - Katoh, Tetsuo
AU - Asano, Kenichiro
AU - Onozaki, Akira
AU - Sakurai, Kaoru
AU - Asahi, Koichi
AU - Nakayama, Masaaki
AU - Watanabe, Tsuyoshi
N1 - Funding Information:
This work was supported by a research grant 11671042 from the Ministry of Education and Science of Japan. We thank Dr. K. Miyazono for generous donations of cDNA clones, and we thank Hiroko Ohashi and Atsuko Hashimoto for technical assistance.
PY - 2012/10
Y1 - 2012/10
N2 - Background Glomerular hypertension aggravates glomerular sclerosis by inducing growth factors, e.g., transforming growth factor-b (TGF-b) to mesangial matrix expansion. Smads are intracellular proteins that transmit signals from TGF-b to nucleus, and Smads are also negatively regulated by inhibitory Smads (I-Smads), Smad6 and Smad7. However, little is known about the role of I-Smads in glomerular hypertension. We studied I-Smad expression in cultured mesangial cells subjected to mechanical stretch as an in vitro model of glomerular hypertension. Methods Rat mesangial cells were cultured under cyclic mechanical stretch conditions using the Flexercell Strain Unit. Phosphorylated Smad1 and Smad2 were determined by Western blots. The expression of Smad6 and Smad7 mRNAs was determined by Northern blots. Stretch-mediated I-Smad mRNAs of cells pre-treated with MAPK-ERK kinase inhibitor, U0126, were also determined. Localization of phospho-Smad1, Smad6 and Smad7 proteins in the glomerulus of Dahl salt-sensitive rats was determined by immunohistochemistry. Results Stretch stress increased phospho-Smad1 levels, and significantly decreased Smad6 mRNA to 32 % of control, and increased Smad7 mRNA to 136 % of control. U0126 significantly attenuated stretch-mediated decreases in Smad6 mRNA, but had no effect on stretch-mediated increases in Smad7 mRNA. Phospho-Smad1, Smad6 and Smad7 proteins were localized in podocytes and mesangial cells of Dahl rats. Conclusion Mechanical stretch increases phospho-Smad1 levels and down-regulates Smad6 mRNA expression in mesangial cells. Stretch-mediated down-regulation of Smad6 is partially involved in ERK1/2 activation. These results indicate that glomerular hypertension might augment Smad1 signaling with concomitant attenuation of Smad6-mediated negative feedback.
AB - Background Glomerular hypertension aggravates glomerular sclerosis by inducing growth factors, e.g., transforming growth factor-b (TGF-b) to mesangial matrix expansion. Smads are intracellular proteins that transmit signals from TGF-b to nucleus, and Smads are also negatively regulated by inhibitory Smads (I-Smads), Smad6 and Smad7. However, little is known about the role of I-Smads in glomerular hypertension. We studied I-Smad expression in cultured mesangial cells subjected to mechanical stretch as an in vitro model of glomerular hypertension. Methods Rat mesangial cells were cultured under cyclic mechanical stretch conditions using the Flexercell Strain Unit. Phosphorylated Smad1 and Smad2 were determined by Western blots. The expression of Smad6 and Smad7 mRNAs was determined by Northern blots. Stretch-mediated I-Smad mRNAs of cells pre-treated with MAPK-ERK kinase inhibitor, U0126, were also determined. Localization of phospho-Smad1, Smad6 and Smad7 proteins in the glomerulus of Dahl salt-sensitive rats was determined by immunohistochemistry. Results Stretch stress increased phospho-Smad1 levels, and significantly decreased Smad6 mRNA to 32 % of control, and increased Smad7 mRNA to 136 % of control. U0126 significantly attenuated stretch-mediated decreases in Smad6 mRNA, but had no effect on stretch-mediated increases in Smad7 mRNA. Phospho-Smad1, Smad6 and Smad7 proteins were localized in podocytes and mesangial cells of Dahl rats. Conclusion Mechanical stretch increases phospho-Smad1 levels and down-regulates Smad6 mRNA expression in mesangial cells. Stretch-mediated down-regulation of Smad6 is partially involved in ERK1/2 activation. These results indicate that glomerular hypertension might augment Smad1 signaling with concomitant attenuation of Smad6-mediated negative feedback.
KW - Glomerular hypertension
KW - Mechanical stress
KW - Smad1
KW - Smad6
KW - Stretch
KW - TGF-b
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U2 - 10.1007/s10157-012-0630-6
DO - 10.1007/s10157-012-0630-6
M3 - Article
C2 - 22581061
AN - SCOPUS:84868355502
VL - 16
SP - 690
EP - 696
JO - Clinical and Experimental Nephrology
JF - Clinical and Experimental Nephrology
SN - 1342-1751
IS - 5
ER -