Induction of SM-α-actin expression by mechanical strain in adult vascular smooth muscle cells is mediated through activation of JNK and p38 MAP kinase☆

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Abstract

Mechanical forces have direct effects on the growth and differentiation of vascular smooth muscle. The goal of this study was to examine the effects of cyclic mechanical strain on expression of smooth muscle-α-actin (SM-α-actin), a marker for the differentiated state of vascular smooth muscle, in cultured rat aortic smooth muscle cells (VSMC). Cells grown on dishes coated with either laminin or pronectin were subjected to mechanical strain and effects on expression of SM-α-actin were evaluated using the Flexercell Strain Unit. Application of mechanical strain to cells in full media increased SM-α-actin protein expression and promoter activity. This was not associated with any effect on growth. Mechanical strain increased activity of all three members of the MAP kinase family (ERKs, JNKs, and p38 MAP kinase), with similar kinetics. Inhibition of either JNKs or p38 MAP kinase blocked the strain-induced increase in SM-α-actin promoter activity, and expression of constitutively active forms of JNK or MKK6, a p38 kinase, increased promoter activity. These studies indicate that in adult VSMC, mechanical strain leads to increased expression of smooth muscle markers, resulting in a more contractile phenotype.

Section snippets

Materials and methods

Cell culture and application of mechanical strain. Rat aortic VSMC were isolated from adult male Sprague–Dawley rats and passaged as previously described [13], [14]. Fetal VSMC were a gift of Dr. Mary Weiser (Department of Pediatrics, UCHSC). Adult cells were maintained in Eagle’s minimum essential medium (EMEM) with 10% fetal bovine serum (FBS) and antibiotics at 37 °C, in a humidified atmosphere of 5% CO2; fetal cells were maintained in DMEM with 10% (FBS). Prior to application of mechanical

Results

SM-α-actin is the most commonly used marker for VSMC phenotypic characterization. We and others have shown that expression of SM-α-actin is regulated by vasoconstrictors, polypeptide growth factors, and extracellular matrix [15], [16], [17], [18]. To examine the effects of cyclic mechanical strain on SM-α-actin expression, strain was applied to adult rat VSMC grown on either pronectin or laminin matrices at a frequency of 60 cycles/min, 5% elongation, for 72 h. SM-α-actin protein levels were

Discussion

Mechanical stresses are innate to the in vivo environment of the vascular smooth muscle cell, due to the pulsatile nature of blood flow. In disease settings, such as atherosclerosis and chronic hypertension, alterations in such mechanical forces likely play a significant role in pathologic changes seen in the vessel wall. As such, the effect of mechanical strain on the phenotypic state of the vascular smooth muscle cell is an important area of investigation. Previous studies have examined the

Acknowledgements

This work was supported by grants from the NIH (HL 62824, DK 19928, and DK 39902).

References (31)

  • B.E. Sumpio et al.

    J. Surg. Res.

    (1988)
  • C. Garat et al.

    J. Biol. Chem.

    (2000)
  • M.B. Hautmann et al.

    J. Biol. Chem.

    (1997)
  • V. Fatigati et al.

    J. Biol. Chem.

    (1984)
  • G.K. Owens et al.

    J. Biol. Chem.

    (1986)
  • H.P. Reusch et al.

    Biochem. Biophys. Res. Commun.

    (1997)
  • H.P. Reusch et al.

    J. Biol. Chem.

    (2001)
  • M.J. Davis et al.

    Am J. Physiol. Heart Circ. Physiol.

    (2001)
  • A.J. Banes et al.

    J. Cell Sci.

    (1985)
  • A.J. Banes et al.

    Am. Biotechnol. Lab.

    (1989)
  • N. Bardy et al.

    Circ. Res.

    (1995)
  • K.G. Birukov et al.

    Mol. Cell. Biochem.

    (1995)
  • E. Wilson et al.

    J. Cell. Biol.

    (1993)
  • A. Hipper et al.

    Pflugers Arch.

    (2000)
  • B.L. Langille et al.

    Am J. Physiol.

    (1989)

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    ☆

    Abbreviations: VSMC, vascular smooth muscle cells; MEM, minimal essential media; MAPK, mitogen-activated protein kinase, ERK, extracellular regulated kinase; JNK, Jun-amino terminal kinase; FCS, fetal calf serum.

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