Stretch-induced contractile differentiation of vascular smooth muscle: sensitivity to actin polymerization inhibitors.
Signaling mechanisms for stretch-dependent growth and differentiation of vascular smooth muscle were investigated in mechanically loaded rat portal veins in organ culture. Stretch-dependent protein synthesis was found to depend on endogenous release of angiotensin II. Autoradiography after [(35)S]methionine incorporation revealed stretch-dependent synthesis of several proteins, of which SM22 and actin were particularly prominent. Inhibition of RhoA activity by cell-permeant C3 toxin increased tissue mechanical compliance and reduced stretch-dependent extracellular signal-regulated kinase (ERK)1/2 activation, growth, and synthesis of actin and SM22, suggesting a role of the actin cytoskeleton. In contrast, inhibition of Rho-associated kinase by Y-27632 did not reduce ERK1/2 phosphorylation or actin and SM22 synthesis and did not affect tissue mechanical compliance but still inhibited overall growth. The actin polymerization inhibitors latrunculin B and cytochalasin D both inhibited growth and caused increased tissue compliance. Whereas latrunculin B concentration-dependently reduced actin and SM22 synthesis, cytochalasin D did so at low (10(-8) M) but not at high (10(-6) M) concentration. The results show that stretch stabilizes the contractile smooth muscle phenotype. Stretch-dependent differentiation marker expression requires an intact cytoskeleton for stretch sensing, control of protein expression via the level of unpolymerized G-actin, or both.
Division of Molecular and Cellular Physiology, Department of Physiological Sciences, Biomedical Center, Lund University, SE-221 84 Lund, Sweden.
Asad
A
Zeidan
Ina
I
Nordström
Sebastian
S
Albinsson
Ulf
U
Malmqvist
Karl
K
Swärd
Per
P
Hellstrand
D000199:Actins / Q000378:metabolism*; D000804:Angiotensin II / Q000378:metabolism; D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000378:metabolism; D002454:Cell Differentiation / Q000502:physiology*; D046508:Culture Techniques; D015638:Cytochalasin D / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000378:metabolism*; D005260:Female; D020935:MAP Kinase Signaling System / Q000502:physiology; D008840:Microfilament Proteins / Q000378:metabolism; D009119:Muscle Contraction / Q000502:physiology*; D009124:Muscle Proteins / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D019384:Nucleic Acid Synthesis Inhibitors / Q000378:metabolism; D011169:Portal Vein; D051381:Rats; D017207:Rats, Sprague-Dawley; D013314:Stress, Mechanical; D013844:Thiazoles / Q000378:metabolism; D053778:Thiazolidines; D020742:rhoA GTP-Binding Protein / Q000378:metabolism
D000199:Actins; D019086:Bridged Bicyclo Compounds, Heterocyclic; D004791:Enzyme Inhibitors; D008840:Microfilament Proteins; D009124:Muscle Proteins; D019384:Nucleic Acid Synthesis Inhibitors; C058992:Tagln protein, mouse; D013844:Thiazoles; D053778:Thiazolidines; C051615:transgelin; D000804:Angiotensin II; D015638:Cytochalasin D; D020742:rhoA GTP-Binding Protein; C037068:latrunculin B