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| 2. |
- Zeidan, Asad, et al.
(författare)
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Cholesterol Dependence of Vascular ERK1/2 Activation and Growth in Response to Stretch. Role of Endothelin-1.
- 2003
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Ingår i: Arteriosclerosis, Thrombosis and Vascular Biology. - 1524-4636. ; 23:9, s. 1528-1534
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Tidskriftsartikel (refereegranskat)abstract
- Objective— Stretch-induced growth of the vascular wall plays a role in hypertension and neointima formation. Its signal pathways involve integrins, cytoskeleton, membrane receptors, and ion channels, some of which are organized in cholesterol-rich, membrane domains such as lipid rafts or caveolae. This study tested the role of rafts/caveolae in stretch-induced vascular growth by manipulation of membrane cholesterol contents. Methods and Results— Growth and protein synthesis were induced by mechanical stretch of rat portal veins in vitro. Sucrose gradient centrifugation showed stretch-induced tyrosine phosphorylation primarily in fractions containing caveolin-1. Disruption of membrane caveolae with use of methyl-ß-cyclodextrin (mßcd) reduced weight gain, protein synthesis, and DNA synthesis to levels in unstretched, control veins. These effects were partially reversed by restoration of cellular cholesterol contents. Inhibited growth was associated with abolished activation of extracellular signal–regulated kinase (ERK) 1/2 in response to stretch and endothelin-1 (ET-1) but not to angiotensin II. Inhibition of ET-1 type A (ETA) receptors by RF139317 or endothelin-converting enzyme by phosphoramidone abolished stretch-induced ERK1/2 activation, which was, however, unaffected by removal of the endothelium. Conclusions— Stretch-induced growth signaling in vascular smooth muscle depends on cholesterol-rich, membrane microdomains by a mechanism involving ETA receptors that respond to endogenous ET-1 production.
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| 3. |
- Zeidan, Asad
(författare)
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Mechanisms of stretch-induced growth and contractile differentiation in vascular smooth muscle
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vascular smooth muscle can adapt to increased intraluminal pressure by remodelling and hypertrophy, as seen in hypertension. The molecular mechanisms responsible for this are still incompletely characterized. We have developed an organ culture system where strips of rat or mouse portal veins are cultured for 1 to 3 days loaded (stretched) by an attached weight and then studied for morphology, function and biochemical composition. Contractility, tissue weight, protein- and DNA synthesis were all greater compared with unloaded veins. The signalling mechanisms include autocrine effects of endogenously released angiotensin II and endothelin-1 and activation of the MAP kinases ERK 1/2. The growth-promoting effects of stretch and endothelin-1, but not angiotensin II, depend on cholesterol-rich membrane domains (caveolae). Inhibitors of RhoA/Rho kinase and of actin polymerisation decreased stretch-induced growth. Protein synthesis was analysed by autoradiography following gel electrophoresis and showed that stretch promotes the synthesis of contractile and cytoskeletal proteins known to be markers for the contractile phenotype of smooth muscle, e.g. a- and g- actin, the actin associated proteins tropomyosin, calponin and SM22a, and intermediate filament proteins. Synthesis of SM22a and actin was reduced by inhibition of RhoA, ERK1/2, and angiotensin II receptor-1, while inhibition of Rho kinase had no effect. Resistance arteries and portal veins from SM22a-deficient mice showed decreased contractility and actin contents, suggesting a role of this protein in actin filament structure and function. Stretch-induced protein synthesis was unaffected by SM22a ablation. Stretch stimulates growth and differentiation of smooth muscle cells in the vessel wall in a maintained contractile phenotype, in contrast to the growth stimulation in a synthetic non-contractile phenotype seen in vessel injury and atherosclerosis.
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| 4. |
- Zeidan, Asad, et al.
(författare)
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Stretch-dependent modulation of contractility and growth in smooth muscle of rat portal vein
- 2000
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Ingår i: Circulation Research. - 0009-7330. ; 87:3, s. 228-234
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Tidskriftsartikel (refereegranskat)abstract
- Increased intraluminal pressure of the rat portal vein in vivo causes hypertrophy and altered contractility in 1 to 7 days. We have used organ cultures to investigate mechanisms involved in this adaptation to mechanical load. Strips of rat portal vein were cultured for 3 days, either undistended or loaded by a weight. Length-force relations were shifted toward longer length in stretched cultured veins compared with freshly dissected veins, whereas the length-force relations of unstretched cultured veins were shifted in the opposite direction. This occurred after culture either with or without 10% FCS to promote growth. The wet weight of loaded veins increased by 56% in the presence of FCS, whereas that of undistended control veins increased by 24%. No weight increase was seen in serum-free culture. The dry/wet weight ratio decreased during culture with FCS but was not affected by stretch. Electron microscopy revealed increased cell cross-sectional area in stretched relative to unstretched veins, and protein contents were greater, as were [(3)H]thymidine and [(3)H]leucine incorporation rates. Growth responses were associated with the activation of stretch-sensitive extracellular signal-regulated kinases 1 and 2 and were inhibited by herbimycin A and PD 98059, inhibitors of extracellular signal-regulated kinases 1 and 2. The results demonstrate that by culture of whole vascular tissue, smooth muscle cells are maintained in the contractile phenotype and respond to stretch with a physiological adaptation involving hypertrophy/hyperplasia and remodeling of the contractile system, similar to that in vivo. Mechanical stimulation and growth factors are both required for functionally significant growth.
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| 5. |
- Zeidan, Asad, et al.
(författare)
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Stretch-induced contractile differentiation of vascular smooth muscle: sensitivity to actin polymerization inhibitors.
- 2003
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Ingår i: American Journal of Physiology: Cell Physiology. - : American Physiological Society. - 1522-1563 .- 0363-6143. ; 284:6, s. 1387-1396
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Tidskriftsartikel (refereegranskat)abstract
- 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 [35S]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.
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