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IGF-I increases bFGF-induced mitogenesis and upregulates FGFR-1 in rabbit vascular smooth muscle cells

IGF-I increases bFGF-induced mitogenesis and upregulates FGFR-1 in rabbit vascular smooth muscle cells
IGF-I increases bFGF-induced mitogenesis and upregulates FGFR-1 in rabbit vascular smooth muscle cells
Insulin-like growth factor-I (IGF-I) and basic fibroblast growth factor (bFGF) have both been implicated in the abnormal proliferation of vascular smooth muscle cells (VSMC) that occurs after injury to the arterial wall in vivo. We have investigated the effects of these growth factors on proliferation of rabbit aortic smooth muscle cells (RASMC) in vitro. IGF-I, in contrast to bFGF, is a weak mitogen for RASMC. However, when IGF-I (10 ng/ml) was added in combination with bFGF for 24 h, the effect of the two growth factors on DNA synthesis was synergistic at all concentrations tested (P > 0.001 compared with summed values of bFGF alone plus IGF-I alone), and this synergy was also observed at the level of RASMC proliferation (P < 0.001). Time-course experiments indicated that although bFGF was able to stimulate DNA synthesis after 16 h, activity peaked at 24 h, and a synergistic response with IGF-I was not observed before 24 h. Northern blot analysis demonstrated that IGF-I (10 ng/ml) could selectively upregulate fibroblast growth factor receptor-1 (FGFR-1) mRNA 4.0 +/- 0.24-fold (P < 0.001) without a significant effect on FGFR-2, and this induction in FGFR-1 mRNA occurs in a time- and dose-dependent manner. In addition, IGF-I increases FGFR-1 protein levels in RASMC 2.7 +/- 0.12-fold (P < 0.01), as demonstrated by Western blotting, and this upregulation occurs before the peak in DNA synthesis. These results suggest that IGF-I may be capable of increasing the responsiveness of VSMC to bFGF through modulation of FGFR-1.

0363-6135
H1141-H1148
Reape, T.J.
db48b50d-9363-4a03-ae33-36c618718480
Kanczler, J.M.
eb8db9ff-a038-475f-9030-48eef2b0559c
Ward, J.P.
f1bee531-eaea-4bbf-ac1d-3fbdc32d878e
Thomas, C.R.
e8a515ac-87be-453f-b0a2-1652a314801d
Reape, T.J.
db48b50d-9363-4a03-ae33-36c618718480
Kanczler, J.M.
eb8db9ff-a038-475f-9030-48eef2b0559c
Ward, J.P.
f1bee531-eaea-4bbf-ac1d-3fbdc32d878e
Thomas, C.R.
e8a515ac-87be-453f-b0a2-1652a314801d

Reape, T.J., Kanczler, J.M., Ward, J.P. and Thomas, C.R. (1996) IGF-I increases bFGF-induced mitogenesis and upregulates FGFR-1 in rabbit vascular smooth muscle cells. American Journal of Physiology: Heart and Circulatory Physiology, 270 (4), H1141-H1148. (PMID:8967350)

Record type: Article

Abstract

Insulin-like growth factor-I (IGF-I) and basic fibroblast growth factor (bFGF) have both been implicated in the abnormal proliferation of vascular smooth muscle cells (VSMC) that occurs after injury to the arterial wall in vivo. We have investigated the effects of these growth factors on proliferation of rabbit aortic smooth muscle cells (RASMC) in vitro. IGF-I, in contrast to bFGF, is a weak mitogen for RASMC. However, when IGF-I (10 ng/ml) was added in combination with bFGF for 24 h, the effect of the two growth factors on DNA synthesis was synergistic at all concentrations tested (P > 0.001 compared with summed values of bFGF alone plus IGF-I alone), and this synergy was also observed at the level of RASMC proliferation (P < 0.001). Time-course experiments indicated that although bFGF was able to stimulate DNA synthesis after 16 h, activity peaked at 24 h, and a synergistic response with IGF-I was not observed before 24 h. Northern blot analysis demonstrated that IGF-I (10 ng/ml) could selectively upregulate fibroblast growth factor receptor-1 (FGFR-1) mRNA 4.0 +/- 0.24-fold (P < 0.001) without a significant effect on FGFR-2, and this induction in FGFR-1 mRNA occurs in a time- and dose-dependent manner. In addition, IGF-I increases FGFR-1 protein levels in RASMC 2.7 +/- 0.12-fold (P < 0.01), as demonstrated by Western blotting, and this upregulation occurs before the peak in DNA synthesis. These results suggest that IGF-I may be capable of increasing the responsiveness of VSMC to bFGF through modulation of FGFR-1.

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Published date: April 1996

Identifiers

Local EPrints ID: 177635
URI: http://eprints.soton.ac.uk/id/eprint/177635
ISSN: 0363-6135
PURE UUID: acc90f54-c9bd-4bd9-b94f-f8e3087e1fce
ORCID for J.M. Kanczler: ORCID iD orcid.org/0000-0001-7249-0414

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Date deposited: 18 Mar 2011 09:19
Last modified: 09 Jan 2022 03:19

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Contributors

Author: T.J. Reape
Author: J.M. Kanczler ORCID iD
Author: J.P. Ward
Author: C.R. Thomas

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