PDGF isoform-induced proliferation and receptor expression in human cultured airway smooth muscle cells.
The effect of recombinant platelet-derived growth factor (PDGF) isoforms (PDGF-AA, -BB and -AB) on mitogenesis of human cultured airway smooth muscle (ASM) was examined using the MTT-reduction assay and [3H]thymidine incorporation. Results were correlated with expression of PDGF receptor (PDGFR)-alpha and -beta subunits in the absence and presence of fetal calf serum (FCS). When FCS was absent PDGF-AB and -BB were potent mitogens, whereas PDGF-AA was weakly mitogenic, evoking <20% of the maximum response induced by the B-chain isoforms. When FCS (2.5%) was present, all PDGF isoforms stimulated marked ASM proliferation with similar efficacy and potency. Cross-competition binding analysis in FCS-deprived cells revealed that ASM cells in culture express mainly PDGFR-beta. Preincubation with PDGF-AA or PDGFR-alpha neutralizing antiserum abolished PDGF-AA binding and decreased total receptor number by approximately 15%. The ratio of PDGFR-alpha to beta subunits was approximately 1:8, supported by intense immunofluorescence staining for PDGFR-beta and weak staining for PDGFR-alpha. In parallel studies, uptake of [3H]thymidine stimulated by PDGF-AA, but not PDGF-AB or -BB, was inhibited by PDGFR-alpha immobilization. Western immunoblot analysis confirmed expression of mature PDGFR-alpha and -beta subunits in ASM cells. FCS did not cause any detectable increase in PDGFR-alpha expression or in PDGF-AA binding. These data support a role for PDGFR-beta mediating ASM mitogenesis during FCS-free conditions, but in the presence of FCS, both PDGFR-alpha and -beta subunits are linked to mitogenesis. The enhanced mitogenicity of PDGF-AA in the presence of FCS was independent of any detectable upregulation of PDGFR-alpha, suggesting that the inability of PDGF-AA to promote mitogenesis in the absence of FCS is not simply due to relative numbers of PDGFR-alpha and PDGFR-beta.
Hirst
S J
SJ
Department of Allergy and Respiratory Medicine, United Medical and Dental Schools, St. Thomas' Hospital, London, United Kingdom.
Barnes
P J
PJ
Twort
C H
CH
D000328:Adult; D000368:Aged; D000077214:Becaplermin; D001980:Bronchi / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D002455:Cell Division / Q000187:drug effects*; D002478:Cells, Cultured; D005260:Female; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D007700:Kinetics; D008175:Lung Neoplasms / Q000473:pathology / Q000601:surgery; D008297:Male; D008875:Middle Aged; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D010982:Platelet-Derived Growth Factor / Q000378:metabolism / Q000494:pharmacology*; D020574:Proto-Oncogene Proteins c-sis; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor / Q000096:biosynthesis*; D011994:Recombinant Proteins / Q000494:pharmacology; D013936:Thymidine / Q000378:metabolism; D013997:Time Factors
D010982:Platelet-Derived Growth Factor; D020574:Proto-Oncogene Proteins c-sis; D011994:Recombinant Proteins; C075278:platelet-derived growth factor A; D000077214:Becaplermin; D020796:Receptor, Platelet-Derived Growth Factor alpha; D020797:Receptor, Platelet-Derived Growth Factor beta; D017479:Receptors, Platelet-Derived Growth Factor; D013936:Thymidine