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Tumor necrosis factor-induced expression of platelet-derived growth factor A-chain messenger RNA in fibroblasts
Y Paulsson1, R Austgulen, E Hofsli
1Department of Pathology, University Hospital, Uppsala, Sweden.
Abstract:
Recombinant tumor necrosis factor (rTNF) induced a transient increase in the expression of the PDGF A-chain mRNA in FS-4 fibroblasts, as determined by Northern blot hybridization. The mRNA transcripts were of the expected sizes 1.9, 2.3, and 2.8 kb. Increased levels of the PDGF A-chain mRNA were detected 1, 2, and 4 h after addition of rTNF, the highest level being detected after 2 h. After 8 h the mRNA level was similar to that in control cultures. No PDGF B-chain mRNA (c-sis) could be detected following addition of rTNF. There was also an accumulation of PDGF receptor-competing activity in the medium of rTNF-exposed fibroblasts, suggesting that rTNF also induced the synthesis and release of functional PDGF A-chain homodimers (PDGF-AA). The fibroblast growth stimulatory activity in supernatants from rTNF-exposed fibroblasts could be neutralized by antiserum against rTNF, and thus rTNF seemed to be able to act as a direct mitogen. Hence rTNF-induced PDGF-AA is not the main mediator of rTNF's mitogenicity under the conditions investigated.
Insights
Recombinant tumor necrosis factor (rTNF) transiently increased platelet-derived growth factor (PDGF) A-chain mRNA in fibroblasts, suggesting rTNF is a direct mitogen, but PDGF-AA is not its primary mediator.
Area of Science:
- Molecular biology
- Cell signaling
- Biochemistry
Background:
- Tumor necrosis factor (TNF) is a cytokine involved in inflammation and immunity.
- Platelet-derived growth factor (PDGF) is a growth factor that plays a role in cell growth and division.
- The relationship between TNF and PDGF in fibroblast regulation is not fully understood.
Purpose of the Study:
- To investigate the effect of recombinant tumor necrosis factor (rTNF) on PDGF A-chain and B-chain mRNA expression in FS-4 fibroblasts.
- To determine if rTNF induces the synthesis and release of functional PDGF A-chain homodimers (PDGF-AA).
- To assess the role of rTNF-induced PDGF-AA in mediating rTNF's mitogenic activity.
Main Methods:
- FS-4 fibroblasts were treated with rTNF.
- Northern blot hybridization was used to detect PDGF A-chain and B-chain mRNA levels.
- PDGF receptor-competing activity in the cell culture medium was measured.
- Fibroblast growth stimulatory activity was assessed and neutralized with antiserum against rTNF.
Main Results:
- rTNF induced a transient increase in PDGF A-chain mRNA expression, peaking at 2 hours and returning to baseline by 8 hours.
- No PDGF B-chain mRNA (c-sis) was detected after rTNF treatment.
- PDGF receptor-competing activity accumulated in the medium, indicating the release of functional PDGF-AA.
- rTNF exhibited direct mitogenic activity on fibroblasts, but rTNF-induced PDGF-AA was not the primary mediator.
Conclusions:
- rTNF upregulates PDGF A-chain mRNA and stimulates the release of PDGF-AA in fibroblasts.
- While PDGF-AA is produced, it does not appear to be the main mediator of rTNF's mitogenic effects.
- rTNF acts as a direct mitogen for fibroblasts, independent of the induced PDGF-AA.