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Published on: September 14, 2021
[Transforming growth factor beta 1 modulates connective tissue growth factor expression via Smad2 signaling pathway
Hai-chang Huang1, Yan Liang, Li-jing Cheng
1Department of Nephrology, Peking University First Hospital, Beijing 100034, China.
Objective:
To assess the expression of connective tissue growth factor (CTGF), and the signaling pathway for the regulation of CTGF by transforming growth factor beta1 (TGF beta(1)) in podocytes.
Methods:
In this study, we observed the effects of three potent profibrotic growth factors-TGF beta(1), Platelet-derived growth factor (PDGF), and Angiotensin II (AngII) on the expression of CTGF protein by Western blot analysis in cultured mouse podocytes, which is one of the most important cell construction of glomerular filter barrier, and we also investigated the underlying ERK and Smads signaling pathway through which TGF beta(1) regulates CTGF expression. The levels of CTGF mRNA were assayed by RT-PCR.
Results:
Basal levels of CTGF protein were observed in cultured podocytes, treatment with 20 ng/ml PDGF and 10(-6) mol/L Ang. II for 24 h did not stimulate the expression of CTGF protein compared with control (P > 0.05), but significantly increase in levels of CTGF protein were seen in 1 ng/ml TGF beta(1) treated cells compared with with control (P < 0.05), and the levels of CTGF were up-regulated in a TGF beta(1) dose-dependent manner; The level of CTGF mRNA was also stimulated by 1 ng/ml TGF beta(1) at 12 h. 1 ng/ml TGF beta(1) induced phosphorylation of Smad(2) and ERK(1/2), and both reached the peak at 30 min; suppression of phosphorylation of Smad(2) with Staurosporine, a Serine/Threonine kinase inhibitor, diminished TGF beta(1)-triggered expression of CTGF protein, while blockade of phosphorylation of ERK(1/2) with PD98059, a specific ERK(1/2) activation inhibitor, did not decrease the TGF beta(1)-triggered expression of CTGF protein.
Conclusion:
TGF beta(1) stimulated the expression of CTGF protein via Smad(2)-dependent and ERK(1/2)-independent signaling pathway in podocyte in vitro.
Insights
Transforming growth factor beta1 (TGF-β1) upregulates connective tissue growth factor (CTGF) in podocytes. This occurs through a Smad2-dependent, ERK1/2-independent pathway, offering insights into kidney disease mechanisms.
Area of Science:
- Nephrology
- Cell Biology
- Molecular Biology
Background:
- Podocytes are crucial for the glomerular filter barrier.
- Connective tissue growth factor (CTGF) plays a role in kidney fibrosis.
- Transforming growth factor beta1 (TGF-β1) is implicated in kidney disease progression.
Purpose of the Study:
- To investigate the regulation of CTGF expression by TGF-β1 in podocytes.
- To elucidate the specific signaling pathways involved in TGF-β1-mediated CTGF regulation.
Main Methods:
- Cultured mouse podocytes were treated with TGF-β1, PDGF, and Angiotensin II.
- CTGF protein and mRNA levels were assessed using Western blot and RT-PCR.
- ERK and Smad signaling pathways were analyzed via phosphorylation assays and inhibitor treatments.
Main Results:
- TGF-β1 significantly increased CTGF protein and mRNA expression in a dose-dependent manner.
- TGF-β1 induced Smad2 and ERK1/2 phosphorylation.
- Inhibition of Smad2 phosphorylation reduced CTGF expression, while ERK1/2 inhibition did not.
Conclusions:
- TGF-β1 stimulates CTGF expression in podocytes.
- The mechanism involves a Smad2-dependent and ERK1/2-independent signaling pathway.
- This finding contributes to understanding the molecular basis of podocyte injury and kidney fibrosis.
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