Induction of Pro-Fibrotic CLIC4 in Dermal Fibroblasts by TGF-β/Wnt3a Is Mediated by GLI2 Upregulation

Area of Science:

• Fibrosis research
• Cell signalling pathways
• Dermatology

Background:

• Chloride intracellular channel 4 (CLIC4) is identified as a key regulator of fibroblast activation.
• Fibroblast activation is implicated in Scleroderma (SSc) and cancer-associated fibroblasts (CAF).
• Transforming growth factor-beta (TGF-β) signaling via SMAD3 regulates CLIC4, but other pathways' roles are unclear.

Purpose of the Study:

• To investigate the role of Wnt-3a and Hedgehog (Hh) signaling in CLIC4 upregulation.
• To explore the interplay between TGF-β, Wnt-3a, and Hh signaling in driving CLIC4 expression.
• To assess CLIC4 as a therapeutic target for fibroblast-driven diseases.

Main Methods:

• Investigated signaling crosstalk between TGF-β/SMAD3, Wnt-3a/β-catenin, and Smoothened/GLI pathways.
• Utilized normal dermal fibroblasts for experimental models.
• Assessed the impact of inhibiting β-catenin, GLI, and CLIC4 on fibroblast activation and pro-fibrotic marker expression.

Main Results:

• TGF-β/SMAD3 signaling cooperates with Wnt-3a/β-catenin and Smoothened/GLI to induce CLIC4 expression.
• Inhibition of β-catenin and GLI abolished TGF-β/SMAD3-dependent CLIC4 induction.
• CLIC4 expression strongly correlated with the pro-fibrotic marker α-smooth muscle actin.
• CLIC4 inhibition reversed morphogen-dependent fibroblast activation.

Conclusions:

• CLIC4 is a common downstream target of TGF-β, Hh, and Wnt-3a signaling through pathway crosstalk.
• CLIC4 plays a critical role in fibroblast activation relevant to fibrotic diseases.
• CLIC4 inhibitors represent a promising therapeutic strategy for Scleroderma and other fibrotic conditions.