Tadalafil and SB204741 block TGFβ/Smad3 signaling in human valve cells, reducing rheumatic heart disease fibrosis
Background
Rheumatic heart disease (RHD) is a severe consequence of acute rheumatic fever, marked by chronic inflammation, fibrosis, and progressive valve degeneration. Current treatments primarily manage symptoms, as the precise molecular mechanisms driving this pathology remain poorly understood. A critical gap exists in identifying specific pathways that can be therapeutically targeted to halt or reverse the immune-fibrotic remodeling. The TGFβ/SMAD3 and ERK1/2 signaling pathways are known drivers of fibrosis in various tissues, making them compelling targets for investigation in RHD.
Study Design
Researchers conducted LC-MS/MS-based proteomic profiling on RHD mitral valve tissue compared to ischemic controls and validated systemic inflammation via peripheral blood analysis. Human valve interstitial cells (hVICs) were isolated and stimulated with proinflammatory agents (TNFα, IFNγ) and profibrotic TGFβ. Macrophage-hVIC interactions were assessed using conditioned media from M1 (LPS (100 ng/ml) + TNFα (10 ng/ml)) and M2c (TGFβ (10 ng/ml)) polarized macrophages. Finally, hVICs were treated with the 5-HT₂B receptor antagonist SB204741 and tadalafil to evaluate their impact on TGFβ-induced Smad3 phosphorylation and fibrotic signaling.
Results
Proteomic analysis of RHD valve tissue revealed significant upregulation of immune response proteins, TGFβ signaling components, and extracellular matrix (ECM) regulators. Peripheral blood analysis confirmed systemic inflammation with elevated levels of IL6, TNFα, and TIMP1. In hVICs, TGFβ stimulation induced morphological changes within 24 hours, consistent with fibrotic transformation, and significantly upregulated fibrotic markers including ACTA2, COL1A1, COL1A2, TIMP1, CTGF, MMP2, and TGFβ, alongside increased collagen deposition. Conversely, TNFα and IFNγ suppressed fibrotic gene expression while upregulating TIMP1. Notably, TGFβ specifically induced canonical Smad3 phosphorylation, a key event in fibrotic signaling. M2c macrophage-conditioned media enhanced profibrotic gene expression in hVICs, whereas M1-conditioned media suppressed it, underscoring the role of immune-fibrotic crosstalk.
The 5-HT₂B receptor antagonist SB204741 and tadalafil effectively inhibited
TGFβ-inducedSmad3phosphorylation in hVICs, thereby reducing downstream fibrotic signaling.
Key Findings
- RHD mitral valve tissue showed upregulation of immune response proteins,
TGFβsignaling, and ECM regulators. - Peripheral blood of RHD patients had elevated
IL6,TNFα, andTIMP1, indicating systemic inflammation. TGFβinduced fibrotic transformation in hVICs, upregulating markers likeACTA2,COL1A1, andMMP2.- M2c macrophage-conditioned media enhanced profibrotic gene expression in hVICs.
- SB204741 and tadalafil effectively inhibited
TGFβ-inducedSmad3phosphorylation in hVICs.
Why It Matters
Tadalafil, an FDA-approved PDE5 inhibitor, and SB204741, a 5-HT₂B receptor antagonist, represent promising candidates for repurposing in rheumatic heart disease (RHD). This study identifies a potential therapeutic strategy to directly target the underlying immune-fibrotic remodeling in RHD by modulating the TGFβ/Smad3 pathway. The ability of these compounds to inhibit Smad3 phosphorylation suggests they could mitigate valve fibrosis and degeneration, offering a novel approach beyond current symptomatic management. Further research is needed to translate these in-vitro findings into in-vivo models and ultimately clinical trials, but this work provides a strong mechanistic rationale for exploring these drugs in RHD patients.
rheumatic-heart-disease
fibrosis
tgfb-signaling
smad3
tadalafil
sb204741