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The Novel Small Molecule BTB Inhibits Pro-Fibrotic Fibroblast Behavior though Inhibition of RhoA Activity.

ABSTRACT: Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, interstitial lung disease with a poor prognosis. Although specific anti-fibrotic medications are now available, the median survival time following diagnosis remains very low, and new therapies are urgently needed. To uncover novel therapeutic targets, we examined how biochemical properties of the fibrotic lung are different from the healthy lung. Previous work identified lactate as a metabolite that is upregulated in IPF lung tissue. Importantly, inhibition of the enzyme responsible for lactate production prevents fibrosis in vivo. Further studies revealed that fibrotic lesions of the lung experience a significant decline in tissue pH, likely due to the overproduction of lactate. It is not entirely clear how cells in the lung respond to changes in extracellular pH, but a family of proton sensing G-protein coupled receptors has been shown to be activated by reductions in extracellular pH. This work examines the expression profiles of proton sensing GPCRs in non-fibrotic and IPF-derived primary human lung fibroblasts. We identify TDAG8 as a proton sensing GPCR that is upregulated in IPF fibroblasts and that knockdown of TDAG8 dampens myofibroblast differentiation. To our surprise, BTB, a proposed positive allosteric modulator of TDAG8, inhibits myofibroblast differentiation. Our data suggest that BTB does not require TDAG8 to inhibit myofibroblast differentiation, but rather inhibits myofibroblast differentiation through suppression of RhoA mediated signaling. Our work highlights the therapeutic potential of BTB as an anti-fibrotic treatment and expands upon the importance of RhoA-mediated signaling pathways in the context of myofibroblast differentiation. Furthermore, this works also suggests that TDAG8 inhibition may have therapeutic relevance in the treatment of IPF.

SUBMITTER: Rackow AR

PROVIDER: S-EPMC9569993 | biostudies-literature | 2022 Oct

REPOSITORIES: biostudies-literature

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The Novel Small Molecule BTB Inhibits Pro-Fibrotic Fibroblast Behavior though Inhibition of RhoA Activity.

Rackow Ashley R AR Nagel David J DJ Zapas Gregory G Clough Ryan S RS Sime Patricia J PJ Kottmann R Matthew RM

International journal of molecular sciences 20221008 19

Idiopathic pulmonary fibrosis (IPF) is a progressive, chronic, interstitial lung disease with a poor prognosis. Although specific anti-fibrotic medications are now available, the median survival time following diagnosis remains very low, and new therapies are urgently needed. To uncover novel therapeutic targets, we examined how biochemical properties of the fibrotic lung are different from the healthy lung. Previous work identified lactate as a metabolite that is upregulated in IPF lung tissue. ...[more]

PMID: 36233248

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Project description:BACKGROUND:Fibroblast apoptosis is a critical component of normal repair and the acquisition of an apoptosis-resistant phenotype contributes to the pathogenesis of fibrotic repair. Fibroblasts from fibrotic lungs of humans and mice demonstrate resistance to apoptosis induced by Fas-ligand and prior studies have shown that susceptibility to apoptosis is enhanced when Fas (CD95) expression is increased in these cells. Moreover, prior work shows that Fas expression in fibrotic lung fibroblasts is reduced by epigenetic silencing of the Fas promoter. However, the mechanisms by which microenvironmental stimuli such as TGF-?1 and substrate stiffness affect fibroblast Fas expression are not well understood. METHODS:Primary normal human lung fibroblasts (IMR-90) were cultured on tissue culture plastic or on polyacrylamide hydrogels with Young's moduli to recapitulate the compliance of normal (400 Pa) or fibrotic (6400 Pa) lung tissue and treated with or without TGF-?1 (10 ng/mL) in the presence or absence of protein kinase inhibitors and/or inflammatory cytokines. Expression of Fas was assessed by quantitative real time RT-PCR, ELISA and Western blotting. Soluble Fas (sFas) was measured in conditioned media by ELISA. Apoptosis was assessed using the Cell Death Detection Kit and by Western blotting for cleaved PARP. RESULTS:Fas expression and susceptibility to apoptosis was diminished in fibroblasts cultured on 6400 Pa substrates compared to 400 Pa substrates. TGF-?1 reduced Fas mRNA and protein in a time- and dose-dependent manner dependent on focal adhesion kinase (FAK). Surprisingly, TGF-?1 did not significantly alter cell-surface Fas expression, but did stimulate secretion of sFas. Finally, enhanced Fas expression and increased susceptibility to apoptosis was induced by combined treatment with TNF-?/IFN-? and was not inhibited by TGF-?1. CONCLUSIONS:Soluble and matrix-mediated pro-fibrotic stimuli promote fibroblast resistance to apoptosis by decreasing Fas transcription while stimulating soluble Fas secretion. These findings suggest that distinct mechanisms regulating Fas expression in fibroblasts may serve different functions in the complex temporal and spatial evolution of normal and fibrotic wound-repair responses.

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The Novel Small Molecule BTB Inhibits Pro-Fibrotic Fibroblast Behavior though Inhibition of RhoA Activity.

Publications

The Novel Small Molecule BTB Inhibits Pro-Fibrotic Fibroblast Behavior though Inhibition of RhoA Activity.

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