MAPK phosphatase 1 inhibition of p38α within lung myofibroblasts is essential for spontaneous fibrosis resolution
Sean M. Fortier, … , Anton M. Bennett, Marc Peters-Golden
Sean M. Fortier, … , Anton M. Bennett, Marc Peters-Golden
Published March 21, 2024
Citation Information: J Clin Invest. 2024;134(10):e172826. https://doi.org/10.1172/JCI172826.
View: Text | PDF
Research Article Cell biology Pulmonology

MAPK phosphatase 1 inhibition of p38α within lung myofibroblasts is essential for spontaneous fibrosis resolution

Abstract

Fibrosis following tissue injury is distinguished from normal repair by the accumulation of pathogenic and apoptosis-resistant myofibroblasts (MFs), which arise primarily by differentiation from resident fibroblasts. Endogenous molecular brakes that promote MF dedifferentiation and clearance during spontaneous resolution of experimental lung fibrosis may provide insights that could inform and improve the treatment of progressive pulmonary fibrosis in patients. MAPK phosphatase 1 (MKP1) influences the cellular phenotype and fate through precise and timely regulation of MAPK activity within various cell types and tissues, yet its role in lung fibroblasts and pulmonary fibrosis has not been explored. Using gain- and loss-of-function studies, we found that MKP1 promoted lung MF dedifferentiation and restored the sensitivity of these cells to apoptosis — effects determined to be mainly dependent on MKP1’s dephosphorylation of p38α MAPK (p38α). Fibroblast-specific deletion of MKP1 following peak bleomycin-induced lung fibrosis largely abrogated its subsequent spontaneous resolution. Such resolution was restored by treating these transgenic mice with the p38α inhibitor VX-702. We conclude that MKP1 is a critical antifibrotic brake whose inhibition of pathogenic p38α in lung fibroblasts is necessary for fibrosis resolution following lung injury.

Authors

Sean M. Fortier, Natalie M. Walker, Loka R. Penke, Jared D. Baas, Qinxue Shen, Jennifer M. Speth, Steven K. Huang, Rachel L. Zemans, Anton M. Bennett, Marc Peters-Golden

×

Figure 5

p38α is the isoform whose inhibition by MKP1 promotes MF dedifferentiation.

Options: View larger image (or click on image) Download as PowerPoint
p38α is the isoform whose inhibition by MKP1 promotes MF dedifferentiati...
(A) Relative p38α and β mRNA expression quantified by qPCR in normal HLFs or MFs and patient-derived IPF fibroblasts. (B) Protein quantification of p38α by Western blotting in normal HLFs following Cas9-mediated deletion of p38α using MAPK14 sgRNA or a NT control. p38α was quantified by subtracting the densitometric value of the total p38 band in the isotype-deleted line from that of the total p38 band of the WT line. (C) Western blot analysis of the fibrosis-associated genes αSMA and Col1A1 and densitometric analysis following Cas9-mediated MAPK14/p38α deletion. (D and E) MFs were treatment with the p38 inhibitor VX-702 (50 μM) for 96 hours (protocol schematic is shown in D). (D) Western blot analysis of αSMA and Col1A1 and densitometric analysis. (E) αSMA stress fibers were identified by immunofluorescence microscopy using an anti–αSMA-FITC–conjugated antibody. Nuclei were stained with DAPI. Scale bars: 20 μm (top row) and 10 μm (bottom row). (F) Schematic of protocol showing that VX-702– or vehicle-treated MFs were treated with an anti-Fas–activating antibody (100 ng/mL) for 24 hours. Apoptosis sensitivity was determined by caspase-3/-7 activity assay or annexin V expression (right). Dashed lines represent caspase-3/-7 activity or annexin V expression in untreated, undifferentiated fibroblasts incubated with anti-Fas antibody. The sample number for each experiment (n) varied between 3 and 5 and is indicated by the number of data points in each histogram. Each blot grouping containing a protein of interest and its corresponding loading control were run on separate gels. **P < 0.01, ***P < 0.001, and ****P < 0.0001 by 2-tailed t test (A, B, and F) and 1-way ANOVA (D).