Biology subjects

Bahudhanapati, H.

Publications and source records attributed to Bahudhanapati, H..

4 recordsLinked to original sources

bioRxiv2022

Single-nucleus chromatin accessibility identifies a critical role for TWIST1 in idiopathic pulmonary fibrosis myofibroblast activity

In idiopathic pulmonary fibrosis (IPF) myofibroblasts are key effectors of fibrosis and architectural distortion by excessive deposition of extracellular matrix and their acquired contractile capacity. Single-cell RNA-sequencing has precisely defined the IPF myofibroblast transcriptome, but identifying critical transcription factor activity by this approach is imprecise. We performed and integrated snATAC-seq and scRNA-seq from human IPF and donor control explants to identify differentially accessible chromatin regions and enriched transcription factor motifs within lung cell populations. TWIST1 and other E-box transcription factor motifs were significantly enriched in IPF myofibroblasts compared to both IPF non-myogenic and control fibroblasts. TWIST1 expression was also selectively upregulated in IPF myofibroblasts. Overexpression of Twist1 in lung COL1A2-expressing fibroblasts in bleomycin-injured mice was associated with increased collagen synthesis. Our studies utilizing human multiomic single-cell analyses combined with in vivo murine disease models confirm a critical regulatory function for TWIST1 in IPF myofibroblast activity in the fibrotic lung. Understanding the global process of opening TWIST1 and other E-box TF motifs that govern myofibroblast differentiation may identify new therapeutic interventions for fibrotic pulmonary diseases.

molecular biology↗

bioRxiv2021

Identification of a distal RXFP1 gene enhancer with differential activity in fibrotic lung fibroblasts involving AP-1

Relaxin/insulin-like family peptide receptor 1 (RXFP1) mediates relaxins antifibrotic effects and has reduced expression in the lung and skin of patients with fibrotic interstitial lung disease (fILD) including idiopathic pulmonary fibrosis (IPF) and systemic sclerosis (SSc). This may explain the failure of relaxin-based anti-fibrotic treatments in SSc, but the regulatory mechanisms controlling RXFP1 expression remain largely unknown. This study aimed to identify regulatory elements of RXFP1 that may function differentially in fibrotic fibroblasts. We identified and evaluated a distal regulatory region of RXFP1 in lung fibroblasts using a luciferase reporter system. Using serial deletions, an enhancer upregulating pGL3-promoter activity was localized to the distal region between -584 to -242bp from the distal transcription start site (TSS). This enhancer exhibited reduced activity in IPF and SSc lung fibroblasts. Bioinformatic analysis identified two clusters of activator protein 1 (AP-1) transcription factor binding sites within the enhancer. Site-directed mutagenesis of the binding sites confirmed that only one cluster reduced activity (-358 to -353 relative to distal TSS). Co-expression of FOS in lung fibroblasts further increased enhancer activity. In vitro complex formation with a labeled probe spanning the functional AP-1 site using nuclear proteins isolated from lung fibroblasts confirmed a specific DNA/protein complex formation. Application of antibodies against JUN and FOS resulted in the complex alteration, while antibodies to JUNB and FOSL1 did not. Analysis of AP-1 binding in 5 pairs of control and IPF lung fibroblasts detected positive binding more frequently in control fibroblasts. Expression of JUN and FOS was reduced and correlated positively with RXFP1 expression in IPF lungs. In conclusion, we identified a distal enhancer of RXFP1 with differential activity in fibrotic lung fibroblasts involving AP-1 transcription factors. Our study provides insight into RXFP1 downregulation in fILD and may support efforts to reevaluate relaxin-based therapeutics alongside upregulation of RXFP1 transcription.

molecular biology↗

bioRxiv2021

High CXCL6 drives matrix expression and correlate with markers of poor outcome in IPF

Signaling via G protein-coupled receptors (GPCRs) can modulate levels of cyclic adenosine monophosphate (cAMP) and shape the functions of fibroblasts in idiopathic pulmonary fibrosis (IPF). We have identified Chemokine (C-X-C) Motif Ligand 6 (CXCL6) as a potential pro-fibrotic GPCR ligand. We tested the function of CXCL6 in ex vivo human donor and fibrotic lung fibroblasts and in an animal model of pulmonary fibrosis. We also measured levels of CXCL6 in the blood and bronchoalveolar lavage (BAL) of patients with IPF. CXCL6 decreased cAMP levels in a dose-dependent manner in Donor and IPF Fibroblasts. CXCL6 mRNA and protein were localized to epithelial cells. Administration of mCXCL5 (LIX, murine CXCL6 homologue) to mice increased collagen synthesis with and without bleomycin. CXCL6 increased Collagen I and -SMA levels in Donor and IPF Fibroblasts. Silencing of CXCR1/2 as well as Reparixin, a CXCR1/2 inhibitor, blocked effects of CXCL6. Treprostinil blocked effects of CXCL6 only on levels of -SMA but not on Collagen I. CXCL6 levels in the BAL of two separate cohorts of patients with IPF was associated with poor survival. We conclude that high CXCL6 drives fibroblast function and correlates with poor outcomes in IPF.

cell biology↗

bioRxiv2017

RXFP1 expression is regulated by miR-144-3p in Fibroblasts from Patients with Idiopathic Pulmonary Fibrosis

Relaxin has been considered as a potential therapy for patients with pulmonary fibrosis. We have previously shown, however, that a potential limitation of relaxin-based therapy for Idiopathic Pulmonary Fibrosis (IPF) is the loss of expression of the relaxin receptor Relaxin/Insulin Like Receptor 1 (RXFP1) expression in fibroblasts. The molecular mechanism for RXFP1 down-regulation in IPF patients remains unclear. To determine whether microRNAs play a role in RXFP1 gene expression, we employed a bioinformatics approach to identify microRNAs (miRs) that are predicted to target RXFP1. By in silico analysis, we identified a putative target site in the RXFP1 mRNA for the miR-144 family. We found that miR-144-3p was upregulated in IPF fibroblasts compared to donor lung fibroblast controls. Forced miR-144-3p mimic expression reduced RXFP1 mRNA and protein levels and increased expression of the myofibroblast marker alpha-smooth muscle actin (-SMA) in donor lung fibroblasts. IPF lung fibroblasts transfected with a miR-144-3p inhibitor increased RXFP1 expression and reduced -SMA expression. A lentiviral luciferase reporter vector carrying the WT 3UTR of RXFP1 was repressed more in lung fibroblasts whereas vector carrying a mutated miR-144-3p binding site exhibited less sensitivity to endogenous miR-144-3p expression, suggesting that RXFP1 is a direct target of miR-144-3p. Thus, miR-144-3p is highly expressed in IPF fibroblasts and acts as a negative regulator of RXFP1 protein expression.

biochemistry↗