Transient Receptor Potential Vanilloid channel regulates fibroblast differentiation and airway remodeling by modulating redox signals through NADPH Oxidase 4

Nosayba Al-Azzam,Kayla Covington,Charles K Thodeti,Samrawit Ghebreigziabher,Sathwika Thodeti,Ignacio Gavilanes,Lakshminarayan Reddy Teegala,Sabita Pokhrel,Sailaja Paruchuri,Tatiana Chachkovskyy

doi:10.1038/s41598-020-66617-2

Abstract

Asthma is characterized by pathological airway remodeling resulting from persistent myofibroblast activation. Although transforming growth factor beta 1 (TGFβ1), mechanical signals, and reactive oxygen species (ROS) are implicated in fibroblast differentiation, their integration is still elusive. We identified that Transient Receptor Potential Vanilloid 4 (TRPV4), a mechanosensitive ion channel mediates lung fibroblast (LF) differentiation and D. farinae-induced airway remodeling via a novel TRPV4-NADPH Oxidase 4 (NOX4) interaction. NOX4-mediated ROS production is essential for TGFβ1-induced LF differentiation via myocardin-related transcription factor-A (MRTF-A) and plasminogen activator inhibitor 1 (PAI-1). Importantly, TRPV4 inhibition prevented TGFβ1-induced NOX4 expression and ROS production. Both TRPV4 and NOX4 are activated by phosphatidylinositol 3-kinase (PI3K) downstream of TGFβ1, and signals from both TRPV4 and Rac are necessary for NOX4 upregulation. Notably, NOX4 expression is higher in fibroblasts derived from asthmatic patients (disease human LF; DHLF) in comparison to non-asthmatics (normal human LF; NHLF). Further, NOX4 expression is up-regulated in the lungs of D.farinae-treated wild type mice (WT) relative to saline-treated WT, which was attenuated in TRPV4 knockout (KO) mice. Our findings suggest that TRPV4 integrates TGFβ1 and ROS signaling through NOX4 and, TRPV4-NOX4 interaction is amenable to target lung remodeling during asthma.

Highlights

Asthma is characterized by inflammation, eosinophilic infiltration, bronchial hyperresponsiveness[1,2], and significant airway remodeling[3,4]
normal human LF (NHLF) transfected with nonspecific (NS) small interfering RNA (siRNA) were used as control
Fibroblast differentiation is critical in physiological airway remodeling, uncontrolled differentiation of fibroblasts to myofibroblasts can lead to lung fibrosis

Summary

Introduction

Asthma is characterized by inflammation, eosinophilic infiltration, bronchial hyperresponsiveness[1,2], and significant airway remodeling[3,4]. Transient Receptor Potential Vanilloid 4 (TRPV4) is a mechanosensitive ion channel that has been shown to regulate lung function[15] and airway hyperresponsiveness in patients with asthma[16], cardiac[17] and lung[18] fibrosis. In addition to soluble and mechanical signals, enhanced ROS production was well documented in asthma with high levels of superoxide generated by nicotinamide adenine dinucleotide phosphate (NADPH) oxidases (NOX)[20]. NOX4 expression and activity (ROS production) is demonstrated to be a driving force for fibroblast differentiation[21,22] and lung fibrosis[21]. Mechanical and redox pathways are implicated in fibroblast differentiation and lung remodeling, little is known regarding their integration and contribution to asthma. We demonstrate that NOX4 integrates TGFβ1 and mechanical signaling in fibroblast differentiation and lung remodeling during asthma

Methods

Results

Conclusion