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NHE1 activity is required for profibrotic agonist activation of cytoskeleton remodeling in lung fibrosis
Author(s) -
Mishika Manchanda,
Nguyentu Trina T.,
Provost Joseph John
Publication year - 2020
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.2020.34.s1.02680
Subject(s) - stress fiber , fibrosis , chemistry , idiopathic pulmonary fibrosis , myofibroblast , microbiology and biotechnology , actin cytoskeleton , transforming growth factor , cell migration , endocrinology , cancer research , medicine , cell , cytoskeleton , lung , biology , biochemistry
Idiopathic pulmonary fibrosis (IPF) is an untreatable chronic lung disorder that is characterized by an accumulation of fibroblasts and scarring tissue due to aberrant tissue remodeling. The lung tissue loses flexibility as the disease upsurges and the affected patient’s alveolar architecture is destroyed. This leads to a disruption of gas exchange, eventual respiratory failure, and death. Sodium hydrogen exchanger isoform 1 (NHE1) is a membrane bound protein that moderates cellular pH, supports cell migration, and regulates cell behavior. NHE1 has also been found to impact the pathophysiology of cancer. Considering that a myriad of signaling pathways that activate tumor cells are also involved in profibrotic activity of fibroblasts and myofibroblasts, the purpose of this study was to investigate if NHE1 exacerbates IPF and if inhibiting NHE1 would decrease the advancing fibrosis. We measured one of the indicators of progressing fibrosis, the remodeling of skeletal proteins, through the formation of actin stress fibers. Actin stress fibers have an important role in cell migration and contractility in fibroblasts. To stimulate this formation, cells were treated with three agonists that increase fibrotic activity: transforming growth factor ‐ β(TGF‐β), serotonin (5HT), and lysophosphatidic acid (LPA) in the presence and absence of ethyl‐isopropyl amiloride (EIPA). LPA induced stress fibers 43.94+/−4.4 percent over the control, and both TGF‐βand 5HT also stimulated the formation of stress fibers by 32.08+/−2.1 and 39.1+/−4.2 percent over the control, non‐treated cells. In each case, addition of EIPA blocked agonist‐induced stress fiber formation, indicating that all three profibrotic factors require NHE1 activity for cytoskeletal remodeling. Interestingly, we also observed that stimulation in any combination of agonists had seemed to block stress fiber formation in comparison to the control. An initial interpretation indicates that the agonists negatively regulate the others in stimulating stress fiber formation. The role of each agonist in fibroblasts isolated from fibrotic patients and control, non‐diseased tissue are presented. Myofibroblasts are a specialized cell type that contribute to fibrosis. The role of NHE1 in TGF‐βinduced fibroblast‐myofibroblast differentiation is also determined. The marker for myofibroblast differentiation, α‐smooth muscle actin (α‐SMA) was measured with and without EIPA to determine the role of NHE1 in advancing disease. Finally, the role of NHE1 in myofibroblasts was investigated with EIPA and stress fiber changes with agonists. This work highlights for the first time that NHE1 has a role supporting profibrotic factors and may be a novel target or adjuvant to fight IPF.