Inhibition of Fgr Prevents Pulmonary Fibrosis

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Pulmonary fibrosis can arise spontaneously as in idiopathic pulmonary fibrosis (IPF), or following ionizing irradiation, silica exposure, or COVID-19 infection. Senescence has been implicated in both radiation-induced pulmonary fibrosis (RIPF) and IPF. Senescence precedes fibrosis in mouse RIPF and reported in COVID-19 patients. Clearance of senescent cells (SCs) by senolytic drugs present an attractive anti-fibrosis strategy. However, senolytics may be non-specific and remove potentially beneficial as well as harmful SCs. Little is known about how senescent cells induce pulmonary fibrosis. SCs exit cell cycle, induce p16, increase senescence associated beta-galactosidase (SA-𝝱-gal), and secrete senescence associated secretory phenotype (SASP) proteins. SASP include proinflammatory cytokines that may initiate and exacerbate fibrosis. Therefore, using radiation as a model system to induce senescence, we propose to establish and validate a specific mitigator of lung fibrosis by targeting one senescent protein while not removing the SCs. By RNA-seq of pure SCs and by single cell RNA-seq (scRNAseq) of irradiated lungs, we discovered that tyrosine kinase Fgr is highly induced in senescent cells. Fgr positive mouse lung cells induce biomarkers of fibrosis in vitro, and Fgr inhibitor, TL02-59 treatment, abrogates the induction of profibrotic genes. Our preliminary data show: 1) in mouse lung senescent cells, Fgr inhibitor TL02-59 abrogates the induction of profibrotic genes in target cells, 2) in lung cells from Fgr knockout mouse, senescence occurs with radiation, but fail to induce profibrotic genes in target cells, 3) human lungs from RIPF, silicosis, and IPF show induction of Fgr and senescent marker p16, 4) TL02-59 reduces secretion of profibrotic SASP chemokines for attracting immunocytes, 5) inhibition of Fgr in vivo, either by TL02-59, or by senescence inhibitor MMS350, reduces expression of fibrotic genes. We hypothesize, Fgr in senescent cells initiates pulmonary fibrosis by secretion of proinflammatory SASP proteins and by recruiting inflammatory immunocytes to the lungs. We further hypothesize that inhibition of Fgr by small molecule TL02-59 or indirectly by the senescence inhibitor, MMS350, will prevent lung fibrosis. We will use mouse primary lung cells from C57BL/6 control and Fgr knockout (Fgr-/-) mice to confirm the role of Fgr in vivo in C57BL/6 and C57BL/6 Fgr-/- mice. Finally, we will establish that specific inhibition of Fgr prevents lung fibrosis. Specific Aim 1 will establish that lung cell senescence induces Fgr and initiates pulmonary fibrosis by the actions of secreted proinflammatory SASP and recruitment to the lungs of bone marrow derived inflammatory cells. Specific Aim 2 will establish that Fgr is required for pulmonary fibrosis using Fgr -/- mice. Specific Aim 3 will establish that specific and targeted pharmacologic inhibition of Fgr blocks lung fibrosis. Our innovative approach will establish that Fgr induction in senescent lung cells causes pulmonary fibrosis through secretion of proinflammatory SASP proteins and chemotactic recruitment of inflammatory cells. Our proposed studies will lead to the development of a new mitigator of pulmonary fibrosis.