Purinergic Signaling in Fibroblast Activation and Lung Fibrosis

/Abstract Idiopathic pulmonary fibrosis (IPF) is a devastating and progressive lung disease characterized by extensive fibrotic remodeling leading to respiratory failure and death. Despite recent advancements, no curative treatments exist for IPF, underscoring the urgent need to identify novel therapeutic targets. Recent studies suggest a potential role for purinergic signaling in IPF pathogenesis, particularly through the actions of extracellular ATP (eATP): Elevated eATP levels have been observed in the bronchoalveolar lavage fluid of IPF patients, implicating this signaling molecule as a potential driver of disease progression. However, the functional impact of eATP in the context of lung fibrosis remains poorly understood. Addressing this knowledge gap, our research has identified the fibroblast-specific ATP receptor P2rx4 as a key mediator of fibrotic signaling. Deletion of P2rx4 in fibroblasts has been shown to reduce lung fibrosis in bleomycin-treated mice, making it a promising target for therapeutic intervention. Notably, P2rx4 is highly expressed in pathologic fibroblasts in both human and mouse models of lung fibrosis, reinforcing its relevance in the fibrotic process. Our preliminary data suggest that the eATP-P2rx4 signaling axis regulates several profibrotic fibroblast phenotypes, including the upregulation of collagen genes, production of the cytokine IL-6, and enhanced fibroblast proliferation. This proposal seeks to dissect the underlying mechanisms by which P2rx4 influences these fibrotic pathways in fibroblasts. In Aim 1, we will test the hypothesis that the eATP-P2rx4-p38 MAP kinase signaling pathway is a critical regulator of fibroblast activation and the emergence of pathologic fibroblasts. We will also investigate the role of mitochondrial reactive oxygen species (mitoROS) in mediating P2rx4-dependent p38 MAP kinase activation. Aim 2 will focus on evaluating the therapeutic potential of targeting P2rx4. P2rx4 inhibition will be tested in both translationally relevant mouse models of lung fibrosis and in precision-cut lung slices derived from IPF patient explants to assess efficacy in reducing collagen deposition and fibrosis. Aim 2 will also test the relevance of the profibrotic eATP-P2rx4-p38 signaling that our preliminary data indicate for mouse in primary human lung fibroblasts from healthy donor and IPF lung explants, by siRNA knockdown of P2rx4 and p38. Taken together, these studies will transform understanding of purinergic signaling in lung fibrosis, providing critical insights into the molecular mechanisms that drive fibroblast activation IPF. By identifying and validating ATP-P2rx4 signaling as a novel therapeutic target, this research has the potential to pave the way for the development of new and effective treatments for IPF. Project Number: 1R01HL180531-01 | Fiscal Year: 2025 | NIH Institute/Center: National Heart Lung and Blood Institute (NHLBI) | Principal Investigator: Mallar Bhattacharya | Institution: UNIVERSITY OF CALIFORNIA, SAN FRANCISCO, SAN FRANCISCO, CA | Award Amount: $728,577 | Activity Code: R01 | Study Section: Special Emphasis Panel[ZRG1 RCCS-B (81)] View on NIH RePORTER: https://reporter.nih.gov/project-details/1R01HL18053101