Highlight
– Activation of prostaglandin I2 receptor (IP) is critical for alveolar type 2 (AT2) cell transdifferentiation into type 1 (AT1) cells.
– IP receptor activation suppresses aberrant JUN signaling and enhances p53-dependent AT1 gene expression.
– Conditional IP receptor knockout worsens lung injury and fibrosis in murine models.
– Pharmacological activation of IP by selexipag promotes lung repair and attenuates fibrosis in idiopathic pulmonary fibrosis (IPF).
Study Background
Alveolar epithelial integrity is vital for maintaining normal lung function and enabling tissue repair after damage. Alveolar type 2 (AT2) cells serve as progenitor cells capable of transdifferentiating into alveolar type 1 (AT1) cells, which are essential for gas exchange. Defects in this regenerative process contribute significantly to chronic lung diseases such as idiopathic pulmonary fibrosis (IPF), characterized by alveolar epithelial injury, aberrant repair, and progressive fibrosis. While the biological importance of AT2-to-AT1 transdifferentiation is recognized, the molecular mechanisms orchestrating this process remain incompletely defined. Prostaglandin signaling, particularly via the prostaglandin I2 receptor (IP), is known to modulate inflammation and vascular tone, but its role in alveolar epithelial regeneration has not been fully elucidated.
Study Design
This translational study employed both in vitro and in vivo approaches to investigate the role of the IP receptor in alveolar regeneration. Primary alveolar organoid cultures were utilized to model AT2-to-AT1 transdifferentiation and examine the impact of pharmacological IP modulation. Murine lung injury models induced by bleomycin and lipopolysaccharide (LPS) simulated acute lung damage and fibrogenesis. Genetic strategies included conditional knockout of the IP receptor specifically in AT2 cells to delineate the cell-autonomous effects. Multi-omics analyses—single-cell RNA sequencing (scRNA-seq) and ATAC-seq—along with biochemical assays assessed downstream signaling and transcriptional regulation linked to IP receptor activity. Intervention with selexipag, a selective IP agonist, evaluated therapeutic potential in both murine models and primary human cells derived from patients with IPF. Primary endpoints encompassed alveolar epithelial regeneration, extent of fibrosis, and molecular markers of transdifferentiation.
Key Findings
The investigation revealed a pivotal role for the IP receptor in alveolar epithelial repair through regulation of transitional AT2 cells converting into functional AT1 cells. Analysis of patient-derived transitional AT2 cells exhibited a strong correlation between IP receptor expression and enrichment of AT1-related gene signatures, implicating IP as a critical modulator in human IPF pathology.
Pharmacologic inhibition or genetic ablation of IP impaired AT2-to-AT1 transdifferentiation capacity in alveolar organoid systems, confirming that IP signaling enhances regenerative potential. In vivo, conditional IP knockout in AT2 cells markedly aggravated lung injury and fibrotic remodeling after bleomycin or LPS exposure. This was accompanied by reduced epithelial regeneration, affirming IP’s protective function in alveolar repair.
Mechanistically, IP receptor deficiency led to dysregulated activation of JUN, a component of the AP-1 transcription factor complex, which negatively regulated p53-dependent transcription of AT1 signature genes. IP activation counteracted this by promoting protein kinase A (PKA)-mediated inhibition of MAP3K5, thereby suppressing the JNK/JUN pathway while enhancing p53-mediated gene expression essential for alveolar differentiation.
Therapeutically, selexipag administration in mice accelerated alveolar epithelial regeneration and reduced fibrotic burden, supporting translational relevance. Additionally, ex vivo treatment of primary human AT2 cells from IPF patients with IP agonists notably increased AT2-to-AT1 transdifferentiation, highlighting potential clinical applicability.
Expert Commentary
This study robustly integrates multi-level evidence emphasizing the prostaglandin I2 receptor as a key regulator of alveolar epithelial homeostasis and repair. The elucidation of the JUN/p53 signaling axis provides mechanistic insight into how IP receptor activation fine-tunes cellular plasticity necessary for restoring the alveolar barrier. These findings align well with emerging paradigms recognizing the centrality of epithelial progenitor cell dynamics in fibrotic lung disease and positing repair enhancement as a viable therapeutic strategy.
Limitations include the incomplete understanding of IP receptor interactions with other signaling networks involved in lung injury and repair, which warrant further investigation. Moreover, while promising, the translation of these findings to clinical use requires careful consideration of selexipag’s pharmacokinetics and safety in chronic lung disease populations.
Conclusion
The prostaglandin I2 receptor emerges as a master regulator of alveolar regeneration by orchestrating AT2-to-AT1 transdifferentiation via modulation of the JUN/p53 pathway. Targeting this pathway offers a novel and promising therapeutic approach to enhance lung epithelial repair and mitigate fibrosis in conditions such as idiopathic pulmonary fibrosis. Future research should aim to expand understanding of IP receptor signaling in the complex lung microenvironment and explore clinical trials of selective IP agonists in relevant lung diseases.
Funding and Clinical Trials
Details on funding sources and clinical trial registrations were not provided in the original publication abstract.
References
Yu T, Liu J, Ma Y, Wang L, Wang Y, Pan T, Chen P, Liu Q, Wang JW, Chen H, Wu X, Chen J, Hu X, Tao B, Shen Y. Prostaglandin I2 receptor activation promotes alveolar regeneration via the JUN/p53 pathway. Am J Respir Crit Care Med. 2026 Jul 1;212(7):1467-1482. PMID: 42085259.
