𝐼𝑛 𝑉𝑖𝑣𝑜 Toxicity and Prophylactic Treatment Efficacy of NR4A1 Agonist 6-Mercaptopurine Loaded Nanostructured Lipid Carriers Protects Against Bleomycin Induced Mouse Pulmonary Fibrosis Mediators and Biomarkers

Idiopathic pulmonary fibrosis (IPF) is a devastating and chronic age-related pulmonary disease with a poor prognosis and inadequate treatment choices. Nintedanib, a high-profile receptor tyrosine kinase inhibitor, is one of the only two listed drugs for treating IPF. Researchers have innovatively engineered a spectrum of nanocarriers for the oral administration of 6-mercaptopurine, driven by progress in pioneering methods for delivering drugs. Of these myriad drug delivery modalities, nanostructured lipid carriers have emerged as a particularly promising vehicle for oral drug delivery, owing to their superior drug loading capacity, augmented bioavailability, and remarkable biocompatibility and biodegradability. Human nuclear receptor 4A1 (NR4A1) has been previously documented to modulate mesenchymal cell activity and attenuate fibrogenic signalling. To mitigate the pro-fibrotic effects of TGF-β, NR4A1 recruits a repressor complex that includes transcription factor SP1, scaffold protein SIN3A, CoREST, lysine-specific histone demethylase 1 (LSD1), and histone deacetylase 1 (HDAC1) to Transforming growth factor β target genes. Nur77/NR4A1 agonists such as Cytosporone B and 6-Mercaptopurine function as TGF-β pathway negative regulators during wound healing. It also implies that pathological circumstances disrupt this Nur77-mediated negative feedback loop, which results in prolonged TGF-β signalling and increased fibrogenesis. The present study aimed to determine the toxic and prophylactic efficacy of a 6-mercaptopurine-loaded nanostructured lipid carrier in BLM- induced pulmonary fibrosis in mice. For that, we investigated the toxicity profile as well as prophylactic efficacy of a 6-mercaptopurine-loaded nanostructured lipid carrier (6-MP-NLC) drug known to promote NR4A1 signalling and could diminish pulmonary fibrosis in the mice. At higher doses, 6-MP-NLC and 6-MP therapy significantly decreased the neutrophil BALF count, hydroxyproline levels, inflammatory-promoting cytokines (TNF-α, IL-1β, IL-6), histopathology endpoints such as inflammation and collagen levels, and immunohistochemistry parameters like COL1A1, α-SMA, and TGF-β. Research suggests that NR4A1 may help reduce fibrotic processes in lung fibrosis, potentially improving management of inflammation-related lung conditions.