Pharmacological inhibition of P300 with C646 ameliorates LPS-induced acute lung injury by modulating CXCL1 in M1 alveolar macrophages.

Objectives: Acute lung injury (ALI) is an excessive inflammatory condition with the involvement of M1 alveolar macrophage (AM) polarization. Given the high mortality rate of ALI, elucidating its underlying mechanisms is crucial for identifying therapeutic targets. Inhibition of P300, a lysine acetyltransferase, has illustrated the potential to alleviate inflammatory diseases through the regulation of immune cell activation. However, little is known whether P300 inhibition could ameliorate ALI through regulating the polarization of M1 AMs.

Methods: We established an LPS-induced ALI model and evaluated the effects of the P300 inhibitor C646 on pulmonary pathology, inflammation and M1 AM polarization via H&E staining, ELISA and flow cytometry. Additionally, the specific inflammatory mediators regulated by P300 in M1 AMs affecting ALI were analyzed by RNA sequencing and validated by intratracheal instillation experiment.

Results: Intratracheal instillation of LPS resulted in neutrophil accumulation within the pulmonary alveoli and interstitial areas, along with increased levels of total inflammatory cells and IL-1β in the lung. However, administration of C646 ameliorated these pulmonary pathology and inflammation, accompanied by a diminished proportion and quantity of M1 AMs in BALF. Furthermore, by taking the intersection of P300-targeted genes in macrophages from the Cistrome, genes upregulated after M1 polarization of AMs, and genes downregulated following C646 treatment in M1 AMs, we identified 'Cxcl1' among the intersecting genes. Also, intratracheal instillation of CXCL1 aggravated pulmonary pathology and inflammation in C646 treated-ALI models.

Conclusion: Our study suggested that pharmacological inhibition of P300 with C646 ameliorated LPS-induced ALI by modulating CXCL1 in M1 AMs.