4-Phenylbutyric acid reduces inflammation in neutrophils by attenuating NF-κB-p65 activation through IRE1α-ERK1/2 signaling pathway

Introduction: Neonatal sepsis remains a major contributor to morbidity and mortality among term and preterm infants and is often accompanied by inflammatory conditions unique to the neonatal period, such as bronchopulmonary dysplasia (BPD), periventricular leukomalacia (PVL) and retinopathy of prematurity (ROP). Neutrophils are the first responders of the immune system, rapidly recruited to sites of infection. However, in preterm infants, their dysregulated activation is strongly associated with adverse outcomes. Modulating neutrophil activity represents a promising therapeutic approach to mitigate both acute and chronic inflammatory conditions. Despite this potential, our understanding of pharmacological agents capable of fine-tuning neutrophil responses remains limited. 4-Phenylbutyric acid (4-PBA), a clinically approved chemical chaperone, is known to alleviate endoplasmic reticulum (ER) stress and dampen immune activation1,2. In this study, we explored the potential of 4-PBA to regulate neutrophil-driven inflammation, with a particular focus on the mechanisms underlying neutrophil recruitment in vitro.

Methods: Murine bone marrow-derived neutrophils were cultured in vitro and subjected to stimulation with 4-PBA (15 mM), lipopolysaccharide (LPS, 100 ng/mL), or a combination of PBA and LPS (pre-treatment with 15 mM 4-PBA for 1 hour followed by exposure to 100 ng/mL LPS) for 12 hours. Cytokine production and reactive oxygen species (ROS) generation were quantified using ELISA and H2DCFDA assays, whereas the underlying signaling cascade was determined by western blotting technique. Neutrophil transmigration was evaluated using transwell chambers, while the expression of neutrophil recruitment markers was determined through real-time PCR analysis [1] [2].

Results: Our data demonstrate that 4-PBA attenuates the production of pro-inflammatory mediators, including TNF-α, IL-6, MCP-1, and ROS, in LPS-stimulated murine bone marrow-derived neutrophils in vitro. Furthermore, 4-PBA treatment was associated with impaired neutrophil recruitment, as evidenced by reduced transmigratory activity and diminished expression of critical adhesion molecules, such as P-selectin glycoprotein ligand-1 (PSGL-1) and integrin αL (CD11a). Mechanistically, the effects of 4-PBA in murine bone marrow neutrophils are primarily mediated by the inhibition of NF-κB-p65 activation through the IRE1α-ERK1/2 signaling axis in vitro.

Summary: Collectively, our data suggest that 4-PBA effectively mitigates neutrophil-driven inflammation and recruitment through the suppression of NF-κB activation via the IRE1α-ERK1/2 pathway. This highlights the putative therapeutic potential of 4-PBA in managing ER stress-related inflammatory diseases by targeting key signaling mechanisms in neutrophil activation and recruitment.

Publication History

Article published online:
19 May 2025

• References

• 1 Chen et al. Sig Transduct Target Ther. 2023 8. 01 352
• 2 Zeng et al. Toxicol Lett. 2017 271. 26-37