Protective Effect of Naringenin Against Lipopolysaccharide-Induced Injury in Normal Human Bronchial Epithelium via Suppression of MAPK Signaling

The present study aimed to evaluate the effect of naringenin on protection in lipopolysaccharide (LPS)-induced injury in normal human bronchial epithelium (NHBE) and to provide insights into the possible underlying mechanisms. NHBE were stimulated by LPS in the presence or absence of the narigenin. In vitro treatment with naringenin led to a significant attenuation in the LPS-induced NHBE secretion of tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6), superoxidase dismutase (SOD), nitricoxide synthase (NOS), myeloperoxidase (MPO), and nitric oxide (NO). RT-qPCR demonstrated that naringenin significantly reduced the LPS-induced upregulation of TNF-α, IL-6, and nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 mRNA expression in a dose-dependent manner. Additionally, Western blot analysis revealed that naringenin effectively suppressed NF-κB activation by inhibiting the degradation of IκB-α and the translocation of p65. Naringenin also attenuated mitogen-activated protein kinase (MAPK) activation by inhibiting the phosphorylation of ERK1/2, c-Jun NH(2)-terminal kinase (JNK), and p38 MAPK. Taken together, these demonstrate that naringenin reduces TNF-α and IL-6 secretion and mRNA expression, possibly by blocking the activation of the NF-κB and MAPK signaling pathways in LPS-treated NHBE. These results indicated that naringenin had a protective effect on LPS-induced injury in NHBE.