Involvement of MAPK/NF-κB signal transduction pathways: Camellia japonica mitigates inflammation and gastric ulcer

Gastric ulcer is an important risk factor for human health globally. Camellia japonica (CJ) is a plant of which the fruits are used as traditional phytomedicine for inflammatory and immunomodulatory diseases; however, the underlying molecular mechanism has not been clarified. The present study aimed to investigate the immunopharmacological activities of Camellia japonica and validate its pharmacological targets. To evaluate the protective roles of Camellia japonica on LPS-induced inflammation in RAW 264.7 cells and HCl/EtOH-induced gastric ulcer in mice; we applied 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), nitric oxide (NO), reactive oxygen species (ROS), histopathology, malondialdehyde (MDA), quantitative real-time polymerase chain reaction (qPCR), immunohistochemistry (IHC), and western blot analyses. We also determined the total phenolic and flavonoid content of Camellia japonica which might possess antioxidant and anti-inflammatory properties. We found the production of NO and ROS in RAW 246.7 cells were both suppressed by Camellia japonica. Moreover, Camellia japonica mitigated the HCl/EtOH-induced oxidative stress in gastric mucosa via the reduction of lipid peroxidation and elevation of NO production. Gastric mucosal damages were prominently improved by Camellia japonica, as confirmed by the histopathological evaluation. The gene expression of inflammatory cytokines and enzymes TNF-α, IL-6, IL-1β, iNOS, and COX-2 was notably downregulated by Camellia japonica. In addition, Camellia japonica markedly attenuated the MAPKs (ERK1/2, JNK, and p38) phosphorylation, COX-2 expression, and activation of transcription factor NF-κB and as well as degradation and phosphorylation of IκBα in gastric mucosa. Taken together, the intimated anti-inflammatory and gastroprotective mechanism of Camellia japonica is mediated by modulation of oxidative stress, inflammatory cytokines, and enzymes via suppression of MAPK/NF-κB signaling pathways.