Vanillic acid alleviates lipopolysaccharides-induced endoplasmic reticulum stress and inflammation in human lung fibroblasts by `inhibiting MAPK and NF-κB pathways

Persistent endoplasmic reticulum stress promotes aberrant inflammation and induces cell death, and inflammation is implicated in the pathogenesis of pneumonia. Vanillic acid exerts pharmacological activities, such as anti-inflammatory, antimicrobial, and antioxidant effects. However, the role of vanillic acid in pneumonia has not been elucidated yet. Human lung fibroblasts (WI-38 and MRC-5) were incubated with different concentrations of lipopolysaccharides to mimic the cell model of pneumonia. Lipopolysaccharides-treated lung fibroblasts were then incubated with different concentrations of vanillic acid. Cell viability and apoptosis were detected by MTT assay and flow cytometry, respectively. Quantitative real-time polymerase chain reaction and enzyme-linked-immunosorbent serologic assay were used to measure the levels of inflammatory factors. Western blot assay was used to detect endoplasmic reticulum stress and downstream pathway. Lipopolysaccharides induced decrease of cell viability in WI-38 and MRC-5 whereas vanillic acid increased cell viability of lipopolysaccharides-treated lung fibroblasts. Lipopolysaccharides-induced increase of cell apoptosis in lung fibroblasts was suppressed by vanillic acid through up-regulation of BCL2, and down-regulation of BCL2 associated X (BAX) and cleaved caspase-3. Vanillic acid reduced levels of tumor necrosis factor-α (TNF-α), Interleukin 6 (IL-6), and IL-1β in lipopolysaccharides-treated lung fibroblasts. Protein expression of glucose-regulated protein 78 (GRP78), X-box binding protein 1 (XBP-1), activating transcription factor-6 (ATF-6), ATF-4, and C/EBP homologous protein (CHOP) in lung fibroblasts were up-regulated by lipopolysaccharides while reduced by vanillic acid. Vanillic acid attenuated lipopolysaccharides-induced decrease of IκBα and increase of p-IκBα, p-p65, p-ERK, and p-JNK in fibroblasts. Vanillic acid exerted anti-inflammatory effect against lipopolysaccharides-induced human lung fibroblasts by inhibiting mitogen-activated protein kinase and nuclear factor kappa B pathways.