Camphorquinone, a popularly-used photoinitiator, induced ER responses in dental pulp cells: Association with MAPK signaling, cytotoxicity, 8-isoprostane and PGE2 production

• After composite resin restoration, released camphorquinone may affect the pulpal viability, and inflammation. • Human dental pulp cells expressed various endoplasmic reticulum stress-related molecules. • Camphorquinone stimulated endoplasmic reticulum stress signaling molecules such as 78-kDa glucose-regulated protein, inositol-requiring enzyme 1α, protein kinase RNA-like ER kinase, and activating transcription factor 6 in human dental pulp cells. • Camphorquinone-induced endoplasmic reticulum stress responses are partly regulated by extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase signaling. • Camphorquinone-induced cytotoxicity, prostaglandin E 2 and 8-isoprostane are differentially regulated by IRE1α and other signaling pathways. • Inhibition of camphorquinone-induced extracellular signal-regulated kinase kinase/extracellular signal-regulated kinase and endoplasmic reticulum stress signaling may potentially affect the pulpal inflammation, vitality or necrosis after operative restoration.