Phosphoproteomic analysis of electroacupuncture analgesia in an inflammatory pain rat model

The phosphorylation changes of nociceptive signaling proteins in the spinal cord dorsal horn (SCDH) are important in creating exaggerated pain following peripheral inflammation. Electroacupuncture (EA) has been widely used to relieve acute and chronic inflammatory pain in human and experimental pain models. In the present study, we performed a phosphoproteomic analysis to investigate whether EA alters protein phosphorylation in SCDH to attenuate pain development. Inflammatory hyperalgesia was induced by intraplantar injection of complete Freund's adjuvant (CFA) into the rat hind paw. EA treatment at ST36 and SP6 acupoints alleviated thermal hyperalgesia of the CFA-induced inflammatory pain model rats. The SCDH proteins from the control, inflammatory pain model and EA treatment rats were separated by 2-dimensional gel electrophoresis and the alterations in phosphoproteins were detected by Pro-Q Diamond staining. Eight proteins were differentially phosphorylated following EA treatment in the inflammatory pain model. Aldolase C, nascent polypeptide-associated complex α, stress-induced phosphoprotein 1 and heat shock protein 90 were identified as phosphoproteins whose expression was increased, whereas GDP dissociation inhibitor 1, thiamine triphosphatase, phosphoglycerate kinase 1 and 14-3-3 γ were phosphoproteins whose expression was decreased. This is the first phosphoproteomic screening study to elucidate the working mechanisms of EA analgesia. The results suggest that the regulation of cellular pathways in which the identified proteins are involved may be associated with an EA analgesic mechanism.