Résumé
Morphine is a frequently used analgesic that activates the mu-opioid receptor(MOR),which has prominent side effects of tolerance.Although the inefficiency of morphine in inducing the endocytosis of MOR underlies the development of morphine tolerance,currently,there is no effective therapy to treat morphine tolerance.In the current study,we aimed to develop a monoclonal antibody(mAb)precisely targeting MOR and to determine its therapeutic efficacy on morphine tolerance and the underlying molecular mechanisms.We successfully prepared a mAb targeting MOR,named 3A5C7,by hybridoma technique using a strategy of deoxyribonucleic acid immunization combined with cell immunization,and identified it as an immunoglobulin G mAb with high specificity and affinity for MOR and binding ability to antigens with spatial conformation.Treatment of two cell lines,HEK293T and SH-SY5Y,with 3A5C7 enhanced morphine-induced MOR endocytosis via a G protein-coupled receptor kinase 2(GRK2)/β-arrestin2-dependent mechanism,as demonstrated by immunofluorescence staining,flow cytometry,Western blotting,coimmunoprecipitation,and small interfering ribonucleic acid(siRNA)-based knock-down.This mAb also allowed MOR recycling from cytoplasm to plasma membrane and attenuated morphine-induced phosphorylation of MOR.We established an in vitro morphine tolerance model using differentiated SH-SY5Y cells induced by retinoic acid.Western blot,enzyme-linked immunosorbent assays,and siRNA-based knockdown revealed that 3A5C7 mAb diminished hyperactivation of adenylate cyclase,the in vitro biomarker of morphine tolerance,via the GRK2/β-arrestin2 pathway.Furthermore,in vivo hotplate test demonstrated that chronic intrathecal administration of 3A5C7 significantly alle-viated morphine tolerance in mice,and withdrawal jumping test revealed that both chronic and acute 3A5C7 intrathecal administration attenuated morphine dependence.Finally,intrathecal electroporation of silencing short hairpin RNA illustrated that the in vivo anti-tolerance and anti-dependence efficacy of 3A5C7 was mediated by enhanced morphine-induced MOR endocytosis via GRK2/β-arrestin2 pathway.Collectively,our study provided a therapeutic mAb,3A5C7,targeting MOR to treat morphine tolerance,mediated by enhancing morphine-induced MOR endocytosis.The mAb 3A5C7 demonstrates promising translational value to treat clinical morphine tolerance.
Résumé
?ig-h_3 was first identified as a transforming growth factor-beta1-inducible gene in human lung adenocarcinoma cell line. It encodes for a secreted extracellular matrix (ECM) protein, which is thought to act on cell attachment and ECM composition. Previous study showed that ?ig-h_3 were highly expressed in human hepatoma cell lines and lowly expressed in human normal hepatic cells. The present study aimed to transfect ?ig-h_3 into 7721 cells to investigate its effect on secretion of MMPs in the transfected human hepatoma cells. Full-length ?ig-h_3 gene,cloned by reverse transcription polymerase chain reaction (RT-PCR) was inserted into the eukaryotic expression vector pEGFP-C_2. The recombinant plasmid was transfected into 7721 cells with Lipofectamine2000 and Gelatin-Zymography were adopted to detect the production of MMPs in the transfected cells. Results showed that ?ig-h_3/pEGFP-C_2 recombinant expression plasmid was successfully constructed and achieved high transfection efficiency. MMPs expression of the transfected cells was promoted significantly. These results suggest that overexpression of ?ig-h_3 promoted the production of MMPs, indicating that ?ig-h_3 may play roles in the invasive and metastatic processes of hepatoma.