RESUMO
OBJECTIVES: To study the role of microRNA-873 (miR-873) in suppressing morphine-induced macrophage apoptosis and morphine dependence, and to identify molecular targets within the miR-873 pathway for the treatment of immune suppression and morphine addiction. METHODS: As morphine elevates TLR9 expression and induces TLR9-mediated apoptosis, we used TLR9 knockout Balb/C mice to study TLR9-independent effects of miR-873 on morphine-induced macrophage apoptosis. Forty TLR9-knockout mice were randomly and equally assigned to morphine group and control group. Following the administration of morphine, miR-873 mimics or miR negative control was injected into mice in each group. Using freshly isolated macrophages from mice and RAW264.7 murine macrophage cell line, miR-873 level was determined by qRT-PCR and morphine induced apoptosis was measured by TUNEL assays. Western blotting was used to detect and quantify the expression level of A20, a protein that negatively regulates inflammation and TNF-induced apoptosis. RESULTS: qRT-PCR analysis revealed a markedly lower expression of miR-873 in freshly isolated peritoneal macrophages, liver tissue and spleen tissue in the morphine group compared with the corresponding tissues in the control group. TUNEL assays showed that the apoptosis rates in the morphine groups treated with miR-873 mimics was markedly lower than their respective control groups. Western blotting results showed that A20 expression level was sharply elevated in the experimental groups treated with miR-873 mimics than the negative and blank control groups. CONCLUSIONS: Our results show that miR-873 elevates A20 levels and inhibits morphine-induced macrophage apoptosis.