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Distinct microRNA expression profile and targeted biological pathways in functional myeloid-derived suppressor cells induced by Delta9-tetrahydrocannabinol in vivo: regulation of CCAAT/enhancer-binding protein alpha by microRNA-690 #MMPMID24202177
Hegde VL; Tomar S; Jackson A; Rao R; Yang X; Singh UP; Singh NP; Nagarkatti PS; Nagarkatti M
J Biol Chem 2013[Dec]; 288 (52): 36810-26 PMID24202177show ga
Delta(9)-Tetrahydrocannabinol (THC), the major bioactive component of marijuana, has been shown to induce functional myeloid-derived suppressor cells (MDSCs) in vivo. Here, we studied the involvement of microRNA (miRNA) in this process. CD11b(+)Gr-1(+) MDSCs were purified from peritoneal exudates of mice administered with THC and used for genome-wide miRNA profiling. Expression of CD31 and Ki-67 confirmed that the THC-MDSCs were immature and proliferating. THC-induced MDSCs exhibited distinct miRNA expression signature relative to various myeloid cells and BM precursors. We identified 13 differentially expressed (>2-fold) miRNA in THC-MDSCs relative to control BM precursors. In silico target prediction for these miRNA and pathway analysis using multiple bioinformatics tools revealed significant overrepresentation of Gene Ontology clusters within hematopoiesis, myeloid cell differentiation, and regulation categories. Insulin-like growth factor 1 signaling involved in cell growth and proliferation, and myeloid differentiation pathways were among the most significantly enriched canonical pathways. Among the differentially expressed, miRNA-690 was highly overexpressed in THC-MDSCs ( approximately 16-fold). Transcription factor CCAAT/enhancer-binding protein alpha (C/EBPalpha) was identified as a potential functional target of miR-690. Supporting this, C/EBPalpha expression was attenuated in THC-MDSCs as compared with BM precursors and exhibited an inverse relation with miR-690. miR-690 knockdown using peptide nucleic acid-antagomiR was able to unblock and significantly increase C/EBPalpha expression establishing the functional link. Further, CD11b(+)Ly6G(+)Ly6C(+) and CD11b(+)Ly6G(-)Ly6C(+) purified subtypes showed high levels of miR-690 with attenuated C/EBPalpha expression. Moreover, EL-4 tumor-elicited MDSCs showed increased miR-690 expression. In conclusion, miRNA are significantly altered during the generation of functional MDSC from BM. Select miRNA such as miR-690 targeting genes involved in myeloid expansion and differentiation likely play crucial roles in this process and therefore in cannabinoid-induced immunosuppression.
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J+Biol+Chem 2013 ; 288 (52): 36810-26
