Exosomes from Melatonin Treated Hepatocellularcarcinoma Cells Alter the Immunosupression Status through STAT3 Pathway in Macrophages

Abstract

Immunosuppression is a significant factor in the progression of tumor invasion and metastasis. Melatonin, a well-known hormone, has certain cytotoxic and immune regulatory effects to inhibit tumor function. Exosomes are small membrane vesicles released by many kinds of cells, which contain different macromolecules, such as mRNAs and microRNAs (miRNAs), and proteins that can mediate communications between cells. Tumor-derived exosomes may cause immunosuppression, however, it is unknown whether melatonin can attenuate an immunosuppressive status by altering the function of tumor-derived exosomes. In the present study, we evaluated the effects of hepatocellularcarcinoma-derived exosomes (Exo-con) and exosomes derived from hepatocellularcarcinoma cells treated with 0.1 mM melatonin (Exo-MT), on the expression of inflammatory factors and programmed death ligand 1(PD-L1) by co-culturing Exo-con and Exo-MT, respectively, with macrophages differentiated from THP-1 cells or RAW264.7 cells. Our in vitro results indicate that Exo-MT can downregulate the expression of PD-L1 on macrophages while Exo-con can upregulate the expression of PD-L1 through flow cytometry and immunofluorescence analysis. In addition, Exo-con upregulates the secretion of cytokines, such as IL-6, IL-10, IL-1β, and TNF-α in macrophages. Accordingly, Exo-MT could attenuate the high expression of these inflammatory cytokines. Furthermore, in vivo experiments confirmed the results found in vitro. PD-L1 expression and cytokine secretion were lower in the Exo-MT group compared with those in the Exo-con group. Working to identify a specific mechanism, our research shows that Exo-MT decreases STAT3 activation compared to the Exo-con group. In summary, we found exosomes from melatonin treated hepatocellularcarcinoma cells alters the immunosupression status through STAT3 pathway in macrophages. Our study may provide a new avenue to investigate the mechanisms of melatonin in regulating an immunosuppressive status.

Melatonin in macrophage biology: Current understanding and future perspectives

“…Similarly, in mice subjected to stress, melatonin promotes the serum level of IL‐10, expression of Arg1 in isolated Kupffer cells and peritoneal macrophages, percentage of M2 macrophages in isolated Kupffer cells and peritoneal macrophages, and activation of STAT‐3 in isolated Kupffer cells . However, exosomes derived from hepatocellular carcinoma cells treated with 0.1 mmol/L melatonin could attenuate the high expression of IL‐10 and decreased STAT‐3 activation in TAM, suggesting that melatonin inhibits the function of M2 macrophages in tumors . Differences in melatonin's actions toward tumor and nontumor cells are not uncommon and concern apoptosis, ROS production, the circadian system, and SIRT1 expression …”

Interactions of Melatonin and MicroRNAs

“…Exosomes from melatonin-treated cells downregulated in the recipient macrophages the secretion of IL-6, IL-10, IL-1β, and TNF-α, whereas those from untreated cells upregulated these cytokines [30]. Unfortunately, the responsible miRNAs were not determined.…”

“…In a rat scopolamine toxicity model of ADlike memory losses, melatonin reversed an increase of miR-124 and thereby corrected the level of the targeted Egr1 (early growth response protein 1) mRNA [27]. In another AD model, Aβ [25][26][27][28][29][30][31][32][33][34][35] peptide added to primary cortical neurons caused downregulation miR-132, an effect that was also reversed by melatonin. The normalization of miR-132 is insofar of importance, as this miRNA transmits anti-apoptotic and other protective properties known from melatonin [28].…”

“…With some likelihood, other data on inflammation may have resulted from transfer of miRNAs. In a study on the immune responsiveness, in vitro differentiated macrophages were exposed to exosomes from hepatocellular carcinoma cells [30]. The cancer cells had either remained untreated or were incubated with melatonin, which obviously changed the composition of the exosomal contents.…”

Exosomes play roles in sequential processes of tumor metastasis

“…In summary, TDEs can modulate the immune systems by triggering the immunosuppressive response, which in turn favors tumor progression. A recent research about exosomes from melatonin (a kind of tumor inhibitory hormone) treated HCC cells altering the immunosuppressive status through STAT3 pathway in macrophages provides a new avenue to investigate the mechanisms between exosomes and immune system . With a better understanding of the immune functions of exosomes in tumors, it may suggest novel and efficient antitumor therapies in the future.…”