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MiR‐16 is a tumour suppressor that is down‐regulated in certain human cancers. However, little is known on its activity in other cell types. In this study, we examined the biological significance and underlying mechanisms of miR‐16 on macrophage polarization and subsequent T‐cell activation. Mouse peritoneal macrophages were isolated and induced to undergo either M1 polarization with 100 ng/ml of interferon‐γ and 20 ng/ml of lipopolysaccharide, or M2 polarization with 20 ng/ml of interleukin (IL)‐4. The identity of polarized macrophages was determined by profiling cell‐surface markers by flow cytometry and cytokine production by ELISA. Macrophages were infected with lentivirus‐expressing miR‐16 to assess the effects of miR‐16. Effects on macrophage–T cell interactions were analysed by co‐culturing purified CD4+ T cells with miR‐16‐expressing peritoneal macrophages, and measuring activation marker CD69 by flow cytometry and cytokine secretion by ELISA. Bioinformatics analysis was applied to search for potential miR‐16 targets and understand its underlying mechanisms. MiR‐16‐induced M1 differentiation of mouse peritoneal macrophages from either the basal M0‐ or M2‐polarized state is indicated by the significant up‐regulation of M1 marker CD16/32, repression of M2 marker CD206 and Dectin‐1, and increased secretion of M1 cytokine IL‐12 and nitric oxide. Consistently, miR‐16‐expressing macrophages stimulate the activation of purified CD4+ T cells. Mechanistically, miR‐16 significantly down‐regulates the expression of PD‐L1, a critical immune suppressor that controls macrophage–T cell interaction and T‐cell activation. MiR‐16 plays an important role in shifting macrophage polarization from M2 to M1 status, and functionally activating CD4+ T cells. This effect is potentially mediated through the down‐regulation of immune suppressor PD‐L1.

Aims Temporal lobe epilepsy (TLE), often associated with cognitive impairment, is one of the most common types of medically refractory epilepsy. Deep brain stimulation (DBS) shows considerable promise for the treatment of TLE. However, the optimal stimulation targets and parameters of DBS to control seizures and related cognitive impairment are still not fully illustrated. Methods In the present study, we evaluated the therapeutic potential of DBS in the medial septum (MS) on seizures and cognitive function in mouse acute and chronic epilepsy models. Results We found that DBS in the MS alleviated the severity of seizure activities in both kainic acid‐induced acute seizure model and hippocampal‐kindled epilepsy model. DBS showed antiseizure effects with a wide window of effective stimulation frequencies. The antiseizure effects of DBS were mediated by the hippocampal theta rhythm, as atropine, which reversed the DBS‐induced augmentation of the hippocampal theta oscillation, abolished the antiseizure effects of DBS. Further, in the kainic acid‐induced chronic TLE model, DBS in the MS not only reduced spontaneous seizures, but also improved behavioral performance in novel object recognition. Conclusion DBS in the MS is a promising approach to attenuate TLE probably through entrainment of the hippocampal theta rhythm, which may be therapeutically significant for refractory TLE treatment.

IL‐10‐producing B cells (B10) are associated with autoimmune diseases, infection and tumours. MiR‐15a/16 as a tumour‐suppressive gene is down‐regulated in several tumours, such as chronic lymphocytic leukaemia, pituitary adenomas and prostate carcinoma. Here, increased frequency of IL‐10‐producing CD19+ Tim‐1+ cells was seen in both aged miR‐15a/16−/− mice (15‐18 months) with the onset of B cell leukaemia and young knockout mice (8‐12 weeks) transplanted with hepatic cancer cells. CD19+ Tim‐1+ cells down‐regulated the function of effector CD4+CD25low T cells ex vivo dependent on IL‐10 production, and adoptive transfer of CD19+ Tim‐1+ cells promoted tumour growth in mice. IL‐10 production by CD19+ Tim‐1+ cells was involved with the STAT3 activation. Bioinformatics analysis shows that miR‐16 targets the 3′‐untranslating region (3′‐UTR) of STAT3 mRNA. Overexpression of miR‐16 in CD19+ Tim‐1+ cells inhibited STAT3 transcription and its protein expression. Thus, the loss of miR‐15a/16 promoted induction of regulatory CD19+ Tim‐1+ cells in tumour microenvironment. These results confirmed that miR‐15a/16 could be used in tumour therapy due to its inhibition of tumour and regulatory B cells.