T Cell Metabolism: MicroRNAs Cap PTEN to Feed the Expanding Crowd

Vitamin D/VDR signaling induces miR-27a/b expression in oral lichen planus

MicroRNA-27a/b are small non-coding RNAs which are reported to regulate inflammatory response and cell proliferation. Although some studies have demonstrated that miR-27b is down-regulated in the oral specimens of patients suffering with oral lichen planus (OLP), the molecular mechanism of miR-27b decrease remains a large mystery, and the expression of miR-27a in OLP is not well explored. Here, we demonstrated both miR-27a and miR-27b, compared with healthy controls, were reduced in the oral biopsies, serum and saliva samples derived from OLP patients. The reductions of miR-27a/b were also confirmed in the lipopolysaccharide (LPS)- or activated CD4⁺ T cell-treated human oral keratinocytes (HOKs). Furthermore, we found vitamin D receptor (VDR) binding sites in the promoters of miR-27a/b genes and verified this finding. We also tested miR-27a/b levels in the oral epithelium from paricalcitol-treated, vitamin D deficient or VDR knockout mice. In the rescue experiments, we confirmed vitamin D and VDR inhibited LPS- or activated CD4⁺ T cell-induced miR-27a/b reductions in HOKs. In sum, our results show that vitamin D/VDR signaling induces miR-27a/b in oral lichen planus.

Emerging roles of microRNAs in the metabolic control of immune cells

Immunometabolism is an emerging field that focuses on the role of cellular metabolism in the regulation of immune cells. Recent studies have revealed an intensive link between the metabolic state and the functions of immune cells. MicroRNAs (miRNAs) are small non-coding, single-stranded RNAs generally consisting of 18-25 nucleotides that exert crucial roles in regulating gene expression at the posttranscriptional level. Although the role of miRNAs in immune regulation has long been recognized, their roles in immunometabolism have not yet been well established. Over the past decade, increasing studies have proven that miRNAs are intensively involved in the metabolic control of immune cells including macrophages, T cells, B cells and dendritic cells. In this review, we highlight recent emerging findings in the miRNA-mediated metabolic control of immune cells.

Cellular metabolism on T-cell development and function

Cell metabolism is closely related to the host immunity in many respects. We herein briefly summarized the recent progress on the roles of cellular metabolism in T-cell development, homeostasis, differentiation and functions. Relatively quiescent naïve T cells only require energy for survival and migration, and they mainly metabolize glucose to carbon dioxide through oxidative phosphorylation. However, activated T cells engage in robust cell proliferation, produce of a range of effector molecules and migrate through peripheral tissues, so they utilizes glycolysis to convert glucose to lactate (termed aerobic glycolysis) to meet the significantly increased metabolic demands. Importantly, the differentiation of T-cell subsets and memory T cells (Tm) was also significantly shaped by distinct cellular metabolic pathways including glucose, amino acids (AA), fatty acids (FA), and others. Understanding the regulatory metabolic networks on immunity may offer new insights into the immune-related disorders and open novel potential therapies to prevent and treat immune diseases.