miR-146b antagomir-treated human Tregs acquire increased GVHD inhibitory potency

MiR-146a/b: a family with shared seeds and different roots

MicroRNAs are small, noncoding, RNAs known for their powerful modulation of molecular processes, making them a major focus for studying pathological mechanisms. The human miR-146 family of microRNAs consists of two member genes, MIR146A and MIR146B These two microRNAs are located on different chromosomes and exhibit differential regulation in many cases. However, they are nearly identical in sequence, sharing a seed region, and are thus predicted to target the same set of genes. A large proportion of the microRNA (miR)-146 literature focuses on its role in regulating the innate immune response in the context of various pathologies by modulating two widely studied target genes in the toll-like receptor signaling cascade. A growing subset of the literature reports a role of miR-146 in cardiovascular and renal disease, and data suggest there is exciting potential for miR-146 as a diagnostic and therapeutic target. Nevertheless, the published literature is confounded by unclear and imprecise language concerning the specific effects of the two miR-146 family members. The present review will compare the genomic origin and regulation of miR-146a and miR-146b, discuss some approaches to overcome analytical and experimental challenges, and summarize findings in major areas of miR-146 research. Moving forward, careful evaluation of miR-146a/b specificity in analytical and experimental approaches will aid researchers in elucidating the functional relevance of differential regulation of the miR-146 family members in health and disease.

MicroRNA-27a promotes podocyte injury via PPARγ-mediated β-catenin activation in diabetic nephropathy

Podocyte injury has a pivotal role in the pathogenesis of diabetic nephropathy (DN). MicroRNA-27a (miR-27a), peroxisome proliferator-activated receptor γ (PPARγ) and β-catenin pathways have been involved in the pathogenesis of DN. Herein, we asked whether miR-27a mediates podocyte injury through PPARγ/β-catenin signaling in DN. The functional relevance of miR-27a, PPARγ and β-catenin were investigated in cultured podocytes and glomeruli of diabetic rats and patients using in vitro and in vivo approaches. Podocyte injury was assessed by migration, invasion and apoptosis assay. Biological parameters were analyzed using enzyme-linked immunosorbent assay. We found that high glucose stimulated miR-27a expression, which, by negatively targeting PPARγ, activated β-catenin signaling as evidenced by upregulation of β-catenin target genes, snail1 and α-smooth muscle actin (α-SMA) and downregulation of podocyte-specific markers podocin and synaptopodin. These changes caused podocyte injury as demonstrated by increased podocyte mesenchymal transition, disrupted podocyte architectural integrity and increased podocyte apoptosis. Furthermore, we provide evidence that miR-27a contributed to unfavorable renal function and increased podocyte injury in diabetic rats. Notably, miR-27a exhibited clinical and biological relevance as it was linked to elevated serum creatinine, proteinuria and reduced creatinine clearance rate. In addition, miR-27a upregulation and activation of PPARγ/β-catenin signaling were verified in renal biopsy samples from DN patients. We propose a novel role of the miR-27a/PPARγ/β-catenin axis in fostering the progression toward more deteriorated podocyte injury in DN. Targeting miR-27a could be a potential therapeutic approach for DN.

Memory CD4+ T cells are suppressed by CD8+ regulatory T cells in vitro and in vivo

BACKGROUND

Acute graft rejection mediated by alloreactive memory CD4⁺ T cells is a major obstacle to transplantation tolerance. It has been reported that CD8⁺ T regulatory cells (Tregs) have the ability to induce graft tolerance by restraining the function of activated CD4⁺ T cells, but not including memory T cells. The aim of this study is to elucidate the effect of CD8⁺ Tregs on alloreactive memory CD4⁺ T cells.

METHODS

We detected Qa-1 expression and performed proliferative assay on memory CD4⁺ T cells. All memory CD4⁺ T cells were purified from mice receiving skin allografts. We performed inhibitory and cytotoxic assays on CD8⁺ Tregs, which were isolated from a T cell vaccination mouse model, and IL-2, IL-4, IL-10 and IFN-γ levels were measured in co-culture supernatants by ELISA. To confirm CD8⁺ Tregs inhibition of memory CD4⁺ T cells in-vivo, we utilized a murine model of cardiac allograft transplantation.

RESULTS

Memory CD4⁺ T cells mediated acute allograft rejection, and CD8⁺ Tregs suppressed the proliferation of memory CD4⁺ T cells. In vitro, memory CD4⁺ T cells were inhibited and lysed by CD8⁺ Tregs. There was a positive correlation between IFN-γ levels, and cell lysis rate induced by CD8⁺ Tregs. In-vivo studies demonstrated CD8⁺ Tregs prolonged graft survival times, by inhibiting CD4⁺ memory T cells, through a Qa-1-peptide-TCR pathway.

CONCLUSIONS

CD8⁺ Tregs inhibit CD4⁺ memory T cell-mediated acute murine cardiac allograft rejection, and further prolong graft survival times. These results provide new insights into immune regulation of organ rejection.