Abstract 193: HDL-Small RNA Intercellular Communication in Systemic Lupus Erythematosus

Abstract

Extracellular small non-coding RNAs (sRNAs) are a new class of disease biomarkers and are transferred between cells by high-density lipoproteins (HDL) in a novel form of intercellular communication. In chronic inflammatory states and auto-immunity, HDL can become dysfunctional, likely through alterations in its diverse cargo, including changes to sRNA signatures. We have previously found that HDL-microRNAs (miRNA) are altered in systemic lupus erythematosus (SLE); however, miRNAs are just one type of sRNAs. As such we hypothesized that changes to HDL-sRNA cargo and cell-to-cell communication in SLE extend beyond miRNAs. To test this hypothesis, HDL was isolated from SLE and control (n=6-8) subjects by density-gradient ultracentrifugation followed by size-exclusion chromatography. High-throughput sRNA sequencing of HDL demonstrated that tRNA-derived sRNAs (tDRs) were the most abundant class of sRNAs on HDL and were significantly altered in SLE subjects compared to controls (26 up, 10 down). In addition, circulating levels of angiogenin, an RNaseIII enzyme capable of cleaving parent tRNAs into tDRs, was also significantly ( P <0.05) increased in SLE plasma. To determine if tDRs are altered in CD4+ T cells in SLE subjects, real-time PCR was used to quantify candidate tDRs, and we found that tDR-GlyGCC levels were significantly increased 4.2-fold in SLE ( P <0.01). Most importantly, we found that T cells exported tDR-GlyGCC to HDL. To determine if T cell exported tDR-GlyGCC is transferred to other cells by HDL, ex vivo studies were completed using Trans-PhotoActivatable-Ribonucleoside-CrossLinking-ImmunoPrecipitation high-throughput Sequencing (Trans-PAR-CLIPseq) to trace sRNAs from human CD4+ T cells to HDL and then to recipient CD14+ monocytes and CD19+ B-cells. Using this approach, we found a cassette of T cell originating sRNAs, including tDR-GlyGCC, transferred by HDL to recipient B cells and monocytes and loaded onto RNA-Induced Silencing Complexes (RISC) targeting genes associated with inflammation. Here, we demonstrate that HDL facilitates the intercellular transfer of sRNAs between immune cells and these sRNAs are altered in SLE. This altered communication may contribute to T cell imbalance and B cell activation observed in SLE.