Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic synovial inflammation and finally leads to variable degrees of bone and cartilage erosion. The diagnosis of RA is not an accurate indicator, but a series of scores and the mechanisms underlying it remain only partially understood. The present study explored whether circular RNAs (circRNAs) contribute to the RA pathophysiological mechanism. Total RNA from peripheral blood mononuclear cells of 10 RA patients and 10 healthy controls were extracted and circRNA expression profiling was followed by microarray analysis. In addition, circRNA interactions with microRNAs were performed and microRNA response elements were listed to identify differentially expressed binding site targets in RA. Reverse transcription-quantitative polymerase chain reaction amplification (RT-qPCR) was used to verify the differential expression of circRNAs. A total of 584 circRNAs were differentially expressed in RA patients vs. healthy controls, by circRNA microarray, including 255 circRNAs which were significantly upregulated and 329 downregulated among the RA samples. RT-qPCR validation demonstrated that the expression levels of hsa_circRNA_104194, hsa_circRNA_104593, hsa_circRNA_103334, hsa_circRNA_101407 and hsa_circRNA_102594 were consistent with the results from the microarray analysis. The current study presented differentially expressed circRNAs and their corresponding microRNA binding sites in RA. circRNAs may exhibit a role in the regulation of expression of symbol genes that influence the occurrence and development of RA.

A good understanding of membrane protein folding at the molecular level requires an effective means to determine the dynamical structural changes on coil-to-helix transition within cell membrane, yet remains challenging. Herein, we demonstrate that the amide III spectral signals of protein backbone, generated in the sum frequency generation vibrational spectroscopy, are a powerful tool to probe the protein folding processes within the membrane in situ, in real time and without exogenous labels. The amide III signals are capable of separating the spectral profiles of the random-coil and α-helical structures at the interface. The intensity ratio of coil and helix peaks becomes a prime indicator that allows to directly capturing the dynamical change of the coil-helix transition. With this approach, using pardaxin as model, the influence of lipid charge on the peptide folding degree at cell membrane surface has been nicely elucidated. It is evident that negative charge of lipid increases the folding degree of pardaxin upon interfacial adsorption and promotes the formation of α-helical structure during the insertion of peptide into lipid bilayer. This robust spectral approach can thus greatly enhance our ability to monitor the dynamics of membrane proteins in a real cell environment in situ.

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