Down-regulation of key regulatory factors in sphingosine-1-phosphate (S1P) pathway in human lung fibroblasts transfected with selected microRNAs.

Sphingosine 1 phosphate (S1P) is involved in the pathogenesis of asthma by stimulation of the alpha-smooth muscle actin (SMA) expression and remodeling of fibroblasts. This study was designed to determine the effects of selected micro RNAs in regulation of S1P and related metabolic pathways in a human lung fibroblast cell line. The fibroblast cell line (CIRC-HLF, C580) was cultured and transfected with individual viral vectors carrying miR124, mi125b, mi133b or mi130a. After 48 hours, expression level of miRNAs and their target genes, sphingosine kinase 1(SPHK1), sphingosine 1-phosphate lyase 1 (SGPL1), sphingosine 1- phosphate receptor 1 (S1PR1) and sphingosine 1- phosphate receptor 2 (S1PR2) were determined. Expression of miRNA and mRNA determined by reverse transcriptionquantitative polymerase chain reaction (qPCR) showed that the expression level of the miRNAs was significantly higher in human lung fibroblasts following transfection compared to controls (vector backbone without miRNA). The expressions of miRNAs-targeted genes were significantly downregulated in transfected fibroblasts compared to control cells (p<0.05). Data show that miR 124, miR 125b, miR 133b and miR130a by targeting regulatory genes in S1P-pathway can down-regulate key factors such as SPHK1, SGPL1, S1PR1 and S1PR2 genes in lung fibroblasts. The results showed that S1P pathway and key factors are suppressed in lung fibroblasts expressing miR124, miR125b, miR130a or miR133b. It appears that suppression of any of the intermediate factors in S1P by miRNA can affect the regulation of the entire S1P pathway.