The results suggested that serum miR-146a and miR-155 participate in the pathophysiology of SLE and might be used as biomarkers of SLE.

MicroRNAs circulating in body fluid have been suggested as biomarkers of various diseases. We studied the serum and urinary level of several miRNA species (miR-200 family, miR-205 and miR-192) in patients with systemic lupus erythematosus (SLE). We studied 40 SLE patients. Serum and urinary miRNA levels were determined and compared with that of healthy controls. The serum levels of miR-200a, miR-200b, miR-200c, miR-429, miR-205 and miR-192, and urinary miR-200a, miR-200c, miR-141, miR-429 and miR-192 of SLE patients were lower than those of controls. Glomerular filtration rate (GFR) correlated with serum miR-200b (r = 0.411, p = 0.008), miR-200c (r  = 0.343, p  = 0.030), miR-429 (r  = 0.347, p = 0.028), miR-205 (r = 0.429, p = 0.006) and miR-192 (r =  0.479, p =  0.002); proteinuria inversely correlated with serum miR-200a (r = -0.375, p = 0.017) and miR-200c (r  = -0.347, p = 0.029). SLE disease activity index (SLEDAI) inversely correlated with serum miR-200a (r = -0.376, p = 0.017). Serum miR-200b (r =  0.455, p = 0.003) and miR-192 (r = 0.589, p < 0.001) correlated with platelet count, while serum miR-205 correlated with red cell count (r = 0.432, p =  0.005) and hematocrit (r = 0.370, p = 0.019). These pilot results suggested that miRNA may take part in the pathogenesis of SLE. Further studies are needed to validate the role of serum miRNA as a biomarker of SLE.

We studied the levels of miR-146a and miR-155 in the urine sediment of SLE patients. The levels of miR-146a and miR-155 in the urine sediment of 40 SLE patients who were receiving calcitriol treatment and 13 healthy controls were determined with real-time quantitative polymerase chain reaction. The levels of urinary miR-146a and miR-155 in patients with SLE were significantly higher than that in healthy controls. Calcitriol treatment reduced the levels of urinary miR-155 in patients with SLE. The level of urinary miR-146a significantly correlated with estimated glomerular filtration rate (r = 0.242, P = 0.008). The level of urinary miR-155 significantly correlated with proteinuria (r = 0.407, P < 0.001) and systemic lupus erythematosus disease activity index (r = 0.278, P = 0.002). The level of urinary miR-146a reversely correlated with the urinary expression of TNF-α (r = -0.247, P = 0.012). Our results suggested that miR-146a and miR-155 might play important roles in the pathophysiology of SLE and the levels of urinary miR-146a and miR-155 could be used as potential markers for diagnosis, disease activity, and therapeutic response.

mtDNA is readily detectable in urinary supernatant and kidney tissue, and their levels correlate with renal function and scarring in DN. Further studies are needed to determine the accuracy of urinary supernatant mtDNA level as a prognostic indicator of DN, as well as its role in other kidney diseases.