Peripheral Blood Gene Expression in Discoid Lupus Erythematosus and Systemic Lupus Erythematosus Patients
MetadataShow full item record
BACKGROUND: Systemic lupus erythematosus (SLE) is an autoimmune disease with variations in clinical presentation that can affect the kidney, blood vessels, heart, lungs, joints, CNS, and/or the skin. The most common cutaneous form is discoid lupus erythematosus (DLE). DLE can occur with or without SLE, and differentiating between the two disease states can be ambiguous. Recent studies have shown type I interferon-related genes to be upregulated in peripheral blood mononuclear cells (PBMCs) of SLE patients and DLE patients compared with normal controls. Other studies have suggested that cytokines could serve as biomarkers of disease progression from DLE to SLE. Identifying differences in the transriptomes of DLE patients versus SLE patients could aid in distinguishing these two groups and forecasting progression from DLE to SLE. AIM: This study aimed to analyze differences in the expression levels of type I interferon-related genes and cytokine genes in whole blood samples of DLE patients, SLE patients, and normal controls. We hypothesized that SLE patients would have increased expression levels of these genes compared to DLE patients, due to their widespread systemic disease. METHODS: Blood samples were collected from DLE, SLE, and normal patients recruited at the outpatient UTSW and Parkland Hospital Dermatology clinics. Reverse transcription polymerase chain reaction (RT-PCR) analysis of ten genes, including five type I interferon-related genes (MX1, LY6E, OAS1, OASL, and ISG15) and five cytokine genes (CXCL10, TNF-α, IL-6, IL-10, and IL-12), was performed. RNA was extracted using RNeasy Lipid Tissue Mini kit, and the RNA was reverse transcribed to cDNA. cDNA of selected genes was amplified with SYBR Green PCR Master Mix using forward and reverse primers. Cycle threshold (Ct) values were standardized to the housekeeping gene GAPDH and converted to fold change using the 2-ΔΔCT formula. Gene expression levels were compared between these groups using the Kruskal-Wallis test. RESULTS AND CONCLUSIONS: All of the interferon-related genes were found to be significantly overexpressed (p<0.05) in the whole blood of DLE and SLE patients compared to normal controls. However none of the interferon-related genes showed a significant difference in gene expression between DLE and SLE patients. Expression of cytokine genes either did not show any significant differences between groups or was too low to detect. Future directions include RT-PCR analyses of cytokine gene expression of stimulated patient PBMCs, and whole blood gene expression of other candidate biomarker genes identified from our whole blood microarray data.