Defining NFκβ-Regulated Biomarkers in Lupus Nephritis Patient Serum

Background: Lupus nephritis (LN) is an autoimmune disease that results from glomerular immune complex deposition and subsequent inflammatory events. Prior studies demonstrate that NF-κβ activation contributes to LN pathogenesis. If NF-κβ-regulated proteins contribute to LN, then we hypothesize that some of these proteins are elevated in LN patients’ serum relative to healthy donors (HD). Methods: The Bio-Plex Pro human immune modulator screening panel was used to measure the contents of serum from 28 LN patients and 8 HD controls. Comparisons of protein concentrations between LN patients and HD were performed using Mann-Whitney tests. Comparisons among HD and the LN genotypes were performed using Kruskal-Wallis tests. Associations between protein concentrations and clinical features were determined using Spearman correlation analyses. All results were corrected for multiple comparisons. Logistic regression models were generated for each independent protein and all possible combinations. Receiver operating characteristic (ROC) curves were used to determine the optimal cutoff concentrations for each protein. Results: Of the 48 NF-κβ-regulated proteins measured, 25 yielded statistically analyzable results. Three of those 25 proteins, IL-2 receptor alpha (IL-2Rα), macrophage colony stimulating factor (M-CSF), and stem cell factor (SCF), were significantly elevated in active LN patients relative to HD. Moreover, serum from patients who were heterozygous for a previously identified NF-κβ-associated LN risk allele, TNIP1 rs49958881, contained significantly more of each protein than homozygous LN patients or HD. M-CSF and SCF were positively correlated with UPCR. IL-2Rα and SCF were positively correlated with serum creatinine. SCF was negatively correlated with glomerular filtration rate. The best fitting model included IL-2Rα and M-CSF. The optimal cutoff concentrations were 47.8 pg/mL for IL-2Rα, 12.69 pg/mL for M-CSF, and 64.47 pg/mL for SCF. Conclusion: The central aim of this project was to characterize immune phenotypes associated with NF-κβ in LN. We’ve identified three NF-κβ-regulated proteins as candidate markers of LN activity that can be obtained relatively non-invasively. Our findings also further characterize approaches to precision medicine by understanding how genetic profiles influence disease progression and response to available therapies. Funding: NIDDK Support