Evaluation of Micro-RNA199 in Systemic Lupus Erythematosus 

Determining the cause of LN will help in early detection and provide better therapeutic intervention to improve clinical outcomes (Ajmani et al., 2018), however the prediction of LN in SLE patient is challenging. In general, increased self-production and deposition of antibodies and altered immune responses increase inflammation and fibrosis and may lead to LN (Sun et al., 2018). LN differs greatly between races and ethnicities and genetic factors appear to play a role in the risk of different clinical manifestations (Pan, et al., 2014).

In the current study, ANA and anti-dsDNA were highly positive in SLE patients. Because of high frequency, sensitivity, and specificity, anti-dsDNA represent the hallmark of SLE patients. Moreover, the presence of anti-dsDNA has been associated with LN (Nowling and Gilkeson, 2011)‏. Despite that, a percentage of SLE patients, ranging from 2 to 30%, result negative for anti-dsDNA with high frequent association with serositis (Cozzani, et al, 2014). However, in our study the results of ANA and anti-ds-DNA showed no statistical difference between LN and non-LN patients. A different genetic background could explain these differences and the hypothesis that anti-dsDNA status influences the clinical and immunological features of SLE patients. Nonetheless, it does not appear to affect disease activity (Fabrizio et al., 2015).

In this study, C3 and C4 levels were significantly lower in SLE patients than control subjects and were lower in LN than non-LN. This may be explained by the consumption of C3 and C4 in immune complex formation and by reduced synthesis. In LN, the initial event is likely caused by immune complex deposition and complement activation within the glomeruli or in the intertubular space in the interstitium (Fu et al., 2019), however, complement didn’t show any significant difference between patient groups in this study. A link between anti-dsDNA and complement in LN was confirmed in previous investigations. Complement receptors affect the development of anti-dsDNA by participating in the elucidation of immune complexes and / or modifying the activation of B cells in response to antigen (Fabrizio et al., 2015).

Elevated ESR in our SLE patients may reflect the inflammatory changes in SLE (Schäfer, 2018‏), therefore it is higher in LN patients. Thrombocytopenia and the anemia reported in our results for SLE patients may explained by the presence of auto-antibodies targeting platelet membrane glycoproteins leading to peripheral platelet destruction and the presence of auto-antibodies against RBC antigens (Ziakas et al., 2006, Voulgarelis et al., 2000). Anemia was more in LN than in non-LN in this study perhaps due to more activity of the disease, the same for arthritis.

Chronic systemic inflammation in SLE leads to activation of endothelial cells and increase in vascular factors that induces inflammation leading to vascular permeability, vascular growth, destruction of blood vessels and internal dysfunction of organs (Cronstein et al., 1999). Among the most commonly affected organs in SLE are the skin and kidneys (Berthier et al., 2017). In this study, malar rash and oral ulcer were the most presented cutaneous manifestations of SLE; moreover, oral ulcer was more evident in LN. These results need further studies on larger samples to highlight the difference in the cutaneous presentations in SLE with and without renal affection. Cutaneous exposure to ultraviolet light has been proposed as a flare trigger for cutaneous disease and can accelerate LN, however, the mechanism remains poorly understood. Clark et al. (2015) described lupus flare induction mediated by epidermal injury in lupus-prone NZM2328 mice. Pathogenic mechanisms include stimulation of chemokine production from mesangial cells within the kidney as well as immune complex stimulation of dendritic and plasmacytoid dendritic cell toll-like receptors and renal macrophages followed by florid nephritis (Clark et al., 2015).

Although kidney biopsy is considered to be the basis for LN diagnosis, it is an invasive process and therefore, the presence of biomarkers to predict and diagnose this condition is needed. In this study, we selected patients with SLE, who suffered from lupus- related skin lesion, with or without the diagnosis of LN, so that we can test a marker that helps in predicting kidney morbidity, which easy the early intervention.

Immune mechanisms control process of protein production through DNA transcription and RNA translation; among these, circulating microRNAs play a significant role (Pan et al., 2104). However, the role of miRNAs in the pathophysiology of LN is not fully understood. The dysregulation of miRNAs can lead to aberrant immune response and antibody production to exogenous antigens or self-antigens, which may contribute to the development of LN, Navarro-Quiroz et al. ( 2017) identified 24 circulating miRNAs with differential abundance between LN stage IV group and controls. These changes in the abundance of miRNAs can be interpreted as changes in the regulatory network of miRNAs-mRNA in the LN before the clinical appearance of the disease. These results opened the way for the identification of vital indicators of the disease for the early diagnosis of LN. In this context, our purpose of the study was to investigate the association of miRNA199 with LN. The study reported down-regulation of relative expression of miRNA199 in SLE patients than in controls and LN had the lowest level.

MiRNAs (as: miR-155, miR-663a / miR-423-5p, and Let-7) are well represented in both nuclear factor (NF)-κB and IFN- γ causing LN (Honarpisheh et al., 2018). NF-κB can induce inflammation and fibrosis in LN by regulating transcription of proinflammatory cytokines (Brightbill et al., 2018). Klotho regulates NF-κB activation and participates in protecting the kidneys by mitigating oxidative stress (Zhao et al., 2011). Reduced Hsa-miR-199a expression was noted in LN stage IV group compared to control group in Navarro-Quiroz et al. (2017) study. Hsa-miR199a may regulate the inhibitory kappa B (IκB) kinase β expression that is needed for NF-κB activation. Increased miR199a and decreased Klotho expression may lead to NFκB activation and accelerate the inflammatory process (ye et al., 2018).

Nevertheless, our results showed a decreased expression of miRNA199 in SLE especially with renal affection, we support the hypothesis that LN is due to the effects of many miRNAs instead of single miRNA. In conclusion, the patterns of miRNA199 expression may represent a new diagnostic method for predicting renal involvement; however, the contribution to other circulating miRNAs on larger samples should be studied.