4.0 Discussion
A large body of evidence has demonstrated that the immune system may play a crucial role in INS[3]. To date, the underlying pathogenesis of INS remains largely unknown. Some researchers hypothesize that INS may be caused by dysregulation of T lymphocytes or an abnormal T cell response[3-8]. MCD is the most common cause of INS[1-2,18-19]. Th2 cells play an important role in allergic inflammatory diseases[9-11,25, 28] . The association of pollen sensitivity and seasonal proteinuria was first reported more than 60 years ago[12]. Minimal change nephrotic syndrome is often associated with clinical features of allergy such as bronchial asthma, allergic rhinitis, atopic dermatitis and urticaria. Some studies have also confirmed that patients with INS also may show increased serum IgE levels, especially in children with repeated recurrence[13-15,18]. However, the causal relationship between the increase of serum IgE or atopy and the pathogenesis of INS remains to be further explored. This study found that the plasma IgE during the active phase was significantly increased in the initial atopic and non-atopic groups compared with the control group, and it also significantly decreased during the remission phase. In remission, the IgE level of non-atopic INS children tended to be normal, while IgE level of atopic was still high. These results suggested that atopic and non-atopic INS have increased serum IgE levels, but further investigation of the cytokine regulating network of serum IgE was necessary to clarify the relationship between IgE production and INS.
IL-13 and IL-4 secreted by Th2 cells can promote the production of IgE in B cells[9-11]. IL-13 is known to induce a switch from IgM to IgE in B cells and induce CD80 expression by podocytes. Concomitantly, increased CD80 expression by podocytes is associated with proteinuria[13-15, 18]. And, IL-13 is present in urine and serum of patients with kidney disease and is associated with a large amount of proteinuria[13-15, 18], which suggesting that IL-13 is related to the pathogenesis of kidney disease, but the mechanisms resulting in IL-13 increasing was still unclear. In recent years, studies have found that Th2-related factors IL-13 and IL-4 are increased in active INS [13-15, 18]. A few studies have also noted that the proportion of Th2 cells in INS is increased[8,18, 21-22], but It is still controversial whether the proportion is abnormally increased, so this article further tested the expression of Th2 cells in peripheral blood and the concentrations of IL-13 and IL-4 in the plasma. our data demonstrate that the expression levels of Th2-related factors ( IL-13, IL-4 ) was significantly increased in the initial atopic and non-atopic groups, at the same time, Th2 cells were over-activation. These results suggested that the proteinuria and increased IgE levels in the initial atopic and non-atopic during the active phase might be related to the high expression of IL-13 and IL-4 which were caused by Th2 drifting, but the mechanism that lead to Th2 drifting still needed to be studied to further explain the pathogenesis of INS immune.
MiRNAs are subtle master controllers of gene expression and therefore play a crucial role in the pathogenesis of human diseases, especially in chronic multifactorial diseases[23-24]. Some specific miRNAs have been reported to be abnormally expressed in various allergic and autoimmune diseases such as asthma, SLE, Lupus Nephritis and are associated with disease activity [25, 29-30 ]. MiRNAs are important for Th2 cell proliferation, differentiation and immune function[25-27]. MiR-24 and 27 suppress allergic inflammation and target a network of regulators of Th2 cell-associated cytokine production[26-27]. However, it is unclear whether changes in miRNAs expression alter Th2 expression in active INS. Therefore, In this study we further observed the expression changes of miR-24 and miR-27 involved in regulating Th2 cell differentiation. The results showed that miR-24 and miR-27 were lowly expressed in children with active non-atopic INS, suggesting that Th2 cells drifting might be related to the low- expression of miR- 24 and miR-27.
In order to verify whether this hypothesis was true, we used cell transfection technology to transfer miRNA24 or miR-27 mimic to non-atopic and healthy control group mononuclear cells to increase the expression level, and transfer miR-24 or miR-27 inhibitor to reduce the expression level. The normal control group was also set up to verify the effect of transfection. The results showed that the proportion of Th2 cells and the expression of Th2 cell-associated cytokine IL-4 were decreased in the miR-24 and miR-27 up-regulated groups. In contrast, the proportion of Th2 cells and the expression of Th2 cell-associated cytokine IL-4 were increased in miR-24 and miR-27 down-regulated groups, indicating that miR-24, miR- 27 negatively regulated Th2 cell expression. Combining the expression trends of miR-24, miR-27 and Th2 cells obtained from patients’ peripheral blood mononuclear cells, our hypothesis was true, miR-24 and miR-27 negatively regulated the change in the proportion of Th2 cells, and they might play an important role in Th2 expression in active period INS.
In conclusion, Th2 related-cytokine IL-13 was related to the pathogenesis of kidney disease, but the mechanisms resulting in IL-13 increasing was still unclear. Our results suggested that there were high IgE in children with both atopic and non-atopic INS during the active period, which might be related to the high expression of IL-13 and IL-4 induced by Th2 cells drifting. The expressions of miR-24 and miR-27 were down-regulated in the initial non-atopic INS, the proportion of Th2 cells and IL-4mRNA expression were remarkably increased, which leading to IL-13 over-expression and increased IgE levels. That was, miR-24 and miR-27 negative regulated the expressions of Th2 cells and played an important role in the change of Th2 expression in children with active INS. Therefore, we speculated that miRNAs would be potential therapeutic targets for kidney disease, our research has provided a new research direction and treatment method for the treatment of INS.