Abstract
Background and Aims
Pathogenesis of idiopathic nephrotic syndrome (INS) is yet to be fully elucidated. Immunological disorders are reported to be involved in the etiology of INS. Due to the efficacy of immunosuppressant agents such as calcineurin inhibitor and rituximab in treating nephrotic syndrome, aberrant activation of the acquired immune system through T and B cells are considered to be the underlying pathogenic mechanisms of INS. Nevertheless, there is a possibility that the innate immune system plays a key role in INS pathogenesis. This study aims to investigate the involvement of innate immunity in INS pathogenesis by examining the expressions of toll-like receptors (TLRs).
Method
Kidney tissue samples from two INS patients were collected at two points of time: the first biopsy was performed during nephrosis and the second during remission. Total RNA was extracted from the kidney tissue samples, and RNA-sequencing was performed to investigate RNA expression profiles. The differences between RNA expression profiles of TLRs and molecules related to TLR pathways in the tissue samples collected during nephrosis and remission were analyzed.
Results
There was a significant decrease in RNA expression of TLR9 and TLR10 during remission compared to nephrosis: fold change in each patient was -2.12 and -2.12 for TLR9, and -2.51 and -2.09 for TLR10. RNA expression of TLR8 also decreased: fold change in each patient was -1.19 and -1.75. There were no significant changes in the RNA expression profiles of TLR1, 2, 3, 4, 5, 6, and 7. In addition, there were no differences in the RNA expression profiles of MYD88, IRAK family, and TRAF family molecules that are associated with TLR pathways. However, RNA expressions of IL6, IL1B, IL12B, and TNF, as well as the cytokines controlled by TLR8 and TLR9 pathways, which were activated during nephrosis, disappeared or decreased during remission.
Conclusion
The involvement of the innate immune system in the pathogenesis of nephrotic syndrome has been suggested in some reports. Based on the fact that the onset or recurrence of nephrosis is triggered by non-specific viral infection, it is highly possible that innate immunity is involved in the pathogenesis of nephrotic syndrome. TLRs play a key role in innate immunity as they elicit the innate immune system after detecting pathogens, induce inflammatory cytokine production, and trigger signaling pathways that activate lymphocytes via maturation of dendritic cells. Specifically, TLR8, 9, and 10 mediate pathways of the first immune response to viral infections. Our study reveals that TLRs play a pivotal role in innate immunity associated with renal tissue during the onset of nephrosis.
The Role of Toll-Like Receptors in Autoimmune Diseases through Failure of the Self-Recognition Mechanism
