Background Glomerulonephritis is one of the major complications and causes of death in systemic lupus erythematosus (SLE). DZ2002 is a reversible S-adenosyl-l-homocysteine hydrolase (SAHH) inhibitor with potent therapeutic activity against lupus nephritis in mice. However, the molecular events underlying the renal protective effects of DZ2002 remained unclear. This study is designed to uncover the molecular mechanisms of DZ2002 on glomerulonephritis of lupus-prone mice.
Methods Female NZB/W F1 mice were treated orally with DZ2002, and the proteinuria level and body weight were monitored. After the mice were euthanized, serum biochemical parameters and renal damage were determined. Splenocytes of NZB/W F1 mice were isolated for ex vivo study. Toll-like receptor (TLR)-stimulated murine bone marrow-derived dendritic cells (BMDCs) were used for in vitro study. The LC-MS-based label-free quantitative (LFQ) proteomic approach was applied to analyze the kidney tissue samples from the NZB/W F1 mice treated with DZ2002 or vehicle. KEGG pathway enrichment and direct protein-protein interaction (PPI) network analyses were used to map the pathways in which the significantly changed proteins (SCPs) involved. The selected proteins from proteomic analysis were validated by Western blot analysis and immunohistochemistry in the kidney tissues.
Results Treatment of the mice with DZ2002 significantly attenuated the progression of glomerulonephritis and improved the overall health. The improvement was accompanied by decreased levels of nephritogenic anti-dsDNA antibodies, serum IL-17, IL-23p19 and TGF-. DZ2002 also significantly suppressed TLR agonists-stimulated up-regulation in IL-6 and IL-23p19 production in murine BMDCs, and prevented Th17 differentiation and suppressed IL-17 secretion by the T cells in a BMDC-T cell co-culture system. Pathway analysis of proteomic data revealed that 13 SCPs were involved in tight junction and focal adhesion process. Further protein expression validation demonstrated that DZ2002 treated NZB/W F1 mice exhibited down-regulation of -actinin-4 and integrin-linked kinase (ILK), as well as the restoration of 1-integrin activation in kidney tissues compare with vehicle treated ones.
Conclusions Our study demonstrated that DZ2002 effectively ameliorates lupus syndrome in NZB/W F1 mice by regulating TLR signaling-mediated antigen presenting cell (APC) responses. Alongside of attenuating glomerular immune complexes deposition and impeding pathologic lymphocytes polarization in SLE, the renal protective effects of DZ2002 may partly attributed to stabilization of the actin cytoskeleton and maintenance of podocyte numbers, in turn, are effective to improve proteinuria and kidney function in lupus nephritis.
Funding Source(s): The National Basic Research Program of China (973 Program) (grant number: 2014CB541906); and the National Nature Science foundation of China (grant number: 81402939)
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