Abstract: FR-PO689

Neuraminidase Activity Mediates IL-6 Production by Lupus Prone Mesangial Cells

Session Information

Category: Glomerular

  • 1001 Glomerular: Basic/Experimental Immunology and Inflammation

Authors

  • Nowling, Tamara, Medical University of South Carolina, Charleston, South Carolina, United States
  • Sundararaj, Kamala, Medical University of South Carolina, Charleston, South Carolina, United States
  • Rodgers, Jessalyn Ierardi, Medical University of South Carolina, Charleston, South Carolina, United States
Background

Glycosphingolipid (GSL) levels and neuraminidase (NEU) (an enzyme that mediates GSL catabolism) activity/expression are altered in the kidneys and/or urine of lupus mice and human patients with proliferative nephritis compared to their non-nephritic counterparts and healthy controls. Specifically, elevated GSL levels were observed in the mesangial region of glomeruli. We hypothesize that activation of mesangial cells (MCs) in the progression of lupus nephritis is mediated in part by NEU activity, contributing to renal inflammation in lupus nephritis. Here we investigated the role and possible mechanisms by which NEU activity contributes to MC activation.

Methods

For these studies, we used the MES13 mouse MC line and primary MCs grown out from glomeruli isolated from MRL/lpr lupus prone mice. MCs were analyzed in the absence or presence of heat aggregated IgG (mimic of immune complex deposition), inhibitors for NEU activity or MAP kinase pathways inhibitors include real-time RTPCR, NEU activity assays, IL-6 and MCP-1 ELISAs, immunohistochemistry of renal sections, and confocal immunofluorescence of MCs.

Results

While HA-IgG alone fails to activate MES13 cells to produce IL-6, over-expressing NEU1 or NEU3 alone results in significant production of IL-6. HA-IgG added to MES13 cells over-expressing NEU1 or NEU3 further increased IL-6 production over NEU1 or NEU3 alone. In primary MCs, Neu1 message levels, NEU activity, and IL-6 and MCP-1 production are dose-dependently and significantly increased following addition of HA-IgG. Addition of an FDA-approved inhibitor of NEU activity significantly and dose-dependently inhibited HA-IgG-induced IL-6 while higher concentrations were required to inhibit MCP-1 production. NEU1 and NEU3 appear to co-localize with HA-IgG at the surface of the MES13 and primary MCs. JNK and p38 MAP kinase inhibitors prevented IL-6 production in response to NEU1 or NEU3 over-expression in MES13 cells.

Conclusion

Together these results suggest that immune complex activated IL-6 production of MCs is mediated by NEU activity. This may occur at the cell surface in a complex of HA-IgG and surface receptor that recognizes HA-IgG. Furthermore, the NEU1/NEU3 mediated IL-6 production appears to involve the p38/JNK stress-activated MAPK pathways. Targeting NEU activity may reduce MC cytokine production and thus renal inflammation in lupus nephritis.

Funding

  • Other U.S. Government Support