Background/Purpose:

Systemic lupus erythematosus (SLE) is an autoimmune disease, resulting in inflammation and tissue damage in several organs. This autoimmune reaction is caused by autoantibodies, e.g. against dsDNA (adsDNAabs). Most patients with SLE develop joint pain and about 70% develop renal symptoms, partly with lupus nephritis leading to proteinuria. It is still unclear why the kidney and especially the postmitotic podocytes are involved in such a dramatic manner during SLE.

Methods:

Antibodies were isolated from SLE-patients, cloned and produced recombinantly in HEK293 cells. Living podocytes were treated with equal amounts of adsDNAabs and control antibodies in time and concentration dependent experiments and examined by immunofluorescence and Western Blot. To investigate the uptake mechanism, antibodies were pretreated with DNaseI. To analyze the degradation mechanism, treated cells were incubated with e.g. Bafilomycin.

Results: adsDNAabs are taken up by cultivated podocytes selectively in a concentration and time dependent manner and turn up in cytosolic aggregates. After treatment of the antibodies with DNAseI, the uptake decreases significantly. In recovery experiments, we could show that these aggregates are eliminated over time in media without adsDNAabs. The aggregates co-localize with different autophagy related proteins. Western Blot analyzes show that autophagy is upregulated after treatment with adsDNAabs. The degradation of adsDNAabs is reduced in experiments under autophagy inhibiting conditions (treatment with Bafilomycin A) and number of aggregates after the inhibition of autophagy rises significantly up to twofold. The number of aggregates of podocytes treated with a control antibody or antibodies against other autoantigens (e.g. Ro) is almost zero.

Conclusion: Podocytes are postmitotic and highly complex cells. Loss of these cells leads to kidney injury and proteinuria. During lupus-nephritis, podocytes are destroyed. We could show that these cells take up adsDNAabs selectively in a complex with their target and are harmed by these antibody-aggregates. Our results indicate that the antibody-complexes in the cells are degraded via autophagy. This should be considered for future therapeutic approaches in lupus nephritis.

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« Back to 2013 ACR/ARHP Annual Meeting

ACR Meeting Abstracts - https://acrabstracts.org/abstract/podocytes-take-up-adsdna-autoantibody-complexes/