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Abstract: FR-PO846

Increased CaMK4 Expression in Podocytes from Renal Biopsies of Patients with lupus Nephritis Is Mirrored by Its Levels in Cultured Podocytes Exposed to Serum IgG and in Urine Podocytes

Session Information

Category: Glomerular Diseases

  • 1202 Glomerular Diseases: Immunology and Inflammation

Authors

  • Bhargava, Rhea, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States
  • Maeda, Kayaho, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States
  • Tsokos, Maria, Harvard Medical School, Boston, Massachusetts, United States
  • Satyam, Abhigyan, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States
  • Tsokos, George C., Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, Massachusetts, United States
Background

Lupus nephritis (LN) is a devastating and potentially fatal disease that mainly affects women of child-bearing age. We previously demonstrated that Calcium/Calmodulin Kinase IV (CaMK4) inhibition in podocytes by cell targeted therapy prevents LN in mice. Here we explore the association of renal CAMK4 expression with the presence of LN in patients with SLE and describe novel noninvasive methods to identify patients prone to develop LN.

Methods

Expression of CaMK4 in frozen renal biopsy specimens from thirty individuals referred to rule out LN was evaluated by immunofluorescence. Logistic regression models were used to analyze the predictive value of CAMK4 in the development of LN. Immortalized human podocytes were examined for CaMK4 expression before and after exposure to IgG from ten SLE patients with and without LN and 5 healthy controls. We further devised a novel method to rapidly isolate urinary podocytes by using magnetic beads and successfully extract RNA.

Results

CaMK4 expression in podocytes is a strong predictor of active LN(p<.01, β 2.36). Culture of podocytes in the presence of IgG from patients with active LN led to increased CaMK4 expression along with reduction in expression of nephrin while no changes were demonstrated in the presence of IgG from normal subjects or from individuals with SLE without nephritis. CaMK4 deficiency or pharmacologic inhibition preserved nephrin expression. CaMK4 inhibited GSK3beta by phosphorylating it at serine 9 which led to stabilization of transcription factor SNAIL and subsequent repression of nephrin transcription. Urinary podocytes from fresh urine were successfully and rapidly isolated by a novel magnetic bead method. Urinary podocytes from patients with active LN, but not from those without kidney disease, displayed increased expression of CaMK4 and CD80.

Conclusion

We conclude that CaMK4 expression in podocytes is a feature of patients with LN and more importantly, we present two novel assays to replace the need for kidney biopsy. We have shown that rapidly isolated urine podocytes from patients with LN, using a new protocol, and cultured podocytes exposed to IgG from patients with LN express CaMK4 which reflects the levels detected in the kidney biopsy material of patients with active LN.

Funding

  • NIDDK Support