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Kidney Week

Abstract: TH-PO014

Effect of Bortezomib on Proximal Tubule Cells Exposed to Free Light Chains Isolated from the Urine of Multiple Myeloma Patients

Session Information

Category: Acute Kidney Injury

  • 103 AKI: Mechanisms

Authors

  • Upadhyay, Rohit, Tulane University Medical School, New Orleans, Louisiana, United States
  • Batuman, Vecihi, Tulane University Medical School, New Orleans, Louisiana, United States
Background

Bortezomib (BTZ, also known as Velcade® and PS-341) is the first 20S proteasome inhibitor used as a drug for Multiple myeloma (MM) patients. Although, BTZ has markedly improved the treatment outcomes of MM patients; several adverse events, including acute kidney injury (AKI) can occur due to off-target effects of BTZ. Kidney proximal tubule cells (PTCs) are a primary target of a vast array of nephrotoxic compounds but direct effects of BTZ on PTC have not been explored in the presence of free light chains (FLCs) derived from the urine of MM patients.

Methods

Human kidney PTCs cultures (RPTECs and HK2 cell lines) were exposed to BTZ, κ, or λ FLCs. Cell supernatant and pellets were used for ELISA and gene expression studies. Cell proliferation, viability, cytotoxicity and apoptosis were evaluated using standard procedures. Immunofluorescence and Western blotting were used to localize NFkβ translocation in subcellular fractions. Mitochondrial membrane potential was measured using TMRE (tetramethylrhodamine, ethyl ester) assay. Data were analyzed using one-way ANOVA with post hoc Tukey test and P values <0.05 were considered significant.

Results

BTZ (50nM) alters cell morphology, significantly decreases proliferation and induces apoptosis in HK2 cells irrespective to FLCs exposure. Toxic effect of BTZ was also apparent from substantial overexpression of LCN2, a known kidney injury marker, and TLR9 upregulation. Additionally, NFkβ phosphorylation was evident in BTZ treated cells, which was further supported by the increased IKKα/β expression and decreased expression of IKβα. BTZ induced LCN2 and NFkβ showed possible immunomodulatory effects in PTCs. Our results indicate probable ROS-mediated mitochondrial injury and activation of TLR9 and LCN2, which may be unique pathway leading to injury in PTCs.

Conclusion

These results show a novel off-target, and potentially toxic action of BTZ in human PTCs.

Funding

  • Private Foundation Support