# Targeting SMPDL3B to Ameliorate Radiation- and Cisplatin-Induced Renal Toxicity

## TL;DR

This study shows that boosting SMPDL3B in kidney cells can protect against kidney damage caused by cancer treatments like radiation and cisplatin.

## Contribution

The study identifies SMPDL3B as a novel target to prevent nephrotoxicity during cancer therapy by maintaining podocyte stability and lipid balance.

## Key findings

- Combined radiation and cisplatin reduce podocyte SMPDL3B, leading to kidney damage and abnormal lipid accumulation.
- Podocyte-specific overexpression of SMPDL3B preserves kidney structure and normalizes lipid levels after injury.
- SMPDL3B is a key regulator of podocyte survival and lipid homeostasis during cancer therapy-induced stress.

## Abstract

What are the main findings?
Combined radiation + cisplatin reduces podocyte SMPDL3B, driving podocyte loss, GBM thickening, mesangial expansion, fibrosis, albuminuria, and accumulation of long-chain C1P linked to inflammation/cell death.Podocyte-specific SMPDL3B overexpression protects kidney structure and function after genotoxic injury and normalizes abnormal C1P accumulation.

Combined radiation + cisplatin reduces podocyte SMPDL3B, driving podocyte loss, GBM thickening, mesangial expansion, fibrosis, albuminuria, and accumulation of long-chain C1P linked to inflammation/cell death.

Podocyte-specific SMPDL3B overexpression protects kidney structure and function after genotoxic injury and normalizes abnormal C1P accumulation.

What are the implications of the main findings?
SMPDL3B is a key regulator of podocyte survival and sphingolipid balance during cancer therapy-associated kidney stress, making it a promising target to prevent nephrotoxicity.Enhancing SMPDL3B activity/expression may expand the therapeutic window for radiotherapy and platinum chemotherapy, improving tumor control while preserving long-term kidney health.

SMPDL3B is a key regulator of podocyte survival and sphingolipid balance during cancer therapy-associated kidney stress, making it a promising target to prevent nephrotoxicity.

Enhancing SMPDL3B activity/expression may expand the therapeutic window for radiotherapy and platinum chemotherapy, improving tumor control while preserving long-term kidney health.

Kidney toxicity remains a major dose-limiting complication of radiation therapy and platinum-based chemotherapy, yet the molecular determinants of renal susceptibility and resilience to these genotoxic treatments are incompletely understood. Podocytes are particularly vulnerable to such insults, and emerging evidence implicates lipid dysregulation in podocyte injury. This study investigated the role of sphingomyelin phosphodiesterase acid-like 3B (SMPDL3B), a podocyte-enriched lipid-modulating enzyme, in radiation- and cisplatin-induced nephrotoxicity. Using a doxycycline-inducible, podocyte-specific SMPDL3B transgenic mouse model, renal injury was assessed following focal kidney irradiation, cisplatin administration, or their combination through functional assays, histopathology, ultrastructural analysis, immunofluorescence, and targeted lipidomics. Combined radiation and cisplatin exposure markedly reduced podocyte SMPDL3B expression, accompanied by podocyte depletion, glomerular basement membrane remodeling, proteinuria, and impaired renal function. These structural and functional abnormalities were associated with the selective accumulation of long-chain ceramide-1-phosphate species. In contrast, podocyte-specific induction of SMPDL3B preserved glomerular architecture, maintained renal function, and prevented pathological ceramide-1-phosphate elevation. Collectively, these findings identify SMPDL3B as a key regulator of podocyte stability and lipid homeostasis during chemoradiation stress. Enhancing SMPDL3B activity may represent a mechanistically grounded strategy to mitigate treatment-induced kidney injury while preserving anticancer efficacy.