Mitochondrial dysfunction is a primary event in renal cell oxalate toxicity

Area of Science:

• Cell Biology
• Renal Physiology
• Biochemistry

Background:

• Oxalate, a component of kidney stones, induces cell death in renal epithelial cells.
• Oxalate toxicity involves reactive oxygen species (ROS) generation, partly mediated by lipid signaling and phospholipase A2 (PLA2) activation.
• Mitochondria are key sites of ROS production and potential targets of oxalate toxicity.

Purpose of the Study:

• To investigate if mitochondria are targets of oxalate toxicity.
• To determine if mitochondrial responses to oxalate are mediated by PLA2 activation.
• To elucidate the role of lipid signaling in oxalate-induced renal cell damage.

Main Methods:

• Mitochondrial membrane potential (DeltaPsim) was measured using JC-1 dye in Madin-Darby canine kidney (MDCK) cells.
• Caspase activation was assayed in response to oxalate and lipid signaling molecules.
• ROS formation was measured in isolated renal mitochondria exposed to oxalate and PLA2-derived lipids.

Main Results:

• Oxalate exposure rapidly decreased MDCK cell DeltaPsim, an effect reduced by PLA2 inhibition.
• Lipid products of PLA2 activation (arachidonic acid, lysophosphatidylcholine) and ceramide depolarized MDCK cell DeltaPsim and increased caspase activation.
• Oxalate, arachidonic acid, lysophosphatidylcholine, and ceramide increased ROS, lipid peroxides, and oxidized proteins in isolated renal mitochondria.

Conclusions:

• Oxalate-induced PLA2 activation releases lipid signaling molecules.
• These lipid mediators induce rapid mitochondrial dysfunction, including depolarization and ROS production.
• Mitochondrial dysfunction triggered by lipid signaling likely mediates oxalate toxicity in renal epithelial cells.