Dihydrolipoamide dehydrogenase and cAMP are associated with cadmium-mediated Leydig cell damage

Cadmium (Cd) directly inhibits testosterone production in Leydig cells, but its mechanism is still unclear. To further explore the signaling pathway of Cd-mediated toxicity to Leydig cells, various concentrations of Cd were cultured with R2C cells for 24h, and two-dimensional gel electrophoresis (2DE)-based proteomics profiling was used to analyze the change of protein expressions. Cd caused a concentration-dependent inhibition of cell viability with IC(25), IC(50) and IC(75) of 2.42×10(-5)M, 4.83×10(-5)M and 7.39×10(-5)M, respectively. Cd significantly reduced progesterone production and mitochondrial membrane potential (ΔΨ(m)) in a concentration-dependent manner. 2DE-based proteomics showed 34 protein spots with altered expression by 2-folds or more, and dihydrolipoamide dehydrogenase (DLD) was the hub in the network of these altered proteins. Real-time polymerase chain reaction (PCR) and Western blotting showed that Cd downregulated the expression of DLD. Cd also decreased intracellular levels of cyclic adenosine monophosphate (cAMP). The results suggest that DLD and cAMP may be key elements related to Cd toxicity to Leydig cells.