Seizure-induced impairment in neuronal ketogenesis: Role of zinc-alpha2-glycoprotein in mitochondria.

Ketone bodies (KBs) were known to suppress seizure. Untraditionally, neurons were recently reported to utilize fatty acids and produce KBs, but the effect of seizure on neuronal ketogenesis has not been researched. Zinc-alpha2-glycoprotein (ZAG) was reported to suppress seizure via unclear mechanism. Interestingly, ZAG was involved in fatty acid beta-oxidation and thus may exert anti-epileptic effect by promoting ketogenesis. However, this promotive effect of ZAG on neuronal ketogenesis has not been clarified. In this study, we performed immunoprecipitation and mass spectrometry to identify potential interaction partners with ZAG. The mechanisms of how ZAG translocated into mitochondria were determined by quantitative coimmunoprecipitation after treatment with apoptozole, a heat shock cognate protein 70 (HSC70) inhibitor. ZAG level was modulated by lentivirus in neurons or adeno-associated virus in rat brains. Seizure models were induced by magnesium (Mg(2+) )-free artificial cerebrospinal fluid in neurons or intraperitoneal injection of pentylenetetrazole kindling in rats. Ketogenesis was determined by cyclic thio-NADH method in supernatant of neurons or brain homogenate. The effect of peroxisome proliferator-activated receptor gamma (PPARgamma) on ZAG expression was examined by Western blot, quantitative real-time polymerase chain reaction (qRT-PCR) and chromatin immunoprecipitation qRT-PCR. We found that seizure induced ketogenesis deficiency via a ZAG-dependent mechanism. ZAG entered mitochondria through a HSC70-dependent mechanism, promoted ketogenesis by binding to four beta-subunits of long-chain L-3-hydroxyacyl-CoA dehydrogenase (HADHB) and alleviated ketogenesis impairment in a neuronal seizure model and pentylenetetrazole-kindled epileptic rats. Additionally, PPARgamma activation up-regulated ZAG expression by binding to promoter region of AZGP1 gene and promoted ketogenesis through a ZAG-dependent mechanism.