PARP-1/AIF Pathway Mediated Impairment Of Cerebral Cortex In Glutaric Acaduria TypeⅠ Rat

Background and ObjectiveGlutaric aciduria type I is an autosomal recessive disorder induced by a deficiency of glutaryl-Co A dehydrogenase(GCDH). And the human GCDH gene has been mapped to chromosome 19p13.2. Biochemical features of GA I include large quantities of glutaric acid(GA), 3-hydroxyglutaric acid(3-HGA) and glutaconic acid(GC) excreted in body fluid and organ. Clinical symptoms include macrocephaly, dystonia, dyskinesia. Childrens commonly developed acute encephalopathic crises during 6-36 months after birth triggered by non-specific diseases(such as infections, immunizations, surgery that caused high metabolic state), leading to acute striatal and cortical damage, even threat to life. The character of imageology is a certern maturation- and region-dependent neuropathological damage, snch as frontotemporal cortical atrophy, striatal degeneration, leukodystrophy, and classic widening of Sylvian fissures. Nevertheless, the pathogenesis of GA I remains unclear, whereas recent studies focus on excitatory neurotoxicity, oxidative stress and energy metabolism disorder.Parthanatos is a new cell death pathway depended on the activation of poly(ADP-ribose) polymerase-1(PARP-1), in which PAR is produced, following the reduction of cellular NAD+, induces the mitochondrial release and nuclear translocation of apoptosis-inducing factor(AIF)to initiate chromatinolysis and cell death. PARP-1 is an DNA repaie enzyme that mainly exists in nucleus,activated and playing a DNA repair function by a right DNA demage. However a large extent of DNA repair could lead to an overactivation of PARP-1 which initiates Parthanatos pathway and result in cell death. Studies suggest that inhibition of PARP-1 has a neuroprotective effect,and it is expected to become a new target for the treatment of such diseases. PJ34 is a competive and optional inhibition of PARP-1, and plays a positive role in Parkinson’s disease, Ischemia-reperfusion injury and diabetes.In this study, we attemptd to build up a GA I model by a chronic subcutaneous injections of glutaric acid in Sprague Dawley rat pups, and PJ34 is intraperitoneally administered. Observe the growth development, the alteration of pathomorphism in frontotemporal neuron of every group, as well as the expression of PARP-1 and AIF, intending to explore the involvement of Parthanatos pathway in impairment of cerebral cortex in Glutaric academia typeⅠand the neuroprotection of PJ34, screening targets of intervention, and providing a new theoretical perspective for clinical treatment. Methods1、SD male rat pups were randomly divided into five groups: normal saline(NS), low-dose glutaric acid(LGA), high-dose glutaric acid(HGA), low-dose plus PJ34(LGA + PJ34) and high-dose plus PJ34(HGA + PJ34).2、The GA were subcutaneously administered triply in dose of 5 μmol GA/g body weight in LGA group,10 μmol GA/g body weight in HGA group and 5 μmol NS/g body weight in NS group from postnatal day 4 to 23 at 7:30 am, 15:00 pm and 22:30 pm. PJ34 was intraperitoneal injection every day by10 mg / kg 30 min before the first GA injection. The rats were killed 12 h after the last injection.3 、 Observe the growth development of five groups. The alteration of pathomorphism in frontotemporal neuron of every group was evalued by HE staining. The expression of PARP-1 and AIF were evalued by Western bloting Results1、The survival rate of HGA group was obviously lower than other four groups. During the injection, there was no significant deviation of weight increase between LGA group and NS group. High-dose glutaric acid apparently decreased the weight increase, especially in the fiset 7 days of injection, and the tendency of inhibition was eased in the following 13 days. However the intervention of PJ34 clearly improved the weight increase of HGA group, which played a little effcct on LGA group. The longer the injection was given, the weaker the weight increase in five groups lasted.2、It was found in histopathology that glutaric acid induced the changes of cellular morphology, arrangement disturbance in frontotemporal neuron, the formation of vacuolation, chromatic agglutination, producing a graver influence in HGA group than LGA group. PJ34 clearly improved the morphology of frontotemporal neuron, lightended the arrangement disturbance and decreased the formation of vacuolation.3、It implied that GA led to the increase of expression of PARP-1 and AIF in frontotemporal cortex, especially with high-dose. The use of PJ34 could inhibit the expression of PARP-1 and AIF induced by GA. Conclusions1. It was concluded that glutaric acid increased the expression of PARP-1 and AIF in frontotemporal cortex, implying that Parthanatos pathway probably participate in the process of pathomechanism in glutaric aciduria type I.2. PJ34 decreased the overactivation of PARP-1 and inhibited the nuclear translocation of AIF induced by glutaric acid, playing a neuroprotective effect. It seemed that it provided a new direction fot the clinical treatment of aciduria type I.