Previous studies showed that many steroidogenic enzymes

Previous studies showed that many steroidogenic enzymes act when the enzyme binds to the cofactor first [30]. In the present study, we showed that HPTE inhibited both AKR1C14 and RDH2 in a mixed mode when cofactor was used. This indicates that HPTE interferes with cofactor-binding residues although it does not bind to the active site of the cofactor substrate. When MXC was administered, it was widely distributed. In rats receiving 80 mg/kg/day MXC, the highest levels in urine, liver, and 3 methyladenine were 4.2 (about 12.5 μM), 0.5 (about 1.45 μM), and 0.2 mg/kg (about 0.58 μM), respectively [31]. MXC was metabolized mainly to mono-hydroxyl methoxychlor or di-hydroxyl methoxychlor (two metabolites are collectively called HPTE), which accounted for about 30% and 20% of MXC [32]. In this regard, a fairly high metabolism of MXC into HPTE was found. The consequences of MXC or HPTE to inhibit the formation of neurosteroids point to their neurotoxicity. Indeed, an EPA report noted that the continuous processes of neurogenesis, migration, synaptogenesis, gliogenesis, and myelination during the development of nervous system are susceptible to endocrine disruptors [7]. Adult mice exposed to MXC (16, 32, or 64 mg/kg/day) for 20 days had a dose-dependent reduction in striatal levels of dopamine and decrease in levels of dopamine transporter and vesicular monoamine transporter 2 [33]. In the present study, we found that HPTE potently inhibited rat AKR1C14, which was critical for the formation of neurosteroids, allopregnanolone and DIOL (Fig. 2B). The minimal effective concentration of HPTE to inhibit AKR1C14 was 10 nM (Fig. 2B). In this regard, HPTE could reach enough concentration to suppress this enzyme. Many organochlorine insecticides, including MXC, are used in agriculture [1,2]. Thus, these compounds contribute to a health risk not only to agricultural workers but also to the general population. Here we identify additional mechanisms of HPTE in regulating neurosteroid formation and reinforce previous observations showing that it has the capacity to cause adverse biological effects, affecting the nerve system.
Acknowledgments The authors thank T.M. Penning for AKR1C14 vector. This research was supported by Health & Family Planning Commission of Zhejiang Province (11-CX29, 2015103197 and 2012ZDA037).
Introduction Development of synucleinopathies, including Parkinson\'s disease (PD), is associated with enhanced expression of α-synuclein in nerve cells, following appearance of neurotoxic oligomers of this protein and deposition of amyloid structures [[1], [2], [3], [4], [5], [6]]. More and more data are accumulated on a diverse influence of α-synuclein on the processes occurring in different types of nerve cells [[7], [8], [9], [10], [11], [12], [13], [14]]. While the action of α-synuclein on synaptic transmission and its toxic effect towards neurons were known for a long time, molecular mechanisms of the influence of α-synuclein on the behavior of microglia cells found in some works remain practically unknown [15,16]. Probably, α-synuclein, being a member of intrinsically disordered proteins, is involved in various protein-protein interactions and participates in regulations of many aspects of vital functions of nerve cells. Among these processes, involving of α-synuclein in regulation of energy metabolism and induction of apoptosis should be noted. Noteworthy that PD pathogenesis is closely related to oxidative stress due to ROS generated by dopamine metabolism, mitochondrial dysfunction and neuroinflammation [[17], [18], [19]]. Different mitochondrial processes, including cytochrome c release [5,20], calcium homeostasis [[21], [22], [23]], control of mitochondrial membrane potential and ATP production [19,23,24], was shown to be directly influenced by α-synuclein. Along with α-synuclein influence on mitochondria, important role of α-synuclein interaction with glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) in glycolysis inhibition as well as in apoptosis initiation was demonstrated [[25], [26], [27], [28]]. Involving of GAPDH in progression of PD was found accidentally. It turned out that some deprenyl derivatives used as potential inhibitors of monoamine oxidase, which was a target protein in PD treatment, do not influence on this protein, but interact with GAPDH and exhibit anti-apoptotic action [25,29]. In our work, we obtained direct evidence of the binding of α-synuclein to partially oxidized form of GAPDH and its further inhibition [28]. Interaction between α-synuclein and GAPDH not only influenced on glycolysis efficiency, but also prevented formation of amyloid structures from α-synuclein. Interaction with fibrillary forms of GAPDH formed under specific conditions also can inhibit α-synuclein amyloidization [30]. Obviously, the regulation of interaction between two proteins, which is so important for development of synucleinopathy, should be influenced by posttranslational modification of α-synuclein and its utilization by protein degradation systems. The data about relation between synucleinopathies and diabetes indirectly indicates that the α-synuclein modification such as glycation can influence on its interaction with target proteins [[31], [32], [33]]. In addition, it was directly shown that glycation of α-synuclein residues, which undergo SUMOylation or ubiquitination in non-modified protein, hinders the degradation of the modified protein by proteasome system [[34], [35], [36]]. Because of the aforementioned reasons, described in details in our review [37], study of the interaction between glycated α-synuclein and glyceraldehyde-3-phosphate dehydrogenase is of special interest.