安藤 達也

Indoleamine 2,3-dioxygenase 2 (IDO2) is an enzyme of the tryptophan-kynurenine pathway that is constitutively expressed in the brain. To provide insight into the physiological role of IDO2 in the brain, behavioral and neurochemical analyses in IDO2 knockout (KO) mice were performed. IDO2 KO mice showed stereotyped behavior, restricted interest and social deficits, traits that are associated with behavioral endophenotypes of autism spectrum disorder (ASD). IDO2 was colocalized immunohistochemically with tyrosine-hydroxylase-positive cells in dopaminergic neurons. In the striatum and amygdala of IDO2 KO mice, decreased dopamine turnover was associated with increased α-synuclein level. Correspondingly, levels of downstream dopamine D1 receptor signaling molecules such as brain-derived neurotrophic factor and c-Fos positive proteins were decreased. Furthermore, decreased abundance of ramified-type microglia resulted in increased dendritic spine density in the striatum of IDO2 KO mice. Both chemogenetic activation of dopaminergic neurons and treatment with methylphenidate, a dopamine reuptake inhibitor, ameliorated the ASD-like behavior of IDO2 KO mice. Sequencing analysis of exon regions in IDO2 from 309 ASD samples identified a rare canonical splice site variant in one ASD case. These results suggest that the IDO2 gene is, at least in part, a factor closely related to the development of psychiatric disorders.

Cisplatin is a chemotherapeutic agent used to treat many types of malignant tumors. However, irrespective of its potent anticancer properties and efficacy, nephrotoxicity is the dose-limiting factor of cisplatin treatment. Cisplatin infiltrates renal tubular cells in the kidneys and is metabolized by cysteine conjugate-beta lyase 1 (CCBL1) to form highly reactive thiol-cisplatin; this may mediate cisplatin's nephrotoxicity. Therefore, CCBL1 inhibition may prevent cisplatin-induced nephrotoxicity. Using a high-throughput screening assay, we identified 2',4',6'-trihydroxyacetophenone (THA) as an inhibitor of CCBL1. THA inhibited human CCBL1 β-elimination activity in a concentration-dependent manner. We further investigated the preventive effect of THA on cisplatin-induced nephrotoxicity. THA attenuated the effect of cisplatin on the viability of confluent renal tubular cells (LLC-PK1 cells) but had no effect on cisplatin-induced reduction of proliferation in the tumor cell lines (LLC and MDA-MB-231). THA pretreatment significantly attenuated cisplatin-induced increases in blood urea nitrogen, creatinine, cell damage score, and apoptosis of renal tubular cells in mice in a dose-dependent manner. Furthermore, THA pretreatment attenuated cisplatin-induced nephrotoxicity without compromising its antitumor activities in mice bearing subcutaneous syngeneic LLC tumors. THA could help prevent cisplatin-induced nephrotoxicity and may provide a new strategy for cisplatin-inclusive cancer treatments.