6-mercaptopurine (6-MP) induces p53-mediated apoptosis of neural progenitor cells in the developing fetal rodent brain

Improvement in the Anticancer Activity of 6-Mercaptopurine via Combination with Bismuth(III)

6-Mercaptopurine (6-MP) is a clinically important antitumor drug and its commercially available form is provided as monohydrate, belonging to biopharmaceuticals classification system (BCS) class II category. The combination of bismuth(III) (Bi(III)) with 6-MP was proved to significantly improve the anticancer activity of 6-MP, leading to the discovery of a new amorphous complex ([Bi(MP)₃(NO₃)₂]NO₃). The prepared [Bi(MP)₃(NO₃)₂]NO₃ was characterized by the matrix assisted laser desorption-ionization time-of-flight (MALDI-TOF)-MS, etc. Noticeably, according to the in vitro evaluations of cytotoxicity, cellular apoptotic, colony formation as well as cell migration, the anticancer activity of amorphous [Bi(MP)₃(NO₃)₂]NO₃ was found to be of high therapeutic effect over 6-MP.

Quinoline-based antimalarial hybrid compounds

Quinoline-containing compounds, such as quinine and chloroquine, have a long-standing history as potent antimalarial agents. However, the increasing resistance of the Plasmodium parasite against these drugs and the lack of licensed malaria vaccines have forced chemists to develop synthetic strategies toward novel biologically active molecules. A strategy that has attracted considerable attention in current medicinal chemistry is based on the conjugation of two biologically active molecules into one hybrid compound. Since quinolines are considered to be privileged antimalarial building blocks, the synthesis of quinoline-containing antimalarial hybrids has been elaborated extensively in recent years. This review provides a literature overview of antimalarial hybrid molecules containing a quinoline core, covering publications between 2009 and 2014.

Apoptosis and gene expression in the developing mouse brain of fusarenon-X-treated pregnant mice

Fusarenon-X (FX), a type B trichothecene mycotoxin, is mainly produced by Fusarium crookwellense, which occurs naturally in agricultural commodities, such as wheat and barley. FX has been shown to exert a variety of toxic effects on multiple targets in vitro. However, the embryonic toxicity of FX in vivo remains unclear. In the present study, we investigated FX-induced apoptosis and the relationship between the genetic regulatory mechanisms and FX-induced apoptosis in the developing mouse brain of FX-treated pregnant mice. Pregnant mice were orally administered FX (3.5 mg/kg b.w.) and were assessed at 0, 12, 24 and 48 h after treatment (HAT). Apoptosis in the fetal brain was determined using hematoxylin and eosin staining, the TUNEL method, immunohistochemistry for PCNA and electron microscopy. Gene expressions were evaluated using microarray and real time-reverse transcription polymerase chain reaction (qRT-PCR). Histopathological changes showed that the number of apoptotic cells in the telencephalon of the mouse fetus peaked at 12 HAT and decreased at 24 and 48 HAT. FX induced the up-regulation of Bax, Trp53 and Casp9 and down-regulated Bcl2 but the expression levels of Fas and Casp8 mRNA remained unchanged. These data suggested that FX induces apoptosis in the developing mouse brain in FX-treated dams. Moreover, the genetic regulatory mechanisms of FX-induced apoptosis are regulated by Bax, Bcl2, Trp53 and Casp9 or can be defined via an intrinsic apoptotic pathway.

Busulfan-induced pathological changes of the cerebellar development in infant rats

Busulfan, an antineoplastic bifunctional-alkylating agent, is known to induce developmental anomalies and fetal neurotoxicity. We previously reported that busulfan induced p53-dependent neural progenitor cell apoptosis in fetal rat brain (Ohira et al., 2012). The present study was carried out to clarify the characteristics and sequence of busulfan-induced pathological changes in infant rat brain. Six-day-old male infant rats were treated with 10, 20, 30 or 50 mg/kg of busulfan, and their brains were examined at 1, 2, 4, 7, and 14 days after treatment (DAT). As a result, histopathological changes were selectively detected in the external granular layer (EGL), deep cerebellar nuclei (DCN) and cerebellar white matter (CWM) in the cerebellum with dose-dependent severity but not in the cerebrum. In the normal infant rat cerebellum, granular cells in the EGL were proliferating and moving to the internal granular layer during the normal developmental process. In the EGL of the busulfan group, apoptotic granular cells increased at 2 DAT simultaneously with increased numbers of p53- and p21-positive cells while mitotic granular cells decreased, suggesting an occurrence of p53-related apoptosis and depression of proliferative activity in granular cells. In the DCN, apoptotic glial cells increased at 2 DAT and glial cells showing abnormal mitosis increased at 4 DAT. In the CWN, edematous change accompanying a few apoptotic cells was found in the CWN, especially in the parafolliculus (PFL), from 2 to 7 DAT. The present study demonstrated for the first time the characteristics and sequence of busulfan-induced pathological changes in infant rat cerebellum.

Metabotropic glutamate receptor 5 (mGluR5) regulates proliferation and differentiation of neuronal progenitors in the developmental hippocampus

Metabotropic glutamate receptor 5 (mGluR5) is involved in neural stem cell self-renewal, proliferation, differentiation and survival. In this study, we aimed to further determine the role of mGluR5 in the development of hippocampus using mGluR5 deficit (mGluR5(-/-)) and wild type (mGluR5(+/+)) mice at different developmental ages. We showed that the number of BrdU, NeuroD and DCX immunopositive cells was reduced significantly in mGluR5(-/-) than in mGluR5(+/+) mice from postnatal 7 days (P7) to P28, but not at P60. The length and intensity of DCX immunopositive apical dendrites in the dentate gyrus of mGluR5(-/-) mice were much shorter and lower than in mGluR5(+/+) mice respectively at P14, P21 and P28. NeuN immunostaining indicated an accelerated maturation of hippocampal neurons in mGluR5(-/-) mice. When mGluR5(+/+) mice were treated with 2-methyl-6-(phenylethynyl) pyridine (MPEP), a selective antagonist of mGluR5, decreased proliferation of progenitor cells was observed in the hippocampus at early postnatal developmental stages. At P14, there were more BrdU(+) cells in the stratum granulosum and subgranular layer of the dentate gyrus in mGluR5(+/+) than in mGluR5(-/-) mice, but the percentage of BrdU(+)+NeuroD(+)/BrdU(+) in the dentate gyrus did not change significantly between the two genotypes of mice. Western Blot study suggested that programmed neuronal death was p53-dependent apoptosis in the developmental hippocampus in mGluR5(+/+) mice.

Sequence of busulfan-induced neural progenitor cell damage in the fetal rat brain

The sequence of neural progenitor cell (NPC) damage induced in fetal rat brain by transplacental exposure to busulfan, an antineoplastic bifunctional-alkylating agent, on gestational day 13 was examined by immunohistochemical and real-time RT-PCR analyses. Following busulfan treatment, pyknotic NPCs first appeared in the medial layer and then extended to the dorsal layer of the ventricular zone (VZ) of the telencephalon. Pyknotic NPCs that were immunohistochemically positive for cleaved caspase-3, i.e. apoptotic NPCs, began to increase at 24 h after treatment, peaked at 48 h, and returned to the control levels at 96 h. On the other hand, the index (%) of phospho-histone H3-positive NPCs, i.e. mitotic NPCs, and that of BrdU-positive NPCs, i.e. S-phase cells, decreased in accordance with the increase in the index of apoptotic NPCs. Prior to the peak time of apoptotic NPCs, the indices of p53- and p21-positive NPCs peaked at 36 h. In addition, the expression levels of p21 and Puma (p53-target genes) mRNAs were elevated in real-time RT-PCR analysis. These findings indicated that busulfan not only induced apoptosis through the p53-mediated intrinsic pathway but also inhibited cell proliferation in NPCs, resulting in a reduction of the width of the telencephalon. On the other hand, in spite of up-regulation of p21 expression, the expression of cyclin D1, part of the cell cycle machinery of the G1/S transition, and the expression levels of Cdc20 and cyclin B1 which are involved in G2/M transition, showed no changes, giving no possible information of busulfan-induced cell cycle arrest in NPCs.

Mechanisms of neurotoxicity induced in the developing brain of mice and rats by DNA-damaging chemicals

It is not widely known how the developing brain responds to extrinsic damage, although the developing brain is considered to be sensitive to diverse environmental factors including DNA-damaging agents. This paper reviews the mechanisms of neurotoxicity induced in the developing brain of mice and rats by six chemicals (ethylnitrosourea, hydroxyurea, 5-azacytidine, cytosine arabinoside, 6-mercaptopurine and etoposide), which cause DNA damage in different ways, especially from the viewpoints of apoptosis and cell cycle arrest in neural progenitor cells. In addition, this paper also reviews the repair process following damage in the developing brain.

The role of mitochondria in brain aging and the effects of melatonin

Melatonin is an endogenous indoleamine present in different tissues, cellular compartments and organelles including mitochondria. When melatonin is administered orally, it is readily available to the brain where it counteracts different processes that occur during aging and age-related neurodegenerative disorders. These aging processes include oxidative stress and oxidative damage, chronic and acute inflammation, mitochondrial dysfunction and loss of neural regeneration. This review summarizes age related changes in the brain and the importance of oxidative/nitrosative stress and mitochondrial dysfunction in brain aging. The data and mechanisms of action of melatonin in relation to aging of the brain are reviewed as well.