N,N'-Bis(2-chloroethyl)- N-nitrosourea (BCNU)-induced Apoptosis of Neural Progenitor Cells in the Developing Fetal Rat Brain

Abstract

N,N’-bis(2-chloroethyl)-N-nitrosourea (BCNU) is one of the major drugs used in chemotherapy against malignant gliomas due to its effects, such as induction of bifunctional alkylation of DNA and formation of interstrand DNA cross-linkages, and induces cortical malformations in the fetal and neonatal rat brain. In this study, pregnant rats were treated with 7.5 mg/kg of BCNU on gestational day 13 (GD 13), and their fetuses were collected from 12 to 72 hours after BCNU treatment in order to examine the timecourses of morphological and immunohistochemical changes in neural progenitor cells in the developing brain. The number of pyknotic cells in the telencephalon peaked at 24 h and then gradually decreased until 72 h. The majority of these pyknotic cells were positive for cleaved caspase-3, a key executioner of apoptosis. The pyknotic cells showed the ultrastructural characteristics of apoptosis. The number of p53-positive cells began to increase prior to the appearance of apoptotic cells and p21-positive cells. The number of phosphorylated-histone H3-positive cells (mitotic cells) decreased from 24 to 36 h. The number of Iba1-positive cells (microglial cells) in the telencephalon increased from 12 to 48 h. These results suggest that BCNU induces p53-dependent apoptosis and reduces proliferative activity, resulting in reduction of the weight of the telencephalon and the thickness of the telencephalic wall in the fetal brain. This study will help to clarify the mechanisms of BCNU-induced fetal brain toxicity.

A density functional theory investigation on the formation mechanisms of DNA interstrand crosslinks induced by chloroethylnitrosoureas

“…These adducts can further lead to single/double‐strand breaks, sister chromatid exchange and chromosome aberrations 9–11. A number of in vivo and in vitro experiments of the anticancer mechanism of CENUs indicated that the covalent crosslinks between G–C complimentary base pair represented the most important types of DNA damage involved in the anticancer process 8, 12–19. The formation of G–C crosslinks with an ethidene was proposed to prevent DNA base pair separation and to impede DNA replication, which could result in DNA double‐strand breaks and further led to apoptosis of cancer cells 15.…”

“…A number of in vivo and in vitro experiments of the anticancer mechanism of CENUs indicated that the covalent crosslinks between G–C complimentary base pair represented the most important types of DNA damage involved in the anticancer process 8, 12–19. The formation of G–C crosslinks with an ethidene was proposed to prevent DNA base pair separation and to impede DNA replication, which could result in DNA double‐strand breaks and further led to apoptosis of cancer cells 15. Fischhaber et al16 performed a quantitative analysis of BCNU‐induced dG–dC crosslinks in synthesized oligonucleotides with various sequences using high‐performance liquid chromatography‐tandem mass spectrometry (HPLC‐MS/MS).…”

Quantification of meCCNU‐induced dG‐dC crosslinks in oligonucleotide duplexes by liquid chromatography/electrospray ionization tandem mass spectrometry

“…These studies demonstrated that DNA ISC were the most important type of DNA modification leading to cytotoxicity by CENUs. This is because such DNA modifications prevented the separation of DNA double strands in the replication process . Bodell et al compared the levels of DNA alkylation products in human glioma cell lines after treatment with 3 H‐CENUs using high‐performance liquid chromatography (HPLC).…”

Assessment of DNA interstrand crosslinks in NIH/3T3 cells induced by Chloroethylnitrosoureas

“…ICLs are extremely toxic to cells since they prevent the separation of the two strands of a DNA double helix for cellular processes, such as replication and transcription, by coordinating chemical reactions with bases on opposing strands [4]. The formation of ICLs between complementary base pair is supposed to be the critical step for the anticancer activity of CENUs [5]. Zhao's group found that the ICLs between the N 1 atom of guanine and the N 3 atom of the complementary cytosine through an ethylene is theoretically determined to be the main crosslinking damage in the reactions of DNA and CENUs [6].…”