γH2AX is immunohistochemically detectable until 7 days after exposure of N-bis (2-hydroxypropyl) nitrosamine (DHPN) in rat lung carcinogenesis

Abstract

It is known that γH2AX, which is formed when there is a double-strand break in DNA, can act as a sensitive marker of genomic instability. In this experiment, the time-course manner of the expression of γH2AX in the lung was examined in the early phase after treatment with a lung carcinogen, N-bis (2-hydroxypropyl) nitrosamine (DHPN). The expression of γH2AX is expected to be one of the useful markers for lung carcinogenesis in early stages. Rats were separated into 10 groups of 5 rats. The DHPN groups were administered 0.1% DHPN in drinking tap water for two weeks, while the control group received drinking tap water. At 0, 1, 3, 7, and 14 days after finishing DHPN treatment, one group each from the DHPN and control groups was sacrificed. The removed lung tissues were examined for immunostaining of γH2AX and PCNA, and positive cells were counted. The γH2AX levels of the DHPN-treated groups were found to be increased significantly at 0, 1, 3, and 7 days (4.4 ± 1.4, 5.1 ± 2.7, 3.3 ± 1.0, and 4.1 ± 1.3%, respectively), and they dropped significantly on day 14 (1.1 ± 0.4%). The experiment showed that the γH2AX-positive score could be effectively measured for up to 7 days after exposure, as a significance difference was observed between the treated group and the control group. It can be deduced that γH2AX is an effective marker for DHPN-induced double-strand breaks in pulmonary epithelial cells.

Early detection of urinary bladder carcinogens in rats by immunohistochemistry for γ-H2AX: a review from analyses of 100 chemicals

“…The field effect is thought to arise from the histologically normal-appearing urothelium at the very beginning of bladder carcinogenesis, and the γ-H2AX formation observed in our study may be a relevant indicator. In addition, the application of γ-H2AX to other organs, such as the lungs and stomach, has recently been investigated in rodents 161 , 162 . Further studies are needed to examine whether these results can be applied to the main target organs typically examined in carcinogenicity tests, including the liver and kidneys.…”

Short-term detection of gastric genotoxicity using the DNA double-strand break marker γ-H2AX

“…However, detection of γ-H2AX and other markers may enable researchers to reduce the number of animals and shorten the experimental period. In particular, it is effective to assess a large number of compounds at the same time 24 , 40 , 41 .…”

Early detection of hepatocarcinogens in rats by immunohistochemistry of γ-H2AX

“…We demonstrated that 28-day administration of bladder carcinogens to rats significantly increased the number of γ-H2AX-positive bladder urothelial cells, whereas carcinogens that do not target the urinary bladder did not cause such changes. The application of γ-H2AX immunostaining for early detection of carcinogens has also been investigated in other organs, such as lung and stomach (Ying et al, 2018;Okabe et al, 2019). However, this approach has not been fully investigated for the liver and kidney, which are the primary target organs for chemical carcinogenicity.…”