ABSTRACT
Objective To determine the effects of Sodium Nitroprusside ( SNP) , superoxide dismutase ( SOD) and catalase ( CAT ) on the expression of catalytic subunit of the DNA-dependent protein kinase ( DNA-PKcs ) and Ku70/80 heterodimer in cardiomycyte H9C2, as well as their expression in the myocardial tissues of SD rats . Methods H9C2 cells were co-cultured with SNP at concentreations of 10, 20 and 40 mmol/L for 6 hours, SD rats were injected with normal saline , SNP, SNP+SOD, SNP+CAT or SNP+SOD+CAT.Western blot and immuno-histochemistry assay were used to examine DNA-PKcs and Ku70/80 protein expression respectively .Results The expression of DNA-PKcs and Ku70/80 increased in H9C2 cells co-cultured with SNP when compared with control group, but they were be decreased when treated with SOD or/and CAT.The expression of DNA-Pkcs and Ku70/80 in myocardial tissues of experimental groups were higher than the control .Conclusions Radical scavengers may play a role as a protective effect for sodium nitroprusside related injury in cardiac myocytes .
ABSTRACT
PURPOSE: DNA-dependent protein kinase (DNA-PK) is a serine/threonine kinase consisting of a 470 kDa catalytic subunit (DNA-PKcs) and a heterodimeric regulatory complex, called Ku, which is composed of 70 kDa (Ku 70) and 86 kDa (Ku 80) proteins. The DNA-PK has been shown to play a pivotal role in rejoining DNA double-strand-breaks (dsb) in mammalian cells. The purpose of this study is to examine the relationship between the level of Ku expression and radiation sensitivity. METHODS AND MATERIALS: Nine head and neck, cancer cell lines showed various intrinsic radiation sensitivities. Among the nine, AMC-HN-3 cell was the most sensitive for X-ray irradiation and AMC-HN-9 cell was the most resistance. The most sensitive and resistant cell lines were selected and the test sensitivity of radiation and expression of Ku were measured. Radiation sensitivity was obtained by colony forming assay and Ku protein expression using Western blot analysis. RESULTS: Ku80 increased expression by radiation, wheres Ku70 did not. Overexpression of Ku80 protein increased radiation resistance in AMC-HN9 cell line. There was a correlation between Ku80 expression and radiation resistance. Ku80 was shown to play an important role in radiation damage response. CONCLUSION: Induction of Ku80 expression had an important role in DNA damage repair by radiation. Ku80 expression may be an effective predictive assay of radiosensitivity on head and neck cancer.