In vitro Study on Role of Hsp70 Expression in DNA Damage of Human Embryonic Lung Cells Exposed to Benzo[a]pyrene

Objective Benzo[a]pyrene (B[a]P), a ubiquitous environmental pollutant, is a potent procarcinogen and mutagen that can elicit tumors, leading to malignancy. Heat shock proteins (Hsp) have been shown to protect cells against damages caused by various stresses including exposure to numerous chemicals. Whether Hsps, or more specifically Hsp70, are involved in repair of B[a]P-induced DNA damage is currently unknown. Methods We assessed the potential role of the inducible form of Hsp70 in B[a]P-induced DNA damage of human embryonic lung (HEL) cells using immunoblot and the comet assay (i.e., the single cell gel electrophoresis assay). Results Exposure to B[a]P induced a dose-dependent decrease in the level of Hsp70, but a dose-dependent +-increase in DNA damage both in untreated (control) HEL cells and in cells preconditioned by a heat treatment. Heat preconditioning prior to B[a]P exposure potentiated the effect of B[a]P at a low dose (10 μmol/L), but appeared to be protective at higher doses. There was a negative correlation between Hsp70 level and DNA damage in the non-preheated as well as in the preconditioned cells. Conclusion These data suggest that exposure of HEL cells to B[a]P may induce a dose-dependent reduction in the levels of the inducible Hsp70. The detailed mechanisms for the reduction of Hsp70 levels by B[a]P and the role of Hsp70 in DNA damage under different concentrations of B[a]P remains to be determined.

Effect of manganese on heat stress protein synthesis of new-born rats

AIM: To study the effect of manganese (Mn) on heat stressprotein 70 (HSP70) synthesis in the brain and liver of new-bom rats whose mother-rats were exposed to Mn.METHODS: 32 female rats were randomly divided into fourgroups. One group was administrated with physiologicalsaline only as control group, the other three groups wereadministrated with 7.5, 15 and 30 mg@ kg-1 manganesechloride (MnCl2) by intraperitioneal injection every two daysfor two weeks. After delivery, the mother-rats receivedMnCl2 unceasingly for a week with the same method. Thenthe contents of Mn、 Zn、 Cu and Fe in the livers of the new-bom rats were determined by atomic absorptionspectroscopy; The level of HSP70 in the brains and thelivers of the new-born rats as detected by Westsrn-dot-blotting, and the SOD activities were measuredsimultaneously.RESULTS: The contents of Mn in the livers of new-bom ratsof the experimental groups(respective 1.38 ± 0.18, 2.73 ±0.65, 3.44 ± 0.89μg @ g-1) were significantly increasedcompared with the control group(0.88 ± 0.18μg@ g-1; p ＜0.01); The contents of Fe in the livers of new-bom rats of 15and 30 mg@ kg-1 experimental groups (426 ± 125,572 ± 175μg@g-1, respectively) were significantly increased comparedwith the control group(286±42μg@g-1; P＜0.05); the levelsof Zn in the livers of the new-bom rats of three experimentalgroups( 254 ± 49, 263 ± 47, 213 ± 28μg@ g-1, respectively)were lower than those of the control group(335 ± 50μg@g-1;respective P＜0.05, P＜0.01); and the levels of Cu showedno significant difference among the four groups (threeexperimental groups: 75 ± 21, 68 ± 241 and 78 ± 18μg@g-1;control group: 83 ± 9μg@ g-1; p ＞ 0.05). There was asignificant increase in the levels of HSP70 in the brains ofnew-bom rats of the 30 mg@kg-1 group (19.5 × 103 ± 1.3 ×103A; control group: 14.3 × 103 ± 1.4 × 103A; P＜ 0.01),andthe levels of HSP70 in the livers of new-bom rats of threeexperinental groups(respective 19.6 × 103 ± 3.9 × 103A, 18.5× 103 ± 3.8 × 103A, 22.4 × 103 ± 1.9 × 103A ) also increasedthan control group(13.3 × 103 ± 1.0 × 103A; P ＜ 0.01), butthe SOD activities showed no significant difference amongbrains of the four groups (experimental groups: 5.04 ± 0.43,4.83±0.48, 4.60±0.84 ku@g-1; control group: 4.91 ± 0.37ku@g-1; P＞ 0.05). The SOD activities in the livers of 15mg@kg-1 group(5.41 ± 0.44 ku@g-1) was lower than the controlgroup(5.95±0.36 ku@g-1; P＜0.05).CONCLUSION: While mother-rats were exposed tomanganese, the metabolisms of Mn、Zn and Fe of new- bornrats in the livers were influenced and were situated in astress status, thus HSP70 syntheses is induced in the brainsand livers of new-bom rats, but the mechanism of this effectin the developmental toxicity of Mn remains to he furtherstudied.