Streptozotocin‐induced toxicity in CHO‐9 and V79 cells

Abstract

The cytotoxicity of streptozotocin (STZ) was investigated in Chinese hamster fibroblast lines (CHO-9 and V79) in comparison to two other alkylating agents, methylnitrosourea (MNU) and ethylnitrosourea (ENU), using cell survival as the endpoint. It was found that V79 cells were far more resistant to methylation induced by STZ and MNU than CHO-9 cells (20 and four times, respectively) but equally sensitive to the ethylating agent ENU. The extent of STZ-induced DNA methylation was estimated by analyzing the extent of O6-metG and N7-metG adducts in the DNA of treated cells through high-performance liquid chromatography (HPLC) with electrochemical detection. The number of adducts as well the efficiencies of their removal from the DNA were similar in both cell lines. The response of these cells to the presence of DNA damage was evaluated by analysis of STZ effects on DNA replication and cell cycle progression. Measurement of [3H]-thymidine incorporation showed a similar pattern of response at the level of inhibition of DNA synthesis in both cell lines. However, analysis of metaphase cells 36 hr after STZ exposure showed an accumulation of cells in the second cycle in the CHO-9 line, indicating induction of a cell cycle arrest. Only a slight effect was observed on cell cycle progression in V79 cells, indicating that the methylation resistance of these cells could be related to their ability to progress through the cell cycle despite the presence of DNA lesions.

Vascular Dysfunction in Streptozotocin-Induced Experimental Diabetes Strictly Depends on Insulin Deficiency

“…Despite the fact that STZ-induced diabetes is an accepted experimental model of diabetes type 1-associated vascular dysfunction and oxidative stress [19,20], several reports speculated on severe systemic toxic side effects of the anticancer drug STZ [23,24]. With the present study we demonstrate that STZ-induced diabetes is a model of insulin-dependent diabetes (type 1) and that STZ-dependent vascular complications are probably not associated with systemic toxic side effects but strictly depend on insulin deficiency.…”

“…It is well established that advanced glycation end products play an important role in the pathogenesis of STZ-induced diabetic complications [21] such as increased oxidative stress [22]. However, several reports speculated on severe systemic toxic side effects of the anticancer drug STZ [23,24] or a different mechanism of pathogenesis of STZ-induced diabetic complications as compared to cytokine-mediated diabetes mellitus type 1 [25,26]. Haughton et al [27] have previously shown that insulin replacement therapy can completely normalize the adverse effects of STZ on blood glucose levels and weight gain, and Kobayashi and Kamata [28] have shown that high-dose insulin therapy (5–30 U/kg/day) can completely normalize endothelial function.…”

Global gene expression profiling of pancreatic islets in mice during streptozotocin-induced β-cell damage and pancreatic Glp-1 gene therapy

“…STZ is a potent alkylating agent, known as an alkylnitrosourea, that directly methylates DNA (Randerath et al, 1981). STZ-induced DNA damage is characterized by N7-methylguanine (N7-MeG): more than 70% of DNA methylation occurs at the N7 position of guanine (Capucci et al, 1995). In addition to covalent adducts (N7-MeG), STZ also induces DNA strand breaks in rat β-cells (LeDoux et al, 1986).…”

Assessment of mechanisms driving non-linear dose–response relationships in genotoxicity testing

“…This led researchers to 48 question the reliability of the general assumption of dose-49 response linearity at low doses for numerous genotoxicants with 50 diverse modes of action (MoA). In this context, the term MoA can 51 be defined as the sequence of key events and processes involved in 52 the interaction of an agent with DNA or other cellular target 53 structures that result in specific DNA damage [10]. 54 Non-linear dose-responses have been reported for low doses of 55 compounds with diverse MoA such as aneugens topoisomerase 56 inhibitors, alkylating agents and oxidants by evaluating different 57 genotoxic endpoints (e.g.…”

“…Although, it seems likely that ENU 307 would elicit a PoD but perhaps at much lower concentrations than 308 tested. There are four possibilities that may explain the differences 309 between these agents: (i) other adducts also contribute to ENU 310 mutagenesis (ii) repair of ethyl adducts is less efficient than methyl 311 adducts (iii) O 6 ethylguanine (O 6 EthG) has a higher miscoding 312 potential than O 6 MeG (iv) O 6 MeG is more cytotoxic lesion; MNU is 313 more toxic than ENU, causing toxicity within the micromolar range 314 compared to milimolar concentrations for ENU in Chinese Hamster 315 cells [53]. Incidentally, at equitoxic concentrations, MNU is more 316 mutagenic than ENU [54] suggesting that methyl adducts are more 317 toxic than ethyl adducts and cell death may lower the mutagenici-318 ty of MNU.…”