Genotoxicity evaluation of metformin and glimepiride by micronucleus assay in exfoliated urothelial cells of type 2 diabetes mellitus patients

Targeting Neutrophil Extracellular Trap Formation: Exploring Promising Pharmacological Strategies for the Treatment of Preeclampsia

Neutrophils, which constitute the most abundant leukocytes in human blood, emerge as crucial players in the induction of endothelial cell death and the modulation of endothelial cell responses under both physiological and pathological conditions. The hallmark of preeclampsia is endothelial dysfunction induced by systemic inflammation, in which neutrophils, particularly through the formation of neutrophil extracellular traps (NETs), play a pivotal role in the development and perpetuation of endothelial dysfunction and the hypertensive state. Considering the potential of numerous pharmaceutical agents to attenuate NET formation (NETosis) in preeclampsia, a comprehensive assessment of the extensively studied candidates becomes imperative. This review aims to identify mechanisms associated with the induction and negative regulation of NETs in the context of preeclampsia. We discuss potential drugs to modulate NETosis, such as NF-κβ inhibitors, vitamin D, and aspirin, and their association with mutagenicity and genotoxicity. Strong evidence supports the notion that molecules involved in the activation of NETs could serve as promising targets for the treatment of preeclampsia.

High-dose metformin induces a low-glucose dependent genotoxic stress

Epidemiological studies have demonstrated that metformin (a cornerstone of diabetes treatment) has anticancer activity, but the underlying mechanism remains elusive. We aimed to investigate whether metformin elicits anticancer activity via increasing genotoxic stress, a state of increased genome damage that becomes tumor-suppressing if it goes beyond an intolerable threshold. We found that metformin (1-16 mM) suppressed proliferation and colony formation in a panel of cancer cell lines (HeLa, A375, A549 and QGY). Metformin induced a dose-dependent increase of genotoxic stress (including micronucleus, nucleoplasmic bridge and nuclear bud) and the increase of genotoxic stress correlated well with metformin's anticancer potential. Metformin deregulated the expression of BUBR1 and MAD2, two core genes of spindle assembly checkpoint (SAC) that surveillances chromosome segregation. Metformin had weakened antiproliferative effect and a corresponding attenuated genotoxic effect in HeLa cells cultured in high glucose (16 mg/ml). Meanwhile, metformin significantly increased genotoxicity in non-cancer cells (NCM460 and HUVECs). Metformin became non-genotoxic to HUVECs in high-glucose (8 and 16 mg/ml) conditions and reduced the genotoxicity of high glucose. Overall, these results infer a new mechanism of high-dose metformin, whereby low-glucose dependent genotoxic stress derived from SAC dysfunction might mediate some of the anticancer effect of this drug.

OUP accepted manuscript

Type 2 diabetes (T2D) is associated with elevated frequencies of micronuclei (MNi) and other DNA damage biomarkers. Interestingly, individuals with T2D are more likely to be deficient in micronutrients (folic acid, pyridoxal-phosphate, cobalamin) that play key roles in one-carbon metabolism and maintaining genomic integrity. Furthermore, it has recently been shown that deficiencies in these nutrients, in particular folic acid leaves cells susceptible to glucose-induced DNA damage. Therefore, we sought to investigate if the B lymphoblastoid WIL2-NS cell line cultured under folic acid-deficient conditions was more sensitive to DNA damage induced by glucose, or the reactive glycolytic byproduct methylglyoxal (MGO) and subsequent advanced glycation endproduct formation. Here, we show that only WIL2-NS cultured under folic acid-deficient conditions (23 nmol/l) experience an increase in MNi frequency when exposed to high concentrations of glucose (45 mmol/l) or MGO (100 µmol/l). Furthermore, we showed aminoguanidine, a well-validated MGO and free radical scavenger was able to prevent further MNi formation in folic acid-deficient cells exposed to high glucose, which may be due to a reduction in MGO-induced oxidative stress. Interestingly, we also observed an increase in MGO and other dicarbonyl stress biomarkers in folic acid-deficient cells, irrespective of glucose concentrations. Overall, our evidence shows that folic acid-deficient WIL2-NS cells are more susceptible to glucose and/or MGO-induced MNi formation. These results suggest that individuals with T2D experiencing hyperglycemia and folic acid deficiency may be at higher risk of chromosomal instability.

Impact of dietary and lifestyle interventions in elderly or people diagnosed with diabetes, metabolic disorders, cardiovascular disease, cancer and micronutrient deficiency on micronuclei frequency - A systematic review and meta-analysis

Chronic diseases such as cardiovascular diseases, type 2 diabetes or cancer are the global leading cause of mortality. Lifestyle interventions are most effective in reducing metabolic risk factors, disease progression or even side effects of a disease. They are also contributing to decelerate the aging process. Genome instability is very often associated with aging or the above-mentioned diseases, and triggered by inflammation and oxidative stress. An established method to measure chromosomal damage is the cytokinesis block micronucleus (CBMN) cytome assay. The aim of this review and meta-analysis is to collect and analyse the current literature regarding the effects of a lifestyle based (dietary) intervention on changes of micronuclei (MNi), nucleoplasmic bridges (NPBs) and nuclear buds (NBUDs) in elderly subjects or people diagnosed with diabetes, metabolic disorders, cardiovascular disease, cancer or micronutrient deficiency. Although the main important diseases were considered as well as the large topic of aging, the number and methodological quality in terms of samples size, duration and rationale of the intervention or an inclusion of a control group of available intervention studies with these backgrounds was low. Most of the studies used antioxidant vitamins or folate, few investigated the whole diet. Only one study showed a physical activity intervention approach. The interventions did not lead to decreased genomic marker despite a few cancer related studies, where particularly MN frequency in mucosa lesions and leukoplakia was reduced by green tea and antioxidants. The performed meta-analysis of the available RCTs did not show a significant reduction of MNi, NBUDs or NPBs of most of the interventions performed, except for green tea. Data show in general a lack of an appropriate number of sound lifestyle based intervention studies linking cytogenetic damage and chronic diseases.

In vitro cytogenetic assessment and comparison of vildagliptin and sitagliptin

Vildagliptin and sitagliptin are commonly used antidiabetic drugs. Chromosomal aberration (CA), sister chromatid exchange (SCE) and cytokinesis-block micronucleus (CBMN) assays were employed to assess and compare cytotoxic and genotoxic effects of these drugs. Peripheral lymphocytes were exposed to 125 μg/ml, 250 μg/ml and 500 μg/ml of vildagliptin and 250 μg/ml, 500 μg/ml and 1000 μg/ml of sitagliptin for 24 h and 48 h with and without exogenous metabolic activation. At the end of the study, it was determined that these drugs and their metabolites had no genotoxic effects on CA, SCE and CBMN. On the other hand, parallel to the increase in dose, vildagliptin showed weak cytotoxicity on the mitotic index, and depending on its increase in dose; sitagliptin caused potential cytotoxicity and cytostatic effect on the mitotic index, nuclear division index and proliferation index. Due to their cytotoxic and cytostatic potential, these drugs inhibit cell proliferation.

Environmental monitoring and the developmental origins of health and disease

Early-life chronic exposure to environmental contaminants, such as bisphenol-A, particulate matter air pollution, organophosphorus pesticides, and pharmaceutical drugs, among others, may affect central tissues, such as the hypothalamus, and peripheral tissues, such as the endocrine pancreas, causing inflammation and apoptosis with severe implications to the metabolism. The Developmental Origins of Health and Disease (DOHaD) concept articulates events in developmental phases of life, such as intrauterine, lactation, and adolescence, to later-life metabolism and health. These developmental phases are more susceptible to environmental changes, such as those caused by environmental contaminants, which may predispose individuals to obesity, metabolic syndrome, and chronic noncommunicable diseases later in life. Alterations in the epigenome are explored as an underlying mechanism to the programming effects on metabolism, as the expression of key genes related with central and peripheral metabolic functions may be altered in response to environmental disturbances. Studies show that environmental contaminants may affect gene expressions in mammals, especially when exposed to during the developmental phases of life, leading to metabolic disorders in adulthood. In this review, we discuss the current obesity epidemics, the DOHaD concept, pollutants' toxicology, environmental control, and the role of environmental contaminants in the central and peripheral programming of obesity and metabolic syndrome. Improving environmental monitoring may directly affect the quality of life of the population and help protect the future generations from metabolic diseases.

The molecular origins and pathophysiological consequences of micronuclei: New insights into an age-old problem

Micronuclei (MN), the small nucleus-like bodies separated from the primary nucleus, can exist in cells with numerical and/or structural chromosomal aberrations in apparently normal tissues and more so in tumors in humans. While MN have been observed for over 100 years, they were merely and constantly considered as passive indicators of chromosome instability (CIN) for a long time. Relatively little is known about the molecular origins and biological consequences of MN. Rapid technological advances are helping to close these gaps. Very recent studies provide exciting evidence that MN act as key platform for chromothripsis and a trigger of innate immune response, suggesting that MN could affect cellular functions by both genetic and nongenetic means. These previously unappreciated findings have reawakened widespread interests in MN. In this review, the diverse mechanisms leading to MN generation and the complex fate profiles of MN are discussed, together with the evidence for their contribution to CIN, inflammation, senescence and cell death. Moreover, we put this knowledge together into a speculative perspective on how MN may be responsible for cancer development and how their presence may influence the choice of treatment. We suggest that the heterogeneous responses to MN may function physiological to ensure the arrestment, elimination and immune clearance of damaged cells, but pathologically, may enable the survival and oncogenic transformation of cells bearing CIN. These insights not only underscore the complexity of MN biology, but also raise a host of new questions and provide fertile ground for future research.

Metformin: Prevention of genomic instability and cancer: A review

The diabetes drug metformin can mitigate the genotoxic effects of cytotoxic agents and has been proposed to prevent or even cure certain cancers. Metformin reduces DNA damage by mechanisms that are only incompletely understood. Metformin scavenges free radicals, including reactive oxygen species and nitric oxide, which are produced by genotoxicants such as ionizing or non-ionizing radiation, heavy metals, and chemotherapeutic agents. The drug may also increase the activities of antioxidant enzymes and inhibit NADPH oxidase, cyclooxygenase-2, and inducible nitric oxide synthase, thereby limiting macrophage recruitment and inflammatory responses. Metformin stimulates the DNA damage response (DDR) in the homologous end-joining, homologous recombination, and nucleotide excision repair pathways. This review focuses on the protective properties of metformin against genomic instability.

Increased Micronuclei Frequency in Oral and Lingual Epithelium of Treated Diabetes Mellitus Patients

Diabetes mellitus (DM) is a metabolic disease characterized by persistent high levels of glucose in plasma. Chronic hyperglycemia is thought to increase oxidative stress and the formation of free radicals that in turn damage cells. Thus, we decided to determine the frequency of nuclear abnormalities in epithelial cells from cheek and tongue mucosa of DM patients with type 1 (DM1, treated only with insulin) and type 2 (DM2, treated with metformin) using the buccal micronucleus cytome (BMCyt) assay. Micronuclei frequency in cheek epithelial cells was higher in both DM1 (0.75 ± 0.31, P < 0.001) and DM2 (0.52 ± 0.27, P < 0.001) patients, as compared to healthy controls (0.07  ±  0.06). Similarly, micronuclei frequency in tongue epithelium was increased in DM1 (0.81  ±  0.22, P < 0.001) and DM2 (0.41  ±  0.21, P < 0.001) groups, in comparison to controls (0.06  ±  0.05). Besides, we found a positive correlation between micronuclei frequency and the onset time of DM2 in both cheek (ρ = 0.69, P < 0.001) and tongue epithelial cells (ρ = 0.71, P < 0.001), but not with onset time of DM1 or age of the patients. Considering all this, we pose that BMCyt could serve as a fast and easily accessible test to assess genotoxic damage during dental visits of DM patients, helping to monitor their disease.

The micronucleus test for the oral mucosa: global trends and new questions

This study reviews global trends in the publication of papers on the micronucleus test of the exfoliated cells of the oral mucosa in mammals as an approach for environmental biomonitoring. This test has been widely used due to its precision for the detection of chromosome damage. Our temporal analysis showed a significant increase (p < 0.05) in the publication of papers on the oral mucosa over the past 33 years. Brazil was the country that published most papers (24% of the total), followed by India (16%), the USA (10%), Mexico (7%), and Turkey (6%). A further 30 countries contributed the other 37% of the papers. Overall, 99% of the micronucleus studies involved human subjects, and only 1% involved other mammals. As many wild mammals are subject to the same environmental pressures as humans, in particular chemical pollution, it seems likely that many species are equally susceptible to genotoxicogical damage. We emphasize the importance of applying this technique to the analysis of the oral mucosa of wild mammals, as well as the evaluation of its effectiveness, as observed in humans, and the expansion of the available approaches to the monitoring of environmental quality.

The radioprotective effect of metformin against cytotoxicity and genotoxicity induced by ionizing radiation in cultured human blood lymphocytes

Metformin is a widely prescribed drug used in the treatment of patients with type 2 diabetes. In this study, the radioprotective effect of metformin was investigated against cytotoxicity and genotoxicity induced by ionizing radiation (IR) in human peripheral blood lymphocytes. Human lymphocytes were treated with metformin at concentrations 10 and 50μM for 2h and irradiated with 6MV X-rays. The radiation antagonistic potential of metformin was assessed by MTT [3-(4,5-dimethyl-2-thiaozolyl)-2,5-diphenyl-2H tetrazolium bromide] assay, chromosomal aberration (CA) analysis, cytokinesis blocked micronucleus (CBMN) assay, and flow cytometry. Observations demonstrated a radiation-dose-dependent decrease in the percentage of cell viability after 24h. It was found that pretreatment with metformin (10 and 50μM) increased the percentage of cell viability. A highly significant dose modifying factor (DMF) 1.35 and 1.42 was observed for 10 and 50μM metformin, respectively. Metformin (10 and 50μM) pretreatment significantly decreased the frequency of dicentrics (DCs), acentric fragments (AFs), rings (RIs), micronuclei (MN), and nucleoplasmic bridges (NPBs) in irradiated human peripheral blood lymphocytes. Also, treatment with metformin (10 and 50μM) without irradiation did not increase the number of MN, NPBs, DCs, AFs, RIs, and did not show a cytostatic effect in the human peripheral blood lymphocytes. On the other hand, metformin treatment (10 and 50μM) 2h prior to irradiation significantly reduced X-radiation-induced apoptotic incidence in human lymphocytes. The present study demonstrates metformin to be an effective radioprotector against DNA damage and apoptosis induced by IR in human lymphocytes. These data have an important application for the protection of lymphocytes from the genetic damage and side-effects induced by radiotherapy in cancer patients.