Impacts of exposure to low concentration of titanium dioxide nanoparticles on cell cycle control and DNA repair in normal, cancer and DNA repair deficient cells.

Nowadays, Titanium dioxide nanoparticles, TiO2 NPs, are produced in huge quantities due to their vast range of applications including paints, food coloring, sunscreens and cosmetics. Consequently, humans are exposed to TiO2 NPs on a daily basis. However, the toxicological profile of TiO2 NPs is not fully elucidated. As a result, this study is carried out to evaluate the genotoxic impact of TiO2 NPs on normal, cancer and DNA repair deficient cells. Since most of the studies evaluated the genotoxic impact of the TIO2 NPs have used the acute exposure scenario: High exposure concentrations and short exposure times, in the present study the genotoxic impact of the NPs would be evaluated using the prolonged exposure scenario: low exposure concentration for long exposure time. Cytotoxicity on a cancer cell line was evaluated using the MTT assay, genotoxicity on normal and cancer cell line was evaluated using immunofluorescent staining for anti-γ-H2AX and anti-total-53BP1, and the impact of the NPs on cell cycle regulation was evaluated using G2/M checkpoint assay on normal and cancer cell lines. In order to study the impact of NPs on DNA repair genotoxicity was evaluated using immunofluorescent staining for anti-γ-H2AX and anti-total-53BP1 on normal and DNA repair deficient cell lines. Finally, the maintenance of cell cycle G2/M checkpoint in absence of DNA repair genes was evaluated using the G2/M checkpoint assay on DNA repair deficient cell lines. In the present study, we have demonstrated that long exposures to TiO2 NPs does not induces cytotoxicity but it causes significant genotoxicity, particularly DNA double strand breaks. More precisely, we verified that NPs induces DNA DSBs at heterochromatin as well as euchromatin regions of the genome. Furthermore, we demonstrated that DNA DSBs repair, during G1 phase, at heterochromatin region is ATM dependent while DNA DSBs repair at Euchromatin regions is ATM independent, and DNA PKcs and Artemis dependent. On the other hand, it was seen that activation of G2/M cell cycle checkpoint after exposure to the NPs has DNA DSBs dependent-threshold. Also, it was shown that the release of the cell cycle checkpoint has DNA DSBs dependent-threshold. Lastly, we observed cell cycle checkpoint adaptation on prolonged exposure scenario. Taken together, we have demonstrated that prolonged exposure scenario does not affect cell viability but it causes DNA damage and cell cycle checkpoint adaptation leading to genetic instability

Impacts of prolonged exposure to low concentration of titanium dioxide nanoparticles on cell cycle control and DNA repair

Although the toxicological profile of titanium dioxide nanoparticles is not fully illuminated, large quantities of titanium dioxide nanoparticles (TiO2NPs) are now produced. In our study, we evaluated the cytotoxic and genotoxic impacts of titanium dioxide nanoparticles on different cell lines (normal, cancer and DNA repair-deficient cells). MTT assay was used to evaluate the cytotoxicity, γ-H2AX and 53BP1 assay was used to evaluate the genotoxicity and G2/M assay was used to study the impacts of titanium dioxide nanoparticles on cell cycle regulation. In this study normal and DNA repair-deficient cell lines were used to study the repair mechanism of titanium dioxide nanoparticles induced DNA damage. G2/M checkpoint maintenance was also evaluated. We demonstrate that prolonged exposure to low concentrations of titanium dioxide nanoparticles does not induce significant cytotoxicity but induces significant genotoxicity, particularly DNA double-strand breaks (DNA DSBs). Furthermore, this study demonstrated that DNA DSBs at heterochromatin region are ATM-dependent and DNA DSBs at euchromatin region are ATM-independent and DNA PKcs dependent. After exposure to titanium dioxide nanoparticles, we show that the activation of G2/M checkpoint is DNA DSBs dependent threshold as does checkpoint release. All in all, we showed that prolonged exposure to low concentrations of titanium dioxide nanoparticles does not affect cell viability but causes DNA damage and cell cycle checkpoint adaptation which may lead to genetic instability. DOI: http://dx.doi.org/10.5281/zenodo.748742

Evaluation of a quality improvement intervention to reduce anastomotic leak following right colectomy (EAGLE): pragmatic, batched stepped-wedge, cluster-randomized trial in 64 countries

Background Anastomotic leak affects 8 per cent of patients after right colectomy with a 10-fold increased risk of postoperative death. The EAGLE study aimed to develop and test whether an international, standardized quality improvement intervention could reduce anastomotic leaks. Methods The internationally intended protocol, iteratively co-developed by a multistage Delphi process, comprised an online educational module introducing risk stratification, an intraoperative checklist, and harmonized surgical techniques. Clusters (hospital teams) were randomized to one of three arms with varied sequences of intervention/data collection by a derived stepped-wedge batch design (at least 18 hospital teams per batch). Patients were blinded to the study allocation. Low- and middle-income country enrolment was encouraged. The primary outcome (assessed by intention to treat) was anastomotic leak rate, and subgroup analyses by module completion (at least 80 per cent of surgeons, high engagement; less than 50 per cent, low engagement) were preplanned. Results A total 355 hospital teams registered, with 332 from 64 countries (39.2 per cent low and middle income) included in the final analysis. The online modules were completed by half of the surgeons (2143 of 4411). The primary analysis included 3039 of the 3268 patients recruited (206 patients had no anastomosis and 23 were lost to follow-up), with anastomotic leaks arising before and after the intervention in 10.1 and 9.6 per cent respectively (adjusted OR 0.87, 95 per cent c.i. 0.59 to 1.30; P = 0.498). The proportion of surgeons completing the educational modules was an influence: the leak rate decreased from 12.2 per cent (61 of 500) before intervention to 5.1 per cent (24 of 473) after intervention in high-engagement centres (adjusted OR 0.36, 0.20 to 0.64; P < 0.001), but this was not observed in low-engagement hospitals (8.3 per cent (59 of 714) and 13.8 per cent (61 of 443) respectively; adjusted OR 2.09, 1.31 to 3.31). Conclusion Completion of globally available digital training by engaged teams can alter anastomotic leak rates. Registration number: NCT04270721 (http://www.clinicaltrials.gov)