Oxidative stress and DNA damage resulting from welding fumes exposure among professional welders: A systematic review and meta-analysis

The present systematic review aimed to evaluate the associations between welding fumes exposure and changes in oxidative stress [superoxide dismutase (SOD) and malondialdehyde (MDA)] and DNA damage [8-hydroxy-2'-deoxyguanosine (8-OHdG) and DNA-protein crosslink (DPC)] markers in professional welders (PROSPERO CRD42022298115). Six electronic bibliographic databases were searched from inception through September 2021 to identify observational epidemiological studies evaluating the association between welding fumes exposures and changes in oxidative stress and DNA damage in professional welders. Two reviewers independently assessed the risk of bias and certainty of the evidence. A narrative synthesis of results was conducted using the Synthesis Without Meta-analysis (SWiM) method. Pooled mean differences with 95% confidence intervals were calculated in a random-effects meta-analysis for the outcomes of interest in the review. From 450 studies identified through the search strategy, 14 observational epidemiological studies were included in the review. Most studies reported significantly higher welding fumes levels in welders than in controls. The narrative synthesis results of SOD showed a significant difference between welders and controls, while the meta-analysis results of MDA did not show a significant difference between the studied groups (MD = 0.26; 95% CI, -0.03, 0.55). The meta-analysis results of 8-OHdG (MD = 9.38; 95% CI, 0.55-18.21) and DPC (MD = 1.07; 95% CI, 0.14-2) revealed significantly differences between the studied groups. The included studies were at high risk of exclusion and confounding bias. The certainty of the evidence for oxidative stress and DNA damage results were very low and moderate, respectively. Exposure to welding fumes and metal particles is associated with DNA damage in professional welders, and 8-OHdG and DPC might be considered reliable markers to assess DNA damage resulting from exposure to welding fumes. We recommend, however, that the evaluation of oxidative stress resulting from welding fumes exposure not be solely based on MDA and SOD.

NRF2 is a critical regulator and therapeutic target of metal implant particle-incurred bone damage

Aseptic metal implant loosening due to wear particle-induced bone damage is a major complication of total joint arthroplasty often leading to revision surgery, of which the key regulators mediating the processes are not clearly defined. Here we reported that in a mouse model of calvarial osteolysis, titanium particles (TiPs) and cobalt-chromium-molybdenum particles induced severe osteolysis accompanied by marked suppression of a master redox transcriptional factor NRF2 (Nuclear factor erythroid derived 2-related factor 2). Nfe2l2 knockout mice treated with TiPs developed worse osteolytic alterations compared with wild-type mice. On the contrary, NRF2 restoration by an NRF2 agonist TBHQ (tert-butylhydroquinone) effectively alleviated the osteolysis and the abnormal expression of NRF2 downstream antioxidant enzymes, inflammatory cytokines and osteogenic factors. Further, TiPs induced adverse osteoblastogenesis and osteoclastogenesis in cultured bone cells, which were substantially blocked by TBHQ in an NRF2 inhibition-sensitive manner. Consistently, the osteoprotective effects of TBHQ observed in wild-type mice were largely limited in Nfe2l2 knockout mice. Collectively, our data suggest that NRF2 suppression is a critical causal event of metal wear particle-incurred osteolysis, and the strategies reinstating NRF2 are effective to lessen the bone damage and potentially reduce the incidence of metal implant loosening.