High serum 8-hydroxy-2'-deoxyguanosine levels predict DNA damage and aging in professional divers

Exposure to fluoride exacerbates the cognitive deficit of diabetic patients living in areas with endemic fluorosis, as well as of rats with type 2 diabetes induced by streptozotocin via a mechanism that may involve excessive activation of the poly(ADP ribose) polymerase-1/P53 pathway

Epidemiology has shown that fluoride exposure is associated with the occurrence of diabetes. However, whether fluoride affects diabetic encephalopathy is unclear. Elderly diabetic patients in areas with endemic (n = 169) or no fluorosis (108) and controls (85) underwent Montreal Cognitive Assessment. Sprague-Dawley rats receiving streptozotocin and/or different fluoride doses were examined for spatial learning and memory, brain morphology, blood-brain barrier, fasting blood glucose and insulin. Cultured SH-SY5Y cells were treated with 50 mM glucose and/or low- or high-dose fluoride, and P53-knockdown or poly-ADP-ribose polymerase-1 (PARP-1) inhibition. The levels of PARP-1, P53, poly-ADP-ribose (PAR), apoptosis-inducing factor (AIF), and phosphorylated-histone H2A.X (ser139) were measured by Western blotting. Reactive oxygen species (ROS), 8-hydroxydeguanosine (8-OHdG), PARP-1 activity, acetyl-P53, nicotinamide adenine dinucleotide (NAD+), activities of mitochondrial hexokinase1 (HK1) and citrate synthase (CS), mitochondrial membrane potential and apoptosis were assessed biochemically. Cognition of diabetic patients in endemic fluorosis areas was poorer than in other regions. In diabetic rats, fasting blood glucose, insulin resistance and blood-brain barrier permeability were elevated, while spatial learning and memory and Nissl body numbers in neurons declined. In these animals, expression and activity of P53 and PARP-1 and levels of NAD+, PAR, ROS, 8-OHdG, p-histone H2A.X (ser139), AIF and apoptosis content increased; whereas mitochondrial HK1 and CS activities and membrane potential decreased. SH-SY5Y cells exposed to glucose exhibited changes identical to diabetic rats. The changes in diabetic rats and cells treated with glucose were aggravated by fluoride. P53-knockout or PARP-1 inhibition mitigated the effects of glucose with/without low-dose fluoride. Elevation of diabetic encephalopathy was induced by exposure to fluoride and the underlying mechanism may involve overactivation of the PARP-1/P53 pathway.

Analyses of oxidative DNA damage among coal vendors via single cell gel electrophoresis and quantification of 8-hydroxy-2'-deoxyguanosine

Looking at the development status of Nigeria and other developing nations, most low-income and rural households often use coal as a source of energy which necessitates its trade very close to the communities. Moreover, the effects of exposure to coal mining activities are rarely explored or yet to be studied, not to mention the numerous street coal vendors in Nigeria. This study investigated the oxidative stress levels in serum and urine through the biomarker 8-OHdG and DNA damage via single cell gel electrophoresis (alkaline comet assay). Blood and urine levels of 8-OHdG from 130 coal vendors and 130 population-based controls were determined by ELISA. Alkaline comet assay was also performed on white blood cells for DNA damage. The average values of 8-OHdG in serum and urine of coal vendors were 22.82 and 16.03 ng/ml respectively, which were significantly greater than those detected in controls (p < 0.001; 15.46 and 10.40 ng/ml of 8-OHdG in serum and urine respectively). The average tail length, % DNA in tail and olive tail moment were 25.06 μm, 18.71% and 4.42 respectively for coal vendors. However, for controls, the average values were 4.72 μm, 3.63% and 1.50 for tail length, % DNA in tail and olive tail moment respectively which were much lower than coal vendors (p < 0.001). Therefore, prolonged exposure to coal dusts could lead to higher serum and urinary 8-OHdG and significant DNA damage in coal vendors observed in tail length, % DNA in tail, and olive tail moment by single cell gel electrophoresis. It is therefore established that coal vendors exhibit a huge risk from oxidative stress and assessment of 8-OHdG with single cell gel electrophoresis has proven to be a feasible tool as biomarkers of DNA damage.