Assessment of mitochondrial DNA damage in little brown bats (Myotis lucifugus) collected near a mercury-contaminated river

Abstract

Historical discharges of Hg into the South River near the town of Waynesboro, VA, USA, have resulted in persistently elevated Hg concentrations in sediment, surface water, ground water, soil, and wildlife downstream of the discharge site. In the present study, we examined mercury (Hg) levels in in little brown bats (Myotis lucifugus) from this location and assessed the utility of a non-destructively collected tissue sample (wing punch) for determining mitochondrial DNA (mtDNA) damage in Hg exposed bats. Bats captured 1 and 3 km from the South River, exhibited significantly higher levels of total Hg (THg) in blood and fur than those from the reference location. We compared levels of mtDNA damage using real-time quantitative PCR (qPCR) analysis of two distinct regions of mtDNA. Genotoxicity is among the many known toxic effects of Hg, resulting from direct interactions with DNA or from oxidative damage. Because it lacks many of the protective protein structures and repair mechanisms associated with nuclear DNA, mtDNA is more sensitive to the effects of genotoxic chemicals and therefore may be a useful biomarker in chronically exposed organisms. Significantly higher levels of damage were observed in both regions of mtDNA in bats captured 3 km from the river than in controls. However, levels of mtDNA damage exhibited weak correlations with fur and blood THg levels, suggesting that other factors may play a role in the site-specific differences.

Effects of methyl and inorganic mercury exposure on genome homeostasis and mitochondrial function in Caenorhabditis elegans

“…In an in vitro study, plausibility for mtDNA damage was established through microscopy images that depicted increased ROS in a qualitative manner and DNA damage co-occurring in cellular space with mitochondria (Sharpe et al 2012). In a field study, some evidence for increased mtDNA damage was obtained in bats from areas with high potential for Hg exposure, but individual-level correlations with Hg levels were poor (Karouna-Renier et al 2014). Here we report the first quantified impacts of mercury on mtDNA in controlled experiments in an in vivo model.…”

“…Epidemiological studies indicate that DNA damage is possible in fish-eating populations, in children, and most importantly at exposure levels lower than those known to adversely impact the nervous system (Franchi et al 1994, Amorim et al 2000, Cebulska-Wasiewska et al 2005, Di Pietro et al 2008, Al-Saleh et al 2012). The focus of previous studies has primarily been on impacts to the nuclear genome, with only one study to date reporting mtDNA impacts (Karouna-Renier et al 2014). Depending on the kind of damage, increased mtDNA damage and damage accumulation in the mitochondrial genome are possible as there are fewer DNA repair pathways in this organelle (Ledoux et al 1992, Scheibye-Knudsen et al 2015, Van Houten et al 2016).…”

Predictors of mitochondrial DNA copy number and damage in a mercury‐exposed rural Peruvian population near artisanal and small‐scale gold mining: An exploratory study

“…A growing body of literature has identified multiple pathways through which mitochondria can be compromised, in particular, from pollutant exposures (Martinez and Greenamyre, ; Meyer et al, ; Brunst et al, ). Inference on the degradation of mitochondria following exposure to toxicants, such as organic chemicals, particulate matter, polycyclic aromatic hydrocarbons and cationic metals, has drawn largely upon controlled laboratory experiments using cell lines, model organisms or animal models (Bucio et al, ; Cakir et al, ; Karouna‐Renier et al, ; Sanders et al, ; Sanders et al, ). This study examines factors influencing mtDNA copy number (CN) and damage in a randomly selected human population in the Peruvian Amazon living in an area with extensive mercury contamination due to artisanal and small‐scale gold mining (ASGM).…”

“…Inference on the degradation of mitochondria following exposure to toxicants, such as organic chemicals, particulate matter, polycyclic aromatic hydrocarbons and cationic metals, has drawn largely upon controlled laboratory experiments using cell lines, model Additional Supporting Information may be found in the online version of this article. organisms or animal models (Bucio et al, 1999;Cakir et al, 2007;Karouna-Renier et al, 2014;Sanders et al, 2014a;Sanders et al, 2014b). This study examines factors influencing mtDNA copy number (CN) and damage in a randomly selected human population in the Peruvian Amazon living in an area with extensive mercury contamination due to artisanal and small-scale gold mining (ASGM).…”

Civa Klorürün mtDNA'da Akut Etkisi

“…But the levels of mtDNA damage exhibited weak correlations with fur and blood Hg levels and the mtDNA damage may not be connected to mercury contamination in the river (Karouna-Renier et al, 2014). In another study, Sharpe and colleagues demonstrated that mtDNA damage was created by thimerosal.…”