RNA Oxidative Damage by the Iron-Fenton Reaction is Influenced by Bicarbonate Concentration and Ligand Strength
Year: 2025
Type: article
Abstract: High Resolution Image Download MS PowerPoint Slide Oxidative damage to RNA is associated with neurodegeneration, cardiovascular diseases, and cancer development. Studies that monitor RNA damage by H 2 O 2 often omit the physiological buffer bicarbonate in the reaction, which fails to account for the influence of the buffer on the iron-Fenton reaction. Herein, we monitored two in vitro systems to understand how bicarbonate redirects the iron-Fenton reaction from a hydroxyl radical (HO • ) generator in the absence of bicarbonate to one that predominantly yields carbonate radical anion (CO 3 •– ) in the presence of this buffer. Using the HO • -selective fluorophore terephthalic acid, we found that the Fe(II)–ligand identity impacted the bicarbonate concentration required to transition the Fenton reaction to predominantly yield CO 3 •– . These findings were then corroborated by following the oxidation of guanosine (rG), which reports on oxidation by both radicals, and uridine (rU) oxidation, which responds to only HO • as the oxidizing species. The studies found that as the Fe(II)–ligand complex stability increased, the bicarbonate concentration inflection point to favor CO 3 •– production and rG oxidation also increased. Regardless of the ligand strength, the crossover values obtained were below physiologically relevant bicarbonate concentrations (<20 mM). Next, Escherichia coli or HEK293T cells were pre-equilibrated with bicarbonate from 0 to 20 mM before a bolus addition of H 2 O 2 . The bicarbonate-dependent inflection points for favoring CO 3 •– over HO • (or ferryl) for E. coli (7.3 mM) and HEK293T (11.3 mM) cells differed, but were below physiologically relevant concentrations, supporting the hypothesis that the cellular iron-Fenton reaction normally yields CO 3 •– . The redox-cycling compound menadione was used for continuous in-cell generation of H 2 O 2 to find bicarbonate dependencies in oxidation reactions of RNA. The studies herein point toward the redirection of the iron-Fenton reaction in cells to predominantly yield CO 3 •– that selectively damages rG sites in the transcriptome.
Source: Chemical Research in Toxicology
Institution: University of Utah
Language: English
Subfield: Molecular Biology
Domain: Life Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Award: G509785364
OpenAlex ID: W4415869845