Research in the Brumaghim Group

Research in the Brumaghim group aims to understand how metal ions form radical species that damage DNA and how antioxidants prevent this damage. Work in our group can be divided into three main categories: DNA damage and prevention, antioxidant coordination chemistry, and cell death prevention in E. coli and mammalian cells. Studying mechanisms for DNA damage and cell death inhibition by antioxidants may lead to treatments for a wide range of chronic diseases, including cardiovascular diseases, Alzheimer's and Parkinson's diseases, cancer, and diabetes. It could also help prevent radiation damage during radiation treatments and long-duration space flight.

Antioxidants prevent DNA damage
In cells, Fe2+ and Cu+ react with hydrogen peroxide (H2O2) to form hydroxyl radical (OH). Reactive hydroxyl radical then oxidizes and damages DNA. This oxidative DNA damage and oxidative stress is an underlying cause of many diseases, including neurodegenerative diseases, cardiovascular diseases, and cancer. Antioxidants prevent hydroxyl radical from damaging DNA and other biomolecules and are therefore of interest to treat and prevent diseases caused by oxidative stress.

Fenton-type reactions

DNA AFM images

Undamaged DNA is separated from damaged (nicked and linear) DNA using gel electrophoresis. Adding an antioxidant prevents DNA damage from metal-generated OH. We quantify the amount of DNA damage inhibition seen in the gels and directly compare the effectiveness of different antioxidants.

Gel electrophoresis image

We discovered that sulfur, selenium, and polyphenol antioxidants prevent metal-mediated DNA damage through metal coordination. Currently we are developing structure-activity relationships for prevention of DNA damage by each of these classes of antioxidants. For example, the ability of polyphenol antioxidants to prevent iron-mediated DNA damage can be predicted simply from the pKa of the first phenolic hydrogen atom. This is because the polyphenol groups must be deprotonated to bind iron. Understanding this novel metal-binding mechanism of antioxidant activity will aid the design of more potent antioxidant compounds. We are also currently investigating the interactions of both antioxidants and metal ions with DNA.

Biological coordination chemistry
Since metal coordination by selenium, sulfur, and polyphenol compounds is a factor in antioxidant activity, we are synthesizing selenium, sulfur, and polyphenol complexes of iron and copper. With these complexes, we examinethe effects of antioxidant coordination on Fe2+/3+ or Cu+/2+ redox potentials and reactivity with H2O2, O2, and other oxidants. Results from these experiments allow us to determine mechanisms for the antioxidant activity of each class of antioxidants.

Coordination complexes

To synthesize our target selenium and sulfur compounds, we use TpR and TpmR (tris(3,5-R- pyrazolyl)borate and -methane, respectively) and selone, thione, or selenoamino acid ligands with Cu(I/II) or Fe(II/III). We are currently synthesizing second-generation sulfur and selenium antioxidants for testing in addition to synthesizing and characterizing our target complexes by NMR, X-ray crystallography, and cyclic voltammetry.

Antioxidants prevent cell death
Cell plates Because we found that antioxidants prevent DNA damage in vitro by metal coordination, we are also interested in testing antioxidant ability to prevent cell death under oxidative stress. When cells (both bacterial and mammalian) are exposed to H2O2 or hypoxic conditions, many die due to the DNA damage caused by metal-generated hydroxyl radical.

We are currently testing antioxidants that prevent DNA damage for their ability to prevent E. coli and mammalian cell death upon H2O2 and other oxidative stress challenges. Cells are incubated with and without the selected antioxidant, H2O2 is added, and the percentages of live and dead cells are quantified. In addition to studying the ability of antioxidants to prevent cell death and DNA damage, we use mutant E. coli strains to determine the cellular pathways that are affected by antioxidant treatment.