Irina Pikuleva, PhD

 Irina Pikuleva, PhD

Irina Pikuleva, PhD

Vice Chair of Research and Professor
Carl F. Asseff, M.D. Professor of Ophthalmology

Research Focus

Cholesterol and age-related macular degeneration

Research Summary

Dr. Pikuleva focuses on cholesterol metabolism and cytochrome P450 enzymes (CYPs or P450s 27A1 and 46A1) whose role is to generate more polar forms of cholesterol for cellular elimination or regulation. The two major areas of research in the laboratory are: 1) the link between cholesterol and diseases of the retina; and 2) effects of pharmacologic enhancement of cholesterol turnover in the brain. The ultimate goal of these studies is to identify new therapeutic targets and treatments for diseases of the eye (age-related macular degeneration and diabetic retinopathy) and the brain (Alzheimer’s disease).

Generation and characterization of Cyp27a1-/-Cyp46a1-/- mice with significantly impaired cholesterol metabolism as well as in vitro and in vivo evaluations of CYP46A1 as a drug target have led to two major findings in Dr. Pikuleva’s laboratory. First, disturbances in cholesterol metabolism in the retina are associated with different types of retinal vascular abnormalities. Second, it is possible to enhance cholesterol turnover in the brain pharmacologically, at least in mice, by FDA-approved medications that are used for indications unrelated to cholesterol. The laboratory is currently further investigating these fascinating findings.

To accomplish the challenging goal of developing new therapeutic approaches, many in vitro and in vivo methodologies are used in Dr. Pikuleva’s laboratory. The utilized in vitro techniques include, but are not limited to, histology and histochemistry, biochemical/biophysical (X-ray crystallography) studies of the purified enzymes, gene profiling, and cutting edge mass spectrometry quantifications of tissue sterol and protein levels. The in vivo work involves generation and ophthalmic characterization of mice with genetic deficiencies in cholesterol metabolism, pharmacologic treatments of these and wild type animals, as well as retinal evaluations by state-of-the-art ultra-high resolution spectral domain optical coherence tomography and fluorescein angiography. Projects are available for medical and graduate students as well as MDs interested in research.

Publications

Art Gallery

Irina Pikuleva, Ph.D. Research

Irina Pikuleva, Ph.D. Research

Irina Pikuleva, Ph.D. Research
Identification of Isolevuglandin-CYP27A1 adducts in human retina. Cadaveric retinal sample was mixed with purified recombinant 15N-CYP27A1 modified with authentic iso[4]levuglandin E2, hydrolyzed, and analyzed by multiple reaction monitoring. Transitions arising from endogenous isoLG-adducts were observed at identical retention times as those arising from the iso[4]LGE2 modified 15N-CYP27A1 used as internal standard.

Irina Pikuleva, Ph.D. Research
Retinal Pathology in CYP27A1 KO Mice As Revealed by Optical Coherence Tomography and Fluorescein Angiography.

Irina Pikuleva, Ph.D. Research
Plasticity of the CYP46A1 Active Site as Revealed by X-Ray Crystallography. Almost every amino acid residue in the active site of CYP46A1 can readjust its position to better fit the inhibitor molecule, thus explaining the unusual ability of this cholesterol-metabolizing P450 to bind pharmaceuticals of different size and shape.

Irina Pikuleva, Ph.D. Research
Structural Basis For Three-step Sequential Catalysis by the Cytochrome P450 11A1 that Catalyzes the Conversion of Cholesterol to Pregnenolone. The network of structural water molecules (in violet) at the entrance to the CYP11A1 active site (contoured in green) allows the "soft" recognition of the hydroxyl group of the first reaction intermediate, 22R-hydroxycholesterol (in yellow) and enables sterol shuttling between the active site entrance and the heme group (in red), the site of catalysis. The protein backbone is represented as a gray ribbon.

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