Stacy Gelhaus Wendell, PhD

Link:  Translational Program Project / Vascular Sub-Phenotypes of Lung Disease  http://www.vmi.pitt.edu/tPPG.html 


Nitrated and oxidized metabolites of omega-3 and omega-6 fatty acids, such as docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), docosapentaenoic acid (DPA) arachidonic acid (AA) and linoleic acid (LA), are potent signaling mediators involved in inflammation and resolution, amongst a variety of other regulatory pathways.  These oxidized metabolites are produced by reactive oxygen and nitrogen species as well as through enzymatic pathways including cyclooxygenase (COX), lipoxygenase (LO), and cytochrome P450s (CYP450).  Dr. Gelhaus’ research is specifically focused on understanding the anti-inflammatory mechanisms of a specific subgroup of these metabolites; the electrophilic fatty acids.  Examples of electrophilic fatty acids include nitrated fatty acids such as nitro-oleic, nitro-linoleic, and nitro-conjugated linoleic acid or oxidized lipids that contain an a-,ß-unsaturated ketone or epoxide moiety.  Electrophilic fatty acid metabolites can exert their effects through the modulation of transcriptional regulatory proteins.  Many transcriptional regulatory proteins contain a nucleophilic amino acid residue, such as a cysteine or histidine, to which the electrophilic moiety of the fatty acid can form a reversible Michael addition.  Many of these interactions have been described with the nitrated fatty acids, particularly nitro-oleic acid.  In terms of cellular signaling, the Freeman lab has described several protein targets of posttranslational nitroalkylation modification, resulting in activation of pro-MMP9, PPARϒ, heat shock factors, Keap1/Nrf2 and the inhibition of the pro-inflammatory transcription factor NF-κB.

 

 

The current focus of Dr. Wendell's research is on the mechanism of these electrophilic fatty acids in asthma.  Asthma is a complicated disease that much like cancer is comprised of numerous disease states and phenotypes.  In many ways it is an umbrella of respiratory diseases that share some similar phenotypes such as airway hyper-responsiveness, increased mucus secretion, increased smooth muscle contraction and decreased airflow.  In the most severe of cases, airway remodeling and corticosteroid resistance are not uncommon.  Asthma affects over 30 million worldwide and is an economic burden with therapeutic costs upwards of $19 billion dollars per year.  While the number of asthmatics in Westernized countries seems to be plateauing, the world-wide number of asthmatics is projected to hit over 100 million by 2025, mostly in low/middle economically developing countries. 

 

Dr. Wendell is looking at the signaling of electrophilic fatty acids in transformed stable cell lines while collaborating with clinicians to study the formation and signaling of electrophilic fatty acids in healthy controls, mild to moderate, and severe asthmatic subjects.  In this study, subjects undergo a baseline bronchoscopy after which they are placed randomly in one of three groups—control, aspirin, or indomethacin.  The thought here is that indomethacin will completely inhibit cyclooxygenase activity; therefore, shunting metabolism to other pathways including lipoxygenase or CYP450.  Aspirin will inactivate COX-1, but acetylate COX-2 at S516, thus altering enzymatic activity and the stereochemistry of product formation.  Following 5 days of treatment, subjects return for a second bronchoscopy.  At each bronchoscopy, blood, urine, bronchoalveolar lavage, and bronchial brushings are taken.   The epithelial cells from the brushings can be cultured at the air liquid interface for mechanistic studies and identification of key electrophilic fatty acids.  To reach these end goals, the lab utilizes molecular biology and analytical techniques, primarily mass spectrometry, (triple quadrupole and ion trap) to elucidate the structures of novel electrophilic species, accurately detect and quantify key electrophilic fatty acid oxidation products in biological matrices, and establish mechanisms of action in asthma and other lung and airway diseases.  Furthermore, the implications of electrophilic fatty acid formation and signaling under inflammatory conditions and the ability of electrophilic fatty acids to decrease airway hyperresponsiveness are being investigated in a house dust mite allergen murine model of asthma.