We are interested in diseases of allergic inflammation. Allergies have become a major health concern with allergic inflammatory diseases increasing exponentially in the past generation, reaching near-epidemic levels globally. Patients are subsequently left with the diagnosis of life-long dependence upon allergy therapeutics. The long-term costs of allergies in terms of quality of life issues as well as impacts upon health care systems are enormous. A comprehensive understanding of the biological basis of allergic inflammation is essential to develop targeted therapies aimed at disease prevention. The underlying pathology of these diseases is based at least partly in members of the arachidonic acid cascade. Accordingly, quantifying oxidized fatty acids is vital to understand their role in a suite of pathophysiological processes. The range of arachidonic oxidation products is produced by the concerted actions of the cyclooxygenase, lipoxygenase and cytochrome P450 cascades. We are developing comprehensive metabolomics-based mass spectrometry methods to quantify multiple members of these cascades simultaneously. These procedures will be useful to 1) understand the fundamental processes behind the allergic response, 2) provide information on cross-talk between the different pathways and 3) identify novel therapeutics and interventions towards the goal of developing a true cure.

Numerous studies have demonstrated the biological importance of metabolic products of arachidonic acid, otherwise known as eicosanoids. These lipid mediators of inflammation consist of oxygenated eicosanoid derivatives and are composed of several chemical classes including: leukotrienes, prostaglandins, thromboxanes, and hydroxy, epoxy and oxo-fatty acids. These mediators act as paracrine hormones and are involved in the regulation of many normal physiological processes. However, unbalanced eicosanoid production may lead to pathological responses including inflammation, pain, fever, leukocyte accumulation and contraction of smooth muscles in the microcirculation and respiratory tract. The cyclooxygenases 1 and 2 (COX-1 and COX-2) are central enzymes in the prostaglandin cascade. Inhibitors of enzymes and receptors in the eicosanoid cascade are marketed as medications against pain (aspirin), arthritis (NSAIDs), and allergic asthma and rhinitis (Singulair).

Our current work involves examining the role of cysteinyl-leukotrienes in eliciting functional responses in mast cells to elucidate the mechanisms of action of “anti-leukotriene drugs”. Upon activation, mast cells release an array of inflammatory mediators including histamine, proteases, cytokines, prostaglandins, and cysteinyl-leukotrienes. We aim to define the role of eicosanoids in the function and migration of mast cells. During inflammation endothelial cells play a pivotal role in the activation, adherence and diapedesis of cells through the vascular wall and into the injured tissue, processes that involve leukotrienes. The expression of leukotriene receptors in these cells, as well as the effects of various anti-inflammatory and anti-allergic drugs on receptor expression and function are being examined using a lipidomics approach to examine for cross-talk across the entire arachidonic acid cascade. This work may reveal novel mechanisms for mast cell- and endothelial cell-dependent allergic reactions with implications for the therapeutic strategy and pharmacological intervention in allergic diseases. Results from these studies may also explain benefits and/or shortcomings of anti-leukotriene drugs, in particular CysLT1R antagonists (e.g. Singulair) for treatment of bronchial asthma. Hence, in addition to increasing knowledge regarding the basic mechanisms of inflammatory allergic reactions, the results of this work may provide improved regimens in the treatment of patients suffering from allergic diseases such as rhinitis, urticaria, dermatitis, and asthma.

We are interested in applying lipidomics to probe the interactions of esterase inhibition and anti-hyperlipidemia treatment upon structural lipid speciation and distribution. Despite recent advances, heart disease, stroke and other cardiovascular diseases remain the number one killer in the United States. One of the most important risk factors for cardiovascular disease is weight. The American Heart Association reports that 65% of American adults are overweight or obese and 11 million children are overweight. Upwards of 80% of the European population is classified as overweight, with up to a third being obese according to the European Union. That translates to ~400 million overweight and 130 million obese adults. Consequently, obesity is a major economic burden responsible for up to 6% of total health costs and 10-13% of deaths in Europe. Obesity has become one of the greatest public health challenges of the 21st century. Obesity occurs when the body possesses excessive fat (hyperlipidemia), and contributes to many life-threatening conditions including Type 2 diabetes, coronary heart disease, hypertension, and a number of different cancers. It is vital to increase our understanding of the causes and implications of obesity and develop effective means of controlling hyperlipidemia. A number of therapeutic interventions are available, including statins and fibrates. Statins are potent cholesterol-lowering agents (decrease low-density lipoprotein levels by 30-50%), whereas fibrates evidence hypolipidemic properties and are more effective at increasing high density lipoprotein. Subsequently both drugs are often co-administered. These treatments, while effective for treating dyslipidemia in some individuals, are not sufficient to deal with the magnitude of the problem and new pharmaceuticals are needed. 

Lipidomics has been used to elucidate the systemic effects of dyslipidemia treatments and is a valuable tool in the study of lipid-based diseases. This area is especially useful in the study of metabolic diseases including diabetes and coronary heart disease. One potential application is the development of “personalized medicine”, which provides large-scale sample screening for patients. For example, serum cholesterol can be elevated due to several mechanisms: (i) increased absorption through the intestine, or (ii) increased endogenous biosynthesis, or (iii) slow conversion to bile acids. All three conditions require distinct treatments, however current medical practice calls for cholesterol screening to be performed by only measuring the endpoint of total cholesterol. A lipidomics profile would be more useful for the medical practitioner to make an appropriate diagnosis regarding the necessary intervention to control a patient’s cholesterol.

Our research involves applying lipidomics to increase our understanding of dyslipidemia and the development of new therapeutics. For example, many esterases are necessary to maintain lipid homeostasis. Cholesterol esterase is involved in the biosynthesis of cholesterol esters and fatty acid ethyl esters, as well as lipases, and potentially carboxylesterases. However, the role of carboxylesterases remains unclear with some studies suggesting a role in cholesterol homeostasis, while others report that carboxylesterases have no cholesterol synthetic activity. It is therefore possible that carboxylesterase and/or cholesterol esterase activity could serve as new therapeutic targets for the control of dyslipidemia. We are exploring the effects of esterase inhibitor treatment upon structural lipid metabolism to elucidate the endogenous role of carboxylesterases and answer the question as to their role in cholesterol homeostasis. We are also interested in investigating the effects of statin and PPAR agonist treatment upon structural lipid composition. Initial studies conducted with clofibrate showed very distinct tissue-selective effects upon structural lipids. As synthetic statins are metabolized by carboxylesterases, it will be interesting to examine the effects of carboxylesterase inhibition upon statin efficacy. These studies will be useful for evaluating the potential effects of drug:drug interactions upon statin efficacy. A significant component of the research efforts involve the applications of structure activity relationship studies (SAR) to elucidate enzyme mechanisms and probe for new pharmaceuticals.