Faculty Research - Pharmacy
Dr. Buhler’s laboratory research focuses on neuronal circuits involved in the modulation of pain. Multiple brainstem regions respond to outside influences such as stress, pain, opioids and disease in order to either increase or decrease the intensity of pain transmission. While analgesic drugs like opioids, acetaminophen and NSAIDs can activate specific pain inhibitory pathways for a time-span of hours, no current drugs can serve as long-term analgesics. Our current research focuses on the neuroanatomical and neurophysiological basis of a long-term analgesia produced by hyperbaric oxygen treatments. Techniques used include tissue sectioning, immunohistochemistry, and fluorescence microscopy.
My research interests revolve around minimizing toxicity and/or drug interactions of xenobiotics through better understanding of their effect on drug metabolizing enzymes (DME), especially Cytochrome P450 (CYP) enzymes. Although CYP enzymes normally generate metabolites with diminished biological activity, there are numerous examples where these enzymes mediate the formation of reactive intermediates from chemically inert agents. These reactive metabolites play a key step in initiating cellular damage and cancers. Modification of the activity or expression level of CYP enzymes through exposure to environmental toxins, drugs, or even herbal remedies could potentially affect the clinical outcome of concomitantly-administered drugs. My research interest focuses on identifying the role of CYP enzymes in toxicity induced by drugs, herbal remedies and environmental toxins. Along with the mission of the Pacific University and the School of Pharmacy, the outcome of this research will be utilized to advance the level of pharmaceutical care within the community and improve health care literacy among patients. The ongoing projects are being conducted in our research facility in HPC2 and/or in collaboration with scientists from Oregon Health and Science University or University of Saskatchewan (Canada).
The broad research emphasis in this lab is the investigation of factors that influence interpatient variability in drug toxicity and response to therapy. The work investigates several areas including reactive metabolite formation, drug-drug /drug-diet interactions, structure-toxicity/ADME relationships, idiosyncratic adverse drug reactions, genetic polymorphisms, and structure-function studies of drug metabolizing enzymes. This research requires an interdisciplinary and collaborative approach and therefore a variety of biophysical methods and bioanalytical tools are used to carry out this work. These include HPLC-fluorescence, mass spectrometry, mechanism-based inhibition, kinetic isotope effects, in vitro-in vivo extrapolation (IVIVE), molecular modeling, protein expression/purification, and metabolite synthesis.
Currently the lab's primary focus is on cytochrome P450 2A6 (CYP2A6). CYP2A6 is the major human nicotine-metabolizing enzyme, and exhibits profound genetic variability leading to diversity in nicotine clearance within the human population. We are conducting structure-function studies of CYP2A6 using plant metabolites (i.e., phenylpropanoids and terpenoids) present in the diet (e.g., cinnamon aldehyde from cinnamon oil) and are investigating the modulation of CYP2A6 and genetic variants by these compounds. This work has potential to provide new mechanistic insights in the areas of smoking cessation, structure-toxicity relationships, cancer chemoprevention, and drug-diet interactions involving CYP2A6.
My background is as a trained Pharmacist with a PhD in Pharmaceutics. My prior research experience, as part of my PhD, was in elucidating the effect of physicochemical properties of nanoparticulate systems on their lymphatic uptake and retention. As such, I was able to correlate the particle size, hydrophobicity, and charge distribution of biodegradable polymeric nanoparticles with their uptake and retention within the lymphatic system. In my post-doctoral study, I worked with micellar nanocarriers composed of biocompatible polymers for delivery of anti-cancer agents. In my current research endeavors I continue to purse my interest in biocompatible and biodegradable polymers as micellar drug delivery systems for cancer therapeutics. Specifically I am interested in designing micellar drug carriers using Pluronic® block copolymers for the concomitant delivery of drugs with additive/synergistic effects. Molecules currently being explored include resveratrol and doxorubicin for the treatment of ovarian and breast cancer. Doxorubicin is a potent anticancer agent, however, its therapeutic use is limited by its side effects, especially cardiotoxicity. Resveratrol, a potent antioxidant found naturally in grapes, nuts, and wine, has been shown to mitigate cardiotoxicity in animal models when used prior to a doxorubicin administration. The goal of our current work is to explore concomitant delivery of resveratrol and doxorubicin to determine the extent of mitigation of cardiotoxicity and efficacy of an established dosage form in ovarian and breast cancer.
The overall objective of my research is to characterize and therapeutically validate the polyamine pathway of the protozoan parasite, Leishmania, which causes devastating and often fatal diseases in humans worldwide. Polyamines are essential cations that are especially important for rapidly proliferating cells such as parasites. The polyamine biosynthetic pathway in Leishmania is essential for parasite survival and significantly disparate from the host’s mechanism of polyamine production. A variety of genetic, cell and molecular biology, as well as biochemical techniques are being used to dissect the pathway. In addition, in vitro macrophage infectivity studies and in vivo murine infectivity models are being utilized to assess the importance of the polyamine pathway for host-parasite interactions and infectivity.
Research in my lab is focused on investigating how subtle changes in the chemical structure of a drug are capable of propagating extraordinary differences in toxicologic outcomes. This type of structure-based comparative toxicology is applied to many structurally similar compounds to determine which cellular mechanisms are disrupted in an attempt to identify causality. The end goal throughout this process is to develop safer chemicals that maximize efficacy while minimizing toxicity. In general, these structure-toxicity relationships are characterized utilizing a triphasic biochemical approach, which includes (1) surveying existing transcriptomic datasets that are freely available through PubMed in the Gene Expression Omnibus (GEO) database repository, (2) generating biologically meaningful hypotheses that can be tested using traditional and well-established biochemical assays, and (3) developing resources to improve chemical design and minimize toxicologic impact. The focal comparison in my research is the elucidation of mechanisms leading to the different toxicologic profiles of acetaminophen (APAP) and its regioisomer, acetyl-m-aminophenol (AMAP). Despite APAP’s widespread use as an analgesic and antipyretic, overdose cases are the most common cause of drug-induced liver injury in the United States annually. AMAP is used as a comparative tool to study APAP-induced toxicity due to its similar structure yet non-toxic profile. A wide array of biochemical techniques are utilized in my lab as well as with my collaborators. Those most commonly applied include: tissue culture, microarray processing, immunoblotting, siRNA, mass spectrometry, qRT-PCR. Pathways that are currently under investigation include apoptosis, MAPK cascades, and growth factor signaling.