Opioid Analgesia in P450 Gene Cluster Knockout Mice: A Search for Analgesia-Relevant Isoforms

Regulatory lipid vicinal diols counteract the biological activity of epoxy fatty acids and can act as biomarkers and mechanisms for disease progression

Polyunsaturated fatty acids (PUFAs) are essential fatty acids required for human health and are obtained primarily from food or synthesized in the body by highly regulated processes. The metabolites of these lipids, formed largely through the action of cyclooxygenase, lipoxygenase, or cytochrome P450 (CYP450) enzymes, are responsible for multiple biological functions including inflammation, tissue repair, cell proliferation, blood vessel permeability, and immune cell behavior. The role of these regulatory lipids in disease has been well studied since their discovery as druggable targets; however, the metabolites generated downstream of these pathways have only recently gained attention for regulating biology. Specifically, the biological activity of lipid vicinal diols formed from the metabolism of CYP450-generated epoxy fatty acids (EpFA) by epoxide hydrolases were previously thought to have little biological activity but increasingly are recognized as promoting inflammation and brown fat adipogenesis, and exciting neurons through the regulation of ion channel activity at low concentrations. These metabolites also appear to balance the action of the EpFA precursor. For example, EpFA demonstrate the ability to resolve inflammation and reduce pain, while some lipid diols, through opposing mechanisms, promote inflammation and pain. This review describes recent studies that highlight the role of regulatory lipids, focusing on the balance between EpFA and their diol metabolites in promoting or resolving disease.

Assessing cytochrome P450 function using genetically engineered mouse models

The ability to knock out and/or humanize different genes in experimental animals, globally or in cell- and tissue-specific patterns, has revolutionized scientific research in many areas. Genetically engineered mouse models, including knockout models, transgenic models, and humanized models, have played important roles in revealing the in vivo functions of various cytochrome P450 (CYP) enzymes. These functions are very diverse, ranging from the biotransformation of drugs and other xenobiotics, events that often dictate their pharmacokinetic or toxicokinetic properties and the associated therapeutic or adverse actions, to the metabolism of endogenous compounds, such as steroid hormones and other bioactive substances, that may determine susceptibility to many diseases, such as cancer and metabolic diseases. In this review, we provide a comprehensive list of Cyp-knockout, human CYP-transgenic, and CYP-humanized mouse models that target genes in the CYP1-4 gene families, and highlight their utility in assessing the in vivo metabolism, bioactivation, and toxicity of various xenobiotic compounds, including therapeutic agents and chemical carcinogens. We aim to showcase the advantages of utilizing these mouse models for in vivo drug metabolism and toxicology studies, and to encourage and facilitate greater utility of engineered mouse models to further improve our knowledge of the in vivo functions of various P450 enzymes, which is integral to our ability to develop safer and more effective therapeutics and to identify individuals predisposed to adverse drug reactions or environmental diseases.

Endogenous Opiates and Behavior: 2016

This paper is the thirty-ninth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2016 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia, stress and social status, tolerance and dependence, learning and memory, eating and drinking, drug abuse and alcohol, sexual activity and hormones, pregnancy, development and endocrinology, mental illness and mood, seizures and neurologic disorders, electrical-related activity and neurophysiology, general activity and locomotion, gastrointestinal, renal and hepatic functions, cardiovascular responses, respiration and thermoregulation, and immunological responses.