The drug discovery and development process is greatly hampered by difficulties in translating in vitro potency to in vivo efficacy. Recent studies suggest that the long-neglected drug-target residence time parameter complements classical drug affinity parameters (KI, Kd, IC50, or EC50) and is a better predictor of in vivo efficacy. Compounds with a long drug-target residence time are often more efficacious in vivo. The impact, however, of the drug-target residence time on in vivo efficacy remains controversial due to difficulties in experimentally determining the in vivo target occupancy during drug treatment. To tackle this problem, an in vivo displacement assay was developed using soluble epoxide hydrolase as a biological model. In this report, we experimentally demonstrated that drug-target residence time affects the duration of in vivo drug-target binding. In addition, the drug-target residence time plays an important role in modulating the rate of drug metabolism which also affects the efficacy of the drug.
BackgroundThe carbohydrate portions of salivary glycoproteins play important roles, including mediating bacterial and leukocyte adhesion. Salivary glycosylation is complex. Many of its glycoproteins present ABO and Lewis blood group determinants. An individual’s genetic complement and secretor status govern the expression of blood group antigens. We queried the extent to which salivary glycosylation varies according to blood group and secretor status. First, we screened submandibular/sublingual and parotid salivas collected as ductal secretions for reactivity with a panel of 16 lectins. We selected three lectins that reacted with the largest number of glycoproteins and one that recognized uncommon lactosamine-containing structures. Ductal salivas representing a secretor with complex blood group expression and a nonsecretor with a simple pattern were separated by SDS-PAGE. Gel slices were trypsin digested and the glycopeptides were individually separated on each of the four lectins. The bound fractions were de-N-glycosylated. LC–MS/MS identified the original glycosylation sites, the peptide sequences, and the parent proteins.ResultsThe results revealed novel salivary N-glycosites and glycoproteins not previously reported. As compared to the secretor, nonsecretor saliva had higher levels of N-glycosylation albeit with simpler structures.ConclusionsTogether, the results suggested a molecular basis for inter-individual variations in salivary protein glycosylation with functional implications for oral health.Electronic supplementary materialThe online version of this article (doi:10.1186/s12014-015-9100-y) contains supplementary material, which is available to authorized users.
Soluble epoxide hydrolase (sEH) is an important therapeutic target of many diseases, such as chronic obstructive pulmonary disease (COPD) and diabetic neuropathic pain. It acts by hydrolyzing and thus regulating specific bioactive long chain polyunsaturated fatty acid epoxides (lcPUFA), like epoxyeicosatrienoic acids (EETs). To better predict which epoxides could be hydrolyzed by sEH, one needs to dissect the important factors and structural requirements that govern the binding of the substrates to sEH. This knowledge allows further exploration of the physiological role played by sEH. Unfortunately, a crystal structure of sEH with a substrate bound has not yet been reported. In this report, new photoaffinity mimics of a sEH inhibitor and EET were prepared and used in combination with peptide sequencing and computational modeling, to identify the binding orientation of different regioisomers and enantiomers of EETs into the catalytic cavity of sEH. Results indicate that the stereochemistry of the epoxide plays a crucial role in dictating the binding orientation of the substrate.
When developing a new drug, it is difficult to predict from in vitro parameters to in vivo efficacy. It is generally accepted that drugs with the strong interactions with their target are more likely to show better efficacy. Therefore, thermodynamic parameter: dissociation constant or inhibition constant (Ki) are often considered as the most important factor to be determined as the first screening to prioritize the drug candidates. However, the kinetic parameter: the dissociation rate constant (koff) of the drugs is often neglected although several reports suggested that koff is as important as or more than Ki to estimate in vivo efficacy. Soluble epoxide hydrolase (sEH) has been proven to play an important role on regulating important lipid mediators, epoxy‐polyunsaturated fatty acid. Inhibition of sEH has been showed to be beneficial to human health in several aspects, anti‐inflammatory, analgesic and promoting tissue regeneration. We recently synthesized a series of new sEH inhibitors with different Kis and koffs. These inhibitors will be used as tools to test if koff can predict in vivo efficacy as equal as or better than the Ki. Here, a series of inhibitors with improved in vitro efficacy will be reported. Our in vivo results suggested that koff is crucial parameters to affect drug efficacy in an alternate way. Grant Funding Source: National Institute of Environ‐ mental Health Sciences (NIEHS) grant ES002710
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