Author Correction: Structure-Activity Relationships of Baicalein and its Analogs as Novel TSLP Inhibitors.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Structure-Activity Relationships of Baicalein and its Analogs as Novel TSLP Inhibitors.

Thymic stromal lymphopoietin (TSLP) plays an important role in the differentiation and proliferation of Th2 cells, resulting in eosinophilic inflammation and numerous allergic diseases. Baicalein (1), a major component of Scutellaria baicalensis, was found to be the first small molecule to block TSLP signaling pathways. It inhibited effectively eosinophil infiltration in house dust mite-induced and ovalbumin-challenged mouse models. Structure-activity relationship studies identified compound 11a, a biphenyl flavanone analog, as a novel human TSLP inhibitor for the discovery and development of new anti-allergic drugs.

Development of Cassette PAMPA for Permeability Screening.

The parallel artificial membrane permeability assay (PAMPA) is widely used in early-stage drug discovery to discriminate compounds by intestinal permeability. The purpose of the current study was to establish a cassette (n-in-1) PAMPA to enable permeability screening of lipophilic compounds. A double-sink PAMPA consisting of a pH gradient (i.e., pH 6.5 and 7.4 for the donor and receiver compartments, respectively) and a lipophilic sink (i.e., a surfactant in the receiver solution) was utilized with cassette incubation of 10 reference compounds. Sample analysis was conducted using selected reaction monitoring (SRM) with a triple quadrupole LC-MS/MS system. Correlation between PAMPA permeability and human intestinal absorption (HIA) of the reference compounds yielded two false negatives, namely propranolol (PPN) and verapamil (VER); these two compounds showed a substantially lower recovery (ca. 10%) than other reference compounds (>69%). This cassette PAMPA was repeated subsequently with polysorbate 80 added to the donor compartments, which resulted in a significant increase in both the recovery and the permeability of the false negatives. Accordingly, the permeability class of all reference compounds could be unambiguously differentiated using this cassette PAMPA. Also, a strong linear correlation (r=0.9845) was observed between the cassette and discrete permeability of all reference compounds.

Analogues of Dehydroacetic Acid as Selective and Potent Agonists of an Ectopic Odorant Receptor through a Combination of Hydrophilic and Hydrophobic Interactions.

Identification of potent agonists of odorant receptors (ORs), a major class of G protein-coupled receptors, remains challenging due to complex receptor-ligand interactions. ORs are present in both olfactory and non-chemosensory tissues, indicating roles beyond odor detection that may include modulating physiological functions in non-olfactory tissues. Selective and potent agonists specific for particular ORs can be used to investigate physiological functions of ORs in non-chemosensory tissues. In this study, we designed and synthesized novel synthetic dehydroacetic acid analogues as agonists of odorant receptor 895 (Olfr895) expressed in bladder. Among the synthesized analogues, (E)-3-((E)-1-hydroxy-3-(piperidin-1-yl)allylidene)-6-methyl-2H-pyran-2,4(3H)-dione (10) exhibited extremely high agonistic activity for Olfr895 in Dual-Glo luciferase reporter (EC50 =9 nm), Ca2+ imaging, and chemotactic migration assays. Molecular docking and site-directed mutagenesis studies suggested that a combination of hydrophilic and hydrophobic interactions is central to the selective and specific binding of 10 to Olfr895. The design of agonists armed with both hydrophilic and hydrophobic portions could therefore lead to highly potent and selective ligands for ectopic ORs.