A Mobile Health App for Facilitating Disease Management in Children With Atopic Dermatitis: Feasibility and Impact Study.

BACKGROUND: Inadequate control of atopic dermatitis (AD) increases the frequency of exacerbations and reduces the quality of life. Mobile health apps provide information and communication technology and may increase treatment adherence and facilitate disease management at home. The mobile health app, Atopic App, designed for patients and their caregivers, and the associated web-based patient education program, Atopic School, provide an opportunity for improving patients' and caregivers' engagement and adherence to the management of AD. OBJECTIVE: This noninterventional, observational study aimed to explore the feasibility and potential impact on the management of AD in children by caregivers using the Atopic App mobile health app. METHODS: The patient-oriented eczema measure (POEM) and numerical rating scale for the grading of pruritus were used as severity scores (scale range: 0-28). The artificial intelligence model of the app was used to assess the severity of AD based on the eczema area and severity index approach. The deidentified data enabled the analysis of the severity of AD, treatment plan history, potential triggers of flare-ups, usage of available features of the app, and the impact of patient education. RESULTS: During a 12-month period, of the 1223 users who installed the app, 910 (74.4%) registered users were caregivers of children with AD. The web-based Atopic School course was accessed by 266 (29.2%) caregivers of children with AD, 134 (50.4%) of whom completed the course. Usage of the app was significantly more frequent among those who completed the Atopic School program than among those who did not access or did not complete the course (P<.001). Users who completed a second POEM 21 to 27 days apart exhibited a significant improvement of AD severity based on the POEM score (P<.001), with an average improvement of 3.86 (SD 6.85) points. The artificial intelligence severity score and itching score were highly correlated with the POEM score (r=0.35 and r=0.52, respectively). CONCLUSIONS: The Atopic App provides valuable real-world data on the epidemiology, severity dynamics, treatment patterns, and exacerbation-trigger correlations in patients with AD. The significant reduction in the POEM score among users of the Atopic App indicates a potential impact of this tool on health care engagement by caregivers of children with AD.

ABCA4 is an N-retinylidene-phosphatidylethanolamine and phosphatidylethanolamine importer.

ATP-binding cassette (ABC) transporters comprise a superfamily of proteins, which actively transport a variety of compounds across cell membranes. Mammalian and most eukaryotic ABC transporters function as exporters, flipping or extruding substrates from the cytoplasmic to the extracellular or lumen side of cell membranes. Prokaryotic ABC transporters function either as exporters or importers. Here we show that ABCA4, an ABC transporter found in retinal photoreceptor cells and associated with Stargardt macular degeneration, is a novel importer that actively flips N-retinylidene-phosphatidylethanolamine from the lumen to the cytoplasmic leaflet of disc membranes, thereby facilitating the removal of potentially toxic retinoid compounds from photoreceptors. ABCA4 also actively transports phosphatidylethanolamine in the same direction. Mutations known to cause Stargardt disease decrease N-retinylidene-phosphatidylethanolamine and phosphatidylethanolamine transport activity of ABCA4. These studies provide the first direct evidence for a mammalian ABC transporter that functions as an importer and provide insight into mechanisms underlying substrate transport and the molecular basis of Stargardt disease.

Nuclear magnetic resonance-based quantification of organic diphosphates.

Phosphorylated compounds are ubiquitous in life. Given their central role, many such substrates and analogs have been prepared for subsequent evaluation. Prior to biological experiments, it is typically necessary to determine the concentration of the target molecule in solution. Here we describe a method where concentrations of stock solutions of organic diphosphates and bisphosphonates are quantified using (31)P nuclear magnetic resonance (NMR) spectroscopy with standard instrumentation using a capillary tube with a secondary standard. The method is specific and is applicable down to a concentration of 200 µM. The capillary tube provides the reference peak for quantification and deuterated solvent for locking.

Evaluation of alkyne-modified isoprenoids as chemical reporters of protein prenylation.

Protein prenyltransferases catalyze the attachment of C15 (farnesyl) and C20 (geranylgeranyl) groups to proteins at specific sequences localized at or near the C-termini of specific proteins. Determination of the specific protein prenyltransferase substrates affected by the inhibition of these enzymes is critical for enhancing knowledge of the mechanism of such potential drugs. Here, we investigate the utility of alkyne-containing isoprenoid analogs for chemical proteomics experiments by showing that these compounds readily penetrate mammalian cells in culture and become incorporated into proteins that are normally prenylated. Derivatization via Cu(I) catalyzed click reaction with a fluorescent azide reagent allows the proteins to be visualized and their relative levels to be analyzed. Simultaneous treatment of cells with these probes and inhibitors of prenylation reveals decreases in the levels of some but not all of the labeled proteins. Two-dimensional electrophoretic separation of these labeled proteins followed by mass spectrometric analysis allowed several labeled proteins to be unambiguously identified. Docking experiments and density functional theory calculations suggest that the substrate specificity of protein farnesyl transferase may vary depending on whether azide- or alkyne-based isoprenoid analogs is employed. These results demonstrate the utility of alkyne-containing analogs for chemical proteomic applications.

Selective labeling of polypeptides using protein farnesyltransferase via rapid oxime ligation.

An aldehyde-containing alternative substrate for protein farnesyltransferase was prepared and shown to be enzymatically incorporated into a peptide and a protein. The protein was subsequently immobilized onto aminooxy-functionalized agarose beads or labeled with a fluorophore. This method for protein modification provides an alternative to the commonly employed Cu(I)-catalyzed click reaction.

Synthesis, properties, and applications of diazotrifluropropanoyl-containing photoactive analogs of farnesyl diphosphate containing modified linkages for enhanced stability.

Photoactive analogs of farnesyl diphosphate (FPP) are useful probes in studies of enzymes that employ this molecule as a substrate. Here, we describe the preparation and properties of two new FPP analogs that contain diazotrifluoropropanoyl photophores linked to geranyl diphosphate via amide or ester linkages. The amide-linked analog (3) was synthesized in 32P-labeled form from geraniol in seven steps. Experiments with Saccharomyces cerevisiae protein farnesyltransferase (ScPFTase) showed that 3 is an alternative substrate for the enzyme. Photolysis experiments with [(32)P]3 demonstrate that this compound labels the beta-subunits of both farnesyltransferase and geranylgeranyltransferase (types 1 and 2). However, the amide-linked probe 3 undergoes a rearrangement to a photochemically unreactive isomeric triazolone upon long term storage making it inconvenient to use. To address this stability issue, the ester-linked analog 4 was prepared in six steps from geraniol. Computational analysis and X-ray crystallographic studies suggest that 4 binds to protein farnesyl transferase (PFTase) in a similar fashion as FPP. Compound 4 is also an alternative substrate for PFTase, and a 32P-labeled form selectively photocrosslinks the beta-subunit of ScPFTase as well as E. coli farnesyldiphosphate synthase and a germacrene-producing sesquiterpene synthase from Nostoc sp. strain PCC7120 (a cyanobacterial source). Finally, nearly exclusive labeling of ScPFTase in crude E. coli extract was observed, suggesting that [32P]4 manifests significant selectivity and should hence be useful for identifying novel FPP-utilizing enzymes in crude protein preparations.

Synthesis and reactivity of 6,7-dihydrogeranylazides: reagents for primary azide incorporation into peptides and subsequent staudinger ligation.

Protein farnesyltransferase (PFTase) catalyzes the attachment of a geranylazide moiety to a peptide substrate, N-dansyl-GCVIA. Because geranylazide is actually a mixture of isomeric, interconverting primary and secondary azides, incorporation of this isoprenoid into peptides can potentially result in a corresponding mixture of prenylated peptides. Here, we first examined the reactivity of geranyl azide in a model Staudinger reaction and determined that a mixture of products is formed. We then describe the synthesis of 6,7-dihydrogeranylazide diphosphate and demonstrate that this compound allows exclusive incorporation of a primary azide into a peptide. The resulting azide-containing peptide was derivatized with a triphenylphosphine-based reagent to generate an O-alkyl imidate-linked product. Finally, we show, using a series of model reactions, that the Staudinger ligation frequently produces small amounts of O-alkyl imidate products in addition to the major amide-linked products. Thus, the alkoxyimidates we have observed as the exclusive products in the reactions of peptides containing prenylated azides also appear to be a common type of product formed using other azide-containing reactants, although at greatly reduced levels. This method for chemical modification of the C-terminus of a protein should be useful for a variety of applications in protein chemistry.