Novel Henna-Related Naphthazarine Photosensitizers for an Effective Photodynamic Therapy of Onychomycosis.

Onychomycosis caused by, e.g., Trichophyton rubrum or Candida albicans is the most common human nail disease with a worldwide prevalence of more than 10%. The therapeutic efficacy of topical antimycotics for the treatment of onychomycosis proved to be inadequate in numerous studies on patients. The main reasons are, above all, the poor bioavailability of the active ingredients in the nail compartment, causing the requirement for extremely long application periods and correspondingly high demands on adherence by the patient. In the present study, we aimed to develop a more effective and prompt photodynamic approach for the treatment of onychomycosis. The principle of photodynamic therapy (PDT) for onychomycosis has already been investigated. However, these studies used photosensitizers such as methylene blue, which were neither optimized for their keratinophilic features nor for their bioavailability in the nail. Hence, we initiated a screening campaign using T. rubrum and C. albicans cell-based assays, infected bovine keratin models, and keratin-penetrating irradiation to identify suitable hit compounds for a PDT approach toward onychomycosis. Here, we report on the discovery of Henna/Lawson-derived keratinophilic naphthazarines that act as highly potent PDT antimycotic photosensitizers with photoresponsiveness when irradiated by light at a keratin-permeable wavelength (>500 nm, e.g., compounds 10 and 11 with PDT-IC50 = 1 and 3 nM, respectively, against T. rubrum), hence with superior efficacy than the positive controls nystatin and clotrimazole. Notably, our photodynamic approach not only affected the actual pathogens but also prevented reinfection of keratin models within 10 days, suggesting an additional efficacy against fungal spores. Compared to established concepts, our proposed PDT approach using the novel naphthazarine photosensitizers could enable an effective, precise, and sustainable therapy option for the future treatment of onychomycosis.

Zebrafish as model system for the biological characterization of CK1 inhibitors.

Introduction: The CK1 family is involved in a variety of physiological processes by regulating different signaling pathways, including the Wnt/ß-catenin, the Hedgehog and the p53 signaling pathways. Mutations or dysregulation of kinases in general and of CK1 in particular are known to promote the development of cancer, neurodegenerative diseases and inflammation. There is increasing evidence that CK1 isoform specific small molecule inhibitors, including CK1δ- and CK1ε-specific inhibitors of Wnt production (IWP)-based small molecules with structural similarity to benzimidazole compounds, have promising therapeutic potential. Methods: In this study, we investigated the suitability of the zebrafish model system for the evaluation of such CK1 inhibitors. To this end, the kinetic parameters of human CK1 isoforms were compared with those of zebrafish orthologues. Furthermore, the effects of selective CK1δ inhibition during zebrafish embryonic development were analyzed in vivo. Results: The results revealed that zebrafish CK1δA and CK1δB were inhibited as effectively as human CK1δ by compounds G2-2 with IC50 values of 345 and 270 nM for CK1δA and CK1δB versus 503 nM for human CK1δ and G2-3 exhibiting IC50 values of 514 and 561 nM for zebrafish CK1δA and B, and 562 nM for human CK1δ. Furthermore, the effects of selective CK1δ inhibition on zebrafish embryonic development in vivo revealed phenotypic abnormalities indicative of downregulation of CK1δ. Treatment of zebrafish embryos with selected inhibitors resulted in marked phenotypic changes including blood stasis, heart failure, and tail malformations. Conclusion: The results suggest that the zebrafish is a suitable in vivo assay model system for initial studies of the biological relevance of CK1δ inhibition.

Newly Developed CK1-Specific Inhibitors Show Specifically Stronger Effects on CK1 Mutants and Colon Cancer Cell Lines.

Protein kinases of the CK1 family can be involved in numerous physiological and pathophysiological processes. Dysregulated expression and/or activity as well as mutation of CK1 isoforms have previously been linked to tumorigenesis. Among all neoplastic diseases, colon and rectal cancer (CRC) represent the fourth leading cause of cancer related deaths. Since mutations in CK1δ previously found in CRC patients exhibited increased oncogenic features, inhibition of CK1δ is supposed to have promising therapeutic potential for tumors, which present overexpression or mutations of this CK1 isoform. Therefore, it is important to develop new small molecule inhibitors exhibiting higher affinity toward CK1δ mutants. In the present study, we first characterized the kinetic properties of CK1δ mutants, which were detected in different tumor entities. Subsequently, we characterized the ability of several newly developed IWP-based inhibitors to inhibit wild type and CK1δ mutants and we furthermore analyzed their effects on growth inhibition of various cultured colon cancer cell lines. Our results indicate, that these compounds represent a promising base for the development of novel CRC therapy concepts.