Anti‐inflammatory control of human skin keratinocytes by targeting nuclear transport checkpoint

Background In the two common inflammatory skin diseases, Atopic Dermatitis (AD) and Psoriasis (Ps), keratinocytes (KCs) respond to immune insults through activation of proinflammatory transcription factors (TFs) and their translocation to the cell’s nucleus. Therein, the TFs induce expression of genes encoding mediators of skin inflammation. The Nuclear Transport Checkpoint Inhibitors (NTCIs) were developed to regulate nuclear translocation of activated TFs, the essential step of inflammatory response. This new class of cell‐penetrating peptide therapeutics controls inflammation caused by allergic, autoimmune, metabolic, and microbial insults. In preclinical model of AD, the treatment with NTCI, cSN50.1 peptide, suppressed the expression of Thymic Stromal Lymphopoietin (TSLP), the key gene in the development of allergic inflammation, among the 15 genes silenced by the NTCI. Here, we report the mechanism of anti‐inflammatory action of NTCI in human skin‐derived KCs. Objectives We aimed to determine whether the NTCI treatment can protect human KCs from harmful inflammatory insults. Methods Human primary KCs were pretreated with NTCI and challenged with the mix of cytokines Tumour Necrosis Factor alpha (TNF‐α) and Interleukin (IL)‐17A, or with Phorbol 12‐Myristate 13‐Acetate (PMA), and analysed for nuclear content of TFs and the expression of genes encoding mediators of inflammation. Results The nuclear import of TFs, Nuclear Factor ĸB (NF‐ĸB) and Signal Transduction and Activator of Transcription 3 (STAT3), was inhibited in cells treated with NTCI. The expression of TSLP, along with genes encoding the core mediators of inflammation (TNF, IL1B, and IL6) was suppressed by NTCI. Noteworthy, NTCI silenced genes encoding Granulocyte‐Macrophage Colony‐Stimulating Factor (CSF2), and chemokine IL‐8 (CXCL8), responsible for skin infiltration by the eosinophils and other myelomonocytic cells. Conclusion The control of inflammatory response in human KCs by NTCI is attributed to the inhibition of nuclear import of proinflammatory TFs. The protection of human KCs by NTCI, adds new perspectives to the completed Phase two clinical trial of the NTCI (AMTX‐100 CF) for AD (NCT04313400). Here we report previously unknown mechanism of the response of human primary, skin‐derived, keratinocytes (KCs) to proinflammatory insults. We found that the Nuclear Transport Checkpoint Inhibitor (NTCI), our Investigational New Drug, arrested the nuclear import of STAT3, the transcription fac