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Fluoxetine is a safe antidepressant with remarkable anti‐inflammatory actions; therefore, we aimed to investigate its effects on immortalized (HaCaT) as well as primary human epidermal keratinocytes in a polyinosinic‐polycytidylic acid (p(I:C))‐induced inflammatory model. We found that a non‐cytotoxic concentration (MTT‐assay, CyQUANT‐assay) of fluoxetine significantly suppressed p(I:C)‐induced expression and release of several pro‐inflammatory cytokines (Q‐PCR, cytokine array, ELISA), and it decreased the release of the itch mediator endothelins (ELISA). These effects were not mediated by the inhibition of the NF‐κB or p38 MAPK pathways (western blot), or by the suppression of the p(I:C)‐induced elevation of mitochondrial ROS production (MitoSOX Red labeling). Instead, unbiased activity profiling revealed that they were most likely mediated via the inhibition of the phosphoinositide 3‐kinase (PI3K) pathway. Importantly, the PI3K‐inhibitor GDC0941 fully mimicked the effects of fluoxetine (Q‐PCR, ELISA). Although fluoxetine was able to occupy the binding site of GDC0941 (in silico molecular docking), and exerted direct inhibitory effect on PI3K (cell‐free PI3K activity assay), it exhibited much lower potency and efficacy as compared to GDC0941. Finally, RNA‐Seq analysis revealed that fluoxetine deeply influenced the transcriptional alterations induced by p(I:C)‐treatment, and exerted an overall anti‐inflammatory activity. Collectively, our findings demonstrate that fluoxetine exerts potent anti‐inflammatory effects, and suppresses the release of the endogenous itch mediator endothelins in human keratinocytes, most likely via interfering with the PI3K pathway. Thus, clinical studies are encouraged to explore whether the currently reported beneficial effects translate in vivo following its topical administration in inflammatory and pruritic dermatoses. [ABSTRACT FROM AUTHOR]

Successful curative treatment of severe pulmonary arterial hypertension with luminal obliteration will require a thorough understanding of the mechanism underlying the development and progression of pulmonary vascular lesions. But the cells that obliterate the pulmonary arterial lumen in severe pulmonary arterial hypertension are incompletely characterized. The goal of our study was to evaluate whether inhibition of CXC chemokine receptor 4 will prevent the accumulation of c-kit+ cells and severe pulmonary arterial hypertension. We detected c-kit+­ cells expressing endothelial (von Willebrand Factor) or smooth muscle cell/myofibroblast (α-smooth muscle actin) markers in pulmonary arterial lesions of SU5416/chronic hypoxia rats. We found increased expression of CXC chemokine ligand 12 in the lung tissue of SU5416/chronic hypoxia rats. In our prevention study, AMD3100, an inhibitor of the CXC chemokine ligand 12 receptor, CXC chemokine receptor 4, only moderately decreased pulmonary arterial obliteration and pulmonary hypertension in SU5416/chronic hypoxia animals. AMD3100 treatment reduced the number of proliferating c-kit+ α-smooth muscle actin+ cells and pulmonary arterial muscularization and did not affect c-kit+ von Willebrand Factor+ cell numbers. Both c-kit+ cell types expressed CXC chemokine receptor 4. In conclusion, our data demonstrate that in the SU5416/chronic hypoxia model of severe pulmonary hypertension, the CXC chemokine receptor 4-expressing c-kit+ α-smooth muscle actin+ cells contribute to pulmonary arterial muscularization. In contrast, vascular lumen obliteration by c-kit+ von Willebrand Factor+ cells is largely independent of CXC chemokine receptor 4. [ABSTRACT FROM AUTHOR]