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Krev interaction trapped protein 1 (KRIT1) is a scaffold protein known to form functional complexes with distinct proteins, including Malcavernin, PDCD10, Rap1 and others. It appears involved in several cellular signaling pathways and exerts a protective role against inflammation and oxidative stress. KRIT1 has been studied as a regulator of endothelial cell functions and represents a determinant in the pathogenesis of Cerebral Cavernous Malformation (CCM), a cerebrovascular disease characterized by the formation of clusters of abnormally dilated and leaky blood capillaries, which predispose to seizures, neurological deficits and intracerebral hemorrhage. Although KRIT1 is ubiquitously expressed, few studies have described its involvement in pathologies other than CCM including cancer. Cutaneous melanoma represents the most fatal skin cancer due to its high metastatic propensity. Despite the numerous efforts made to define the signaling pathways activated during melanoma progression, the molecular mechanisms at the basis of melanoma growth, phenotype plasticity and resistance to therapies are still under investigation., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Alkaptonuria (AKU) is a rare metabolic disease correlated with the deficiency of homogentisate 1,2-dioxygenase and leading to an accumulation of the metabolite homogentisic acid (HGA) which can be subjected to oxidation and polymerization reactions. These events are considered a trigger for the induction of oxidative stress in AKU but, despite the large description of an altered redox status, the underlying pathogenetic processes are still unstudied. In the present study, we investigated the molecular mechanisms responsible for the oxidative damage present in an osteoblast-based cellular model of AKU. Bone, in fact, is largely affected in AKU patients: severe osteoclastic resorption, osteoporosis, even for pediatric cases, and an altered rate of remodeling biomarkers have been reported. In our AKU osteoblast cell model, we found a clear altered redox homeostasis, determined by elevated hydrogen peroxide (H 2 O 2 ) levels and 4HNE protein adducts formation. These findings were correlated with increased NADPH oxidase (NOX) activity and altered mitochondrial respiration. In addition, we observed a decreased activity of superoxide dismutase (SOD) and reduced levels of thioredoxin (TRX) that parallel the decreased Nrf2-DNA binding. Overall, our results reveal that HGA is able to alter the cellular redox homeostasis by modulating the endogenous ROS production via NOX activation and mitochondrial dysfunctions and impair the cellular response mechanism. These findings can be useful for understanding the pathophysiology of AKU, not yet well studied in bones, but which is an important source of comorbidities that affect the life quality of the patients., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Psoriasis is a skin disease characterized by abnormal keratinocyte proliferation and inflammation. Currently, there are no cures for this disease, so the goal of treatment is to decrease inflammation and slow down the associated rapid cell growth and shedding. Recent advances have led to the usage of phosphodiesterase 4 (PDE4) inhibitors for treatment of this condition. For example, apremilast is an oral, selective PDE4 inhibitor that is able to reduce skin inflammation and is Food and Drug Administration (FDA)-approved to treat adults with moderate to severe psoriasis and/or psoriatic arthritis. However, common target-related adverse events, including diarrhea, nausea, headache, and insomnia limit the usage of this drug. To circumvent these effects, the usage of PDE4 inhibitors specifically designed for topical treatment, such as CHF6001, may combine local anti-inflammatory activity with limited systemic exposure, improving tolerability. In this study, we showed that CHF6001, currently undergoing clinical development for COPD, suppresses human keratinocyte proliferation as assessed via BrdU incorporation. We also observed decreased re-epithelialization in a scratch-wound model after CHF6001 treatment. At the molecular level, CHF6001 inhibited translocation of phosphorylated NF-κB subunit p65, promoting loss of nuclear cyclin D1 accumulation and an increase of cell cycle inhibitor p21. Furthermore, CHF6001 decreased oxidative stress, measured by assessing lipid peroxidation (4-HNE adduct formation), through the inactivation of the NADPH oxidase. These results suggest that CHF6001 has the potential to treat skin disorders associated with hyperproliferative keratinocytes, such as psoriasis by targeting oxidative stress, abnormal re-epithelization, and inflammation., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Background: The main functions of the skin are to protect against environmental insults and prevent water loss, which are performed by the complex lipid- and protein matrix present in the outermost layers of the epithelium. The lipidome of these outer layers is mainly composed of ceramides, fatty acids, and cholesterol, which regulates keratinocyte differentiation and skin barrier function. SR-B1 is a multifunctional scavenger receptor that is best known for facilitating uptake of cholesterol from HDL particles in the liver, but it is also expressed in the skin., Objective: To determine the role of SR-B1 in keratinocyte differentiation., Methods: We investigated the relationship between SR-B1 and keratinocyte differentiation using a physiologically relevant model, organotypic skin equivalents (SEs), wherein SR-B1 was knocked down via siRNA transfection. To assess effects of SR-B1 knockdown on keratinocyte differentiation, we performed hematoxylin/eosin staining, RT-PCR, western blotting, and immunohistochemistry. We also examined the effect of SR-B1 knockdown on lipid production by performing Oil Red O staining and thin layer chromatography., Results: SR-B1 knockdown resulted in decreased lipid levels in SEs, specifically ceramides, and in decreased transcript levels of LDLR, PPAR-α and PPAR-γ, which are factors involved in regulating ceramide synthesis. In addition, filaggrin levels increased in SR-B1 KD tissues, but neither keratin 14 nor keratin 10 were affected., Conclusion: We conclude that one of the main functions of SR-B1 in the skin is to regulate ceramide levels and thereby maintain the barrier function of the skin, resulting in the protection of cutaneous tissues from outdoor insults., (Copyright © 2019 Elsevier Inc. All rights reserved.)