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Summary Posttranslational modification of metazoan nucleocytoplasmic proteins with N-acetylglucosamine (O-GlcNAc) is essential, dynamic, and inducible and can compete with protein phosphorylation in signal transduction. Inhibitors of O-GlcNAcase, the enzyme removing O-GlcNAc, are useful tools for studying the role of O-GlcNAc in a range of cellular processes. We report the discovery of nanomolar OGA inhibitors that are up to 900,000-fold selective over the related lysosomal hexosaminidases. When applied at nanomolar concentrations on live cells, these cell-penetrant molecules shift the O-GlcNAc equilibrium toward hyper-O-GlcNAcylation with EC50 values down to 3 nM and are thus invaluable tools for the study of O-GlcNAc cell biology., Highlights ► Structure-guided design of human O-GlcNAcase inhibitors, GlcNAcstatins ► The GlcNAcstatins are competitive, nanomolar inhibitors ► The molecular basis of the exquisite selectivity revealed by crystallography ► First direct evidence of O-GlcNAcase inhibitors penetrating cells

1. The extracellular proteins caeruloplasmin and transferrin have important antioxidant properties by virtue of the fact that they inhibit iron-dependent free radical production, and ensuing damage to cells. 2. Albumin is a plasma protein which can loosely bind iron, but the redox activity of this iron has not been fully investigated. 3. The ability of albumin to bind iron and to prevent iron-dependent lipid peroxidation in vitro was investigated using liposomes and a rat brain homogenate system. 4. The iron-binding capacity of albumin was found to be substantial, and albumin inhibited lipid peroxidation in a concentration-dependent manner in both systems used. 5. This antioxidant property of albumin may be especially important in the plasma of babies born prematurely, in whom transferrin and caeruloplasmin concentrations are often very low, and in whom non-transferrin-bound iron has been detected in the plasma.

We have previously shown that peroxisome proliferator activating receptor ß/δ (PPAR β/δ is overexpressed in psoriasis. PPAR β/δ is not present in adult epidermis of mice. Targeted expression of PPAR β/δ and activation by a selective synthetic agonist is sufficient to induce an inflammatory skin disease resembling psoriasis. Several signalling pathways dysregulated in psoriasis are replicated in this model, suggesting that PPAR β/δ activation contributes to psoriasis pathogenesis. Thus, inhibition of PPAR β/δ might harbour therapeutical potential. Since PPAR β/δ has pleiotropic functions in metabolism, skin-targeted inhibition offer the potential of reducing systemic adverse effects. Here, we report that three selective PPAR β/δ antagonists, GSK0660, compound 3 h, and GSK3787 can be formulated for topical application to the skin and that their skin concentration can be accurately quantified using ultra-high performance liquid chromatography (UPLC)/mass spectrometry. These antagonists show efficacy in our transgenic mouse model in reducing psoriasis-like changes triggered by activation of PPAR β/δ. PPAR β/δ antagonists GSK0660 and compound 3 do not exhibit systemic drug accumulation after prolonged application to the skin, nor do they induce inflammatory or irritant changes. Significantly, the irreversible PPAR β/δ antagonist (GSK3787) retains efficacy when applied topically only three times per week which could be of practical clinical usefulness. Our data suggest that topical inhibition of PPAR β/δ to treat psoriasis may warrant further exploration.