Guselkumab treatment normalizes the stratum corneum ceramide profile and alleviates barrier dysfunction in psoriasis: results of a randomized controlled trial.

INTRODUCTION: The epidermal inflammation associated with psoriasis drives skin barrier perturbations. The skin barrier is primarily located in stratum corneum (SC). Its function depends on the SC lipid matrix of which ceramides constitute important components. Changes in the ceramide profile directly correlate to barrier function. In this study, we characterized the dynamics of the barrier function and ceramide profile of psoriatic skin during anti-Interleukin-23 therapy with guselkumab. METHODS: We conducted a double-blind, randomized controlled trial in which 26 mild-to-severe plaque psoriasis patients were randomization 3:1 to 100mg guselkumab or placebo for 16 weeks and barrier dynamics monitored throughout. Barrier function was measured by trans-epidermal Water loss measurements. Untargeted ceramide profiling was performed using liquid chromatography-mass spectrometry after SC was harvested using tape-stripping. RESULTS: The barrier function and ceramide profile of lesional skin normalized to that of controls during treatment with guselkumab, but not placebo. This resulted in significant differences compared to placebo at the end of treatment. Changes in the lesional ceramide profile during treatment correlated with barrier function and target lesion severity. Non-lesional skin remained similar throughout treatment. CONCLUSION: Guselkumab therapy restored the skin barrier in psoriasis. Concomitant correlations between skin barrier function, the ceramide profile and disease severity demonstrate their interdependency.

The effect of membrane thickness on the membrane permeabilizing activity of the cyclic lipopeptide tolaasin II.

Tolaasin II is an amphiphilic, membrane-active, cyclic lipopeptide produced by Pseudomonas tolaasii and is responsible for brown blotch disease in mushroom. To better understand the mode of action and membrane selectivity of tolaasin II and related lipopeptides, its permeabilizing effect on liposomes of different membrane thickness was characterized. An equi-activity analysis served to distinguish between the effects of membrane partitioning and the intrinsic activity of the membrane-bound peptide. It was found that thicker membranes require higher local peptide concentrations to become leaky. More specifically, the mole ratio of membrane-bound peptide per lipid needed to induce 50% leakage of calcein within 1 h, Re 50, increased monotonically with membrane thickness from 0.0016 for the 14:1 to 0.0070 for the 20:1 lipid-chains. Moreover, fast but limited leakage kinetics in the low-lipid regime were observed implying a mode of action based on membrane asymmetry stress in this time and concentration window. While the assembly of the peptide to oligomeric pores of defined length along the bilayer z-axis can in principle explain inhibition by increasing membrane thickness, it cannot account for the observed limited leakage. Therefore, reduced intrinsic membrane-permeabilizing activity with increasing membrane thickness is attributed here to the increased mechanical strength and order of thicker membranes.