Crisaborole Inhibits Itch and Pain by Preventing Neutrophil Infiltration in a Mouse Model of Atopic Dermatitis

Crisaborole, a phosphodiesterase 4 (PDE4) inhibitor, has been approved for the treatment of mild to moderate atopic dermatitis. Atopic dermatitis is often associated with increased pain. Using a mouse model, this study investigated whether crisaborole suppresses pain associated with atopic dermatitis and the potential mechanisms underlying it. The mouse model for atopic dermatitis was developed by repeatedly applying MC903. MC903-treated mice had increased spontaneous scratching (itch-related behaviour) and wiping behaviour (pain-related behaviour). Crisaborole was topically applied to the cheek skin of MC903-treated mice, and it reduced both itch- and pain-related behaviours in these mice. Immunofluorescence staining revealed that crisaborole reduced neutrophil infiltration and interaction of neutrophils with sensory neurones. Intradermal injection of S100A8/A9, proinflammatory neutrophil mediator, enhanced not only itch-related behaviours evoked by histamine or chloroquine, but also pain-related behaviours evoked by capsaicin. Calcium imaging of mouse dorsal root ganglion neurones revealed that pretreatment with S100A8/A9 significantly increased calcium responses to histamine and capsaicin, and the proportion of chloroquine-sensitive neurones. These findings suggest that the PDE4 inhibitor reduces itch and pain, in part by inhibiting infiltration of S100A8/A9-containing neutrophils in a mouse model of MC903-induced atopic dermatitis.

Dynorphinergic Projections from the Central Amygdala to the Parabrachial Nucleus Regulate Itch

The amygdala plays a key role in the processing of itch and pain signals as well as emotion. A previous study revealed that the central nucleus of the amygdala (CeA)-parabrachial nucleus (PBN) pathway is involved in pain regulation. The same pathway might also control itch. To test this possibility, prodynorphin (Pdyn)-Cre mice were used to optogenetically manipulate Pdyn+ CeA-to-PBN projections. We found that optogenetic stimulation of Pdyn+ amygdala neurons or Pdyn+ CeA-to-PBN projections inhibited histamine-evoked and chloroquine-evoked scratching. The number of Fos-positive neurons in the PBN increased following intradermal injection of chloroquine. Optogenetic stimulation of Pdyn+ CeA-to-PBN projections suppressed the increase in Fos expression in the PBN. Optogenetic stimulation of Pdyn+ CeA-to-PBN projections increased thermal and mechanical thresholds without affecting anxiety-like behavior. These results highlight the importance of dynorphinergic projections from the central amygdala to the parabrachial nucleus in the regulation of itch signaling.SIGNIFICANCE STATEMENT The central nucleus of the amygdala (CeA)-parabrachial nucleus (PBN) pathway regulates pain signaling. Using prodynorphin (Pdyn)-cre mice, we investigated the role of Pdyn+ CeA-to-PBN projections in itch. Optogenetic stimulation of Pdyn+ CeA-to-PBN projections inhibited pruritogen-evoked scratching and neuronal activity (c-Fos expression) in the PBN. Together, dynorphinergic projections from the central amygdala to the parabrachial nucleus are important for regulating itch information.

IL-23 modulates histamine-evoked itch and responses of pruriceptors in mice

Accumulating evidence has highlighted the essential roles of cytokines in itch processing. Although IL-23 and Th17 cytokines are elevated in inflammatory skin disorders, their role in itch is unknown. Here, we investigated the role of IL-23 and IL-17A in itch response using an in vitro calcium imaging of mouse dorsal root ganglion (DRG) neurons and an in vivo behaviour test. Calcium imaging studies revealed that a few DRG neurons (~5%) responded to either IL-23 or IL-17A. Pretreatment cells with IL-23 significantly reduced calcium responses to histamine and capsaicin but not chloroquine. Behaviour experiments showed neither IL-23 nor IL-17A evoked scratching. IL-23 significantly decreased histamine-evoked scratching without affecting chloroquine-evoked scratching. There was no difference in scratching between IL-17A- and vehicle-treated groups. These results indicate that IL-23 might play a role in regulating histaminergic itch via modulation of TRPV1 activity.

Ex vivo evaluation of the blood compatibility of mixed matrix haemodialysis membranes

The patients with end stage kidney disease need haemodialysis therapies, using an artificial kidney. Nevertheless, the current therapies cannot remove a broad range of uremic toxins compared to the natural kidney. Adsorption therapies, using sorbent-based columns, can improve the clearance of uremic toxins, but the sorbent particles often require polymeric coatings to improve their haemocompatibility leading to mass transfer limitations and to lowering of their performance. Earlier, we have developed a dual layer Mixed Matrix fiber Membrane (MMM) based on polyethersulfone/polyvinylpyrrolidone (PES/PVP) polymer blends. There, the sorbent activated carbon particles are embedded in the outer membrane layer for achieving higher removal whereas the inner blood contacting selective membrane layer should achieve optimal blood compatibility. In this work, we evaluate in detail the haemocompatibility of the MMM following the norm ISO 10993-4. We study two generations of MMM having different dimensions and transport characteristics; one with low flux and no albumin leakage and another with high flux but some albumin leakage. The results are compared to those of home-made PES/PVP single layer hollow fiber and to various control fibers already applied in the clinic. Our results show that the low flux MMM successfully avoids contact of blood with the activated carbon and has good haemocompatibility, comparable to membranes currently used in the clinic. STATEMENT OF SIGNIFICANCE: Haemodialysis is a life-sustaining extracorporeal treatment for renal disease, however a broad range of uremic toxins cannot still be removed. In our previous works we showed that a double layer Mixed Matrix Membrane (MMM) composed of polyethersulfone/polyvinylpyrrolidone and activated carbon can achieve higher removal of uremic toxics compared to commercial haemodialysers. In this work we evaluate the haemocompatibility profile of the MMM in order to facilitate its clinical implementation. The lumen particle-free layer of the MMM successfully avoids the contact of blood with the poorly blood-compatible activated carbon. Moreover, thanks to the high amount of polyvinylpyrrolidone and to the smoothness of the lumen layer, the MMM has very good haemocompatibility, comparable to membranes currently used in the clinic.

Why does stress aggravate itch? A possible role of the amygdala

Stress is the exacerbating factor of itch across patients with chronic itch due to different origins. However, the precise mechanisms behind stress-induced exacerbation of itch remain unknown. Chronic stress induces hyperexcitability of the amygdala, the centre of emotional processing. Recent findings on the itch neuronal pathways support a pivotal role of the amygdala for itch processing. We hypothesized that itch is enhanced by stress through hyperexcitation of the amygdala. Modulation of amygdala activity, therefore, may have therapeutic potential in the treatment of chronic itch.

Carbon Adsorbents With Dual Porosity for Efficient Removal of Uremic Toxins and Cytokines from Human Plasma

The number of patients with chronic kidney disease increases while the number of available donor organs stays at approximately the same level. Unavoidable accumulation of the uremic toxins and cytokines for these patients comes as the result of malfunctioning kidneys and their high levels in the blood result in high morbidity and mortality. Unfortunately, the existing methods, like hemodialysis and hemofiltration, provide only partial removal of uremic toxins and/or cytokines from patients' blood. Consequently, there is an increasing need for the development of the extracorporeal treatments which will enable removal of broad spectrum of uremic toxins that are usually removed by healthy kidneys. Therefore, in this work we developed and tested ordered mesoporous carbons as new sorbents with dual porosity (micro/meso) that provide selective and efficient removal of a broad range of uremic toxins from human plasma. The new sorbents, CMK-3 are developed by nanocasting methods and have two distinct pore domains, i.e. micropores and mesopores, therefore show high adsorption capacity towards small water soluble toxins (creatinine), protein-bound molecules (indoxyl sulfate and hippuric acid), middle molecules (β-2-microglobulin) and cytokines of different size (IL-6 and IL-8). Our results show that small amounts of CMK-3 could provide selective and complete blood purification.