Synthesis and activity of the salicylic acid ester of bakuchiol in psoriasis-surrogate keratinocytes and skin substitutes

BACKGROUND

Topical retinoids are effective in retarding skin ageing and restoring homeostasis in skin conditions such as psoriasis. However their adverse effects (AEs), which include irritation (retinoid dermatitis), photosensitivity and teratogenicity, limit their use and patient compliance. Development of retinoid analogues with minimal AEs would allow a broader and more compliant use.

AIM

To synthesise a novel molecule, bakuchiol salicylate (bakusylan), with a modulatory gene expression profile similar to retinoids, using as reference three prescription retinoids: tretinoin, tazarotene and adapalene.

METHODS

We hypothesized that because bakuchiol salicylate has a structure entirely different from existing retinoids, there would be at least a partial uncoupling of AEs from the skin-normalizing activity of this retinoid. This hypothesis was tested at the transcriptional level in psoriatic cytokine-treated cultures of keratinocytes and organotypic skin substitutes, using DNA microarrays and custom PCR arrays.

RESULTS

Evaluation of the gene expression profile of bakuchiol salicylate revealed elimination of several components of the retinoid-like proinflammatory response and teratogenic signature, without a substantial loss of normalizing potential. A possible mechanism of action, consisting of keratinocyte desensitization to psoriatic cytokine signalling through inhibition of the signal transducer and regulator of transcription (STAT)1/3/interferon inflammatory signal transduction axis was also identified.

CONCLUSION

Bipartite materials obtained by merging two skin-active entities with specific, complementary bioactivities, such as bakuchiol and salicylic acid, may yield a new class of functional retinoids.

Early tissue responses in psoriasis to the antitumour necrosis factor-α biologic etanercept suggest reduced interleukin-17 receptor expression and signalling

BACKGROUND

Antitumour necrosis factor (anti-TNF)-α therapy has made a significant impact on the treatment of psoriasis. Despite these agents being designed to neutralize TNF-α activity, their mechanism of action in the resolution of psoriasis remains unclear.

OBJECTIVES

To understand better the mechanism of action of etanercept by examining very early changes in the lesional skin of patients with psoriasis responding to etanercept.

METHODS

Twenty patients with chronic plaque psoriasis were enrolled and received etanercept 50 mg twice weekly. Skin biopsies were obtained before treatment and on days 1, 3, 7 and 14 post-treatment. Skin mRNA expression was analysed by quantitative reverse-transcription polymerase chain reaction and microarray; cytokine and phosphoprotein levels were assessed using multiplexed bead arrays.

RESULTS

In etanercept responders, we observed no significant changes in interleukin (IL)-17A, IL-22 or interferon-γ mRNA or protein in the first week of treatment; however, there was a 2·5-fold downregulation of IL-17 receptor C (IL-17RC) mRNA (P < 0·05) after day 1, accompanied by decreased extracellular signal-regulated kinase-1/2 phosphorylation. Transcriptional analysis revealed that genes suppressed by etanercept significantly overlapped with IL-17A-induced genes, and a marked overlap was also observed between the genes suppressed by etanercept and by the anti-IL-17A agent ixekizumab. Finally we show that TNF-α enhances the expression of IL-17RC, and short hairpin RNA inhibition of IL-17R expression abrogates synergistic gene induction by TNF and IL-17A.

CONCLUSIONS

These results suggest that the early responses of psoriasis plaques to etanercept may be due to decreased tissue responsiveness to IL-17A due to suppressed IL-17RC expression in keratinocytes, blunting the strong synergy between TNF-α and IL-17, which contributes to the maintenance of psoriasis lesions.

Plastic and adaptive gene expression patterns associated with temperature stress in Arabidopsis thaliana

Transcriptional profiling using DNA microarrays has become a widely used approach for identifying genes with important roles in stress-regulatory networks. In previous studies, genes exhibiting a plastic expression pattern with respect to stress and control treatments have been identified as candidates with putative roles in stress-response pathways. This approach, however, often identifies numerous genes, and it is difficult to discern which genes have major effects that impact the fitness of individuals under stress. In this study, we investigated the impacts of temperature stress (cold and heat) on gene expression in the Arabidopsis thaliana model system. We identified genes exhibiting plastic patterns of gene expression with respect to temperature stress, but in contrast to previous studies, we also considered the adaptive significance of genes by examining their expression patterns among 10 Arabidopsis ecotypes indigenous to a range of latitudes. Our findings support a general association between plasticity of gene expression and adaptive value. In comparison to non-plastic genes, genes exhibiting plastic expression patterns were associated with greater among-ecotype variation in expression levels, and such variation was more strongly correlated with geographical temperature gradients. Surprisingly, while more than 16,000 genes were associated with plastic expression patterns, significant evidence of both expression plasticity and adaptive value was obtained for only 43 genes. These selected genes represent strong candidates for future experimental investigations into the molecular basis of temperature acclimation in the A. thaliana model system.

Reduced inbreeding depression due to historical inbreeding in Drosophila melanogaster: evidence for purging

An important issue in conservation biology and the study of evolution is the extent to which inbreeding depression can be reduced or reversed by natural selection. If the deleterious recessive alleles causing inbreeding depression can be 'purged' by natural selection, outbred populations that have a history of inbreeding are expected to be less susceptible to inbreeding depression. This expectation, however, has not been realized in previous laboratory experiments. In the present study, we used Drosophila melanogaster as a model system to test for an association between inbreeding history and inbreeding depression. We created six 'purged' populations from experimental lineages that had been maintained at a population size of 10 male-female pairs for 19 generations. We then measured the inbreeding depression that resulted from one generation of full-sib mating in the purged populations and in the original base population. The magnitude of inbreeding depression in the purged populations was approximately one-third of that observed in the original base population. In contrast to previous laboratory experiments, therefore, we found that inbreeding depression was reduced in populations that have a history of inbreeding. The large purging effects observed in this study may be attributable to the rate of historical inbreeding examined, which was slower than that considered in previous experiments.