Reactive skin is characterized by marked sensitivity to physical (heat, cold, wind) or chemical (topically applied products) stimuli and by the impairment of the skin barrier's ability to repair itself. Several lines of evidence suggest that beyond their capacity to positively influence the composition of intestinal microbiota, some probiotic bacteria can modulate the immune system both at local and systemic levels, thereby improving immune defense mechanisms and ⁄ or down-regulating immune disorders such as allergies and intestinal inflammation. Several recent human clinical trials clearly suggest that probiotic supplementation might be beneficial to the skin. Using a probiotic lysate, Bifidobacterium longum sp. extract (BL), we demonstrated first in vitro, and then in a clinical trial, that this non-replicating bacteria form applied to the skin was able to improve sensitive skin. The effect of BL were evaluated first on two different models. Using ex vivo human skin explant model we found a statistically significant improvement versus placebo in various parameters associated with inflammation such as a decrease in vasodilation, oedema, mast cell degranulation and TNF-alpha release. Moreover, using nerve cell cultures in vitro, we showed that after 6 h of incubation in culture medium (0.3-1%), the probiotic lysate significantly inhibited capsaicin-induced CGRP release by neurones. Then, a topical cream containing the active extract was tested in a randomized, double-blind, placebocontrolled trial. Sixty-six female volunteers with reactive skin were randomly given either the cream with the bacterial extract at 10% (n = 33) or the control cream (n = 33). The volunteers applied the cream to the face, arms and legs twice a day for two months.Skin sensitivity was assessed by stinging test (lactic acid) and skin barrier recovery was evaluated by measuring trans-epidermal water loss following barrier disruption induced by repeated tapestripping at D1, D29 and D57. The results demonstrated that the volunteers who applied the cream with bacterial extract had a significant decrease in skin sensitivity at the end of the treatment. Moreover, the treatment led to increase skin resistance against physical and chemical aggression compared to the group of volunteers who applied the control cream. Notably, the number of strippings required to disrupt skin barrier function was significantly increased for volunteers treated with the active cream. Clinical and self-assessment scores revealed a significant decrease in skin dryness after 29 days for volunteers treated with the cream containing the 10% bacterial extract. Since in vitro studies demonstrated that, on one hand, isolate sensitive neurones release less CGRP under capsaicin stimulation in the presence of the bacterial extract and, on the other hand, increased skin resistance in volunteers applying the test cream, we speculate that this new ingredient may decrease skin sensitivity by reducing neurone reactivity and neurone accessibility. The results of this studi...
In order to define the respective involvement of steroidogenesis enzymes subtypes in the control of hair follicle homeostasis, we evaluated, by semiquantitative RT/PCR, the expression levels of mRNAs coding for 17 β-hydroxysteroid dehydrogenase type 1 and type 2, 3β-hydroxysteroid dehydrogenase, Cyt.P450-aromatase, steroid 5α-reductase type 1 and type 2 and 11 β-hydroxysteroid dehydrogenase. These assays were performed for several components of the pilosebaceous unit (PSU); fresh plucked anagen hairs, sebaceous glands and primary culture of dermal papilla, as well as other tissues involved in an active steroid metabolism (human testis, liver, placenta, prostate, ovary, uterus and adrenals) as controls. We found that plucked hair (i.e. mainly keratinocytes from the inner and outer root sheaths) expressed: (1) very high levels of 17β-hydroxysteroid dehydrogenase type 2 corresponding to levels found in liver and placenta; (2) high levels of steroid 5-α-reductase type 1 corresponding to levels found in testis, liver and ovary, and moderate levels of 17 β-hydroxysteroid dehydrogenase type 1, which corresponded to the expression in testis, prostate and uterus. In contrast, Cyt.P450-aromatase, 3β-hydroxysteroid dehydrogenase and steroid 5α-reductase type 2 were poorly expressed in the pilosebaceous unit as compared with other tissues. Interestingly, expression patterns of these enzymes in primary cultures of dermal papilla were distinctive since 5α-reductase type 1 and 11 β-hydroxysteroid dehydrogenase were the only mRNA detected. Taken together, these results suggest that not only sebaceous gland but also outer root sheath keratinocytes may contribute, through the activity of the steroid 5α-reductase type 1, to the pathogenesis of androgen-dependent alopecia.
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