To investigate the effects of topically applied 17beta-estradiol on the expression of extracellular matrix proteins in aged human skin, 17beta-estradiol (0.01%) and its vehicle (70% propylene glycol, 30% ethanol) were applied to aged (68-82 y, eight females and five males) human buttock skin under occlusion for 2 wk (three times per week). Topical 17beta-estradiol was found to increase the expression of type 1 procollagen mRNA and protein significantly in human aged skin in vivo. In addition, metalloproteinase (MMP-1 protein levels were reduced by topical 17beta-estradiol. The expressions of TGF-beta1, TGF-beta type II receptor, and Sma and Mad related (Smad)3 were increased by topical 17 beta-estradiol in aged human skin, and TGF-beta1 neutralizing antibody inhibited 17beta-estradiol-induced procollagen synthesis in cultured fibroblasts. We also found that the expressions of tropoelastin and fibrillin-1 mRNA and protein, and elastic fibers in aged skin were also increased by topical 17beta-estradiol. Topical 17beta-estradiol also increased keratinocyte proliferation and the epidermal thickness in aged human skin. We also observed the same effects of topical 17beta-estradiol in young skin. In conclusion, our results suggest that topical 17beta-estradiol treatment may improve the cutaneous function of aged human skin by improving the connective tissue and increasing epidermal thickness.

Several recent reports have demonstrated that photoreceptors are expressed in human skin. The rod and cone photoreceptor-like proteins are expressed in human skin and rhodopsin, long wavelength-opsin, and short wavelength-opsin are also present in cultured murine melanocytes. Furthermore, the photopigment rhodopsin is expressed in human melanocytes and is involved in ultraviolet A phototransduction which induces early melanin synthesis. In this study, we investigated whether rhodopsin is expressed and plays any physiological roles in the normal human epidermal keratinocytes (NHEKs). We found that rhodopsin was expressed and localized on the plasma membrane in NHEKs, and only violet light among several wavelengths within the visible range significantly increased the expression of rhodopsin mRNA. We further found that rhodopsin over-expression decreased the mRNA expression levels of keratinocyte differentiation markers, such as keratin-1 and keratin-10, and violet light also decreased the mRNA expression levels of keratinocyte differentiation markers and these decreased expression levels were recovered by a rhodopsin-directed siRNA. Moreover, we further demonstrated that violet light significantly decreased the phosphorylation levels of cAMP responsive element-binding protein (CREB) and that it more effectively decreased the phosphorylation of CREB when rhodopsin was over-expressed. In addition, we observed that pertussis toxin, a Gαi protein inhibitor, restored the rhodopsin-induced decrease in the differentiation markers in NHEKs. Taken together, these results suggest that rhodopsin down-regulates the expression levels of specific keratinocyte differentiation markers via the Gαi signaling pathway in NHEKs.

Liver X receptors (LXRs) are nuclear receptors that act as ligand-activated transcription factors regulating lipid metabolism and inflammation. In the skin, activation of LXRs stimulates differentiation of keratinocytes and augments lipid synthesis in sebocytes. However, the function of LXRs in melanocytes remains largely unknown. We investigated whether LXR activation would affect melanogenesis. In human primary melanocytes, MNT-1, and B16 melanoma cells, TO901317, a synthetic LXR ligand, inhibited melanogenesis. Small interfering RNA (siRNA) experiments revealed the dominant role of LXRβ in TO901317-mediated antimelanogenesis. Enzymatic activities of tyrosinase were unaffected, but the expression of tyrosinase, tyrosinase-related protein-1 (TRP-1), and TRP-2 was suppressed by TO901317. Expressions of microphthalmia-associated transcription factor (MITF), a master transcriptional regulator of melanogenesis, and cAMP-responsive element-binding activation were not affected. It is noteworthy that the degradation of MITF was accelerated by TO901317. Extracellular signal-regulated kinase (ERK) contributed to TO901317-induced antimelanogenesis, which was evidenced by recovery of melanogenesis with ERK inhibitor. Other LXR ligands, 22(R)-hydroxycholesterol (22(R)HC) and GW3965, also activated ERK and suppressed melanogenesis. The intermediary role of Ras was confirmed in TO901317-induced ERK phosphorylation. Finally, antimelanogenic effects of TO901317 were confirmed in vivo in UVB-tanning model in brown guinea pigs, providing a previously unreported line of evidence that LXRs may be important targets for antimelanogenesis.

No abstract

Psychological stress (PS) increases endogenous glucocorticoids (GC) by activating the hypothalamic-pituitary-adrenal axis. The negative effects of GC on skin barrier function under PS have been well-established. However, endogenous GC can also be active when cortisone (inactive form) is converted to cortisol (active form) by 11β-hydroxysteroid dehydrogenase type I (11ß-HSD1) in the peripheral tissue. Here, we evaluated the changes in 11ß-HSD1 and barrier function under PS. Elevated 11ß-HSD1 in oral mucosa correlated with increased cortisol in the stratum corneum and deteriorated barrier function. Expression of 11ß-HSD1 in the oral mucosa correlated with that in the epidermal keratinocytes. We further investigated whether barrier function improved when PS was relieved using a selective serotonin reuptake inhibitor (SSRI) in patients with anxiety. Decreased 11ß-HSD1 and improved barrier function were observed after SSRI treatment. The collective findings suggest that elevated 11ß-HSD1 under PS increases the level of cutaneous GC and eventually impairs barrier function. PS-alleviating drugs, such as SSRI, may help to treat PS-aggravated skin diseases.