Marked improvement induced in photoaged skin of hairless mouse by ER36009, a novel RARgamma-specific retinoid, but not by ER35794, an RXR-selective agonist

Alterations in microRNA expression in stress-induced cellular senescence

We investigated miRNA expression changes associated with stress-induced premature senescence (SIPS) in primary cultures of human diploid fibroblast (HDF) and human trabecular meshwork (HTM) cells. Twenty-five miRNAs were identified by miRNA microarray analysis and their changes in expression were validated by TaqMan real-time RT-PCR in three independent cell lines of HTM and HDF. SIPS in both HTM and HDF cell types was associated with significant down-regulation of four members of the miR-15 family and five miRNAs of the miR-106b family located in the oncogenic clusters miR-17-92, miR-106a-363, and miR-106b-25. SIPS was also associated with up-regulation of two miRNAs (182 and 183) from the miR-183-96-182 cluster. Transfection with miR-106a agomir inhibited the up-regulation of p21(CDKN1A) associated with SIPS while transfection with miR-106a antagomir led to increased p21(CDKN1A) expression in senescent cells. In addition, we identified retinoic acid receptor gamma (RARG) as a target of miR-182 and showed that this protein was down-regulated during SIPS in HDF and HTM cells. These results suggest that changes in miRNA expression might contribute to phenotypic alterations of senescent cells by modulating the expression of key regulatory proteins such as p21(CDKN1A) as well as by targeting genes that are down-regulated in senescent cells such as RARG.

Alitretinoin: a comprehensive review

BACKGROUND

Alitretinoin (9-cis-retinoic acid) is a unique panagonist retinoid, capable of binding to all six known retinoid receptors (RAR-alpha, -beta, -gamma, and RXR-alpha, -beta, -gamma). Studies are being carried out to determine how best to utilize this characteristic in treatments for conditions such as chronic hand dermatitis.

OBJECTIVE

To review the literature on alitretinoin.

METHODS

The scope of the review encompasses ways that alitretinoin is currently and may potentially be utilized.

RESULTS/CONCLUSIONS

Orally administered alitretinoin is a safe and effective treatment for chronic hand dermatitis. Topical treatment with alitretinoin can be expanded into other areas such as photoaged skin and cutaneous T-cell lymphoma. Despite these benefits, oral alitretinoin will face a difficult path attaining approval for use in the US.

K6PC-5, a novel sphingosine kinase activator, improves long-term ultraviolet light-exposed aged murine skin

Sphingosine-1-phosphate (S1P), which is formed by phosphorylation of sphingosine through a process catalysed by sphingosine kinase (SK), is a multifunctional mediator of a variety of cellular responses including proliferation, differentiation, motility, and survival. K6PC-5, which was recently synthesized as a novel SK activator, is expected to increase S1P levels. Indeed studies have already demonstrated that K6PC-5 exhibits anti-aging effects on intrinsic aged murine skin by increasing fibroblasts, collagen synthesis, dermal thickness, and epidermal differentiation. However, photoaging and intrinsic aging have highly different clinical and histopathological properties. In this study, we developed a photoaged murine model by exposing mice that were 56 weeks old to ultraviolet (UV)B and UVA radiation for 8 weeks. We then investigated whether K6PC-5, as an SK activator, had anti-aging effects on photoaged murine skin in addition to its effects on intrinsic aged murine skin and determined the mechanism. K6PC-5 increased dermal collagen density in photoaged skin through increases in fibroblasts and collagen production. Photoaged murine skin treated with K6PC-5 showed an increase in stratum corneum (SC) integrity with increased corneodesmosome density and an improvement in barrier recovery rate. Matrix metalloproteinase 13 remained unchanged. These results indicate that topical application of K6PC-5 improves photoaged skin by improving skin barrier and increasing fibroblast count and function. In conclusion, K6PC-5, as an S1P activator, improves long-term UV-exposed aged skin as well as intrinsic aged skin.