Poria cocos Extract from Mushrooms Stimulates Aquaporin-3 via the PI3K/Akt/mTOR Signaling Pathway

Background

Poria cocos (PC), a fungus, has been used for more than 2000 years as a food and medicine in China. PC and its components have various pharmacological effects on the skin, including immunomodulatory activities, barrier function improvement, and anti-tumor effects. However, the effect of PC in aquaporin-3 (AQP3) expression, which is essential for epidermal water permeability barrier maintenance, was not reported.

Methods

This study examined the mechanism through which the ethanol extract of the sclerotium of PC (EPC) promoted the expression of AQP3 in cultured human keratinocytes. Western blotting was used to investigate the expression of AQPs and the activation of phosphoinositide 3-kinase (PI3K)/Akt-related signaling molecules in HaCaT cells. Cells were treated with inhibitors of PI3K/Akt and mechanistic target of rapamycin (mTOR) prior to EPC treatment.

Results

EPC promoted the expression of AQP3 in HaCaT cells without affecting AQP1 and AQP2 expression. Phosphorylated Akt levels were increased by EPC treatment, and the inhibition of PI3K by LY2940002 resulted in a reduction in EPC-induced AQP3 expression. Furthermore, EPC stimulated the phosphorylation of p70S6K and Akt^Ser473, which are downstream targets of mTORC1 and mTORC2, respectively. The mTOR complex inhibitors, rapamycin and Torin 1, partially reduced EPC-induced AQP3 expression.

Conclusion

These results suggest that EPC increased expression of AQP3, which is important for skin moisturization, by activating the PI3K/Akt/mTOR signaling pathway in human keratinocytes.

dDAVP Downregulates the AQP3-Mediated Glycerol Transport via V1aR in Human Colon HCT8 Cells

Vasopressin (AVP) plays a key function in controlling body water and salt balance through the activation of the vasopressin receptors V1aR and V2R. Abnormal secretion of AVP can cause the syndrome of inappropriate antidiuresis that leads to hyponatremia, which is an electrolyte disorder often observed in the elderly hospitalized and oncologic patients. Beyond kidneys, the colonic epithelium modulates water and salt homeostasis. The water channel AQP3, expressed in villus epithelial cells is implicated in water absorption across human colonic surface cells. Here, the action of dDAVP, a stable vasopressin analog, was evaluated on the AQP3 expression and function using human colon HCT8 cells as an experimental model. Confocal and Western Blotting analysis revealed that HCT8 cells express both V1aR and V2R. Long-term (72 h) treatment with dDAVP reduced glycerol uptake and cell viability. These effects were prevented by SR49059, a synthetic antagonist of V1aR, but not by tolvaptan, a specific V2R antagonist. Of note, the SR49059 action was impaired by DFP00173, a selective inhibitor of AQP3. Interestingly, compared to the normal colonic mucosa, in the colon of patients with adenocarcinoma, the expression of V1aR was significantly decreased. These findings were confirmed by gene expression analysis with RNA-Seq data. Overall, data suggest that dDAVP, through the V1aR dependent pathway, reduces AQP3 mediated glycerol uptake, a process that is reversed in adenocarcinoma, suggesting that the AVP-dependent AQP3 pathway may represent a novel target in colon diseases associated with abnormal cell growth.

18ß-glycyrrhetinic acid derivative promotes proliferation, migration and aquaporin-3 expression in human dermal fibroblasts

Licorice (Glycyrrhiza) species have been widely used as a traditional medicine and a natural sweetener in foods. The 18β-glycyrrhetinic acid (18β-GA) is a bioactive compound in licorice that exhibits potential anti-cancer, anti-inflammatory, and anti-microbial activities. Many synthesized derivatives of 18β-GA have been reported to be cytotoxic and suggested for the treatment of malignant diseases. In this study, we explored the possible pharmacological roles of an 18β-GA derivative in skin biology using primary human dermal fibroblasts and HaCaT keratinocytes as cell models. We found that this 18β-GA derivative did not cause cell death, but significantly enhanced the proliferation of dermal fibroblasts and HaCaT keratinocytes. A scratch wound healing assay revealed that the 18β-GA derivative promoted the migration of fibroblasts. Due to the important role of aquaporin-3 in cell migration and proliferation, we also investigated the expression of aquaporin-3 and found this compound up-regulated the expression of aquaporin-3 in dermal fibroblasts and HaCaT keratinocytes. In dermal fibroblasts, the 18β-GA derivative induced the phosphorylation of Akt, ERK, and p38. The inhibitor of Akt predominantly suppressed the 18β-GA derivative-induced expression of aquaporin-3. Collectively, this compound had a positive effect on the proliferation, migration, and aquaporin-3 expression of skin cells, implying its potential role in the treatment of skin diseases characterized by impaired wound healing or dermal defects.

Regulation of the Glycerol Transporter, Aquaporin-3, by Histone Deacetylase-3 and p53 in Keratinocytes

Aquaporin- (AQP) 3, a water and glycerol channel, plays an important role in epidermal function, with studies showing its involvement in keratinocyte proliferation, differentiation, and migration and in epidermal wound healing and barrier repair. Increasing speculation about the use of histone deacetylase (HDAC) inhibitors to treat skin diseases led us to investigate HDAC's role in the regulation of AQP3. The broad-spectrum HDAC inhibitor suberoylanilide hydroxamic acid induced AQP3 mRNA and protein expression in a dose- and time-dependent manner in normal keratinocytes. The SAHA-induced increase in AQP3 levels resulted in enhanced [³H]glycerol uptake in normal but not in AQP3-knockout keratinocytes, confirming that the expressed AQP3 was functional. Use of HDAC inhibitors with different specificities limited our exploration of the responsible HDAC member to HDAC1, HDAC2, or HDAC3. Cre-recombinase-mediated knockdown and overexpression of HDAC3 suggested a role for HDAC3 in suppressing AQP3 expression basally. Further investigation implicated p53 as a transcription factor involved in regulating HDAC inhibitor-induced AQP3 expression. Thus, our study supports the regulation of AQP3 expression by HDAC3 and p53. Because suberoylanilide hydroxamic acid is already approved to treat cutaneous T-cell lymphoma, it could potentially be used as a therapy for skin diseases like psoriasis, where AQP3 is abnormally expressed.

Ginseng in traditional herbal prescriptions

Panax ginseng Meyer has been widely used as a tonic in traditional Korean, Chinese, and Japanese herbal medicines and in Western herbal preparations for thousands of years. In the past, ginseng was very rare and was considered to have mysterious powers. Today, the efficacy of drugs must be tested through well-designed clinical trials or meta-analyses, and ginseng is no exception. In the present review, we discuss the functions of ginseng described in historical documents and describe how these functions are taken into account in herbal prescriptions. We also discuss the findings of experimental pharmacological research on the functions of ginseng in ginseng-containing prescriptions and how these prescriptions have been applied in modern therapeutic interventions. The present review on the functions of ginseng in traditional prescriptions helps to demystify ginseng and, as a result, may contribute to expanding the use of ginseng or ginseng-containing prescriptions.

Gypsum fibrosum and its major component CaSO4 increase cutaneous aquaporin-3 expression levels

ETHNOPHARMACOLOGICAL RELEVANCE

We have previously reported that Byakkokaninjinto improves cutaneous pruritus by increasing the expression level of aquaporin-3 (AQP3). In this study, we examined the effect of Gypsum fibrosum (main component: CaSO(4)), which is the main component of Byakkokaninjinto, on the cutaneous AQP3 expression level.

MATERIALS AND METHODS

KKAy mice were given a diet containing 0.3% Gypsum fibrosum extract, or a diet containing 0.3% CaSO(4) for 4 weeks. The urine volume, plasma glucose levels, cutaneous AQP3 protein expression, and the Ca(2+) content were measured.

RESULTS

The 24-h urine volumes and the plasma glucose levels in the Gypsum fibrosum extract group were not significantly different from those in the control group. In the Gypsum fibrosum extract group, the cutaneous AQP3 protein levels increased significantly, by approximately 3.2-fold, compared to the control group. The cutaneous Ca(2+) content in the control group was approximately 35μg/g. In the Gypsum fibrosum extract group, the Ca(2+) content increased to approximately 51μg/g, which was significant compared to the control group. In the CaSO(4) group, an increase in the AQP3 protein expression levels and Ca(2+) content were observed; the extent of these increases were similar to those in the Gypsum fibrosum extract group.

CONCLUSIONS

The results of this study suggest that Gypsum fibrosum plays an important role in the increased levels of cutaneous AQP3 expression enhanced by Byakkokaninjinto. The results also indicate that the increase in AQP3 caused by Gypsum fibrosum is attributable to an increase in the cutaneous Ca(2+) content from its main component, CaSO(4).

Inhibitory Effect of Polyphenol-Rich Fraction from the Bark of Acacia mearnsii on Itching Associated with Allergic Dermatitis

We examined the inhibitory effect of polyphenol-rich aqueous extract from the bark of Acacia mearnsii (PrA) on itching associated with atopic dermatitis (AD). HR-1 mice were fed a normal diet, special diet (AD group), or special diet containing 3% PrA (PrA group) for 6 weeks. In the AD group, itching frequency and transepidermal water loss increased compared to the control group. In the PrA group, an improvement in atopic dermatitis symptoms was observed. Ceramide expression in the skin decreased in the AD group compared to the control group, but no decrease was observed in the PrA group. mRNA expression of ceramidase decreased in the PrA group compared to the AD group. The results of this study have revealed that PrA inhibits itching in atopic dermatitis by preventing the skin from drying. It is considered that the mechanism by which PrA prevents the skin from drying involves the inhibition of increased ceramidase expression associated with atopic dermatitis.