Inhibitory Effect of Arctigenin from Fructus Arctii Extract on Melanin Synthesis via Repression of Tyrosinase Expression

Phytochemical analysis, antioxidant, antimicrobial, and anti-enzymatic properties of Alpinia coriandriodora (sweet ginger) rhizome

Alpinia coriandriodora, also known as sweet ginger, is a medicinal and edible plant. A. coriandriodora rhizome is popularly utilized in traditional Chinese medicine and as flavouring spices, but there are few reports on its constituents and bioactivities. This study analyzed the phytochemical components of A. coriandriodora rhizome by GC-MS and UHPLC-Q-Orbitrap-MS and evaluated its antioxidant, antimicrobial, and anti-enzymatic properties. According to the GC-FID/MS data, its rhizome essential oil (EO) consisted mainly of (E)-2-decenal (53.8%), (E)-2-decenyl acetate (24.4%), (Z)-3-dodecenyl acetate (3.5%), and (E)-2-octenal (3.5%). Its water extract (WE) and 70% ethanol extract (EE) showed high total phenolic content (TPC, 52.99-60.49 mg GAEs/g extract) and total flavonoid content (TFC, 260.69-286.42 mg REs/g extract). In addition, the phytochemicals of WE and EE were further characterized using UHPLC-Q-Orbitrap-MS, and a total of sixty-three compounds were identified, including fourteen phenolic components and twenty-three flavonoid compounds. In the antioxidant assay, WE and EE revealed a potent scavenging effect on DPPH (IC50: 6.59 ± 0.88 mg/mL and 17.70 ± 1.15 mg/mL, respectively), surpassing the BHT (IC50: 21.83 ± 0.89 mg/mL). For the antimicrobial activities, EO displayed excellent antibacterial capabilities against Proteus vulgaris, Enterococcus faecalis, Bacillus subtilis, Escherichia coli, and Staphylococcus aureus with DIZ (12.60-22.17 mm), MIC (0.78-1.56 mg/mL), and MBC (3.13 mg/mL) and significantly inhibited Aspergillus flavus growth (MIC = 0.313 mg/mL, MFC = 0.625 mg/mL, respectively). In addition to weak tyrosinase and cholinesterase inhibition, EE and WE had a prominent inhibitory effect against α-glucosidase (IC50: 0.013 ± 0.001 mg/mL and 0.017 ± 0.002 mg/mL), which was significantly higher than acarbose (IC50: 0.22 ± 0.01 mg/mL). Hence, the rhizome of A. coriandriodora has excellent potential for utilization in the pharmaceutical and food fields as a source of bioactive substances.

Anti-Melanogenic Potential of Natural and Synthetic Substances: Application in Zebrafish Model

Melanogenesis is a biosynthetic pathway for the formation of the pigment melanin in human skin. A key enzyme in the process of pigmentation through melanin is tyrosinase, which catalyzes the first and only limiting step in melanogenesis. Since the discovery of its methanogenic properties, tyrosinase has been the focus of research related to the anti-melanogenesis. In addition to developing more effective and commercially safe inhibitors, more studies are required to better understand the mechanisms involved in the skin depigmentation process. However, in vivo assays are necessary to develop and validate new drugs or molecules for this purpose, and to accomplish this, zebrafish has been identified as a model organism for in vivo application. In addition, such model would allow tracking and studying the depigmenting activity of many bioactive compounds, important to genetics, medicinal chemistry and even the cosmetic industry. Studies have shown the similarity between human and zebrafish genomes, encouraging their use as a model to understand the mechanism of action of a tested compound. Interestingly, zebrafish skin shares many similarities with human skin, suggesting that this model organism is suitable for studying melanogenesis inhibitors. Accordingly, several bioactive compounds reported herein for this model are compared in terms of their molecular structure and possible mode of action in zebrafish embryos. In particular, this article described the main metabolites of Trichoderma fungi, in addition to substances from natural and synthetic sources.

Arctigenin-Enriched Burdock Seed Oil (ABSO): A New Skin Brightening Botanical Extract

The Arctium lappa L. plant, commonly known as burdock, has been used therapeutically for hundreds of years. Arctigenin (ATG) is an active ingredient in burdock, albeit at low quantities or mostly in the form of acrtiin (arctigenin-4-glucoside). ATG has been touted for its anti-inflammatory properties in many cell types and disease states; however, its role in skin and melanin production has not been extensively studied. Our aims for this study were to develop a burdock seed extract enriched for ATG that is amenable to quasi-drug development, determine in vitro brightening activity, and evaluate safety and skin brightening efficacy clinically in human subjects. Arctiin and ATG content were measured by high-performance liquid chromatography (HPLC). In vitro studies utilized EpiDermTM tissues for skin irritation test, and MelanoDermTM tissues for melanin reduction capacity. A 45 subject clinical study was performed in adult subjects ranging in age from 30 to 60 years old (mean = 41.9 ± 6.7) to test the safety and skin brightening potential of 1% ABSO lotion. We demonstrate by HPLC that ABSO is a natural extract that contains ~5-times more arctigenin than BSO. Furthermore, ABSO inhibits melanin production better than BSO and retains the same melanin-reducing capacity as synthetic ATG in vitro in MelanoDerm™ 3D skin cultures. ABSO also adheres to quasi-drug criteria according to the Japanese Standards of Quasi-Drug Ingredients as determined by infrared absorption spectrum method, unsaponifiable matter, heavy metal and arsenic content, and acid, saponification, and iodine value methods. Clinical assessment of 1% ABSO lotion shows it is well-tolerated in human skin and demonstrates improved brightness and skin tone evenness. ABSO is a natural arctigenin-enriched burdock seed extract that reduces melanin content in vitro and clinically improves skin brightness.

Plants as Modulators of Melanogenesis: Role of Extracts, Pure Compounds and Patented Compositions in Therapy of Pigmentation Disorders

The kingdom of plants as a "green biofabric" of valuable bioactive molecules has long been used in many ailments. Currently, extracts and pure compounds of plant origin are used to aid in pigmentation skin problems by influencing the process of melanogenesis. Melanin is a very important pigment that protects human skin against ultraviolet radiation and oxidative stress. It is produced by a complex process called melanogenesis. However, disturbances in the melanogenesis mechanism may increase or decrease the level of melanin and generate essential skin problems, such as hyperpigmentation and hypopigmentation. Accordingly, inhibitors or activators of pigment formation are desirable for medical and cosmetic industry. Such properties may be exhibited by molecules of plant origin. Therefore, that literature review presents reports on plant extracts, pure compounds and compositions that may modulate melanin production in living organisms. The potential of plants in the therapy of pigmentation disorders has been highlighted.

The Modulation of Melanogenesis in B16 Cells Upon Treatment with Plant Extracts and Isolated Plant Compounds

Plants are a rich source of secondary metabolites that exhibit numerous desired properties. The compounds may influence the biology of melanocytes, pigment cells that produce melanin, by modulating numerous signaling pathways, including cAMP/PKA, MAPKs and PI3K/AKT. Its downstream target is microphthalmia-associated transcription factor, responsible for the expression of the tyrosinase enzyme, which plays a major role in melanogenesis. Therefore, this literature review aims to provide insights related to melanogenesis modulation mechanisms of plant extracts and isolated plant compounds in B16 cells. Database searches were conducted using online-based library search instruments from 2012 to 2022, such as NCBI-PubMed and Google Scholar. Upregulation or downregulation of signaling pathways by phytochemicals can influence skin hypo- and hyperpigmentation by changing the level of melanin production, which may pose a significant cosmetic issue. Therefore, plant extracts or isolated plant compounds may be used in the therapy of pigmentation disorders.

Antimelanogenesis Effects of Leaf Extract and Phytochemicals from Ceylon Olive (Elaeocarpus serratus) in Zebrafish Model

The melanogenesis inhibition effect in zebrafish (Danio rerio) and antityrosinase activity of the ethanolic extract and its phytochemicals from Ceylon olive (Elaeocarpus serratus Linn.) leaves were investigated in this study. Among the leaf extract and four soluble fractions, the ethyl acetate soluble fraction exhibits the best antityrosinase and antimelanogenesis activities. One phenolic acid, gallic acid, and two flavonoids, myricetin and mearnsetin, are isolated from the active subfractions through the bioassay-guided isolation; their structures are elucidated based on the 1D and 2D NMR, FTIR, UV, and MS spectroscopic analyses. These compounds have significant antityrosinase activity whether using l-tyrosine or l-DOPA as the substrate; mearnsetin shows the optimal activity. In the enzyme kinetic investigation, both gallic acid and mearnsetin are the competitive-type inhibitors against mushroom tyrosinase, and myricetin acts as a mixed-type tyrosinase inhibitor. Leaf extract and an ethyl acetate soluble fraction show effective performance in the inhibition of melanin formation in zebrafish embryos. Mearnsetin also possesses a promising antimelanogenesis effect, which is superior to the positive control, arbutin. Results reveal that the Ceylon olive leaf extract and its phytochemicals, especially mearnsetin, have the potential to be used as antimelanogenesis and skin-whitening ingredients.

Arctium lappa Extract Suppresses Inflammation and Inhibits Melanoma Progression

Background: Arctium lappa has been used as popular medicinal herb and health supplement in Chinese societies. Bioactive components from A. lappa have attracted the attention of researchers due to their promising therapeutic effects. In this study, we investigated the effects of A. lappa hydroalcoholic extract (Alhe) during different models of inflammation, in vivo. Methods: The anti-inflammatory activity was evaluated through the air pouch model. For this, mice received an inflammatory stimulus with lipopolysaccharide (LPS) and were later injected with Alhe. To assess anti-tumoral activity, the animals were inoculated with B16F10 cells and injected with Alhe every 5 days, along the course of 30 days. Controls were submitted to the same conditions and injected with the vehicle. Peritoneal or air pouch fluids were collected to evaluate leukocyte counting or cellular activation via quantification of cytokines and nitric oxide. Results: Alhe injection reduced the neutrophil influx and production of inflammatory mediators in inflammatory foci after LPS or tumor challenges. Furthermore, Alhe injection reduced tumor growth and enhanced mice survival. Conclusions: Collectively, these data suggest that Alhe regulates immune cell migration and activation, which correlates with favorable outcome in mouse models of acute inflammation and melanoma progression.

Discovery of new depigmenting compounds and their efficacy to treat hyperpigmentation: Evidence from in vitro study

Human skin pigmentation is a result of constitutive and facultative pigmentation. Facultative pigmentation is frequently stimulated by UV radiation, pharmacologic drugs, and hormones whereby leads to the development of abnormal skin hyperpigmentation. To date, many state-of-art depigmenting compounds have been studied using in vitro model to treat hyperpigmentation problems for cosmetic dermatological applications; little attention has been made to compare the effectiveness of these depigmenting compounds and their mode of actions. In this present article, new and recent depigmenting compounds, their melanogenic pathway targets, and modes of action are reviewed. This article compares the effectiveness of these new depigmenting compounds to modulate several melanogenesis-regulatory enzymes and proteins such as tyrosinase (TYR), TYR-related protein-1 (TRP1), TYR-related protein-2 (TRP2), microphthalmia-associated transcription factor (MITF), extracellular signal-regulated kinase (ERK) and N-terminal kinases (JNK) and mitogen-activated protein kinase p38 (p38 MAPK). Other evidences from in vitro assays such as inhibition on melanosomal transfer, proteasomes, nitric oxide, and inflammation-induced melanogenesis are also highlighted. This article also reviews analytical techniques in different assays performed using in vitro model as well as their advantages and limitations. This article also provides an insight on recent finding and re-examination of some protocols as well as their effectiveness and reliability in the evaluation of depigmenting compounds. Evidence and support from related patents are also incorporated in this present article to give an overview on current patented technology, latest trends, and intellectual values of some depigmenting compounds and protocols, which are rarely highlighted in the literatures.

A Zebrafish Embryo as an Animal Model for the Treatment of Hyperpigmentation in Cosmetic Dermatology Medicine

For years, clinical studies involving human volunteers and several known pre-clinical in vivo models (i.e., mice, guinea pigs) have demonstrated their reliability in evaluating the effectiveness of a number of depigmenting agents. Although these models have great advantages, they also suffer from several drawbacks, especially involving ethical issues regarding experimentation. At present, a new depigmenting model using zebrafish has been proposed and demonstrated. The application of this model for screening and studying the depigmenting activity of many bioactive compounds has been given great attention in genetics, medicinal chemistry and even the cosmetic industry. Depigmenting studies using this model have been recognized as noteworthy approaches to investigating the antimelanogenic activity of bioactive compounds in vivo. This article details the current knowledge of zebrafish pigmentation and its reliability as a model for the screening and development of depigmenting agents. Several methods to quantify the antimelanogenic activity of bioactive compounds in this model, such as phenotype-based screening, melanin content, tyrosinase inhibitory activity, other related proteins and transcription genes, are reviewed. Depigmenting activity of several bioactive compounds which have been reported towards this model are compared in terms of their molecular structure and possible mode of actions. This includes patented materials with regard to the application of zebrafish as a depigmenting model, in order to give an insight of its intellectual value. At the end of this article, some limitations are highlighted and several recommendations are suggested for improvement of future studies.

Arctii Fructus Inhibits Colorectal Cancer Cell Proliferation and MMPs Mediated Invasion via AMPK

Although Arctii Fructus (AF) has been shown to have various pharmacological effects, there have been no studies concerning the inhibitory effects of AF on the metastatic properties of colorectal cancer (CRC). The aim of this study was to investigate whether AF could suppress CRC progression by inhibiting cell growth, epithelial-mesenchymal transition (EMT), migration, and the invasion ability of CRC cells. AF decreased proliferation of CRC cells by inducing cell cycle arrest and apoptosis via extrinsic and intrinsic apoptotic pathways. Regarding metastatic properties, AF inhibited EMT by increasing the expression of the epithelial marker, E-cadherin, and decreasing the expression of the mesenchymal marker, N-cadherin, in CT26 cells. Moreover, AF decreased the migration and invasion of CT26 cells by inhibiting matrix metalloproteinase-2 (MMP-2) and MMP-9 activity. We confirmed that the decreased invasion ability and MMP-9 activity by AF treatment involved AMP-activated protein kinase (AMPK) activation. Collectively, this study demonstrates that AF inhibits the proliferation and metastatic properties of CRC cells.

N-(4-methoxyphenyl) caffeamide-induced melanogenesis inhibition mechanisms

Background

The derivative of caffeamide exhibits antioxidant and antityrosinase activity. The activity and mechanism of N-(4-methoxyphenyl) caffeamide (K36E) on melanogenesis was investigated.

Methods

B16F0 cells were treated with various concentrations of K36E; the melanin contents and related signal transduction were studied. Western blotting assay was applied to determine the protein expression, and spectrophotometry was performed to identify the tyrosinase activity and melanin content.

Results

Our results indicated that K36E reduced α-melanocyte-stimulating hormone (α-MSH)-induced melanin content and tyrosinase activity in B16F0 cells. In addition, K36E inhibited the expression of phospho-cyclic adenosine monophosphate (cAMP)-response element-binding protein, microphthalmia-associated transcription factor (MITF), tyrosinase, and tyrosinase-related protein-1 (TRP-1). K36E activated the phosphorylation of protein kinase B (AKT) and glycogen synthase kinase 3 beta (GSK3β), leading to the inhibition of MITF transcription activity. K36E attenuated α-MSH induced cAMP pathways, contributing to hypopigmentation.

Conclusions

K36E regulated melanin synthesis through reducing the expression of downstream proteins including p-CREB, p-AKT, p-GSK3β, tyrosinase, and TRP-1, and activated the transcription factor, MITF. K36E may have the potential to be developed as a skin whitening agent.

Modifying effects of carboxyl group on the interaction of recombinant S100A8/A9 complex with tyrosinase

Tyrosinase is a determinant enzyme for modulating melanin production as its abnormal activity can result in an increased amount of melanin. Reduction of tyrosinase activity has been targeted for preventing and healing hyperpigmentation of skin, such as melanoma and age related spots. The aim of this systematic study is to investigate whether recombinant S100A8/A9 and its modified form reduce the activity of mushroom tyrosinase (MT) through changing its structure. Recombinant His-Tagged S100A8 and S100A9 are expressed in Escherichia coli BL21 (DE3) and modified using Woodward's reagent K which is a carboxyl group modifier. The structures of S100A8/A9 and its modified form are studied using fluorescence and circular dichroism spectroscopy, and the activity of MT is measured using UV-visible spectrophotometry in the presence of its substrate, L-3,4-dihydroxyphenylalanine (L-DOPA). The results show a lower stability of the modified protein when compared with its unmodified form. The interaction of S100A8/A9 with MT changes the structure and successfully reduces the activity of mushroom tyrosinase. Recombinant S100A8/A9 complex decreases MT activity which can control malignant melanoma, the most dangerous type of skin cancer.

Isolation of 4,5-O-Dicaffeoylquinic Acid as a Pigmentation Inhibitor Occurring in Artemisia capillaris Thunberg and Its Validation In Vivo

There is a continual need to develop novel and effective melanogenesis inhibitors for the prevention of hyperpigmentation disorders. The plant Artemisia capillaris Thunberg (Oriental Wormwood) was screened for antipigmentation activity using murine cultured cells (B16-F10 malignant melanocytes). Activity-based fractionation using HPLC and NMR analyses identified the compound 4,5-O-dicaffeoylquinic acid as an active component in this plant. 4,5-O-Dicaffeoylquinic acid significantly reduced melanin synthesis and tyrosinase activity in a dose-dependent manner in the melanocytes. In addition, 4,5-O-dicaffeoylquinic acid treatment reduced the expression of tyrosinase-related protein-1. Significantly, we could validate the antipigmentation activity of this compound in vivo, using a zebrafish model. Moreover, 4,5-O-dicaffeoylquinic acid did not show toxicity in this animal model. Our discovery of 4,5-O-dicaffeoylquinic acid as an inhibitor of pigmentation that is active in vivo shows that this compound can be developed as an active component for formulations to treat pigmentation disorders.

Arctigenin Inhibits Adipogenesis by Inducing AMPK Activation and Reduces Weight Gain in High-Fat Diet-Induced Obese Mice

Although arctigenin (ARC) has been reported to have some pharmacological effects such as anti-inflammation, anti-cancer, and antioxidant, there have been no reports on the anti-obesity effect of ARC. The aim of this study is to investigate whether ARC has an anti-obesity effect and mediates the AMP-activated protein kinase (AMPK) pathway. We investigated the anti-adipogenic effect of ARC using 3T3-L1 pre-adipocytes and human adipose tissue-derived mesenchymal stem cells (hAMSCs). In high-fat diet (HFD)-induced obese mice, whether ARC can inhibit weight gain was investigated. We found that ARC reduced weight gain, fat pad weight, and triglycerides in HFD-induced obese mice. ARC also inhibited the expression of peroxisome proliferator-activated receptor gamma (PPARγ) and CCAAT/enhancer-binding protein alpha (C/EBPα) in in vitro and in vivo. Furthermore, ARC induced the AMPK activation resulting in down-modulation of adipogenesis-related factors including PPARγ, C/EBPα, fatty acid synthase, adipocyte fatty acid-binding protein, and lipoprotein lipase. This study demonstrates that ARC can reduce key adipogenic factors by activating the AMPK in vitro and in vivo and suggests a therapeutic implication of ARC for obesity treatment. J. Cell. Biochem. 117: 2067-2077, 2016. © 2016 Wiley Periodicals, Inc.

Development of Tyrosinase Promoter-Based Fluorescent Assay for Screening of Anti-melanogenic Agents

For screening of skin-whitening ingredients that modulate inhibition of melanogenesis, tyrosinase promoter-based assay using a three-dimensional (3D) spheroid culture technique is a beneficial tool to improve the accuracy of raw material screening in cosmetics through mimicking of the in vivo microenvironment. Although the advantages of high-throughput screening (HTS) are widely known, there has been little focus on specific cell-based promoter assays for HTS in identifying skin-whitening ingredients that inhibit accumulation of melanin. The aim of this study was therefore to develop a large-scale compatible assay through pTyr-EGFP, an enhanced green fluorescent protein (EGFP)-based tyrosinase-specific promoter, to seek potential melanogenesis inhibitors for cosmetic use. Herein, a stably transfected human melanoma cell line expressing EGFP under the control of a 2.2-kb fragment derived from the tyrosinase gene was generated. Spontaneous induction of the tyrosinase promoter by 3D spheroid culture resulted in increased expression of EGFP, providing a significant correlation with the tyrosinase mRNA level, and subsequent inhibition of tyrosinase activity. Importantly, the pTyr-EGFP system provided successful tracking of the changes in the live image and real-time monitoring. Thus tyrosinase promoter-based fluorescent assay using a 3D spheroid culture can be useful as a screening system for exploring the efficiency of anti-melanogenesis ingredients.

Anti-melanogenic activity of the novel herbal medicine, MA128, through inhibition of tyrosinase activity mediated by the p38 mitogen-activated protein kinases and protein kinase signaling pathway in B16F10 cells

Background:

Recently, our research group developed MA128, a novel herbal medicine, and demonstrated that MA128 is effective for the treatment of asthma and atopic dermatitis (AD). In particular, postinflammatory hyper-pigmentation in AD mice was improved with MA128 treatment. Thus, in this study, we determined the effect of MA128 on melanogenesis and its underlying mechanism in murine B16F10 melanoma cells.

Materials and Methods:

After treatment with MA128 at 100 and 250 μg/mL and/or alpha-melanocyte stimulating hormone (α-MSH) (1 μM), cellular melanin content and tyrosinase activity in B16F10 cells were measured. Using western blotting, expression levels of tyrosinase, tyrosinase-related protein-1 (TRP-1), TRP-2, microphthalmia-associated transcription factor (MITF), and activation of c-AMP-dependent protein kinase (PKA), c-AMP-related element binding protein (CREB) and mitogen-activated protein kinases (MAPKs) were examined.

Results:

MA128 significantly inhibited melanin synthesis and tyrosinase activity in a resting state as well as α-MSH-stimulating condition, and significantly decreased the expression of tyrosinase, TRP-1, TRP-2 and MITF. In addition, phosphorylation of PKA and CREB by α-MSH stimulation was efficiently blocked by MA128 pretreatment. Moreover, MA128 as an herbal mixture showed synergistic anti-melanogenic effects compared with each single constituent herb.

Conclusion:

MA128 showed anti-melanogenic activity through inhibition of tyrosinase activity mediated by p38 MAPK and PKA signaling pathways in B16F10 cells. These results suggest that MA128 may be useful as an herbal medicine for controlling hyper-pigmentation and as a skin-whitening agent.

Assessment of Cuscuta chinensis seeds׳ effect on melanogenesis: comparison of water and ethanol fractions in vitro and in vivo

ETHNOPHARMACOLOGICAL RELEVANCE

Cuscuta chinensis seeds have traditionally been used to treat freckles and melasma in Asia, although recent reports have revealed that Semen cuscutae is a promoter of melanogenesis. The present study aims to investigate the mechanism of this opposite effect of Semen cuscutae on melanogenesis.

MATERIALS AND METHODS

In accordance with traditional usage, the water fraction and the ethanol fraction from Semen cuscutae (WFSC/EFSC) were extracted to determine the herbal effects by examining the activity of mushroom tyrosinase, cellular melanin contents, tyrosinase activity assay, quantitative-reverse transcription polymerase chain reaction (qRT-PCR), and Western blot analysis for tyrosinase in B16F10 mouse melanoma cells. The melanocyte phenotypes of zebrafish larvae were observed while the in vivo melanin contents and tyrosinase activity were determined.

RESULTS

The activity of mushroom tyrosinase assay shown that WFSC was an uncompetitive inhibitor of mushroom tyrosinase, while EFSC indicated dose-dependent activation of the mushroom tyrosinase activity. The WFSC markedly inhibited 3-isobutyl-1-methylxanthine (IBMX)-stimulated melanin synthesis and tyrosinase activity in vitro. Howeveran accelerant role in melanin synthesis and tyosinase activity. Neither fraction had any effect on the IBMX-induced expression of tyrosinase protein or mRNA. The WFSC strongly inhibited melanin synthesis and cellular tyrosinase activity in vivo. Furthermore, with the function of WFSC at a higher concentration, a punctate melanocyte pattern appeared that was similar to the pattern induced by arbutin or Mequinol (MQ). The EFSC had no effect on the melanocytes of zebrafish larvae. It was discovered that WFSC did not show a stable inhibitory effect until it was extracted 1 month later.

CONCLUSIONS

These results suggest that the opposite effects of Cuscuta chinensis seeds were caused by the extraction methods and that time has an important role on the effect of WFSC. Both WFSC and EFSC significantly influence melanogenesis by regulating enzymatic activity of tyrosinase. In addition, the data indicate that wildtype (WT) zebrafish may be an ideal model for testing inhibitors of melanogenesis from clinically active herbs.

Sho-saiko-to, a traditional herbal medicine, regulates gene expression and biological function by way of microRNAs in primary mouse hepatocytes

BACKGROUND

Sho-saiko-to (SST) (also known as so-shi-ho-tang or xiao-chai-hu-tang) has been widely prescribed for chronic liver diseases in traditional Oriental medicine. Despite the substantial amount of clinical evidence for SST, its molecular mechanism has not been clearly identified at a genome-wide level.

METHODS

By using a microarray, we analyzed the temporal changes of messenger RNA (mRNA) and microRNA expression in primary mouse hepatocytes after SST treatment. The pattern of genes regulated by SST was identified by using time-series microarray analysis. The biological function of genes was measured by pathway analysis. For the identification of the exact targets of the microRNAs, a permutation-based correlation method was implemented in which the temporal expression of mRNAs and microRNAs were integrated. The similarity of the promoter structure between temporally regulated genes was measured by analyzing the transcription factor binding sites in the promoter region.

RESULTS

The SST-regulated gene expression had two major patterns: (1) a temporally up-regulated pattern (463 genes) and (2) a temporally down-regulated pattern (177 genes). The integration of the genes and microRNA demonstrated that 155 genes could be the targets of microRNAs from the temporally up-regulated pattern and 19 genes could be the targets of microRNAs from the temporally down-regulated pattern. The temporally up-regulated pattern by SST was associated with signaling pathways such as the cell cycle pathway, whereas the temporally down-regulated pattern included drug metabolism-related pathways and immune-related pathways. All these pathways could be possibly associated with liver regenerative activity of SST. Genes targeted by microRNA were moreover associated with different biological pathways from the genes not targeted by microRNA. An analysis of promoter similarity indicated that co-expressed genes after SST treatment were clustered into subgroups, depending on the temporal expression patterns.

CONCLUSIONS

We are the first to identify that SST regulates temporal gene expression by way of microRNA. MicroRNA targets and non-microRNA targets moreover have different biological roles. This functional segregation by microRNA would be critical for the elucidation of the molecular activities of SST.