Jian-Hong Chu

Involvement of p38 MAPK signaling pathway in the anti-melanogenic effect of San-bai-tang, a Chinese herbal formula, in B16 cells

AIM OF THE STUDY San-bai-tang (SBT), a Chinese herbal formula, is traditionally used as a skin whitener in China. In our previous screening assays, SBT was identified as an effective tyrosinase inhibitor. In this study, we aim to investigate the anti-melanogenic effect and mechanisms of SBT in B16 cells. MATERIALS AND METHODS Cell viability was examined by the MTT assay. Cellular tyrosinase activity and melanin content were determined using spectrophotographic methods. Protein expression was analyzed by immunoblotting. RESULTS SBT inhibited tyrosinase activity with an IC(50) of 215.6 ± 10.3 μg/ml, and decreased cellular melanin content with an IC(50) of 254.8 ± 14.5 μg/ml at 48 h. MTT assay demonstrated that 48-h SBT (50-400 μg/ml) treatment did not show obvious cytotoxicity. Immunoblot analysis showed that SBT (100, 200 or 400 μg/ml) treatment for 48 h down-regulated the expression levels of phosphorylated-p38, MITF, tyrosinase, TRP-1 and TRP-2 in a dose-dependent manner. CONCLUSIONS SBT inhibited melanogenesis in B16 cells, and suppression of p38 MAPK signaling pathway contributed to the anti-melanogenic effect of SBT by down-regulating the expression of MITF and melanogenic enzymes. These novel findings demonstrated the anti-melanogenic effect and mechanisms of SBT, and provide pharmacological basis for the traditional use of SBT.

Flavonoids, apigenin and icariin exert potent melanogenic activities in murine B16 melanoma cells

We aimed to screen for melanogenic agents among 35 botanical compounds. The compounds were first assessed with regard to their effects on tyrosinase activity in B16 cells. At 100 μM, 13 compounds showed tyrosinase activity-enhancing effects, ranging from 2.6 to 372.8% activation. Five of them showed more than 50% enhancement and were further tested for their EC(50) values. Compared with 8-Methoxypsoralen, an effective tyrosinase activator with an EC(50) of 7.26 μM, 3 compounds exhibited smaller EC(50) values (apigenin, 0.45 μM; hyperosid, 0.92 μM; and icariin, 1.01 μM for enhancing tyrosinase activity). The 3 compounds significantly increased cellular melanin contents without affecting cell proliferation. Compared with 8-Methoxypsoralen (EC(50), 35.94 μM for stimulating pigmentation), apigenin (EC(50), 17.46 μM) and icariin (EC(50), 32.77 μM) showed better melanogenic activity, while hyperosid (EC(50), 70.4 μM) was less potent. Western blot analysis demonstrated that the 3 compounds could differentially increase the expression levels of tyrosinase, and tyrosinase-related proteins 1 and 2. Together these data suggest that apigenin and icariin exert potent melanogenic activities through, at least in part, upregulating the protein expression levels of melanogenic enzymes in B16 cells. Thus, further investigations are merited to ascertain their potential application in treating hypopigmentation disorders.

Effects of Sesquiterpenes Isolated From Largehead Atractylodes Rhizome on Growth, Migration, and Differentiation of B16 Melanoma Cells

The aims of this study were to isolate sesquiterpene compounds from the largehead atractylodes rhizome (LAR) and to investigate their effects on B16 cancer cells. A total of 8 sesquiterpenes from LAR were identified, of which eudesm-4 (15), 7-diene-9α, 11-diol (7) was isolated for the first time. All 8 compounds inhibited growth of B16 cells, and atractylenolide I (AT-I), atractylenolide II (AT-II), and atractylenolactam (ATR) were the most potent, with IC50 values of 76.46, 84.02, and 54.88 μΜ, respectively. Monomer lactone or lactam structures in the 8 compounds appeared to be critical for their antiproliferative activities. In addition, AT-I, AT-II, and ATR could induce cell differentiation and inhibit cell migration. Western blot analysis indicated that 2 of the compounds, AT-I and AT-II, could inactivate ERK, where all 3 inhibited AKT activation, suggesting that Ras/ERK and PI3K/AKT signaling pathways are involved in the action mechanisms of the LAR sesquiterpene compounds.

Inhibition of the STAT3 signaling pathway contributes to apigenin-mediated anti-metastatic effect in melanoma.

Signal transducer and activator of transcription 3 (STAT3) signaling is constantly activated in human melanoma, and promotes melanoma metastasis. The dietary flavonoid apigenin is a bioactive compound that possesses low toxicity and exerts anti-metastatic activity in melanoma. However, the anti-metastasis mechanism of apigenin has not been fully elucidated. In the present study, we showed that apigenin suppressed murine melanoma B16F10 cell lung metastasis in mice, and inhibited cell migration and invasion in human and murine melanoma cells. Further study indicated that apigenin effectively suppressed STAT3 phosphorylation, decreased STAT3 nuclear localization and inhibited STAT3 transcriptional activity. Apigenin also down-regulated STAT3 target genes MMP-2, MMP-9, VEGF and Twist1, which are involved in cell migration and invasion. More importantly, overexpression of STAT3 or Twist1 partially reversed apigenin-impaired cell migration and invasion. Our data not only reveal a novel anti-metastasis mechanism of apigenin but also support the notion that STAT3 is an attractive and promising target for melanoma treatment.

Screening of Chinese herbal medicines for antityrosinase activity in a cell free system and B16 cells

AIM OF THE STUDY Tyrosinase inhibitors are becoming increasingly important in controlling skin hyperpigmentation. We aimed to screen 50 extracts from traditional Chinese medicines (TCM) for tyrosinase activity-inhibiting agents. MATERIALS AND METHODS The 50 herbal extracts were prepared from 32 herbs and 18 TCM formulas, which are used as folk skin whiteners in China and have not been investigated for their skin-whitening mechanisms. Each herb and formula was extracted with 30% ethanol and water, respectively, and followed by column chromatography for isolating bioactive substances such as saponins, flavonoids and alkaloids for the antityrosinase activity study. Every extract was tested using the cell free mushroom tyrosinase inhibitory assay at 2 mg/ml for the single herb extracts and 1mg/ml for formula extracts. Extracts showing greater than 50% inhibition against mushroom tyrosinase activity were further examined by cellular tyrosinase assay in mouse B16 cells. The cytotoxicity in B16 cells was measured by methyl thiazolyl tetrazolium bromide (MTT) assay. RESULTS In the cell-free assay, 10 out of the 50 extracts demonstrated more than 50% inhibition against mushroom tyrosinase activity. These 10 extracts were further assessed by cellular tyrosinase assay, and 6 showed>50% inhibition with IC(50) values <1 mg/ml. The 6 extracts are from 3 herbs namely Ampelopsis japonica, Lindera aggregata, and Polygonatum odoratum, and 3 formulas namely Qian-wang-hong-bai-san, Qiong-yu-gao, and San-bai-tang. As compared with vitamin C, these 6 extracts showed similar or greater ratio of cell growth IC(50) to cellular tyrosinase IC(50). As compared with arbutin, extract from Ampelopsis japonica, Lindera aggregata, Qian-wang-hong-bai-san, or San-bai-tang had a similar, although extract from Polygonatum odoratum or Qiong-yu-gao had a greater, IC(50) value against murine tyrosinase activity. CONCLUSIONS From the screening assays we identified three Chinese medicinal herbs and three TCM formulas that have appreciable antityrosinase activity. Further studies are warranted to develop them as skin-whitening agents with convenient dosage forms or to identify active constituents from the extracts as useful leads for the development of skin whiteners.

Inhibitory effect of schisandrin B on free fatty acid-induced steatosis in L-02 cells

AIM To investigate the effects of schisandrin B (Sch B) on free fatty acid (FFA)-induced steatosis in L-02 cells. METHODS Cellular steatosis was induced by incubating L-02 cells with a FFA mixture (oleate and palmitate at the ratio of 2:1) for 24 h. Cytotoxicity and apoptosis were evaluated by 3-(4, 5-dmethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide assay and Annexin V/propidium iodide staining, respectively. Cellular total lipid was determined using a photocolorimetric method after Nile red staining, and triglyceride content was measured using an enzymatic kit. To study the effects of Sch B on steatosis, L-02 cells were treated with Sch B (1-100 μmol/L) in the absence or presence of 1 mmol/L FFA for 24 h, and cellular total lipid and triglyceride levels were measured. To explore the mechanisms of action of Sch B in the steatotic L-02 cells, mRNA levels of several regulators of hepatic lipid metabolism including adipose differentiation related protein (ADRP), sterol regulatory element binding protein 1 (SREBP-1), peroxisome proliferator-activated receptor (PPAR)-α and PPAR-γ were measured by quantitative real-time polymerase chain reaction (PCR), and protein levels of ADRP and SREBP-1 were measured by immunoblotting. RESULTS Treatment with 1 mmol/L FFA for 24 h induced intracellular lipid accumulation in L-02 cells comparable to that in human steatotic livers without causing apparent apoptosis and cytotoxicity. Sch B mitigated cellular total lipid and triglyceride accumulations in the steatotic L-02 cells in a dose-dependent manner. Quantitative real-time PCR and Western blot analyses revealed that treatment of L-02 cells with 100 μmol/L Sch B reverted the FFA-stimulated up-regulation of ADRP and SREBP-1. CONCLUSION Sch B inhibits FFA-induced steatosis in L-02 cells by, at least in part, reversing the up-regulation of ADRP and SREBP-1.

Atractylenolide II induces G1 cell-cycle arrest and apoptosis in B16 melanoma cells.

ETHNOPHARMACOLOGICAL RELEVANCE Atractylenolide II (AT-II) is a sesquiterpene compound isolated from the dried rhizome of Atractylodes macrocephala (Baizhu in Chinese), which is traditionally prescribed for melanoma treatment by Chinese medicine practitioners. Our previous study showed that AT-II can inhibit B16 cells proliferation. Here we investigate the mechanistic basis for the anti-proliferative activity of AT-II in B16 melanoma cells. MATERIALS AND METHODS Cell viability was examined by MTT assay. Cell cycle distribution and apoptosis were determined by flow cytometry. Protein expression was determined by Western blotting. RESULTS AT-II treatment for 48 h dose-dependently inhibited cell proliferation with an IC(50) of 82.3 μM, and induced G1 phase cell cycle arrest. Moreover, treatment with 75 μM AT-II induced apoptosis. These observations were associated with the decrease of the expression of Cdk2, phosphorylated-Akt, phosphorylated-ERK and Bcl-2, the increase of the expression of phosphorylated-p38, phosphorylated-p53, p21, p27, and activation of caspases-8, -9 and -3. In addition, a chemical inhibitor of p53, PFTα, significantly decreased AT-II-mediated growth inhibition and apoptosis. CONCLUSIONS We demonstrated that the G1-arresting and apoptotic effects of AT-II in B16 cells involve p38 activation as well as ERK and Akt inactivation, and the cytotoxic/apoptotic effects of AT-II are potentially p53 dependent. These findings provided chemical and pharmacological basis for the traditional application of Baizhu in melanoma treatment.

Activation of p38 MAPK pathway contributes to the melanogenic property of apigenin in B16 cells

Abstract:  We investigated the involvement of MAPK pathways in the melanogenic effect of apigenin in B16 cells. Apigenin treatment for 48 h dose (5–20 μm)‐dependently up‐regulated protein expression levels of microphthalmia‐associated transcription factor (MITF) and melanogenic enzymes including tyrosinase, tyrosinase‐related protein‐1 (TRP‐1) and TRP‐2 and enhanced the phosphorylation of p38 MAPK, without affecting the phosphorylation of JNK or ERK MAPK. Treatment with 10 μm apigenin time (6‐48 h)‐dependently elevated the protein expressions of p‐p38, MITF and melanogenic enzymes. Moreover, PD169316, a selective inhibitor of p38 kinase, suppressed the stimulatory effects of apigenin on tyrosinase activity and melanin synthesis, which were accompanied by decreased MITF protein expression. In conclusion, apigenin increased melanogenesis in B16 cells, at least in part, by activating the p38 MAPK pathway. The novel findings of this study shed light on the molecular mechanisms underlying the melanogenic activity of apigenin and suggest that apigenin/its derivatives may be potentially used for treating hypopigmentation disorders.

Furanodienone inhibits cell proliferation and survival by suppressing ERα signaling in human breast cancer MCF-7 cells.

Estrogen receptor alpha (ERα) plays an important role in the development and progression of breast cancer and thus the attenuation of ERα activities is a promising treatment strategy. Furanodienone is one of the main bioactive chemical components of Rhizoma Curcumae which is commonly used in Chinese medicine for the treatment of cancer. In this study, we investigated the effects of furanodienone on human breast cancer MCF‐7, T47D, and MDA‐MB‐231 cells. Our results showed that furanodienone could inhibit MCF‐7, T47D, and MDA‐MB‐231 cells proliferation in a dose (10–160 µM) dependent manner. ERα‐negative MDA‐MB‐231 cells were less sensitive to furanodienone than ERα‐positive MCF‐7 and T47D cells. Furanodienone could effectively block 17β‐estradiol (E2)‐stimulated MCF‐7 cell proliferation and cell cycle progression and induce apoptosis evidenced by the flow cytometric detection of sub‐G1 DNA content and the appearance of apoptotic nuclei after DAPI staining. Furanodienone specifically down‐regulated ERα protein and mRNA expression levels without altering ERβ expression. Furanodienone treatment inhibited E2‐stimulation of estrogen response element (ERE)‐driven reporter plasmid activity and ablated E2‐targeted gene (e.g., c‐Myc, Bcl‐2, and cyclin D1) expression which resulted in the inhibition of cell cycle progression and cell proliferation, and in the induction of apoptosis. Knockdown of ERα in MCF‐7 cells by ERα‐specific siRNA decreased the cell growth inhibitory effect of furanodienone. These findings suggest that effects of furanodienone on MCF‐7 cells are mediated, at least in part, by inhibiting ERα signaling. J. Cell. Biochem. 112: 217–224, 2011.

ERp57 is up‐regulated in free fatty acids‐induced steatotic L‐02 cells and human nonalcoholic fatty livers

Pathogenesis of nonalcoholic fatty liver disease (NAFLD) is not clear. In this study we aimed to identify proteins involved in NAFLD development in free fatty acids (FFA)‐induced hepatosteatotic cells and in human liver biopsies. Steatosis was induced by incubating a normal human hepatocyte‐derived cell line L‐02 with FFA. Differentially expressed proteins in the steatotic cells were analyzed by two‐dimensional gel electrophoresis‐based proteomics. Involvement of one of the up‐regulated proteins in steatosis was characterized using the RNA interference approach with the steatotic cells. Protein expression levels in liver biopsies of patients with NAFLD were assessed by immunohistochemistry. Proteomic analysis of L‐02 steatotic cells revealed the up‐regulation of ERp57, a condition not previously implicated in NAFLD. Knockdown of ERp57 expression with siRNA significantly reduced fat accumulation in the steatotic cells. ERp57 expression was detected in 16 out of 17 patient biopsies and correlated with inflammation grades or fibrosis stages, while in 5 normal biopsies ERp57 expression was not detectable in hepatocytes. In conclusion, ERp57 was up‐regulated in FFA‐induced steatotic hepatic cells and in NAFLD patient livers and demonstrated steatotic properties in cultured cells. Further investigations are warranted to verify the involvement of ERp57 in NAFLD development. J. Cell. Biochem. 110: 1447–1456, 2010.