Melanin content and MC1R function independently affect UVR-induced DNA damage in cultured human melanocytes

Malignant transformation of melanocytes leads to melanoma, the most fatal form of skin cancer. Ultraviolet radiation (UVR)-induced DNA photoproducts play an important role in melanomagenesis. Cutaneous melanin content represents a major photoprotective mechanism against UVR-induced DNA damage, and generally correlates inversely with the risk of skin cancer, including melanoma. Melanoma risk is also determined by susceptibility genes, one of which is the melanocortin 1 receptor (MC1R) gene. Certain MC1R alleles are strongly associated with melanoma. We hereby present experimental evidence for the role of two melanoma risk factors, constitutive pigmentation, as assessed by total melanin, eumelanin and pheomelanin contents, and MC1R genotype and function, in determining the induction and repair of DNA photoproducts in cultured human melanocytes after irradiation with increasing doses of UVR. We found that total melanin and eumelanin contents (MC and EC) correlated inversely with the extent of UVR-induced growth arrest, apoptosis and induction of cyclobutane pyrimidine dimers (CPD), but not with hydrogen peroxide release in melanocytes expressing functional MC1R. In comparison, melanocytes with loss-of-function MC1R, regardless of their MC or EC, sustained more UVR-induced apoptosis and CPD, and exhibited reduced CPD repair. Therefore, MC, mainly EC, and MC1R function are independent determinants of UVR-induced DNA damage in melanocytes.     

Mouse homologue of skin-specific retroviral-like aspartic protease involved in wrinkle formation

Retroviral proteases are encoded in the retroviral genome and are responsible for maturation and assembly of infectious virus particles. A number of retroviral protease sequences with retroviral elements are integrated in every eukaryotic genome as endogenous retroviruses. Recently, retroviral-like aspartic proteases that were not embedded within endogenous retroviral elements were identified throughout the eukaryotic and prokaryotic genomes. However, the physiological role of this novel protease family, especially in mammals, is not known. During the high throughput in situ hybridization screening of mouse epidermis, as a granular layer-expressing clone, we identified a mouse homologue of SASPase (Skin ASpartic Protease), a recently identified retroviral-like aspartic protease. We detected and purified the endogenous 32-kDa (mSASP32) and 15-kDa (mSASP15) forms of mSASP from mouse stratum corneum extracts and determined their amino acid sequences. Next, we bacterially produced recombinant mSASP15 via autoprocessing of GST-mSASP32. Purified recombinant mSASP15 cleaved a quenched fluorogenic peptide substrate, designed from the autoprocessing site for mSASP32 maximally at pH 5.77, which is close to the pH of the epidermal surface. Finally, we generated mSASP-deficient mice that at 5 weeks of age showed fine wrinkles that ran parallel on the lateral trunk without apparent epidermal differentiation defects. These results indicate that the retroviral-like aspartic protease, SASPase, is involved in prevention of fine wrinkle formation via activation in a weakly acidic stratum corneum environment. This study provides the first evidence that retroviral-like aspartic protease is functionally important in mammalian tissue organization.     

Spawning habitat selection and suitability for Japanese dace, Tribolodon hakonensis

We have investigated the effects of three current velocities and three substrate sizes (gravel to cobble) on the spawning behavior of Japanese dace, Tribolodon hakonensis, in spawning-induction and habitat-selection experiments. In the spawning-induction experiment under laboratory conditions the number of females induced to spawn was significantly fewer at low current velocity (ca. 5 cm s^–1) than at medium (ca. 30 cm s^–1) or high (ca. 50 cm s^–1) current velocity. Females spawned independently of substrate size in the experimental tank, and did not bury their eggs in the substrate bed. In the habitat-selection experiment under field conditions, females selected the substrate microhabitat and spawned more frequently at a site with medium substrate size (very coarse gravel; major axis ca. 40 mm) than at sites with small (fine gravel; ca. 8 mm) or large (cobble; ca. 70 mm) substrate size. We conclude that Japanese dace select spawning sites at least partly on the basis of current velocity and substrate size, which affects the survival rate of eggs.     

Sunitinib induces apoptosis in pheochromocytoma tumor cells by inhibiting VEGFR2/Akt/mTOR/S6K1 pathways through modulation of Bcl-2 and BAD

Sunitinib is an oral multitargeted receptor tyrosine kinase inhibitor with antiangiogenic and antitumor activity that mainly targets vascular endothelial growth factor receptors (VEGFRs). Very recently, sunitinib has been shown to be an active agent for the treatment of malignant pheochromocytomas. However, it is unclear whether sunitinib acts only through an antiangiogenic mechanism or whether it may also directly target tumor cells. Sunitinib markedly induced apoptosis of PC12 cells in a dose-dependent and time-dependent manner. Furthermore, in support of these findings, we found that sunitinib induced a reduction in the expression of the antiapoptotic molecule Bcl-2 as well as dephosphorylation of the proapoptotic molecule BAD, which results in the activation of BAD in these cells. Consistent with these apoptotic effects, our results showed that sunitinib inhibited phosphorylation of Akt and mTOR and was followed by a reduction of S6K1, which is a well-known target of mTOR. Knockdown of VEGFR-2 attenuated the sunitinib-induced effects, including apoptosis and inhibition of signaling pathways such as the phosphorylation of Akt as well as mTOR, and Bcl-2, which confirmed that these effects could be mediated by VEGFR-2. In addition, silencing of S6K1 induced apoptosis accompanied by a decrease in the phosphorylation of BAD and Bcl-2, similar to that observed with sunitinib treatment. Thus, these results together suggest that sunitinib initially exerts its apoptotic effect through the inhibition of VEGFR-2, which, when followed by reduction of its downstream effectors, including Akt/mTOR/S6K1, may lead to inhibition of the antiapoptotic molecule Bcl-2 and activation of the proapoptotic molecule BAD in PC12 cells. However, PC12 cells do not precisely reflect the pathogenesis of malignant cells. Therefore, we confirmed the key findings by replicating these experiments in human neuroblastoma SK-N-SH cells.     

Characterization of bisphenol A metabolites produced by Portulaca oleracea cv. by liquid chromatography coupled with tandem mass spectrometry

The garden plant portulaca (Portulaca oleracea cv.) efficiently removes bisphenol A (BPA), an endocrine-disrupting chemical, from a hydroponic solution, but the molecular mechanisms underlying BPA metabolism by portulaca remain unclear. In this study, BPA metabolites converted by portulaca were analyzed by liquid chromatography coupled with tandem mass spectrometry. We observed the hydroxylation of BPA and the oxidization of it to quinone. Polyphenol oxidases are likely to contribute to BPA degradation by portulaca.     

Modelling the global distribution of fungal species: new insights into microbial cosmopolitanism

Microbes are usually believed to have cosmopolitan distributions. However, for estimating the global distributions of microorganisms, discriminating among cryptic species and eliminating undersampling biases are important challenges. We used a novel approach to address these problems and infer the global distribution of a given fungal ecological guild. We collected mushroom‐forming fungi from Yakushima, Japan. We sequenced the internal transcribed spacer 2 (ITS2) from these samples and queried their sequences against GenBank. After identifying similar sequences, we tracked down the geographical origins of samples that yielded those sequences. We used Bayesian zero‐inflated models to allow for species whose DNA sequences have not yet been deposited in GenBank. Results indicated that the geographical distribution of ectomycorrhizal (ECM) fungi was strongly constrained by host specificity, resulting in the occurrence of these fungi intensively in the neighbouring regions. On the other hand, saprotrophic (SAP) fungi were less constrained by climatic conditions, resulting in a much broader distribution range. We inferred that differences in constraints during colonization between ECM and SAP fungi were responsible for the different geographical distribution ranges. We hypothesize that the degree of host/habitat specificity and the degree of isolation of potentially suitable habitats determine microbial biogeographic patterns.     

Effect of <Emphasis Type="Italic">Cordyceps sinensis</Emphasis> on TIMP-1 secretion from mouse melanoma cell

Cordyceps sinensis is a Chinese medicinal fungus traditionally used in cancer treatments. In a previous study, we investigated the antimetastatic activity of Cordyceps sinensis (WECS) extract using liver metastatic model mice injected with B16-F0 mouse melanoma cells into the spleen. WECS reduced the number of metastatic nodules of B16-F0 cells in the liver of C57BL/6 mice, and significantly prolonged survival of the mice. Furthermore, we examined the effects of WECS on hepatocyte growth factor (HGF)-accelerated invasion of B16-F0 cells using a chemo-invasion assay in vitro. WECS was shown to significantly reduce HGF-accelerated B16-F0 cell invasion. In the present study, we investigated the effect of WECS on Tissue Inhibitor of Metalloproteinase (TIMP)-1 secretion from B16-F0 cells in order to identify clues to the mechanism underlying the anti-invasive action of WECS. As a result, WECS significantly increased the secretion of TIMP-1 from B16-F0 cells. Moreover, we investigated the effect of cordycepin (3′-deoxyadenosine), a component of WECS, on TIMP-1 secretion from B16-F0 cells to potentially identify the pharmacologically active ingredient in WECS extract. Cordycepin was shown to significantly accelerate the release of TIMP-1 from cells. These findings suggest that WECS exerts anti-invasive activity, in part by increasing TIMP-1 secretion from melanoma cells, and that cordycepin potentially functions as the effective component.     

Complement activation plays a key role in antibody-induced infusion toxicity in monkeys and rats

Infusion reactions are a major side effect of the administration of therapeutic Abs and are the result of a complex immune reaction. In this study, we report that substitutions of Fc amino acids in the anti-HLA-DR Ab HD8 reduce its ability to induce infusion reactions in rats and monkeys. We first showed that i.v. administration of IgG1- and IgG2-subclass HD8 Abs induces severe infusion reactions in monkeys. These Abs express strong complement-dependent cytotoxicity (CDC), and in vivo depletion of complement in rats by pretreatment with cobra venom factor abrogated the lethal infusion reactions generated by HD8-IgG1. Thus, the infusion reactions appear to be largely driven by the complement system. To reduce the CDC function of HD8-IgG1, its Fc region was modified by two amino acid substitutions at Pro(331)Ser and Lys(322)Ala. The modified Ab was incapable of expressing CDC in vitro and did not induce severe infusion reactions in rats and monkeys, even at extremely high doses. The modified Ab retained its Ab-dependent cellular cytotoxicity function as well as its antitumor activity in a tumor-bearing mouse model. In summary, complement appears to drive infusion reactions, and modifications that eliminate the CDC activity of an Ab also reduce its ability to induce infusion reactions.     

COX-2 and CCR2 induced by CD40 ligand and MCP-1 are linked to VEGF production in endothelial cells

Recent studies have reported that expression of MCP-1 and its receptor, CCR2; and CD40-CD40 ligand (CD40L) interaction on mesenchymal cells play important roles in tumor development. Studies have also connected MCP-1, CCR2, and CD40L to COX-2 expression. The aim of this study was to examine the effect of MCP-1/CCR2 and CD40-CD40L interaction on COX-2 and VEGF expression in endothelial cells. We also investigated the localization of these proteins in gastric cancer tissue. COX-2 and CCR2 levels were evaluated in CD40L-stimulated HUVECs by Western blot and real-time PCR. VEGF secreted in the culture media was quantified by ELISA. Localizations of MCP-1, CD40L, CD34, CD40 and CCR2 in 34 gastric cancer tissue specimens were evaluated by immunohistochemistry. CD40-CD40L interaction-induced COX-2 production and subsequently, upregulated COX-2 production contributed to elevated VEGF and CCR2 levels in CD40L-stimulated HUVECs. CD40L-stimulated VEGF production was COX-2 but not COX-1 dependent. RS-102895, a CCR2-specific antagonist, significantly reduced VEGF production in CD40L- and MCP-1-stimulated HUVECs. MCP-1 had a synergistic effect on COX-2, CCR2 and VEGF levels in CD40L-stimulated HUVECs. In gastric cancer tissue, there was significant correlation between microvessel density and scores for CD40L, MCP-1 and CCR2 protein expression. Thus, MCP-1 had a synergistic effect on COX-2 and CCR2 protein expression in CD40L-stimulated HUVECs and thereby stimulated VEGF production in these cells.