Monohydroxylated polycyclic aromatic hydrocarbons inhibit both osteoclastic and osteoblastic activities in teleost scales

金沢大学環日本海域環境研究センター生物多様性研究部門Aims: We previously demonstrated that monohydroxylated polycyclic aromatic hydrocarbons (OHPAHs) bound to a human estrogen receptor (ER) by a yeast two-hybrid assay, but polycyclic aromatic hydrocarbons did not have a binding activity. Therefore, the direct effect of 3-hydroxybenz[a]anthracene (3-OHBaA) and 4-hydroxybenz[a]anthracene (4-OHBaA) on osteoclasts and osteoblasts in teleosts was examined. As a negative control, 1-hydroxypyrene (1-OHPy), which has no binding activity to human ER, was used. Main methods: The effect of OHPAHs on osteoclasts and osteoblasts was examined by an assay system using teleost scale as each marker: tartrate-resistant acid phosphatase for osteoclasts and alkaline phosphatase for osteoblasts. Changes in cathepsin K (an osteoclastic marker) and insulin-like growth factor-I (IGF-I) (an osteoblastic marker) mRNA expressions in 4-OHBaA-treated goldfish scales were examined by using a reverse transcription-polymerase chain reaction. Key findings: In both goldfish (a freshwater teleost) and wrasse (a marine teleost), the osteoclastic activity in the scales was significantly suppressed by 3-OHBaA and 4-OHBaA, although 1-OHPy did not affect the osteoclastic activity. In reference to osteoblasts, the osteoblastic activity decreased with both 3-OHBaA and 4-OHBaA and did not change with the 1-OHPy treatment. However, 17β-estradiol (E2) significantly increased both the osteoclastic and osteoblastic activities in the scales of both goldfish and wrasse. The mRNA expressions of both cathepsin K and IGF-I decreased in the 4-OHBaA-treated scales but increased in the E2-treated scales. Significance: The current data are the first to demonstrate that 3-OHBaA and 4-OHBaA inhibited both osteoclasts and osteoblasts and disrupted the bone metabolism in teleosts. © 2009 Elsevier Inc. All rights reserved

Static and dynamic hypergravity responses of osteoblasts and osteoclasts in medaka scales

Fish scales are a form of calcified tissue similar to that found in human bone. In medaka scales, we detected both osteoblasts and osteoclasts and subsequently developed a new scale assay system. Using this system, we analyzed the osteoblastic and osteoclastic responses under 2-, 3-, and 4-gravity (G) loading by both centrifugation and vibration. After loading for 10 min, the scales from centrifugal and vibration loading were incubated for 6 and 24 hrs, respectively, after which the osteoblastic and osteoclastic activities were measured. Osteoblastic activity significantly increased under 2- to 4-G loading by both centrifugation and vibration. In contrast, we found that osteoclastic activity significantly decreased under 2- and 3-G loading in response to both centrifugation and vibration. Under 4-G loading, osteoclastic activity also decreased on centrifugation, but significantly increased under 4-G loading by vibration, concomitant with markedly increased osteoblastic activity. Expression of the receptor activator of the NF-αB ligand (RANKL), an activation factor of osteoclasts expressed in osteoblasts, increased significantly under 4-G loading by vibration but was unchanged by centrifugal loading. A protein sequence similar to osteoprotegerin (OPG), which is known as an osteoclastogenesis inhibitory factor, was found in medaka using our sequence analysis. The ratio of RANKL/OPG-like mRNAs in the vibration-loaded scales was significantly higher than that in the control scales, although there was no difference between centrifugal loaded scales and the control scales. Accordingly, medaka scales provide a useful model by which to analyze bone metabolism in response to physical strain. © 2013 Zoological Society of Japan

The first life science experiments in ISS: reports of "Rad Gene"-space radiation effects on human cultured cells-

To clarify the biological effects of space environment, especially space radiations, a proposal of "Rad Gene" was performed as the first life science experiment with two human lymphoblastoid cell lines bearing wild-type p53 gene (wtp53) and mutated p53 gene (mp53) in an International Space Station (ISS)for 133 days. We scheduled four projects: (1) DNA damage induced by space radiations including the high linear energy transfer (LET) particles was detected as a track of gamma H2AX foci in the nuclei of these frozen cells. (2) To examine the biological effects of microgravity and space radiations on gene and protein expression of p53-dependent regulated genes, these cells were grown under microgravity and 1 gravity in ISS, and on ground for 8 days and analyzed by DNA and protein arrays. (3) p53-Dependent regulated genes were analyzed in the cultured cells after spaceflight at frozen state exposed to space radiations. (4) To clarify the effects of space radiations on the radio-adaptive response, the space flown cells at frozen state were cultured, and then exposed to challenging X-ray-irradiation. All of the radio-adaptive responses of cell killing, apoptosis, chromosomal aberrations and mutations were found only in wtp53 cells, but not in the mp53 cells