Effects of Inorganic Mercury and Methylmercury on Osteoclasts and Osteoblasts in the Scales of the Marine Teleost as a Model System of Bone

Abstract

To evaluate the effects of inorganic mercury (InHg) and methylmercury (MeHg) on bone metabolism in a marine teleost, the activity of tartrate-resistant acid phosphatase (TRAP) and alkaline phosphatase (ALP) as indicators of such activity in osteoclasts and osteoblasts, respectively, were examined in scales of nibbler fish (Girella punctata). We found several lines of scales with nearly the same TRAP and ALP activity levels. Using these scales, we evaluated the influence of InHg and MeHg. TRAP activity in the scales treated with InHg (10 -5 and 10 -4 M) and MeHg (10 -6 to 10 -4 M) during 6 hrs of incubation decreased significantly. In contrast, ALP activity decreased after exposure to InHg (10 -5 and 10 -4 M) and MeHg (10 -6 to 10 -4 M) for 18 and 36 hrs, although its activity did not change after 6 hrs of incubation. As in enzyme activity 6 hrs after incubation, mRNA expression of TRAP (osteoclastic marker) decreased significantly with InHg and MeHg treatment, while that of collagen (osteoblastic marker) did not change significantly. At 6 hrs after incubation, the mRNA expression of metallothionein, which is a metal-binding protein in osteoblasts, was significantly increased following treatment with InHg or MeHg, suggesting that it may be involved in the protection of osteoblasts against mercury exposure up to 6 hrs after incubation. To our knowledge, this is the first report of the effects of mercury on osteoclasts and osteoblasts using marine teleost scale as a model system of bone.

Low-intensity pulsed ultrasound induces apoptosis in osteoclasts: Fish scales are a suitable model for the analysis of bone metabolism by ultrasound

“…The method for measuring TRAP activity was as follows (Yachiguchi et al, 2014). An aliquot of 100 μl of an acid buffer (0.1 M sodium acetate, including 20 mM tartrate, pH 5.3) was added to each well.…”

Sodium fluoride induces hypercalcemia resulting from the upregulation of both osteoblastic and osteoclastic activities in goldfish, Carassius auratus

“…Several osteoblastic markers (such as osteocalcin, type 1 collagen, and osterix) were also detected in the scales of goldfish (Thamamongood et al, 2012). Therefore, we have developed an in vitro assay system with goldfish scales and have analyzed the influence of calcemic hormones (calcitonin: Suzuki et al, 2000;Sekiguchi et al, 2009;parathyroid hormone: Suzuki et al, 2011a;prostaglandin E2: Omori et al, 2012) and environmental pollutants (bisphenol-A: Suzuki and Hattori, 2003;heavy metal: Suzuki et al, 2004a;Suzuki et al, 2011b;Yachiguchi et al, 2014a;tributyltin: Suzuki et al, 2006;polychlorinated biphenyl: Yachiguchi et al, 2014b) on osteoblasts and osteoclasts. Therefore, we strongly believe that scale can be utilized as a model for bone, and that our in vitro scale assay system is effective for analyzing fluoride in fish bone metabolism.…”

Seawater Polluted with Highly Concentrated Polycyclic Aromatic Hydrocarbons Suppresses Osteoblastic Activity in the Scales of Goldfish,Carassius auratus

“…The enzyme activity in one scale can be detected by transferring it into a 96-well microplate and directly incubating it with the substrate in each well. Using this in vitro system, the effects of endocrine disrupters-such as bisphenol-A (Suzuki and Hattori, 2003), tributyltin (Suzuki et al, 2006), and polychlorinated biphenyl (Yachiguchi et al, 2014a)-and heavy metals (i.e., cadmium and organic mercury) (Suzuki et al, 2004;Suzuki et al, 2011b;Yachiguchi et al, 2014a) M) (Yachiguchi et al, 2014b). In the present study, we can sensitively evaluate the effect of seawater polluted by PAHs and NPAHs on osteoblasts for short incubation times.…”