It is known that the teleost scale regenerates after being removed. We previously reported that the osteogenesis in regenerating scales was very similar to that in calvarial bone, which suggests that regenerating scale can be used as a model for osteogenesis to analyze the inte raction b e t we e n oste oblasts and osteoclasts. In the present study, we developed an assay system using regenerating scales by modifying our assay system with normal scales. The weight of one regenerating scale cannot be measured precisely because the rate of calcification in regenerating scales is lower than that in normal scales. In regenerating scales, thus, the respective marker enzyme activit y, i.e ., alkaline phosphatase (ALP) for osteoblasts and tartrate-resistant acid phosphatase (TRAP) for osteoclasts, was normalized by the surface area (mm 2) of each goldfish scale. With this modified method, we were able to detect ALP and TRAP activities with no variation in the lines of regenerating scales. In addition, we found that the ALP activity in the regenerating scales significantly increased under 3G acceleration loading by vibration, while the TRAP activity in the loaded regenerating scales significantly decreased. We strongly believe that the regenerating scale is a good material for the analysis of bone me tabolism unde r dif fe re nt gravit y environments.

A growing body of recent evidence indicates that ATP plays an important role in neuronal-glial communications. In this study, the authors demonstrated that extracellular ATP elicits the gene expression of brain-derived neurotrophic factor (BDNF), especially BDNF exon IV mRNA, in primary cultured rat cortical astrocytes but not in neurons. To investigate the mechanism by which ATP induces BDNF exon IV mRNA expression, the authors used immortalized astrocyte cell line RCG-12. ATP dose-dependently increased the expression of BDNF exon IV mRNA and activated BDNF promoter IV. P2Y receptor agonists (ADP and 2MeS-ADP) but not a P2X receptor agonist (alphabetaMeATP) induced the expression of BDNF exon IV mRNA. Moreover, ATP-induced BDNF exon IV mRNA upregulation was inhibited by a P2Y antagonist (MRS2179) but not by P2X antagonists (TNP-ATP and PPADS). These findings suggest the involvement of P2Y receptors in the ATP-induced transcription of the BDNF gene. Among the signal transduction inhibiters examined in this study, intracellular Ca(2+) chelator (BAPTA-AM) and Ca(2+)/calmodulin-dependent kinase (CaM kinase) inhibitors (KN-93 and W-7) attenuated ATP-induced BDNF exon IV mRNA upregulation. ATP transiently induced the phosphorylation of cAMP-responsive element-binding protein (CREB). ATP-induced CREB phosphorylation was repressed by P2Y antagonists, BAPTA-AM, and CaM kinase inhibitors. Overexpression of dominant negative CREB mutants reduced the activation of BDNF promoter IV and attenuated the upregulation of BDNF exon IV mRNA expression. These results suggest that ATP induces BDNF expression through P2Y receptor followed by the activation of CaM kinase and CREB in astrocytes. These mechanisms are likely to contribute to the enhancement of neuronal-glial networks.

Exposure to the space environment induces a number of pathophysiological outcomes in astronauts, including bone demineralization, sleep disorders, circadian clock dysregulation, cardiovascular and metabolic dysfunction, and reduced immune system function. A recent report describing experiments aboard the Space Shuttle mission, STS-132, showed that the level of melatonin, a hormone that

Macrophages play critical roles in the pathogenesis of non-alcoholic steatohepatitis (NASH). However, it is unclear which macrophage subsets are critically involved in the development of inflammation and fibrosis in NASH. In TSNO mice fed a high-fat/cholesterol/cholate-based diet, which exhibit advanced liver fibrosis that mimics human NASH, we found that Kupffer cells (KCs) were less abundant and recruited macrophages were more abundant, forming hepatic crown-like structures (hCLS) in the liver. The recruited macrophages comprised two subsets: CD11c+/Ly6C− and CD11c−/Ly6C+ cells. CD11c+ cells were present in a mesh-like pattern around the lipid droplets, constituting the hCLS. In addition, CD11c+ cells colocalized with collagen fibers, suggesting that this subset of recruited macrophages might promote advanced liver fibrosis. In contrast, Ly6C+ cells were present in doughnut-like inflammatory lesions, with a lipid droplet in the center. Finally, RNA sequence analysis indicates that CD11c+/Ly6C− cells promote liver fibrosis and hepatic stellate cell (HSC) activation, whereas CD11c−/Ly6C+ cells are a macrophage subset that play an anti-inflammatory role and promote tissue repair in NASH. Taken together, our data revealed changes in liver macrophage subsets during the development of NASH and shed light on the roles of the recruited macrophages in the pathogenesis of advanced fibrosis in NASH.

We have previously reported that microgravity promotes the activation of osteoclasts in cultured regenerating scales. This osteoclastic activation was induced by increased levels of receptor activator of the nuclear factor-κB ligand (RANKL). Therefore, we determined that RANKL is an important factor in evaluating osteoclastogenesis in bone tissue. However, the role of RANKL in fish scales is poorly understood. In the present study, we prepared antiserum against goldfish RANKL in rabbits and detected RANKL-producing cells in regenerating goldfish scales. Furthermore, we studied osteoclastic activation by the addition of RANKL to examine exogenous RANKL on osteoclastogenesis in regenerating goldfish scales. As a result, RANKL immunepositive cells were detected in grooves of regenerating scales. In addition, treating the regenerating scales with mammalian RANKL for 3 h significantly increased the expression of the nuclear factor of activated T cells, cytoplasmic 1 (NFATc1), which is essential for osteoclast differentiation. After 6 h of incubation with RANKL, the expression of cathepsin K, a functional osteoclastic gene, significantly increased. Furthermore, the molecules for osteoclast multinucleation and differentiation significantly increased following treatment with mammalian RANKL. Therefore, in fish scales as well as mammalian bone, we concluded that RANKL plays an important role in osteoclastogenesis. ©2020 Jpn. Soc. Biol. Sci.