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1,25(OH)2D3 dependent overt hyperactivity phenotype in klotho-hypomorphic mice.

ABSTRACT: Klotho, a protein mainly expressed in kidney and cerebral choroid plexus, is a powerful regulator of 1,25(OH)2D3 formation. Klotho-deficient mice (kl/kl) suffer from excessive plasma 1,25(OH)2D3-, Ca(2+)- and phosphate-concentrations, leading to severe soft tissue calcification and accelerated aging. NH4Cl treatment prevents tissue calcification and premature ageing without affecting 1,25(OH)2D3-formation. The present study explored the impact of excessive 1,25(OH)2D3 formation in NH4Cl-treated kl/kl-mice on behavior. To this end kl/kl-mice and wild-type mice were treated with NH4Cl and either control diet or vitamin D deficient diet (LVD). As a result, plasma 1,25(OH)2D3-, Ca(2+)- and phosphate-concentrations were significantly higher in untreated and in NH4Cl-treated kl/kl-mice than in wild-type mice, a difference abrogated by LVD. In each, open field, dark-light box, and O-maze NH4Cl-treated kl/kl-mice showed significantly higher exploratory behavior than untreated wild-type mice, a difference abrogated by LVD. The time of floating in the forced swimming test was significantly shorter in NH4Cl treated kl/kl-mice compared to untreated wild-type mice and to kl/kl-mice on LVD. In wild-type animals, NH4Cl treatment did not significantly alter 1,25(OH)2D3, calcium and phosphate concentrations or exploratory behavior. In conclusion, the excessive 1,25(OH)2D3 formation in klotho-hypomorphic mice has a profound effect on murine behavior.

SUBMITTER: Leibrock CB

PROVIDER: S-EPMC4843009 | biostudies-other | 2016 Apr

REPOSITORIES: biostudies-other

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Project description:Monoamine oxidase (MAO)-A is a key enzyme for the degradation of brain serotonin (5-hydroxytryptamine, 5-HT) and norepinephrine (NE). In humans and mice, total MAO-A deficiency results in high 5-HT and NE levels, as well as elevated reactive aggression. Here we report the generation of MAO-A(Neo) mice, a novel line of hypomorphic MAO-A mutants featuring the insertion of a floxed neomycin-resistance cassette in intron-12 of the Maoa gene. This construct resulted in a chimeric, non-functional variant of the Maoa-Neo transcript, with a truncated C-terminus, likely due to aberrant splicing; these deficits notwithstanding, small amounts of functional Maoa transcript were found in the brain of MAO-A(Neo) mice. In the prefrontal cortex and amygdala, MAO-A(Neo) mice showed low, yet detectable, MAO-A catalytic activity, as well as 5-HT levels equivalent to WT littermates; conversely, the hippocampus and midbrain of MAO-A(Neo) mice featured a neurochemical profile akin to MAO-A-knockout (KO) mice, with undetectable MAO-A activity and high 5-HT concentrations. MAO-A(Neo) mice showed significant increases in dendritic length in the pyramidal neurons of orbitofrontal cortex, but not basolateral amygdala, in comparison with WT littermates; by contrast, the orbitofrontal cortex of MAO-A KO mice showed significant reductions in basilar dendritic length, as well as a profound increase in apical dendritic length. MAO-A(Neo) mice showed a unique set of behavioral abnormalities, encompassing reduced open-field locomotion, perseverative responses, such as marble burying and water mist-induced grooming, and a lack of anxiety-like behaviors in the elevated plus-maze and light-dark box paradigms. Notably, whereas MAO-A(Neo) and KO mice showed significant reductions in social interaction, only the latter genotype showed increases in resident-intruder aggression. Taken together, our findings indicate that MAO A hypomorphism results in behavioral and morphological alterations distinct from those featured by MAO-A KO mice.

Project description:The proximal tubule is the sensing site of sodium and phosphorus and the main place for the synthesis and metabolism of 1,25 (OH)2D3. Sodium may share the sensing mechanism with phosphate in proximal tubule epithelial cells; whether sodium cooperates with phosphate or plays an independent role in the regulation of phosphorus homeostasis remains unknown. In this in vitro study, we investigated the effects of high sodium on the synthesis and function of active vitamin D and local phosphorus regulation in proximal tubular epithelial cells. Human proximal tubule epithelial (HK-2) cells were treated with different concentrations of sodium/phosphorus. The expression of 1α-OHase (Cyp27b1) and 24-OHase (Cyp24a1) was determined by RT-PCR and Western Blot. Liquid chromatography/mass spectrometry (LC/MS) and enzyme-linked immunosorbent assay (ELISA) were used to detect the levels of 1,25 (OH)2D3. Intracellular Ca2+ ([Ca2+]i) was detected with the Ca2+ indicator dye Fura-4. Chromatin samples were immunoprecipitated with antibodies against parathyroid receptor 1 (PTH1R) and Klotho. High sodium decreased the expression of 1,25 (OH)2D3 by reducing 1α-OHase and 24-OHase in HK-2 cells, reduced the expression of PTH1R and Klotho, and increased the intracellular calcium concentration. These effects were reversed by sodium phosphorus transporter inhibitor (PFA), sodium hydrogen transporter inhibitor (Caliporide), and a chelator of the extracellular calcium, whereas enhanced by ouabain. Vitamin D receptor agonists significantly increased the recruitment of VDR to the Vitamin D response element (VDRE) of PTH1R and Klotho promoter, thus increasing the expression of PTH1R and Klotho. High extracellular sodium can decrease the synthesis of active vitamin D in the proximal tubules, affect the gene regulation of 1,25 (OH)2D3/VDR, and significantly reduce the expression of PTH1R and Klotho. The data reveal the influence of a high-sodium diet on mineral metabolism and the core role of vitamin D in kidney mineral metabolism.

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1,25(OH)2D3 dependent overt hyperactivity phenotype in klotho-hypomorphic mice.

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