Renal Endocytic Regulation of Vitamin D Metabolism during Maturation and Aging in Laying Hens.

Egg-laying hens undergo a specific and dramatic calcium metabolism to lay eggs with eggshells composed of calcium carbonate. Calcium metabolism is mainly regulated by vitamin D3. Although vitamin D3 metabolism is closely related to the deterioration of eggshell quality associated with aging and heat stress, the details of the mechanisms regulating vitamin D3 metabolism are not clear. In mammals, the vitamin D3 metabolite (25(OH)D3) produced in the liver binds to the vitamin binding protein (DBP), is subsequently taken up by renal proximal tubular cells via the endocytic receptors megalin (Meg) and cubilin (CUB), and is metabolized to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3). Therefore, the present study aimed to examine the expression and localization of Meg and CUB in the kidneys of immature chicks and mature and aged laying hens to prevent eggshell quality deterioration. As a result, we showed that as circulating 1,25(OH)2D3 concentrations increased from 156.0 ± 13.5 pg/mL to 815.5 ± 61.4 pg/mL with maturation in immature chicks, relative expression levels (arbitrary units; AU) of Meg and CUB mRNA in the kidneys of mature hens significantly increased 1.92- and 2.75-fold, respectively, compared to those in immature chicks. On the other hand, the Meg mRNA expression levels of mature hens did not change with age, while CUB mRNA expression levels (1.03 ± 0.11 AU) were significantly decreased compared to mature hens (2.75 ± 0.24 AU). Immunohistochemical observations showed that Meg and CUB proteins were localized to the apical membrane of renal proximal tubular epithelial cells in immature chicks, mature hens, and aged hens, and that DBP protein was observed as granular endosomes in the cytoplasm of proximal tubular cells from the apical membrane to the cell nucleus. Especially in mature hens, the endosomes were larger and more numerous than those in immature chicks. In contrast, in aged hens, DBP-containing endosomes were smaller and limited to the apical cytoplasm. These results indicate that with maturation, the expression of Meg and CUB is promoted in the renal proximal tubules of laying hens, facilitating the uptake of the 25(OH)D3-DBP complex and its conversion to 1,25(OH)2D3, and regulating calcium metabolism in eggshell formation. On the other hand, it is suggested that the age-related decrease in CUB expression suppresses the uptake of the 25(OH)D3-DBP complex in the kidney, resulting in a deterioration of eggshell quality.

Postischemic Anhedonia Associated with Neurodegenerative Changes in the Hippocampal Dentate Gyrus of Rats.

Poststroke depression is one of the major symptoms observed in the chronic stage of brain stroke such as cerebral ischemia. Its pathophysiological mechanisms, however, are not well understood. Using the transient right middle cerebral artery occlusion- (MCAO-, 90 min) operated rats as an ischemia model in this study, we first observed that aggravation of anhedonia spontaneously occurred especially after 20 weeks of MCAO, and it was prevented by chronic antidepressants treatment (imipramine or fluvoxamine). The anhedonia specifically associated with loss of the granular neurons in the ipsilateral side of hippocampal dentate gyrus and was also prevented by an antidepressant imipramine. Immunohistochemical analysis showed increased apoptosis inside the granular cell layer prior to and associated with the neuronal loss, and imipramine seemed to recover the survival signal rather than suppressing the death signal to prevent neurons from apoptosis. Proliferation and development of the neural stem cells were increased transiently in the subgranular zone of both ipsi- and contralateral hippocampus within one week after MCAO and then decreased and almost ceased after 6 weeks of MCAO, while chronic imipramine treatment prevented them partially. Overall, our study suggests new insights for the mechanistic correlation between poststroke depression and the delayed neurodegenerative changes in the hippocampal dentate gyrus with effective use of antidepressants on them.

Role of glial cells in neurotoxin-induced animal models of Parkinson's disease.

Dopaminergic neurons are selectively vulnerable to oxidative stress and inflammatory attack. The neuronal cell loss in the substantia nigra is associated with a glial response composed markedly of activated microglia and, to a lesser extent, of reactive astrocytes although these glial responses may be the source of neurotrophic factors and can protect against oxidative stress such as reactive oxygen species and reactive nitrogen species. However, the glial response can also mediate a variety of deleterious events related to the production of pro-inflammatory, pro-oxidant reactive species, prostaglandins, cytokines, and so on. In this review, we discuss the possible protective and deleterious effects of glial cells in the neurodegenerative diseases and examine how these factors may contribute to the pathogenesis of Parkinson's disease. This review suggests that further investigation concerning glial reaction in Parkinson's disease may lead to disease-modifying therapeutic approaches and may contribute to the pathogenesis of this disease.

Therapeutic effect of a novel anti-parkinsonian agent zonisamide against MPTP (1-methyl-4-phenyl-1,2,3,6- tetrahydropyridine) neurotoxicity in mice.

We investigated the therapeutic effect of zonisamide against 1-methyl-4-phenyl- 1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in mice, using Western blot analysis, immunohistochemistry and behavioral test. Our Western blot analysis and immunohistochemical study showed that the post-treatment with zonisamide prevented significantly dopaminergic cell damage, the depletion of tyrosine-hydroxylase (TH) protein levels and the proliferation of microglia in the striatum and/or substantia nigra 8 days after MPTP treatment. Furthermore, our behavioral study showed that the post-treatment with zonisamide attenuated significantly the motor deficits 7 days after MPTP treatment. These results show that zonisamide has the therapeutic effect in the MPTP model of Parkinson's disease (PD) in mice. Our study also demonstrates the neuroprotective effect of zonisamide against dopaminergic cell damage after MPTP treatment in mice. Thus our present findings suggest that therapeutic strategies targeted to the activation of TH protein and/or the inhibition of microglial activation with zonisamide may offer a great potential for restoring the functional capacity of the surviving dopaminergic neurons in individuals affected with PD.

Damage to neurons and oligodendrocytes in the hippocampal CA1 sector after transient focal ischemia in rats.

Focal brain lesions such as transient focal cerebral ischemia can lead to neuronal damage in remote areas, including the ipsilateral substantia nigra and hippocampus, as well as in the ischemic core. In this study, we investigated acute changes in the ipsilateral hippocampus from 1 up to 7 days after 90 min of transient focal cerebral ischemia in rats, using anti-NeuN (neuronal nuclei), anti-Cu/Zn-superoxide dismutase (Cu/Zn-SOD), anti-Mn-SOD, anti-neuronal nitric oxide synthase (nNOS), anti-inducible NOS (iNOS), anti-glial fibrillary acidic protein (GFAP), anti-ionized calcium-binding adaptor molecule 1(Iba 1) and anti-2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) antibodies. In our western blot and histochemical analyses, present results show that transient focal cerebral ischemia in rats can cause a severe and acute damage of neurons and oligodendrocytes in the ipsilateral hippocampal CA1 sector. The present findings also demonstrate that the expression of iNOS produced by Iba 1-immunopositive microglia precedes the damage of neurons and oligodendrocytes in the ipsilateral hippocampal CA1 sector after transient focal cerebral ischemia. In contrast, our results suggest that increased reactive oxygen species (ROS) production during reperfusion cannot lead to damage of neurons and oligodendrocytes in the ipsilateral hippocampal CA1 sector after transient focal cerebral ischemia, because of an insufficient expression of Cu/Zn-SOD and Mn-SOD. Our double-labeled immunohistochemical study demonstrates that the overexpression of iNOS produced by Iba 1-immunopositive microglia may play a pivotal role in the damage of neurons and oligodendrocytes in the ipsilateral hippocampal CA1 sector at an acute stage after transient focal cerebral ischemia.

Therapeutic effect of a novel anti-parkinsonian agent zonisamide against MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) neurotoxicity in mice.

We investigated the therapeutic effect of zonisamide against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in mice, using Western blot analysis, immunohistochemistry and behavioral test. Our Western blot analysis and immunohistochemical study showed that the post-treatment with zonisamide prevented significantly dopaminergic cell damage, the depletion of tyrosine-hydroxylase (TH) protein levels and the proliferation of microglia in the striatum and/or substantia nigra 8 days after MPTP treatment. Furthermore, our behavioral study showed that the post-treatment with zonisamide attenuated significantly the motor deficits 7 days after MPTP treatment. These results show that zonisamide has the therapeutic effect in the MPTP model of Parkinson's disease (PD) in mice. Our study also demonstrates the neuroprotective effect of zonisamide against dopaminergic cell damage after MPTP treatment in mice. Thus our present findings suggest that therapeutic strategies targeted to the activation of TH protein and/or the inhibition of microglial activation with zonisamide may offer a great potential for restoring the functional capacity of the surviving dopaminergic neurons in individuals affected with PD.

Long-term changes in the ipsilateral substantia nigra after transient focal cerebral ischaemia in rats.

Transient focal cerebral ischaemia can cause neuronal damage in remote areas, including the ipsilateral thalamus and subsutantia nigra, as well as in the ischaemic core. In the present study, we investigated long-term changes in the ipsilateral substantia nigra from 1 up to 20 weeks after 90 min of transient focal cerebral ischaemia in rats, using tyrosine hydroxylase (TH), neuronal nuclei (NeuN), Iba-1, glial fibrillary acidic protein (GFAP) and brain-derived neurotrophic factor (BDNF) immunostaining. These results show that transient focal cerebral ischaemia in rats can cause a severe and prolonged neuronal damage in the ipsilateral striatum. Our results with TH and NeuN immunostaining also demonstrate that the atrophy of the ipsilateral substantia nigra after transient focal cerebral ischaemia was not static but progressive. Furthermore, our double-labelled immunohistochemical study suggests that BDNF released by GFAP-positive astrocytes may play a key role in the survival of dopaminergic neurones in the ipsilateral substantia nigra at the chronic stage after transient focal cerebral ischaemia, although the areas of the ipsilateral substantia nigra are decreased progressively after ischaemia. Thus our study provides further valuable information for the pathogenesis of neuronal damage after transient focal cerebral ischaemia.

Poly(ADP-ribose)polymerase inhibitor can attenuate the neuronal death after 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced neurotoxicity in mice.

An excessive expression of poly(ADP-ribose)polymerase (PARP) has been demonstrated to play a key role in the pathogenesis of Parkinson's disease (PD). Here we investigated the therapeutic effect of the PARP inhibitor benzamide against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in mice. In our HPLC and Western blot analysis, pretreatment with benzamide showed a neuroprotective effect against MPTP neurotoxicity in mice. Posttreatment with benzamide also attenuated MPTP neurotoxicity in mice. Furthermore, our immunohistochemical study showed that posttreatment with benzamide significantly prevented neuronal damage by suppressing overexpression of neuronal, microglial, and astroglial PARP after MPTP treatment. These findings have important implications for the therapeutic time window and choice of PARP inhibitors in PD patients. Our present findings provide further evidence that PARP inhibitor may offer a novel therapeutic strategy for PD.