Blockade of the KATP channel Kir6.2 by memantine represents a novel mechanism relevant to Alzheimer's disease therapy.

Here, we report a novel target of the drug memantine, ATP-sensitive K+ (KATP) channels, potentially relevant to memory improvement. We confirmed that memantine antagonizes memory impairment in Alzheimer's model APP23 mice. Memantine increased CaMKII activity in the APP23 mouse hippocampus, and memantine-induced enhancement of hippocampal long-term potentiation (LTP) and CaMKII activity was totally abolished by treatment with pinacidil, a specific opener of KATP channels. Memantine also inhibited Kir6.1 and Kir6.2 KATP channels and elevated intracellular Ca2+ concentrations in neuro2A cells overexpressing Kir6.1 or Kir6.2. Kir6.2 was preferentially expressed at postsynaptic regions of hippocampal neurons, whereas Kir6.1 was predominant in dendrites and cell bodies of pyramidal neurons. Finally, we confirmed that Kir6.2 mutant mice exhibit severe memory deficits and impaired hippocampal LTP, impairments that cannot be rescued by memantine administration. Altogether, our studies show that memantine modulates Kir6.2 activity, and that the Kir6.2 channel is a novel target for therapeutics to improve memory impairment in Alzheimer disease patients.

Lower values of handgrip strength and adductor pollicis muscle thickness are associated with hepatic encephalopathy manifestations in cirrhotic patients.

Hepatic encephalopathy (HE) is a late complication of liver cirrhosis and is clearly associated with poor outcomes. Chronic liver insufficiency leads to progressive muscle wasting, impairing ammonia metabolism and thus increasing the risk for HE. Given the association between lean mass and adductor pollicis muscle thickness (APMT), it has been used to predict outcome and complications in many conditions, but not yet in cirrhotic patients. Therefore, this article aimed to study the association between HE manifestations and measures related to muscle mass and strength. This cross-sectional study included 54 cirrhotic outpatients with HE varying from subclinical to grade II according to the West-Haven criteria, who were submitted to neuropsychometric tests, electroencephalogram, brain Single Photon Emission Computed Tomography (SPECT), anthropometric measurements, handgrip strength (HGS) and dual energy X-ray absorptiometry exam (DXA). Multiple logistic regression analysis was performed to investigate the association between body composition measures and HE grade. Analysis of the area under the receiver operator characteristic (AUROC) curve revealed the values related to neurological manifestations (HE grades I and II). Reductions in APMT and HGS were associated with higher HE grades, suggesting a big impact caused by the loss of muscle mass and function on HE severity. The link between HE manifestations and anthropometric measures, namely APMT and HGS, point to a significant relation concerning skeletal muscles and the neurological impairment in this population.

Rivastigmine improves hippocampal neurogenesis and depression-like behaviors via 5-HT1A receptor stimulation in olfactory bulbectomized mice.

Rivastigmine is a non-competitive inhibitor of both acetylcholinesterase (AChE) and butylcholinesterase (BuChE) used to treat mild to moderate dementia in Alzheimer's disease (AD) patients. Although rivastigmine reportedly ameliorates cognitive dysfunction in these patients, its ability to improve Behavioral and Psychological Symptoms of Dementia (BPSD) remains unclear. To determine whether rivastigmine treatment antagonizes depression-like behaviors, we chronically administered rivastigmine (0.1-1.0mg/kg) to olfactory bulbectomized (OBX) mice once a day for 2weeks, starting 2weeks after bulbectomy. Chronic treatment at 0.3 or 1.0mg/kg dose dependently and significantly improved depression-like behaviors, as assessed by tail suspension (TST), forced swim (FST), locomotion and novelty-suppressed feeding (NSFT) tests. Importantly, co-administration with WAY-100635 (1.0mg/kg), a 5-HT1A receptor antagonist, but not ketanserin (1.0mg/kg,), a 5-HT2A receptor antagonist, completely blocked rivastigmine-induced anti-depressive effects, suggesting that 5-HT1A receptor stimulation mediates this activity. Consistent with this observation, rivastigmine treatment significantly rescued impaired neurogenesis observed in OBX mice in a 5-HT1A receptor-dependent manner. Furthermore, enhanced protein kinase B (Akt) and extracellular signal-regulated kinase (ERK) phosphorylation seen following rivastigmine treatment was closely associated with improved neurogenesis. These effects were blocked by WAY-100635 but not ketanserin treatment. Finally, we confirmed that 5-HT1A but not 5-HT2A receptor stimulation by specific agonists mimicked rivastigmine-induced anti-depression activity and promoted hippocampal neurogenesis. We conclude that, in addition to enhancing the cholinergic system, rivastigmine treatment restores normal function of the hippocampal serotonergic system, an activity that likely ameliorates depressive behaviors in AD patients.

Decreased CaMKII and PKC activities in specific brain regions are associated with cognitive impairment in neonatal ventral hippocampus-lesioned rats.

Neonatal ventral hippocampus (NVH)-lesioned rats represent a neurodevelopmental impairment model of schizophrenia. Previous observations indicate that postpubertal NVH-lesioned rats exhibit impairments in prepulse inhibition (PPI), spontaneous locomotion and social interaction behavior. Here, we document the neurochemical basis of those defects. PPI impairment but not cognitive impairment was improved by acute risperidone treatment (0.30mg/kgi.p.). Immunohistochemical analyses using anti-autophosphorylated Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) antibody indicated significantly reduced CaMKII autophosphorylation, especially in the medial prefrontal cortex (mPFC), striatum and hippocampal CA1 region, of NVH-lesioned rats relative to control animals. We also confirmed that reduced CaMKII autophoshorylation in the mPFC, striatum and hippocampal CA1 region causes decreased phosphorylation of α-amino-3-hydroxy-5-methyl-4-isoxazolpropionic acid-type glutamate receptor subunit 1 (GluR1) (Ser 831), a CaMKII substrate. Like CaMKII, PKCα (Ser 657) autophosphorylation and NR1 (Ser 896) phosphorylation were decreased both in the mPFC and CA1 region. Interestingly, phosphorylation of DARPP-32 (Thr 34) was decreased in the mPFC but increased in the striatum and CA1 region of NVH-lesioned rats compared to controls. Risperidone treatment restored increased DARPP-32 phosphorylation in the striatum and CA1 regions of NVH-lesioned rats but did not rescue CaMKII and PKCα autophosphorylation. Taken together, we find that impaired cognition observed in NVH-lesioned rats is associated with decreased CaMKII and PKCα activities in memory-related brain regions, changes not rescued by risperidone treatment.

Platelet-activating factor-induced synaptic facilitation is associated with increased calcium/calmodulin-dependent protein kinase II, protein kinase C and extracellular signal-regulated kinase activities in the rat hippocampal CA1 region.

Platelet-activating factor (PAF) is an important inflammatory lipid mediator affecting neural plasticity. In the present study, we demonstrated how PAF affects synaptic efficacy through activation of protein kinases in the rat hippocampal CA1 region. In cultured hippocampal neurons, 10 to 1000 nM PAF stimulated autophosphorylation of calcium/calmodulin-dependent protein kinase II (CaMKII) and phosphorylation of synapsin I and myristoylated alanine-rich protein kinase C substrate (MARCKS). In hippocampal CA1 slices, field excitatory postsynaptic potentials (fEPSPs) induced by stimulation of the Schaffer collateral/commissural pathways were significantly increased 10-50 min after exposure to 100 to 1000 nM PAF. Immunoblotting analysis showed that 100 nM PAF treatment for 10 or 50 min significantly and persistently increased CaMKII autophosphorylation in the hippocampal CA1 region. Increased protein kinase Calpha (PKCalpha) autophosphorylation was also seen at the same time point after PAF exposure. By contrast, extracellular signal-regulated kinase (ERK) phosphorylation was slightly but significantly increased at 10 min after PAF exposure. Consistent with increased CaMKII autophosphorylation, AMPA-type glutamate receptor subunit 1 (GluR1) (Ser-831) phosphorylation as a CaMKII postsynaptic substrate significantly increased after 10 or 50 min of treatment, whereas synapsin I (Ser-603) phosphorylation as a presynaptic substrate increased at 10 min in the hippocampal CA1 region. Phosphorylation of MARCKS (Ser-152/156) and NMDA receptor subunit 1 (NR1) (Ser-896) as PKCalpha substrates also significantly increased after 10 min but had not further increased by 50 min in the CA1 region. Increased of fEPSPs induced by PAF treatment completely and/or partly inhibited by KN93 and/or U0126 treatment. These results suggest that PAF induces synaptic facilitation through activation of CaMKII, PKC and ERK in the hippocampal CA1 region.

Nefiracetam and galantamine modulation of excitatory and inhibitory synaptic transmission via stimulation of neuronal nicotinic acetylcholine receptors in rat cortical neurons.

The cholinergic and glutamatergic systems are known to be downregulated in the brain of Alzheimer's disease patients. Galantamine and nefiracetam have been shown to potentiate the phasic activity of nicotinic acetylcholine receptors (nAChRs) in the brain. Stimulation of nAChRs is also known to cause release of various neurotransmitters including glutamate and gamma-aminobutyric acid (GABA). We have previously reported that nefiracetam and galantamine potentiate the activity of nAChRs. Therefore, nefiracetam and galantamine are hypothesized to cause stimulations of the glutamate and GABA systems via stimulation of nAChRs. The present study was set out to test this hypothesis by measuring the effects of these drugs on spontaneous miniature excitatory postsynaptic currents (mEPSCs) and spontaneous miniature inhibitory postsynaptic currents (mIPSCs) recorded by the whole-cell patch clamp technique from rat cortical neurons in primary cultures. Acetylcholine (ACh) at 30 nM generated a steady inward current and increased the frequency of mEPSCs and mIPSCs. Nefiracetam at 10 nM plus 30 nM ACh increased the frequency of mEPSCs and mIPSCs beyond the levels increased by ACh alone. The potentiating action of nefiracetam was abolished by dihydro-beta-erythroidine. None of these treatments affected the amplitude of mEPSCs or mIPSCs. Galantamine at 1 muM plus ACh did not significantly potentiate the frequency. Nefiracetam at 10 nM had no effect on neurons that did not respond to 30 nM ACh. It was concluded that the nefiracetam released glutamate via stimulation of the alpha4beta2 nAChRs.

The vanadium (IV) compound rescues septo-hippocampal cholinergic neurons from neurodegeneration in olfactory bulbectomized mice.

The bilateral olfactory bulbectomy (OBX) mouse exhibits neurodegeneration of cholinergic neurons in the medial septum with concomitant cognitive deficits. Consistent with our previous observations, choline acetyltransferase (ChAT) protein levels in the medial septum decreased by 43.5% 2 weeks after OBX without changes in glutamic acid decarboxylase-65 (GAD65) levels. Interestingly, levels of the vesicular acetylcholine transporter (VAChT), which is localized at cholinergic neuron terminals, decreased both in hippocampal CA1 and CA3 regions following OBX. Confocal microscopy showed that VAChT expression was more severely reduced in CA3 14 days after OBX compared with CA1. Intriguingly, chronic treatment with a vanadium (IV) compound, VO(OPT) [bis(1-N-oxide-pyridine-2-thiolato)oxovanadium(IV)] (0.5-1 mg as vanadium (V)/kg/day, i.p.), significantly rescued cholinergic neurons in the medial septum in a dose-dependent manner. VO(OPT) treatment also prevented decreased VAChT immunoreactivity both in CA1 and CA3 regions in the hippocampus. Consistent with these findings, an impaired hippocampal long-term potentiation (LTP) and memory deficits seen in OBX mice were significantly prevented by VO(OPT) treatment. Taken together, OBX induces neurodegeneration of septo-hippocampal cholinergic neurons and impairment of memory-related behaviors. The neuroprotective effect of VO(OPT) could lead to novel therapeutic strategies to ameliorate cognitive deficits associated with cholinergic neuron degeneration in Alzheimer's disease and other neurodegenerative disorders.

Activation of phosphatidylinositol 3-kinase/protein kinase B pathway by a vanadyl compound mediates its neuroprotective effect in mouse brain ischemia.

We previously reported that orthovanadate composed of vanadate (V(5+)) activates phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling through inhibition of protein tyrosine phosphatases, thereby eliciting neuroprotection in brain ischemia/reperfusion injury. However, therapeutic doses of orthovanadate are associated with diarrhea due to inhibition of ATPase. By contrast, vanadyl (V(4+)) organic compounds show low cytotoxicity. Since both vanadate and vanadyl inhibit protein tyrosine phosphatases, we tested whether bis(1-oxy-2-pyridinethiolato)oxovanadium(IV) [VO(OPT)] in a vanadyl form elicits a neuroprotection in brain ischemia. In a mouse transient middle cerebral artery occlusion (MCAO) model, pre- and post-treatments with VO(OPT) significantly reduced infarct volume in a dose-dependent manner. Like orthovanadate, activation of the PI3K/Akt pathway mediated neuroprotective action. VO(OPT) treatment inhibited reduced Akt phosphorylation at Ser-473 following brain ischemia and restored decreased phosphorylation of forkhead box class O (FOXO) family members such as FKHR, FKHRL1, and AFX. Consistent with inhibition of FOXO dephosphorylation, VO(OPT) treatment blocked elevated expression of Fas-ligand, Bim and active caspase-3 24 h after ischemia/reperfusion. Taken together, a vanadyl compound, VO(OPT) elicits neuroprotective effects on brain ischemia/reperfusion injury without apparent side effects.

Detection of COL1A1-PDGFB fusion transcripts and platelet-derived growth factor alpha and beta receptors in giant cell fibroblastoma of the postsacrococcygeal region.

We describe a 2-year-old girl with recurrent giant cell fibroblastoma (GCF) of the postsacrococcygeal region. Both the initial and recurrent tumours contained solid and angiectoid areas. The former was composed of loosely arranged wavy spindle cells and giant cells with a well-vascularized myxoid to collagenous stroma. The angiectoid spaces were often lined by multinucleated giant cells. Immunohistochemically, the tumour cells and small vessels in the tumour tissue were positive for platelet-derived growth factor (PDGF) alpha and beta receptors. Molecular analysis revealed fusion of collagen type Ialpha1 exon 26 with PDGF-B chain exon 2 that induced unscheduled production of PDGF-BB. These findings suggest that PDGF and its receptors significantly contribute to the development of GCF in both an autocrine and a paracrine manner.

Phagocytosis of alveolar macrophages after conagenin injection to rats.

Phagocytic functions of rat alveolar macrophages (AM) following intraperitoneal injection of conagenin (CNG) and of AM sub-populations fractionated by Percoll discontinuous gradient centrifugation were investigated. Phagocytosis of opsonized-sheep red blood cells (SRBC) following in vitro incubation with CNG showed a significant increase in a higher density of AM (fraction IV). In addition, phagocytosis was also increased in lower density ones (fractions I and II) by macrophage-activating factor (MAF) co-cultivation. CNG-injected rats for 5 consecutive days showed a dose-dependent increase in phagocytosis of AM compared to the control rats. Although the distribution of AM sub-population in rats injected CNG was not significantly different compared to the control rats, phagocytosis was significantly increased in AM of a lower density fraction (fraction II). These results suggest that CNG directly increases phagocytosis of AM in a higher density fraction, and indirectly enhances phagocytosis in AM of a lower density fraction via increasing MAF-like material production.

Involvement of enhanced sensitivity of N-methyl-D-aspartate receptors in vulnerability of developing cortical neurons to methylmercury neurotoxicity.

The developing cortical neurons have been well documented to be extremely vulnerable to the toxic effect of methylmercury (MeHg). In the present study, a possible involvement of N-methyl-D-aspartate (NMDA) receptors in MeHg neurotoxicity was examined because the sensitivity of cortical neurons to NMDA neurotoxicity has a similar developmental profile. Rats on postnatal day 2 (P2), P16, and P60 were orally administered MeHg (10 mg/kg) for 7 consecutive days. The most severe neuronal damage was observed in the occipital cortex of P16 rats. When MK-801 (0.1 mg/kg), a non-competitive antagonist of NMDA, was administered intraperitoneally with MeHg, MeHg-induced neurodegeneration was markedly ameliorated. Furthermore, there was a marked accumulation of nitrotyrosine, a reaction product of peroxynitrite and L-tyrosine, after chronic treatment of MeHg in the occipital cortex of P16 rats. The accumulation of nitrotyrosine was also significantly suppressed by MK-801. In the present electrophysiological study, the amplitude of synaptic responses mediated by NMDA receptors recorded in cortical neurons of P16 rats was significantly larger than those from P2 and P60 rats. These observations strongly suggest that a generation of peroxynitrite through activation of NMDA receptors is a major causal factor for MeHg neurotoxicity in the developing cortical neurons. Furthermore, enhanced sensitivity of NMDA receptors may make the cortical neurons of P16 rats most susceptible to MeHg neurotoxicity.

Vitamin E and immunity.

Vitamin E is a potent antioxidant and has an ability to modulate host immune functions. This chapter consists of five parts: (1) vitamin E deficiency and immunity, (2) vitamin E supplementation and immunity, (3) vitamin E and the decreased cellular immunity with aging, (4) vitamin E and T-cell differentiation in the thymus, and (5) vitamin E and acquired immune deficiency syndrome (AIDS). In vitamin E deficiency most of the immune parameters show a downward trend, which is associated with increased infectious diseases and the incidence of tumors. In contrast, vitamin E supplementation has various beneficial effects on the host immune system. The decreased cellular immunity with aging or during the development of AIDS is markedly improved by the intake of a high vitamin E diet. In addition, vitamin E plays an important role in the differentiation of immature T cells in thymus. Vitamin E deficiency induces the decreased differentiation of immature T cells, which results in the early decrease of cellular immunity with aging in spontaneously hypertensive rats. Conversely, vitamin E supplementation induces a higher differentiation of immature T cells via increased positive selection by thymic epithelial cells, which results in the improvement of decreased cellular immunity in the aged. Furthermore, vitamin E supplementation induces the early recovery of thymic atrophy following X-ray irradiation. Taken together, these results suggest that vitamin E is an important nutrient for maintaining the immune system, especially in the aged.

[Cellular immunity and vitamins].

The purpose of this review is to introduce the informations on cellular immunity and vitamins. Until now, many literatures have addressed the evidences showing the close relationship between cellular immunity and vitamins. In water-soluble vitamins, it is well-known that their deficiences induce the marked decrease of cellular immunity, although their supplementations have little effect. In contrast, lipid-soluble vitamins such as vitamin A and E markedly affect cellular immunity in both deficient and excess state. Vitamin A supplementation induces the increase of cellular immunity such as phagocytic and tumoricidal activities in human monocytes or mouse peritoneal macrophages. High intake of vitamin E has an ability to improve the decreased cellular immunity in the aged, which appears to be associated with the decreased production of prostaglandin E2 (PGE2). In summary, since vitamins are important nutrients to maintain and promote cellular immunity, the beneficial use of vitamins for the health of human should be considered.

Conagenin derived from Streptomyces roseosporus enhances macrophage functions.

In contrast to the studies that describes the effects of conagenin (CNG) on the cellular immunity of lymphocytes (references), we investigated the in vitro effect of CNG on macrophage function. Phagocytosis of alveolar macrophages (AM) against opsonized-sheep red blood cells (SRBC) was significantly enhanced following in vitro incubation with CNG for 12 hours at 37 degrees C, which was closely associated with increased expression of Fc-receptor in AM membranes. Macrophage-activating factor (MAF), prepared from splenic lymphocytes in vitro stimulated with concanavarin A (Con A) for 48 hours at 37 degrees C, had also the enhancing effect on phagocytosis of AM against opsonized-SRBC. Preincubation with CNG (0.1 microg/ml) and MAF (1/100 dilution) induced the additional effect on phagocytosis of AM, which was associated with the increased expression of Fc-receptor in AM membranes. These results suggest that CNG enhances AM phagocytosis by increasing the expression of Fc-receptor on their membranes via either effecting different sub-populations of AM cells or by activating independent mechanism on the same AM cell population.

The role of vitamin E in T-cell differentiation and the decrease of cellular immunity with aging.

Spontaneously hypertensive rats (SHR) as a model for aging were used in this experiment and fed a regular (50 IU/Kg diet) or high vitamin E (500 IU/Kg diet) diet for 6 weeks. At 12 weeks old, they were killed and assayed. Although proliferation of thymic lymphocytes was significantly decreased in SHR fed the regular diet compared to Wistar Kyoto rats (WKY) fed the same diet, high vitamin E diet enhanced proliferation of thymic lymphocytes in SHR to almost the levels in WKY fed the regular diet. In addition, the expressions of both CD4 and CD8 antigens on CD+CD8+ T cells, immature T cells existing in thymic cortex, were also decreased in SHR, and significantly improved by high vitamin E diet. These results suggest that high vitamin E diet enhances thymic lymphocyte proliferation through increased T-cell differentiation in thymus. Then, the effect of vitamin E on T-cell differentiation in thymus was investigated by using male Fisher rats. Rats were divided into three groups; vitamin E-free, regular and high vitamin E groups and fed a diet containing various levels of vitamin E (0, 50 and 500 IU/Kg diet) for 7 weeks. Although the percentages of CD4+CD8- and CD4-CD8+ T cells in thymocytes were significantly greater in the high vitamin E group, the percentage of CD4+CD8- T cells inversely decreased in the vitamin E-free group compared to the regular group. We have tried to investigate the mechanism of the increased T-cell differentiation in thymus of rats fed the high vitamin E diet through cytokine production, and thymic epithelial cell (TEC) and macrophage functions. We have found that vitamin E enhances T-cell differentiation through the increase of not macrophage but TEC function in thymus, which is associated with the increased binding capacity of TEC to immature T cells via increased expression of adhesion molecule, ICAM-1. These results suggest that vitamin E is a potent nutrient for promoting health in the aged via the improvement of cellular immunity decreased with aging.

Decreased mitogen response of splenic lymphocytes in obese Zucker rats is associated with the decreased expression of glucose transporter 1 (GLUT-1).

We reported previously that obesity is a risk factor for deteriorating cellular immune functions in aging. However, the mechanism by which obesity decreases cellular immunity remains to be elucidated. To determine the mechanism of the decrease in cellular immunity with obesity, lean (Fa/?) and obese (fa/fa) 12-mo-old Zucker rats were used. The mitogen response of splenic lymphocytes in obese Zucker rats was significantly lower than that of lean Zucker rats, which was not restored by in vitro treatment with indomethacin (10 micromol/L), an inhibitor of prostaglandin E2 (PGE2). In addition, PGE2 production by splenic lymphocytes was not greater in obese than in lean Zucker rats. Glucose consumption by splenic lymphocytes after in vitro incubation with concanavalin A (conA) for 48 h was also significantly lower in obese Zucker rats. Expression of glucose transporter 1 (GLUT-1), analyzed by Western blot analysis, was lower in splenic lymphocytes of obese than in lean Zucker rats. However, the expression of the conA receptor in splenic lymphocytes, analyzed by flow cytometry with fluorescein isothiocyanate-conjugated conA, was not significantly different between lean and obese Zucker rats. In conclusion, the decreased mitogen response of splenic lymphocytes in obese Zucker rats may be due in part to the decreased uptake of glucose as the main energy source for lymphocytes at the stage of proliferation and may be associated with the decreased expression of GLUT-1.

Central administration of a nitric oxide synthase inhibitor causes pressor responses via the sympathetic nervous system and the renin-angiotensin system in Wistar rats.

The central roles of nitric oxide (NO) in regulations of the blood pressure and heart rate were examined in anesthetized rats. Intracerebroventricular (i.c.v.) injection of Nomega-nitro-L-arginine methyl ester (L-NAME) caused dose-dependent increase in the blood pressure and heart rate. The pressor response of the blood pressure to L-NAME (2 micromol, i.c.v.) was reduced by L-arginine (5 micromol, i.c.v). Pretreatment with a ganglionic blocker, pentolinium (10 mg/kg, i.v.), significantly inhibited both pressor responses induced by L-NAME (2 micromol, i.c.v). The later pressor response of the blood pressure to L-NAME was also inhibited by the angiotensin II AT-1 blocker losartan (10 mg/kg, i.v). These results suggest that the response of the blood pressure to L-NAME is mediated by both the sympathetic nervous system and the renin-angiotensin system.

The role of vitamin E in T-cell differentiation and the decrease of cellular immunity with aging.

The purpose of this study is to investigate the effects of vitamin E on both the decrease of cellular immunity with aging (Section 2) and the differentiation of T-cells in thymus (Section 3). In Section 2, spontaneously hypertensive rats (SHR) as a model for aging were used in this experiment and fed regular (50 IU/kg diet) or a high vitamin E (500 IU/kg diet) diet for 6 weeks. At 12 weeks old, they were killed and assayed. Although proliferation of thymic lymphocytes was significantly decreased in SHR fed the regular diet compared to that of Wistar Kyoto rats (WKY) fed the same diet, the high vitamin E diet induced higher proliferation of thymic lymphocytes in SHR, which was almost the same as that of WKY fed the regular diet. In addition, the expressions of both CD4 and CD8 antigens on CD4+ CD8+ T-cells were also decreased in SHR, which was significantly improved by a high vitamin E diet. These results suggest that a high vitamin E diet enhances thymic lymphocyte proliferation through increased T-cell differentiation in the thymus. Then, the effect of vitamin E on T-cell differentiation in the thymus was investigated by using male Fisher rats. Rats were divided into three groups; vitamin E-free, regular and high vitamin E groups and fed a diet containing various levels of vitamin E (0, 50 and 500 IU/kg diet) for 7 weeks. Although the proportions of CD4+ CD8- and CD4- CD8+ T-cells in thymocytes were significantly greater in the high vitamin E group, the proportion of CD4+ CD8- T-cells inversely decreased in the vitamin E-free group compared to that of the regular group. We have tried to investigate the mechanism on the increased T-cell differentiation in the thymus of rats fed the high vitamin E diet through cytokine production, thymic epithelial cell (TEC) and macrophage functions. As their results, we have found that vitamin E enhances T-cell differentiation through the increase of not macrophage but TEC function in the thymus, which is associated with the increased binding capacity of TEC to immature T-cells via increased expression of the adhesion molecule, ICAM-1. These results suggest that vitamin E is a potent nutrient for promoting health in the aged via the improvement of cellular immunity decreased with aging.

Exercise training restores decreased cellular immune functions in obese Zucker rats.

This study investigated whether exercise training had a beneficial effect on the decreased mitogen response and improved a decreased expression of glucose transporter 1 (GLUT-1) in splenocytes from obese Zucker rats. Experimental groups were lean and sedentary and exercise-trained obese Zucker rats. Exercise training, running on a motor-driven treadmill for 5 days/wk for 40 wk, did not induce a significant decrease in body weight in obese Zucker rats. The plasma insulin concentration, showing a significant increase compared with lean Zucker rats, was unaffected by exercise training. However, the plasma triglyceride concentration in obese Zucker rats was significantly depressed by exercise training, whereas it was still higher than that in lean Zucker rats. In addition, natural killer cell activity and concanavalin A-induced mitogenesis of splenic lymphocytes of obese Zucker rats were significantly restored. In these splenic lymphocytes, glucose uptake was significantly lower compared with that in lean Zucker rats, which was also improved by exercise training. Although the expression of GLUT-1, the major glucose transporter in immune cells, was depressed in splenic lymphocytes of obese Zucker rats, exercise training induced a significant improvement. These results suggest that exercise training has a beneficial effect on the decreased cellular immune functions in obese Zucker rats, which is associated, in part, with the improvement in GLUT-1 expression.

Long-term feeding of high vitamin E diet improves the decreased mitogen response of rat splenic lymphocytes with aging.

This study was performed to investigate whether the long-term feeding of a high vitamin E (VE) diet has a beneficial effect on the decreased cellular immune functions caused by aging. Male Fisher rats, 12 weeks old, were fed a regular (50 mg VE/kg diet) or high VE diet (585 mg VE/kg diet) for 12 months. Then, the rats were sacrificed under anesthesia and their cellular immune functions were measured. The proliferation of splenic lymphocytes with PHA or Con A was significantly lower in old rats fed the regular diet as compared to that of young rats (two months old). In contrast, the proliferation of splenic lymphocytes in old rats fed the high VE diet was similar to that of young rats. The in vitro effect of macrophages (M phi) on the proliferation of splenic lymphocytes from young rats was investigated under Con A stimulation. Although splenic M phi isolated from old rats fed the regular diet did not have any effect on the proliferation of splenic lymphocytes, M phi from old rats fed the high VE diet significantly enhanced the proliferation of splenic lymphocytes. The responsiveness of splenic lymphocytes isolated from each group to the M phi of young rats under Con A stimulation was not significantly different between the young rats and old rats fed the regular diet. In old rats fed the high VE diet, the responsiveness of splenic lymphocytes to young rat M phi was significantly higher than that of the young rats or old rats fed the regular diet. Furthermore, the high VE diet induced a significant increase in interleukin 2 (IL2) production from splenocytes in both young rats and old rats following in vitro stimulation with Con A for 48 h. These results suggest that VE has the ability to improve the decreased cellular immune functions caused by aging, and appears to be associated with the enhancement of both M phi functions and lymphocyte responsiveness.