Acute severe exercise facilitates neutrophil extracellular trap formation in sedentary but not active subjects.

UNLABELLED: Neutrophil extracellular trap (NET), a newly revealed antimicrobial strategy, is usually evoked by reactive oxygen species (ROS) and nicotinamide adenine denucleotide phosphate (NADPH) oxidase activation. In addition, the acute severe exercise (ASE)-induced oxidative stress in neutrophils depends on the subject's physical fitness. PURPOSE: We investigated whether ASE exerted differential effects on NET formation in sedentary and physically active subjects. METHODS: Young males, 10 sedentary and 10 physically active, underwent an ASE (pedaling on a bicycle ergometer with increasing loads until exhaustion). Neutrophils were isolated from blood specimens drawn before and immediately after ASE for assaying NET formation along with redox-related parameters and mitochondrial membrane potential (ΔΨm). RESULTS: In the sedentary group, (1) after ASE, NET formation increased spontaneously and in response to stimulation with phorbol 12-myristate 13-acetate; (2) ASE increased cytosolic ROS, decreased glutathione, and suppressed ΔΨm in neutrophils; (3) removing ROS or inhibiting NADPH oxidase prevented the ASE-facilitated NET formation; and (4) suppressing ΔΨm prevented the ASE-facilitated NET formation. On the contrary, these ASE effects on neutrophils did not happen in the active group. CONCLUSIONS: ASE in sedentary but not active subjects facilitated NET formation via elevating the NADPH oxidase-generated ROS and suppressing the ΔΨm.

Early postinjury exercise reverses memory deficits and retards the progression of closed-head injury in mice.

Closed-head injury (CHI) usually involves both physical damage of neurons and neuroinflammation. Although exercise promotes neuronal repair and suppresses neuroinflammation, CHI patients currently often remain resting during the post-traumatic period. This study aimed to investigate whether and how postinjury exercise benefited the brain structure and function in mice after CHI. Closed-head injury immediately caused an elevated neurological severity score, with rapid loss of object recognition memory, followed by progressive location-dependent brain damage (neuronal loss and activation of microglia in the cortex and hippocampus). An early exercise protocol at moderate intensity (starting 2 days postimpact and lasting for 7 or 14 days) effectively restored the object recognition memory and prevented the progressive neuronal loss and activation of microglia. However, if the exercise started 9 days postimpact, it was unable to recover recognition memory deficits. In parallel, early exercise intervention drastically promoted neurite regeneration, while late exercise intervention was much less effective. We also tested the possible involvement of brain-derived neurotrophic factor (BDNF) and mitogen-activated protein kinase phosphatase-1 (MKP-1) in the exercise-induced beneficial effects. Exercise gradually restored the impact-abolished hippocampal expression of BDNF and MPK-1, while oral administration of triptolide (a synthesis inhibitor of MKP-1 and an antagonist of nuclear factor-B) before each bout of exercise blocked the restorative effects of exercise on MKP-1 and recognition memory, as well as the exercise-induced retardation of neuronal loss. Although triptolide treatment alone inhibited activation of microglia and maintained neuronal numbers, it did not recover the injury-hampered recognition memory. Overall, moderate exercise shortly after CHI reversed the deficits in recognition memory and prevented the progression of brain injury.

Chronic treadmill exercise in rats delicately alters the Purkinje cell structure to improve motor performance and toxin resistance in the cerebellum.

Although exercise usually improves motor performance, the underlying cellular changes in the cerebellum remain to be elucidated. This study aimed to investigate whether and how chronic treadmill exercise in young rats induced Purkinje cell changes to improve motor performance and rendered the cerebellum less vulnerable to toxin insults. After 1-wk familiarization of treadmill running, 6-wk-old male Wistar rats were divided into exercise and sedentary groups. The exercise group was then subjected to 8 wk of exercise training at moderate intensity. The rotarod test was carried out to evaluate motor performance. Purkinje cells in cerebellar slices were visualized by lucifer yellow labeling in single neurons and by calbindin immunostaining in groups of neurons. Compared with sedentary control rats, exercised rats not only performed better in the rotarod task, but also showed finer Purkinje cell structure (higher dendritic volume and spine density with the same dendritic field). The exercise-improved cerebellar functions were further evaluated by monitoring the long-lasting effects of intraventricular application of OX7-saporin. In the sedentary group, OX7-saporin treatment retarded the rotarod performance and induced ∼60% Purkinje cell loss in 3 wk. As a comparison, the exercise group showed much milder injuries in the cerebellum by the same toxin treatment. In conclusion, exercise training in young rats increased the dendritic density of Purkinje cells, which might play an important role in improving the motor performance. Furthermore, as Purkinje cells in the exercise group were relatively toxin resistant, the exercised rats showed good motor performance, even under toxin-treated conditions.

Blood pressure variations real-time reflect the conditioned fear learning and memory.

The conditioned fear learning and memory occurs when a neutral conditioned stimulus (CS) is paired with an aversive unconditioned stimulus (US). This process is critically dependent on the amygdala and inevitably involves blood pressure (BP) alterations. We hypothesized that BP variations could instantaneously reveal individual steps during conditioned fear learning and memory. An implanted telemetric probe was used to monitor the BP real-time in rats during training and testing sessions of the fear-potentiated startle. Our results showed that (i) the conditioned fear learning during the training sessions was reflected by light (CS)-induced rapid BP elevations and by electric shock (US)-evoked sympathetic tone elevations; (ii) these two BP-related parameters were not only negatively correlated with each other but also coupled to each other in the training session trials; (iii) both parameters closely predicted the performance of fear-potentiated startle on the next day; and (iv) although local blocking of one of the two fear-conditioned pathways in the training session partially inhibited fear learning, the fear memory retrieval still used both pathways. Altogether, real-time blood pressure variations faithfully revealed the critical steps involved in conditioned fear learning and memory, and our results supported a coupling between the cued learning and the post-shock calmness.

Differential effects of acute and chronic exercise on human neutrophil functions.

UNLABELLED: Exercise effects on immunity are highly dependent on exercise intensity, duration, and frequency. PURPOSE: Because neutrophils play an essential role in innate immunity, we investigated whether acute severe exercise (ASE) and chronic moderate exercise (CME) differentially regulate human neutrophil functions. METHODS: Thirteen sedentary young males underwent an initial ASE (pedaling on a bicycle ergometer with increasing loads until exhaustion), and they were subsequently divided into exercise (n = 8) and control groups (n = 5). The exercise group underwent 2 months of CME (pedaling on the ergometer at a moderate intensity for 30 min each day) followed by 2 months of detraining. The control group was abstained from regular exercise during these 4 months. Additional ASE paradigms were performed every month (in the exercise group) or every 2 months (in the control group). Neutrophils were isolated from blood specimens drawn at rest and immediately after each ASE for assaying chemotaxis, phagocytosis, citrate synthase activity, and mitochondrial membrane potential (ΔΨm). Additional blood specimens were drawn from the exercise group before and immediately after the first bout of CME to determine the acute moderate exercise (AME) effects on neutrophil functions. RESULTS: The study's results are the following: 1) the initial ASE enhanced chemotaxis and induced ΔΨm depolarization; 2) AME did not influence any measured parameter in neutrophils; 3) CME increased chemotaxis, phagocytosis, citrate synthase activity, and ΔΨm; 4) the CME effects remained after detraining except phagocytosis; and 5) the ASE effects disappeared after CME and were partially restored after detraining. CONCLUSIONS: ASE and CME differentially affected neutrophil functions, whereas AME was ineffective. Moreover, the fact that CME improves neutrophil functions may partially explain why physically active subjects have a low risk of infection.

Chronic treadmill running in normotensive rats resets the resting blood pressure to lower levels by upregulating the hypothalamic GABAergic system.

OBJECTIVE: The cardiovascular integration center not only sends out signals to offset the stimulus-induced responses but also resets the resting blood pressure. We hypothesize that GABAergic adaptations in the hypothalamus participate in the chronic exercise-induced cardiovascular resetting effects in conscious normotensive animals. METHODS: Male Wistar rats were subjected to chronic moderate exercise (CME, 8-week treadmill running at moderate intensity). A biotelemetry system was used to measure blood pressure, heart rate, autonomic nervous activities, baroreflex sensitivity and endogenous GABAergic activities in the paraventricular nucleus and the posterior hypothalamic area. Hypothalamic specimens were collected for quantifying GABA-related proteins and GABAergic neurons. RESULTS: CME reduced resting blood pressure, heart rate, sympathetic activity and enhanced parasympathetic activity and baroreflex sensitivity. Additionally, CME elevated the resting level of hypothalamic GABAergic activities, increased the percentage of GABAergic neurons in the hypothalamus and upregulated the hypothalamic protein levels of neuronal nitric oxide synthase, GAD67 and gephyrin, but not GABAA receptor. Moreover, a single bout of moderate exercise transiently elevated blood pressure and heart rate with prolonged high levels of neural controls (sympathetic activity, baroreflex sensitivity and hypothalamic GABAergic activities). CME accelerated the postexercise recovery in cardiovascular parameters and neural control alterations. CONCLUSION: Chronic treadmill running in normotensive rats augmented the GABAergic system in both paraventricular nucleus and posterior hypothalamic area, resulting in lower resting blood pressure, heart rate and sympathetic tone under conscious unrestraint conditions. This study provides insight into mechanisms important for explaining how chronic exercise resets the resting blood pressure.

Severe exercise and exercise training exert opposite effects on human neutrophil apoptosis via altering the redox status.

Neutrophil spontaneous apoptosis, a process crucial for immune regulation, is mainly controlled by alterations in reactive oxygen species (ROS) and mitochondria integrity. Exercise has been proposed to be a physiological way to modulate immunity; while acute severe exercise (ASE) usually impedes immunity, chronic moderate exercise (CME) improves it. This study aimed to investigate whether and how ASE and CME oppositely regulate human neutrophil apoptosis. Thirteen sedentary young males underwent an initial ASE and were subsequently divided into exercise and control groups. The exercise group (n = 8) underwent 2 months of CME followed by 2 months of detraining. Additional ASE paradigms were performed at the end of each month. Neutrophils were isolated from blood specimens drawn at rest and immediately after each ASE for assaying neutrophil spontaneous apoptosis (annexin-V binding on the outer surface) along with redox-related parameters and mitochondria-related parameters. Our results showed that i) the initial ASE immediately increased the oxidative stress (cytosolic ROS and glutathione oxidation), and sequentially accelerated the reduction of mitochondrial membrane potential, the surface binding of annexin-V, and the generation of mitochondrial ROS; ii) CME upregulated glutathione level, retarded spontaneous apoptosis and delayed mitochondria deterioration; iii) most effects of CME were unchanged after detraining; and iv) CME blocked ASE effects and this capability remained intact even after detraining. Furthermore, the ASE effects on neutrophil spontaneous apoptosis were mimicked by adding exogenous H(2)O(2), but not by suppressing mitochondrial membrane potential. In conclusion, while ASE induced an oxidative state and resulted in acceleration of human neutrophil apoptosis, CME delayed neutrophil apoptosis by maintaining a reduced state for long periods of time even after detraining.

The effects of systemic chemical sympathectomy on local bone loss induced by sciatic neurectomy.

BACKGROUND: It has been suggested that the sympathetic nervous system (SNS) is involved in bone metabolism and that blockade of the SNS could reduce bone loss and stimulate bone formation. However, the question of whether suppression of SNS tone could compensate for mechanical unloading-induced bone loss must be further clarified. The purpose of this study was to investigate whether systemically inhibiting sympathetic nervous system (SNS) tone could prevent bone loss from mechanical-inactivity-induced osteopenia. METHODS: Female Wistar rats (12 weeks old) were randomly assigned to three groups: the SN group (n = 10), or single leg sciatic neurectomy group; the SNP group (n = 12), or single leg sciatic neurectomy + propranolol treatment (0.5 g/L in dietary water) group; and the CON group (n = 10), or single leg sham-operated group. Animals were fed with distilled water or propranolol in water, in accordance with their group design, for 30 days. Histomorphometry, geometry, tissue weight, and serum markers were assessed. RESULTS: Propranolol-treated animals drank significantly less water, but did not differ in daily chow consumption or body weight gain. In histomorphometric analysis, the spongy bone volume ratio in proximal tibiae was significantly lower in the two sciatic neurectomy groups, but there was no difference between the SN and SNP groups. Architecture analysis showed that the SN group had significantly thinner trabeculae and fewer trabeculae than the CON group (p < 0.05), but there was no difference between the SNP and CON groups. There were no significant differences for tissue weight, geometric measurement, or serum markers assay. CONCLUSION: It was observed that blockade of the SNS prevented neurectomy-induced bone resorption, as demonstrated by various histomorphometric data, although the difference between SN and SNP did not reach significance. In further work it would be valuable to study possible gender, age, and dose-dependent efficacy of propranolol on bone metabolism.

NO signaling in exercise training-induced anti-apoptotic effects in human neutrophils.

Short-lived neutrophils play a predominant role in innate immunity, the effects of exercise training on neutrophil survival is unclear. In this study, we investigated the underlying mechanisms of training effects on human neutrophil apoptosis. Healthy male subjects were trained on a cycling ergometer for 8 weeks and followed by 4 weeks of detraining. Blood neutrophils were collected before exercise, after training, and after detraining. Comparing with pre-exercise specimens, neutrophils collected after training showed reduced apoptosis rate, which partially returned after detraining. Various intracellular proteins, including iNOS, Mcl-1, A1, Grp78, and IL-8, were upregulated by training, and they remained high after detraining. Upregulated iNOS was closely correlated with these anti-apoptotic molecules in neutrophils. Furthermore, the possible mechanism by which iNOS suppressed apoptosis was explored. Neutrophil apoptosis was accelerated by blocking and retarded by stimulating the endogenous iNOS activity. As an anti-apoptosis mediator of NO signaling, the Mcl-1 level dropped by depletion of the major NO downstream molecule cGMP and such loss of Mcl-1 was avoidable when supplying exogenous NO. Upon activation of NO-cGMP signaling, neutrophils held increased Mcl-1 expression and delayed apoptosis. Collectively, our results suggested that exercise training may retard neutrophil apoptosis by upregulating the iNOS-NO-cGMP-Mcl-1 pathway.

Exercise training upregulates macrophage MKP-1 and affects immune responses in mice.

PURPOSE: Currently, it is unclear how chronic exercise affects immunity. Mitogen-activated protein kinase (MAPK) mediates the production of proinflammatory cytokines, whereas MAPK phosphatase-1 (MKP-1) plays an essential role in intracellular homeostasis by negatively regulating macrophage MAPK activation. We hypothesized that chronic exercise might upregulate macrophage MKP-1 and thus prevent excessive inflammatory responses. METHODS: To verify this hypothesis, we compared the basal immune status and lipopolysaccharide (LPS)-evoked immune responses between sedentary and 8-wk treadmill exercise-trained male C57BL/6 mice. RESULTS: Although the basal levels of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) were undetectable in the serum of both groups, the exercised mice showed the following immune adaptations in vivo: (i) higher basal MKP-1 mRNA level in peritoneal macrophages, (ii) lower basal p38 MAPK activity and enhanced MKP-1 immunostaining in macrophages, and (iii) lower serum levels of IL-6 and TNF-α and less leukocyte infiltration into peritoneal cavity after systemic administration of LPS when compared with sedentary controls. In addition, when peritoneal macrophages isolated from exercised mice were exposed to LPS in vitro, they showed (i) accelerated MKP-1 protein expression, (ii) reduced p38 MAPK activity, and (iii) reduced cytokine secretion of IL-6, TNF-α, and monocyte chemotactic protein-1. Finally, 2 months of deconditioning completely reversed the exercise-enhanced basal MKP-1 immunostaining in macrophages and the exercise-suppressed cytokine secretion under LPS-evoked conditions. CONCLUSIONS: Exercise training upregulated basal macrophage MKP-1 expression, accelerated LPS-evoked MKP-1 up-regulation, and affected LPS-evoked immune responses in mice.

Differential effects of treadmill running and wheel running on spatial or aversive learning and memory: roles of amygdalar brain-derived neurotrophic factor and synaptotagmin I.

Chronic exercise has been reported to improve cognitive function. However, whether and how different types of exercise affect various learning and memory tasks remain uncertain. To address this issue, male BALB/c mice were trained for 4 weeks under two different exercise protocols: moderate treadmill running or voluntary wheel running. After exercise training, their spatial memory and aversive memory were evaluated by a Morris water maze and by one-trial passive avoidance (PA), respectively. Levels of neural plasticity-related proteins, i.e. brain-derived neurotrophic factor (BDNF), tropomyosin-related kinase B (TrkB) and synaptotagmin I (Syt I), in hippocampus and amygdala were determined by ELISA or immunoblotting. Finally, the functional roles of these proteins in the basolateral amygdala were verified by locally blocking them with K252a (a TrkB kinase inhibitor), or lentivirus expressing Syt I shRNA. We found that (1) although both moderate treadmill running and wheel running improved the Morris water maze performance, only the former improved PA performance; (2) likewise, both exercise protocols upregulated the BDNF-TrkB pathway and Syt I in the hippocampus, whereas only treadmill exercise upregulated their expression levels in the amygdala; (3) local injection of K252a abolished the treadmill exercise-facilitated PA performance and upregulation of amygdalar TrkB and Syt I; and (4) local administration of Syt I shRNA abolished the treadmill exercise-facilitated PA performance and upregulation of amygdalar Syt I. Therefore, our results support the notion that different forms of exercise induce neuroplasticity changes in different brain regions, and thus exert diverse effects on various forms of learning and memory.

Exercise training modulates the effects of lipoproteins on acetylcholine-induced endothelial calcium signaling in rat aortas.

Exercise training improves vascular endothelial functions, while oxidized low-density lipoproteins (oxLDLs) impede them. We proposed that exercise training might influence the endothelial sensitivity to lipoprotein-induced vascular changes. Male Wistar rats either exercised on a leveled treadmill for 8 weeks or remained sedentary as the control. The endothelial intracellular calcium level (EC [Ca(2+)](i)) in vitro was examined using dissected aortic segments treated with different lipoproteins, including native low-density lipoprotein (nLDL), various oxLDLs, and high-density lipoprotein (HDL). Our results indicated that i) none of the various lipoproteins directly evoked EC [Ca(2+)](i) elevation; ii) the acetylcholine-evoked EC [Ca(2+)](i) elevation in the control group was increased by nLDL and progressively suppressed by oxLDLs with increasing degrees of oxidation; iii) exercise training ameliorated the oxLDL-induced suppressive effects on acetylcholine-evoked EC [Ca(2+)](i) elevation; iv) HDL potentiated the acetylcholine-evoked EC [Ca(2+)](i) elevation in vessel segments from exercised rats but not those from control rats; and v) when HDL was present, the suppressive effects of extensively modified oxLDLs were reduced. Furthermore, comparing with the effects of various lipoproteins on EC calcium signaling, the lipoprotein effects on endothelium-dependent vasorelaxing response appeared to be similar but less pronounced. Taken together, one of the beneficial effects of exercise training on vascular functions might be to make blood vessels more resistant to oxLDLs and more sensitive to HDL.

Glucocorticoid signaling and exercise-induced downregulation of the mineralocorticoid receptor in the induction of adult mouse dentate neurogenesis by treadmill running.

Physical exercise is known to promote adult neurogenesis, although the underlying mechanisms remain unclear. Glucocorticoid (corticosterone in rodents) is a factor that is known to affect neurogenesis. As physical exercise modulates corticosterone secretion, we hypothesized that corticosterone signaling is involved in exercise-induced adult neurogenesis. We chose treadmill running (TR) to accurately define the intensity and duration of exercise. Our results showed that 5 weeks of TR increased the doublecortin (DCX)-positive neuronal progenitor cells (NPCs) in adult hippocampus and transiently increased the serum corticosterone level at the end of the TR protocol. This protocol reduced the levels of hippocampal mineralocorticoid receptor (MR); however, glucocorticoid receptor levels were unaltered. We then investigated whether reducing corticosterone levels by bilateral adrenalectomy (ADX) attenuated the TR-enhanced adult neurogenesis. Our results showed that ADX not only blocked the TR-induced downregulation of MR, but also reduced the number of TR-enhanced NPCs. In order to examine the role of MR downregulation in TR-induced adult neurogenesis, animals were treated repeatedly with a selective MR antagonist, spironolactone, for 3 weeks. The results revealed that spironolactone increased the number of spontaneously occurring and TR-induced NPC in the dentate area. Further analysis revealed that spironolactone treatment did not alter precursor cell proliferation, but increased the number of DCX-positive NPCs, suggesting that blockage of MR signaling either facilitates the differentiation of progenitor cells towards neurons and/or enhances the survival of NPCs. Taken together, the data indicated that induction of NPCs in the dentate area of adult hippocampus by TR is partly due to the downregulation of glucocorticoid/MR signaling, which subsequently enhances differentiation along a neuronal lineage and/or NPC survival.

Low-intensity pulsed ultrasound-promoted bone healing is not entirely cyclooxgenase 2 dependent.

OBJECTIVE: The purpose of this study was to investigate whether low-intensity pulsed ultrasound (LIPUS) promotes bone healing through the cyclooxgenase 2 (COX-2) pathway. METHODS: Each male Sprague Dawley rat (n = 48 total) in the study underwent bilateral drilled hole injury in the proximal tibiae. Then the animals were randomly assigned to 2 groups: a COX-2 inhibitor (COX-2in) group, treated with the selective COX-2 inhibitor rofecoxib (3 mg/kg/d), and a control (CON) group, treated with distilled water. Low-intensity pulsed ultrasound was applied to the injured site of a single limb of each rat for 20 min/d at a consistent intensity (30 mW/cm(2)) and frequency (1.5 MHz). Subsets of animals from both groups were killed after 3, 7, or 14 days of single-limb LIPUS treatment. Tissue sections were subjected to alcian blue staining, and the healing status was quantified according to a scoring system. RESULTS: After 3 and 7 days, the CON group's LIPUS-treated limbs had significantly higher healing scores than its nontreated limbs and the COX-2in group's LIPUS-treated limbs (P < .05). Interestingly, after the 14-day treatment, the COX-2in group's LIPUS-treated limbs had significantly higher healing scores than its nontreated limbs (P < .05) but showed no difference when compared with the CON group. CONCLUSIONS: Low-intensity pulsed ultrasound did show accelerative efficacy on bone healing. Selective inhibition of COX-2 could delay but not entirely block the benefits of LIPUS on bone healing. Low-intensity ultrasound treatment could promote bone healing through other, non-COX-2-dependent, pathways.

Exercise enhances the proliferation of neural stem cells and neurite growth and survival of neuronal progenitor cells in dentate gyrus of middle-aged mice.

Aging is an important determinant of adult hippocampal neurogenesis as the proliferation of neural stem/precursor cells (NSCs) declines dramatically before middle age. Contrary to this, physical exercise is known to promote adult hippocampal neurogenesis. The objective of this study is to investigate the effects of mandatory treadmill running (TR) on neurogenesis, including 1) NSCs proliferation, 2) neurite outgrowth of neuronal progenitor cells, and 3) the survival of newborn neurons in dentate area of middle-aged animals. Compared with 3-mo-old mice, numbers of mitotic cells and neuronal progenitor cells decreased dramatically by middle age and remained at low levels after middle age. Five weeks of TR not only increased NSC proliferation and the number of immature neurons but also promoted the maturation and survival of immature neurons in middle-aged mice. The neurogenic and neurotrophic effects of TR were not due to the reduction of the age-related elevation of serum corticosterone. Significantly, 5 wk of TR restored the age-dependent decline of brain-derived neurotrophic factor and its receptor, TrkB, which are known to promote neuronal differentiation and survival. Taken together, mandatory running exercise alters the brain chemistries of middle-aged animals toward an environment that is favorable to NSC proliferation, survival, and maturation.

Onion decreases the ovariectomy-induced osteopenia in young adult rats.

It has been suggested that fruit and vegetable consumption are associated with good bone health. Onion, in particular, has been verified in its efficacy in bone resorption activity. In this study, we further investigated the effects of an onion-containing diet on ovariectomy-induced bone loss using methods of serum marker assay, histomorphometric analysis and biomechanical tests. Sixty-four female Wistar rats (14-week-old) with sham operations or ovariectomy were assigned to 6 groups: CON, sham-operated control group; OVX, ovariectomized group; ALN, ovariectomized rats treated with alendronate (1 mg/kg/day, p.o.); and 3% ON, 7% ON and 14% ON, ovariectomized rats fed with diets containing 3%, 7% and 14% (wt/wt) onion powder, respectively. Animals were sacrificed after a six-week treatment course. In the serum marker assay, alendronate and all three onion-enriched diets significantly decreased serum calcium level (p<0.05). Both 14% ON group and the ALN group even showed similarly lower level of serum osteocalcin (p<0.05), suggesting a down-regulation of bone turnover. The histomorphometric analysis showed that ovariectomy markedly decrease bone trabeculae. The ALN and 14% ON rats were 80% and 46% higher, respectively, in BV/TV than the OVX rats (p<0.05), and the rats fed with onion-enriched food showed a lesser ovariectomy-induced bone loss in a dose-dependent manner. Additionally, both ALN and 14% ON groups had significantly more trabecular number, less separated trabeculae, and fewer osteoclasts (p<0.05), but the protective efficacy from the 14% onion-enriched diet was slightly inferior to that of alendronate. Ovariectomy also significantly decreased tissue weight and biomechanical strength in the OVX group (p<0.05). The ALN and 14% ON groups equivalently showed a lesser decrease in tissue weight, though the difference was not significant. On the other hand, both the ALN and 14% ON groups represented similar biomaterial properties of femurs, and both reduced the ovariectomy-induced decrease in bending load and bending energy (p<0.05). The present study further verified that an onion-enriched diet could counteract ovariectomy-induced bone loss and deterioration of biomechanical properties.

Upregulation of hippocampal TrkB and synaptotagmin is involved in treadmill exercise-enhanced aversive memory in mice.

Cognitive functions usually involve various synaptic proteins and neurotrophic factors in the hippocampus. However, whether treadmill exercise can improve learning and memory by upregulating some of these molecules remain unraveled. To address this question, male BALB/c mice were divided into control and exercise groups, the latter group went through 4 weeks of treadmill exercise training. At the end of exercise training period, they were either tested for passive avoidance (PA) performance or sacrificed for quantifying the hippocampal levels of brain-derived neurotrophic factor (BDNF), tropomyosin-related kinase B (TrkB, the BDNF receptor), synaptotagmin (a Ca(2+)-dependent synaptic vesicle protein), and SNAP-25 (a presynaptic vesicular fusion protein). Our results showed that treadmill exercise training (1) increased the retention latency without affecting the fear acquisition in the PA test, (2) transiently increased the hippocampal BDNF level at 1, 2, and 4h after the completion of exercise training, and (3) persistently increased the hippocampal protein levels of full-length TrkB, phosphorylated TrkB and synaptotagmin, but not truncated TrkB or SNAP-25. Moreover, the protein expression level of full-length TrkB or synaptotagmin was positively correlated with PA performance in mice. Finally, inhibition of TrkB signaling by K252a abolished the exercise-facilitated PA performance and upregulation of TrkB and synaptotagmin. Taken together, these data suggest that the upregulation of TrkB and synaptotagmin in the hippocampus contributes to the exercise-facilitated aversive memory.

Mutual enhancement of central neurotoxicity induced by ketamine followed by methamphetamine.

We hereby report that repeated administration of ketamine (350 mg/kg in total) and methamphetamine (30 mg/kg in total) causes specific glutamatergic and dopaminergic neuron deficits, respectively, in adult mouse brain. Acute ketamine did not affect basal body temperature or the later methamphetamine-induced hyperthermia. However, pretreatment with repeated doses of ketamine aggravated methamphetamine-induced dopaminergic terminal loss as evidenced by a drastic decrease in the levels of dopamine, 3,4-dihydroxyphenylacetic acid, and dopamine transporter density as well as poor gait balance performance. In contrast, methamphetamine-induced serotonergic depletion was not altered by ketamine pretreatment. Likewise, the subsequent treatment with methamphetamine exacerbated the ketamine-induced glutamatergic damage as indicated by reduced levels of the vesicular glutamate transporter in hippocampus and striatum and poor memory performance in the Morris water maze. Finally, since activation of the D1 and AMPA/kainate receptors has been known to be involved in the release of glutamate and dopamine, we examined the effects of co-administration of SCH23390, a D1 antagonist, and CNQX, an AMPA/kainate antagonist. Intraventricular CNQX infusion abolished ketamine's potentiation of methamphetamine-induced dopamine neurotoxicity, while systemic SCH23390 mitigated methamphetamine's potentiation of ketamine-induced glutamatergic toxicity. We conclude that repeated doses of ketamine potentiate methamphetamine-induced dopamine neurotoxicity via AMPA/kainate activation and that conjunctive use of methamphetamine aggravates ketamine-induced glutamatergic neurotoxicity possibly via D1 receptor activation.

Long-term compulsive exercise reduces the rewarding efficacy of 3,4-methylenedioxymethamphetamine.

Although exercise has been known to regulate brain plasticity, its impact on psychostimulant reward and the associated mesolimbic dopamine system remained scarcely explored. A psychostimulant, 3,4-methylenedioxymethamphetamine (MDMA), is currently a worldwide abused drug of choice. We decided to examine the modulating effects of long-term, compulsive treadmill exercise on the hedonic value of MDMA in male C57BL/6J mice. MDMA-induced conditioned place preference (CPP) was used as a behavioral paradigm to indicate the reward efficacy of MDMA. We observed that sedentary control mice all demonstrated reliable MDMA-induced CPP with our conditioning protocol. Interestingly, pre-exposure to a treadmill exercise decreased the later MDMA-induced CPP in a running period-dependent manner. Specifically, mice undergoing a 12-week treadmill running exercise did not exhibit any approaching bias toward the MDMA-associated compartment in this CPP paradigm. Twelve weeks of treadmill running did not alter peripheral metabolism of MDMA 30min following single intraperitoneal injection of MDMA (3mg/kg). We further used microdialysis technique to study the underlying mechanisms for the impaired MDMA reward produced by the12-week exercise pre-exposure. We found that acute MDMA-stimulated dopamine release in nucleus accumbens was abolished in the exercised mice, whereas an obvious elevation of accumbal dopamine release was observed in sedentary control mice. Finally, the 12-week exercise program did not alter the protein levels of primary dopamine receptors, vesicular or membrane transporters in this area. We conclude that the long-term, compulsive exercise is effective in curbing the reward efficacy of MDMA possibly via its direct effect on reversing the MDMA-stimulated dopamine release in nucleus accumbens.

Treadmill exercise enhances passive avoidance learning in rats: the role of down-regulated serotonin system in the limbic system.

While serotonin (5-HT) may impair learning and memory, exercise has been reported to improve them. Whether chronic exercise can facilitate fear memory via regulating the serotonin system is unknown. We examined the effects of 4-week treadmill exercise training on levels of 5-HT and its metabolite 5-hydroxyindoleacetic acid (5-HIAA), the protein expression of its receptor 5-HT(1A) and transporter in the amygdala, hippocampus and prefrontal cortex of male Sprague-Dawley rats. Our results demonstrated that treadmill exercise (1) improved the passive avoidance learning performance; (2) decreased the 5-HT level in the hippocampus; (3) decreased the expression of 5-HT(1A) receptor in the amygdala without altering the transporter expression. Moreover, pretreatment with 0.1 mg/kg 8-hydroxy-di-n-propylamino tetralin, a selective 5-HT(1A) receptor agonist, impaired the passive avoidance performance and completely abolished the exercise-enhanced fear memory. Our results suggest that down-regulation of the 5-HT system in the limbic system, i.e., the reduction of the hippocampus 5-HT content and the amygdala 5-HT(1A) receptor expression, may be involved in the exercise-enhanced fear memory.