Mitochondrial Calcium Uniporter (MCU) is Involved in an Ischemic Postconditioning Effect Against Ischemic Reperfusion Brain Injury in Mice.

The phenomenon of ischemic postconditioning (PostC) is known to be neuroprotective against ischemic reperfusion (I/R) injury. One of the key processes in PostC is the opening of the mitochondrial ATP-dependent potassium (mito-KATP) channel and depolarization of the mitochondrial membrane, triggering the release of calcium ions from mitochondria through low-conductance opening of the mitochondrial permeability transition pore. Mitochondrial calcium uniporter (MCU) is known as a highly sensitive transporter for the uptake of Ca2+ present on the inner mitochondrial membrane. The MCU has attracted attention as a new target for treatment in diseases, such as neurodegenerative diseases, cancer, and ischemic stroke. We considered that the MCU may be involved in PostC and trigger its mechanisms. This research used the whole-cell patch-clamp technique on hippocampal CA1 pyramidal cells from C57BL mice and measured changes in spontaneous excitatory post-synaptic currents (sEPSCs), intracellular Ca2+ concentration, mitochondrial membrane potential, and N-methyl-D-aspartate receptor (NMDAR) currents under inhibition of MCU by ruthenium red 265 (Ru265) in PostC. Inhibition of MCU increased the occurrence of sEPSCs (p = 0.014), NMDAR currents (p < 0.001), intracellular Ca2+ concentration (p < 0.001), and dead cells (p < 0.001) significantly after reperfusion, reflecting removal of the neuroprotective effects in PostC. Moreover, mitochondrial depolarization in PostC with Ru265 was weakened, compared to PostC (p = 0.004). These results suggest that MCU affects mitochondrial depolarization in PostC to suppress NMDAR over-activation and prevent elevation of intracellular Ca2+ concentrations against I/R injury.

Granulocyte macrophage colony-stimulating factor-induced macrophages of individuals with autism spectrum disorder adversely affect neuronal dendrites through the secretion of pro-inflammatory cytokines.

BACKGROUND: A growing body of evidence suggests that immune dysfunction and inflammation in the peripheral tissues as well as the central nervous system are associated with the neurodevelopmental deficits observed in autism spectrum disorder (ASD). Elevated expression of pro-inflammatory cytokines in the plasma, serum, and peripheral blood mononuclear cells of ASD has been reported. These cytokine expression levels are associated with the severity of behavioral impairments and symptoms in ASD. In a prior study, our group reported that tumor necrosis factor-α (TNF-α) expression in granulocyte-macrophage colony-stimulating factor-induced macrophages (GM-CSF MΦ) and the TNF-α expression ratio in GM-CSF MΦ/M-CSF MΦ (macrophage colony-stimulating factor-induced macrophages) was markedly higher in individuals with ASD than in typically developed (TD) individuals. However, the mechanisms of how the macrophages and the highly expressed cytokines affect neurons remain to be addressed. METHODS: To elucidate the effect of macrophages on human neurons, we used a co-culture system of control human-induced pluripotent stem cell-derived neurons and differentiated macrophages obtained from the peripheral blood mononuclear cells of five TD individuals and five individuals with ASD. All participants were male and ethnically Japanese. RESULTS: Our results of co-culture experiments showed that GM-CSF MΦ affect the dendritic outgrowth of neurons through the secretion of pro-inflammatory cytokines, interleukin-1α and TNF-α. Macrophages derived from individuals with ASD exerted more severe effects than those derived from TD individuals. LIMITATIONS: The main limitations of our study were the small sample size with a gender bias toward males, the use of artificially polarized macrophages, and the inability to directly observe the interaction between neurons and macrophages from the same individuals. CONCLUSIONS: Our co-culture system revealed the non-cell autonomous adverse effects of GM-CSF MΦ in individuals with ASD on neurons, mediated by interleukin-1α and TNF-α. These results may support the immune dysfunction hypothesis of ASD, providing new insights into its pathology.

Brain-derived neurotrophic factor from microglia regulates neuronal development in the medial prefrontal cortex and its associated social behavior.

Microglia and brain-derived neurotrophic factor (BDNF) are essential for the neuroplasticity that characterizes critical developmental periods. The experience-dependent development of social behaviors-associated with the medial prefrontal cortex (mPFC)-has a critical period during the juvenile period in mice. However, whether microglia and BDNF affect social development remains unclear. Herein, we aimed to elucidate the effects of microglia-derived BDNF on social behaviors and mPFC development. Mice that underwent social isolation during p21-p35 had increased Bdnf in the microglia accompanied by reduced adulthood sociability. Additionally, transgenic mice overexpressing microglial Bdnf-regulated using doxycycline at different time points-underwent behavioral, electrophysiological, and gene expression analyses. In these mice, long-term overexpression of microglial BDNF impaired sociability and excessive mPFC inhibitory neuronal circuit activity. However, administering doxycycline to normalize BDNF from p21 normalized sociability and electrophysiological function in the mPFC, whereas normalizing BDNF from later ages (p45-p50) did not normalize electrophysiological abnormalities in the mPFC, despite the improved sociability. To evaluate the possible role of BDNF in human sociability, we analyzed the relationship between adverse childhood experiences and BDNF expression in human macrophages, a possible proxy for microglia. Results show that adverse childhood experiences positively correlated with BDNF expression in M2 but not M1 macrophages. In summary, our study demonstrated the influence of microglial BDNF on the development of experience-dependent social behaviors in mice, emphasizing its specific impact on the maturation of mPFC function, particularly during the juvenile period. Furthermore, our results propose a translational implication by suggesting a potential link between BDNF secretion from macrophages and childhood experiences in humans.

Ischemic Postconditioning Reduces NMDA Receptor Currents Through the Opening of the Mitochondrial Permeability Transition Pore and KATP Channel in Mouse Neurons.

Ischemic postconditioning (PostC) is known to reduce cerebral ischemia/reperfusion (I/R) injury; however, whether the opening of mitochondrial ATP-dependent potassium (mito-KATP) channels and mitochondrial permeability transition pore (mPTP) cause the depolarization of the mitochondrial membrane that remains unknown. We examined the involvement of the mito-KATP channel and the mPTP in the PostC mechanism. Ischemic PostC consisted of three cycles of 15 s reperfusion and 15 s re-ischemia, and was started 30 s after the 7.5 min ischemic load. We recorded N-methyl-D-aspartate receptors (NMDAR)-mediated currents and measured cytosolic Ca2+ concentrations, and mitochondrial membrane potentials in mouse hippocampal pyramidal neurons. Both ischemic PostC and the application of a mito-KATP channel opener, diazoxide, reduced NMDAR-mediated currents, and suppressed cytosolic Ca2+ elevations during the early reperfusion period. An mPTP blocker, cyclosporine A, abolished the reducing effect of PostC on NMDAR currents. Furthermore, both ischemic PostC and the application of diazoxide potentiated the depolarization of the mitochondrial membrane potential. These results indicate that ischemic PostC suppresses Ca2+ influx into the cytoplasm by reducing NMDAR-mediated currents through mPTP opening. The present study suggests that depolarization of the mitochondrial membrane potential by opening of the mito-KATP channel is essential to the mechanism of PostC in neuroprotection against anoxic injury.

Distinct purinergic receptor-mediated currents of rat oculomotor integrator neurons characterized by different firing patterns.

The prepositus hypoglossi nucleus (PHN) and the interstitial nucleus of Cajal (INC) are oculomotor neural integrators involved in the control of horizontal and vertical gaze, respectively. We previously reported that local application of adenosine 5'-trisphosphate (ATP) to PHN neurons induced P2X receptor-mediated fast inward currents, P2Y receptor-mediated slow inward currents, and/or adenosine P1 receptor-mediated slow outward currents. In contrast to the findings on PHN neurons, the expression of functional purinergic receptors in INC neurons has not been examined. In this study, we investigated ATP-induced current responses in INC neurons and the distributions of the three current types across distinct firing patterns in PHN and INC neurons using whole cell recordings of rat brainstem slices. The application of ATP induced all three current types in INC neurons. Pharmacological analyses indicated that the fast inward and slow outward currents were mainly mediated by the P2X and P1 subtypes, respectively, corresponding to the receptor subtypes in PHN neurons. However, agonists of the P2Y subtype did not induce the slow inward current in INC neurons, suggesting that other subtypes or mechanisms are responsible for this current. Analysis of the distribution of the three current types in PHN and INC neurons revealed that the proportions of the currents were distinctly dependent on the firing patterns of PHN neurons whereas the proportion of the fast inward current was higher during all firing patterns of INC neurons. The different distributions of ATP-induced currents suggest distinct modes of purinergic modulation specific to horizontal and vertical integrators.NEW & NOTEWORTHY The roles of purinergic signaling on vertical (mediated by the interstitial nucleus of Cajal; INC) and horizontal (prepositus hypoglossal nucleus; PHN) gaze control are not understood. Here, we report three current types induced by ATP in INC neurons; the distribution of these current types across different types of INC neurons is different from that in PHN neurons. These results suggest distinct modes of purinergic modulation in horizontal and vertical gaze control centers.

Acceptance of Love and Remarriage Among Older Adults in the Philippines.

Objectives: Later-life re-partnership has been linked to healthy aging, but little is known about Philippine older adults' perception of love and remarriage in older age. Methods: Using two nationally representative surveys on aging in the Philippines, we estimated the proportion of older adults reporting acceptance. Using weighted logistic regression, we assessed sociodemographic and health factors associated with acceptance as well as the relationship of this acceptance with social activity and health behaviors. Results: Only seventeen percent of respondents reported acceptance. Per multivariable analyses, unmarried men and married women reported acceptance, and acceptance was associated with increased social activity and smoking in men, less smoking in women, and more drinking in both genders. Discussion: Most older adults in the Philippines reported love and remarriage in old age as unacceptable. Through these results, we can understand how attitudes toward later-life relationship impact older adults' health and well-being.

The Role of Underweight in Active Life Expectancy Among Older Adults in Japan.

OBJECTIVES: It is underweight, rather than overweight or obesity, that has been a pressing public health concern in Japan. This study examines the impact of being underweight on the health of older Japanese men and women, measured by active life expectancy at age 65. Following the Japanese government's guideline, underweight in this study is defined using the body mass index (BMI) value of 20. METHOD: Data came from five waves (1999-2009) of the Nihon University Japanese Longitudinal Study of Aging (NUJLSOA). We used the Interpolation of Markov Chain approach to estimate the number of years underweight (BMI < 20), normal weight (20 < BMI < 25), and overweight (25 < BMI) individuals were expected to live without difficulty in activities of daily living (ADLs) or instrumental ADLs. RESULTS: We found differences in life and health expectancies across the three weight categories. Underweight people were expected to live the shortest lives and spend the fewest years in an active state compared with normal and overweight individuals. Results remained unchanged even when accounting for educational attainment, smoking history, and a count of existing chronic conditions. DISCUSSION: Being underweight is associated with poor quality of life lived among Japanese older adults. This finding suggests the importance of maintaining proper weight and avoids nutritional risks at advanced ages.

Ischemic postconditioning prevents surge of presynaptic glutamate release by activating mitochondrial ATP-dependent potassium channels in the mouse hippocampus.

A mild ischemic load applied after a lethal ischemic insult reduces the subsequent ischemia-reperfusion injury, and is called ischemic postconditioning (PostC). We studied the effect of ischemic PostC on synaptic glutamate release using a whole-cell patch-clamp technique. We recorded spontaneous excitatory post-synaptic currents (sEPSCs) from CA1 pyramidal cells in mouse hippocampal slices. The ischemic load was perfusion of artificial cerebrospinal fluid (ACSF) equilibrated with mixed gas (95% N2 and 5% CO2). The ischemic load was applied for 7.5 min, followed by ischemic PostC 30 s later, consisting of three cycles of 15 s of reperfusion and 15 s of re-ischemia. We found that a surging increase in sEPSCs frequency occurred during the immediate-early reperfusion period after the ischemic insult. We found a significant positive correlation between cumulative sEPSCs and the number of dead CA1 neurons (r = 0.70; p = 0.02). Ischemic PostC significantly suppressed this surge of sEPSCs. The mitochondrial KATP (mito-KATP) channel opener, diazoxide, also suppressed the surge of sEPSCs when applied for 15 min immediately after the ischemic load. The mito-KATP channel blocker, 5-hydroxydecanoate (5-HD), significantly attenuated the suppressive effect of both ischemic PostC and diazoxide application on the surge of sEPSCs. These results suggest that the opening of mito-KATP channels is involved in the suppressive effect of ischemic PostC on synaptic glutamate release and protection against neuronal death. We hypothesize that activation of mito-KATP channels prevents mitochondrial malfunction and breaks mutual facilitatory coupling between glutamate release and Ca2+ entry at presynaptic sites.

Longitudinal relationship between sleep deficiency and pain symptoms among community-dwelling older adults in Japan and Singapore.

The association of sleep with pain is well documented among adult populations. Even though both sleep problems and pain are prevalent in older adults, the longitudinal and bidirectional relationship between sleep deficiency (i.e. insufficient and poor sleep) and pain is less well established. This study investigated the association between sleep deficiency and pain among community-dwelling adults aged 65 years and older across a 2- to 3-year period. We analyzed cross-country data from the Nihon University Japanese Longitudinal Study of Aging (N = 2888) and the Panel on Health and Aging of Singaporean Elderly (N = 2111). Sleep deficiency was operationalized as self-reported short sleep duration (<6 hours), frequent restlessness during the night, and/or non-restorative sleep. Pain was characterized in terms of any pain, multiple pain locations, and pain-related disability. Demographics, smoking, nap duration, depressive symptoms, chronic conditions, and body mass index were included as covariates. Baseline sleep deficiency was associated with any pain, multiple pain locations, and pain-related disability among older adults at follow-up, although differences by country of residence were observed. In Singaporeans, sleep deficiency predicted the new onset of any pain, and any pain also predicted the new emergence of sleep deficiency. Improving sleep of older adults may improve pain-related symptoms and help intervene on the vicious cycle of pain and sleep deficiency.

Purinergic modulation of neuronal activity in the rat prepositus hypoglossi nucleus.

In the nervous system, adenosine 5'-trisphosphate (ATP) functions as a neurotransmitter and binds to ionotropic P2X receptors and metabotropic P2Y receptors. Although ATP receptors are expressed in the prepositus hypoglossi nucleus (PHN), which is a brainstem structure involved in controlling horizontal gaze, it is unclear whether ATP indeed affects the activity of PHN neurons. In this study, we investigated the effects of ATP on spontaneous firing of PHN neurons using whole-cell recordings in rat brainstem slices. Bath application of ATP increased or decreased the spontaneous firing rate of the neurons in a dose-dependent manner, indicating that ATP indeed affects PHN neuronal activity. To clarify the mechanisms of the ATP effects, we investigated the current responses of PHN neurons to a local application of ATP. The ATP application induced a fast inward (FI) current, a slow inward (SI) current, and/or a slow outward (SO) current in the neurons. The agonists of P2X and P2Y receptors induced FI and SI currents, respectively. The SO currents were not induced by the ATP agonists but were induced by adenosine, which may be extracellularly converted from ATP by ectonucleotidases. An antagonist of adenosine P1 (A1 ) receptors abolished the adenosine-induced SO currents and bath application of adenosine decreased the spontaneous firing rate of all PHN neurons tested. These results indicate that PHN neurons express functional purinoceptors and show that the FI, SI, and SO currents were mediated via P2X, P2Y, and A1 receptors, respectively.

Sociodemographic correlates of four indices of blood pressure and hypertension among older persons in Japan.

BACKGROUND: High blood pressure is a significant risk factor for cardiovascular disease and mortality. Japan has traditionally had higher levels of measured blood pressure than many Western countries, and reducing levels of hypertension has been a major focus of Japanese health policy over recent decades. In the West, hypertension is strongly associated with sociodemographic and behavioral (smoking and body mass index, BMI) factors; studies of the association between sociodemographic factors and biological indicators have not been fully explored in the elderly population of Japan using nationally representative survey data. OBJECTIVE: To describe hypertension prevalence rates with increasing age and to examine the link between sociodemographic and behavioral factors (including age, gender, education, residence, smoking, and BMI) and measures of blood pressure and overall hypertension in the Japanese population aged ≥68 years. METHODS: Data were collected in 2006 during the fourth wave of the Nihon University Japanese Longitudinal Study of Aging, a nationally representative sample of those ≥68. The analytic sample includes 2,634 participants. Pulse pressure, systolic, diastolic, and mean blood pressure, as well as hypertension, were regressed on sociodemographic and behavioral factors. RESULTS: There is no significant difference in the prevalence of overall hypertension by age for men and women from ages 68-69 to 90+. Higher BMI and older age were linked to higher blood pressure and higher chance of having hypertension. More years of education and being female were associated with a lower likelihood of measured hypertension. Smoking, rural residence, and living alone were not significantly associated with the outcome measures. CONCLUSION: The increase in hypertension with higher BMI raises concerns about future health in Japan as BMI increases. The lack of a relationship between smoking and any measure of blood pressure or hypertension is an indicator that smoking may have different effects in Japan than in other countries. Because there is no effect of living alone on blood pressure, compliance with drug regimes may not be enhanced by living with others in Japan.

Association between subjective well-being and sleep among the elderly in Japan.

OBJECTIVE: The purpose of this study was to examine the association between sleep and subjective quality of life in an elderly Japanese population. METHODS: Elderly people aged 70 years or more (n=1,769) were selected randomly from all areas of Japan. They were visited and interviewed in November 2003. Subjective well-being of the subjects was assessed using the Philadelphia Geriatric Center (PGC) Morale Scale. A logistic regression analysis was performed using sleep-related factors as explanatory variables. RESULTS: A positive linear association was observed between subjective sleep sufficiency and the mean PGC Morale Scale score. The crude and adjusted odds ratios for sleep disorders such as difficulty initiating sleep, excessive daytime sleepiness, and restless legs syndrome were significantly low. The mean score was highest for a sleep duration of 7-8h and became lower at sleep durations of <6 and 9h (inverted U-shaped association). However, the adjusted odds ratio for sleep duration did not show a significant reduction. CONCLUSIONS: In order to improve the subjective well-being of the elderly, better subjective sleep sufficiency and alleviation of sleep disorders are necessary. Different mechanisms may reduce subjective well-being in individuals who sleep less than 6h or who sleep 9h or more.