MicroRNA-Let-7a regulates the function of microglia in inflammation

Microglia have multiple functions in cerebrovascular and neurodegenerative diseases. Regulation of microglial function during inflammatory stress is important for treatment of central nervous system (CNS) diseases because microglia secrete various substances that affect neurons and glia. MicroRNA-Let-7a (miR-Let-7a) is a tumor suppressor miRNA that has been reported to target transcripts that encode proteins involved in apoptosis. In the present study, we examined the essential role of miR-Let-7a in inflammatory stress by over-expressing miR-Let-7a to investigate its role in determining the BV2 microglial phenotype, a cell line often used as a model of activated microglia. We found that inflammatory factors and Reactive Oxygen Species (ROS) production levels were altered according to miR-Let-7a expression level as measured by Western blot analysis, reverse transcription PCR, quantitative real time PCR, the measurement of nitrite (indicative of the nitric oxide (NO) pathway), and immunocytochemistry (ICC). Our results suggest that miR-Let-7a is involved in the function of microglia in the setting of inflammatory injury. In response to inflammation, miR-Let-7a participates in the reduction of nitrite production and the expression of inducible nitric oxide synthase (iNOS), interleukin (IL)-6 and is involved in increased expression of brain derived neurotrophic factor (BDNF), interleukin (IL)-10, and IL-4 in microglia. Thus, miRNA-Let-7a could act as a regulator of the function of microglia in inflammation.ope

Phase stability and flux pinning control of SmBa2Cu3O7-δ superconducting thin films

학위논문 (석사)-- 서울대학교 대학원 : 재료공학부, 2014. 2. 유상임.본 연구에서는 낮은 산소 분압 조건에서의 SmBa2Cu3O7-δ (SmBCO) 의 상안정도를 실험적으로 정밀하게 규명하였다. 또한 규명된 SmBCO 상안정도를 기반으로 PLD법으로 증착된 SmBCO 초전도 박막을 후열처리하여 자속피닝특성을 향상시키기 위한 연구를 실시하였다. 구체적인 연구 결과는 다음과 같다. 첫째, 비정질 전구체 막을 이용하여 낮은 산소 분압 하 SmBCO 초전도 막의 상 안정성을 규명하였다. 전구체 막은 펄스레이저 증착법(Pulsed laser deposition: PLD)을 이용하여 200 °C 로 유지된 LaAlO3 (LAO) (001) 단결정 기판 위에 증착하였다. 증착된 비정질 전구체 막을 이용하여 릴투릴(reel-to-reel)기능이 있는 석영관 퍼니스 안에서 다양한 온도, 낮은 산소 분압에서 상을 형성시킨 후 급냉 후 시편의 상과 미세구조를 분석하여 SmBCO의 상 안정성을 정밀하게 규명할 수 있었다. 먼저 20 – 100 mTorr의 산소분압 조건에서 실험적으로 결정된 SmBCO 상 안정 영역과 불안정 영역의 경계선을 최소자승법을 사용해 Log PO2 (Torr) = 19.22 – 24,292/T (K) 의 관계식을 얻을 수 있었다. 아울러, SmBCO의 상 안정 영역의 경계에서는 SmBCO ↔ Sm2BaO4 + Liquid (L1)의 pseudobinary peritectic reaction 이 일어나는 것을 확인하였고 이는 기존의 공기와 같은 높은 산소분압을 가지는 분위기에서 일어나는 것으로 알려진SmBCO ↔ Sm2BaCuO5 (Sm211) + Liquid (L)의 pseudobinary peritectic reaction 과는 다른 분해 생성물을 갖는 것을 알 수 있었다. 마찬가지 방법으로 1 – 10 mTorr 영역의 보다 낮은 산소분압 영역에서SmBCO의 상 경계선 또한 Log PO2 (Torr) = 17.73 – 22,582/T (K) 의 관계식을 얻을 수 있었다. 또한 이러한 산소분압 조건에서는 위 상 경계선에서 SmBCO ↔ Sm2O3 + Sm2BaO4 + Liquid (L2)의 삼원계 포정반응 (ternery peritectic reaction)이 일어난다는 것을 규명하였다. 마지막으로, Sm2BaO4 + L1 과 Sm2O3 + Sm2BaO4 + L2 이 존재하는 영역 사이에서는 L1 ↔ Sm2O3 + L2 의 편정 반응 (monotectic reaction)이 일어남을 실험적으로 규명하였다. 이렇게 낮은 산소분압에서 실험적으로 결정된 SmBCO의 상안정도를 기반으로 하여, Sm2O3-Ba2CuOy-Cu2O 삼성분계의 등온단면도(isothermal section)를 구성할 수 있었으며, 이를 통해 각 상이 존재하는 영역에서의 고상-액상간의 상평형을 도식적으로 설명할 수 있었다. 둘째, SmBCO 초전도 박막의 자속피닝특성을 향상시키기 위한 후열처리 공정을 SmBCO 상안정도를 기반으로 시행하여 자속피닝특성이 향상된 SmBCO 박막을 얻을 수 있었다. Sm2O3 nanoparticle이 도핑된 epitaxial SmBCO 초전도 박막 제조를 위해 SmBCO 타겟 면적 넓이의 2.5 % 넓이를 가지는 Sm2O3 타겟을 조각낸 후 붙여 하나의 타겟처럼 제조한 타겟을 이용해 Nd:YAG(λ= 355 nm) 레이저 PLD 법으로 800 °C 로 유지된 LAO (001) 단결정 기판 위에 증착한 후 각각 산소분압 20 mTorr, 온도구간760, 800, 840, 880 °C, 30분 동안 열처리하여 열처리 전 후를 비교하였다. 그 결과, Sm2O3 nanoparticle이 도핑된 필름의 TC, zero 값은 86.1 K 이었고, 840 °C 에서 열처리를 시행한 경우 TC, zero 값이89.4 K으로 상승하다가 880 °C 에서 열처리한 박막의 TC, zero 값은 87.3 K을 기록하여 800 °C 에서 열처리한 시편의 TC, zero 값인 88.2 K보다 낮은 상승 폭을 보였다. 아울러, JC-B결과를 비교하여 보았을 때 열처리한 시편 모두 열처리하지 않은 시편보다 자속피닝 특성이 향상된 결과를 나타내었다.In this study, we accurately constructed the stability phase diagram of SmBa2Cu3O7-δ (SmBCO) in low oxygen pressures experimentally, and also on the basis of determined stability phase diagram of SmBCO, studied the enhanced flux pinning properties of SmBCO superconducting thin films via the post-annealing process. The details are as follows. First, we report the phase stability of SmBCO in low oxygen pressures regime from 1 mTorr to 100 mTorr. For this study, the amorphous Sm-Ba-Cu-O precursor films were deposited on LaAlO3 (LAO) (001) substrate at 200 °C by using the Pulsed laser deposition (PLD) process. As-deposited precursor films were annealed at various temperatures in the PO2 regime of 1 mTorr – 100 mTorr and then quenched using the reel-to-reel furnace. The stability phase diagram of SmBCO was precisely determined by analyzing the phase and microstructure of the as-quenched samples. The stability line of SmBCO in the PO2 regime of 20 – 100 mTorr on the the PO2 versus 1/T diagram is expressed by the equation of Log PO2 (Torr) = 19.22 – 24,292/T (K) this PO2 regime, the pseudobinary peritectic reaction of SmBCO ↔ Sm2BaO4 + Liquid(L1) occurs at the stability boundary of SmBCO. This reaction is different from the well-known pseudobinary peritectic reaction of SmBCO ↔ Sm2BaCuO5 (Sm211) + Liquid (L) in high PO2 like air. The stability line of SmBCO in the PO2 regime of 1 – 10 mTorr on the PO2 versus 1/T diagram can be expressed by the equation of Log PO2 (Torr) = 17.73 – 22,582/T (K) and in this PO2 regime, the ternary peritectic reaction of SmBCO ↔ Sm2BaO4 + Sm2O3 + Liquid(L2) occurs at the stability boundary of SmBCO. In addition, the monotectic reaction of L1 Sm2O3+ L2 occurs between the phase region of Sm2BaO4 + L1 and Sm2O3 + Sm2BaO4 + L2. On the basis of the SmBCO stability phase diagram, the isothermal sections of three different phase fields on log PO2 vs. 1/T diagram were schematically constructed within the Sm2O3-Ba2CuOy-Cu2O ternary system, and the solid-liquid phase equilibria in each phase field were also described. Second, we report the enhanced flux pinning properties of SmBCO superconducting thin films by the post-annealing process. Initially, we modified a SmBCO target by attaching a Sm2O3 sector of which area is about 2.5 % of the SmBCO target surface area. Using this target, Sm2O3-doped SmBCO thin films were deposited on LAO (001) substrate at 800 °C by the PLD process using Nd:YAG (λ= 355 nm) laser. Subsequently, as-deposited films are post-annealed at 760, 800, 840 and 880 °C in the PO2 of 20 mTorr for 30 min. While TC, zero value of as-deposited film is 86.1 K, that of film annealed at 840 °C is increased up to 89.4 K. After annealing at 880 °C, however, TC, zero value of the film is 87.3 K which is slightly lower than that of the film annealed at 800 °C (88.2 K). Also from the JC-B curves, we could find that the flux pinning property of all post-annealed films was enhanced compared with that of the as-deposited film.I 서론 II 문헌연구 II.1 SmBCO의 구조 및 초전도 특성 II.2 SmBCO의 상 안정성 II.3 자속피닝점에 대한 연구 II.3.1 PLD 공정을 이용한 자속피닝점 도입 III 실험방법 III.1 SmBCO의 상 안정성 실험 III.1.1 시편준비 III.1.1.1 타겟 제조 III.1.1.2 기판 준비 및 증착 공정 III.1.1.3 열처리 공정 III.1.2 SmBCO의 상 분석 III.1.2.1 XRD 및 SEM 분석 III.2 SmBCO 초전도 박막의 자속 피닝 특성 제어 실험 III.2.1 시편준비 III.2.1.1 타겟 제조 III.2.1.2 기판 준비 및 증착 공정 III.2.1.3 열처리 공정 III.2.2 SmBCO 초전도 박막의 상 및 특성 분석 III.2.2.1 XRD 및 SEM 분석 III.2.2.2 초전도 특성 평가 IV 실험 결과 및 고찰 IV.1 SmBCO의 상 안정성 연구 IV.1.1 산소분압20 – 100 mTorr 영역에서 SmBCO의 Psedobinary peritectic reaction IV.1.2 산소분압 1 – 10 mTorr 영역에서 SmBCO의 삼성분계 포정 반응 IV.1.3 산소분압 1 – 10 mTorr 영역에서 SmBCO의 편정 반응 IV.1.4 상 안정도 IV.1.5 Sm2O3-Ba2CuOy-Cu2O 삼성분계의 등온단면도 IV.1.5.1 Psedobinary peritectic reaction: SmBCO ↔ Sm2O3 + L1 IV.1.5.2 삼성분계 포정 반응: SmBCO ↔ Sm2O3 + Sm2BaO4 + L2 IV.1.5.3 편정 반응: L1 ↔ L2 + Sm2O3 IV.2 SmBCO 초전도 박막의 자속 피닝 특성 제어 연구 IV.2.1 SmBCO 초전도 박막 증착 IV.2.1.1 SmBCO 타겟을 이용한 증착 IV.2.1.2 변형된 SmBCO 타겟을 이용한 증착 IV.2.2 후열처리 공정을 이용한 자속피닝특성이 향상된 SmBCO 박막의 제조 V 결론 VI 참고문헌 VII AbstractMaste

The protective effect of melatonin on neural stem cell against LPS-induced inflammation

Stem cell therapy for tissue regeneration has several limitations in the fact that transplanted cells could not survive for a long time. For solving these limitations, many studies have focused on the antioxidants to increase survival rate of neural stem cells (NSCs). Melatonin, an antioxidant synthesized in the pineal gland, plays multiple roles in various physiological mechanisms. Melatonin exerts neuroprotective effects in the central nervous system. To determine the effect of melatonin on NSCs which is in LPS-induced inflammatory stress state, we first investigated nitric oxide (NO) production and cytotoxicity using Griess reagent assays, LDH assay, and neurosphere counting. Also, we investigated the effect of melatonin on NSCs by measuring the mRNA levels of SOX2, TLX, and FGFR-2. In addition, western blot analyses were performed to examine the activation of PI3K/Akt/Nrf2 signaling in LPS-treated NSCs. In the present study, we suggested that melatonin inhibits NO production and protects NSCs against LPS-induced inflammatory stress. In addition, melatonin promoted the expression of SOX2 and activated the PI3K/Akt/Nrf2 signaling under LPS-induced inflammation condition. Based on our results, we conclude that melatonin may be an important factor for the survival and proliferation of NSCs in neuroinflammatory diseasesope

Adiponectin as a new paradigm for approaching Alzheimer's disease

Adiponectin is an adipocytokine released by the adipose tissue and has multiple roles in the immune system and in the metabolic syndromes such as cardiovascular disease, Type 2 diabetes, obesity and also in the neurodegenerative disorders including Alzheimer's disease. Adiponectin regulates the sensitivity of insulin, fatty acid catabolism, glucose homeostasis and anti-inflammatory system through various mechanisms. Previous studies demonstrated that adiponectin modulates memory and cognitive impairment and contributes to the deregulated glucose metabolism and mitochondrial dysfunction observed in Alzheimer's disease. Here, we aim to summarize recent studies that suggest the potential correlation between adiponectin and Alzheimer's disease.ope

Dehydroascorbic Acid Attenuates Ischemic Brain Edema and Neurotoxicity in Cerebral Ischemia: An in vivo Study

Ischemic stroke results in the diverse phathophysiologies including blood brain barrier (BBB) disruption, brain edema, neuronal cell death, and synaptic loss in brain. Vitamin C has known as the potent anti-oxidant having multiple functions in various organs, as well as in brain. Dehydroascorbic acid (DHA) as the oxidized form of ascorbic acid (AA) acts as a cellular protector against oxidative stress and easily enters into the brain compared to AA. To determine the role of DHA on edema formation, neuronal cell death, and synaptic dysfunction following cerebral ischemia, we investigated the infarct size of ischemic brain tissue and measured the expression of aquaporin 1 (AQP-1) as the water channel protein. We also examined the expression of claudin 5 for confirming the BBB breakdown, and the expression of bcl 2 associated X protein (Bax), caspase-3, inducible nitric oxide synthase (iNOS) for checking the effect of DHA on the neurotoxicity. Finally, we examined postsynaptic density protein-95 (PSD-95) expression to confirm the effect of DHA on synaptic dysfunction following ischemic stroke. Based on our findings, we propose that DHA might alleviate the pathogenesis of ischemic brain injury by attenuating edema, neuronal loss, and by improving synaptic connection.ope

miR-Let7A Modulates Autophagy Induction in LPS-Activated Microglia

Microglia regulate the secretion of various immunomediators in central nervous system diseases. Microglial autophagy is the crucial process for cell's survival and cytokine productions. Recent studies have reported that several microRNAs are involved in the autophagy system. miR-Let7A is such a microRNA that plays a role in various inflammation responses, and is magnified as a key modulator particularly in the autophagy system. In present study, we investigated whether miR-Let7A is involved in autophagy in activating microglia. Overexpression of miR-Let7A in LPS-stimulated BV2 microglial cells promoted the induction of the autophagy related factors such as LC3II, Beclin1, and ATG3. Our results suggest a potential role of miR-Let7A in the autophagy process of microglia during CNS inflammation.ope

ASK1 modulates the expression of microRNA Let7A in microglia under high glucose in vitro condition

Hyperglycemia results in oxidative stress and leads to neuronal apoptosis in the brain. Diabetes studies show that microglia participate in the progression of neuropathogenesis through their involvement in inflammation in vivo and in vitro. In high-glucose-induced inflammation, apoptosis signal regulating kinase 1 (ASK1) triggers the release of apoptosis cytokines and apoptotic gene expression. MicroRNA-Let7A (miR-Let7A) is reported to be a regulator of inflammation. In the present study, we investigated whether miR-Let7A regulates the function of microglia by controlling ASK1 in response to high-glucose-induced oxidative stress. We performed reverse transcription (RT) polymerase chain reaction, Taqman assay, real-time polymerase chain reaction, and immunocytochemistry to confirm the alteration of microglia function. Our results show that miR-Let7A is associated with the activation of ASK1 and the expression of anti-inflammatory cytokine (interleukin (IL)-10) and Mycs (c-Myc and N-Myc). Thus, the relationship between Let-7A and ASK1 could be a novel target for enhancing the beneficial function of microglia in central nervous system (CNS) disorders.ope

miR-155 is involved in Alzheimer's disease by regulating T lymphocyte function

Alzheimer's disease (AD) is considered the most common cause of sporadic dementia. In AD, adaptive and innate immune responses play a crucial role in clearance of amyloid beta and maintenance of cognitive functions. In addition to other changes in the immune system, AD alters the T-cell responses that affect activation of glial cells, neuronal cells, macrophages, and secretion of pro-inflammatory cytokines. These changes in the immune system influence AD pathogenesis. Micro-RNA (miRNA)-155 is a multifunctional miRNA with a distinct expression profile. It is involved in diverse physiological and pathological mechanisms, such as immunity and inflammation. Recent studies indicate that miR-155 regulates T-cell functions during inflammation. In this article, we summarize recent studies describing the therapeutic potential of miR-155 via regulation of T cells in AD. Further, we propose that regulation of miR-155 might be a new protective approach against AD pathogenesis.ope

Glutathione suppresses cerebral infarct volume and cell death after ischemic injury: involvement of FOXO3 inactivation and Bcl2 expression

Ischemic stroke interrupts the flow of blood to the brain and subsequently results in cerebral infarction and neuronal cell death, leading to severe pathophysiology. Glutathione (GSH) is an antioxidant with cellular protective functions, including reactive oxygen species (ROS) scavenging in the brain. In addition, GSH is involved in various cellular survival pathways in response to oxidative stress. In the present study, we examined whether GSH reduces cerebral infarct size after middle cerebral artery occlusion in vivo and the signaling mechanisms involved in the promotion of cell survival after GSH treatment under ischemia/reperfusion conditions in vitro. To determine whether GSH reduces the extent of cerebral infarction, cell death after ischemia, and reperfusion injury, we measured infarct size in ischemic brain tissue and the expression of claudin-5 associated with brain infarct formation. We also examined activation of the PI3K/Akt pathway, inactivation of FOXO3, and expression of Bcl2 to assess the role of GSH in promoting cell survival in response to ischemic injury. Based on our results, we suggest that GSH might improve the pathogenesis of ischemic stroke by attenuating cerebral infarction and cell death.ope

Agmatine improves cognitive dysfunction and prevents cell death in Streptozotocin-induced Alzheimer rat model.

PURPOSE: Alzheimer's disease (AD) results in memory impairment and neuronal cell death in the brain. Previous studies demonstrated that intracerebroventricular administration of streptozotocin (STZ) induces pathological and behavioral alterations similar to those observed in AD. Agmatine (Agm) has been shown to exert neuroprotective effects in central nervous system disorders. In this study, we investigated whether Agm treatment could attenuate apoptosis and improve cognitive decline in a STZ-induced Alzheimer rat model. MATERIALS AND METHODS: We studied the effect of Agm on AD pathology using a STZ-induced Alzheimer rat model. For each experiment, rats were given anesthesia (chloral hydrate 300 mg/kg, ip), followed by a single injection of STZ (1.5 mg/kg) bilaterally into each lateral ventricle (5 μL/ventricle). Rats were injected with Agm (100 mg/kg) daily up to two weeks from the surgery day. RESULTS: Agm suppressed the accumulation of amyloid beta and enhanced insulin signal transduction in STZ-induced Alzheimer rats [experimetal control (EC) group]. Upon evaluation of cognitive function by Morris water maze testing, significant improvement of learning and memory dysfunction in the STZ-Agm group was observed compared with the EC group. Western blot results revealed significant attenuation of the protein expressions of cleaved caspase-3 and Bax, as well as increases in the protein expressions of Bcl2, PI3K, Nrf2, and γ-glutamyl cysteine synthetase, in the STZ-Agm group. CONCLUSION: Our results showed that Agm is involved in the activation of antioxidant signaling pathways and activation of insulin signal transduction. Accordingly, Agm may be a promising therapeutic agent for improving cognitive decline and attenuating apoptosis in AD.ope