突触可塑性在抗抑郁中的研究进展

抑郁症是一种以情绪低落为主要特征、兴趣缺失并常伴有自杀倾向的情感障碍性疾病,严重威胁人类健康和生活质量。由于抑郁症致病机制未完全阐明,抗抑郁药物的研发受到很大限制。现临床使用的抗抑郁药物因起效慢、副作用大等缺陷极大地限制了抑郁症的治疗。近年来,越来越多的研究表明,突触可塑性损伤与抑郁症的发生有着紧密的联系,改善突触可塑性有利于逆转抑郁症状及其伴随的认知功能下降。本文将综述突触可塑性对抑郁症发生的影响及其与脑源性神经营养因子、星形胶质细胞及小胶质细胞之间的关系。     

甲基强的松龙对伽玛刀照射后胶质细胞Cx43和GFAP表达的影响

目的 研究甲基强的松龙（MP）对伽玛刀照射后胶质细胞缝隙连接蛋白43（Cx43）和胶质纤维酸蛋白（GFAP）表达的影响。方法体外培养原代星形胶质细胞,经伽玛刀照射（边缘剂量32Gy）并培养36h后随机分为1μg／ml、5μg／ml、10μg／ml、20μg／ml、30μg／ml、40μg/ml组及实验对照组,各组进一步随机分为48h、72h、96h、120h4个亚组。将各组胶质细胞与相应剂量MP共培养,于48、72、96、120h各时间点采用免疫组化方法检测GFAP及Cx43的表达。结果伽玛刀照射后,胶质细胞Cx43表达降低,GFAp表达增高。添加MP后,20μg／ml、30μg／ml组Cx43呈时间依赖性上调;GFAP表达虽呈时间依赖性上升,但其峰值低于实验对照组,峰值出现时间亦晚于实验对照组。结论MP可上凋伽玛刀照射后胶质细胞Cx43的表达,抑制GFAP表达的上升趋势。     

小鼠大脑中动脉缺血再灌注后缺血区及周边区星形胶质细胞的变化

目的 探讨小鼠大脑中动脉缺血再灌注后脑梗死体积、星形胶质细胞(AS)病理形态及其蛋白表达的变化.方法 选取69只成年健康雄性KM小鼠,将小鼠随机分为脑缺血2h再灌注1、4、10、24、48、72 h模型组(n=9)以及假手术组(n=6,仅结扎右侧颈总动脉)和正常组(n=9).采用线栓法制备小鼠大脑中动脉局灶性脑缺血再灌注模型.应用2,3,5-氯化三苯基四氮唑(TTC)染色法观察脑梗死的部位与体积;免疫组化法观察脑缺血中心区与周边区不同再灌注时间点胶质纤维酸性蛋白(GFAP)的表达.结果 缺血再灌注1h开始出现脑梗死灶,且再灌注24 h时梗死体积最大,之后逐渐缩小(F=745.534,P=0.000).小鼠脑缺血再灌注后缺血中心区AS肿胀、肥大进而较快发生凋亡,其GFAP表达水平低于周边区(P＜0.05);而缺血周边区GFAP阳性表达的AS出现反应性活化,进而发生形态学改变;缺血周边区及对侧相应脑组织区域GFAP的表达量均随再灌注时间的延长呈现增加趋势(P＜0.05).结论 AS反应性活化可能是一种缺血后的全脑保护性防御机制,尤其是在缺血周边区,其活化程度影响脑组织的存活与修复,提示在脑缺血再灌注过程中AS反应性活化可能在脑损伤后可塑性形态及功能改变中发挥重要作用.     

Review: Astrocytes in Alzheimer's disease and other age‐associated dementias: a supporting player with a central role

Astrocytes have essential roles in the central nervous system and are also implicated in the pathogenesis of neurodegenerative disease. Forming non‐overlapping domains, astrocytes are highly complex cells. Immunohistochemistry to a variety of proteins can be used to study astrocytes in tissue, labelling different cellular components and sub‐populations, including glial fibrillary acidic protein, ALDH1L1, CD44, NDRG2 and amino acid transporters, but none of these labels the entire astrocyte population. Increasing heterogeneity is recognized in the astrocyte population, a complexity that is relevant both to their normal function and pathogenic roles. They are involved in neuronal support, as active components of the tripartite synapse and in cell interactions within the neurovascular unit (NVU), where they are essential for blood–brain barrier maintenance and neurovascular coupling. Astrocytes change with age, and their responses may modulate the cellular effects of neurodegenerative pathologies, which alone do not explain all of the variance in statistical models of neurodegenerative dementias. Astrocytes respond to both the neurofibrillary tangles and plaques of Alzheimer's disease, to hyperphosphorylated tau and Aβ, eliciting an effect which may be neuroprotective or deleterious. Not only astrocyte hypertrophy, in the form of gliosis, occurs, but also astrocyte injury and atrophy. Loss of normal astrocyte functions may contribute to reduced support for neurones and dysfunction of the NVU. Understanding how astrocytes contribute to dementia requires an understanding of the underlying heterogeneity of astrocyte populations, and the complexity of their responses to pathology. Enhancing the supportive and neuroprotective components of the astrocyte response has potential translational applications in therapeutic approaches to dementia.     

Melatonin exacerbates acute experimental autoimmune encephalomyelitis by enhancing the serum levels of lactate: A potential biomarker of multiple sclerosis progression

Melatonin has a beneficial role in adult rat models of multiple sclerosis (MS). In this study, melatonin treatment (10 mg/kg/d) was investigated in young age (5‐6 weeks old) Lewis rat model of acute experimental autoimmune encephalomyelitis (EAE) followed by assessing serum levels of lactate and melatonin. Results showed that clinical outcomes were exacerbated in melatonin‐ (neurological score = 6) vs PBS‐treated EAE rats (score = 5). Melatonin caused a significant increase in serum IFN‐γ, in comparison to PBS‐treated EAE rats whereas no considerable change in IL‐4 levels were found, although they were significantly lower than those of controls. The ratio of IFN‐γ/IL‐4, an indicator of Th‐1/Th‐2, was significantly higher in PBS‐ and melatonin‐ treated EAE rats, in comparison to controls. Moreover, results showed increased lymphocyte infiltration, activated astrocytes (GFAP+ cells) but also higher demyelinated plaques (MBP‐deficient areas) in the lumbar spinal cord of melatonin‐treated EAE rats. Finally, serum levels of lactate, but not melatonin, significantly increased in the melatonin group, compared to untreated EAE and normal rats. In conclusion, our results indicated a relationship between age and the development of EAE since a negative impact was found for melatonin on EAE recovery of young rats by enhancing IFN‐γ, the ratio of Th1/Th2 cells, and astrocyte activation, which seems to delay the remyelination process. While melatonin levels decline in MS patients, lactate might be a potential diagnostic biomarker for prediction of disease progression. Early administration of melatonin in the acute phase of MS might be harmful and needs further investigations.     

The metastatic infiltration at the metastasis/brain parenchyma-interface is very heterogeneous and has a significant impact on survival in a prospective study

The current approach to brain metastases resection is macroscopic removal of metastasis until reaching the glial pseudo-capsule (gross total resection (GTR)). However, autopsy studies demonstrated infiltrating metastatic cells into the parenchyma at the metastasis/brain parenchyma (M/BP)-interface. Aims/Methods: To analyze the astrocyte reaction and metastatic infiltration pattern at the M/BP-interface with an organotypic brain slice coculture system. Secondly, to evaluate the significance of infiltrating metastatic tumor cells in a prospective biopsy study. Therefore, after GTR, biopsies were obtained from the brain parenchyma beyond the glial pseudo-capsule and analyzed histomorphologically. Results: The coculture revealed three types of cancer cell infiltration. Interestingly, the astrocyte reaction was significantly different in the coculture with a benign, neuroectodermal-derived cell line. In the prospective biopsy study 58/167 (34.7%) samples revealed infiltrating metastatic cells. Altogether, 25/39 patients (64.1%) had proven to exhibit infiltration in at least one biopsy specimen with significant impact on survival (OS) (3.4 HR; p = 0.009; 2-year OS was 6.6% versus 43.5%). Exceptionally, in the non-infiltrating cohort three patients were long-term survivors. Conclusions: Metastatic infiltration has a significant impact on prognosis. Secondly, the astrocyte reaction at the M/BP-interface is heterogeneous and supports our previous concept of the organ-specific defense against metastatic (organ-foreign) cells.     

Postnatal development of the amygdala: A stereological study in rats

The amygdala is the central component of a functional brain system regulating fear and emotional behaviors. Studies of the ontogeny of fear behaviors reveal the emergence of distinct fear responses at different postnatal ages. Here, we performed a stereological analysis of the rat amygdala to characterize the cellular changes underlying its normal structural development. Distinct amygdala nuclei exhibited different patterns of postnatal development, which were largely similar to those we have previously shown in monkeys. The combined volume of the lateral, basal, and accessory basal nuclei increased by 113% from 1 to 3 weeks of age and by an additional 33% by 7 months of age. The volume of the central nucleus increased only 37% from 1 to 2 weeks of age and 38% from 2 weeks to 7 months. At 1 week of age, the medial nucleus was 77% of the 7‐month‐old's volume and exhibited a constant, marginal increase until 7 months. Neuron number did not differ in the amygdala from 1 week to 7 months of age. In contrast, astrocyte number decreased from 3 weeks to 2 months of age in the whole amygdala. Oligodendrocyte number increased in all amygdala nuclei from 3 weeks to 7 months of age. Our findings revealed that distinct amygdala nuclei exhibit different developmental profiles and that the rat amygdala is not fully mature for an extended period postnatally. We identified different periods of postnatal development of distinct amygdala nuclei and cellular components, which are concomitant with the ontogeny of different fear and emotional behaviors. J. Comp. Neurol. 520:3745–3763, 2012. © 2012 Wiley Periodicals, Inc.     

Continuous interleukin-6 application in vivo via macroencapsulation of interleukin-6-expressing COS-7 cells induces massive gliosis

The inflammatory cytokine interleukin-6 (IL-6) was found in senile plaques of Alzheimer's patients and might be involved in the pathology of Parkinson's disease and multiple sclerosis. Interestingly, an astocytosis is also found in these neurodegenerative disorders. To evaluate the direct effects of IL-6 in vivo on glial cells, we created a new in vivo model. IL-6 and mock-transfected (control group) COS-7 cells were encapsulated in a poly-acryl-nitril membrane for implantation into the rat striatum. Afterward, the host immune reaction to the membrane without encapsulated cells and the biological action of IL-6-producing capsules was evaluated. Animals with an implanted membrane without cells showed a moderate astrocytosis 5 days after the operation. Furthermore, microglia and T-cells could be detected and after 30 days the astrocytosis decreased to a small layer around the membrane. In comparison to the control group, which received a sham operation, our results demonstrate that the response of glial cells is caused by the mechanical damage of the surgical procedure itself rather than due to the introduced membrane material. In contrast, we found a massive proliferation and activation of astrocytes and microglia after 10 days by IL-6-secreting capsules, indicating that IL-6 is involved in the induction of gliosis. Control animals that received encapsulated mock-transfected COS-7 cells showed only a weak response. These data point to an involvement of IL-6 in the proliferation and activation of glial cells as seen in neurodegenerative disorders.     

Alpha-cyano-4-hydroxycinnamate decreases both glucose and lactate metabolism in neurons and astrocytes: implications for lactate as an energy substrate for neurons.

The rates of uptake and oxidation of [U-(14)C]lactate and [U-(14)C]glucose were determined in primary cultures of astrocytes and neurons from rat brain, in the presence and absence of the monocarboxylic acid transport inhibitor alpha-cyano-4-hydroxycinnamate (4-CIN). The rates of uptake for 1 mM lactate and glucose were 7.45 +/- 1.35 and 8.80 +/- 1.0 nmol/30 sec/mg protein in astrocytes and 2.36 +/- 0.19 and 1.93 +/- 0.16 nmol/30 sec/mg protein in neuron cultures, respectively. Lactate transport into both astrocytes and neurons was significantly decreased by 0.25-1.0 mM 4-CIN; however, glucose uptake was not affected. The rates of (14)CO(2) formation from 1 mM lactate and glucose were 12.49 +/- 0.77 and 3.42 +/- 0.67 nmol/hr/mg protein in astrocytes and 29.32 +/- 2.81 and 10.04 +/- 1.79 nmol/hr/mg protein in neurons, respectively. Incubation with 0.25 mM 4-CIN decreased the oxidation of lactate and glucose to 57.1% and 54.1% of control values in astrocytes and to 13.2% and 41.6% of the control rates in neurons, respectively. Preincubation with 4-CIN further decreased the oxidation of both glucose and lactate. Studies with glucose specifically labeled in the one and six positions demonstrated that 4-CIN decreased mitochondrial glucose oxidation but did not impair the metabolism of glucose via the pentose phosphate pathway in the cytosol. The lack of effect of 4-CIN on glutamate oxidation demonstrated that overall mitochondrial metabolism was not impaired. These findings suggest that the impaired neuronal function and tissue damage in the presence of 4-CIN observed in other studies may be due in part to decreased uptake of lactate; however, the effects of 4-CIN on mitochondrial transport would significantly decrease the oxidative metabolism of pyruvate derived from both glucose and lactate.     

星形胶质细胞在脑缺血损伤中的保护作用及中药干预作用

脑缺血损伤后,通常认为主要是对神经元的损伤,但缺血的梗死区包括着其它细胞,如星形胶质细胞（astrocytes,AS）、脑微血管内皮细胞、小胶质细胞等。在脑中风损伤初期AC支持神经元的存活,所以对AS功能完整性的保护将在今后的研究中将受到进一步的重视。文章将探讨AS在脑缺血导致的神经损伤的发病机制中的基础作用及中药对其的保护作用。