AQP4对隐球菌性脑膜脑炎脑水肿发生机制的研究进展

隐球菌性脑膜脑炎的发病率逐年提高,对人类健康危害大,死亡率高,颅内压增高是其最危险的临床表现之一,这主要与发病后炎症所致的脑水肿有关.本文就隐球菌性脑膜脑炎的病因、发病机制及其研究进展进行综述.     

隐球菌感染小鼠模型脑组织含水量的变化

目的探讨隐球菌中枢神经系统感染小鼠模型脑组织含水量变化。方法尾静脉接种隐球菌构建中枢神经系统隐球菌感染的小鼠模型,小鼠随机分为实验组和对照组,免疫抑制后实验组小鼠尾静脉注射隐球菌菌悬液,对照组小鼠尾静脉注射生理盐水。两组分别采用干湿重法动态观察小鼠脑组织含水量变化。结果小鼠隐球菌中枢神经系统感染后脑组织含水量于6h开始明显升高,24h达高峰,后渐下降,与对照组比较差异有统计学意义。结论成功构建了隐球菌中枢神经系统感染脑水肿小鼠模型。     

山苍子油对小鼠系统性新生隐球菌感染的实验研究

目的研究山苍子油治疗小鼠系统性新生隐球菌感染的疗效。方法建立小鼠系统性新生隐球菌感染模型,观察给药后小鼠的中位生存时间,检测小鼠肾脏及肺菌落形成单位计数。结果山苍子油不仅能够显著延长感染小鼠的中位生存时间,提高其生存率,而且可显著增加感染小鼠肾脏及肺菌落清除率。结论山苍子油对系统性新生隐球菌感染小鼠具有治疗作用。     

侧脑室接种隐球菌感染大鼠模型的脑组织含水量变化研究

目的探讨隐球菌中枢神经系统感染大鼠模型的脑组织含水量变化。方法侧脑室接种隐球菌构建中枢神经系统隐球菌感染的大鼠模型,大鼠随机分为实验组和对照组,实验组大鼠侧脑室注射隐球菌菌悬液,对照组大鼠侧脑室注射生理盐水。两组分别采用干湿重法于6h、12h、24h、48h、72h动态检测大鼠脑组织含水量的变化。结果大鼠隐球菌中枢神经系统感染后,脑组织含水量于6h开始明显升高,12h到达高峰,后逐渐下降,但仍明显高于对照组;与对照组差异有统计学意义。结论隐球菌中枢神经系统感染后的大鼠脑组织含水量与对照组差异明显。     

CD44在隐球菌性脑膜炎发病机制中的作用研究

目的测定隐球菌性脑膜炎小鼠脑组织中CD44表达,探讨CD44在隐球菌性脑膜炎发病机制中的作用。方法隐球菌性脑膜炎免疫抑制小鼠为实验组,未接种隐球菌的免疫抑制小鼠为对照组,应用免疫组化法检测实验组6h、12h、24h、48h、72h、4d、7d小鼠脑组织CD44表达与对照组的变化。结果对照组小鼠脑组织CD44均匀分布在脑细胞膜上。实验组隐球菌作用小鼠48h、72h后,CD44在小鼠脑组织脑膜侧分布增加,而在脑实质侧CD44的分布明显减少。病灶周围的脑组织CD44分布也一侧增加,另一侧分布减少。结论隐球菌侵入小鼠脑组织后,隐球菌诱导CD44向脑组织的一侧移行,向脑膜方向聚集。病灶周围脑组织CD44分布也不均匀。说明隐球菌性脑膜炎的发生与CD44有密切的关系。     

水通道蛋白4与脑水肿研究进展

水通道蛋白4(AQP4)是膜水通道蛋白家族的一员,在脑组织中高表达,是控制水进出脑组织的通道。近年来发现,AQP4的功能和表达与脑水肿密切相关。同时脑水肿又是和脑疾病治疗密切相关的病理过程,对两者的研究或许可以为我们带来更多的临床治疗新思路。本文综述了AQP4的结构、表达、调控与功能以及AQP4与脑水肿关系的研究进展。     

肾移植与隐球菌感染

肾移植是目前开展最广泛的器官移植项目,由于免疫抑制剂及糖皮质激素的大量使用,肾移植术后的真菌感染已经成为一个重要医学课题。隐球菌病是器官移植患者常见的深部真菌感染,本文对肾移植术后发生隐球菌感染的易感因素、临床表现以及治疗和预防等方面做一论述。     

新生隐球菌生物膜动物模型构建及PMT4对生物膜形成的影响

目的构建新生隐球菌的PMT4基因缺陷株及新生隐球菌生物膜的体内、外模型;研究PMT4基因对生物膜形成的影响。方法采用PCR介导的长侧翼同源重组的方法敲除新生隐球菌H99的PMT4基因;采用基础培养基96孔板培养的方法建立生物膜体外模型;兔中心静脉插管、管内放置聚苯乙烯薄膜的方法建立生物膜动物模型;用倒置显微镜、共聚集激光扫描显微镜、MTT、CFU计数等方法研究PMT4缺陷株与野生株生物膜的异同。结果新生隐球菌在体内、外模型中均能形成生物膜;PMT4缺陷株与野生株生物膜在生物量和结构方面存在明显差异。结论本实验的生物膜动物模型可行;PMT4基因缺陷可造成隐球菌生物膜代谢活性下降,并形成假菌丝样结构。     

播散性隐球菌病1例及其实验研究

目的 播散性隐球菌病1例临床及实验研究.方法 患者男,72岁,红皮病1年2个月,口服醋酸泼尼松治疗,双下肢出现结节、溃烂6个月.皮损组织病理、皮损组织真菌培养、尿素酶试验、PCR扩增测序比对明确诊断,同时做胸部及脑部CT.结果 皮损组织病理显示为感染肉芽肿改变,可见大量圆形和椭圆形酵母细胞.皮损组织真菌培养可见酵母样菌落生长,菌株尿素酶试验阳性,ITS区测序比对鉴定为新生隐球菌grubii变种.血清隐球菌荚膜多糖抗原乳胶凝集试验阳性(++++).胸部CT显示左下肺后基底段空洞性病灶.依据临床及实验室检查确诊为由新生隐球菌grubii变种引起的 播散性隐球菌病.给予患者静滴氟康唑400 mg/d治疗2周,之后改口服300 mg/d治疗,3个月后结节性皮损全部消退,胸片显示左肺陈旧性病变,血清隐球菌荚膜多糖抗原乳胶凝集试验阳性(++).治疗15个月后,血清隐球菌荚膜多糖抗原乳胶凝集试验仍阳性(++).结论 对该病例的临床和实验室研究为临床明确诊断和治疗提供了依据,确定菌种需要进行分子生物学研究.     

隐球菌性脑膜炎的诊断与治疗

隐球菌性脑膜炎是由隐球菌属,特别是新生隐球菌及格特隐球菌引起的机会性感染,在免疫抑制者及正常人群均可发病。隐球菌性脑膜炎早期诊断困难,即便接受治疗,患者死亡率仍然很高。在过去几年中,快速及时的检测及早期隐球菌抗原检查取得了重大进展。对晚期HIV感染者行血隐球菌荚膜抗原筛查并进行抢先治疗,有望阻止其进展为临床感染。目前抗真菌药物主要包括多烯类、唑类及氟胞嘧啶,未来药物研究的重点是疗效更好、毒性更小的新型口服抗真菌药。本文总结近几年隐球菌性脑膜炎的相关诊断及治疗进展,旨在对隐脑患者诊疗提供帮助。     

The role of AQP3 and AQP4 channels in cisplatin-induced cardiovascular edema and the protective effect of melatonin

Molecular Biology Reports - The present study evaluates the development of edema, the change in the AQP3, AQP4, p53 and Bax gene expressions, and the protective effects of melatonin in rat hearts...     

Aquaporin-4 gene disruption in mice reduces brain swelling and mortality in pneumococcal meningitis

The astroglial water channel aquaporin-4 (AQP4) facilitates water movement into and out of brain parenchyma. To investigate the role of AQP4 in meningitis-induced brain edema, Streptococcus pneumoniae was injected into cerebrospinal fluid (CSF) in wild type and AQP4 null mice. AQP4-deficient mice had remarkably lower intracranial pressure (9 +/- 1 versus 25 +/- 5 cm H2O) and brain water accumulation (2 +/- 1 versus 9 +/- 1 microl) at 30 h, and improved survival (80 versus 0% survival) at 60 h, through comparable CSF bacterial and white cell counts. Meningitis produced marked astrocyte foot process swelling in wild type but not AQP4 null mice, and slowed diffusion of an inert macromolecule in brain extracellular space. AQP4 protein was strongly up-regulated in meningitis, resulting in a approximately 5-fold higher water permeability (P(f)) across the blood-brain barrier compared with non-infected wild type mice. Mathematical modeling using measured P(f) and CSF dynamics accurately simulated the elevated lower intracranial pressure and brain water produced by meningitis and predicted a beneficial effect of prevention of AQP4 upregulation. Our findings provide a novel molecular mechanism for the pathogenesis of brain edema in acute bacterial meningitis, and suggest that inhibition of AQP4 function or up-regulation may dramatically improve clinical outcome.     

儿童隐球菌性脑膜炎临床分析

目的分析并讨论儿童隐球菌性脑膜炎的临床特点、诊断及治疗方法等。方法回顾性分析上海长征医院皮肤科在1993年3月至2008年6月间16例经病原学确诊的隐球菌性脑膜炎患儿临床资料。结果患儿平均年龄7．25岁（2～15岁）,男女比例2．2：1,主要症状包括头痛（87．5％）、发热（81．25％）、恶心呕吐（75％）等,10例颅内压升高。确诊依据脑脊液真菌涂片、培养或隐球菌抗原检查。治疗采用两性霉素B和（或）两性霉素B脂质体静滴,5一氟胞嘧啶口服,辅以两性霉素B鞘内注射,联合氟康唑、伊曲康唑等药物治疗。16例患儿痊愈9例,病情明显好转5例,死亡2例。结论儿童隐球菌性脑膜炎起病缓慢,临床症状缺乏特异性,对疑有中枢神经系统感染性疾病时,应及早行脑脊液检查,并反复多次检查、联合检查以确定诊断,减少误诊、漏诊。早期诊断和及时、系统、足量、长程的抗真菌治疗是提高治愈率和患儿生存质量的关键。     

Targeting AQP4 localization as a novel therapeutic target in CNS edema

CNS edema is a pathological phenomenon after trauma, infection, tumor growth, or obstruction of blood supply, and it also can be fatal or lead to long-term disability, psychiatric disorders, substance abuse, or self-harm [1,2]. One exciting possibility would be to control excessive water accumulation in cells. However, all trials that inhibit water channel protein failed in clinic. A recent study by Kitchen et al. [3] reported that targeting the astrocytes’ surface localization of water channel protein aquaporin-4 (AQP4) significantly relieves CNS edema. Astrocytes are the most abundant cell type of the brain and generally have a greater capacity than neurons to survive stresses [4]. Astrocyte cell function is critically affected by the lack of oxygen supply (hypoxia) to the brain, which is usually associated with CNS edema [5]. Their work holds new promise for our ability to use water-transfer strategies to treat CNS edema. Cytotoxic and vasogenic edema are primary interrelated etiological factors for the progress of CNS edema [6]. Vasogenic edema also depends on the extent of cytotoxic edema and the nature/severity of the underlying cause of the cytotoxic edema. So, understanding the pathogenesis of cytotoxic edema is important for the treatment of CNS edema. Aquaporins (AQPs) are historically known to be passive transporters of water. Lines of evidence in the last decade have highlighted the diverse function of AQPs beyond water homeostasis, including regulation of renal water balance, brain-fluid homeostasis, triglyceride cycling, and skin hydration [7]. Moreover, a subgroup of AQP water channels, termed ‘aquaglyceroporins’, also facilitates transmembrane diffusion of small, polar solutes not only water but also solutes [8,9]. AQP4 is the major subtype of AQPs expressed in astrocytes throughout the nervous system and facilitates astroglial cell migration via increasing plasma membrane water permeability, which in turn upregulates the transmembrane water fluxes during astroglial cell movement and is thus considered as an interesting therapeutic target in various neurological disorders. Astrocyte swellingmay also cause cytotoxic component disruptions of the blood–brain barrier, suggesting that astrocytes seem so sensitive to cytotoxic edema. AQP4 is a recognized contributor for the formation of cytotoxic brain edema, which is mainly a phenomenon of intracellular swelling of astrocytes. Knockdown of ‘AQP4’ or removal of the perivascular AQP4 pool by α-syntrophin or α-syntrophin deletion has been convincingly proven to counteract osmotically induced acute brain edema following ischemia and other brain injuries [10–12]. A previous study revealed that the NH2-cytosolic terminus of AQP4 interacts with metabotropic glutamate receptor 5 and assembles with the catalytic subunit of Na,K-ATPase to form a complex that has the potential function for the regulation of water permeability and potassium homeostasis in the astrocytes [13] (Fig. 1). In addition, AQP4 may trigger astrocytic Ca2+ responses, which is partly dependent on autocrine purinergic signaling (P2 purinergic receptor) activation in response to hypoosmotic stress [14] (Fig. 1). Additionally, subcellular relocalization of AQP4 in primary astrocytes is induced by calmodulin (CaM), calcium, and PKA in response to hypotonicity [15]. Further study proved that hypoxia-driven astrocyte swelling induces the increased abundance of AQP4 and initiates AQP4 cell-surface relocalization in a CaM- and PKA-dependent manner [3] (Fig. 1).     

Decreased expression of AQP2 and AQP4 water channels and Na,K-ATPase in kidney collecting duct in AQP3 null mice

BACKGROUND INFORMATION: Phenotype analysis has demonstrated that AQP3 (aquaporin 3) null mice are polyuric and manifest a urinary concentration defect. In the present study, we report that deletion of AQP3 is also associated with an increased urinary sodium excretion. To investigate further the mechanism of the decreased urinary concentration and significant natriuresis, we examined the segmental and subcellular localization of collecting duct AQPs [AQP2, p-AQP2 (phosphorylated AQP2), AQP3 and AQP4], ENaC (epithelial sodium channel) subunits and Na,K-ATPase by immunoperoxidase and immunofluorescence microscopy in AQP3 null (-/-), heterozygous (+/-) mice, wild-type and unrelated strain of normal mice. RESULTS: The present study confirms that AQP3 null mice exhibit severe polyuria and polydipsia and demonstrated that they exhibit increased urinary sodium excretion. In AQP3 null mice, there is a marked down-regulation of AQP2 and p-AQP2 both in CNT (connecting tubule) and CCD (cortical collecting duct). Moreover, AQP4 is virtually absent from CNT and CCD in AQP3 null mice. Basolateral AQP2 was virtually absent from AQP3 null mice and normal mice in contrast with rat. Thus the above results demonstrate that no basolateral AQPs are expressed in CNT and CCD of AQP3 null mice. However, in the medullary-collecting ducts, there is no difference in the expression levels and subcellular localization of AQP2, p-AQP2 and AQP4 between AQP3 +/- and AQP3 null mice. Moreover, a striking decrease in the immunolabelling of the alpha1 subunit of Na,K-ATPase was observed in CCD in AQP3 null mice, whereas a medullary-collecting duct exhibited normal labelling. Immunolabelling of all the ENaC subunits in the collecting duct was comparable between the two groups. CONCLUSIONS: The results improve the possibility that the severe urinary concentrating defect in AQP3 null mice may in part be caused by the decreased expression of AQP2, p-AQP2 and AQP4 in CNT and CCD, whereas the increased urinary sodium excretion may in part be accounted for by Na,K-ATPase in CCD in AQP3 null mice.     

Aquaporin-4 deletion in mice reduces brain edema after acute water intoxication and ischemic stroke

Cerebral edema contributes significantly to morbidity and death associated with many common neurological disorders. However, current treatment options are limited to hyperosmolar agents and surgical decompression, therapies introduced more than 70 years ago. Here we show that mice deficient in aquaporin-4 (AQP4), a glial membrane water channel, have much better survival than wild-type mice in a model of brain edema caused by acute water intoxication. Brain tissue water content and swelling of pericapillary astrocytic foot processes in AQP4-deficient mice were significantly reduced. In another model of brain edema, focal ischemic stroke produced by middle cerebral artery occlusion, AQP4-deficient mice had improved neurological outcome. Cerebral edema, as measured by percentage of hemispheric enlargement at 24 h, was decreased by 35% in AQP4-deficient mice. These results implicate a key role for AQP4 in modulating brain water transport, and suggest that AQP4 inhibition may provide a new therapeutic option for reducing brain edema in a wide variety of cerebral disorders.     

Aquaporin-4 gene deletion in mice increases focal edema associated with staphylococcal brain abscess

Brain abscess is associated with local vasogenic edema, which leads to increased intracranial pressure and significant morbidity. Aquaporin-4 (AQP4) is a water channel expressed in astroglia at the blood-brain and brain-CSF barriers. To investigate the role of AQP4 in brain abscess-associated edema, live Staphylococcus aureus (10(5) colony-forming units) was injected into the striatum to create a focal abscess. Wild-type and AQP4-deficient mice had comparable immune responses as measured by brain abscess volume (approximately 3.7 mm3 at 3 days), bacterial count and cytokine levels in brain homogenates. Blood-brain barrier permeability was increased comparably in both groups as assessed by extravasation of Evans blue dye. However, at 3 days the AQP4 null mice had significantly higher intracranial pressure (mean +/- SEM 27 +/- 2 vs. 17 +/- 2 mmHg; p < 0.001) and brain water content (81.0 +/- 0.3 vs. 79.3 +/- 0.5 % water by weight in the abscess-containing hemisphere; p < 0.01) than wild-type mice. Reactive astrogliosis was found throughout the abscess-containing hemisphere; however, only a subset of astrocytes in the peri-abscess region of wild-type mice had increased AQP4 immunoreactivity. Our findings demonstrate a protective effect of AQP4 on brain swelling in bacterial abscess, suggesting that AQP4 induction may reduce vasogenic edema associated with cerebral infection.     

Chemotactic activity of cerebrospinal fluid in experimental cryptococcal meningitis

Cerebrospinal fluid from rabbits with chronic cryptococcal meningitis was tested for its chemotactic activity towards polymorphonuclear cells and monocytes. CSF chemotactic activity was present; it peaked 5-8 days after infection, coinciding with the time when the number of inflammatory cells in CSF was greatest. However, little chemotactic activity could be found in the early stages of infection, during the initial ingress of inflammatory cells. The chemotactic activity appeared to be host-derived, with characteristics consistent with lymphokine(s) or C5a. Treatment with cortisone significantly reduced the CSF chemotactic activity for both cell types; this reduction may contribute to the severe CSF leukopenia observed in cortisone-treated animals, which are unable to eradicate this yeast infection. Modulation of CSF chemotactic activity may be important to the success or failure of the host central nervous system response to Cryptococcus neoformans.