Pathological and therapeutic effects of extracellular vesicles in neurological and neurodegenerative diseases

Extracellular vesicles are released by all cell types and contain proteins,microRNAs,mRNAs,and other bioactive molecules.Extracellular vesicles play an important role in intercellular communication and in the modulation of the immune system and neuroinflammation.The cargo of extra cellular vesicles(e.g.,proteins and microRNAs)is altered in pathological situations.Extracellular vesicles contribute to the pathogenesis of many pathologies associated with sustained inflammation and neuroinflammation,including cance r,diabetes,hype rammonemia and hepatic encephalopathy,and other neurological and neurodegenerative diseases.Extracellular vesicles may cross the blood-brain barrier and transfer pathological signals from the periphery to the brain.This contributes to inducing neuroinflammation and cognitive and motor impairment in hyperammonemia and hepatic encephalopathy and in neurodegenerative diseases.The mechanisms involved are beginning to be unde rstood.For example,increased tumor necrosis factor a in extracellular vesicles from plasma of hype rammonemic rats induces neuroinflammation and motor impairment when injected into normal rats.Identifying the mechanisms by which extracellular vesicles contribute to the pathogenesis of these diseases will help to develop new treatments and diagnostic tools for their easy and early detection.In contrast,extra cellular vesicles from mesenchymal stem cells have therapeutic utility in many of the above pathologies,by reducing inflammation and neuroinflammation and improving cognitive and motor function.These extra cellular vesicles recapitulate the beneficial effects of mesenchymal stem cells and have advantages as therapeutic tools:they are less immunoge nic,may not diffe rentiate to malignant cells,cross the blood-brain barrier,and may reach more easily target organs.Extracellular vesicles from mesenchymal stem cells have beneficial effects in models of ischemic brain injury,Alzheimer's and Parkinson's diseases,hyperammonemia,and hepatic encephalopathy.Extracellular vesicles from mesenchymal stem cells modulate the immune system,promoting the shift from a pro-inflammato ry to an anti-inflammatory state.For example,extracellular vesicles from mesenchymal stem cells modulate the Th17/Treg balance,promoting the anti-inflammatory Treg.Extracellular vesicles from mesenchymal stem cells may also act directly in the brain to modulate microglia activation,promoting a shift from a pro-inflammatory to an anti-inflammatory state.This reduces neuroinflammation and improves cognitive and motor function.Two main components of extracellular vesicles from mesenchymal stem cells which contribute to these beneficial effects are transforming growth factor-βand miR-124.Identifying the mechanisms by which extracellular vesicles from mesenchymal stem cells induce the beneficial effects and the main molecules(e.g.,proteins and mRNAs)involved may help to improve their therapeutic utility.The aims of this review are to summarize the knowledge of the pathological effects of extracellular vesicles in different pathologies,the therapeutic potential of extra cellular vesicles from mesenchymal stem cells to recover cognitive and motor function and the molecular mechanisms for these beneficial effects on neurological function.

Non invasive blood flow measurement in cerebellum detects minimal hepatic encephalopathy earlier than psychometric tests

AIM: To assess whether non invasive blood flow measurement by arterial spin labeling in several brain regions detects minimal hepatic encephalopathy. METHODS: Blood flow(BF) was analyzed by arterial spin labeling(ASL) in different brain areas of 14 controls, 24 cirrhotic patients without and 16 cirrhotic patients with minimal hepatic encephalopathy(MHE). Images were collected using a 3 Tesla MR scanner(Achieva 3T-TX, Philips, Netherlands). Pulsed ASL was performed. Patients showing MHE were detected using the battery Psychometric Hepatic Encephalopathy Score(PHES) consisting of five tests. Different cognitive and motor functions were also assessed: alterations in selective attention were evaluated using the Stroop test. Patients and controls also performed visuo-motor and bimanual coordination tests. Several biochemical parameters were measured: serum pro-inflammatory interleukins(IL-6 and IL-18), 3-nitrotyrosine, cGMP and nitrates+nitrites in plasma, and blood ammonia. Bivariate correlations were evaluated.RESULTS: In patients with MHE, BF was increased in cerebellar hemisphere(P = 0.03) and vermis(P = 0.012) and reduced in occipital lobe(P = 0.017). BF in cerebellar hemisphere was also increased in patients without MHE(P = 0.02). Bimanual coordination was impaired in patients without MHE(P = 0.05) and much more in patients with MHE(P < 0.0001). Visuo-motor coordination was impaired only in patients with MHE(P < 0.0001). Attention was slightly affected in patients without MHE and more strongly in patients with MHE(P< 0.0001). BF in cerebellar hemisphere and vermis correlated with performance in most tests of PHES [(number connection tests A(NCT-A), B(NCT-B)and line tracing test] and in the congruent task of Stroop test. BF in frontal lobe correlated with NCT-A. Performance in bimanual and visuomotor coordination tests correlated only with BF in cerebellar hemisphere. BF in occipital lobe correlates with performance in the PHES battery and with CFF. BF in cerebellar hemisphere correlates with plasma cGMP and nitric oxide(NO) metabolites. BF in vermis cerebellar also correlates with NO metabolites and with 3-nitrotyrosine. IL-18 in plasma correlates with BF in thalamus and occipital lobe.CONCLUSION: Non invasive BF determination in cerebellum using ASL may detect MHE earlier than the PHES. Altered NO-cGMP pathway seems to be associated to altered BF in cerebellum.

Contribution of altered signal transduction associated to glutamate receptors in brain to the neurological alterations of hepatic encephalopathy

Patients with liver disease may present hepatic enceph- alopathy (HE), a complex neuropsychiatric syndrome covering a wide range of neurological alterations, including cognitive and motor disturbances. HE reduces the quality of life of the patients and is associated with poor prognosis. In the worse cases HE may lead to coma or death. The mechanisms leading to HE which are not well known are being studied using animal models. The neurological alterations in HE are a consequence of impaired cerebral function mainly due to alterations in neurotransmission. We review here some studies indicating that alterations in neurotransmission associated to different types of glutamate receptors are responsible for some of the cognitive and motor alterations present in HE. These studies show that the function of the signal transduction pathway glutamate-nitric oxide-cGMP associated to the NMDA type of glutamate receptors is impaired in brain in vivo in HE animal models as well as in brain of patients died of HE. Activation of NMDA receptors in brain activates this pathway and increases cGMP. In animal models of HE this increase in cGMP induced by activation of NMDA receptors is reduced, which is responsible for the impairment in learning ability in these animal models. Increasing cGMP by pharmacological means restores learning ability in rats with HE and may be a new therapeutic approach to improve cognitive function in patients with HE. However, it is necessary to previously assess the possible secondary effects.Patients with HE may present psychomotor slowing, hypokinesia and bradykinesia. Animal models of HE also show hypolocomotion. It has been shown in rats with HE that hypolocomotion is due to excessive activation of metabotropic glutamate receptors (mGluRs) in substantia nigra pars reticulata. Blocking mGluR1 in this brain area normalizes motor activity in the rats, suggesting that a similar treatment for patients with HE could be useful to treat psychomotor slowing and hypokinesia. However, the possible secondary effects of mGluR1 antagonists should be previously evaluated. These studies are setting the basis for designing therapeutic procedures to specifically treat the individual neurological alterations in patients with HE.

Phosphate-activated glutaminase activity is enhanced in brain, intestine and kidneys of rats following portacaval anastomosis

瞄准：估计在老鼠的门腔静脉吻合(PCA ) 是否在肾影响蛋白质表示或谷酰胺酶的活动，肠并且在外皮的三个大脑区域，基础轧了神经胶质和小脑并且解释在肝的脑病发现的神经病学的改变(他) 。方法：称 250-350 g 的十六只男 Wistar 老鼠被组织进假冒操作的控制(n=8 ) 或 portacaval (n=8 ) 。在过程以后的 28 天，动物被牺牲。十二指肠，肾和大脑被移开， homogenised 和线粒体被孤立。氨在大脑和血被测量。激活磷酸盐的谷酰胺酶(PAG ) 活动被与 O-phthalaldehyde (OPA ) 和每蛋白质(蛋白质的 mukat/g ) 的克以单位表示的特殊活动在 37 摄氏度测量氨生产追随者孵化一个小时决定。蛋白质表示被弄污的免疫测量。结果：十二指肠并且和蛋白质内容的肾 PAG 活动比在 PCA 组是显著地更高的在控制或假冒操作老鼠(十二指肠 PAG 活动是在 PCA 老鼠对在假冒操作老鼠的蛋白质的 429.19+/-126.92mukat/g 的蛋白质的 976.95+/-268.87 mukat/g；肾 PAG 活动是在 PCA 老鼠对在控制的蛋白质的 669.67+/-400.8 mukat/g 的 1259.18+/-228.79 mukat/g 蛋白质， P【0.05；十二指肠的蛋白质内容：173% 在 PCA 对假冒操作老鼠；在肾，蛋白质的内容在 PCA 对假冒操作老鼠是 152%) 。在 PCA 老鼠的 PAG 活动和蛋白质表示在外皮是更高的并且基础在假冒操作老鼠比那些轧了神经胶质(外皮：蛋白质的 6646.6+/-1870.4 mukat/g 对在控制老鼠的蛋白质的 3573.8+/-2037.4 mukat/g， P【0.01；基础轧了神经胶质， PAG 活动是在 PCA 老鼠对在假冒的操作老鼠的蛋白质的 2271.2+/-384 mukat/g 的蛋白质的 3657.3+/-1469.6 mukat/g， P【0.05；在小脑，分别地， PAG 活动是蛋白质的 2471.6+/-701.4 mukat/g 对在 PCA 和假冒的老鼠的蛋白质的 1452.9+/-567.8 mukat/g P【0.05；蛋白质的内容：大脑皮质：162%+/-40% 对 100%+/-26% ， P【0.009；并且基础轧了神经胶质：140%+/-39% 对 100%+/-14% ， P【0.05；然而并非在里面小脑：100%+/-25% 对 100%+/-16% ， P=ns ) 。结论：在肾和十二指肠的增加的 PAG 活动能在 PCA 老鼠显著地作出贡献到 hyperammonaemia，脑病的动物模型。PAG 从外皮在 non-synaptic 线粒体被增加并且基础轧了神经胶质并且能在肝的脑病的致病被含有。因此， PAG 能是为处理的一个可能的目标他或肝机能障碍。

Neuroinflammation and neurological alterations in chronic liver diseases

Several million people with chronic liver diseases(cirrhosis,hepatitis)show neurological alterations,named hepatic encephalopathy(HE)with cognitive and motor alterations that impair quality of life and reduces life span.Inflammation acts synergistically with hyperammonemia to induce cognitive and motor alterations in patients with chronic liver disease and minimal hepatic encephalopathy(MHE).Previous studies in animal models have suggested that neuroinflammation is a major player in HE.This would also be the case in patients with liver cirrhosis or hepatitis C with HE.Rats with MHE show microglial activation and neuroinflammation that is associated with cognitive impairment and hypokinesia.The anti-inflammatory drug ibuprofen reduces microglial activation and neuroinflammation and restores cognitive and motor functions in rats with MHE.Chronic hyperammonemia per se induces neuroinflammation.Both peripheral inflammation and hyperammonemia would contribute to neuroinflammation in chronic liver failure.Therefore,neuroinflammation may be a key therapeutic target to improve the cognitive and motor alterations in MHE and overt HE.Identifying new targets to reduce neuroinflammation in MHE without inducing secondary effects would serve to develop new therapeutic tools to reverse the cognitive and motor alterations in patients with HE associated with chronic liver diseases.