Showing papers by "Vicente Felipo published in 2015"

Sildenafil reduces neuroinflammation and restores spatial learning in rats with hepatic encephalopathy: underlying mechanisms

Abstract: Background There are no specific treatments for the neurological alterations of cirrhotic patients with minimal hepatic encephalopathy (MHE). Rats with MHE due to portacaval shunt (PCS) show impaired spatial learning. The underlying mechanisms remain unknown. The aims of this work were to assess: (a) whether PCS rats show neuroinflammation in hippocampus, (b) whether treatment with sildenafil reduces neuroinflammation and restores spatial learning in PCS rats, and (c) analyze the underlying mechanisms.

Gender Differences in Spatial Learning, Synaptic Activity, and Long-Term Potentiation in the Hippocampus in Rats: Molecular Mechanisms

Abstract: In tests of spatial ability, males outperform females both in rats and in humans. The mechanism underlying this gender differential learning ability and memory in spatial tasks remains unknown. Long-term potentiation (LTP) in the hippocampus is considered the basis for spatial learning and memory. The aims of this work were (a) to assess spatial learning and memory in male and female rats in the radial and Morris mazes; (b) to assess whether basal synaptic activity and LTP in the hippocampus are different in male and female rats; and (c) to identify the molecular mechanisms responsible for the gender differences in LTP. We analyzed in young male and female rats (a) performance in spatial tasks in the radial and Morris water mazes; (b) basal synaptic activity in hippocampal slices; and (c) LTP and some mechanisms modulating its magnitude. The results reported allow us to conclude that female rats show larger AMPA receptor-mediate synaptic responses under basal conditions, likely due to enhanced phosphoryla...

GR3027 antagonizes GABAA receptor-potentiating neurosteroids and restores spatial learning and motor coordination in rats with chronic hyperammonemia and hepatic encephalopathy

Abstract: Hepatic encephalopathy (HE) is one of the primary complications of liver cirrhosis. Current treatments for HE, mainly directed to reduction of ammonia levels, are not effective enough because they cannot completely eliminate hyperammonemia and inflammation, which induce the neurological alterations. Studies in animal models show that overactivation of GABAA receptors is involved in cognitive and motor impairment in HE and that reducing this activation restores these functions. We have developed a new compound, GR3027, that selectively antagonizes the enhanced activation of GABAA receptors by neurosteroids such as allopregnanolone and 3α,21-dihydroxy-5α-pregnan-20-one (THDOC). This work aimed to assess whether GR3027 improves motor incoordination, spatial learning, and circadian rhythms of activity in rats with HE. GR3027 was administered subcutaneously to two main models of HE: rats with chronic hyperammonemia due to ammonia feeding and rats with portacaval shunts (PCS). Motor coordination was assessed in beam walking and spatial learning and memory in the Morris water maze and the radial maze. Circadian rhythms of ambulatory and vertical activity were also assessed. In both hyperammonemic and PCS rats, GR3027 restores motor coordination, spatial memory in the Morris water maze, and spatial learning in the radial maze. GR3027 also partially restores circadian rhythms of ambulatory and vertical activity in PCS rats. GR3027 is a novel approach to treatment of HE that would normalize neurological functions altered because of enhanced GABAergic tone, affording more complete normalization of cognitive and motor function than current treatments for HE.

The expression levels of prolyl oligopeptidase responds not only to neuroinflammation but also to systemic inflammation upon liver failure in rat models and cirrhotic patients

Abstract: Liver failure in experimental animals or in human cirrhosis elicits neuroinflammation. Prolyl oligopeptidase (PREP) has been implicated in neuroinflammatory events in neurodegenerative diseases: PREP protein levels are increased in brain glial cells upon neuroinflammatory insults, but the circulating PREP activity levels are decreased in multiple sclerosis patients in a process probably mediated by bioactive peptides. In this work, we studied the variation of PREP levels upon liver failure and correlated it with several inflammatory markers to conclude on the relation of PREP with systemic and/or neuroinflammation. PREP enzymatic activity and protein levels measured with immunological techniques were determined in the brain and plasma of rats with portacaval shunt (PCS) and after treatment with ibuprofen. Those results were compared with the levels of PREP measured in plasma from cirrhotic patients with or without minimal hepatic encephalopathy (MHE). Levels of several pro-inflammatory cytokines and those of NO/cGMP homeostasis metabolites were measured in PCS rats and cirrhotic patients to conclude on the role of PREP in inflammation. In PCA rats, we found that PREP levels are significantly increased in the hippocampus, striatum and cerebellum, that in the cerebellum the PREP increase was significantly found in the extracellular space and that the levels were restored to those measured in control rats after administration of an anti-inflammatory agent, ibuprofen. In cirrhotic patients, circulatory PREP activity was found to correlate to systemic and neuroinflammatory markers and had a negative correlation with the severity of the disease, although no clear relation to MHE. These results support the idea that PREP levels could be used as indicators of cirrhosis severity in humans, and using other markers, it might contribute to assessing the level of neuroinflammation in those patients. This work reports, for the first time, that PREP is secreted to the extracellular space in the cerebellum most probably due to glial activation and supports the role of the peptidase in the inflammatory response.

Neuroinflammation and neurological alterations in chronic liver diseases

Abstract: 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.

Roles of the NMDA Receptor and EAAC1 Transporter in the Modulation of Extracellular Glutamate by Low and High Affinity AMPA Receptors in the Cerebellum in Vivo: Differential Alteration in Chronic Hyperammonemia

Abstract: The roles of high- and low-affinity AMPA receptors in modulating extracellular glutamate in the cerebellum remain unclear. Altered glutamatergic neurotransmission is involved in neurological alterations in hyperammonemia, which differently affects high- and low-affinity AMPA receptors. The aims were to assess by in vivo microdialysis (a) the effects of high- and low-affinity AMPA receptor activation on extracellular glutamate in the cerebellum; (b) whether chronic hyperammonemia alters extracellular glutamate modulation by high- and/or low-affinity AMPA receptors; and (c) the contribution of NMDA receptors and EAAC1 transporter to AMPA-induced changes in extracellular glutamate. In control rats, high affinity receptor activation does not affect extracellular glutamate but increases glutamate if NMDA receptors are blocked. Low affinity AMPA receptor activation increases transiently extracellular glutamate followed by reduction below basal levels and return to basal values. The reduction is associated with ...

Rats with Mild Bile Duct Ligation Show Hepatic Encephalopathy with Cognitive and Motor Impairment in the Absence of Cirrhosis: Effects of Alcohol Ingestion

Abstract: Studies in animal models allow identifying mechanisms and treatments for cognitive and motor alterations in hepatic encephalopathy (HE). Liver diseases leading to HE in humans have different aetiologies (alcoholic, viral, etc.). The International Society for Hepatic Encephalopathy points out that satisfactory model for HE resulting from alcoholic cirrhosis are lacking. This work aimed to develop and characterize an animal model for HE in alcoholic liver cirrhosis. To potentiate the effects of alcohol on liver we administered it (5, 8 or 10 % in drinking water) to rats showing mild liver damage induced by “mild” bile duct ligation (MBDL), obtained by sectioning 3 out of 5 bile ducts. MBDL rats show increased markers of cholestasis and liver damage, hyperammonemia and inflammation. MBDL rats also show motor in-coordination, hypokinesia, impaired learning ability in a Y maze and reduced spatial memory in the Morris water maze. Ingesting 10 % ethanol does not induce relevant liver damage in control rats but potentiates liver damage in MBDL rats. In contrast, ethanol did not enhance the biochemical or neurological alterations in MBDL rats. This supports that the combination of certain levels of hyperammonemia and inflammation is enough to induce mild cognitive impairment, even in the absence of liver cirrhosis. Rats with MBDL and MBDL-OH survived more than 3 months, allowing performing long-term studies on cognitive and motor alterations and on underlying mechanisms. MBDL-OH rats are a good model to study the mechanisms of ethanol-induced liver cirrhosis and the factors making the liver susceptible to ethanol damage.

Rats with minimal hepatic encephalopathy show reduced cGMP-dependent protein kinase activity in hypothalamus correlating with circadian rhythms alterations.

Abstract: Patients with liver cirrhosis show disturbances in sleep and in its circadian rhythms which are an early sign of minimal hepatic encephalopathy (MHE). The mechanisms of these disturbances are poorly understood. Rats with porta-caval shunt (PCS), a model of MHE, show sleep disturbances reproducing those of cirrhotic patients. The aims of this work were to characterize the alterations in circadian rhythms in PCS rats and analyze the underlying mechanisms. To reach these aims, we analyzed in control and PCS rats: (a) daily rhythms of spontaneous and rewarding activity and of temperature, (b) timing of the onset of activity following turning-off the light, (c) synchronization to light after a phase advance and (d) the molecular mechanisms contributing to these alterations in circadian rhythms. PCS rats show altered circadian rhythms of spontaneous and rewarding activities (wheel running). PCS rats show more rest bouts during the active phase, more errors in the onset of motor activity and need less time to re...

Steroid compound for use in the treatment of hepatic encephalopathy

Abstract: The present invention provides the steroidal compound3-ethynyl-3- hydroxyandrostan-17-one oxime,or a pharmaceutically acceptable saltthereof,for usein treatment ofhepaticencephalopathy.