Brain cholinergic impairment in liver failure.

The cholinergic system is involved in specific behavioural responses and cognitive processes. Here, we examined potential alterations in the brain levels of key cholinergic enzymes in cirrhotic patients and animal models with liver failure. An increase (~30%) in the activity of the acetylcholine-hydrolyzing enzyme, acetylcholinesterase (AChE) is observed in the brain cortex from patients deceased from hepatic coma, while the activity of the acetylcholine-synthesizing enzyme, choline acetyltransferase, remains unaffected. In agreement with the human data, AChE activity in brain cortical extracts of bile duct ligated (BDL) rats was increased (~20%) compared to controls. A hyperammonemic diet did not result in any further increase of AChE levels in the BDL model, and no change was observed in hyperammonemic diet rats without liver disease. Portacaval shunted rats which display increased levels of cerebral ammonia did not show any brain cholinergic abnormalities, confirming that high ammonia levels do not play a role in brain AChE changes. A selective increase of tetrameric AChE, the major AChE species involved in hydrolysis of acetylcholine in the brain, was detected in both cirrhotic humans and BDL rats. Histological examination of BDL and non-ligated rat brains shows that the subcellular localization of both AChE and choline acetyltransferase, and thus the accessibility to their substrates, appears unaltered by the pathological condition. The BDL-induced increase in AChE activity was not parallelled by an increase in mRNA levels. Increased AChE in BDL cirrhotic rats leads to a pronounced decrease (~50-60%) in the levels of acetylcholine. Finally, we demonstrate that the AChE inhibitor rivastigmine is able to improve memory deficits in BDL rats. One week treatment with rivastigmine (0.6 mg/kg; once a day, orally, for a week) resulted in a 25% of inhibition in the enzymatic activity of AChE with no change in protein composition, as assessed by sucrose density gradient fractionation and western blotting analysis. In conclusion, this study is the first direct evidence of a cholinergic imbalance in the brain as a consequence of liver failure and points to the possible role of the cholinergic system in the pathogenesis of hepatic encephalopathy.

Reelin is overexpressed in the liver and plasma of bile duct ligated rats and its levels and glycosylation are altered in plasma of humans with cirrhosis.

Reelin is an extracellular matrix protein secreted by a variety of cell types in both embryonic and adult tissues, including the liver. However, the physiological significance of Reelin in normal and cirrhotic liver has thus far not been elucidated. We have investigated Reelin levels in the liver and plasma of bile duct ligated (BDL) rats. We observe a 115% increase in full-length Reelin and its 310- and 180-kDa fragments in liver extracts from BDL rats, compared to sham-operated controls (p = 0.005). The overall increase in protein levels was associated with a 30% increase of Reelin transcripts (p = 0.03). Immunohistochemical analysis demonstrated that hepatic stellate cells are the major source of Reelin in the injured liver. Increased liver Reelin in BDL rats leads to a pronounced 165% increase in the plasma levels (p < 0.001), particularly in the less abundant 180-kDa fragment (300% increase; p < 0.001). The data provides evidence that a fraction of plasma Reelin is synthesized in the liver. In human subjects suffering liver cirrhosis the level of the 180-kDa fragment was also increased by 140% in the plasma (p < 0.001). Analysis of Reelin glycosylation by lectin binding demonstrated that the 180- and predominant 310-kDa Reelin fragments in the plasma of cirrhotic patients are differentially glycosylated compared to non-diseased control subjects. The data show that Reelin is up-regulated in experimental liver cirrhosis and that its levels and glycosylation are altered in plasma from patients with cirrhosis, thereby supporting that Reelin is involved in the pathogenesis of liver disease.

Brain edema and inflammatory activation in bile duct ligated rats with diet-induced hyperammonemia: A model of hepatic encephalopathy in cirrhosis.

Studies of the pathogenesis of hepatic encephalopathy are hampered by the lack of a satisfactory animal model. We examined the neurological features of rats after bile duct ligation fed a hyperammonemic diet (BDL+HD). Six groups were studied: sham, sham pair-fed, hyperammonemic, bile duct ligation (BDL), BDL pair fed, and BDL+HD. The BDL+HD rats were made hyperammonemic via an ammonia-containing diet that began 2 weeks after operation. One week later, the animals were sacrificed. BDL+HD rats displayed an increased level of cerebral ammonia and neuroanatomical characteristics of hepatic encephalopathy (HE), including the presence of type II Alzheimer astrocytes. Both BDL and BDL+HD rats showed activation of the inflammatory system. BDL+HD rats showed an increased amount of brain glutamine, a decreased amount of brain myo-inositol, and a significant increase in the level of brain water. In coordination tests, BDL+HD rats showed severe impairment of motor activity and performance as opposed to BDL rats, whose results seemed only mildly affected. In conclusion, the BDL+HD rats displayed similar neuroanatomical and neurochemical characteristics to human HE in liver cirrhosis. Brain edema and inflammatory activation can be detected under these circumstances.

Changes in liver and plasma acetylcholinesterase in rats with cirrhosis induced by bile duct ligation.

Classical studies of cholinesterase activity during liver dysfunction have focused on butyrylcholinesterase (BuChE), whereas acetylcholinesterase (AChE) has not received much attention. In the current study, liver and plasma AChE levels were investigated in rats with cirrhosis induced after 3 weeks of bile duct ligation (BDL). BDL rats showed a pronounced decrease in liver AChE levels (approximately 50%) compared with sham-operated (non-ligated, NL) controls; whereas liver BuChE appeared unaffected. A selective loss of tetrameric (G4) AChE was detected in BDL rats, an effect also observed in rats with carbon tetrachloride-induced cirrhosis. In accordance, SDS-PAGE analysis showed that the major 55-kd immunoreactive AChE band was decreased in BDL as compared with NL. A 65-kd band, attributed in part to inactive AChE, was increased as became the most abundant AChE subunit in BDL liver. The overall decrease in AChE activity in BDL liver was not accompanied by a reduction of AChE transcripts. The loss of G4 was also reflected by changes observed in AChE glycosylation pattern attributable to different liver AChE forms being differentially glycosylated. BDL affects AChE levels in both hepatocytes and Kupffer cells; however, altered AChE expression was mainly reflected in an alteration in hepatocyte AChE pattern. Plasma from BDL rats had approximately 45% lower AChE activity than controls, displaying decreased G4 levels and altered lectin-binding patterns. In conclusion, the liver is an important source of serum AChE; altered AChE levels may be a useful biomarker for liver cirrhosis.

Animal models in the study of episodic hepatic encephalopathy in cirrhosis.

The availability of an animal model is crucial in studying the pathophysiological mechanisms of disease and to test possible therapies. Now, there are several models for the study of liver diseases, but there still remains a lack of a satisfactory animal model of chronic liver disease with hepatic encephalopathy (HE) and abnormalities in nitrogen metabolism, as seen in humans. In rats, two models of chronic HE are widely used: rats after portacaval anastomosis (PCA) and rats with chronic hyperammonemia. The first one mimics the situation induced in cirrhosis by collateral circulation, and has the problem of the absence of hepatocellular injury. The model of hyperammonemia is useful to study the effect of ammonia as a brain toxic substance, but also lacks liver failure. Bile-duct ligation has been used to induce cirrhosis and could also be a model of HE, probably with the addition of a precipitant factor. An ideal model of HE in chronic liver disease must have liver cirrhosis and a precipitant factor of HE; it must also show neuropathological characteristic findings of HE, neurochemical alterations in the main pathways impaired in these complications of cirrhosis, and low-grade brain edema.

¿Es necesaria la profilaxis antibiótica en lacirugía protésica de la hernia inguinal? / Is antibiotic prophylaxis required in prosthetic inguinal hernia repair?

Introducción. Clásicamente, se ha indicado la profilaxis antibiótica en la cirugía limpia cuando se instaure material protésico. Una de las intervenciones más habituales de este tipo es la herniorrafia inguinal. Debido a los bajos índices de infección de herida y al reducido tamaño del material protésico implantado, existen dudas razonables sobre la utilidad de la profilaxis antibiótica en esta intervención. Por eso, hemos realizado un estudio para conocer si la presencia o ausencia de profilaxis antibiótica modifica la tasa de infecciones de la herniorrafia inguinal con prótesis. Pacientes y método. Estudio de intervención sin asignación aleatoria ni cegamiento, en pacientes intervenidos de herniorrafia inguinal con prótesis en el Servicio de Cirugía General del Hospital Clínico Universitario Sant Joan de Alicante. El estudio se realizó entre los años 1998 y 2002, ambos incluidos. Los criterios de exclusión fueron: pacientes inmunodeprimidos y/o con hernia inguinal bilateral. Los pacientes fueron divididos en dos grupos: un grupo sometido a profilaxis antibiótica preoperatoria (PAP), consistente en 1,5 g de cefuroxima i.v. en la inducción anestésica y otro grupo de pacientes sin profilaxis. Se estandarizó la técnica quirúrgica. La infección de herida se definió según los criterios de los CDC (Centers for Disease Control). Los pacientes fueron seguidos a la semana, al mes y al año de la intervención quirúrgica. Análisis estadístico. Se analizó la incidencia acumulada (IA) de infección de herida quirúrgica, junto con su intervalo de confianza (IC), en cada uno de los grupos y si la diferencia era significativa entre los dos grupos. También se calculó el NNT (número de individuos tratados necesario para que se observe un efecto beneficioso). Resultados. El estudio incluyó a un total de 425 pacientes (408 varones y 17 mujeres), 358 de ellos aquejados de hernia primaria y 67 de hernia recidivada, con unas edades medianas de 59 y 63 años, respectivamente. Se realizó profilaxis antibiótica en el 48,6 por ciento de los pacientes con hernia inguinal primaria y en el 49,2 por ciento de las hernias recidivadas. Sufrieron complicaciones 45 pacientes intervenidos de hernia inguinal primaria (12,5 por ciento de este grupo y 10,6 por ciento de toda la serie), frente a ocho del grupo de hernias recidivadas (11,9 por ciento de este grupo y 1,9 por ciento de toda la serie). Se documentaron dos infecciones de herida quirúrgica (0,47 por ciento), ambas en pacientes intervenidos por hernia primaria, una en el grupo de PAP y otra en el grupo sin PAP. Entre los 207 pacientes con PAP el riesgo de infección fue del 0,48 por ciento (IC del 95 por ciento, 0,461,42 por ciento), y para los 218 que no la realizaron fue del 0,45 por ciento (IC del 95 por ciento, 0,43-1,33 por ciento), sin que la diferencia alcanzara significación estadística. Tampoco hubo diferencias en la incidencia de aparición de otras complicaciones distintas de la infección de localización quirúrgica. El número necesario de pacientes (NNT) intervenidos de hernia inguinal que deben recibir quimioprofilaxis antibiótica perioperatoria para observar un efecto beneficioso con la aplicación de PAP, es decir, la ausencia de infección en un paciente, fue de 3.333 pacientes. Conclusión. Dada la presencia de una mínima cantidad de "cuerpo extraño" con la prótesis habitual de una herniorrafia, es poco probable la presencia de infecciones, sobre todo cuando la prótesis está mallada y multiperforada. Por ello, parece que se puede prescindir sistemáticamente de la profilaxis antibiótica en las intervenciones de herniorrafia con prótesis sin que se incremente significativamente el riesgo de infección de la herida quirúrgica ni las complicaciones locales derivadas de su ausencia, limitando su uso únicamente a pacientes con factores de riesgo (AU)