Aspectos moleculares de la encefalopatía hepática

Cirrosis hepática o falla hepática crónica agudizada: definición y clasificación

La cirrosis se considera el estadio crónico e irreversible de la lesión hepática. Su etiología es diversa y abarca causas como las infecciones víricas, tóxicos como el alcohol, medicamentos, patologías autoinmunes y otras. La descompensación de la cirrosis hepática es consecuencia de cambios fisiopatológicos que se dan con el tiempo como ascitis, peritonitis bacteriana espontánea, hemorragia del tubo digestivo, síndrome hepatorrenal, encefalopatía hepática o hipertensión portopulmonar, mientras que la falla hepática crónica agudizada debe considerarse como una entidad que debe diferenciarse de la anterior, ya que es una falla multiorgánica de curso rápido, por lo regular en pacientes hospitalizados en unidad de cuidado intensivo, a menudo secundaria a desencadenantes como estados de choque. El clínico debe identificarlas para su abordaje y evaluación. El método actual adecuado para estadificar esta entidad es el puntaje CLIFF SOFA, que evalúa la mortalidad a 28 y 90 días, permitiendo intervenciones adecuadas en cada caso.

Involvement of opioidergic and nitrergic systems in memory acquisition and exploratory behaviors in cholestatic mice

Bile duct ligation (BDL) is an animal model used in cholestatic disease research. Both opioidergic and nitrergic systems are known to be involved in cholestasis. The aim of this study was to investigate the possible interaction between these two systems in BDL-induced memory formation and exploratory behaviors in mice. Male mice weighing 25-30 g were divided into nonoperated controls, sham-operated, and BDL groups. One-trial step-down and hole-board paradigms were used to assess memory acquisition and exploratory behaviors, respectively. Cholestasis did not alter memory acquisition while increasing exploratory behaviors 7 days after BDL. A pretraining intraperitoneal injection of L-arginine (50, 100, and 200 mg/kg), L-NG-nitroarginine methyl ester (L-NAME) (5, 10, 20, and 40 mg/kg), or naloxone (0.125, 0.25, and 0.5 mg/kg) did not alter memory acquisition or exploratory behaviors, whereas morphine (5 and 7.5 mg/kg) decreased memory acquisition in sham-operated animals. Moreover, although injection of L-NAME and naloxone exerted no effect on memory acquisition in the 7 days post-BDL mice, L-arginine (100 and 200 mg/kg) and morphine (2.5, 5, and 7.5 mg/kg) injection reduced it. In contrast, L-NAME and naloxone, but not morphine or L-arginine, reduced the BDL-induced exploratory behaviors. Coadministration of subthreshold doses of morphine (1.25 mg/kg) and L-arginine (50 mg/kg) caused a memory deficit in 7 days post-BDL mice. However, the memory deficit induced by the effective doses of morphine (2.5 mg/kg) or L-arginine (200 mg/kg) in these mice was restored by the administration of either naloxone (0.5 mg/kg) or L-NAME (40 mg/kg). In addition, naloxone and L-NAME reduced the exploratory behaviors in L-arginine-pretreated mice but not in morphine-pretreated mice. We conclude that there appears to be a synergistic effect between opioidergic and nitrergic systems on memory acquisition and exploratory behaviors in cholestatic mice.

Effects of CA1 glutamatergic systems upon memory impairments in cholestatic rats

BACKGROUND

Bile duct ligation (BDL) is shown to induce cholestasis-related liver function impairments as well as consequent cognitive dysfunctions (i.e. impaired learning and memory formation). Glutamatergic neurotransmission plays an important role in hippocampal modulation of learning and memory function. The present study aimed to investigate the possible involvement of dorsal hippocampal (CA1) glutamatergic systems upon cholestasis-induced amnesia.

METHOD

Cholestasis was induced in male Wistar rats through double-ligation of the main bile duct (at two points) and transection of the interposed segment. Step-through passive avoidance test was employed to examine rats' learning and memory function. All drugs were injected into CA1 region of the hippocampus.

RESULTS

our results indicated a decrease in memory retrieval following cholestasis (11, 17 and 24 days post BDL). Only subthreshold doses of N-methyl-d-aspartate (NMDA; 0.125 and 0.25 μg/μl) but not its effective dose (0.5 μg/μl), restored the cholestasis-induced amnesia in step-through passive avoidance test, 11, 17 and 24 days post BDL. This effect was blocked by the subthreshold dose of D-[1]-2-amino-7-phosphonoheptanoic acid (D-AP7, NMDA receptor antagonist; 0.0625 μg/μl, intra-CA1) at 0.125 μg/μl and 0.25 μg/μl doses of NMDA. Moreover, our data revealed that only effective doses of D-AP7 (0.125 and 0.25 μg/μl, intra-CA1) potentiate memory impairments in 11 days after BDL. It was noted that none of applied drugs/doses exerted an effect on memory acquisition and locomotors activity, 10 and 12 days post laparotomy, respectively.

CONCLUSION

Our findings suggest the potential involvement of CA1 glutamatergic system(s) in cholestasis-induced memory deficits.

Influence of liver pathology on markers of postmortem brain tissue quality

BACKGROUND

Postmortem brain tissue provides an important resource to investigate various brain disorders, including those resulting from the effects of alcohol abuse. Unlike the traditionally recognized confounders to tissue quality (e.g., coma, hypoxia), our understanding of the effects of liver disease is incomplete. The aim of this study was to determine the effects of liver pathology, and in particular cirrhosis resulting in hepatic encephalopathy (HE), on 2 postmortem brain tissue quality markers, brain pH and RNA integrity.

METHODS

We measured tissue quality markers in a cohort of alcohol abuse and control cases collected by the NSW Tissue Resource Centre. Cerebellar tissue was used to evaluate both brain pH and RNA quality (as indicated by the RNA integrity number: RIN). A histological assessment was performed on each case to exclude coexisting pathologies (e.g., cerebrovascular disease, hypoxic encephalopathy, neurodegenerative disease) and to assess the presence or absence of HE. Autopsy reports were reviewed for liver pathology and toxicology.

RESULTS

Analysis revealed that cases of alcohol abuse had a lower mean (±SD) brain pH, 6.46 (±0.3) as compared with the control mean 6.64 (±0.2). The mean RIN for the alcohol abuse group was 6.97 (±1.3) and controls 7.66 (±0.5). The severity of liver pathology affected both brain pH (p < 0.0001) and RIN (p < 0.0001). The comparison between cirrhotic cases highlighted increased degradation of RNA in cases with cirrhosis resulting in HE (p = 0.0095). A similar effect was seen on brain pH (p = 0.0019).

CONCLUSIONS

The results show that the presence of cirrhosis and, more so, HE reduces the pH and RIN of postmortem brain tissue.