Hepatic encephalopathy

Finasteride Has Regionally Different Effects on Brain Oxidative Stress and Acetylcholinesterase Activity in Acute Thioacetamide-Induced Hepatic Encephalopathy in Rats

Finasteride (FIN) inhibits neurosteroid synthesis and potentially improves the course of hepatic encephalopathy (HE). This study aimed to investigate the effects of FIN on brain oxidative stress and acetylcholinesterase (AchE) activity in acute thioacetamide-induced HE in rats. Male Wistar rats were divided into groups: 1. control; 2. thioacetamide-treated group (TAA; 900 mg/kg); 3. finasteride-treated group (FIN; 150 mg/kg); 4. group treated with FIN and TAA (FIN+TAA). Daily doses of FIN (50 mg/kg) and TAA (300 mg/kg) were administered intraperitoneally during three days and in FIN+TAA group FIN was administered 2h before every dose of TAA. FIN pretreatment prevented TAA-induced rise in malondialdehyde level in the cortex due to restoration of catalase activity and increased expression of superoxide dismutase 1 (SOD1) and induced an increase in malondialdehyde level in the thalamus due to reduction of glutathione peroxidase (GPx) and glutathione reductase (GR) activity. Although FIN pretreatment did not affect malondialdehyde level in hippocampus and caudate nucleus, hippocampal SOD1 expression was higher (p<0.05) and GR activity lower in FIN+TAA vs. TAA group (p<0.05). GPx activity was lower in caudate nucleus in FIN+TAA vs. TAA group (p<0.01). FIN pretreatment prevented TAA-induced rise in AchE activity in the thalamus and caudate nucleus and AchE activity correlates inversely in the thalamus (p<0.05) and positively in caudate nucleus (p<0.01) with malondialdehyde level. FIN has regionally selective effects on oxidative stress and AchE activity in the brain in acute TAA-induced HE in rats. The prooxidant role of FIN in the thalamus may be causally linked with inhibition of AchE.

Finasteride improves motor, EEG, and cellular changes in rat brain in thioacetamide-induced hepatic encephalopathy

Neurosteroids are involved in the pathogenesis of hepatic encephalopathy (HE). This study evaluated the effects of finasteride, inhibitor of neurosteroid synthesis, on motor, EEG, and cellular changes in rat brain in thioacetamide-induced HE. Male Wistar rats were divided into the following groups: 1) control; 2) thioacetamide-treated group, TAA (300 mg·kg(-1)·day(-1)); 3) finasteride-treated group, FIN (50 mg·kg(-1)·day(-1)); and 4) group treated with FIN and TAA (FIN + TAA). Daily doses of TAA and FIN were administered in three subsequent days intraperitoneally, and in the FIN + TAA group FIN was administered 2 h before every dose of TAA. Motor and reflex activity was determined at 0, 2, 4, 6, and 24 h, whereas EEG activity was registered about 24 h after treatment. The expressions of neuronal (NeuN), astrocytic [glial fibrilary acidic protein (GFAP)], microglial (Iba1), and oligodendrocyte (myelin oligodendrocyte glycoprotein) marker were determined 24 h after treatment. While TAA decreased all tests, FIN pretreatment (FIN + TAA) significantly improved equilibrium, placement test, auditory startle, head shake reflex, motor activity, and exploratory behavior vs. the TAA group. Vital reflexes (withdrawal, grasping, righting and corneal reflex) together with mean EEG voltage were significantly higher (P < 0.01) in the FIN + TAA vs. the TAA group. Hippocampal NeuN expression was significantly lower in TAA vs. control (P < 0.05). Cortical Iba1 expression was significantly higher in experimental groups vs. control (P < 0.05), whereas hippocampal GFAP expression was increased in TAA and decreased in the FIN + TAA group vs. control (P < 0.05). Finasteride improves motor and EEG changes in TAA-induced HE and completely prevents the development of hepatic coma.

Aquaporin-4 deletion in mice reduces encephalopathy and brain edema in experimental acute liver failure

Brain edema and associated astrocyte swelling leading to increased intracranial pressure are hallmarks of acute liver failure (ALF). Elevated blood and brain levels of ammonia have been implicated in the development of brain edema in ALF. Cultured astrocytes treated with ammonia have been shown to undergo cell swelling and such swelling was associated with an increase in the plasma membrane expression of aquaporin-4 (AQP4) protein. Further, silencing the AQP4 gene in cultured astrocytes was shown to prevent the ammonia-induced cell swelling. Here, we examined the evolution of brain edema in AQP4-null mice and their wild type counterparts (WT-mice) in different models of ALF induced by thioacetamide (TAA) or acetaminophen (APAP). Induction of ALF with TAA or APAP significantly increased brain water content in WT mice (by 1.6% ± 0.3 and 2.3 ± 0.4%, respectively). AQP4 protein was significantly increased in brain plasma membranes of WT mice with ALF induced by either TAA or APAP. In contrast to WT-mice, brain water content did not increase in AQP4-null mice. Additionally, AQP4-null mice treated with either TAA or APAP showed a remarkably lesser degree of neurological deficits as compared to WT mice; the latter displayed an inability to maintain proper gait, and demonstrated a markedly reduced exploratory behavior, with the mice remaining in one corner of the cage with its head tilted downwards. These results support a central role of AQP4 in the brain edema associated with ALF.

Spectral analysis of thioacetamide-induced electroencephalographic changes in rats

Thioacetamide (TAA) is widely used as a model of hepatic encephalopathy (HE). The aim of our study was to investigate the effects of TAA on electroencephalographic (EEG) changes in rats and to compare them with human HE. Male Wistar rats were divided into groups: (1) saline-treated group and (2) TAA-treated groups: TAA300 (300 mg/kg), TAA600 (600 mg/kg), and TAA900 (900 mg/kg). Daily dose of TAA (300 mg/kg) was administered intraperitoneally once (TAA300), twice (TAA600), or thrice (TAA900) in subsequent days. EEG changes were recorded about 24 h after the last dose of TAA. Absolute and relative power density in alpha bands were significantly higher in TAA300 versus control group. In TAA300, absolute beta power density was higher and relative beta power density was lower versus control group. Absolute alpha, theta, delta, and relative theta power were significantly lower, while relative power in delta band was significantly higher in TAA900 versus control group ( p < 0.01). In conclusion, decrease in EEG voltage with an increase in delta relative power, which correspond to the EEG manifestations of severe HE in humans, was observed in TAA900 group. Electrical activity in TAA300 group correlates with mild HE in humans.

Behavioral and electroencephalographic manifestations of thioacetamide-induced encephalopathy in rats

The aim of our study was to investigate the behavioral and electroencephalographic manifestations of thioacetamide-induced encephalopathy in rats. Male Wistar rats were divided among (i) control, saline-treated, and (ii) thioacetamide-treated groups (TAA(300) (300 mg/kg body mass); TAA(600) (600 mg/kg); and TAA(900) (900 mg/kg)). The daily dose of thioacetamide (300 mg/kg) was administered intraperitoneally once (TAA(300)), twice (TAA(600)), or 3 times (TAA(900)), on subsequent days. Behavioral manifestations were determined at 0, 2, 4, 6, and 24 h, while electroencephalographic changes were recorded 22-24 h after the last dose. General motor activity and exploratory behavior, as well as head shake, auditory startle reflex, placement, and equlibrium tests were diminished in the TAA(600) and TAA(900) groups compared with the control, and were absent in the TAA(900) group 24 h after treatment. Corneal, withdrawal, grasping, and righting reflexes were significantly diminished in the TAA(900) group compared with the control. Mean electroencephalographic power spectra density was significantly higher in TAA(300) and TAA(600) and lower in the TAA(900) group by comparison with the control. Only a score of 3 (mean dominant frequency ≤ 7.3 Hz and δ relative power ≥ 45%) was observed in the TAA(900) group. Thioacetamide induces encephalopathy in rats in a dose-dependent manner. A dose of 900 mg/kg TAA may be used as a suitable model of all stages of hepatic encephalopathy.

Brain aquaporin-4 in experimental acute liver failure

Intracranial hypertension caused by brain edema and associated astrocyte swelling is a potentially lethal complication of acute liver failure (ALF). Mechanisms of edema formation are not well understood, but elevated levels of blood and brain ammonia and its by-product glutamine have been implicated in this process. Since aquaporin-4 (AQP4) has been implicated in brain edema in other conditions, we examined its role in a rat model of ALF induced by the hepatotoxin thioacetamide. Rats with ALF showed increased AQP4 protein in the plasma membrane (PM). Total tissue levels of AQP4 protein and mRNA levels were not altered, indicating that increased AQP4 is not transcriptionally mediated but likely reflects a more stable anchoring of AQP4 to the PM and/or interference with its degradation. An increase inAQP4 immunoreactivity in thePM was observed in perivascular astrocytes in ALF. Rats with ALF also showed increased levels of α-syntrophin, a protein involved in anchoringAQP4 to perivascular astrocytic end-feet. Increased AQP4 andα-syntrophin levels were inhibited by L-histidine, an inhibitor of glutamine transport into mitochondria, suggesting a role for glutamine in the increase of PM levels of AQP4. These results indicate that increased AQP4 PM levels in perivascular astrocytic end-feet are likely critical to the development of brain edema in ALF.

Lack of therapeutic effects of gabexate mesilate on the hepatic encephalopathy in rats with acute and chronic hepatic failure

BACKGROUND AND AIM

Inflammation plays a pivotal role in liver injury. Gabexate mesilate (GM, a protease inhibitor) inhibits inflammation by blocking various serine proteases. This study examined the effects of GM on hepatic encephalopathy in rats with acute and chronic liver failure.

METHODS

Acute and chronic liver failure (cirrhosis) were induced by intraperitoneal TAA administration (350 mg/kg/day for 3 days) and common bile duct ligation, respectively, in male Sprague-Dawley rats. Rats were randomized to receive either GM (50 mg/10 mL/kg) or saline intraperitoneally for 5 days. Severity of encephalopathy was assessed by the Opto-Varimex animal activity meter and hemodynamic parameters, mean arterial pressure and portal pressure, were measured (only in chronic liver failure rats). Plasma levels of liver biochemistry, ammonia, nitrate/nitrite, interleukins (IL) and tumor necrosis factor (TNF)-alpha were determined.

RESULTS

In rats with acute liver failure, GM treatment significantly decreased the plasma levels of alanine aminotransferase (P = 0.02), but no significant difference of motor activity, plasma levels of ammonia, IL-1beta, IL-6, IL-10 and TNF-alpha or survival was found. In chronic liver failure rats, GM significantly lowered the plasma TNF-alpha levels (P = 0.04). However, there was no significant difference of motor activity, other biochemical tests or survival found. GM-treated chronic liver failure rats had higher portal pressure (P = 0.04) but similar mean arterial pressure in comparison with saline-treated rats.

CONCLUSIONS

Chronic GM treatment does not have a major effect on hepatic encephalopathy in rats with TAA-induced acute liver failure and rats with chronic liver failure induced by common bile duct ligation.

Brain edema in acute liver failure: inhibition by L-histidine

Brain edema and the associated increase in intracranial pressure are potentially lethal complications of acute liver failure (ALF). Astrocyte swelling (cytotoxic edema) represents a significant component of the brain edema in ALF, and elevated blood and brain ammonia levels have been strongly implicated in its formation. We earlier showed in cultured astrocytes that oxidative stress (OS) and the mitochondrial permeability transition (mPT) play major roles in the mechanism of ammonia-induced astrocyte swelling. Glutamine, a byproduct of ammonia metabolism, has also been shown to induce OS, the mPT, and astrocyte swelling. Such effects of glutamine were suggested to be mediated by its hydrolysis in mitochondria, potentially yielding high levels of ammonia in this organelle and leading to OS and the mPT. L-histidine, an inhibitor of mitochondrial glutamine transport, was recently shown to mitigate OS, mPT, and cell swelling in cultured astrocytes treated with ammonia. The present study examined whether L-histidine similarly abolishes OS, the mPT, and brain edema in a rat model of ALF. Treatment of rats with thioacetamide caused a significant degree of brain edema, which was associated with induction of OS and the mPT. These changes were completely abolished by L-histidine, supporting a key role of mitochondrial glutamine transport and hydrolysis in the mechanism of the brain edema associated with ALF.

Simvastatin for rats with thioacetamide-induced liver failure and encephalopathy

BACKGROUND AND AIM

Nitric oxide (NO) inhibition aggravates hepatic damage and encephalopathy and increases mortality in rats with thioacetamide (TAA)-induced acute liver failure. Statins enhance NO synthase expression beyond their lipid-lowering capability, but the impact on encephalopathy remains unexplored. The aim of this study was to assess the effects of simvastatin on rats with TAA-induced acute liver damage and hepatic encephalopathy.

METHODS

Sprague-Dawley rats received TAA (350 mg/kg/day) or normal saline (NS) by intraperitoneal injection for 3 consecutive days. Two days before injections, each group was divided into three subgroups, taking (i) distilled water; (ii) simvastatin (20 mg/kg/day); or (iii) simvastatin plus N(G)-nitro-l-arginine methyl ester (L-NAME, 25 mg/kg/day) by oral gavage for 5 days. On the fifth day, severity of encephalopathy was assessed and plasma levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), total bilirubin and ammonia were measured.

RESULTS

The TAA subgroups showed higher ALT, AST, bilirubin and ammonia levels and lower motor activity counts as compared with the NS subgroups. Among the TAA-treated subgroups, rats with simvastatin treatment exerted higher motor activity counts and survival rate (P = 0.043), and a trend of lower ALT, AST, bilirubin and ammonia levels than those receiving saline. All rats that underwent simvastatin plus L-NAME treatment died during or after TAA injections.

CONCLUSIONS

Simvastatin improved encephalopathy and survival in TAA-administered rats. The beneficial effect was offset by L-NAME, suggesting the role of NO in liver damage and encephalopathy.

Methimazole alleviates hepatic encephalopathy in bile-duct ligated cirrhotic rats

BACKGROUND

Acute or chronic liver damage may lead to hepatic encephalopathy. Previous studies have indicated the hemodynamic and hormonal mimicry between portal hypertension and hyperthyroidism. Furthermore, medically or surgically induced hypothyroidism has been found to be beneficial in ameliorating hyperdynamic circulation in the portal hypertensive state and in alleviating acute or chronic liver injury in rats. However, the effect of chronic thyroid hormone inhibition on chronic hepatic encephalopathy in cirrhosis remains unknown.

METHODS

Liver cirrhosis was induced by bile-duct ligation (BDL) in male Sprague-Dawley rats. Three weeks after BDL, rats were randomized to receive either tap water (control) or 0.04% methimazole in drinking water for 3 weeks. At the end of 6 weeks after BDL, severity of encephalopathy was assessed by the Opto-Varimex animal activity meter and hemodynamic parameters were measured. Blood samples were collected for determination of thyroid stimulating hormone, ammonia and liver biochemistry.

RESULTS

The heart rate of the methimazole-treated group was significantly lower than that of the control group (p = 0.015), whereas there were no differences in the mean arterial pressure and portal pressure. The total amount of movements were significantly increased in the methimazole group (p = 0.029). Plasma levels of ammonia, aspartate aminotransferase and alkaline phosphatase were significantly lower (p = 0.01) and thyroid stimulating hormone significantly higher (p = 0.035) in the methimazole group.

CONCLUSION

Chronic methimazole treatment alleviates hepatic encephalopathy and liver damage in rats with BDL-induced hepatic cirrhosis.

Lack of detrimental or therapeutic effects of cyclooxygenase inhibition in bile duct-ligated rats with hepatic encephalopathy

BACKGROUND

The pathogenetic mechanisms of hepatic encephalopathy (HE) are not fully understood. Cerebral blood flow regulated by cyclooxygenase (COX) may be involved in the development of HE. There are no comprehensive data concerning the effects of COX inhibition on HE in chronic liver disease.

METHODS

Male Sprague-Dawley rats weighing 240-270 g at the time of surgery were selected for experiments. Secondary biliary cirrhosis was induced by bile duct ligation (BDL). Those rats were then divided into two groups to receive i.p. injection of indomethacin (5 mg/kg per day) or distilled water for 7 days from day 36 to day 42 after BDL. The control group consisted of rats receiving a sham operation. Severity of encephalopathy was assessed by counts of motor activity. Plasma levels of tumor necrosis factor (TNF)-alpha and 6-keto-prostaglandin F(1alpha) (6-keto-PGF(1alpha)), and liver biochemistry tests were determined after treatment.

RESULTS

The motor activity in both groups of BDL rats were significantly lower than that of the control group (P < 0.001). As compared with the BDL rats treated with distilled water, BDL rats treated with indomethacin had significant lower levels of 6-keto-PGF(1alpha), but the motor activity, TNF-alpha levels and serum biochemistry tests were not significantly different between both BDL groups.

CONCLUSIONS

Chronic indomethacin administration did not have significantly detrimental or therapeutic effects on the severity of encephalopathy in BDL rats.

Detrimental effects of nitric oxide inhibition on hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure: role of nitric oxide synthase isoforms

BACKGROUND

Hepatic encephalopathy is a complex neuropsychiatric syndrome. A previous study showed that chronic nitric oxide (NO) inhibition aggravated the severity of encephalopathy in thioacetamide (TAA)-treated rats. The present study investigated the relative contribution of NO synthase (NOS) isoforms on the severity of hepatic encephalopathy in TAA-treated rats.

METHOD

Fulminant hepatic failure was induced in male Sprague-Dawley rats by intraperitoneal injection of TAA (350 mg/kg/day) for 3 days. Rats were divided into three groups to receive N(omega)-nitro-L-arginine methyl ester (L-NAME, a non-selective NOS inhibitor, 25 mg/kg/day in tap water), L-canavanine (an inducible NOS inhibitor, 100 mg/kg/day via intraperitoneal injection) or normal saline (N/S) from 2 days prior to TAA administration and lasting for 5 days. Severity of encephalopathy was assessed by the counts of motor activity. Plasma levels of tumor necrosis factor-alpha (TNF- alpha) were determined by enzyme-linked immunosorbent assay (ELISA), and total bilirubin, alanine aminotransferase (ALT) and creatinine were determined by colorimetric assay.

RESULTS

Compared with L-canavanine or N/S-treated rats (0% and 4%, respectively), the mortality rate was significantly higher in rats receiving L-NAME administration (29%, P < 0.005). Inhibition of NO created detrimental effects on the counts of motor activities (P < 0.05). Rats treated with L-NAME had significantly higher plasma levels of total bilirubin, ALT, creatinine and TNF- alpha as compared with rats treated with L-canavanine or N/S (P < 0.01).

CONCLUSION

Chronic L-NAME administration, but not L-canavanine, had detrimental effects on the severity of hepatic damage and motor activities in TAA-treated rats. These results suggest that constitutive NOS activities play a major protective role in rats with fulminant hepatic failure.

Evidence against a role for endotoxin in the hepatic encephalopathy of rats with thioacetamide-induced fulminant hepatic failure

BACKGROUND AND AIMS

Endotoxin has been proposed to participate in the development of hepatic encephalopathy. However, there is no published data concerning the effects of endotoxin neutralization on the degree of hepatic encephalopathy. The present study investigated the effect of chronic intraperitoneal injection of polymyxin B, a neutralizing antagonist of endotoxin, on hepatic encephalopathy in rats with thioacetamide (TAA)-induced fulminant hepatic failure.

METHODS

Male Sprague-Dawley rats weighing 300-350 g were used. Fulminant hepatic failure was induced by intraperitoneal injection of TAA (350 mg/kg/day) for 3 days. Two series of rats were designed to compare the effects of low dose (0.1 mg) or high dose (0.2 mg) intraperitoneal polymyxin B administration versus normal saline (NS) on hepatic encephalopathy. The injection was twice daily started from 2 days prior to TAA administration and lasted for 5 days. Severity of encephalopathy was assessed by the counts of motor activity in an Opto-Varimex animal activity meter. Plasma levels of endotoxin and tumor necrosis factor-alpha (an index of liver injury) were measured by Limulus assay and the ELISA method, respectively.

RESULTS

Neutralization of endotoxin by either low dose or high dose polymyxin B administration did not significantly alleviate the degree of hepatic encephalopathy, as represented by the counts of motor activities (P > 0.05). Plasma levels of endotoxin and tumor necrosis factor-alpha were comparable between rats treated with polymyxin B or NS (P > 0.05).

CONCLUSION

Our findings do not support the notion that endotoxin plays a major role in the pathogenesis of hepatic encephalopathy in rats with TAA-induced fulminant hepatic failure.

Prostacyclin inhibition by indomethacin aggravates hepatic damage and encephalopathy in rats with thioacetamide-induced fulminant hepatic failure

AIM: Vasodilatation and increased capillary permeability have been proposed to be involved in the pathogenesis of acute and chronic form of hepatic encephalopathy. Prostacyclin (PGI₂) and nitric oxide (NO) are important contributors to hyperdynamic circulation in portal hypertensive states. Our previous study showed that chronic inhibition of NO had detrimental effects on the severity of encephalopathy in thioacetamide (TAA)-treated rats due to aggravation of liver damage. To date, there are no detailed data concerning the effects of PGI₂ inhibition on the severity of hepatic encephalopathy during fulminant hepatic failure.

METHODS: Male Sprague-Dawley rats weighing 300-350 g were used. Fulminant hepatic failure was induced by intraperitoneal injection of TAA (350 mg/(kg.d) for 3 d. Rats were divided into two groups to receive intraperitoneal injection of indomethacin (5 mg/(kg.d), n = 20) or normal saline (N/S, n = 20) for 5 d, starting 2 d before TAA administration. Severity of encephalopathy was assessed by the counts of motor activity measured with Opto-Varimex animal activity meter. Plasma tumor necrosis factor-α (TNF-α, an index of liver injury) and 6-keto-PGF_1α (a metabolite of PGI₂) levels were measured by enzyme-linked immunosorbent assay.

RESULTS: As compared with N/S-treated rats, the mortality rate was significantly higher in rats receiving indomethacin (20% vs 5%, P<0.01). Inhibition of PGI₂ created detrimental effects on total movement counts (indomethacin vs N/S: 438±102 vs 841±145 counts/30 min, P<0.05). Rats treated with indomethacin had significant higher plasma levels of TNF-α (indomethacin vs N/S: 22±5 vs 10±1 pg/mL, P<0.05) and lower plasma levels of 6-keto-PGF_1α (P<0.001), but not total bilirubin or creatinine (P>0.05), as compared with rats treated with N/S.

CONCLUSION: Chronic indomethacin administration has detrimental effects on the severity of encephalopathy in TAA-treated rats and this phenomenon may be attributed to the aggravation of liver injury. This study suggests that PGI₂ may provide a protective role in the development of fulminant hepatic failure.

Relationship between tumor necrosis factor-alpha and ammonia in patients with hepatic encephalopathy due to chronic liver failure

BACKGROUND

We have recently demonstrated that in humans, circulating levels of tumor necrosis factor-alpha (TNF) correlate positively with severity of hepatic encephalopathy (HE) due to chronic liver failure.AIM. The main aim of this larger population study is to determine the relationship between TNF and ammonia in patients with HE and chronic liver failure due to liver cirrhosis.

METHODS

Circulating levels of TNF and ammonia were measured in 108 patients with liver cirrhosis due to various etiologies in various clinical grades of HE (grades 0-4). TNF concentrations were measured in venous serum using commercially available solid-phase high sensitivity enzyme-linked immunosorbent assay. Ammonia levels were determined in venous plasma by the enzymatic method, using the glutamate dehydrogenase reaction.

RESULTS

The mean+/-SEM values of circulating levels of TNF and ammonia at presentation in patients with grade 0 of HE (n = 30) were 3.89+/-0.2 pg/mL and 49.8+/-2.8 microg/mL respectively, in patients with grade 1 of HE (n = 26) were 8.56+/-0.34 pg/mL and 101.6+/-6.5 microg/mL respectively, in patients with grade 2 of HE (n = 22) were 11.59+/-0.48 pg/mL and 160.3+/-10.7 microg/mL respectively, in patients with grade 3 of HE (n = 20) were 19.98+/-0.94 pg/mL and 228.8+/-16.1 microg/mL respectively, and in patients with grade 4 of HE (n = 10) were 51.53+/-8.59 pg/mL and 284.2+/-20.3 microg/mL respectively. A significant positive correlation was found between circulating levels of TNF and those of ammonia (r = 0.62, P< 0.0001), and also between circulating levels of both substances and severity of HE in these patients (r = 0.95, P<0.0001, and r = 0.9, P<0.0001 respectively). TNF and ammonia were both significant independent predictors of severity of HE (P<0.0001 for both variables).

CONCLUSION

The results of this study demonstrate a significant relationship between TNF and ammonia in patients with chronic liver failure and HE, and so strengthen the suggestion that TNF could be strongly involved in the pathogenesis of HE in these patients. Hence, we suggest a new theory in the pathogenesis of HE, the "TNF theory".

Serum levels of tumor necrosis factor-alpha correlate with severity of hepatic encephalopathy due to chronic liver failure

BACKGROUND

Several studies have shown that serum levels of tumor necrosis factor-alpha (TNF) are significantly elevated in patients with acute and chronic liver diseases, where these elevations are independent of the etiology of the underlying disease. Serum levels of TNF are significantly higher in patients with cirrhosis than in those without cirrhosis, reaching the highest levels in decompensated cirrhosis. It has also been shown that plasma levels of TNF correlate with the severity of hepatic encephalopathy (HE) in fulminant hepatic failure. However, still there are no published data regarding the relationship between blood levels of TNF and the presence or severity of HE in patients with chronic liver failure.

AIM

The aim of this study is to determine the relationship between serum levels of TNF and clinical grades of HE in patients with liver cirrhosis.

METHODS

Using a commercially available high-sensitivity enzyme-linked immunosorbent assay kit, serum levels of TNF were measured in 74 patients with liver cirrhosis in various clinical grades of HE (grades 0-4).

RESULTS

The mean+/-SEM values of serum levels of TNF at presentation in patients with grade 0 of HE (n=23), grade 1 (n=12), grade 2 (n=14), grade 3 (n=16), and grade 4 (n=9) were 4.50+/-0.46, 9.10+/-1.0, 12.98+/-1.22, 21.51+/-2.63, and 58.26+/-19.7 pg/ml, respectively. A significant positive correlation was found between serum levels of TNF and the severity of HE (P<0.0001).

CONCLUSION

Serum levels of TNF correlate positively with the severity of HE in patients with chronic liver failure.

Lack of detrimental effects of nitric oxide inhibition in bile duct-ligated rats with hepatic encephalopathy

BACKGROUND

The pathogenetic mechanisms of hepatic encephalopathy (HE) are not fully understood. Vasodilatation induced by nitric oxide (NO) may be involved in the development of HE. There is no comprehensive data concerning the effects of NO inhibition on HE in chronic liver disease.

METHODS

Male Sprague-Dawley rats weighing 240-270 g at the time of surgery were selected for experiments. Secondary biliary cirrhosis was induced by bile duct ligation (BDL). Counts of movements were compared between BDL rats and rats receiving a sham operation. In another series of experiments, BDL rats received either Nomega-nitro-L-arginine methyl ester (L-NAME, 25 mg kg-1 day-1 in tap water) or tap water (control) from the 36th to 42nd days after BDL. Besides motor activities, plasma levels of tumour necrosis factor (TNF)-alpha and nitrate/nitrite, liver biochemistry tests and haemodynamics were determined after treatment.

RESULTS

Compared with the sham-operated rats, the total, ambulatory and vertical movements were significantly decreased in the BDL rats (P </= 0.001). The L-NAME group had a significantly higher mean arterial pressure than that of the control group (119.0 +/- 2.5 mmHg vs. 97.3 +/- 2.8 mmHg, P = 0.002). However, the counts of motor activities, plasma levels of TNF-alpha and nitrate/nitrite, and serum biochemistry tests were not significantly different between the L-NAME and control groups.

CONCLUSIONS

Bile duct ligation may induce HE evidenced by a decrease in motor activities. However, chronic L-NAME administration did not have significantly detrimental or therapeutic effects on the severity of encephalopathy in BDL rats.

Bioartificial liver support devices: historical perspectives

Fulminant hepatic failure (FHF) is an important cause of death worldwide. Despite significant improvements in critical care therapy there has been little impact on survival with mortality rates approaching 80%. In many patients the cause of the liver failure is reversible and if short-term hepatic support is provided, the liver may regenerate. Survivors recover full liver function and a normal life expectancy. For many years the only curative treatment for this condition has been liver transplantation, subjecting many patients to replacement of a potentially self-regenerating organ, with the lifetime danger of immunosuppression and its attendant complications, such as malignancy. Because of the shortage of livers available for transplantation, many patients die before a transplant can be performed, or are too ill for operation by the time a liver becomes available. Many patients with hepatic failure do not qualify for liver transplantation because of concomitant infection, metastatic cancer, active alcoholism or concurrent medical problems. The survival of patients excluded from liver transplantation or those with potentially reversible acute hepatitis might be improved with temporary artificial liver support. With a view to this, bioartificial liver support devices have been developed which replace the synthetic, metabolic and detoxification functions of the liver. Some such devices have been evaluated in clinical trials. During the last decade, improvements in bioengineering techniques have been used to refine the membranes and hepatocyte attachment systems used in these devices, in the hope of improving function. The present article reviews the history of liver support systems, the attendant problems encountered, and summarizes the main systems that are currently under evaluation.

Detrimental effects of nitric oxide inhibition on hepatic encephalopathy in rats with thioacetamide-induced fulminant hepatic failure

Hepatic encephalopathy is a complex neuropsychiatric syndrome seen secondary to acute liver failure, chronic parenchymal liver disease, or portal-systemic anastomosis. Vasodilatation induced by nitric oxide (NO) may be involved in the development of hepatic coma. However, there are no comprehensive data concerning the effects of NO inhibition on the severity of hepatic encephalopathy. Male Sprague-Dawley rats weighing 300-350 g were used. Fulminant hepatic failure was induced by intraperitoneal injection of thioacetamide (TAA, 350 mg kg-1 day-1) for 3 days. Rats were divided into two groups to receive either NG-nitro-L-arginine methyl ester (L-NAME, 20 mg kg-1 day-1 via intragastric gavage) or normal saline (N/S) from 2 days prior to TAA administration for 5 days. Severity of encephalopathy was assessed by counts of motor activity and neurobehaviour test scores. Plasma levels of endotoxin, tumour necrosis factor-alpha and nitrate/nitrite were determined by the chromogenic Limulus assay, enzyme-linked immunosorbent assay and colorimetric assay, respectively. Compared with N/S-treated rats, the mortality rate was significantly higher in rats receiving L-NAME (59% vs. 18%, P < 0.01). Inhibition of NO had detrimental effects on the counts of motor activities (P < 0.05) and neurobehaviour score (P < 0.01). Rats treated with L-NAME had significantly higher plasma levels of endotoxin (26.7 +/- 3.8 pg mL-1) and tumour necrosis factor-alpha (29.4 +/- 6.5 pg mL-1) compared with rats treated with N/S (13.2 +/- 2.7 pg mL-1 and 11.2 +/- 2.6 pg mL-1, respectively, P < 0.01). Plasma levels of endotoxin and tumour necrosis factor-alpha, but not of nitrate/nitrite, were significantly correlated with the severity of hepatic encephalopathy (P < 0.05). Chronic L-NAME administration had detrimental effects on the severity of encephalopathy in TAA-treated rats, suggesting a protective role of NO in the development of fulminant hepatic failure.

Encephalopathy with idiopathic hyperammonaemia and Alzheimer type II astrocytes in equidae

In 3 mature female horses of varying breeds, episodes of colic and depression for 14 days preceded an encephalopathic disorder with maniacal behaviour, anxiety, profuse sweating and, in one case, terminal opisthotonus. Blood ammonia levels were elevated approximately 10-fold. At necropsy, there were gastrointestinal serosal and mesenteric haemorrhages. Histologically, all 3 cases revealed diffuse Alzheimer type II astrocytes in the cerebral grey matter. Alzheimer type II astrocytes were glial fibrillary acidic protein (GFAP) negative or only weakly positive, weakly S-100 positive, and vimentin negative. In the absence of primary hepatic and/or renal lesions, an increase in intestinal ammonia absorption due to ileus or increased ammonia production by colonic bacteria is hypothesised.

Endogenous benzodiazepine activity in the peripheral and portal blood of dogs with congenital portosystemic shunts

OBJECTIVE

The purpose of this study was to determine whether an endogenous benzodiazepine receptor ligand (EBZ) was present in the arterial and portal blood of dogs with congenital portosystemic shunts (CPSS).

STUDY DESIGN

The presence or absence of an EBZ was determined by the collection of systemic and portal blood from dogs with CPSS.

ANIMALS

Fifteen client-owned dogs with a confirmed CPSS. All dogs had historical signs compatible with hepatic encephalopathy. Eight healthy dogs were used as controls.

METHODS

In all dogs, systemic blood samples were collected after they were anesthetized. Portal blood samples were collected intraoperatively. EBZ was measured by radioreceptor assay.

RESULTS

In 10 of 15 dogs, the portal blood concentration of EBZ was significantly elevated compared with normal dogs (mean, 13.2 +/- 18.55 ng/mL). Five dogs had elevated systemic blood EBZ levels (mean, 8.2 +/- 16.08 ng/mL). Eleven of 15 dogs had a higher portal than systemic blood concentration of EBZ. In contrast, control dogs had extremely low EBZ concentrations detected in their portal blood (mean, 0.16 +/- 0.3 ng/mL) and systemic blood (0 ng/mL). The mean portal and systemic blood concentrations in dogs with CPSS were significantly greater than in control dogs (P < .05).

CONCLUSIONS

Elevated blood levels of EBZ were found in dogs with CPSS. The portosystemic gradient noted in 11 dogs suggests the gastrointestinal tract as a possible source for the endogenous ligand.

CLINICAL RELEVANCE

Generalized motor seizures have been reported in dogs after surgical correction of CPSS. If the presence of a CPSS results in stimulation of brain receptors for benzodiazepines, post-CPSS ligation seizures may result from a withdrawal of EBZ after ligation of the portosystemic shunt.

Glutamine metabolism and neuropathological disorders in experimental hepatic encephalopathy: effect of transplanted hepatocytes

BACKGROUND

Physiopathology of hepatic encephalopathy remains unclear. Recent studies have suggested that ammonia would not act by itself but through an increase in glutamine in the brain. We have previously demonstrated that transplantation of syngeneic hepatocytes into the spleen was able to correct both behavioral deficits and plasma amino acid changes observed in portacaval shunted rats. The aim of the present work was to show a correlation between the correction of chronic hepatic encephalopathy by means of intrasplenic hepatocyte transplantation and two parameters, brain glutamine concentration and ultrastructural aspects of astrocytes.

METHODS

Inbred male Wistar Furth rats were divided into three groups: sham-operated rats (n = 10), rats subjected to portacaval shunt (n = 10), and rats subjected to portacaval shunt and intrasplenic hepatocellular transplantation of 10(7) hepatocytes isolated from livers of syngeneic rats (n = 10). Chronic hepatic encephalopathy was quantified 30 and 60 days after operation by means of nose-poke exploration and spontaneous activity. Pathologic examination and measurement of glutamine concentrations in the corpus striatus and in the cerebral cortex were performed 60 days after operation.

RESULTS

Portacaval shunt rats showed reduced spontaneous activity and nose-poke exploration scores. After portacaval shunt a significant glutamine increase occurred in the corpus striatus and in the cerebral cortex when compared with sham rats (p < 0.05). Ultrastructural examination showed modification of astrocytes named Alzheimer type II after portacaval shunt. Correction of behavioral abnormalities by means of intrasplenic hepatocyte transplantation was associated with partial correction of striatal glutamine increase and with decrease in astrocyte alterations. Cortex glutamine concentration in portacaval shunt-intrasplenic hepatocyte transplantation group and in portacaval shunt rats did not differ significantly.

CONCLUSIONS

These data show that intrasplenic hepatocyte transplantation not only prevents neurologic disorders of hepatic encephalopathy but can also decrease glutamine and ultrastructural alterations in the corpus striatus in an experimental model of chronic liver failure. These data are in favor of the involvement of glutamine in chronic hepatic encephalopathy. These results suggest that intrasplenic hepatocyte transplantation might be of therapeutic interest in chronic liver failure.

Brain magnetic resonance imaging in non-alcoholic cirrhosis

Twenty-six patients with stable non-alcoholic cirrhosis and normal neurological examination were investigated by brain MRI (inversion recovery sequences) and compared with 16 controls. Brain MRI findings were correlated with the clinical and metabolic status of the patients and analysis of variance and, when necessary, co-variance was performed. Five of the patients (19%) and all 16 controls showed no MRI changes. Twelve patients (46%) showed moderately high signal in the globus pallidus (score 1), and nine (35%) very high signal (score 2). Analysis of variance showed that age was the only significant variable (P = 0.038). Analysis of co-variance after adjustment for age showed that high pallidal signal was correlated only to ammonia level (P = 0.02) but not to any other clinical or biological parameter. We conclude that T1 high intensity pallidal signal is common in non-alcoholic cirrhosis even when neurological examination is normal, but its significance remains unclear.

Temporary abolition of seizure activity by flumazenil in a case of valproate-induced non-convulsive status epilepticus

We report on a 33-year-old female suffering from frequent complex-partial seizures who developed a non-convulsive status epilepticus after one week of antiepileptic therapy with valproate (VPA) which had been added to a basic medication with barbexaclone (BBC) in rapidly increasing dosage. The electroencephalogram (EEG) showed continuous rhythmic generalized sharp and slow wave activity with a frontal maximum. Intravenous administration of 3.0 mg of the benzodiazepine (BZ) receptor antagonist flumazenil under monitoring with video-EEG led to an immediate and marked electroclinical improvement, whereas 6.0 mg of the BZ receptor agonist midazolam was followed by a deterioration both clinically and in the EEG. We discuss the concept of VPA-encephalopathy and the possible mechanisms of the action of flumazenil on VPA-induced as well as on other toxic and metabolic encephalopathies. Flumazenil might antagonize increased benzodiazepine receptor activity with agonistic and even convulsive properties in these encephalopathic syndromes. Further investigations are needed concerning the relation of drug-induced or metabolic encephalopathies and central benzodiazepine receptor activity. We recommend a therapeutic trial with flumazenil, if stupor or decreased seizure control develop in patients treated with valproate.

Fulminant hepatic failure

FHF is an uncommon but devastating condition affecting otherwise healthy persons which causes significant morbidity and mortality. The etiologic factor is most commonly viral infection, with drugs and metabolic disorders being relatively less common causes. Hopefully, newer diagnostic techniques such as PCR will increase our understanding of the causes and pathogenesis of this disorder. Medical management at the present time must focus on anticipating, preventing, and rapidly identifying and treating complications that may affect every major organ system. Encouraging research continues on the clinical application of hepatotrophic drugs and artificial liver support systems, both as potentially definitive therapies and as maintenance for patients awaiting transplantation. Consultation with physicians at a transplant center should be sought early in the course of the patient's hospitalization when OLT is being considered. Liver transplantation has dramatically changed the outlook for patients with FHF, with current survival rates in the 55% to 75% range. The continuing challenge for the transplant team is to allocate available donor organs to those patients who would not otherwise survive, but also to provide OLT in a timely fashion to ensure the best chance of post-transplantation recovery. Newer techniques such as heterotopic liver transplantation, reduced-size organ transplantation, and the utilization of living related donors may further improve the survival of these patients.

Pallidal hyperintensity on magnetic resonance imaging in cirrhotic patients: clinical correlations

Patients with cirrhosis show increased signal intensity in the globus pallidus on T1-weighted magnetic resonance imaging of the brain. This abnormal appearance of the basal ganglia has been related to the severity of liver failure and to the presence of portal-systemic shunting, although its cause and clinical significance remain unknown. We prospectively assessed the metabolic, neurological and neuropsychological statuses of 30 stable cirrhotic patients and correlated these clinical variables with computed measurements of globus pallidus signals. Some metabolic variables denoting disease severity appeared to be significantly related to image changes, although the strongest association was found with plasma ammonia levels. After adjustment for ammonia level, on multiple regression analysis, the other variables were not significant. Furthermore, pallidal changes were associated with specific neurological symptoms and neurological functions, symptoms and functions that also had a significant correlation with ammonia levels. Our findings suggest that globus pallidus signal abnormality could arise as a marker of brain impairment related to hyperammonemia.

Changes in brain ECF amino acids in rats with experimentally induced hyperammonemia

Using microdialysis, we studied brain extracellular fluid (ECF) amino acid metabolism in rats with experimentally induced hyperammonemia and regional elevation of brain ECF ammonia levels. The total brain ECF amino acid level was increased by an elevation of the blood ammonia level. Hyperammonemia elevated brain ECF aromatic amino acids and reduced arterial blood branched chain amino acids. When rats with hyperammonemia were intravenously administered norleucine, the brain ECF norleucine level rose markedly, suggesting increased permeability of the blood-brain barrier. When rats with hyperammonemia were infused with a branched chain amino acid-rich preparation, the elevated brain ECF aromatic amino acids level was not suppressed. Following local intracerebral ammonia infusion, only glutamate levels showed a marked elevation. These results suggest that impairment of the blood-brain barrier related to hyperammonemia increases the inflow of low molecular weight substances including amino acids. Furthermore, the ammonia-induced increase of glutamate in the cerebral ECF suggests that high ammonia levels may increase the excitability of the brain. Thus, ammonia may serve as a key factor in the onset of hepatic encephalopathy.

Regional cerebral blood flow and cognitive function in patients with chronic liver disease

Subtle impairments of cognitive function may be an important cause of occupational and psychosocial morbidity in patients with chronic liver disease. Correlation of structural brain abnormalities with cognitive deficits has yielded inconsistent results. 10 patients with cirrhotic liver disease were compared with 10 age, education, and intelligence matched control subjects. Neuropsychological assessment revealed significant overall cognitive impairments in cirrhotic patients compared with controls (p = 0.02). Regional cerebral blood flow was measured by single photon emission computed tomography (SPET or SPECT) and showed increased uptake of radiotracer in the right and left posterior parts of the basal ganglia and right occipital lobe, together with reduced uptake in the right anterior cingulate region. The degree of cognitive impairment was directly correlated with functional abnormalities in the basal ganglia and limbic cortex (p less than 0.05). Our results suggest that impaired cognitive status may be associated with abnormalities of regional brain function in patients with chronic liver disease. Since these deficits are clinically inapparent, our findings have important implications for identification and management of patients with chronic liver disease.