Different biochemical correlates for different neuropsychiatric abnormalities in patients with cirrhosis.

UNLABELLED: The diagnosis of hepatic encephalopathy (HE) relies on clinical, neurophysiological, psychometric and laboratory variables. The relationships between such tests remain debated. The aim of this study was to determine the laboratory correlates/prognostic value of neurophysiological/psychometric abnormalities in patients with cirrhosis. Seventy-two patients and 14 healthy volunteers underwent EEG and paper-and-pencil psychometry (PHES). Blood was obtained for C reactive protein (CRP), interleukin 6 (IL6), tumor necrosis factor (TNF)α, ammonia and indole/oxindole. Patients were followed prospectively for a median of 22 months in relation to the occurrence of death, transplantation and HE-related hospitalizations. Thirty-three patients had normal PHES and EEG, 6 had abnormal PHES, 18 abnormal EEG and 13 abnormal PHES and EEG. Patients with abnormal PHES had higher CRP (17 ± 22 vs 7 ± 6, P < 0.01), IL6 (32 ± 54 vs 12 ± 13, P < 0.05) and TNFα (17 ± 8 vs 11 ± 7, P < 0.001) levels than those with normal PHES. Patients with abnormal EEG had higher indole (430 ± 270 vs 258 ± 255, P < 0.01) and ammonia (66 ± 35 vs 45 ± 27, P < 0.05) levels than those with normal EEG. Psychometric test scores showed significant correlations with CRP, TNFα and IL6; EEG indices with ammonia and IL6. CRP and TNFα concentrations were independent predictors of abnormal PHES, ammonia and indole of abnormal EEG on multivariate analysis. Seven patients were lost to follow-up; of the remaining 65, 20 died and 14 underwent transplantation; 15 developed HE requiring hospitalization. PHES and EEG performance were independent predictors of HE and death (P < 0.05). CONCLUSION: PHES and EEG abnormalities in patients with cirrhosis have partially different biochemical correlates and independently predict outcome.

Peripheral and splanchnic indole and oxindole levels in cirrhotic patients: a study on the pathophysiology of hepatic encephalopathy.

OBJECTIVES: Intestinal bacteria metabolize tryptophan into indole, which is then further metabolized into oxindole, a sedative compound putatively involved in the pathophysiology of hepatic encephalopathy (HE). The aim of this study was to measure indole and oxindole levels in patients with cirrhosis with or without HE and to establish whether an intestinal production and a hepatic metabolism of these substances exist. METHODS: We studied 10 healthy subjects (controls) and 51 cirrhotic patients: 17 without HE, 14 with a minimal HE, 8 with overt HE, and 12 who had undergone a transjugular intrahepatic portosystemic shunt (TIPS) procedure. In the last group, blood was collected from the artery, and the portal and hepatic veins during TIPS construction and from the peripheral veins before, immediately after, and at weekly intervals during the first month after TIPS. RESULTS: Plasma indole levels were significantly higher in patients with overt HE. Oxindole levels were higher in cirrhotics than in controls. Indole and ammonia were significantly correlated (r=0.66). Peripheral and splanchnic determinations showed that indole was produced in the intestine and cleared by the liver, similar to ammonia. TIPS implantation increased both indole and ammonia levels. After TIPS, the psychometric performance worsened in 4 of the 12 patients. The increase in indole plasma concentrations in these four patients was higher than in those who remained stable after undergoing TIPS. CONCLUSIONS: Indole correlates with HE and has a significant intestinal production and hepatic extraction; its level increases after TIPS and is related to psychometric performance. These data suggest that indole may be involved in the pathophysiology of HE.

Metabotropic glutamate 1 (mGlu1) receptor antagonists enhance GABAergic neurotransmission: a mechanism for the attenuation of post-ischemic injury and epileptiform activity?

Selective antagonists of mGlu1 metabotropic glutamate receptors attenuate neuronal death in models of cerebral ischemia. Because GABAergic mechanisms have recently been proposed to contribute to these neuroprotective effects, we examined the effects of selective mGlu1 antagonists characterized in our laboratory on GABAergic transmission in three different models of neuropathology. In rat organotypic hippocampal slices exposed to oxygen-glucose deprivation, the mGlu1 antagonists AIDA, CBPG and 3-MATIDA reduced CA1 pyramidal cell loss when added to the medium during the insult and the subsequent recovery period. This effect was mimicked by the GABA(A) and GABA(B) agonists muscimol and baclofen and partially prevented by the antagonists bicuculline and CGP 55845. In gerbils subjected to global ischemia, protection of CA1 pyramidal cells by transdialytic perfusion of AIDA and CBPG was associated with a significant increase in the basal and ischemic output of GABA and minor changes in the output of glutamate. In a mouse cortical wedge model, both muscimol and 3-MATIDA reduced the frequency of spontaneous bursts induced by 4-aminopyridine and this reduction was prevented by co-perfusion with bicuculline. Taken together, our results suggest that the release of GABA, and the subsequent activation of GABA receptors, may contribute to the attenuation of post-ischemic neuronal damage and epileptiform activity induced by mGlu1 receptor antagonists.

Synthesis and biological evaluation of a new set of pyrazolo[1,5-c]quinazoline-2-carboxylates as novel excitatory amino acid antagonists.

In recent papers (Catarzi, D.; et al. J. Med. Chem. 1999, 42, 2478-2484; 2000, 43, 3824-3826; 2001, 44, 3157-3165) we reported the synthesis of a set of 4,5-dihydro-4-oxo-1,2,4-triazolo[1,5-a]quinoxaline-2-carboxylates (TQXs) that were active at the Gly/NMDA and/or AMPA receptors. In the present work the synthesis and Gly/NMDA, AMPA, and KA receptor binding affinities of a set of 5,6-dihydro-5-oxo-pyrazolo[1,5-c]quinazoline-2-carboxylates 1a,b-4a,b, 5a, 6a, and 7a,b-9a,b, (+/-)-5,6-dihydro-pyrazolo[1,5-c]quinazoline-2,5-dicarboxylates 10a,b and 11a,b, and (+/-)-1,5,6,10b-tetrahydro-5-oxo-pyrazolo[1,5-c]quinazoline-2-carboxylates 12a,b-14a,b are reported. The binding results indicate that compounds 1a,b-4a,b, 5a, 6a, and 7a,b-9a,b show good Gly/NMDA and/or AMPA receptor binding affinities, demonstrating that the pyrazoloquinazoline tricyclic system is an adequate alternative to the triazoloquinoxaline framework for anchoring at both receptor types. Moreover, the inactivity of the 2,5-dicarboxylate derivatives 10a,b and 11a,b at the Gly/NMDA and AMPA receptors indicates that the presence of a glycine moiety in the southern portion of the pyrazoloquinazoline framework is deleterious for receptor-ligand interaction. Finally, the binding data of compounds 12a,b-14a,b indicate that lack of planarity in the northeastern region of the molecules shifts selectivity toward the Gly/NMDA receptor, depending on the benzofused substitutions. In general, the pyrazoloquinazoline derivatives herein reported were inactive at the KA receptor. A study of the functional antagonism at both the AMPA receptor and the NMDA receptor-ion channel complex was also performed on some selected compounds.

Synthesis and biological evaluation of analogues of 7-chloro-4,5-dihydro-4- oxo-8-(1,2,4-triazol-4-yl)-1,2,4-triazolo[1,5-a]quinoxaline-2-carboxylic acid (TQX-173) as novel selective AMPA receptor antagonists.

In recent papers (Catarzi, D.; et al. J. Med. Chem. 2000, 43, 3824-3826; 2001, 44, 3157-3165) we reported chemical and biological studies on 4,5-dihydro-4-oxo-1,2,4-triazolo[1,5-a]quinoxaline-2-carboxylates (TQXs) bearing different nitrogen-containing heterocycles at position-8. In particular, from these studies it emerged that both the 7-chloro-4,5-dihydro-4-oxo-8-(1,2,4-triazol-4-yl)-1,2,4-triazolo[1,5-a] quinoxaline-2-carboxylic acid TQX-173 (compound B) and its corresponding ethyl ester (compound A) were the most active and selective compounds of this series. In pursuing our investigation on the structure-activity relationships of these TQX derivatives, different electron-withdrawing groups (CF(3), NO(2)) were introduced at position 7 on the TQX ring system, replacing the 7-chloro substituent of B and of other selected 8-heteroaryltriazoloquinoxaline-2-carboxylates previously described. All the newly synthesized compounds were biologically evaluated for their binding at the Gly/NMDA, AMPA, and KA high-affinity receptors. Gly/NMDA binding assays were performed to assess the selectivity of the reported compounds toward the AMPA receptor. Compounds endowed with micromolar binding affinity for the KA high-affinity binding site were also evaluated for their binding at the KA low-affinity receptor. Some selected compounds were also tested for their functional antagonist activity at the AMPA and NMDA receptor-ion channel complex. The results obtained in this study have pointed out that 4,5-dihydro-7-nitro-4-oxo-8-(3-carboxypyrrol-1-yl)-1,2,4-triazolo[1,5-a]quinoxaline-2-carboxylic acid (9b) and its corresponding ethyl ester (9a) are the most potent and selective AMPA receptor antagonists reported to date among the TQX series.

G-protein coupled receptor 35 (GPR35) activation and inflammatory pain: Studies on the antinociceptive effects of kynurenic acid and zaprinast.

G-protein coupled receptor 35 (GPR35) is a former "orphan receptor" expressed in brain and activated by either kynurenic acid or zaprinast. While zaprinast has been studied as a phosphodiesterase inhibitor, kynurenic acid (KYNA) is a tryptophan metabolite and has been proposed as the endogenous ligand for this receptor. In the present work, we showed that GPR35 is present in the dorsal root ganglia and in the spinal cord and in order to test the hypothesis that GPR35 activation could cause analgesia, we administered suitable doses of zaprinast or we increased the local concentration of KYNA by administering a precursor (kynurenine) or by inhibiting its disposal from the CNS (with probenecid). We used the "writhing test" induced by acetic acid i.p. injection in mice. KYNA and kynurenine plasma and spinal cord levels were measured with HPLC techniques. Kynurenine (30, 100, 300 mg/kg s.c.) increased plasma and spinal cord levels of KYNA and decreased the number of writhes in a dose dependent manner. Similarly, probenecid was able to increase KYNA levels in plasma and spinal cord, to reduce the number of writes and to amplify kynurenine effects. Furthermore, zaprinast had antinociceptive effects in the writhing test without affecting KYNA levels. In agreement with its affinity for GPR35 receptor (approximately 10 times higher than that of KYNA), zaprinast action occurred at relatively low doses. No additive actions were obtained when kynurenine and zaprinast were administered at maximally active doses. Our results suggest that GPR35 could be an interesting target for innovative pharmacological agents designed to reduce inflammatory pain. This article is part of a Special Issue entitled 'Trends in neuropharmacology: in memory of Erminio Costa'.