Antonella Bertazzo

Recent Advances in Tryptophan Research

A high percentage of patients with human immunodeficiency virus infection presents with decreased tryptophan concentrations in serum and cerebrospinal fluid. In parallel degradation products of tryptophan like kynurenine and quinolinic acid are increased. We investigated the behavior of tryptophan concentrations in 14 patients with HIV infection before and during treatment with zidovudine, and we found a significant increase of tryptophan in serum and cerebrospional fluid after 4-14 months of therapy. In parallel, neopterin concentrations decreased signficantly. Moreover, an association existed in cerebrospinal fluid between the degree of tryptophan increase and neopterin decrease. Thus, treatment with zidovudine contributes to a gradual normalization of tryptophan metabolism in patients with HIV-I infection. The data imply that zidovudine therapy is associated not only with a reduction of virus replication but also immune activation is reduced.

Monoamine oxidase A gene promoter methylation and transcriptional downregulation in an offender population with antisocial personality disorder

BACKGROUND Antisocial personality disorder (ASPD) is characterised by elevated impulsive aggression and increased risk for criminal behaviour and incarceration. Deficient activity of the monoamine oxidase A (MAOA) gene is suggested to contribute to serotonergic system dysregulation strongly associated with impulsive aggression and antisocial criminality. AIMS To elucidate the role of epigenetic processes in altered MAOA expression and serotonin regulation in a population of incarcerated offenders with ASPD compared with a healthy non-incarcerated control population. METHOD Participants were 86 incarcerated participants with ASPD and 73 healthy controls. MAOA promoter methylation was compared between case and control groups. We explored the functional impact of MAOA promoter methylation on gene expression in vitro and blood 5-HT levels in a subset of the case group. RESULTS Results suggest that MAOA promoter hypermethylation is associated with ASPD and may contribute to downregulation of MAOA gene expression, as indicated by functional assays in vitro, and regression analysis with whole-blood serotonin levels in offenders with ASPD. CONCLUSIONS These results are consistent with prior literature suggesting MAOA and serotonergic dysregulation in antisocial populations. Our results offer the first evidence suggesting epigenetic mechanisms may contribute to MAOA dysregulation in antisocial offenders.

Protein profiles in sera of patients with malignant cutaneous melanoma

Seventeen samples of sera from patients with malignant cutaneous melanoma at various stages and 14 samples from healthy subjects were analysed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. Results highlighted the presence of several protein species at molecular weights lower than 30000 Da, presumably originating from proteolysis, in the sera of the patients with melanoma. These species were completely absent in healthy subjects. In particular, the presence and abundance of species with molecular weights in the range 2500-3500 Da exhibit significant variations related to the different clinical stages of the disease.

Determination of copper and zinc levels in human hair: influence of sex, age, and hair pigmentation.

The Cu and Zn levels of both 607 men (1–85 y old) and 649 women (1–92 y old) were determined by atomic absorption spectrometry. Sex does not influence Cu (14.89±0.89 μg/g and 15.26±0.79 μg/g hair for males and females, respectively) and Zn contents (200.97±9.68 μg/g for men and 209.81±9.49 μg/g hair for women). Age influences Cu and Zn concentrations, but only significantly in females: Cu levels decrease over 60 y of age; whereas Zn levels increase significantly from age groups 2–5 to 20–40 years. Hair color influences Cu concentrations in both males and females. In males, white hair containes less Cu than black hair; in females, white hairs Cu levels are significantly lower than those of dark blond, red, light brown, and brown hair. There are no significant differences in Zn concentrations with respect to different hair colors, in either males or females.

Effects of PEG-interferon alpha plus ribavirin on tryptophan metabolism in patients with chronic hepatitis C.

The currently recommended therapy for chronic hepatitis C (HCV) is a combination of pegylated interferon-alpha (PEG-IFN alpha) and ribavirin. Psychiatric disorders, including depression, are frequent in HCV patients under therapy. We investigated the effect of the antiviral treatment on tryptophan (Trp) metabolism along both serotonin pathway (via 5-hydroxytryptophan, 5-HTP) and kynurenine (Kyn) pathway and on the onset of depressive symptoms in patients with HCV. The key enzyme of the Kyn pathway is indoleamine 2,3-dioxygenase (IDO), an intracellular haem protein enzyme expressed in several tissues. It was also investigated the influence of the therapy with PEG-IFN-alpha-2a or PEG-IFN-alpha-2b plus oral ribavirin and possible differences between genders. Free and total Trp, 5-hydroxytryptophan (5-HTP) and Kyn serum concentrations and the presence of depressive symptoms [Beck Depression Inventory (BDI) scores] were evaluated in 45 patients with HCV infection treated with PEG-IFN alpha-2a or -2b at four different times: baseline (before treatment), 1 and 6 months during therapy, and 3 months after the end of therapy. The concentration of serum total TRP (free+protein bound) as well as that of 5-HTP significantly decreased after 1 and 6 months of therapy, and then returned to baseline values 3 months after the end of therapy, while the levels of free TRP did not vary significantly during and after the therapy. On the contrary, the time course of Kyn markedly arose during treatment, paralleled by a significant increase of [Kyn/Trp]×10(3) ratio, an index used to measure IDO activity. No significant difference was detected between males and females neither between PEG-IFN-alpha-2a or -2b treatment. The BDI scores significantly increased during therapy, and returned to baseline values 3 months after the end of therapy. Our results support the hypothesis that the increased IDO-mediated tryptophan metabolism along the Kyn pathway, leading to plasma Trp depletion and a decline of serotonin pathway, concurs to the development of depressive symptoms observed in HCV patients undergoing IFN-alpha therapy.

Enzyme activities involved in tryptophan metabolism along the kynurenine pathway in rabbits

The following enzyme activities of the tryptophan-nicotinic acid pathway were studied in male New Zealand rabbits: liver tryptophan 2,3-dioxygenase, intestine indole 2,3-dioxygenase, liver and kidney kynurenine 3-monooxygenase, kynureninase, kynurenine-oxoglutarate transaminase, 3-hydroxyanthranilate 3,4-dioxygenase, and aminocarboxymuconate-semialdehyde decarboxylase. Intestine superoxide dismutase and serum tryptophan were also determined. Liver tryptophan 2,3-dioxygenase exists only as holoenzyme, but intestine indole 2,3-dioxygenase is very active and can be considered the key enzyme which determines how much tryptophan enters the kynurenine pathway also under physiological conditions. The elevated activity of indole 2,3-dioxygenase in the rabbit intestine could be related to the low activity of superoxide dismutase found in intestine. Kynurenine 3-monooxygenase appeared more active than kynurenine-oxoglutarate transaminase and kynureninase, suggesting that perhaps a major portion of kynurenine available from tryptophan may be metabolized to give 3-hydroxyanthranilic acid, the precursor of nicotinic acid. In fact, 3-hydroxyanthranilate 3,4-dioxygenase is much more active than the other previous enzymes of the kynurenine pathway. In the rabbit liver 3-hydroxyanthranilate 3,4-dioxygenase and aminocarboxymuconate-semialdehyde decarboxylase show similar activities, but in the kidney 3-hydroxyanthranilate 3,4-dioxygenase activity is almost double. These data suggest that in rabbit tryptophan is mainly metabolized along the kynurenine pathway. Therefore, the rabbit can also be a suitable model for studying tryptophan metabolism in pathological conditions.

Tryptophan Catabolism in Synovial Fluid of Various Arthropathies and its Relationship with Inflammatory Cytokines

Synovial fluids (SF) from patients with rheumatoid arthritis (RA), psoriatic arthritis (PsA), gout, and osteoarthritis (OA) were investigated for the levels of interleukin (IL)-1 beta, IL-6 and IL-8, tryptophan (Trp) and indoleamine 2,3-dioxygenase (IDO) activity. Significant differences exist in the levels of IL-1 beta between inflammatory arthritides RA, PsA and gout and non inflammatory arthritis, such as OA. The highest concentration of IL-1 beta was found in RA, that showed high levels also of IL-6 and IL-8. In the same disease we also found the highest IDO activity and the lowest Trp concentration. In addition, IDO activity seems to be related with the decrease in Trp, as demonstrated by the inverse correlation found between these two substances in the SF of all patients.

Enzyme activities of tryptophan metabolism along the kynurenine pathway in various species of animals.

The purpose of this study was to investigate variations in the enzyme activities of the kynurenine pathway in various mammals (rabbit, mouse, rat, guinea-pig). Liver tryptophan 2,3-dioxygenase, small intestine indole 2,3-dioxygenase, liver and kidney kynurenine 3-monooxygenase, kynureninase, kynurenine-oxoglutarate transaminase, 3-hydroxyanthranilate 3,4-dioxygenase and aminocarboxymuconate-semialdehyde decarboxylase were analysed. Small intestine superoxide dismutase activity and free and total serum tryptophan were also measured. Liver tryptophan 2,3-dioxygenase was present as both holoenzyme and apoenzyme only in rat, while in the other species only holoenzyme activity was observed. Also, small intestine indole 2,3-dioxygenase activity was more abundant in rat than in the other animals studied. The highest activity of small intestine superoxide dismutase was found in rat, and the lowest in rabbit. Liver and kidney kynurenine 3-monooxygenase activity was very elevated and higher in mouse, followed by rat; rabbit showed the lowest activity. Kynureninase activity appeared to be much lower among the enzymes of the kynurenine pathway. However, guinea-pig showed higher activity in both liver and kidney in comparison with other species. With regard to kynurenine-oxoglutarate transaminase, all species examined here presented more abundant enzyme activity in kidney, the value being similar between rat and mouse. Guinea-pig was the animal with the lowest activity. 3-Hydroxyanthranilate 3,4-dioxygenase showed the highest activity of all the enzymes evaluated in the study, but with different levels in liver and kidney, varying among species. The most elevated activity of aminocarboxymuconate-semialdehyde decarboxylase was present in kidney of guinea-pig, and the lowest in rabbit. Serum concentrations of tryptophan were higher in rat, followed by mouse, rabbit and guinea-pig. In conclusion, the present study demonstrates that the enzyme activities of the kynurenine pathway are very active in tissues of the four species of mammals investigated. The proposed method of in vitro enzyme determination represents a valid alternative to study of the tryptophan metabolic route.

Importance of L-Tryptophan Metabolism in Trypanosomiasis

African trypanosomiasis or sleeping sickness is caused by extracellular trypanosomes. The presence of seric antibodies directed to a tryptophan-like epitope in trypanosome infected patients and animals led us to investigate the roles of tryptophan in trypanosomiasis. These antibodies are directed against a tryptophan-rich conserved sequence inside the major parasite surface glycoprotein. In vitro, a rapid uptake of tryptophan by trypanosomes is measured. Seric tryptophan levels are decreased during trypanosomiasis. This decrease may be linked with an increase in indoleamine 2,3-dioxygenase (IDO) induced by Interferon-gamma. In vivo inhibition of IDO by norharman provokes a dramatic increase in circulating parasite number. All these data show the essential role of tryptophan in parasite growth. Moreover, antibodies against tryptophan, the decreased concentration of the neurotransmitter serotonin in the brain following infection and the tryptophan metabolites (tryptophol) produced by trypanosomes may participate to the pathophysiological mechanisms provoking sleeping sickness.

Kynurenine pathway enzymes in different species of animals.

Kynurenine pathway enzyme activities, liver tryptophan 2,3-dioxygenase (TDO), small intestine indole 2,3-dioxygenase (IDO), liver and kidney kynurenine 3-monooxygenase, kynurenine-oxoglutarate transaminase, kynureninase, 3-hydroxyanthranilate 3,4-dioxygenase and aminocarboxymuconate-semialdehyde decarboxylase, were assayed in rabbits, rats, mice and guinea pigs. Their activities varied among species. Especially, TDO was present as both holoenzyme and apoenzyme only in rat, while the other species, rabbit, mouse and guinea pig, only showed holoenzyme activity. Mitochondrial liver and kidney kynurenine 3-monooxygenase activities were much higher in mouse and rat, with rabbit showing the lowest activity. Kynureninase activity showed similar values in both liver and kidney in each species. However, lower activity was present in rabbit. As regards kynurenine-oxoglutarate transaminase, the highest activity appeared in kidney, in all species studied. 3-Hydroxyanthranilate 3,4-dioxygenase activity showed different behaviour in the four species. In rabbit, its activity was higher in kidney than in liver; in rat and mouse, it was viceversa; and in guinea pig, both liver and kidney had similar activity. Instead, the activity of aminocarboxymuconate-semialdehyde decarboxylase was higher in kidney than in liver only in guinea pig. Serum tryptophan concentrations were also determined. Rabbit and guinea pig showed similar values, whereas in rat and mouse, serum tryptophan levels were higher, rat having the highest concentrations. In all species assayed, the free fraction was present as 11-12% of total tryptophan.