Hans-Willi Clement

Cortisol reactivity in boys with attention-deficit/hyperactivity disorder and disruptive behavior problems: the impact of callous unemotional traits.

There is a body of literature demonstrating an association between altered hypothalamic pituitary adrenal (HPA) axis reactivity and aggressive behavior. Aggressive and disruptive behavior also is highly prevalent in children with attention deficit/hyperactivity disorder (ADHD). Findings on HPA-axis reactivity in ADHD, however, are rather inconsistent. Specific temperamental risk factors previously were associated with a specific subtype of severe disruptive behavior. These traits might also be characterized by a distinct neurobiological profile across ADHD and disruptive behavior disorders. In this study we focus on psychopathic traits, notably callous unemotional (CU) traits. The main objective of the present study was to investigate whether two groups of ADHD patients with high or low CU traits differed in cortisol reactivity. Subjects were 36 boys with ADHD and disruptive behavior symptoms aged 8 to 14 years. Salivary cortisol probes were taken before and repeatedly after an experimental standardized stress test. Patients scoring high on CU traits showed a blunted HPA axis reactivity to the experimentally induced stress. Results underscore the need to consider specific personality traits in investigating neurobiological correlates in ADHD with disruptive behavior problems.

Blood biogenic amines during clozapine treatment of early-onset schizophrenia

SummaryThe aims of this investigation were to evaluate long-term and short-term effects of clozapine-treatment on plasma biogenic amines and psychopathology measures in adolescents with schizophrenia (DSM-III-R criteria). The long-term study was conducted in a study sample of 40 young patients (age 14–22 years) following a mean of 3.4 years of neuroleptic treatment. During the study, 20 patients received clozapine, and the other 20 patients were treated with standard neuroleptic medications. At the beginning of the open clinical trials, the patients had already been receiving clozapine treatment for 24 ± 15 months. Assessment of the biochemical and psychopathological measures was performed on six occasions at consecutive 6-week intervals during maintenance treatment with clozapine or conventional neuroleptics. Blood levels of serotonin, 3-methoxy-4-hydroxy-phenylglycol (MHPG), norepinephrine, and epinephrine were significantly higher in clozapine-treated patients than in conventionally treated patients. During long-term treatment, higher serotonin levels were associated with significantly fewer negative symptoms of schizophrenia, whereas higher MHPG levels were correlated with less depression. The short-term effects of clozapine were assessed in a second and independent study sample. After failing on conventional neuroleptics in clinical trials lasting a mean of 1.6 years, 15 inpatients (aged 11–20 years) received clozapine. Weekly ratings of psychopathological symptoms using standard rating scales were performed in parallel to blood samplings for measurements of biogenic amines and serum levels of clozapine. These measures were obtained for 6 weeks during conventional neuroleptic treatment and for 6 weeks during the open-label clozapine trial. Serum levels of serotonin and plasma norepinephrine levels were significantly higher during treatment with clozapine than during pretreatment with typical neuroleptics. A comparison of plasma epinephrine levels in responders (n=7) and nonresponders (n=8) to clozapine revealed that response to clozapine can be predicted by epinephrine levels prior to initiation of treatment with clozapine (responders ranging from 32.2 to 90.3 pg/ml; nonresponders ranging from 92.5 to 473.5 pg/ml). Additionally, subjects who responded to clozapine showed increased mean plasma concentrations of MHPG and epinephrine during treatment with this drug in comparison to the levels measured during pretreatment with typical neuroleptic medication. Nonresponders to clozapine failed to show this increase. Finally, in responders to clozapine a negative linear relationship between negative symptoms of schizophrenia and the concentrations of plasma norepinephrine and serum serotonin were observed. In conclusion, our results demonstrate that plasma epinephrine levels prior to initiation of clozapine therapy predict response to this atypical neuroleptic. Our findings derived from short-term and maintenance treatment with clozapine suggest involvement of norepinephrine, epinephrine and serotonin in the therapeutic actions of the atypical neuroleptic clozapine.

Serum levels of olanzapine and its N-desmethyl and 2-hydroxymethyl metabolites in child and adolescent psychiatric disorders: effects of dose, diagnosis, age, sex, smoking, and comedication.

Abstract: The aim of this study was to assess dose-related steady-state serum concentrations of olanzapine (OLZ) and its metabolites N-desmethyl OLZ (DMO) and 2-hydroxymethyl OLZ (2-OH-OLZ) (assessed by high-performance liquid chromatography) in 122 child and adolescent psychiatric patients (age 16.9 ± 2.2, range, 10-21 years; 74 males, 48 females) with a variety of diagnoses: schizophrenia group (n = 80); nonschizophrenia group (n = 29); anorexia nervosa (AN) group (n = 13). Median OLZ serum concentrations were 32.7 (range, 1-118; all patients), 37.7 (2-115; schizophrenia group), and 18.7 (1-63, AN group) ng/mL. The median OLZ concentration-to-dose (C/D) ratio (n = 122) was 2.6, with 90% of the distribution between 0.8 and 5.5 (ng/mL)/(mg/d). OLZ concentration was significantly correlated with DMO (r = 0.567; P < 0.0005) but not with 2-OH-OLZ (r = 0.122; P = 0.188). Daily OLZ dose was correlated with OLZ concentration in all (r = 0.684; P < 0.0005), schizophrenic (r = 0.542; P < 0.0005), and AN (r = 0.805; P = 0.001) patients, respectively. Patients aged less than 16 years displayed similar C/D for OLZ (P = 0.58) but higher C/D for DMO (P = 0.003) than those 16 years or older. AN patients received lower median OLZ doses (7.5; 5-15 mg) than schizophrenic patients (12.5; 2.5-40 mg), even after correcting for body mass index (P = 0.02). OLZ dose did not differ (P = 0.088) between smokers and nonsmokers, but smokers showed lower C/D for OLZ than nonsmokers (P = 0.008). C/D for OLZ was 38% higher (P = 0.041) under comedication with selective serotonin reuptake inhibitors when compared with OLZ monotherapy. Multiple linear regression analysis revealed that 46% of the variation of OLZ concentration can be explained by dose, diagnosis, age, sex, smoking, and comedication. The data are compared with the literature, and the relevance of therapeutic antipsychotic drug monitoring in previously sparsely investigated subgroups, such as children and adolescents or patients with AN, is emphasized.

1-trichloromethyl-1,2,3,4-tetrahydro-β-carboline-induced apoptosis in the human neuroblastoma cell line SK-N-SH

Trichloroethylene, a common industrial solvent and a metabolic precursor of chloral hydrate, occurs widely in the environment. Chloral hydrate, which is also used as a hypnotic, has been found to condense spontaneously with tryptamine, in vivo, to give rise to a highly unpolar 1‐trichloromethyl‐1,2,3,4‐tetrahydro‐β‐carboline (TaClo) that has a structural analogy to the dopaminergic neurotoxin N‐methyl‐4‐phenyl‐1,2,3,6‐tetrahydropyridine (MPTP). Earlier studies have revealed the relative permeability of the molecule through the blood–brain barrier and its ability to induce Parkinson‐like symptoms in rats. In this study, we report that TaClo induces an apoptotic pathway in the human neuroblastoma cell line, SK‐N‐SH, involving the translocation of mitochondrial cytochrome c to the cytosol and activation of caspase 3. TaClo‐induced apoptosis shows considerable differences from that mediated by other Parkinson‐inducing agents such as MPTP, rotenone and manganese. Although it is not clear if the clinically administered dosage of chloral hydrate or the relatively high environmental levels of trichloroethylene could lead to an onset of Parkinsons disease, the spontaneous in vivo formation of TaClo and its pro‐apoptotic properties, as shown in this report, should be considered.

Local stimulation of the adenosine A2B receptors induces an increased release of IL-6 in mouse striatum: an in vivo microdialysis study.

Both adenosine and interleukin‐6 (IL‐6) have been implicated in the pathophysiology of, e.g., epileptic seizures, traumatic brain injury, and affective disorders. Stimulation of adenosine A2B receptors on astrocytes in vitro leads to the increased synthesis and secretion of IL‐6. We investigated whether or not activation of adenosine receptors evokes an increase of IL‐6 release also in vivo. 5′‐N‐ethylcarboxamidoadenosine, a non‐specific adenosine‐agonist or vehicle was administered into the striatum of freely moving mice by reverse microdialysis. A statistical significant increase of the IL‐6 concentration in the perfusate was detected already 60 min after 5′‐N‐ethylcarboxamidoadenosine administration. IL‐6 increased progressively and reached a maximum after 240 min. This effect appears to be mediated through adenosine A2B receptors since it was counteracted by the specific A2B receptor antagonist MRS1706 but not by the specific A1 receptor antagonist DPCPX. We conclude that adenosine via activation of A2B receptors evokes IL‐6 release also in vivo.

Effects of antipsychotics and vitamin C on the formation of reactive oxygen species

There is evidence that reactive oxygen species (ROS) are involved in the pathophysiology of psychiatric disorders such as schizophrenia. Indirect biochemical alterations of ROS formation have been shown for patients treated with antipsychotics as well as for untreated patients. Only one study measured directly the ROS formation after treatment with antipsychotics by using electron spin resonance spectroscopy. The aim of the present examination was to demonstrate the effects of haloperidol, clozapine and olanzapine in concentrations of 18, 90 and 180 μg/mL on the formation of ROS in the whole blood of rats by using electron spin resonance spectroscopy after incubation for 30 min. To test the protective capacity of vitamin C we incubated the highest concentration of each drug with vitamin C (1 mM). Under all treatment conditions, olanzapine led to a significantly higher formation of ROS compared with control conditions, whereas in the cases of haloperidol and clozapine the two higher concentrations induced a significantly enhanced formation of ROS. Vitamin C reduced the ROS production of all drugs tested and for haloperidol and clozapine the level of significance was reached. Our study demonstrated that antipsychotics induce the formation of ROS in the whole blood of rats, which can be reduced by the application of vitamin C.

Effects of quetiapine, risperidone, 9-hydroxyrisperidone and ziprasidone on the survival of human neuronal and immune cells in vitro

Because there are reports on cytotoxic and cytoprotective effects of antipsychotics, the aim of the present study was to evaluate the impacts of different concentrations (1.6—50 μg/mL) of atypical antipsychotics on the survival of human neuronal (neuroblastoma SH-SY5Y) and immune (monocytic U-937) cells and on energy metabolism (ATP level after the incubation with antipsychotics in the concentration of 25 μg/mL). Statistical analysis showed that incubation for 24 h with the antipsychotics quetiapine, risperidone, 9-hydroxyrisperidone and ziprasidone led to a significantly enhanced cell survival in both cell lines in the lower concentrations. Higher concentrations exerted in part cytotoxic effects with the exception of quetiapine, but therapeutically relevant concentrations of the drugs were not cytotoxic in our experiments. Measurement of ATP contents in the neuronal cell line showed significantly increased levels after a 24-h treatment with 25 μg/mL risperidone and 9-hydroxyrisperidone. The other substances produced no effects. Our results show that the antipsychotic substances under investigation exert concentration-dependent effects on cell survival in both cell lines examined.

Highly Halogenated Tetrahydro-β-Carbolines as a New Class of Dopaminergic Neurotoxins

The Pictet-Spengler condensation of 2-arylethylamines with aldehydes or α-keto acids (Callaway et al., 1994) is not only the most efficient pathway for the chemical synthesis of tetrahydro-β-carbolines (TH-βCs), but has also been found to play a role in human organisms, leading to endogenous “mammalian alkaloids” (Bringmann, 1979; Buckholtz, 1980; Airaksinen and Kari, 1981a; Airaksinen and Kari, 198 lb; Collins, 1986a; Rommelspacher and Susilo, 1985; Brossi, 1993). During the last three decades, the biological potential of the simple, formaldehyde- and acetaldehyde-derived THβCs tryptoline (1) and eleagnine (2) (see Fig. 1) has been investigated thoroughly because these compounds and related derivatives were regarded as causative links between alcoholism and opioid mania (Davis and Walsh, 1970; Rommelspacher et al., 1984; Myers, 1989). Furthermore, since the merely synthetic neurotoxin MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) was found to induce parkinsonism in humans, monkeys, and mice (Burns et al., 1983; Singer et al., 1993), special attention has been focused on the potential role of THβCs as inducers of parkinsonism, closely related in structure, yet occurring in Nature. Indeed, for several β-carbolines toxic behavior towards dopaminergic neurons was demonstrated (Collins et al., 1986b; Albores et al., 1990; Sayre et al., 1991).

Impact of drugs approved for treating ADHD on the cell survival and energy metabolism: an in-vitro study in human neuronal and immune cells

The oxidative and antioxidative properties of psychostimulants such as methylphenidate and amphetamine are discussed controversially. The aim of the present study was to evaluate the impact of psychostimulants and atomoxetine in different concentrations between 31.25 and 5000 ng/ml on the survival of human neuronal (neuroblastoma SH-SY5Y) and immune (monocytic U-937) cells and the impact of psychostimulants and atomoxetine in different concentrations between 500 and 5000 ng/ml on energy metabolism (adenosine triphosphate [ATP] content) in SH-SY5Y cells. Statistical analysis revealed that incubation for 24 h with amphetamine led to a significantly enhanced cell survival in both cell lines after treatment with various (32.5, 125, 250 and 1250 ng/ml) concentrations. Methylphenidate and atomoxetine induced a significantly enhanced cell survival at lower concentrations in the SH-SY5Y cell line, whereas in the U-937 cell line higher concentrations increased the cell survival. Incubation with the highest concentration of methylphenidate (5000 ng/ml) caused a significant reduction of cell survival in both cell types. Measurement of ATP contents in the neuronal cell line revealed no significant effects of the investigated compounds. Our results show that the examined substances exert concentration-dependent effects on cell survival in both applied cell lines.

Diurnal variation of phenylalanine and tyrosine concentrations in adult patients with phenylketonuria: subcutaneous microdialysis is no adequate tool for the determination of amino acid concentrations

BackgroundMetabolic control and dietary management of patients with phenylketonuria (PKU) are based on single blood samples obtained at variable intervals. Sampling conditions are often not well-specified and intermittent variation of phenylalanine concentrations between two measurements remains unknown. We determined phenylalanine and tyrosine concentrations in blood over 24 hours. Additionally, the impact of food intake and physical exercise on phenylalanine and tyrosine concentrations was examined. Subcutaneous microdialysis was evaluated as a tool for monitoring phenylalanine and tyrosine concentrations in PKU patients.MethodsPhenylalanine and tyrosine concentrations of eight adult patients with PKU were determined at 60 minute intervals in serum, dried blood and subcutaneous microdialysate and additionally every 30 minutes postprandially in subcutaneous microdialysate. During the study period of 24 hours individually tailored meals with defined phenylalanine and tyrosine contents were served at fixed times and 20 min bicycle-ergometry was performed.ResultsSerum phenylalanine concentrations showed only minor variations while tyrosine concentrations varied significantly more over the 24-hour period. Food intake within the patients’ individual diet had no consistent effect on the mean phenylalanine concentration but the tyrosine concentration increased up to 300% individually. Mean phenylalanine concentration remained stable after short-term bicycle-exercise whereas mean tyrosine concentration declined significantly. Phenylalanine and tyrosine concentrations in dried blood were significantly lower than serum concentrations. No close correlation has been found between serum and microdialysis fluid for phenylalanine and tyrosine concentrations.ConclusionsSlight diurnal variation of phenylalanine concentrations in serum implicates that a single blood sample does reliably reflect the metabolic control in this group of adult patients. Phenylalanine concentrations determined by subcutaneous microdialysis do not correlate with the patients’ phenylalanine concentrations in serum/blood.