Differences in potential biomarkers of delirium between acutely ill medical and elective cardiac surgery patients.

BACKGROUND/AIMS: The pathophysiology of delirium is poorly understood. Increasing evidence suggests that different pathways might be involved in the pathophysiology depending on the population studied. The aim of the present study was to investigate potential differences in mean plasma levels of neopterin, amino acids, amino acid ratios and homovanillic acid between two groups of patients with delirium. METHODS: Data from acutely ill medical patients aged 65 years and older, and patients aged 70 years and older undergoing elective cardiac surgery, were used. Differences in biomarker levels between the groups were investigated using univariate ANOVA with adjustments for age, sex, comorbidities, C-reactive protein (CRP) and the estimated glomerular filtration rate (eGFR), where appropriate. Linear regression analysis was used to identify potential determinants of the investigated biochemical markers. RESULTS: Eighty patients with delirium were included (23 acutely ill medical patients and 57 elective cardiac surgery patients). After adjustment, higher mean neopterin levels (93.1 vs 47.3 nmol/L, P=0.001) and higher phenylalanine/tyrosine ratios (1.39 vs 1.15, P=0.032) were found in acutely ill medical patients when compared to elective cardiac surgery patients. CRP levels were positively correlated with neopterin levels in acutely ill medical patients, explaining 28.4% of the variance in neopterin levels. eGFR was negatively correlated with neopterin in elective cardiac surgery patients, explaining 53.7% of the variance in neopterin levels. CONCLUSION: In this study, we found differences in mean neopterin levels and phenylalanine/tyrosine ratios between acutely ill medical and elective cardiac surgery patients with delirium. Moreover, our findings may suggest that in acutely ill medical patients, neopterin levels are mainly determined by inflammation/oxidative stress whereas in elective cardiac surgery patients, neopterin levels are mainly driven by renal function/fluid status. These findings suggest that the markers and pathways that might be involved in the pathophysiology of delirium may differ between specific groups of patients.

Cerebrospinal fluid levels of neopterin are elevated in delirium after hip fracture.

BACKGROUND: The inflammatory cell product neopterin is elevated in serum before and during delirium. This suggests a role for disordered cell-mediated immunity or oxidative stress. Cerebrospinal fluid (CSF) neopterin levels reflect brain neopterin levels more closely than serum levels. Here we hypothesized that CSF neopterin levels would be higher in delirium. METHODS: In this prospective cohort study, 139 elderly patients with acute hip fracture were recruited in Oslo and Edinburgh. Delirium was diagnosed with the confusion assessment method performed daily pre-operatively and on the first 5 days post-operatively. Paired CSF and blood samples were collected at the onset of spinal anaesthesia. Neopterin levels were measured using high-performance liquid chromatography. RESULTS: Sixty-four (46 %) of 139 hip fracture patients developed delirium perioperatively. CSF neopterin levels were higher in delirium compared to controls (median 29.6 vs 24.7 nmol/mL, p = 0.003), with highest levels in patients who developed delirium post-operatively. Serum neopterin levels were also higher in delirium (median 37.0 vs 27.1 nmol/mL, p = 0.003). CSF neopterin remained significantly associated with delirium after controlling for relevant risk factors. Higher neopterin levels were associated with poorer outcomes (death or new institutionalization) 1 year after surgery (p = 0.02 for CSF and p = 0.03 for serum). CONCLUSIONS: This study is the first to examine neopterin in CSF from patients with delirium. Our findings suggest potential roles for activation of cell-mediated immune responses or oxidative stress in the delirium process. High levels of serum or CSF neopterin in hip fracture patients may also be useful in predicting poor outcomes.

Relationship between plasma homovanillic acid and outcome in patients with psychosis spectrum disorders.

BACKGROUND: Psychosis spectrum disorders, especially schizophrenia, have been linked to disturbed dopaminergic activity in the brain. Plasma homovanillic acid (pHVA) levels partly represent dopaminergic metabolism in the central nervous system. In the present study associations between (changes in) pHVA levels, symptom severity and symptomatic improvement in patients with psychoses were investigated. METHODS: From a total of 80 patients, 58 fulfilled all inclusion criteria and their symptom profile and severity were assessed by means of the Comprehensive Assessment of Symptoms and History (CASH), the Positive and Negative Syndrome Scale (PANSS) and the Clinical Global Impression Scale for Severity and Improvement (CGI-S/CGI-I) at baseline and after 6 weeks of antipsychotic treatment. After inclusion, all patients were prescribed first- or second-generation antipsychotics by their treating psychiatrist. A total of 12 patients had first-episode psychosis (FEP). At both time points, pHVA levels were measured. Subsequently, pHVA levels were compared with an age-matched control sample and changes in pHVA levels (ΔpHVA) after treatment were associated with clinical parameters. RESULTS: Before analyses, data were scrutinized for possible confounders, particularly gender, smoking, medication status (including antipsychotic class), and recent drug use. The pHVA levels in patients were not different from those in controls. Treatment resulted in a significant decrease of all parameters. Symptomatic improvement as well as ΔpHVA was most pronounced in FEP patients. CONCLUSION: These findings show that patients with FEP have a more favourable outcome than non-FEP patients and that greater ΔpHVA also suggests that FEP patients still have the capacity to adjust dopaminergic neurotransmission.

Neopterin: a potential biomarker for delirium in elderly patients.

BACKGROUND/AIMS: The diagnosis of delirium is not supported by specific biomarkers. In a previous study, high neopterin levels were found in patients with a postoperative delirium. In the present study, we investigated levels of neopterin, interleukin-6 (IL-6) and insulin-like growth factor-1 (IGF-1) in acutely ill admitted elderly patients with and without a delirium. METHODS: Plasma/serum levels of neopterin, IL-6 and IGF-1 were determined in patients aged ≥65 years admitted to the wards of Internal Medicine and Geriatrics. Differences in biomarker levels between patients with and without a delirium were investigated by the analysis of variance in models adjusted for age, gender, comorbidities and eGFR (when appropriate). RESULTS: Eighty-six patients were included; 23 of them with a delirium. In adjusted models, higher mean levels of neopterin (70.5 vs. 45.9 nmol/l, p = 0.009) and IL-6 (43.1 vs. 18.5 pg/ml, p = 0.034) and lower mean levels of IGF-1 (6.3 vs. 9.3 nmol/l, p = 0.007) were found in patients with a delirium compared to those without. CONCLUSIONS: The findings of this study suggest that neopterin might be a potential biomarker for delirium which, through oxidative stress and activation of the immune system, may play a role in the pathophysiology of delirium.

The tryptophan kynurenine pathway, neopterin and IL-6 during vulvectomy and abdominal hysterectomy.

BACKGROUND: Surgery has wide ranging immunomodulatory properties of which the mechanism is poorly understood. In order to investigate how different types of surgery influence inflammation, we designed a longitudinal observational study investigating two inflammatory profiles of two separate patient groups undergoing gynaecological operations of differing severity. In addition to measuring the well known inflammatory markers neopterin and IL-6, we also determined the kynurenine/tryptophan ratio. This study was a prospective, single center, two-armed observational study involving 28 female patients. Plasma levels of tryptophan, kynurenine, neopterin and IL-6 were determined from samples taken at: 24 hrs pre-operative, prior to induction, ten minutes before the operation was expected to end, and at 24 and 96 hours post operative in patients undergoing abdominal hysterectomy and vulvectomy. RESULTS: There were 15 and 13 patients included in the vulvectomy and abdominal hysterectomy groups, respectively. In this study we show that anesthesia and surgery significantly increases the enzyme activity of indoleamine 2, 3 dioxygenase (IDO) as measured by the kynurenine/tryptophan ratio (P=0.003), while maintaining stable neopterin levels. However, abdominal hysterectomy causes a considerable IL-6 increase (P<0.001). CONCLUSION: Surgery and associated anesthesia cause a significant tryptophan level decrease while significantly increasing IDO activity. Both types of surgery produce nearly identical neopterin time curve relationships, with no significant change occurring in either group. However, even though neopterin is unaffected by the severity of surgery, IL-6 responded to surgical invasiveness by revealing a significant increase during abdominal hysterectomy.

Tryptophan depletion in chronic fatigue syndrome, a pilot cross-over study.

BACKGROUND: Chronic fatigue syndrome (CFS) is still an enigmatic disorder. CFS can be regarded as a complex disorder with tremendous impact on lives of CFS-patients. Full recovery without treatment is rare. A somatic explanation for the fatigue is lacking. There is clinical and experimental evidence implicating enhanced serotonergic neurotransmission in CFS. Genetic studies and imaging studies support the hypothesis of upregulated serotonin system in CFS. In line with the hypothesis of an increased serotonergic state in CFS, we performed a randomised clinical trial investigated the effect of 5-HT3 receptor antagonism in CFS. No benefit was found of the 5-HT3 receptor antagonist ondansetron compared to placebo.To further investigate the involvement of serotonin in CFS we performed a placebo controlled cross over pilot study investigating the effect of Acute Tryptophan Depletion. FINDINGS: Five female CFS-patients who met the US Center for Disease Control and Prevention criteria for CFS were recruited. There were two test days, one week apart. Each participant received placebo and ATD. To evaluate the efficacy of the ATD procedure tryptophan and the large neutral amino acids were measured. The outcome measures were fatigue severity, concentration and mood states. ATD resulted in a significant plasma tryptophan to large neutral amino acid ratio reduction of 96%. There were no significant differences in fatigue-, depression and concentration between the placebo- and ATD condition. CONCLUSIONS: These first five CFS-patients did not respond to the ATD procedure. However, a much larger sample size is needed to draw final conclusions on the hypothesis of an increased serotonergic state in the pathophysiology of CFS. TRIAL REGISTRATION: ISRCTN07518149.

Effect of major and minor surgery on plasma levels of arginine, citrulline, nitric oxide metabolites, and ornithine in humans.

OBJECTIVE: To determine the effect of surgical invasiveness on plasma levels of arginine, citrulline, ornithine, and nitric oxide (NO) in humans. BACKGROUND: Surgical trauma may have a profound effect on the metabolism of NO. However, human studies reported both increased and decreased NO levels after hemorrhagic shock. Arginine, citrulline, and ornithine are key amino acids involved in NO metabolism, but studies evaluating these amino acids together with NO and during 2 types of surgery are lacking. This study tests the hypothesis that major surgery has a more profound effect on plasma levels of arginine, citrulline, NO, and ornithine than minor surgery. METHODS: Fifteen patients undergoing minor surgery (vulvectomy) and 13 patients undergoing major surgery (laparotomy) were prospectively followed up for 4 days. Plasma was collected for evaluation of levels of arginine, citrulline, NO, and ornithine. RESULTS: Throughout the experiment, arginine levels did not significantly differ between experimental groups. Perioperative plasma citrulline levels were significantly lower in the laparotomy group than in the vulvectomy group, whereas both groups showed a decrease in citrulline levels at the end of the operation and 24 hours postoperatively. Roughly the same pattern was seen for plasma NO and ornithine levels. However, ornithine levels in the laparotomy group showed a more drastic decrease at the end of the operation and 24 hours postoperatively than citrulline and NO levels. CONCLUSIONS: The level of surgical invasiveness has the most profound effect on plasma levels of ornithine. In addition, heavier surgical trauma is paired with lower postoperative levels of citrulline and NO metabolites than lighter surgery. It is suggested that surgical trauma stimulates the laparotomy group to consume significantly more ornithine, possibly for use in wound healing.

High preoperative plasma neopterin predicts delirium after cardiac surgery in older adults.

OBJECTIVES: To examine the association between plasma levels of pterins and amino acids and postoperative delirium. DESIGN: Prospective cohort study. SETTING: Cardiothoracic service in an university hospital in Rotterdam, the Netherlands. PARTICIPANTS: One hundred twenty-five individuals aged 70 and older undergoing elective cardiac surgery. MEASUREMENTS: Plasma pterins and amino acids were measured pre- and postoperatively. Using multiple logistic regression analyses, the associations between pterins and amino acid levels and postoperative delirium were examined in relation to age, sex, comorbidity, cognitive functioning (Mini-Mental State Examination (MMSE) score), and cardiac risk factors. RESULTS: Delirium incidence in the main study group was 31.3%. The preoperative measures associated with delirium were neopterin (odds ratio (OR) = 1.05, P = .009); MMSE score less than 28 (OR = 4.39, P = .001); European System for Cardiac Operative Risk Evaluation score greater than 6 (OR = 2.84, P = .03); and combined coronary artery bypass graft (CABG) and aortic, mitral, or tricuspid valve surgery (OR = 4.32, P = .01). Postoperative measures associated with delirium were neopterin (OR = 3.84, P = .02), homovanillic acid (HVA, OR = 1.01, P = .04), and preoperative MMSE score less than 28 (OR = 3.32, P = .008). CONCLUSION: Preoperatively high neopterin levels predicted delirium after cardiac surgery in older adults, in addition to the well-known risk factors of poor cognitive function, high cardio-surgical risk, and combined CABG and valve surgery. Postoperative neopterin and HVA levels were also found to be associated with delirium, together with preoperative cognitive functioning. Plasma neopterin may be a candidate biomarker for delirium after cardiac surgery in these older adults.

Awake craniotomy induces fewer changes in the plasma amino acid profile than craniotomy under general anesthesia.

In this prospective, observational, 2-armed study, we compared the plasma amino acid profiles of patients undergoing awake craniotomy to those undergoing craniotomy under general anesthesia. Both experimental groups were also compared with a healthy, age-matched and sex-matched reference group not undergoing surgery. It is our intention to investigate whether plasma amino acid levels provide information about physical and emotional stress, as well as pain during awake craniotomy versus craniotomy under general anesthesia. Both experimental groups received preoperative, perioperative, and postoperative dexamethasone. The plasma levels of 20 amino acids were determined preoperative, perioperative, and postoperatively in all groups and were correlated with subjective markers for pain, stress, and anxiety. In both craniotomy groups, preoperative levels of tryptophan and valine were significantly decreased whereas glutamate, alanine, and arginine were significantly increased relative to the reference group. Throughout time, tryptophan levels were significantly lower in the general anesthesia group versus the awake craniotomy group. The general anesthesia group had a significantly higher phenylalanine/tyrosine ratio, which may suggest higher oxidative stress, than the awake group throughout time. Between experimental groups, a significant increase in large neutral amino acids was found postoperatively in awake craniotomy patients, pain was also less and recovery was faster. A significant difference in mean hospitalization time was also found, with awake craniotomy patients leaving after 4.53+/-2.12 days and general anesthesia patients after 6.17+/-1.62 days; P=0.012. This study demonstrates that awake craniotomy is likely to be physically and emotionally less stressful than general anesthesia and that amino acid profiling holds promise for monitoring postoperative pain and recovery.

Nitric oxide production and monoamine oxidase activity in cancer patients during interferon-alpha therapy.

Both increased and decreased nitric oxide (NO) synthesis have been reported in patients treated with interferon-alpha (IFN-alpha). Animal studies showed that IFN-alpha administration results in increased levels of biogenic amines, subsequent activation of monoamine oxidases (MAOs), and finally in a change in NO production due to the H(2)O(2) generated by MAOs. We examined the potential relationship between NO production in plasma and MAO-B activity in platelets of 43 cancer patients during 8 weeks of treatment with IFN-alpha. NO synthesis was quantitated by measuring both the ratio of citrulline and arginine (CIT/ARG-ratio) and total nitrite/nitrate (NOx) levels. Compared to baseline, MAO activity and NOx increased, while the CIT/ARG-ratio decreased. No associations were found between NOx, MAO and CIT/ARG-ratio. Only few associations were observed between changes in the biochemical parameters and changes in psychopathology induced by IFN-alpha, of which the association between changes in CIT and lassitude was the most consistent. The results suggest that peripheral NO production and MAO activity are unrelated to each other, and that peripheral changes in these biochemical parameters induced by IFN-alpha are unlikely to contribute to definite psychiatric disturbance.

Neurotoxic and neuroprotective metabolites of kynurenine in patients with renal cell carcinoma treated with interferon-alpha: course and relationship with psychiatric status.

AIMS: Immunotherapy with interferon-alpha (IFN-alpha) is associated with psychiatric side-effects, including depression. One of the putative pathways underlying these psychiatric side-effects involves tryptophan (TRP) metabolism. Cytokines including IFN-alpha induce the enzyme indoleamine 2,3-dioxygenase (IDO), which converts TRP to kynurenine (KYN), leading to a shortage of serotonin (5-HT). In addition, the production of neurotoxic metabolites of KYN such as 3-hydroxykynurenine and quinolinic acid (QA) might increase and contribute to IFN-alpha-induced psychopathology. In contrast, other catabolites of KYN, such as kynurenic acid (KA), are thought to have neuroprotective properties. METHODS: In a group of 24 patients treated with standard IFN-alpha for metastatic renal cell carcinoma (RCC), combined psychiatric and laboratory assessments were performed at baseline, 4 and 8 weeks, and at 6 months. RESULTS: No psychopathology was observed, despite an increase in neurotoxic challenge as reflected in indices for the balance between neurotoxic and neuroprotective metabolites of KYN. CONCLUSIONS: The present hypothesis that a shift in the balance between neurotoxic and neuroprotective metabolites of KYN underlies the neuropsychiatric side-effects of IFN-alpha-based immunotherapy, is neither supported nor rejected.

Chorionic gonadotropin induces dendritic cells to express a tolerogenic phenotype.

The pregnancy hormone human chorionic gonadotropin (hCG) has been suggested to play an immunoregulatory role in addition to its endocrine function, thus contributing to the prevention of fetal rejection. We hypothesized that hCG is involved in the maternal-fetal immune tolerance by the regulation of dendritic cell (DC) function. Therefore, we studied the effect of hCG on DC maturation. Upon hCG treatment in combination with LPS, mouse bone marrow-derived DC (BMDC) increased the ratio of IL-10:IL-12p70, down-regulated TNF-alpha, and decreased antigen-specific T cell proliferation. Addition of hCG together with LPS and IFN-gamma blocked MHC class II up-regulation, increased IL-10 production, and decreased the antigen-specific T cell proliferation by DC. Splenic DC showed similar results. Upon hCG treatment, IDO mRNA expression and its metabolite kynurenine were increased by LPS- and IFN-gamma-stimulated DC, suggesting its involvement in the decreased T cell proliferation. To study the effect of hCG on DC differentiation from precursors, BMDC were generated in the continuous presence of hCG. Under this condition, hCG decreased cytokine production and the induction of T cell proliferation. These data are suggestive for a contribution of hCG to the maternal-fetal tolerance during pregnancy by modifying DC toward a tolerogenic phenotype.

Interferon-alpha influences tryptophan metabolism without inducing psychiatric side effects.

BACKGROUND: Interferon-alpha (IFN-alpha) treatment is often associated with psychiatric side effects and has been found to lower the amount of tryptophan (TRP) available to the brain. The alterations in tryptophan metabolism might underlie the psychiatric side effects during treatment with IFN-alpha. METHODS: In this study, 43 oncology patients treated with IFN-alpha were included. In order to study de novo depressions, depressed patients at baseline were excluded. Psychiatric evaluation comprising clinical judgment combined with a structured psychiatric interview and observer-based and self-report rating scales was performed at baseline and at 4 weeks, 8 weeks and 6 months after the start of treatment with IFN-alpha, and in the case of emerging psychopathology. Blood samples were drawn at the same evaluation times and assessed for concentrations of TRP, large neutral amino acids, kynurenine, 5-hydroxyindole acetic acid, neopterin and biopterin. RESULTS: During treatment with IFN-alpha, several alterations in laboratory parameters occurred that were consistent with an increased degradation of peripheral TRP. Psychometric ratings revealed hardly any psychiatric changes. No consistent associations were found between changes in the laboratory assessments determined and the diverse psychiatric measures. CONCLUSION: In this study, IFN-alpha was found to alter TRP metabolism without inducing psychiatric side effects. Therefore, a possible relationship between TRP metabolism and depression was not substantiated by this study.

Platelet MAO activity during treatment with pegylated interferon-alfa in melanoma patients.

Depression and cognitive disturbance are well-known neuropsychiatric side effects of therapy with interferon-alfa (IFN-alfa). Aggression and irritability are also reported as side effects. Probably, central nervous system (CNS) serotonergic dysfunction is one of the underlying pathophysiological mechanisms of IFN-alfa-induced neuropsychiatric toxicity. Platelet activity of monoamine oxidase-B (MAO; EC1.4.3.4) is a possible indicator of central serotonergic function. Moreover, low platelet MAO activity is linked to impulsiveness, addiction and personality disorder. In this exploratory study in 17 high-risk melanoma patients, platelet counts, whole blood MAO, and platelet MAO activity were measured before and during therapy with IFN-alfa. Patients were randomized to treatment either with pegylated IFN-alfa (PEG-IFN-alfa) once a week at a dose of 6 microg/kg/week subcuteanously (s.c.) during 8 weeks, followed by a maintenance treatment of 3 microg/kg/week s.c. for a total of 5 years, or to observation only. Blood samples were taken at baseline, 4 and 8 weeks and 3 months. During treatment with IFN-alfa, platelet counts decreased at 4 and 8 weeks and 3 months, while platelet MAO activity increased, both compared to baseline and compared to non-treated controls. Compared to non-treated controls, platelet MAO activity increased with 86.4% (95 CI: 52.9-127.2). No significant changes in platelet MAO activity were observed in the control group. This indicates that platelet MAO activity is influenced by IFN-alfa. Since platelet MAO activity is a model for CNS MAO-B activity, it may be speculated that CNS MAO-B activity will also be increased. This could influence serotonin (5-HT) metabolism and thereby contribute to the development of psychiatric disturbance. However, a preferential inhibition of platelet production cannot be ruled out. Hypothetically, the antiproliferative effects of IFN-alfa could interfere more strongly with the synthesis of platelets than with the synthesis of mitochondria. In that case, increased platelet MAO activity reflects an increased number of mitochondria per platelet.

Pegylated interferon-alpha2b treatment in melanoma patients: influence on amino acids, 5-hydroxyindolacetic acid and pteridine plasma concentrations.

Our objective was to study the influence of pegylated interferon-alpha2b (PEG-IFN-alpha) on the metabolism of amino acids and pteridines. We used an exploratory study into plasma concentrations of large neutral amino acids, 5-hydroxyindolacetic acid (5-HIAA), total biopterin (BIOP) and neopterin (NEOP) in 40 high-risk melanoma patients. Patients were randomized to treatment with PEG-IFN-alpha once a week in a dose of 6 microg/kg/week s.c. during 8 weeks, followed by a maintenance treatment of 3 microg/kg/week s.c. or to observation only. We found that treatment with PEG-IFN-alpha decreases tryptophan (TRP) concentrations in the first 3 months of treatment to a maximum of 25.3% compared to controls [95% confidence interval (CI): 14.9 to 34.4]. The TRP:LNAA ratio, an index for the availability of TRP to the central nervous system (CNS), decreases during 6 months with 18.8% (95% CI: 11.9 to 25.2). Concentrations of NEOP rose; however, concentrations of BIOP, the sum of tetrahydrobiopterin [BH4] and its oxidative products, did not decrease. The ratio of phenylalanine to tyrosine was increased with 11.7% (95% CI: 1.0 to 23.5) during 6 months. We conclude that, like conventional IFN-alpha, PEG-IFN-alpha lowers TRP concentrations and decreases the availability of TRP to the CNS. PEG-IFN-alpha has a similar influence on pteridine metabolism as standard IFN-alpha. If a lowered availability of TRP and a consequent decrease of serotonergic neurotransmission are indeed a mechanism underlying neuropsychiatric side-effects of IFN-alpha, patients on PEG-IFN-alpha are not at a lower risk of developing neuropsychiatric side-effects as patients on conventional IFN-alpha.

Osmotic swelling-provoked release of organic osmolytes in human intestinal epithelial cells.

Human Intestine 407 cells respond to osmotic cell swelling by the activation of Cl(-)- and K(+)-selective ionic channels, as well as by stimulating an organic osmolyte release pathway readily permeable to taurine and phosphocholine. Unlike the activation of volume-regulated anion channels (VRAC), activation of the organic osmolyte release pathway shows a lag time of approximately 30-60 s, and its activity persists for at least 8-12 min. In contrast to VRAC activation, stimulation of organic osmolyte release did not require protein tyrosine phosphorylation, active p21(rho), or phosphatidylinositol 3-kinase activity and was insensitive to Cl(-) channel blockers. Treatment of the cells with putative organic anion transporter inhibitors reduced the release of taurine only partially or was found to be ineffective. The efflux was blocked by a subclass of organic cation transporter (OCT) inhibitors (cyanine-863 and decynium-22) but not by other OCT inhibitors (cimetidine, quinine, and verapamil). Brief treatment of the cells with phorbol esters potentiated the cell swelling-induced taurine efflux, whereas addition of the protein kinase C (PKC) inhibitor GF109203X largely inhibited the response, suggesting that PKC is involved. Increasing the level of intracellular Ca(2+) by using A-23187- or Ca(2+)-mobilizing hormones, however, did not affect the magnitude of the response. Taken together, the results indicate that the hypotonicity-induced efflux of organic osmolytes is independent of VRAC and involves a PKC-dependent step.

Craving for cigarettes among low and high dependent smokers: impact of norharman.

Besides nicotine, other chemicals in tobacco smoke, such as norharman, may contribute to the addictive properties of cigarettes. More specifically, elevated blood plasma levels of norharman may reduce feelings of craving among tobacco-dependent individuals. To test this hypothesis, plasma concentrations of norharman were measured in 38 male smokers (at least 15 cigarettes per day) at three time-points on 3 different days spread over a 4-month period. The first measurement (T0) was conducted in the morning at 8.30 a.m., after 12 hours of smoking abstinence. The T1 and T2 measurements were conducted at 13.00 p.m. and 16.30 p.m., during a period of ad libitum smoking (after the T0 measurement, participants were not restricted in their smoking behaviour). At each of the nine time-points, craving was assessed by means of a shortened version of the Questionnaire of Smoking Urges. The Fagerström Test of Nicotine Dependence was used to obtain an indication of nicotine dependence. The results showed that, after a period of smoking abstinence, craving was stronger in those with a high tobacco dependence than in those with a low tobacco dependence. After resumption of smoking, craving declined to a similar low level in both low and high dependent smokers. Measurements during periods of ad libitum smoking indicate that plasma levels of norharman are related negatively to craving among low nicotine-dependent smokers, but not among high dependent smokers.

Serum amino acids, biopterin and neopterin during long-term immunotherapy with interferon-alpha in high-risk melanoma patients.

Immunotherapy with interferon-alpha (IFN-alpha) induces neuropsychiatric side effects, most notably depression. One of the presumed pathophysiological mechanisms is an effect on tryptophan metabolism. As tryptophan is the precursor of serotonin, decreased availability of tryptophan to the central nervous system could result in serotonin deficiency. Tetrahydrobiopterin (BH((4))) is a cofactor for one of the enzymes synthesizing serotonin. We conducted an exploratory study into the serum concentrations of large neutral amino acids (AA), biopterin (BIOP) and neopterin (NEOP), of 67 patients with high-risk melanoma, who were either treated with two different doses of IFN-alpha or were part of an observation-only control group. We found evidence for IFN-alpha to decrease concentrations of all AA except phenylalanine. The decrease in tryptophan concentration was most prominent and consistent. These changes persisted throughout a year of maintenance treatment. Concentrations of NEOP rose sharply, whereas, those of BIOP did not change. Except for the increase in NEOP and the increase in the ratio between phenylalanine (PHE) and tyrosine (TYR), no support for derangement in BH((4)) metabolism was found. The increase in the ratio between PHE and TYR suggests inhibition of the enzyme phenylalanine hydroxylase. Patients with IFN-alpha induced anxiety and depression had higher pretreatment concentrations of NEOP. Changes in tryptophan metabolism may play a role in the pathophysiology of the neuropsychiatric side effects of IFN-alpha, and further research into the predictive potential of NEOP is warranted.

The impact of smoking and drinking on plasma levels of norharman.

The hypothesized role of the beta-carboline norharman in processes of drug dependence forms the basis for several studies on plasma levels of norharman among substance-using populations, particularly among alcoholics and smokers. However, it is not clear whether norharman is implicated in processes of dependence to both substances, or only to tobacco smoke. In the present study plasma concentrations of norharman were measured among four groups of participants regarding heavy smokers who do or do not drink alcohol excessively and nonsmokers who do or do not drink alcohol excessively. All measurements were conducted on three different days with an interval of 2 months in between and at three times during the day to account for possible circadian or seasonal variations. Results showed that elevated plasma levels of norharman appear only in heavy smokers regardless of their drinking profile. The norharman plasma levels of nonsmoking excessive drinkers showed a similar pattern to that of the control group. The findings indicate that elevated plasma levels of norharman are due to heavy smoking and not to excessive drinking.