Moderate hyperhomocysteinaemia and immune activation in Parkinson's disease.

Moderate hyperhomocysteinaemia has been linked to an increased risk for cardiovascular diseases. Increased homocysteine concentrations may follow folate depletion due to insufficient dietary intake of the vitamin, but there is also some indication that immune activation could play a role. In this preliminary study, homocysteine, folate, and vitamin B(12) concentrations were measured in 19 patients with Parkinson's disease, 61-90 years of age, and compared to a healthy control group of similar age and to neopterin concentrations as an indicator of immune activation. A subgroup of patients presented with increased homocysteine and low folate concentrations. Homocysteine levels correlated inversely with vitamins folate and B(12) and positively with neopterin concentrations. Disturbed homocysteine metabolism in Parkinson's disease may be associated with vitamin deficiency and with immune system activation which may underlie folate depletion.

Increased neopterin production and tryptophan degradation in advanced Parkinson's disease.

Large amounts of neopterin are produced by interferon-(IFN)-gamma-stimulated human monocytes/macrophages, and increased neopterin concentrations indicate cellular immune activation. In parallel, IFN-gamma induces indoleamine 2,3-dioxygenase which degrades 1-tryptophan to kynurenine. Increased tryptophan degradation rates are indicated by an increased kynurenine/tryptophan ratio (kyn/trp-ratio), reflecting immune system activation, too. In 22 patients with Parkinson's disease (PD) and in 11 age-matched controls, serum and cerebrospinal fluid (CSF) neopterin concentrations were measured by ELISA. Tryptophan and kynurenine concentrations were determined by HPLC. Neopterin concentrations and kyn/trp-ratios were increased both in serum and CSF of patients as compared to controls. Serum tryptophan was lower in patients. Patients with the highest disease activity presented with highest degree of immune activation. Significant correlations existed between neopterin concentrations and kyn/trp-ratios in serum and CSF. Increased formation of neopterin and enhanced degradation of tryptophan suggest activated cell-mediated immune response in a subgroup of patients with advanced Parkinson's disease.

Serum tryptophan decrease correlates with immune activation and impaired quality of life in colorectal cancer.

Cancer-related indoleamine (2,3)-dioxygenase up-regulation by interferon-gamma might influence quality of life by depleting serum tryptophan. We correlated serum tryptophan levels with immune activation and quality of life in patients with colorectal liver metastases. Venous blood was sampled from patients with primary colorectal cancer and from patients with metachronous colorectal liver metastases who completed quality of life and psychological questionnaires. Serum tryptophan, kynurenine, neopterin, interleukin 2 soluble receptor alpha (IL-2 sRalpha), soluble tumour necrosis factor receptor I (sTNF RI), interleukin 6, and C-reactive protein were measured. Liver metastasis volume was estimated by computerised tomography, and survival from blood sampling was noted. Sixty-six patients with colorectal cancer were studied (39 males; median age 66 years) of whom 25 had colorectal liver metastases only (17 males; median age 62 years; median liver metastasis volume 208 ml; median survival 234 days). Reduced serum tryptophan was significantly associated with Rotterdam Symptom Checklist physical symptom (r=-0.51, P=0.01) and Sickness Impact Profile (r=-0.42, P=0.04) scores, and correlated with increased serum neopterin (r=-0.36, P=0.003), IL-2 sRalpha (r=-0.51, P=0.01) and sTNF RI (r=-0.45, P=0.02) levels. Stepwise regression analyses suggested that serum tryptophan was an independent predictor of Rotterdam Symptom Checklist physical symptom (regression coefficient -20.78, P=0.01) and Sickness Impact Profile (regression coefficient -109.09, P=0.04) scores. The results supported a role for interferon-gamma-mediated serum tryptophan decrease in cancer-induced quality of life deterioration.

Neopterin as a marker for immune system activation.

Increased amounts of neopterin are produced by human monocytes/macrophages upon stimulation with the cytokine interferon-y. Therefore, measurement of neopterin concentrations in body fluids like serum, cerebrospinal fluid or urine provides information about activation of T helper cell 1 derived cellular immune activation. Increased neopterin production is found in infections by viruses including human immunodeficiency virus (HIV), infections by intracellular living bacteria and parasites, autoimmune diseases, malignant tumor diseases and in allograft rejection episodes. But also in neurological and in cardiovascular diseases cellular immune activation indicated by increased neopterin production, is found. Major diagnostic applications of neopterin measurements are, e.g. monitoring of allograft recipients to recognize immunological complications early. Neopterin production provides prognostic information in patients with malignant tumor diseases and in HIV-infected individuals, high levels being associated with poorer survival expectations. Neopterin measurements are also useful to monitor therapy in patients with autoimmune disorders and in individuals with HIV infection. Screening of neopterin concentrations in blood donations allows to detect acute infections in a non-specific way and improves safety of blood transfusions. As high neopterin production is associated with increased production of reactive oxygen species and with low serum concentrations of antioxidants like alpha-tocopherol, neopterin can also be regarded as a marker of reactive oxygen species formed by the activated cellular immune system. Therefore, by neopterin measurements not only the extent of cellular immune activation but also the extent of oxidative stress can be estimated.

Hyperhomocysteinemia, pteridines and oxidative stress.

Tetrahydrofolate is an essential cofactor for the conversion of homocysteine to methionine, and hyperhomocysteinemia is considered as a risk factor for cardiovascular and cerebrovascular diseases. In subjects with hyperhomocysteinemia usually an inverse relationship exists to folic acid levels, and supplementation with folic acid is able to lower homocysteine concentrations. The pathogenesis of most if not all diseases which are accompanied with moderate hyperhomocysteinemia involves cellular immune activation and therefore in patients very often exists also a positive correlation between homocysteine concentrations and the degree of immune activation which is indicated, e.g. by increased neopterin concentrations. Since neopterin concentrations also serves as an estimate of oxidative stress merging from immune system activation, this association suggests that cellular immune activation and oxidative stress could be involved in the development of hyperhomocysteinemia. Because tetrahydrofolate is very susceptible to oxidation, an increased oxidative degradation of tetrahydrofolates may become relevant under oxidative stress conditions. In this way folate deficiency may develop despite normal dietary intake of the vitamin. In our patients, hyperhomocysteinemia is considered as an indirect consequence of hyperconsumption of antioxidant vitamins during prolonged states of immune activation.

Is hyperhomocysteinemia due to the oxidative depletion of folate rather than to insufficient dietary intake?

Hyperhomocysteinemia is considered as a risk factor for cardiovascular diseases. Usually, an inverse relationship exists between homocysteine and folate levels, and supplementation with folate lowers homocysteine concentrations in patients. Therefore, hyperhomocysteinemia is mainly ascribed to the insufficient dietary intake of folate. Hyperhomocysteinemia has also been observed in infections and inflammatory diseases. Oxidative stress appears to be involved in the pathogenesis of these disorders, and associations have been found between homocysteine and e.g., neopterin concentration. Increased neopterin concentration indicates immune system activation and also allows an estimate of thus elicited oxidative stress. It may be relevant that the active cofactor, tetrahydrofolate, is very susceptible to oxidation. Immunologically induced oxidative stress could lead to folate depletion resulting in hyperhomocysteinemia. Thus, hyperhomocysteinemia in patients can be considered as an indirect consequence of hyperconsumption of antioxidant vitamins during prolonged states of immune activation.

Neopterin production and tryptophan degradation in humans infected by Streptococcus pyogenes.

Streptococcus pyogenes may cause tonsillitis, scarlet fever and so-called "streptococcal toxic shock-like syndrome" (STSS). These streptococci produce exotoxins which are implicated as superantigens in the pathogenesis of STSS and scarlet fever. Using human peripheral blood-derived mononuclear cells in vitro, such toxins were shown to induce neopterin production and degradation of the amino acid tryptophan to metabolites such as kynurenine by activating indoleamine (2,3)-dioxygenase via interferon-gamma. We investigated the sera of seven patients with streptococcal tonsillitis and of four patients with STSS. Those with STSS showed higher serum neopterin concentrations (median: 152 nmol/l; 95th percentile in healthy controls: 8.7 nmol/l) than those with tonsillitis (median: 12 nmol/l). Similarly, kynurenine to tryptophan ratios were increased in tonsillitis and extremely high in patients with STSS. Highly increased neopterin production and tryptophan degradation in patients with STSS suggest an association between a high degree of T cell activation and the severity of the disease manifestation.

Induction of apoptosis by 7,8-dihydroneopterin: involvement of radical formation.

Interferon-gamma is a cytokine released in large amounts during cell-mediated immune response. It induces the expression of proinflammatory cytokines and enhances macrophage capacity to secrete reactive oxygen intermediates and the pteridines neopterin and 7,8-dihydroneopterin. To assay the role of these pteridines in the immune system several studies were performed. Thereby, 7,8-dihydroneopterin was found to induce apoptosis in T lymphocytes. In this study we report that caspases are involved in 7,8-dihydroneopterin-mediated apoptosis in Jurkat T cells. In connection with this result we found that 7,8-dihydroneopterin can increase Fas ligand expression detected in Western blot analysis and promoter reporter assays. Antioxidants potently reduced the effect of 7,8-dihydroneopterin on Fas ligand promoter activation suggesting an involvement of oxidative stress. In further investigations, ESR-measurements were performed to evaluate the role of 7,8-dihydroneopterin in the formation of radicals. We found that the pteridine in combination with the spin trap DMPO induces the production of DMPO-OH spin adducts. This reaction was sensitive to the presence of chelated metal ions and could completely be blocked by the addition of superoxide dismutase. These data suggest that 7,8-dihydroneopterin in aqueous solution leads to the formation of .OH radicals via generation of superoxide anion. We hypothesize that an overproduction of radicals caused by high levels of 7,8-dihydroneopterin is likely to be responsible for the pro-apoptotic effects observed in cell cultures and possibly contributes to the pathogenesis of diseases involving immune activation and elevated concentrations of neopterin-derivatives.

Fructose malabsorption is associated with decreased plasma tryptophan.

BACKGROUND: Fructose malabsorption is characterized by the inability to absorb fructose efficiently. As a consequence fructose reaches the colon where it is broken down by bacteria to short fatty acids, CO2, H2, CH4 and lactic acid. Bloating, cramps, osmotic diarrhea and other symptoms of irritable bowel syndrome are the consequence and can be seen in about 50% of fructose malabsorbers. Recently it was found that fructose malabsorption was associated with early signs of depressive disorders. Therefore, it was investigated whether fructose malabsorption is associated with abnormal tryptophan metabolism. METHODS: Fifty adults (16 men, 34 women) with gastrointestinal discomfort were analyzed by measuring breath hydrogen concentrations after an oral dose of 50 g fructose after an overnight fast. They were classified as normals or fructose malabsorbers according to their breath H2 concentrations. All patients filled out a Beck depression inventory questionnaire. Blood samples were taken for plasma tryptophan and kynurenine measurements. RESULTS: Fructose malabsorption (breath deltaH2 production >20 ppm) was detected in 35 of 50 individuals (70%). Subjects with fructose malabsorption showed significantly lower plasma tryptophan concentrations and significantly higher scores in the Beck depression inventory compared to those with normal fructose absorption. CONCLUSIONS: Fructose malabsorption is associated with lower tryptophan levels that may play a role in the development of depressive disorders. High intestinal fructose concentration seems to interfere with L-tryptophan metabolism, and it may reduce availability of tryptophan for the biosynthesis of serotonin (5-hydroxytryptamine). Fructose malabsorption should be considered in patients with symptoms of depression and disturbances of tryptophan metabolism.

Inverse relationship between neopterin and immunoglobulin E.

Polarized human T helper (Th) cells play a key role in the network of the specific immune system compartments. Cell-mediated immune response depends on activation of Th1-type cells, typically producing and releasing interferon-gamma and interleukin-2, whereas activation of Th2-type cells and production of cytokines such as interleukin-4, -5, and -10 are involved in humoral immune response and the production of immunoglobulins. Increased amounts of neopterin are produced during the Th1-type immune response by human monocytes/macrophages upon stimulation with the Th1-derived cytokine interferon-gamma, and thus the determination of neopterin concentrations allows us to monitor Th1-type immune response. We compared serum concentrations of neopterin with immunoglobulin E (IgE), a typical product of the Th2-type immune response, in order to examine the relationship between Th1-type and Th2-type immune system stimulation in 709 healthy outpatients, who visited the physician's office for a medical health checkup. Eleven percent presented with serum neopterin concentrations >8.7 nmol/L; 26% had increased serum concentrations of IgE (>100 kIU/L). There existed an inverse correlation between serum neopterin and IgE concentrations (Spearman's rank correlation coefficient: r(s) = -0.100; P < 0.01) which was stronger when excluding data < or = 8.7 nmol/L neopterin and < or = 100 kIU/L IgE (n = 246; r(s) = -0.519; P < 0.0001). Data indicate that increased serum neopterin concentrations are associated with low serum IgE and increased serum IgE with low serum neopterin concentrations. This finding fully agrees with the current understanding that in humans the activation of Th1 and Th2 cell-mediated immune responses are down-regulating each other.

Monitoring of immune activation using biochemical changes in a porcine model of cardiac arrest.

In animal models, immune activation is often difficult to assess because of the limited availability of specific assays to detect cytokine activities. In human monocytes/macrophages, interferon-gamma induces increased production of neopterin and an enhanced activity of indoleamine 2,3-dioxygenase, which degrades tryptophan via the kynurenine pathway. Therefore, monitoring of neopterin concentrations and of tryptophan degradation can serve to detect the extent of T helper cell 1-type immune activation during cellular immune response in humans. In a porcine model of cardiac arrest, we examined the potential use of neopterin measurements and determination of the tryptophan degradation rate as a means of estimating the extent of immune activation. Urinary neopterin concentrations were measured with high-performance liquid chromatography (HPLC) and radioimmunoassay (RIA) (BRAHMS Diagnostica, Berlin, Germany). Serum and plasma tryptophan and kynurenine concentrations were also determined using HPLC. Serum and urine neopterin concentrations were not detectable with HPLC in these specimens, whereas RIA gave weakly (presumably false) positive results. The mean serum tryptophan concentration was 39.0 +/- 6.2 micromol/l, and the mean kynurenine concentration was 0.85 +/- 0.33 micromol/l. The average kynurenine-per-tryptophan quotient in serum was 21.7 +/- 8.4 nmol/micromol, and that in plasma was 20.7 +/- 9.5 nmol/micromol (n = 7), which corresponds well to normal values in humans. This study provides preliminary data to support the monitoring of tryptophan degradation but not neopterin concentrations as a potential means of detecting immune activation in a porcine model. The kynurenine-per-tryptophan quotient may serve as a short-term measurement of immune activation and hence permit an estimate of the extent of immune activation.

Fructose- and sorbitol-reduced diet improves mood and gastrointestinal disturbances in fructose malabsorbers.

BACKGROUND: Fructose malabsorption is characterized by the inability to absorb fructose efficiently. As a consequence fructose reaches the colon where it is broken down by bacteria to short fatty acids, CO2 and H2. Bloating, cramps, osmotic diarrhea and other symptoms of irritable bowel syndrome are the consequences and can be seen in about 50% of fructose malabsorbers. We have previously shown that fructose malabsorption is associated with early signs of mental depression and low serum tryptophan concentrations. It was therefore of interest whether a fructose-reduced diet could not only improve gastrointestinal complaints but also depressive signs seen in fructose malabsorbers. METHODS: Fifty-three adults (12 males, 41 females), who were identified as fructose malabsorbers according to their breath-H2 concentrations, filled out a Beck's depression inventory-questionnaire, and a questionnaire with arbitrary scales for measurement of meteorism, stool frequency and quality of life for a 4-week period before dietary intervention and 4 weeks after dietary change as for fructose- and sorbitol-reduced diet. RESULTS: Depression scores were reduced by 65.2% after 4 weeks of diet (P < 0.0001), and there was a significant reduction of meteorism (P < 0.0001) and stool frequency (P < 0.01). Improvement of signs of depression and of meteorism was more pronounced in females than in males. CONCLUSION: Fructose- and sorbitol-reduced diet in subjects with fructose malabsorption does not only reduce gastrointestinal symptoms but also improves mood and early signs of depression.

Cellular immune activation, neopterin production, tryptophan degradation and the development of immunodeficiency.

Cellular (Th1-type) immune response is centrally involved in the pathogenesis of various diseases. Within the immunological cascades of Th1-type immunity, interferon gamma (IFN-gamma), among other cytokines, is critically involved. It triggers a series of immune-relevant reactions mostly directed towards forward regulation of the antigen specific immune response. However, in chronic states of immune activation, systemically increased IFN-gamma is no longer antigen specific and is associated with the development of immunodeficiency. IFN-gamma also stimulates the production of neopterin, a low-mass compound, in human monocytes/macrophages. Accordingly, neopterin concentrations in humans reflect the degree of Th1-type immune activation. Since IFN-gamma also stimulates the release of reactive oxygen species (ROS) from immunocompetents cells, the amount of neopterin produced also serves as an indirect estimate of oxidative stress. In parallel, IFN-gamma activates the degradation of tryptophan, which appears to limit the growth of intracellular pathogens and the proliferation of cells, including T lymphocytes. Thus, during persisting states of immune activation, the production of IFN-gamma is not only associated with forward regulation of the immune response, but also with immunosuppressive mechanisms. The increased formation of neopterin and degradation of tryptophan may result in a decreased T cell responsiveness and development of immunodeficiency.

Oxidation of 7,8-dihydroneopterin by hypochlorous acid yields neopterin.

In vitro, interferon-gamma stimulates primate monocytes/macrophages to produce the pteridines neopterin and 7,8-dihydroneopterin. These pteridines are capable of modulating the oxidative potential of reactive species. Neopterin is pro-oxidative whereas 7, 8-dihydroneopterin is an effective antioxidant. In the presence of oxygen, 7,8-dihydroneopterin is rapidly oxidized and after loosing the side chain 7,8-dihydroxanthopterin is formed. It is considered that under physiological conditions, 7,8-dihydroneopterin cannot be a source for neopterin production. In this study it is demonstrated that hypochlorous acid is capable to oxidize 7,8-dihydroneopterin yielding neopterin. Neopterin is less affected by hypochlorous acid, and in a mixture of both pteridines similar to the in vivo situation, only 7,8-dihydroneopterin is oxidized, thereby increasing the ratio towards neopterin. The findings may beat relevance for the in vivo situation since hypochlorous acid shifts the neopterin/7, 8-dihydroneopterin ratio towards the side of neopterin, hence probably increasing the oxidative potential in a micro-environment.

Carbohydrate malabsorption syndromes and early signs of mental depression in females.

Fructose and lactose malabsorption are characterized by impaired duodenal fructose transport or by the deficiency of mucosal lactase, respectively. As a consequence, the nonabsorbed saccharides reach the colon, where they are broken down by bacteria to short fatty acids, CO2, and H2. Bloating, cramps, osmotic diarrhea, and other symptoms of irritable bowel syndrome are the consequence and can be seen in about 50% of carbohydrate malabsorbers. We have previously shown that fructose as well as lactose malabsorption were associated with signs of mental depression. It was therefore of interest to investigate possible interactions between fructose and lactose malabsorption and their influence on the development of signs of depression. In all, 111 otherwise healthy volunteers (81 females and 30 males) with gastrointestinal complaints were analyzed by measuring breath H2 concentrations after an oral dose of 50 g lactose and of 50 g fructose one week apart. They were classified as normals, isolated fructose malabsorbers, isolated lactose malabsorbers, and combined fructose/lactose malabsorbers. All patients filled out a Beck's depression inventory-questionnaire. Twenty-five individuals (22.5%) were neither fructose nor lactose malabsorbers (group 1), 69 (62.2%) were only fructose malabsorbers (group 2), 4 (3.6%) were only lactose malabsorbers (group 3), and 13 (11.7%) presented with fructose and lactose malabsorption together (group 4). Isolated fructose malabsorption and combined fructose/lactose malabsorption was significantly associated with a higher Beck's depression score. Further analysis of the data show that this association was strong in females (P < 0.01), but there was no such association between carbohydrate malabsorption and early signs of depression in males. In conclusion, the data confirm that fructose malabsorption may play a role in the development of mental depression in females and additional lactose malabsorption seems to further increase the risk for development of mental depression.

Immune reaction links disease progression in cancer patients with depression.

Mood disturbances and depression are supposed to have a negative impact on patients' outcome in malignant tumour disease. On the other hand, poor prognosis in cancer patients is associated with chronic immune challenge which is paralleled by enhanced degradation of the essential amino acid tryptophan and thus decreased plasma tryptophan concentrations. Because tryptophan is precursor for the biosynthesis of the neurotransmitter serotonin (= 5-hydroxytryptamine, 5HT), low tryptophan concentrations will lead to decreased availability of serotonin which finally increases the susceptibility for the development of mood disturbances and depression in the patients. Thus, the development of depression in cancer patients may result from chronic cellular immune stimulation. In conclusion, a more aggressive tumour rather than depression will be responsible for worse outcome of cancer patients and will be associated with a more drastic challenge of the immune system, as a side effect leading to neurotransmitter disturbances.