Band 10, Heft 4

In plant cells, the interconversion of formyl- and methylene-tetrahydrofolates is catalyzed by a bifunctional protein possessing methenyltetrallydrofolate cydohydrolase (EC 3.5.4.9) and methylenetetrahydrofolate dehydrogenase (EC 1.5.1.5) activities. The present work reports the isolation and sequencing of a cDNA that encodes this protein. Polydonal antibodies, raised against purified pea cytosolic dehydrogenase:cyclohydrolase, were used to screen a λgt 11 cDNA expression library, constructed from leaf extracts of this species. The screen identified a phage containing a cDNA insert with an open reading frame encoding a 294 amino acid protein (M r 31,344). The deduced primary structure of this protein contained most of the conserved regions found in other dehydrogenase:cyclohydrolase proteins including the corresponding domains of the trifunctional C 1 -THF synthases of mammalian and yeast origins.

In 30 atherosclerotic patients different serum analytes and neopterin concentrations in serum and urine were determined before and after Heparin-Induced Extracorporeal LDL and Fibrinogen Precipitation therapy. Neopterin concentrations in serum of all 30 patients were increased (mean=9.18 nmol/l, SD=3.23) compared to age matched healthy people (mean=5.34 nmol/l, SD=2.70) and were significantly lowered after H.E.L.P therapy (mean=S.22 nmol/l; SD=3.22, p=0.002, t-test) . These results suggest the involvement of the cellular immune system in the occurrence of atherosclerosis. Further neopterin, the macrophagederived immune activation marker, is significantly correlated with fibrinogen (linear correlation coefficient r=0.36, p=0.05). Long-term neopterin concentrations in serum of 4 patients (three with coronary heart disease and one with Papilla edema), from the first up to the 9 th , respectively 12 th therapy decreased, in contrast to fibrinogen which stayed stable or even increased during long-term treatment.

The purpose of the study was to characterize the immune status in 88 patients (64 women and 24 men) with thyroid diseases and in 36 healthy blood donors as control group. The clinical material consisted of 37 patients with nontoxic nodular goitre, 10 patients with thyroiditis, 27 patients with thyroid adenoma and 14 patients with thyroid carcinoma. The studied parameters included serum neopterin,interleukin-6 (IL-6), also anti-thyroglobulin autoantibodies (ATG) and anti-thyroid microsomal autoantibodies (MAB). The aim of the study was to investigate whether serum neopterin, IL-6, ATG and MAE have any value in distinction between non-toxic nodular goitre, thyroiditis, thyroid adenoma and thyroid carcinoma. 36.4% patients with thyroid carcinoma, 16.7% patients with nontoxic nodular goitre and 9.1 % patients with thyroid adenoma had neopterin levels higher than 10 nmol/1. In patients and in the control group the mean serum levels of neopterin were in normal range. The highest mean level of neopterin was found in patients with thyroid carcinoma (7.14± 5.95 nmol/1). The difference was statistically significant in comparison to the control (p < 0.001) and patients with thyroiditis and thyroid adenoma (p < 0.05). The significantly higher levels of IL-6 were in all patients in comparison to the control (p < 0.0001). Autoantibodies ATG were detected in serum of 45 patients (51.1 %) and autoantibodies MAE were in serum of 34 patients (38.6 % ). Mean levels of these autoantibodies in patients were statistically significantly higher than in the control ' p < 0.05). In patients with ATG and/or MAE mean level of neopterin was significantly higher than in patients without these autoantibodies (p < 0.05). This study has shown that neopterin represents an additional parameter with potential interest in clinical diagnosis of thyroid diseases.

It has been previously reported that 5,6,7,S-tetrahydrobiopterin (BH 4 ) modulates HL-60 cell death induced by a nitric oxide (NO) donor, S-nitroso-N-acetyl-D, L-penicillamine (SNAP). In this study, the role of endogenous BH4 was investigated in lipopolysaccharide (LPS)-induced apoptotic cell death. LPS induced an increase of DNA fragmentation and of nitrite and nitrate content (NOx content) in the macrophage- like RAW 264.7 cell line. 2,4-Diamino-6-hydroxypyrimidine (DAHP) , an inhibitor of BH 4 synthesis, suppressed both of them. The NOx content of cells treated with LPS and interferon-y was much higher than that of cells treated with LPS alone. However, the degree of apoptotic cell death induced by LPS and interferon-y did not differ significantly from that induced by LPS alone. Further investigation revealed that LPS-induced cell death of RAW264.7 cells was mainly mediated by reactive oxygen species, such as hydrogen peroxide (H 2 O 2 ). From these data, it was speculated that BH4 might be a modulator in NO-induced apoptosis, in which BH4 involves LPS-induced cell death by its function asa cofactor of inducible NO synthase and it suppresses the cell death mediated by NO and/or H 2 O 2 via an antioxidative activity.

Activation of cellular immunity, mainly cytotoxic T cells, plays an important role in the · mechanisms of cyclic acute exacerbation of hepatocellular damage (AE) in hepatitis B virus (HBV) carriers. Monitoring of the dynamics of immunoreactivity is clinically important to manage the patients and recognize the mechanism of liver damage. Serum neopterin has been widely- recognized as a marker of actiyation of cell-mediated immunity. We observed the clinical course of five hepatitis Be antigen I HBeAg ) positive HBV carriers with recurrent AE for mean eighteen months by monitoring of serum neopterin using a RIA kit. Alanine amino transferase (ALT) and HBeAg were also measured serially as markers for hepatocne necrosis and viral replication, respectively During follow-up period. each patient had several episodes of AE alternating with normal or nearly normal liver function. The levels of serum neopterin changed dynamically related to those of HBeAg and ALT Temporal analysis of these makers before, during and after the episodes of AE showed a close involvement of the viral replication prior to the hepatocellular injury as well as the activation of cellular immunity following the viral replication. Immunological monitoring of serum neopterin could provide useful information about the dynamic interaction between virus replication, cellular immunoreactivity and hepatocellular damage. It was thought that serum neopterin can be used as a complementary marker to follow and manage chronic hepatitis B patients.

We examined the effects of insulin on tetrahydrobiopterin (BH4) synthesis in mouse brain microvascular endothelial cells (MBMECs). Treatment of MBMECs with insulin increased the intracellular BH4 content in a time- and concentration-dependent manner. The insulin-induced increase in BH4 content was inhibited by treatment with 2,4-diamino-6-hydroxypyrimidine, a selective inhibitor of GTP cyclohydrolase I, and Nacetylserotonin, a selective inhibitor of sepiapterin reductase. These findings indicate that insulin stimulates BH4 synthesis in MBMECs through a de novo synthetic pathway of BH4.

Median neopterin concentration in amniotic fluid at delivery was 72 nM which is approximately 10-fold the maternal and fetal serum concentration. A strong correlation existed between neopterin concentrations in amniotic fluid and urine, except an unproportionally high level in amniotic fluid in one case with an intrauterine infection.

In patients with different forms of dementia we compared serum and cerebrospinal fluid concentrations of α-tocopherol (vitamin-E), the major circulating lipid-soluble antioxidant, and neopterin, a product released from monocytic cells upon stimulation with interferon-γ. A significant inverse correlation was found between the concentrations of both compounds in the cerebrospinal fluid. The data point to a role of oxidative stress to reduce antioxidant levels in elderly demented patients with neurodegenerative diseases.