Induction of GTP-cyclohydrolase I mRNA expression by lectin activation and interferon-gamma treatment in human cells associated with the immune response

The development of tetrahydrobiopterin synthesis during lectin stimulation of resting human T lymphocytes (Kerler et al. [1989] FEBS Lett., 250:622-624), the interferon-gamma induced neopterin production by human monocytes/macrophages (Huber et al. [1984] J. Exp. Med., 160:310-316), and the control of tetrahydrobiopterin synthesis in activated T cells by the synergistic action of interferon-gamma and interleukin 2 (Ziegler et al. [1990] J. Biol. Chem. 265:17026-17030) were previously explained by modulation of the apparent GTP-cyclohydrolase I activation. In this study we demonstrate that increases in GTP-cyclohydrolase I activity which occur after lectin induction and after cytokine treatment correlate with increased steady state mRNA levels specific for this enzyme. The enhancement of interferon-gamma induced enzyme activity in primed T cells by interleukin 2 also corresponds to further increases in mRNA expression. The steady state GTP-cyclohydrolase I mRNA levels in primed T cells, however, do not correlate with the steep decline which follows the culmination of enzyme activity 44 hours after treatment. This indicates that the down-regulation of apparent GTP-cyclohydrolase I activity is caused by posttranslational modification of the protein.

Detection of a novel sepiapterin reductase mRNA: assay of mRNA in various cells and tissues of various species

Fragments of cDNA coding for rat, murine, and human sepiapterin reductase (SR) were amplified by PCR via primer positioning close to the reported 3'-end of the coding region in the rat enzyme. They were sequenced and used as probes for mRNA detection. Northern blot analysis detected two mRNA species for SR. Their sizes were 1.3 and 2.1 kb for rat, 1.3 and 2.3 kb for mouse, and 1.6 and 2.1 kb for human cell lines. Comparison of rat cell lines and rat tissues indicated that in tissues only the 1.3-kb species is present. Washing of the Northern blots under different stringency conditions indicated a more stable interaction of the 1.3-kb mRNA species with the cDNA probe as compared to the 2.3-kb species. The 1.3-kb species corresponds to the reported 28.2-kDa molecular mass of rat SR monomer. SR mRNA expression is absent in the human NK-like cell line YT and in the murine erythroleukemia subclone B8/3, which both lack SR activity. Moreover, the relative mRNA expression correlates with the enzymatic activities of different cell lines within the same species. This indicates that SR activity is regulated by its steady state mRNA levels.

Species and tissue specificity of mammalian GTP cyclohydrolase I messenger RNA

Northern blot analysis of rat RNA from cell lines and isolated organs with a specific rat cDNA probe detected two GTP cyclohydrolase I mRNA species of approx. 1.4 and 3.6 kb. The ratio between these two species varies between 0.6 and 2.4 in different rat organs. Using primers derived from highly conserved regions in the rat and Escherichia coli cDNA sequences a human GTP cyclohydrolase I probe was obtained by means of reverse transcription and PCR (polymerase chain reaction). The human PCR product consisting of 555 bp was cloned and sequenced. It shows a 92% identity with the published sequence of the rat gene. The analysis of various human cell lines with this specific probe shows only one species of GTP cyclohydrolase I mRNA with an approximate size of 3.6 kb.

[Results of electroconvulsive therapy in restrictive indications. A retrospective study of 15 years]

In Tübingen ECT is restricted to severely ill patients who do not respond to other somatic therapies; especially to patients with endogenous depression and pernicious catatonia. Between 1976 and 1990, 45 patients were treated with ECT, of whom 22 suffered from endogenous depression and 10 from pernicious catatonia. Thirteen patients with other diagnoses (schizophrenic and schizoaffective psychoses, borderline schizophrenia and obsessive-compulsive disorder) were treated with ECT for severe depressive states after failure of psychopharmacological therapy. A positive therapeutic response to ECT was observed in 46% of patients with endogenous depression and in all 10 with pernicious catatonia. In the patients with schizophrenia and schizoaffective psychosis, borderline schizophrenia and obsessive-compulsive disorder, an amelioration of the depressive or anxiety syndrome was observed only in individual cases. Side effects of ECT were transit syndromes (20%), reversible amnestic syndromes (20%) and cardiac arrhythmias (6%). According to our results, ECT is highly effective in therapy-resistant endogenous depression and pernicious catatonia, and therefore remains a necessary part of psychiatric therapy.

Control of cell-cycle-associated tetrahydrobiopterin synthesis in rat thymocytes

The cell-cycle progression of rat thymocytes from G0 through G1 to DNA synthesis is associated with a transient synthesis of H4biopterin, the concentration of which reaches a maximum at the time of S-phase entry and then decreases. This synthesis of H4biopterin is controlled by the specific activity of GTP cyclohydrolase I, which peaks in G1/S cells. In contrast, the catalytic activity of sepiapterin reductase remains constant throughout the cell-cycle. At G0 the steady state mRNA levels specific for GTP cyclohydrolase I and sepiapterin reductase, respectively, are below the limits of detection. Both accumulate as the thymocytes progress through the cell-cycle but lack cyclic down regulation. The data indicate that the variations in H4biopterin synthesis during the cell-cycle are caused by growth regulated increase in GTP cyclohydrolase I mRNA expression, with subsequent post-translational inactivation. This latter is likely due to the degree of enzyme phosphorylation.

T-wave response in cervical root lesions

T-wave responses of biceps and triceps brachii muscles were recorded electrophysiologically from 31 normal subjects and 15 patients with unilateral lesions of the cervical C6 or C7 roots. Pathological T-wave responses were found in 11 (73%) patients. Patients with radiological correlate showed electromyographic (EMG) pathology in 60% but a pathological T-wave response in 90%. All patients with radiological correlate also showed pathological electrophysiological tests (EMG or T-wave responses). Electrophysiological measurement of the T-wave response appears to be a potentially useful tool in the diagnosis of cervical radiculopathies.

Control of pteridine biosynthesis in the natural killer-like cell line YT

The natural killer-like cell line YT constitutively expresses GTP-cyclohydrolase activity whereas 6-pyruvoyltetrahydropterin synthase and sepiapterin reductase are absent. The product, dihydroneopterin triphosphate, is dephosphorylated and oxidized causing neopterin to accumulate in the cells. The activities of the H4biopterin synthesizing enzymes are not controlled by IFN-gamma or the synergistic action of both IFN-gamma and IL-2 as has been shown for monocytes/macrophages (Huber C. et al. (1984) J. Exp. Med. 160, 310) and CD4+ T cells, respectively (Ziegler I. et al. (1990) J. Biol. Chem. 265, 17026). Sepiapterin reductase specifically is induced by incubation of the cells with sepiapterin, leaving GTP-cyclohydrolase, 6-pyruvoyltetrahydropterin synthase and other enzymes related to pteridine metabolism (dihydropteridine reductase, dihydrofolate reductase) unaffected. The data indicate that H4biopterin synthesis is individually regulated in the diverse cellular components of the immune system.

The use of protease inhibitors in experimental allergic neuritis

In experimental allergic neuritis (EAN) break-down of myelin is attributed to macrophages, which among other factors contain and secrete proteases. In vitro studies have shown that cathepsin D, an acidic aspartyl endopeptidase, and plasmin can degrade myelin proteins. In order to elucidate a potential therapeutic effect of protease inhibitors we treated Lewis rats, immunized with bovine peripheral nervous system myelin, with epsilon-amino-caproic acid (EACA) or pepstatin. EACA or pepstatin was administered twice daily by intraperitoneal injection beginning on day 6 postimmunization or from the onset of disease (on day 12) through day 24. Compared to saline-treated controls, animals treated with either of the inhibitors showed delayed development of clinical signs and electrophysiological abnormalities. Maximal severity and the further course of disease, however, were not different in control and treated groups. Immunohistological evaluation of sciatic nerve specimens on day 24 postimmunization showed equal numbers of cells positive for ED1 (macrophages) and cathepsin D in all animal groups. There was also no difference in the spontaneous proteolytic activity of the sciatic nerve homogenates at pH 2.8, 5.0, and 7.4. Incubation of the homogenates with pepstatin, however, significantly reduced proteolytic activity at pH 2.8 and 5.0, while EACA had no effect at any pH tested. These results imply that treatment to limit the infiltration of cathepsin D-positive cells or to reduce the induction or activity of cathepsin D may provide a therapeutic avenue for treating inflammatory demyelination of the peripheral nervous system.

Control of tetrahydrobiopterin synthesis in T lymphocytes by synergistic action of interferon-gamma and interleukin-2

The control of (6R)-5,6,7,8-tetrahydrobiopterin (H4biopterin) synthesis in primed T cells was analyzed by using the human T cell leukemia virus type I (HTLV-I)-transformed T cell line MT-2. In contrast to the slowly progressing induction of H4biopterin synthesis during activation of resting T cells, it is completed during a 59-h period and is directed by a synergism of interferon-gamma (IFN-gamma) and interleukin-2 (IL-2). Both GTP cyclohydrolase and (6R)-(1',2'-dioxopropyl)-5,6,7,8-tetrahydropterin synthase activities are induced by IFN-gamma. They are further enhanced by combined treatment with IL-2, which per se is ineffective. Furthermore, the combined treatment synchronizes the time periods of both maximum activities, now extending from 33 to 44 h. This period correlates with high cellular H4biopterin levels. It is preceded by a fast and transient period of H4biopterin increase which depends on the synergistic action of both IFN-gamma and IL-2. It coincides with a transient increase in sepiapterin reductase activity. In contrast to MT-2 cells, HTLV-I-transformed HUT 102 cells constitutively secrete IFN-gamma and express IFN-gamma mRNA. The accumulation of H4biopterin is suppressed by anti-IFN-gamma polyclonal antibody and correlates with constitutive expression of all H4 biopterin-synthesizing enzymes.

Proteolysis of peripheral nerve myelin in acute experimental allergic neuritis

Proteolysis of peripheral nerve myelin was studied in rats with experimental allergic neuritis (EAN). In vitro measurements using rat sciatic nerve homogenate and denatured bovine myelin as a substrate showed two myelin specific enzyme activities at pH 3.8 (inhibited by pepstatin) and pH 5.8 (inhibited by PMSF) in the normal rat and newly appearing activities at pH 2.8 (inhibited by pepstatin) and pH 5.0 (not characterized) in the EAN rat. In EAN the proteolytic activity was not restricted to myelin substrate but degraded total sciatic nerve protein as well. Endogenous sciatic nerve protease at pH 5.8 did not significantly change in activity during the course of disease. On the contrary, activity of acid protease at pH 2.8 corresponded well to the disease. Myelin degradation in EAN, therefore, appears to be mainly due to exogenous non-tissue protease.

The lumazine synthase-riboflavin synthase complex of Bacillus subtilis. Crystallization of reconstituted icosahedral beta-subunit capsids

The lumazine synthase-riboflavin synthase complex (heavy riboflavin synthase) of Bacillus subtilis consists of an icosahedral capsid of 60 beta-subunits containing a core of three alpha-subunits. The enzyme has been purified from the derepressed mutant H 94 of B. subtilis by a novel efficient procedure using column chromatography and preparative crystallization. Beta-Subunits were isolated after dissociation of the enzyme at pH 8.0. Ligand-driven renaturation of beta-subunits yields hollow icosahedral beta 60 capsids which could be crystallized in 1.55 M phosphate, pH 8.7, in three different modifications. A monoclinic modification belongs to space group C2 with unit cell dimensions of a = 235.5, b = 191.2, and c = 165.4 A and alpha = gamma = 90 degrees and beta = 134.4 degrees. The crystals contain two hollow beta 60 particles/unit cell and diffract to approximately 2.8-A resolution. A hexagonal modification has the space group P6(3)22 with unit cell dimensions of a = b = 157.2 and c = 300.8 A and alpha = beta = 90 degrees and gamma = 120 degrees. These cell parameters are similar to the dimensions of hexagonal crystals of native heavy riboflavin synthase (alpha 3 beta 60). A second hexagonal modification shows unit cell parameters of a = b = 156.3 and c = 622.6 A and alpha = beta = 90 degrees and gamma = 120 degrees. The space group of this modification could not be determined unambiguously.

Prednisolone therapy of experimental allergic neuritis in Lewis rats does not induce relapsing or chronic disease

The effects of therapeutic prednisolone treatment on experimental allergic neuritis (EAN) in Lewis rats were evaluated in a controlled clinical and electrophysiological study. Since steroid therapy has been suspected to cause relapsing or chronic disease, monitoring was extended over 200 days. Short-term steroid treatment (5 days of 15 mg/kg prednisolone, n = 8) with sudden steroid withdrawal was compared with long-term application (30 days, beginning at 7.5 mg/kg) in descending dosage (n = 8). The experiment included saline-injected controls (n = 8) and controls for stress possibly exerted by the handling of the animals. Treatment was begun at the onset of clinical signs. The clinical and electrophysiological data indicated that deterioration, recovery and mild (insignificant) relapse (after day 30 and day 108) occurred in all groups at the same time. Both steroid application schemes significantly (p less than 0.03) attenuated the severity and shortened the duration of EAN. Relapse was not aggravated after steroid treatment. The clinical course and electrophysiological findings were unaltered by the experimental procedures and by mild experimental stress.

Riboflavin synthases of Bacillus subtilis. Purification and amino acid sequence of the alpha subunit

Bacillus subtilis has two different riboflavin synthases characterized by the subunit structures alpha3 (light enzyme) and alpha3beta60 (heavy enzyme). The light enzyme was purified by a novel procedure with increased yield and excellent reproducibility. The proposed trimer structure was confirmed by cross-linking experiments with dimethyl suberimidate. Fragments of alpha subunits were prepared by cleavage with cyanogen bromide, trypsin, protease Lys-C, and Staphylococcus aureus protease V8, respectively. Sequences were determined by automated liquid or gas phase Edman degradation. The complete sequence (202 amino acids) was established by direct sequencing of the N terminus and sequencing of overlapping peptides. The sequence shows marked internal homology between the NH2-terminal and COOH-terminal half encompassing 26 identical positions and 23 conservative replacements. This suggests that the protomer forms two structurally similar domains. Since it is known that the enzyme has two binding sites per subunit for the substrate 6,7-dimethyl-8-ribityllumazine, it appears likely that each of the homologous protein domains provides one binding site. The stereochemical features of the enzyme mechanism and the structural relation of the alpha trimer to the beta60 capsid of heavy riboflavin synthase suggest that the six domains corresponding to the alpha subunit trimer are related by pseudo 32 symmetry.

Biochemical and developmental features of experimental phenylketonuria induced by L-ethionine in suckling rats

Suckling rats were injected subcutaneously with doses of L-ethionine (0.1 mumole/g body wt) at intervals of 12 hr. In the latter group, phenylalanine hydroxylase was effectively inhibited in vivo resulting in hyperphenylalaninemia and phenylketonuria. Due to the well-known sex-specific differences in L-ethionine metabolism female rats were much more affected by chronic administration of L-ethionine. The underlying mechanism of enzyme inhibition by ethionine could be disturbed protein synthesis and impaired protein phosphorylation, which was suggested by pronounced decreases in ATP content in liver. In the high dosage group depletions mainly of the branched-chain amino acids and lysine occurred in serum and brain, whereas the concentrations of methionine and tryptophan were increased. Tyrosine tended to be decreased in the course of hyperphenylalaninemia. Hyperphenylalaninemia and other resulting amino acid imbalances obviously impaired brain development during the early postnatal period. Concomitantly with reductions in protein concentrations, the activity of cathepsin D, a major intralysosomal acid proteinase, was increased in brain, suggesting also higher protein catabolism in brain. Side effects of this treatment, however, were higher mortality, loss of body weight, and a general impression of delayed development, resembling a state of undernutrition to some extent. These obvious side effects of ethionine limit the usefulness of ethionine as a suitable model for classic phenylketonuria in suckling rats.

Neuroleptically induced dystonia in Huntington's disease: a case report

A patient with Huntington's disease developed acute dystonia whilst treated with tiapride. Sulpiride and tetrabenazine also induced dystonia. The anticholinergic biperiden depressed the syndrome but worsened psychopathology. Finally a combination of tetrabenazine and clozapine was successful in treatment of both chorea and dystonia. According to this observation, acute dystonia may occur in Huntington's disease as a consequence of neuroleptic treatment.