Biological activity of 26,26,26,27,27,27-hexafluorinated analogs of vitamin D3 in inhibiting interleukin-2 production by peripheral blood mononuclear cells stimulated by phytohemagglutinin

Vitamin D compounds suppress the production of interleukin-2 (IL-2) by peripheral blood mononuclear cells (PBMCs) stimulated with phytohemagglutinin in a dose-dependent manner. We used this suppression to test 26,26,26,27,27,27-hexafluorinated analogs of vitamin D3 for their immunosuppressive activity in PBMCs. 26,26,26,27,27,27-Hexafluoro-1,25-dihydroxyvitamin D3 and 26,26,26,27,27,27-hexafluoro-1,24-dihydroxyvitamin D3 were approximately 10 times more potent than 1,25-dihydroxyvitamin D3 in suppressing IL-2 production. 26,26,26,27,27,27-Hexafluoro-1-hydroxyvitamin D3 was 20 to 30 times less potent than 1,25-dihydroxyvitamin D3 in causing this effect. The relative biopotency of each vitamin D3 analog toward PBMC proliferation was roughly similar to that toward IL-2 production by PBMCs. Suppression of PBMC proliferation by vitamin D3 analogs seemed to be a secondary effect of their inhibition of IL-2 production.

Biological activity of fluorinated vitamin D analogs at C-26 and C-27 on human promyelocytic leukemia cells, HL-60

Vitamin D compounds added to the culture medium induce HL-60 cells to differentiate into macrophage/monocytes via a receptor mechanism. This system provides a biologically relevant assay for the study of biopotency of vitamin D analogs. Using this system, the biological activity of various fluorinated derivatives of vitamin D3 was compared with that of 1,25-dihydroxyvitamin D3 (1,25-(OH)2D3). As assessed by cell morphology, nitroblue tetrazolium reduction and nonspecific esterase activity, 26,26,26,27,27,27-hexafluoro-1,25-dihydroxyvitamin D3 (26,27-F6-1,25-(OH)2D3) and 26,26,26,27,27,27-hexafluoro-1,24-dihydroxyvitamin D3 (26,27-F6-1,24-(OH)2D3) were about 10 times as potent as 1,25-(OH)2D3 in suppressing HL-60 cell proliferation and inducing cell differentiation. The biological activity of 26,26,26,27,27,27-hexafluoro-1-hydroxyvitamin D3 (26,27-F6-1-OH-D3) was equal to that of 1,25-(OH)2D3 in this system. 1,25-(OH)2D3 and its fluorinated analogs exerted their effects on HL-60 cells in a dose-dependent manner. HL-60 cells have a specific receptor for 1,25-(OH)2D3 with an apparent Kd of 0.25 nM, identical with that of chick intestinal receptor. While the binding affinities of 26,27-F6-1,25-(OH)2D3 and 26,27-F6-1,24-(OH)2D3 for chick intestinal receptor were lower than that of 1,25-(OH)2D3 by factors of 3 and 1.5, respectively, they were as competent as 1,25-(OH)2D3 in binding to HL-60 cell receptor. The ability of 26,27-F6-1-OH-D3 to compete for receptor protein from HL-60 cells and chick intestine was about 1/70 that of 1,25-(OH)2D3. These results indicate that trifluorination of carbons 26 and 27 of vitamin D3 can markedly enhance the effect on HL-60 cells.

Reversible conversion of tyrosine hydroxylase to an inactive form by antipain

Tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of catecholamines, was reversibly inactivated by incubation with antipain, which is known as a microbial protease inhibitor. The inactivation was a time-dependent reaction and it was prominent when the enzyme was assayed at a neutral pH but not when assayed at an acidic pH. The inactivated enzyme was markedly activated by cyclic AMP-dependent protein kinase. Other microbial protease inhibitors such as leupeptin, chymostatin, and pepstatin did not induce such as inactivation of the enzyme.

A case of hyponatremia in panhypopituitarism caused by the primary empty sella syndrome

A 64-year-old woman was admitted for evaluation of hyponatremia. She was maintained on hypertonic saline administration. Without this therapy, the serum Na concentration decreased progressively to 127 mEq/L and the plasma osmolality to 254 mOsm/Kg H2O, on Day 3. At that time, the concentration of antidiuretic hormone (ADH) was as high as 3.5 pg/ml. A skull radiogram revealed an enlarged sella turcica. Computed tomography (CT) revealed a low density in the sella, and magnetic resonance imaging revealed equal intensity of the sella turcica and the cerebrospinal fluid. A diagnosis of empty sella syndrome was made by metrizamide cisternography in conjunction with CT scanning. A diagnosis of panhypopituitarism was made by endocrine function tests. 123I-thyroidal uptake was 6% when her serum TSH was 10.9 microU/ml, suggesting that she might also have primary hypothyroidism. When this patient was given glucocorticoid before levothyroxine replacement, her serum Na concentration rose up to about 140 mEq/L and a normal relationship between her plasma ADH level (2.4 pg/ml) and plasma osmolality (281 mOsm/kg H2O) was restored. Therefore, it was suggested that ADH hypersecretion induced by the glucocorticoid deficiency might in part contribute to the development of hyponatremia. This is the case of primary empty syndrome associated with panhypopituitarism, in whom initial symptom was caused by hyponatremia.

A hereditary dysfibrinogenemia: fibrinogen Awaji

Abnormal function of fibrinogen was observed in a 25-year-old woman with no symptoms attributable to dysfibrinogenemia. Disturbed polymerization of fibrin monomer was identified, but the release of fibrinopeptide from the purified fibrinogen and the cross-linking by factor XIII were normal. Other abnormal findings included a high value of fibrinogen degradation products, rapid mobility on immunoelectrophoresis and abnormal spot of gamma-chain on two-dimensional polyacrylamide gel electrophoresis. Similar abnormalities were also observed among the patient's family members.

Propylthiouracil inducible glutathione transferases. Selective induction of ligandin (glutathione transferase 1-1)

Repeated administration of propylthiouracil (PTU) resulted in an increase in glutathione (GSH) transferases activity in rat liver cytosol toward various substrates except for epoxy(p-nitrophenoxy)propane. The enzyme from rat treated with PTU showed high activity with 1-chloro-2,4-dinitrobenzene (CDNB) and ethacrynic acid. GSH transferases were separated into five forms by CM-Sephadex C-50 column chromatography to detect which isozymes were induced by PTU treatment. Although the activity of the unretained fraction obtained from the column was slightly increased by PTU treatment, the treatment markedly elevated the activity of GSH transferase 1-1. On the other hand, the activities of GSH transferases 1-2, 3-3 and 2-2 were little changed. In addition, an analysis of GSH transferase 1-1 from CM-Sephadex C-50 using SDS-PAGE confirmed that it comprised the 1-1 homodimer. This fraction was then further purified by passing it through a hydroxylapatite column and the partially purified GSH transferase 1-1 from rats treated with PTU was found to have the same characteristics as the control, e.g. the same Km values for GSH and CDNB and the same substrate spectrum. It was concluded that PTU specifically induced GSH transferase 1-1 among the cationic transferases.

Inhibition of hepatic glutathione transferases by propylthiouracil and its metabolites

The effects of propylthiouracil (PTU) and its metabolites on the activity of GSH transferases were examined using rat liver cytosol. PTU inhibited the enzyme activity toward both CDNB and DCNB in a concentration-dependent manner. At the concentration of 10 mM, PTU caused 25% inhibition, which was the maximum effect. PTU derivatives such as propyluracil and thiouracil showed the same effect as the parent compound. On the other hand, S-oxides of PTU such as PTU-SO2 and PTU-SO3, which were chemically synthesized by the oxidation of PTU, were more potent inhibitors of GSH transferases than the parent PTU. A significant inhibition was observed at a concentration of 0.1 mM of PTU S-oxides. At a concentration of 10 mM the S-oxides caused an 80% inhibition of the enzyme activity. PTU inhibited the transferase activity by competing with GSH but the S-oxides of PTU acted by another mechanism. In contrast to the effect on GSH transferases, PTU-SO3 had a weak inhibitory effect on GSH peroxidase activity. Thus, oxidation of PTU leads to products which are potent inhibitors of GSH transferases.

Aspartate aminotransferase of Escherichia coli: nucleotide sequence of the aspC gene

The nucleotide sequence of the aspartate aminotransferase [EC 2.6.1.1] structural gene, aspC, of Escherichia coli K-12 was determined. The coding region of the aspC gene contained 1,188 nucleotide residues and encoded 396 amino acid residues. The amino acid sequence deduced from the nucleotide sequence agreed perfectly with that of the protein recently determined for the aspartate aminotransferase of E. coli B (Kondo, K., Wakabayashi, S., Yagi, T., & Kagamiyama, H. (1984) Biochem. Biophys. Res. Commun. 122, 62-67).

A new mechanism for regulation of tyrosine 3-monooxygenase by end product and cyclic AMP-dependent protein kinase

Tyrosine 3-monooxygenase activity of the crude extract from rat striatum had a sharp pH optimum at pH 5.4 and showed almost no activity at or above pH 7. When the crude extract was partially purified by pH precipitation and chromatography on DEAE-cellulose, the enzyme showed a high activity in the pH range of 5.8 to 7.4. Incubation of the partially purified enzyme with catecholamines such as dopamine, norepinephrine, and epinephrine resulted in a remarkable decrease in the enzyme activity, as assayed at a neutral pH. This suppression of the enzyme activity by catecholamines differed from the well-known feedback inhibition which is competitive with respect to the pterin cofactor; the former occurred at a very much lower concentration of catecholamines even in the presence of a near-saturating concentration of a pterin cofactor, and the former was a time-dependent reaction. The enzyme, the activity of which had been suppressed by the incubation with dopamine, was remarkably activated by the incubation with the catalytic subunit of cyclic AMP-dependent protein kinase in the presence of an ATP-generating system. These results suggest that the activity of tyrosine 3-monooxygenase may be suppressed by its end products in a normal state and it may be stimulated by cyclic AMP-dependent protein kinase as occasion demands.

A comparative study of tyrosine 3-monooxygenase from rat adrenal and brainstem

Spleen cells from a CBF1 (BALB/c X C57BL/6) mouse immunized with rat tyrosine 3-monooxygenase were fused with NS-1 mouse myeloma cells. From 188 hybrid cells, 2 stable clones secreting anti-tyrosine 3-monooxygenase antibody were obtained. Antibody from one clone was coupled to CNBr-activated Sepharose 4B and the monoclonal antibody-Sepharose was shown to be very useful for isolating rat tyrosine 3-monooxygenase from crude preparations. Analyses by monoclonal antibody chromatography followed by SDS-polyacrylamide gel electrophoresis and by gel filtration revealed that tyrosine 3-monooxygenases from nerve cell bodies, nerve terminals, and adrenal medullae were indistinguishable with respect to their molecular structures. However, there were serious differences in the catalytic properties between the enzymes from the brain tissues and adrenal medullae, although there appeared to be no significant difference between the enzymes from nerve cell bodies and nerve terminals. The possibility that the activity of the enzyme may be strongly suppressed especially at the physiological pH in brain tissues is also discussed.

Urinary excretion rate of antithrombin III related antigen in cerebral stroke

The urinary excretion rate of antithrombin III related antigen (AT III RA) was examined in cerebral stroke. The excretion rate of AT III RA in cerebral hemorrhage (CH) was 12.33 +/- 1.61 X 10(-4) ml/min. The patients with CH were further classified into two groups: in group CH-I, whose consciousness state was stupor or further deteriorated including coma on admission, the excretion rate of AT III RA was 18.08 +/- 2.50 X 10(-4) ml/min. In group CH-II, whose consciousness state was clear on admission, the excretion rate of AT III RA was significantly lower than that in CH-I (6.20 +/- 1.56 X 10(-4) ml/min). The excretion rate in cerebral thrombosis (CT) was 1.96 +/- 0.25 X 10(-4) ml/min, which was significantly lower than that in CH. The excretion rate of AT III RA in both CH and CT was significantly higher than that in the healthy control group (0.29 +/- 0.04 X 10(-4) ml/min). Thus, AT III may change dynamically in cerebral stroke.

Role of calmodulin in neurotransmitter synthesis

Tyrosine 3-monooxygenase (EC 1.14.16.2) and tryptophan 5-monooxygenase (EC 1.14.16.4) are generally believed to be the rate-limiting enzymes in the biosynthesis of the neurotransmitters, catecholamines and serotonin, respectively, and therefore the regulation of their activities is of particular importance. At least three calmodulin-dependent protein kinases differed in their molecular weights and substrate specificities, designated I, II, and III in the order of decreasing molecular weight, in rat brain cytosol. Among them, calmodulin-dependent protein kinase II with a molecular weight of about 540,000 appeared to occur only in the nervous tissues. Kinase II was found, on the one hand, to phosphorylate tyrosine 3-monooxygenase and tryptophan 5-monooxygenase, leading to the activation of these monooxygenases in the presence of activator protein and, on the other hand, to phosphorylate tubulin and microtubule-associated protein 2, which results in disassembly of the microtubules that had been assembled. These results suggest the possibility that both the secretion and biosynthesis of monoamine neurotransmitters stimulated by Ca2+ influx in the nervous system may be regulated by calmodulin-dependent protein kinase II via the phosphorylation of microtubule proteins and the phosphorylation of the monooxygenases that are the rate-limiting enzymes in the biosynthesis of the neurotransmitters.

The activity of tyrosine 3-monooxygenase is usually suppressed by an endogenous factor in brain

Tyrosine 3-monooxygenase activity of the crude extract from rat striatum had a sharp pH optimum at pH 5.6 and showed almost no activity at pH 7 and higher. When the crude extract was adjusted to pH 5.2, the resulting precipitate showed high activity in the pH range of 6 to 7.5. Incubation of the acid-precipitated fraction with the acid-soluble fraction resulted in a remarkable decrease in the enzyme activity, as assayed at a neutral pH. These findings suggest that there is an endogenous factor inhibiting the activity of tyrosine 3-monooxygenase in rat brain.

Purification and characterization of rat dopamine beta-monooxygenase and monoclonal antibodies to the enzyme

Dopamine beta-monooxygenase was extensively purified from rat adrenal. The specific activity of the final preparation was approx. 1500 nmol/min per mg protein, which was much higher than the highest yet reported. As judged by gel filtration on Ultrogel AcA22, SDS-polyacrylamide gel electrophoresis, and cross-linking studies, the enzyme appeared to be composed of four identical subunits, each possessing a molecular weight of 88 000. The isoelectric point of the enzyme was estimated to be pH 6.6 in the presence of 8 M urea. Spleen cells from BALB/c mice immunized with rat dopamine beta-monooxygenase were fused to P3-X63-Ag8-653 mouse myeloma cells. From 55 hybrid cells, 10 stable clones secreting anti-dopamine beta-monooxygenase antibody were obtained. Antibody from one clone was coupled to CNBr-activated Sepharose 4B and the monoclonal antibody-Sepharose was shown to be very useful to isolate rat dopamine beta-monooxygenase from crude preparations.