Oxidation Products of Kaempferol by Superoxide Anion Radical

Kaempferol (3,4',5,7-tetrahydroxyflavone) was oxidized by O₂^–to 4-hydroxyphenylglyoxylic acid and phloroglucinolcarboxylicacid as identified by UV spectroscopy and high-performance liquidchromatography. The molar yields of the two compounds on thebasis of kaempferol oxidation were 19% and 21%, respectively,at pH 8. In addition to these two products, a compound whichwas hydrolyzed to 4-hydroxybenzoic acid and an unidentifiedcompound was produced. (Received November 21, 1986; Accepted April 10, 1987)     

Role of N-acetyl-D-galactosamine residue on B151K12-derived T cell-replacing factor (B151-TRF) molecule in B cell-receptor binding and -stimulating activity

The role of sugar moiety on T cell-replacing factor molecule derived from a monoclonal T cell hybridoma B151K12 (B151-TRF) was analyzed with respect to the interaction with receptor on B cells. The induction of B cell differentiation into Ig-secreting cells by B151-TRF was specifically inhibited by addition of N-acetyl-D-galactosamine (GalNAc) to culture. Such inhibition appeared to be attributed to the interference of GalNAc in the interaction of TRF with its receptor, because absorption of TRF activity with B cells was notably inhibited by the presence of GalNAc. To substantiate this point further, we established binding assay of B151-TRF molecule to the receptor on B cells by using 125I-labeled TRF fraction enriched by reversed-phase high-performance liquid chromatography and gel filtration. The results revealed that the binding of 125I-TRF molecule to the B cells was almost completely blocked by GalNAc. Moreover, the existence of GalNAc residue(s) on B151-TRF molecule was evidenced by the facts that 1) the TRF activity was eluted from lectin gels with specificity for GalNAc as revealed by the functional assay, and 2) the 125I-TRF molecule specifically bound to such lectin gels. Thus, the GalNAc residue(s) on B151-TRF molecule plays an important role in binding of TRF molecule to the receptor and in the stimulation of B cells. The molecular properties of B cell-stimulatory B151-TRF and its mode of interaction with corresponding receptor on B cells were discussed in the context of B151-TRF as a glycosylated lymphokine molecule and B151-TRF receptor as a carbohydrate-binding protein (animal lectin).     

Formation of singlet molecular oxygen in illuminated chloroplasts. Effects on photoinactivation and lipid peroxidation

The formation of singlet molecular oxygen (¹O₂) in illuminatedchloroplasts and the effects of ¹O₂ on oxidation or destructionof components and functional integrity of chloroplasts werestudied. The rate of photoreduction of 2,6-dichloroindophenol(DCIP) and the extent of the 515-nm absorbance change were decreasedby light irradiation and by xanthine oxidase treatment. Malondialdehyde(MDA) formation, an indicator of lipid peroxidation, was observedin the light-irradiated chloroplast fragments, but not in thexanthine-xanthine oxidase-treated chloroplast fragments. MDAformation was absent under anaerobic conditions. MDA formation was stimulated when electron transfer on the oxidizingside of photosystem II (or I) was inhibited or inactivated bycarbonylcyanide m-chlorophenylhydrazone (CCCP), Tris-treatment,prolonged illumination, etc. MDA formation was also stimulatedby 3-(3,4-dichlorophenyl)-1, 1-dimethylurea (DCMU) when electrontransfer between water and the reaction center of photosystemII was intact. CCCPor DCMU-stimulated MDA formation was inhibitedby 1,4-diazabicyclo[2.2.2]octane, a quencher of singlet molecularoxygen (¹O₂). DCMU and electron donors for photosystem II, suchas ascorbate, hydroquinone and semicarbazide, inhibited MDAformation by illumination of the Tris-washed or CCCP-poisonedchloroplast fragments. Reduced DCIP, an electron donor for photosystemI, also inhibited MDA formation in the presence of DCMU. These results lead to the conclusion that MDA formation wasinitiated by ¹O₂ formed in illuminated chloroplasts. Of thethree mechanisms discussed for ¹O₂ generation in illuminatedchloroplasts, the formation by the electron transfer reactionbetween superoxide anion radical and the oxidant formed on theoxidizing side of photosystem II (or I) is mostimportant. (Received March 31, 1975; )     

Ia-restricted B-B cell interaction. I. The MHC haplotype of bone marrow cells present during B cell ontogeny dictates the self-recognition specificity of B cells in the polyclonal B cell activation by a B cell differentiation factor, B151-TRF2

We have demonstrated that B cell recognition of Ia molecules is involved in polyclonal B cell differentiation by B151-TRF2. The present study was undertaken to examine the Ia recognition specificity of B151-TRF2-responsive B cells in fully major histocompatibility complex (MHC)-allogeneic P1----P2, semiallogeneic P1----(P1 x P2)F1, and double donor (P1 + P2)----(P1 x P2)F1 and (P1 + P2)----P1 radiation bone marrow chimeras. The B cells from both P1----P2 and P1----(P1 x P2)F1 chimeras could give rise to in vitro immunoglobulin M-producing cells upon stimulation with B151-TRF2 comparable in magnitude to that of normal P1 B cells, and their responses were inhibited by anti-I-AP1 but not by anti-I-AP2 monoclonal antibody even in the presence of mitomycin C-treated T cell-depleted P2 spleen cells as auxiliary cells. In contrast, the B151-TRF2 responses of P1 B cells isolated from both (P1 + P2)----(P1 x P2)F1 and (P1 + P2)----P1 double bone marrow chimeras became sensitive to the inhibition of not only anti-I-AP1 but also anti-I-AP2 monoclonal antibody only when the culture was conducted in the presence of P2 auxiliary cells, demonstrating that they adaptively differentiate to recognize as self-structures allogeneic as well as syngeneic Ia molecules. Moreover, the experiments utilizing B cells from H-2-congenic mice and B cell hybridoma clones as auxiliary cells revealed that B151-TRF2-responsive B cells recognize Ia molecules expressed on B cells. Taken together, these results demonstrate that B151-TRF2-responsive B cells recognize Ia molecules expressed by B cells as self-structures and that their self-recognition specificity is dictated by the MHC haplotype of bone marrow cells present during the B cell ontogeny but not by the MHC haplotype of a radiation-resistant host environment.     

Polyclonal B cell activation by a B cell differentiation factor, B151-TRF2. II. Evidence for interaction of B151-TRF2 with glycoprotein on B cell membrane via recognition of terminal N-acetyl-D-glucosamine residue(s)

We investigated the role of carbohydrates in the interaction of a B cell differentiation factor designated as B151-TRF2 derived from B151K12 T cell hybridoma with the corresponding receptor on B cells. Induction of polyclonal differentiation of unprimed B cells into IgM-secreting cells by B151-TRF2 was specifically inhibited by addition of N-acetyl-D-glucosamine (GlcNAc) but not by structurally unrelated monosaccharides such as D-galactose, D-glucose, and N-acetyl-D-galactosamine (GalNAc). Absorption of B151-TRF2 activity with spleen cells was specifically inhibited by the presence of GlcNAc. These results indicate that GlcNAc residues are involved in the interaction of B151-TRF2 with the receptor on B cells. To gain insight into mechanism by which GlcNAc inhibits B151-TRF2-mediated B cell responses, the existence of GlcNAc residues was examined on the B151-TRF2 molecule and the corresponding receptor on the B cell surface. The results revealed that B151-TRF2 molecule was not bound to various lectin-coupled agarose beads so far tested, suggesting absence of carbohydrate moieties on the B151-TRF2 molecule. By contrast, pretreatment of spleen cells with trypsin or glycosidase mixture abolished their ability to absorb B151-TRF2 activity. Moreover, B151-TRF2-absorbing ability of spleen cells disappeared by the pretreatment with beta-N-acetylglucosaminidase, which cleaves terminal GlcNAc. The fact that pnitrophenyl (PNP)-GlcNAc specifically inhibited such enzyme activity on target cells indicates that terminal GlcNAc on the B cell surface plays a crucial role in the interaction with B151-TRF2 molecule. Interestingly, it was also found that B151-TRF2 activity was trapped and eluted from GlcNAc-coupled agarose beads. Taken collectively, these results strongly suggest that B cell membrane receptors for B151-TRF2 comprise glycoproteins with a terminal GlcNAc residue(s), and that binding of B151-TRF2 with terminal GlcNAc on the receptor is important for the subsequent activation of B cells.     

Identification of two distinct factors, B151-TRF1 and B151-TRF2, inducing differentiation of activated B cells and small resting B cells into antibody-producing cells

We demonstrated previously that cellfree supernatant of the B151K12 T cell hybridoma (B151-CFS) contained T cell-replacing factor (here in after referred to as B151-TRF1) capable of inducing growth and differentiation of antigen-activated B cells into antigen-specific plaque-forming cells (PFC). In the present study, we have identified in B151-CFS another unique lymphokine activity (referred to as B151-TRF2), which induces polyclonal differentiation of unstimulated B cells into IgM-secreting cells without concomitant stimulation of antigen, mitogen, or anti-Ig antibody. The B151-TRF2 activity induced polyclonal IgM PFC responses via the action on surface Ig-positive small resting B cells from normal unprimed mice. This activation was effective across an H-2 barrier, and apparently independent of the presence of T cells and accessory cells. Interestingly, the B151-TRF2 activity notably stimulated B cells of neonatal and mutant DBA/2Ha mice, which are nonresponders to B151-TRF1, whereas it failed to activate the xid B cells from CBA/N mice. To substantiate that B151-TRF1 and B151-TRF2 activities are mediated by mutually distinguishable molecules, an absorption experiment of B151-CFS was performed by utilizing DBA/2Ha B cells which are lacking in B151-TRF1 receptor. It was found that DBA/2Ha B cells could absorb B151-TRF2 activity but not B151-TRF1 activity. In contrast, murine chronic B cell leukemia BCL1 cells, which were shown to differentiate into IgM-secreting cells by stimulation with B151-CFS, selectively removed B151-TRF1 activity but not B151-TRF2 activity. Furthermore, biochemical analysis revealed that the B151-TRF2 was a heat (56 degrees C for 30 min)-sensitive protein with an apparent m.w. of 30,000 by gel filtration, whereas B151-TRF1 was a heat-resistant glycoprotein with m.w. of 50,000. In addition, it was shown that prostaglandin E2 selectively inhibited B151-TRF2-mediated B cell responses. These results demonstrate clearly that B151-TRF1 and B151-TRF2 are distinct B cell differentiation factors involved in the different activation pathways of distinct B cell subpopulations. The immunologic implication of B151-TRF2 activity in B cell differentiation is discussed in comparison with other lymphokines so far reported to activate small resting B cells.     

Spectrophotometric study on the oxidation of rutin by horseradish peroxidase and characteristics of the oxidized products

Rutin (3',4',5,7-tetrahydroxyflavone-3-rutinoside) was oxidized by a horseradish peroxidase-H2O2 system to an ascorbate-reducible product which had an absorption maximum at about 290 nm and a shoulder at about 440 nm at pH 4. At pH 7.8, ascorbate-reducible compounds and sodium hydrosulfite-reducible and -nonreducible compounds were formed by the oxidation. The ascorbate-reducible compounds consisted of at least two components, the absorption bands of which were at 460-480 nm and about 620 nm. The sodium hydrosulfite-reducible compounds also consisted of two components, and one of the components which had an absorption maximum at about 480 nm seems to be formed from the ascorbate-reducible component of an absorption maximum at the blue region by a nonenzymatic reaction. A mixture of oxidized products of rutin formed by tert-butyl hydroperoxide-dependent oxidation was similar to that formed by the enzymatic reaction. It is discussed that the 3'- and 4'-OH groups of rutin were oxidized by the horseradish peroxidase-H2O2 system and that the oxidized product which could be reduced by ascorbate is an o-quinone derivative.     

Piperidine levels in the brain and peripheral organs in rats during cold exposure

Piperidine is one of biogenic amines possessing nicotine-like synaptotropic actions on the nervous systems. Since piperidine produces multiplex pharmacological actions, a role for the amine as a modulator in neuroendocrine as well as neuronal functions has been supposed. In the present study, piperidine levels in the brain and peripheral organs in rats during cold exposure were examined by use of a mass fragmentographic technique and it was found that piperidine concentrations in the brain and peripheral endocrine glands significantly increased at 180 min following exposure to 4°C. The significance of the findings is discussed with respect to the neurohormone-releasing effect of piperidine.     

The clinical significance of murine monoclonal antibody (1H1) prepared against human pancreatic cancer cell line BxPC-3

A new murine monoclonal antibody (1H1) was prepared by immunizing mice i.p. with human pancreatic cancer cell line (BxPC-3). The antibody reacted with 8 of 48 cultured cell lines that were all adenocarcinoma. Thin sections of normal and cancerous tissues were examined by immunoperoxidase staining. Thirty-nine of 48 (81%) pancreatic cancers, 11 of 23 (48%) gastric cancers, 12 of 18 (67%) colorectal cancers, 9 of 19 (48%) breast cancers, 2 of 5 (40%) lung cancers and 2 of 2 (100%) duodenal cancers were stained positively, but 5 islet cell tumors, 3 esophageal cancers and 2 hepatomas were not stained positively. Normal gastro-intestinal tract of adult or fetus was stained weakly or hardly stained. SDS-PAGE showed that 1H1 antigen recognized by 1H1 Mab had a relative molecular weight of over 400 K. Da. Immunoelectron microscopical study has shown that the antigen recognized by 1H1 antibody was localized in the cell membranes of the BxPC-3 cells. 1H1 antigen was found to be present in culture-spent medium of BxPC-3 cells by ELISA. Thus, 1H1 antibody may be useful for early detection of pancreatic cancers.     

Hydrogen peroxide-dependent oxidation of flavonols by intact spinach chloroplasts

Externally added quercetin (100 micromolar) was oxidized by intact spinach chloroplasts at a rate of 30 micromoles per mg chlorophyll per hour in the presence of 100 micromolar H₂O₂. The oxidation rate was increased by about 20% in a hypotonic reaction mixture. The thylakoid fraction also oxidized the flavonol in the presence of H₂O₂, and the rate was about 25% of that by intact chloroplasts. The oxidation of quercetin was inhibited by KCN and NaN₃. Ascorbate, which permeates slowly across chloroplast envelope, only slightly suppressed the initial rate of quercetin oxidation by intact chloroplasts, while the oxidation by ruptured chloroplasts was suppressed by ascorbate by about 60%. Quercetin glycosides, quercitrin and rutin, were also oxidized by chloroplasts in the presence of H₂O₂. These results suggest that flavonols are oxidized by peroxidase-like activity in chloroplasts and that externally added flavonols can permeate into the stroma through the envelope of intact chloroplasts.