Antigenicity of sulfanilamide and its metabolites using fluorescent-labelled compounds

In order to clarify the onset mechanisms of drug-induced allergies, three fluorescent-labelled compounds were synthesized by subjecting sulfanilamide (SA), a base compound for sulfonamides, and its active metabolites, i.e. sulfanilamide hydroxylamine and sulfanilamide nitroso, to dansylation using dansylchloride. In other words, 5-dimethylamino-N-(4-aminobenzyl)-naphthalenesulfonamide (DNS-4ABA), 5-dimethylamino-N-(4-hydroxylaminobenzyl)-1-naphthalenesulfonamide (DNS-4HABA) and 5-dimethylamino-N-(4-nitrosobenzyl)-1-naphthalenesulfonamide (DNS-4NSBA) were synthesized as model haptens. When analysed by HPLC, a conjugate of DNS-4HABA and glutathione (GSH) with nucleophilic amino acids had two peaks (P-1 and P-2). FAB-MS and 1H-NMR revealed that the DNS-4HABA-GSH conjugate consisted of sulphinamide and semimercaptal. The reactivity of GSH to DNS-4ABA, DNS-4HABA and DNS-4NSBA was quantified by HPLC using an oxidization system (horseradish peroxidase/H2O2). The results show that production of DNS-4NSBA-GSH-conjugate was four to eight times higher than that of DNS-4HABA-GSH conjugate, but that DNS-4ABA did not bind with GSH. Skin reactions were assessed using guinea pigs, and strong delayed erythema was seen with DNS-4NSBA, which bound most strongly with GSH, whereas weak delayed erythema was seen with DNS-4ABA, which did not bind with GSH. This suggests a correlation between GSH conjugate production and skin reactions. DNS-4HABA enzymatically bound with proteins in rat and guinea pig liver cytosol and microsomal fractions. The proteins that bound to DNS-4HABA were purified by HPLC and then subjected to N-terminal amino acid analysis. Ubiquitin (10 kDa) and fatty acid binding protein (30 kDa) were detected in the rat liver cytosol fraction; retinol-dehydrogenase (35 kDa) in the rat microsomal fraction; and glutathione-S-transferase B (mmu) (25 kDa) in the guinea pig liver cytosol fraction. When DNS-4HABA or DNS-4NSBA binds to proteins that play important roles in the body, unexpected adverse reactions may occur. Furthermore, by utilizing our technique using model compounds, it may be possible to identify the carrier proteins of various compounds, including pharmaceutical agents.

Plasminogen activator inhibitor-1 aids nerve growth factor-induced differentiation and survival of pheochromocytoma cells by activating both the extracellular signal-regulated kinase and c-Jun pathways

Astrocytes are thought to be critical to neurons' surviving damage caused by ischemic stroke or other injury. Plasminogen activator inhibitor-1 is one of the active soluble factors released by astrocytes and regulates plasminogen activator-plasmin proteolytic sequence in the CNS as a serpin. In this study, we show that plasminogen activator inhibitor-1 can promote neurite outgrowth and survival of rat pheochromocytoma cells in serum-deprived conditions, and that this neuroprotective activity is correlated with enhanced activation of both extracellular signal-regulated kinases following a direct phosphorylation of nerve growth factor receptor, Trk A, and of c-Jun. Our results suggest that plasminogen activator inhibitor-1 can act as a neurotrophic factor, protecting neurons from serum deprivation-induced neuron death not only by compensating for nerve growth factor functions, but also by activating the c-Jun/activating protein-1 pathway.

Cloning and characterization of the CYP2D1-binding protein, retinol dehydrogenase

A CYP2D1-binding protein, 29 k-protein (p29), has been isolated and its N-terminal amino acid sequence has been reported (Ohishi et al. (1993) Biochim. Biophys. Acta 1158, 227-236). In this study, p29 cDNA was isolated by PCR with oligonucleotide probes designed from the N-terminal amino acid sequence and p29 was found to be a microsomal retinol dehydrogenase, a member of the short-chain alcohol dehydrogenase family which metabolize hydroxysteroids and prostaglandins. CYP2D1 and p29 were expressed in Saccharomyces cerevisiae to characterize these proteins. CYP2D1 had an absorption maximum at 448 nm in a CO-reduced form. Expressed p29 in yeast cells was detected with anti-p29 antibody. Solubilized CYP2D1 and p29 from yeast microsomes were mixed and applied to an anti-CYP2D1 antibody-binding column. Both proteins were retained in the column and eluted with glycine buffer (pH 2.8). However, when applied alone, p29 was not retained in the column. The findings indicated that CYP2D1 bound tightly with p29. Catalytic activities of p29 expressed in yeast were investigated. p29 had retinal reductase activity in the presence of NADPH. Addition of CYP2D1 and NADPH-P450 reductase increased the retinal reductase activity of p29. These findings suggest that the complex of CYP2D1, p29, and NADPH-P450 reductase has an important role in the metabolism of retinoids.

Studies of paracetamol/phenacetin toxicity: isolation and characterization of p-aminophenol-glutathione conjugate

1. p-Aminophenol, a minor metabolite of phenacetin, is a potent nephrotoxic agent. 2. We have examined the binding of p-aminophenol to glutathione (GSH), a model amino acid, in the presence of horseradish peroxidase, which catalyses one electron oxidation. 3. The reaction product was purified by preparative h.p.l.c., and its structure was determined by FAB mass spectrometry and 1H-n.m.r. to be a p-aminophenol-GSH conjugate. The conjugate was formed between the ortho carbon of the amino group of p-aminophenol and the SH group of GSH. 4. It was confirmed by h.p.l.c. and 1H-n.m.r. that formation of the conjugate was catalysed in vitro by rat liver microsomes and cumene hydroperoxide.

Metabolism and nephrotoxicity of phenacetin and sulfanilamide

The mechanisms of renal damage produced by sulfanilamide and phenacetin were studied. N-Hydroxyphenacetin, 4-hydroxylaminobenzenesulfonamide (4-HABSA) and p-aminophenol were established to be nephrotoxic metabolites. As well as N-hydroxylase activity of sulfanilamide, that of phenacetin in kidney microsomes of rats was increased about 4 times by pretreatment with 3, 4, 5, 3', 4'-pentachlorobiphenyl (PenCB) which is a potent inducer of cytochrome P-448. Parallel to this enzyme induction, pretreatment with PenCB enhanced the nephrotoxicity of phenacetin and sulfanilamide in rats. On the other hand, the formation of p-aminophenol from phenacetin was also confirmed in rat kidney in vitro. These results suggested that 4-HABSA, N-hydroxyphenacetin and p-aminophenol formed in kidney play an important role in the renal damage produced by sulfanilamide and phenacetin.

Enhancement of sulfanilamide N4-hydroxylase activity in kidney and liver microsomes of rats by pretreatment with 3-methylcholanthrene type-polychlorinated biphenyl

N4-Hydroxylation of sulfanilamide was studied with kidney and liver microsomes of rats by means of high performance liquid chromatography. In kidney microsomes, both contents of cytochrome P-450 (448) and activity of N4-hydroxylase were markedly increased by pretreatment with 3,4,5,3',4'-pentachlorobiphenyl (PenCB) (about 4 times), although neither one was increased by 3-methylcholanthrene (3-MC) and phenobarbital (PB) pretreatments. In liver microsomes, on the other hand, both N4-hydroxylase activity and cytochrome P-450 (448) contents were increased by either PenCB or 3-MC pretreatment, whereas by PB pretreatment, N4-hydroxylase activity was not changed although cytochrome P-450 contents was increased 2-fold.

Positive skin reaction induced by 4,4'-azoxybenzenedisulfonamide in relationship to the sulfanilamide allergy

All guinea pigs sensitized to sulfanilamide or 4-hydroxylaminobenzenesulfonamide in the absence of ultraviolet irradiation exhibited positive skin reactions to 4,4'-azoxybenzenedisulfonamide, 4-nitrosobenzenesulfonamide, and 4-hydroxylaminobenzenesulfonamide.