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Noncirrhotic portal hypertension in association with juvenile nephropathic cystinosis: case presentation and review of the literature.

We report a case of portal hypertension and oesophageal varices arising in an 18-year-old female renal transplant recipient with juvenile nephropathic cystinosis diagnosed at 6 years of age. The patient had a history of poor compliance with her prescribed cysteamine therapy. Routine examination revealed normal liver function without hepatomegaly but asymptomatic splenomegaly. An abdominal ultrasound suggested mild oesophageal varices, confirmed later on endoscopy. A liver biopsy revealed an abundance of cystine crystals within the hepatic Kupffer cells, with preserved hepatic architecture. Although the pathophysiology of this rare complication is unclear, in the absence of other aetiologies the likely cause is the patient's poorly controlled cystinosis. As cystinotic patients live longer with improved renal transplant management and cysteamine therapy, it is of interest to characterize the long-term course of the illness after renal transplantation. An understanding of the pathophysiology of hepatic dysfunction will be required to manage this potential late complication of the disease.

Adult↗

A possible prebiotic synthesis of pantetheine, a precursor to coenzyme A.

The involvement of coenzyme A in many enzyme reactions suggests that it acted in this capacity very early in the development of life on Earth. Particularly relevant in this regard is its role in the activation of amino acids and hydroxy acids in the biosynthesis of some peptide antibiotics--a mechanism of peptide synthesis that forms the basis for the proposal that a thioester world could have preceded the RNA world. The components of coenzyme A have been shown to be probable prebiotic compounds: beta-alanine, pantoyl lactone and cysteamine and possibly adenosine. We show here that the pantetheine moiety of coenzyme A (which also occurs in a number of enzymes) can be synthesized in yields of several per cent by heating pantoyl lactone, beta-alanine and cysteamine at temperatures as low as 40 degrees C. These components are extremely soluble and so would have been preferentially concentrated in evaporating bodies of water, for example on beaches and at lagoon margins. Our results show that amide bonds can be formed at temperatures as low as 40 degrees C, and provide circumstantial support for the suggestion that pantetheine and coenzyme A were important in the earliest metabolic systems.

4-Butyrolactone↗

Sulphydryls, ascorbate and oxygen as modifiers of the toxicity and metabolism of misonidazole in vitro.

Equimolar concentrations of cysteamine and reduced glutathione protected against the cytotoxicity of 5 mM misonidazole (MISO), whereas 5mM ascorbate enhanced its toxicity to hypoxic CHO and HeLa cells in vitro. Protection (reappearance of a shoulder region) could also be seen when cysteamine was added at later incubation times. These changes in toxicity were accompanied by changes in drug metabolism, as evidenced by radiochromatograms of cell extracts obtained after treatment with 14C-labelled MISO. In contrast, radiochromatograms obtained from cells treated with toxic levels of MISO (75 mM) under aerobic conditions indicated no drug metabolism. Both toxicity and drug metabolism could be immediately halted by introducing O2 during hypoxic exposure to MISO. These observations are discussed in terms of a possible model for the metabolism-mediated toxicity of MISO and the roles which sulphydryls and O2 may play.

Animals↗

Review article: transcription factors and growth factors in ulcer healing.

This review is focused on recent investigations demonstrating a pharmacological and pathophysiologic role in gastroduodenal ulceration for growth factors such as basic fibroblast growth factor (bFGF), platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF), as well as for transcription factors. Our experiments revealed accelerated healing, without decreased gastric acid secretion, of chronic cysteamine-induced duodenal ulcers in rats treated daily for 3 weeks with intragastric administration of bFGF, PDGF or VEGF. Our recent studies also indicate a pathophysiological role of endogenous growth factors in the natural history of experimental duodenal ulcer development and healing. More recently, we investigated the genetic regulation of these growth factors in experimental duodenal ulceration. Since gene expression is most effectively controlled by transcription factors, proteins that bind to cis-acting elements of DNA and guide the binding of polymerase II to start the transcription of specific mRNA, we tested the hypothesis that the expression of IEGs and their transcription factor products, such as Egr-1 and Sp1, might precede the increased synthesis of bFGF, PDGF and VEGF in duodenal ulcer healing. Indeed, the duodenal ulcerogen cysteamine, but not its nonulcerogen and toxic analogue ethanolamine, rapidly increased duodenal (but not gastric) mucosal levels of ET-1, which was followed by enhanced expression of Egr-1 and a decrease in Sp1 in the preulcerogenic stage of duodenal ulceration. These changes in levels of ET-1 and expression of transcription factors were also accompanied by increased expression of the CDK inhibitor p21. Thus, not only growth factors such as bFGF, PDGF and VEGF, but also transcription factors such as Egr-1 and Sp1 and the cell cycle regulator p21, may play a role in the natural history of experimental duodenal ulceration.

Animals↗

Duodenal ulcer prevalence: experimental evidence for the possible role of dietary lipids.

BACKGROUND AND AIMS: Mapping the geographical distribution of duodenal ulcer in relation to staple diets, and experiments on animal peptic ulcer models suggested that the lipid fraction in certain foodstuffs had a protective effect which was most marked in the lipid obtained from Horse gram (Dolichos biflorus). Lipid obtained from stored polished rice or rice bran was ulcerogenic. Further animal experiments were designed to investigate the protective and healing effects of Horse gram lipid (HGL) against peptic ulceration. METHODS: Three effects were investigated in rats: (i) the protective effect of HGL on peptic ulceration produced by using pyloric ligation in combination with South Indian diet or rice bran oil, or by cysteamine, alcohol or aspirin; (ii) the effect of HGL on mast cell degranulation in response to pyloric ligation and rice bran oil; and (iii) the healing effect of HGL on acute gastric ulceration produced by alcohol, on chronic gastric ulceration produced by topical acetic acid or on chronic duodenal ulcer following cysteamine. RESULTS: Horse gram lipid was shown to be protective and to promote ulcer healing in all the models used. Mast cell degranulation was inhibited. CONCLUSION: The experiments confirm the presence of a lipid in certain staple foods that have protective and healing properties in experimental peptic ulcer animal models. The differences in the prevalence of duodenal ulceration between different regions in some developing countries with a high prevalence of Helicobacter pylori infection might be explained by the presence or absence of protective lipids or ulcerogenic factors in the staple diet.

Acetic Acid↗

Effect of centrally administered prolactin on gastric and duodenal ulcers in rats.

The effect of centrally administered prolactin on gastric acid secretion and experimentally-induced gastric and duodenal ulcers was studied. The acute gastric ulcer models used were pylorus ligation, indomethacin-induced and ethanol-induced gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by cysteamine hydrochloride. In pylorus ligated rats, prolactin (1 microg/kg icv) produced 45% increase in gastric content volume, significant increase in free acidity (P < 0.001), total acidity (P < 0.001) and ulcer index (P < 0.001). It did not show any significant effect on ethanol-induced and indomethacin-induced gastric ulcers. Prolactin increased the ulcer index (P < 0.001) and ulcer score (P < 0.05) in acetic acid-induced chronic gastric ulcers. It also increased ulcer area (P < 0.05) in cysteamine-induced duodenal ulcers. Therefore, the proulcerogenic activity of prolactin was due to its gastric hypersecretory effect.

Acetic Acid↗

Anti-ulcer actions of phytosphingosine hydrochloride in different experimental rat ulcer models.

The gastroprotective activity of phytosphingosine hydrochloride (PS-HCl, CAS 554-62-1) was assessed in four different rat models of experimentally induced gastric ulcer. Various doses (2.5-10 mg/kg) of PS-HCI were orally administered to rats 30 min before the treatment with HCl/ethanol, indometacin, cysteamine, or to rats with ligated pylorus. Oral administration of PS-HCl (2.5-10 mg/kg) to rats prevented the acute ulcer formation in 4 different types of ulcer in a dose-dependent manner as follows: (1) HCl/ethanol-induced gastric mucosal membrane lesions (20.1-47.8% inhibition), (2) indometacin-induced gastric mucosal membrane lesions (4.6-31.9% inhibition), (3) duodenal ulcer induced by cysteamine (10-20% inhibition), (4) gastric secretion and ulceration following pylorus ligation (33.3-61.9% inhibition). These results indicate that PS-HCI may be useful for the prevention of gastric ulcer.

Animals↗

Effect of radiomodifying agents on the ratios of X-ray-induced lesions in cellular DNA: use in lethal lesion determination.

The effect of three radiomodifying agents, cysteamine, hyperthermia, and hypoxia, on the induction of the major classes of X-ray-induced DNA lesions, was studied using mouse L cells and Chinese hamster V79 cells. The use of filter elution techniques allowed most of these studies to be conducted at X-ray doses within the survival-curve range. Cysteamine was found to protect against DNA single-strand breakage (ssb), DNA base damage, and DNA-protein crosslinkage. Hyperthermia had no effect on the level of DNA ssb or DNA base damage, but in L cells (but not in V79 cells) it increased the level of DNA-protein crosslinkage relative to DNA ssb. Hypoxia protected against DNA ssb, had no significant effect on the level of DNA base damage, and enhanced the level of DNA-protein crosslinkage relative to DNA ssb. These results support the previous suggestion that the X-ray-induced lethal lesion is DNA double-strand breakage. Implications of these findings for the mechanisms of formation of X-ray-induced DNA lesions are also discussed.

Animals↗

The effects of counter-ion condensation and co-ion depletion upon the rates of chemical repair of poly(U) radicals by thiols.

Bimolecular rate constants for reactions of poly(U) radicals with a series of thiols of varying net charge (Z) were measured by pulse radiolysis with conductivity detection at low ionic strength. At pH 7 and 18 degrees C the values of k2 (M-1s-1) were: reduced glutathione (Z = -1), less than 500; 2-mercaptoethanesulphonic acid (Z = -1), 1.5 x 10(3); 2-mercaptoethanol (Z = 0), 1.8 x 10(5); cysteine (Z = 0), 2.0 x 10(5); cysteamine (Z = +1), 4.1 x 10(7). Values determined at pH 4 were: 2-mercaptoethanol, 6.1 x 10(5); cysteamine 2.2 x 10(8); N-(2-mercaptoethyl)-1,3-diaminopropane (WR-1065, Z = +2), 4.6 x 10(8). The variation in rate with structure could not reasonably be attributed to inherent reactivity differences in the thiols and was ascribed to inhomogeneous distributions of the thiols in solution resulting from electrostatic interactions. Thus, cationic thiols are concentrated approximately 100-fold near poly(U), relative to neutral thiols, as a consequence of counter-ion condensation, whereas anionic thiols have approximately 100-fold lower concentration near poly(U) than neutral thiols as a result of co-ion depletion. These results show that the ability of a thiol to repair radical sites in a polyanion is dramatically influenced by its net charge as a consequence of the counter-ion condensation and co-ion depletion phenomena.

Cysteamine↗

Cystamine inhibits HIV type 1 replication in cells of monocyte/macrophage and T cell lineages.

The effects of cysteamine (2-aminoethanethiol, MEA) and its disulfide, cystamine, on the human immunodeficiency virus (HIV-1) expression in chronically infected promonocytic cells (U1), T cell line (ACH-2), and peripheral blood monocyte-derived macrophages (MDM) were investigated. U1 and ACH-2 cells constitutively express low levels of virus, which is increased by the addition of tumor necrosis factor (TNF-alpha), interleukin 6 (IL-6), granulocyte-macrophage-colony-stimulating factor (GM-CSF), and other inducers. Cystamine, in noncytotoxic doses, suppressed in a concentration-dependent fashion the induction of HIV-1 expression mediated by TNF-alpha, IL-6, GM-CSF, and monokine-enriched monocyte culture supernatants in both U1 and ACH-2 cells as determined by HIV-1 reverse transcriptase (RT) activity. Similarly, HIV-1 expression was substantially reduced in the cystamine-treated primary MDM cultures compared with the untreated control cultures. The addition of cystamine into HIV-1 chronically infected MDM (12 days after infection was established) also suppressed 80-90% of RT activity in comparison to the untreated controls. HIV-1 (Bal) infected MDM cultures (without cystamine treatment) demonstrated giant syncytium formation, whereas cystamine-treated cultures lacked the giant syncytia induced by HIV-1 infection. Cystamine also inhibited LPS-induced TNF production in MDM. In contrast to cystamine, cysteamine showed no significant effects on either the monokine-induced HIV-1 expression in U1 or ACH-2 or acute and chronic HIV-1 infection in MDM.(ABSTRACT TRUNCATED AT 250 WORDS)

Antiviral Agents↗

Galanin-induced growth hormone secretion in conscious rats: evidence for a possible involvement of somatostatin.

Intracerebroventricular administration of galanin (GAL) potently evoked growth hormone (GH) secretion in conscious male rats. Pretreatments with neostigmine and cysteamine blunted the GAL-induced GH secretion. Pretreatment of animals with a specific anti-somatostatin serum significantly inhibited the GAL-induced GH secretion. On the contrary, GH-releasing hormone-induced GH secretion was significantly enhanced with cysteamine and anti-somatostatin serum. These results suggest that somatostatin is involved in GAL-induced GH secretion in rats.

Animals↗

Formaldehyde scavenging from peritoneal dialysis solutions using reduced aminothiol compounds.

BACKGROUND: Aldehydes were identified in clinical solutions, including peritoneal dialysis (PD) and cryoprotection solutions, which were used to freeze cells, tissues and embryos. Aldehydes are associated with increased cellular injury and may contribute to peritoneal membrane damage that occurs in patients on peritoneal dialysis. Recently, it was demonstrated that aldehydes could be 'scavenged' from these solutions by using aminothiol compounds. Although aldehydes were removed during the scavenging process, the kinetics of scavenging and the products formed were not characterized. METHODS: Proton nuclear magnetic resonance (NMR) spectroscopy was used to investigate formaldehyde scavenging from an artificial PD solution supplemented with aminothiol compounds, cysteamine or l-cysteine. Artificial PD solutions were formulated on the basis of commercial PD solutions and consisted of 132 mmol/L NaCl, 0.25 mmol/L MgCl2, 1.25 mmol/L CaCl2, and buffered with lactate (4.0 mmol/L) and lacked d-glucose. Formaldehyde scavenging was a two-step process involving an intermediate step followed by the formation of stable thiazolidine compounds. These included the derivatives of cysteamine and l-cysteine; thiazolidine and thiazolidine-4-carboxylic acid, respectively. CONCLUSION: Scavenging with aminothiol compounds masked the destructive carbonyl group (C = O) of formaldehyde and formed a compound that has antioxidant properties. The addition of aminothiol compounds may improve the biocompatibility of commercial PD solutions.

Cysteamine↗

Effects of lathyrogens on the mechanical strength of the periodontal ligament in the rat mandibular first molar.

Effects of lathyrogens such as aminoacetonitrile (AAN), beta-aminopropionitrile (BAPN) and cysteamine--known inhibitors of cross-linking of collagen--on the mechanical strength of the periodontal ligament of the rat mandibular first molar were examined by measuring the ultimate load required to extract the tooth from its socket in the dissected jaw. Single injections of AAN (40 approximately 100 mg/100 g body weight) or of BAPN (100 mg/100 g body weight) caused significant decreases of the mechanical strength 24 h after administration of the drugs but that of cysteamine (30 mg/100 g body weight) did not. Significant correlations between the dose of AAN or of BAPN and the mechanical strength were found following daily administrations of the drugs for 5 days. The relative potency of AAN to BAPN was estimated to be 4.5 by a slope ratio assay. The rapid appearance and disappearance of the effect of lathyrogens on the mechanical strength of the periodontal ligament of the rat mandibular first molar provide further evidence that the turnover of the collagen in the tissue is fast. The half-time of collagen synthesis was estimated to be approximately 3 d.

Acetonitriles↗

Novel 1,4 substituted piperidine derivatives. Synthesis and correlation of antioxidant activity with structure and lipophilicity.

A series of novel piperidine derivatives was prepared and their lipophilicity was determined (as RM values). These compounds as well as two intermediate alpha-keto-esters were tested for antioxidant activity. It was found that the cysteamine derivatives were efficient antioxidants, i.e. they could inhibit lipid peroxidation, act as hydroxyl radical scavengers and interact with 2,2-diphenyl-1-picrylhydrazyl radicals. This interaction could be attributed to the free SH group and this activity seemed to be favoured by increased lipophilicity. Replacement of SH by NH2 or OH resulted in a decreased antioxidant activity of the compounds. However, the described activities seem not to be connected with any O2-.scavenging ability, at least under the experimental conditions applied. Furthermore, cysteamine derivatives seem to induce O2-.generation, a phenomenon often observed with thiol compounds. The antioxidant activity of the intermediate alpha-keto-esters varied and is probably mediated by different mechanisms.

Animals↗

Gastric and duodenal anti-ulcer activity of SKF 38393, a dopamine D1-receptor agonist in rats.

The effect of SKF 38393 (1-phenyl-7,8-diol-2,3,4,5-tetrahydro-1H-3-benzazepine), a specific dopamine D1-receptor agonist, was studied on pylorus-ligation and water immersion plus restraint stress-induced gastric ulcers, and cysteamine-induced duodenal ulcers in rats. Repeated administration of SKF 38393 (5 and 10 mg kg-1, p.o.) for six days was found to be effective in the prevention of gastric ulceration induced by water immersion plus restraint stress in rats. In 19-h pylorus-ligated rats, repeated treatment with SKF 38393 showed a significant reduction in the number and severity of ulcers. SKF 38393 did not alter the total gastric-mucosal carbohydrates:protein ratio; however, the gastric content volume and the free and total acidity were significantly reduced. In cysteamine-induced duodenal ulcers, the treatment with SKF 38393 for 6 days prevented the duodenal lesions. Our data suggests the involvement of dopamine D1 receptors in the anti-ulcer activity of SKF 38393, which could be largely attributed to its anti-secretory effect. Its anti-ulcer activity against water immersion plus restraint, also points towards a central mode of action, but its failure to alter the carbohydrate:protein ratio rules out any protective effect through the strengthening of the gastric mucosal barrier.

2,3,4,5-Tetrahydro-7,8-dihydroxy-1-phenyl-1H-3-ben↗

Contribution of dithiol ligands to in vitro and in vivo trypanocidal activities of dithiaarsanes and investigation of ligand exchange in an aqueous solution.

Twelve new dithiaarsanes were evaluated for their in vitro and in vivo trypanocidal properties in regard to their three parent molecules, 4-amino-phenylarsenoxide, melarsenoxide, and 4-dansylamino-phenylarsenoxide. The most potent dithiaarsane, compound 2b, had a minimum effective concentration of 1.5 nM after 48 h of incubation and at a dose of 0.39 micromol/kg of body weight (0.2 mg/kg) administered subcutaneously cured 100% of mice acutely infected with Trypanosoma brucei brucei CMP. With this model, the chemotherapeutic index of compound 2b was 512, compared to 256 for melarsamine dihydrochloride (Cymelarsan) under the same conditions. With a chronic infection produced by T. brucei brucei GVR, compound 2b cured 100% of mice after treatment at a dose of 25 micromol/kg (12.5 mg/kg) for 4 consecutive days, whereas melarsamine dihydrochloride and potassium melarsonyl (Trimelarsan) cured less than 50% mice at this dose. For both acute and late-stage infections, dithiaarsanes having a melaminophenyl ring exhibited the most-potent trypanocidal activity. Compound 2b is thus one of the most active organoarsenicals described in a mouse trypanosomiasis model. Considering that the main intracellular targets of organoarsenicals are thiol groups, we studied the possibility of ligand exchange between Cymelarsan and several dithiols. In aqueous solution, we observed a rapid exchange of cysteamine from melarsamine with free cysteamine and also with various dithiols always in favor of more stable cyclic derivatives. These ligand exchanges suggest the ability of trivalent organoarsenicals to react with targets such as trypanothione and dihydrolipoic acid. Among several ligands, a 1,3-dimercaptopropane moiety appeared the most suitable for trypanocidal activity.

Animals↗

Renal metabolism of amino acids in vivo: studies on serine and glycine fluxes.

The pathway of serine synthesis by the rat kidney has been investigated in vivo by measuring the net flux in the presence and absence of specific inhibitors of the glycine cleavage system, phosphoenol-pyruvate carboxykinase and gamma-glutamyltranspeptidase. In normal animals serine release was 705 +/- 187 nmol X min-1 X animal-1, whereas glycine uptake was only 28% of this value. Inhibition of the glycine cleavage system (cysteamine infusion) resulted in a reversal of glycine flux with no change in serine production. In similar experiments with mercaptopicolinate serine release was decreased by 55% with no change in glycine removal. AT-125, a potent inhibitor of gamma-glutamyltranspeptidase, had no effect on renal serine and glycine fluxes. In chronically acidotic rats serine synthesis was unchanged, but there were significant increases in the uptake of glutamine (fourfold) and glycine (2.5-fold). Infusion of cysteamine into these animals caused a 50% decrease in serine release with a significant reversal of the glycine flux. Infusion of mercaptopicolinate had effects similar to those observed in normal animals. These results show that renal serine synthesis can occur by both the phosphorylated-intermediate pathway and serine hydroxymethyltransferase in vivo. Furthermore, they demonstrate that glycine can contribute significantly to ammoniagenesis during acidosis.

Amino Acids↗

Influence of brain histamine on growth hormone secretion induced by alpha-2-receptor activation.

The effects of histamine (HA) and of (R) alpha-methyl-histamine (alpha-MeHA; a drug that decreases histaminergic tone through activation of presynaptic H3 receptors) on growth hormone (GH) secretion induced by clonidine (CLO), an alpha 2-adrenergic agonist, were examined in rats. HA (0.1 mumol/rat intracerebroventricularly) and alpha-MeHA (10 mg/kg i.a.) were administered 5 min and 3 h, respectively, before CLO (0.25 mg/kg i.a.). Blood samples for hormone determination were drawn from freely moving rats at various times before and after drug treatment. To characterize the mechanisms underlying the inhibition of GH secretion by HA, the effect of HA on GH induced by CLO was examined in rats depleted of catecholamine by pretreatment (2 h before) with alpha-methyl-p-tyrosine (alpha-MpT, 200 mg/kg s.c.) and in rats depleted of somatostatin by pretreatment (4 h before) with cysteamine (300 mg/kg s.c.). HA completely suppressed the GH-releasing effect of CLO whereas alpha-MeHA significantly enhanced the GH response to CLO. Neither alpha-MpT nor cysteamine pretreatment modified the inhibitory activity of HA on GH secretion elicited by CLO. The present results indicate that the inhibitory activity of brain HA on GH release consequent to activation of central alpha 2-receptors does not involve a modulatory action on catecholaminergic or somatostatinergic neurons but probably other mechanisms like the modulation of neurons synthetizing GH-releasing hormone.

Animals↗