Cysteamine hydrochloride affects ocular development and triggers associated inflammation in zebrafish

The increasing use of cosmetics has raised widespread concerns regarding their ingredients. Cysteamine hydrochloride (CSH) is a newly identified allergenic component in cosmetics, and therefore its potential toxicity needs further elucidation. Here, we investigated the in vivo toxicity of CSH during ocular development utilizing a zebrafish model. CSH exposure was linked to smaller eyes, increased vasculature of the fundus and decreased vessel diameter in zebrafish larvae. Moreover, CSH exposure accelerated the process of vascular sprouting and enhanced the proliferation of ocular vascular endothelial cells. Diminished behavior in response to visual stimuli and ocular structural damage in zebrafish larvae after CSH treatment were confirmed by analysis of the photo-visual motor response and pathological examination, respectively. Through transcriptional assays, transgenic fluorescence photography and molecular docking analysis, we determined that CSH inhibited Notch receptor transcription, leading to an aberrant proliferation of ocular vascular endothelial cells mediated by Vegf signaling activation. This process disrupted ocular homeostasis, and induced an inflammatory response with neutrophil accumulation, in addition to the generation of high levels of reactive oxygen species, which in turn promoted the occurrence of apoptotic cells in the eye and ultimately impaired ocular structure and visual function during zebrafish development.

Bile acid-cysteamine conjugates: structural properties, gelation, and toxicity evaluation

Design, synthesis, and characterization of six novel bile acid-cysteamine conjugates together with investigation of their structural studies, gelation properties, and preliminary toxicity evaluation, are reported. Solid state properties of selected compounds were studied by means of X-ray diffraction and (13)C CPMAS NMR spectroscopy. N-(2-thioethyl)-3α,7α,12α-trihydroxy-5β-cholan-24-amide was shown to exhibit (pseudo)polymorphism, and a single crystal structure of its non-stoichiometric hydrate is reported herein. Cholyl and dehydrocholyl derivatives bearing three functionalities in their steroidal backbone were shown to undergo self-assembly leading to gelation in certain organic solvents. Preliminary morphology studies of the formed gels by scanning electron microscopy (SEM) were performed. The standard model mouse fibroblast cell line together with the MTT and NR tests were utilized for evaluating the toxicity of the prepared compounds. Lithocholyl, ursodeoxycholyl, and dehydrocholyl derivatives turned out to be relatively non-toxic in the conditions studied.

Prophylactic role of a herbomineral drug "Thamira parpam" against cysteamine-induced oxidative stress in liver and duodenum of rats

Copper is known as Gunma Kaalan in Siddha literature, which means that the drug is effective for healing ulcers. The herbomineral drug "Thamira parpam" is prepared by calcining the purified copper foils with rock salt, lime juice, bracteated birth wort juice, and Alangium root decoction according to Siddha medicine. Our study investigated the possible role of Thamira parpam (TP) in the management of cysteamine-induced duodenal ulcers. Cysteamine (400 mg kg(-1) body weight(-1), two doses at 4 h interval) orally given to rats resulted in high ulcer index, increased TBARS with concomitant depletion of antioxidants such as superoxide dismutase, glutathione, glutathione peroxidase, and inflammatory markers cathepsin D, and myeloperoxidase (p < 0.01). Herbomineral drug TP (0.5, 1, and 2 mg/kg, p.o.) challenged with cysteamine attenuated the elevation of TBARS and imbalance of antioxidants. In the increases in liver inflammatory markers, tissue histopathology changes were not severe in TP treatment. Positive control omeprazole (25 mg/kg, body weight, orally) showed considerable protection against anomaly in biochemical parameters and tissue histology. Hence, our results indicate that the attenuation of oxidative stress by the herbomineral drug in experimentally induced damage to liver and duodenum of rats could be mediated by free radical quenching property.

The presentation and organization of adaptive cytoprotection in the rat stomach, duodenum, and colon. Dedicated to André Robert the founder of the concept of cytoprotection and adaptive cytoprotection

BACKGROUND

Adaptive cytoprotection could be demonstrated in lesion attenuation within the whole gastrointestinal tract, in particular sequences, with onset and duration longer than the initial short-lasting period (i.e. one hour) defined by Robert in the stomach only.

MATERIAL/METHODS

Adaptive cytoprotection possibly appeared and lesions were attenuated when the stomach, duodenum or colon, in various combinations and sequences, were challenged with initial (mild) and/or final (strong) irritants over a two-week period. Rats were challenged with the mild or strong irritants 25% or 96% ethanol intragastrically 1 ml/rat (stomach) and cysteamine 40 mg or 400 mg/kg subcutaneously (duodenum), or intrarectally (colon). To postulate the prostaglandin relationship known in Robert's cytoprotection and adaptive cytoprotection, indomethacin (1 mg/kg subcutaneously) was given simultaneously with the second challenge.

RESULTS

Administering the mild and strong irritant protocols within the same part of the gastrointestinal tract, adaptive cytoprotection presents in the stomach (1 h to 14 days), duodenum (2 h to 14 days), but not in the colon. With these protocols applied to different parts of the gastrointestinal tract, adaptive cytoprotection cross-reaction was evident in the stomach-duodenum, duodenum-stomach (1 h-14 days and 2 h-14 days), stomach-colon, and duodenum-colon (both 2-24 hours), but not in the colon-stomach or colon-duodenum. This protection was fully antagonized with indomethacin.

CONCLUSIONS

As observed for a day and even weeks, stomach-duodenum-colon adaptive cytoprotection is an important new defensive phenomenon.

Synthesis and Antimelanoma Activity of Reversed Amide Analogues of N-Acetyl-4-S-cysteaminylphenol

The melanin biosynthetic pathway from tyrosine is a potential target for combating malignant melanoma. N-Acetyl-4-S-cysteaminylphenol 1 is a previously synthesized analogue of tyrosine that probably acts by this pathway. It interferes with cell growth and proliferation via selective oxidation in melanocytes to an oquinone that can alkylate cellular nucleophiles. We previously synthesized a range of analogues of the original lead compound 1 most of which displayed greater cytotoxicity than 1. Eighteen new analogues with the amide group reversed have now been synthesized and tested for antimelanoma activity. Most of these reverse amides showed greater cytotoxicity than N-acetyl-4-S-cysteaminylphenol towards five representative melanoma cell lines. The highest cytotoxicity was observed for the piperidine and hexamethyleneimine derivatives 7, 8, 12, 13, and 17 and the catechol 18. The most active compound, 7, had cytotoxicity comparable to cisplatin against the five melanoma cell lines. The moderate activity of 7 and 18 against SK-Mel-24 (non-tyrosinase containing) and an ovarian cell line suggests that interference with the melanin pathway may not be the only mode of action of these compounds. Assays of some of the compounds as substrates for tyrosinase showed that the catechol 18 was the best substrate and that the piperidine derivative 7 was the best substrate of the phenolic compounds synthesized.

Gastric antisecretory and antiulcer activity of oxytocin in rats and guinea pigs

The effect of oxytocin (1 mg/kg s.c) on gastric acid secretion and on different experimentally induced gastric and duodenal ulcers was studied. The acute gastric ulcer models used were pylorus ligation, indomethacin, ethanol and histamine induced acute gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by cysteamine hydrochloride. Oxytocin showed significant antisecretory and antiulcer activity in pylorus ligated rats. Similarly oxytocin reduced the ulcer index in histamine induced gastric ulcers in guinea pigs and cysteamine induced duodenal ulcers in rats. The antiulcer and antisecretory effect was comparable to that of ranitidine (50mg/kg, i.p) though less in intensity. However, it did not show any gastric cytoprotective effect in ethanol and indomethacin induced ulcer models but ranitidine showed protection (p<0.05) in later model. Oxytocin enhanced gastric ulcer healing in acetic acid induced chronic gastric ulcer model. The reversal of oxytocin effect by atosiban, an oxytocin receptor antagonist indicates a role for oxytocin receptors. The antiulcer activity of oxytocin can be attributed to its antisecretory effect.

Effect of hyperprolactinaemia as induced by pituitary homografts under kidney capsule on gastric and duodenal ulcers in rats

The effect of hyperprolactinaemia, induced by two or four pituitary homografts under the kidney capsule, on gastric and duodenal ulcers has been studied. The acute gastric ulcer models used were pylorus ligation, indometacin-induced and ethanol-induced gastric ulcers. Chronic gastric ulcers were induced using acetic acid and duodenal ulcers by mercaptamine hydrochloride. After pylorus ligation, there was an approximate 30-40% increase in gastric secretion, a significant increase in total acidity (P < 0.01) and in the ulcer index (P < 0.01) in rats bearing pituitary homografts under the kidney capsule when compared with the sham-operated control. Hyperprolactinaemia did not affect the formation of ethanol-induced gastric ulcers but showed a 40% reduction in the development of indometacin-induced gastric ulcers. It also produced a 20% increase in the ulcer index in acetic acid-induced chronic gastric ulcers and a 30% increase in ulcer area in mercaptamine-induced duodenal ulcers. Our results showed that hyperprolactinaemia induced gastric acid secretion and thereby aggravated gastric and duodenal ulcers in rats. Hyperprolactinaemia did not affect gastric cytoprotection.

Mechanisms for the cytotoxicity of cysteamine

The major aim of this study was to quantitatively assess the contribution of H2O2 generation to the cytotoxicity induced by cysteamine. Cysteamine produces H2O2 at levels that correlate with its toxicity between 23 and 160 microM. A maximum of 6.9 microM H2O2 is generated by 625 microM cysteamine. When compared to the toxicity of exogenous H2O2, cysteamine-derived peroxide accounted for 57% of its toxicity. This corresponded to the percent toxicity due to 23 to 91 microM cysteamine. The remaining 43% toxicity appears to involve the inhibition of glutathione peroxidase, because activity of both the cellular and purified enzyme were inhibited by 200 microM cysteamine concentrations. CCRF-CEM cells have no catalase activity, so the inhibition of glutathione peroxidase may sensitize these cells to the less than toxic levels of peroxide generated by this aminothiol. Cysteamine also stimulated the production of cellular glutathione in a manner that was not related to its H2O2 generation. The production of glutathione did not influence toxicity but may reflect the accumulation of cysteamine to levels that inhibit glutathione peroxidase.

[Oxidative metabolism of HIV-infected macrophages: the role of glutathione and a pharmacologic approach]

Oxidative stress and glutathione deficiency seem to play a major role in the pathogenesis of HIV infection, as suggested by the increased survival of HIV-infected patients treated with N-acetylcysteine, a prodrug of glutathione. However, beneficial effects of GSH-replenishing drugs are restricted in vivo by the high concentrations needed to obtain biological effects and their low bioavailability. In this study, we evaluated the antiretroviral and antioxidant activities of new more lipophilic GSH-replenishing molecules, in macrophages infected in vitro with HIV-1. In these experimental conditions, a prodrug of N-acetylcystéine and beta-mercaptoethylamine, I-152 demonstrated a potent anti-HIV activity, increased intracellular GSH level, and decreased TNF-alpha production. Altogether, these results suggest that I-152 could be beneficial as adjuvant therapy of antiretrovirals in HIV-infected patients, especially in those with damages to the central nervous system or with mitochondrial damages associated with highly active antiretroviral therapy.

Reduction of gastrointestinal toxicity of NSAIDs via molecular modifications leading to antioxidant anti-inflammatory drugs

Reactive oxygen species and free radical reactions are related to several pathologic conditions including inflammation and gastric ulceration. The latter is the major undesired side-effect of almost all NSAIDs. Since this effect of NSAIDs is greatly influenced not only by the type of cyclooxygenase which is inhibited but also by the acidic nature of the molecule, we considered it interesting to modify their structure in such a way that it would lead to an antioxidant, neutral molecule or a molecule with greatly reduced acidic character. Thus, we synthesized amide derivatives of four well-known NSAIDs, i.e. diclofenac acid, tolfenamic acid, ibuprofen and indomethacin, with cysteamine, a well-known antioxidant. The synthesized derivatives, with demonstrated good anti-inflammatory and antioxidant activities, showed very significant reduction of ulcerogenicity in the investigation of gastrointestinal (GI) toxicity. As indices of ulcerogenic toxicity in rats, we used the mortality (%), the incidence of GI ulcers (%), body weight reduction (g/100 g BW) and the incidence of melena. All amide derivatives of the NSAIDs with cysteamine were almost non-toxic in the GI tract, under our experimental conditions, in contrast to their parent NSAIDs. These results are attributed to the acquired antioxidant activity as well as to the reduction of acidic character compared with the parent compounds. Therefore, it can be concluded that the combination of these two properties, anti-inflammatory and antioxidant activity, with a simultaneous drastic reduction of acidic character, may lead to the development of novel, useful anti-inflammatory and cytoprotective pharmacomolecules, with potentially important therapeutic applications.

Comparison of in vitro cytotoxicity of N-acetyl and N-propionyl derivatives of phenolic thioether amines in melanoma and neuroblastoma cells and the relationship to tyrosinase and tyrosine hydroxylase enzyme activity

Our laboratory has synthesized two new phenolic thioether amines, N-propionyl-4-S-cysteaminylphenol (N-Pr-4-S-CAP) and N[2-[(4-propionyloxyphenyl)thio]ethyl] propionamide (N,O-diPr-4-S-CAP). These compounds, along with the previously described phenolic thioether amine N-acetyl-4-S-cysteaminylphenol (N-Ac-4-S-CAP) and its acetyl form (N,O-diAc-4-S-CAP), are tyrosine-amine derivative analogues. The cytotoxicity of these compounds is thought to be tyrosinase dependent, which may make them suitable for targeted anti-melanoma therapy since only melanocytes and their malignant counterparts contain this active enzyme. To further investigate this hypothesis, we performed MTT [3-(4,5-dimethylthiazol-2-yl)2,5-diphenyltetrazolium bromide] assays to determine the cytotoxicity of these compounds in 10 different cell lines. Specifically, we examined to what extent cytotoxicity is related to tyrosinase and tyrosine hydroxylase activity using melanoma and neuroblastoma cells, which have a common metabolic pathway using tyrosinase and tyrosine hydroxylase, respectively. The most sensitive cell line was the highly pigmented SK-MEL-23 melanoma cell line, which shows a very high tyrosinase activity with the highest melanin pigmentation. KAN and SK-NSH (two neuroblastoma cell lines), which have no tyrosinase activity but high tyrosine hydroxylase, were also sensitive. However, C32 (a non-pigmented melanoma with a lower tyrosinase activity) was also sensitive, and MeWo (a moderately pigmented melanoma with a high tyrosinase activity) was less sensitive. This in vitro study may indicate that there is a non-tyrosinase-mediated mechanism of cytotoxicity for phenolic thioether amines in addition to the tyrosinase-mediated one described previously.

Effects of pre- and postnatal cysteamine exposure on renal function in the rat

The safety of cysteamine after renal transplantation and during pregnancy is an important issue, since girls with cystinosis are in better health on cysteamine therapy and thus more likely to become pregnant. In the first study, cysteamine was given to pregnant rats on days 6.5-18.5 post conception in oral doses of 0, 37.5, 75, 100, and 150 mg/kg per day. The dams were sacrificed on day 20.5, the fetal kidneys removed and prepared for histological examination. In the second study, cysteamine was given to dams on days 6.5-19.5 post conception in oral doses of 0, 37.5, 50, and 75 mg/kg per day. Dams were allowed to give birth naturally and pups were given cysteamine on days 4-21 to yield the same oral doses of cysteamine given to the dam. Renal function was evaluated on day 35. Histological examination of fetal kidneys revealed no changes even in kidneys from fetuses with growth retardation and malformations. Furthermore, there were no alterations in renal function in offspring on day 35. These findings demonstrate that cysteamine therapy does not affect renal development in the rat. Further investigations will be required to prove whether cysteamine therapy has the potential to affect renal development in the human.

Dual effect of female sex steroids on drug-induced gastroduodenal ulcers in the rat

Since the sexual dimorphism of gastroduodenal ulcers is well known and might possibly relate to the actions of sex hormones, we studied the role of the female sex steroids, progesterone and 17beta-estradiol in cysteamine-induced mucosal ulcers in female Wistar rats (200-220 g). Administration of cysteamine (400 mg/kg, s.c.) provoked macroscopic gastroduodenal mucosa injury as assessed planimetrically, an increase in microvascular permeability in the stomach and the duodenum as assessed by extravasation of radiolabelled albumin, and decreased gastroduodenal mucus levels as assessed by the Alcian blue technique. Ovariectomy (2 weeks before cysteamine) decreased plasma 17beta-estradiol level as assessed by radioimmunoassay, gastroduodenal macroscopic injury and albumin extravasation, and increased mucus levels following cysteamine challenge. Administration of progesterone (10-50 mg/kg/week, s.c.) attenuated in a dose-dependent manner cysteamine-induced gastroduodenal mucosa injury and microvascular leakage, while it increased mucus levels in the stomach and the duodenum. In contrast, administration of 17beta-estradiol (1-5 mg/kg/week, s.c.) dose-dependently augmented gastric and duodenal macroscopic mucosa lesions and microvascular injury provoked by cysteamine, and caused a further reduction in gastroduodenal mucus levels observed after cysteamine administration. In different experiments, ovariectomy decreased indomethacin-induced gastroduodenal injury. The injection of 17beta-estradiol (1-5 mg/kg/week) did not affect gastroduodenal damage, while treatment with progesterone (10-50 mg/kg/week) protected against indomethacin-provoked mucosa ulcers. It is concluded that female sex steroids play a role in drug-induced gastroduodenal ulcers by modulating microvascular permeability and mucus secretion.

Developmental toxicity of cysteamine in the rat: effects on embryo-fetal development

The reproductive and developmental safety of cysteamine has become an important issue to children with cystinosis because renal transplants and treatment with cysteamine reduce the complications associated with cystinosis and increase the lifespan of the affected children. In addition, there is the potential to decrease the severity or the incidence of renal Fanconi syndrome with administration of cysteamine to pregnant women carrying fetuses with cystinosis, and to ease significantly the burden of this disease throughout their lives. If cysteamine increases significantly the risk of fetal death, growth retardation or birth defects at doses used to treat women with cystinosis, treatment of the affected female should cease during pregnancy and would not be considered for fetal treatment. The goal of this study was to assess the developmental safety of exposure in utero to cysteamine in the rat. Pregnant rats were given cysteamine (as phosphocysteamine) from day 6.5 through day 18.5 postconception and fetuses were assessed for survival, growth, and structural abnormalities on day 20.5. Cysteamine was administered orally in doses of 0, 37.5, 75, 100, or 150 mg/kg/day. Cysteamine produced dose-dependent developmental toxicity with an apparent no adverse effect observed level of 75 mg/kg/day. Specific malformations were associated with this effect (cleft palate, kyphosis), as well as intrauterine growth retardation and fetal death at 100-150 mg/kg/day, without signs of maternal toxicity. Investigations continue into the mechanism for the developmental toxicity of cysteamine.

Comparison of antimelanoma effects of 4-S-cysteaminylphenol and its homologues

4-S-Cysteaminylphenol (4-S-CAP), a phenolic thioether, has been evaluated for melanocytotoxicity. We have recently shown that dihydro-1,4-benzothiazine-6,7-dione (benzothiazine BQ) is the ultimate toxic metabolite produced by tyrosinase oxidation of 4-SCAP. In this study we compared the antimelanoma effects of 4-SCAP and its two homologues, alpha-methyl-4-S-cysteaminylphenol (alpha-Me-4-SCAP) and 4-S-homocysteaminylphenol (4-S-Homo-CAP). Biochemical experiments showed that upon tyrosinase oxidation alpha-Me-S-CAP and 4-S-Homo-CAP also produced homologues of BQ which reacted rapidly with reduced glutathione (GSH) and also inhibited alcohol dehydrogenase, an SH enzyme. In vitro experiments showed that 4-S-CAP and its two homologues were taken up into B16-F1 melanoma cells at comparable rates but that 4-S-Homo-CAP was least effective in GSH deprivation, which was reflected in the low cytotoxicity of this phenol, and that the cytotoxicity of the phenols was tyrosinase dependent, as proved by the negligible effects on B16-G4F cells which have a much lower tyrosinase activity. In vivo experiments showed that direct intratumoral administration of these phenols inhibited the subcutaneous growth of B16 melanoma, with 4-S-Homo-CAP being the least effective, and that indirect Intraperitoneal administration of 4-S-CAP inhibited melanoma growth much more effectively than the two homologues. These results indicate that 4-S-CAP is the most promising antimelanoma agent among the three phenols examined.

Damaging actions of testosterone on cysteamine-induced gastroduodenal ulceration and vascular leakage in the rat

The sexual dimorphism of gastroduodenal ulceration is suggested on the basis of clinical and experimental observations. This difference probably relates to the actions of endogenous sexual steroids. In the present study, the role of testosterone was evaluated in the generation of gastroduodenal mucosal injury provoked by cysteamine (400 mg/kg, s.c.). We found that macroscopic mucosal damage and microvascular (125)I-human serum albumin leakage (2 microCi/kg, i.v.) developed in the stomach and duodenum of male rats 24 h after the administration of cysteamine. This mucosal injury was prevented by orchidectomy and by the pretreatment with the antiandrogen, cyproterone acetate (12 mg/kg per day for 8 consecutive days). It was also shown that pretreatment with testosterone (4-20 mg/kg per week) dose-dependently aggravated cysteamine-induced gastroduodenal mucosal injury. Our results thus suggest an aggressive role of testosterone in the generation of cysteamine-induced gastroduodenal ulceration.

Pentadecapeptide BPC 157, cimetidine, ranitidine, bromocriptine, and atropine effect in cysteamine lesions in totally gastrectromized rats: a model for cytoprotective studies

A superior effectiveness in various lesion assays was noted for the novel pentadecapeptide BPC 157, originated from human gastric juice protein (BPC) and claimed to be a cytoprotective agent. From this viewpoint, as a previously untreated experimental improvement to create an acid-free environmental for cytoprotection studies, total gastrectomy was done 24 hr before the ulcerogenic procedure. In the absence of stomach and gastric acid, the damaging effects of cysteamine (400 mg/kg subcutaneously, death 24 hr thereafter), to date thought to be an acid-related duodenal ulcerogen, and the BPC 157 cytoprotective effect (10 microg or 10 ng/kg intraperitoneally) were further challenged. BPC 157 was compared with reference agents [cimetidine (50), ranitidine (10), omeprazole (10), bromocriptine (10) and atropine (10) (mg/kg intraperitoneally, 1 hr before cysteamine] known to be also cytoprotective. In naive rats, with intact stomach, all of them showed a strong beneficial effect. Interestingly, in gastrectomized animals, the application of BPC 157 or the reference agents before cysteamine significantly prevented the otherwise severe duodenal lesion development noted in the control gastrectomized cysteamine rats. In groups without cysteamine, no lesions were noted (laparotomy, gastrectomy only, 24 or 48 hr postsurgical period), nor was lesion potentiation seen in cysteamine-treated laparotomized animals. In summary, these findings--equal damaging effect of cysteamine and equal protection of pentadecapeptide BPC 157 and reference agents in gastrectomized and rats with intact stomach--seem to be particularly relevant for a cytoprotective viewpoint. Without a stomach, the cysteamine damaging effect was convincingly defined as an essential gastric acid-independent injury (analogous to ethanol gastric lesions). Likewise, a high "cytoprotective capacity," apparently acid independent, common for all tested agents (novel pentadecapeptide BPC 157, cimetidine, ranitidine, omeprazole and atropine) could be clearly stressed.

Effect of cysteamine on gastric nerve fibers containing gastrin-releasing peptide in the rat

In rats, changes in gastric nerve fibers containing gastrin-releasing peptide (GRP) in cysteamine-induced duodenal ulcer were investigated in relation to the dynamics of gastrin-producing cells (G-cells). Marked increases in gastric acid secretion and serum gastrin level were observed from 2 h after the administration of cysteamine. The number of G-cells was significantly decreased from 2 h after the injection of cysteamine. Two and 4 h after the administration of cysteamine, the G-cells showed ultrastructural changes characterized by a markedly decreased number of secretory granules. Circulating GRP levels were significantly elevated from 2 h after the administration of cysteamine. In the control group given vehicle only, nerve fibers showing immunoreaction for GRP formed a fine network in the gastric wall and were densely distributed in the oxyntic mucosa, located close to capillaries and demonstrated varicosities that contained either small clear vesicles or GRP-immunopositive vesicles with large cores. Eight h after the administration of cysteamine, there was depleted GRP immunoreactivity, evidenced by a markedly decreased number of vesicles, with large electron-dense cores, in the oxyntic mucosa. These findings suggest that, in cysteamine-induced duodenal ulcer, alterations in gastric nerve fibers containing GRP may be related to hypergastrinemia.

Endogenous zinc concentrations in cysteamine-induced duodenal ulcers in the rat

Exogenously administered zinc compounds have been shown to possess anti-ulcer activity against a wide variety of ulcerogenic agents, both in laboratory animal models and in human peptic ulcer disease. However, a strong possibility exists that endogenous zinc may also play an important role during noxious events by various mechanisms. Therefore, the aim of this study was to focus on the changes of endogenous zinc serum and tissue concentrations in cysteamine-induced duodenal lesions. We used atomic absorption spectrophotometry to determine the tissue and serum concentrations of zinc in normal (control) rats and those with cysteamine-induced duodenal ulcers. The results obtained in this study indicated that the onset, development and spontaneous healing of ulcer lesions were associated with certain shifts in zinc serum and tissue concentrations. Prior to ulcer formation, a significant increase was noted in serum zinc values. With the onset of duodenal lesions, zinc serum concentrations significantly decreased, while there was a significant increase in duodenal tissue concentrations when compared to healthy control animals. Zinc tissue concentrations decreased and returned to starting values by the end of the first week of spontaneous healing. This decrease in zinc tissue concentration corresponded to the healing rate of the duodenal ulcers. Serum zinc concentrations also returned to starting values within the first week period. These observations indicate and confirm that zinc could play an important role in duodenal ulcer disease and represent a natural defense system in the body.

Limited impairment of learning performances in mice treated with cysteamine

Cysteamine has been reported to disturb learning performance in rats. Our study was made to determine if this is also true in mice. Adult male ddY mice were subjected to a battery of learning tests following our standard experimental protocols. Cysteamine injected 30 min prior to the learning trial dose-dependently increased the number of errors in the testing trial of step-down test, and its effect was statistically significant at a dose of 200 mg/kg. In the lever press test, 200 mg/kg injection of cysteamine also suppressed the conditioned avoidance rate. However, no significant changes were observed in other tests. These results suggest that the learning disorder induced by cysteamine in mice is restricted to a specific type of behavioral performance. In conclusion, the mechanism by which cysteamine generates learning deficiency in mice may differ from that in rats.

Induction of micronucleated erythrocytes by MEA, AET, WR-2721 and X-rays

The induction of micronucleated polychromatic erythrocytes (MNPCEs) was assessed in the bone marrow of adult male Swiss mice treated with MEA (cysteamine HCl), AET (2-aminoethylisothiouronium Br.HBr), or WR-2721 (S-2-(3-aminopropylamino)ethyl phosphorothioic acid), at a dose of 200 mg/kg body weight, and/or exposed to 6 Gy X-rays. MEA, AET, or WR-2721 was given alone or 15 min prior to X-ray exposure, and the frequency of MNPCEs was determined 24 h after the aminothiol treatment and X-irradiation of mice. A genotoxic effect was shown for MEA, AET, WR-2721, and X-rays, as well as a protective effect of the aminothiols against X-ray-induced genotoxicity in the mouse erythropoietic system. The aminothiol drugs given alone, without subsequent X-irradiation, elevated the frequency of MNPCEs, and WR-2721 appeared to be less toxic than AET and MEA. After exposure of mice to X-rays, the number of MNPCEs was distinctly increased. MEA, AET, or WR-2721 administration prior to X-irradiation resulted in a reduction of the X-ray-induced elevation of the frequency of micronuclei, but a stronger radioprotective effect was obtained following WR-2721 and AET treatment than after MEA application. So, the genotoxic and radioprotective effect of the aminothiols was dependent on the compound applied.

[Decrease of toxic effects of aminothiol radiation-protective agents and increase of chemical protection action against ionizing radiation by the use of unithiol]

It has been shown that unithiol diminishes toxic action of cysteamine, AET, and disulfide of WR-1065 on mice. This permits to enhance protection of animals against X-rays by increasing of protector doses. The effect of unithiol on cysteamine action in rats was the same. Antitoxic effect of unithiol on cysteamine was shown both at i.p. and p.o. protector administration. The effect was also revealed in Chinese hamster V-79 cell culture. Combined disulfide of cysteamine and unithiol was synthetized, which ensures effective prolonged protection against ionizing radiation.

Diamine oxidase activity in the duodenal mucosa of rats with cysteamine-induced ulceration

Cysteamine administration to rats is followed by a high incidence of duodenal ulceration. The effect of cysteamine on the activity of diamine oxidase (DAO, histaminase) in the duodenal mucosa of the rat was investigated. Rats were injected subcutaneously with cysteamine on 2 successive days at doses of 10, 20 and 40 mg/100 g body weight and killed 24 h after the second dose. The results indicated that cysteamine at a dose of 40 mg/100 g body weight inhibited enzyme activity by about 27% (p less than 0.05). Lower doses of cysteamine did not significantly affect enzyme activity. In another experiment, rats were injected subcutaneously with either saline (control) or cysteamine at a single dose of 40 mg/100 g body weight and killed 4, 8, 12, 24, 48 and 60 h thereafter. The ulcerogen produced progressive reductions in enzyme activity, which were significant at 12 h (22% reduction) and 24 h (25% reduction). At 60 h, enzyme activity was not significantly different from that of control.

Cysteamine can induce duodenal ulceration in rats without depletion of immunoreactive somatostatin

Single subcutaneous administration of cysteamine (2-aminoethanethiol, CSH) produces duodenal ulceration in rats within 24 h. Depletion of circulating and tissue somatostatin (SOM), hypergastrinemia and gastric acid hypersecretion have all been postulated as the pathophysiological response to CSH leading to ulceration. The purpose of this study was to analyze the synthesis, storage and secretion of gastrin and SOM as well as structural changes in SOM peptide after CSH treatment. Injection of 300 mg/kg (s.c.) of CSH caused macroscopic duodenal ulcers in seven out of eight rats at 24 h. Hypergastrinemia was seen within 30 min (from 23 +/- 4 to 74 +/- 20 pmol/l), and persisted for 4 h. Antral gastrin content was elevated at 30 min (2539 +/- 114 pmol/g) when compared to saline controls (1589 +/- 101 pmol/g). Plasma SOM did not change over the 24 h but antral SOM increased at 30 min (from 120 +/- 3 to 230 +/- 23 pmol/g) and remained elevated at 2 h (374 +/- 48 pmol/g) and 4 h (357 +/- 37 pmol/g). Fundic and duodenal SOM followed a similar pattern. Antral SOM mRNA was also elevated over the first 4 h (3-fold increase, P less than 0.05). HPLC analysis of antral tissue extracts revealed the presence of additional molecular forms of SOM which, however, differed from the major products of in vitro reduction with either CSH or dithiothreitol. Thus, the in vivo effect of CSH on SOM cannot be solely explained by a reductive opening of the disulphide bond. These results suggest that duodenal ulceration in rats treated with CSH is not related in a simple fashion to depletion of immunoreactive SOM. Early induction of hypergastrinemia may be important in the onset of ulceration. The value of CSH as a SOM depleting tool in gastrointestinal tissue must remain in doubt.

Cysteamine-induced duodenal ulcer and the hepatoduodenal branch of the vagus nerve

We investigated the role of the autonomic nervous system in gastric acid secretion, somatostatin concentration and PAS-positive mucus production in Brunner's glands in cysteamine-induced duodenal ulcer. Vagotomized rats were used. No ulcers occurred in the groups with vagotomies of the hepatoduodenal, truncal or gastric branches after cysteamine administration. However, in the hepatoduodenal branch vagotomized group, there was an increase in gastric acid secretion after cysteamine administration. A similar increase was observed in the control group, but the decreases in somatostatin concentration and PAS-positive mucus seen in the control group were not found in the hepatoduodenal vagotomized group. These results suggest that the hepatoduodenal branch of the vagus nerve might play an important role in the ulcerogenic process of cysteamine-induced duodenal ulcer.

Effect of duodenal ulcerogens mepirizole and propionitrile on small intestinal and liver alkaline phosphatase activity in rats

Duodenal ulcer could be induced in rats by a single subcutaneous injection of the anti-inflammatory agent mepirizole (M) or by the alkyl chemical propionitrile (P). Contrary to M, P provokes HCl hypersecretion as well. We used these animal models of duodenal ulcer to study the preulcerogenic molecular changes in the mucosal cells and their causal relationship to HCl hypersecretion. It was found that M and P induced the dose- and time-dependent decrease of duodenal alkaline phosphatase (DAP) activity. The decrease was detected at 4 h, with a nadir at 12 h after the injection of both drugs. The decrease of alkaline phosphatase activity was organ-specific after P administration and it was even regional-specific along the small intestine after M administration. At the level of mucosal cells of duodenum the effect of the ulcerogens was enzyme-selective. Both ulcerogens decreased protein and alkaline phosphatase activities; however, they had no effect on lysosomal acid phosphatase. Contrary to cysteamine (C), the effect of M and P on DAP depletion could not be reproduced under in vitro conditions. An interference of P and a slight additive effect of C on DAP depletion after simultaneous subcutaneous administration with M to the rats was found. The results indicate that the DAP depletion after in vivo administration of the three duodenal ulcerogens could be provoked by at least two different mechanisms. The decrease of DAP activity seems to be a general property of the duodenal ulcerogens independent of their effects on gastric acid secretion or on the suppression of alkaline secretion in the duodenum. As a late molecular event most probably elicited by the early morphological changes, the decrease of DAP activity could rather be related to ulcer healing than to its pathogenesis.

Pathogenesis of the earliest epithelial cell damage induced by mepirizole and cysteamine in the rat duodenum

Mepirizole (200 mg/kg) and cysteamine (100 mg/kg) induced epithelial cell damage in the proximal duodenum of rats within 30 min after s.c. administration. The injury induced was severe 60 min later. Gastric acid secretion determined in intact animals was stimulated by these agents 30 and 60 min later when the intraluminal pH of the duodenum was significantly decreased. Duodenal blood flow was significantly decreased beginning 5 min after administration up to 60 min. Oral treatment with sodium bicarbonate (300 mg/kg), cimetidine (100 mg/kg), omeprazole or NC-1300 (gastric proton pump inhibitors, 30 mg/kg) and 16,16-dimethyl prostaglandin E2 (10 micrograms/kg) protected the epithelium from damage induced by the two duodenal ulcerogens. Epithelial cell damage in the duodenum in response to mepirizole and cysteamine appears to be related to the increased gastric acid secretion followed by lowered intraduodenal pH of the duodenum having decreased blood flow.

The relationship of intraduodenal pH and delayed gastric emptying in duodenal ulceration induced by mepirizole or cysteamine in rats

Subcutaneous administration of mepirizole (60 and 200 mg/kg) and cysteamine (100 and 300 mg/kg) to fasted rats consistently induced localized villous damage to the proximal duodenum after 6 to 8 hr. The severity of the damage in animals treated with the low doses remained unchanged at 12 hr. With the high doses, however, well-defined deep ulcers were evident by that time, the incidence being high. The agents caused a significant accumulation of highly acidic gastric contents for 6 to 8 hr, but the accumulated gastric contents had markedly decreased by 12 hr. The intraduodenal pH in these animals was significantly lowered for 8 hr with the low doses, but for 12 hr with the high doses. Both mepirizole and cysteamine significantly delayed gastric emptying which was quantitated by weighing the food residue in refed animals. This delay in emptying was observed for 6 to 8 hr with the low doses and for 12 hr with the high doses. We conclude that this prolonged accumulation of gastric contents for up to 8 hr, resulting in a continuous lowering of the intraduodenal pH for 12 hr, is a crucial factor for the progression from duodenal villous damage to visible ulcers in response to mepirizole and cysteamine.

Pirenzepine prevents cysteamine-induced formation of gastroduodenal ulcers and reduction of mesenteric circulation

The effects of pirenzepine on gastric and duodenal ulceration and barrier mucus levels, as well as on changes of superior mesenteric artery diameter caused by cysteamine, were investigated in rats and compared with those of atropine. Cysteamine induced severe gastric and duodenal ulcers and decreased both barrier mucus levels and mesenteric blood flow. Pirenzepine reduced gastric and duodenal ulceration induced by cysteamine. Moreover, pirenzepine significantly increased basal mesenteric artery diameter and fully prevented cysteamine-induced decrease in mesenteric blood flow. Under the same conditions, atropine failed to prevent gastric and duodenal ulceration or mesenteric artery changes caused by cysteamine. Both pirenzepine and atropine were without any effect on cysteamine-induced inhibition of gastric and duodenal barrier mucus levels. The present results are consistent with the view that pirenzepine protects against gastroduodenal ulceration caused by cysteamine by increasing blood flow at the level of the ulcerated mucosa. The higher affinity of pirenzepine for the muscarinic receptors of sympathetic ganglia may explain the difference between the effects of pirenzepine and atropine. In addition to this, the measurement of superior mesenteric artery diameter changes may represent an accurate and reproducible method, suitable for studying the gastrointestinal protective mechanisms of the drugs.

Effect of duodenal ulcerogens cysteamine, mepirizole, and MPTP on duodenal myoelectric activity in rats

Increased gastric acid secretion, enhanced acid delivery to the duodenum, and reduced alkaline secretion in the proximal duodenum are relatively well-established pathophysiologic abnormalities in duodenal ulcer. Impaired duodenal motility, however, may also contribute to duodenal ulceration by altering the distribution of acid and alkaline secretions along the upper digestive tract. We tested the hypothesis that the duodenal ulcerogens cysteamine, MPTP, and mepirizole modify duodenal motility in the rat and that motility changes might be a common and early alteration in experimental duodenal ulceration. All three duodenal ulcerogens rapidly produced extensive changes in duodenal myoelectric activity and reduced the frequency of myoelectric slow waves. Cysteamine induced marked hypermotility for at least 6 hr; MPTP rapidly decreased motility and fragmented the myoelectric migrating pattern. Mepirizole induced biphasic changes: an early hypermotility phase of about 30 min was followed by profound hypomotility. These results indicate that marked alterations of duodenal motility are common during experimental duodenal ulceration. In light of the differential effect of the ulcerogens on duodenal motility, it remains to be determined how these changes influence acid neutralization in the proximal duodenum. Nevertheless, our results suggest that all three duodenal ulcerogens, which are different in structure, alter duodenal motility.

Influence of buthionine sulfoximine on the lethality of ifosfamide and ifosfamide-induced urotoxicity in mice

Buthionine sulfoximine (500 mg/kg, i.p.), a glutathione-depleting agent, was found to increase the acute lethal toxicity and urotoxicity induced by ifosfamide in mice.

The effect of prostacyclin and its analogues on cysteamine-induced duodenal ulceration of rats

The effect of prostacyclin and its analogues, -6-keto-prostaglandin-F1 alpha and 6-beta-prostaglandin-I1, on cysteamine induced duodenal ulceration of rats has been investigated. It seems that neither prostacyclin nor its analogues have antiulcerogenic effect in this model.

Role of prostanoids in experimental duodenal ulcer in rat

The purposes of this study were to determine whether inhibition of cyclooxygenase is a mechanism by which cysteamine and mepirizole produce duodenal ulcers, identify qualitative or quantitative differences in prostanoid production between gastric mucosa and duodenum, and determine whether differences in cyclooxygenase sensitivity to inhibition by aspirin exist between these two tissues. In fed female rats, gastric mucosal prostaglandin E2 (PGE2) and prostacyclin (PGI2) generation was 235 +/- 25 and 832 +/- 40 ng/g/min, respectively, whereas full-thickness duodenal PGE2 and PGI2 generation was 665 +/- 46 and 662 +/- 49 ng/g/min, respectively. Over an intraperitoneal dose range of 0-25 mg/kg, aspirin-induced cyclooxygenase inhibition was dose-dependent and similar for the two tissues. Duodenal ulceration (16.7 mm2) produced by cysteamine, 425 mg/kg, was associated with a 46% reduction in duodenal PGE2 generation, while having no effect on PGI2 generation; however, cysteamine, 213 mg/kg, produced no visible duodenal mucosa injury yet reduced duodenal PGE2 generation 39% compared to control values. In fed male rats, gastric mucosal PGE2 and PGI2 generation was 179 +/- 18 and 813 +/- 61 ng/g/min, respectively, whereas duodenal PGE2 and PGI2 generation was 321 +/- 27 and 454 +/- 38 ng/g/min, respectively. Duodenal ulceration (7.7 +/- 2.3 mm2) produced by oral mepirizole was associated with a 63% reduction in duodenal PGE2 generation compared to control values, while having no effect on PGI2 generation. Subcutaneous aspirin, 100 mg/kg, which reduced duodenal PGE2 generation to a greater degree than either ulcerogen, given in conjunction with pentagastrin, did not produce visible duodenal ulceration.(ABSTRACT TRUNCATED AT 250 WORDS)

From cysteamine to MPTP: structure-activity studies with duodenal ulcerogens

Cysteamine is the first chemical identified that induces acute and chronic duodenal ulcers in rodents. Structure-activity studies with cysteamine, propionitrile and their derivatives, as well as with analogues of toluene, revealed numerous alkyl and aryl duodenal ulcerogens. Among these, one of the most interesting from an etiologic and pathogenetic point of view is the dopaminergic neurotoxin MPTP, which shows structural similarities with toluene. The chemically-induced duodenal ulcers are similar and localized on the anterior and posterior wall of the duodenal bulb. Both cysteamine and MPTP affect endogenous dopamine; MPTP is especially potent in depleting central dopamine and inducing lesions in the substantia nigra. MPTP given in high doses induces Parkinson's disease-like syndrome and gastric ulcers. Cysteamine and propionitrile also cause dyskinesia in large and multiple doses. The motility disorders and duodenal ulcers are abolished by dopamine agonists. Cysteamine and MPTP have been known to increase and decrease gastric acid secretion, respectively. However, both compounds induced duodenal dysmotility, decreased bicarbonate production, and reduced its delivery from distal to proximal duodenum. These factors decrease acid neutralization in the duodenal bulb and contribute to duodenal ulceration. Thus, studies with animal models may reveal endogenous mediators and specific receptors which might be involved in the pathogenesis of duodenal ulceration. Specific structure-activity studies in toxicology may lead to new insights in the pathogenesis and pharmacology of a poorly understood human disorder such as duodenal ulceration.

Range of toxicity of topical cysteamine in rabbit eyes

Cysteamine eye drops in concentrations from 0.1% to 10% were tested in albino rabbits in both short and long-term experiments. Toxicity, consisting of an inflammatory response, was proportional to the cysteamine concentration and absent at concentrations at or below 0.5%.

[Effect of the ulcerogenic agent cysteamine on the content of glutathione and glutathione-dependent enzymes in the mucous membrane of the gastroduodenal region in the rat]

A comparative study of reduced and oxidized glutathione forms and the activity of glutathione-dependent enzymes (glutathione peroxidase, glutathione-S-transferase, and glutathione reductase) has been performed in the rat mucous membranes of different gastroduodenal areas 24 hours after the injection of cysteamine--a specific ulcerogenic agent. It has been shown that cysteamine causes a decrease in the concentration of reduced and an increase in the concentration of oxidized glutathione forms in all gastroduodenal areas. The fall in reduced glutathione form concentration is the greatest in the duodenal mucosa. A considerable decrease in glutathione-dependent enzyme activity, especially glutathione-S-transferase, was observed in duodenal mucosa. It is concluded that glutathione and glutathione-dependent enzyme system may be directly related to pathogenetic mechanisms of gastroduodenal ulcer formation.

Capsaicin-sensitive mechanisms and experimentally induced duodenal ulcers in rats

The incidence and degree of cysteamine- or dulcerozine-induced duodenal ulcers are increased by systemic capsaicin desensitization (50 mg kg-1 s.c. 4 days before) in adult rats. Acute administration of capsaicin, but not neurokinins or CGRP, produced a small but distinct plasma extravasation (Evans blue leakage) in the rat proximal duodenum which was absent in capsaicin-pretreated rats. These findings indicate the existence of a capsaicin-sensitive 'duodenal defence mechanism' in rats.

Mechanism of selective toxicity of 4-S-cysteinylphenol and 4-S-cysteaminylphenol to melanocytes

Our previous studies showed that 4-S-cysteinylphenol (4-S-CP) and 4-S-cysteaminylphenol (4-S-CAP) inhibit the growth of malignant melanoma and cause depigmentation of black skin. In this study we examined kinetic constants of CP and CAP as substrates for tyrosinases and their properties as sulphydryl scavengers. 4-S-CP and 4-S-CAP were found to be much better substrates for mushroom tyrosinase than L-tyrosine while their 2-S isomers were not the substrates. 4-S-CP and 4-S-CAP were also good substrates for mammalian tyrosinase. Upon tyrosinase oxidation the two phenols conjugated with cysteine to form the cysteinyl derivatives of the corresponding catechols via o-quinone forms. The tyrosinase oxidation product of 4-S-CP had a poor ability to conjugate with alcohol dehydrogenase, a sulphydryl enzyme, while that of 4-S-CAP had a much higher ability. These results suggest that in melanocytes these phenols are oxidised by tyrosinase to the corresponding o-quinone forms, some of which conjugate with sulphydryl enzymes through cysteine residues, thus exerting cytotoxic effects.

Regulation of somatostatin-14 and gastrin I binding sites in rat gastrointestinal mucosa by ulcerogenic dose of cysteamine

A single duodenal ulcerogenic dose of cysteamine administered into rats induced time-dependent depletion of immunoreactive somatostatin in the gastric corporeal, antral, and duodenal mucosa with a parallel increase (up-regulation) of somatostatin binding sites. The concentration of somatostatin binding sites returned to the control level in the corporeal mucosa when measured at 24 hrs; however, in the duodenal mucosa there was only a partial return to the control level. Somatostatin binding sites in the antral mucosa did not return to control level even after 24 hrs. Except for the duodenum mucosal immunoreactive gastrin level was unaffected by cysteamine administration, but corporeal mucosal gastrin I binding sites were diminished (down-regulation) after 24 hrs.

[The site (central or peripheral) of the anti-ulcer action of dalargin, a synthetic analog of endogenous opioids in an experimental model of cysteamine-induced duodenal ulcer in rats]

Dalargin injected subcutaneously at a dose of 10 micrograms/kg decreased 4-5 fold ulcer manifestations in rats with cysteamine-induced duodenal ulcers. Intracerebroventricular dose of 2 micrograms diminished the manifestations to a lesser extent Dalargin only at a dose exceeding 500 micrograms intraperitoneally decreased significantly the in vivo binding of 3H-D-Ala2, D-Leu5-enkephalin with brain opiate receptors. We believe that Dalargin injected peripherally in small doses does not penetrate the blood-brain barrier and that its antiulcer activity is due to the interaction with peripheral opioid receptors. It seems possible that the disturbances in the central/peripheral ratio of the opioid activity plays an important role in the pathogenesis of duodenal peptic ulcer.

Early ultrastructural changes in rat duodenal mucosa associated with cysteamine-induced ulcer

The early morphologic sequelae induced by the duodenal ulcerogen, cysteamine, have been studied in rats by transmission electron microscopy. Cysteamine was administered per os at 70 mg/100 g body wt to groups of female rats sacrificed at 30 min, 1, 2, 4, 8, 12, 20, and 24 hr after chemical treatment, and duodenal tissue sampled from the antimesenteric side of the proximal duodenum, where ulcers develop, was studied. Emphasis was placed on early times as our previous scanning electron microscopic data had demonstrated enhanced in situ cellular necrosis and surface cavitation at 2-4 hr after cysteamine treatment. Results indicated intracellular changes as early as 30 min after treatment and prior to damage of the columnar cell microvilli or epithelial tight junctions. A staging of observed cellular degenerative changes suggested early apical endoplasmic reticular swelling and loss of cytoplasmic ground substance, followed later by moderate internal disruption of mitochondria. Through these stages the cell surface microvilli remained morphologically normal. Subsequently, microvilli degenerated and mitochondrial fine structure became severely disrupted and cell contents were expelled. Deeper villous changes such as separation of columnar cells from the lamina propria and alterations of selected elements within the lamina propria were observed. These data suggest that intracellular cytotoxic reactions at the villous tips occur early and may precede the influence of intraluminal damaging factors induced by cysteamine.

Development and significance of cysteamine and propionitrile models of duodenal ulcer

Cysteamine is widely used in rodents to induce duodenal ulcer. Herein, the pathogenesis of duodenal ulceration in its earliest stages was reviewed using findings from cysteamine- and propionitrile-induced duodenal ulcer in rodent models, especially taking into account changes in the secretion of gastric acid, duodenal and pancreatic bicarbonate as well as gastroduodenal motility. The effect of cysteamine-HCl in inducing ulcers in rats is circadian rhythm-dependent. The effect is greatest from just before the end of diurnal rest to just after the start of nocturnal activity. The chronobiologic effect may be in part due to the circadian rhythm-dependent increased gastric acid production from cysteamine. Titratable acidity was found to be twice as great in the gastric juice of rodents when cysteamine was given by injection at 2000 (just after the start of nocturnal activity) in comparison to when given at 0800 or 1200 (at the beginning or middle span of daily rest). Further studies have shown that adrenalectomy of rats 7 days before cysteamine administration obliterated the observed circadian susceptibility to ulcer formation. Duodenal ulceration, at least in the cysteamine model, appears to be under chronobiologic neuroendocrine control or influence, seemingly mediated by the adrenal glands.

Depigmentation of black guinea pig skin by topical application of cysteaminylphenol, cysteinylphenol, and related compounds

Phenol and catechol were combined with sulfur to develop new melanocytotoxic agents. Among these synthetic compounds, 4-S-cysteaminylphenol (4-S-CAP) and 4-S-cysteinylphenol (4-S-CP), which showed an in vivo antimelanoma effect, were evaluated for cytotoxicity to normal epidermal melanocytes using hydroquinone (HQ) as the control. Topical application of 4-S-CAP on the skin of black guinea pigs revealed a marked depigmentation of black skin. 4-S-Cysteinylphenol also showed some depigmenting potency. 2-S-Cysteinylhydroquinone, which was made by combining cystine with HQ, on the other hand, did not show any depigmenting effect. Depigmentation of black skin by 4-S-CAP appeared to derive from: a decrease in the number of functioning melanocytes; a decrease in the number of melanosomes synthesized within the melanocytes and transferred to keratinocytes; and destruction of the membranous organelles of the melanocytes. None of these degenerative changes was observed in the keratinocytes, indicating the selective effect of 4-S-CAP on melanocytes.

Effects of indomethacin on the duodenal mucosa of rats: comparative study with cysteamine

Effects of indomethacin and cysteamine on the duodenal mucosa of rats were studied microscopically (using scanning electron microscopy) and also functionally. Indomethacin (5 mg/kg, s.c.) induced no microscopic damage to the duodenal epithelium for up to 6 hr after administration. Indomethacin had no effects on gastric H+ output and the amount of H+ in the duodenum, but did reduce the duodenal HCO3- secretion (both basal and 10 mM-HCl stimulated). PGE2 contents in the duodenal mucosa were markedly reduced by indomethacin for 6 hr. These results suggest that reductions of duodenal HCO3- secretion and endogenous prostaglandins per se do not impair the H+ disposal system of the duodenum and so do not damage the epithelial cells. In contrast, cysteamine (100 mg/kg, s.c.) produced microscopic damage to the duodenal epithelium as early as 2 hr later. Cysteamine significantly increased gastric H+ output and reduced duodenal HCO3- secretion, resulting in an increased amount of H+ in the duodenum 3 hr later. Cysteamine had no effect on PGE2 contents in the duodenum. The time lag between damage formation and functional changes suggests that the earliest damage caused by cysteamine occurs by mechanisms other than erosive action of H+ emptied by the stomach. The increased amount of H+ may contribute to an enhancement of the initial damage.

[Effect of testosterone, its 5 alpha-reduced metabolites, estradiol and progesterone on the formation of an experimental duodenal ulcer in male rats]

The influence of different doses (0.01, 0.1, 1.0, 10.0, 100.0, 250.0, 1,000.0, 2,500.0 gamma/kg body weight) of testosterone, dihydrotestosterone, 5 alpha-androstane-3 alpha, 17 beta-diol, 5 alpha-androstane-3 beta, 17 beta-diall, 4-androsterone-3,17-dione, estradiol and progesterone on the formation of cysteamine-induced duodenal ulcer was studied in mature male rats. It has been shown that all the steroids, but for progesterone, bring down the ulcer index after six days of i/p administration, the effect depending on the nature and dose of a steroid. Estradiol and 4-androstene-3,17-dione proved to be the most effective in the given dose range. The results do not only confirm the role of androgens and estradiol in the pathogenesis of duodenal ulcer, but also indicate the participation of their precursors and metabolites in the ulcer induction. The prospects of using steroids in the treatment of ulcer are discussed.

Gastric mucosal protection against ulcerogenic factors in the rat mediated by capsaicin-sensitive afferent neurons

Treatment of newborn rats with capsaicin (0.16 mmol/kg) is known to cause a permanent degeneration of certain, primarily unmyelinated, afferent neurons. In this study, experimentally induced gastric ulceration was investigated in adult rats treated with capsaicin as neonates. It was found that in capsaicin-treated animals the formation of gastric mucosal lesions in response to indomethacin, ethanol, or cysteamine was significantly enhanced as compared with vehicle-treated controls. The duodenal ulceration caused by cysteamine was not altered after capsaicin treatment. In further experiments the possible pathways involved in the effect of capsaicin treatment on gastric mucosal protection were explored. It was found that the capacity of gastric tissue to release prostaglandins E2 and I2 was unchanged after capsaicin treatment. Atropine, hexamethonium, cimetidine, or terbutaline all reduced gastric ulceration in response to indomethacin in both solvent- and capsaicin-treated rats but did not counteract the enhancement of the ulcerogenic effect of indomethacin in capsaicin-treated rats. Guanethidine enhanced the ulcerogenic effect of indomethacin in solvent-treated but not in capsaicin-treated animals. Ethanol-induced formation of gastric lesions remained unaltered by guanethidine in both solvent- and capsaicin-treated rats. These results indicate that capsaicin-sensitive afferent neurons are involved in gastric mucosal protection against ulcerogenic factors. The data further suggest that this type of gastric defense is primarily due to a local mechanism initiated by sensory nerve endings in the gastric mucosa.

Induction and suppression of seizures by cysteamine in hippocampal kindled rats

Cysteamine has a biphasic effect in kindled rats. At a dose of 200 mg/kg (i.p.), hippocampal kindled rats all have myoclonic seizures during the first hour after injection, while naive rats seldom do. Four hours after cysteamine, the animals exhibited stage 5 seizures when stimulated. However, kindled seizures could not subsequently be elicited for up to 10 days in these animals.