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.

Hepatic lipid metabolism disorders and immunotoxicity induced by cysteamine in early developmental stages of zebrafish.

Cysteamine, a sulfhydryl compound, is an intermediate in the metabolism of coenzyme A to taurine in living organisms. However, the potential side effects of cysteamine such as hepatotoxicity in pediatric patients have been reported in some studies. To evaluate the impact of cysteamine on infants and children, larval zebrafish (a vertebrate model) were exposed to 0.18, 0.36 and 0.54 mM cysteamine from 72 hpf to 144 hpf. Alterations in general and pathological evaluation, biochemical parameters, cell proliferation, lipid metabolism factors, inflammatory factors and Wnt signaling pathway levels were examined. Increased liver area and lipid accumulation were observed in liver morphology, staining and histopathology in a dose-dependent manner with cysteamine exposure. In addition, the experimental cysteamine group exhibited higher alanine aminotransferase, aspartate aminotransferase, total triglyceride and total cholesterol levels than the control group. Meanwhile, the levels of lipogenesis-related factors ascended whereas lipid transport-related factors descended. Oxidative stress indicators such as reactive oxygen species, MDA and SOD were upregulated after cysteamine exposure. Afterwards, transcription assays revealed that biotinidase and Wnt pathway-related genes were upregulated in the exposed group, and inhibition of Wnt signaling partially rescued the abnormal liver development. The current study found that cysteamine-induced hepatotoxicity in larval zebrafish is due to inflammation and abnormal lipid metabolism, which is mediated by biotinidase (a potential pantetheinase isoenzyme) and Wnt signaling. This provides a perspective on the safety of cysteamine administration in children and identifies potential targets for protection against adverse reactions.

A novel treatment of cystic fibrosis acting on-target: cysteamine plus epigallocatechin gallate for the autophagy-dependent rescue of class II-mutated CFTR.

We previously reported that the combination of two safe proteostasis regulators, cysteamine and epigallocatechin gallate (EGCG), can be used to improve deficient expression of the cystic fibrosis transmembrane conductance regulator (CFTR) in patients homozygous for the CFTR Phe508del mutation. Here we provide the proof-of-concept that this combination treatment restored CFTR function and reduced lung inflammation (P<0.001) in Phe508del/Phe508del or Phe508del/null-Cftr (but not in Cftr-null mice), provided that such mice were autophagy-competent. Primary nasal cells from patients bearing different class II CFTR mutations, either in homozygous or compound heterozygous form, responded to the treatment in vitro. We assessed individual responses to cysteamine plus EGCG in a single-centre, open-label phase-2 trial. The combination treatment decreased sweat chloride from baseline, increased both CFTR protein and function in nasal cells, restored autophagy in such cells, decreased CXCL8 and TNF-α in the sputum, and tended to improve respiratory function. These positive effects were particularly strong in patients carrying Phe508del CFTR mutations in homozygosity or heterozygosity. However, a fraction of patients bearing other CFTR mutations failed to respond to therapy. Importantly, the same patients whose primary nasal brushed cells did not respond to cysteamine plus EGCG in vitro also exhibited deficient therapeutic responses in vivo. Altogether, these results suggest that the combination treatment of cysteamine plus EGCG acts 'on-target' because it can only rescue CFTR function when autophagy is functional (in mice) and improves CFTR function when a rescuable protein is expressed (in mice and men). These results should spur the further clinical development of the combination treatment.

HEC-cysteamine conjugates: influence of degree of thiolation on efflux pump inhibitory and permeation enhancing properties.

Within the present study hydroxyethyl cellulose-cysteamine conjugates are investigated regarding biocompatibility, in situ gelling, permeation enhancing and efflux pump inhibitory properties. For this purpose, a series of concentrations of sodium periodate was prepared to oxidize HEC leading to ring opening of glucose subunits. The resulting polymers showing varying degrees of oxidation (DO) were then conjugated with cysteamine stabilized via reductive amination. Consequently, HEC-cysteamine conjugates with increasing degree in thiolation were obtained. Since the conjugates are positively charged, potency of cytotoxicity was tested by resazurin assay. In situ gelling properties of the conjugates were studied to investigate change of their viscosity due to inter- and/or intramolecular crosslinking via disulfide bonds. The influence of the presence of the conjugates on transport of rhodamine 123 and fluoresceinisothiocyanate-dextran 4 (FD4) representing model compounds for P-glycoprotein (P-gp) inhibition and permeation enhancing studies, respectively, across Caco-2 cell monolayers was determined. The conjugates showed a degree of thiolation in the range of 316-2158 µmol/g. Within 30 min, dynamic viscosity of the conjugate with the lowest degree of thiolation 0.5% (m/v) increased up to 300-fold. The conjugates showed a degree of thiolation-dependent increase in cytotoxicity but they all were found comparatively low cytotoxic. The addition of the conjugate with thiol group content of 1670 µmol/g resulted in the highest improvement in the transport of both rhodamine 123 and FD4 as compared to buffer control. Accordingly, the degree of thiolation strongly influences the properties of the conjugates and the modulation of the degree of thiolation could be exploited for development of various drug delivery systems.

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-5ß-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.

Effects of captopril on the cysteamine-induced duodenal ulcer in the rat.

Oxidative stress is important factor underlying in a variety of diseases. Antioxidative enzymes such as superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) are part of the physiological defenses against oxidative stress. Malondialdehyde (MDA) is a lipid peroxidation biomarker and its elevated level in various diseases is related to free radical damage. Cysteamine is a cytotoxic agent, acting through generation of reactive oxygen species (ROS) and may decrease defense activity of antioxidative enzymes against ROS and induce duodenal ulcer. Captopril, acts as free radical scavengers and protect against injuries from oxidative damage to tissues.The aim of this study was the evaluation of the effect of captopril against cysteamine-induced duodenal ulcer by determining duodenal damage, duodenal tissue SOD and GSH-PX activities and plasma MAD level. This study was performed on 3 groups of 7 rats each: saline, cysteamine and cysteamine plus captopril treated groups. The effect of captopril against cysteamine-induced duodenal ulcer is determined by evaluating the duodenal damage, duodenal tissue SOD and GSH-PX activities and plasma MDA level. All animals were euthanized 24h after the last treatment and 2 ml blood and duodena samples were collected for calculation of ulcer index, histopathological assessment and measurement of tissue SOD, GSH-PX activities and plasma MDA level. Cysteamine produced severe duodenal damage, decreased the activity of duodenal tissue SOD and GSH-PX and increased the plasma MDA level compared with saline pretreated rats. Pretreatment with captopril decreased the cysteamine-induced duodenal damage and plasma level of MDA and increased the activities of SOD and GSH-PX in duodenal tissue compared with cysteamine pretreated animal. Our results suggest that captopril protects against cysteamine-induced duodenal ulcer and inhibits the decrease in SOD and GSH-PX activities and lipid peroxidation by increasing antioxidant defenses.

Cysteamine toxicity in patients with cystinosis.

OBJECTIVE: To report new adverse effects of cysteamine. STUDY DESIGN: Detailed clinical information was obtained from the patients' physicians. RESULTS: New adverse events were reported in 8 of 550 patients with cystinosis treated with cysteamine in Europe during the last 5 years. Detailed clinical information was not available for 2 of these patients, 1 of whom died from cerebral ischemia. The 6 evaluable patients developed vascular elbow lesions (6/6), neurologic symptoms (1/6), bone and muscle pain (2/6), and/or skin striae (2/6). Analysis of biopsy specimens from the elbow lesions demonstrated angioendotheliomatosis with irregular collagen fibers. In 3 of the 6 patients, the daily cysteamine dose exceeded the recommended maximum of 1.95 g/m(2)/day. Dose reduction led to improvement of signs and symptoms in all 6 patients, suggesting a causal relationship with cysteamine administration. CONCLUSION: Cysteamine administration can be complicated by the development of skin, vascular, neurologic, muscular, and bone lesions. These lesions improve after cysteamine dose reduction. Doses >1.95 g/m(2)/day should be prescribed with great caution, but underdosing is not advocated.

Pharmacological efficacy of argemone mexicana plant extract, against cysteamine-induced duodenal ulceration in rats.

OBJECTIVE: The plant Argemone mexicana is traditionally used as diuretic, anti-inflammatory, antibacterial, antifungal agent, and has wound-healing property. This study was carried out to evaluate the effect of A. mexicana aerial part of the plant (methanolic and aqueous extract p.o.) on duodenal ulceration. MATERIALS AND METHODS: The study was carried out on the duodenal ulceration model by using cysteamine hydrochloride. Ranitidine (20 mg/kg) was used as standard drug. RESULTS: Both the extracts of the plant A. mexicana produced a significant activity in cysteamine-induced duodenal ulceration. The aqueous extract at the dose-dependent manner showed the potent activity than methanolic extract. CONCLUSION: The plant A. mexicana Linn. Increased healing of gastric ulceration and prevented the development of experimentally induced duodenal ulceration in rats.

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.

Formulation and in vitro evaluation of cysteamine hydrochloride viscous solutions for the treatment of corneal cystinosis.

In the present study, viscous solutions of cysteamine hydrochloride (CH) were prepared by using 0.5%, 1.0%, 1.5% or 3.0% of hydroxypropylmethylcellulose (HPMC) and were evaluated for their in-vitro characteristics and stability. Osmolalities, pH and viscosity of the formulations were determined. The influence of benzalkonium chloride and autoclave sterilization on solution characteristics was also investigated. For stability assessment, the viscous solutions were stored at +4 and +25 degrees C over 12 months. In-vitro characteristics and CH contents of the stored solutions were monitored. Irritation tests for the formulations were evaluated on rabbit eyes. Dialysis sac technique was used to perform in vitro release study of the solutions containing 1.0% and 1.5% HPMC. All of the viscous solutions tested showed non-newtonian (dilatant) flow behavior. Osmolality values were ranked between 351.2+/-6.2 and 355.1+/-7.9 mOsm kg(-1), and pH values were between 3.97+/-0.1 and 3.98+/-0.2 for all the solutions. Furthermore, no significant changes in dilatant behavior, osmolality or pH values of the pure HPMC solutions were observed. After addition of the excipients or CH-excipients, increased viscosity values were noted in these formulations. Neither benzalkonium chloride nor autoclave sterilization had any influence on viscosity, pH or osmolality values of the solution containing 1.5% HPMC. Stability studies showed that a faster decrease in the concentration of CH was observed in the formulations stored at 25 degrees C compared to those kept at 4 degrees C; no changes were determined in osmolality values of the solutions at all storage conditions. Increased pH and decreased viscosity values were noted in HPMC solutions containing CH and excipients, while no changes in these values were observed for pure HPMC solutions kept at 4 and 25 degrees C. In vitro release tests revealed that 81.2% and 85.3% of CH were released from the viscous solutions containing 1.5% and 1% HPMC, respectively, in 8h. No irritation was observed when the viscous solutions were tested on rabbit and human eyes.

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.

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.

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.

[Oxidative metabolism of HIV-infected macrophages: the role of glutathione and a pharmacologic approach]. / Métabolisme oxydatif dans les macrophages infectés par le VIH: rôle du glutathion et approche pharmacologique.

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.

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.

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.

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.