Growth hormone and somatostatin interaction in the ulcerogenic effect of cysteamine in female rats

It is known that cysteamine's ulcerogenic effect depends, among others, on a depletion of somatostatin (SRIH). Since growth hormone (GH) affects the release of hypothalamic SRIH, we have studied the influence of GH and the GH-SRIH interaction on the severity of gastric mucosa lesions induced by cysteamine. Female rats of the Sprague-Dawley strain were pretreated with GH (1 mg/kg) and subjected to cysteamine-induced gastric lesions. We found that these animals showed an increased mortality and severity of gastric lesions. Pretreatment with SRIH (25 or 50 μg/kg) was followed by a decrease in mortality and of incidence and severity of gastric mucosa lesions as compared to those found in control animals pretreated with saline. The dose of 5μg/kg was ineffective in this respect. The combined administration of GH and SRIH revealed that cysteamine ulcerogenic action remained unchanged. It is possible that high levels of plasma GH, as induced by exogenous GH administration, may decrease the release of gastro-intestinal SRIH and this in turn may potentiate the ulcerogenic activity of cysteamine.     

Effect of hyperthermia on the radioprotective action of cysteamine and isoproterenol

Heating of mouse bone marrow cells up to 42 degrees C was shown to increase their radiosensitivity (DMF = 0.80 +/- 0.12). At this temperature, the radioprotective efficiency of cysteamine was lost completely (DMF = 0.78 +/- 0.09), and radioprotective activity of d,l-isoproterenol significantly decreased (DMF declined from 2.41 +/- 0.23 to 1.67 +/- 0.16). It is assumed that the radioprotective effect of cysteamine on mammalian cells is associated with the processes of the postirradiation DNA repair for just these processes are inhibited by heating. The mechanism of action of a beta-agonist of isoproterenol is perhaps only partially associated with DNA repair.     

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.     

Antiulcerous efficacy of reamberin at the background of the stress ulcerogenic factor action

The effect of reamberin on morphofunctional changes in the small intestine mucous membrane due to stress ulcerogenesis was studied. Normalization of the lipid modifications in the tissue structure, evident of the drug antiulcerous properties, was observed.     

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.     

Metabolic interactions between cysteamine and epigallocatechin gallate

Phase II clinical trials indicate that the combination of cysteamine plus epigallocatechin gallate (EGCG) is effective against cystic fibrosis in patients bearing the most frequent etiological mutation (CFTRΔF508). Here, we investigated the interaction between both agents on cultured respiratory epithelia cells from normal and CFTRΔF508-mutated donors. We observed that the combination of both agents affected metabolic circuits (and in particular the tricarboxylic acid cycle) in a unique way and that cysteamine plus EGCG reduced cytoplasmic protein acetylation more than each of the 2 components alone. In a cell-free system, protein cross-linking activity of EGCG was suppressed by cysteamine. Finally, EGCG was able to enhance the conversion of cysteamine into taurine in metabolic flux experiments. Altogether, these results indicate that multiple pharmacological interactions occur between cysteamine and EGCG, suggesting that they contribute to the unique synergy of both agents in restoring the function of mutated CFTRΔF508.     

Interrelation between structure and protective action of normal and pathological ceruloplasmins during copper-induced lysis of red blood cells

The origin of the difference between the protective action of ceruloplasmin (CP) from healthy donors blood and of ceruloplasmin-like protein (p-CP) from blood of patients with Wilson disease which they exert during copper-induced lysis of red blood cells (RBC) was elucidated. The difference is due to a significant change in the carbohydrate moiety of p-CP the major proportion of which (65%) does not contain mannose and acetylglucosamine residues. The data of chromatography on lentil lectin reveal that only 4% of p-CP molecules contain the fragment [table: see text] required for binding to RBC receptors. It was shown that the time-courses of copper accumulation in RBC of normal donors and in RBC of patients with Wilson disease (p-RBC) during copper-induced lysis differ markedly from each other. The p-CP is able to prevent copper accumulation in RBC and p-RBC to a significantly less degree than CP. It was also established that CP prevents the decrease of reduced glutathione (GSH) level in RBC to a greater extent than p-CP. In contrast to CP, the p-CP exerts no effect on the decrease in GSH concentration in p-RBC. These results may indicate that no interaction between Cu2+ and reduced glutathione takes place in p-RBC, in contrast to the situation occurring in normal RBC.     

Computer search for molecular mechanisms of ulcerogenic action of non-steroidal anti-inflammatory drugs

Peptic ulcers are the most frequent side effect of therapy with non-steroidal anti-inflammatory drugs (NSAIDs). Good experimental evidence exists that pathogenesis of peptic ulcers cannot be attributed only to inhibition of cyclooxygenases. The knowledge about other molecular mechanisms of drug action associated with development of peptic ulcers could be useful for design of new safer NSAIDs. However, considerable time and material resources are needed for corresponding experimental studies. For simplification of the experimental search, we have developed an approach for in silico identification of putative molecular mechanisms of drug actions associated with their side effects. We have generated a data set of 85 NSAIDs, which includes information about their structures and side effects. Unknown molecular mechanisms of action of these NSAIDs were evaluated by the computer program PASS (Prediction of Activity Spectra for Substances) predicting more than 3000 molecular mechanisms of action based on structural formula of sub-stances. Statistically significant associations have been found between predicted molecular mechanisms of action and development of peptic ulcers. Twenty six molecular mechanisms of action probably associated with development of peptic ulcers have been found: two of them were known previously and 24 were quite new. Analyzing Gene Ontology data, data on signal and metabolic pathways, and available MEDLINE publication data, we proposed hypotheses on the role of 10 molecular mechanisms of action in the pathogenesis of peptic ulcer.     

Synergistic action of cysteamine and BrdU-substituted DNA in the induction of sister chromatid exchanges

The effect of different BrdU-concentrations on the cysteamine-induced SCE-rate was investigated in V-79 Chinese hamster cell monolayer cultures. Both cysteamine and its auto-oxidation product cystamine act synergistically with BrdU in the induction of SCEs. A given concentration of these substances produces a low SCE-frequency at low BrdU-concentrations — but the incidence of SCEs is significantly increased at increased BrdU-concentrations. — Using one-cycle substitution experiments and the determination of the relative level of substitution by means of ³HBrdU-incorporation, this synergism was shown to depend on the BrdU incorporated in the DNA and on the extent to which this incorporation takes place.     

Interrelation between thrombin structure and its stability

Temperature inactivation of human thrombin has been studied when finding out the mechanism of this enzyme stabilization by amino acids. Effect of a number of amino acids on thrombin in the conditions (pH) of the highest activity of proteinase has been investigated. It is established that most amino acids are characterized to more or less extent by the protective action, when hampering the temperature inactivation of the enzyme. The correspondence was mainly found between the stabilizing effect of amino acids and thrombin specificity. Thrombin is stabilized by L-arginine and DL-lysine more intensively than by other amino acids. A stabilizing effect of L-glutamic acid was shown in contrast to the action of the latter on trypsin that was obviously connected with the original structure of the active centre of thrombin, that is the availability of anionic binding centre which includes Lys68, Arg72, Arg77. High thrombin stabilization by such amino acids as phenylalanine, DL-serine, DL-methonine was an exception. It was established that amino acids stabilize thrombin with formation of a compound with the reactive centre of its molecule, like the compounds enzyme-substrate. The macrostructure stability probably depends, to a considerable extent, on the state of the enzyme reactive centre: thrombin molecules, which contain a free reactive centre, are more labile than those which reactive centre is bound to the reagent of more or less specific character. The inhibition of the autolysis process may be another manifestation of thrombin stabilization by amino acids.     

Interrelation between penicillin productivity and growth rate

Summary Fermentations were carried out in an 801 tower-loop reactor with pellets of Penicillium chrysogenum. The development of the inner structure of the pellets with regard to various fermentation conditions was observed by means of histological preparations of the pellets. Under conditions of energy-source-limitation mycelial tip growth and lysis of other mycelial parts exist simultaneously. Thus the net growth rate (formation rate of cell mass) is higher than the gross growth rate (multiplication rate of cell mass). Under conditions of nitrogen limitation, gross growth rate and net growth rate are identical. A very strict correlation between gross growth rate and penicillin production rate was found as long as sufficient oxygen supply could be maintained and carbon catabolite repression was avoided. The energy source requirement of the biomass can be described with the sum of three terms that correspond to gross growth, lysis compensation growth and maintenance.Symbols a Constant 1/l h - b Constant - K Decay rate constant for product 1/h - K ₁ Substrate inhibition constant g/l - K _op Controls saturation constant for oxygen g/l - K _p Saturation constant for substrate g/l - m Maintenance coefficient 1/h - ms Apparent maintenance coefficient 1/h - O Dissolved oxygen concentration g/l - P Product concentration g/l - p Exponent of O - q Specific productivity 1/h - S Substrate concentration g/l - t Time h - t ₁ Beginning of production phase h - t ₂ Time of pellet dissolution h - V Liquid volume of fermentation broth l - X Dry cell mass concentration g/l - Y Yield of dry cell mass from energy substrate - g Specific gross growth rate of biomass 1/h - l Specific lysis rate of cell mass 1/h - n Specific net growth rate of cell mass 1/h - p Maximum specific rate of product formation 1/h     

Interrelation between thrombin structure and its stability

Data concerning peculiarities of fermentative nature and structure of thrombin in water-salt solution have been generalized; regularities of stabilizing effect made on thrombin by various polyols and other substances have been analyzed. It has been shown that formation of thrombin optimum macrostructure is one of the methods of its stabilization. Presence of different dissolving additives changes this enzymes hydration and this affects its stability and activity. There exist some systems to stabilize thrombin solutions. The systems consist of various salts, low-molecular and high-molecular polyols, surfactants, protein chain, composition buffer, etc. It has been shown that optimal concentrations of polyols, buffer salts and surfactants, as well as protein interaction increase considerably thrombin stability, preserving secondary structure even under its low concentration in the solution.     

Interrelation between gluconeogenesis and hepatic protein sysnthesis

Acute administration of glucagon to the rat in vivo inhibits hepatic polypeptide chain elongation by about 30% This effect was not observed in adrenalectomized rats, despite the significant increases in the hepatic content of cyclic AMP. Fatty acid administration mimics the glucagon action on protein systhesis; however, in adrenalectomized animals they were ineffective. Whether glucagon or fatty acids were administered, there was a significant increase in the state of reduction of the NAD system in normal as well as in adrenalectomized rats. This observation rules out the change in the cellular state of reduction as the mediator of their action on protein synthesis. A correlation was observed between the ability of glucagon or fatty acids to inhibits proteinp synthesis and to stimulate gluconeogenesis. An increased phosphorylation state of as reflected by an increased gluconeogenesis flux is accompanied by a decreased phosphorylation state of adenine nucleotides that might be responsible for the inhibitory effect on protein sysnthesis. In adrenalectomized animals in which neither glucagon nor fatty acids stimulate gluconeogenesis, no effects on phosphorylation state or on the rate of protein synthesis were detected.     

The preventive influence of cysteamine on the teratogenic action of 5-azacytidine.

The radioprotective agent cysteamine can prevent the teratogenic action of 5-azacytidine in rat fetuses. The preventive influence of cysteamine was observed when applied to the mother not only 3 hours and 30 minutes before the 5-azacytidine administration, but also 30 minutes after it. However, the application of cysteamine 3 hours after the administration of 5-azacytidine showed no preventive influence.