Prodrugs of Peptides. 13. Stabilization of Peptide Amides Against α-Chymotrypsin by the Prodrug Approach

Various derivatives of the C-terminal amide group in N-protected amino acid and peptide amides were synthesized to assess their suitability as prodrug forms with the aim of protecting the amide or peptide bond against cleavage by -chymotrypsin. Whereas N-acetylation, N-hydroxymethylation, and N-phthalidylation did not afford any protection but, in fact, accelerated the terminal amide bond cleavage, condensation with glyoxylic acid to produce peptidyl--hydroxyglycine derivatives and, to a minor extent, N-aminomethylation were found to improve the stability of the parent amides. Besides protecting the terminal, derivatized amide moiety toward cleavage by -chymotrypsin, -hydroxyglycine derivatization resulted in a significant protection, by a factor ranging from 5 to 75, of the internal peptide bond in various N-protected dipeptide amides. These derivatives are readily bioreversible, the conversion to the parent peptide or amino acid amide taking place either by spontaneous hydrolysis at physiological pH, as demonstrated for the N-Mannich bases, or by catalysis by plasma, as for peptidyl--hy-droxyglycine derivatives.     

Effect of rifampicin.treatment on the metabolism of oestradiol and 17α-ethinyloestradiol by human liver microsomes

Summary Liver biopsies were obtained from four patients treated with rifampicin 600 mg for 6–10 days. Hepatic microsomes were incubated with an NADPH-regenerating system and the substrates [2, 4, 6, 7--³H] oestradiol, [6, 7-³H] oestradiol, [2, 4, 6, 7-³H] ethinyloestradiol and [6, 7-³H] ethinyloestradiol. The hydroxylation rates of these steroids at the labelled positions of rings A and B were determined by measuring the transformation of tritium into HTO by the microsomal enzymes. Comparison with previously published data showed that treatment with rifampicin caused a fourfold increase in the rate of hydroxylation of oestradiol and ethinyloestradiol at positions C-2/C-4 of ring A and C-6/C-7 of ring B. The acceleration of oestrogen hydroxylation by rifampicin was paralleled by an increase in microsomal cytochrome P-450, and also by microsomal reduction of rifampicin-quinone, a reactive metabolite of rifampicin. The increased aromatic hydroxylation of oestradiol and ethinyloestradiol leads to enhancement of their irreversible binding to microsomal protein. The data provide an explanation for the diminished efficacy of oestrogens in contraceptive formulations given to patients under treatment with rifampicin.Part of the results described in this paper has been presented in preliminary form (Bolt, Kappus and Bolt, 1974a)     

Use of the Peptide Carrier System to Improve the Intestinal Absorption of L-α-Methyldopa: Carrier Kinetics,Intestinal Permeabilities,and In Vitro Hydrolysis of Dipeptidyl Derivatives of L-α-Methyldopa

Intestinal permeabilities of five dipeptidyl derivatives of L--methyldopa (I) were studied by an in situ intestinal perfusion method. The dipeptides displayed a significant increase in their permeabilities compared to L--methyldopa. The increases ranged from 4 to 20 times. These results suggest that the peptide transport system is less structurally specific than the amino acid transport systems and can be used as an absorption pathway for peptide analogues. The kinetic advantage demonstrated by the dipeptide, L--methyldopa-L-phenylalanine, over the amino acid analogue, L--methyldopa, suggests that the peptide carrier would be a possible route for improving the intestinal absorption of pharmacologically active amino acid analogues. Furthermore, the preliminary results of in vitro hydrolysis studies of selected dipeptidyl derivatives indicate that the peptide carrier system could be used as a base for a prodrug strategy.     

Corrigendum to “Inhibition of Key Digestive Enzymes Related to Diabetes and Hyperlipidemia and Protection of Liver-Kidney Functions by Trigonelline in Diabetic Rats” [Sci Pharm. 2013; 81: 233–246]

This is a corrigendum to the article ‘Inhibition of Key Digestive Enzymes Related to Diabetes and Hyperlipidemia and Protection of Liver-Kidney Functions by Trigonelline in Diabetic Rats’ [Sci Pharm. 2013; 81: 233–246]. Figure 6 is replaced.     

Characterization of the Pharmacology of Recombinant Human GABAA Receptor Complexes Containing A2（α1 isoleucin 148 to valine） or A2（α1 asparatic acid 151 to asparagin） or A2 （α1 threonine 149 to glutamine） in Combination with β2γ2s Subu

Recombinant human GABAA receptors were investigated in vitro by coexpression of cDNAs coding for α1,β2 and γ2 subunits in the baculovirus/Sf-9 insect cell system,A single amino acid exchange α1(asparatic acid 151 to asparagin or α1(threonine 149 to glutamine) in the N-terminal,extracellular part of the α1 subunit induced about 10 fold decrease in an antagonist pitrazepine affinity.Other GABAA receptor ligands had little difference in their affinity.It was likely that 151 and 149 amino acid residues were essential for the binding affinity and efficacy of pitrazepine to GABAA receptor combinations containiαααααααααng an α1 subunit.     

Human exposure to synthetic endocrine disrupting chemicals (S-EDCs) is generally negligible as compared to natural compounds with higher or comparable endocrine activity. How to evaluate the risk of the S-EDCs?

ABSTRACT

Theoretically, both synthetic endocrine-disrupting chemicals (S-EDCs) and natural (exogenous and endogenous) endocrine-disrupting chemicals (N-EDCs) can interact with endocrine receptors and disturb hormonal balance. However, compared to endogenous hormones, S-EDCs are only weak partial agonists with receptor affinities several orders of magnitude lower than S-EDCs. Thus, to elicit observable effects, S-EDCs require considerably higher concentrations to attain sufficient receptor occupancy or to displace natural hormones and other endogenous ligands.

Significant exposures to exogenous N-EDCs may result from ingestion of foods such as soy-based diets, green tea, and sweet mustard. While their potencies are lower as compared to natural endogenous hormones, they usually are considerably more potent than S-EDCs.

Effects of exogenous N-EDCs on the endocrine system were observed at high dietary intakes. A causal relation between their mechanism of action and these effects is established and biologically plausible. In contrast, the assumption that the much lower human exposures to S-EDCs may induce observable endocrine effects is not plausible. Hence, it is not surprising that epidemiological studies searching for an association between S-EDC exposure and health effects have failed.

Regarding testing for potential endocrine effects, a scientifically justified screen should use in vitro tests to compare potencies of S-EDCs with those of reference N-EDCs. When the potency of the S-EDC is similar or smaller than that of the N-EDC, further testing in laboratory animals and regulatory consequences are not warranted.     

Human exposure to synthetic endocrine disrupting chemicals (S-EDCs) is generally negligible as compared to natural compounds with higher or comparable endocrine activity. How to evaluate the risk of the S-EDCs?

Theoretically, both synthetic endocrine disrupting chemicals (S-EDCs) and natural (exogenous and endogenous) endocrine disrupting chemicals (N-EDCs) can interact with endocrine receptors and disturb hormonal balance. However, compared to endogenous hormones, S-EDCs are only weak partial agonists with receptor affinities several orders of magnitude lower. Thus, to elicit observable effects, S-EDCs require considerably higher concentrations to attain sufficient receptor occupancy or to displace natural hormones and other endogenous ligands.Significant exposures to exogenous N-EDCs may result from ingestion of foods such as soy-based diets, green tea and sweet mustard. While their potencies are lower as compared to natural endogenous hormones, they usually are considerably more potent.Effects of exogenous N-EDCs on the endocrine system were observed at high dietary intakes. A causal relation between their mechanism of action and these effects is established and biologically plausible. In contrast, the assumption that the much lower human exposures to S-EDCs may induce observable endocrine effects is not plausible. Hence, it is not surprising that epidemiological studies searching for an association between S-EDC exposure and health effects have failed.Regarding testing for potential endocrine effects, a scientifically justified screen should use in vitro tests to compare potencies of S-EDCs with those of reference N-EDCs. When the potency of the S-EDC is similar or smaller than that of the N-EDC, further testing in laboratory animals and regulatory consequences are not warranted.     

Human exposure to synthetic endocrine disrupting chemicals (S-EDCs) is generally negligible as compared to natural compounds with higher or comparable endocrine activity. How to evaluate the risk of the S-EDCs?

Theoretically, both synthetic endocrine disrupting chemicals (S-EDCs) and natural (exogenous and endogenous) endocrine disrupting chemicals (N-EDCs) can interact with endocrine receptors and disturb hormonal balance. However, compared to endogenous hormones, S-EDCs are only weak partial agonists with receptor affinities several orders of magnitude lower. Thus, to elicit observable effects, S-EDCs require considerably higher concentrations to attain sufficient receptor occupancy or to displace natural hormones and other endogenous ligands.Significant exposures to exogenous N-EDCs may result from ingestion of foods such as soy-based diets, green tea and sweet mustard. While their potencies are lower as compared to natural endogenous hormones, they usually are considerably more potent than S-EDCs.Effects of exogenous N-EDCs on the endocrine system were observed at high dietary intakes. A causal relation between their mechanism of action and these effects is established and biologically plausible. In contrast, the assumption that the much lower human exposures to S-EDCs may induce observable endocrine effects is not plausible. Hence, it is not surprising that epidemiological studies searching for an association between S-EDC exposure and health effects have failed.Regarding testing for potential endocrine effects, a scientifically justified screen should use in vitro tests to compare potencies of S-EDCs with those of reference N-EDCs. When the potency of the S-EDC is similar or smaller than that of the N-EDC, further testing in laboratory animals and regulatory consequences are not warranted.     

Strain specific induction of pyometra and differences in immune responsiveness in mice exposed to 17α-ethinyl estradiol or the endocrine disrupting chemical bisphenol A

Pyometra is an inflammatory disease of the uterus that can be caused by chronic exposure to estrogens. It is unknown whether weakly estrogenic endocrine disruptors can cause pyometra. We investigated whether dietary exposures to the estrogenic endocrine disruptor bisphenol A (BPA) induced pyometra. Pyometra did not occur in CD1 mice exposed to different dietary doses of BPA ranging from 4.1 to >4000μg/kg-d or 17α-ethinyl estradiol (EE; 1.2 to >150μg/kg-d). In the C57BL/6 strain, pyometra occurred in the 15μg/kg-d EE and 33μg/kg-d BPA treatment groups. At the effective concentration of BPA, histological analysis revealed pathological alterations of uterine morphology associated with a >5.3-fold increase in macrophage numbers in non-pyometra uteri of C57BL/6 mice exposed to BPA. These results suggest that BPA enhances immune responsiveness of the uterus and that heightened responsiveness in C57BL/6 females is related to increased susceptibility to pyometra.     

Effect of selective phosphodiesterase 4 inhibitor,rolipram, on cytokine and gelatinase B （MMP-9） release in the whole blood from adult patients with cystic fibrosis.

AIM: Inflammation plays a critical role in lung disease progression in cystic fibrosis being able to be associated with the development of tissue remodeling. These processes are mainly due to pro-inflammatory cytokines release and to an imbalance between proteases and antiproteases involving matrix metalloproteinases (MMP). Phosphodiesterase 4 (PDE4) inhibitors, by elevating intracellular cAMP, are known to be potent inhibitors of