Importance of monoamine oxidase A in the bioactivation of neurotoxic analogs of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) is a potent dopaminergic neurotoxin that causes biochemical, pharmacological, and pathological deficits in experimental animals similar to those seen in human parkinsonian patients. All of the deficits can be prevented by treating mice with selective inhibitors of monoamine oxidase B (MAO-B), including deprenyl, prior to MPTP administration. We now report that the dopaminergic neurotoxicity of two potent MPTP analogs, namely the 2'-methyl and 2'-ethyl derivatives (2'-MeMPTP and 2'-EtMPTP), cannot be prevented by deprenyl pretreatment. However, the neurotoxicity of these two analogs can be prevented by pretreatment with a combination of deprenyl and the selective MAO-A inhibitor clorgyline at doses that are sufficient to almost completely inhibit both MAO-B and MAO-A activities. Moreover, the neurotoxicity of 2'-EtMPTP (but not of 2'-MeMPTP and MPTP) can be significantly attenuated by clorgyline alone. There was a parallel between the capacity of the MAO inhibitors to decrease the brain content of the pyridinium species after administration of the tetrahydropyridines and the capacity of the MAO inhibitors to protect against the neurotoxic action of the tetrahydropyridines. The data support the conclusion that both 2'-MeMPTP and 2'-EtMPTP are bioactivated to pyridinium species to a significant extent by MAO-A. Further, it appears that the formation of the pyridinium species plays an important role in the neurotoxic process.     

Structural and biologic characterization of pegylated recombinant IFN-alpha2b.

The type I interferon-alpha (IFN-alpha) family is a family of natural small proteins that have clinically important anti-infective and antitumor activity. We have developed a semisynthetic protein-polymer conjugate of IFN-alpha2b (Intron A) by attaching a 12,000-Da monomethoxypolyethylene glycol (PEG-12000) polymer to the protein. PEG conjugation is thought to increase the serum half-life and thereby prolong patient exposure to IFN-alpha2b without altering the biologic potency to the protein. Matrix-assisted laser desorption ionization/mass spectrometry (MALDI-MS), high-performance size exclusion chromatography (HPSEC), circular dichroism (CD) analysis and tryptic digestion peptide analysis of PEG Intron demonstrated that the IFN-alpha2b protein was approximately 95% monopegylated and that the primary, the secondary, and the tertiary structures were unaltered. Pegylation did not affect the epitope recognition of antibodies used for Intron A quantitation. An extensive analysis of the pegylated positional isomers revealed that approximately 50% of PEG Intron was monopegylated on the His(34) residue of the IFN-alpha2b protein. The highest antiviral activity of the pegylated positional isomers for PEG Intron was associated with the His(34) pegylated isomer. The specific activity for PEG Intron in an antiviral cytopathic protection assay was 28%, relative to Intron A. However, the potency of PEG Intron, defined as bioactivity independent of protein concentration, was comparable to Intron A at both the molecular and cellular levels in a battery of in vitro assays. Equivalent units of PEG Intron and Intron A were indistinguishable for the induction of several key IFN-induced genes, including 2',5'-oligoadenylate synthetase (2',5'-OAS) and protein kinase R (PKR), in Molt 4 cells. The antiviral dose-response curves revealed that there were no significant differences between PEG Intron and Intron A. This demonstrated that the introduction of more IFN-alpha2b protein associated with equivalent unit dosing of PEG Intron did not create any antagonism or agonism in the antiviral assay. In assays for the immune response, PEG Intron and Intron A displayed comparable potency for both natural-killer (NK) and lymphokine-activated killer (LAK) cell cytolytic activity and for the induction of class I major histocompatibility protein. These results demonstrate that PEG Intron maintains an in vitro biologic potency profile for both antiviral and immunotherapeutic activity that is highly comparable to that of Intron A.     

Structure-activity study of the mechanism of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced neurotoxicity. II. Evaluation of the biological activity of the pyridinium metabolites formed from the monoamine oxidase-catalyzed oxidation of MPTP analogs

In the accompanying paper, several tetrahydropyridine analogs of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) were screened for their abilities to be oxidized by monoamine oxidase (MAO) to pyridiniums and to produce neurotoxicity in mice. We reported that most of the analogs were oxidized by MAO to pyridiniums and some of the analogs were neurotoxic. We concluded that the capacity of a tetrahydropyridine MPTP analog to be oxidized by MAO to a pyridinium was a necessary, but not sufficient, condition for the compound to be a neurotoxin. In the present paper we attempt to explain further the neurotoxicity or lack of neurotoxicity of these analogs by evaluating the abilities of the pyridinium compounds to serve as substrates for the neostriatal dopamine (DA) transport system and as inhibitors of mitochondrial respiration. We now report that all of the neurotoxic MPTP analogs are oxidized to pyridiniums that are good substrates for the neostriatal DA carrier and good inhibitors of mitochondrial respiration. The results are consistent with an important role for both uptake of the pyridiniums by the DA carrier and inhibition by the pyridiniums of mitochondrial respiration in the neurotoxicity induced by MPTP and its analogs.     

The impact of past COVID-19 infection on pregnancy rates in frozen embryo transfer cycles

Journal of Assisted Reproduction and Genetics - To study the effect of SARS-CoV-2 infection on pregnancy rates in frozen embryo transfer (FET) cycles. A retrospective cohort study including women...     

1-Methyl-4-(2'-methylphenyl)-1,2,3,6-tetrahydropyridine (2'-CH3-MPTP) is a more potent dopaminergic neurotoxin than MPTP in mice

The administration to mice of 1-methyl-4-(2'-methylphenyl)-1,2,3, 6-tetrahydropyridine (2'-CH3-MPTP), a substituted analog of the dopaminergic neurotoxin MPTP caused even more dopaminergic toxicity than MPTP itself. Under conditions in which MPTP was relatively ineffective (i.e. two injections per day of 0.113 mmol/kg at an interval of 6 h for one or two days), 2'-CH3-MPTP caused a very large decrement in the neostriatal content of dopamine and its metabolites and a corresponding decrement in the capacity of a neostriatal synaptosomal preparation to take up [3H]dopamine. Moreover, 2'-CH3-MPTP administration (as few as four injections) caused a virtually complete loss of nerve cells in the zona compacta of the substantia nigra. This compound, like MPTP, may prove to be a valuable research tool.     

In vivo intracerebral microdialysis studies in rats of MPP+ analogues and related charged species

The in vivo dopaminergic neurotoxic properties of 45 MPTP and MPP+ analogues and related compounds were examined by an intrastriatal microdialysis assay in conscious rats. MPP(+)-like toxicity, as evidenced by the irreversible effects on DA release and enhancement of lactate formation, was observed with a variety of structural types although no compound was more toxic than MPP+. The following global structure-toxicity relationships could be derived: (1) only permanently charged compounds showed neurotoxic effects; (2) with the exception of amino groups, hydrophilic substituents abolished toxicity; (3) activity was enhanced by lipophilic groups although increased steric bulk around the nitrogen atom tended to decrease activity; (4) nonaromatic, quaternary systems (methiodide of MPTP, guanidinium derivatives) were only weakly toxic; and (5) certain bi- and tricyclic systems, including putative metabolites of potential endogenous MPTP-like compounds, were weakly toxic. The lack of toxic effects following perfusions with DA itself confirmed that MPTP dopaminergic neurotoxicity is not likely to be mediated by the MPP(+)-induced release of DA. With some interesting exceptions, these in vivo data correlate reasonably well with in vitro data on the nerve terminal uptake properties and the inhibitory effects on mitochondrial respiration of these compounds.     

Premarketing surveillance of ibuprofen suppositories in febrile children

In many countries, ibuprofen is available only in oral formulations. The authors aimed to investigate parental satisfaction and possible adverse reactions among children receiving newly marketed ibuprofen suppositories, prior to their arrival at the pharmaceutical points of distribution. Children needing antipyretic medication were recruited from 11 pediatric wards and clinics in Israel. Each patient received ibuprofen suppositories (5-10 mg/kg/dose) after completing a data collection form. After 3 to 7 days of treatment, information regarding parent satisfaction, possible adverse reactions, and concomitant use of drugs was obtained. Overall, 490 children completed the study. Parents' satisfaction was high (4.5 ± 0.47 on a scale of 1-5), and 92.2% reported that they would use the medication in the future. Adverse reactions were reported in 8 patients (1.63%, 95% confidence interval = 1.77-3.25), the most common being diarrhea. Rectal administration of ibuprofen suppositories is well tolerated and overall satisfaction and the repeated expected use were high.     

Structure,biology, and therapeutic implications of pegylated interferon alpha-2b

Derivatization of protein-based therapeutics with polyethylene glycol (pegylation) can often improve pharmacokinetic and pharmacodynamic properties of the proteins and thereby, improve efficacy and minimize dosing frequency. This review will provide an overview of pegylation technology and pegylated protein-based drugs being used or investigated clinically. The novel therapeutic, PEG Intron(R), formed by attaching a 12-kDa mono-methoxy polyethylene glycol (PEG) to the interferon alpha-2b protein, will be discussed in detail in terms of its structure, biological activities, pharmacokinetic properties, and clinical efficacy for the treatment of chronic hepatitis C. Detailed physicochemical and biological characterization studies of PEG Intron revealed its composition of pegylated positional isomers and the specific anti-viral activity associated with each of them. Pegylation of Intron A at pH 6.5 results in a mixture of > or = 95% mono-pegylated isoforms with the predominant species (approximately 50%) derivatized to the His(34) residue with the remaining positional isomers pegylated at various lysines, the N-terminal cysteine, as well as serine, tyrosine, and another histidine residue. The anti-viral activity for each pegylated isomer showed that the highest specific activity (37%) was associated with the His(34)-pegylated isomer. Though pegylation decreases the specific activity of the interferon alpha-2b protein in vitro, the potency of PEG Intron was comparable to the Intron A standard at both the molecular and cellular level. The substituted IFN had an enhanced pharmacokinetic profile in both animal and human studies, and, when combined with ribavirin, was very effective in reducing hepatitis C viral load and maintaining sustained viral suppression in patients.