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TMPyP4, a Stabilizer of Nucleic Acid Secondary Structure, Is a Novel Acetylcholinesterase Inhibitor.

Fujiwara N, Mazzola M, Cai E, Wang M, Cave JW - PLoS ONE (2015)

Bottom Line: Intraperitoneal administration of low TMPyP4 doses (10mg/kg), similar to those used for photosensitization, did not significantly reduce Th transcript levels in several catecholaminergic regions.Administration of a high dose (40 mg/kg), similar to those used for tumor xenograph reduction, unexpectedly induced flaccid paralysis in an age and sex-dependent manner.Age-dependent differences in HO-2 expression levels may account for some of the variable in vivo effects of high TMPyP4 doses.

View Article: PubMed Central - PubMed

Affiliation: Burke Medical Research Institute, White Plains, New York, United States of America.

ABSTRACT
The porphyrin compound, TMPyP4 (5,10,15,20-Tetrakis-(N-methyl-4-pyridyl)porphine), is widely used as a photosensitizer and a modulator of nucleic acid secondary structure stability. Our group recently showed in cultured cells and forebrain slice cultures that this compound can also down regulate expression of Tyrosine hydroxylase (Th), which encodes the rate-limiting enzyme in catecholamine biosynthesis, by stabilizing DNA secondary structures in the Th proximal promoter. The current study sought to establish whether treatment with TMPyP4 could modify mouse Th expression levels in vivo. Intraperitoneal administration of low TMPyP4 doses (10mg/kg), similar to those used for photosensitization, did not significantly reduce Th transcript levels in several catecholaminergic regions. Administration of a high dose (40 mg/kg), similar to those used for tumor xenograph reduction, unexpectedly induced flaccid paralysis in an age and sex-dependent manner. In vitro analyses revealed that TMPyP4, but not putative metabolites, inhibited Acetylcholinesterase activity and pre-treatment of TMPyP4 with Hemeoxygenase-2 (HO-2) rescued Acetylcholinesterase function. Age-dependent differences in HO-2 expression levels may account for some of the variable in vivo effects of high TMPyP4 doses. Together, these studies indicate that only low doses of TMPyP4, such as those typically used for photosensitization, are well tolerated in vivo. Thus, despite its widespread use in vitro, TMPyP4 is not ideal for modifying neuronal gene expression in vivo by manipulating nucleic acid secondary structure stability, which highlights the need to identify more clinically suitable compounds that can modulate nucleic acid secondary structure and gene expression.

No MeSH data available.


Related in: MedlinePlus

TMPyP4 inhibits AChE activity.A, oxidation of heme by Hemeoxygenase (HO) enzymes produces biliverdin and carbon monoxide. B, oxidation of TMPyP4 by HO enzymes is expected to generate either 4-formyl-1-methylpyridinium (4F-MP) or 4-carboxy-1-methylpyridinium (4C-MP). Both 4F-MP and 4C-MP have a structural resemblance to acetylcholine. C, fluorometric assay of AChE activity in presence of TMPyP2, TMPyP4, 4F-MP, 4C-MP and an established AChE inhibitor (Donepezil). D, pre-incubation of TMPyP4 with recombinant HO-2 prior rescued AChE activity in a concentration-dependent manner.
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pone.0139167.g003: TMPyP4 inhibits AChE activity.A, oxidation of heme by Hemeoxygenase (HO) enzymes produces biliverdin and carbon monoxide. B, oxidation of TMPyP4 by HO enzymes is expected to generate either 4-formyl-1-methylpyridinium (4F-MP) or 4-carboxy-1-methylpyridinium (4C-MP). Both 4F-MP and 4C-MP have a structural resemblance to acetylcholine. C, fluorometric assay of AChE activity in presence of TMPyP2, TMPyP4, 4F-MP, 4C-MP and an established AChE inhibitor (Donepezil). D, pre-incubation of TMPyP4 with recombinant HO-2 prior rescued AChE activity in a concentration-dependent manner.

Mentions: Given the symptoms observed following exposure to the higher dose of TMPyP4, we addressed whether TMPyP4 or one of its putative metabolic products impaired AChE, which degrades the neurotransmitter acetylcholine within neuromuscular junctions and is essential for control of muscular function. Porphyrin compounds are typically oxidized by either of two HO isoforms. HO-1 is an inducible isoform and HO-2 is a constitutively and widely expressed enzyme. Metabolism of heme by HO-1/2 generates carbon monoxide and biliverdin (Fig 3A). Based on this mechanism, oxidation of TMPyP4 by HO enzymes would be expected to generate either 4F-MP or 4C-MP (Fig 3B). Both of these putative metabolites resemble acetylcholine and may bind the AChE binding site.


TMPyP4, a Stabilizer of Nucleic Acid Secondary Structure, Is a Novel Acetylcholinesterase Inhibitor.

Fujiwara N, Mazzola M, Cai E, Wang M, Cave JW - PLoS ONE (2015)

TMPyP4 inhibits AChE activity.A, oxidation of heme by Hemeoxygenase (HO) enzymes produces biliverdin and carbon monoxide. B, oxidation of TMPyP4 by HO enzymes is expected to generate either 4-formyl-1-methylpyridinium (4F-MP) or 4-carboxy-1-methylpyridinium (4C-MP). Both 4F-MP and 4C-MP have a structural resemblance to acetylcholine. C, fluorometric assay of AChE activity in presence of TMPyP2, TMPyP4, 4F-MP, 4C-MP and an established AChE inhibitor (Donepezil). D, pre-incubation of TMPyP4 with recombinant HO-2 prior rescued AChE activity in a concentration-dependent manner.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4581631&req=5

pone.0139167.g003: TMPyP4 inhibits AChE activity.A, oxidation of heme by Hemeoxygenase (HO) enzymes produces biliverdin and carbon monoxide. B, oxidation of TMPyP4 by HO enzymes is expected to generate either 4-formyl-1-methylpyridinium (4F-MP) or 4-carboxy-1-methylpyridinium (4C-MP). Both 4F-MP and 4C-MP have a structural resemblance to acetylcholine. C, fluorometric assay of AChE activity in presence of TMPyP2, TMPyP4, 4F-MP, 4C-MP and an established AChE inhibitor (Donepezil). D, pre-incubation of TMPyP4 with recombinant HO-2 prior rescued AChE activity in a concentration-dependent manner.
Mentions: Given the symptoms observed following exposure to the higher dose of TMPyP4, we addressed whether TMPyP4 or one of its putative metabolic products impaired AChE, which degrades the neurotransmitter acetylcholine within neuromuscular junctions and is essential for control of muscular function. Porphyrin compounds are typically oxidized by either of two HO isoforms. HO-1 is an inducible isoform and HO-2 is a constitutively and widely expressed enzyme. Metabolism of heme by HO-1/2 generates carbon monoxide and biliverdin (Fig 3A). Based on this mechanism, oxidation of TMPyP4 by HO enzymes would be expected to generate either 4F-MP or 4C-MP (Fig 3B). Both of these putative metabolites resemble acetylcholine and may bind the AChE binding site.

Bottom Line: Intraperitoneal administration of low TMPyP4 doses (10mg/kg), similar to those used for photosensitization, did not significantly reduce Th transcript levels in several catecholaminergic regions.Administration of a high dose (40 mg/kg), similar to those used for tumor xenograph reduction, unexpectedly induced flaccid paralysis in an age and sex-dependent manner.Age-dependent differences in HO-2 expression levels may account for some of the variable in vivo effects of high TMPyP4 doses.

View Article: PubMed Central - PubMed

Affiliation: Burke Medical Research Institute, White Plains, New York, United States of America.

ABSTRACT
The porphyrin compound, TMPyP4 (5,10,15,20-Tetrakis-(N-methyl-4-pyridyl)porphine), is widely used as a photosensitizer and a modulator of nucleic acid secondary structure stability. Our group recently showed in cultured cells and forebrain slice cultures that this compound can also down regulate expression of Tyrosine hydroxylase (Th), which encodes the rate-limiting enzyme in catecholamine biosynthesis, by stabilizing DNA secondary structures in the Th proximal promoter. The current study sought to establish whether treatment with TMPyP4 could modify mouse Th expression levels in vivo. Intraperitoneal administration of low TMPyP4 doses (10mg/kg), similar to those used for photosensitization, did not significantly reduce Th transcript levels in several catecholaminergic regions. Administration of a high dose (40 mg/kg), similar to those used for tumor xenograph reduction, unexpectedly induced flaccid paralysis in an age and sex-dependent manner. In vitro analyses revealed that TMPyP4, but not putative metabolites, inhibited Acetylcholinesterase activity and pre-treatment of TMPyP4 with Hemeoxygenase-2 (HO-2) rescued Acetylcholinesterase function. Age-dependent differences in HO-2 expression levels may account for some of the variable in vivo effects of high TMPyP4 doses. Together, these studies indicate that only low doses of TMPyP4, such as those typically used for photosensitization, are well tolerated in vivo. Thus, despite its widespread use in vitro, TMPyP4 is not ideal for modifying neuronal gene expression in vivo by manipulating nucleic acid secondary structure stability, which highlights the need to identify more clinically suitable compounds that can modulate nucleic acid secondary structure and gene expression.

No MeSH data available.


Related in: MedlinePlus