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Xenobiotic metabolism in brain
V Ravindranath1, S Bhamre, S V Bhagwat
1Department of Neurochemistry, National Institute of Mental Health and Neuroscience, Bangalore, India.
Abstract:
Recent hypothesis suggesting a role for environmental toxins in the pathogenesis of neurodegenerative disorders has stimulated interest in research on xenobiotic metabolizing capability of the brain. In addition to possible irreversible loss of neurons through bioactivation in situ in the nervous tissue, the metabolism of psychoactive drugs in the target tissue can lead to local pharmacological modulation at the site of action. The major drug metabolizing enzymes, cytochromes P-450 (P450) and flavin-containing monooxygenase (FMO) have been detected in rodent brain and human brain tissue obtained at autopsy. The brain microsomal and mitochondrial P450 systems are capable of metabolizing a variety of xenobiotics, while the brain FMO efficiently metabolizes a variety of psychoactive drugs to their respective N-oxides. Immunocytochemical studies have revealed the regional heterogeneity in the distribution of multiple forms of P450 in the brain and the co-localization of P450 and FMO predominantly in the neuronal cells. Although the brain P450 and FMO share many common features with similar enzymes present in other tissues such as liver and lung, there are some distinctive differences. It is evident from the studies carried out so far that the brain can metabolize a variety of lipophilic xenobiotics that enter by way of the blood stream.
Insights
The brain possesses drug-metabolizing enzymes like cytochromes P-450 (P450) and flavin-containing monooxygenase (FMO). These enzymes metabolize environmental toxins and psychoactive drugs, influencing neurodegenerative disease research.
Area of Science:
- Neuroscience
- Pharmacology
- Toxicology
Background:
- Emerging hypotheses link environmental toxins to neurodegenerative disorders.
- Understanding xenobiotic metabolism in the brain is crucial for neuroprotection.
- Brain enzymes may modulate drug action and contribute to neuronal health.
Purpose of the Study:
- To investigate the presence and function of xenobiotic metabolizing enzymes in the brain.
- To explore the role of these enzymes in the metabolism of drugs and toxins.
- To examine the distribution and characteristics of brain-specific enzymes.
Main Methods:
- Detection of cytochromes P-450 (P450) and flavin-containing monooxygenase (FMO) in rodent and human brain tissue.
- Analysis of brain microsomal and mitochondrial enzyme systems.
- Immunocytochemical studies to determine enzyme distribution and localization.
Main Results:
- P450 and FMO enzymes are present in the brain, metabolizing various xenobiotics and psychoactive drugs.
- Regional heterogeneity in P450 distribution was observed.
- These enzymes are predominantly localized in neuronal cells, with some distinct differences from liver/lung counterparts.
Conclusions:
- The brain possesses significant xenobiotic metabolizing capabilities, particularly for lipophilic compounds entering via bloodstream.
- Brain P450 and FMO play a role in modulating drug action and potentially in neurodegenerative processes.
- Further research into brain xenobiotic metabolism is warranted for understanding neurological diseases.