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Cytochrome P-450 expression in sudden infant death syndrome
J M Treluyer1, G Cheron, M Sonnier
1INSERM U75, Université René Descartes, Paris, France.
Insights
Sudden Infant Death Syndrome (SIDS) infants show increased CYP2C, a cytochrome P-450 isoform. This precocious expression may lead to fatal apnea in newborns, impacting drug metabolism and pulmonary function.
Area of Science:
- Biochemistry
- Pediatrics
- Toxicology
Background:
- The first months of life are critical for liver cytochrome P-450 isoform development.
- Sudden Infant Death Syndrome (SIDS) is linked to viral infections and drug hypersensitivity during this vulnerable period.
Purpose of the Study:
- To investigate cytochrome P-450 isoform expression in SIDS infants.
- To compare P-450 levels in SIDS infants with control groups.
Main Methods:
- Postmortem liver samples from SIDS infants and controls were analyzed.
- Hepatic microsomes were assessed for P-450 content, specific isoform levels (CYP1A2, CYP2E1, CYP4A, CYP3A, CYP2C), and enzymatic activities.
- RNA was extracted and probed for CYP gene expression.
Main Results:
- Overall hepatic P-450 content was unchanged in SIDS infants.
- CYP2C isoform levels were significantly increased in SIDS infants.
- Increased CYP2C RNA accumulation correlated with enhanced diazepam demethylation activity.
Conclusions:
- Precocious CYP2C expression in SIDS infants may alter neonatal metabolism.
- Elevated CYP2C could increase epoxyeicosatrienoic acid production, potentially causing pulmonary smooth muscle relaxation and fatal apnea.
- This finding suggests a novel mechanism contributing to SIDS pathophysiology.
Abstract:
In the human liver, the major rise of the cytochrome P-450 isoform content occurs during the first months following birth (e.g., the high vulnerability period to sudden infant death syndrome (SIDS), a syndrome frequently associated with viral infection and drug hypersensitivity. We examined the expression of individual P-450 isoforms in liver samples collected postmortem from SIDS infants and compared values with those of control adults and children of the same age suffering from various pathologies. Hepatic microsomes were prepared and examined for their content in total P-450, the level of individual isoforms (CYP1A2, CYP2E1, CYP4A, CYP3A, and CYP2C) determined with specific antibodies and for their enzymatic activities. Total RNA was extracted and probed with several CYP cDNAs and oligomers. The overall hepatic P-450 content was not modified in SIDS infants. Among cytochrome P-450 isoforms, only CYP2C was markedly increased. This rise resulted from an accumulation of RNA encoding CYP2C and was associated with a stimulation of diazepam demethylation. The precocious expression of CYP2C in SIDS could result in a higher production of epoxyeicosatrienoic acids in the neonate, believed to act as relaxant of pulmonary smooth muscles. Its consequence might be the induction of fatal apnea in SIDS.