Exposure-disease continuum for 2-chloro-2'-deoxyadenosine, a prototype ocular teratogen. 3. Intervention with PK11195.
BACKGROUND
Treatment of pregnant mice with 2-chloro-2'-deoxyadenosine (2CdA) on Day 8 of gestation induces microphthalmia through a mechanism linked to the p53 tumor suppressor pathway. The present study defines the response of Day 8 mouse embryos through time with respect to pharmacologic intervention with PK11195, a ligand of the mitochondrial peripheral benzodiazepine receptor (Bzrp).


METHODS
Pregnant CD-1 mice dosed with 2CdA with or without PK11195 on gestation Day 8 provided fetuses for teratologic evaluation on Day 14 and Day 17; HPLC measured pyridine nucleotides (NADH/NAD+) at 1.5 hr, RT-PCR measured mitochondrial 16S rRNA abundance at 3.0 hr, and p53 protein induction was assessed with immunostaining at 4.5 hr postexposure.


RESULTS
The mean incidences of malformed fetuses were significantly higher in the 7.5 mg/kg 2CdA treatment group (50.2% malformed) vs. the 2CdA + 4.0 mg/kg PK11195 co-treatment group (4.4% malformed). Malformed fetuses displayed a range of ocular defects that included microphthalmia and keratolenticular dysgenesis (Peters anomaly). No malformations were observed in the control or PK11195 alone groups. PK11195 also protected litters from increased resorption rates and fetal weight reduction. It did not rescue early effects on NADH balance (1.5 hr) or 16S rRNA expression (3.0 hr); however, the p53 response (4.5 hr) was downgraded in 2CdA + PK11195 embryos vs. 2CdA alone. By delaying the administration of PK11195 in 1.5 hr intervals it was determined that the window for protection closed between 4.5 to 6.0 hr after 2CdA.


CONCLUSIONS
The capacity of PK11195 to suppress the pathogenesis of microphthalmia implies a critical role for mitochondrial peripheral benzodiazepine receptors in the p53-dependent mode of action of 2CdA on ocular development.
Charlap
Jeffrey H
JH
Department of Pathology, Anatomy and Cell Biology, Jefferson Medical College, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
Donahue
Ronald J
RJ
Knudsen
Thomas B
TB
D000818:Animals; D016048:Dideoxyadenosine / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000037:antagonists & inhibitors / Q000633:toxicity*; D004353:Drug Evaluation, Preclinical; D005124:Eye Abnormalities / Q000139:chemically induced* / Q000517:prevention & control; D005260:Female; D005326:Fetal Proteins / Q000096:biosynthesis / Q000235:genetics; D005327:Fetal Resorption / Q000139:chemically induced / Q000517:prevention & control; D005333:Fetus / Q000187:drug effects; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D016158:Genes, p53; D005865:Gestational Age; D007546:Isoquinolines / Q000494:pharmacology / Q000627:therapeutic use*; D051379:Mice; D008850:Microphthalmos / Q000139:chemically induced / Q000517:prevention & control; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism; D009243:NAD / Q000378:metabolism; D011247:Pregnancy; D012336:RNA, Ribosomal, 16S / Q000096:biosynthesis; D011963:Receptors, GABA-A / Q000187:drug effects; D013723:Teratogens / Q000633:toxicity*; D016159:Tumor Suppressor Protein p53 / Q000096:biosynthesis / Q000502:physiology
D005326:Fetal Proteins; D007546:Isoquinolines; D012336:RNA, Ribosomal, 16S; D011963:Receptors, GABA-A; D013723:Teratogens; D016159:Tumor Suppressor Protein p53; D009243:NAD; C055504:2-chloro-2',3'-dideoxyadenosine; D016048:Dideoxyadenosine; C037850:PK 11195