Acute hypoxia-induced alterations of calbindin-D28k immunoreactivity in cerebellar Purkinje cells of the guinea pig fetus at term.
Purkinje cells (PCs) are vulnerable to hypoxic/ischemic insults and rich in calcium and calcium-buffering/sequestering systems, including calcium-binding proteins (CaBPs). Calbindin-D28k is an EF-hand CaBP, which is highly expressed in PCs where it acts primarily as a cellular Ca++ buffer. Elevation of [Ca++] in the cytosol and nuclei of PCs is pivotal in hypoxic/ischemic cell death. We hypothesize that hypoxia results in decreased concentration, or availability of calbindin-D28k in PCs, thereby decreasing their buffering capacity and resulting in increase of intracellular and intranuclear [Ca++]. Cerebellar tissues from normoxic fetuses were compared to fetuses obtained from term pregnant guinea pigs exposed to hypoxia [7% FiO2] for 60 min. The pregnant guinea pigs were either killed upon delivery immediately following hypoxia (Hx0h) or were subsequently allowed to recover for 24 h (Hx24h) or 72 h (Hx72h). Fetal brain hypoxia was documented biochemically by a decrease in brain tissue levels of ATP and phosphocreatine. Compared to normoxic fetuses, there is a predominantly somatodendritic loss or decrease of calbindin-D28k immunohistochemical staining in PCs of Hx0h (p < 0.005), Hx24h (p < 0.05), and Hx72h (p < 0.005) fetuses. Hypoxia-induced alterations of calbindin-D28k immunoreactivity are qualitatively similar at all time points and include a distinctive intranuclear localization in subpopulations of PCs. A similar trend is demonstrated by immunoblotting. Subpopulations of TUNEL+/calbindin-D28k- PCs lacking morphologic features of apoptosis or necrosis are demonstrated in Hx24h and Hx72h fetuses. The present study demonstrates an abrogating effect of perinatal hypoxia on calbindin-D28k immunoreactivity in cerebellar PCs. The perturbation of this Ca++ buffer protein in hypoxia-induced neuronal injury may herald delayed cell death or degeneration.
Katsetos
C D
CD
Department of Pediatrics, St. Christopher Hospital for Children, Philadelphia, PA 19134, USA.
Spandou
E
E
Legido
A
A
Taylor
M L
ML
Zanelli
S A
SA
de Chadarevian
J P
JP
Christakos
S
S
Mishra
O P
OP
Delivoria-Papadopoulos
M
M
D000208:Acute Disease; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D064026:Calbindins; D002531:Cerebellum / Q000196:embryology* / Q000473:pathology; D005311:Fetal Hypoxia / Q000378:metabolism*; D005333:Fetus / Q000378:metabolism; D006168:Guinea Pigs; D015151:Immunoblotting; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D011689:Purkinje Cells / Q000378:metabolism*; D012016:Reference Values; D064030:S100 Calcium Binding Protein G / Q000378:metabolism*; D014018:Tissue Distribution; D014404:Tubulin / Q000378:metabolism
D064026:Calbindins; D064030:S100 Calcium Binding Protein G; D014404:Tubulin; D000255:Adenosine Triphosphate