Abstract
Osteopontin (OPN) is a multi-functional protein that binds to integrin and calcium-binding phosphoprotein. OPN is required for normal neuronal development and its axonal myelination. We studied the combined effect of lead (Pb) and ascorbic acid treatment on OPN expression in the developing cerebellum. We randomly divided pregnant female rats into three groups: control, Pb (lead acetate, 0.3%, drinking water), and Pb plus ascorbic acid (PA; ascorbic acid, 100 mg/kg, oral intubation) groups. The blood level of Pb was significantly increased, while ascorbic acid reduced Pb levels in the dams and pups. At postnatal day (PND) 21, results from Nissl staining and OPN immunohistochemistry demonstrated that OPN was detected in the Purkinje cell layer in the cerebellum. Ascorbic acid treatment mitigated Pb exposure-induced reduction in the number of intact Purkinje cells and OPN immunoreactive Purkinje cells in the cerebellum of pups. In addition, Pb-induced reduction in the number of oligodendrocytes and myelin-associated glycoprotein is associated with the malformation of the myelin sheath. Ascorbic acid provided protection from Pb-induced impairments. Pb-induced structural deficits in the cerebellum resulted in functional deterioration observed during locomotive tests (bar holding test and wire mesh ascending test), while ascorbic acid ameliorated these harmful effects. Present results suggest that the change of OPN is associated with myelination in the developing cerebellum. The results also demonstrated that exposure to Pb is harmful, while ascorbic acid treatment is beneficial.
Highlights
Osteopontin (OPN) is known as a glycosylated phosphoprotein with calcium- and integrin-binding capabilities [1]
Public Health 2019, 16, 983 brain’s development and maturation, and we previously reported that lead (Pb) exposure impairs the normal development of the hippocampus and cerebellum [16,17]
The results showed a similar pattern of change; Pb-induced reduction of OPN (74.75% of that in the control group, p < 0.01) and Brain-Derived Neurotrophic Factor (BDNF) (65.90% of that in the control group, p < 0.01) and ascorbic acid-mediated attenuation of the reduction (OPN, 94.64% of that in the control group; BDNF, 91.52% of that in the control group, p < 0.05) (Figure S2)
Summary
Osteopontin (OPN) is known as a glycosylated phosphoprotein with calcium- and integrin-binding capabilities [1]. Alternative splicing generates various forms of OPN; these are associated with numerous functions including inflammatory response [1,2], tissue mineralization [1,3], cancer and metastatic proficiency [4], tissue repair [5], and development [6]. Research on OPN has focused on its pathophysiological role. Jiang et al [15] recently described the functional role of OPN in brain development. They focused on the fact that OPN is transferred from the mother to the offspring through the milk produced by the mother, and that OPN is produced in the mammary glands and the brain [15]
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