Calcium binding proteins mediate dioxin-induced motor deficit in sheep

Introduction: Sheep from environmental dioxin contaminated areas show motor discoordination suggesting a pathophysiology in cerebellar function. Since Calcium binding proteins are known to play a role in the Ca2+ homeostasis in neurons and during neurotransmission, we have investigated the role of these proteins in motor deficits in dioxin exposed adult and neonate sheep. We present herein the study of the expression patterns of Calcium binding proteins, Calbindin (CB) and Parvalbumin (PV) in cerebellum of adult and neonatal sheep chronically exposed to dioxin in comparison with those in cerebellum of sheep from uncontaminated area of the Campania Region. Methods: Sheep environmentally exposed to chronic dioxin were obtained from Acerra of Campania Region and the uncontaminated control sheep were from Chiusano S. Domenico of the same Region. Cerebella from control and dioxin-exposed adults and neonates were fixed in paraformaldehyde and processed for immunohistochemistry on paraffin sections, using polyclonal primary antibodies against PV and CB, biotin-avidin detection system using DAB as chromogen. Results: In control animals CB and PV showed specific and different staining patterns in adult and neonatal cerebellum but those in neonates were uniformly more intense than those in adults. Both CB and PV expressions decreased in dioxin exposed cerebellum of adult and neonatal sheep in most cerebellar subpopulations of both stages. Significantly, the fibres of white matter in adult and neonate showed uniformly increased CB and PV expression in animals from dioxin contaminated area. Conclusions: Present results confirm that CB and PV expressions are altered in majority of the cerebellar neurones in chronic environmental dioxin-exposed animals and dioxin is possibly responsible for the pathophysiology of their cerebellum. Thus modifications in the expression patterns of calcium binding proteins could be one of the mechanisms by which environmental dioxin alters the functional aspects of the cerebellar circuit inducing motor and ambulatory deficits. Approved by the Veterinary Scientific Committee of the University of Naples Federico II (art. 3 D.LVO 116/ 92)