Lubeluzole Pretreatment Does Not Provide Neuroprotection Against Transient Global Cerebral Ischemia in Fetal Sheep Near Term

Abstract

The aim of the present study was to test the neuroprotective effect of the novel benzothiazol compound lubeluzole on neuronal cell damage in fetal sheep arising from global cerebral ischemia. Thirteen fetal sheep were prepared at a mean gestational age of 127 Ϯ 1 d (term is at 147 d). Six fetuses were treated with lubeluzole (0.33 mg/kg estimated body weight) before induction of global cerebral ischemia (Ϫ90, Ϫ60, and Ϫ30 min), while the remainder (n ϭ 7) received solvent. Cerebral ischemia was induced by occluding both carotid arteries for 30 min. Cerebral blood flow was measured by injecting radiolabeled microspheres before (Ϫ90 min), during (ϩ3 min and ϩ27 min), and after (ϩ40 min, ϩ3 h, and ϩ72 h) cerebral ischemia. Neuronal cell damage was assessed in the cerebrum and deeper brain structures by light microscopy. Values are given as means Ϯ SD. In control fetuses, blood flow to the cerebrum was reduced from 100 Ϯ 25 mL·100 g Ϫ1 min Ϫ1 to less than 20 mL·100 g Ϫ1 min Ϫ1 during ischemia. Shortly after ischemia, hyperperfusion occurred (217 Ϯ 66 mL·100 g Ϫ1 min Ϫ1 ) followed by a tendency toward hypoperfusion (72 Ϯ 17 mL·100 g Ϫ1 min Ϫ1 ) later on (ϩ3 h). Significant differences in blood flow to the various brain structures between the control and study groups could not be observed. Neuronal cell damage was concentrated in the parasagittal regions of the cerebrum. Hypoxic-ischemic cerebral damage is an important contributor to perinatal mortality and morbidity including long-term neurologic sequelae in term and preterm fetuses (1). Although over the last decade many therapeutic strategies have been developed in various animal models to reduce neuronal cell damage caused by ischemic insults, their clinical application has often been rejected due to major drug-related side-effects (2). Especially after application of calcium antagonists and inhibitors of NOS, alterations of fetal cardiovascular control have been observed (3, 4). However, the recently developed benzothiazole compound lubeluzole seems to justify further research in this field. The neuroprotective efficiency of this drug has been shown in a variety of in vitro as well as in vivo experiments (5-10). In clinical safety studies, severe drugrelated side-effects could be excluded (11). Phase III trials have provided different results. Whereas Grotta (12) described a neuroprotective effect of lubeluzole in patients suffering from acute ischemic stroke, this finding could not be confirmed in other trials (13,14).The present knowledge on the safety profile and efficiency of lubeluzole seems to be promising enough to warrant further studies in immature animals. Recently, we were able to show that lubeluzole does not affect fetal circulatory centralization during acute asphyxia. This mechanism is of major importance, because it protects the fetal brain from neuronal injury by increasing blood flow to the central organs, i.e. brain, heart, adrenals, when oxygen is in short supply (15). The present study was performed to clarify whether lubeluzole protects the ...