Anti‐IL‐6 neutralizing antibody modulates blood‐brain barrier function in the ovine fetus

Abstract

Impaired blood-brain barrier function represents an important component of hypoxic-ischemic brain injury in the perinatal period. Proinflammatory cytokines could contribute to ischemia-related blood-brain barrier dysfunction. IL-6 increases vascular endothelial cell monolayer permeability in vitro. However, contributions of IL-6 to blood-brain barrier abnormalities have not been examined in the immature brain in vivo. We generated pharmacologic quantities of ovine-specific neutralizing anti-IL-6 mAbs and systemically infused mAbs into fetal sheep at 126 days of gestation after exposure to brain ischemia. Anti-IL-6 mAbs were measured by ELISA in fetal plasma, cerebral cortex, and cerebrospinal fluid, bloodbrain barrier permeability was quantified using the bloodto-brain transfer constant in brain regions, and IL-6, tight junction proteins, and plasmalemma vesicle protein (PLVAP) were detected by Western immunoblot. Anti-IL-6 mAb infusions resulted in increases in mAb (P < 0.05) in plasma, brain parenchyma, and cerebrospinal fluid and decreases in brain IL-6 protein. Twenty-four hours after ischemia, anti-IL-6 mAb infusions attenuated ischemiarelated increases in blood-brain barrier permeability and modulated tight junction and PLVAP protein expression in fetal brain. We conclude that inhibiting the effects of IL-6 protein with systemic infusions of neutralizing antibodies attenuates ischemia-related increases in blood-brain barrier permeability by inhibiting IL-6 and modulates tight junction proteins after

Interleukin-1β Transfer across the Blood–Brain Barrier in the Ovine Fetus

“…14,37,40 Moreover, the biologic importance of cytokine transport across the BBB has been established because memory impairment induced by IL-1α depends directly on the ability of this cytokine to cross the BBB. 40 In addition, there are several lines of evidence to support the contention intact cytokines cross the BBB: (1) previous rigorous analysis by Banks et al in several manuscripts established that a number of cytokines cross the adult BBB undegraded; 13,14,26,27,37,[40][41][42] (2) free iodine does not cross the BBB well because of a brain-to-blood efflux system for iodine; 43 (3) we have previously shown that brain levels of cytokines are decreased when antibodies against that specific cytokine were infused into the blood; 19,44 and (4) transport of the labeled ovine cytokines across the BBB is inhibited by unlabeled murine cytokine. 16 This latter finding is particularly important, as unlabeled cytokines would not be expected to inhibit brain uptake of free iodine.…”

Opposing effects of prostaglandin receptor EP2 signaling in mouse immune cells and neurons after status epilepticus

“…This finding suggests that IL-6 production is induced in an EP2-dependent manner, whereas more complex signaling pathways might be responsible for the other mediators and glial markers. Interestingly, IL-6 has been implicated in BBB dysfunction in a fetal ovine brain ischemia model (24). Thus, protection of the BBB integrity in McKO mice after SE might be related to dampened IL-6 induction.…”

Neutralizing anti-interleukin-1β antibodies reduce ischemia-related interleukin-1β transport across the blood–brain barrier in fetal sheep

“…We adjusted the dose to account for the larger blood volume of the fetus and the potential for mAbs to be sequestered within the placenta (Stonestreet et al, 1989, Chen et al, 2015, Zhang et al, 2015). Two doses of mAbs were given after ischemia over an extended time to allow for sustained exposure of the endothelial microvasculature to mAbs before the BBB permeability studies were performed (Chen et al, 2015, Zhang et al, 2015). The highest plasma level of anti-IL-1β mAb, 139 ± 35.7 ng/ml, was observed at 4 h of reperfusion and the final concentration at 24 h of reperfusion remained elevated (108 ± 25.4 ng/ml) suggesting that the half-life of anti-IL-1β mAb could be more than 24 hours in the fetal circulation.…”

“…In our experience, cytokine assays designed for mouse, rat or human do not work in sheep. However, it would be feasible to measure levels of IL-6 cytokine in ovine fetal circulation in future using our specifically designed ovine IL-6 cytokine assay (Zhang et al, 2015). …”