Effects of Volatile Anesthetics versus Ketamine on Blood-Brain Barrier Permeability via Lipid-Mediated Alterations of Endothelial Cell Membranes

Abstract

The purpose of this study was to investigate the effects of volatile anesthetic agents isoflurane and sevoflurane, at clinically relevant concentrations, on the fluidity of lipid membranes and permeability of the blood-brain barrier (BBB). We analyzed the in vitro effects of isoflurane or ketamine using erythrocyte ghosts (sodium fluorescein permeability) monolayers of brain microvascular endothelial cells ([ 13 C]sucrose and fluorescein permeability), or liposomes (fluorescence anisotropy). Additionally, we determined the effects of 30-min exposure of mice to isoflurane on the brain tight junction proteins.Finally, we investigated in vivo brain uptake of [ 13 C]mannitol and [ 13 C]sucrose after IV administration in mice under anesthesia with isoflurane, sevoflurane, or ketamine/xylazine in addition to the awake condition. Isoflurane at 1-and 5-mM concentrations increased fluorescein efflux from the erythrocyte ghosts in a concentration-dependent manner. Similarly, in endothelial cell monolayers exposed to 3% (v/v) isoflurane, permeability coefficients rose by about 25% for fluorescein and 40% for [ 13 C]sucrose, while transendothelial resistance and cell viability remained unaffected. Whereas isoflurane caused a significant decrease in liposomes anisotropy values, ketamine/xylazine did not show any effects. Brain uptake clearance (apparent K in ) of the passive permeability markers in vivo in mice approximately doubled under isoflurane or sevoflurane anesthesia, compared to either ketamine/xylazine anesthesia or the awake condition. In vivo exposure of mice to isoflurane did not change any of the brain tight junction proteins. Our data support membrane permeabilization rather than loosening of intercellular tight junctions as an underlying mechanism for increased permeability of the endothelial cell monolayers and the BBB in vivo. Significance Statement:The BBB controls the entry of endogenous substances and xenobiotics from the circulation into the central nervous system. Volatile anesthetic agents like isoflurane alter the lipid structure of cell membranes, transiently facilitating the brain uptake of otherwise poorly permeable, hydrophilic small molecules. Clinical implications may arise when potentially neurotoxic drugs gain enhanced access to the CNS under inhalational anesthetics.

Mesoscopic mapping of hemodynamic responses and neuronal activity during pharmacologically induced interictal spikes in awake and anesthetized mice

“…Most anesthetics, including isoflurane, not only suppress neural activity but affect neurovascular coupling. 53 Isoflurane increases the vascular membrane permeability, 54 increases the membrane transport of endothelial cells, 55 and affects pericytes that control the vasoactive constriction/relaxation. Isoflurane is a potent vasodilator through its action on ATP-sensitive potassium channels and calcium currents in smooth muscle cells.…”

Higher Brain Uptake of Gentamicin and Ceftazidime under Isoflurane Anesthesia Compared to Ketamine/Xylazine

“…The blood–brain barrier (BBB) maintains a stable microenvironment within the central nervous system (CNS) and is essential to protecting the brain against the entry of harmful endogenous substances and xenobiotics [ 1 , 2 ]. Some drugs of abuse (nicotine, cocaine, methamphetamine) are known to cause BBB dysfunction [ 3 , 4 ], and in recent years, there has been mounting evidence that volatile anesthetic agents in common clinical use, including isoflurane and sevoflurane, increase the permeability of the BBB [ 5 , 6 , 7 , 8 , 9 , 10 ]. While some of these studies investigated the influence of anesthesia on the BBB in the context of surgery [ 10 ] or traumatic brain injury [ 9 ], others studied the effects of the agents alone [ 5 , 6 , 7 , 8 ].…”

“…Some drugs of abuse (nicotine, cocaine, methamphetamine) are known to cause BBB dysfunction [ 3 , 4 ], and in recent years, there has been mounting evidence that volatile anesthetic agents in common clinical use, including isoflurane and sevoflurane, increase the permeability of the BBB [ 5 , 6 , 7 , 8 , 9 , 10 ]. While some of these studies investigated the influence of anesthesia on the BBB in the context of surgery [ 10 ] or traumatic brain injury [ 9 ], others studied the effects of the agents alone [ 5 , 6 , 7 , 8 ]. In order to characterize the principal mechanisms underlying alterations in BBB integrity by anesthetic agents, initially applying a reductionist in vitro approach with liposomes proved advantageous.…”

“…Our group recently demonstrated increased fluidity in different lipid membranes at clinical concentrations of isoflurane (1 mM) using fluorescence anisotropy analysis [ 11 ]. In contrast, ketamine/xylazine at clinical concentrations does not affect lipid membranes [ 6 ]. Proceeding with an in vivo animal model in mice, we found that short exposure (30–45 min) to either isoflurane or sevoflurane, but not to ketamine/xylazine, caused an increase in BBB permeability.…”

“…Proceeding with an in vivo animal model in mice, we found that short exposure (30–45 min) to either isoflurane or sevoflurane, but not to ketamine/xylazine, caused an increase in BBB permeability. Both isoflurane and sevoflurane displayed a two-fold increase in the brain uptake clearance (apparent K in ) of the hydrophilic marker [ 13 C 12 ]sucrose compared to either ketamine/xylazine anesthesia or an awake condition [ 6 ]. The expression of tight junction proteins (claudin-5, occludin and ZO-1) in the brain capillaries of these animals remained unchanged.…”