Diclofenac Attenuates the Regional Effect of -Carrageenan on Blood-Brain Barrier Function and Cytoarchitecture

ABSTRACT The microenvironment of the brain requires tight regulation for proper neuronal function. Protecting the central nervous system (CNS) from the varying concentrations of ions, proteins, and toxins in the periphery is the dynamically regulated blood-brain barrier (BBB). Recent studies have demonstrated significant modulation of the BBB in a number of diseases and physiological states, including pain. This study expands on previous explorations of acute and chronic pain-induced effects on the function and molecular cytoarchitecture of the barrier. It describes the role of cyclooxygenase (COX) up-regulation by blocking with diclofenac (30 mg/kg, i.p.), and it examines the variation in BBB regulation through various brain regions. Edema and hyperalgesia were induced by -carrageenan and attenuated by the additional administration of diclofenac. Examination of unidirectional [ 14 C]sucrose permeability with multitime in situ perfusion studies demonstrated that -carrageenan significantly increased cerebral permeability and decreased brainstem permeability. There were no significant changes in any of the other brain regions examined. These permeability changes correlated with up-and down-regulation of the tight junction (TJ) protein claudin-5 in the cerebrum and brainstem, respectively. Diclofenac administration attenuated the cerebral permeability uptake as well as the claudin-5 up-regulation. In addition, diclofenac reversed the lowered permeability in the brainstem, but it did not attenuate TJ protein expression. These studies demonstrate the complex regulation of the BBB occurring during inflammatory pain and the role of COX in this process. An understanding of BBB regulation during pain states is critically important for pharmacotherapy, and it holds great promise for new therapies to treat central nervous system pathologies. The central nervous system (CNS) is one of the most vital and delicate systems of the human body, requiring tight regulation. Ion and nutrient concentrations within the extracellular and interstitial fluid of the brain are precisely controlled. Independence from the peripheral circulation is essential for such control, protecting the CNS from fluctuation in ion concentrations, toxins, and the immune system. This environmental maintenance is carried out by the blood-CNS barrier, consisting of the blood-brain barrier (BBB) and the blood-cerebrospinal fluid barrier The basis of the blood-brain barrier is the cerebral capillary endothelium with a continuous and large surface area that selectively allows passage into the CNS. The BBB endothelial cells are characterized by a lack of fenestrations, decreased pinocytosis, and the presence of tight junction (TJ) proteins, multiple transport systems, and enzymatic detoxification enzyme

Diclofenac Attenuates the Regional Effect of λ-Carrageenan on Blood-Brain Barrier Function and Cytoarchitecture

The microenvironment of the brain requires tight regulation for proper neuronal function. Protecting the central nervous system (CNS) from the varying concentrations of ions, proteins, and toxins in the periphery is the dynamically regulated blood-brain barrier (BBB). Recent studies have demonstrated significant modulation of the BBB in a number of diseases and physiological states, including pain. This study expands on previous explorations of acute and chronic pain-induced effects on the function and molecular cytoarchitecture of the barrier. It describes the role of cyclooxygenase (COX) up-regulation by blocking with diclofenac (30 mg/kg, i.p.), and it examines the variation in BBB regulation through various brain regions. Edema and hyperalgesia were induced by γ-carrageenan and attenuated by the additional administration of diclofenac. Examination of unidirectional [14C]sucrose permeability with multitime in situ perfusion studies demonstrated that γ-carrageenan significantly increased cerebral permeability and decreased brainstem permeability. There were no significant changes in any of the other brain regions examined. These permeability changes correlated with up- and down-regulation of the tight junction (TJ) protein claudin-5 in the cerebrum and brain-stem, respectively. Diclofenac administration attenuated the cerebral permeability uptake as well as the claudin-5 up-regulation. In addition, diclofenac reversed the lowered permeability in the brainstem, but it did not attenuate TJ protein expression. These studies demonstrate the complex regulation of the BBB occurring during inflammatory pain and the role of COX in this process. An understanding of BBB regulation during pain states is critically important for pharmacotherapy, and it holds great promise for new therapies to treat central nervous system pathologies

Oxidative stress increases blood–brain barrier permeability and induces alterations in occludin during hypoxia–reoxygenation

The blood–brain barrier (BBB) has a critical role in central nervous system homeostasis. Intercellular tight junction (TJ) protein complexes of the brain microvasculature limit paracellular diffusion of substances from the blood into the brain. Hypoxia and reoxygenation (HR) is a central component to numerous disease states and pathologic conditions. We have previously shown that HR can influence the permeability of the BBB as well as the critical TJ protein occludin. During HR, free radicals are produced, which may lead to oxidative stress. Using the free radical scavenger tempol (200 mg/kg, intraperitoneal), we show that oxidative stress produced during HR (6% O2 for 1 h, followed by room air for 20 min) mediates an increase in BBB permeability in vivo using in situ brain perfusion. We also show that these changes are associated with alterations in the structure and localization of occludin. Our data indicate that oxidative stress is associated with movement of occludin away from the TJ. Furthermore, subcellular fractionation of cerebral microvessels reveals alterations in occludin oligomeric assemblies in TJ associated with plasma membrane lipid rafts. Our data suggest that pharmacological inhibition of disease states with an HR component may help preserve BBB functional integrity