Diclofenac Attenuates the Regional Effect of λ-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 (Sharma et al., 2004). The BBB, situated at the level of endothelial tight junctions of cerebral microvessels (Reese and Karnovsky, 1967;Brightman et al., 1970), is critical for regulating and maintaining the brain microenvironment and, thus, proper neuronal function.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 enzym...

Tempol modulates changes in xenobiotic permeability and occludin oligomeric assemblies at the blood-brain barrier during inflammatory pain

“…Recently, we have begun to delineate specific biochemical mechanisms that enable peripheral pain/inflammation to "transmit" upstream signals and alter TJ protein expression and/or BBB permeability. For example, Brooks et al (5) administered diclofenac, a commonly prescribed nonsteroidal anti-inflammatory drug, to rats subjected to CIP and demonstrated that this therapeutic compound attenuated the increase in BBB permeability to sucrose observed in CIP animals (5). The results of this study and others (7) have clearly shown that cyclooxygenase activity is a critical regulator of BBB functional integrity.…”

“…Increased presence of 3-nitrotysine protein adducts is indicative of oxidative stress, which leads to disruption of TJ protein complexes. Specifically, occludin oligomeric assemblies are modulated (4), which then leads to increased paracellular permeability and enhanced access of the brain extracellular milieu to therapeutic agents such as codeine (5). Administration of SOD mimetics such as tempol prevents endothelial cell damage and protects the blood-brain barrier from pathological changes associated with pain/inflammation (i.e., increased permeability to circulating solutes and disruption of TJ protein complexes).…”

“…Our laboratory (5,6,29) has identified various physiological and biochemical mechanisms that modulate BBB integrity under conditions of peripheral inflammatory pain; however, the role of reactive oxygen species (ROS) such as superoxide anion and subsequent oxidative stress in mediating these BBB changes during pain/inflammation have not been elucidated.…”

Maternal glucocorticoid exposure alters tight junction protein expression in the brain of fetal sheep

“…They found that TNF-␣ treatment had differential effects on endothelia from the cerebrum and cerebellum because the barrier function was affected to a greater extent in the cerebellar than cerebral endothelium, and TNF-␣ treatment resulted in decreases in claudin-1, claudin-3, claudin-5, and occludin mRNA levels in the cerebellar endothelium (41). Brooks et al (5) showed that inflammatory pain is associated with regionally specific molecular and functional regulation of the blood-brain barrier. Hence, taken together with our findings, it appears that treatments that reinforce (29,39,44,45) or damage the barrier (5, 41) have differential effects on the barrier endothelium in different brain regions.…”

Inflammatory Pain Signals an Increase in Functional Expression of Organic Anion Transporting Polypeptide 1a4 at the Blood-Brain Barrier

“…Our laboratory has shown, in vivo, modifications in functional BBB integrity and changes in CNS drug delivery induced by peripheral inflammatory pain (Huber et al, 2001;Hau et al, 2004;Brooks et al, 2006Brooks et al, , 2008Seelbach et al, 2007;Campos et al, 2008;Ronaldson et al, 2009). The critical link between inflammation in peripheral tissues and altered BBB permeability and/or transport may involve changes in serum cytokines such as transforming growth factor-␤ (TGF-␤).…”