Blood-brain barrier tight junctions are altered during a 72-h exposure to λ-carrageenan-induced inflammatory pain

Abstract

In this study, we examined the effect of λ-carrageenan-induced inflammatory pain on the functional and structural properties of the rat blood-brain barrier (BBB) over a 72-h time period. Systemic inflammation was induced by an intraplantar injection of 3% λ-carrageenan into the right hind paw of female Sprague-Dawley rats. In situ brain perfusion and Western blot analyses were performed at 1, 3, 6, 12, 24, 48, and 72 h. In situ brain perfusion showed λ-carrageenan significantly increased brain uptake of [14C]sucrose at 1, 3, 6, and 48 h (139 ± 9%, 166 ± 19%, 138 ± 13%, and 146 ± 7% compared with control, respectively). Capillary depletion analysis insured the increased brain uptake was due to increased BBB permeability and not vascular trapping. Western blot analyses for zonula occludens-1 (ZO-1) and occludin were performed on isolated cerebral microvessels. ZO-1 expression was significantly increased at 1, 3, and 6 h and returned to control expression levels by 12 h. Total occludin expression was significantly reduced at 1, 3, 6, 12, and 48 h. This investigation demonstrated that λ-carrageenan-induced inflammatory pain elicits a biphasic increase in BBB permeability with the first phase occurring from 1–6 h and the second phase occuring at 48 h. Furthermore, changes in BBB function are correlated with altered tight junctional protein expression of occludin and ZO-1. Changes in the structure of tight junctions may have important clinical ramifications concerning central nervous system homeostasis and therapeutic drug delivery.

Biphasic cytoarchitecture and functional changes in the BBB induced by chronic inflammatory pain

“…This TJ disruption correlated with increased BBB paracellular permeability of [ 14 C]sucrose within the cerebral hemispheres. These data are in agreement with our previous findings that inflammatory hyperalgesia leads to functional changes in the BBB (Brooks et al, 2005;Hau et al, 2004;Huber et al, 2001Huber et al, , 2002aHuber et al, , b, 2006, and extends those findings to describe the earlier (i.e. 0-72 h) molecular alterations in TJ expression and co-localization, and changes in paracellular BBB integrity.…”

“…Alterations in expression or location of these proteins have been correlated to decreased barrier function. Decreased occludin expression, such as seen in both the present and previous studies 72 h post-CFA treatment, will disrupt BBB function (Bolton et al, 1998;Brooks et al, 2005;Brown and Davis, 2005;Hawkins and Davis, 2005;Huber et al, 2002a). Similarly, modulation of JAM-1 protein expression and/or localization is linked to a decrease in normal barrier function, and increased paracellular transport (Dobrogowska and Vorbrodt, 2004;Liang et al, 2002;Mandell and Parkos, 2005).…”

“…In the present study, we have demonstrated both an early (24 h) and a late (72 h) disruption in BBB paracellular transport, which correlate to distinct molecular alterations in the TJ, suggesting differential regulation of the BBB during inflammatory pain states. Such a biphasic trend in TJ protein alterations and the loss BBB functional integrity has also been seen with other models of inflammatory pain, and highlights the dynamic nature of the barrier (Huber et al, 2002a).…”

“…While the claudins are critical for cell-cell adhesion, their function is dependent on the interaction with other TJ proteins (Bazzoni and Dejana, 2004;Hawkins and Davis, 2005;Huber et al, 2002a;Wolka et al, 2003). A disruption of TJ protein interactions may be responsible for the BBB integrity loss observed in this study, as opposed to changes in only a single protein.…”

“…In addition to increased codeine transport into the brain, increased antinociceptive efficacy was noted. These changes in barrier function correlated with alterations in TJ proteins (Brooks et al, 2005;Hau et al, 2004;Huber et al, 2001Huber et al, , 2002a.…”