Evidence for differential changes of junctional complex proteins in murine neurocysticercosis dependent upon CNS vasculature

Abstract

The delicate balance required to maintain homeostasis of the central nervous system (CNS) is controlled by the blood brain barrier (BBB). Upon injury, the BBB is disrupted compromising the CNS. BBB disruption has been represented as a uniform event. However, our group has shown in a murine model of neurocysticercosis (NCC) that BBB disruption varies depending upon the anatomical site/vascular bed analyzed. In this study further understanding of the mechanisms of BBB disruption were explored in blood vessels located in leptomeninges (pial vessels) and brain parenchyma (parenchymal vessels) by examining the expression of junctional complex proteins in murine brain infected with Mesocestoides corti. Both pial and parenchymal vessels from mock infected animals showed significant colocalization of junctional proteins and displayed an organized architecture. Upon infection, the patterned organization was disrupted and in some cases, particular tight junction and adherens junction proteins were undetectable or appeared to be undergoing proteolysis. The extent and timing of these changes differed between both types of vessels (pial vessel disruption within days versus weeks for parenchymal vessels). To approach potential mechanisms, the expression and activity of matrix metalloproteinase-9 (MMP-9) was evaluated by in situ zymography. The results indicated an increase in MMP-9 activity at sites of BBB disruption exhibiting leukocyte infiltration. Moreover, the timing of MMP activity in pial and parenchymal vessels correlated with the timing of permeability disruption. Thus, breakdown of the BBB is a mutable process despite the similar structure of the junctional complex between pial and parenchymal vessels and involvement of MMP activity.

Multiple expression of matrix metalloproteinases in murine neurocysticercosis: Implications for leukocyte migration through multiple central nervous system barriers

“…In contrast, collagenolysis activity in leukocytes was mostly undetectable in these animals ( Table 1). This is consistent with our previous studies in which few leukocytes could be found infiltrating into the CNS of control or mock infected animals [2,4]. It is probable that some degree of MMP activity in the form of gelatinolytic activity is required for leukocytes extravasating into the CNS under normal physiological conditions.…”

“…MMP-9 expression and activity has been demonstrated in this process [4], but upregulation of multiple MMPs upon infection (Fig 1) may indicate that simultaneous activity of different MMPs is necessary to support leukocyte extravasation into the CNS. To test this hypothesis we studied both the expression and potential enzymatic activity of distinct MMPs in leukocytes exiting pial vessels of mock and parasite infected animals.…”

“…Our studies in a mouse model of NCC have revealed differential breakdown of the BBB and the blood-cerebrospinal fluid barrier (BCB) dependant upon the vascular bed, accumulation of blood derived leukocytes, production of inflammatory cytokines and differential expression of MMP-9 [2][3][4]. Many of these pathophysiological conditions have been described in other CNS disorders, and MMPs have been linked to associated mechanisms [28,43,63].…”

“…In addition, we showed that MMP-9 is an important player in this process using MMP9 −/− mice [4]. To further understand the role of MMPs in the breakdown of parenchymal vessels, the expression and potential enzymatic activity of additional MMPs were studied.…”

“…Particular emphasis was given to the expression of MMPs in leukocytes extravasating different types of vasculature as the kinetics of infiltration differs among distinct areas of the mouse brain [2][3][4]. Total mRNA isolated from brains after different post infection times was analyzed using a macroarray specific for MMPs.…”