MMP9 deficiency does not decrease blood–brain barrier disruption, but increases astrocyte MMP3 expression during viral encephalomyelitis

Abstract

Expression of matrix metalloproteinases (MMPs), especially MMP9 correlates with blood brain barrier (BBB) disruption during many neuroinflammatory diseases. During neurotropic coronavirus virus (JHMV) induced encephalomyelitis, MMP9 activity is restricted to neutrophils. Furthermore, myeloid cell depletion implicated MMP9 in facilitating leukocyte central nervous system (CNS) infiltration via loss of BBB integrity. The requirement of MMP9 in BBB disruption was thus assessed in JHMV infected MMP9 deficient (MMP9−/−) mice. Depletion of neutrophils reduced CNS accumulation of monocytes and T cells, albeit without affecting overall pathogenesis. By contrast, infected MMP9−/− mice revealed no differences in CNS leukocyte infiltration, composition or localization, consistent with BBB disruption similar to wild type (WT) mice. Unimpaired T cell mediated virus control supported an unexpectedly redundant role of MMP9 in promoting leukocyte access to the brain parenchyma. While MMP9 deficiency did not expand the overall limited pattern of MMP expression during JHMV infection, it coincided with MMP3 upregulation. MMP3 expression remained largely confined to astrocytes, similar to WT mice. These data demonstrate that neutrophil-derived MMP9 is not the sole mediator facilitating parenchymal leukocyte entry via BBB disruption during viral encephalomyelitis. Moreover, significantly enhanced MMP3 expression by astrocytes in infected MMP9−/− mice suggests an active role of resident cells in participating and potentially collaborating with infiltrating cells in regulating BBB permeability. Overall, these results highlight the complexity of targeting individual MMPs as a strategy to regulate inflammation.

Zymographic patterns of MMP-2 and MMP-9 in the CSF and cerebellum of dogs with subacute distemper leukoencephalitis

“…The characterization of separate roles for individual MMPs is complicated by the wide variation of expression patterns, kinetics, substrate, and cell specificity in different inflammatory settings (Savarin et al, 2011). By zymography, there was no way of detecting a constant profile of MMPs in the CSF and the cerebellar tissue of the dogs and establishing a secure biomarker for the subacute inflammatory phase of the CDV infection; however, pro-MMP-2 was present in most of the CSF samples and pro-MMP-2 and pro-MMP-9 were increased in the cerebellum.…”

Ifit2 Deficiency Results in Uncontrolled Neurotropic Coronavirus Replication and Enhanced Encephalitis via Impaired Alpha/Beta Interferon Induction in Macrophages

“…MHV-A59 was propagated and plaque assayed on delayed brain tumor (DBT) astrocytoma cell monolayers. Mice were infected intracranially in the left hemisphere with 1,000 PFU of MHV-A59 diluted in endotoxin-free Dulbecco's phosphate-buffered saline (PBS) in a final volume of 30 l. Clinical disease severity was graded daily using the following scale: 0, no disease symptoms; 1, ruffled fur; 2, hunched back/inability to turn upright; 3, severe hunching/wasting/hind limb paralysis; 4, moribund condition or death (33,34). Intraperitoneal infections were carried out with 1,000 PFU MHV-A59 in 300 l Dulbecco's PBS.…”

“…RNA extraction, reverse transcription, and gene expression analysis. RNA was extracted using TRIzol reagent (Invitrogen, Carlsbad, CA) according to the manufacturer's instructions and subjected to real-time PCR analysis as described previously (34). In brief, snapfrozen tissues were dissociated with TRIzol in a Tissuelyser II (Qiagen, Valencia, CA), treated with chloroform, and RNA was precipitated with isopropyl alcohol, washed with 75% ethanol, and resuspended in RNase-free water (Gibco/Invitrogen, Grand Island, NY).…”

Disruption of in vitro endothelial barrier integrity by Japanese encephalitis virus‐Infected astrocytes

“…Astrocytes have a regulatory effect on integrating neuronal function, neuronal support, and the maintenance of BBB integrity. Virus‐infected or stressed astrocytes produced elevated levels of BBB disrupting molecules and compromised the integrity of the BBB in vitro (Eugenin et al, ; Li et al, ; Lu et al, ; Savarin et al, ; Argaw et al, ). To extend the scope of our understanding of cellular mechanisms associated with Japanese encephalitis‐associated BBB disruption, this study was designed to study the impact of astrocytes on the barrier properties of brain microvascular endothelial cells in response to JEV infection.…”