Granzyme B mediates neurotoxicity through a G-protein-coupled receptor.

Department of Neurology, Johns Hopkins University, Baltimore, Maryland, USA.
The FASEB Journal (Impact Factor: 5.48). 07/2006; 20(8):1209-11. DOI: 10.1096/fj.05-5022fje
Source: PubMed

ABSTRACT Neuroinflammatory diseases such as multiple sclerosis (MS) are characterized by focal regions of demyelination and axonal loss associated with infiltrating T cells. However, the role of activated T cells in causing neuronal injury remains unclear. CD4 and CD8 T cells were isolated from normal donors and polyclonally activated using plate-bound anti-CD3 and soluble anti-CD28. The conditioned T cell supernatants caused toxicity to cultured human fetal neurons, which could be blocked by immunodepleting the supernatants of granzyme B (GrB). Recombinant GrB also caused toxicity in neurons by caspase-dependent pathways but no toxicity was seen in astrocytes. The neurotoxicity was independent of perforin and could not be blocked by mannose-6-phosphate. However, GrB-induced neurotoxicity was sensitive to pertussis toxin, implicating the stimulation of Gialpha protein-coupled receptors. GrB caused a decrease in cAMP levels but only modest increases in intracellular calcium. The effect on intracellular calcium could be markedly potentiated by stromal-derived factor 1alpha. GrB-induced neurotoxicity could also be blocked by vitamin E and a neuroimmunophilin ligand. In conclusion, GrB may be an important mediator of neuronal injury in T cell-mediated neuroinflammatory disorders.

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    • "In contrast, murine astrocytes quickly respond to degranulation (release of lytic enzymes) by cytotoxic CD8 + T cells [21]. Cell death of human neurons has been observed upon the addition of granzyme B [22], another lytic enzyme than perforin. Moreover, cytotoxic CD8 + T cells can selectively attack neuronal neurites supporting the notion that axonal damage observed in MS lesions could be mediated by these cells [23]. "
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    ABSTRACT: Multiple sclerosis (MS) is an inflammatory disease of the central nervous system (CNS) characterized by multi-focal demyelination, axonal loss, and immune cell infiltration. Numerous immune mediators are detected within MS lesions, including CD4(+) and CD8(+) T lymphocytes suggesting that they participate in the related pathogenesis. Although CD4(+) T lymphocytes are traditionally considered the main actors in MS immunopathology, multiple lines of evidence suggest that CD8(+) T lymphocytes are also implicated in the pathogenesis. In this review, we outline the recent literature pertaining to the potential roles of CD8(+) T lymphocytes both in MS and its animal models. The CD8(+) T lymphocytes detected in MS lesions demonstrate characteristics of activated and clonally expanded cells supporting the notion that these cells actively contribute to the observed injury. Moreover, several experimental in vivo models mediated by CD8(+) T lymphocytes recapitulate important features of the human disease. Whether the CD8(+) T cells can induce or aggravate tissue destruction in the CNS needs to be fully explored. Strengthening our understanding of the pathogenic potential of CD8(+) T cells in MS should provide promising new avenues for the treatment of this disabling inflammatory disease.
    Biochimica et Biophysica Acta 02/2011; 1812(2):151-61. DOI:10.1016/j.bbadis.2010.07.006 · 4.66 Impact Factor
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    • "For example, the extent of axonal damage is directly related to the numbers of infiltrated T cells in multiple sclerosis plaques (Kuhlmann et al., 2002). In vitro studies have also shown that activated T cells can induce direct neuronal damage, through both cell contact-dependent (Giuliani et al., 2003) and – independent pathways(Wang et al., 2006). In the present study, we observed that patients with multiple sclerosis had higher levels of GrB compared to controls in their CSF. "
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    ABSTRACT: There is a great need for pharmacological approaches to enhance neural progenitor cell (NPC) function particularly in neuroinflammatory diseases with failed neuroregeneration. In diseases such as multiple sclerosis and stroke, T-cell infiltration occurs in periventricular zones where NPCs are located and is associated with irreversible neuronal loss. We studied the effect of T-cell activation on NPC functions. NPC proliferation and neuronal differentiation were impaired by granzyme B (GrB) released by the T-cells. GrB mediated its effects by the activation of a Gi-protein-coupled receptor leading to decreased intracellular levels of cAMP and subsequent expression of the voltage-dependent potassium channel, Kv1.3. Importantly, blocking channel activity with margatoxin or blocking its expression reversed the inhibitory effects of GrB on NPCs. We have thus identified a novel pathway in neurogenesis. The increased expression of Kv1.3 in pathological conditions makes it a novel target for promoting neurorestoration.
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    • "COLLATERAL NEURONAL APOPTOSIS IN CNS INFLAMMATION GLIA ent with previous reports showing the (relative) resistance of astrocytes against cell death by purified perforin (Wang et al., 2006; Zeine et al., 2001), granzyme B (Wang et al., 2006), and FasL (Becher et al., 1998; Lee et al., 2000) in vitro. "
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    ABSTRACT: Peripheral nerve injury induces a profound local inflammatory response that involves T cells and macrophages and augments the generation of neuropathic pain. The mechanisms underlying immune cell activation or inhibition in the peripheral nervous system, however, are unknown. The co-inhibitory molecule B7-H1 (PD-L1, CD274) attenuates immune cell proliferation and cytokine production and protects from inflammation-induced tissue damage. We analyzed the temporal gene expression profile of B7-H1 and different cytokines after chronic constriction injury (CCI) of the sciatic nerve, a lesion paradigm inducing neuropathic pain, by quantitative real-time polymerase chain reaction and immunohistochemistry in B7-H1(-/-) mice and wild-type (WT) controls. B7-H1 mRNA was markedly induced in WT nerves after CCI, and macrophages could be identified as major B7-H1 source. The proinflammatory mediators tumor necrosis factor alpha (TNFalpha) and monocyte chemoattractant protein-1 (MCP-1) displayed a strong, but transient expression in degenerating nerves on day 1 after CCI in WT mice, while a biphasic expression peak on day 1 and day 28 was found in B7-H1(-/-) mice. Overall, TNFalpha and MCP-1 levels in B7-H1-deficient nerves dramatically exceeded those in WT controls. In contrast, induction of the anti-inflammatory cytokine interleukin(IL)-10 was restricted to WT nerves. The observation that B7-H1 deficiency enhances inflammation upon CCI was further corroborated by immunohistochemistry showing increased numbers of T cells and macrophages in injured nerves from B7-H1(-/-) mice. Interestingly, mechanical hyperalgesia was more pronounced in the absence of B7-H1. Our study identifies B7-H1 as an important suppressor of the inflammatory response and neuropathic pain occurring after peripheral nerve injury.
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