Upregulation of chemokine receptor gene expression in brains of Borna disease virus (BDV)-infected rats in the absence and presence of inflammation

Genistein induces deleterious effects during its acute exposure in Swiss mice

Genistein is a soy derived isoflavone. It has wide variety of therapeutic effects against certain diseases including cancer. Although toxic effects of genistein have been studied, its effect on the gene expression and the reason behind toxicity have not been identified yet. In the present study, genistein was administered to age and body weight matched Swiss mice at the doses of 125, 250, 500 and 1000 mg/kg. The biomarkers of hepatotoxicity in serum, liver histology, oxidative stress parameters in tissue homogenates, and global gene expression were examined. Elevated alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase (ALP) levels and degenerated liver tissue were observed in 500, and 1000 mg/kg genistein treated groups. Oxidative stress was significant at these doses as considerable increase in lipid peroxidation (LPO) and decrease in total glutathione (GSH) were observed. Gene expression analysis showed 40 differentially expressed genes at twofold change and P < 0.05. Differentially expressed genes were corresponding to different biologically relevant pathways including metabolic and oxidative stress pathways. In 500 mg/kg group, Cyp4a14, Sult1e1, Gadd45g, Cidec, Mycs, and so forth genes were upregulated. These results suggested that the higher dose of genistein can produce several undesirable effects by affecting multiple cellular pathways.

Altered regulation of CXCR4 expression during aging contributes to increased CXCL12-dependent chemotactic migration of CD4(+) T cells

Chemokine-dependent migration of T lymphocytes assures recirculation of naïve T cells to secondary lymphoid organs and tissue-specific trafficking of memory-effector T cells. Previous studies carried out in rodents have demonstrated age-associated modulation of the expression of chemokine receptors such as CXCR4 and CCR5; however, little is known about the molecular mechanisms that regulate receptor expression and turnover in T cells, during advancing age in humans. Our recent results demonstrating increased chemotactic migration in response to CXCL12 in CD4(+) T cells obtained from the elderly, as compared to those from young donors, led us to hypothesize that increase in surface expression, because of altered endocytic regulation of CXCR4 on T cells during aging, might be directly responsible for increased migration toward CXCL12. Studies presented here demonstrate a significant increase in the surface expression of CXCR4 in CD4(+) T cells from elderly human donors, relative to those from the young. Additionally, CXCL12-mediated endocytosis of CXCR4 was differentially regulated during aging, which could be attributed to alterations in the ubiquitination of CXCR4. Thus, altered ubiquitination of CXCR4 may contribute to the increased surface expression and enhanced T-cell migration to chemotactic stimuli in the elderly.

The chemokine receptor CCR5 in the central nervous system

The expression and the role of the chemokine receptor CCR5 have been mainly studied in the context of HIV infection. However, this protein is also expressed in the brain, where it can be crucial in determining the outcome in response to different insults. CCR5 expression can be deleterious or protective in controlling the progression of certain infections in the CNS, but it is also emerging that it could play a role in non-infectious diseases. In particular, it appears that, in addition to modulating immune responses, CCR5 can influence neuronal survival. Here, we summarize the present knowledge about the expression of CCR5 in the brain and highlight recent findings suggesting its possible involvement in neuroprotective mechanisms.

Long-term expression of tissue-inhibitor of matrix metalloproteinase-1 in the murine central nervous system does not alter the morphological and behavioral phenotype but alleviates the course of experimental allergic encephalomyelitis

Tissue inhibitors of metalloproteinases (TIMPs) are a family of closely related proteins that inhibit matrix metalloproteinases (MMPs). In the central nervous system (CNS), TIMPs 2, 3, and 4 are constitutively expressed at high levels, whereas TIMP1 can be induced by various stimuli. Here, we studied the effects of constitutive expression of TIMP1 in the CNS in transgenic mice. Transgene expression started prenatally and persisted throughout lifetime at high levels. Since MMP activity has been implicated in CNS development, in proper function of the adult CNS, and in inflammatory disorders, we investigated Timp1-induced CNS alterations. Despite sufficient MMP inhibition, high expressor transgenic mice had a normal phenotype. The absence of compensatory up-regulation of MMP genes in the CNS of Timp1 transgenic mice indicates that development, learning, and memory functions do not require the entire MMP arsenal. To elucidate the effects of strong Timp1 expression in CNS inflammation, we induced experimental allergic encephalomyelitis. We observed a Timp1 dose-dependent mitigation of both experimental allergic encephalomyelitis symptoms and histological lesions in the CNS of transgenic mice. All in all, our data demonstrate that (1) long-term CNS expression of TIMP1 with complete suppression of gelatinolytic activity does not interfere with physiological brain function and (2) TIMP1 might constitute a promising candidate for long-term therapeutic treatment of inflammatory CNS diseases such as multiple sclerosis.

64Cu-AMD3100--a novel imaging agent for targeting chemokine receptor CXCR4

CXCR4 is a chemokine receptor which has been shown to be exploited by various tumors for increased survival, invasion, and homing to target organs. We developed a one step radiosynthesis for labeling the CXCR4-specific antagonist AMD3100 with Cu-64 to produce (64)Cu-AMD3100 with a specific activity of 11.28Ci/ micromol (417GBq/ micromol) at the end of radiosynthesis. Incorporation of Cu(II) ion into AMD3100 did not change its ability to inhibit cellular migration in response to the (only) CXCR4 ligand, SDF-1/CXCL12. (64)Cu-AMD3100 binding affinity to CXCR4 was found to be 62.7 microM. Biodistribution of (64)Cu-AMD3100 showed accumulation in CXCR4-expressing organs and tissues, a renal clearance pathway, and an anomalous specific accumulation in the liver. We conclude that (64)Cu-AMD3100 exhibits promise as a potential PET imaging agent for visualization of CXCR4-positive tumors and metastases and might be used to guide and monitor anti-CXCR4 tumor therapy.

Deubiquitination of CXCR4 by USP14 is critical for both CXCL12-induced CXCR4 degradation and chemotaxis but not ERK ativation

The chemokine receptor CXCR4 plays important roles in the immune and nervous systems. Abnormal expression of CXCR4 contributes to cancer and inflammatory and neurodegenerative disorders. Although ligand-dependent CXCR4 ubiquitination is known to accelerate CXCR4 degradation, little is known about counter mechanisms for receptor deubiquitination. CXCL12, a CXCR4 agonist, induces a time-dependent association of USP14 with CXCR4, or its C terminus, that is not mimicked by USP2A, USP4, or USP7, other members of the deubiquitination catalytic family. Co-localization of CXCR4 and USP14 also is time-dependent following CXCL12 stimulation. The physical interaction of CXCR4 and USP14 is paralleled by USP14-catalyzed deubiquitination of the receptor; knockdown of endogenous USP14 by RNA interference (RNAi) blocks CXCR4 deubiquitination, whereas overexpression of USP14 promotes CXCR4 deubiquitination. We also observed that ubiquitination of CXCR4 facilitated receptor degradation, whereas overexpression of USP14 or RNAi-induced knockdown of USP14 blocked CXCL12-mediated CXCR4 degradation. Most interestingly, CXCR4-mediated chemotactic cell migration was blocked by either overexpression or RNAi-mediated knockdown of USP14, implying that a CXCR4-ubiquitin cycle on the receptor, rather than a particular ubiquitinated state of the receptor, is critical for the ligand gradient sensing and directed motility required for chemokine-mediated chemotaxis. Our observation that a mutant of CXCR4, HA-3K/R CXCR4, which cannot be ubiquitinated and does not mediate a chemotactic response to CXCL12, indicates the importance of this covalent modification not only in marking receptors for degradation but also for permitting CXCR4-mediated signaling. Finally, the indistinguishable activation of ERK by wild typeor 3K/R-CXCR4 suggests that chemotaxis in response to CXCL12 may be independent of the ERK cascade.

Astrocytes play a key role in activation of microglia by persistent Borna disease virus infection

Neonatal Borna disease virus (BDV) infection of the rat brain is associated with microglial activation and damage to certain neuronal populations. Since persistent BDV infection of neurons is nonlytic in vitro, activated microglia have been suggested to be responsible for neuronal cell death in vivo. However, the mechanisms of activation of microglia in neonatally BDV-infected rat brains remain unclear. Our previous studies have shown that activation of microglia by BDV in culture requires the presence of astrocytes as neither the virus nor BDV-infected neurons alone activate microglia. Here, we evaluated the mechanisms whereby astrocytes can contribute to activation of microglia in neuron-glia-microglia mixed cultures. We found that persistent infection of neuronal cells leads to activation of uninfected astrocytes as measured by elevated expression of RANTES. Activation of astrocytes then produces activation of microglia as evidenced by increased formation of round-shaped, MHCI-, MHCII- and IL-6-positive microglia cells. Our analysis of possible molecular mechanisms of activation of astrocytes and/or microglia in culture indicates that the mediators of activation may be soluble heat-resistant, low molecular weight factors. The findings indicate that astrocytes may mediate activation of microglia by BDV-infected neurons. The data are consistent with the hypothesis that microglia activation in the absence of neuronal damage may represent initial steps in the gradual neurodegeneration observed in brains of neonatally BDV-infected rats.

Activation of microglia by borna disease virus infection: in vitro study

Neonatal Borna disease virus (BDV) infection of the rat brain is associated with microglial activation and damage to the certain neuronal populations. Since persistent BDV infection of neurons in vitro is noncytolytic and noncytopathic, activated microglia have been suggested to be responsible for neuronal cell death in vivo. However, the mechanisms of activation of microglia in neonatally BDV-infected rat brain have not been investigated. To address these issues, activation of primary rat microglial cells was studied following exposure to purified BDV or to persistently BDV-infected primary cortical neurons or after BDV infection of primary mixed neuron-glial cultures. Neither purified virus nor BDV-infected neurons alone activated primary microglia as assessed by the changes in cell shape or production of the proinflammatory cytokines. In contrast, in the BDV-infected primary mixed cultures, we observed proliferation of microglia cells that acquired the round morphology and expressed major histocompatibility complex molecules of classes I and II. These manifestations of microglia activation were observed in the absence of direct BDV infection of microglia or overt neuronal toxicity. In addition, compared to uninfected mixed cultures, activation of microglia in BDV-infected mixed cultures was associated with a significantly greater lipopolysaccharide-induced release of tumor necrosis factor alpha, interleukin 1beta, and interleukin 10. Taken together, the present data are the first in vitro evidence that persistent BDV infection of neurons and astrocytes rather than direct exposure to the virus or dying neurons is critical for activating microglia.

Regulation of neuroinflammation: the role of CXCL10 in lymphocyte infiltration during autoimmune encephalomyelitis

The movement of lymphocytes from the microvasculature into the central nervous system (CNS) parenchyma is an essential step in the pathogenesis of a variety of infectious and autoimmune neuroinflammatory diseases. The lymphocyte chemoattractant CXCL10 and its receptor, CXCR3, are expressed by the CNS and by CNS infiltrating lymphocytes, respectively, only in patients with ongoing CNS inflammation, suggesting an important role for these molecules in the pathogenic process. Numerous studies utilizing animal models and transgenic approaches have indeed supported a role for CXCL10 in the intraparenchymal trafficking of lymphocytes during acute CNS inflammation; however, other studies suggest that its expression is not required for the development of autoimmune forms of CNS inflammation and, in fact, that interference with CXCL10 signaling could lead to increased neuroinflammation. This review will consider the data from these studies and attempt to reconcile them through comparisons of both the neuroinflammatory models and the effects of CXCL10 in the CNS versus lymphoid tissues. Finally, it will define directions for future analyses of CXCL10 and CXCR3 in CNS inflammation so that their potential therapeutic utility can be more completely determined.

Cerebral expression of interleukin-12 induces neurological disease via differential pathways and recruits antigen-specific T cells in virus-infected mice

Transgenic expression of interleukin-12 (IL-12) in astrocytes causes a spontaneous inflammatory central nervous system disorder in aged mice. Here we show that spontaneous disorder developed only when both mature lymphocytes and interferon (IFN)-gamma were present. Infection with noncytolytic Borna disease virus (BDV) did not affect wild-type mice but accelerated disease of IL-12 transgenic mice. Infection of transgenic mice lacking lymphocytes did not result in neurological symptoms. In contrast, BDV infection of transgenic mice lacking IFN-gamma induced neurological disease with delayed onset of symptoms that resembled those in infected transgenic mice with a functional IFN-gamma gene. In BDV-infected transgenic mice devoid of IFN-gamma no cerebellar calcification was observed, and multiplication of BDV was not inhibited. To determine the antigen specificity of lymphocytes in brains of diseased animals, the IL-12 transgene was introduced into an H-2k genetic background. Infection of IL-12 transgenic H-2k mice resulted in extensive lymphocytic infiltration into the cerebellum but not into other brain regions that also contained viral antigen but expressed the transgene at lower levels. Tetramer analysis revealed that most CD8 T cells in the cerebellum of such mice were BDV-specific. Our results thus demonstrate that IFN-gamma secreting lymphocytes are responsible for disease of IL-12 transgenic mice. They further suggest that expression of IL-12 in the central nervous system may lead to localized recruitment of T cells that recognize antigens expressed in the brain.