Evaluation of [¹²³I]-CLINDE as a potent SPECT radiotracer to assess the degree of astroglia activation in cuprizone-induced neuroinflammation.

PURPOSE: The purpose of this study was to assess the feasibility and sensitivity of the high-affinity translocator protein (TSPO) ligand [(123)I]-CLINDE in imaging TSPO changes in vivo and characterise and compare astroglial and TSPO changes in the cuprizone model of demyelination and remyelination in C57BL/6 mice. METHODS: C57BL/6 mice were fed with cuprizone for 4 weeks to induce demyelination followed by 2-4 weeks of standard diet (remyelination). Groups of mice were followed by in vivo single photon emission computed tomography (SPECT)/CT imaging using [(123)I]-CLINDE and uptake correlated with biodistribution, autoradiography, immunohistochemistry, immunofluorescence and real-time polymerase chain reaction (RT-PCR). RESULTS: The uptake of [(123)I]-CLINDE in the brain as measured by SPECT imaging over the course of treatment reflects the extent of the physiological response, with significant increases observed during demyelination followed by a decrease in uptake during remyelination. This was confirmed by autoradiography and biodistribution studies. A positive correlation between TSPO expression and astrogliosis was found and both activated astrocytes and microglial cells expressed TSPO. [(123)I]-CLINDE uptake reflects astrogliosis in brain structures such as corpus callosum, caudate putamen, medium septum and olfactory tubercle as confirmed by both in vitro and in vivo results. CONCLUSION: The dynamics in the cuprizone-induced astroglial and TSPO changes, observed by SPECT imaging, were confirmed by immunofluorescence, RT-PCR and autoradiography. The highly specific TSPO radioiodinated ligand CLINDE can be used as an in vivo marker for early detection and monitoring of a variety of neuropathological conditions using noninvasive brain imaging techniques.

Demyelination caused by the copper chelator cuprizone halts T cell mediated autoimmune neuroinflammation.

Myelin reactive T cells are central in the development of the autoimmune response leading to CNS destruction in Multiple Sclerosis and Experimental Autoimmune Encephalomyelitis (EAE). Investigations on the mechanisms underlying the activation and expansion of myelin reactive T have stressed the importance of non-autoimmune conditions impinging the autoimmune repertoire potentially involved in the disease. Here, we show that CNS injury caused by the toxic cuprizone results in the generation of immunoreactivity towards several myelin components. Paradoxically, exposure to CNS injury does not increase the susceptibility to develop EAE, but render mice protected to the pathogenic autoimmune response against myelin antigens.

Indomethacin, ibuprofen and gentamicin administered during late stages of glomerulogenesis do not reduce glomerular number at 14 days of age in the neonatal rat.

Premature neonates are frequently administered indomethacin, ibuprofen and gentamicin during the period of active glomerulogenesis. These drugs are known to have nephrotoxic effects, but the morphological effect of these drugs is unknown. The purpose of this study was to determine whether administration of these drugs during the late stages of glomerulogenesis in the rat has an effect on glomerular endowment. Rat pups were given, intraperitoneally, indomethacin, ibuprofen or indomethacin and gentamicin for the first 5 days of their postnatal life. The pups were killed at 14 days of age at completion of glomerulogenesis. The total number of glomeruli in the left kidney was determined by the physical disector/fractionator stereological technique. There was no difference between treatment groups in total number of glomeruli per kidney (P = 0.45). There were significantly fewer glomeruli per gram of kidney in those rat pups that had received indomethacin or ibuprofen (P < 0.0001). The reduction in the number of glomeruli per gram of kidney may indicate augmented growth of nephron tubules and/or collecting ducts, and/or be a consequence of oedema secondary to drug exposure. Further study is required to determine whether reduced glomerular number is seen in older animals or following exposure to these drugs at different time-points in kidney development.

The innate immune response to adjuvants dictates the adaptive immune response to autoantigens.

To elucidate the role of innate immunity in susceptibility to the animal model of multiple sclerosis, experimental autoimmune encephalomyelitis (EAE), we induced EAE by immunization with spinal cord homogenate (SCH) plus complete Freund adjuvant or carbonyl iron in 3 inbred rat strains. Lewis are considered "susceptible," PVG/c-Rt7a (PVG) as "semisusceptible," and Brown Norway (BN) as "resistant" to EAE. Immunization with SCH-carbonyl iron resulted in clinical disease in all 3 strains, but the pathologic features of EAE in the resistant BN and the semisusceptible PVG rats differed from those in the Lewis and PVG model of EAE induced with SCH-complete Freund adjuvant. In BN and PVG rats, there were numerous inflammatory lesions with prominent involvement of microglia and, to a lesser extent, perivascular macrophages. These data suggest that different levels of activation of the innate immune system by different adjuvants determine whether EAE will or will not develop. Accordingly, the widely accepted scale of susceptibility to EAE development (Lewis > PVG > BN) should be revised because it does not take into account the important contribution of the composition of the adjuvant to the quality and quantity of the innate immune response and, consequently, to the generation and extent of the pathogenic T-cell-mediated, that is, adaptive, autoimmune disease.

The contribution of nitric oxide and interferon gamma to the regulation of the neuro-inflammation in experimental autoimmune encephalomyelitis.

Nitric oxide (NO) is a key messenger involved in physiological functions including endothelium-dependent vascular relaxation, inhibition of platelet adhesion and aggregation and regulation of inflammatory and immune responses. Here we briefly introduce NO and its functions and then describe our work over the past several years examining the role of NO in EAE in both the rat and the mouse. We show that NO plays a significant role in determining the resistance or susceptibility to EAE in various strains and or sexes of animals. We demonstrate that NO down-regulates several aspects of CNS inflammation but also has a dual role in that it is required for inflammation in some situations.

Renal glomeruli and tubular injury following indomethacin, ibuprofen, and gentamicin exposure in a neonatal rat model.

Indomethacin, ibuprofen, and gentamicin are commonly administered to neonates between 24 and 28 wk gestation when glomerulogenesis is still occurring. Indomethacin is known to cause renal failure in up to 25% of infants treated. Possible morphologic effects of these drugs are largely unknown. The purpose of this study was to determine the type of renal changes found on light (LM) and electron microscopy (EM) following administration of indomethacin, ibuprofen, and gentamicin in a neonatal rat model. Rat pups were exposed to indomethacin or ibuprofen and/or gentamicin antenatally for 5 d before birth or postnatally for 5 d from d 1 of life. Pups were killed at 14 d of age. LM examination in all indomethacin- and ibuprofen-treated pups both antenatally and postnatally showed vacuolization of the epithelial proximal tubules, interstitial edema, intratubular protein deposition but no significant glomerular changes. EM examination showed pleomorphic mitochondria and loss of microvilli in the tubules. The glomeruli showed extensive foot process effacement and irregularities of the glomerular basement membrane. EM changes were most marked in pups treated antenatally with ibuprofen, and indomethacin with gentamicin postnatally. Indomethacin, ibuprofen, and gentamicin cause significant change in glomerular and tubular structure in the neonatal rat model.

Expression of the heparan sulfate-degrading enzyme heparanase is induced in infiltrating CD4+ T cells in experimental autoimmune encephalomyelitis and regulated at the level of transcription by early growth response gene 1.

The heparan sulfate-cleaving enzyme heparanase (HPSE) plays an important role in remodeling of the basement membrane and extracellular matrix during inflammation. Inducible HPSE enzymatic activity has been reported in leukocytes; however, little is known of the molecular mechanisms that regulate HPSE gene expression during inflammatory disease. In this study, HPSE expression and regulation in the T cell-mediated disease model, experimental autoimmune encephalomyelitis (EAE), were investigated. Expression analysis showed that HPSE mRNA is induced in rat CD4+ antigen-specific T lymphocytes upon activation and correlates with the encephalitogenicity of the cells. Examination of the kinetics and cell type-specific expression of HPSE throughout the progression of active EAE in rats, indicated that HPSE was highly expressed in CD4+ T cells infiltrating the central nervous system (CNS) during clinical disease. Little or no HPSE expression was observed in CD8+ T cells, macrophages, or astrocytes during disease progression. To investigate the mechanism of inducible HPSE gene regulation in T cells, studies were extended into human primary T cells. HPSE mRNA, protein, and enzymatic activity were induced upon activation. Functional analysis of the human HPSE promoter identified an EGR1 binding motif that contained high inducible activity and was transactivated by EGR1. Furthermore, the treatment of primary T lymphocytes with an EGR1 siRNA inhibited inducible HPSE mRNA expression. These data provide evidence to suggest that inducible HPSE expression in primary T lymphocytes is regulated at the transcriptional level by EGR1 and is important in facilitating CD4+ T cell infiltration into the CNS to promote EAE.

Expression of the heparan sulfate-degrading enzyme heparanase is induced in infiltrating CD4+ T cells in experimental autoimmune encephalomyelitis and regulated at the level of transcription by early growth response gene.

The heparan sulfate-cleaving enzyme heparanase (HPSE) plays an important role in remodeling of the basement membrane and extracellular matrix during inflammation. Inducible HPSE enzymatic activity has been reported in leukocytes; however, little is known of the molecular mechanisms that regulate HPSE gene expression during inflammatory disease. In this study, HPSE expression and regulation in the T cell-mediated disease model, experimental autoimmune encephalomyelitis (EAE), were investigated. Expression analysis showed that HPSE mRNA is induced in rat CD4+ antigen-specific T lymphocytes upon activation and correlates with the encephalitogenicity of the cells. Examination of the kinetics and cell type-specific expression of HPSE throughout the progression of active EAE in rats, indicated that HPSE was highly expressed in CD4+ T cells infiltrating the central nervous system (CNS) during clinical disease. Little or no HPSE expression was observed in CD8+ T cells, macrophages, or astrocytes during disease progression. To investigate the mechanism of inducible HPSE gene regulation in T cells, studies were extended into human primary T cells. HPSE mRNA, protein, and enzymatic activity were induced upon activation. Functional analysis of the human HPSE promoter identified an EGR1 binding motif that contained high inducible activity and was transactivated by EGR1. Furthermore, the treatment of primary T lymphocytes with an EGR1 siRNA inhibited inducible HPSE mRNA expression. These data provide evidence to suggest that inducible HPSE expression in primary T lymphocytes is regulated at the transcriptional level by EGR1 and is important in facilitating CD4+ T cell infiltration into the CNS to promote EAE.

Neuronal nitric oxide synthase plays a key role in CNS demyelination.

Nitric oxide (NO) is a small, short-lived molecule released from a variety of cells that is implicated in a multitude of biological processes. In pathological conditions, overproduction of NO may lead to the generation of highly reactive species, such as peroxynitrite and stable nitrosothiols, that may cause irreversible cell damage. Accordingly, several studies have suggested that NO may be involved in the pathogenesis of various neuroinflammatory/degenerative diseases. Increased concentrations of NO in the CNS in such cases are usually attributed to an increase in the inducible isoform of NO synthase (iNOS) usually produced by inflammatory cells. However, recent reports have suggested that the constitutive isoforms of NOS, neuronal (nNOS) and endothelial (eNOS), can also play a role. Here we examined the role that the constitutive isoforms of NOS might play in the cuprizone-induced model of demyelination/remyelination. Our results demonstrate that demyelination was greatly prevented in mice lacking nNOS. Protection was associated with a dramatic increase in mature oligodendrocyte survival and a decrease in apoptosis. Moreover, nNOS-/- mice did not respond to cuprizone with the extensive recruitment of microglia/macrophages and astrocytes, which is a typical feature in wild-type mice. Although demyelinating less, nNOS-/- mice exhibited a delay in remyelination. In eNOS-/- mice, demyelination progressed to the same extent as in wild type, but they showed a slight delay in spontaneous remyelination. In conclusion, this study highlights the importance of considering the source of NO when assessing its role in neuroinflammation/degeneration and emphasizes the differing pathological effects driven by the different NOS isoforms.

Deleterious role of IFNgamma in a toxic model of central nervous system demyelination.

Interferon-gamma (IFNgamma) is a pleiotropic cytokine that plays an important role in many inflammatory processes, including autoimmune diseases such as multiple sclerosis (MS). Demyelination is a hallmark of MS and a prominent pathological feature of several other inflammatory diseases of the central nervous system, including experimental autoimmune encephalomyelitis, an animal model of MS. Accordingly, in this study we followed the effect of IFNgamma in the demyelination and remyelination process by using an experimental autoimmune encephalomyelitis model of demyelination/remyelination after exposure of mice to the neurotoxic agent cuprizone. We show that demyelination in response to cuprizone is delayed in mice lacking the binding chain of IFNgamma receptor. In addition, IFNgammaR(-/-) mice exhibited an accelerated remyelination process after cuprizone was removed from the diet. Our results also indicate that the levels of IFNgamma were able to modulate the microglia/macrophage recruitment to the demyelinating areas. Moreover, the accelerated regenerative response showed by the IFNgammaR(-/-) mice was associated with a more efficient recruitment of oligodendrocyte precursor cells in the demyelinated areas. In conclusion, this study suggests that IFNgamma regulates the development and resolution of the demyelinating syndrome and may be associated with toxic effects on both mature oligodendrocytes and oligodendrocyte precursor cells.

Nitric oxide contributes to the resistance of young SJL/J mice to experimental autoimmune encephalomyelitis.

EAE development in SJL/J mice is age and sex dependent: young males are EAE resistant; females and adult males are EAE susceptible. By studying splenocytes' IFNgamma and NO production and the induction or the suppression of actively induced EAE by manipulating NO systemic levels, we provide evidence that the failure of young male SJL/J mice to develop EAE lies in the activation of the innate immune system by the immunising stimulus.

Nitric oxide contributes to resistance of the Brown Norway rat to experimental autoimmune encephalomyelitis.

The Brown Norway (BN) rat is reported to be resistant to the induction of experimental autoimmune encephalomyelitis (EAE) and a number of mechanisms have been suggested to explain this resistance. In work reported here we provide evidence that such resistance in the BN rat can be accounted for, at least in part, by their ability to produce higher levels of nitric oxide (NO) than susceptible strains of rats. Spleen cells from the BN rat make significantly more NO following in vitro stimulation than do cells from the Lewis or PVG rat and following in vivo immunization using complete Freund's adjuvant (CFA) the BN rat makes substantially more NO than either susceptible strain. If carbonyl iron is used as adjuvant in vivo there is no increase in NO levels in the BN rat and they are rendered highly susceptible to EAE. Immunizing with CFA simultaneously with neuroantigen and carbonyl iron drives up NO levels and the resistance is restored. EAE produced using carbonyl iron is characterized by extensive macrophage/microglia presence in the central nervous system lesions of the BN rat yet the cytokine profile in the lymph nodes does not differ from that in the EAE Lewis rats.

Expression of rat I-TAC/CXCL11/SCYA11 during central nervous system inflammation: comparison with other CXCR3 ligands.

The chemokines are a large gene superfamily with critical roles in development and immunity. The chemokine receptor CXCR3 appears to play a major role in the trafficking of activated Th1 lymphocytes. There are at least three major ligands for CXCR3: mig/CXCL9, IP-10/CXCL10 and I-TAC/CXCL11, and of these three ligands, CXCL11 is the least well-characterized. In this study, we have cloned a rat ortholog of CXCL11, evaluated its function, and examined its expression in the Th-1-mediated disease, experimental autoimmune encephalomyelitis (EAE) in the rat. Based on its predicted primary amino-acid sequence, rat I-TAC/CXCL11 was synthesized and shown to induce chemotaxis of activated rat T lymphocytes in vitro and the in vivo migration of T lymphocytes when injected into the skin. I-TAC/CXCL11 expression, as determined by RT-PCR, increased in lymph node and spinal cord tissue collected from rats in which EAE had been actively induced, and in spinal cord tissue from rats in which EAE had been passively induced. The kinetics of expression were similar to that of CXCR3 and IP-10/CXCL10, although expression of both CXCR3 and IP-10/CXCL10 was more intense than that of I-TAC/CXCL11 and increased more rapidly in both lymph nodes and the spinal cord. Only minor levels of expression of the related chemokine mig/CXCL9 were observed. Immunohistochemistry revealed that the major cellular source of I-TAC/CXCL11 in the central nervous system (CNS) during EAE is likely to be the astrocyte. Together, these data indicate that I-TAC/CXCL11 is expressed in the CNS during the clinical phase of EAE. However, the observation that I-TAC/CXCL11 is expressed after receptor expression is detected suggests that it is not essential for the initial migration of CXCR3-bearing cells into the CNS.

A role for macrophage inflammatory protein-3 alpha/CC chemokine ligand 20 in immune priming during T cell-mediated inflammation of the central nervous system.

Chemokines are a family of cytokines that exhibit selective chemoattractant properties for target leukocytes and play a significant role in leukocyte migration. In this study, we have investigated the role of the C-C chemokine, macrophage inflammatory protein (MIP)-3alpha/CC chemokine ligand 20, in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), a model of T cell-dependent inflammation. Expression in the CNS of MIP-3alpha, as determined by RT-PCR, increased in a time-dependent manner such that peak expression correlated with peak clinical disease. Similarly, levels of immunoreactive MIP-3alpha in the draining lymph nodes increased up to 10-fold 9 days postimmunization and remained elevated for up to 21 days postimmunization. The increased production of MIP-3alpha coincided with onset of clinical disease. Treatment of mice with specific neutralizing anti-MIP-3alpha Abs significantly reduced the severity of both clinical EAE and neuroinflammation by inhibiting the sensitization of lymphocytes to the specific Ag and release of lymphocytes from the draining lymph nodes. In contrast, adoptive transfer experiments indicated that MIP-3alpha was not essential for the effector phase of EAE. Together, these data demonstrate that MIP-3alpha plays a critical role in the sensitization phase of EAE.

Nitric oxide induces polarization of actin in encephalitogenic T cells and inhibits their in vitro trans-endothelial migration in a p70S6 kinase-independent manner.

Nitric oxide (NO) inhibits both actively induced and transferred autoimmune encephalomyelitis. To explore potential mechanisms, we examined the ability of NO to inhibit migration of T lymphoblasts through both collagen matrices and monolayers of rat brain endothelial cells. The NO donor 1-hydroxy-2-oxo-3, 3-bis (2-aminoethyl)-1-triazene (HOBAT) inhibited migration in a concentration-dependent manner. NO pretreatment of T cells inhibited migration through untreated endothelial cells, but NO pretreatment of endothelial cells had no inhibitory effect on untreated T cells. Therefore NO's migration inhibitory action was mediated through its effect on T cells and not endothelial cells. HOBAT did not inhibit migration by inducing T-cell death but rather by polarizing the T cells, resulting in a morphology suggestive of migrating cells. P70S6 kinase, shown to have a role in NO-induced migration inhibition in fibroblasts, had no role in the inhibitory effect of NO on T-cell migration. Thus, HOBAT did not alter p70S6K activity nor did rapamycin, a specific inhibitor of p70S6K, inhibit HOBAT-induced T-cell morphological changes or T-cell migration. We suggest that NO-induced morphological changes result in T cells with predefined migratory directionality, thus limiting the ability of these cells to respond to other migratory signals.

Macrophages and nitric oxide as the possible cellular and molecular basis for strain and gender differences in susceptibility to autoimmune central nervous system inflammation.

PVG rats are resistant to actively induced experimental autoimmune encephalomyelitis (EAE) and this appears to be directly related to high and sustained systemic levels of reactive nitrogen intermediates(RNI) following sensitization for EAE when compared to the highly susceptible Lewis rat. An apparent cellular basis for the different EAE susceptibility between the two rat strains is described. Spleens of PVG rats have increased monocyte/macrophage numbers(NO producing cells) and lower erythrocyte (NO scavengers) to nucleated spleen cell ratios compared with Lewis rats. Splenectomy demonstrated the pivotal role of the spleen in resistance to EAE as splenectomized PVG rats were rendered completely susceptible to disease induction. It was further demonstrated that EAE resistance in PVG rats is limited only to females and that only female PVG rats have increased splenic macrophage and an enhanced NO production following immunization. The males are fully susceptible to EAE and their spleen cell populations are similar to those of Lewis rats of either gender. Despite being resistant to active disease induction, immunized female PVG rats can generate EAE effector cells that are capable of passively transferring disease.Furthermore, female PVG rats are fully susceptible to passively transferred EAE. Thus, there appears to be no defect in the female PVG target tissue or in the processing or presentation of antigen,but a block at the level of effector cell expansion and/or recirculation and transmigration into the target tissue in actively induced EAE.