Transgenic inhibition of astroglial NF-κB protects from optic nerve damage and retinal ganglion cell loss in experimental optic neuritis

Background

Optic neuritis is an acute, demyelinating neuropathy of the optic nerve often representing the first appreciable symptom of multiple sclerosis. Wallerian degeneration of irreversibly damaged optic nerve axons leads to death of retinal ganglion cells, which is the cause of permanent visual impairment. Although the specific mechanisms responsible for triggering these events are unknown, it has been suggested that a key pathological factor is the activation of immune-inflammatory processes secondary to leukocyte infiltration. However, to date, there is no conclusive evidence to support such a causal role for infiltrating peripheral immune cells in the etiopathology of optic neuritis.

Methods

To dissect the contribution of the peripheral immune-inflammatory response versus the CNS-specific inflammatory response in the development of optic neuritis, we analyzed optic nerve and retinal ganglion cells pathology in wild-type and GFAP-IκBα-dn transgenic mice, where NF-κB is selectively inactivated in astrocytes, following induction of EAE.

Results

We found that, in wild-type mice, axonal demyelination in the optic nerve occurred as early as 8 days post induction of EAE, prior to the earliest signs of leukocyte infiltration (20 days post induction). On the contrary, GFAP-IκBα-dn mice were significantly protected and showed a nearly complete prevention of axonal demyelination, as well as a drastic attenuation in retinal ganglion cell death. This correlated with a decrease in the expression of pro-inflammatory cytokines, chemokines, adhesion molecules, as well as a prevention of NAD(P)H oxidase subunit upregulation.

Conclusions

Our results provide evidence that astrocytes, not infiltrating immune cells, play a key role in the development of optic neuritis and that astrocyte-mediated neurotoxicity is dependent on activation of a transcriptional program regulated by NF-κB. Hence, interventions targeting the NF-κB transcription factor in astroglia may be of therapeutic value in the treatment of optic neuritis associated with multiple sclerosis.

Interleukin-7 receptor α contributes to experimental autoimmune encephalomyelitis (171.42)

Multiple sclerosis (MS) is a neurodegenerative disease characterized by inflammation, demyelination, and axonal damage. Recently, a mutation in the interleukin-7 receptor alpha (IL7Rα) locus has been identified as a risk factor for MS. IL7Rα has well-documented roles in lymphocyte development, function, and homeostasis, but its involvement in disease settings is largely understudied. Here we show that IL7Rα defective mice (IL7RTgIL7R-/-) display a less severe form of experimental autoimmune encephalomyelitis (EAE), a model for MS. Compared to wild type (WT), IL7RTgIL7R-/- exhibit reduced levels of paralysis, myelin damage, and inflammation. Furthermore, diseased WT treated with neutralizing anti-IL7Rα show significant recovery in EAE clinical scores and reduced lymphocyte infiltration into the CNS. A series of chimeric mice were then generated by bone marrow (BM) transplantation to identify IL7Rα+ cellular compartments contributing to EAE. Rag-/- mice engrafted with IL7RTgIL7R-/- or WT BM display equivalent disease severity, suggesting that IL7Rα on non-hematopoietic cells contributes to EAE. Lymphodeplete IL7R-/- mice reconstituted with WT or IL7RTgIL7R-/- BM showed dramatic reductions in EAE only with IL7RTgIL7R-/- engraftment and not WT, suggesting that IL7Rα signaling on lymphocytes contributes to disease. Taken together, IL7Rα signaling blockade in multiple cell types is necessary for marked reductions in EAE, and should be considered as a new therapeutic target for MS.

Inhibition of soluble tumour necrosis factor is therapeutic in experimental autoimmune encephalomyelitis and promotes axon preservation and remyelination

Tumour necrosis factor is linked to the pathophysiology of various neurodegenerative disorders including multiple sclerosis. Tumour necrosis factor exists in two biologically active forms, soluble and transmembrane. Here we show that selective inhibition of soluble tumour necrosis factor is therapeutic in experimental autoimmune encephalomyelitis. Treatment with XPro1595, a selective soluble tumour necrosis factor blocker, improves the clinical outcome, whereas non-selective inhibition of both forms of tumour necrosis factor with etanercept does not result in protection. The therapeutic effect of XPro1595 is associated with axon preservation and improved myelin compaction, paralleled by increased expression of axon-specific molecules (e.g. neurofilament-H) and reduced expression of non-phosphorylated neurofilament-H which is associated with axon damage. XPro1595-treated mice show significant remyelination accompanied by elevated expression of myelin-specific genes and increased numbers of oligodendrocyte precursors. Immunohistochemical characterization of tumour necrosis factor receptors in the spinal cord following experimental autoimmune encephalomyelitis shows tumour necrosis factor receptor 1 expression in neurons, oligodendrocytes and astrocytes, while tumour necrosis factor receptor 2 is localized in oligodendrocytes, oligodendrocyte precursors, astrocytes and macrophages/microglia. Importantly, a similar pattern of expression is found in post-mortem spinal cord of patients affected by progressive multiple sclerosis, suggesting that pharmacological modulation of tumour necrosis factor receptor signalling may represent an important target in affecting not only the course of mouse experimental autoimmune encephalomyelitis but human multiple sclerosis as well. Collectively, our data demonstrate that selective inhibition of soluble tumour necrosis factor improves recovery following experimental autoimmune encephalomyelitis, and that signalling mediated by transmembrane tumour necrosis factor is essential for axon and myelin preservation as well as remyelination, opening the possibility of a new avenue of treatment for multiple sclerosis.

Interleukin-7 receptor alpha contributes to experimental autoimmune encephalomyelitis (148.24)

Multiple sclerosis (MS) is a neurodegenerative disease characterized by extensive inflammation, demyelination, and axonal damage. The interleukin-7 receptor alpha (IL7Rα) chain is an essential subunit for the signaling receptors of both interleukin-7 (IL7) and thymic stromal lymphopoietin (TSLP), which are involved in lymphocyte development, function, and homeostasis. Recently a mutation in the IL7Rα chain locus has been identified as a risk factor for MS. We show that mice with IL7Rα expression limited to thymic tissue (IL7RTgIL7R-/-) display a less severe form of experimental autoimmune encephalomyelitis (EAE), an animal model for MS. However, TSLPR-/- mice showed no protection from disease. Furthermore, anti-IL7Rα treatment in wild type (WT) mice after disease onset significantly decreased EAE severity and lymphocyte infiltration into the CNS, which was accompanied by a relative increase in resident microglia. Additionally, Rag-/- chimeric mice grafted with IL7RTgIL7R-/- or WT bone marrow cells displayed equivalent disease severity, implying that IL7Rα on a non-hematopoietic cell population contributes to EAE. Taken together, our data shows that systemic blockade of IL7Rα reduces EAE severity, and therefore serves as an optimal target for MS therapies.

Glial NF-κB inhibition alters neuropeptide expression after sciatic nerve injury in mice

We utilized a transgenic mouse model where nuclear factor kappa B (NF-κB) is selectively inhibited in glial fibrillary acidic protein (GFAP) expressing cells. The transgene, GFAP-IκBα-dn, overexpresses a dominant negative form of the inhibitor of NF-κB (IκBα) under the control of the GFAP promoter. In the present work, we sought to understand the impact of glial NF-κB inhibition on the expression of pain mediating sensory neuropeptides galanin and calcitonin gene related peptide (CGRP) in a model of neuropathic pain in mice. Chronic constriction injury (CCI) of the left sciatic nerve was performed on wild type (WT) and GFAP-IκBα-dn transgenic mice. RT-PCR and immunohistological staining were performed in sciatic nerve and/or L4-L5 DRG tissue for galanin, CGRP and macrophage marker CD11b. GFAP-IκBα-dn mice had less mechanical and thermal hyperalgesia compared to WT mice post-CCI. After CCI, we observed galanin upregulation in DRG and sciatic nerve, which was less in GFAP-IκBα-dn mice. CGRP gene expression in the DRG increased transiently on day 1 post-CCI in WT but not in GFAP-IκBα-dn mice, and no evidence of CGRP upregulation in sciatic nerve post-CCI was found. After CCI, upregulation of CD11b in sciatic nerve was less in GFAP-IκBα-dn mice compared to WT mice, indicative of less macrophage infiltration. Our results showed that glial NF-κB inhibition reduces galanin and CGRP expression, which are neuropeptides that correlate with pain behavior and inflammation after peripheral nerve injury.

Transgenic inhibition of glial NF-kappa B reduces pain behavior and inflammation after peripheral nerve injury

The transcription factor nuclear factor kappa B (NF-kappaB) is a key regulator of inflammatory processes in reactive glial cells. We utilized a transgenic mouse model (GFAP-IkappaBalpha-dn) where the classical NF-kappaB pathway is inactivated by overexpression of a dominant negative (dn) form of the inhibitor of kappa B (IkappaBalpha) in glial fibrillary acidic protein (GFAP)-expressing cells, which include astrocytes, Schwann cells, and satellite cells of the dorsal root ganglion (DRG) and sought to determine whether glial NF-kappaB inhibition leads to a reduction in pain behavior and inflammation following chronic constriction injury (CCI) of the sciatic nerve. As expected, following CCI nuclear translocation, and hence activation, of NF-kappaB was detected only in the sciatic nerve of wild type (WT) mice, and not in GFAP-IkappaBalpha-dn mice, while upregulation of GFAP was observed in the sciatic nerve and DRGs of both WT and GFAP-IkappaBalpha-dn mice, indicative of glial activation. Following CCI, mechanical and thermal hyperalgesia were reduced in GFAP-IkappaBalpha-dn mice compared to those in WT, as well as gene and protein expression of CCL2, CCR2 and CXCL10 in the sciatic nerve. Additionally, gene expression of TNF, CCL2, and CCR2 was reduced in the DRGs of transgenic mice compared to those of WT after CCI. We can therefore conclude that transgenic inhibition of NF-kappaB in GFAP-expressing glial cells attenuated pain and inflammation after peripheral nerve injury. These findings suggest that targeting the inflammatory response in Schwann cells and satellite cells may be important in treating neuropathic pain.

[Analysis of the active components of a complex intervention for the care management of stroke patients: impact on in-hospital mortality]

We conducted a cohort observational study in 29 Italian hospitals to identify which factors of the acute care management process of ischemic stroke patient can reduce in-hospital mortality. This complex intervention is based on some potential organizational and clinical active components, so data are collected both at organizational unit and individual patient level. We built the variables in relation to presence/absence of clinical-demographic, care-process and organizational characteristics. We compared categorical variables and evaluated the studied independent variables effects on the in-hospital mortality risk at 7 and 30 days from admission. One of the main care success determinants is to be admitted in a stroke unit during the acute-stroke-phase. The most important organizational factor is to be short-time assessed by a stroke team: active role in patients' needs evaluation is provided by the stroke specialists' multidisciplinary team. Antithrombotic therapy is influencing mortality at 7 and 30 days likewise: it is a indispensable factor for the clinical protocols. Our study emphasizes the fact that higher access to different and integrated levels of organized care is associated to better stroke outcomes and that some active and interactive components of the patient's care management have to be identified in the complex intervention.

Inactivation of astroglial NF-kappa B promotes survival of retinal neurons following ischemic injury

Reactive astrocytes have been implicated in neuronal loss following ischemic stroke. However, the molecular mechanisms associated with this process are yet to be fully elucidated. In this work, we tested the hypothesis that astroglial NF-kappaB, a key regulator of inflammatory responses, is a contributor to neuronal death following ischemic injury. We compared neuronal survival in the ganglion cell layer (GCL) after retinal ischemia-reperfusion in wild-type (WT) and in GFAP-IkappaBalpha-dn transgenic mice, where the NF-kappaB classical pathway is suppressed specifically in astrocytes. The GFAP-IkappaBalpha-dn mice showed significantly increased survival of neurons in the GCL following ischemic injury as compared with WT littermates. Neuroprotection was associated with significantly reduced expression of pro-inflammatory genes, encoding Tnf-alpha, Ccl2 (Mcp1), Cxcl10 (IP10), Icam1, Vcam1, several subunits of NADPH oxidase and NO-synthase in the retinas of GFAP-IkappaBalpha-dn mice. These data suggest that certain NF-kappaB-regulated pro-inflammatory and redox-active pathways are central to glial neurotoxicity induced by ischemic injury. The inhibition of these pathways in astrocytes may represent a feasible neuroprotective strategy for retinal ischemia and stroke.

Transgenic inhibition of astroglial NF-kappa B leads to increased axonal sparing and sprouting following spinal cord injury

We previously showed that Nuclear Factor kappaB (NF-kappaB) inactivation in astrocytes leads to improved functional recovery following spinal cord injury (SCI). This correlated with reduced expression of pro-inflammatory mediators and chondroitin sulfate proteoglycans, and increased white matter preservation. Hence we hypothesized that inactivation of astrocytic NF-kappaB would create a more permissive environment for axonal sprouting and regeneration. We induced both contusive and complete transection SCI in GFAP-Inhibitor of kappaB-dominant negative (GFAP-IkappaBalpha-dn) and wild-type (WT) mice and performed retrograde [fluorogold (FG)] and anterograde [biotinylated dextran amine (BDA)] tracing 8 weeks after injury. Following contusive SCI, more FG-labeled cells were found in motor cortex, reticular formation, and raphe nuclei of transgenic mice. Spared and sprouting BDA-positive corticospinal axons were found caudal to the lesion in GFAP-IkappaBalpha-dn mice. Higher numbers of FG-labeled neurons were detected immediately rostral to the lesion in GFAP-IkappaBalpha-dn mice, accompanied by increased expression of synaptic and axonal growth-associated molecules. After transection, however, no FG-labeled neurons or BDA-filled axons were found rostral and caudal to the lesion, respectively, in either genotype. These data demonstrated that inhibiting astroglial NF-kappaB resulted in a growth-supporting terrain promoting sparing and sprouting, rather than regeneration, of supraspinal and propriospinal circuitries essential for locomotion, hence contributing to the improved functional recovery observed after SCI in GFAP-IkappaBalpha-dn mice.

Transgenic inhibition of astroglial NF-kappa B improves functional outcome in experimental autoimmune encephalomyelitis by suppressing chronic central nervous system inflammation

In the CNS, the transcription factor NF-kappaB is a key regulator of inflammation and secondary injury processes. Following trauma or disease, the expression of NF-kappaB-dependent genes is activated, leading to both protective and detrimental effects. In this study, we show that transgenic inactivation of astroglial NF-kappaB (glial fibrillary acidic protein-IkappaB alpha-dominant-negative mice) resulted in reduced disease severity and improved functional recovery following experimental autoimmune encephalomyelitis. At the chronic stage of the disease, transgenic mice exhibited an overall higher presence of leukocytes in spinal cord and brain, and a markedly higher percentage of CD8(+)CD122(+) T regulatory cells compared with wild type, which correlated with the timing of clinical recovery. We also observed that expression of proinflammatory genes in both spinal cord and cerebellum was delayed and reduced, whereas the loss of neuronal-specific molecules essential for synaptic transmission was limited compared with wild-type mice. Furthermore, death of retinal ganglion cells in affected retinas was almost abolished, suggesting the activation of neuroprotective mechanisms. Our data indicate that inhibiting NF-kappaB in astrocytes results in neuroprotective effects following experimental autoimmune encephalomyelitis, directly implicating astrocytes in the pathophysiology of this disease.

Transgenic inhibition of astroglial NF-κB improves functional recovery in EAE by suppressing chronic neuroinflammation. (50.7)

In the CNS the transcription factor NF-κB is a key regulator of inflammation and secondary injury processes. Following trauma or disease, the expression of NF-κB-dependent genes is activated, leading to both protective and detrimental effects. Here we show that transgenic inactivation of astroglial NF-κB (GFAP-IκBα-dn mice) resulted in reduced disease severity and improved functional recovery following experimental autoimmune encephalomyelitis (EAE). At the chronic stage of the disease, transgenic mice exhibited an overall higher presence of leukocytes in spinal cord and brain, and a markedly higher percentage of CD8+CD122+ T regulatory cells compared to WT, which correlated with the timing of clinical recovery. We also observed that expression of proinflammatory genes in both spinal cord and cerebellum was delayed and reduced, while the loss of neuronal-specific molecules essential for synaptic transmission was limited compared to WT mice. Furthermore, death of retinal ganglion cells in affected retinas was almost abolished, suggesting the activation of neuroprotective mechanisms. Our data indicate that inhibiting NF-κB in astrocytes results in neuroprotective effects following EAE, directly implicating astrocytes in the pathophysiology of this disease.

Multipotential neural precursors transplanted into the metachromatic leukodystrophy brain fail to generate oligodendrocytes but contribute to limit brain dysfunction

Neural stem cells appear to be best suited for regenerative therapy in neurological diseases. However, the effects of high levels of potentially toxic substances such as sulfatides--which accumulate in metachromatic leukodystrophy (MLD)--on this regenerative ability are still largely unclear. To start addressing this question, in vitro and in vivo experiments were used to examine the behavior of multipotential neural precursors exposed to abnormally high levels of sulfatides. Following transplantation of dissociated neurospheres into the brain of presymptomatic MLD pups, the majority of donor-derived cells were distributed in a caudal to rostral direction, with higher numbers in the cortex. Most if not all of the donor cells acquired an astroglial phenotype. We found no evidence of oligodendrocyte or neuronal commitment of transplanted cells in long-term-treated MLD mice (e.g. up to 1.5 years of age). This was in line with our in vitro findings of sulfatides blocking oligodendrocyte formation after induction of differentiation in sulfatide-treated epidermal growth factor/fibroblast growth factor responsive neurospheres. Transplanted MLD mice showed an improved arylsulfatase A (ARSA) activity and a significant amelioration of sulfatide metabolism, neurodegeneration and motor-learning/memory deficits. Furthermore, transplanted cells were shown to act as a source of ARSA enzyme that accumulated in endogenous brain cells, indicating the occurrence of enzyme cross-correction between transplanted and host cells. These results provide a first insight into the effect of sulfatides on the stemness properties of neural stem cells and on the effects of the MLD environment on the in vivo expectations of using neural stem cells in cell therapy.

[Risk management: the opinions of nursing staff and coordinators in a local health district in the Piemonte region (Italy)]

Clinical risk management includes a set of clinical and administrative activities performed to identify, evaluate and reduce risks for patients, staff and visitors as well as the organization itself. The first fundamental step in risk management is to evaluate risk factors; it is impossible to implement corrective actions and modify and eliminate risk factors if these are not known. The aim of this study was to evaluate the degree to which selected sentinel events were perceived by nursing staff as being severe and whether the degree of perceived severity of an event was associated with specific variables such as nursing work area (medical, surgical, intensive care), years of experience, degree and position. The study also aimed to evaluate the level of knowledge of clinical risk management, identify the main categories of errors within the organization, and evaluate nursing staff opinions on the use of an anonymous system to report errors. A sample of 98 nurses (91 female, 7 male), working in three hospitals in a local health district in the Piemonte region (Italy) participated in the study. The mean age of participants was 37 years (range 22-61). Participants were interviewed between 30 October and 6 November 2006, by using a structured questionnaire. Most participants (93%) were aware of the definition of risk management but over 60% did not use any tool for identifying clinical errors. Nurses perceived infections to be the most serious error, followed by medication errors and surgery and post-operative complications. Almost all participants (99%) considered it right to report errors and 59% admitted to having made errors, most frequently medication errors. Over 90% of participants agreed that an anonymous report form should be used for reporting. Healthcare professionals' willingness to cooperate and their ability to not play down the importance of sentinel events but rather voluntarily bring these to light are essential to the success of risk management in an organization. Clearly, patient safety does not depend on the single individual but rather on an interdisciplinary approach to problem notification and solving and collaboration among interdisciplinary team members.

Astroglial nuclear factor-kappaB regulates learning and memory and synaptic plasticity in female mice

Astrocytes play a pivotal role in regulating synaptic plasticity and synapse formation. The nuclear factor-kappa B (NF-kappaB) family of transcription factors has recently been demonstrated to be an important modulator of synaptic plasticity and learning/memory. In this study, we investigated the role of astroglial NF-kappaB in synaptic plasticity and learning/memory using transgenic mice over-expressing an N-terminal truncated form of inhibitor of NF-kappaB alpha (IkappaBalpha) in astrocytes (GFAP-IkappaBetaalpha-dn). We demonstrated that female transgenic mice, but not males, have robust deficits in hippocampal and extra-hippocampal-dependent learning and memory. We also determined that there are significant deficits in LTP and expression of metabotropic glutamate receptor 5 and post-synaptic density protein 95 (PSD95) in female transgenic mice. These findings indicate that astroglial NF-kappaB is an important regulator of learning/memory and synaptic plasticity.

Safety of Arylsulfatase A Overexpression for Gene Therapy of Metachromatic Leukodystrophy

Successful gene therapy approaches for metachromatic leukodystrophy (MLD), based either on hematopoietic stem/progenitor cells (HSPCs) or direct central nervous system (CNS) gene transfer, highlighted a requirement for high levels of arylsulfatase A (ARSA) expression to achieve correction of disease manifestations in the mouse model. Full assessment of the safety of ARSA expression above physiological levels thus represents a prerequisite for clinical translation of these approaches. Here, using lentiviral vectors (LVs), we generated two relevant models for the stringent evaluation of the consequences of ARSA overexpression in transduced cells. We first demonstrated that ARSA overexpression in human HSPCs does not affect their clonogenic and multilineage differentiation capacities in clonogenic assays and in a neonatal hematochimeric mouse model. Further, we studied ARSA overexpression in all body tissues by generating transgenic mice overexpressing the ARSA enzyme by LV up to 15-fold above the normal range and carrying multiple copies of LV in their genome. Characterization of these mice demonstrated the safety of ARSA overexpression in two main gene therapy targets, HSPCs and neurons, with maintenance of the complex functions of the hematopoietic and nervous system in the presence of supraphysiological enzyme levels. The activity of other sulfatases dependent on the same common activator, sulfatase-modifying factor-1 (SUMF1), was tested in ARSA-overexpressing HSPCs and in transgenic mice, excluding the occurrence of saturation phenomena. Overall, these data indicate that from the perspective of clinical translation, therapeutic levels of ARSA overexpression can be safely achieved. Further, they demonstrate an experimental platform for the preclinical assessment of the safety of new gene therapy approaches.

Photoprotective activity of oral polypodium leucotomos extract in 25 patients with idiopathic photodermatoses

BACKGROUND

The incidences of idiopathic photodermatoses (IP) are increasing and the available therapeutic methods are often inadequate.

AIM

To evaluate whether, in subjects affected by IP not responding to the usual available therapies, the oral administration of an extract of Polypodium leucotomos (PL) could provide an effective photoprotective activity.

METHODS

26 patients with polymorphic light eruption and two with solar urticaria were recruited to enter the study. The protocol excluded the use of ultraviolet protection filters or other drugs that could in some way interfere with exposure to light. All patients exposed themselves to sunlight while consuming 480 mg/day of PL orally. The response of the skin to sunlight exposure of 25 evaluable patients was compared with that occurring previously without administration of PL.

RESULTS

With PL, we observed a relevant and statistically significant reduction of skin reaction and subjective symptoms. The tolerance of the drug has been excellent.

CONCLUSION

PL extract administration has shown to be an effective and safe method, leading to a significant protection of skin in IP.

High-throughput genotyping with infrared fluorescence allele specific hybridization (iFLASH): A simple, reliable and low-cost alternative

OBJECTIVES

To develop and validate a novel genotyping approach, named infrared Fluorescence Allele Specific Hybridization (iFLASH), which combines the principles of allele specific oligonucleotide (ASO) hybridization with the advanced possibilities of infrared imaging.

DESIGN AND METHODS

As an example, we genotyped the 55L > M and the 192Q > R common genetic variants of the paraoxonase-1 gene in 92 DNA samples using the iFLASH technique, and validated the outcomes with the restriction fragment length polymorphism (RFLP) and TAQman genotyping assays.

RESULTS

There was a 100 percent agreement in genotype outcome among the three methods.

CONCLUSIONS

Although we found complete unity in genotype outcome, the iFLASH assay has essential advantages over the RFLP and TAQman genotyping assays. First, the iFLASH technique is capable of handling up to 1536 samples per assay, which makes it a suitable technique for high-throughput genotyping. Secondly, because the costs per assay are lower, high-throughput genotyping with iFLASH is affordable.

Cerebellar neurons and glial cells are transducible by lentiviral vectors without decrease of cerebellar functions

Due to the profuse connections of the cerebellum to the rest of the central nervous system, cerebellar dysfunction impacts tremendously on movement coordination, maintenance of equilibrium, muscle tone and motor memory. Efficient gene transfer of therapeutic genes to this central nervous system structure would constitute a relevant step ahead the design of treatments to ameliorate cerebellar dysfunction. Lentiviral vectors (LVs) have been used as efficient vehicles to integrate transgenes into dividing and non-dividing cells, such as postmitotic adult neurons, with minimal toxicity and immune response. This study aimed to use LVs carrying green fluorescent protein (GFP) cDNA for transduction of cerebellar cells in vivo without compromising neurological cerebellar functions. Our results indicate that LVs, injected in the lobulus simplex, transduced different cerebellar neurons including stellate, Purkinje cells, granular neurons and glial cells such as astrocytes, oligodendrocytes, and that this gene transfer approach was not accompanied by cerebellar deficits.

Onset mechanism of paroxysmal atrial fibrillation detected by ambulatory Holter monitoring

AIMS

The aim of this study was to evaluate the mechanisms of induction of paroxysmal atrial fibrillation (PAF) by analysis of its onset recorded on Holter monitoring (HM).

METHODS AND RESULTS

One hundred and seven HM were evaluated in 90 patients (mean age 67.7, cardiac disease in 31.1%), with one or more self-terminating episodes of PAF, lasting >or=30 s. Two hundred and thirty-three episodes of PAF were detected. A triggering premature atrial complex (PAC) was present in 222/233 episodes (95.3%); 118/233 episodes were preceded by a bradyarrhythmic event (BE) or a post-extrasystolic pause (50.6%). According to the polarity of the ectopic P-wave, triggering PACs were left atrial origin in 74.3%, right atrial in 15.3%, not determined in 10.4% of cases. Coupling interval (CI) of triggering PACs was shorter in episodes preceded by BEs; it was shorter than that of non-triggering PACs. Frequency of PACs was significantly higher in the hour preceding the onset of PAF. During the day, three periods of higher frequency of PAF onsets were found from noon to 2 p.m., 6 p.m. to 2 a.m., and 4 a.m. to 6 a.m. Heart rate variability analysis showed a vagal prevalence in the 5 min preceding the onset of arrhythmia, both in the time and in the frequency domain.

CONCLUSION

Paroxysmal atrial fibrillation is generally triggered by a PAC, with left atrial origin in two-thirds of cases: CI and neuroendocrine balance are factors affecting the induction of the arrhythmia.

Inhibition of astroglial nuclear factor kappaB reduces inflammation and improves functional recovery after spinal cord injury

In the central nervous system (CNS), the transcription factor nuclear factor (NF)-kappaB is a key regulator of inflammation and secondary injury processes. After trauma or disease, the expression of NF-kappaB-dependent genes is highly activated, leading to both protective and detrimental effects on CNS recovery. We demonstrate that selective inactivation of astroglial NF-kappaB in transgenic mice expressing a dominant negative (dn) form of the inhibitor of kappaB alpha under the control of an astrocyte-specific promoter (glial fibrillary acidic protein [GFAP]-dn mice) leads to a dramatic improvement in functional recovery 8 wk after contusive spinal cord injury (SCI). Histologically, GFAP mice exhibit reduced lesion volume and substantially increased white matter preservation. In parallel, they show reduced expression of proinflammatory chemokines and cytokines, such as CXCL10, CCL2, and transforming growth factor-beta2, and of chondroitin sulfate proteoglycans participating in the formation of the glial scar. We conclude that selective inhibition of NF-kappaB signaling in astrocytes results in protective effects after SCI and propose the NF-kappaB pathway as a possible new target for the development of therapeutic strategies for the treatment of SCI.

NIBP, a novel NIK and IKK(beta)-binding protein that enhances NF-(kappa)B activation

The transcription factor NF-kappaB plays an important role in both physiological and pathological events in the central nervous system. Nevertheless, the mechanisms of NF-kappaB-mediated regulation of gene expression, and the signaling molecules participating in the NF-kappaB pathway in the central nervous system are, to date, poorly understood. To identify such molecules, we conducted a yeast two-hybrid screen of a human brain cDNA library using NIK as bait. As a result, we identified a novel NIK and IKK(beta) binding protein designated NIBP that is mainly expressed in brain, muscle, heart, and kidney. Interestingly, low levels of expression were detected in immune tissues such as spleen, thymus, and peripheral blood leukocytes, where NF-kappaB is known to modulate immune function. We demonstrated by immunohistochemistry that NIBP expression in the brain is localized to neurons. NIBP physically interacts with NIK, IKK(beta), but not IKK(alpha) or IKK(gamma). NIBP overexpression potentiates tumor necrosis factor-alpha-induced NF-kappaB activation through increased phosphorylation of the IKK complex and its downstream I(kappa)B(alpha) and p65 substrates. Finally, knockdown of NIBP expression by small interfering RNA reduces tumor necrosis factor-alpha-induced NF-kappaB activation, prevents nerve growth factor-induced neuronal differentiation, and decreases Bcl-xL gene expression in PC12 cells. Our data demonstrate that NIBP, by interacting with NIK and IKK(beta), is a new enhancer of the cytokine-induced NF-(kappa)B signaling pathway. Because of its neuronal expression, we propose that NIBP may be a potential target for modulating the NF-(kappa)B signaling cascade in neuronal pathologies dependent upon abnormal activation of this pathway.

Sustained sympathoinhibitory effects of cardiac resynchronization therapy in severe heart failure

Evidence is available that in heart failure, cardiac resynchronization therapy by biventricular pacing improves myocardial function and exercise capacity. Whether this is accompanied by a sustained inhibition of heart failure-dependent sympathoexcitation is uncertain. In 11 heart failure patients (mean+/-SEM age, 68.4+/-1.5 years) in New York Heart Association (NYHA) class III and IV under medical treatment with an intraventricular conduction delay (QRS duration > or =130 ms), with a markedly depressed left ventricular ejection fraction, and undergoing implantation of a biventricular pacemaker, we measured beat-to-beat blood pressure and muscle sympathetic nerve traffic. Measurements, which also included echocardiographic and clinical variables, were performed before and approximately 10 weeks after successful resynchronization therapy. Ten age- and NYHA class-matched heart failure patients who were under medical treatment for the same time period served as controls. Long-term resynchronization therapy improved cardiac function and caused a significant increase in systolic blood pressure coupled with an improvement in maximal oxygen consumption and exercise capacity. These effects were coupled with a significant and marked reduction in sympathetic nerve traffic when expressed both as burst frequency over time (44.1+/-3.6 vs 30.7+/-3.0 bs/min, -30.5%, P<0.02) and as burst frequency corrected for heart rate (68.3+/-5.9 vs 47.3+/-4.3 bs/100 beats, -32.1%, P<0.02). No significant change in the aforementioned parameters was seen in the control group. These data provide the first direct evidence that in severe heart failure, resynchronization therapy exerts a marked and sustained sympathoinhibition. Because in heart failure sympathetic overactivity adversely affects prognosis, this may have important clinical implications.

TNAP, a novel repressor of NF-kappaB-inducing kinase, suppresses NF-kappaB activation

NF-kappaB-inducing kinase (NIK) has been implicated as an essential component of NF-kappaB activation. However, the regulatory mechanism of NIK signaling remains elusive. We have identified a novel NIK interacting protein, TNAP (for TRAFs and NIK-associated protein). In mammalian cells, TNAP physically interacts with NIK, TRAF2, and TRAF3 but not IKK1 or IKK2. TNAP specifically inhibits NF-kappaB activation induced by tumor necrosis factor (TNF)-alpha, TNF receptor 1, TRADD, RIP, TRAF2, and NIK but does not affect IKK1- and IKK2-mediated NF-kappaB activation. Knockdown of TNAP by lentiviral-mediated small interference RNA potentiates TNF-alpha-induced NF-kappaB activation. TNAP suppresses NIK kinase activity and subsequently reduces p100 processing, p65 phosphorylation, and IkappaBalpha degradation. These data suggest that TNAP is a repressor of NIK activity and regulates both the classical and alternative NF-kappaB signaling pathways.

Effects of heart rate changes on arterial distensibility in humans

In rats, an increase in heart rate by pacing is accompanied by progressive large-artery stiffening. Whether this is also the case in humans is unknown. We enrolled 20 patients who were chronically implanted with a pacemaker because of atrioventricular block or sick sinus syndrome. Arterial distensibility was measured by an echo-tracking device. In 10 patients, the evaluation was performed on the radial artery by using continuous finger blood pressure measurements, whereas in the remaining 10 patients, the common carotid artery was studied with a semiautomatic measure of brachial artery blood pressure. Diastolic diameter, systodiastolic diameter change, and distensibility were obtained at baseline (heart rate 63+/-2 beats/min) and after atrial and ventricular sequential pacing at a heart rate of 90 and 110 beats/min. At baseline, the diameter was 7.8+/-0.3 mm in the carotid artery and 2.4+/-0.1 mm in the radial artery; the respective systodiastolic diameter change values were 375.4+/-31.0 and 55.9+/-9.0 (microm) and the distensibility values were 1.4+/-0.1 and 0.7+/-0.1 (1/mm Hg 10-3). Blood pressure and diameter were not significantly modified by increasing heart rate, which markedly modified systodiastolic diameter change and distensibility. In the radial artery, distensibility was reduced by 47% (P<0.05) at a heart rate of 90 beats/min with no further reduction at 110 beats/min. In the carotid artery, distensibility was reduced by 20% at a heart rate of 90 beats/min (P<0.05) with a further reduction at 110 beats/min (45%, P<0.05). These data provide the first evidence in humans that acute increases in heart rate markedly affect arterial distensibility and that this occurs in both large- and middle-size muscle arteries within the range of "normal" heart rate values.

Nucleotide-mediated calcium signaling in rat cortical astrocytes: Role of P2X and P2Y receptors

ATP is the dominant messenger for astrocyte-to-astrocyte calcium-mediated communication. Definition of the exact ATP/P2 receptors in astrocytes and of their coupling to intracellular calcium ([Ca(2+)](i)) has important implications for brain physiology and pathology. We show that, with the only exception of the P2X(6) receptor, primary rat cortical astrocytes express all cloned ligand-gated P2X (i.e., P2X(1-5) and P2X(7)) and G-protein-coupled P2Y receptors (i.e., P2Y(1), P2Y(2), P2Y(4), P2Y(6), and P2Y(12)). These cells also express the P2Y-like UDP-glucose receptor, which has been recently recognized as the P2Y(14) receptor. Single-cell image analysis showed that only some of these receptors are coupled to [Ca(2+)](i). While ATP induced rapid and transient [Ca(2+)](i) increases (counteracted by the P2 antagonists suramin, pyridoxal-phosphate-6-azophenyl-2'-4'-disulfonic acid and oxidized ATP), the P2X(1)/P2X(3) agonist alphabetameATP produced no changes. Conversely, the P2X(7) agonist BzATP markedly increased [Ca(2+)](i); the presence and function of the P2X(7) receptor was also confirmed by the formation of the P2X(7) pore. ADP and 2meSADP also produced [Ca(2+)](i) increases antagonized by the P2Y(1) antagonist MRS2179. Some cells also responded to UTP but not to UDP. Significant responses to sugar-nucleotides were also detected, which represents the first functional response reported for the putative P2Y(14) receptor in a native system. Based on agonist preference of known P2 receptors, we conclude that, in rat astrocytes, ATP-induced calcium rises are at least mediated by P2X(7) and P2Y(1) receptors; additional receptors (i.e., P2X(2), P2X(4), P2X(5), P2Y(2), P2Y(4), and P2Y(14)) may also contribute.

Blockade of A2A adenosine receptors prevents basic fibroblast growth factor-induced reactive astrogliosis in rat striatal primary astrocytes

Previous literature data show that blockade of A(2A) adenosine receptors via selective antagonists induces protection in various models of neurodegenerative diseases. The mechanisms underlying this effect are still largely unknown. Since it is known that excessive reactive astrogliosis is a factor contributing to cell death in diseases characterized by neurodegenerative events, the present study has been aimed at determining whether selective A(2A) receptor antagonists can counteract the formation of reactive astrocytes induced in vitro by basic fibroblast growth factor (bFGF), a typical trigger of this reaction. Exposure of primary rat striatal astrocytes to the selective A(2A) antagonist SCH58261 resulted in concentration-dependent abolition of bFGF induction of astrogliosis in vitro. This effect could also be reproduced with the chemically unrelated A(2A) antagonist KW-6002. The direct activation of A(2A) adenosine receptors by selective receptor agonists was not sufficient per se to induce astrogliosis, suggesting that the A(2A) receptor needs to act in concert with other bFGF-induced genes to trigger the formation of reactive astrocytes. These results provide a mechanism at the basis of the neuroprotection induced by A(2A) receptor antagonists in models of brain damage and highlight this adenosine receptor subtype as a novel target for the pharmacological modulation of the gliotic reaction.

Induction of COX-2 and reactive gliosis by P2Y receptors in rat cortical astrocytes is dependent on ERK1/2 but independent of calcium signalling

The present study has been aimed at characterizing the ATP/P2 receptor (and transductional pathways) responsible for the morphological changes induced in vitro by alphabetamethyleneATP on rat astrocytes obtained from cerebral cortex, a brain area highly involved in neurodegenerative diseases. Exposure of cells to this purine analogue resulted in elongation of cellular processes, an event reproducing in vitro a major hallmark of in vivo reactive gliosis. alphabetamethyleneATP-induced gliosis was prevented by the P2X/P2Y blocker pyridoxalphosphate-6-azophenyl-2'-4'-disulfonic acid, but not by the selective P2X antagonist 2',3'-O-(2,4,6-trinitrophenyl)-ATP, ruling out a role for ligand-gated P2X receptors. Conversely, the Gi/Go protein inactivator pertussis toxin completely prevented alphabetamethyleneATP-induced effects. No effects were induced by alphabetamethyleneATP on intracellular calcium concentrations. RT-PCR and western blot analysis showed that alphabetamethyleneATP-induced gliosis involves up-regulation of cyclooxygenase-2 (but not lipooxygenase). Also this effect was fully prevented by pyridoxalphosphate-6-azophenyl-2'-4'-disulfonic acid. Experiments with inhibitors of mitogen-activated protein kinases (MAPK) suggest that extracellular signal regulated protein kinases (ERK)1/2 mediate both cyclooxygenase-2 induction and the associated in vitro gliosis. These findings suggest that purine-induced gliosis involves the activation of a calcium-independent G-protein-coupled P2Y receptor linked to ERK1/2 and cyclooxygenase-2. Based on the involvement of cyclooxygenase-2 and inflammation in neurodegenerative diseases, these findings open up new avenues in the identification of novel biological targets for the pharmacological manipulation of neurodegeneration.

Cellular mechanisms of striatum-dependent behavioral plasticity and drug addiction

The striatum has long been known to be involved in the control of motor behavior, since disruption of dopamine-mediated function in this brain structure is directly linked to Parkinson's disease and other disorders of movement. However, it is now accepted that both dorsal and ventral striatal nuclei are also essential for a variety of cognitive processes, which depend on reward-based stimulus-response learning. Since the neuroanatomical and neurochemical organization of dorsal and ventral striatum is only partially overlapping, it is likely that both common and nucleus-specific cellular and molecular events contribute to synaptic plasticity, learning and memory processes mediated by these cerebral structures. Alterations in cell signaling in the striatum may be particularly important in the response to both acute and chronic administration of drugs of abuse, resulting in maladaptive changes in the reward-based associative learning involved in addiction, withdrawal and relapse.

Alveolar--capillary membrane gas conductance: a novel prognostic indicator in chronic heart failure

AIMS

Lung dysfunction occurring in chronic heart failure worsens clinical status and exercise performance. The prognostic value of airway and alveolar function measurements in chronic heart failure has not been explored. We aimed to evaluate the prognostic value of lung function tests in a population of patients with stable chronic heart failure.

METHODS AND RESULTS

One hundred and six stable chronic heart failure patients (whose left ventricular ejection fraction averaged 33 +/- 1%) underwent echocardiography, metabolic stress testing, assessment of pulmonary function at rest (by spirometry), of alveolar diffusing capacity (DLco) (with carbon monoxide technique) and of its membrane (DM) and capillary blood volume (Vc) components. Prognostic relevance of pulmonary variables was assessed by the Kaplan-Meier approach with log-rank testing and by Cox regression analysis. Cut-off values of lung parameters were based on the 33rd and 66th centiles. Seventeen patients died for cardiac reasons. Non-survivors compared to survivors showed lower forced expiratory volume in 1 s (2 X 1 +/- 0 X 1 vs 2 X 4 +/- 0 X 1 l; P<0 X 01), forced vital capacity (2 X 6 +/- 0 X 1 vs 2 X 9 +/- 0 X 1 l; P<0 X 01), maximal voluntary ventilation (80 X 7 +/- 2 X 5 vs 95 X 4 +/- 2 X 7 l; P<0 X 01), DLco (16 X 5 +/- 1 X 1 vs 19 X 3 +/- 0 X 6 ml . min(-1) . mmHg(-1); P<0 X 01) and DM (25 X 1 +/- 1 X 8 vs 31 X 9 +/- 1 X 5 ml . min(-1) . mmHg(-1); P<0 X 01). They also exhibited a smaller peak VO2 (14 X 6 +/- 0 X 7 vs 15 X 9 +/- 0 X 6 ml . min(-1) . kg(-1); P<0 X 05) and a steeper VE/VCO2 slope (45 X 0 +/- 1 X 7 vs 41 X 9 +/- 1 X 5; P<0 X 01). Multivariate analysis revealed that DM was the only independent predictor of cardiac death. Cases at high risk for adverse outcome were identified by a DM<24 X 7 ml . min(-1) . mmHg(-1). Patients receiving ACE-inhibitors presented with a higher DM (32 X 1 +/- 1 X 7 vs 27 X 9 +/- 1 X 7 ml . min(-1) . mmHg(-1), P<0 X 05) as well as a better Cox estimated survival rate.

CONCLUSIONS

Impaired DM is a powerful independent predictor of worse prognosis in stable chronic heart failure and may be considered an additional index of disease severity, as well as a specific therapeutic target.

Involvement of CDC25Mm/Ras-GRF1-dependent signaling in the control of neuronal excitability

Ras-GRF1 is a neuron-specific guanine nucleotide exchange factor for Ras proteins. Mice lacking Ras-GRF1 (-/-) are severely impaired in amygdala-dependent long-term synaptic plasticity and show higher basal synaptic activity at both amygdala and hippocampal synapses (Brambilla et al., 1997). In the present study we investigated the effects of Ras-GRF1 deletion on hippocampal neuronal excitability. Electrophysiological analysis of both primary cultured neurons and adult hippocampal slices indicated that Ras-GRF1-/- mice displayed neuronal hyperexcitability. Ras-GRF1-/- hippocampal neurons showed increased spontaneous activity and depolarized resting membrane potential, together with a higher firing rate in response to injected current. Changes in the intrinsic excitability of Ras-GRF1-/- neurons can entail these phenomena, suggesting that Ras-GRF1 deficiency might alter the balance between ionic conductances. In addition, we showed that mice lacking Ras-GRF1 displayed a higher seizure susceptibility following acute administration of convulsant drugs. Taken together, these results demonstrated a role for Ras-GRF1 in neuronal excitability.

Modulation of cyclooxygenase-2 and brain reactive astrogliosis by purinergic P2 receptors

Astroglial cells respond to trauma and ischemia with reactive gliosis, a reaction characterized by increased astrocytic proliferation and hypertrophy. Although beneficial to a certain extent, excessive gliosis may be detrimental, contributing to neuronal death in neurodegenerative diseases. We have tested the hypothesis that ATP may act as a trigger of reactive gliosis in an in vitro model (rat brain primary astrocytes) where reactive astrogliosis can be quantified as elongation of astrocytic processes. Challenge of cells with the ATP analog alpha,beta methyleneATP (alpha,beta meATP) resulted in concentration dependent elongation of astrocytic processes, an effect that was fully counteracted by the non-selective ATP/P2 receptor antagonists suramin and pyridoxalphosphate-6-azophenyl-2',4'-disulphonic acid (PPADS). Signalling studies revealed that alpha,beta meATP-induced gliosis is mediated by a novel G-protein-coupled receptor (a P2Y receptor) coupled to an early release of arachidonic acid. Challenge of cells with alpha,beta meATP also resulted in an increase of inducible cyclooxygenase-2 (COX-2), the activity of which has been reported to be pathologically increased in a variety of neurodegenerative diseases characterized by inflammation and astrocytic activation. Induction of COX-2 by alpha,beta meATP was causally related to reactive astrogliosis, since the selective COX-2 inhibitor NS-398 prevented both the purine-induced elongation of astrocytic processes and the associated COX-2 increase. Preliminary data on the putative receptor-to-nucleus pathways responsible for purine-induced gliosis suggest that induction of the COX-2 gene may occur through the protein kinase C/mitogen activated protein kinase system, and may involve the formation of activated AP-1 transcription complexes. We speculate that antagonists selective at this novel P2Y receptor subtype may represent a novel class of neuroprotective agents able to slow down neurodegeneration by counteracting the inflammatory events contributing to neuronal cell death.

Influence of ACE-inhibition on salt-mediated worsening of pulmonary gas exchange in heart failure

AIMS

In congestive heart failure (CHF), pulmonary gas exchange, as evaluated by carbon monoxide diffusion (DLCO), is impaired. ACE-inhibition improves DLCO. Infusion of saline worsens DLCO, because of upregulated sodium and water transport to the alveolar interstitium, which thickens the alveolar-capillary interface and lengthens the diffusion path for gas exchange. We investigated whether enalapril can readjust the capillary permeability to sodium.

METHODS

In 10 NYHA class II-III CHF patients, we measured DLCO, its two subcomponents (VC, capillary blood volume available for gas exchange, and DM, alveolar-capillary membrane diffusion), left and right ventricular filling pressures, plasma noradrenaline, aldosterone and renin activity, at baseline and following saline infusion in the main pulmonary artery stem, before and after 1 week enalapril treatment (20 mg daily).

RESULTS

Saline (150 ml) significantly reduced DLCO (-9.1%) and DM (-9.8%) and augmented VC (+ 10.7%). Responses to 750 ml saline were somewhat greater and qualitatively similar. Enalapril produced a significant improvement of DLCO and DM at rest as well as after saline, that was not associated with variations in ventricular filling pressures, cardiac output and left ventricular ejection fraction, and was not accounted for by humoral changes.

CONCLUSIONS

In CHF, ACE-inhibition attenuates the deterioration of pulmonary gas transfer produced by saline infusion, suggesting an ability to readjust the upregulated sodium transport across the pulmonary microvascular endothelium.

Inhibition of gap-junctional communication induces the trans-differentiation of osteoblasts to an adipocytic phenotype in vitro

Osteoblasts and adipocytes are thought to differentiate from a common stromal progenitor cell. These two phenotypically mature cell types show a high degree of plasticity, which can be observed when cells are grown under specific culture conditions. Gap junctions are abundant among osteoblastic cells in vivo and in vitro, whereas they are down-regulated during adipogenesis. Gap junctional communication (GJC) modulates the expression of genes associated with the mature osteoblastic phenotype. Inhibition of GJC utilizing 18-alpha-glycyrrhetinic acid (AGRA) blocks the maturation of pre-osteoblastic cells in vitro. Moreover, cytoplasmic lipid droplets are detectable at the end of the culture period, suggesting that GJC inhibition may favor an adipocytic phenotype. We used several human osteoblastic cell lines, as well as bone-derived primary osteoblastic cells, to show that confluent cultures of human osteoblastic cells grown under osteogenic conditions developed an adipocytic phenotype after 3 days of complete inhibition of GJC using AGRA or oleamide, two dissimilar nontoxic reversible inhibitors. Development of an adipogenic phenotype was confirmed by the accumulation of triglyceride droplets and the increase in mRNA expression of the adipocytic markers peroxisome proliferator-activated receptor gamma2 and lipoprotein lipase. Glycyrrhizic acid, a noninhibitory AGRA analog, or alpha-bromopalmitate, a nondegradable fatty acid, had no effect. Modulation of skeletal GJC may represent a new pharmacological target by which inhibition of marrow adipogenesis can take place with the parallel enhancement of osteoblastogenesis, thus providing a novel therapeutic approach to the treatment of human age-related osteopenic diseases and postmenopausal osteoporosis.

A novel gliotic P2 receptor mediating cyclooxygenase-2 induction in rat and human astrocytes

In astrocytic cultures maintained in vitro, a brief challenge with the ATP analog alpha,beta methyleneATP (alpha,betameATP) results, 3 days later, in marked elongation of astrocytic processes, an event that resembles the astrocytic hypertrophy known to occur in vivo during reactive astrogliosis. alpha,beta meATP-induced effects were observed in primary astrocytes obtained from both rat striatum and cortex (a brain area highly involved in chronic neurodegenerative pathologies), as well as in human astrocytoma cells (ADF cells). Purine-induced gliosis could be reversed by the non-selective P2X/P2Y receptor antagonist pyridoxalphosphate-6-azophenyl-2', 4'-disulphonic acid (PPADS), but not by oxidized ATP (an antagonist of the P2X(7) receptor), in line with previous studies of our laboratory suggesting the involvement of a P2Y receptor subtype. Induction of reactive gliosis was preceded by increased expression of cyclooxygenase-2 (COX-2), an enzyme whose excessive activation has been implicated in both acute and chronic neurodegenerative diseases. The selective COX-2 inhibitor NS-398 prevented both purine-induced astrogliosis and the associated COX-2 induction, suggesting that inhibition of the transcription of the COX-2 gene may also contribute to the anti-inflammatory properties of this agent. Significant blockade of both alpha,beta meATP-mediated reactive gliosis and COX-2 induction was also observed with PPADS. These data suggest that COX-2 mediates P2Y receptor-induced reactive astrogliosis, and that antagonists selective for this receptor subtype may represent a novel class of anti-inflammatory agents of potential interest in acute and chronic neurological disorders characterized by an inflammatory component and reactive gliosis.

Ras-related and MAPK signalling in neuronal plasticity and memory formation

Ras-related guanosine triphosphatases (GTPases) couple receptor activity to a number of intracellular signalling events culminating in the control of cell morphology and gene transcription. In culture cells, the best-understood Ras-dependent signalling pathway involves the mitogen-activated protein kinase/extracellular-regulated kinase (MAPK/ERK) cascade. A growing body of evidence has recently been accumulating to suggest a crucial role of Ras and MAPK signalling in neuronal functions connected to synaptic plasticity. In the present review article we discuss the experimental basis supporting the notion that the Ras/MAPK pathway interacts with other synaptic mechanisms to regulate invertebrate and vertebrate behavioural responses such as those implicated in learning and memory processes.