Neuroinflammation associates with antioxidant heme oxygenase-1 response throughout the brain in persons living with HIV.

Previous studies showed that persons living with HIV (PLWH) demonstrate higher brain prefrontal cortex neuroinflammation and immunoproteasome expression compared to HIV-negative individuals; these associate positively with HIV levels. Lower expression of the antioxidant enzyme heme oxygenase 1 (HO-1) was observed in PLWH with HIV-associated neurocognitive impairment (HIV-NCI) compared to neurocognitively normal PLWH. We hypothesized that similar expression patterns occur throughout cortical, subcortical, and brainstem regions in PLWH, and that neuroinflammation and immunoproteasome expression associate with lower expression of neuronal markers. We analyzed autopsied brains (15 regions) from 9 PLWH without HIV-NCI and 7 matched HIV-negative individuals. Using Western blot and RT-qPCR, we quantified synaptic, inflammatory, immunoproteasome, endothelial, and antioxidant biomarkers, including HO-1 and its isoform heme oxygenase 2 (HO-2). In these PLWH without HIV-NCI, we observed higher expression of neuroinflammatory, endothelial, and immunoproteasome markers in multiple cortical and subcortical regions compared to HIV-negative individuals, suggesting a global brain inflammatory response to HIV. Several regions, including posterior cingulate cortex, globus pallidus, and cerebellum, showed a distinct pattern of higher type I interferon (IFN)-stimulated gene and immunoproteasome expression. PLWH without HIV-NCI also had (i) stable or higher HO-1 expression and positive associations between (ii) HO-1 and HIV levels (CSF, plasma) and (iii) HO-1 expression and neuroinflammation, in multiple cortical, subcortical, and brainstem regions. We observed no differences in synaptic marker expression, suggesting little, if any, associated neuronal injury. We speculate that this may reflect a neuroprotective effect of a concurrent HO-1 antioxidant response despite global neuroinflammation, which will require further investigation.

Cerebral patterns of neuropsychological disturbances in hepatitis C patients.

Neuropsychiatric symptoms and cognitive impairment have been consistently reported in patients with hepatitis C virus (HCV) infection. Since the mechanisms behind remain to be established, the present study attempted to assess whether neuropsychological impairments in HCV-infected patients are accompanied by structural alterations in the brain. Therefore, 19 anti-HCV-antibody-positive women with mild liver disease and 16 healthy controls underwent extensive neuropsychological testing and cranial magnetic resonance imaging (MRI) examination. Nine of the patients and five controls were followed up after 6-7 years. Voxel-based morphometry and magnetization transfer imaging were utilized to study HCV-associated structural gray and white matter changes. The HCV-infected patients had significantly worse fatigue and depression scores and significantly poorer performance on attention and memory tests than controls. The patients displayed gray matter (GM) atrophy in the bilateral insula and thalamus and a profound GM volume increases in the cerebellum. Microstructural GM changes in the insula were also evident by a reduced magnetization transfer ratio. Structural white matter changes were observed along several descending and crossing fiber tracts. Follow-up at 7 years revealed increased GM atrophy in the left amygdala and left parahippocampal regions over time. We conclude that our data provide evidence for structural alterations in the brains of patients with chronic HCV infection. Disturbances of cerebellothalamocortical regions and circuits, linking cerebellar projections to the prefrontal cortex through the thalamus, underpin the emotional and cognitive dysfunction characteristically observed in these patients.

Adeno-associated viral serotypes differentially transduce inhibitory neurons within the rat amygdala.

Recombinant adeno-associated viruses (AAV) are frequently used to make localized genetic manipulations within the rodent brain. It is accepted that the different viral serotypes possess differing affinities for particular cell types, but it is not clear how these properties affect their ability to transduce specific neuronal cell sub-types. Here, we examined ten AAV serotypes for their ability to transduce neurons within the rat basal and lateral nuclei of the amygdala (BLA) and the central nucleus of the amygdala (CeA). AAV2 based viral genomes designed to express either green fluorescent protein (GFP) from a glutamate decarboxylase (GAD65) promoter or the far-red fluorescent protein (E2-Crimson) from a phosphate-activated glutaminase (PAG) promoter were created and pseudotyped as AAV2/1, AAV2/4, AAV2/5, AAV2/6, AAV2/7, AAV 2/8, AAV2/9, AAV2/rh10, AAV2/DJ and AAV2/DJ8. These viruses were infused into the BLA and CeA at equal titers and twenty-one days later tissue within the amygdala was examined for viral transduction efficiency. These serotypes transduced neurons with similar efficiency, except for AAV4 and AAV5, which exhibited significantly less efficient neuronal transduction. Notably, AAV4 and AAV5 possess the most divergent capsid protein sequences compared to the other commonly available serotypes. We found that the Gad65-GFP virus did not exclusively express GFP within inhibitory neurons, as assessed by fluorescent in situ hybridization (FISH), but when this virus was used to transduce CeA neurons, the majority of the neurons that expressed GFP were in fact inhibitory neurons and this was likely due to the fact that this nucleus contains a very high percentage of inhibitory neurons.

Viral delivery of shRNA to amygdala neurons leads to neurotoxicity and deficits in Pavlovian fear conditioning.

The use of viral vector technology to deliver short hairpin RNAs (shRNAs) to cells of the nervous system of many model organisms has been widely utilized by neuroscientists to study the influence of genes on behavior. However, there have been numerous reports that delivering shRNAs to the nervous system can lead to neurotoxicity. Here we report the results of a series of experiments where adeno-associated viruses (AAV), that were engineered to express shRNAs designed to target known plasticity associated genes (i.e. Arc, Egr1 and GluN2A) or control shRNAs that were designed not to target any rat gene product for depletion, were delivered to the rat basal and lateral nuclei of the amygdala (BLA), and auditory Pavlovian fear conditioning was examined. In our first set of experiments we found that animals that received AAV (3.16E13-1E13 GC/mL; 1 µl/side), designed to knockdown Arc (shArc), or control shRNAs targeting either luciferase (shLuc), or nothing (shCntrl), exhibited impaired fear conditioning compared to animals that received viruses that did not express shRNAs. Notably, animals that received shArc did not exhibit differences in fear conditioning compared to animals that received control shRNAs despite gene knockdown of Arc. Viruses designed to harbor shRNAs did not induce obvious morphological changes to the cells/tissue of the BLA at any dose of virus tested, but at the highest dose of shRNA virus examined (3.16E13 GC/mL; 1 µl/side), a significant increase in microglia activation occurred as measured by an increase in IBA1 immunoreactivity. In our final set of experiments we infused viruses into the BLA at a titer of (1.60E+12 GC/mL; 1 µl/side), designed to express shArc, shLuc, shCntrl or shRNAs designed to target Egr1 (shEgr1), or GluN2A (shGluN2A), or no shRNA, and found that all groups exhibited impaired fear conditioning compared to the group which received a virus that did not express an shRNA. The shEgr1 and shGluN2A groups exhibited gene knockdown of Egr1 and GluN2A compared to the other groups examined respectively, but Arc was not knocked down in the shArc group under these conditions. Differences in fear conditioning among the shLuc, shCntrl, shArc and shEgr1 groups were not detected under these circumstances; however, the shGluN2A group exhibited significantly impaired fear conditioning compared to most of the groups, indicating that gene specific deficits in fear conditioning could be observed utilizing viral mediated delivery of shRNA. Collectively, these data indicate that viral mediated shRNA expression was toxic to neurons in vivo, under all viral titers examined and this toxicity in some cases may be masking gene specific changes in learning. Therefore, the use of this technology in behavioral neuroscience warrants a heightened level of careful consideration and potential methods to alleviate shRNA induced toxicity are discussed.

Pathogenic Role of Human Herpesvirus 6B Infection in Mesial Temporal Lobe Epilepsy.

BACKGROUND: Human herpesvirus 6B (HHV-6B) is the causative agent for exanthem subitum. HHV-6B was associated with mesial temporal sclerosis (MTS), leading to mesial temporal lobe epilepsy (MTLE). In this study, we sought to elucidate the pathogenic role of HHV-6B in patients with MTLE. METHODS: Seventy-five intractable MTLE patients, including 52 MTS patients and 23 non-MTS patients, were enrolled in this study. Resected hippocampus, amygdala, and mixed samples of amygdala and uncus samples were examined by real-time polymerase chain reaction (PCR) and reverse-transcriptase PCR to detect viral DNA and messenger RNA (mRNA), respectively. Host gene expressions, including neural markers, were measured using the TaqMan Gene Expression Assay. RESULTS: Detection of HHV-6 DNA was higher in MTS patients than non-MTS patients (median/interquartile range: 19.1/0-89.2 vs 0.0/0.0-0.0 copies/µg DNA; P = .004). HHV-6B viral DNA was determined in 12/27 HHV-6 DNA-positive samples, and no HHV-6B mRNA were detected in all samples. In MTS patients, expression of monocyte chemotactic protein-1 (P = .029) and glial fibrillary acidic protein (P = .043) were significantly higher in the amygdala samples with HHV-6 DNA than those without viral DNA. CONCLUSIONS: This study suggests that HHV-6B may play an important role in the pathogenesis of MTS via modification of host gene expression.

Adeno-associated viral serotypes produce differing titers and differentially transduce neurons within the rat basal and lateral amygdala.

BACKGROUND: In recent years, there has been an increased interest in using recombinant adeno-associated viruses (AAV) to make localized genetic manipulations within the rodent brain. Differing serotypes of AAV possess divergent capsid protein sequences and these variations greatly influence each serotype's ability to transduce particular cell types and brain regions. We therefore aimed to determine the AAV serotype that is optimal for targeting neurons within the Basal and Lateral Amygdala (BLA) since the transduction efficiency of AAV has not been previously examined within the BLA. This region is desirable to genetically manipulate due to its role in emotion, learning & memory, and numerous psychiatric disorders. We accomplished this by screening 9 different AAV serotypes (AAV2/1, AAV2/2, AAV2/5, AAV2/7, AAV2/8, AAV2/9, AAV2/rh10, AAV2/DJ and AAV2/DJ8) designed to express red fluorescent protein (RFP) under the regulation of an alpha Ca2+/calmodulin-dependent protein kinase II promoter (αCaMKII). RESULTS: We determined that these serotypes produce differing amounts of virus under standard laboratory production. Notably AAV2/2 consistently produced the lowest titers compared to the other serotypes examined. These nine serotypes were bilaterally infused into the rat BLA at the highest titers achieved for each serotype and at a normalized titer of 7.8E + 11 GC/ml. Twenty one days following viral infusion the degree of transduction was quantitated throughout the amygdala. These viruses exhibited differential transduction of neurons within the BLA. AAV2/7 exhibited a trend toward having the highest efficiency of transduction and AAV2/5 exhibited significantly lower transduction efficiency as compared to the serotypes examined. AAV2/5's decreased ability to transduce BLA neurons correlates with its significantly different capsid protein sequences as compared to the other serotypes examined. CONCLUSIONS: For laboratories producing their own recombinant adeno-associated viruses, the use of AAV2/2 is likely less desirable since AAV2/2 produces significantly lower titers than many other serotypes of AAV. Numerous AAV serotypes appear to efficiently transduce BLA neurons, with the exception of AAV2/5. Taking into consideration the ability of certain serotypes to achieve high titers and transduce BLA neurons well, in our hands AAV2/DJ8 and AAV2/9 appear to be ideal serotypes to use when targeting neurons within the BLA.

Amygdala connections with jaw, tongue and laryngo-pharyngeal premotor neurons.

As the central nucleus (CE) is the only amygdaloid nucleus to send axons to the pons and medulla, it is thought to be involved in the expression of conditioned responses by accessing hindbrain circuitry generating stereotypic responses to aversive stimuli. Responses to aversive oral stimuli include gaping and tongue protrusion generated by central pattern generators and other premotor neurons in the ponto-medullary reticular formation. We investigated central nucleus connections with the reticular formation by identifying premotor reticular formation neurons through the retrograde trans-synaptic transport of pseudorabies virus (PRV) inoculated into masseter, genioglossus, thyroarytenoid or inferior constrictor muscles in combination with anterograde labeling of CE axons with biotinylated dextran amine. Three dimensional mapping of PRV infected premotor neurons revealed specific clusters of these neurons associated with different oro-laryngo-pharyngeal muscles, particularly in the parvicellular reticular formation. CE axon terminals were concentrated in certain parvicellular clusters but overall putative contacts were identified with premotor neurons associated with all four oro-laryngo-pharyngeal muscles investigated. We also mapped the retrograde trans-synaptic spread of PRV through the various nuclei of the amygdaloid complex. Medial CE was the first amygdala structure infected (4 days post-inoculation) with trans-synaptic spread to the lateral CE and the caudomedial parvicellular basolateral nucleus by day 5 post-inoculation. Infected neurons were only very rarely found in the lateral capsular CE and the lateral nucleus and then at only the latest time points. The data demonstrate that the CE is directly connected with clusters of reticular premotor neurons that may represent complex pattern generators and/or switching elements for the generation of stereotypic oral and laryngo-pharyngeal movements during aversive oral stimulation. Serial connections through the amygdaloid complex linked with the oro-laryngo-pharyngeal musculature appear quite distinct from those believed to sub-serve fear responses, suggesting there are distinct "channels" for the acquisition and expression of particular conditioned behaviors.

Sinus node arrest secondary to HSV encephalitis.

We report a patient with herpes simplex virus (HSV) encephalitis presenting as recurrent syncope due to sinus node arrest. Although the patient's initial presentation suggested a primary cardiac cause, an eventual diagnosis of HSV encephalitis was supported by computed tomography scan and magnetic resonance imaging, and confirmed by HSV polymerase chain reaction. The mechanism of cardiac arrhythmias in HSV encephalitis remains unclear; however, cardiac monitoring should be considered in all patients in whom the diagnosis is suspected. With diagnosis and appropriate management, a permanent pacemaker is generally not indicated. This case report highlights the importance of considering potentially reversible causes of collapse secondary to sinus node dysfunction beyond primary cardiac causes.

Memory of social defeat is facilitated by cAMP response element-binding protein overexpression in the amygdala.

The cAMP-responsive element binding protein (CREB) is a transcription factor that regulates synaptic plasticity and memory formation. Studies that have used conditioned fear models have established that CREB is important for the acquisition and consolidation of fear learning. The authors demonstrate that overexpression of CREB within the basolateral amygdala (BLA) of animals that are exposed to social defeat enhances subsequent defeat-induced changes in social behavior. This effect is specific to the acquisition of defeat-induced behaviors; overexpression of CREB has no effect on the expression of these behaviors if the overexpression occurs after the initial defeat. These data demonstrate that CREB is important for regulating learning not only to explicit cues but also for mediating behavioral plasticity in ethologically relevant social contexts.

Postsynaptic receptor trafficking underlying a form of associative learning.

To elucidate molecular, cellular, and circuit changes that occur in the brain during learning, we investigated the role of a glutamate receptor subtype in fear conditioning. In this form of learning, animals associate two stimuli, such as a tone and a shock. Here we report that fear conditioning drives AMPA-type glutamate receptors into the synapse of a large fraction of postsynaptic neurons in the lateral amygdala, a brain structure essential for this learning process. Furthermore, memory was reduced if AMPA receptor synaptic incorporation was blocked in as few as 10 to 20% of lateral amygdala neurons. Thus, the encoding of memories in the lateral amygdala is mediated by AMPA receptor trafficking, is widely distributed, and displays little redundancy.

Effects of altered amygdalar neuropeptide Y expression on anxiety-related behaviors.

Neuropeptide Y (NPY) decreases anxiety-related behaviors in various animal models of anxiety. The purpose of the present study was to examine the role of the amygdalar NPY system in anxiety-related responses in the elevated plus maze. The first experiment determined if herpes virus-mediated alterations in amygdalar NPY levels would alter anxiety-related behaviors in the elevated plus maze. Viral vectors encoding NPY, NPY antisense, or LacZ (control virus) were bilaterally injected into the amygdala, and 4 days postinjection, rats were tested in the elevated plus maze test. NPY-like immunoreactivity (NPY-ir) was measured in the amygdala of these rats. In rats injected with the viral vector encoding NPY, reduced anxiety-related behaviors in the elevated plus maze accompanied by moderate increases in NPY-ir were detected compared to NPY-antisense viral vector-treated subjects. Elevated plus maze behavior did not differ compared to LacZ-treated controls. NPY overexpression at this time point was also suggested by enhanced NPY mRNA expression seen in the amygdala 4 days postinjection using real-time polymerase chain reaction analysis. Experiment 2 was conducted to provide further evidence for a role of amygdalar NPY in regulating anxiety-related behaviors in the elevated plus maze test. The nonpeptide NPY Y1 receptor antagonist, BIBP 3226 (1.5 microg/microl), was bilaterally injected into the amygdala and rats were tested in the elevated plus maze test. Rats receiving BIBP 3226 exhibited increased anxiety-related behaviors in this test. The results of these experiments provide further support for the role of amygdalar NPY in anxiety-related behaviors.

Effects of cyclic adenosine monophosphate response element binding protein overexpression in the basolateral amygdala on behavioral models of depression and anxiety.

BACKGROUND: Chronic antidepressant administration increases the cyclic adenosine monophosphate response element binding protein (CREB) in the amygdala, a critical neural substrate involved in the physiologic responses to stress, fear, and anxiety. METHODS: To determine the role of CREB in the amygdala in animal models of depression and anxiety, a viral gene transfer approach was used to selectively express CREB in this region of the rat brain. RESULTS: In the learned helplessness model of depression, induction of CREB in the basolateral amygdala after training decreased the number of escape failures, an antidepressant response. However, expression of CREB before training increased escape failures, and increased immobility in the forced swim test, depressive effects. Expression of CREB in the basolateral amygdala also increased behavioral measures of anxiety in both the open field test and the elevated plus maze, and enhanced cued fear conditioning. CONCLUSIONS: Taken together, these data demonstrate that CREB expression in the basolateral amygdala influences behavior in models of depression, anxiety, and fear. Moreover, in the basolateral amygdala, the temporal expression of CREB in relation to learned helplessness training, determines the qualitative outcome in this animal model of depression.

Neuropathology and neurodegeneration in rodent brain induced by lentiviral vector-mediated overexpression of alpha-synuclein.

Two mutations in alpha-synuclein, the main constituent of Lewy bodies, have been identified in familial Parkinson's disease. We have stereotactically injected lentiviral vectors encoding wild-type and A30P mutant human alpha-synuclein in different brain regions (striatum, substantia nigra, amygdala) of mice. Overexpression of alpha-synuclein induced time-dependent neuropathological changes reminiscent of Lewy pathology: abnormal accumulation of alpha-synuclein in cell bodies and neurites, alpha-synuclein-positive neuritic varicosities and cytoplasmic inclusions that stained with ubiquitin antibodies and became larger and more frequent with time. After one year, alpha-synuclein- and ubiquitin-positive neurons displayed a degenerative morphology and a significant loss of alpha-synuclein-positive cells was observed. Similar findings were observed with both the wild-type and the A30P mutant form of alpha-synuclein and this in different brain regions. This indicates that overexpression of alpha-synuclein is sufficient to induce Lewy-like pathology and neurodegeneration and that this effect is not restricted to dopaminergic cells. Our data also demonstrate the use of lentiviral vectors to create animal models for neurodegenerative diseases.

Herpes simplex replication and dissemination is not increased by corticosteroid treatment in a rat model of focal Herpes encephalitis.

Neurological damage in Herpes simplex type 1 encephalitis results from neuronal cell death secondary to viral invasion, and from inflammatory changes and cerebral oedema secondary to the immune response to the virus. Corticosteroids could have an important role in the management of Herpes simplex encephalitis because their anti-inflammatory action reduces cerebral oedema. However their use has been limited by concerns that their immunosuppressive actions could increase viral replication and spread. The present study examined this issue in a rat model in which injection of HSV-1 into the cervical vagus nerve produced a well-defined focal encephalitis, characterised by an orderly progression of the virus through central neural pathways connected with vagal afferent termination sites in the medulla oblongata. After injection of HSV-1, rats were treated twice a day, either with vehicle (saline, 400 microl i.p.), with acyclovir (30 mg/kg i.p.), with dexamethasone (5 mg/kg i.p.), or with both acyclovir and dexamethasone. Animals were sacrificed after 72 h, and viral load in different brain regions was quantified by computer-assisted measurement of the area occupied by immunohistochemical reaction product. Treatment with acyclovir reduced viral load to 17 +/- 5% of the saline value (P < 0.01). After dexamethasone treatment, the viral load (63 +/- 13% of the saline value) was also reduced (P < 0.05). Treatment with both acyclovir and dexamethasone reduced viral load to 26 +/- 8% of the saline value (P < 0.01 compared with saline, and P > 0.05 compared to acyclovir alone). Our results confirm the effectiveness of acyclovir in a new model of HSV-1 infection, and provide evidence that corticosteroids do not inhibit the antiviral action of acyclovir. In addition corticosteroids may decrease the extent of infection in their own right. The acute time course studied in our model parallels the time course of acute Herpes simplex encephalitis in humans. Our data suggests that corticosteroids are not detrimental when combined with acyclovir in the management of this condition.

Transneuronal spread of the pseudorabies virus after injection into the central nucleus of the amygdala in the rat.

The pseudorabies virus (PRV) is a swine alpha herpes virus that is widely used as a neural tracer because of its marked neurotropism and transneuronal transmissibility (Card et al., 1991, 1992; Strack and Loewy 1990). PRV has been used to retrogradely identify spinal cord and brainstem connections to various peripheral organs, but few anatomical studies have used CNS inoculation of PRV to investigate intrinsic brain connectivity. Improved knowledge of the mode and temporal pattern of transneuronal spread is essential for interpretation of PRV tracing studies, and is also a prerequisite to the use of this and other herpes viruses as vectors in the CNS. This study investigated the distribution of PRV labelling in the CNS at various time points after its injection into the central nucleus of the amygdala (CA). The results indicate that detection of PRV in a retrogradely labelled site at any given time after injection is not only a function of the number of synapses in the pathway from the injection site, but is also highly dependent on the axon lengths involved, much more than would be expected if fast axonal transport were the limiting factor. In addition, the window of time during which PRV may be detected in a given site is limited ultimately by neuronal destruction.