Tamir Ben Hur

Intrahippocampal Transplantation of Transgenic Neural Precursor Cells Overexpressing Interleukin-1 Receptor Antagonist Blocks Chronic Isolation-Induced Impairment in Memory and Neurogenesis

The proinflammatory cytokine interleukin-1 (IL-1) within the brain is critically involved in mediating the memory impairment induced by acute inflammatory challenges and psychological stress. However, the role of IL-1 in memory impairment and suppressed neurogenesis induced by chronic stress exposure has not been investigated before now. We report here that mice that were isolated for 4 weeks displayed a significant elevation in hippocampal IL-1β levels concomitantly with body weight loss, specific impairment in hippocampal-dependent memory, and decreased hippocampal neurogenesis. To examine the causal role of IL-1 in these effects, we developed a novel approach for long-term delivery of IL-1 receptor antagonist (IL-1ra) into the brain, using transplantation of neural precursor cells (NPCs), obtained from neonatal mice with transgenic overexpression of IL-1ra (IL-1raTG) under the glial fibrillary acidic protein promoter. Four weeks following intrahippocampal transplantation of IL-1raTG NPCs labeled with PKH-26, the transplanted cells were incorporated within the dentate gyrus and expressed mainly astrocytic markers. IL-1ra levels were markedly elevated in the hippocampus, but not in other brain regions, by 10 days and for at least 4 weeks post-transplantation. Transplantation of IL-1raTG NPCs completely rescued the chronic isolation-induced body weight loss, memory impairment, and suppressed hippocampal neurogenesis, compared with isolated mice transplanted with WT cells or sham operated. The transplantation had no effect in group-housed mice. These findings elucidate the role of IL-1 in the pathophysiology of chronic isolation and suggest that transplantation of IL-1raTG NPCs may provide a useful therapeutic procedure for IL-1-mediated memory disturbances in chronic inflammatory and neurological conditions.

Astrocytes support hippocampal-dependent memory and long-term potentiation via interleukin-1 signaling.

Recent studies indicate that astrocytes play an integral role in neural and synaptic functioning. To examine the implications of these findings for neurobehavioral plasticity we investigated the involvement of astrocytes in memory and long-term potentiation (LTP), using a mouse model of impaired learning and synaptic plasticity caused by genetic deletion of the interleukin-1 receptor type I (IL-1RI). Neural precursor cells (NPCs), derived from either wild type (WT) or IL-1 receptor knockout (IL-1rKO) neonatal mice, were labeled with bromodeoxyuridine (BrdU) and transplanted into the hippocampus of either IL-1rKO or WT adult host mice. Transplanted NPCs survived and differentiated into astrocytes (expressing GFAP and S100β), but not to neurons or oligodendrocytes. The NPCs-derived astrocytes from WT but not IL-1rKO mice displayed co-localization of GFAP with the IL-1RI. Four to twelve weeks post-transplantation, memory functioning was examined in the fear-conditioning and the water maze paradigms and LTP of perforant path-dentate gyrus synapses was assessed in anesthetized mice. As expected, IL-1rKO mice transplanted with IL-1rKO cells or sham operated displayed severe memory disturbances in both paradigms as well as a marked impairment in LTP. In contrast, IL-1rKO mice transplanted with WT NPCs displayed a complete rescue of the impaired memory functioning as well as partial restoration of LTP. These findings indicate that astrocytes play a critical role in memory functioning and LTP, and specifically implicate astrocytic IL-1 signaling in these processes. The results suggest novel conceptualization and therapeutic targets for neuropsychiatric disorders characterized by impaired astrocytic functioning concomitantly with disturbed memory and synaptic plasticity.

Extrathymic malignancies in patients with myasthenia gravis.

INTRODUCTION Myasthenia gravis (MG) is considered a paraneoplastic phenomenon of thymomas in 15% of patients. Co-existence of MG with extrathymic malignancies, and an increased risk of second malignancy in patients with thymoma have been reported. Data on clinical characteristics of MG patients with extrathymic malignancies and the role of concomitant diseases and their treatment are lacking. METHODS The clinical records of 188 consecutive MG patients were studied retrospectively. We examined whether gender, age, generalized disease, seropositivity for acetyl-choline receptor antibodies, occurrence of thymoma, immunosuppressive therapy and occurrence of other autoimmune diseases determined an increased risk for development of extrathymic malignancy. RESULTS This group followed the typical epidemiological characteristics of MG. Thirty-three patients (17.6%) had a thymoma. Twenty-nine patients (15.4%) had 30 extrathymic malignant tumors of various origins. Only four patients with extrathymic tumors had an associated thymoma. Tumors were diagnosed between 20 years prior to and 35 years after the appearance of MG. Older age of MG onset was the only risk factor identified for development of malignancy in MG. DISCUSSION Extrathymic malignancies are common in MG patients, especially in the older age group. There are no specific clinical features of the subgroup of MG patients with cancer. Although MG is not a paraneoplastic phenomenon of extrathymic malignancy, the association between MG and malignancy may be due to a common background of immune dysregulation.

Intra-Hippocampal Transplantation of Neural Precursor Cells with Transgenic Over-Expression of IL-1 Receptor Antagonist Rescues Memory and Neurogenesis Impairments in an Alzheimer’s Disease Model

Ample evidence implicates neuroinflammatory processes in the etiology and progression of Alzheimers disease (AD). To assess the specific role of the pro-inflammatory cytokine interleukin-1 (IL-1) in AD we examined the effects of intra-hippocampal transplantation of neural precursor cells (NPCs) with transgenic over-expression of IL-1 receptor antagonist (IL-1raTG) on memory functioning and neurogenesis in a murine model of AD (Tg2576 mice). WT NPCs- or sham-transplanted Tg2576 mice, as well as naive Tg2576 and WT mice served as controls. To assess the net effect of IL-1 blockade (not in the context of NPCs transplantation), we also examined the effects of chronic (4 weeks) intra-cerebroventricular (i.c.v.) administration of IL-1ra. We report that 12-month-old Tg2576 mice exhibited increased mRNA expression of hippocampal IL-1β, along with severe disturbances in hippocampal-dependent contextual and spatial memory as well as in neurogenesis. Transplantation of IL-1raTG NPCs 1 month before the neurobehavioral testing completely rescued these disturbances and significantly increased the number of endogenous hippocampal cells expressing the plasticity-related molecule BDNF. Similar, but less-robust effects were also produced by transplantation of WT NPCs and by i.c.v. IL-1ra administration. NPCs transplantation produced alterations in hippocampal plaque formation and microglial status, which were not clearly correlated with the cognitive effects of this procedure. The results indicate that elevated levels of hippocampal IL-1 are causally related to some AD-associated memory disturbances, and provide the first example for the potential use of genetically manipulated NPCs with anti-inflammatory properties in the treatment of AD.

Use of DWI-only MR protocol for screening stroke mimics.

PURPOSE Patients presenting with focal neurological symptoms may suffer from stroke or stroke mimics. Diffusion weighted MRI (DWI) is highly sensitive for identifying acute ischemia. Therefore, we aimed to explore whether a DWI-only protocol would help differentiate stroke from stroke mimics. METHODS We identified all patients with possible but not definite stroke that underwent DWI-only MRI between 6/2010 and 8/2011. Patients with a positive DWI lesion were compared to those with negative DWI findings on demographics, risk factor profile, final discharge diagnoses, and outcome. RESULTS A total of 124 patients were included with a median age of 63.5 (53% male). DWI MRI was positive for acute ischemia in 46 patients (37%). The most frequent stroke mimics were peripheral vertigo (n=19), acute confusion (n=10), seizures (n=9) and migraine with aura (n=8). Most ischemic lesions were small on DWI (<2 cm) and patients had minor disability (mean NIHSS 4.9±3.9) with 81% of patients having good outcomes (modified Rankin Score≤2) at 3 months. On univariate analysis patients with positive DWI studies had higher frequencies of having more than one clinical symptom (56% vs. 13% respectively; P<0.001) and this variable remained a significant predictor for stroke on multivariate analysis (OR 9.4 95% CI 3.8-23.5). CONCLUSIONS A short DWI-only MRI protocol can effectively differentiate stroke from stroke mimics and could be used in settings of the emergency department as well as later on for diagnostic purposes. The chances for finding positive DWI lesions are increased in patients with multiple symptoms and signs.

Should DWI MRI be the primary screening test for stroke

Patients presenting with focal neurological symptoms may suffer from ischemic stroke, intracerebral hemorrhage, or stroke mimics. Such patients are usually screened with a noncontrast-enhanced computed tomography to rule out hemorrhage and to detect early signs of ischemia. However, the sensitivity of noncontrast-enhanced computed tomography for acute stroke is far inferior to that of diffusion-weighted magnetic resonance imaging and the latter is also very sensitive for identifying acute intracerebral hemorrhage. Most centers perform a magnetic resonance imaging stroke protocol that takes long to accomplish and may therefore delay therapy. Herein, we propose that a short diffusionweighted imaging-only magnetic resonance imaging protocol can effectively differentiate ischemic stroke from intracerebral hemorrhage and stroke mimics and could therefore be used as the first line screening test for stroke. Adopting such a screening strategy will result in increased diagnostic accuracy and avoidance of unnecessary treatment of stroke mimics with thrombolysis but may come at the increased cost of performing a magnetic resonance imaging at the emergency department. Whether such a strategy will be cost effective or not remains to be tested in future studies.

Incidence of DWI-positive stroke in patients with vertigo of unclear etiology, preliminary results.

Abstract Background: Acute vertigo may be secondary to stroke or to non-ischemic causes. Accurate identification of vertigo secondary to ischemia may lead to appropriate timely intervention that can minimize stroke-related damage and can help in tailoring the most appropriate individual therapy for affected patients. Diffusion weighted MRI (DWI) is very accurate for diagnosing stroke and we therefore aimed to test whether it can aid in making a correct diagnosis of vertigo secondary to stroke. Methods: All patients presenting with vertigo in which the diagnosis of stroke was considered underwent DWI only MRI. Data regarding the symptoms and neurological deficits, vascular risk factors, imaging findings, and outcomes was accrued. Patients with stroke on DWI were compared with those without ischemia. Results: Between June 2010 and August 2011, 28 patients fulfilling the entry criteria were identified with a mean age of 62·2±12·8 (60% male). The final diagnosis was stroke in 11 patients (39%). Patients with stroke did not differ from those without stroke in their risk factor profile. However, patients with stroke more often tended to present with vertigo accompanied by other neurological symptoms (73% versus 12% respectively, P = 0·001). After adjusting for age and the presence of diabetes, the presence of multiple symptoms remained the only variable that was associated with a positive DWI scan (odds ratio: 30: 95% confidence interval: 2·6–349). Most patients with stroke had very mild strokes with a median admission NIHSS score of 3 and DWI lesion volumes >2 cm were found in only three patients. Most stroke patients made a good recovery (modified Rankin score ≤2 in seven of nine patients with 90 day data). The most common diagnosis in patients without stroke was of vertigo of peripheral origin (14/17). Conclusions: DWI only MRI can be used to rapidly screen patients presenting with vertigo and suspected vertebrobasilar stroke. The occurrence of vertigo in combination with other focal neurological symptoms may increase the accuracy of stroke diagnosis but is not sensitive or specific enough. Combining clinical presentation patterns with DWI data may enable rapid decision making as to treatment options.

150. IL-1 signaling in astrocytes is essential for hippocampal-dependent memory functioning

Chronic stress in older adults is associated with greater morbidity and mortality. However, the mechanisms are not fully understood. Endocrine-immune dysregulation associated with aging and/or chronic stress may impact on frequency and severity of infections. To test the hypothesis that aging and chronic stress alter glucocorticoid sensitivity for antigen stimulated cytokine secretion, Fisher rats (n = 24) were stratified by age (18 mo and 6 mo) and housing: double or single (isolation stress) for 28 days, rats were sacrificed, and trunk blood collected; in vitro, 3 ng/ml lipopolysaccharide (LPS) stimulated IL-6 levels were measured following lymphocyte preincubation with 0, 10, 50 and 100 nM dexamethazone (DEX). A 2 (age) 2 (housing) 4 (concentrations of DEX) repeated measures analysis of variance (ANOVA) revealed age (p = 0.001) and age x DEX concentration (p = 0.049) effects for stimulated IL-6. Older rats appeared to have greater lymphocyte glucocorticoid (DEX) sensitivity with increased suppression of stimulated IL-6, which may indicate dampen immune responsiveness and increased susceptibility to infection. There was also an age x housing interaction (p = .05) with increased stimulated IL-6 only in younger single housed animals, possibly indicating chronic stress associated resistance to glucocorticoids. In conclusion, younger age may protect against infectious diseases during chronic stress by increasing resistance to glucocorticoids. Whereas, aging itself may increase susceptibility to infectious disease, and with age immune resistance to glucocorticoids may be diminished during chronic stress, thereby reducing protection against infection.

Intrahippocampal transplantation of transgenic IL-1ra over-expressing glial cells blocks IL-1-mediated stress-induced decline in memory and neurogenesis

Previous studies demonstrated that elevation in the levels of the pro-inflammatory cytokine interleukin-1 (IL-1) within the brain is involved in mediating the memory impairments associated with inflammation and aging. In the present study, we used a model of chronic stress, in which each mouse was isolated in an individual cage for 3 weeks. In both the contextual fear conditioning (FC) test and the spatial version of the Morris water maze (MWM) paradigm, which depend on hippocampal functioning, isolated mice displayed significant memory impairments. Isolation had no effect on the hippocampus independent auditory-cued FC and the non-spatial version of the MWM. Isolation caused a significant elevation in hippocampal IL-1 levels as well as a significant decrease in hippocampal neurogenesis. To explore the role of hippocampal IL-1 in stress-induced memory impairments and suppressed neurogenesis, neural precursor cells (NPCs) were isolated from neonatal mice with transgenic over-expression of IL-1 receptor antagonist (IL-1raTG) under the GFAP promoter, labeled with PKH-26 and transplanted into the hippocampus of WT mice. Three weeks later, transplanted cells, expressing mainly astrocytic markers, could be observed within the hippocampus, and the levels of hippocampal IL-1ra were markedly elevated. In isolated mice, transplantation of IL1raTG NPCs completely rescued the memory impairments and significantly increased hippocampal neurogenesis, compared with isolated mice transplanted with WT cells or sham-operated only. The transplantation had no effect in non-stressed mice. These findings elucidate the role of IL-1 in the pathophysiology of chronic stress and suggest that the intra-hippocampal transplantation of transgenic IL-1raTG NPCs may provide a useful therapeutic procedure for IL-1-mediated memory disturbances in other conditions, particularly neurodegenerative diseases.