Complement C3-Deficient Mice Fail to Display Age-Related Hippocampal Decline.

The complement system is part of the innate immune response responsible for removing pathogens and cellular debris, in addition to helping to refine CNS neuronal connections via microglia-mediated pruning of inappropriate synapses during brain development. However, less is known about the role of complement during normal aging. Here, we studied the role of the central complement component, C3, in synaptic health and aging. We examined behavior as well as electrophysiological, synaptic, and neuronal changes in the brains of C3-deficient male mice (C3 KO) compared with age-, strain-, and gender-matched C57BL/6J (wild-type, WT) control mice at postnatal day 30, 4 months, and 16 months of age. We found the following: (1) region-specific and age-dependent synapse loss in aged WT mice that was not observed in C3 KO mice; (2) age-dependent neuron loss in hippocampal CA3 (but not in CA1) that followed synapse loss in aged WT mice, neither of which were observed in aged C3 KO mice; and (3) significantly enhanced LTP and cognition and less anxiety in aged C3 KO mice compared with aged WT mice. Importantly, CA3 synaptic puncta were similar between WT and C3 KO mice at P30. Together, our results suggest a novel and prominent role for complement protein C3 in mediating aged-related and region-specific changes in synaptic function and plasticity in the aging brain. Significance statement: The complement cascade, part of the innate immune response to remove pathogens, also plays a role in synaptic refinement during brain development by the removal of weak synapses. We investigated whether complement C3, a central component, affects synapse loss during aging. Wild-type (WT) and C3 knock-out (C3 KO) mice were examined at different ages. The mice were similar at 1 month of age. However, with aging, WT mice lost synapses in specific brain regions, especially in hippocampus, an area important for memory, whereas C3 KO mice were protected. Aged C3 KO mice also performed better on learning and memory tests than aged WT mice. Our results suggest that complement C3, or its downstream signaling, is detrimental to synapses during aging.

The struggle for equity: an examination of surgical services at two NGO hospitals in rural Haiti.

BACKGROUND: Health systems must deliver care equitably to serve the poor. Both L'Hôpital Albert Schweitzer (HAS) and L'Hôpital Bon Sauveur (HBS) have longstanding commitments to provide equitable surgical care in rural Haiti. HAS charges fees that reflect a preference for the rural population near the hospital, with free care available for the poorest. HBS does not charge fees. The two hospitals are otherwise similar in surgical capacity and rural location. Using geography as a proxy for poverty, we analysed the equity achieved under the financial system at both hospitals. METHODS: We retrospectively reviewed operative case-logs for general surgery and orthopaedic cases at both hospitals from June 1, to Aug 31, 2012. The records were compared by total number of operations, geographic distribution of patients, and number of elective operations. The service areas were defined as the governmental administrative units closest to both hospitals. For HAS, we analysed the number of operations performed on patients from the most poor and least poor regions within the service area; similarly detailed geographic information was not available from HBS. Rates were compared with χ(2) tests. The Ethics Committees at both hospitals and the Institutional Review Board at Partners Healthcare approved the study. FINDINGS: Patients from the rural service area received 306 operations (86·2%) at HAS compared with 149 (38·1%) at HBS (p<0·0001). Only 16 operations (4·5%) at HAS were performed on patients from outside the service area for elective conditions compared with 179 (47·0%) at HBS (p<0·0001). Within its rural service area, HAS performed fewer operations on patients from the most destitute areas compared with other locations (4·0 operations per 10 000 population vs 10·1 operations per 10 000 population; p<0·0001). INTERPRETATION: Use of fees as part of an equity strategy will likely disadvantage the poorest patients, while providing care without fees might encourage patients to travel from urban areas that contain other hospitals. Health systems striving to serve the poor should continually evaluate and seek to improve equity, even within systems that provide free care. FUNDING: None.

The Struggle for Equity: An Examination of Surgical Services at Two NGO Hospitals in Rural Haiti.

BACKGROUND: Health systems must deliver care equitably in order to serve the poor. Both L'Hôpital Albert Schweitzer (HAS) and L'Hôpital Bon Sauveur (HBS) have longstanding commitments to provide equitable surgical care in rural Haiti. HAS charges fees that demonstrate a preference for the rural population near the hospital, with free care available for the poorest. HBS does not charge fees. The two hospitals are otherwise similar in surgical capacity and rural location. METHODS: We retrospectively reviewed operative case-logs at both hospitals from June 1 to Aug 31, 2012. The records were compared by total number of operations, geographic distribution of patients and number of elective operations. Using geography as a proxy for poverty, we analyzed the equity achieved under the financial systems at both hospitals. RESULTS: Patients from the rural service area received 86% of operations at HAS compared to 38% at HBS (p < 0.001). Only 5% of all operations at HAS were performed on patients from outside the service area for elective conditions compared to 47% at HBS (p < 0.001). Within its rural service area, HAS performed fewer operations on patients from the most destitute areas compared to other locations (40.3 vs. 101.3 operations/100,000 population, p < 0.001). CONCLUSIONS: Using fees as part of an equity strategy will likely disadvantage the poorest patients, while providing care without fees may encourage patients to travel from urban areas that contain other hospitals. Health systems striving to serve the poor should continually evaluate and seek to improve equity, even within systems that provide free care.

Interleukin-1ß mediated amyloid plaque clearance is independent of CCR2 signaling in the APP/PS1 mouse model of Alzheimer's disease.

Neuroinflammation is a key component of Alzheimer's disease (AD) pathogenesis. Particularly, the proinflammatory cytokine interleukin-1 beta (IL-1ß) is upregulated in human AD and believed to promote amyloid plaque deposition. However, studies from our laboratory have shown that chronic IL-1ß overexpression in the APPswe/PSEN1dE9 (APP/PS1) mouse model of AD ameliorates amyloid pathology, increases plaque-associated microglia, and induces recruitment of peripheral immune cells to the brain parenchyma. To investigate the contribution of CCR2 signaling in IL-1ß-mediated amyloid plaque clearance, seven month-old APP/PS1/CCR2(-/-) mice were intrahippocampally transduced with a recombinant adeno-associated virus serotype 2 containing the cleaved form of human IL-1ß (rAAV2-IL-1ß). Four weeks after rAAV2-IL-1ß transduction, we found significant reductions in 6E10 and Congo red staining of amyloid plaques that was confirmed by decreased levels of insoluble Aß1-42 and Aß1-40 in the inflamed hippocampus. Bone marrow chimeric studies confirmed the presence of infiltrating immune cells following IL-1ß overexpression and revealed that dramatic reduction of CCR2(+) peripheral mononuclear cell recruitment to the inflamed hippocampus did not prevent the ability of IL-1ß to induce amyloid plaque clearance. These results suggest that infiltrating CCR2(+) monocytes do not contribute to IL-1ß-mediated amyloid plaque clearance.

Behavioral, structural and molecular changes following long-term hippocampal IL-1ß overexpression in transgenic mice.

Chronic neuroinflammation is associated with many neurodegenerative and neurocognitive disorders, yet few animal models exist to study the behavioral effects of prolonged neuroinflammation. Therefore, we recently developed a transgenic mouse model harboring an interleukin-1ß excisional activation transgene (IL-1ß(XAT)). These mice display localized IL-1ß overexpression and resultant neuroinflammation for up to 1 year following transgene induction. Initial behavioral studies demonstrated long-term memory deficits after 2 weeks of hippocampal IL-1ß overexpression. In the present studies, we extend these behavioral studies both in scope and timing. We find long-term contextual but not auditory fear memory impairments following 3 months of IL-1ß overexpression. On a battery of other behavioral tests, IL-1ß overexpression in IL-1ß(XAT) mice increased locomotor activity, especially in female mice, and had slight anxiolytic effects. No differences were found in operant conditioning or in basal or stress-induced CORT levels, despite profound hippocampal glial activation. Interestingly, the volume of discrete hippocampal cell layers was reduced after 6 but not 3 months of IL-1ß overexpression. Therefore, this animal model provides a novel tool for examining the effects of chronic inflammation on discrete brain regions.

Chronic IL-1ß-mediated neuroinflammation mitigates amyloid pathology in a mouse model of Alzheimer's disease without inducing overt neurodegeneration.

Neuroinflammation is a local tissue response to injurious stimuli in the central nervous system (CNS) and is characterized by glial reactivity, induction of cytokines and chemokines, and vascular permeability. The cytokine interleukin (IL)-1ß is rapidly induced following CNS insult, and is chronically expressed in neurodegenerative disorders such as Alzheimer's disease (AD). We recently developed a novel method of sustained IL-1ß production in the brain to study the link between IL-1ß and AD pathogenesis. Utilizing this model, we have previously demonstrated reduction of plaque size and frequency accompanied by a robust neuroinflammatory response. These observations were limited to a single early time point in the course of AD plaque deposition and did not investigate other neurodegenerative endpoints. To extend these observations to other stages of disease progression and evaluate additional pathologic markers, we investigated the effects of age and duration of IL-1ß overexpression in the APPswe/PS-1dE9 AD model on a congenic C57BL/6 background. We now report that IL1ß overexpression leads to decreased 6E10 immunopositive plaque pathology regardless of age or duration. We also investigated whether IL-1ß overexpression led to neuronal apoptosis or cholinergic axonal degeneration in the context of this AD model. Although we could demonstrate apoptosis of infiltrating inflammatory cells, we found no evidence for IL-1 associated apoptosis of neurons or cholinergic axon degeneration even after 5 months of chronic neuroinflammation. Together, these observations point to a neuroprotective role for IL-1ß in AD neuropathogenesis.

Cyclooxygenase-1 mediates prostaglandin E(2) elevation and contextual memory impairment in a model of sustained hippocampal interleukin-1beta expression.

Interleukin (IL)-1beta is a proinflammatory cytokine implicated in several neurodegenerative disorders. Downstream actions of IL-1beta include production of prostaglandin (PG) E(2) by increasing expression of cyclooxygenase (COX) enzymes and prostaglandin E synthase (PGES) isoforms. We recently developed a transgenic mouse carrying a dormant human IL-1beta eXcisional Activation Transgene (XAT) for conditional and chronic up-regulation of IL-1beta in selected brain regions. This model is characterized by regionally specific glial activation, immune cell recruitment, and induction of cytokines and chemokines. Here, we aimed to elucidate the effects of long-term IL-1beta expression on the PGE(2) synthetic pathway and to determine the effects of PGs on inflammation and memory in our model. As expected, PGE(2) levels were significantly elevated after IL-1beta up-regulation. Quantitative real-time PCR analysis indicated significant induction of mRNAs for COX-1 and membranous PGES-1, but not COX-2 or other PGES isoforms. Immunohistochemistry revealed elevation of COX-1 but no change in COX-2 following sustained IL-1beta production. Furthermore, pharmacological inhibition of COX-1 and use of COX-1 knockout mice abrogated IL-1beta-mediated PGE(2) increases. Although COX-1 deficient mice did not present a dramatically altered neuroinflammatory phenotype, they did exhibit improved contextual fear memory. This data suggests a unique role for COX-1 in mediating chronic neuroinflammatory effects through PGE(2) production.

Sustained hippocampal IL-1beta overexpression impairs contextual and spatial memory in transgenic mice.

Neuroinflammatory conditions such as traumatic brain injury, aging, Alzheimer's disease, and Down syndrome are often associated with cognitive dysfunction. Much research has targeted inflammation as a causative mediator of these deficits, although the diverse cellular and molecular changes that accompany these disorders obscure the link between inflammation and impaired memory. Therefore, we used a transgenic mouse model with a dormant human IL-1beta excisional activation transgene to direct overexpression of IL-1beta with temporal and regional control. Two weeks of hippocampal IL-1beta overexpression impaired long-term contextual and spatial memory in both male and female mice, while hippocampal-independent and short-term memory remained intact. Human IL-1beta overexpression activated glia, elevated murine IL-1beta protein and PGE(2) levels, and increased pro-inflammatory cytokine and chemokine mRNAs specifically within the hippocampus, while having no detectable effect on inflammatory mRNAs in the liver. Sustained neuroinflammation also reduced basal and conditioning-induced levels of the plasticity-related gene Arc.

Chronic interleukin-1beta expression in mouse brain leads to leukocyte infiltration and neutrophil-independent blood brain barrier permeability without overt neurodegeneration.

The proinflammatory cytokine interleukin-1beta (IL-1beta) plays a significant role in leukocyte recruitment to the CNS. Although acute effects of IL-1beta signaling in the mouse brain have been well described, studies elucidating the downstream effects of sustained upregulation have been lacking. Using the recently described IL-1beta(XAT) transgenic mouse model, we triggered sustained unilateral hippocampal overexpression of IL-1beta. Transgene induction led to blood-brain barrier leakage, induction of MCP-1 (monocyte chemoattractant protein 1) (CCL2), ICAM-1 (intercellular adhesion molecule 1), and dramatic infiltration of CD45-positive leukocytes comprised of neutrophils, T-cells, macrophages, and dendritic cells. Despite prolonged cellular infiltration of the hippocampus, there was no evidence of neuronal degeneration. Surprisingly, neutrophils were observed in the hippocampal parenchyma as late as 1 year after transgene induction. Their presence was coincident with upregulation of the potent neutrophil chemotactic chemokines KC (keratinocyte-derived chemokine) (CXCL1) and MIP-2 (macrophage inflammatory protein 2) (CXCL2). Knock-out of their sole receptor CXCR2 abrogated neutrophil infiltration but failed to reduce leakage of the blood-brain barrier.