Magnetic resonance imaging of human brain macrophage infiltration

Specific nanoprobe design for MRI: Targeting laminin in the blood-brain barrier to follow alteration due to neuroinflammation

Chronic neuroinflammation is characterized by increased blood-brain barrier (BBB) permeability, leading to molecular changes in the central nervous system that can be explored with biomarkers of active neuroinflammatory processes. Magnetic resonance imaging (MRI) has contributed to detecting lesions and permeability of the BBB. Ultra-small superparamagnetic particles of iron oxide (USPIO) are used as contrast agents to improve MRI observations. Therefore, we validate the interaction of peptide-88 with laminin, vectorized on USPIO, to explore BBB molecular alterations occurring during neuroinflammation as a potential tool for use in MRI. The specific labeling of NPS-P88 was verified in endothelial cells (hCMEC/D3) and astrocytes (T98G) under inflammation induced by interleukin 1β (IL-1β) for 3 and 24 hours. IL-1β for 3 hours in hCMEC/D3 cells increased their co-localization with NPS-P88, compared with controls. At 24 hours, no significant differences were observed between groups. In T98G cells, NPS-P88 showed similar nonspecific labeling among treatments. These results indicate that NPS-P88 has a higher affinity towards brain endothelial cells than astrocytes under inflammation. This affinity decreases over time with reduced laminin expression. In vivo results suggest that following a 30-minute post-injection, there is an increased presence of NPS-P88 in the blood and brain, diminishing over time. Lastly, EAE animals displayed a significant accumulation of NPS-P88 in MRI, primarily in the cortex, attributed to inflammation and disruption of the BBB. Altogether, these results revealed NPS-P88 as a biomarker to evaluate changes in the BBB due to neuroinflammation by MRI in biological models targeting laminin.

Non-classical monocytes promote neurovascular repair in cerebral small vessel disease associated with microinfarctions via CX3CR1

Cerebral small vessel disease (cSVD) constitutes a major risk factor for dementia. Monocytes play important roles in cerebrovascular disorders. Herein, we aimed to investigate the contribution of non-classical C-X3-C motif chemokine receptor (CX3CR)1 monocytes to cSVD pathobiology and therapy. To this end, we generated chimeric mice in which CX3CR1 in non-classical monocytes was either functional (CX3CR1GFP/+) or dysfunctional (CX3CR1GFP/GFP). cSVD was induced in mice via the micro-occlusion of cerebral arterioles, and novel immunomodulatory approaches targeting CX3CR1 monocyte production were used. Our findings demonstrate that CX3CR1GFP/+ monocytes transiently infiltrated the ipsilateral hippocampus and were recruited to the microinfarcts 7 days after cSVD, inversely associated with neuronal degeneration and blood-brain barrier (BBB) disruption. Dysfunctional CX3CR1GFP/GFP monocytes failed to infiltrate the injured hippocampus and were associated with exacerbated microinfarctions and accelerated cognitive decline, accompanied with an impaired microvascular structure. Pharmacological stimulation of CX3CR1GFP/+ monocyte generation attenuated neuronal loss and improved cognitive functions by promoting microvascular function and preserving cerebral blood flow (CBF). These changes were associated with elevated levels of pro-angiogenic factors and matrix stabilizers in the blood circulation. The results indicate that non-classical CX3CR1 monocytes promote neurovascular repair after cSVD and constitute a promising target for the development of new therapies.

Tumor Necrosis Factor (TNF)-α-Stimulated Gene 6 (TSG-6): A Promising Immunomodulatory Target in Acute Neurodegenerative Diseases

Tumor necrosis factor (TNF)-α-stimulated gene 6 (TSG-6), the first soluble chemokine-binding protein to be identified in mammals, inhibits chemotaxis and transendothelial migration of neutrophils and attenuates the inflammatory response of dendritic cells, macrophages, monocytes, and T cells. This immunoregulatory protein is a pivotal mediator of the therapeutic efficacy of mesenchymal stem/stromal cells (MSC) in diverse pathological conditions, including neuroinflammation. However, TSG-6 is also constitutively expressed in some tissues, such as the brain and spinal cord, and is generally upregulated in response to inflammation in monocytes/macrophages, dendritic cells, astrocytes, vascular smooth muscle cells and fibroblasts. Due to its ability to modulate sterile inflammation, TSG-6 exerts protective effects in diverse degenerative and inflammatory diseases, including brain disorders. Emerging evidence provides insights into the potential use of TSG-6 as a peripheral diagnostic and/or prognostic biomarker, especially in the context of ischemic stroke, whereby the pathobiological relevance of this protein has also been demonstrated in patients. Thus, in this review, we will discuss the most recent data on the involvement of TSG-6 in neurodegenerative diseases, particularly focusing on relevant anti-inflammatory and immunomodulatory functions. Furthermore, we will examine evidence suggesting novel therapeutic opportunities that can be afforded by modulating TSG-6-related pathways in neuropathological contexts and, most notably, in stroke.

The Translational Potential of Microglia and Monocyte-Derived Macrophages in Ischemic Stroke

The immune response to ischemic stroke is an area of study that is at the forefront of stroke research and presents promising new avenues for treatment development. Upon cerebral vessel occlusion, the innate immune system is activated by danger-associated molecular signals from stressed and dying neurons. Microglia, an immune cell population within the central nervous system which phagocytose cell debris and modulate the immune response via cytokine signaling, are the first cell population to become activated. Soon after, monocytes arrive from the peripheral immune system, differentiate into macrophages, and further aid in the immune response. Upon activation, both microglia and monocyte-derived macrophages are capable of polarizing into phenotypes which can either promote or attenuate the inflammatory response. Phenotypes which promote the inflammatory response are hypothesized to increase neuronal damage and impair recovery of neuronal function during the later phases of ischemic stroke. Therefore, modulating neuroimmune cells to adopt an anti-inflammatory response post ischemic stroke is an area of current research interest and potential treatment development. In this review, we outline the biology of microglia and monocyte-derived macrophages, further explain their roles in the acute, subacute, and chronic stages of ischemic stroke, and highlight current treatment development efforts which target these cells in the context of ischemic stroke.

Mapping the acute time course of immune cell infiltration into an ECM hydrogel in a rat model of stroke using 19F MRI

Extracellular matrix (ECM) hydrogel implantation into a stroke-induced tissue cavity invokes a robust cellular immune response. However, the spatio-temporal dynamics of immune cell infiltration into peri-infarct brain tissues versus the ECM-bioscaffold remain poorly understood. We here tagged peripheral immune cells using perfluorocarbon (PFC) nanoemulsions that afford their visualization by ¹⁹F magnetic resonance imaging (MRI). Prior to ECM hydrogel implantation, only blood vessels could be detected using ¹⁹F MRI. Using "time-lapse" ¹⁹F MRI, we established the infiltration of immune cells into the peri-infarct area occurs 5-6 h post-ECM implantation. Immune cells also infiltrated through the stump of the MCA, as well as a hydrogel bridge that formed between the tissue cavity and the burr hole in the skull. Tissue-based migration into the bioscaffold was observed between 9 and 12 h with a peak signal measured between 12 and 18 h post-implantation. Fluorescence-activated cell sorting of circulating immune cells revealed that 9% of cells were labeled with PFC nanoemulsions, of which the vast majority were neutrophils (40%) or monocytes (48%). Histology at 24 h post-implantation, in contrast, indicated that macrophages (35%) were more numerous in the peri-infarct area than neutrophils (11%), whereas the vast majority of immune cells within the ECM hydrogel were neutrophils (66%). Only a small fraction (12%) of immune cells did not contain PFC nanoemulsions, indicating a low type II error for ¹⁹F MRI. ¹⁹F MRI hence provides a unique tool to improve our understanding of the spatio-temporal dynamics of immune cells invading bioscaffolds and effecting biodegradation.

NogoA-expressing astrocytes limit peripheral macrophage infiltration after ischemic brain injury in primates

Astrocytes play critical roles after brain injury, but their precise function is poorly defined. Utilizing single-nuclei transcriptomics to characterize astrocytes after ischemic stroke in the visual cortex of the marmoset monkey, we observed nearly complete segregation between stroke and control astrocyte clusters. Screening for the top 30 differentially expressed genes that might limit stroke recovery, we discovered that a majority of astrocytes expressed RTN4A/ NogoA, a neurite-outgrowth inhibitory protein previously only associated with oligodendrocytes. NogoA upregulation on reactive astrocytes post-stroke was significant in both the marmoset and human brain, whereas only a marginal change was observed in mice. We determined that NogoA mediated an anti-inflammatory response which likely contributes to limiting the infiltration of peripheral macrophages into the surviving parenchyma.

CD163 as a Potential Biomarker of Monocyte Activation in Ischemic Stroke Patients

In ischemic stroke patients, a higher monocyte count is associated with disease severity and worse prognosis. The complex correlation between subset phenotypes and functions underscores the importance of clarifying the role of monocyte subpopulations. We examined the subtype-specific distribution of the CD163+ and CD80+ circulating monocytes and evaluated their association with the inflammatory status in 26 ischemic stroke patients and 16 healthy controls. An increased percentage of CD163+/CD16+ and CD163+/CD14++ events occurred 24 and 48 h after a stroke compared to the controls. CD163+ expression was more pronounced in CD16+ non-classical and intermediate monocytes, as compared to CD14+ classical subtype, 24 h after stroke. Conversely, the percentage of CD80+/CD16+ events was unaffected in patients; meanwhile, the percentage of CD80+/CD14+ events significantly increased only 24 h after stroke. Interleukin (IL)-1beta, TNF-alpha, and IL-4 mRNA levels were higher, while IL-10 mRNA levels were reduced in total monocytes from patients versus controls, at either 24 h or 48 h after stroke. The percentage of CD163+/CD16+ events 24 h after stroke was positively associated with NIHSS score and mRS at admission, suggesting that stroke severity and disability are relevant triggers for CD163+ expression in circulating CD16+ monocytes.

A comprehensive review of the therapeutic potential of curcumin nanoformulations

Today, due to the prevalence of various diseases such as the novel coronavirus (SARS-CoV-2), diabetes, central nervous system diseases, cancer, cardiovascular disorders, and so on, extensive studies have been conducted on therapeutic properties of natural and synthetic agents. A literature review on herbal medicine and commercial products in the global market showed that curcumin (Cur) has many therapeutic benefits compared to other natural ingredients. Despite the unique properties of Cur, its use in clinical trials is very limited. The poor biopharmaceutical properties of Cur such as short half-life in plasma, low bioavailability, poor absorption, rapid metabolism, very low solubility (at acidic and physiological pH), and the chemical instability in body fluids are major concerns associated with the clinical applications of Cur. Recently, nanoformulations are emerging as approaches to develop and improve the therapeutic efficacy of various drugs. Many studies have shown that Cur nanoformulations have tremendous therapeutic potential against various diseases such as SARS-CoV-2, cancer, inflammatory, osteoporosis, and so on. These nanoformulations can inhibit many diseases through several cellular and molecular mechanisms. However, successful long-term clinical results are required to confirm their safety and clinical efficacy. The present review aims to update and explain the therapeutic potential of Cur nanoformulations.

Characterization of CB2 Receptor Expression in Peripheral Blood Monocytes of Acute Ischemic Stroke Patients

Both preclinical and clinical evidence supports the involvement of the endocannabinoid system in the pathobiology of cerebral ischemia. Selective cannabinoid-2 (CB2) receptor agonists exert significant neuroprotection in animal models of focal brain ischemia through a robust anti-inflammatory effect, involving both resident and peripheral immune cells. Nevertheless, no definitive studies demonstrating the relevance of CB2 receptors in human stroke exist.Using rtPCR and flow cytometry assays, we investigated CB2 receptor expression in circulating monocytes from 26 acute ischemic stroke patients and 16 age-matched healthy controls (CT). We also evaluated miR-665 expression, as potential CB2 receptor regulator. The median mRNA levels of CB2 were significantly (p < 0.0001) increased in total monocytes 24 h and 48 h after stroke as compared with CT. This was paralleled by elevation of miR-665 levels in monocytes collected from patients 24 h (p < 0.05 vs CT) and 48 h (p < 0.05 vs CT and p < 0.0001 vs 24 h) after ischemic stroke. Furthermore, an increased percentage of CB2+/CD16+ events, but not CB2+/CD14+ events, was found 24 h [20.17% (IQR, 17.22-23.58)] and 48 h [18.61% (IQR, 15.44-22.06)] after ischemic stroke when compared with CT [10.96% (IQR, 9.185-13.32)]. The percentage of CB2+/CD16+ events in monocytes was positively correlated with NIHSS score at entrance (r = 0.4327, p = 0.027). The potential beneficial functions of CD16+ intermediate and nonclassical monocytes in stroke and the elevated expression of CB2 receptor in these subsets strongly suggest that CB2 receptor agonists can be exploited for the treatment of ischemic stroke patients.

Neurotheranostics as personalized medicines

The discipline of neurotheranostics was forged to improve diagnostic and therapeutic clinical outcomes for neurological disorders. Research was facilitated, in largest measure, by the creation of pharmacologically effective multimodal pharmaceutical formulations. Deployment of neurotheranostic agents could revolutionize staging and improve nervous system disease therapeutic outcomes. However, obstacles in formulation design, drug loading and payload delivery still remain. These will certainly be aided by multidisciplinary basic research and clinical teams with pharmacology, nanotechnology, neuroscience and pharmaceutic expertise. When successful the end results will provide "optimal" therapeutic delivery platforms. The current report reviews an extensive body of knowledge of the natural history, epidemiology, pathogenesis and therapeutics of neurologic disease with an eye on how, when and under what circumstances neurotheranostics will soon be used as personalized medicines for a broad range of neurodegenerative, neuroinflammatory and neuroinfectious diseases.

Subchronic and chronic toxicity evaluation of inorganic nanoparticles for delivery applications

Inorganic nanoparticles provide the opportunity to localize bioactive agents to the target sites and protect them from degradation. In many cases, acute toxicities of inorganic nanoparticles used for delivery applications have been investigated. However, little information is available regarding the long-term toxicity of such materials. This review focuses on the importance of subchronic and chronic toxicity assessment of inorganic nanoparticles investigated for delivery applications. We have attempted to provide a comprehensive review of the available literature for chronic toxicity assessment of inorganic nanoparticles. Where possible correlations are made between particle composition, physiochemical properties, duration, frequency and route of administration, as well as the sex of animals, with tissue and blood toxicity, immunotoxicity and genotoxicity. A critical gap analysis is provided and important factors that need to be considered for long-term toxicology of inorganic nanoparticles are discussed.

Resident Microglia Activate before Peripheral Monocyte Infiltration and p75NTR Blockade Reduces Microglial Activation and Early Brain Injury after Subarachnoid Hemorrhage

Early brain injury (EBI) after aneurysmal subarachnoid hemorrhage (SAH) contributes to high morbidity and mortality. Although it is well recognized that acute neuroinflammation reaction is one of the most important triggers of EBI, pharmacotherapy proved to be clinically effective against the initiating of neuroinflammation after SAH is lacking. The resident microglia and infiltrated peripheral monocyte are two main types of immune cells in central nervous system (CNS) and control the inflammation process in brain after SAH. But the time course and relative contributions of these two immune cell activations after SAH are unknown. The p75 neurotrophin receptor (p75NTR), member of TNF receptor superfamily, expresses on infiltrated peripheral monocytes and suppresses their proinflammatory action after brain insults. But the p75NTR expression on resident microglia in vivo is rarely explored and their function keeps elusive. Therefore, we designed this study to investigate the time course of resident microglia activation and peripheral monocyte infiltration, as well as the microglial expression of p75NTR by using CX3C-chemokine receptor 1 (Cx3cr1) and chemokine receptor 2 (Ccr2) double transgenic mice (Cx3cr1GFP/+Ccr2RFP/+) after SAH. The results showed activated microglia was observed in cortex as early as 24 h and further increased at 48 and 72 h post SAH, while the infiltrated monocyte was not found until 72h. In addition, activated microglia expressed p75NTR acutely and p75NTR specific antagonist TAT-Pep5 significantly reduced microglia activation, neuroinflammation and EBI from 24 to 72 h. Together, these data suggest that the early neuroinflammation reaction might be initiated and intensified mainly by resident microglia rather than infiltrated monocyte at least in the first 48 h after SAH and p75NTR blockading by TAT-Pep5P might alleviate EBI through mediating microglial activation.

Spatio-temporal profile, phenotypic diversity, and fate of recruited monocytes into the post-ischemic brain

Background

A key feature of the inflammatory response after cerebral ischemia is the brain infiltration of blood monocytes. There are two main monocyte subsets in the mouse blood: CCR2⁺Ly6C^hi “inflammatory” monocytes involved in acute inflammation, and CX3CR1⁺Ly6C^lo “patrolling” monocytes, which may play a role in repair processes. We hypothesized that CCR2⁺Ly6C^hi inflammatory monocytes are recruited in the early phase after ischemia and transdifferentiate into CX3CR1⁺Ly6C^lo “repair” macrophages in the brain.

Methods

CX3CR1^GFP/+CCR2^RFP/+ bone marrow (BM) chimeric mice underwent transient middle cerebral artery occlusion (MCAo). Mice were sacrificed from 1 to 28 days later to phenotype and map subsets of infiltrating monocytes/macrophages (Mo/MΦ) in the brain over time. Flow cytometry analysis 3 and 14 days after MCAo in CCR2^−/− mice, which exhibit deficient monocyte recruitment after inflammation, and NR4A1^−/− BM chimeric mice, which lack circulating CX3CR1⁺Ly6C^lo monocytes, was also performed.

Results

Brain mapping of CX3CR1^GFP/+ and CCR2^RFP/+ cells 3 days after MCAo showed absence of CX3CR1^GFP/+ Mo/MΦ but accumulation of CCR2^RFP/+ Mo/MΦ throughout the ischemic territory. On the other hand, CX3CR1⁺ cells accumulated 14 days after MCAo at the border of the infarct core where CCR2^RFP/+ accrued. Whereas the amoeboid morphology of CCR2^RFP/+ Mo/MΦ remained unchanged over time, CX3CR1^GFP/+ cells exhibited three distinct phenotypes: amoeboid cells with retracted processes, ramified cells, and perivascular elongated cells. CX3CR1^GFP/+ cells were positive for the Mo/MΦ marker Iba1 and phenotypically distinct from endothelial cells, smooth muscle cells, pericytes, neurons, astrocytes, or oligodendrocytes. Because accumulation of CX3CR1⁺Ly6C^lo Mo/MΦ was absent in the brains of CCR2 deficient mice, which exhibit deficiency in CCR2⁺Ly6C^hi Mo/MΦ recruitment, but not in NR4A1^−/− chimeric mice, which lack of circulating CX3CR1⁺Ly6C^lo monocytes, our data suggest a local transition of CCR2⁺Ly6C^hi Mo/MΦ into CX3CR1⁺Ly6C^lo Mo/MΦ phenotype.

Conclusions

CX3CR1⁺Ly6C^lo arise in the brain parenchyma from CCR2⁺Ly6C^hi Mo/MΦ rather than being de novo recruited from the blood. These findings provide new insights into the trafficking and phenotypic diversity of monocyte subtypes in the post-ischemic brain.

Electronic supplementary material

The online version of this article (doi:10.1186/s12974-016-0750-0) contains supplementary material, which is available to authorized users.

Tunable Lipidoid-Telodendrimer Hybrid Nanoparticles for Intracellular Protein Delivery in Brain Tumor Treatment

A strategy to precisely engineer lipidoid-telodendrimer binary hybrid nanoparticles that offer enhanced cell membrane permeability for therapeutic proteins to reach the intracellular targets is established. The highly controllable biochemical and physical properties of the nanoparticles make them promising for protein-based brain cancer treatment with the assistance of convection-enhanced delivery.

Pre-Labeling of Immune Cells in Normal Bone Marrow and Spleen for Subsequent Cell Tracking by MRI

Iron particles are intravenously (IV) administered to label cells in vivo during magnetic resonance imaging. This technique has been extensively used to monitor immune cells in the context of inflammatory diseases. Here, we have investigated whether resting immune cells can be labeled in vivo in healthy mice before disease onset or injury, thus allowing visualization of critical early cellular events. Using 1.5 T magnetic resonance imaging, we were able to detect signal loss in bone marrow, liver, and spleen as early as 1 hour after the IV injection of superparamagnetic iron oxide nanoparticles (Feridex; 80 to 120 nm in diameter) or larger micron-sized iron oxide particles (Bangs; 0.9 μm in diameter). Results were confirmed via histology. Further, flow cytometric analysis confirmed the presence of iron-labeled CD19⁺ B cells, CD3⁺ T cells, and CD11b⁺ myeloid cells within the spleen and the bone marrow. Extending this work to a murine model of multiple sclerosis, we IV administered superparamagnetic iron oxide to healthy mice 1 week before inducing experimental autoimmune encephalomyelitis. Images acquired 1 week after the onset of hindlimb paralysis showed regions of signal hypointensity in the mouse brain that corresponded with iron-labeled macrophages. In summary, we show that resting immune cells in the healthy mouse liver, spleen, and bone marrow can be prelabeled with iron oxide nanoparticles. Furthermore, iron oxide preloading of immune cells in the reticuloendothelial system can be used to detect cellular infiltration in the brains of experimental autoimmune encephalomyelitis mice.

Blood circulating microparticle species in relapsing-remitting and secondary progressive multiple sclerosis. A case-control, cross sectional study with conventional MRI and advanced iron content imaging outcomes

BACKGROUND

Although multiple sclerosis (MS) is thought to represent an excessive and inappropriate immune response to several central nervous system (CNS) autoantigens, increasing evidence also suggests that MS may also be a neurovascular inflammatory disease, characterized by endothelial activation and shedding of cell membrane microdomains known as 'microparticles' into the circulation.

OBJECTIVE

To investigate the relationships between these endothelial biomarkers and MS.

METHODS

We examined the relative abundance of CD31(+)/PECAM-1, CD51(+)CD61(+) (αV-β3) and CD54(+) (ICAM-1) bearing microparticles in sera of healthy individuals, patients with relapsing-remitting MS, and secondary-progressive MS. We also investigated the correlation among circulating levels of different microparticle species in MS with conventional MRI (T2- and T1-lesion volumes and brain atrophy), as well as novel MR modalities [assessment of iron content on susceptibility-weighted imaging (SWI)-filtered phase].

RESULTS

Differences in circulating microparticle levels were found among MS groups, and several microparticle species (CD31(+)/CD51(+)/CD61(+)/CD54(+)) were found to correlate with conventional MRI and SWI features of MS.

CONCLUSION

These results indicate that circulating microparticles' profiles in MS may support mechanistic roles for microvascular stress and injury which is an underlying contributor not only to MS initiation and progression, but also to pro-inflammatory responses.

Cell tracking technologies for acute ischemic brain injury

Stem cell therapy has showed considerable potential in the treatment of stroke over the last decade. In order that these therapies may be optimized, the relative benefits of growth factor release, immunomodulation, and direct tissue replacement by therapeutic stem cells are widely under investigation. Fundamental to the progress of this research are effective imaging techniques that enable cell tracking in vivo. Direct analysis of the benefit of cell therapy includes the study of cell migration, localization, division and/or differentiation, and survival. This review explores the various imaging tools currently used in clinics and laboratories, addressing image resolution, long-term cell monitoring, imaging agents/isotopes, as well as safety and costs associated with each technique. Finally, burgeoning tracking techniques are discussed, with emphasis on multimodal imaging.

Toll-like receptor-4 knockout mice are more resistant to optic nerve crush damage than wild-type mice

BACKGROUND

This study aims to investigate the role of the inflammatory response following optic nerve crush (ONC) in knockout mice for the toll-like receptor-4 gene (TLR4-/-) compared to wild-type (WT) mice.

METHODS

ONC was induced in TLR4-/- and C57BL6 WT mice. Histological sections of the retina and optic nerve were analysed on days 1, 3 or 21 after injury. Molecular analysis with real-time quantitative polymerase chain reaction was used to study the expression of CD45, tumour necrosis-alpha (TNF-α) and glial fibrillary acidic protein, as well as retinal ganglion cell (RGC) markers THY-1 and Brn3b.

RESULTS

There was a 25.5% and 38% loss in the RGC layer of the ONC-injured eyes of the TLR4-/- and the WT mice, respectively (with 27% and 9% of the remaining cells positive for Brn3a, respectively). Mean levels of Thy-1 and Brn3b were higher in the TLR4-/- mice. CD45 and Iba1 staining revealed infiltration of inflammatory cells into the injured nerve and retina in both groups. Molecular analysis of the optic nerve on day 1 showed increased TNF-α expression and reduced CD45 and GFAP expression; on day 3, CD45 reverted to baseline but GFAP remained low; on day 21, all 3 markers were at baseline in the TLR4-/- group and decreased in the WT group.

CONCLUSION

Inflammation plays a major role in the response to ONC injury. Reduced levels of inflammation are associated with improved RGC preservation. The increase in TNF-α and reduction in CD45 in both TLR4-/- and WT mice may indicate the presence of an alternative pathway for induction of RGC death.

Superparamagnetic iron oxide nanoparticles for in vivo molecular and cellular imaging

In the last decade, the biomedical applications of nanoparticles (NPs) (e.g. cell tracking, biosensing, magnetic resonance imaging (MRI), targeted drug delivery, and tissue engineering) have been increasingly developed. Among the various NP types, superparamagnetic iron oxide NPs (SPIONs) have attracted considerable attention for early detection of diseases due to their specific physicochemical properties and their molecular imaging capabilities. A comprehensive review is presented on the recent advances in the development of in vitro and in vivo SPION applications for molecular imaging, along with opportunities and challenges.

The HIF-1/glial TIM-3 axis controls inflammation-associated brain damage under hypoxia

Inflammation is closely related to the extent of damage following cerebral ischaemia, and the targeting of this inflammation has emerged as a promising therapeutic strategy. Here, we present that hypoxia-induced glial T-cell immunoglobulin and mucin domain protein (TIM)-3 can function as a modulator that links inflammation and subsequent brain damage after ischaemia. We find that TIM-3 is highly expressed in hypoxic brain regions of a mouse cerebral hypoxia-ischaemia (H/I) model. TIM-3 is distinctively upregulated in activated microglia and astrocytes, brain resident immune cells, in a hypoxia-inducible factor (HIF)-1-dependent manner. Notably, blockade of TIM-3 markedly reduces infarct size, neuronal cell death, oedema formation and neutrophil infiltration in H/I mice. Hypoxia-triggered neutrophil migration and infarction are also decreased in HIF-1α-deficient mice. Moreover, functional neurological deficits after H/I are significantly improved in both anti-TIM-3-treated mice and myeloid-specific HIF-1α-deficient mice. Further understanding of these insights could serve as the basis for broadening the therapeutic scope against hypoxia-associated brain diseases.

New findings about iron oxide nanoparticles and their different effects on murine primary brain cells

The physicochemical properties of superparamagnetic iron oxide nanoparticles (SPIOs) enable their application in the diagnostics and therapy of central nervous system diseases. However, since crucial information regarding side effects of particle–cell interactions within the central nervous system is still lacking, we investigated the influence of novel very small iron oxide particles or the clinically approved ferucarbotran or ferumoxytol on the vitality and morphology of brain cells. We exposed primary cell cultures of microglia and hippocampal neurons, as well as neuron–glia cocultures to varying concentrations of SPIOs for 6 and/or 24 hours, respectively. Here, we show that SPIO accumulation by microglia and subsequent morphological alterations strongly depend on the respective nanoparticle type. Microglial viability was severely compromised by high SPIO concentrations, except in the case of ferumoxytol. While ferumoxytol did not cause immediate microglial death, it induced severe morphological alterations and increased degeneration of primary neurons. Additionally, primary neurons clearly degenerated after very small iron oxide particle and ferucarbotran exposure. In neuron–glia cocultures, SPIOs rather stimulated the outgrowth of neuronal processes in a concentration- and particle-dependent manner. We conclude that the influence of SPIOs on brain cells not only depends on the particle type but also on the physiological system they are applied to.

Macrophage targeted theranostics as personalized nanomedicine strategies for inflammatory diseases

Inflammatory disease management poses challenges due to the complexity of inflammation and inherent patient variability, thereby necessitating patient-specific therapeutic interventions. Theranostics, which integrate therapeutic and imaging functionalities, can be used for simultaneous imaging and treatment of inflammatory diseases. Theranostics could facilitate assessment of safety, toxicity and real-time therapeutic efficacy leading to personalized treatment strategies. Macrophages are an important cellular component of inflammatory diseases, participating in varied roles of disease exacerbation and resolution. The inherent phagocytic nature, abundance and disease homing properties of macrophages can be targeted for imaging and therapeutic purposes. This review discusses the utility of theranostics in macrophage ablation, phenotype modulation and inhibition of their inflammatory activity leading to resolution of inflammation in several diseases.

Engineered nanoparticles. How brain friendly is this new guest?

In the last 30 years, the use of engineered nanoparticles (NPs) has progressively increased in many industrial and medical applications. In therapy, NPs may allow more effective cellular and subcellular targeting of drugs. In diagnostic applications, quantum dots are exploited for their optical characteristics, while superparamagnetic iron oxides NPs are used in magnetic resonance imaging. NPs are used in semiconductors, packaging, textiles, solar cells, batteries and plastic materials. Despite the great progress in nanotechnologies, comparatively little is known to date on the effects that exposure to NPs may have on the human body, in general and specifically on the brain. NPs can enter the human body through skin, digestive tract, airways and blood and they may cross the blood-brain barrier to reach the central nervous system. In addition to the paucity of studies describing NP effects on brain function, some of them also suffer of insufficient NPs characterization, inadequate standardization of conditions and lack of contaminant evaluation, so that results from different studies can hardly be compared. It has been shown in vitro and in vivo in rodents that NPs can impair dopaminergic and serotoninergic systems. Changes of neuronal morphology and neuronal death were reported in mice treated with NPs. NPs can also affect the respiratory chain of mitochondria and Bax protein levels, thereby causing apoptosis. Changes in expression of genes involved in redox pathways in mouse brain regions were described. NPs can induce autophagy, and accumulate in lysosomes impairing their degradation capacity. Cytoskeleton and vesicle trafficking may also be affected. NPs treated animals showed neuroinflammation with microglia activation, which could induce neurodegeneration. Considering the available data, it is important to design adequate models and experimental systems to evaluate in a reliable and controlled fashion the effects of NPs on the brain, and generate data representative of effects on the human brain, thereby useful for developing robust and valid nanosafety standards.

Magnetic resonance imaging of transplanted stem cell fate in stroke

Nowadays, scientific findings in the field of regeneration of nervous system have revealed the possibility of stem cell based therapies for damaged brain tissue related disorders like stroke. Furthermore, to achieve desirable outcomes from cellular therapies, one needs to monitor the migration, engraftment, viability, and also functional fate of transplanted stem cells. Magnetic resonance imaging is an extremely versatile technique for this purpose, which has been broadly used to study stroke and assessment of therapeutic role of stem cells. In this review we searched in PubMed search engine by using following keywords; "Stem Cells", "Cell Tracking", "Stroke", "Stem Cell Transplantation", "Nanoparticles", and "Magnetic Resonance Imaging" as entry terms and based on the mentioned key words, the search period was set from 1976 to 2012. The main purpose of this article is describing various advantages of molecular and magnetic resonance imaging of stem cells, with focus on translation of stem cell research to clinical research.

Type-1 interferons contribute to oxygen glucose deprivation induced neuro-inflammation in BE(2)M17 human neuroblastoma cells

BACKGROUND

Hypoxic-ischaemic injuries such as stroke and traumatic brain injury exhibit features of a distinct neuro-inflammatory response in the hours and days post-injury. Microglial activation, elevated pro-inflammatory cytokines and macrophage infiltration contribute to core tissue damage and contribute to secondary injury within a region termed the penumbra. Type-1 interferons (IFNs) are a super-family of pleiotropic cytokines that regulate pro-inflammatory gene transcription via the classical Jak/Stat pathway; however their role in hypoxia-ischaemia and central nervous system neuro-inflammation remains unknown. Using an in vitro approach, this study investigated the role of type-1 IFN signalling in an inflammatory setting induced by oxygen glucose deprivation (OGD).

METHODS

Human BE(2)M17 neuroblastoma cells or cells expressing a type-1 interferon-α receptor 1 (IFNAR1) shRNA or negative control shRNA knockdown construct were subjected to 4.5 h OGD and a time-course reperfusion period (0 to 24 h). Q-PCR was used to evaluate IFNα, IFNβ, IL-1β, IL-6 and TNF-α cytokine expression levels. Phosphorylation of signal transducers and activators of transcription (STAT)-1, STAT-3 and cleavage of caspase-3 was detected by western blot analysis. Post-OGD cellular viability was measured using a MTT assay.

RESULTS

Elevated IFNα and IFNβ expression was detected during reperfusion post-OGD in parental M17 cells. This correlated with enhanced phosphorylation of STAT-1, a downstream type-1 IFN signalling mediator. Significantly, ablation of type-1 IFN signalling, through IFNAR1 knockdown, reduced IFNα, IFNβ, IL-6 and TNF-α expression in response to OGD. In addition, MTT assay confirmed the IFNAR1 knockdown cells were protected against OGD compared to negative control cells with reduced pro-apoptotic cleaved caspase-3 levels.

CONCLUSIONS

This study confirms a role for type-1 IFN signalling in the neuro-inflammatory response following OGD in vitro and suggests its modulation through therapeutic blockade of IFNAR1 may be beneficial in reducing hypoxia-induced neuro-inflammation.

High-resolution MRI and nanoparticles: the future of brain imaging

ABSTRACT: Cellular MRI uses superparamagnetic iron oxide nanoparticles to label cells (in vitro or in vivo) for detection in magnetic resonance images. The infiltration of inflammatory macrophages can be visualized in brain diseases, such as multiple sclerosis, stroke and Alzheimer‘s disease, and correlates with disease severity and responses to treatments. Mesenchymal stromal cells, neural stem cells and immune cells used as cell therapies in CNS diseases can be tracked in vivo over time to determine their migration and dispersion. Tracking labeled cancer cells provides information about metastasis and proliferative status in preclinical tumor models. Ongoing technical improvements come from the development of new particles, the use of fluorine-based contrast agents and the refinement of high-field MRI for cell tracking.

Herbal medicines for ischemic stroke: combating inflammation as therapeutic targets

Stroke is a debilitating disease for which limited therapeutic approaches are available currently. Thus, there is an urgent need for developing novel therapies for stroke. Astrocytes, endothelial cells and pericytes constitute a neurovascular network for metabolic requirement of neurons. During ischemic stroke, these cells contribute to post-ischemic inflammation at multiple stages of ischemic cascades. Upon ischemia onset, activated resident microglia and astrocytes, and infiltrated immune cells release multiple inflammation factors including cytokines, chemokines, enzymes, free radicals and other small molecules, not only inducing brain damage but affecting brain repair. Recent progress indicates that anti-inflammation is an important therapeutic strategy for stroke. Given a long history with direct experience in the treatment of human subjects, Traditional Chinese Medicine and its related natural compounds are recognized as important sources for drug discovery. Last decade, a great progress has been made to identify active compounds from herbal medicines with the properties of modulating post-ischemic inflammation for neuroprotection. Herein, we discuss the inflammatory pathway in early stage and secondary response to injured tissues after stroke from initial artery occlusion to brain repair, and review the active ingredients from natural products with anti-inflammation and neuroprotection effects as therapeutic agents for ischemic stroke. Further studies on the post-ischemic inflammatory mechanisms and corresponding drug candidates from herbal medicine may lead to the development of novel therapeutic strategies in stroke treatment.

Activation of renal haeme oxygenase-1 alleviates gentamicin-induced acute nephrotoxicity in rats

Objectives

This study aimed to investigate whether activation of haeme oxygenase (HO)-1 enzyme by haemin would have beneficial effects on the functional and histological outcome against gentamicin-induced renal damage in rats and sought to elucidate the underlying mechanisms of the therapeutic action.

Methods

Nephrotoxicity was induced by injection of gentamicin (80 mg/kg, i.p.) once daily for seven days. Haemin (50 μmol/kg, i.p.) was given to the control and gentamicin-treated rats in the presence or absence of a HO-1 inhibitor, zinc protoporphyrin IX (ZnPP, 50 μmol/kg per day, i.p.).

Key findings

Haemin treatment prevented gentamicin-induced elevated serum creatinine, urinary protein levels and ameliorated the impaired creatinine clearance. Haemin compensated the deficits in antioxidant enzyme activity and attenuated lipid peroxidation along with decreased reactive oxygen species (ROS) production in renal tissues due to gentamicin. Moreover, haemin pre-administration evoked increased renal HO-1 activity. Additionally, haemin significantly attenuated elevated renal tumour necrosis factor-α (TNF-α), nuclear factor-kappaB (NF-κB) levels and caspase-3 activity alongside ameliorating glomerular pathology. These therapeutic effects were abolished by ZnPP pretreatment.

Conclusions

Here is the first evidence demonstrating the protective effect of HO-1 against gentamicin-associated nephrotoxicity. Suppression of oxidative/inflammatory insults alongside the corresponding decline of apoptosis were presumably responsible for this renoprotection.

Pivotal roles of monocytes/macrophages in stroke

Stroke is an important issue in public health due to its high rates both of morbidity and mortality, and high rate of disability. Hypertension, cardiovascular disease, arterial fibrillation, diabetes mellitus, smoking, and alcohol abuse are all risk factors for stroke. Clinical observations suggest that inflammation is also a direct risk factor for stroke. Patients with stroke have high levels of inflammatory cytokines in plasma, and immune cells, such as macrophages and T-lymphocytes, are noted within stroke lesions. These inflammatory events are considered as a result of stroke. However, recent studies show that plasma levels of inflammatory cytokines or soluble adhesion molecules are high in patients without stroke, and anti-inflammatory therapy is effective at reducing stroke incidence in not only animal models, but in humans as well. Statins have been shown to decrease the stroke incidence via anti-inflammatory effects that are both dependent and independent of their cholesterol-lowering effects. These reports suggest that inflammation might directly affect the onset of stroke. Microglial cells and blood-derived monocytes/macrophages play important roles in inflammation in both onset and aggravation of stroke lesions. We review the recent findings regarding the role of monocytes/macrophages in stroke.

Neuroinflammatory imaging biomarkers: relevance to multiple sclerosis and its therapy

Magnetic resonance imaging is an established tool in the management of multiple sclerosis (MS). Loss of blood brain barrier integrity assessed by gadolinium (Gd) enhancement is the current standard marker of MS activity. To explore the complex cascade of the inflammatory events, other magnetic resonance imaging, but also positron emission tomographic markers reviewed in this article are being developed to address active neuroinflammation with increased sensitivity and specificity. Alternative magnetic resonance contrast agents, positron emission tomographic tracers and imaging techniques could be more sensitive than Gd to early blood brain barrier alteration, and they could assess the inflammatory cell recruitment and/or the associated edema accumulation. These markers of active neuroinflammation, although some of them are limited to experimental studies, could find great relevance to complete Gd information and thereby increase our understanding of acute lesion pathophysiology and its noninvasive follow-up, especially to monitor treatment efficacy. Furthermore, such accurate markers of inflammation combined with those of neurodegeneration hold promise to provide a more complete picture of MS, which will be of great benefit for future therapeutic strategies.

ROCKs as immunomodulators of stroke

INTRODUCTION

Stroke is the third leading cause of death and a major cause of long-term disability in the adult population. Growing evidence suggests that inflammation may play an important role in the evolution of stroke. Because Rho-associated coiled-coil containing kinases (ROCKs) are important mediators of inflammation, they may contribute to stroke and stroke recovery.

AREAS COVERED

The pathophysiological role of ROCKs in mediating inflammation at different phases of stroke, and the therapeutic opportunities for stroke prevention and stroke treatment with ROCK inhibitors will be discussed.

EXPERT OPINION

Inflammation is a double-edged sword during the evolution of stroke. Immunomodulation might provide a novel therapeutic approach for stroke prevention and stroke treatment. ROCK plays an important role in mediating the inflammatory response following vascular injury as well as platelet activation and thrombus formation. ROCK inhibitors have been shown to be beneficial in stroke prevention, acute neuroprotection and chronic stroke recovery by affecting inflammatory-mediated platelet and endothelial function, smooth muscle contraction and neuronal regeneration. Thus, ROCK-mediated inflammation could be a potential therapeutic target for stroke prevention and stroke treatment. However, the mechanism by which ROCKs regulate the inflammatory response is unclear, and the role of the two ROCK isoforms in stroke and stroke recovery remains to be determined.

Therapeutics, imaging and toxicity of nanomaterials in the central nervous system

Treatment and diagnosis of neurodegenerative diseases and other CNS disorders are nowadays considered some of the most challenging tasks in modern medicine. The development of effective strategies for the prevention, diagnosis and treatment of CNS pathologies require better understanding of neurological disorders that is still lacking. The use of nanomaterials is thought to contribute to our further understanding of the CNS and the development of novel therapeutic and diagnostic modalities for neurological interventions. Even though the application of nanoparticles in neuroscience is still embryonic, this article attempts to illustrate the use of different types of nanomaterials and the way in which they have been used in various CNS applications in an attempt to limit or reverse neuropathological processes.

Cerebral microinfarcts: a systematic review of neuropathological studies

Vascular cognitive impairment is an umbrella term for cognitive dysfunction associated with and presumed to be caused by vascular brain damage. Autopsy studies have identified microinfarcts as an important neuropathological correlate of vascular cognitive impairment that escapes detection by conventional magnetic resonance imaging (MRI). As a frame of reference for future high-resolution MRI studies, we systematically reviewed the literature on neuropathological studies on cerebral microinfarcts in the context of vascular disease, vascular risk factors, cognitive decline and dementia. We identified 32 original patient studies involving 10,515 people. The overall picture is that microinfarcts are common, particularly in patients with vascular dementia (weighted average 62%), Alzheimer's disease (43%), and demented patients with both Alzheimer-type and cerebrovascular pathology (33%) compared with nondemented older individuals (24%). In many patients, multiple microinfarcts were detected. Microinfarcts are described as minute foci with neuronal loss, gliosis, pallor, or more cystic lesions. They are found in all brain regions, possibly more so in the cerebral cortex, particularly in watershed areas. Reported sizes vary from 50 μm to a few mm, which is within the detection limit of current high-resolution MRI. Detection of these lesions in vivo would have a high potential for future pathophysiological studies in vascular cognitive impairment.

Nanoparticles in the treatment and diagnosis of neurological disorders: untamed dragon with fire power to heal

The incidence of neurological diseases of unknown etiology is increasing, including well-studied diseases such as Alzhiemer's, Parkinson's, and multiple sclerosis. The blood-brain barrier provides protection for the brain but also hinders the treatment and diagnosis of these neurological diseases, because the drugs must cross the blood-brain barrier to reach the lesions. Thus, attention has turned to developing novel and effective delivery systems that are capable of carrying drug and that provide good bioavailability in the brain. Nanoneurotechnology, particularly application of nanoparticles in drug delivery, has provided promising answers to some of these issues in recent years. Here we review the recent advances in the understanding of several common forms of neurological diseases and particularly the applications of nanoparticles to treat and diagnose them. In addition, we discuss the integration of bioinformatics and modern genomic approaches in the development of nanoparticles.

FROM THE CLINICAL EDITOR

In this review paper, applications of nanotechnology-based diagnostic methods and therapeutic modalities are discussed addressing a variety of neurological disorders, with special attention to blood-brain barrier delivery methods. These novel nanomedicine approaches are expected to revolutionize several aspects of clinical neurology.

Neural injury following stroke: are Toll-like receptors the link between the immune system and the CNS?

The CNS can exhibit features of inflammation in response to injury, infection or disease, whereby resident cells generate inflammatory mediators, including cytokines, prostaglandins, free radicals and complement, chemokines and adhesion molecules that recruit immune cells, and activate glia and microglia. Cerebral ischaemia triggers acute inflammation, which exacerbates primary brain damage. The regulation of inflammation after stroke is multifaceted and comprises vascular effects, distinct cellular responses, apoptosis and chemotaxis. There are many cell types that are affected including neurons, astrocytes, microglia and endothelial cells, all responding to the resultant neuroinflammation in different ways. Over the past 20 years, researchers examining brain tissue at various time intervals after stroke observed the presence of inflammatory cells, neutrophils and monocytes at the site of injury, as well as the activation of endogenous glia and microglia. This review examines the involvement of these cells in the progression of neural injury and proposes that the Toll-like receptors (TLRs) are likely to be an integral component in the communication between the CNS and the periphery. This receptor system is the archetypal pathogen sensing receptor system and its presence and signalling in the brain following neural injury suggests a more diverse role. We propose that the TLR system presents excellent pharmacological targets for the design of a new generation of therapeutic agents to modulate the inflammation that accompanies neural injury.

Inflammation induced neurological handicap processes in multiple sclerosis: new insights from preclinical studies

Multiple sclerosis (MS) is described as originating from incompletely explained neuroinflammatory processes, dysfunction of neuronal repair mechanisms and chronicity of inflammation events. Blood-borne immune cell infiltration and microglia activation are causing both neuronal destruction and myelin loss, which are responsible for progressive motor deficiencies, organic and cognitive dysfunctions. MRI as a non-invasive imaging method offers various ways to visualise de- and remyelination, neuronal loss, leukocyte infiltration, blood-brain barrier modification and new sensors are emerging to detect inflammatory lesions at an early stage. We describe studies performed on experimental autoimmune encephalomyelitis (EAE) animal models of MS that shed new light on mechanisms of functional impairments to understand the neurological handicap in MS. We focus on examples of neuroinflammation-mediated inhibition of CNS repair involving adult neurogenesis in the sub-ventricular zone and hippocampus and such experimentally observed inhibitions could reflect deficient plasticity and activation of compensatory mechanisms in MS. In parallel with cognitive decline, organic deficits such as bladder dysfunction are described in most of MS patients. Neuropharmacological interventions, electrical stimulation of nerves, MRI and histopathology follow-up studies helped in understanding the operating events to remodel the neurological networks and to compensate the inflammatory lesions both in spinal cord and in cortical regions. At the molecular level, the local production of reactive products is a well-described phenomenon: oxidative species disturb cellular physiology and generate new molecular epitopes that could further promote immune reactions. The translational research from EAE animal models to MS patient cohorts helps in understanding the mechanisms of the neurological handicap and in development of new therapeutic concepts in MS.

Chapter 8 - Nanoparticles: Transport across the olfactory epithelium and application to the assessment of brain function in health and disease

The exciting advances within nanotechnology are beginning to be harnessed by the medical field. Nanoparticles have been used for drug delivery into the brain and have been explored for imaging, sensing, and analytical purposes. The science of nanoparticles encompasses a vast array of biological, chemical, physical, and engineering research, different aspects of which are specifically addressed in each of the chapters of this volume. Nanomaterials such as nanospheres, nanotubes, nanowires, fullerene derivatives (buckyballs), and quantum dots (Qdots) are at the forefront of scientific attention, as they provide new consumer products and advance the scientific development of novel analytical tools in medicine and in the physical sciences. This chapter will briefly survey some aspects of nanoparticle biology focusing on the following: (1) the role of olfactory nanoparticle transport into the central nervous system (CNS), both as a potential route for effective drug delivery and as a route for the passage of noxious substances into the brain proper; (2) nanoparticles as sensors of cell function and toxicity; and (3) some adverse effects of nanoparticles on the dysregulation of brain redox status.

Inflammatory mechanisms in ischemic stroke: role of inflammatory cells

Inflammation plays an important role in the pathogenesis of ischemic stroke and other forms of ischemic brain injury. Experimentally and clinically, the brain responds to ischemic injury with an acute and prolonged inflammatory process, characterized by rapid activation of resident cells (mainly microglia), production of proinflammatory mediators, and infiltration of various types of inflammatory cells (including neutrophils, different subtypes of T cells, monocyte/macrophages, and other cells) into the ischemic brain tissue. These cellular events collaboratively contribute to ischemic brain injury. Despite intense investigation, there are still numerous controversies concerning the time course of the recruitment of inflammatory cells in the brain and their pathogenic roles in ischemic brain injury. In this review, we provide an overview of the time-dependent recruitment of different inflammatory cells following focal cerebral I/R. We discuss how these cells contribute to ischemic brain injury and highlight certain recent findings and currently unanswered questions about inflammatory cells in the pathophysiology of ischemic stroke.

Nanoassembled capsules as delivery vehicles for large payloads of high relaxivity Gd3+ agents

Nanoassembled capsules (NACs) that incorporate a polymer aggregate inside a silica shell may be loaded with agents that are of particular interest for therapeutic or diagnostic applications. NACs formed using the MRI contrast agent GdDOTP(5-) in the internal polymer aggregate are reported herein, the smaller of which show promise as potential MRI contrast agents. Unlike many other nanoencapsulated systems, water access to the inner core of these NACs does not appear to be limited and consequently the water relaxivity per Gd(3+) agent can reach as high as 24 mM(-1) s(-1). Robust, spherical capsules were formed using polyallylamine or poly-L-lysine ranging from 0.2 to 5 microm in diameter. The greatest gains in relaxivity were observed for smaller NACs, for which water accessibility remained high but molecular rotation of the Gd(3+) chelate was effectively restricted. Larger NACs did not afford such large gains in relaxivity, the result of poorer water accessibility combined with less-effective rotational restriction.

Neurodegenerative disorders and nanoformulated drug development

Degenerative and inflammatory diseases of the CNS include, but are not limited to, Alzheimer's and Parkinson's disease, amyotrophic lateral sclerosis, stroke, multiple sclerosis and HIV-1-associated neurocognitive disorders. These are common, debilitating and, unfortunately, hold few therapeutic options. In recent years, the application of nanotechnologies as commonly used or developing medicines has served to improve pharmacokinetics and drug delivery specifically to CNS-diseased areas. In addition, nanomedical advances are leading to therapies that target CNS pathobiology and as such, can interrupt disordered protein aggregation, deliver functional neuroprotective proteins and alter the oxidant state of affected neural tissues. This article focuses on the pathobiology of common neurodegenerative disorders with a view towards how nanomedicine may be used to improve the clinical course of neurodegenerative disorders.

[Magnetic resonance imaging of central nervous system inflammation]

Magnetic resonance imaging (MRI) is widely used to explore central nervous system inflammatory disorders, especially multiple sclerosis (MS). Advanced MRI methods are bringing more sensitive and specific tools for each step of the inflammatory process. In this review, we discuss the different MRI approaches for inflammatory disorders exploration, especially MS. We give particular emphasize on sensibility and specificity of each MRI approach and we also discuss the current knowledge concerning biological and histopathological substratum that could explain MRI signal with each modality.

[Implication of the blood-brain barrier in neurological diseases: part II]

The main characteristic of the blood-brain-barrier (BBB) is its extremely low permeability, due to tight intercellular endothelial junctions and a variety of transporters, which provides the brain with a unique protection against the potential toxicity of several xenobiotics, but also constitutes a major limitation to drug delivery to the central nervous system. Several dysfunctions of the BBB have been recently implicated in the pathophysiology of neurological diseases: inflammatory, vascular, tumoral, infectious and neurodegenerative diseases. Based on a better knowledge of the BBB biology, new therapeutic strategies are emerging, which by-pass the BBB or take advantage of the selective expression of membrane proteins by brain endothelial cells or circulating leucocytes to target new drugs, such as the anti-VLA4 antibody recently approved for multiple sclerosis treatment. This review will focus on the recently described BBB dysfunctions presumably involved in various neurological diseases.

Early-stage investigations of ultrasmall superparamagnetic iron oxide-induced signal change after permanent middle cerebral artery occlusion in mice

BACKGROUND AND PURPOSE

MR signal changes after intravenous ultrasmall superparamagnetic iron oxide (USPIO) injection are related to inflammatory cells at the subacute stages after focal cerebral injury. However, at the early stages, the interpretation of USPIO-related MR signal alterations remains controversial. Here, we compared MR signal changes after intravenous USPIO injection with the histological iron and macrophage distribution during the first 24 hours in a rodent model of acute stroke.

METHODS

Multiparametric MRI at 7T and histological USPIO distribution were confronted from 6 to 24 hours after permanent middle cerebral artery occlusion in mice. Blood-brain barrier disruption was assessed using gadolinium MRI and immunoglobulin staining. Prussian blue staining was performed to depict the USPIO brain distribution. USPIO uptake by phagocytes was assessed by immunochemistry on brain tissue, peripheral blood cells, and monocyte cells derived from bone marrow culture.

RESULTS

After USPIO injection, 4 areas of early signal change were observed on every MRI. In all these areas, iron particles were mostly free whether detected in the vascular and cerebrospinal fluid compartments or in the interstitium. Within the first 24 hours, USPIO-loaded cells were not detected in the blood of injured mice or in cultured monocytic cells incubated with USPIO at plasmatic concentration.

CONCLUSIONS

These results suggest that, in this model, early reproducible USPIO-related MR signal changes are mainly caused by passive diffusion of free USPIO after blood-brain barrier leakage and by intravascular trapping rather than by peripheral phagocyte infiltration.

USPIO (Ferumoxtran-10)-enhanced MRI to visualize reticuloendothelial system cells in neonatal rats: feasibility and biodistribution study

PURPOSE

To investigate whether USPIO-enhanced magnetic resonance imaging (MRI) detected reticuloendothelial system (RES) cells in newborn normal rats.

MATERIALS AND METHODS

Newborn normal rats were imaged in vivo on a 1.5 T MR system, 2-96 hours after intraperitoneal Ferumoxtran-10 (n = 38) or saline injection (control group, n = 5). Signals from liver, spleen, and vertebral bone marrow were measured (T2-weighted Turbo Spin Echo) to describe the kinetics of enhancement. The pups were sacrificed and iron concentrations in plasma and peritoneal fluid were measured using atomic absorption spectrometry. Prussian blue-labeled cells density in liver, spleen, and vertebral bone marrow was assessed.

RESULTS

Significant (P < 0.05) negative enhancement of the liver, spleen, and vertebral bone marrow was noted after Ferumoxtran-10 injection (2-96 hours for liver and spleen, 4-96 hours for bone marrow). Ferumoxtran-10 was absorbed from the peritoneum in the first 8 hours postinjection, entering the circulation with a plasma peak (8 hours); then Ferumoxtran-10 returned over the baseline in plasma (96 hours). Important intracellular iron deposition in liver and spleen was measured postinjection (3-96 hours, P < 0.05). Limited but significant intracellular iron deposition was noted in vertebral bone marrow postinjection (96 hours, P < 0.05), suggesting that Ferumoxtran-10 selectively labeled RES cells after 96 hours and produced nonspecific labeling at earlier timepoints.

CONCLUSION

Ferumoxtran-10-enhanced MRI visualizes RES cells in vivo in newborn rats.

The blood-brain barrier in brain homeostasis and neurological diseases

Brain endothelial cells are unique among endothelial cells in that they express apical junctional complexes, including tight junctions, which quite resemble epithelial tight junctions both structurally and functionally. They form the blood-brain-barrier (BBB) which strictly controls the exchanges between the blood and the brain compartments by limiting passive diffusion of blood-borne solutes while actively transporting nutrients to the brain. Accumulating experimental and clinical evidence indicate that BBB dysfunctions are associated with a number of serious CNS diseases with important social impacts, such as multiple sclerosis, stroke, brain tumors, epilepsy or Alzheimer's disease. This review will focus on the implication of brain endothelial tight junctions in BBB architecture and physiology, will discuss the consequences of BBB dysfunction in these CNS diseases and will present some therapeutic strategies for drug delivery to the brain across the BBB.

Magnetic resonance imaging of neural circuits

A major goal of modern MRI research is to be able to image neural circuits in the central nervous system. Critical to this mission is the ability to describe a number of important parameters associated with neural circuits. These parameters include neural architecture, functional activation of neural circuits, anatomical and functional connectivity of neural circuits, and factors that might alter neural circuits, such as trafficking of immune cells and brain precursor cells in the brain. Remarkably, a variety of work in human and animal brains has demonstrated that all these features of neural circuits can be visualized with MRI. In this Article we provide a brief summary of the new directions in neural imaging research, which should prove useful in future analyses of normal and pathological human brains and in studies of animal models of neurological and psychiatric disorders. At present, few MRI data characterizing the neural circuits in the heart are available, but in this Article we discuss the applicable present developments and the prospects for the future.