Anti-inflammatory and anti-oxidant activity of anionic dendrimer-N-acetyl cysteine conjugates in activated microglial cells

The key roles of reactive oxygen species in microglial inflammatory activation: Regulation by endogenous antioxidant system and exogenous sulfur-containing compounds

Aberrant innate immunity in the brain has been implicated in the pathogenesis of several central nervous system (CNS) disorders, including Alzheimer's disease, Huntington's disease, Parkinson's disease, stroke, amyotrophic lateral sclerosis, and depression. Except for extraparenchymal CNS-associated macrophages, which predominantly afford protection against peripheral invading pathogens, it has been reported that microglia, a population of macrophage-like cells governing CNS immune defense in nearly all neurological diseases, are the main CNS resident immune cells. Although microglia have been recognized as the most important source of reactive oxygen species (ROS) in the CNS, ROS also may underlie microglial functions, especially M1 polarization, by modulating redox-sensitive signaling pathways. Recently, endogenous antioxidant systems, including glutathione, hydrogen sulfide, superoxide dismutase, and methionine sulfoxide reductase A, were found to be involved in regulating microglia-mediated neuroinflammation. A series of natural sulfur-containing compounds, including S-adenosyl methionine, S-methyl-L-cysteine, sulforaphane, DMS, and S-alk(enyl)-l-cysteine sulfoxide, modulating endogenous antioxidant systems have been discovered. We have summarized the current knowledge on the involvement of endogenous antioxidant systems in regulating microglial inflammatory activation and the effects of sulfur-containing compounds on endogenous antioxidant systems. Finally, we discuss the possibilities associated with compounds targeting the endogenous antioxidant system to treat neuroinflammation-associated diseases.

Targeted Microglial Attenuation through Dendrimer-Drug Conjugates Improves Glaucoma Neuroprotection

Retinal microglial/macrophage activation and optic nerve (ON) microglial/macrophage activation are glaucoma biomarkers and potential therapeutic targets for this blinding disease. We report targeting of activated microglia by PAMAM dendrimers in a rat glaucoma model and neuroprotection by N-acetylcysteine-conjugated dendrimer (D-NAC) conjugates in a post-injury rescue experiment. Intravitreally delivered fluorescently labeled dendrimer (D-Cy5) conjugates targeted and were retained in Iba-1-positive cells (90% at 7 days and 55% after 28 days) in the retina following intraocular pressure (IOP) elevation, while systemically delivered D-Cy5 targeted ON cells. A single intravitreal D-NAC dose given 1 week after IOP elevation significantly reduced transcription of pro-inflammatory (IL-6, MCP-1, IL-1β) and A1 astrocyte (Serping1, Fkbp5, Amigo2) markers and increased survival of retinal ganglion cells (39 ± 12%) versus BSS- (20 ± 15%, p = 0.02) and free NAC-treated (26 ± 14%, p = 0.15) eyes. These results highlight the potential of dendrimer-targeted microglia and macrophages for early glaucoma detection and as a neuroprotective therapeutic target.

Dendrimers in Alzheimer’s Disease: Recent Approaches in Multi-Targeting Strategies

Nanomaterials play an increasingly important role in current medicinal practice. As one of the most significant causes of human mortality, and one that is increasing year by year, Alzheimer’s disease (AD) has been the subject of a very great body of research and is an area in which nanomedicinal approaches show great promise. Dendrimers are a class of multivalent nanomaterials which can accommodate a wide range of modifications that enable them to be used as drug delivery systems. By means of suitable design, they can incorporate multiple functionalities to enable transport across the blood–brain barrier and subsequently target the diseased areas of the brain. In addition, a number of dendrimers by themselves often display therapeutic potential for AD. In this review, the various hypotheses relating to the development of AD and the proposed therapeutic interventions involving dendrimer–base systems are outlined. Special attention is focused on more recent results and on the importance of aspects such as oxidative stress, neuroinflammation and mitochondrial dysfunction in approaches to the design of new treatments.

Azithromycin Protects Retinal Glia Against Oxidative Stress-Induced Morphological Changes, Inflammation, and Cell Death

The reactivity of retinal glia in response to oxidative stress has a significant effect on retinal pathobiology. The reactive glia change their morphology and secret cytokines and neurotoxic factors in response to oxidative stress associated with retinal neurovascular degeneration. Therefore, pharmacological intervention to protect glial health against oxidative stress is crucial for maintaining homeostasis and the normal function of the retina. In this study, we explored the effect of azithromycin, a macrolide antibiotic with antioxidant, immunomodulatory, anti-inflammatory, and neuroprotective properties against oxidative stress-induced morphological changes, inflammation, and cell death in retinal microglia and Müller glia. Oxidative stress was induced by H₂O₂, and the intracellular oxidative stress was measured by DCFDA and DHE staining. The change in morphological characteristics such as the surface area, perimeter, and circularity was calculated using ImageJ software. Inflammation was measured by enzyme-linked immunosorbent assays for TNF-α, IL-1β, and IL-6. Reactive gliosis was characterized by anti-GFAP immunostaining. Cell death was measured by MTT assay, acridine orange/propidium iodide, and trypan blue staining. Pretreatment of azithromycin inhibits H₂O₂-induced oxidative stress in microglial (BV-2) and Müller glial (MIO-M1) cells. We observed that azithromycin inhibits oxidative stress-induced morphological changes, including the cell surface area, circularity, and perimeter in BV-2 and MIO-M1 cells. It also inhibits inflammation and cell death in both the glial cells. Azithromycin could be used as a pharmacological intervention on maintaining retinal glial health during oxidative stress.

Linking Inflammation, Aberrant Glutamate-Dopamine Interaction, and Post-synaptic Changes: Translational Relevance for Schizophrenia and Antipsychotic Treatment: a Systematic Review

Evidence from clinical, preclinical, and post-mortem studies supports the inflammatory/immune hypothesis of schizophrenia pathogenesis. Less evident is the link between the inflammatory background and two well-recognized functional and structural findings of schizophrenia pathophysiology: the dopamine-glutamate aberrant interaction and the alteration of dendritic spines architecture, both believed to be the “quantal” elements of cortical-subcortical dysfunctional network. In this systematic review, we tried to capture the major findings linking inflammation, aberrant glutamate-dopamine interaction, and post-synaptic changes under a direct and inverse translational perspective, a paramount picture that at present is lacking. The inflammatory effects on dopaminergic function appear to be bidirectional: the inflammation influences dopamine release, and dopamine acts as a regulator of discrete inflammatory processes involved in schizophrenia such as dysregulated interleukin and kynurenine pathways. Furthermore, the link between inflammation and glutamate is strongly supported by clinical studies aimed at exploring overactive microglia in schizophrenia patients and maternal immune activation models, indicating impaired glutamate regulation and reduced N-methyl-D-aspartate receptor (NMDAR) function. In addition, an inflammatory/immune-induced alteration of post-synaptic density scaffold proteins, crucial for downstream NMDAR signaling and synaptic efficacy, has been demonstrated. According to these findings, a significant increase in plasma inflammatory markers has been found in schizophrenia patients compared to healthy controls, associated with reduced cortical integrity and functional connectivity, relevant to the cognitive deficit of schizophrenia. Finally, the link between altered inflammatory/immune responses raises relevant questions regarding potential new therapeutic strategies specifically for those forms of schizophrenia that are resistant to canonical antipsychotics or unresponsive to clozapine.

Dendrimer-2PMPA selectively blocks upregulated microglial GCPII activity and improves cognition in a mouse model of multiple sclerosis

Cognitive impairment is a common aspect of multiple sclerosis (MS) for which there are no treatments. Reduced brain N-acetylaspartylglutamate (NAAG) levels are linked to impaired cognition in various neurological diseases, including MS. NAAG levels are regulated by glutamate carboxypeptidase II (GCPII), which hydrolyzes the neuropeptide to N-acetyl-aspartate and glutamate. GCPII activity is upregulated multifold in microglia following neuroinflammation. Although several GCPII inhibitors, such as 2-PMPA, elevate brain NAAG levels and restore cognitive function in preclinical studies when given at high systemic doses or via direct brain injection, none are clinically available due to poor bioavailability and limited brain penetration. Hydroxyl-dendrimers have been successfully used to selectively deliver drugs to activated glia.

Methods: We attached 2-PMPA to hydroxyl polyamidoamine (PAMAM) dendrimers (D-2PMPA) using a click chemistry approach. Cy5-labelled-D-2PMPA was used to visualize selective glial uptake in vitro and in vivo. D-2PMPA was evaluated for anti-inflammatory effects in LPS-treated glial cultures. In experimental autoimmune encephalomyelitis (EAE)-immunized mice, D-2PMPA was dosed biweekly starting at disease onset and cognition was assessed using the Barnes maze, and GCPII activity was measured in CD11b+ hippocampal cells.

Results: D-2PMPA showed preferential uptake into microglia and robust anti-inflammatory activity, including elevations in NAAG, TGFβ, and mGluR3 in glial cultures. D-2PMPA significantly improved cognition in EAE mice, even though physical severity was unaffected. GCPII activity increased >20-fold in CD11b+ cells from EAE mice, which was significantly mitigated by D-2PMPA treatment.

Conclusions: Hydroxyl dendrimers facilitate targeted drug delivery to activated microglia. These data support further development of D-2PMPA to attenuate elevated microglial GCPII activity and treat cognitive impairment in MS.

N-Acetylcysteine Reverses Monocrotophos Exposure-Induced Hepatic Oxidative Damage via Mitigating Apoptosis, Inflammation and Structural Changes in Rats

Oxidative stress-mediated tissue damage is primarily involved in hepatic injuries and dysfunctioning. Natural antioxidants have been shown to exert hepatoprotective, anti-inflammatory and antiapoptotic properties. The present study evaluated the effect of N-acetylcysteine (NAC) against monocrotophos (MCP) exposure-induced toxicity in the rat liver. Albino Wistar rats were divided into four groups: (1) control, (2) NAC-treated, (3) MCP-exposure, (4) NAC and MCP-coexposure group. The dose of MCP (0.9 mg/kg b.wt) and NAC (200 mg/kg b.wt) were administered orally for 28 days. Exposure to MCP caused a significant increase in lipid peroxidation, protein oxidation and decreased glutathione content along with the depletion of antioxidant enzyme activities. Further MCP exposure increased pro-inflammatory cytokines levels and upregulated Bax and Caspase-3 expressions. MCP exposure also caused an array of structural alternations in liver tissue, as depicted by the histological and electron microscopic analysis. Thepretreatment of NAC improved glutathione content, restored antioxidant enzyme activities, prevented oxidation of lipids and proteins, decreased pro-inflammatory cytokines levels and normalized apoptotic protein expression. Treatment of NAC also prevented histological and ultrastructural alternations. Thus, the study represents the therapeutic efficacy and antioxidant potential of NAC against MCP exposure in the rat liver.

A non-invasive nanoparticle-based sustained dual-drug delivery system as an eyedrop for endophthalmitis

Endophthalmitis is an infectious disease that affects the entire eye spreading to the internal retinal layers and the vitreous and causes severe sight-threatening conditions. Current treatment strategies rely on intraocular injections of antibiotics that are invasive, may lead to procedural complications and, ultimately, blindness. In this study, we developed a non-invasive strategy as an eyedrop containing nanoparticle-based dual-drug delivery system in which the hydrophobic poly-L-lactide core was loaded with azithromycin or triamcinolone acetonide, and the hydrophilic shell was made of chitosan. The developed nanoparticles were ~200-250 nm in size, spherical in shape, moderately hydrophilic, lysozyme tolerant, cytocompatible, and hemocompatible. Application of these chitosan-coated nanoparticles as eye drops to C57BL/6 mice showed higher bioavailability in choroid and retina when compared to the uncoated nanoparticles. The delivery system showed sustained release of drug for 300 h and exhibited antimicrobial effects against Gram-positive and Gram-negative bacteria and anti-inflammatory effects on activated microglial cells. Interestingly, the combination of the nanoparticles loaded with azithromycin and the nanoparticles loaded with triamcinolone acetonide acted synergistically as compared to either of the nanoparticles/drugs alone. Overall, the developed dual-drug delivery system is non-invasive, has antimicrobial and anti-inflammatory effects, and shows potential as an eye drop formulation against endophthalmitis.

Fetal Neuroprotective Strategies: Therapeutic Agents and Their Underlying Synaptic Pathways

Synaptic signaling is integral for proper brain function. During fetal development, exposure to inflammation or mild hypoxic-ischemic insult may lead to synaptic changes and neurological damage that impairs future brain function. Preterm neonates are most susceptible to these deleterious outcomes. Evaluating clinically used and novel fetal neuroprotective measures is essential for expanding treatment options to mitigate the short and long-term consequences of fetal brain injury. Magnesium sulfate is a clinical fetal neuroprotective agent utilized in cases of imminent preterm birth. By blocking N-methyl-D-aspartate receptors, magnesium sulfate reduces glutamatergic signaling, which alters calcium influx, leading to a decrease in excitotoxicity. Emerging evidence suggests that melatonin and N-acetyl-L-cysteine (NAC) may also serve as novel putative fetal neuroprotective candidates. Melatonin has important anti-inflammatory and antioxidant properties and is a known mediator of synaptic plasticity and neuronal generation. While NAC acts as an antioxidant and a precursor to glutathione, it also modulates the glutamate system. Glutamate excitotoxicity and dysregulation can induce perinatal preterm brain injury through damage to maturing oligodendrocytes and neurons. The improved drug efficacy and delivery of the dendrimer-bound NAC conjugate provides an opportunity for enhanced pharmacological intervention. Here, we review recent literature on the synaptic pathways underlying these therapeutic strategies, discuss the current gaps in knowledge, and propose future directions for the field of fetal neuroprotective agents.

Nanoparticles: A Hope for the Treatment of Inflammation in CNS

Neuroinflammation, an inflammatory response within the central nervous system (CNS), is a main hallmark of common neurodegenerative diseases, including Alzheimer’s disease (AD), Parkinson’s disease (PD), and amyotrophic lateral sclerosis (ALS), among others. The over-activated microglia release pro-inflammatory cytokines, which induces neuronal death and accelerates neurodegeneration. Therefore, inhibition of microglia over-activation and microglia-mediated neuroinflammation has been a promising strategy for the treatment of neurodegenerative diseases. Many drugs have shown promising therapeutic effects on microglia and inflammation. However, the blood–brain barrier (BBB)—a natural barrier preventing brain tissue from contact with harmful plasma components—seriously hinders drug delivery to the microglial cells in CNS. As an emerging useful therapeutic tool in CNS-related diseases, nanoparticles (NPs) have been widely applied in biomedical fields for use in diagnosis, biosensing and drug delivery. Recently, many NPs have been reported to be useful vehicles for anti-inflammatory drugs across the BBB to inhibit the over-activation of microglia and neuroinflammation. Therefore, NPs with good biodegradability and biocompatibility have the potential to be developed as an effective and minimally invasive carrier to help other drugs cross the BBB or as a therapeutic agent for the treatment of neuroinflammation-mediated neurodegenerative diseases. In this review, we summarized various nanoparticles applied in CNS, and their mechanisms and effects in the modulation of inflammation responses in neurodegenerative diseases, providing insights and suggestions for the use of NPs in the treatment of neuroinflammation-related neurodegenerative diseases.

The Role of Natural Compounds and their Nanocarriers in the Treatment of CNS Inflammation

Neuroinflammation, which is involved in various inflammatory cascades in nervous tissues, can result in persistent and chronic apoptotic neuronal cell death and programmed cell death, triggering various degenerative disorders of the central nervous system (CNS). The neuroprotective effects of natural compounds against neuroinflammation are mainly mediated by their antioxidant, anti-inflammatory, and antiapoptotic properties that specifically promote or inhibit various molecular signal transduction pathways. However, natural compounds have several limitations, such as their pharmacokinetic properties and stability, which hinder their clinical development and use as medicines. This review discusses the molecular mechanisms of neuroinflammation and degenerative diseases of CNS. In addition, it emphasizes potential natural compounds and their promising nanocarriers for overcoming their limitations in the treatment of neuroinflammation. Moreover, recent promising CNS inflammation-targeted nanocarrier systems implementing lesion site-specific active targeting strategies for CNS inflammation are also discussed.

Let's get small (and smaller): Combining zebrafish and nanomedicine to advance neuroregenerative therapeutics

Several key attributes of zebrafish make them an ideal model system for the discovery and development of regeneration promoting therapeutics; most notably their robust capacity for self-repair which extends to the central nervous system. Further, by enabling large-scale drug discovery directly in living vertebrate disease models, zebrafish circumvent critical bottlenecks which have driven drug development costs up. This review summarizes currently available zebrafish phenotypic screening platforms, HTS-ready neurodegenerative disease modeling strategies, zebrafish small molecule screens which have succeeded in identifying regeneration promoting compounds and explores how intravital imaging in zebrafish can facilitate comprehensive analysis of nanocarrier biodistribution and pharmacokinetics. Finally, we discuss the benefits and challenges attending the combination of zebrafish and nanoparticle-based drug optimization, highlighting inspiring proof-of-concept studies and looking toward implementation across the drug development community.

Nanoparticles and neurotoxicity: Dual response of glutamatergic receptors

Although the use of nanoparticles for neuro-diagnostic and neurotherapeutic purposes provides superior benefits than the conventional approaches, it may be potentially toxic in central nervous system. In this respect, nanotechnological research focuses on nanoneurotoxicity-nanoneurosafety concepts. Despite these efforts, nanoparticles (NPs) may cause neurotoxicity, neuroinflammation, and neurodegeneration by penetrating the brain-olfactory route and blood-brain barrier (BBB). Indeed, due to their unique structures nanomaterials can easily cross biological barriers, thus avoid drug delivery problems. Despite the advancement of nanotechnology for designing therapeutic agents, toxicity of these nanomaterials is still a concern. Activation of neurons by astrocytic glutamate is a result of NPs-mediated astrocyte-neuron crosstalk. Increased extracellular glutamate levels due to enhanced synthesis and reduced reuptake may induce neuronal damage by abnormal activation of extrasynaptic N-methyl d-aspartate receptor (NMDAR) subunits. NMDAR is the key factor that mediates the disturbances in intracellular calcium homeostasis, mitochondrial dysfunction and generation of reactive oxygen species in NPs exposed neurons. While some NPs cause neuronal death by inducing NMDARs, others may be neurotoxic through the alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors or protect the neurons via blocking NMDARs. However, mechanisms of dual effects of NPs, neurotoxicity or neuroprotection are not precisely known. Some NPs present neuroprotective effect either by selectively inhibiting extrasynaptic subunit of NMDARs or by attenuating oxidative stress. NPs-related proinflammatory activation of microglia contributes to the dysfunction and cytotoxicity in neurons. Therefore, investigation of the interaction of NPs with the neuronal signaling molecules and neuronal receptors is necessary for the better understanding of the neurotoxicity or neurosafety of nanomaterials.

Development of near-infrared region luminescent N-acetyl-L-cysteine-coated Ag2S quantum dots with differential therapeutic effect

AIM

N-acetyl-L-cysteine (NAC) is a free radical scavenger. We developed NAC-coated Ag₂S (NAC-Ag₂S) quantum dot (QD) as an optical imaging and therapeutic agent.

MATERIALS & METHODS

QDs were synthesized in water. Their optical imaging potential and toxicity were studied in vitro.

RESULTS

NAC-Ag₂S QDs have strong emission, that is tunable between 748 and 840 nm, and are stable in biologically relevant media. QDs showed significant differences both in cell internalization and toxicity in vitro. QDs were quite toxic to breast and cervical cancer cells but not to lung derived cells despite the higher uptake. NAC-Ag₂S reduces reactive oxygen species (ROS) but causes cell death via DNA damage and apoptosis.

CONCLUSION

NAC-Ag₂S QDs are stable and strong signal-generating theranostic agents offering selective therapeutic effects.

Improvement of N-Acetylcysteine Loaded in PLGA Nanoparticles by Nanoprecipitation Method

N-Acetylcysteine (NAC) is a hydrophilic compound with a low bioavailability. It has been used as an effective antioxidant agent. This research seeks to enhance the entrapment of NAC in PLGA nanoparticles for drug delivery systems. The nanoparticles were made using the nanoprecipitation method and changing the following parameters: the solvent/nonsolvent nature, its viscosity, pH, NAC addition to the nonsolvent, the polymer concentration and molecular weight, and NAC concentration in the solvent. The results showed that an increase in the nonsolvent viscosity produces NAC concentration in the solvent, and the nonsolvent rises its entrapment in the nanoparticles. Nanoparticles with 235.5 ± 11.4 nm size with an entrapment efficiency of 0.4 ± 0.04% and a specific load of 3.14 ± 0.33% were obtained. The results suggest that besides efficiently entrapping hydrophobic compounds, the nanoprecipitation method also has a high potential as an alternative entrapment method for hydrophilic compounds as well. However, its use in the pharmaceutical industry, as a proper specific load vehicle, still depends on the improvement of the load capacity.

Scalable synthesis and validation of PAMAM dendrimer-N-acetyl cysteine conjugate for potential translation

Dendrimer-N-acetyl cysteine (D-NAC) conjugate has shown significant promise in multiple preclinical models of brain injury and is undergoing clinical translation. D-NAC is a generation-4 hydroxyl-polyamidoamine dendrimer conjugate where N-acetyl cysteine (NAC) is covalently bound through disulfide linkages on the surface of the dendrimer. It has shown remarkable potential to selectively target and deliver NAC to activated microglia and astrocytes at the site of brain injury in several animal models, producing remarkable improvements in neurological outcomes at a fraction of the free drug dose. Here we present a highly efficient, scalable, greener, well-defined route to the synthesis of D-NAC, and validate the structure, stability and activity to define the benchmarks for this compound. This newly developed synthetic route has significantly reduced the synthesis time from three weeks to one week, uses industry-friendly solvents/reagents, and involves simple purification procedures, potentially enabling efficient scale up.

Preferential and Increased Uptake of Hydroxyl-Terminated PAMAM Dendrimers by Activated Microglia in Rabbit Brain Mixed Glial Culture

Polyamidoamine (PAMAM) dendrimers are multifunctional nanoparticles with tunable physicochemical features, making them promising candidates for targeted drug delivery in the central nervous system (CNS). Systemically administered dendrimers have been shown to localize in activated glial cells, which mediate neuroinflammation in the CNS. These dendrimers delivered drugs specifically to activated microglia, producing significant neurological improvements in multiple brain injury models, including in a neonatal rabbit model of cerebral palsy. To gain further insight into the mechanism of dendrimer cell uptake, we utilized an in vitro model of primary glial cells isolated from newborn rabbits to assess the differences in hydroxyl-terminated generation 4 PAMAM dendrimer (D4-OH) uptake by activated and non-activated glial cells. We used fluorescently-labelled D4-OH (D-Cy5) as a tool for investigating the mechanism of dendrimer uptake. D4-OH PAMAM dendrimer uptake was determined by fluorescence quantification using confocal microscopy and flow cytometry. Our results indicate that although microglial cells in the mixed cell population demonstrate early uptake of dendrimers in this in vitro system, activated microglia take up more dendrimer compared to resting microglia. Astrocytes showed delayed and limited uptake. We also illustrated the differences in mechanism of uptake between resting and activated microglia using different pathway inhibitors. Both resting and activated microglia primarily employed endocytotic pathways, which are enhanced in activated microglial cells. Additionally, we demonstrated that hydroxyl terminated dendrimers are taken up by primary microglia using other mechanisms including pinocytosis, caveolae, and aquaporin channels for dendrimer uptake.

Dendrimer-mediated delivery of N-acetyl cysteine to microglia in a mouse model of Rett syndrome

Background

Rett syndrome (RTT) is a pervasive developmental disorder that is progressive and has no effective cure. Immune dysregulation, oxidative stress, and excess glutamate in the brain mediated by glial dysfunction have been implicated in the pathogenesis and worsening of symptoms of RTT. In this study, we investigated a new nanotherapeutic approach to target glia for attenuation of brain inflammation/injury both in vitro and in vivo using a Mecp2-null mouse model of Rett syndrome.

Methods

To determine whether inflammation and immune dysregulation were potential targets for dendrimer-based therapeutics in RTT, we assessed the immune response of primary glial cells from Mecp2-null and wild-type (WT) mice to LPS. Using dendrimers that intrinsically target activated microglia and astrocytes, we studied N-acetyl cysteine (NAC) and dendrimer-conjugated N-acetyl cysteine (D-NAC) effects on inflammatory cytokines by PCR and multiplex assay in WT vs Mecp2-null glia. Since the cysteine-glutamate antiporter (Xc⁻) is upregulated in Mecp2-null glia when compared to WT, the role of Xc⁻ in the uptake of NAC and l-cysteine into the cell was compared to that of D-NAC using BV2 cells in vitro. We then assessed the ability of D-NAC given systemically twice weekly to Mecp2-null mice to improve behavioral phenotype and lifespan.

Results

We demonstrated that the mixed glia derived from Mecp2-null mice have an exaggerated inflammatory and oxidative stress response to LPS stimulation when compared to WT glia. Expression of Xc⁻ was significantly upregulated in the Mecp2-null glia when compared to WT and was further increased in the presence of LPS stimulation. Unlike NAC, D-NAC bypasses the Xc⁻ for cell uptake, increasing intracellular GSH levels while preventing extracellular glutamate release and excitotoxicity. Systemically administered dendrimers were localized in microglia in Mecp2-null mice, but not in age-matched WT littermates. Treatment with D-NAC significantly improved behavioral outcomes in Mecp2-null mice, but not survival.

Conclusions

These results suggest that delivery of drugs using dendrimer nanodevices offers a potential strategy for targeting glia and modulating oxidative stress and immune responses in RTT.

Electronic supplementary material

The online version of this article (10.1186/s12974-017-1004-5) contains supplementary material, which is available to authorized users.

Post-Operative Cognitive Dysfunction: An exploration of the inflammatory hypothesis and novel therapies

Post-Operative Cognitive Dysfunction (POCD) is a highly prevalent condition with significant clinical, social and financial impacts for patients and their communities. The underlying pathophysiology is becoming increasingly understood, with the role of neuroinflammation and oxidative stress secondary to surgery and anaesthesia strongly implicated. This review aims to describe the putative mechanisms by which surgery-induced inflammation produces cognitive sequelae, with a focus on identifying potential novel therapies based upon their ability to modify these pathways.

Activated Microglia Targeting Dendrimer-Minocycline Conjugate as Therapeutics for Neuroinflammation

Brain-related disorders have outmatched cancer and cardiovascular diseases worldwide as the leading cause of morbidity and mortality. The lack of effective therapies and the relatively dry central nervous system (CNS) drug pipeline pose formidable challenge. Superior, targeted delivery of current clinically approved drugs may offer significant potential. Minocycline has shown promise for the treatment of neurological diseases owing to its ability to penetrate the blood-brain barrier (BBB) and potency. Despite its potential in the clinic and in preclinical models, the high doses needed to affect a positive therapeutic response have led to side effects. Targeted delivery of minocycline to the injured site and injured cells in the brain can be highly beneficial. Systemically administered hydroxyl poly(amidoamine) (PAMAM) generation-6 (G6) dendrimers have a longer blood circulation time and have been shown to cross the impaired BBB. We have successfully prepared and characterized the in vitro efficacy and in vivo targeting ability of hydroxyl-G6 PAMAM dendrimer-9-amino-minocycline conjugate (D-mino). Minocycline is a challenging drug to carry out chemical transformations due to its inherent instability. We used a combination of a highly efficient and mild copper catalyzed azide-alkyne click reaction (CuAAC) along with microwave energy to conjugate 9-amino-minocycline (mino) to the dendrimer surface via enzyme responsive linkages. D-mino was further evaluated for anti-inflammatory and antioxidant activity in lipopolysaccharides-activated murine microglial cells. D-mino conjugates enhanced the intracellular availability of the drug due to their rapid uptake, suppressed inflammatory cytokine tumor necrosis factor α (TNF-α) production, and reduced oxidative stress by suppressing nitric oxide production, all significantly better than the free drug. Fluorescently labeled dendrimer conjugate (Cy5-D-mino) was systematically administered (intravenous, 55 mg/kg) on postnatal day 1 to rabbit kits with a clinically relevant phenotype of cerebral palsy. The in vivo imaging study indicates that Cy5-D-mino crossed the impaired blood-brain barrier and co-localized with activated microglia at the periventricular white matter areas, including the corpus callosum and the angle of the lateral ventricle, with significant implications for positive therapeutic outcomes. The enhanced efficacy of D-mino, when combined with the inherent neuroinflammation-targeting capability of the PAMAM dendrimers, may provide new opportunities for targeted drug delivery to treat neurological disorders.

Maternal dendrimer-based therapy for inflammation-induced preterm birth and perinatal brain injury

Preterm birth is a major risk factor for adverse neurological outcomes in ex-preterm children, including motor, cognitive, and behavioral disabilities. N-acetyl-L-cysteine therapy has been used in clinical studies; however, it requires doses that cause significant side effects. In this study, we explore the effect of low dose N-acetyl-L-cysteine therapy, delivered using a targeted, systemic, maternal, dendrimer nanoparticle (DNAC), in a mouse model of intrauterine inflammation. Our results demonstrated that intraperitoneal maternal DNAC administration significantly reduced the preterm birth rate and altered placental immune profile with decreased CD8⁺ T-cell infiltration. Furthermore, we demonstrated that DNAC improved neurobehavioral outcomes and reduced fetal neuroinflammation and long-term microglial activation in offspring. Our study is the first to provide evidence for the role of CD8⁺ T-cell in the maternal-fetal interface during inflammation and further support the efficacy of DNAC in preventing preterm birth and prematurity-related outcomes.

Redox Potential-Sensitive N-Acetyl Cysteine-Prodrug Nanoparticles Inhibit the Activation of Microglia and Improve Neuronal Survival

One hallmark of neuroinflammation is the activation of microglia, which triggers the production and release of reactive oxygen species (ROS), nitrate, nitrite, and cytokines. N-Acetyl cysteine (NAC) is a free radical scavenger that is involved in the intracellular and extracellular detoxification of reactive oxygen species in the brain. However, the clinical application of NAC is limited by its low bioavailability and short half-life. Herein, NAC was conjugated to a polymer through a disulfide bond to form a NAC-prodrug nanoparticle (NAC-NP). Dynamic light scattering found that the NAC-NP has a size of around 50 nm. In vitro studies revealed that the release of NAC from NAC-NP is responsive to its environmental redox potential. For mimicking neuroinflammation in vitro, microglial cells were stimulated by a lipopolysaccharide (LPS), and the effect of NAC-NP on activated microglia was investigated. The study found that the morphology as well as the expression of microgliosis marker Iba-1 of the cells treated with NAC-NPs and LPS were close to those of control cells, indicating that NAC-NPs can inhibit the activation of microglia stimulated by LPS. Compared with free NAC, the production of ROS, NO₃-, NO₂-, tumor necrosis factor-α (TNF-α), and interleukin (IL)-1β from the LPS-stimulated microglia was considerably decreased when the cells were pretreated with NAC-NPs. Furthermore, LPS-induced microglial phagocytocis of neurons was inhibited in the presence of NAC-NPs. These results indicated that NAC-NPs are more effective than free NAC for reversing the effect of LPS on microglia and subsequently protecting neurons.

Inflammation and the neural diathesis-stress hypothesis of schizophrenia: a reconceptualization

An interaction between external stressors and intrinsic vulnerability is one of the longest standing pathoaetiological explanations for schizophrenia. However, novel lines of evidence from genetics, preclinical studies, epidemiology and imaging have shed new light on the mechanisms that may underlie this, implicating microglia as a key potential mediator. Microglia are the primary immune cells of the central nervous system. They have a central role in the inflammatory response, and are also involved in synaptic pruning and neuronal remodeling. In addition to immune and traumatic stimuli, microglial activation occurs in response to psychosocial stress. Activation of microglia perinatally may make them vulnerable to subsequent overactivation by stressors experienced in later life. Recent advances in genetics have shown that variations in the complement system are associated with schizophrenia, and this system has been shown to regulate microglial synaptic pruning. This suggests a mechanism via which genetic and environmental influences may act synergistically and lead to pathological microglial activation. Microglial overactivation may lead to excessive synaptic pruning and loss of cortical gray matter. Microglial mediated damage to stress-sensitive regions such as the prefrontal cortex and hippocampus may lead directly to cognitive and negative symptoms, and account for a number of the structural brain changes associated with the disorder. Loss of cortical control may also lead to disinhibition of subcortical dopamine-thereby leading to positive psychotic symptoms. We review the preclinical and in vivo evidence for this model and consider the implications this has for treatment, and future directions.

In vivo proinflammatory activity of generations 0-3 (G0-G3) polyamidoamine (PAMAM) nanoparticles

OBJECTIVE AND DESIGN

The aim of this study was to determine whether different generations (G) polyamidoamine (PAMAM) dendrimers possess proinflammatory activities in vivo.

MATERIAL OR SUBJECTS

Several hundred female CD-1 mice were used to test four different PAMAM dendrimers using the murine air pouch model.

TREATMENT

Mice received appropriate negative and positive controls or G0-G3 PAMAM nanoparticles at 100 and 500 µg/ml into air pouches.

METHODS

Exudates were harvested after 3, 6, 24 and 48 h. Cell pellets and supernatants were used to determine the number of total leukocytes and neutrophils and to detect the production of several analytes by an antibody array approach, respectively. One-way analysis of variance was used for statistical analysis.

RESULTS

PAMAM dendrimers rapidly increased a leukocyte influx after 3 h, the vast majority of cells being neutrophils. This was also observed after 6 and 24 h, and resolution of inflammation was noted after 48 h. In general, the increased production of a greater number of analytes detected in the exudates after 6 h correlated with the number of dendrimer generations (G3 > G2 > G1 > G0).

CONCLUSIONS

PAMAM dendrimers devoid of any delivering molecules possess proinflammatory activities in vivo by themselves, probably via the production of different chemokines released by air pouch lining cells.

Dendrimers Target the Ischemic Lesion in Rodent and Primate Models of Nonarteritic Anterior Ischemic Optic Neuropathy

Introduction

Polyamidoamine dendrimer nanoparticles (~ 4 nanometers) are inert polymers that can be linked to biologically active compounds. These dendrimers selectively target and accumulate in inflammatory cells upon systemic administration. Dendrimer-linked compounds enable sustained release of therapeutic compounds directly at the site of damage. The purpose of this study was to determine if dendrimers can be used to target the optic nerve (ON) ischemic lesion in our rodent and nonhuman primate models of nonarteritic anterior ischemic optic neuropathy (NAION), a disease affecting >10,000 individuals in the US annually, and for which there currently is no effective treatment.

Methods

NAION was induced in male Long-Evans rats (rNAION) and in one adult male rhesus monkey (pNAION) using previously described procedures. Dendrimers were covalently linked to near-infrared cyanine-5 fluorescent dye (D-Cy5) and injected both intravitreally and systemically (in the rats) or just systemically (in the monkey) to evaluate D-Cy5 tissue accumulation in the eye and optic nerve following induction of NAION.

Results

Following NAION induction, Cy-5 dendrimers selectively accumulated in astrocytes and circulating macrophages. Systemic dendrimer administration provided the best penetration of the ON lesion site when injected shortly after induction. Systemic administration 1 day post-induction in the pNAION model gave localization similar to that seen in the rats.

Conclusions

Dendrimers selectively target the ischemic ON lesion after induction of both rNAION and pNAION. Systemic nanoparticle-linked therapeutics thus may provide a powerful, targeted and safe approach to NAION treatment by providing sustained and focused treatment of the cells directly affected by ischemia.

Multiprobe molecular imaging of an NMDA receptor hypofunction rat model for glutamatergic dysfunction

There are many indications of a connection between abnormal glutamate transmission through N-methyl-d-aspartate (NMDA) receptor hypofunction and the occurrence of schizophrenia. The importance of metabotropic glutamate receptor subtype 5 (mGluR5) became generally recognized due to its physical link through anchor proteins with NMDAR. Neuroinflammation as well as the kynurenine (tryptophan catabolite; TRYCAT) pathway are equally considered as major contributors to the pathology. We aimed to investigate this interplay between glutamate release, neuronal activation and inflammatory markers, by using small-animal positron emission tomography (PET) in a rat model known to induce schizophrenia-like symptoms. Daily intraperitoneal injection of MK801 or saline were administered to induce the model together with N-Acetyl-cysteine (NAc) or saline as the treatment in 24 male Sprague Dawley rats for one month. Biweekly in vivo [(11)C]-ABP688 microPET was performed together with mGluR5 immunohistochemistry. Simultaneously, weekly in vivo [(18)F]-FDG microPET imaging data for glucose metabolism was acquired and microglial activation was investigated with biweekly in vivo [(18)F]-PBR111 scans versus OX42 immunohistochemistry. Finally, plasma samples were analyzed for TRYCAT metabolites. We show that chronic MK801 administration (and thus elevated endogenous glutamate) causes significant tissue loss in rat brain, enhances neuroinflammatory pathways and may upregulate mGluR5 expression.

In vitro analysis of a novel controlled release system designed for intratympanic administration of N-acetylcysteine: a preliminary report

The aim of this in-vitro experimental study was to design a novel drug delivery system that may permit controlled release of N-acetylcysteine (NAC) following intratympanic administration. The system was composed of two different solutions that attained a hydrogel form within seconds after getting into contact with each other. The authors performed swelling, pH and temperature tests and analysis of controlled release of NAC from this novel controlled release system. For the structure and porosity analysis of the hydrogel, an environmental scanning electron microscope (SEM) was used. The diameter of designed hydrogel showed an increase when pH was increased. In addition, in comparison to acidic values, the pore diameter of the hydrogel increased significantly especially in physiological level. The increase in the pore diameter was also directly proportional to the increase in temperature. Spectrophotometric analysis showed that the amount of NAC released into the medium was statistically significant (p=0.038, t=-2.18, 95% CI; DF: 27). SEM analysis of the samples revealed a smooth surface topography and numerous porous structures. The authors are of the opinion that the designed hydrogel may be used as an alternative method for intratympanic delivery of NAC for otoprotective purposes. The disadvantages of intratympanic injection of the drug in its liquid form, including leakage through eustachian tube, restraining the patient in an uncomfortable position, necessity for repetitive injections and dose dependent inflammation of the middle ear epithelium, may also be avoided. Further in vivo studies should be conducted to assess its tolerability and effectivity.

Systemic and Intravitreal Delivery of Dendrimers to Activated Microglia/Macrophage in Ischemia/Reperfusion Mouse Retina

PURPOSE

Microglial activation and associated neuroinflammation play a key role in the pathogenesis of many diseases of the retina, including viral infection, diabetes, and retinal degeneration. Strategies to target activated microglia and macrophages and attenuate inflammation may be valuable in treating these diseases. We seek to develop dendrimer-based formulations that target retinal microglia and macrophages in a pathology-dependent manner, and deliver drugs, either intravenously or intravitreally.

METHODS

Retinal uptake of cyanine dye (Cy5)-conjugated dendrimer (D-Cy5) was assessed in normal and ischemia/reperfusion (I/R) mouse eyes. Microglia/macrophage uptake of the dendrimer was assessed with immunofluorescence using rabbit Iba-1 antibody with Cy3-tagged secondary antibody (microglia/macrophage). Uptake in retina and other organs was quantified using fluorescence spectroscopy.

RESULTS

Clearance of D-Cy5 from normal eyes was almost complete by 72 hours after intravitreal injection and 24 hours after intravenous delivery. In eyes with activated microglia after I/R injury, D-Cy5 was retained by activated microglia/macrophage (Iba1+ cells) up to 21 days after intravitreal and intravenous administration. In I/R eyes, the relative retention of intravitreal and intravenous D-Cy5 was comparable, if a 30-fold higher intravenous dose was used.

CONCLUSIONS

Intravitreal and systemic dendrimers target activated microglia and show qualitatively similar retinal biodistribution when administered by either route. Results provide proof-of-concept insights for developing dendrimer drug formulations as treatment options for retinal diseases associated with microglia or macrophage activation such as age-related macular degeneration, diabetic retinopathy, and retinal degenerations.

Caruifolin D from artemisia absinthium L. inhibits neuroinflammation via reactive oxygen species-dependent c-jun N-terminal kinase and protein kinase c/NF-κB signaling pathways

This work aims to evaluate the anti-neuroinflammatory effects of natural sesquiterpene dimer caruifolin D from Artemisia absinthium L., which is an edible vegetable or traditional medicinal food in East Asia due to its sedation, anti-asthma and antipruritic effects. In this study, we reported that caruifolin D significantly inhibited the productions of various neuroinflammatory mediators from microglia in response to bacterial lipopolysaccharide stimulation. Moreover, anti-inflammatory mechanism study showed that caruifolin D markedly suppressed the production of intracellular reactive oxygen species, which was an important player involved in neuroinflammation, leading to inhibitory effects on the activations of protein kinase C (PKC) and c-Jun N-terminal kinase (JNK), which were two major neuroinflammatory signaling pathways in the brains. Furthermore, caruifolin D protected neurons against microglia-mediated neuronal inflammatory damages by up-regulating neuronal viability and maintaining healthy neuronal morphology. Taken together, these results expanded our knowledge about the anti-neuroinflammatory and neuroprotective mechanism of Artemisia absinthium L., and also suggested that caruifolin D was a major anti-inflammatory component from Artemisia absinthium L., which might be developed as a drug candidate for neuroinflammation-related diseases.

Dendritic Polyglycerol Sulfate Inhibits Microglial Activation and Reduces Hippocampal CA1 Dendritic Spine Morphology Deficits

Hyperactivity of microglia and loss of functional circuitry is a common feature of many neurological disorders including those induced or exacerbated by inflammation. Herein, we investigate the response of microglia and changes in hippocampal dendritic postsynaptic spines by dendritic polyglycerol sulfate (dPGS) treatment. Mouse microglia and organotypic hippocampal slices were exposed to dPGS and an inflammogen (lipopolysaccharides). Measurements of intracellular fluorescence and confocal microscopic analyses revealed that dPGS is avidly internalized by microglia but not CA1 pyramidal neurons. Concentration and time-dependent response studies consistently showed no obvious toxicity of dPGS. The adverse effects induced by proinflammogen LPS exposure were reduced and dendritic spine morphology was normalized with the addition of dPGS. This was accompanied by a significant reduction in nitrite and proinflammatory cytokines (TNF-α and IL-6) from hyperactive microglia suggesting normalized circuitry function with dPGS treatment. Collectively, these results suggest that dPGS acts anti-inflammatory, inhibits inflammation-induced degenerative changes in microglia phenotype and rescues dendritic spine morphology.

Intracellular delivery of dendrimer triamcinolone acetonide conjugates into microglial and human retinal pigment epithelial cells

Triamcinolone acetonide (TA) is a potent, intermediate-acting, steroid that has anti-inflammatory and anti-angiogenic activity. Intravitreal administration of TA has been used for diabetic macular edema, proliferative diabetic retinopathy and exudative age-related macular degeneration (AMD). However, the hydrophobicity, lack of solubility, and the side effects limit its effectiveness in the treatment of retinal diseases. In this study, we explore a PAMAM dendrimer-TA conjugate (D-TA) as a potential strategy to improve intracellular delivery and efficacy of TA to target cells. The conjugates were prepared with a high drug payload (∼ 21%) and were readily soluble in saline. Compared to free TA, D-TA demonstrated a significantly improved toxicity profile in two important target [microglial and human retinal pigment epithelium (RPE)] cells. The D-TA was ∼ 100-fold more effective than free TA in its anti-inflammatory activity (measured in microglia), and in suppressing VEGF production (in hypoxic RPE cells). Dendrimer-based delivery may improve the efficacy of TA towards both its key targets of inflammation and VEGF production, with significant clinical implications.

Nanoneuromedicines for degenerative, inflammatory, and infectious nervous system diseases

Interest in nanoneuromedicine has grown rapidly due to the immediate need for improved biomarkers and therapies for psychiatric, developmental, traumatic, inflammatory, infectious and degenerative nervous system disorders. These, in whole or in part, are a significant societal burden due to growth in numbers of affected people and in disease severity. Lost productivity of the patient and his or her caregiver, and the emotional and financial burden cannot be overstated. The need for improved health care, treatment and diagnostics is immediate. A means to such an end is nanotechnology. Indeed, recent developments of health-care enabling nanotechnologies and nanomedicines range from biomarker discovery including neuroimaging to therapeutic applications for degenerative, inflammatory and infectious disorders of the nervous system. This review focuses on the current and future potential of the field to positively affect clinical outcomes. From the clinical editor: Many nervous system disorders remain unresolved clinical problems. In many cases, drug agents simply cannot cross the blood-brain barrier (BBB) into the nervous system. The advent of nanomedicines can enhance the delivery of biologically active molecules for targeted therapy and imaging. This review focused on the use of nanotechnology for degenerative, inflammatory, and infectious diseases in the nervous system.

Protective effects and mechanisms of G5 PAMAM dendrimers against acute pancreatitis induced by caerulein in mice

In this study, generation 5 (G5) polyamidoamine (PAMAM) dendrimers with two different surface groups, G4.5-COOH and G5-OH, were investigated for their protective effects on pancreas injury in a caerulein-induced acute pancreatitis (AP) mouse model. Both dendrimers significantly decreased pathological changes in the pancreas and reduced the inflammatory infiltration of macrophages in pancreatic tissues. In addition, the expression of pro-inflammatory cytokines was significantly inhibited by the two dendrimers, not only in pancreatic tissues from AP mice but also in vitro in mouse peritoneal macrophages with LPS-induced inflammation. G4.5-COOH, which had better in vivo protective effects for AP than G5-OH, led to a significant reduction in the total number of plasma white blood cells (WBCs) and monocytes in AP mice, and its anti-inflammatory mechanism was related to inhibition of the nuclear translocation of NF-κB in macrophages.

Dendrimer encapsulation enhances anti-inflammatory efficacy of silver nanoparticles

BACKGROUND

Our previous studies revealed that silver nanoparticles (AgNPs) promoted wound healing in part through their anti-inflammatory actions. As recent reports also suggested anti-inflammatory effects of dendrimers, we therefore undertook this study using dendrimer as the delivery system for AgNP to explore any potential synergistic anti-inflammatory efficacy.

METHODS

Lipopolysaccharide (LPS) was added to cultured RAW264.7 and J774.1 cells to mimic in vitro inflammation condition, followed by the addition of either silver dendrimer nanocomposite (Ag-DNC), AgNPs, or dendrimer. The levels of inflammatory markers TNF-alpha and interleukin-6 were assessed using ELISA assay. Furthermore, in vivo effects such of Ag-DNC, AgNPs, or dendrimer were studied in a burn wound model in mice.

RESULTS

Our results confirmed that both naked dendrimer and AgNPs had anti-inflammatory properties. In in vitro study, Ag-DNC was shown to have the best anti-inflammatory efficacy than AgNPs or dendrimer alone. In-vivo experiments also indicated that animals in the Ag-DNC group had the fastest healing time with the least inflammation.

CONCLUSION

Our study would suggest that dendrimer could provide additional anti-inflammatory benefits and might be an excellent delivery system for silver nanoparticles for future clinical application.

Redox control of microglial function: molecular mechanisms and functional significance

Neurodegenerative diseases are characterized by chronic microglial over-activation and oxidative stress. It is now beginning to be recognized that reactive oxygen species (ROS) produced by either microglia or the surrounding environment not only impact neurons but also modulate microglial activity. In this review, we first analyze the hallmarks of pro-inflammatory and anti-inflammatory phenotypes of microglia and their regulation by ROS. Then, we consider the production of reactive oxygen and nitrogen species by NADPH oxidases and nitric oxide synthases and the new findings that also indicate an essential role of glutathione (γ-glutamyl-l-cysteinylglycine) in redox homeostasis of microglia. The effect of oxidant modification of macromolecules on signaling is analyzed at the level of oxidized lipid by-products and sulfhydryl modification of microglial proteins. Redox signaling has a profound impact on two transcription factors that modulate microglial fate, nuclear factor kappa-light-chain-enhancer of activated B cells, and nuclear factor (erythroid-derived 2)-like 2, master regulators of the pro-inflammatory and antioxidant responses of microglia, respectively. The relevance of these proteins in the modulation of microglial activity and the interplay between them will be evaluated. Finally, the relevance of ROS in altering blood brain barrier permeability is discussed. Recent examples of the importance of these findings in the onset or progression of neurodegenerative diseases are also discussed. This review should provide a profound insight into the role of redox homeostasis in microglial activity and help in the identification of new promising targets to control neuroinflammation through redox control of the brain.

Glutathione metabolism and Parkinson's disease

It has been established that oxidative stress, defined as the condition in which the sum of free radicals in a cell exceeds the antioxidant capacity of the cell, contributes to the pathogenesis of Parkinson disease. Glutathione is a ubiquitous thiol tripeptide that acts alone or in concert with enzymes within cells to reduce superoxide radicals, hydroxyl radicals, and peroxynitrites. In this review, we examine the synthesis, metabolism, and functional interactions of glutathione and discuss how these relate to the protection of dopaminergic neurons from oxidative damage and its therapeutic potential in Parkinson disease.

Dendrimer nanoscaffolds for potential theranostics of prostate cancer with a focus on radiochemistry

Dendrimers are a class of structurally defined macromolecules featured with a central core, a low-density interior formed by repetitive branching units, and a high-density exterior terminated with surface functional groups. In contrast to their polymeric counterparts, dendrimers are nanosized and symmetrically shaped, which can be reproducibly synthesized on a large scale with monodispersity. These unique features have made dendrimers of increasing interest for drug delivery and other biomedical applications as nanoscaffold systems. Intended to address the potential use of dendrimers for the development of theranostic agents, which combines therapeutics and diagnostics in a single entity for personalized medicine, this review focuses on the reported methodologies of using dendrimer nanoscaffolds for targeted imaging and therapy of prostate cancer. Of particular interest, relevant chemistry strategies are discussed due to their important roles in the design and synthesis of diagnostic and therapeutic dendrimer-based nanoconjugates and potential theranostic agents, targeted or nontargeted. Given the developing status of nanoscaffolded theranostics, major challenges and potential hurdles are discussed along with the examples representing current advances.

Proteomic analysis of midtrimester amniotic fluid to identify novel biomarkers for preterm delivery

OBJECTIVE

The aim of this study was to identify possible biomarkers for preterm delivery by analyzing midtrimester amniotic fluid.

METHODS

Thirty-two amniotic fluid samples were studied; 16 patients had a spontaneous preterm delivery and 16 patients delivered at term. The proteomic technique consisted of surface-enhanced laser desorption ionization time-of-flight (SELDI-TOF) using different types of solid chromatographic chips (Q10, CM10 and IMAC30).

RESULTS

Mass spectrometry tracings were obtained from the amniotic fluids of both patients who delivered preterm and patients who delivered at term. Seven potential markers were identified to be differentially expressed in patients who delivered preterm.

CONCLUSIONS

Proteomic analysis of amniotic fluid obtained in the midtrimester reveals the presence of a set of proteins in patients at risk for preterm delivery.

Modulation of inflammatory signaling and cytokine release from microglia by celastrol incorporated into dendrimer nanocarriers

Aim: This study investigates the capacity of a potent anti-inflammatory nanomedicine, celastrol, incorporated into poly(amidoamine) dendrimers, to inhibit endotoxin-mediated signaling in microglia. Materials & methods: Celastrol was incorporated into amino (Cel/G4-NH2) and hydroxyl (Cel/G4-OH) terminus poly(amidoamine) (G4) dendrimers. Cell viability, release of nitric oxide, IL-6, TNF-α and activation of MAPK (e.g., p38 and JNK) and NF-κB were assessed in endotoxin (i.e., lipopolysaccharide) stimulated microglial cells. Results: G4-OH and G4-NH2 increased celastrol aqueous solubility by seven- and 12-fold, respectively. G4-OH and Cel/G4-OH suppressed lipopolysaccharide-mediated release of proinflammatory mediators, such as nitric oxide and IL-6, but not TNF-α, without reducing microglial cell viability, while Cel/G4-NH2 potentiated cytotoxicity and cytokine release. Blockade of proinflammatory signaling was accompanied by attenuation of p38 MAPK activation. Conclusion: This study supports the potential use of poly(amidoamine) dendrimers for effective anti-inflammatory therapy in the chronically inflamed CNS.

Original submitted 22 July 2011; Revised submitted 8 December 2011; Published online 4 April 2012

N-acetylcysteine is effective for prevention but not for treatment of folic acid-induced acute kidney injury in mice

OBJECTIVES

There is controversy regarding the benefits of N-acetylcysteine in acute kidney injury. This study was to compare three commonly used regimens and explore which regimen is best for the protection of acute kidney injury.

DESIGN

Prospective experimental study.

SETTING

University research laboratory.

INTERVENTIONS

Acute kidney injury was induced with folic acid intraperitoneal injection in mice. Mice in pretreatment were treated with a subcutaneous injection of N-acetylcysteine before the folic acid injection. Mice in posttreatment were treated with N-acetylcysteine after folic acid. Mice in pre- + posttreatment were treated with N-acetylcysteine before folic acid and after folic acid. Placebo mice received vehicle only using the pre- + posttreatment protocol. Fourteen healthy animals were given N-acetylcysteine to evaluate for toxicity and the other 24 mice subjected to folic acid were killed for kidney histology and analysis for oxidative injury. The same studies were also carried out in milder acute kidney injury (lower folic acid) model.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of creatinine, cystatin C, and reduced glutathione were measured. Survival time was assessed up to 7 days. The survival rates in N-acetylcysteine pretreatment mice were significantly better (73.33% vs. 46.67%, p < .04) and acute kidney injury was significantly less compared with placebo. However, mice with posttreatment exhibited significantly worse survival and more severe acute kidney injury. Histologic findings were consistent with functional parameters. Glutathione levels decreased less in N-acetylcysteine pretreatment but also increased beginning on day 2 compared with placebo (11.5 vs. 8.1 μg/mL, p < .05). Glutathione levels did not increase in N-acetylcysteine posttreatment. However, three different N-acetylcysteine interventions neither significantly improved nor worsened renal function in the milder acute kidney injury model.

CONCLUSION

N-acetylcysteine pretreatment was effective in reducing the incidence and severity of acute kidney injury as well as in increasing survival. However, N-acetylcysteine posttreatment worsened folic acid toxicity. Only pretreatment was effective in increasing glutathione. These data may help explain the variation from clinical studies of N-acetylcysteine use.

Chemical nature and structure of organic coating of quantum dots is crucial for their application in imaging diagnostics

BACKGROUND

One of the most attractive properties of quantum dots is their potential to extend the opportunities for fluorescent and multimodal imaging in vivo. The aim of the present study was to clarify whether the composition and structure of organic coating of nanoparticles are crucial for their application in vivo.

METHODS

We compared quantum dots coated with non-crosslinked amino-functionalized polyamidoamine (PAMAM) dendrimers, quantum dots encapsulated in crosslinked carboxyl-functionalized PAMAM dendrimers, and silica-shelled amino-functionalized quantum dots. A multimodal fluorescent and paramagnetic quantum dot probe was also developed and analyzed. The probes were applied intravenously in anesthetized animals for visualization of brain vasculature using two-photon excited fluorescent microscopy and visualization of tumors using fluorescent IVIS(®) imaging (Caliper Life Sciences, Hopkinton, MA) and magnetic resonance imaging.

RESULTS

Quantum dots coated with non-crosslinked dendrimers were cytotoxic. They induced side effects in vivo, including vasodilatation with a decrease in mean arterial blood pressure and heart rate. The quantum dots penetrated the vessels, which caused the quality of fluorescent imaging to deteriorate. Quantum dots encapsulated in crosslinked dendrimers had low cytotoxicity and were biocompatible. In concentrations <0.3 nmol quantum dots/kg bodyweight, these nanoparticles did not affect blood pressure and heart rate, and did not induce vasodilatation or vasoconstriction. PEGylation (PEG [polyethylene glycol]) was an indispensable step in development of a quantum dot probe for in vivo imaging, based on silica-shelled quantum dots. The non-PEGylated silica-shelled quantum dots possessed low colloidal stability in high-salt physiological fluids, accompanied by rapid aggregation in vivo. The conjugation of silica-shelled quantum dots with PEG1100 increased their stability and half-life in the circulation without significant enhancement of their size. In concentrations <2.5 nmol/kg bodyweight, these quantum dots did not affect the main physiological variables. It was possible to visualize capillaries, which makes this quantum dot probe appropriate for investigation of mediators of vasoconstriction, vasodilatation, and brain circulation in intact animals in vivo. The multimodal silica-shelled quantum dots allowed visualization of tumor tissue in an early stage of its development, using magnetic resonance imaging.

CONCLUSION

THE PRESENT STUDY SHOWS THAT THE TYPE AND STRUCTURE OF ORGANIC/BIOORGANIC SHELLS OF QUANTUM DOTS DETERMINE THEIR BIOCOMPATIBILITY AND ARE CRUCIAL FOR THEIR APPLICATION IN IMAGING IN VIVO, DUE TO THE EFFECTS OF THE SHELL ON THE FOLLOWING PROPERTIES: colloidal stability, solubility in physiological fluids, influence of the basic physiological parameters, and cytotoxicity.

Intrinsic targeting of inflammatory cells in the brain by polyamidoamine dendrimers upon subarachnoid administration

AIM

Understanding the interactions between nanomaterials and disease processes is crucial for designing effective therapeutic approaches. This article explores the unusual neuroinflammation targeting of dendrimers (with no targeting ligands) in the brain, with significant consequences for nanoscale materials in medicine.

METHOD

The in vivo biodistribution of fluorescent-labeled neutral generation-4- polyamidoamine dendrimers (∼4 nm) in a rabbit model of cerebral palsy was explored following subarachnoid administration.

RESULTS

These dendrimers, with no targeting ligands, were localizing in activated microglia and astrocytes (cells responsible for neuroinflammation), even in regions far moved from the site of injection, in newborn rabbits with maternal inflammation-induced cerebral palsy.

CONCLUSION

This intrinsic ability of dendrimers to localize inactivated microglia and astrocytes can enable targeted delivery of therapeutics in disorders such as cerebral palsy, Alzheimer's and multiple sclerosis.