Elizabeth Nance

Microglial migration and interactions with dendrimer nanoparticles are altered in the presence of neuroinflammation

BackgroundMicroglial cells have been implicated in neuroinflammation-mediated injury in the brain, including neurodevelopmental disorders such as cerebral palsy (CP) and autism. Pro-inflammatory activation of microglial cells results in the impairment of their neuroprotective functions, leading to an exaggerated, ongoing immune dysregulation that can persist long after the initial insult. We have previously shown that dendrimer-mediated delivery of an anti-inflammatory agent can attenuate inflammation in a rabbit model of maternal inflammation-induced CP and significantly improve the motor phenotype, due to the ability of the dendrimer to selectively localize in activated microglia.MethodsTo elucidate the interactions between dendrimers and microglia, we created an organotypic whole-hemisphere brain slice culture model from newborn rabbits with and without exposure to inflammation in utero. We then used this model to analyze the dynamics of microglial migration and their interactions with dendrimers in the presence of neuroinflammation.ResultsMicroglial cells in animals with CP had an amoeboid morphology and impaired cell migration, demonstrated by decreased migration distance and velocity when compared to cells in healthy, age-matched controls. However, this decreased migration was associated with a greater, more rapid dendrimer uptake compared to microglial cells from healthy controls.ConclusionsThis study demonstrates that maternal intrauterine inflammation is associated with impaired microglial function and movement in the newborn brain. This microglial impairment may play a role in the development of ongoing brain injury and CP in the offspring. Increased uptake of dendrimers by the “impaired” microglia can be exploited to deliver drugs specifically to these cells and modulate their functions. Host tissue and target cell characteristics are important aspects to be considered in the design and evaluation of targeted dendrimer-based nanotherapeutics for improved and sustained efficacy. This ex vivo model also provides a rapid screening tool for evaluation of the effects of various therapies on microglial function.

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

BackgroundRett 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.MethodsTo 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.ResultsWe 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.ConclusionsThese 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.

Systems-level thinking for nanoparticle-mediated therapeutic delivery to neurological diseases.

Neurological diseases account for 13% of the global burden of disease. As a result, treating these diseases costs

Brain-Penetrating Nanoparticles for Analysis of the Brain Microenvironment

750 billion a year. Nanotechnology, which consists of small (~1-100 nm) but highly tailorable platforms, can provide significant opportunities for improving therapeutic delivery to the brain. Nanoparticles can increase drug solubility, overcome the blood-brain and brain penetration barriers, and provide timed release of a drug at a site of interest. Many researchers have successfully used nanotechnology to overcome individual barriers to therapeutic delivery to the brain, yet no platform has translated into a standard of care for any neurological disease. The challenge in translating nanotechnology platforms into clinical use for patients with neurological disease necessitates a new approach to: (1) collect information from the fields associated with understanding and treating brain diseases and (2) apply that information using scalable technologies in a clinically-relevant way. This approach requires systems-level thinking to integrate an understanding of biological barriers to therapeutic intervention in the brain with the engineering of nanoparticle material properties to overcome those barriers. To demonstrate how a systems perspective can tackle the challenge of treating neurological diseases using nanotechnology, this review will first present physiological barriers to drug delivery in the brain and common neurological disease hallmarks that influence these barriers. We will then analyze the design of nanotechnology platforms in preclinical in vivo efficacy studies for treatment of neurological disease, and map concepts for the interaction of nanoparticle physicochemical properties and pathophysiological hallmarks in the brain. WIREs Nanomed Nanobiotechnol 2017, 9:e1422. doi: 10.1002/wnan.1422 For further resources related to this article, please visit the WIREs website.

Group B streptococcus exploits vaginal epithelial exfoliation for ascending infection

The past decade has witnessed explosive growth in the development of nanoparticle-based therapies for the treatment of neurological disorders and diseases. The systemic delivery of therapeutic carriers to the central nervous system (CNS) is hindered by both the blood-brain barrier (BBB) and the porous and electrostatically charged brain extracellular matrix (ECM), which acts as a steric and adhesive barrier. Therapeutic delivery to the brain is influenced by changes in the brain microenvironment, which can occur as a function of physiology, biology, pathology, and developmental age. Brain-penetrating nanoparticles (BPNs) are an optimal platform not only for therapeutic delivery to the brain, but also for evaluating changes in the brain microenvironment. BPNs possess both the capability to readily move within their local environment to survey their surroundings and the ability to reach the diffuse disease cells often associated with CNS disorders. To achieve effective delivery of BPNs to specific locations within the brain requires careful control over the nanoparticles transport properties. Here, we describe the process of conjugating a dense layer of poly(ethylene glycol) (PEG) to the surface of nonbiodegradable nanoparticles to achieve brain-penetrating capabilities.

Curcumin-loaded polymeric nanoparticles for neuroprotection in neonatal rats with hypoxic-ischemic encephalopathy

Thirteen percent of pregnancies result in preterm birth or stillbirth, accounting for fifteen million preterm births and three and a half million deaths annually. A significant cause of these adverse pregnancy outcomes is in utero infection by vaginal microorganisms. To establish an in utero infection, vaginal microbes enter the uterus by ascending infection; however, the mechanisms by which this occurs are unknown. Using both in vitro and murine models of vaginal colonization and ascending infection, we demonstrate how a vaginal microbe, group B streptococcus (GBS), which is frequently associated with adverse pregnancy outcomes, uses vaginal exfoliation for ascending infection. GBS induces vaginal epithelial exfoliation by activation of integrin and &bgr;-catenin signaling. However, exfoliation did not diminish GBS vaginal colonization as reported for other vaginal microbes. Rather, vaginal exfoliation increased bacterial dissemination and ascending GBS infection, and abrogation of exfoliation reduced ascending infection and improved pregnancy outcomes. Thus, for some vaginal bacteria, exfoliation promotes ascending infection rather than preventing colonization. Our study provides insight into mechanisms of ascending infection by vaginal microbes.

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

Hypoxic-ischemic encephalopathy is the leading cause of permanent brain injury in term newborns and currently has no cure. Inflammatory processes play a key role in the progression of this disease and may be amenable to a targeted pharmaceutical intervention. Curcumin is a dietary compound with potent anti-inflammatory, antioxidant, and antiapoptotic properties but is limited in therapeutic applications due to its low aqueous solubility, low bioavailability, and rapid first-pass hepatic metabolism. To address these limitations, loading curcumin into poly(lactic-co-glycolic acid)-poly(ethylene glycol) (PLGA-PEG) nanoparticles may increase relevant pharmacokinetic parameters and allow for effective drug delivery to the brain. Using the Vannucci model of unilateral hypoxic-ischemic brain injury in neonatal rats, we studied the in vivo effect of curcumin-loaded PLGA-PEG nanoparticles on brain uptake and diffusion of curcumin and on neuroprotection. The curcumin-loaded nanoparticles were able to overcome the impaired blood–brain barrier, diffuse effectively through the brain parenchyma, localize in regions of injury, and deliver a protective effect in the injured neonatal brain. The application of curcumin and PLGA-PEG nanoparticle-mediated delivery to a clinically relevant model of neonatal brain injury provides greater opportunities for clinical translation of targeted therapies for hypoxic-ischemic encephalopathy.

Determining dominant driving forces affecting controlled protein release from polymeric nanoparticles

After publication of the article [1], it has been brought to our attention that an author’s name has been formatted incorrectly.

Platelets prefer to be shaken, not stirred

Enzymes play a critical role in many applications in biology and medicine as potential therapeutics. One specific area of interest is enzyme encapsulation in polymer nanostructures, which have applications in drug delivery and catalysis. A detailed understanding of the mechanisms governing protein/polymer interactions is crucial for optimizing the performance of these complex systems for different applications. Using a combined computational and experimental approach, this study aims to quantify the relative importance of molecular and mesoscale driving forces to protein release from polymeric nanoparticles. Classical molecular dynamics (MD) simulations have been performed on bovine serum albumin (BSA) in aqueous solutions with oligomeric surrogates of poly(lactic-co-glycolic acid) copolymer, poly(styrene)-poly(lactic acid) copolymer, and poly(lactic acid). The simulated strength and location of polymer surrogate binding to the surface of BSA have been compared to experimental BSA release rates from nanoparticles formulated with these same polymers. Results indicate that the self-interaction tendencies of the polymer surrogates and other macroscale properties may play governing roles in protein release. Additional MD simulations of BSA in solution with poly(styrene)-acrylate copolymer reveal the possibility of enhanced control over the enzyme encapsulation process by tuning polymer self-interaction. Last, the authors find consistent protein surface binding preferences across simulations performed with polymer surrogates of varying lengths, demonstrating that protein/polymer interactions can be understood in part by studying the interactions and affinity of proteins with small polymer surrogates in solution.

Ketogenic bugs as epilepsy drugs

Turbulent-flow bioreactors enable clinical scale production of mature, functional platelets. Turbulent-flow bioreactors enable clinical scale production of mature, functional platelets.