Orally Deliverable Iron-Ceria Nanotablets for Treatment of Inflammatory Bowel Disease.

Ceria-based nanoparticles are versatile in treating various inflammatory diseases, but their feasibility in clinical translation is undermined by safety concerns and a limited delivery system. Meanwhile, the idiopathic nature of inflammatory bowel disease (IBD) calls for a wider variety of therapeutics via moderation of the intestinal immune system. In this regard, the synthesis and oral formulation of iron-ceria nanoparticles (CF NPs) with enhanced nanozymic activity and lower toxicity risk than conventional ceria-based nanoparticles are reported. CF NPs are clustered in calcium phosphate (CaP) and coated with a pH-responsive polymer to provide the enteric formulation of iron-ceria nanotablets (CFNT). CFNT exhibits a marked alleviative efficacy in the dextran sodium sulfate (DSS)-induced enterocolitis model in vivo by modulating the pro-inflammatory behavior of innate immune cells including macrophages and neutrophils, promoting anti-inflammatory cytokine profiles, and downregulating key transcription factors of inflammatory pathways.

Co-Delivery of Metabolic Modulators Leads to Simultaneous Lactate Metabolism Inhibition and Intracellular Acidification for Synergistic Cancer Therapy.

Simultaneous lactate metabolism inhibition and intracellular acidification (LIIA) is a promising approach for inducing tumor regression by depleting ATP. However, given the limited efficacy of individual metabolic modulators, a combination of various modulators is required for highly efficient LIIA. Herein, a co-delivery system that combines lactate transporter inhibitor, glucose oxidase, and O2 -evolving nanoparticles is proposed. As a vehicle, a facile room-temperature synthetic method for large-pore mesoporous silica nanoparticles (L-MSNs) is developed. O2 -evolving nanoparticles are then conjugated onto L-MSNs, followed by immobilizing the lactate transporter inhibitor and glucose oxidase inside the pores of L-MSNs. To load the lactate transporter inhibitor, which is too small to be directly loaded into the large pores, it is encapsulated in albumin by controlling the albumin conformation before being loaded into L-MSNs. Notably, inhibiting lactate efflux shifts the glucose consumption mechanism from lactate metabolism to glucose oxidase reaction, which eliminates glucose and produces acid. This leads to synergistic LIIA and subsequent ATP depletion in cancer cells. Consequently, L-MSN-based co-delivery of modulators for LIIA shows high anticancer efficacy in several mouse tumor models without toxicity in normal tissues. This study provides new insights into co-delivery of small-molecule drugs, proteins, and nanoparticles for synergistic metabolic modulation in tumors.

Minimally-Invasive and In-Vivo Hydrogel Patterning Method for In Situ Fabrication of Implantable Hydrogel Devices.

Despite advances in a wide range of device applications of hydrogels, including implantable ones, a method for deploying patterned hydrogel devices into the body in a minimally-invasive manner is not available yet. However, in situ patterning of the hydrogel in vivo has an obvious advantage, by which incision surgery for implantation of the hydrogel device can be avoided. Here, a minimally-invasive and in vivo hydrogel patterning method for in situ fabrication of implantable hydrogel devices is presented. The sequential application of injectable hydrogels and enzymes, with assistance of minimally-invasive surgical instruments, enables the in vivo and in situ hydrogel patterning. This patterning method can be achieved by adopting an appropriate combination of the sacrificial mold hydrogel and the frame hydrogel, in consideration of unique material properties of the hydrogels such as high softness, facile mass transfer, biocompatibility, and diverse crosslinking mechanisms. In vivo and in situ patterning of the hydrogels functionalized with nanomaterials is also demonstrated to fabricate the wireless heater and tissue scaffold, showcasing broad applicability of the patterning method.

Penetrative and Sustained Drug Delivery Using Injectable Hydrogel Nanocomposites for Postsurgical Brain Tumor Treatment.

Postsurgical treatment of glioblastoma multiforme (GBM) by systemic chemotherapy and radiotherapy is often inefficient. Tumor cells infiltrating deeply into the brain parenchyma are significant obstacles to the eradication of GBM. Here, we present a potential solution to this challenge by introducing an injectable thermoresponsive hydrogel nanocomposite. As a liquid solution that contains drug-loaded micelles and water-dispersible ferrimagnetic iron oxide nanocubes (wFIONs), the hydrogel nanocomposite is injected into the resected tumor site after surgery. It promptly gelates at body temperature to serve as a soft, deep intracortical drug reservoir. The drug-loaded micelles target residual GBM cells and deliver drugs with a minimum premature release. Alternating magnetic fields accelerate diffusion through heat generation from wFIONs, enabling penetrative drug delivery. Significantly suppressed tumor growth and improved survival rates are demonstrated in an orthotopic mouse GBM model. Our system proves the potential of the hydrogel nanocomposite platform for postsurgical GBM treatment.

Geometric Tuning of Single-Atom FeN4 Sites via Edge-Generation Enhances Multi-Enzymatic Properties.

Single-atom nanozymes (SAzymes) are considered promising alternatives to natural enzymes. The catalytic performance of SAzymes featuring homogeneous, well-defined active structures can be enhanced through elucidating structure-activity relationship and tailoring physicochemical properties. However, manipulating enzymatic properties through structural variation is an underdeveloped approach. Herein, the synthesis of edge-rich Fe single-atom nanozymes (FeNC-edge) via an H2 O2 -mediated edge generation is reported. By controlling the number of edge sites, the peroxidase (POD)- and oxidase (OXD)-like performance is significantly enhanced. The activity enhancement results from the presence of abundant edges, which provide new anchoring sites to mononuclear Fe. Experimental results combined with density functional theory (DFT) calculations reveal that FeN4 moieties in the edge sites display high electron density of Fe atoms and open N atoms. Finally, it is demonstrated that FeNC-edge nanozyme effectively inhibits tumor growth both in vitro and in vivo, suggesting that edge-tailoring is an efficient strategy for developing artificial enzymes as novel catalytic therapeutics.

Enhanced Chemodynamic Therapy by Cu-Fe Peroxide Nanoparticles: Tumor Microenvironment-Mediated Synergistic Fenton Reaction.

An urgent need in chemodynamic therapy (CDT) is to achieve high Fenton catalytic efficiency at small doses of CDT agents. However, simple general promotion of the Fenton reaction increases the risk of damaging normal cells along with the cancer cells. Therefore, a tailored strategy to selectively enhance the Fenton reactivity in tumors, for example, by taking advantage of the characteristics of the tumor microenvironment (TME), is in high demand. Herein, a heterogeneous CDT system based on copper-iron peroxide nanoparticles (CFp NPs) is designed for TME-mediated synergistic therapy. CFp NPs degrade under the mildly acidic conditions of TME, self-supply H2O2, and the released Cu and Fe ions, with their larger portions at lower oxidation states, cooperatively facilitate hydroxyl radical production through a highly efficient catalytic loop to achieve an excellent tumor therapeutic efficacy. This is distinct from previous heterogeneous CDT systems in that the synergism is closely coupled with the Cu+-assisted conversion of Fe3+ to Fe2+ rather than their independent actions. As a result, almost complete ablation of tumors at a minimal treatment dose is demonstrated without the aid of any other therapeutic modality. Furthermore, CFp NPs generate O2 during the catalysis and exhibit a TME-responsive T1 magnetic resonance imaging contrast enhancement, which are useful for alleviating hypoxia and in vivo monitoring of tumors, respectively.

Localized Delivery of Theranostic Nanoparticles and High-Energy Photons using Microneedles-on-Bioelectronics.

The low delivery efficiency of light-responsive theranostic nanoparticles (NPs) to target tumor sites, particularly to brain tumors due to the blood-brain barrier, has been a critical issue in NP-based cancer treatments. Furthermore, high-energy photons that can effectively activate theranostic NPs are hardly delivered to the target region due to the strong scattering of such photons while penetrating surrounding tissues. Here, a localized delivery method of theranostic NPs and high-energy photons to the target tumor using microneedles-on-bioelectronics is presented. Two types of microneedles and flexible bioelectronics are integrated and mounted on the edge of surgical forceps. Bioresorbable microneedles containing theranostic NPs deliver the NPs into target tumors (e.g., glioblastoma, pituitary adenoma). Magnetic resonance imaging can locate the NPs. Then, light-guiding/spreading microneedles deliver high-energy photons from bioelectronics to the NPs. The high-energy photons activate the NPs to treat tumor tissues by photodynamic therapy and chemotherapy. The controlled thermal actuation by the bioelectronics accelerates the diffusion of chemo-drugs. The proposed method is demonstrated with mouse tumor models in vivo.

Deep Tumor Penetration of Drug-Loaded Nanoparticles by Click Reaction-Assisted Immune Cell Targeting Strategy.

Nanoparticles have been extensively used to deliver therapeutic drugs to tumor tissues through the extravasation of a leaky vessel via enhanced permeation and retention effect (EPR, passive targeting) or targeted interaction of tumor-specific ligands (active targeting). However, the therapeutic efficacy of drug-loaded nanoparticles is hampered by its heterogeneous distribution owing to limited penetration in tumor tissue. Inspired by the fact that cancer cells can recruit inflammatory immune cells to support their survival, we developed a click reaction-assisted immune cell targeting (CRAIT) strategy to deliver drug-loaded nanoparticles deep into the avascular regions of the tumor. Immune cell-targeting CD11b antibodies are modified with trans-cyclooctene to enable bioorthogonal click chemistry with mesoporous silica nanoparticles functionalized with tetrazines (MSNs-Tz). Sequential injection of modified antibodies and MSNs-Tz at intervals of 24 h results in targeted conjugation of the nanoparticles onto CD11b+ myeloid cells, which serve as active vectors into tumor interiors. We show that the CRAIT strategy allows the deep tumor penetration of drug-loaded nanoparticles, resulting in enhanced therapeutic efficacy in an orthotopic 4T1 breast tumor model. The CRAIT strategy does not require ex vivo manipulation of cells and can be applied to various types of cells and nanovehicles.

Muramyl dipeptide potentiates a Bacillus anthracis poly-γ-d-glutamic acid capsule surrogate that induces maturation and activation of mouse dendritic cells.

Poly-γ-d-glutamic acid (PGA) of anthrax is an important pathogenic factor due to its anti-phagocytic activity. Additionally, PGA has the ability to activate mouse macrophages for the secretion of cytokines through Toll-like receptor (TLR) 2. Peptidoglycan (PGN), a major bacterial cell-wall component, induces inflammatory responses in the host. We assessed whether PGA can induce maturation and cytokine expression in immature mouse dendritic cells (DCs) in the existence of muramyl dipeptide (MDP), the minimum motif of PGN with immunostimulatory activity. Stimulation of immature DCs with PGA or MDP alone augmented expression of costimulatory molecules and MHC class II proteins, which are all cell surface markers indicative of maturation. The observed effects were further enhanced by costimulation of PGA and MDP. PGA alone was sufficient to induce expression of TNF-α, IL-6, MCP-1, and MIP1-α, whereas MDP alone did not under the same conditions. Treatment with MDP enhanced PGA-induced expression of the tested inflammatory mediators; however, the synergistic effect found for PGA and MDP was not observed in TLR2- or nucleotide-binding oligomerization domain (NOD) 2-knockout DCs. Additionally, MDP augmented PGA-induced MAP kinases and NF-κB activation, which is crucial for expression of cytokines. Furthermore, MAP kinase and NF-κB inhibitors attenuated MDP enhancement of PGA-induced cytokine production. In addition, co-culture of splenocytes and PGA/MDP-matured DCs induced higher expression of IL-2 and IFN-γ compared to that of splenocytes and PGA-matured DCs. Collectively, our results suggest that PGA and MDP cooperatively induce inflammatory responses in mouse DCs through TLR2 and NOD2 via MAP kinase and NF-κB pathways, subsequently leading to lymphocyte activation.

Multifunctional nanoparticles as a tissue adhesive and an injectable marker for image-guided procedures.

Tissue adhesives have emerged as an alternative to sutures and staples for wound closure and reconnection of injured tissues after surgery or trauma. Owing to their convenience and effectiveness, these adhesives have received growing attention particularly in minimally invasive procedures. For safe and accurate applications, tissue adhesives should be detectable via clinical imaging modalities and be highly biocompatible for intracorporeal procedures. However, few adhesives meet all these requirements. Herein, we show that biocompatible tantalum oxide/silica core/shell nanoparticles (TSNs) exhibit not only high contrast effects for real-time imaging but also strong adhesive properties. Furthermore, the biocompatible TSNs cause much less cellular toxicity and less inflammation than a clinically used, imageable tissue adhesive (that is, a mixture of cyanoacrylate and Lipiodol). Because of their multifunctional imaging and adhesive property, the TSNs are successfully applied as a hemostatic adhesive for minimally invasive procedures and as an immobilized marker for image-guided procedures.

In vitro photodynamic effects of scavenger receptor targeted-photoactivatable nanoagents on activated macrophages.

Scavenger receptors (SRs) expressed on the activated macrophages in inflammation sites have been considered as the most interesting and important target biomarker for targeted drug delivery, imaging and therapy. In the present study, we fabricated the scavenger receptor-A (SR-A) targeted-photoactivatable nanoagents (termed as Ce6/DS-DOCA) by entrapping chlorin e6 (Ce6) into the amphiphilic dextran sulfate-deoxycholic acid (DS-DOCA) conjugates via physically hydrophobic interactions. Insoluble Ce6 was easily encapsulated into DS-DOCA nanoparticles by a dialysis method and the loading efficiency was approximately 51.7%. The Ce6/DS-DOCA formed nano-sized self-assembled aggregates (28.8±5.6nm in diameter), confirmed by transmission electron microscope, UV/Vis and fluorescence spectrophotometer. The Ce6/DS-DOCA nanoagents could generate highly reactive singlet oxygen under laser irradiation. Also, in vitro studies showed that they were more specifically taken up by lipopolysaccharide (LPS)-induced activated macrophages (RAW 264.7) via a SR-A-mediated endocytosis, relative to by non-activated macrophages, and notably induced cell death of activated macrophages under laser irradiation. Therefore, SR-A targetable and photoactivatable Ce6/DS-DOCA nanoagents with more selective targeting to the activated macrophages will have great potential for treatment of inflammatory diseases.

Intravascular optical imaging of high-risk plaques in vivo by targeting macrophage mannose receptors.

Macrophages mediate atheroma expansion and disruption, and denote high-risk arterial plaques. Therefore, they are substantially gaining importance as a diagnostic imaging target for the detection of rupture-prone plaques. Here, we developed an injectable near-infrared fluorescence (NIRF) probe by chemically conjugating thiolated glycol chitosan with cholesteryl chloroformate, NIRF dye (cyanine 5.5 or 7), and maleimide-polyethylene glycol-mannose as mannose receptor binding ligands to specifically target a subset of macrophages abundant in high-risk plaques. This probe showed high affinity to mannose receptors, low toxicity, and allowed the direct visualization of plaque macrophages in murine carotid atheroma. After the scale-up of the MMR-NIRF probe, the administration of the probe facilitated in vivo intravascular imaging of plaque inflammation in coronary-sized vessels of atheromatous rabbits using a custom-built dual-modal optical coherence tomography (OCT)-NIRF catheter-based imaging system. This novel imaging approach represents a potential imaging strategy enabling the identification of high-risk plaques in vivo and holds promise for future clinical implications.

The poly-γ-d-glutamic acid capsule surrogate of the Bacillus anthracis capsule induces nitric oxide production via the platelet activating factor receptor signaling pathway.

The poly-γ-d-glutamic acid (PGA) capsule, a major virulence factor of Bacillus anthracis, confers protection of the bacillus from phagocytosis and allows its unimpeded growth in the host. PGA capsules released from B. anthracis are associated with lethal toxin in the blood of experimentally infected animals and enhance the cytotoxic effect of lethal toxin on macrophages. In addition, PGA capsule itself activates macrophages and dendritic cells to produce proinflammatory cytokine such as IL-1ß, indicating multiple roles of PGA capsule in anthrax pathogenesis. Here we report that PGA capsule of Bacillus licheniformis, a surrogate of B. anthracis capsule, induces production of nitric oxide (NO) in RAW264.7 cells and bone marrow-derived macrophages. NO production was induced by PGA in a dose-dependent manner and was markedly reduced by inhibitors of inducible NO synthase (iNOS), suggesting iNOS-dependent production of NO. Induction of NO production by PGA was not observed in macrophages from TLR2-deficient mice and was also substantially inhibited in RAW264.7 cells by pretreatment of TLR2 blocking antibody. Subsequently, the downstream signaling events such as ERK, JNK and p38 of MAPK pathways as well as NF-κB activation were required for PGA-induced NO production. In addition, the induced NO production was significantly suppressed by treatment with antagonists of platelet activating factor receptor (PAFR) or PAFR siRNA, and mediated through PAFR/Jak2/STAT-1 signaling pathway. These findings suggest that PGA capsule induces NO production in macrophages by triggering both TLR2 and PAFR signaling pathways which lead to activation of NF-kB and STAT-1, respectively.

The Poly-γ-d-Glutamic Acid Capsule Surrogate of the Bacillus anthracis Capsule Is a Novel Toll-Like Receptor 2 Agonist.

Bacillus anthracis is a pathogenic Gram-positive bacterium that causes a highly lethal infectious disease, anthrax. The poly-γ-d-glutamic acid (PGA) capsule is one of the major virulence factors of B. anthracis, along with exotoxins. PGA enables B. anthracis to escape phagocytosis and immune surveillance. Our previous study showed that PGA activates the human macrophage cell line THP-1 and human dendritic cells, resulting in the production of the proinflammatory cytokine interleukin-1ß (IL-1ß) (M. H. Cho et al., Infect Immun 78:387-392, 2010, http://dx.doi.org/10.1128/IAI.00956-09). Here, we investigated PGA-induced cytokine responses and related signaling pathways in mouse bone marrow-derived macrophages (BMDMs) using Bacillus licheniformis PGA as a surrogate for B. anthracis PGA. Upon exposure to PGA, BMDMs produced proinflammatory mediators, including tumor necrosis factor alpha (TNF-α), IL-6, IL-12p40, and monocyte chemoattractant protein 1 (MCP-1), in a concentration-dependent manner. PGA stimulated Toll-like receptor 2 (TLR2) but not TLR4 in Chinese hamster ovary cells expressing either TLR2 or TLR4. The ability of PGA to induce TNF-α and IL-6 was retained in TLR4(-/-) but not TLR2(-/-) BMDMs. Blocking experiments with specific neutralizing antibodies for TLR1, TLR6, and CD14 showed that TLR6 and CD14 also were necessary for PGA-induced inflammatory responses. Furthermore, PGA enhanced activation of mitogen-activated protein (MAP) kinases and nuclear factor-kappa B (NF-κB), which are responsible for expression of proinflammatory cytokines. Additionally, PGA-induced TNF-α production was abrogated not only in MyD88(-/-) BMDMs but also in BMDMs pretreated with inhibitors of MAP kinases and NF-κB. These results suggest that immune responses induced by PGA occur via TLR2, TLR6, CD14, and MyD88 through activation of MAP kinase and NF-κB pathways.

Glycol chitosan-based fluorescent theranostic nanoagents for cancer therapy.

Theranostics is an integrated nanosystem that combines therapeutics with diagnostics in attempt to develop new personalized treatments with enhanced therapeutic efficacy and safety. As a promising therapeutic paradigm with cutting-edge technologies, theranostic agents are able to simultaneously deliver therapeutic drugs and diagnostic imaging agents and also monitor the response to therapy. Polymeric nanosystems have been intensively explored for biomedical applications to diagnose and treat various cancers. In recent years, glycol chitosan-based nanoagents have been developed as dual-purpose materials for simultaneous diagnosis and therapy. They have shown great potential in cancer therapies, such as chemotherapeutics and nucleic acid and photodynamic therapies. In this review, we summarize the recent progress and potential applications of glycol chitosan-based fluorescent theranostic nanoagents for cancer treatments and discuss their possible underlying mechanisms.

Anti-inflammatory effect of tanshinone I in neuroprotection against cerebral ischemia-reperfusion injury in the gerbil hippocampus.

Tanshinone I (TsI) is an important lipophilic diterpene extracted from Danshen (Radix Salvia miltiorrhizae) and has been used in Asia for the treatment of cerebrovascular diseases such as ischemic stroke. In this study, we examined the neuroprotective effect of TsI against ischemic damage and its neuroprotective mechanism in the gerbil hippocampal CA1 region (CA1) induced by 5 min of transient global cerebral ischemia. Pre-treatment with TsI protected pyramidal neurons from ischemic damage in the stratum pyramidale (SP) of the CA1 after ischemia-reperfusion. The pre-treatment with TsI increased the immunoreactivities and protein levels of anti-inflammatory cytokines [interleukin (IL)-4 and IL-13] in the TsI-treated-sham-operated-groups compared with those in the vehicle-treated-sham-operated-groups; however, the treatment did not increase the immunoreactivities and protein levels of pro-inflammatory cytokines (IL-2 and tumor necrosis factor-α). On the other hand, in the TsI-treated-ischemia-operated-groups, the immunoreactivities and protein levels of all the cytokines were maintained in the SP of the CA1 after transient cerebral ischemia. In addition, we examined that IL-4 injection into the lateral ventricle did not protect pyramidal neurons from ischemic damage. In conclusion, these findings indicate that the pre-treatment with TsI can protect against ischemia-induced neuronal death in the CA1 via the increase or maintenance of endogenous inflammatory cytokines, and exogenous IL-4 does not protect against ischemic damage.

High-resolution three-photon biomedical imaging using doped ZnS nanocrystals.

Three-photon excitation is a process that occurs when three photons are simultaneously absorbed within a luminophore for photo-excitation through virtual states. Although the imaging application of this process was proposed decades ago, three-photon biomedical imaging has not been realized yet owing to its intrinsic low quantum efficiency. We herein report on high-resolution in vitro and in vivo imaging by combining three-photon excitation of ZnS nanocrystals and visible emission from Mn(2+) dopants. The large three-photon cross-section of the nanocrystals enabled targeted cellular imaging under high spatial resolution, approaching the theoretical limit of three-photon excitation. Owing to the enhanced Stokes shift achieved through nanocrystal doping, the three-photon process was successfully applied to high-resolution in vivo tumour-targeted imaging. Furthermore, the biocompatibility of ZnS nanocrystals offers great potential for clinical applications of three-photon imaging.

Cyclin D1 immunoreactivity changes in CA1 pyramidal neurons and dentate granule cells in the gerbil hippocampus after transient forebrain ischemia.

OBJECTIVES: Cyclin D1, a member of the G1 cyclin family, plays a critical role in the progression of the cell cycle. In the present study, we investigated chronological alterations in cyclin D1 immunoreactivity and its protein levels in the gerbil hippocampus after ischemia/reperfusion. METHODS: Chronological alterations in cyclin D1 immunoreactivity and its levels were examined in the gerbil hippocampus after ischemia/reperfusion using immunohistochemistry and western blot analysis. RESULTS: Changes in cyclin D1 immunoreactivity in the ischemic hippocampus were distinct in pyramidal neurons of the CA1 region and granule cells of the dentate gyrus. Cyclin D1 immunoreactivity in pyramidal neurons of the CA1 region was increased up to 1 day after ischemia/reperfusion, although a transient decrease of cyclin D1 immunoreactivity was detected at 12 hour after ischemia/reperfusion. Thereafter, cyclin D1 immunoreactivity in the CA1 pyramidal neurons was very weak 2 days and disappeared nearly 4 and 7 days after ischemia/reperfusion. However, 4 days after ischemia/reperfusion, the cyclin D1 immunoreactivity in non-pyramidal neurons of the CA1 region was very strong. In the CA2/3 region, cyclin D1 immunoreactivity was higher than that in the CA1 region and not changed after ischemia/reperfusion. In the dentate gyrus, chronological change in cyclin D1 immunoreactivity was observed. Cells in the granule cell layer showed distinct change in cyclin D1 immunoreactivity after ischemia/reperfusion: the cyclin D1 immunoreactivity was lowest at 12 hours and strong 1 and 4 days after ischemia/reperfusion. In addition, change in cyclin D1 protein level was found in the ischemic hippocampus. CONCLUSION: Our results indicate that cyclin D1 may play an important role in cellular events related with neuronal damage following ischemia/reperfusion.

Chronic treatment of exendin-4 affects cell proliferation and neuroblast differentiation in the adult mouse hippocampal dentate gyrus.

Exendin-4 isolated from Heloderma suspectum venom acts via glucagon-like peptide 1 (GLP-1) receptor and has clinically been used in the type 2 diabetes. In this study, we investigated the effects of exendin-4 on cell proliferation and neuroblast differentiation in the subgranular zone (SGZ) of the dentate gyrus in mice. Exendin-4 was treated intraperitoneally to male ICR mice twice a day for 21 days. The exendin-4-treated group showed a significantly higher number of Ki67- (1.51-fold), doublecortin (DCX)- (2.5-fold) and 5-bromo-2'-deoxyuridine (BrdU)+DCX- (2.46-fold) immunoreactive cells in the SGZ of the dentate gyrus compared to the control group. The results of this study showed that treatment with exendin-4 increased cell proliferation neuroblast differentiation in the SGZ of the dentate gyrus, suggesting that exendin-4 promotes structural plasticity in the dentate gyrus.

Neuroprotective effects of onion extract and quercetin against ischemic neuronal damage in the gerbil hippocampus.

Onion has several well-known biological functionalities, including antioxidant effects, and contains quercetin (3,3',4,5,7-pentahydroxyflavone), a powerful antioxidant. In the present study, we observed neuroprotective effects of onion extract (OE) and its major component, quercetin, on ischemic damage in the gerbil hippocampus, which is related to memory function. Repeated treatment with 100 mg/kg OE and 20 mg/kg quercetin for 15 days before ischemic surgery protected pyramidal neurons of the hippocampal CA1 region from ischemic damage. In the OE-treated ischemic group, gliosis (activation of astrocytes and microglia) was attenuated in the CA1 4 days after ischemia/reperfusion. In addition, treatment with OE and quercetin decreased protein levels of 4-hydroxy-2-nonenal (a marker for lipid peroxidation) in the ischemic CA1. We suggest that repeated administration of OE and quercetin can protect against neuronal damage from transient cerebral ischemia.