Epigenetic alterations in creatine transporter deficiency: a new marker for dodecyl creatine ester therapeutic efficacy monitoring.

Creatine transporter deficiency (CTD) is an X-linked disease caused by mutations in the Slc6a8 gene. The impaired creatine uptake in the brain leads to developmental delays with intellectual disability. We hypothesized that deficient creatine uptake in CTD cerebral cells impact methylation balance leading to alterations of genes and proteins expression by epigenetic mechanism. In this study, we determined the status of nucleic acid methylation in both Slc6a8 knockout mouse model and brain organoids derived from CTD patients' cells. We also investigated the effect of dodecyl creatine ester (DCE), a promising prodrug that increases brain creatine content in the mouse model of CTD. The level of nucleic acid methylation was significantly reduced compared to healthy controls in both in vivo and in vitro CTD models. This hypo-methylation tended to be regulated by DCE treatment in vivo. These results suggest that increased brain creatine after DCE treatment restores normal levels of DNA methylation, unveiling the potential of using DNA methylation as a marker to monitor the drug efficacy.

Dodecyl creatine ester therapy: from promise to reality.

Pathogenic variants in SLC6A8, the gene which encodes creatine transporter SLC6A8, prevent creatine uptake in the brain and result in a variable degree of intellectual disability, behavioral disorders (e.g., autism spectrum disorder), epilepsy, and severe speech and language delay. There are no treatments to improve neurodevelopmental outcomes for creatine transporter deficiency (CTD). In this spotlight, we summarize recent advances in innovative molecules to treat CTD, with a focus on dodecyl creatine ester, the most promising drug candidate.

A Fab of trastuzumab to treat HER2 overexpressing breast cancer brain metastases.

Despite major therapeutic advances for two decades, including the most recently approved anti-HER2 drugs, brain metastatic localizations remain the major cause of death for women with metastatic HER2 breast cancer. The main reason is the limited drug passage of the blood-brain barrier after intravenous injection and the significant efflux of drugs, including monoclocal antibodies, after administration into the cerebrospinal fluid. We hypothesized that this efflux was linked to the presence of a FcRn receptor in the blood-brain barrier. To overcome this efflux, we engineered two Fab fragments of trastuzumab, an anti-HER2 monoclonal antibody, and did a thorough preclinical development for therapeutic translational purpose. We demonstrated the safety and equal efficacy of the Fabs with trastuzumab in vitro, and in vivo using a patient-derived xenograft model of HER2 overexpressing breast cancer. For the pharmacokinetic studies of intra-cerebrospinal fluid administration, we implemented original rat models with catheter implanted into the cisterna magna. After intraventricular administration in rats, we demonstrated that the brain-to-blood efflux of Fab was up to 10 times lower than for trastuzumab, associated with a two-fold higher brain penetration compared to trastuzumab. This Fab, capable of significantly reducing brain-to-blood efflux and enhancing brain penetration after intra-cerebrospinal fluid injection, could thus be a new and original effective drug in the treatment of HER2 breast cancer brain metastases, which will be demonstrated by a phase I clinical trial dedicated to women in resort situations.

Brain organoids for hypoxic-ischemic studies: from bench to bedside.

Our current knowledge regarding the development of the human brain mostly derives from experimental studies on non-human primates, sheep, and rodents. However, these studies may not completely simulate all the features of human brain development as a result of species differences and variations in pre- and postnatal brain maturation. Therefore, it is important to supplement the in vivo animal models to increase the possibility that preclinical studies have appropriate relevance for potential future human trials. Three-dimensional brain organoid culture technology could complement in vivo animal studies to enhance the translatability of the preclinical animal studies and the understanding of brain-related disorders. In this review, we focus on the development of a model of hypoxic-ischemic (HI) brain injury using human brain organoids to complement the translation from animal experiments to human pathophysiology. We also discuss how the development of these tools provides potential opportunities to study fundamental aspects of the pathophysiology of HI-related brain injury including differences in the responses between males and females.

Deciphering neuronal deficit and protein profile changes in human brain organoids from patients with creatine transporter deficiency.

Creatine transporter deficiency (CTD) is an X-linked disease caused by mutations in the SLC6A8 gene. The impaired creatine uptake in the brain results in intellectual disability, behavioral disorders, language delay, and seizures. In this work, we generated human brain organoids from induced pluripotent stem cells of healthy subjects and CTD patients. Brain organoids from CTD donors had reduced creatine uptake compared with those from healthy donors. The expression of neural progenitor cell markers SOX2 and PAX6 was reduced in CTD-derived organoids, while GSK3ß, a key regulator of neurogenesis, was up-regulated. Shotgun proteomics combined with integrative bioinformatic and statistical analysis identified changes in the abundance of proteins associated with intellectual disability, epilepsy, and autism. Re-establishment of the expression of a functional SLC6A8 in CTD-derived organoids restored creatine uptake and normalized the expression of SOX2, GSK3ß, and other key proteins associated with clinical features of CTD patients. Our brain organoid model opens new avenues for further characterizing the CTD pathophysiology and supports the concept that reinstating creatine levels in patients with CTD could result in therapeutic efficacy.

Proteolytically Stable Diaza-Peptide Foldamers Mimic Helical Hot Spots of Protein-Protein Interactions and Act as Natural Chaperones.

A novel class of peptidomimetic foldamers based on diaza-peptide units are reported. Circular dichroism, attenuated total reflection -Fourier transform infrared, NMR, and molecular dynamics studies demonstrate that unlike the natural parent nonapeptide, the specific incorporation of one diaza-peptide unit at the N-terminus allows helical folding in water, which is further reinforced by the introduction of a second unit at the C-terminus. The ability of these foldamers to resist proteolysis, to mimic the small helical hot spot of transthyretin-amyloid ß (Aß) cross-interaction, and to decrease pathological Aß aggregation demonstrates that the introduction of diaza-peptide units is a valid approach for designing mimics or inhibitors of protein-protein interaction and other therapeutic peptidomimetics. This study also reveals that small peptide foldamers can play the same role as physiological chaperone proteins and opens a new way to design inhibitors of amyloid protein aggregation, a hallmark of more than 20 serious human diseases such as Alzheimer's disease.

Molecular Heterogeneity of the Brain Endothelium.

The blood-brain barrier (BBB) is part of a neurovascular structure located in the brain's micro vessels, that is essential to maintain brain homeostasis, but prevents the brain uptake of most drugs. Because of its importance in neuro-pharmacotherapy, the BBB has been the subject of extensive research since its discovery over 100 years ago. Major advances in understanding the structure and function of the barrier have been made. Drugs are re-designed to cross the BBB. However, despite these efforts, overcoming the BBB efficiently to treat brain diseases safely remains challenging. The majority of BBB research studies focus on the BBB as a homogenous structure throughout the different brain regions. However, this simplification may lead to an inadequate understanding of the BBB function with significant therapeutic consequences. From this perspective, we analyzed the gene and protein expression profiles of the BBB in the micro vessels from the brains of mice that were isolated from two different brain regions, namely the cortex and the hippocampus. The expression profile of the inter-endothelial junctional protein (claudin-5), three ABC transporters (P-glycoprotein, Bcrp and Mrp-1), and three BBB receptors (lrp-1, TRF and GLUT-1) were analyzed. Our gene and protein analysis showed that the brain endothelium in the hippocampus exhibits different expression profiles compared to the brain cortex. Specifically, brain endothelial cells (BECs) of the hippocampus express higher gene levels of abcb1, abcg2, lrp1, and slc2a1 compared to the BECs of the cortex regions with a trend of increase for claudin-5, while BECs of the cortex express higher gene levels of abcc1 and trf compared to the hippocampus. At the protein levels, the P-gp expression was found to be significantly higher in the hippocampus compared to the cortex, while TRF was found to be up-regulated in the cortex. These data suggest that the structure and function of the BBB are not homogeneous, and imply that drugs are not delivered similarly among the different brain regions. Appreciation of the BBB heterogeneity by future research programs is thus critical for efficient drug delivery and the treatment of brain diseases.

Dodecyl creatine ester improves cognitive function and identifies key protein drivers including KIF1A and PLCB1 in a mouse model of creatine transporter deficiency.

Creatine transporter deficiency (CTD), a leading cause of intellectual disability is a result of the mutation in the gene encoding the creatine transporter SLC6A8, which prevents creatine uptake into the brain, causing mental retardation, expressive speech and language delay, autistic-like behavior and epilepsy. Preclinical in vitro and in vivo data indicate that dodecyl creatine ester (DCE) which increases the creatine brain content, might be a therapeutic option for CTD patients. To gain a better understanding of the pathophysiology and DCE treatment efficacy in CTD, this study focuses on the identification of biomarkers related to cognitive improvement in a Slc6a8 knockout mouse model (Slc6a8-/y) engineered to mimic the clinical features of CTD patients which have low brain creatine content. Shotgun proteomics analysis of 4,035 proteins in four different brain regions; the cerebellum, cortex, hippocampus (associated with cognitive functions) and brain stem, and muscle as a control, was performed in 24 mice. Comparison of the protein abundance in the four brain regions between DCE-treated intranasally Slc6a8-/y mice and wild type and DCE-treated Slc6a8-/y and vehicle group identified 14 biomarkers, shedding light on the mechanism of action of DCE. Integrative bioinformatics and statistical modeling identified key proteins in CTD, including KIF1A and PLCB1. The abundance of these proteins in the four brain regions was significantly correlated with both the object recognition and the Y-maze tests. Our findings suggest a major role for PLCB1, KIF1A, and associated molecules in the pathogenesis of CTD.

Barriers to the Intestinal Absorption of Four Insulin-Loaded Arginine-Rich Nanoparticles in Human and Rat.

Peptide drugs and biologics provide opportunities for treatments of many diseases. However, due to their poor stability and permeability in the gastrointestinal tract, the oral bioavailability of peptide drugs is negligible. Nanoparticle formulations have been proposed to circumvent these hurdles, but systemic exposure of orally administered peptide drugs has remained elusive. In this study, we investigated the absorption mechanisms of four insulin-loaded arginine-rich nanoparticles displaying differing composition and surface characteristics, developed within the pan-European consortium TRANS-INT. The transport mechanisms and major barriers to nanoparticle permeability were investigated in freshly isolated human jejunal tissue. Cytokine release profiles and standard toxicity markers indicated that the nanoparticles were nontoxic. Three out of four nanoparticles displayed pronounced binding to the mucus layer and did not reach the epithelium. One nanoparticle composed of a mucus inert shell and cell-penetrating octarginine (ENCP), showed significant uptake by the intestinal epithelium corresponding to 28 ± 9% of the administered nanoparticle dose, as determined by super-resolution microscopy. Only a small fraction of nanoparticles taken up by epithelia went on to be transcytosed via a dynamin-dependent process. In situ studies in intact rat jejunal loops confirmed the results from human tissue regarding mucus binding, epithelial uptake, and negligible insulin bioavailability. In conclusion, while none of the four arginine-rich nanoparticles supported systemic insulin delivery, ENCP displayed a consistently high uptake along the intestinal villi. It is proposed that ENCP should be further investigated for local delivery of therapeutics to the intestinal mucosa.

miR-27a-3p regulates expression of intercellular junctions at the brain endothelium and controls the endothelial barrier permeability.

BACKGROUND: The brain endothelial barrier permeability is governed by tight and adherens junction protein complexes that restrict paracellular permeability at the blood-brain barrier (BBB). Dysfunction of the inter-endothelial junctions has been implicated in neurological disorders such as multiple sclerosis, stroke and Alzheimer's disease. The molecular mechanisms underlying junctional dysfunction during BBB impairment remain elusive. MicroRNAs (miRNAs) have emerged as versatile regulators of the BBB function under physiological and pathological conditions, and altered levels of BBB-associated microRNAs were demonstrated in a number of brain pathologies including neurodegeneration and neuroinflammatory diseases. Among the altered micro-RNAs, miR-27a-3p was found to be downregulated in a number of neurological diseases characterized by loss of inter-endothelial junctions and disruption of the barrier integrity. However, the relationship between miR-27a-3p and tight and adherens junctions at the brain endothelium remains unexplored. Whether miR-27a-3p is involved in regulation of the junctions at the brain endothelium remains to be determined. METHODS: Using a gain-and-loss of function approach, we modulated levels of miR-27a-3p in an in-vitro model of the brain endothelium, key component of the BBB, and examined the resultant effect on the barrier paracellular permeability and on the expression of essential tight and adherens junctions. The mechanisms governing the regulation of junctional proteins by miR-27a-3p were also explored. RESULTS: Our results showed that miR-27a-3p inhibitor increases the barrier permeability and causes reduction of claudin-5 and occludin, two proteins highly enriched at the tight junction, while miR-27a-3p mimic reduced the paracellular leakage and increased claudin-5 and occludin protein levels. Interestingly, we found that miR-27-3p induces expression of claudin-5 and occludin by downregulating Glycogen Synthase Kinase 3 beta (GSK3ß) and activating Wnt/ß-catenin signaling, a key pathway required for the BBB maintenance. CONCLUSION: For the first time, we showed that miR-27a-3p is a positive regulator of key tight junction proteins, claudin-5 and occludin, at the brain endothelium through targeting GSK3ß gene and activating Wnt/ß-catenin signaling. Thus, miR-27a-3p may constitute a novel therapeutic target that could be exploited to prevent BBB dysfunction and preserves its integrity in neurological disorders characterized by impairment of the barrier's function.

Regulation of P-glycoprotein by miR-27a-3p at the Brain Endothelial Barrier.

Multi-drug resistance P-glycoprotein (P-gp/MDR1) is one of the most clinically relevant ABC transporters, highly enriched at the blood-brain barrier (BBB) with a broad substrate spectrum including therapeutic drugs and metabolic waste products. Altered P-gp transport function has been implicated in multi-drug resistance and in the pathogenesis and progression of neurological diseases. Recent studies have shown that P-gp expression is modulated by micro-RNAs in peripheral organs. Particularly, miR-27a-3p has been shown to play a critical role in the regulation of P-gp in multi-drug resistant cancer cells. In brain disorders, altered levels of miR-27a-3p were reported in several diseases associated with alterations in P-gp expression at the BBB. However, effect of altered miR-27a-3p expression on P-gp expression at the BBB remains to be determined. In this study, we investigated the role of miR-27a-3p in the regulation of P-gp expression and activity at the brain endothelium. Levels of miR-27a-3p were modulated by mimic and inhibitor transfection in an in-vitro model of human brain endothelial hCMEC/D3 cells. Effect of miR-27a-3p modulation on P-gp expression and activity was examined and the underlying regulatory mechanisms explored. Our results showed that transfection of hCMEC/D3 cells with miR-27a-3p mimic induces expression and activity of P-gp while miR-27a-3p inhibition exerted opposite effects. Mechanistic studies revealed that miR-27a-3p regulates P-gp by mediating Glycogen Synthase Kinase 3 Beta (GSK3ß) inhibition and activating Wnt/ß-catenin signaling. These findings shed light on miR-27a-3p/GSK3ß/ß-catenin as a novel axis that could be exploited to modulate P-gp efflux activity at the brain endothelium and help improving CNS diseases treatment or brain protection.

Combinatorial targeting of microRNA-26b and microRNA-101 exerts a synergistic inhibition on cyclooxygenase-2 in brain metastatic triple-negative breast cancer cells.

PURPOSE: Extravasation of triple-negative (TN) metastatic breast cancer (BC) cells through the brain endothelium (BE) is a critical step in brain metastasis (BM). During extravasation, metastatic cells induce alteration in the inter-endothelial junctions and transmigrate through the endothelial barrier. Transmigration of metastatic cells is mediated by the upregulation of cyclooxygenase-2 (COX-2) that induces matrix metalloproteinase-1 (MMP-1) capable of degrading inter-endothelial junctional proteins. Despite their important role in BM, the molecular mechanisms upregulating COX-2 and MMP-1 in TNBC cells remain poorly understood. In this study, we unraveled a synergistic effect of a pair of micro-RNAs (miR-26b-5p and miR-101-3p) on COX-2 expression and the brain transmigration ability of BC cells. METHODS: Using a gain-and-loss of function approach, we modulated levels of miR-26b-5p and miR-101-3p in two TNBC cell lines (the parental MDA-MB-231 and its brain metastatic variant MDA-MB-231-BrM2), and examined the resultant effect on COX-2/MMP-1 expression and the transmigration of cancer cells through the BE. RESULTS: We observed that the dual inhibition of miR-26b-5p and miR-101-3p in BC cells results in higher increase of COX-2/MMP-1 expression and a higher trans-endothelial migration compared to either micro-RNA alone. The dual restoration of both micro-RNAs exerted a synergistic inhibition on COX-2/MMP-1 by targeting COX-2 and potentiated the suppression of trans-endothelial migration compared to single micro-RNA. CONCLUSION: These findings provide new insights on a synergism between miR-26-5p and miR-101-3p in regulating COX-2 in metastatic TNBC cells and shed light on miR-26-5p and miR-101-3p as prognostic and therapeutic targets that can be exploited to predict or prevent BM.

Silencing miR-202-3p increases MMP-1 and promotes a brain invasive phenotype in metastatic breast cancer cells.

BACKGROUND: Brain metastasis (BM) is a major cause of morbidity and mortality in breast cancer (BC) and its molecular mechanism remains poorly understood. Transmigration of metastatic cells through the brain endothelium is an essential step in BM. Metalloproteinase-1 (MMP-1) overexpression plays a key role in promoting trans-endothelial migration by degrading the inter-endothelial junctions and disrupting the endothelial integrity. However, little is known about the molecular mechanisms that induce MMP-1 in metastatic cells granting them a brain invasive phenotype. MiR-202-3p is downregulated in brain metastases compared to primary breast tumors and directly targets MMP-1. Here, we unraveled a critical role of miR-202-3p loss in MMP-1 upregulation promoting transmigration of metastatic cells through the brain endothelium. METHODS: A variant of the MDA-MB-231 human BC cell line (MDA-MB-231-BrM2) selected for its propensity to form brain metastases was found to express high levels of MMP-1 and low levels of miR-202-3p compared to the parental cells. Using a gain-and-loss of function approach, we modulated levels of miR-202-3p and examined the resultant effect on MMP-1 expression. Effect of miR-202-3p modulation on integrity of the brain endothelium and the transmigrative ability of BC cells were also examined. RESULTS: Loss of miR-202-3p in breast cancer cells enhanced their transmigration through the brain endothelium by upregulating MMP-1 and disrupting the inter-endothelial junctions (claudin-5, ZO-1 and ß-catenin). Restoring miR-202-3p exerted a metastasis-suppressive effect and preserved the endothelial barrier integrity. CONCLUSIONS: Our study identified a critical regulatory role of miR-202-3p in brain metastasis and shed light on miR-202-3p/MMP-1 axis as a novel prognostic and therapeutic target that can be exploited to predict and prevent brain metastasis in breast cancer patients.

Author Correction: A Small Compound Targeting Prohibitin with Potential Interest for Cognitive Deficit Rescue in Aging mice and Tau Pathology Treatment.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

A Small Compound Targeting Prohibitin with Potential Interest for Cognitive Deficit Rescue in Aging mice and Tau Pathology Treatment.

Neurodegenerative diseases, including Alzheimer's and Parkinson's disease, are characterized by increased protein aggregation in the brain, progressive neuronal loss, increased inflammation, and neurogenesis impairment. We analyzed the effects of a new purine derivative drug, PDD005, in attenuating mechanisms involved in the pathogenesis of neurodegenerative diseases, using both in vivo and in vitro models. We show that PDD005 is distributed to the brain and can rescue cognitive deficits associated with aging in mice. Treatment with PDD005 prevents impairment of neurogenesis by increasing sex-determining region Y-box 2, nestin, and also enhances synaptic function through upregulation of synaptophysin and postsynaptic density protein 95. PDD005 treatment also reduced neuro-inflammation by decreasing interleukin-1ß expression, activation of astrocytes, and microglia. We identified prohibitin as a potential target in mediating the therapeutic effects of PDD005 for the treatment of cognitive deficit in aging mice. Additionally, in the current study, glycogen synthase kinase appears to attenuate tau pathology.

Proof-of-Concept Study of Drug Brain Permeability Between in Vivo Human Brain and an in Vitro iPSCs-Human Blood-Brain Barrier Model.

The development of effective central nervous system (CNS) drugs has been hampered by the lack of robust strategies to mimic the blood-brain barrier (BBB) and cerebrovascular impairments in vitro. Recent technological advancements in BBB modeling using induced pluripotent stem cells (iPSCs) allowed to overcome some of these obstacles, nonetheless the pertinence for their use in drug permeation study remains to be established. This mandatory information requires a cross comparison of in vitro and in vivo pharmacokinetic data in the same species to avoid failure in late clinical drug development. Here, we measured the BBB permeabilities of 8 clinical positron emission tomography (PET) radioligands with known pharmacokinetic parameters in human brain in vivo with a newly developed in vitro iPSC-based human BBB (iPSC-hBBB) model. Our findings showed a good correlation between in vitro and in vivo drug brain permeability (R2 = 0.83; P = 0.008) which contrasted with the limited correlation between in vitro apparent permeability for a set of 18 CNS/non-CNS compounds using the in vitro iPSCs-hBBB model and drug physicochemical properties. Our data suggest that the iPSC-hBBB model can be integrated in a flow scheme of CNS drug screening and potentially used to study species differences in BBB permeation.

Dodecyl creatine ester-loaded nanoemulsion as a promising therapy for creatine transporter deficiency.

Creatine transporter (CrT) deficiency is an X-linked intellectual disability caused by mutations of CrT. Aim: This work focus on the preclinical development of a new therapeutic approach based on a microemulsion (ME) as drug delivery system for dodecyl creatine ester (DCE). Materials & methods: DCE-ME was prepared by titration method. Novel object recognition (NOR) tests were performed before and after DCE-ME treatment on Slc6a8-/y mice. Results: Intranasal administration with DCE-ME improved NOR performance in Slc6a8-/y mice. Slc6a8-/y mice treated with DCE-ME had increased striatal ATP levels mainly in the striatum compared with vehicle-treated Slc6a8-/y mice which was associated with increased expression of synaptic markers. Conclusion: These results highlight the potential value of DCE-ME as promising therapy for creatine transporter deficiency.

Small-molecule induction of Aß-42 peptide production in human cerebral organoids to model Alzheimer's disease associated phenotypes.

Human mini-brains (MB) are cerebral organoids that recapitulate in part the complexity of the human brain in a unique three-dimensional in vitro model, yielding discrete brain regions reminiscent of the cerebral cortex. Specific proteins linked to neurodegenerative disorders are physiologically expressed in MBs, such as APP-derived amyloids (Aß), whose physiological and pathological roles and interactions with other proteins are not well established in humans. Here, we demonstrate that neuroectodermal organoids can be used to study the Aß accumulation implicated in Alzheimer's disease (AD). To enhance the process of protein secretion and accumulation, we adopted a chemical strategy of induction to modulate post-translational pathways of APP using an Amyloid-ß Forty-Two Inducer named Aftin-5. Secreted, soluble Aß fragment concentrations were analyzed in MB-conditioned media. An increase in the Aß42 fragment secretion was observed as was an increased Aß42/Aß40 ratio after drug treatment, which is consistent with the pathological-like phenotypes described in vivo in transgenic animal models and in vitro in induced pluripotent stem cell-derived neural cultures obtained from AD patients. Notably in this context we observe time-dependent Aß accumulation, which differs from protein accumulation occurring after treatment. We show that mini-brains obtained from a non-AD control cell line are responsive to chemical compound induction, producing a shift of physiological Aß concentrations, suggesting that this model can be used to identify environmental agents that may initiate the cascade of events ultimately leading to sporadic AD. Increases in both Aß oligomers and their target, the cellular prion protein (PrPC), support the possibility of using MBs to further understand the pathophysiological role that underlies their interaction in a human model. Finally, the potential application of MBs for modeling age-associated phenotypes and the study of neurological disorders is confirmed.

PEG-PGA enveloped octaarginine-peptide nanocomplexes: An oral peptide delivery strategy.

The objective of this work was the development of a new drug nanocarrier intended to overcome the barriers associated to the oral modality of administration and to assess its value for the systemic or local delivery of peptides. The nanocarrier was rationally designed taking into account the nature of the intestinal barriers and was loaded with insulin, which was selected as a model peptide. The nanocarrier consisted of a complex between insulin and a hydrophobically-modified cell penetrating peptide (CPP), enveloped by a protecting polymer. The selected CPP was octaarginine (r8), chemically conjugated with cholesterol (Chol) or lauric acid (C12), whereas the protecting polymer was poly (glutamic acid)-poly (ethylene glycol) (PGA-PEG). This enveloping material was intended to preserve the stability of the nanocomplex in the intestinal medium and facilitate its diffusion across the intestinal mucus. The enveloped nanocomplexes (ENCPs) exhibited a number of key features, namely (i) a unimodal size distribution with a mean size of 200 nm and a neutral zeta potential, (ii) the capacity to associate insulin (~100% association efficiency) and protect it from degradation in simulated intestinal fluids, (iii) the ability to diffuse through intestinal mucus and, most importantly, (iv) the capacity to interact with the Caco-2 model epithelium, resulting in a massive insulin cell uptake (47.59 ±â€¯5.79%). This enhanced accumulation of insulin at the epithelial level was not translated into an enhanced insulin transport. In fact, only 2% of insulin was transported across the monolayer, and this was correlated with a moderate response of insulin following oral administration to healthy rats. Despite of this, the accumulation of the insulin-loaded nanocarriers in the intestinal mucosa could be verified in vivo upon their labeling with 99mTc. Overall, these data underline the capacity of the nanocarriers to overcome substantial barriers associated to the oral modality of administration and to facilitate the accumulation of the associated peptide at the intestinal level.

Brain Inflammation, Blood Brain Barrier dysfunction and Neuronal Synaptophysin Decrease after Inhalation Exposure to Titanium Dioxide Nano-aerosol in Aging Rats.

Notwithstanding potential neurotoxicity of inhaled titanium dioxide nanoparticles (TiO2 NPs), the toxicokinetics and consequences on blood-brain barrier (BBB) function remain poorly characterized. To improve risk assessment, we need to evaluate the impact on BBB under realistic environmental conditions and take into account vulnerability status such as age. 12-13 week and 19-month-old male rats were exposed by inhalation to 10 mg/m3 of TiO2 nano-aerosol (6 hrs/day, 5 day/week, for 4 weeks). We showed an age-dependent modulation of BBB integrity parameters suggesting increased BBB permeability in aging rats. This alteration was associated with a significant increase of cytokines/chemokines in the brain, including interleukin-1ß, interferon-γ, and fractalkine as well as a decreased expression of synaptophysin, a neuronal activity marker. These observations, in absence of detectable titanium in the brain suggest that CNS-related effects are mediated by systemic-pathway. Moreover, observations in terms of BBB permeability and brain inflammation underline age susceptibility. Even if TiO2 NPs were not evidenced in the brain, we observed an association between the exposure to TiO2 NPs and the dysregulation of BBB physiology associated with neuroinflammation and decreased expression of neuronal activity marker, which was further exacerbated in the brain of aged animal's.