A Systematic Review on Drugs Acting as Nicotinic Acetylcholine Receptor Agonists in the Treatment of Dementia.

Acetylcholine signaling is attenuated in early Alzheimer's disease (AD) and other dementias. A significant reduction in the expression of nicotinic acetylcholine receptors (nAChRs) in the brain of AD patients has also been reported in several molecular biological and in situ labeling studies. The modulation of the functional deficit of the cholinergic system as a pharmacological target could therefore have a clinical benefit, which is not to be neglected. This systematic review was conducted to identify clinical trials, which evaluated the safety and efficacy of nicotinic acetylcholine receptor agonists using Clinicaltrial (CT) and EudraCT databases. Structured searches identified 39 trials, which used 15 different drugs designed to increase the function of the nAChRs. Most of the identified clinical trials were phase II trials, with some of them classified as ongoing for several years. The systematic screening of the literature led to the selection of 14 studies out of the 8261 bibliographic records retrieved. Six trials reported detailed data on adverse events associated with the intervention, while twelve trials reported data on efficacy measures, such as attention, behavior and cognition. Overall, smost of the physical side effects of cholinergic agonists were reported to be well tolerated. Some trials also reported improvements in attention. However, the efficacy of these drugs in other cognitive and behavioral outcomes remains highly controversial.

Vitamin B12 Deficiency and the Nervous System: Beyond Metabolic Decompensation-Comparing Biological Models and Gaining New Insights into Molecular and Cellular Mechanisms.

Vitamin B12 (VitB12) is a micronutrient and acts as a cofactor for fundamental biochemical reactions: the synthesis of succinyl-CoA from methylmalonyl-CoA and biotin, and the synthesis of methionine from folic acid and homocysteine. VitB12 deficiency can determine a wide range of diseases, including nervous system impairments. Although clinical evidence shows a direct role of VitB12 in neuronal homeostasis, the molecular mechanisms are yet to be characterized in depth. Earlier investigations focused on exploring the biochemical shifts resulting from a deficiency in the function of VitB12 as a coenzyme, while more recent studies propose a broader mechanism, encompassing changes at the molecular/cellular levels. Here, we explore existing study models employed to investigate the role of VitB12 in the nervous system, including the challenges inherent in replicating deficiency/supplementation in experimental settings. Moreover, we discuss the potential biochemical alterations and ensuing mechanisms that might be modified at the molecular/cellular level (such as epigenetic modifications or changes in lysosomal activity). We also address the role of VitB12 deficiency in initiating processes that contribute to nervous system deterioration, including ROS accumulation, inflammation, and demyelination. Consequently, a complex biological landscape emerges, requiring further investigative efforts to grasp the intricacies involved and identify potential therapeutic targets.

M2 muscarinic receptors negatively modulate cell migration in human glioblastoma cells.

Glioblastoma (GB) is a very aggressive human brain tumor. The high growth potential and invasiveness make this tumor surgically and pharmacologically untreatable. Our previous work demonstrated that the activation of the M2 muscarinic acetylcholine receptors (M2 mAChRs) inhibited cell proliferation and survival in GB cell lines and in the cancer stem cells derived from human biopsies. The aim of the present study was to investigate the ability of M2 mAChR to modulate cell migration in two different GB cell lines: U87 and U251. By wound healing assay and single cell migration analysis performed by time-lapse microscopy, we demonstrated the ability of M2 mAChRs to negatively modulate cell migration in U251 but not in the U87 cell line. In order to explain the different effects observed in the two cell lines we have evaluated the possible involvement of the intermediate conductance calcium-activated potassium (IKCa) channel. IKCa channel is present in the GB cells, and it has been demonstrated to modulate cell migration. Using the perforated patch-clamp technique we have found that selective activation of M2 mAChR significantly reduced functional density of the IKCa current in U251 but not in U87 cells. To understand whether the M2 mAChR mediated reduction of ion channel density in the U251 cell line was relevant for the cell migration impairment, we tested the effects of TRAM-34, a selective inhibitor of the IKCa channel, in wound healing assay. We found that it was able to markedly reduce U251 cell migration and significantly decrease the number of invadopodia-like structure formations. These results suggest that only in U251 cells the reduced cell migration M2 mAChR-mediated might involve, at least in part, the IKCa channel.

α7 Nicotinic Acetylcholine Receptors May Improve Schwann Cell Regenerating Potential via Metabotropic Signaling Pathways.

BACKGROUND: Schwann cells (SCs) are glial cells involved in peripheral axon myelination. SCs also play a strategic role after peripheral nerve injury, regulating local inflammation and axon regeneration. Our previous studies demonstrated the presence of cholinergic receptors in SCs. In particular, the α7 nicotinic acetylcholine receptors (nAChRs) are expressed in SCs after peripheral axotomy, suggesting their involvement in the regulation of SC-regenerating properties. To clarify the role that α7 nAChRs may play after peripheral axon damage, in this study we investigated the signal transduction pathways triggered by receptor activation and the effects produced by their activation. METHODS: Both ionotropic and metabotropic cholinergic signaling were analyzed by calcium imaging and Western blot analysis, respectively, following α7 nAChR activation. In addition, the expression of c-Jun and α7 nAChRs was evaluated by immunocytochemistry and Western blot analysis. Finally, the cell migration was studied by a wound healing assay. RESULTS: Activation of α7 nAChRs, activated by the selective partial agonist ICH3, did not induce calcium mobilization but positively modulated the PI3K/AKT/mTORC1 axis. Activation of the mTORC1 complex was also supported by the up-regulated expression of its specific p-p70 S6KThr389 target. Moreover, up-regulation of p-AMPKThr172, a negative regulator of myelination, was also observed concomitantly to an increased nuclear accumulation of the transcription factor c-Jun. Cell migration and morphology analyses proved that α7 nAChR activation also promotes SC migration. CONCLUSIONS: Our data demonstrate that α7 nAChRs, expressed by SCs only after peripheral axon damage and/or in an inflammatory microenvironment, contribute to improve the SCs regenerating properties. Indeed, α7 nAChR stimulation leads to an upregulation of c-Jun expression and promotes Schwann cell migration by non-canonical pathways involving the mTORC1 activity.

M2 Muscarinic Receptor Stimulation Induces Autophagy in Human Glioblastoma Cancer Stem Cells via mTOR Complex-1 Inhibition.

BACKGROUND: Although autophagy is a pro-survival process of tumor cells, it can stimulate cell death in particular conditions and when differently regulated by specific signals. We previously demonstrated that the selective stimulation of the M2 muscarinic receptor subtype (mAChR) negatively controls cell proliferation and survival and causes oxidative stress and cytotoxic and genotoxic effects in both GBM cell lines and GBM stem cells (GSCs). In this work, we have evaluated whether autophagy was induced as a downstream mechanism of the observed cytotoxic processes induced by M2 mAChR activation by the orthosteric agonist APE or the dualsteric agonist N8-Iper (N8). METHODS: To assess the activation of autophagy, we analyzed the expression of LC3B using Western blot analysis and in LC3B-EGFP transfected cell lines. Apoptosis was assessed by measuring the protein expression of Caspases 3 and 9. RESULTS: Our data indicate that activation of M2 mAChR by N8 promotes autophagy in both U251 and GB7 cell lines as suggested by the LC3B-II expression level and analysis of the transfected cells by fluorescence microscopy. Autophagy induction by M2 mAChRs is regulated by the decreased activity of the PI3K/AKT/mTORC1 pathway and upregulated by pAMPK expression. Downstream of autophagy activation, an increase in apoptosis was also observed in both cell lines after treatment with the two M2 agonists. CONCLUSIONS: N8 treatment causes autophagy via pAMPK upregulation, followed by apoptosis in both investigated cell lines. In contrast, the absence of autophagy in APE-treated GSC cells seems to indicate that cell death could be triggered by mechanisms alternative to those observed for N8.

Retinoic acid-induced 1 gene haploinsufficiency alters lipid metabolism and causes autophagy defects in Smith-Magenis syndrome.

Smith-Magenis syndrome (SMS) is a neurodevelopmental disorder characterized by cognitive and behavioral symptoms, obesity, and sleep disturbance, and no therapy has been developed to alleviate its symptoms or delay disease onset. SMS occurs due to haploinsufficiency of the retinoic acid-induced-1 (RAI1) gene caused by either chromosomal deletion (SMS-del) or RAI1 missense/nonsense mutation. The molecular mechanisms underlying SMS are unknown. Here, we generated and characterized primary cells derived from four SMS patients (two with SMS-del and two carrying RAI1 point mutations) and four control subjects to investigate the pathogenetic processes underlying SMS. By combining transcriptomic and lipidomic analyses, we found altered expression of lipid and lysosomal genes, deregulation of lipid metabolism, accumulation of lipid droplets, and blocked autophagic flux. We also found that SMS cells exhibited increased cell death associated with the mitochondrial pathology and the production of reactive oxygen species. Treatment with N-acetylcysteine reduced cell death and lipid accumulation, which suggests a causative link between metabolic dyshomeostasis and cell viability. Our results highlight the pathological processes in human SMS cells involving lipid metabolism, autophagy defects and mitochondrial dysfunction and suggest new potential therapeutic targets for patient treatment.

The activation of M2 muscarinic receptor inhibits cell growth and survival in human epithelial ovarian carcinoma.

Ovarian cancer is the fifth leading cause of cancer-related deaths in females. Many ovarian tumor cell lines express muscarinic receptors (mAChRs), and their expression is correlated with reduced survival of patients. We have characterized the expression of mAChRs in two human ovarian carcinoma cell lines (SKOV-3, TOV-21G) and two immortalized ovarian surface epithelium cell lines (iOSE-120, iOSE-398). Among the five subtypes of mAChRs (M1-M5 receptors), we focused our attention on the M2 receptor, which is involved in the inhibition of tumor cell proliferation. Western blot analysis and real-time PCR analyses indicated that the levels of M2 are statistically downregulated in cancer cells. Therefore, we investigated the effect of arecaidine propargyl ester hydrobromide (APE), a preferential M2 agonist, on cell growth and survival. APE treatment decreased cell number in a dose and time-dependent manner by decreasing cell proliferation and increasing cell death. FACS and immunocytochemistry analysis have also demonstrated the ability of APE to accumulate the cells in G2/M phase of the cell cycle and to increase the percentage of abnormal mitosis. The higher level of M2 receptors in the iOSE cells rendered these cells more sensitive to APE treatment than cancer cells. The data here reported suggest that M2 has a negative role in cell growth/survival of ovarian cell lines, and its downregulation may favor tumor progression.

Effects Mediated by Dimethyl Fumarate on In Vitro Oligodendrocytes: Implications in Multiple Sclerosis.

BACKGROUND: Dimethyl fumarate (DMF) is a drug currently in use in oral therapy for the treatment of relapsing-remitting multiple sclerosis (RRMS) due to its immunomodulatory and neuroprotective effects. The mechanisms by which DMF exerts its therapeutic effects in MS and in particular its influence on the oligodendrocytes (OLs) survival or differentiation have not yet been fully understood. METHODS: Characterization of Oli neu cells was performed by immunocytochemistry and RT-PCR. The effect of DMF on cell proliferation and morphology was assessed by MTT assay, trypan blue staining, RT-PCR and Western blot analysis. The antioxidant and anti-inflammatory properties of DMF were analysed by ROS detection through DCFDA staining and lipid content analysis by Oil Red O staining and TLC. RESULTS: DMF has been observed to induce a slowdown of cell proliferation, favoring the oligodendrocyte lineage cells (OLCs) differentiation. DMF has an antioxidant effect and is able to modify the lipid content even after the LPS-mediated inflammatory stimulus in Oli neu cells. CONCLUSIONS: The results obtained confirm that DMF has anti-inflammatory and antioxidant effects also on Oli neu cells. Interestingly, it appears to promote the OLCs differentiation towards mature and potentially myelinating cells.

Analysis of Signal Transduction Pathways Downstream M2 Receptor Activation: Effects on Schwann Cell Migration and Morphology.

BACKGROUND: Schwann cells (SCs) express cholinergic receptors, suggesting a role of cholinergic signaling in the control of SC proliferation, differentiation and/or myelination. Our previous studies largely demonstrated that the pharmacological activation of the M2 muscarinic receptor subtype caused an inhibition of cell proliferation and promoted the expression of pro-myelinating differentiation genes. In order to elucidate the molecular signaling activated downstream the M2 receptor activation, in the present study we investigated the signal transduction pathways activated by the M2 orthosteric agonist arecaidine propargyl ester (APE) in SCs. METHODS: Using Western blot we analyzed some components of the noncanonical pathways involving ß1-arrestin and PI3K/AKT/mTORC1 signaling. A wound healing assay was used to evaluate SC migration. RESULTS: Our results demonstrated that M2 receptor activation negatively modulated the PI3K/Akt/mTORC1 axis, possibly through ß1-arrestin downregulation. The involvement of the mTORC1 complex was also supported by the decreased expression of its specific target p-p70 S6KThr389. Then, we also analyzed the expression of p-AMPKαthr172, a negative regulator of myelination that resulted in reduced levels after M2 agonist treatment. The analysis of cell migration and morphology allowed us to demonstrate that M2 receptor activation caused an arrest of SC migration and modified cell morphology probably by the modulation of ß1-arrestin/cofilin-1 and PKCα expression, respectively. CONCLUSIONS: The data obtained demonstrated that M2 receptor activation in addition to the canonical Gi protein-coupled pathway modulates noncanonical pathways involving the mTORC1 complex and other kinases whose activation may contribute to the inhibition of SC proliferation and migration and address SC differentiation.

Notch Signal Mediates the Cross-Interaction between M2 Muscarinic Acetylcholine Receptor and Neuregulin/ErbB Pathway: Effects on Schwann Cell Proliferation.

The cross-talk between axon and glial cells during development and in adulthood is mediated by several molecules. Among them are neurotransmitters and their receptors, which are involved in the control of myelinating and non-myelinating glial cell development and physiology. Our previous studies largely demonstrate the functional expression of cholinergic muscarinic receptors in Schwann cells. In particular, the M2 muscarinic receptor subtype, the most abundant cholinergic receptor expressed in Schwann cells, inhibits cell proliferation downregulating proteins expressed in the immature phenotype and triggers promyelinating differentiation genes. In this study, we analysed the in vitro modulation of the Neuregulin-1 (NRG1)/erbB pathway, mediated by the M2 receptor activation, through the selective agonist arecaidine propargyl ester (APE). M2 agonist treatment significantly downregulates NRG1 and erbB receptors expression, both at transcriptional and protein level, and causes the internalization and intracellular accumulation of the erbB2 receptor. Additionally, starting from our previous results concerning the negative modulation of Notch-active fragment NICD by M2 receptor activation, in this work, we clearly demonstrate that the M2 receptor subtype inhibits erbB2 receptors by Notch-1/NICD downregulation. Our data, together with our previous results, demonstrate the existence of a cross-interaction between the M2 receptor and NRG1/erbB pathway-Notch1 mediated, and that it is responsible for the modulation of Schwann cell proliferation/differentiation.

Emerging Roles of Cholinergic Receptors in Schwann Cell Development and Plasticity.

The cross talk between neurons and glial cells during development, adulthood, and disease, has been extensively documented. Among the molecules mediating these interactions, neurotransmitters play a relevant role both in myelinating and non-myelinating glial cells, thus resulting as additional candidates regulating the development and physiology of the glial cells. In this review, we summarise the contribution of the main neurotransmitter receptors in the regulation of the morphogenetic events of glial cells, with particular attention paid to the role of acetylcholine receptors in Schwann cell physiology. In particular, the M2 muscarinic receptor influences Schwann cell phenotype and the α7 nicotinic receptor is emerging as influential in the modulation of peripheral nerve regeneration and inflammation. This new evidence significantly improves our knowledge of Schwann cell development and function and may contribute to identifying interesting new targets to support the activity of these cells in pathological conditions.

The Mechanisms Mediated by α7 Acetylcholine Nicotinic Receptors May Contribute to Peripheral Nerve Regeneration.

Due to the microenvironment created by Schwann cell (SC) activity, peripheral nerve fibers are able to regenerate. Inflammation is the first response to nerve damage and the removal of cellular and myelin debris is essential in preventing the persistence of the local inflammation that may negatively affect nerve regeneration. Acetylcholine (ACh) is one of the neurotransmitters involved in the modulation of inflammation through the activity of its receptors, belonging to both the muscarinic and nicotinic classes. In this report, we evaluated the expression of α7 nicotinic acetylcholine receptors (nAChRs) in rat sciatic nerve, particularly in SCs, after peripheral nerve injury. α7 nAChRs are absent in sciatic nerve immediately after dissection, but their expression is significantly enhanced in SCs after 24 h in cultured sciatic nerve segments or in the presence of the proinflammatory neuropeptide Bradykinin (BK). Moreover, we found that activation of α7 nAChRs with the selective partial agonist ICH3 causes a decreased expression of c-Jun and an upregulation of uPA, MMP2 and MMP9 activity. In addition, ICH3 treatment inhibits IL-6 transcript level expression as well as the cytokine release. These results suggest that ACh, probably released from regenerating axons or by SC themselves, may actively promote through α7 nAChRs activation an anti-inflammatory microenvironment that contributes to better improving the peripheral nerve regeneration.

The Combined Treatment with Chemotherapeutic Agents and the Dualsteric Muscarinic Agonist Iper-8-Naphthalimide Affects Drug Resistance in Glioblastoma Stem Cells.

BACKGROUND: Glioblastoma multiforme (GBM) is characterized by heterogeneous cell populations. Among these, the Glioblastoma Stem Cells (GSCs) fraction shares some similarities with Neural Stem Cells. GSCs exhibit enhanced resistance to conventional chemotherapy drugs. Our previous studies demonstrated that the activation of M2 muscarinic acetylcholine receptors (mAChRs) negatively modulates GSCs proliferation and survival. The aim of the present study was to analyze the ability of the M2 dualsteric agonist Iper-8-naphthalimide (N-8-Iper) to counteract GSCs drug resistance. METHODS: Chemosensitivity to M2 dualsteric agonist N-8-Iper and chemotherapy drugs such as temozolomide, doxorubicin, or cisplatin was evaluated in vitro by MTT assay in two different GSC lines. Drug efflux pumps expression was evaluated by RT-PCR and qRT-PCR. RESULTS: By using sub-toxic concentrations of N-8-Iper combined with the individual chemotherapeutic agents, we found that only low doses of the M2 agonist combined with doxorubicin or cisplatin or temozolomide were significantly able to counteract cell growth in both GSC lines. Moreover, we evaluated as the exposure to high and low doses of N-8-Iper downregulated the ATP-binding cassette (ABC) drug efflux pumps expression levels. CONCLUSIONS: Our results revealed the ability of the investigated M2 agonist to counteract drug resistance in two GSC lines, at least partially by downregulating the ABC drug efflux pumps expression. The combined effects of low doses of conventional chemotherapy and M2 agonists may thus represent a novel promising pharmacological approach to impair the GSC-drug resistance in the GBM therapy.

M2 Muscarinic Receptor Activation Impairs Mitotic Progression and Bipolar Mitotic Spindle Formation in Human Glioblastoma Cell Lines.

BACKGROUND: Glioblastoma multiforme (GBM) is characterized by several genetic abnormalities, leading to cell cycle deregulation and abnormal mitosis caused by a defective checkpoint. We previously demonstrated that arecaidine propargyl ester (APE), an orthosteric agonist of M2 muscarinic acetylcholine receptors (mAChRs), arrests the cell cycle of glioblastoma (GB) cells, reducing their survival. The aim of this work was to better characterize the molecular mechanisms responsible for this cell cycle arrest. METHODS: The arrest of cell proliferation was evaluated by flow cytometry analysis. Using immunocytochemistry and time-lapse analysis, the percentage of abnormal mitosis and aberrant mitotic spindles were assessed in both cell lines. Western blot analysis was used to evaluate the modulation of Sirtuin2 and acetylated tubulin-factors involved in the control of cell cycle progression. RESULTS: APE treatment caused arrest in the M phase, as indicated by the increase in p-HH3 (ser10)-positive cells. By immunocytochemistry, we found a significant increase in abnormal mitoses and multipolar mitotic spindle formation after APE treatment. Time-lapse analysis confirmed that the APE-treated GB cells were unable to correctly complete the mitosis. The modulated expression of SIRT2 and acetylated tubulin in APE-treated cells provides new insights into the mechanisms of altered mitotic progression in both GB cell lines. CONCLUSIONS: Our data show that the M2 agonist increases aberrant mitosis in GB cell lines. These results strengthen the idea of considering M2 acetylcholine receptors a novel promising therapeutic target for the glioblastoma treatment.

Cholinergic Modulation of Neuroinflammation: Focus on α7 Nicotinic Receptor.

All nervous system pathologies (e.g., neurodegenerative/demyelinating diseases and brain tumours) develop neuroinflammation, a beneficial process during pathological events, aimed at removing damaged cells, toxic agents, and/or pathogens. Unfortunately, excessive inflammation frequently occurs during nervous system disorders, becoming a detrimental event capable of enhancing neurons and myelinating glial cell impairment, rather than improving their survival and activity. Consequently, targeting the neuroinflammation could be relevant for reducing brain injury and rescuing neuronal and glial cell functions. Several studies have highlighted the role of acetylcholine and its receptors in the regulation of central and peripheral inflammation. In particular, α7 nicotinic receptor has been described as one of the main regulators of the "brain cholinergic anti-inflammatory pathway". Its expression in astrocytes and microglial cells and the ability to modulate anti-inflammatory cytokines make this receptor a new interesting therapeutic target for neuroinflammation regulation. In this review, we summarize the distribution and physiological functions of the α7 nicotinic receptor in glial cells (astrocytes and microglia) and its role in the modulation of neuroinflammation. Moreover, we explore how its altered expression and function contribute to the development of different neurological pathologies and exacerbate neuroinflammatory processes.

Expression of Cholinergic Markers and Characterization of Splice Variants during Ontogenesis of Rat Dorsal Root Ganglia Neurons.

Dorsal root ganglia (DRG) neurons synthesize acetylcholine (ACh), in addition to their peptidergic nature. They also release ACh and are cholinoceptive, as they express cholinergic receptors. During gangliogenesis, ACh plays an important role in neuronal differentiation, modulating neuritic outgrowth and neurospecific gene expression. Starting from these data, we studied the expression of choline acetyltransferase (ChAT) and vesicular ACh transporter (VAChT) expression in rat DRG neurons. ChAT and VAChT genes are arranged in a "cholinergic locus", and several splice variants have been described. Using selective primers, we characterized splice variants of these cholinergic markers, demonstrating that rat DRGs express R1, R2, M, and N variants for ChAT and V1, V2, R1, and R2 splice variants for VAChT. Moreover, by RT-PCR analysis, we observed a progressive decrease in ChAT and VAChT transcripts from the late embryonic developmental stage (E18) to postnatal P2 and P15 and in the adult DRG. Interestingly, Western blot analyses and activity assays demonstrated that ChAT levels significantly increased during DRG ontogenesis. The modulated expression of different ChAT and VAChT splice variants during development suggests a possible differential regulation of cholinergic marker expression in sensory neurons and confirms multiple roles for ACh in DRG neurons, both in the embryo stage and postnatally.

Current Nanocarrier Strategies Improve Vitamin B12 Pharmacokinetics, Ameliorate Patients' Lives, and Reduce Costs.

Vitamin B12 (VitB12) is a naturally occurring compound produced by microorganisms and an essential nutrient for humans. Several papers highlight the role of VitB12 deficiency in bone and heart health, depression, memory performance, fertility, embryo development, and cancer, while VitB12 treatment is crucial for survival in inborn errors of VitB12 metabolism. VitB12 is administrated through intramuscular injection, thus impacting the patients' lifestyle, although it is known that oral administration may meet the specific requirement even in the case of malabsorption. Furthermore, the high-dose injection of VitB12 does not ensure a constant dosage, while the oral route allows only 1.2% of the vitamin to be absorbed in human beings. Nanocarriers are promising nanotechnology that can enable therapies to be improved, reducing side effects. Today, nanocarrier strategies applied at VitB12 delivery are at the initial phase and aim to simplify administration, reduce costs, improve pharmacokinetics, and ameliorate the quality of patients' lives. The safety of nanotechnologies is still under investigation and few treatments involving nanocarriers have been approved, so far. Here, we highlight the role of VitB12 in human metabolism and diseases, and the issues linked to its molecule properties, and discuss how nanocarriers can improve the therapy and supplementation of the vitamin and reduce possible side effects and limits.

Transient Anomalous Diffusion MRI in Excised Mouse Spinal Cord: Comparison Among Different Diffusion Metrics and Validation With Histology.

Neural tissue is a hierarchical multiscale system with intracellular and extracellular diffusion compartments at different length scales. The normal diffusion of bulk water in tissues is not able to detect the specific features of a complex system, providing nonlocal, diffusion measurement averaged on a 10-20 µm length scale. Being able to probe tissues with sub-micrometric diffusion length and quantify new local parameters, transient anomalous diffusion (tAD) would dramatically increase the diagnostic potential of diffusion MRI (DMRI) in detecting collective and sub-micro architectural changes of human tissues due to pathological damage. In DMRI, the use of tAD parameters quantified using specific DMRI acquisition protocols and their interpretation has often aroused skepticism. Although the derived formulas may accurately fit experimental diffusion-weighted data, the relationships between the postulated dynamical feature and the underlying geometrical structure remains elusive, or at most only suggestive. This work aimed to elucidate and validate the image contrast and information that can be obtained using the tAD model in white matter (WM) through a direct comparison between different diffusion metrics and histology. Towards this goal, we compared tAD metrics extracted from pure subdiffusion (α-imaging) and super-pseudodiffusion (γ-imaging) in excised mouse spinal cord WM, together with T2 and T2* relaxometry, conventional (normal diffusion-based) diffusion tensor imaging (DTI) and q-space imaging (QSI), with morphologic measures obtained by optical microscopy, to determine which structural and topological characteristics of myelinated axons influenced tAD contrast. Axon diameter (AxDiam), the standard deviation of diameters (SD ax.diam ), axonal density (AxDens) and effective local density (ELD) were extracted from optical images in several WM tracts. Among all the diffusion parameters obtained at 9.4 T, γ-metrics confirmed a strong dependence on magnetic in-homogeneities quantified by R2* = 1/T2* and showed the strongest associations with AxDiam and ELD. On the other hand, α-metrics showed strong associations with SD ax.diam and was significantly related to AxDens, suggesting its ability to quantify local heterogeneity degree in neural tissue. These results elucidate the biophysical mechanism underpinning tAD parameters and show the clinical potential of tAD-imaging, considering that both physiologic and pathologic neurodegeneration translate into alterations of WM morphometry and topology.

Novel Therapeutic Delivery of Nanocurcumin in Central Nervous System Related Disorders.

Nutraceuticals represent complementary or alternative beneficial products to the expensive and high-tech therapeutic tools in modern medicine. Nowadays, their medical or health benefits in preventing or treating different types of diseases is widely accepted, due to fewer side effects than synthetic drugs, improved bioavailability and long half-life. Among herbal and natural compounds, curcumin is a very attractive herbal supplement considering its multipurpose properties. The potential effects of curcumin on glia cells and its therapeutic and protective properties in central nervous system (CNS)-related disorders is relevant. However, curcumin is unstable and easily degraded or metabolized into other forms posing limits to its clinical development. This is particularly important in brain pathologies determined blood brain barrier (BBB) obstacle. To enhance the stability and bioavailability of curcumin, many studies focused on the design and development of curcumin nanodelivery systems (nanoparticles, micelles, dendrimers, and diverse nanocarriers). These nanoconstructs can increase curcumin stability, solubility, in vivo uptake, bioactivity and safety. Recently, several studies have reported on a curcumin exosome-based delivery system, showing great therapeutical potential. The present work aims to review the current available data in improving bioactivity of curcumin in treatment or prevention of neurological disorders.