Depression and the Glutamate/GABA-Glutamine Cycle.

Many features of major depressive disorder are mirrored in rodent models of psychological stress. These models have been used to examine the relationship between the activation of the hypo- thalamic-pituitary axis in response to stress, the development of oxidative stress and neuroinflamma- tion, the dominance of cholinergic neurotransmission and the associated increase in REM sleep pres- sure. Rodent models have also provided valuable insights into the impairment of glycolysis and brain glucose utilization by the brain under stress, the resulting decrease in brain energy production and the reduction in glutamate/GABA -glutamine cycling. The rapidly acting antidepressants, scopolamine, ketamine and ECT, all raise extracellular glutamate and scopolamine and ketamine have specifically been shown to increase glutamate/GABA-glutamine cycling in men and rodents with corresponding short-term relief of depression. The nightly use of gammahydroxybutyrate (GHB) may achieve more permanent results and may even act prophylactically to prevent the development or recurrence of de- pression. GHB is a GABAB agonist and restores the normal balance between cholinergic and mono- aminergic neurotransmission by inhibiting cholinergic neurotransmission. It relieves REM sleep pres- sure. GHB's metabolism generates NADPH, a key antioxidant cofactor. Its metabolism also generates succinate, the tricarboxylic acid cycle intermediate, to provide energy to the cell and to synthesize glu- tamate. In both animals and man, GHB increases the level of brain glutamate.

Exploring neonicotinoid effects on Drosophila: insights into olfactory memory, neurotransmission, and synaptic connectivity.

Neonicotinoid insecticides, the fastest-growing class in recent decades, interfere with cholinergic neurotransmission by binding to the nicotinic acetylcholine receptor. This disruption affects both targeted and non-targeted insects, impairing cognitive functions such as olfaction and related behaviors, with a particular emphasis on olfactory memory due to its ecological impact. Despite the persistent presence of these chemicals in the environment, significant research gaps remain in understanding the intricate interplay between cognitive function, development, neuronal activity, and neonicotinoid-induced toxicity. This study focuses on the fruit fly Drosophila melanogaster, chosen for its genetic tractability, well-characterized neural circuitry, and remarkable parallels with bees in neurotransmitter systems and brain structures. Our aim is to establish the fruit fly as a valuable model organism for studying the effects of neonicotinoids on behavior and neuronal circuitry, with particular attention to olfactory memory and associated brain circuitries. To achieve this aim, we conducted experiments to investigate the effects of short-term exposure to sublethal doses of the neonicotinoid imidacloprid, mimicking realistic environmental insecticide exposure, on the formation of odor memories. Additionally, we evaluated synaptic contacts and cholinergic neurotransmission within the mushroom body, the primary memory network of insects. Our results showed significant impairments in odor memory formation in flies exposed to imidacloprid, with exposure during the adult stage showing more pronounced effects than exposure during the larval stage. Additionally, functional studies revealed a decrease in synaptic contacts within the intrinsic olfactory projection neurons and the mushroom body. Furthermore, another experiment showed an odor-dependent reduction in cholinergic neurotransmission within this network. In summary, employing Drosophila as a model organism provides a robust framework for investigating neonicotinoid effects and understanding their diverse impacts on insect physiology and behavior. Our study initiates the establishment of the fruit fly as a pivotal model for exploring neonicotinoid influences, shedding light on their effects on olfactory memory, neuronal integrity, and synaptic transmission.

Glucagon-like Peptide-2 Depresses Ileal Contractility in Preparations from Mice through Opposite Modulatory Effects on Nitrergic and Cholinergic Neurotransmission.

Glucagon-like peptide-2 (GLP-2) has been reported to influence gastrointestinal motor responses, exerting a modulatory role on enteric neurotransmission. To our knowledge, no data on GLP-2 effects on the motility of the isolated ileum are available; therefore, we investigated whether GLP-2 affects the contractile activity of mouse ileal preparations and the neurotransmitters engaged. Ileal preparations showed tetrodotoxin (TTX)- and atropine-insensitive spontaneous contractile activity, which was unaffected by the nitric oxide synthesis inhibitor, L-NNA. GLP-2 depressed the spontaneous contractility, an effect that was abolished by TTX or L-NNA and not influenced by atropine. Electrical field stimulation induced TTX- and atropine-sensitive contractile responses, which were reduced in amplitude by GLP-2 even in the presence of L-NNA. Immunohistochemical results showed a significant increase in nNOS-positive fibers in the ileal muscle wall and a significant decrease in ChAT-positive myenteric neurons in GLP-2-exposed preparations. The present results offer the first evidence that GLP-2 acts on ileal preparations. The hormone appears to depress ileal contractility through a dual opposite modulatory effect on inhibitory nitrergic and excitatory cholinergic neurotransmission. From a physiological point of view, it could be hypothesized that GLP-2 inhibitory actions on ileal contractility can increase transit time, facilitating nutrient absorption.

Proteomics Evidence of the Role of TDMQ20 in the Cholinergic System and Synaptic Transmission in a Mouse Model of Alzheimer's Disease.

The interaction between copper ions and amyloid peptide Aß has been reported to be involved in Alzheimer's disease (AD) pathology. Based on copper coordination biochemistry, we designed specific copper chelators [tetradentate monoquinolines (TDMQs)] in order to regulate copper homeostasis in the AD brain and inhibit the deleterious oxidative stress catalyzed by copper-Aß complexes. We previously reported that TDMQ20, a highly selective copper chelator selected as a drug candidate, was able to extract copper from the Cu-Aß1-16 complex and restore cognitive and behavioral deficits in AD mouse models. For a better understanding of the mechanism of action of TDMQ20, we decided to investigate the change of profile of proteins expressed in 5xFAD mice after an oral treatment of TDMQ20 (dose = 10 mg/kg, once every two days for 3 months, in total 45 times). Clioquinol (CQ), a non-specific chelator, has been used as a comparator. Here, we report the proteomic alterations in the cortex of 5xFAD mice using iTRAQ (isobaric tags for relative and absolute quantification) proteomics technology. The results indicated that 178 differentially expressed proteins (DEPs) have been identified in the AD mouse group with respect to wild type (WT) animals (AD/WT). After treatment by TDMQ20, 35 DEPs were found common in AD/WT and TDMQ20/AD groups in an opposite change manner (up- or down-regulated, respectively). In addition, among the 35 DEPs mentioned above, 10 common target proteins have been identified in AD/WT, TDMQ20/AD, and CQ/AD groups, among which 3 target proteins were successfully validated by western blot analysis. In particular, the expression levels of ChAT and CHRM4 are significantly increased upon TDMQ20 treatment with respect to 5xFAD mice, while CQ did not significantly change the expression of these proteins. Our study suggests the involvement of the copper chelator TDMQ20 on the cholinergic system, a feature that may explain the improved cognitive and behavioral performance in AD mice upon oral treatment of TDMQ20.

Dorsal hippocampal muscarinic cholinergic receptors orchestrate behavioral and autonomic changes induced by contextual fear retrieval.

Re-exposure of rats to a previously fear-conditioned environment arouses great alterations in behavioral and cardiovascular parameters. Pieces of works provide putative evidence for the contribution of the dorsal hippocampus (dHC) to contextual conditioning. dHC gathers massive cholinergic inputs from the basal forebrain, and dHC acetylcholine (ACh) is often described as triggering the retrieval of defensive behavior. ACh acts partially through muscarinic receptors (mAChRs) M1R and M3R subtypes. Hence, activation of mAChRs facilitates autonomic and behavioral responses associated with threats and dangers. Therefore, this study explored the likely involvement of M1R and M3R in rat dHC to establish the behavioral and autonomic changes associated with contextual fear retrieval. Male Wistar rats had stainless steel guide cannula implanted into the dHC before being submitted to contextual fear conditioning (6 footshocks, 1.5 mA, 3 s). A catheter placed within the femoral artery allowed autonomic recordings. A variety of drugs were delivered into the dHC 10 min before contextual re-exposure. The choline reuptake inhibitor hemicholinium induced a decrease of the fear conditioned responses, while did not modify it in non-conditioned animals. The non-selective mAChR antagonist atropine also reduced the fear-conditioned responses, as did the selective M1/M3 mAChRs antagonist fumarate. On the other hand, the M1 selective mAChR antagonist pirenzepine inhibited all the autonomic fear responses without affecting animal freezing. These findings support that cholinergic neurotransmission present in the dHC acts through mAChRs to coordinate the expression of fear evoked by contextual conditioning.

DE-71 affected the cholinergic system and locomotor activity via disrupting calcium homeostasis in zebrafish larvae.

Polybrominated diphenyl ethers (PBDEs) can induce neurotoxicity, but the mechanism of their toxicity on the cholinergic system and locomotion behavior remains unclear. In this paper, zebrafish embryos were exposed to DE-71 (0, 1, 3, 10, 30, and 100 µg/L) until 120 h post fertilization, and its effects on the behavior and cholinergic system of zebrafish larvae and its possible mechanism were investigated. Results indicated a general locomotor activity impairment in the light-dark transition stimulation without affecting the secondary motoneurons. However, with the extension of test time in the dark or light, the decreased locomotor activity was diminished, a significant decrease only observed in the 100 µg/L DE-71 exposure groups in the last 10 min. Furthermore, whole-body acetylcholine (ACh) contents decreased after DE-71 exposure, whereas no changes in NO contents and inducible nitric oxide synthase activity were found. The expression of certain genes encoding calcium homeostasis proteins (e.g., grin1a, camk2a, and crebbpb) and the concentrations of calcium in zebrafish larvae were significantly decreased after DE-71 exposure. After co-exposure with calcium channel agonist (±)-BAY K8644, calcium concentrations, ACh contents, and locomotor activity in the light-dark transition stimulation was significantly increased compared with the same concentrations of DE-71 exposure alone, whereas no significant difference was observed compared with the control, indicating that calcium homeostasis is involved in the impairment of cholinergic neurotransmission and locomotor activity. Overall, our results suggested that DE-71 can impair the cholinergic system and locomotor activity by impairing calcium homeostasis. Our paper provides a better understanding of the neurotoxicity of PBDEs.

Constructing and Tuning Excitatory Cholinergic Synapses: The Multifaceted Functions of Nicotinic Acetylcholine Receptors in Drosophila Neural Development and Physiology.

Nicotinic acetylcholine receptors (nAchRs) are widely distributed within the nervous system across most animal species. Besides their well-established roles in mammalian neuromuscular junctions, studies using invertebrate models have also proven fruitful in revealing the function of nAchRs in the central nervous system. During the earlier years, both in vitro and animal studies had helped clarify the basic molecular features of the members of the Drosophila nAchR gene family and illustrated their utility as targets for insecticides. Later, increasingly sophisticated techniques have illuminated how nAchRs mediate excitatory neurotransmission in the Drosophila brain and play an integral part in neural development and synaptic plasticity, as well as cognitive processes such as learning and memory. This review is intended to provide an updated survey of Drosophila nAchR subunits, focusing on their molecular diversity and unique contributions to physiology and plasticity of the fly neural circuitry. We will also highlight promising new avenues for nAchR research that will likely contribute to better understanding of central cholinergic neurotransmission in both Drosophila and other organisms.

Erratum: Regulation of the Muscarinic M3 Receptor by Myocardin-Related Transcription Factors.

[This corrects the article DOI: 10.3389/fphys.2021.710968.].

Influence of Tilia tomentosa Moench Extract on Mouse Small Intestine Neuromuscular Contractility.

Functional gastrointestinal disorders (FGIDs) are characterized by abdominal pain, bloating and bowel disturbances. FGID therapy is primarily symptomatic, including treatment with herbal remedies. Flower extract of Tilia tomentosa Moench (TtM) is occasionally used as an anti-spasmodic in popular medicine. Since its effect on intestinal response is unknown, we evaluated the influence of TtM extract on small intestine contractility. Ileal preparations from C57BL/6J mice were mounted in organ baths to assess changes in muscle tension, following addition of TtM extract (0.5-36 µg/mL) or a vehicle (ethanol). Changes in contractile response to receptor- and non-receptor-mediated stimuli were assessed in ileal preparations pretreated with 12 µg/mL TtM. Alterations in the enteric nervous system neuroglial network were analyzed by confocal immunofluorescence. Increasing addition of TtM induced a marked relaxation in ileal specimens compared to the vehicle. Pretreatment with TtM affected cholinergic and tachykininergic neuromuscular contractions as well as K+-induced smooth muscle depolarization. Following incubation with TtM, a significant reduction in non-adrenergic non-cholinergic-mediated relaxation sensitive to Nω-Nitro-L-arginine methyl ester hydrochloride (pan-nitric oxide synthase inhibitor) was found. In vitro incubation of intestinal specimens with TtM did not affect the myenteric plexus neuroglial network. Our findings show that TtM-induced intestinal relaxation is mediated by nitric oxide pathways, providing a pharmacological basis for the use of TtM in FGIDs.

Homomeric and Heteromeric α7 Nicotinic Acetylcholine Receptors in Health and Some Central Nervous System Diseases.

Nicotinic acetylcholine receptors (nAChRs) are pentameric ligand-gated ion channels involved in the modulation of essential brain functions such as memory, learning, and attention. Homomeric α7 nAChR, formed exclusively by five identical α7 subunits, is involved in rapid synaptic transmission, whereas the heteromeric oligomers composed of α7 in combination with ß subunits display metabotropic properties and operate in slower time frames. At the cellular level, the activation of nAChRs allows the entry of Na+ and Ca2+; the two cations depolarize the membrane and trigger diverse cellular signals, depending on the type of nAChR pentamer and neurons involved, the location of the intervening cells, and the networks of which these neuronal cells form part. These features make the α7 nAChR a central player in neurotransmission, metabolically associated Ca2+-mediated signaling, and modulation of diverse fundamental processes operated by other neurotransmitters in the brain. Due to its ubiquitous distribution and the multiple functions it displays in the brain, the α7 nAChR is associated with a variety of neurological and neuropsychiatric disorders whose exact etiopathogenic mechanisms are still elusive.

Regulation of the Muscarinic M3 Receptor by Myocardin-Related Transcription Factors.

Myocardin-related transcription factors (MRTFs: myocardin/MYOCD, MRTF-A/MRTFA, and MRTF-B/MRTFB) are co-factors of serum response factor (SRF) that activate the smooth muscle cell (SMC) gene program and that play roles in cardiovascular development and mechanobiology. Gain and loss of function experiments have defined the SMC gene program under control of MRTFs, yet full understanding of their impact is lacking. In the present study, we tested the hypothesis that the muscarinic M3 receptor (CHRM3) is regulated by MRTFs together with SRF. Forced expression of MYOCD (8d) in human coronary artery (SMC) followed by RNA-sequencing showed increased levels of M2, M3, and M5 receptors (CHRM2: 2-fold, CHRM3: 16-fold, and CHRM5: 2-fold). The effect of MYOCD on M3 was confirmed by RT-qPCR using both coronary artery and urinary bladder SMCs, and correlation analyses using human transcriptomic datasets suggested that M3 may also be regulated by MRTF-B. Head-to-head comparisons of MYOCD, MRTF-A and MRTF-B, argued that while all MRTFs are effective, MRTF-B is the most powerful transactivator of CHRM3, causing a 600-fold increase at 120h. Accordingly, MRTF-B conferred responsiveness to the muscarinic agonist carbachol in Ca2+ imaging experiments. M3 was suppressed on treatment with the MRTF-SRF inhibitor CCG-1423 using SMCs transduced with either MRTF-A or MRTF-B and using intact mouse esophagus in culture (by 92±2%). Moreover, silencing of SRF with a short hairpin reduced CHRM3 (by >60%) in parallel with α-actin (ACTA2). Tamoxifen inducible knockout of Srf in smooth muscle reduced Srf (by 54±4%) and Chrm3 (by 41±6%) in the urinary bladder at 10days, but Srf was much less reduced or unchanged in aorta, ileum, colon, trachea, and esophagus. Longer induction (21d) further accentuated the reduction of Chrm3 in the bladder and ileum, but no change was seen in the aorta. Single cell RNA-sequencing revealed that Mrtfb dominates in ECs, while Myocd dominates in SMCs, raising the possibility that Chrm3 may be driven by Mrtfb-Srf in the endothelium and by Myocd-Srf in SMCs. These findings define a novel transcriptional control mechanism for muscarinic M3 receptors in human cells, and in mice, that could be targeted for therapy.

The Mechanisms of Sevoflurane-Induced Neuroinflammation.

Sevoflurane is one of the most commonly used inhaled anesthetics due to its low blood gas coefficient, fast onset, low airway irritation, and aromatic smell. However, recent studies have reported that sevoflurane exposure may have deleterious effects on cognitive function. Although neuroinflammation was most widely mentioned among the established mechanisms of sevoflurane-induced cognitive dysfunction, its upstream mechanisms have yet to be illustrated. Thus, we reviewed the relevant literature and discussed the most mentioned mechanisms, including the modulation of the microglial function, blood-brain barrier (BBB) breakdown, changes in gut microbiota, and ease of cholinergic neurotransmission to help us understand the properties of sevoflurane, providing us new perspectives for the prevention of sevoflurane-induced cognitive impairment.

Beneficial Effects of Choline Alphoscerate on Amyloid-ß Neurotoxicity in an In vitro Model of Alzheimer's Disease.

BACKGROUND: Alzheimer's disease (AD) is the most common form of neurodegenerative disorder characterized by cognitive impairment, which represents an urgent public health concern. Given the worldwide impact of AD, there is a compelling need for effective therapies to slow down or halt this disorder. OBJECTIVE: Choline alphoscerate (α-GPC) represents a potentially effective cholinergic neurotransmission enhancing agent with an interesting clinical profile in cognitive dysfunctions improvement, although only scanty data are available about the mechanisms underlying such beneficial effects. METHODS: The SH-SY5Y neuronal cell line, differentiated for 1 week with 10 µm of all-trans-retinoic acid (RA), to achieve a switch towards a cholinergic phenotype, was used as an in vitro model of AD. SH-SY5Y cells were pre-treated for 1h with α-GPC (100nM) and treated for 72 h with Aß25-35 (10µM). RESULTS: α-GPC was able to antagonize Aß25-35 mediated neurotoxicity and attenuate the Aß-induced phosphorylation of the Tau protein. Moreover, α-GPC exerted its beneficial effects by employing the NGF/TrkA system, knocked down in AD and, consequently, by sustaining the expression level of synaptic vesicle proteins, such as synaptophysin. CONCLUSION: Taken together, our data suggest that α-GPC can have a role in neuroprotection in the course of toxic challenges with Aß. Thus, a deeper understanding of the mechanism underlying its beneficial effect, could provide new insights into potential future pharmacological applications of its functional cholinergic enhancement, with the aim to mitigate AD and could represent the basis for innovative therapy.

Ligand design for human acetylcholinesterase and nicotinic acetylcholine receptors, extending beyond the conventional and canonical.

We detail here distinctive departures from lead classical cholinesterase re-activators, the pyridinium aldoximes, to achieve rapid CNS penetration and reactivation of AChE in the CNS (brain and spinal cord). Such reactivation is consistent with these non-canonical re-activators enhancing survival parameters in both mice and macaques following exposure to organophosphates. Thus, the ideal cholinesterase re-activator should show minimal toxicity, limited inhibitory activity in the absence of an organophosphate, and rapid CNS penetration, in addition to its nucleophilic potential at the target, the conjugated AChE active center. These are structural properties directed to reactivity profiles at the conjugated AChE active center, reinforced by the pharmacokinetic and tissue disposition properties of the re-activator leads. In the case of nicotinic acetylcholine receptor (nAChR) agonists and antagonists, with the many existing receptor subtypes in mammals, we prioritize subtype selectivity in their design. In contrast to nicotine and its analogues that react with panoply of AChR subtypes, the substituted di-2-picolyl amine pyrimidines possess distinctive ionization characteristics reflecting in selectivity for the orthosteric site at the α7 subtypes of receptor. Here, entry to the CNS should be prioritized for the therapeutic objectives of the nicotinic agent influencing aberrant CNS activity in development or in the sequence of CNS ageing (longevity) in mammals, along with general peripheral activities controlling inflammation.

Efficacy of scopolamine plus propofol in the treatment of recalcitrant psoriasis: A pilot study.

Accumulating evidence suggests that botulinum neurotoxins (BoNTs), which inhibit acetylcholine release, can be used for treating plaque psoriasis. The therapeutic effects of scopolamine occur through antagonism of central muscarinic acetylcholine receptors. Thus, scopolamine has potential for the treatment of psoriasis. We aimed to evaluate the efficacy and safety of scopolamine plus propofol for the treatment of recalcitrant psoriasis. Twelve patients with recalcitrant psoriasis were enrolled. Patients received intravenous injection of scopolamine plus propofol for 5 consecutive days per month for a total of 3 months. Clinical efficacy was evaluated using a Psoriasis Area and Severity Index (PASI) score. Efficacy outcome was ≥75% reduction in PASI score (PASI75) from baseline. Two patients were lost to follow-up. At week 8, two of 10 patients (20%) achieved PASI75, and at week 12, seven of 10 (70%) achieved PASI75. Treatment was well tolerated, with no reported adverse events. Our study revealed the efficacy and safety of scopolamine plus propofol for the treatment of recalcitrant psoriasis. Scopolamine plus propofol therapy may be a new treatment for recalcitrant psoriasis.

Gestational and lactational exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin in mice: Neurobehavioral effects on female offspring.

Emerging evidence suggests that perinatal dioxin exposure affects neurodevelopment and impairs multiple brain functions, including cognitive, language, learning and emotion, in the offspring. However, the impacts of gestational and lactational exposure to dioxin on behavior and related molecular events are still not fully understood. In this study, female C57BL/6J mice were orally administered three doses of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin (TCDD) (0.1 or 10 µg/kg body weight (bw)) during the pregnancy and lactation periods. The locomotion, exploration and anxiety-related behaviors were examined by an open field test of the young adult female offspring at postnatal day 68. We found that the maternal TCDD exposure, particularly at a low dose, increased movement ability, novelty-exploration and certain anxiety-related behaviors in the offspring. Such hyperactivity-like behaviors were accompanied by the upregulation of certain genes associated with cholinergic neurotransmission or synaptogenesis in the offspring brain. In accordance with the potential enhancement of cholinergic neurotransmission due to the gene upregulations, the enzymatic activity of acetylcholinesterase was decreased, which might lead to excess acetylcholine and consequent hyper-excitation at the synapses. Thus, we found that gestational and lactational TCDD exposure at low dose caused hyperactivity-like behaviors in young adult female offspring and speculated the enhancement of cholinergic neurotransmission and synaptogenesis as potential molecular events underlying the neurobehavioral effects.

Snake three-finger α-neurotoxins and nicotinic acetylcholine receptors: molecules, mechanisms and medicine.

Snake venom three-finger α-neurotoxins (α-3FNTx) act on postsynaptic nicotinic acetylcholine receptors (nAChRs) at the neuromuscular junction (NMJ) to produce skeletal muscle paralysis. The discovery of the archetypal α-bungarotoxin (α-BgTx), almost six decades ago, exponentially expanded our knowledge of membrane receptors and ion channels. This included the localisation, isolation and characterization of the first receptor (nAChR); and by extension, the pathophysiology and pharmacology of neuromuscular transmission and associated pathologies such as myasthenia gravis, as well as our understanding of the role of α-3FNTxs in snakebite envenomation leading to novel concepts of targeted treatment. Subsequent studies on a variety of animal venoms have yielded a plethora of novel toxins that have revolutionized molecular biomedicine and advanced drug discovery from bench to bedside. This review provides an overview of nAChRs and their subtypes, classification of α-3FNTxs and the challenges of typifying an increasing arsenal of structurally and functionally unique toxins, and the three-finger protein (3FP) fold in the context of the uPAR/Ly6/CD59/snake toxin superfamily. The pharmacology of snake α-3FNTxs including their mechanisms of neuromuscular blockade, variations in reversibility of nAChR interactions, specificity for nAChR subtypes or for distinct ligand-binding interfaces within a subtype and the role of α-3FNTxs in neurotoxic envenomation are also detailed. Lastly, a reconciliation of structure-function relationships between α-3FNTx and nAChRs, derived from historical mutational and biochemical studies and emerging atomic level structures of nAChR models in complex with α-3FNTxs is discussed.

Pharmacogenetic considerations when prescribing cholinesterase inhibitors for the treatment of Alzheimer's disease.

INTRODUCTION: Cholinergic dysfunction, demonstrated in the late 1970s and early 1980s, led to the introduction of acetylcholinesterase inhibitors (AChEIs) in 1993 (Tacrine) to enhance cholinergic neurotransmission as the first line of treatment against Alzheimer's disease (AD). The new generation of AChEIs, represented by Donepezil (1996), Galantamine (2001) and Rivastigmine (2002), is the only treatment for AD to date, together with Memantine (2003). AChEIs are not devoid of side-effects and their cost-effectiveness is limited. An option to optimize the correct use of AChEIs is the implementation of pharmacogenetics (PGx) in the clinical practice. AREAS COVERED: (i) The cholinergic system in AD, (ii) principles of AD PGx, (iii) PGx of Donepezil, Galantamine, Rivastigmine, Huperzine and other treatments, and (iv) practical recommendations. EXPERT OPINION: The most relevant genes influencing AChEI efficacy and safety are APOE and CYPs. APOE-4 carriers are the worst responders to AChEIs. With the exception of Rivastigmine (UGT2B7, BCHE-K), the other AChEIs are primarily metabolized via CYP2D6, CYP3A4, and UGT enzymes, with involvement of ABC transporters and cholinergic genes (CHAT, ACHE, BCHE, SLC5A7, SLC18A3, CHRNA7) in most ethnic groups. Defective variants may affect the clinical response to AChEIs. PGx geno-phenotyping is highly recommended prior to treatment.

Lessons from nature: Structural studies and drug design driven by a homologous surrogate from invertebrates, AChBP.

It has been almost 20 years since the discovery and crystallization of a structural surrogate, the Lymnaea stagnalis acetylcholine binding protein (Ls-AChBP), comprising the extracellular domain of the nicotinic acetylcholine receptors (nAChRs). Structural characterization of this soluble protein has increased our understanding of the requirements for agonist and antagonist interactions at the ligand recognition site of the nAChRs. Application can be extended to orthologs in the pentameric ligand-gated ion channel superfamily, encompassing receptors that depolarize or hyperpolarize upon neurotransmitter association. Despite the lack of transmembrane and intracellular motifs, the highly conserved binding or recognition loci have made these soluble binding proteins, and mutants derived from them, prototypic tools for molecular recognition and structural studies of pentameric ligand-gated ion channels. Targeting nAChRs has been a major goal as this family is associated with neurodegenerative diseases and disorders. Accordingly, the ligand binding site has played a key role to the development of selective ligands for modulation of this transmembrane proteins. In this review article, we cover both the potential and limitations of soluble surrogates, termed the AChBP family, in drug development. This article is part of the special issue on 'Contemporary Advances in Nicotine Neuropharmacology'.

Current Status of Drug Targets and Emerging Therapeutic Strategies in the Management of Alzheimer's Disease.

Alzheimer's disease (AD) is a chronic neurodegenerative disease affecting the elderly. AD is associated with a progressive decline in memory and cognitive abilities, drastic changes in behavioural patterns and other psychiatric manifestations. It leads to a significant decline in the quality of life at personal, household as well as national level. Although AD was described about hundred years back and multiple theories have been proposed, its exact pathophysiology is unknown. There is no cure for AD and the life expectancy of AD patients remains low at 3-9 years. An accurate understanding of the molecular mechanism(s) involved in the pathogenesis of AD is imperative to devise a successful treatment strategy. This review explains and summarises the current understanding of different therapeutic strategies based on various molecular pathways known to date. Different strategies based on anti-amyloid pathology, glutamatergic pathway, anti-tau, neuroprotection through neurotrophic factors and cholinergic neurotransmission have been discussed. Further, the use of anti-inflammatory drugs, nutraceuticals, and dietary interventions has also been explained in the management of AD. It further describes different pharmacological and dietary interventions being used in treating and/or managing AD. Additionally, this article provides a thorough review of the literature for improving the therapeutic paradigm of AD.