Mouse Acetylcholine Receptor Research Articles

Recombinant Acetylcholine Receptor Immunization Induces a Robust Model of Experimental Autoimmune Myasthenia Gravis in Mice.

Myasthenia gravis (MG) is a prototypical autoimmune disease of the neuromuscular junction (NMJ). The study of the underlying pathophysiology has provided novel insights into the interplay of autoantibodies and complement-mediated tissue damage. Experimental autoimmune myasthenia gravis (EAMG) emerged as a valuable animal model, designed to gain further insight and to test novel therapeutic approaches for MG. However, the availability of native acetylcholine receptor (AChR) protein is limited favouring the use of recombinant proteins. To provide a simplified platform for the study of MG, we established a model of EAMG using a recombinant protein containing the immunogenic sequence of AChR in mice. This model recapitulates key features of EAMG, including fatigable muscle weakness, the presence of anti-AChR-antibodies, and engagement of the NMJ by complement and a reduced NMJ density. Further characterization of this model demonstrated a prominent B cell immunopathology supported by T follicular helper cells. Taken together, the herein-presented EAMG model may be a valuable tool for the study of MG pathophysiology and the pre-clinical testing of therapeutic applications.

Scrutinizing pathways of nicotine effect on renal Alpha-7 nicotinic acetylcholine receptor and Mitogen-activated protein kinase (MAPK) expression in Ehrlich ascites carcinoma-bearing mice: Role of Chlorella vulgaris

Nicotine is one of several physiologically stable and active chemicals found in tobacco. The mechanism through which nicotine causes kidney damage is still obscure. As a result, the goal of this research was to investigate how oral nicotine intake can lead to kidney damage. Naturaly occurring superfood green algae are immense supplements help us using extra chemicals during cancer prevalence if the patient is exposed to nicotine. Hence, the mitigating role of Chlorella vulgaris extract (CVE) against nicotine-nephrotoxic impact in Ehrlich ascites carcinoma (EAC)-bearing mice was studied. For this purpose, four groups of Swiss female mice were assigned, nicotine group (NIC) (100 µg/ml/kg), CVE group (100 mg/kg), CVE + Nicotine, and a control group. Renal dysfunction was evaluated by estimating serum biomarkers ofrenal damage. The expression pattern of Nf-KB, MAPK, P53, and α7-nAchR, lipid peroxidation biomarker, and antioxidant enzyme activities were evaluated in kidney tissue. Also, micro-morphometric examination and apoptosis immunohistochemical reactivity of kidney tissue were applied. The obtained results indicated up-regulation of all estimated genes and oxidative stress. Moreover, a significant (P < 0.05) increment in the apoptotic marker Caspase-3 and declined BCL-2 proteins were recorded. In serum, a significant (P < 0.05) elevation of urea, creatinine, TNF-α, IL-1β, and Kim-1 were evident. Histological investigation reinforced the aforementioned data, revealing structural changes involving the tubules, glomeruli, and interstitium of mice kidneys. CVE may be a strong contender for protecting renal tissue damage since it reduces renal tissue injury and oxidative stress. Cancer patients who regularly use nicotine through direct smoking or second-hand exposure can benefit from CVE usage as a dietary supplement.

Social cognitive improvement via activation of the hippocampal α7 nicotinic acetylcholine receptor in stressed mice

Social cognitive improvement via activation of the hippocampal α7 nicotinic acetylcholine receptor in stressed mice

GW29-e1791 Nicotine promotes atherosclerosis development in apolipoprotein E-deficient mice through alpha 1 nicotinic acetylcholine receptor on RAW264.7 and MOVAS cells

In our study, we investigated whether nicotine promotes the development of atherosclerosis throughout alpha 1 nicotinic acetylcholine receptor in apolipoprotein E-deficient mice .In vitro, we investigated whether the migration and proliferation of VSMC and macrophage by α1nAChRs via Calpain-1, MMP-

A0872 Nicotine promotes atherosclerosis development in apolipoprotein E-deficient mice through alpha 1 nicotinic acetylcholine receptor on RAW264.7 and MOVAS cells

Objectives: In our study, we investigated whether nicotine promotes the development of atherosclerosis throughout alpha 1 nicotinic acetylcholine receptor in apolipoprotein E-deficient mice. In vitro, we investigated whether the migration and proliferation of VSMC and macrophage by α1nAChRs via Calpain-1, MMP-2/MMP-9 signaling pathway. Methods: In vivo experiment, atherosclerosis was established by feeding the ApoE−/− mice with a high-fat diet (HFD) for 12 weeks as well as nicotine concentrations of 2.0 mg/kg/d. Silencing of α1nAChR by adeno-associated virus (AAV). We use Oil Red O and HE assay to assess the lesion area in the aortic root section and the whole aorta. Smooth muscle cells (SMCs), macrophages and nAChRα1 content were evaluated by Immunohistochemistry. The serum levels of IL-6, IL-10 and TNF-α and the blood lipid were assessed ELISA. In vitro experiment, we used siRNA to downregulate the expression of α1nAChR on RAW264.7 and MOVAS cells. The proliferation and migration of two cells were detected by CCK-8, transwell and wound-induced migration assay. The levels of α1nAChR, Calpain-1, MMP-2/MMP-9 were tested by Real-time PCR and Western Blot. Results: Silencing of α1nAChR by adeno-associated virus (AAV) decreased atherosclerotic size, lesion macrophage content, the circulating inflammatory cytokines, and suppressed the expression of α1nAChR, Calpain-1, MMP-2, and MMP-9 in the nicotine group. In vitro, nicotine induced expression of α1nAChR, Calpain-1, MMP-2, and MMP-9 in MOVAS and RAW264.7, and enhanced the ability of migration and proliferation of these cells. Silencing of α1nAChR inhibited these effects induced by nicotine. Conclusion: These data suggest that α1nAChRs could be a potential the therapeutic target for the control of nicotine-induced atherosclerosis.

Cigarette toxin 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) induces experimental pancreatitis through α7 nicotinic acetylcholine receptors (nAChRs) in mice.

Clinical studies have shown that cigarette smoking is a dose-dependent and independent risk factor for acute pancreatitis. Cigarette smoke contains nicotine which can be converted to the potent receptor ligand and toxin, NNK [4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone]. Previously, we have shown that NNK induces premature activation of pancreatic zymogens in rats, an initiating event in pancreatitis, and this activation is prevented by pharmacologic inhibition of nicotinic acetylcholine receptors (nAChR). In this study, we determined whether NNK mediates pancreatitis through the α7 isoform of nAChR using α7nAChR knockout mice. PCR analysis confirmed expression of non-neuronal α7nAChR in C57BL/6 (WT) mouse and human acinar cells. NNK treatment stimulated trypsinogen activation in acini from WT but not α7nAChR-/- mice. NNK also stimulated trypsinogen activation in human acini. To further confirm these findings, WT and α7nAChR-/- mice were treated with NNK in vivo and markers of pancreatitis were measured. As observed in acini NNK treatment induced trypsinogen activation in WT but not α7nAChR-/- mice. NNK also induced other markers of pancreatitis including pancreatic edema, vacuolization and pyknotic nuclei in WT but not α7nAChR-/- animals. NNK treatment led to increased neutrophil infiltration, a marker of inflammation, in WT mice and to a significantly lesser extent in α7nAChR-/- mice. We also examined downstream targets of α7nAChR activation and found that calcium and PKC activation are involved down stream of NNK stimulation of α7nAChR. In this study we used genetic deletion of the α7nAChR to confirm our previous inhibitor studies that demonstrated NNK stimulates pancreatitis by activating this receptor. Lastly, we demonstrate that NNK can also stimulate zymogen activation in human acinar cells and thus may play a role in human disease.

Reversal of Nicotine Withdrawal Signs Through Positive Allosteric Modulation of α4β2 Nicotinic Acetylcholine Receptors in Male Mice.

Nicotine withdrawal symptoms are important factors in determining the relapse rate to tobacco smoking and drugs that diminish these symptoms would potentially have a higher success rate as smoking cessation aids. Unlike US Food and Drug administration approved smoke cessation aids (nicotine and varenicline) which act as nicotinic acetylcholine receptors (nAChRs) agonists, desformylflustrabromine (dFBr) acts as a nAChR positive allosteric modulator with higher selectivity to the α4β2 nAChR. In animal studies, dFBr was well tolerated and reduced intravenous nicotine self-administration. In this study, we use behavioral test in mouse model of spontaneous nicotine withdrawal to assess the effect of dFBr on nicotine withdrawal symptoms. Spontaneous nicotine withdrawal in nicotine-dependent ICR male mice was established 18-24 h after termination (minipump removal) of 14 days infusion of nicotine. After that (day 15), spontaneous signs of nicotine withdrawal were examined in the following order: anxiety-like behaviors, somatic signs, and then hyperalgesia using previously published behavioral protocols. Fifteen minutes before withdrawal signs testing, mice received a subcutaneous acute injection of vehicle or dFBr at the doses of 0.02, 0.1, and 1 mg/kg to determine the effect of dFBr on nicotine withdrawal symptoms. dFBr produced dose-dependent reversal of nicotine withdrawal signs in mouse model of spontaneous nicotine withdrawal. Positive allosteric modulators of nAChR such as dFBr reduce nicotine withdrawal symptoms supporting the potential clinical use of this novel class of nAChR-based therapeutics as smoking cessation aid.

Effects of chronic inhalation of electronic cigarettes containing nicotine on glial glutamate transporters and α-7 nicotinic acetylcholine receptor in female CD-1 mice

Alteration in glutamate neurotransmission has been found to mediate the development of drug dependence, including nicotine. We and others, through using western blotting, have reported that exposure to drugs of abuse reduced the expression of glutamate transporter-1 (GLT-1) as well as cystine/glutamate antiporter (xCT), which consequently increased extracellular glutamate concentrations in the mesocorticolimbic area. However, our previous studies did not reveal any changes in glutamate/aspartate transporter (GLAST) following exposure to drugs of abuse. In the present study, for the first time, we investigated the effect of chronic exposure to electronic (e)-cigarette vapor containing nicotine, for one hour daily for six months, on GLT-1, xCT, and GLAST expression in frontal cortex (FC), striatum (STR), and hippocampus (HIP) in outbred female CD1 mice. In this study, we also investigated the expression of alpha-7 nicotinic acetylcholine receptor (α-7 nAChR), a major pre-synaptic nicotinic receptor in the glutamatergic neurons, which regulates glutamate release. We found that inhalation of e-cigarette vapor for six months increased α-7 nAChR expression in both FC and STR, but not in the HIP. In addition, chronic e-cigarette exposure reduced GLT-1 expression only in STR. Moreover, e-cigarette vapor inhalation induced downregulation of xCT in both the STR and HIP. We did not find any significant changes in GLAST expression in any brain region. Finally, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) techniques, we detected high concentrations of nicotine and cotinine, a major metabolite of nicotine, in the FC tissues of e-cigarette exposed mice. These data provide novel evidence about the effects of chronic nicotine inhalation on the expression of key glial glutamate transporters as well as α-7 nAChR. Our work may suggest that nicotine exposure via chronic inhalation of e-cigarette vapor may be mediated in part by alterations in the glutamatergic system.

Expression of M3 acetylcholine receptor in asthmatic mice and bronchial airway remodeling prediction.

This study aimed to investigate the role of M3 acetylcholine receptor (M3-AChR) expression in airway remodeling. Additionally, we aimed to evaluate the effects of ipratropium bromide solution inhaled in an early phase of asthma on airway remodeling in ovalbumin (OVA)-sensitized and challenged mice. Thirty BALB/c mice were divided into three groups, namely, control group (saline sensitized/challenged mice), asthma group (OVA sensitized/challenged mice), and treatment group (OVA sensitized/challenged mice treated by ipratropium bromide). Pathological changes were detected by histological staining in the bronchopulmonary tissue of mice. WAt/Pbm (the airway wall area /basement membrane perimeter) ratio of the asthma group (25.37 ± 4.25) increased significantly (P < 0.05) when compared with that of the control (12.89 ± 1.71) and treatment group (15.82 ± 2.91). WAm/Pbm (smooth muscle wall area / basement membrane perimeter) ratio of the asthma group (7.58 ± 2.16) increased significantly (P < 0.05) when compared with that of the control (2.55 ± 0.72) and treatment group (3.36 ± 1.69). M3-AChR concentration increased in the treatment group (29.24 ± 3.59) and was significantly different (P < 0.05) from that of the control group (25.50 ± 1.83). During asthma treatment, SAMA can alleviate airway remodeling in murine model by lessening the thickness of bronchial walls and inhibiting the proliferation of smooth muscle cells. There were no obvious changes in M3-AChR density in the murine model of asthma characterized by airway remodeling. However, ipratropium bromide may up-regulate the expression of M3-AChR in bronchial walls of asthmatic murine model.

Rivastigmine improves isolation rearing-induced prepulse inhibition deficits via muscarinic acetylcholine receptors in mice.

The acetylcholinesterase inhibitors donepezil, galantamine, and rivastigmine are used for the treatment of Alzheimer's disease. We previously demonstrated that donepezil and galantamine differentially affect isolation rearing-induced prepulse inhibition (PPI) deficits and that this might be due to differential effects on brain muscarinic acetylcholine (mACh) receptor function in mice. We examined the effects of rivastigmine on isolation rearing-induced PPI deficits, brain ACh levels, and mACh receptor function in mice. Acoustic startle responses were measured in a startle chamber. Microdialysis was performed, and the levels of dopamine and ACh in the prefrontal cortex were measured. Rivastigmine (0.3 mg/kg) improved PPI deficits, and this improvement was antagonized by the mACh receptor antagonist telenzepine but not by the nicotinic ACh receptor antagonist mecamylamine. Rivastigmine increased extracellular ACh levels by approximately 2-3-fold, less than the increase produced by galantamine. Rivastigmine enhanced the effect of the mACh receptor agonist N-desmethylclozapine on prefrontal dopamine release, a marker of mACh receptor function, and this increase was blocked by telenzepine. In contrast, galantamine did not affect N-desmethylclozapine-induced dopamine release. Furthermore, rivastigmine did not affect cortical dopamine release induced by the serotonin1A receptor agonist osemozotan, suggesting that the effect of rivastigmine has specificity for mACh receptors. Taken together with our previous finding that marked increases in ACh levels are required for the PPI deficit improvement induced by galantamine, our present results suggest that rivastigmine improves isolation rearing-induced PPI deficits by increasing ACh levels and by concomitantly enhancing mACh receptor function.

Varenicline aggravates plaque formation through α7 nicotinic acetylcholine receptors in ApoE KO mice

Varenicline is one of the most widely used drugs for smoking cessation. However, whether an adverse effect of varenicline is associated with the risk of serious cardiovascular events remains controversial. In this study, we determined if varenicline increases the risk of cardiovascular events using apolipoprotein E knockout (ApoE KO) mice. ApoE KO mice (8weeks old) were injected with varenicline 0.5mgkg−1day−1 for 3weeks. Varenicline aggravated atherosclerotic plaque formation in whole aorta from ApoE KO mice compared with vehicle. Methyllycaconitine, an α7 nicotinic acetylcholine receptor (nAChR) antagonist, inhibited varenicline-induced aggravated plaque formation. Our findings show that varenicline progresses atherosclerotic plaque formation through α7 nAChR, and thereby increases the risk of cardiovascular events.

Metabolism and disposition of ABT-894, a novel α4β2 neuronal acetylcholine receptor agonist, in mice and monkeys

1. Metabolism and disposition of ABT-894 was investigated in hepatocytes, in mice and monkeys receiving [14C]ABT-894.2. In hepatocytes, turnover rate of ABT-894 was slow in all species with more than 90% of parent remaining. M3 (carbamoyl glucuronide) and M6 (mono-oxidation) were detected across species.3. ABT-894 showed species-specific disposition profiles. ABT-894 was primarily eliminated by renal secretion in mice. Whereas, monkey mainly cleared ABT-894 metabolically.4. ABT-894 underwent two primary routes of metabolism in monkeys: N-carbamoyl glucuronidation to form M3 and oxidation product M1. M3 was the major metabolite in monkey excreta. M3 was observed in mice urine. Circulating levels of M3 in terms of M3/ABT-894 ratios were essentially absent in mice, but were high in monkeys.5. Understanding the species difference in the clearance mechanism is the key to the accurate projection of the human clearance and preclinical safety assessment. Lack of species difference in the metabolism of ABT-894 in hepatocytes certainly creates a challenge in predicting its metabolism and pharmacokinetics in human. Based on available metabolism and pharmacokinetic data of ABT-894 in human, monkey is the preferred species in predicting human clearance since it presents a similar clearance mechanism from that observed in human.

Possible Involvement of Endogenous Opioid System Located Downstream of α7 Nicotinic Acetylcholine Receptor in Mice With Physical Dependence on Nicotine

We previously reported that nicotine (NIC)-induced analgesia was elicited in part by activation of the endogenous opioid system. Moreover, it is well known that NIC has physical-dependence liability, but its mechanism is unclear. Therefore, we examined whether physical dependence on NIC was mediated by activation of the endogenous opioid system in ICR mice. We evaluated increased serum corticosterone (SCS) as an indicator of NIC withdrawal, as it is a quantitative indicator of naloxone (opioid receptor antagonist, NLX)-precipitated morphine withdrawal in mice. In this study, NLX precipitated an SCS increase in mice receiving repeated NIC, by a dose-dependent mechanism, and correlated with the dose and number of days of repeated NIC administration. When an opioid receptor antagonist (naltrexone) was concomitantly administered with repeated NIC, the NLX-precipitated SCS increase was not elicited. Concomitant administration of the α7 nicotinic acetylcholine receptor (nAChR) antagonist (methyllycaconitine) with repeated NIC, but not the α4β2 nAChR antagonist (dihydro-β-erythroidine), did not elicit an SCS increase by NLX. Thus, a physical dependence on NIC was in part mediated by the activation of the endogenous opioid system, located downstream of α7 nAChR.

Asymmetric transmitter binding sites of fetal muscle acetylcholine receptors shape their synaptic response

Neuromuscular acetylcholine receptors (AChRs) have two transmitter binding sites: at α-δ and either α-γ (fetal) or α-ε (adult) subunit interfaces. The γ-subunit of fetal AChRs is indispensable for the proper development of neuromuscular synapses. We estimated parameters for acetylcholine (ACh) binding and gating from single channel currents of fetal mouse AChRs expressed in tissue-cultured cells. The unliganded gating equilibrium constant is smaller and less voltage-dependent than in adult AChRs. However, the α-γ binding site has a higher affinity for ACh and provides more binding energy for gating compared with α-ε; therefore, the diliganded gating equilibrium constant at -100 mV is comparable for both receptor subtypes. The -2.2 kcal/mol extra binding energy from α-γ compared with α-δ and α-ε is accompanied by a higher resting affinity for ACh, mainly because of slower transmitter dissociation. End plate current simulations suggest that the higher affinity and increased energy from α-γ are essential for generating synaptic responses at low pulse [ACh].

Mecamylamine-precipitated nicotine withdrawal syndrome and its prevention with baclofen: An autoradiographic study of α4β2 nicotinic acetylcholine receptors in mice

A previous study from our laboratory showed that baclofen (BAC, GABAB receptor agonist) was able to prevent the behavioral expression of nicotine (NIC) withdrawal syndrome. To further investigate the mechanisms underlying this effect, we conducted this study, with the aims of analyzing α4β2 nicotinic receptor density during NIC withdrawal and, in case we found any changes, of determining whether they could be prevented by pretreatment with BAC. Swiss Webster albino mice received NIC (2.5 mg/kg, s.c.) 4 times daily, for 7 days. On the 8th day, NIC-treated mice received the nicotinic antagonist mecamylamine (MEC; 2 mg/kg, i.p.) 1 h after the last dose of NIC. A second group of NIC-treated mice received BAC (2 mg/kg, i.p.) prior to MEC administration. Thirty minutes after MEC, mice were sacrificed and brain autoradiography with [(3)H]epibatidine was carried out at five different anatomical levels. Autoradiographic mapping showed a significant increase of α4β2 nicotinic receptor labeling during NIC withdrawal in the nucleus accumbens shell (AcbSh), medial habenular nucleus (HbM), thalamic nuclei, dorsal lateral geniculate (DLG) nucleus, fasciculus retroflexus (fr), ventral tegmental area, interpeduncular nucleus and superior colliculus. BAC pretreatment prevented the increased α4β2 nicotinic receptor binding sites in the AcbSh, MHb, thalamic nuclei, DLG nucleus and fr. The present results suggest a relationship between BAC's preventive effect of the expression of NIC withdrawal signs, and its ability to restore the changes in α4β2 nicotinic receptor labeling, evidenced in specific brain areas in NIC withdrawn animals.

Nicotinic Receptor Transduction Zone: Invariant Arginine Couples to Multiple Electron-Rich Residues

Gating of the muscle-type acetylcholine receptor (AChR) channel depends on communication between the ACh-binding site and the remote ion channel. A key region for this communication is located within the structural transition zone between the ligand-binding and pore domains. Here, stemming from β-strand 10 of the binding domain, the invariant αArg209 lodges within the hydrophobic interior of the subunit and is essential for rapid and efficient channel gating. Previous charge-reversal experiments showed that the contribution of αArg209 to channel gating depends strongly on αGlu45, also within this region. Here we determine whether the contribution of αArg209 to channel gating depends on additional anionic or electron-rich residues in this region. Also, to reconcile diverging findings in the literature, we compare the dependence of αArg209 on αGlu45 in AChRs from different species, and compare the full agonist ACh with the weak agonist choline. Our findings reveal that the contribution of αArg209 to channel gating depends on additional nearby electron-rich residues, consistent with both electrostatic and steric contributions. Furthermore, αArg209 and αGlu45 show a strong interdependence in both human and mouse AChRs, whereas the functional consequences of the mutation αE45R depend on the agonist. The emerging picture shows a multifaceted network of interdependent residues that are required for communication between the ligand-binding and pore domains.

Riluzole blocks human muscle acetylcholine receptors

Riluzole, the only drug available against amyotrophic lateral sclerosis (ALS), has recently been shown to block muscle ACh receptors (AChRs), raising concerns about possible negative side-effects on neuromuscular transmission in treated patients. In this work we studied riluzole's impact on the function of muscle AChRs in vitro and on neuromuscular transmission in ALS patients, using electrophysiological techniques. Human recombinant AChRs composed of α(1)β(1)δ subunits plus the γ or ε subunit (γ- or ε-AChR) were expressed in HEK cells or Xenopus oocytes. In both preparations, riluzole at 0.5 μm, a clinically relevant concentration, reversibly reduced the amplitude and accelerated the decay of ACh-evoked current if applied before coapplication with ACh. The action on γ-AChRs was more potent and faster than on ε-AChRs. In HEK outside-out patches, riluzole-induced block of macroscopic ACh-evoked current gradually developed during the initial milliseconds of ACh presence. Single channel recordings in HEK cells and in human myotubes from ALS patients showed that riluzole prolongs channel closed time, but has no effect on channel conductance and open duration. Finally, compound muscle action potentials (CMAPs) evoked by nerve stimulation in ALS patients remained unaltered after a 1 week suspension of riluzole treatment. These data indicate that riluzole, while apparently safe with regard to synaptic transmission, may affect the function of AChRs expressed in denervated muscle fibres of ALS patients, with biological consequences that remain to be investigated.

The intrinsic energy of the gating isomerization of a neuromuscular acetylcholine receptor channel

Nicotinic acetylcholine receptor (AChR) channels at neuromuscular synapses rarely open in the absence of agonists, but many different mutations increase the unliganded gating equilibrium constant (E0) to generate AChRs that are active constitutively. We measured E0 for two different sets of mutant combinations and by extrapolation estimated E0 for wild-type AChRs. The estimates were 7.6 and 7.8 × 10−7 in adult-type mouse AChRs (−100 mV at 23°C). The values are in excellent agreement with one obtained previously by using a completely different method (6.5 × 10−7, from monoliganded gating). E0 decreases with depolarization to the same extent as does the diliganded gating equilibrium constant, e-fold with ∼60 mV. We estimate that at −100 mV the intrinsic energy of the unliganded gating isomerization is +8.4 kcal/mol (35 kJ/mol), and that in the absence of a membrane potential, the intrinsic chemical energy of this global conformational change is +9.4 kcal/mol (39 kJ/mol). Na+ and K+ in the extracellular solution have no measureable effect on E0, which suggests that unliganded gating occurs with only water occupying the transmitter binding sites. The results are discussed with regard to the energy changes in receptor activation and the competitive antagonism of ions in agonist binding.

Agarwood (Aquilaria Crassna) Extracts Decrease High-protein High-fat Diet-induced Intestinal Putrefaction Toxins in Mice

Agarwood (Aquilaria spp.) is famous for its aromatic resin, but its leaves are also prized as a healthy tea in South East Asia. Previously, we reported that agarwood extract (Aquilaria sinensis and Aquilaria crassna) shows laxative effect via acetylcholine receptors in constipation model mice and rats. In the present study, we investigated the effects of agarwood (Aquilaria crassna) on intestinal toxins, such as indole derivatives and ammonium to investigate the enteral environment. Male mice received regimens of three types of food, CE-7 (normal diet), CE-2 (high-protein normal diet), and Quick Fat (high-protein high-fat diet). Extracts of agarwood (water extract of agarwood: WEA and ethanol extract of agarwood: EEA) were orally administered once daily for a week. We measured the contents of indole derivatives and ammonium in feces and also examined the Minimum Inhibitory Concentrations (MICs) of agarwood against nine strains of enterobacteria in vitro. As compared with CE-7, Quick Fat increased the contents of indoles and ammonium in fecal beads. Single administration and multiple administrations for 7 days of WEA at 1,000 mg/kg/day decreased the contents of indoles and ammonium in fecal beads; on the other hand, multiple administrations of EEA decreased contents of indoles, but not those of ammonium. Interruption of administration abolished the effects of WEA and EEA. Quick Fat delayed carmine egestion in the digestive tract and administration of WEA and EEA accelerated the carmine egestion. Both WEA and EEA showed significant antimicrobial activity against some urease-positive bacteria, such as Staphylococcus aureus, Clostridium difficile, and Bacteroides spp. In conclusion, feeding with Quick Fat (high-protein high-fat diet) increased fecal-containing toxins and delayed carmine egestion in mice. Administrations of WEA and EEA decreased fecal-containing toxins and accelerated carmine egestion, and the decrement of fecal-containing toxins was abolished in response to interruption of the administration.

Reduced TrkB expression results in precocious age-like changes in neuromuscular structure, neurotransmission, and muscle function

Acute blockade of signaling through the tyrosine kinase receptor B (TrkB) attenuates neuromuscular transmission and fragments postsynaptic acetylcholine receptors (AChRs) in adult mice, suggesting that TrkB signaling is a key regulator of neuromuscular function. Using immunohistochemical, histological, and in vitro muscle contractile techniques, we tested the hypothesis that constitutively reduced TrkB expression would disrupt neuromuscular pre- and postsynaptic structure, neurotransmission, muscle fiber size, and muscle function in the soleus muscle of 6- to 8-mo-old TrkB⁺/⁻ mice compared with age-matched littermates. Age-like expansion of postsynaptic AChR area, AChR fragmentation, and denervation was observed in TrkB⁺/⁻ mice similar to that found in 24-mo-old wild-type mice. Neurotransmission failure was increased in TrkB⁺/⁻ mice, suggesting that these morphologic changes were sufficient to alter synaptic function. Reduced TrkB expression resulted in decreased muscle strength and fiber cross-sectional area. Immunohistochemical and muscle retrograde labeling experiments show that motor neuron number and size are unaffected in TrkB⁺/⁻ mice. These results suggest that TrkB- signaling at the neuromuscular junction plays a role in synaptic stabilization, neurotransmission, and muscle function and may impact the aging process of sarcopenia.