Glutamate acts on acid-sensing ion channels to worsen ischaemic brain injury.

Glutamate is traditionally viewed as the first messenger to activate NMDAR (N-methyl-D-aspartate receptor)-dependent cell death pathways in stroke1,2, but unsuccessful clinical trials with NMDAR antagonists implicate the engagement of other mechanisms3-7. Here we show that glutamate and its structural analogues, including NMDAR antagonist L-AP5 (also known as APV), robustly potentiate currents mediated by acid-sensing ion channels (ASICs) associated with acidosis-induced neurotoxicity in stroke4. Glutamate increases the affinity of ASICs for protons and their open probability, aggravating ischaemic neurotoxicity in both in vitro and in vivo models. Site-directed mutagenesis, structure-based modelling and functional assays reveal a bona fide glutamate-binding cavity in the extracellular domain of ASIC1a. Computational drug screening identified a small molecule, LK-2, that binds to this cavity and abolishes glutamate-dependent potentiation of ASIC currents but spares NMDARs. LK-2 reduces the infarct volume and improves sensorimotor recovery in a mouse model of ischaemic stroke, reminiscent of that seen in mice with Asic1a knockout or knockout of other cation channels4-7. We conclude that glutamate functions as a positive allosteric modulator for ASICs to exacerbate neurotoxicity, and preferential targeting of the glutamate-binding site on ASICs over that on NMDARs may be strategized for developing stroke therapeutics lacking the psychotic side effects of NMDAR antagonists.

Screening of Amino Acids as a Safe Energy Source for Isolated Rat Pancreatic Acini.

OBJECTIVES: Amino acids play an essential role in protein synthesis, metabolism, and survival of pancreatic acini. Adequate nutritional support is important for acute pancreatitis treatment. However, high concentrations of arginine and lysine may induce acute pancreatitis. The study aimed to identify the most suitable l -amino acids as safe energy sources for pancreatic acinar cells. MATERIALS AND METHODS: Pancreatic acini were isolated from male Wistar rats. Effects of amino acids (0.1-20 mM) on uncoupled respiration of isolated acini were studied with a Clark electrode. Cell death was evaluated with fluorescent microscopy and DNA gel electrophoresis. RESULTS: Among the tested amino acids, glutamate, glutamine, alanine, lysine, and aspartate were able to stimulate the uncoupled respiration rate of isolated pancreatic acini, whereas arginine, histidine, and asparagine were not. Lysine, arginine, and glutamine (20 mM) caused complete loss of plasma membrane integrity of acinar cells after 24 hours of incubation. Glutamine also caused early (2-4 hours) cell swelling and blebbing. Aspartate, asparagine, and glutamate only moderately decreased the number of viable cells, whereas alanine and histidine were not toxic. DNA fragmentation assay and microscopic analysis of nuclei showed no evidence of apoptosis in cells treated with amino acids. CONCLUSIONS: Alanine and glutamate are safe and effective energy sources for mitochondria of pancreatic acinar cells.

Effects of a manganese complex with lysine and glutamic acid on growth performance, manganese deposition, and emission, antioxidant capacity and metacarpal strength in weaned piglets.

The present study sought to assess the effects of manganese complexes with lysine and glutamic acid (Mn-LG) as manganese (Mn) sources on growth performance, trace element deposition, antioxidant capacity, and metacarpal strength in weaned piglets. The study involved 288 healthy Duroc × Landrace × Yorkshire piglets that were weaned at 25 to 28 d of age and weighed 8.66 ±â€…0.96 kg. These piglets were randomly divided into six groups: a control group (Mn-LG-0, receiving a basal diet without Mn supplementation), a Mn sulfate group (basal diet supplemented with 40 mg·kg-1 diet of Mn, Mn-S-40 group), and four Mn-LG groups (Mn-LG-20, Mn-LG-40, Mn-LG-60, Mn-LG-80, supplemented with 20, 40, 60, and 80 mg·kg-1 Mn from Mn-LG in the basal diet). Grouping began at weaning on the 0th day of the experiment. The corn-soybean-based basal diet during the early (days 0 to 14) and late (days 15 to 42) phases of the experiment contained 20.88 and 30.12 mg·kg-1 Mn, respectively. Blood samples were collected on days 14 and 42, and pigs were sacrificed for sample collection on day 42. The results indicated no significant differences in average daily gain, average daily feed intake, or feed-to-gain ratio among the groups (P > 0.05). The diarrhea rates of all Mn-LG groups and the Mn-S-40 group were significantly lower in the 0 to 14 d and during the entire experimental period than in the Mn-LG-0 group (P < 0.001). The Mn-LG-40 group exhibited a significant increase in liver Mn concentration and serum Mn superoxide dismutase (Mn-SOD) activity on day 42 (P < 0.01), as well as a significant decrease in fecal Mn concentration (P < 0.05), compared to those of the Mn-S-40 group. Significant differences (P < 0.05) were detected in the serum, liver, and fecal Mn concentrations, as well as in the serum and liver Mn-SOD activity, across the different Mn-LG groups. The serum and fecal Mn concentrations and serum Mn-SOD activity increased linearly or quadratically (P < 0.01) with increasing Mn-LG supplementation. No significant differences (P > 0.05) were found in kidney, heart, or metacarpal bone Mn concentrations or in bone strength indices. In summary, compared with the Mn-LG-0 diet, dietary supplementation with Mn-LG enhanced serum Mn deposition and Mn-SOD activity and decreased the incidence of diarrhea. Additionally, the fecal Mn concentration was lower in the Mn-LG group than in the inorganic group at equivalent dosages.

This research explored the effects of a manganese complex containing lysine and glutamic acid (Mn-LG) on various health parameters in weaned piglets. Utilizing samples of 288 piglets, the study investigated how Mn-LG supplementation influences growth performance, Mn deposition and emission, antioxidant capacity, and metacarpal strength. Key findings include an increase in serum Mn levels and Mn superoxide dismutase (Mn-SOD) activity, a reduction in diarrhea incidence, and no significant effects in bone strength indices in piglets receiving Mn-LG. Additionally, the fecal Mn concentration was notably lower in the Mn-LG group than in the group receiving inorganic Mn at equivalent dosages.

Activity of the Sodium Leak Channel Maintains the Excitability of Paraventricular Thalamus Glutamatergic Neurons to Resist Anesthetic Effects of Sevoflurane in Mice.

BACKGROUND: Stimulation of the paraventricular thalamus has been found to enhance anesthesia recovery; however, the underlying molecular mechanism by which general anesthetics modulate paraventricular thalamus is unclear. This study aimed to test the hypothesis that the sodium leak channel (NALCN) maintains neuronal activity in the paraventricular thalamus to resist anesthetic effects of sevoflurane in mice. METHODS: Chemogenetic and optogenetic manipulations, in vivo multiple-channel recordings, and electroencephalogram recordings were used to investigate the role of paraventricular thalamus neuronal activity in sevoflurane anesthesia. Virus-mediated knockdown and/or overexpression was applied to determine how NALCN influenced excitability of paraventricular thalamus glutamatergic neurons under sevoflurane. Viral tracers and local field potentials were used to explore the downstream pathway. RESULTS: Single neuronal spikes in the paraventricular thalamus were suppressed by sevoflurane anesthesia and recovered during emergence. Optogenetic activation of paraventricular thalamus glutamatergic neurons shortened the emergence period from sevoflurane anesthesia, while chemogenetic inhibition had the opposite effect. Knockdown of the NALCN in the paraventricular thalamus delayed the emergence from sevoflurane anesthesia (recovery time: from 24 ± 14 to 64 ± 19 s, P < 0.001; concentration for recovery of the righting reflex: from 1.13% ± 0.10% to 0.97% ± 0.13%, P < 0.01). As expected, the overexpression of the NALCN in the paraventricular thalamus produced the opposite effects. At the circuit level, knockdown of the NALCN in the paraventricular thalamus decreased the neuronal activity of the nucleus accumbens, as indicated by the local field potential and decreased single neuronal spikes in the nucleus accumbens. Additionally, the effects of NALCN knockdown in the paraventricular thalamus on sevoflurane actions were reversed by optical stimulation of the nucleus accumbens. CONCLUSIONS: Activity of the NALCN maintains the excitability of paraventricular thalamus glutamatergic neurons to resist the anesthetic effects of sevoflurane in mice.

Protective effects of different lyoprotectants on survival of clinical bacterial isolates in a hospital biobank.

Nowadays the significant role of biobanks in medical, diagnostic, industrial, and environmental research is well known. Bacterial biobanks could be used as a good resource for designing new treatments, biomedical and industrial researches, and laboratory diagnostics. To have a collection of bacteria from clinical samples and maintain their long-term viability, their preservation needs appropriate protective agents, like cryoprotectants and lyoprotectants. In this study, we collected and characterized Gram-negative and Gram-positive bacteria carrying important antibiotic resistance markers from different clinical samples of hospitalized children. Sucrose (10%), skimmed milk (10%), skimmed milk plus sodium glutamate (10% + 1%), and bovine serum albumin (BSA, 10%) were used as lyoprotectants during the freeze-drying procedure. The survival rate of the lyophilized samples was calculated by dilution plating and measuring the colony forming unit (CFU) after 3 months of storage. The culture analysis results indicated that 25 of the 27 studied bacterial genera (Dilutions 10-3 to 10-6), including Shigella, Methicillin-resistant S. aureus, Acinetobacter spp., Escherichia spp., Pseudomonas spp., Klebsiella spp., Enterococcus spp., were recovered in cultured fractions from all preservation conditions, while 2 genera were only detected in a single preservation condition (2/27, 7.4%). Based on the results, sucrose (10%) and skimmed milk (10%) presented the most protective features. The survival rates varied significantly according to types of the bacteria. Collectively, our results showed a diversity in the recovery of different bacterial genera after lyophilization. While statistically no significant difference was detected among the studied protective agents, sucrose (10%) and skimmed milk (10%) exhibited more effective lyoprotective properties for both Gram-positive and Gram-negative bacteria among the clinical isolates in our study.

Suppressive effect of Yokukansan on glutamate released from canine keratinocytes.

Background: Canine atopic dermatitis (CAD) is caused by skin barrier dysfunction due to allergen exposure. Excessive glutamate release in the skin is associated with delayed skin barrier function recovery and epidermal thickening and lichenification. Treatment with Yokukansan (YKS), a traditional Japanese medicine, reduces dermatitis severity and scratching behavior in NC/Nga mice by decreasing epidermal glutamate levels. However, the association between canine keratinocytes and glutamate and the mechanism by which YKS inhibits glutamate release from keratinocytes remains unknown. Aim: We aimed to investigate glutamate release from canine progenitor epidermal keratinocytes (CPEKs) and the inhibitory effect of YKS on this release. We also explored the underlying mechanism of YKS to enable its application in CAD treatment. Methods: Glutamate produced from CPEKs in the medium at 24 hours was measured. The measurement conditions varied in terms of cell density and YKS concentration. CPEKs were treated with a glutamate receptor antagonist (MK-801), a glutamate transporter antagonist (THA), and a glutamate dehydrogenase inhibitor (epigallocatechin gallate; EGCG), and the inhibitory effect of YKS, YKS + THA, MK-801, and EGCG on this release was determined. MK-801 and glutamate dehydrogenase inhibitor were tested alone, and THA was tested in combination with YKS. Finally, glutamine incorporated into CPEKs at 24 hours was measured using radioisotope labeling. Results: CPEKs released glutamate in a cell density-dependent manner, inhibited by YKS in a concentration-dependent manner. Moreover, YKS reduced the intracellular uptake of radioisotope-labeled glutamine in a concentration-dependent manner. No involvement of glutamate receptor antagonism or activation of glutamate transporters was found, as suggested by previous studies. In addition, EGCG could inhibit glutamate release from CPEKs. Conclusion: Our findings indicated that glutamate release from CPEKs could be effectively inhibited by YKS, suggesting the utility of YKS in maintaining skin barrier function during CAD. In addition, CPEKs are appropriate for analyzing the mechanism of YKS. However, we found that the mechanism of action of YKS differs from that reported in previous studies, suggesting that it may have had a similar effect to EGCG in this study. Further research is warranted to understand the exact mechanism and clinical efficacy in treating CAD.

Vagotomy blunts cardiorespiratory responses to vagal afferent stimulation via pre- and postsynaptic effects in the nucleus tractus solitarii.

Viscerosensory information travels to the brain via vagal afferents, where it is first integrated within the brainstem nucleus tractus solitarii (nTS), a critical contributor to cardiorespiratory function and site of neuroplasticity. We have shown that decreasing input to the nTS via unilateral vagus nerve transection (vagotomy) induces morphological changes in nTS glia and reduces sighs during hypoxia. The mechanisms behind post-vagotomy changes are not well understood. We hypothesized that chronic vagotomy alters cardiorespiratory responses to vagal afferent stimulation via blunted nTS neuronal activity. Male Sprague-Dawley rats (6 weeks old) underwent right cervical vagotomy caudal to the nodose ganglion, or sham surgery. After 1 week, rats were anaesthetized, ventilated and instrumented to measure mean arterial pressure (MAP), heart rate (HR), and splanchnic sympathetic and phrenic nerve activity (SSNA and PhrNA, respectively). Vagal afferent stimulation (2-50 Hz) decreased cardiorespiratory parameters and increased neuronal Ca2+ measured by in vivo photometry and in vitro slice imaging of nTS GCaMP8m. Vagotomy attenuated both these reflex and neuronal Ca2+ responses compared to shams. Vagotomy also reduced presynaptic Ca2+ responses to stimulation (Cal-520 imaging) in the nTS slice. The decrease in HR, SSNA and PhrNA due to nTS nanoinjection of exogenous glutamate also was tempered following vagotomy. This effect was not restored by blocking excitatory amino acid transporters. However, the blunted responses were mimicked by NMDA, not AMPA, nanoinjection and were associated with reduced NR1 subunits in the nTS. Altogether, these results demonstrate that vagotomy induces multiple changes within the nTS tripartite synapse that influence cardiorespiratory reflex responses to afferent stimulation. KEY POINTS: Multiple mechanisms within the nucleus tractus solitarii (nTS) contribute to functional changes following vagal nerve transection. Vagotomy results in reduced cardiorespiratory reflex responses to vagal afferent stimulation and nTS glutamate nanoinjection. Blunted responses occur via reduced presynaptic Ca2+ activation and attenuated NMDA receptor expression and function, leading to a reduction in nTS neuronal activation. These results provide insight into the control of autonomic and respiratory function, as well as the plasticity that can occur in response to nerve damage and cardiorespiratory disease.

Modulation of thioredoxin by chlorogenic acid in an ischemic stroke model and glutamate-exposed neurons.

Ischemic stroke increases the production of reactive oxygen species (ROS), which can eventually lead to neuronal death. Thioredoxin is a small reductase protein that acts as an eliminator of ROS and protects neurons from brain damage. Chlorogenic acid is known as a phenolic compound that has a neuroprotective effect. We investigated the change of thioredoxin expression by chlorogenic acid in a middle cerebral artery occlusion (MCAO) animal model. Adult rats were injected intraperitoneally with phosphate buffered saline or chlorogenic acid (30 mg/kg) 2 h after MCAO. MCAO damage induced neurological defects and increased ROS and lipid peroxidation levels, however, chlorogenic acid mitigated these changes. MCAO damage reduced thioredoxin expression, which was mitigated by chlorogenic acid treatment. The interaction between thioredoxin and apoptosis signal-regulating kinase 1 (ASK1) was decreased in MCAO animals, chlorogenic acid treatment prevented this decrease. In cultured neurons, chlorogenic acid dose-dependently attenuated glutamate-induced decreases in cell viability and thioredoxin expression. Glutamate toxicity downregulated bcl-2 and upregulated bax, cytochrome c, and caspase-3, however, chlorogenic acid attenuated these changes. The mitigating effect of chlorogenic acid was lower in thioredoxin siRNA-transfected cells than in non-transfected cells. These results provide evidence that chlorogenic acid exerts potent antioxidant and neuroprotective effects through regulation of thioredoxin and modulation of ASK1 and thioredoxin binding in ischemic brain injury. These findings indicate that chlorogenic acid exerts a neuroprotective effect by regulating thioredoxin expression in cerebral ischemia and glutamate exposure conditions.

Evidence for a Role of 5-HT-glutamate Co-releasing Neurons in Acute Stress Mechanisms.

A major subpopulation of midbrain 5-hydroxytryptamine (5-HT) neurons expresses the vesicular glutamate transporter 3 (VGLUT3) and co-releases 5-HT and glutamate, but the function of this co-release is unclear. Given the strong links between 5-HT and uncontrollable stress, we used a combination of c-Fos immunohistochemistry and conditional gene knockout mice to test the hypothesis that glutamate co-releasing 5-HT neurons are activated by stress and involved in stress coping. Acute, uncontrollable swim stress increased c-Fos immunoreactivity in neurons co-expressing VGLUT3 and the 5-HT marker tryptophan hydroxylase 2 (TPH2) in the dorsal raphe nucleus (DRN). This effect was localized in the ventral DRN subregion and prevented by the antidepressant fluoxetine. In contrast, a more controllable stressor, acute social defeat, had no effect on c-Fos immunoreactivity in VGLUT3-TPH2 co-expressing neurons in the DRN. To test whether activation of glutamate co-releasing 5-HT neurons was causally linked to stress coping, mice with a specific deletion of VGLUT3 in 5-HT neurons were exposed to acute swim stress. Compared to wildtype controls, the mutant mice showed increased climbing behavior, a measure of active coping. Wildtype mice also showed increased climbing when administered fluoxetine, revealing an interesting parallel between the behavioral effects of genetic loss of VGLUT3 in 5-HT neurons and 5-HT reuptake inhibition. We conclude that 5-HT-glutamate co-releasing neurons are recruited by exposure to uncontrollable stress. Furthermore, natural variation in the balance of 5-HT and glutamate co-released at the 5-HT synapse may impact stress susceptibility.

Wound microenvironment regulatory poly(L-glutamic acid) composite hydrogels containing metal ion-coordinated nanoparticles for effective hemostasis and wound healing.

Regulating the wound microenvironment to promote proliferation, vascularization, and wound healing is challenging for hemostats and wound dressings. Herein, polypeptide composite hydrogels have been simply fabricated by mixing a smaller amount of metal ion-coordinated nanoparticles into dopamine-modified poly(L-glutamic acid) (PGA), which had a microporous size of 10-16 µm, photothermal conversion ability, good biocompatibility, and multiple biological activities. In vitro scratch healing of fibroblast L929 cells and the tube formation of HUVECs provide evidence that the PGA composite hydrogels could promote cell proliferation, migration, and angiogenesis with the assistance of mild photothermia. Moreover, these composite hydrogels plus mild photothermia could effectively eliminate reactive oxygen species (ROS), alleviate inflammation, and polarize the pro-inflammatory M1 macrophage phenotype into the pro-healing M2 phenotype to accelerate wound healing, as assessed by means of fluorescent microscopy, flow cytometry, and quantitative real-time polymerase chain reaction (qRT-PCR). Meanwhile, a rat liver bleeding model illustrates that the composite hydrogels reduced the blood loss ratio to about 10% and shortened the hemostasis time to about 25 s better than commercial chitosan-based hemostats. Furthermore, the full-thickness rat skin defect models showcase that the composite hydrogels plus mild photothermia could proheal wounds completely with a fast healing rate, optimal neovascularization, and collagen deposition. Therefore, the biodegradable polypeptide PGA composite hydrogels are promising as potent wound hemostats and dressings.

Synthesis and pharmacological characterization of conformationally restricted 2-amino-Adipic acid analogs and carboxycyclopropyl glycines as selective metabotropic glutamate 2 receptor agonists.

The metabotropic glutamate (Glu) receptors (mGluRs) are G-protein coupled receptors, which play a central role in modulating excitatory neurotransmission in the central nervous system (CNS). Thus, the development of tool compounds thereto, continues to interest the scientific community. In this study, we report the design and synthesis of new conformationally restricted 2-aminoadipic acid (2AA) 2-4, and glutamic acid 5, 6 analogs, which share the cyclopropane ring as the restrictor. The analogs were characterized at rat mGlu1-8 in an IP-One functional assay. While the 2AA analogs 3a, 4a and CCG-I analog 5a were shown to be selective mGlu2 agonists with low micromolar potencies, CCG-II analog 5b was shown to be a potent full agonist at mGlu2 (EC50 = 82 nM) with ∼15-fold selectivity over mGlu3, >25-fold selectivity over group III, and >60-fold selectivity over group I subtypes. An in silico study was performed to address this significant change (>3500 fold) in potency upon introduction of this methyl group (L-CCG-II vs 5b).

Hindering the unlimited proliferation of tumor cells synergizes with destroying tumor blood vessels for effective cancer treatment.

The rational combination of chemotherapy drugs can improve the curative effect of cancer treatment. As two early recognized tumor hallmarks, the limitless replicative potential of tumor cells is essential for the development of their malignant growth state, and sustained angiogenesis is a prerequisite to the rapid growth of tumors. Based on this, we propose a combination therapy that hinders the unlimited proliferation of tumor cells and destroys tumor blood vessels. Herein, 7-ethyl-10-hydroxycamptothecin (SN38), a typical topoisomerase I inhibitor, was bonded to poly(L-glutamic acid) (PLG) to prepare the nanodrug SN38-NPs, which hinders the unlimited proliferation of tumor cells. A poly(L-glutamic acid)-combretastatin A4 conjugate (CA4-NPs), a representative vascular disrupting agent (VDA), was used to selectively disrupt the tumor blood vessels, cutting off the necessary nutrients and oxygen for the proliferation of tumor cells. In the 4T1 tumor model with an initial volume of about 400 mm3, the combined treatment of SN38-NPs and CA4-NPs showed an excellent cancer treatment effect with a tumor suppression rate of 94.3% and a synergistic interaction (Q = 1.25). Our study provides a new combination therapy approach for chemotherapy, with the hope of further improving the curative effect of anti-cancer therapy.

Modulation of the swallowing reflex by stimulation of the gigantocellular reticular nucleus in the rat.

OBJECTIVES: The gigantocellular reticular nucleus (Gi) projects to the nuclues of the solitary tract nucleus (NTS) and the lateral reticular formation (LRF) above the nucleus ambiguus. The swallowing central pattern generator comprises the NTS and the LRF. The present study examined whether stimulation of the Gi affects the swallowing reflex. METHODS: Experiments were performed on urethane-anesthetized rats. The swallowing reflex was evoked by repetitive electrical stimulation of the superior laryngeal nerve and responses were recorded from the mylohyoid muscle on an electromyogram. The Gi was stimulated electrically. In addition, glutamate was injected into the Gi. The Friedman's test, followed by the Wilcoxon signed-rank test with Bonferroni correction, were used to assess the effects of electrical stimulation of the Gi. The Wilcoxon signed-rank test was used to assess the effects of glutamate injection into the Gi. Differences were considered significant at the P < 0.05 level. RESULTS: The number of swallows was significantly increased or decreased by electrical stimulation of the Gi or after injection of glutamate into the Gi. In both electrical stimulation of the Gi and injection of glutamate into the Gi, the onset latency of the first swallow was prolonged when the number of swallows was decreased but showed no change when the number of swallows was increased. CONCLUSIONS: The present results suggest that the Gi is involved in the control of swallowing.

Mercury-induced excitotoxicity in presynaptic brain nerve terminals: modulatory effects of carbonaceous airborne particulate simulants.

Multipollutant approach is a breakthrough in up-to-date environmental quality and health risk estimation. Both mercury and carbonaceous air particulate are hazardous neurotoxicants. Here, the ability of carbonaceous air particulate simulants, i.e. carbon dots obtained by heating of organics, and nanodiamonds, to influence Hg2+-induced neurotoxicity was monitored using biological system, i.e. presynaptic rat cortex nerve terminals. Using HgCl2 and classical reducing/chelating agents, an adequate synaptic parameter, i.e. the extracellular level of key excitatory neurotransmitter L-[14C]glutamate, was selected for further analysis. HgCl2 starting from 5 µM caused an acute and concentration-dependent increase in the extracellular L-[14C]glutamate level in nerve terminals. Combined application of Hg2+ and carbon dots from heating of citric acid/urea showed that this simulant was able to mitigate in an acute manner excitotoxic Hg2+-induced increase in the extracellular L-[14C]glutamate level in nerve terminals by 37%. These carbon dots and Hg2+ acted as a complex in nerve terminals that was confirmed with fluorimetric data on Hg2+-induced changes in their spectroscopic features. Nanodiamonds and carbon dots from ß-alanine were not able to mitigate a Hg2+-induced increase in the extracellular L-[14C]glutamate level in nerve terminals. Developed approach can be applicable for monitoring capability of different particles/compounds to have Hg2+-chelating signs in the biological systems. Therefore, among testing simulants, the only carbon dots from citric acid/urea were able to mitigate acute Hg2+-induced neurotoxicity in nerve terminals, thereby showing a variety of effects of carbonaceous airborne particulate in situ and its potential to interfere and modulate Hg2+-associated health hazard.

Effects of junk-food on food-motivated behavior and nucleus accumbens glutamate plasticity; insights into the mechanism of calcium-permeable AMPA receptor recruitment.

In rats, eating obesogenic diets increases calcium-permeable AMPA receptor (CP-AMPAR) transmission in the nucleus accumbens (NAc) core, and enhances food-motivated behavior. Interestingly, these diet-induced alterations in NAc transmission are pronounced and sustained in obesity-prone (OP) male rats and absent in obesity-resistant (OR) populations. However, effects of diet manipulation on food motivation, and the mechanisms underlying this NAc plasticity in OPs is unknown. Using male selectively-bred OP and OR rats, we assessed food-motivated behavior following ad lib access to chow (CH), junk-food (JF), or 10d of JF followed by a return to chow diet (JF-Dep). Motivation for food was greater in OP than OR rats, as expected. However, JF-Dep only produced enhancements in food-seeking in OP groups, while continuous JF access reduced food-seeking in both OPs and ORs. Additionally, optogenetic, chemogenetic, and pharmacological approaches were used to examine NAc CP-AMPAR recruitment following diet manipulation and ex vivo treatment of brain slices. Reducing excitatory transmission in the NAc was sufficient to recruit CP-AMPARs to synapses in OPs, but not ORs. In OPs, JF-induced increases in CP-AMPARs occurred in mPFC-, but not BLA-to-NAc inputs. Together results show that diet differentially affects behavioral and neural plasticity in obesity susceptible populations. We also identify conditions for acute recruitment of NAc CP-AMPARs; these results suggest that synaptic scaling mechanisms contribute to NAc CP-AMPAR recruitment. Overall, this work helps elucidate how diet interacts with obesity susceptibility to influence food-motivated behavior and extends our fundamental understanding of NAc CP-AMPAR recruitment.

Effects of pre-slaughter fasting on antemortem skeletal muscle protein degradation levels and postmortem muscle free amino acid concentrations in broiler chickens.

This study investigated the effects of pre-slaughter fasting time on the relationship between skeletal muscle protein degradation levels at slaughter and chicken meat quality after 48 h of postmortem aging. Twenty-four broiler chicks at 0 d of age were used in this study until 28 d of age. At 27 d of age, the chickens were assigned to 4 treatment groups: 0 h of fasting (0H), 8 h of fasting (8H), 16 h of fasting (16H), or 24 h of fasting (24H). They were slaughtered at 28 d of age. Blood samples were collected before fasting and immediately before slaughter. Plasma Nτ-methylhistidine concentration, an index of skeletal muscle protein degradation level, and muscle free amino acid concentration were analyzed. Antemortem changes in individual plasma Nτ-methylhistidine concentrations were significantly increased in 8H, 16H, and 24H compared to that in 0H (P < 0.05). After 48 h of postmortem storage, the glutamic acid content in the pectoralis major muscles increased with fasting time (P < 0.05), and the umami taste of chicken soup in the fasting groups (8H, 16H, 24H) was higher than that in the 0H group (P < 0.05). The antemortem changes in plasma Nτ-methylhistidine concentrations were correlated with glutamic acid content in the pectoralis major muscles (r = 0.57, P < 0.05) and umami taste (r = 0.66, P < 0.05). These results suggest that skeletal muscle protein degradation levels at slaughter are related to postmortem chicken meat quality, especially glutamic acid content and umami taste.

A glutamatergic pathway between the medial habenula and the rostral ventrolateral medulla may regulate cardiovascular function in a rat model of post-traumatic stress disorder.

Post-traumatic stress disorder (PTSD) is a serious psychiatric disorder, and there is an association between it and the development of cardiovascular disease. The aim of this study was to explore whether there is a glutamatergic pathway connecting the medial habenula (MHb) with the rostral ventrolateral medulla (RVLM) that is involved in the regulation of cardiovascular function in a rat model of PTSD. Vesicular glutamate transporter 2 (VGLUT2)-positive neurons in the MHb region were retrogradely labeled with FluoroGold (FG) by the double-labeling technique of VGLUT2 immunofluorescence and FG retrograde tracing. Rats belonging to the PTSD model group were microinjected with artificial cerebrospinal fluid (ACSF) or kynurenic acid (KYN; a nonselective glutamate receptor blocker) into their RVLM. Subsequently, with electrical stimulation of MHb, the discharge frequency of the RVLM neurons, heart rate, and blood pressure were found to be significantly increased after microinjection of ACSF using an in vivo multichannel synchronous recording technology; however, this effect was inhibited by injection of KYN. The expression of N-methyl-D-aspartic acid (NMDA) and α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptor subunits was significantly increased in RVLM of PTSD model rats analyzed by the Western blotting technique. These findings suggest that there may be a glutamatergic pathway connection between MHb and RVLM and that this pathway may be involved in the regulation of cardiovascular function in the PTSD model rats, by acting on NMDA and AMPA receptors in the RVLM.

Diet's Impact on Post-Traumatic Brain Injury Depression: Exploring Neurodegeneration, Chronic Blood-Brain Barrier Destruction, and Glutamate Neurotoxicity Mechanisms.

Traumatic brain injury (TBI) has a profound impact on cognitive and mental functioning, leading to lifelong impairment and significantly diminishing the quality of life for affected individuals. A healthy blood-brain barrier (BBB) plays a crucial role in guarding the brain against elevated levels of blood glutamate, making its permeability a vital aspect of glutamate regulation within the brain. Studies have shown the efficacy of reducing excess glutamate in the brain as a treatment for post-TBI depression, anxiety, and aggression. The purpose of this article is to evaluate the involvement of dietary glutamate in the development of depression after TBI. We performed a literature search to examine the effects of diets abundant in glutamate, which are common in Asian populations, when compared to diets low in glutamate, which are prevalent in Europe and America. We specifically explored these effects in the context of chronic BBB damage after TBI, which may initiate neurodegeneration and subsequently have an impact on depression through the mechanism of chronic glutamate neurotoxicity. A glutamate-rich diet leads to increased blood glutamate levels when contrasted with a glutamate-poor diet. Within the context of chronic BBB disruption, elevated blood glutamate levels translate to heightened brain glutamate concentrations, thereby intensifying neurodegeneration due to glutamate neurotoxicity.

Effect of Glutamate Antibody F(ab)2 Fragments on Memory Changes in Aged C57BL/6 Mice.

Intranasal administration of F(ab)2 fragments of anti-glutamate antibodies to 12-month-old C57BL/6 mice improves passive avoidance conditioning and have no effect on horizontal and vertical locomotor activity in the open-field test. In contrast to full-length antibodies to glutamate, their F(ab)2 fragments significantly increase the number of animals developed a conditioned passive avoidance reflex.

Scanning Ion-Conductance Microscopy for Studying Mechanical Properties of Neuronal Cells during Local Delivery of Glutamate.

Mechanical properties of neuronal cells have a key role for growth, generation of traction forces, adhesion, migration, etc. Mechanical properties are regulated by chemical signaling, neurotransmitters, and neuronal ion exchange. Disturbance of chemical signaling is accompanied by several diseases such as ischemia, trauma, and neurodegenerative diseases. It is known that the disturbance of chemical signaling, like that caused by glutamate excitotoxicity, leads to the structural reorganization of the cytoskeleton of neuronal cells and the deviation of native mechanical properties. Thus, to investigate the mechanical properties of living neuronal cells in the presence of glutamate, it is crucial to use noncontact and low-stress methods, which are the advantages of scanning ion-conductance microscopy (SICM). Moreover, a nanopipette may be used for the local delivery of small molecules as well as for a probe. In this work, SICM was used as an advanced technique for the simultaneous local delivery of glutamate and investigation of living neuronal cell morphology and mechanical behavior caused by an excitotoxic effect of glutamate.