Spermine reverses lipopolysaccharide-induced memory deficit in mice

Probiotics and the microbiota-gut-brain axis in neurodegeneration: Beneficial effects and mechanistic insights

Neurodegenerative diseases (NDs) are a group of heterogeneous disorders with a high socioeconomic burden. Although pharmacotherapy is currently the principal therapeutic approach for the management of NDs, mounting evidence supports the notion that the protracted application of available drugs would abate their dopaminergic outcomes in the long run. The therapeutic application of microbiome-based modalities has received escalating attention in biomedical works. In-depth investigations of the bidirectional communication between the microbiome in the gut and the brain offer a multitude of targets for the treatment of NDs or maximizing the patient's quality of life. Probiotic administration is a well-known microbial-oriented approach to modulate the gut microbiota and potentially influence the process of neurodegeneration. Of note, there is a strong need for further investigation to map out the mechanistic prospects for the gut-brain axis and the clinical efficacy of probiotics. In this review, we discuss the importance of microbiome modulation and hemostasis via probiotics, prebiotics, postbiotics and synbiotics in ameliorating pathological neurodegenerative events. Also, we meticulously describe the underlying mechanism of action of probiotics and their metabolites on the gut-brain axis in different NDs. We suppose that the present work will provide a functional direction for the use of probiotic-based modalities in promoting current practical treatments for the management of neurodegenerative-related diseases.

CaMKIIα mediates spermidine-induced memory enhancement in rats: A potential involvement of PKA/CREB pathway

Memory consolidation is associated with the regulation of protein kinases, which impact synaptic functions and promote synaptogenesis. The administration of spermidine (SPD) has been shown to modulate major protein kinases associated with memory improvement, including the Ca2+-dependent protein kinase (PKC) and cAMP-dependent protein kinase (PKA), key players in the cAMP response element-binding protein (CREB) activation. Nevertheless, the initial mechanism underlying SPD-mediated memory consolidation remains unknown, as we hypothesize a potential involvement of the memory consolidation precursor, Ca2+/calmodulin-dependent protein kinase II-α (CaMKIIα), in this process. Based on this, our study aimed to investigate potential interactions among PKC, PKA, and CREB activation, mediated by CaMKIIα activation, in order to elucidate the SPD memory consolidation pathway. Our findings suggest that the post-training administration of the CaMKII inhibitor, KN-62 (0.25 nmol, intrahippocampal), prevented the memory enhancement induced by SPD (0.2 nmol, intrahippocampal) in the inhibitory avoidance task. Through western immunoblotting, we observed that phosphorylation of CaMKIIα in the hippocampus was facilitated 15 min after intrahippocampal SPD administration, resulting in the activation of PKA and CREB, 180 min after infusion, suggesting a possible sequential mechanism, since SPD with KN-62 infusion leads to a downregulation in CaMKIIα/PKA/CREB pathway. However, KN-62 does not alter the memory-facilitating effect of SPD on PKC, possibly demonstrating a parallel cascade in memory acquisition via PKA, without modulating CAMKIIα. These results suggest that memory enhancement induced by SPD administration involves crosstalk between CaMKIIα and PKA/CREB, with no PKC interaction.

A review on polyamines as promising next-generation neuroprotective and anti-aging therapy

Neurodegenerative disorders are diseases characterized by progressive degeneration of neurons and associated structures and are a major global issue growing more widespread as the global population's average age increases. Despite several investigations on their etiology, the specific cause of these disorders remains unknown. However, there are few symptomatic therapies to treat these disorders. Polyamines (PAs) (putrescine, spermidine, and spermine) are being studied for their role in neuroprotection, aging and cognitive impairment. They are ubiquitous polycations which have relatively higher concentrations in the brain and possess pleiotropic biochemical activities, including regulation of gene expression, ion channels, mitochondria Ca2+ transport, autophagy induction, programmed cell death, and many more. Their cellular content is tightly regulated, and substantial evidence indicates that their altered levels and metabolism are strongly implicated in aging, stress, cognitive dysfunction, and neurodegenerative disorders. In addition, dietary polyamine supplementation has been reported to induce anti-aging effects, anti-oxidant effects, and improve locomotor abnormalities, and cognitive dysfunction. Thus, restoring the polyamine level is considered a promising pharmacological strategy to counteract neurodegeneration. This review highlights PAs' physiological role and the molecular mechanism underpinning their proposed neuroprotective effect in aging and neurodegenerative disorders.

Possible Prophylactic Effects of Sulforaphane on LPS-Induced Recognition Memory Impairment Mediated by Regulating Oxidative Stress and Neuroinflammatory Proteins in the Prefrontal Cortex Region of the Brain

BACKGROUND

Alzheimer's disease (AD) presents a significant global health concern, characterized by neurodegeneration and cognitive decline. Neuroinflammation is a crucial factor in AD development and progression, yet effective pharmacotherapy remains elusive. Sulforaphane (SFN), derived from cruciferous vegetables and mainly from broccoli, has shown a promising effect via in vitro and in vivo studies as a potential treatment for AD. This study aims to investigate the possible prophylactic mechanisms of SFN against prefrontal cortex (PFC)-related recognition memory impairment induced by lipopolysaccharide (LPS) administration.

METHODOLOGY

Thirty-six Swiss (SWR/J) mice weighing 18-25 g were divided into three groups (n = 12 per group): a control group (vehicle), an LPS group (0.75 mg/kg of LPS), and an LPS + SFN group (25 mg/kg of SFN). The total duration of the study was 3 weeks, during which mice underwent treatments for the initial 2 weeks, with daily monitoring of body weight and temperature. Behavioral assessments via novel object recognition (NOR) and temporal order recognition (TOR) tasks were conducted in the final week of the study. Inflammatory markers (IL-6 and TNF), antioxidant enzymes (SOD, GSH, and CAT), and pro-oxidant (MDA) level, in addition to acetylcholine esterase (AChE) activity and active (caspase-3) and phosphorylated (AMPK) levels, were evaluated. Further, PFC neuronal degeneration, Aβ content, and microglial activation were also examined using H&E, Congo red staining, and Iba1 immunohistochemistry, respectively.

RESULTS

SFN pretreatment significantly improved recognition memory performance during the NOR and TOR tests. Moreover, SFN was protected from neuroinflammation and oxidative stress as well as neurodegeneration, Aβ accumulation, and microglial hyperactivity.

CONCLUSION

The obtained results suggested that SFN has a potential protective property to mitigate the behavioral and biochemical impairments induced by chronic LPS administration and suggested to be via an AMPK/caspase-3-dependent manner.

D-ribose-L-cysteine exhibits restorative neurobehavioral functions through modulation of neurochemical activities and inhibition oxido-inflammatory perturbations in rats exposed to polychlorinated biphenyl

Polychlorinated biphenyl (PCB) is potentially harmful environmental toxicant causing cognitive decline with depressive features. PCB-induced behavioral deficits are associated with neurochemical dysfunctions, immune changes, and oxidative stress. This study investigated the neuroprotective effects of D-ribose-L-cysteine (DRLC), a neuroprotective precursor element of glutathione on PCB-induced neurobehavioral impairments. Following the initial 15 days of PCB (2 mg/kg) exposure to rats, DRLC (50 mg/kg) was given orally for an additional 15 days, from days 16 to 30. Animals were assessed for behavioral effect such as changes in locomotion, cognition, and depression. Oxidative/nitrergic stress markers; antioxidant regulatory proteins paraoxonase-1 (PON-1), heme oxygenase-1 (HO-1), nuclear factor erythroid 2-related factor 2 (Nfr2), NADPH oxidase-1 (NOX-1), NAD(P)H quinone oxidoreductase 1 (NQO1), and neuroinflammation (NF-kβ, and TNF-α); and neurochemical metabolizing enzymes (acetylcholinesterase (AChE), monoamine oxidase-A and -B (MAO-A, MAO-B)) were carried out. The PCB-induced decline in locomotion, cognitive performance, and depressive-like features were reversed by DRLC. More specifically, PCB-induced oxidative and nitrergic stress, typified by reduced levels GSH, CAT, and SOD, accompanied by elevated MDA and nitrite were attenuated by DRLC. Additionally, DRLC restored the neuroinflammatory milieu indicated by decreased NF-kβ and TNF-α levels toward normal. Hyperactivities of AChE, MAO-A, MAO-B, PON-1, and NOX-1 levels as well as Nfr2, NQO1, and PON-1 due to PCB exposure were mitigated by DLRC. Our results suggest DRLC as a prospective neurotherapeutic agent against PCB-induced neurobehavioral impairments such as cognitive deficit and depressive-like feature through antioxidative and anti-nitrergic stress, anti-neuroinflammation, inhibition of brain metabolizing enzymes, and normalization of neurochemical homeostasis.

m-Terphenylamines, Acting as Selective COX-1 Inhibitors, Block Microglia Inflammatory Response and Exert Neuroprotective Activity

Inhibition of cyclooxygenase-2 (COX-2) has been extensively studied as an approach to reduce proinflammatory markers in acute brain diseases, but the anti-neuroinflammatory role of cyclooxygenase-1 (COX-1) inhibition has been rather neglected. We report that m-terphenylamine derivatives are selective COX-1 inhibitors, able to block microglia inflammatory response and elicit a neuroprotective effect. These compounds were synthesized via a three-component reaction of chalcones, β-ketoesters, and primary amines, followed by hydrolysis/decarboxylation of the ester group. Together with their synthetic intermediates and some urea derivatives, they were studied as inhibitors of COX-1 and COX-2. The m-terphenylamine derivatives, which were selective COX-1 inhibitors, were also analyzed for their ability to block microglia inflammatory and oxidative response. Compound 3b presented an interesting anti-inflammatory and neuroprotective profile by reducing nitrite release, ROS overproduction, and cell death in organotypic hippocampal cultures subjected to LPS. We thus show that COX-1 inhibition is a promising approach to provide enhanced neuroprotection against acute inflammatory processes, which are crucial in the development of a plethora of acute neurodegenerative injuries.

N-methyl-D-aspartate receptor hypofunction as a potential contributor to the progression and manifestation of many neurological disorders

N-methyl-D-aspartate receptors (NMDA) are glutamate-gated ion channels critical for synaptic transmission and plasticity. A slight variation of NMDAR expression and function can result in devastating consequences, and both hyperactivation and hypoactivation of NMDARs are detrimental to neural function. Compared to NMDAR hyperfunction, NMDAR hypofunction is widely implicated in many neurological disorders, such as intellectual disability, autism, schizophrenia, and age-related cognitive decline. Additionally, NMDAR hypofunction is associated with the progression and manifestation of these diseases. Here, we review the underlying mechanisms of NMDAR hypofunction in the progression of these neurological disorders and highlight that targeting NMDAR hypofunction is a promising therapeutic intervention in some neurological disorders.

Modeling the innate inflammatory cGAS/STING pathway: sexually dimorphic effects on microglia and cognition in obesity and prediabetes

Introduction

The prevalence of obesity, prediabetes, and diabetes continues to grow worldwide. These metabolic dysfunctions predispose individuals to neurodegenerative diseases and cognitive impairment, including dementias such as Alzheimer's disease and Alzheimer's disease related dementias (AD/ADRD). The innate inflammatory cGAS/STING pathway plays a pivotal role in metabolic dysfunction and is an emerging target of interest in multiple neurodegenerative diseases, including AD/ADRD. Therefore, our goal was to establish a murine model to specifically target the cGAS/STING pathway to study obesity- and prediabetes-induced cognitive impairment.

Methods

We performed two pilot studies in cGAS knockout (cGAS-/-) male and female mice designed to characterize basic metabolic and inflammatory phenotypes and examine the impact of high-fat diet (HFD) on metabolic, inflammatory, and cognitive parameters.

Results

cGAS-/- mice displayed normal metabolic profiles and retained the ability to respond to inflammatory stimuli, as indicated by an increase in plasma inflammatory cytokine production in response to lipopolysaccharide injection. HFD feeding caused expected increases in body weight and decreases in glucose tolerance, although onset was accelerated in females versus males. While HFD did not increase plasma or hippocampal inflammatory cytokine production, it did alter microglial morphology to a state indicative of activation, particularly in female cGAS-/- mice. However, HFD negatively impacted cognitive outcomes in male, but not female animals.

Discussion

Collectively, these results suggest that cGAS-/- mice display sexually dimorphic responses to HFD, possibly based on differences in microglial morphology and cognition.

LPS induces microglial activation and GABAergic synaptic deficits in the hippocampus accompanied by prolonged cognitive impairment

Neuroinflammation impacts the brain and cognitive behavior through microglial activation. In this study, we determined the temporal sequence from microglial activation to synaptic dysfunction and cognitive behavior induced by neuroinflammation in mice. We found that LPS injection activated microglia within a short period, followed by impairments in GABAergic synapses, and that these events led to long-term cognitive impairment. We demonstrated that, 3 days after LPS injection, microglia in the hippocampus were significantly activated due to the LPS-induced inflammation in association with alterations in cellular morphology, microglial density, and expression of phagocytic markers. GABAergic synaptic impairments were detected at 4-6 days after LPS treatment, a time when microglia activity had returned to normal. Consequently, memory impairment persisted for 6 days after injection of LPS. Our results suggest that neuroinflammation induces microglia activation, GABAergic synaptic deficits and prolonged memory impairment over a defined temporal sequence. Our observations provide insight into the temporal sequence of neuroinflammation-associated brain pathologies. Moreover, the specific loss of inhibitory synapses accompanying the impaired inhibitory synaptic transmission provides mechanistic insight that may explain the prolonged cognitive deficit observed in patients with neuroinflammation. Thus, this study provides essential clues regarding early intervention strategies against brain pathologies accompanying neuroinflammation.

A decrease in NR2B expression mediated by DNA hypermethylation induces perioperative neurocognitive disorder in aged mice

AIMS

This study was designed to investigate the role of NR2B and the contribution of DNA methylation to NR2B expression in the pathogenesis of PND.

METHODS

Eighteen-month-old C57BL/6J mice were subjected to experimental laparotomy under 1.4% isoflurane anesthesia. Hippocampus-dependent learning and memory were evaluated by using the Barnes maze and contextual fear conditioning tests. The protein and mRNA expression levels of NR2B were evaluated by western blotting and qRT-PCR respectively, and the methylation of the NR2B gene was examined by using targeted bisulfite sequencing. Long-term synaptic plasticity (LTP) was measured by electrophysiology.

RESULTS

Mice that underwent laparotomy exhibited hippocampus-dependent cognitive deficits accompanied by decreased NR2B expressions and LTP deficiency. The overexpression of NR2B in the dorsal hippocampus could improve learning and memory in mice subjected to laparotomy. In particular, the decreased NR2B expressions induced by laparotomy was attributed to the NR2B gene hypermethylation. Preoperative administration of S-adenosylmethionine (SAM) could hypomethylate the NR2B gene, upregulate NR2B expression and improve LTP, exerting a dose-dependent therapeutic effect against PND. Moreover, inhibiting NR2B abrogated the benefits of SAM pretreatment.

CONCLUSIONS

Laparotomy cause hippocampus-dependent cognitive decline by hypermethylating the NR2B gene, allowing us to understand the pathogenesis of PND in an epigenetic landscape.

L-Type Ca2+ Channel Inhibition Rescues the LPS-Induced Neuroinflammatory Response and Impairments in Spatial Memory and Dendritic Spine Formation

Ca2+ signaling is implicated in the transition between microglial surveillance and activation. Several L-type Ca2+ channel blockers (CCBs) have been shown to ameliorate neuroinflammation by modulating microglial activity. In this study, we examined the effects of the L-type CCB felodipine on LPS-mediated proinflammatory responses. We found that felodipine treatment significantly diminished LPS-evoked proinflammatory cytokine levels in BV2 microglial cells in an L-type Ca2+ channel-dependent manner. In addition, felodipine leads to the inhibition of TLR4/AKT/STAT3 signaling in BV2 microglial cells. We further examined the effects of felodipine on LPS-stimulated neuroinflammation in vivo and found that daily administration (3 or 7 days, i.p.) significantly reduced LPS-mediated gliosis and COX-2 and IL-1β levels in C57BL/6 (wild-type) mice. Moreover, felodipine administration significantly reduced chronic neuroinflammation-induced spatial memory impairment, dendritic spine number, and microgliosis in C57BL/6 mice. Taken together, our results suggest that the L-type CCB felodipine could be repurposed for the treatment of neuroinflammation/cognitive function-associated diseases.

Pharmacological Activation of GPR55 Improved Cognitive Impairment Induced by Lipopolysaccharide in Mice

Our previous research found that activation of GPR55 can alleviate cognitive impairment induced by amyloid-beta 1-42 (Aβ_1-42) and streptozotocin in mice, but the role of GPR55 in the pathogenesis of cognitive impairment remains unknown. Here, we used a lipopolysaccharide (LPS) mouse model to further investigate the role and mechanism of O-1602, a GPR55 agonist, on cognitive dysfunction. ICR mice were treated with an intracerebroventricular (i.c.v.) injection of LPS, followed by cognitive function tests. The expression of GPR55, NF-κB p65, caspase-3, Bax, and Bcl-2 in the hippocampus was examined by Western blotting. Inflammatory cytokines and microglia were detected by ELISA kit and immunohistochemical analyses, respectively. The levels of MDA, GSH, SOD, and CAT were examined by assay kits. Furthermore, TUNEL-staining was used to detect neuronal apoptosis. Our results showed that i.c.v. injection of LPS in mice exhibited impaired performance in the behavior tests, which were ameliorated by O-1602 treatment (2.0 or 4.0 μg/mouse, i.c.v.). Importantly, we found that O-1602 treatment reversed GPR55 downregulation, decreased the expression of NF-κB p65, suppressed the accumulation of proinflammatory cytokines and microglia activation, increased the anti-inflammatory cytokines, and reduced the levels of MDA, increased the levels of GSH, SOD, and CAT in the hippocampus. In addition, O-1602 treatment also significantly reduced Bax and increased Bcl-2 expression as well as decreased caspase-3 activity and TUNEL-positive cells in the hippocampus. These observations indicate that O-1602 may ameliorate LPS-induced cognition deficits via inhibiting neuroinflammation, oxidative stress, and apoptosis mediated by the NF-κB pathway in mice.

Neuropharmacological effects of honey in lipopolysaccharide-induced neuroinflammation, cognitive impairment, anxiety and motor impairment

Objectives: Honey contains phenolic acids and flavonoids, which are significant in developing drugs against neuroinflammation. The study was designed to evaluate the ameliorative potential of honey in lipopolysaccharides-induced neuroinflammation.Methods: Thirty male Wistar rats were divided into six groups, namely: the control group (10 mL/kg vehicle), the LPS only group (250 µg/kg), the honey (0.26, 0.31 and 0.36 g/kg) and the ibuprofen (100 mg/kg). LPS (250 µg/kg i.p) was administered for 7days followed by the treatment with honey and Ibuprofen for another 7days. Animals were assessed for memory impairment and anxiety levels using a Novel object recognition test (NORT), elevated plus maze (EPM), and open field test (OFT). Brain levels of pro-inflammatory cytokine level, acetylcholinesterase activity, and oxidative stress were determined. The neuronal alteration was assessed histologically using cresyl fast violet staining of the hippocampus, prefrontal cortex, and striatum.Results: Honey (0.31 and 0.36 g/kg) significantly ameliorated LPS-induced memory impairment on NORT and increased time spent in the open arm and increased the locomotor activity in the OFT. Honey significantly (p < 0.05) reduced LPS-induced elevation of tumor necrosis factor (TNF-α) and interleukin-6 (IL-6). It significantly reduced malondialdehyde and nitrite levels in mice brains and reversed depletion of reduced glutathione levels. Honey attenuated LPS-induced elevation of acetylcholinesterase activity in rat brains. Cresyl violet staining showed the restoration of neuronal organization and Nissl body distribution in the hippocampus, prefrontal cortex and striatum compared to the LPS only group.Discussion: Honey effectively ameliorated LPS-induced poor cognitive performance, anxiety, motor coordination responses to neuroinflammation, and oxidative stress.

Spermine alleviates experimental autoimmune encephalomyelitis via regulating T cell activation and differentiation

Multiple sclerosis (MS) is a chronic neuroinflammatory disease which causes demyelination, axonal damage and even disability. Th1 and Th17 cells, more precisely, the IFNγ/IL17a double producing CD4⁺ T cells, have been known to play critical roles in the pathogenesis of MS and EAE, a mouse model of MS. Polyamines not only regulate the immune system, but also are essential for the normal function of the central nervous system (CNS). In this study, we demonstrate that the supplementation of spermine (SPM), a biogenic polyamine, significantly suppresses EAE progression in both preventative and therapeutic ways. Further study suggests that spermine significantly reduces IFNγ⁺/IL17a^-, IFNγ^-/IL17a⁺ and IFNγ⁺/IL17a⁺ cells in periphery, and thus reducing the infiltration of these pathogenic cells into the CNS. In vitro, spermine has been shown to suppress the activation and proliferation of CD4⁺ T cells and also significantly impede the polarization of T effector cells in a dose-dependent manner, accompanied by the inhibition of ERK phosphorylation. Consistently, a number of MEK/ERK inhibitors (including PD0325901, FR180204 and selumetinib) have been found to mimic the effects of spermine in inhibiting CD4⁺ T cell activation and T effector cell differentiation. Collectively, spermine alleviates EAE progression by inhibiting CD4⁺ T cells activation and T effector cell differentiation in a MAPK/ERK-dependent manner, suggesting this pathway might be a target to develop effective therapies for MS.

Activation of GPR55 attenuates cognitive impairment and neurotoxicity in a mouse model of Alzheimer's disease induced by Aβ1-42 through inhibiting RhoA/ROCK2 pathway

The accumulation of amyloid-β (Aβ) peptides in the brain is considered to be the initial event in the Alzheimer's disease (AD). Neurotoxicity mediated by Aβ has been demonstrated to damage the cognitive function. In the present study, we sought to determine the effects of O-1602, a specific G-protein coupled receptor 55 (GPR55) agonist, on the impairment of learning and memory induced by intracerebroventricular (i.c.v.) of Aβ_1-42 (400 pmol/mouse) in mice. Our results showed that i.c.v. injection of aggregated Aβ_1-42 into the brain of mice resulted in cognitive impairment and neurotoxicity. In contrast, O-1602 (2.0 or 4.0 μg/mouse, i.c.v.) can improve memory impairment induced by Aβ_1-42 in the Morris water maze (MWM), and novel object recognition (NOR) tests. Besides, we found that O-1602 reduced the activity of β-secretase 1 (BACE1) and the level of soluble Aβ_1-42 in the hippocampus and frontal cortex. Importantly, O-1602 treatment reversed Aβ_1-42-induced GPR55 down-regulation, decreased pro-inflammatory cytokines, and the level of malondialdehyde (MDA), increased the levels of glutathione (GSH), superoxide dismutase (SOD), and catalase (CAT), as well as suppressed apoptosis as indicated by decreased TUNEL-positive cells, and increased the ratio of Bcl-2/Bax. O-1602 treatment also pronouncedly ameliorated synaptic dysfunction by promoting the upregulation of PSD-95 and synaptophysin (SYN) proteins. Moreover, O-1602 concurrently down regulated the protein levels of RhoA, and ROCK2, the critical proteins in the RhoA/ROCK2 pathway. This study indicates that O-1602 may reverse Aβ_1-42-induced cognitive impairment and neurotoxicity in mice by inhibiting RhoA/ROCK2 pathway. Taken together, these findings suggest that GPR55 could be a novel and promising target for the treatment of AD.

DSS-induced inflammation in the colon drives a proinflammatory signature in the brain that is ameliorated by prophylactic treatment with the S100A9 inhibitor paquinimod

Background

Inflammatory bowel disease (IBD) is established to drive pathological sequelae in organ systems outside the intestine, including the central nervous system (CNS). Many patients exhibit cognitive deficits, particularly during disease flare. The connection between colonic inflammation and neuroinflammation remains unclear and characterization of the neuroinflammatory phenotype in the brain during colitis is ill-defined.

Methods

Transgenic mice expressing a bioluminescent reporter of active caspase-1 were treated with 2% dextran sodium sulfate (DSS) for 7 days to induce acute colitis, and colonic, systemic and neuroinflammation were assessed. In some experiments, mice were prophylactically treated with paquinimod (ABR-215757) to inhibit S100A9 inflammatory signaling. As a positive control for peripheral-induced neuroinflammation, mice were injected with lipopolysaccharide (LPS). Colonic, systemic and brain inflammatory cytokines and chemokines were measured by cytokine bead array (CBA) and Proteome profiler mouse cytokine array. Bioluminescence was quantified in the brain and caspase activation was confirmed by immunoblot. Immune cell infiltration into the CNS was measured by flow cytometry, while light sheet microscopy was used to monitor changes in resident microglia localization in intact brains during DSS or LPS-induced neuroinflammation. RNA sequencing was performed to identify transcriptomic changes occurring in the CNS of DSS-treated mice. Expression of inflammatory biomarkers were quantified in the brain and serum by qRT-PCR, ELISA and WB.

Results

DSS-treated mice exhibited clinical hallmarks of colitis, including weight loss, colonic shortening and inflammation in the colon. We also detected a significant increase in inflammatory cytokines in the serum and brain, as well as caspase and microglia activation in the brain of mice with ongoing colitis. RNA sequencing of brains isolated from DSS-treated mice revealed differential expression of genes involved in the regulation of inflammatory responses. This inflammatory phenotype was similar to the signature detected in LPS-treated mice, albeit less robust and transient, as inflammatory gene expression returned to baseline following cessation of DSS. Pharmacological inhibition of S100A9, one of the transcripts identified by RNA sequencing, attenuated colitis severity and systemic and neuroinflammation.

Conclusions

Our findings suggest that local inflammation in the colon drives systemic inflammation and neuroinflammation, and this can be ameliorated by inhibition of the S100 alarmin, S100A9.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-021-02317-6.

Involvement of striatal oxido-inflammatory, nitrosative and decreased cholinergic activity in neurobehavioral alteration in adult rat model with oral co-exposure to erythrosine and tartrazine

Overuse or overconsumption of food additive or colorant cannot be ignored in our society and there are several reports of it harmful effect on the body system. This study investigated the toxicity effect of tartrazine and erythrosine (ET, 50:50) on neurobehavioral alteration, striatal oxido-nitrosative and pro-inflammatory stress and striatal acetylcholinesterase activity in experimental rat model. Rats were co-exposed to ET (2 mg/kg, 6 mg/kg and 10 mg/kg) and distilled water (control), p.o for 6 weeks. The change in neurobehavioral function (Open field test, Forced swimming test and Tail suspension test), Lipid peroxidation (Malonaldehyde, MDA), Antioxidants (Glutathione, GSH; Catalase, CAT) Nitrite, Pro-inflammatory cytokine (Tumor necrosis factor-alpha, TNF-α) and Acetylcholinesterase (AChE) activity were evaluated. Results showed significant decrease in neurobehavioral functions after co-exposure to ET. Moreover, there were significant increase in MDA and Nitrite level, significant decrease in the concentration of GSH and CAT and a significant increase TNF-α concentration and AChE activity after co-exposure to ET. Oral co-exposure to tartrazine and erythrosine induced decrease in locomotion and exploration, increase anxiety and depression-like behavior and altered the cholinergic system through upregulation of oxido-nitrosative stress, pro-inflammatory cytokine and acetylcholinesterase activity.

Positive allosteric modulation of NMDA receptors: mechanisms, physiological impact and therapeutic potential

NMDA receptors (NMDARs) are glutamate-gated ion channels that play key roles in synaptic transmission and plasticity. Both hyper- and hypo-activation of NMDARs are deleterious to neuronal function. In particular, NMDAR hypofunction is involved in a wide range of neurological and psychiatric conditions like schizophrenia, intellectual disability, age-dependent cognitive decline, or Alzheimer's disease. While early medicinal chemistry efforts were mostly focused on the development of NMDAR antagonists, the last 10 years have seen a boom in the development of NMDAR positive allosteric modulators (PAMs). Here we review the currently developed NMDAR PAMs, their pharmacological profiles and mechanisms of action, as well as their physiological effects in healthy animals and animal models of NMDAR hypofunction. In light of the complexity of physiological outcomes of NMDAR PAMs in vivo, we discuss the remaining challenges and questions that need to be addressed to better grasp and predict the therapeutic potential of NMDAR positive allosteric modulation.

Polyamines: Functions, Metabolism, and Role in Human Disease Management

Putrescine, spermine, and spermidine are the important polyamines (PAs), found in all living organisms. PAs are formed by the decarboxylation of amino acids, and they facilitate cell growth and development via different cellular responses. PAs are the integrated part of the cellular and genetic metabolism and help in transcription, translation, signaling, and post-translational modifications. At the cellular level, PA concentration may influence the condition of various diseases in the body. For instance, a high PA level is detrimental to patients suffering from aging, cognitive impairment, and cancer. The levels of PAs decline with age in humans, which is associated with different health disorders. On the other hand, PAs reduce the risk of many cardiovascular diseases and increase longevity, when taken in an optimum quantity. Therefore, a controlled diet is an easy way to maintain the level of PAs in the body. Based on the nutritional intake of PAs, healthy cell functioning can be maintained. Moreover, several diseases can also be controlled to a higher extend via maintaining the metabolism of PAs. The present review discusses the types, important functions, and metabolism of PAs in humans. It also highlights the nutritional role of PAs in the prevention of various diseases.

Methyl Jasmonate: Behavioral and Molecular Implications in Neurological Disorders

Methyl jasmonate (MJ) is a derivative of the jasmonate family which is found in most tropical regions of the world and present in many fruits and vegetables such as grapevines, tomato, rice, and sugarcane. MJ is a cyclopentanone phytohormone that plays a vital role in defense against stress and pathogens in plants. This has led to its isolation from plants for studies in animals. Many of these studies have been carried out to evaluate its therapeutic effects on behavioral and neurochemical functions. It has however been proposed to have beneficial potential over a wide range of neurological disorders. Hence, this review aims to provide an overview of the neuroprotective properties of MJ and its probable mechanisms of ameliorating neurological disorders. The information used for this review was sourced from research articles and scientific databases using 'methyl jasmonate', 'behavior', 'neuroprotection', 'neurodegenerative diseases', and 'mechanisms' as search words. The review highlights its influences on behavioral patterns of anxiety, aggression, depression, memory, psychotic, and stress. The molecular mechanisms such as modulation of the antioxidant defense, inflammatory biomarkers, neurotransmitter regulation, and neuronal regeneration, underlying its actions in managing neurodegenerative diseases like Alzheimer's and Parkinson's diseases are also discussed. This review, therefore, provides a detailed evaluation of methyl jasmonate as a potential neuroprotective compound with the ability to modify behavioral and molecular biomarkers underlying neurological disorders. Hence, MJ could be modeled as a guided treatment for the management of brain diseases.

4R-cembranoid confers neuroprotection against LPS-induced hippocampal inflammation in mice

BACKGROUND

Chronic brain inflammation has been implicated in the pathogenesis of various neurodegenerative diseases and disorders. For example, overexpression of pro-inflammatory cytokines has been associated with impairments in hippocampal-dependent memory. Lipopolysaccharide (LPS) injection is a widely used model to explore the pathobiology of inflammation. LPS injection into mice causes systemic inflammation, neuronal damage, and poor memory outcomes if the inflammation is not controlled. Activation of the alpha-7 nicotinic receptor (α7) plays an anti-inflammatory role in the brain through vagal efferent nerve signaling. 4R-cembranoid (4R) is a natural compound that crosses the blood-brain barrier, induces neuronal survival, and has been shown to modulate the activity of nicotinic receptors. The purpose of this study is to determine whether 4R reduces the deleterious effects of LPS-induced neuroinflammation and whether the α7 receptor plays a role in mediating these beneficial effects.

METHODS

Ex vivo population spike recordings were performed in C57BL/6J wild-type (WT) and alpha-7-knockout (α7KO) mouse hippocampal slices in the presence of 4R and nicotinic receptor inhibitors. For in vivo studies, WT and α7KO mice were injected with LPS for 2 h, followed by 4R or vehicle for 22 h. Analyses of IL-1β, TNF-α, STAT3, CREB, Akt1, and the long-term novel object recognition test (NORT) were performed for both genotypes. In addition, RNA sequencing and RT-qPCR analyses were carried out for 12 mRNAs related to neuroinflammation and their modification by 4R.

RESULTS

4R confers neuroprotection after NMDA-induced neurotoxicity in both WT and α7KO mice. Moreover, hippocampal TNF-α and IL-1β levels were decreased with 4R treatment following LPS exposure in both strains of mice. 4R restored LPS-induced cognitive decline in NORT. There was a significant increase in the phosphorylation of STAT3, CREB, and Akt1 with 4R treatment in the WT mouse hippocampus following LPS exposure. In α7KO mice, only pAkt levels were significantly elevated in the cortex. 4R significantly upregulated mRNA levels of ORM2, GDNF, and C3 following LPS exposure. These proteins are known to play a role in modulating microglial activation, neuronal survival, and memory.

CONCLUSION

Our results indicate that 4R decreases the levels of pro-inflammatory cytokines; improves memory function; activates STAT3, Akt1, and CREB phosphorylation; and upregulates the mRNA levels of ORM2, GDNF, and C3. These effects are independent of the α7 nicotinic receptor.

N-Docosahexanoylethanolamine Reduces Microglial Activation and Improves Hippocampal Plasticity in a Murine Model of Neuroinflammation

Chronic neuroinflammation is a common pathogenetic link in the development of various neurological and neurodegenerative diseases. Thus, a detailed study of neuroinflammation and the development of drugs that reduce or eliminate the negative effect of neuroinflammation on cognitive processes are among the top priorities of modern neurobiology. N-docosahexanoylethanolamine (DHEA, synaptamide) is an endogenous metabolite and structural analog of anandamide, an essential endocannabinoid produced from arachidonic acid. Our study aims to elucidate the pharmacological activity of synaptamide in lipopolysaccharide (LPS)-induced neuroinflammation. Memory deficits in animals were determined using behavioral tests. To study the effects of LPS (750 µg/kg/day, 7 days) and synaptamide (10 mg/kg/day, 7 days) on synaptic plasticity, long-term potentiation was examined in the CA1 area of acute hippocampal slices. The Golgi-Cox method allowed us to assess neuronal morphology. The production of inflammatory factors and receptors was assessed using ELISA and immunohistochemistry. During the study, functional, structural, and plastic changes within the hippocampus were identified. We found a beneficial effect of synaptamide on hippocampal synaptic plasticity and morphological characteristics of neurons. Synaptamide treatment recovered hippocampal neurogenesis, suppressed microglial activation, and significantly improved hippocampus-dependent memory. The basis of the phenomena described above is probably the powerful anti-inflammatory activity of synaptamide, as shown in our study and several previous works.

Endogenous antagonists of N-methyl-d-aspartate receptor in schizophrenia

Schizophrenia is a chronic neuropsychiatric brain disorder that has devastating personal impact and rising healthcare costs. Dysregulation of glutamatergic neurotransmission has been implicated in the pathobiology of the disease, attributed largely to the hypofunction of the N-methyl-d-aspartate (NMDA) receptor. Currently, there is a major gap in mechanistic analysis as to how endogenous modulators of the NMDA receptors contribute to the onset and progression of the disease. We present a systematic review of the neurobiology and the role of endogenous NMDA receptor antagonists in animal models of schizophrenia, and in patients. We discuss their neurochemical origin, release from neurons and glia with action mechanisms, and functional effects, which might contribute toward the impairment of neuronal processes underlying this complex pathological state. We consider clinical evidence suggesting dysregulations of endogenous NMDA receptor in schizophrenia, and highlight the pressing need in future studies and emerging directions, to restore the NMDA receptor functions for therapeutic benefits.

What animal models can tell us about long-term cognitive dysfunction following sepsis: A systematic review

Survivors of sepsis often develop long-term cognitive impairments. This review aimed at exploring the results of the behavioral tools and tests which have been used to evaluate cognitive dysfunction in different animal models of sepsis. Two independent investigators searched for sepsis- and cognition-related keywords. 6323 publications were found, of which 355 were selected based on their title, and 226 of these were chosen based on manuscript review. LPS was used to induce sepsis in 171 studies, while CLP was used in 55 studies. Inhibitory avoidance was the most widely used method for assessing aversive memory, followed by fear conditioning and continuous multi-trial inhibitory avoidance. With regard to non-aversive memory, most studies used the water maze, open-field, object recognition, Y-maze, plus maze, and radial maze tests. Both CLP and LPS models of sepsis were effective in inducing short- and long-term behavioral impairment. Our findings help elucidate the mechanisms involved in the pathophysiology of sepsis-induced cognitive changes, as well as the available methods and tests used to study this in animal models.

Warmth Prevents Bone Loss Through the Gut Microbiota

Osteoporosis is the most prevalent metabolic bone disease, characterized by low bone mass and microarchitectural deterioration. Here, we show that warmth exposure (34°C) protects against ovariectomy-induced bone loss by increasing trabecular bone volume, connectivity density, and thickness, leading to improved biomechanical bone strength in adult female, as well as in young male mice. Transplantation of the warm-adapted microbiota phenocopies the warmth-induced bone effects. Both warmth and warm microbiota transplantation revert the ovariectomy-induced transcriptomics changes of the tibia and increase periosteal bone formation. Combinatorial metagenomics/metabolomics analysis shows that warmth enhances bacterial polyamine biosynthesis, resulting in higher total polyamine levels in vivo. Spermine and spermidine supplementation increases bone strength, while inhibiting polyamine biosynthesis in vivo limits the beneficial warmth effects on the bone. Our data suggest warmth exposure as a potential treatment option for osteoporosis while providing a mechanistic framework for its benefits in bone disease.

Mechanisms by which autophagy regulates memory capacity in ageing

Autophagy agonists have been proposed to slow down neurodegeneration. Spermidine, a polyamine that acts as an autophagy agonist, is currently under clinical trial for the treatment of age‐related memory decline. How Spermidine and other autophagy agonists regulate memory and synaptic plasticity is under investigation. We set up a novel mouse model of mild cognitive impairment (MCI), in which middle‐aged (12‐month‐old) mice exhibit impaired memory capacity, lysosomes engulfed with amyloid fibrils (β‐amyloid and α‐synuclein) and impaired task‐induced GluA1 hippocampal post‐translation modifications. Subchronic treatment with Spermidine as well as the autophagy agonist TAT‐Beclin 1 rescued memory capacity and GluA1 post‐translational modifications by favouring the autophagy/lysosomal‐mediated degradation of amyloid fibrils. These findings provide new mechanistic evidence on the therapeutic relevance of autophagy enhancers which, by improving the degradation of misfolded proteins, slow down age‐related memory decline.

Chrysophyllum albidum (African star apple) fruit-supplemented diet enhances cognitive functions and attenuates lipopolysaccharide-induced memory impairment, oxidative stress, and release of proinflammatory cytokines

Purpose

Fruit-based supplement has an important role in protecting the brain against oxido-inflammatory stress. Chrysophyllum albidum fruit contained several phytonutrients that possess antioxidants and anti-inflammatory properties. Hence, this study investigated the effect of C. albidum fruit supplemented diet (CAFD) on cognitive functions and lipopolysaccharide (LPS)-induced memory impairment and oxido-inflammatory response in mice.

Methods

Mice were randomized into two experiments. Experiment 1 with naïve mice contained four groups (n = 6) while experiment 2 with LPS contains five groups (n = 6). Mice in experiments 1 and 2 were fed on CAFD (5%, 10%, and 20%) in naïve (6 weeks) and LPS (250 μg/kg, i.p.) in the 7th week, respectively. Cognitive performance was tested using Y-maze test (YMT) and novel object recognition test (NORT) in the naïve and LPS mice. Brain samples were obtained for determination of oxido-inflammatory parameters and acetylcholinesterase activity.

Results

The CAFD significantly enhanced cognitive performance in the YMT and NORT in naïve and LPS mice, as evidenced by increased % alternation and discrimination index, respectively. CAFD supplementation significantly reduced acetylcholinesterase enzyme activity while it attenuated depletion of reduced glutathione and catalase activities in brains of naive and LPS-treated animals. The CAFD significantly reduced LPS-induced increased malondialdehyde levels in mice brains. CAFD supplementation significantly attenuated LPS-induced pro-inflammatory cytokines (IL-6, TNF-α) in mice brains.

Conclusion

Chrysophyllum albidum fruit supplementation in diet enhances memory function and prevents cognitive deficits induced by LPS via mechanisms associated with inhibition of oxidative stress-related processes, acetylcholinesterase activity, and pro-inflammatory mediators.

Nrf2 Deficiency Exacerbates Cognitive Impairment and Reactive Microgliosis in a Lipopolysaccharide-Induced Neuroinflammatory Mouse Model

The transcription factor Nrf2 is a central regulator of anti-inflammatory and antioxidant mechanisms that contribute to the development and progression of various neurological disorders. Although the direct and indirect Nrf2 regulatory roles on inflammation have been reviewed in recent years, the in vivo evidence of Nrf2 function on lipopolysaccharide (LPS)-induced cognitive decline and characteristic alterations of reactive microglia and astrocytes remains incomplete. During the 3-5 days after LPS or saline injection, 5-6-month-old wildtype (WT) and Nrf2^-/- C57BL/6 mice were subjected to the novel object recognition task. Immunohistochemistry staining was employed for analyses of brain cells. The Nrf2^-/- mice displayed exacerbated LPS-induced cognition impairment (28.1 ± 9.6% in the discrimination index of the novel object recognition task), enhanced hippocampal reactive microgliosis and astrogliosis, and an increased expression level of the water channel transmembrane protein aquaporin 4 when compared with WT controls. In addition, similar overt effects of Nrf2 deficiency on LPS-induced characteristic alterations of brain cells were observed in the cortex and striatum regions of mice. In summary, this transgenic loss-of-function study provides direct in vivo evidence that highlights the functional importance of Nrf2 activation in regulating LPS-induced cognitive alteration, glial responses, and aquaporin 4 expression. This finding provides a better understanding of the complex nature of Nrf2 signaling and neuroprotection.

Spermidine, a positive modulator of the NMDA receptor, facilitates extinction and prevents the reinstatement of morphine-induced conditioned place preference in mice

RATIONALE

Individuals with opioid use disorders often relapse into drug-seeking behavior after recalling memories linked to the drug use experience. Improving extinction efficacy has been used as a strategy to treat substance use disorders and suppress relapse. Although N-methyl-D-aspartate receptor (NMDAr) agonists facilitate acquisition, consolidation, and extinction, no study has addressed whether spermidine (SPD), a natural polyamine ligand of the NMDA receptor, facilitates the extinction and reinstatement of morphine-induced conditioned place preference (CPP).

OBJECTIVES AND METHODS

The aim of the present study was to investigate the effect of SPD, an NMDAr agonist, on the extinction and reinstatement of morphine-induced CPP in mice. Adult male albino Swiss mice received saline (0.9% NaCl) or morphine (5 mg/kg) intraperitoneally (i.p.) and were respectively confined to a black or a white compartment for 30 min for four consecutive days for CPP induction. SPD (10-30 mg/kg, i.p.) or ifenprodil (NMDAr antagonist, 0.1-1 mg/kg, i.p.) were injected 15 min before extinction training.

RESULTS

SPD and ifenprodil facilitated the extinction of morphine-induced CPP. SPD treatment during the extinction period impaired reinstatement induced by a priming dose of morphine (1.25 mg/kg). Ifenprodil (0.1 mg/kg) prevented the facilitatory effect of spermidine on the extinction of morphine-induced CPP but did not prevent reinstatement induced by morphine.

CONCLUSIONS

These results suggest that SPD facilitated the extinction of morphine-induced CPP by modulating the polyamine binding site of the NMDA receptor. Our findings reveal important effects of SPD and ifenprodil on the re-exposure-induced decrease in morphine-induced CPP, which may be promising for developing novel pharmacological strategies to treat opioid use disorder.

D-Ribose-L-cysteine attenuates lipopolysaccharide-induced memory deficits through inhibition of oxidative stress, release of proinflammatory cytokines, and nuclear factor-kappa B expression in mice

D-Ribose-L-cysteine (DRLC), an analog of cysteine that boosts glutathione (GSH) content, has been reported to mitigate oxidative stress-mediated diseases. This study seeks to evaluate the effects of DRLC on memory deficits and the biochemical and histo-morphological changes induced by lipopolysaccharide (LPS) in mice. Male Swiss mice (n = 10) were pre-treated orally with three doses of DRLC (25 mg/kg, 50 mg/kg, and 100 mg/kg), donepezil (1 mg/kg), or vehicle (saline) for 30 min prior to the intraperitoneal injection of LPS (0.25 mg/kg) daily for 7 days. Memory functions were evaluated using the Y-maze, object recognition, and social recognition tests. The specific brain regions (prefrontal cortex and hippocampus) were evaluated to determine oxidative stress biomarkers (malondialdehyde, GSH, and catalase), acetyl-cholinesterase activity, proinflammatory cytokines (tumor necrosis factor-α and interleukin-6), expression of nuclear factor-kappa B (NF-κB), and neuronal cell morphology. DRLC (25-100 mg/kg) reversed the memory deficits in the LPS-treated mice (p < 0.05). The increased oxidative stress and proinflammatory cytokines in the brain regions of the LPS-treated mice were significantly (p < 0.05) reduced by DRLC. DRLC (50 mg/kg and 100 mg/kg) also reduced acetyl-cholinesterase activity and decreased NF-κB expression in the brains of LPS-treated mice. Finally, it attenuated the cytoarchitectural distortions and loss of neuronal cells of the prefrontal cortex and hippocampus that were induced by LPS in mice. The results of this study suggest that DRLC attenuates memory deficit induced by LPS in mice through mechanisms related to the inhibition of oxidative stress, release of proinflammatory cytokines, and expression of NF-κB in mice.

Polyamines in mammalian pathophysiology

Polyamines (PAs) are essential organic polycations for cell viability along the whole phylogenetic scale. In mammals, they are involved in the most important physiological processes: cell proliferation and viability, nutrition, fertility, as well as nervous and immune systems. Consequently, altered polyamine metabolism is involved in a series of pathologies. Due to their pathophysiological importance, PA metabolism has evolved to be a very robust metabolic module, interconnected with the other essential metabolic modules for gene expression and cell proliferation/differentiation. Two different PA sources exist for animals: PA coming from diet and endogenous synthesis. In the first section of this work, the molecular characteristics of PAs are presented as determinant of their roles in living organisms. In a second section, the metabolic specificities of mammalian PA metabolism are reviewed, as well as some obscure aspects on it. This second section includes information on mammalian cell/tissue-dependent PA-related gene expression and information on crosstalk with the other mammalian metabolic modules. The third section presents a synthesis of the physiological processes described as modulated by PAs in humans and/or experimental animal models, the molecular bases of these regulatory mechanisms known so far, as well as the most important gaps of information, which explain why knowledge around the specific roles of PAs in human physiology is still considered a "mysterious" subject. In spite of its robustness, PA metabolism can be altered under different exogenous and/or endogenous circumstances so leading to the loss of homeostasis and, therefore, to the promotion of a pathology. The available information will be summarized in the fourth section of this review. The different sections of this review also point out the lesser-known aspects of the topic. Finally, future prospects to advance on these still obscure gaps of knowledge on the roles on PAs on human physiopathology are discussed.

The effects of exercise on hippocampal inflammatory cytokine levels, brain oxidative stress markers and memory impairments induced by lipopolysaccharide in rats

The exercise effects on behavioral tests, hippocampal and cortical oxidative stress, and hippocampal inflammatory cytokines of lipopolysaccharide (LPS) administered rats were investigated. The rats were divided into four groups (N = 8): (1) control; (2) moderate training (MT, 15 m/min, 30 min/day, 9 weeks); (3) LPS (1 mg/kg LPS) and (4) LPS + MT (1 mg/kg LPS; 15 m/min, 30 min/day, 9 weeks). LPS was injected 2 h before the behavioral experiments during the last week of training. Finally, the rats' brain were removed for biochemical assessments. LPS increased escape latency and traveled distance to reach the platform in Morris water maze (MWM) test (P < 0.05-P < 0.001). In the passive avoidance (PA) test, LPS decreased the latency to enter the dark compartment and the time spent in the light compartment and increased the time spent in the dark compartment (P < 0.01-P < 0.001), while MT improved the rats performances in MWM and PA tests (P < 0.01-P < 0.001). Additionally, LPS increased tumor necrosis factor α (TNF-α), interleukin 1 beta (IL-1β) and C-reactive protein levels in the hippocampal tissues, malondialdehyde (MDA) and nitric oxide metabolite in hippocampal and cortical tissues, and decreased thiol contents and catalase (CAT) and superoxide dismutase (SOD) activity in hippocampal and cortical tissues compared to the control group (P < 0.01-P < 0.001); while moderate training decreased the levels of TNF-α, IL-1β and MDA; increased thiol contents, and SOD and CAT activity in the LPS + MT compared to the LPS group (P < 0.001). These results indicated that moderate training improved LPS-induced learning and memory impairments by attenuating the hippocampal cytokine levels and brain oxidative damage.

Spermidine/spermine-N1-acetyltransferase ablation impacts tauopathy-induced polyamine stress response

BACKGROUND

Tau stabilizes microtubules; however, in Alzheimer's disease (AD) and tauopathies, tau becomes hyperphosphorylated, aggregates, and results in neuronal death. Our group recently uncovered a unique interaction between polyamine metabolism and tau fate. Polyamines exert an array of physiological effects that support neuronal function and cognitive processing. Specific stimuli can elicit a polyamine stress response (PSR), resulting in altered central polyamine homeostasis. Evidence suggests that elevations in polyamines following a short-term stressor are beneficial; however, persistent stress and subsequent PSR activation may lead to maladaptive polyamine dysregulation, which is observed in AD, and may contribute to neuropathology and disease progression.

METHODS

Male and female mice harboring tau P301L mutation (rTg4510) were examined for a tau-induced central polyamine stress response (tau-PSR). The direct effect of tau-PSR byproducts on tau fibrillization and oligomerization were measured using a thioflavin T assay and a N2a split superfolder GFP-Tau (N2a-ssGT) cell line, respectively. To therapeutically target the tau-PSR, we bilaterally injected caspase 3-cleaved tau truncated at aspartate 421 (AAV9 Tau ΔD421) into the hippocampus and cortex of spermidine/spermine-N¹-acetyltransferase (SSAT), a key regulator of the tau-PSR, knock out (SSAT-/-), and wild type littermates, and the effects on tau neuropathology, polyamine dysregulation, and behavior were measured. Lastly, cellular models were employed to further examine how SSAT repression impacted tau biology.

RESULTS

Tau induced a unique tau-PSR signature in rTg4510 mice, notably in the accumulation of acetylated spermidine. In vitro, higher-order polyamines prevented tau fibrillization but acetylated spermidine failed to mimic this effect and even promoted fibrillization and oligomerization. AAV9 Tau ΔD421 also elicited a unique tau-PSR in vivo, and targeted disruption of SSAT prevented the accumulation of acetylated polyamines and impacted several tau phospho-epitopes. Interestingly, SSAT knockout mice presented with altered behavior in the rotarod task, the elevated plus maze, and marble burying task, thus highlighting the impact of polyamine homeostasis within the brain.

CONCLUSION

These data represent a novel paradigm linking tau pathology and polyamine dysfunction and that targeting specific arms within the polyamine pathway may serve as new targets to mitigate certain components of the tau phenotype.

Preventive Effects of Tryptophan-Methionine Dipeptide on Neural Inflammation and Alzheimer's Pathology

Preventive approaches for age-related memory decline and dementia have become a high priority in the aging society because of the lack of therapeutic approaches. Recent epidemiological studies have reported that fermented dairy products can help prevent dementia. Previously, we identified tryptophan-tyrosine (WY) and tryptophan-methionine (WM) peptides as the suppressants of activation of the primary microglia and showed that WY peptide consumption suppresses inflammation in the brains of Alzheimer's disease model mice. However, the effects of the WM peptide on inflammation in the brain and Alzheimer's pathology have not been investigated. Here, we evaluated the effect of WM peptide consumption on Alzheimer's disease model (5×FAD) mice. In 5×FAD mice, intake of WM peptide suppressed the production of inflammatory cytokines, activation of microglia, and infiltration of activated microglia around β amyloid (Aβ) depositions. WM peptide intake reduced Aβ deposition in the cortex and hippocampus and then improved the object recognition memory. Taken together with previous reports, the current findings indicate that ingestion of tryptophan-related peptides or food material rich in tryptophan-related peptides, thereby regulating microglial activity, represents a potential preventive approach for cognitive decline and dementia related to inflammation.

Metabolomic study of polyamines in rat urine following intraperitoneal injection of γ-hydroxybutyric acid

INTRODUCTION

Recently, illegal abuse of γ-hydroxybutyric acid (GHB) has increased in drug-facilitated crimes, but the determination of GHB exposure and intoxication is difficult due to rapid metabolism of GHB. Its biochemical mechanism has not been completely investigated. And a metabolomic study by polyamine profile and pattern analyses was not performed in rat urine following intraperitoneal injection with GHB.

OBJECTIVES

Urinary polyamine (PA) profiling by gas chromatography-tandem mass spectrometry was performed to monitor an altered PA according to GHB administration.

METHODS

Polyamine profiling analysis by gas chromatography-mass spectrometry combined with star pattern recognition analysis was performed in this study. The multivariate statistical analysis was used to evaluate discrimination among control and GHB administration groups.

RESULTS

Six polyamines were determined in control, single and multiple GHB administration groups. Star pattern showed distorted hexagonal shapes with characteristic and readily distinguishable patterns for each group. N¹-Acetylspermine (p < 0.001), putrescine (p < 0.006), N¹-acetylspermidine (p < 0.009), and spermine (p < 0.027) were significantly increased in single administration group but were significantly lower in the multiple administration group than in the control group. N¹-Acetylspermine was the main polyamine for discrimination among control, single and multiple administration groups. Spermine showed similar levels in single and multiple administration groups.

CONCLUSIONS

The polyamine metabolic pattern was monitored in GHB administration groups. N¹-Acetylspermine and spermine were evaluated as potential biomarkers of GHB exposure and addiction.

Dietary and Gut Microbiota Polyamines in Obesity- and Age-Related Diseases

The polyamines putrescine, spermidine, and spermine are widely distributed polycationic compounds essential for cellular functions. Intracellular polyamine pools are tightly regulated by a complex regulatory mechanism involving de novo biosynthesis, catabolism, and transport across the plasma membrane. In mammals, both the production of polyamines and their uptake from the extracellular space are controlled by a set of proteins named antizymes and antizyme inhibitors. Dysregulation of polyamine levels has been implicated in a variety of human pathologies, especially cancer. Additionally, decreases in the intracellular and circulating polyamine levels during aging have been reported. The differences in the polyamine content existing among tissues are mainly due to the endogenous polyamine metabolism. In addition, a part of the tissue polyamines has its origin in the diet or their production by the intestinal microbiome. Emerging evidence has suggested that exogenous polyamines (either orally administrated or synthetized by the gut microbiota) are able to induce longevity in mice, and that spermidine supplementation exerts cardioprotective effects in animal models. Furthermore, the administration of either spermidine or spermine has been shown to be effective for improving glucose homeostasis and insulin sensitivity and reducing adiposity and hepatic fat accumulation in diet-induced obesity mouse models. The exogenous addition of agmatine, a cationic molecule produced through arginine decarboxylation by bacteria and plants, also exerts significant effects on glucose metabolism in obese models, as well as cardioprotective effects. In this review, we will discuss some aspects of polyamine metabolism and transport, how diet can affect circulating and local polyamine levels, and how the modulation of either polyamine intake or polyamine production by gut microbiota can be used for potential therapeutic purposes.

Memory deficits in males and females long after subchronic immune challenge

Memory impairments and cognitive decline persist long after recovery from major illness or injury, and correlate with increased risk of later dementia. Here we developed a subchronic peripheral immune challenge model to examine delayed and persistent memory impairments in females and in males. We show that intermittent injections of either lipopolysaccharides or Poly I:C cause memory decline in both sexes that are evident eight weeks after the immune challenge. Importantly, we observed sex-specific patterns of deficits. Females showed impairments in object recognition one week after challenge that persisted for at least eight weeks. In contrast, males had intact memory one week after the immune challenge but exhibited broad impairments in memory tasks including object recognition, and both context and tone fear conditioning several months later. The differential patterns of memory deficits in males and in females were observed without sustained microglial activation or changes in blood-brain barrier permeability. Together, these data suggest that transient neuroimmune activity results in differential vulnerabilities of females and males to memory decline after immune challenge. This model will be an important tool for determining the mechanisms in both sexes that contribute to memory impairments that develop over the weeks and months after recovery from illness. Future studies using this model will provide new insights into the role of chronic inflammation in the pathogenesis of long-lasting memory decline and dementias.

Berberine ameliorates lipopolysaccharide-induced learning and memory deficit in the rat: insights into underlying molecular mechanisms

Systemic lipopolysaccharide (LPS) triggers neuroinflammation with consequent development of behavioral and cognitive deficits. Neuroinflammation plays a crucial role in the pathogenesis of neurodegenerative disorders including Alzheimer's disease (AD). Berberine is an isoquinoline alkaloid in Berberis genus with antioxidant and anti-inflammatory property and protective effects in neurodegenerative disorders. In this research, beneficial effect of this alkaloid against LPS-induced cognitive decline was assessed in the adult male rats. LPS was intraperitoneally administered at a dose of 1 mg/kg to induce neuroinflammation and berberine was given via gavage at doses of 10 or 50 mg/kg, one h after LPS, for 7 days. Treatment of LPS group with berberine at a dose of 50 mg/kg (but not at a dose of 10 mg/kg) improved spatial recognition memory in Y maze, performance in novel object recognition task (NORT), and prevented learning and memory dysfunction in passive avoidance tasks. Furthermore, berberine lowered hippocampal activity of acetylcholinesterase (AChE), malondialdehyde (MDA), protein carbonyl, activity of caspase 3, and DNA fragmentation and improved antioxidant capacity through enhancing glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase, and glutathione (GSH). Besides, berberine attenuated inflammation-related indices, as was evident by lower levels of nuclear factor-kappa B (NF-κB), toll-like receptor 4 (TLR4), tumor necrosis factor α (TNFα), and interleukin 6 (IL-6). Berberine also appropriately restored hippocampal 3-nitrotyrosine (3-NT), cyclooxygenase 2 (Cox 2), glial fibrillary acidic protein (GFAP), sirtuin 1, and mitogen-activated protein kinase (p38 MAPK) with no significant alteration of brain-derived neurotrophic factor (BDNF). In summary, berberine could partially ameliorate LPS-induced cognitive deficits via partial suppression of apoptotic cascade, neuroinflammation, oxido-nitrosative stress, AChE, MAPK, and restoration of sirtuin 1.

Inhibitory effect of INT-777 on lipopolysaccharide-induced cognitive impairment, neuroinflammation, apoptosis, and synaptic dysfunction in mice

Neuroinflammation plays an important role in the pathophysiology of Alzheimer's disease (AD) and memory impairment. Herein, we evaluated the neuroprotective effects of 6-ethyl-23(S)-methyl-cholic acid (INT-777), a specific G-protein coupled bile acid receptor 1 (TGR5) agonist, in the LPS-treated mouse model of acute neurotoxicity. Single intracerebroventricular (i.c.v.) injection of LPS remarkably induced mouse behavioral impairments in Morris water maze, novel object recognition, and Y-maze avoidance tests, which were ameliorated by INT-777 (1.5 or 3.0 μg/mouse, i.c.v.) treatment. Importantly, INT-777 treatment reversed LPS-induced TGR5 down-regulation, suppressed the increase of nuclear NF-κB p65, and mitigated neuroinflammation, evidenced by lower proinflammatory cytokines, less activation of microglia, and increased the ratio of p-CREB/CREB or mBDNF/proBDNF in the hippocampus and frontal cortex. In addition, INT-777 treatment also suppressed neuronal apoptosis, as indicated by the reduction of TUNEL-positive cells, decreased activation of caspase-3, increased the ratio of Bcl-2/Bax, and ameliorated synaptic dysfunction as evidenced by the upregulation of PSD95 and synaptophysin in the hippocampus and frontal cortex. Taken together, this study showed the potential neuroprotective effects of INT-777 against LPS-induced cognitive impairment, neuroinflammation, apoptosis, and synaptic dysfunction in mice.

Hemp (Cannabis sativa L.) Seed Phenylpropionamides Composition and Effects on Memory Dysfunction and Biomarkers of Neuroinflammation Induced by Lipopolysaccharide in Mice

Hempseed has achieved a growing popularity in human nutrition, particularly regarding essential amino acids and fatty acids. The multiple positive attributes of hempseed have led to the further study of its constituents. In this study, hempseed extract containing phenylpropionamides (TPA) was obtained and its chemical profile and content were obtained using high-performance liquid chromatography technology based on previous study. The anti-neuroinflammatory effect of TPA extract was evaluated using a lipopolysaccharide (LPS)-induced mouse model. Fourteen phenylpropionamides (TPA) were identified in the obtained extract with a total content of 233.52 ± 2.50 μg/mg extract. In mice, TPA prevented the learning and spatial memory damage induced by LPS. Increased brain levels of IL-1β, IL-6, and TNF-α in the LPS-induced mice were reduced by TPA treatment. Furthermore, TPA attenuated LPS-induced hippocampal neuronal damage in mice. This study demonstrates the nutraceutical potential of hempseed from a neuroprotective perspective.

Spermine protects alpha-synuclein expressing dopaminergic neurons from manganese-induced degeneration

Manganese exposure is among the many environmental risk factors linked to the progression of neurodegenerative diseases, such as manganese-induced parkinsonism. In animal models, chronic exposure to manganese causes loss of cell viability, neurodegeneration, and functional deficits. Polyamines, such as spermine, have been shown to rescue animals from age-induced neurodegeneration in an autophagy-dependent manner; nonetheless, it is not understood whether polyamines can prevent manganese-induced toxicity. In this study, we used two model systems, the Caenorhabditis elegans UA44 strain and SK-MEL-28 cells, both expressing the protein alpha-synuclein (α-syn) to determine whether spermine could ameliorate manganese-induced toxicity. Manganese caused a substantial reduction in the viability of SK-MEL-28 cells and hastened neurodegeneration in the UA44 strain. Spermine protected both the SK-MEL-28 cells and the UA44 strain from manganese-induced toxicity. Spermine also reduced the age-associated neurodegeneration observed in the UA44 strain compared with a control strain without α-syn expression and led to improved avoidance behavior in a functional assay. Treatment with berenil, an inhibitor of polyamine catabolism, which leads to increased intracellular polyamine levels, also showed similar cellular protection against manganese toxicity. While both translation blocker cycloheximide and autophagy blocker chloroquine caused a reduction in the cytoprotective effect of spermine, transcription blocker actinomycin D had no effect. This study provides new insights on the effect of spermine in preventing manganese-induced toxicity, which is most likely via translational regulation of several candidate genes, including those of autophagy. Thus, our results indicate that polyamines positively influence neuronal health, even when exposed to high levels of manganese and α-syn, and supplementing polyamines through diet might delay the onset of diseases involving degeneration of dopaminergic neurons.

An Aqueous Extract of Herbal Medicine ALWPs Enhances Cognitive Performance and Inhibits LPS-Induced Neuroinflammation via FAK/NF-κB Signaling Pathways

Recent studies have shown that Liuwei Dihuang pills (LWPs) can positively affect learning, memory and neurogenesis. However, the underlying molecular mechanisms are not understood. In the present study, we developed ALWPs, a mixture of Antler and LWPs, and investigated whether ALWPs can affect neuroinflammatory responses. We found that ALWPs (500 mg/ml) inhibited lipopolysaccharide (LPS)-induced proinflammatory cytokine IL-1β mRNA levels in BV2 microglial cells but not primary astrocytes. ALWPs significantly reduced LPS-induced cell-surface levels of TLR4 to alter neuroinflammation. An examination of the molecular mechanisms by which ALWPs regulate the LPS-induced proinflammatory response revealed that ALWPs significantly downregulated LPS-induced levels of FAK phosphorylation, suggesting that ALWPs modulate FAK signaling to alter LPS-induced IL-1β levels. In addition, treatment with ALWPs followed by LPS resulted in decreased levels of the transcription factor NF-κB in the nucleus compared with LPS alone. Moreover, ALWPs significantly suppressed LPS-induced BV2 microglial cell migration. To examine whether ALWPs modulate learning and memory in vivo, wild-type C57BL/6J mice were orally administered ALWPs (200 mg/kg) or PBS daily for 3 days, intraperitoneally injected (i.p.) with LPS (250 μg/kg) or PBS, and assessed in Y maze and NOR tests. We observed that oral administration of ALWPs to LPS-injected wild-type C57BL/6J mice significantly rescued short- and long-term memory. More importantly, oral administration of ALWPs to LPS-injected wild-type C57BL/6J mice significantly reduced microglial activation in the hippocampus and cortex. Taken together, our results suggest that ALWPs can suppress neuroinflammation-associated cognitive deficits and that ALWPs have potential as a drug for neuroinflammation/neurodegeneration-related diseases, including Alzheimer's disease (AD).

Ferulic Acid Rescues LPS-Induced Neurotoxicity via Modulation of the TLR4 Receptor in the Mouse Hippocampus

Microglia play a crucial role in the inflammatory brain response to infection. However, overactivation of microglia is neurotoxic. Toll-like receptor 4 (TLR4) is involved in microglial activation via lipopolysaccharide (LPS), which triggers a variety of cytotoxic pro-inflammatory markers that produce deleterious effects on neuronal cells. Ferulic acid (FA) is a phenolic compound that exerts antioxidant and anti-inflammatory effects in neurodegenerative disease. However, the manner in which FA inhibits neuroinflammation-induced neurodegeneration is poorly understood. Therefore, we investigated the anti-inflammatory effects of FA against LPS-induced neuroinflammation in the mouse brain. First, we provide evidence that FA interferes with TLR4 interaction sites, which are required for the activation of microglia-induced neuroinflammation, and further examined the potential mechanism of its neuroprotective effects in the mouse hippocampus using molecular docking simulation and immunoblot analysis. Our results indicated that FA treatment inhibited glial cell activation, p-JNK, p-NF_KB, and downstream signaling molecules, such as iNOS, COX-2, TNF-α, and IL-1β, in the mouse hippocampus and BV2 microglial cells. FA treatment strongly inhibited mitochondrial apoptotic signaling molecules, such as Bax, cytochrome C, caspase-3, and PARP-1, and reversed deregulated synaptic proteins, including PSD-95, synaptophysin, SNAP-25, and SNAP-23, and synaptic dysfunction in LPS-treated mice. These findings demonstrated that FA treatment interfered with the TLR4/MD2 complex binding site, which is crucial for evoking neuroinflammation via microglia activation and inhibited NF_KB likely via a JNK-dependent mechanism, which suggests a therapeutic implication for neuroinflammation-induced neurodegeneration.

Deoxyelephantopin ameliorates lipopolysaccharides (LPS)-induced memory impairments in rats: Evidence for its anti-neuroinflammatory properties

AIM

Neuroinflammation is a critical pathogenic mechanism of most neurodegenerative disorders especially, Alzheimer's disease (AD). Lipopolysaccharides (LPS) are known to induce neuroinflammation which is evident from significant upsurge of pro-inflammatory mediators in in vitro BV-2 microglial cells and in vivo animal models. In present study, we investigated anti-neuroinflammatory properties of deoxyelephantopin (DET) isolated from Elephantopus scaber in LPS-induced neuroinflammatory rat model.

MATERIALS AND METHODS

In this study, DET (0.625. 1.25 and 2.5 mg/kg, i.p.) was administered in rats for 21 days and those animals were challenged with single injection of LPS (250 μg/kg, i.p.) for 7 days. Cognitive and behavioral assessment was carried out for 7 days followed by molecular assessment on brain hippocampus. Statistical significance was analyzed with one-way analysis of variance followed by Dunnett's test to compare the treatment groups with the control group.

KEY FINDINGS

DET ameliorated LPS-induced neuroinflammation by suppressing major pro-inflammatory mediators such as iNOS and COX-2. Furthermore, DET enhanced the anti-inflammatory cytokines and concomitantly suppressed the pro-inflammatory cytokines and chemokine production. DET treatment also reversed LPS-induced behavioral and memory deficits and attenuated LPS-induced elevation of the expression of AD markers. DET improved synaptic-functionality via enhancing the activity of pre- and post-synaptic markers, like PSD-95 and SYP. DET also prevented LPS-induced apoptotic neurodegeneration via inhibition of PARP-1, caspase-3 and cleaved caspase-3.

SIGNIFICANCE

Overall, our studies suggest DET can prevent neuroinflammation-associated memory impairment and neurodegeneration and it could be developed as a therapeutic agent for the treatment of neuroinflammation-mediated and neurodegenerative disorders, such as AD.

Pistacia lentiscus oil attenuates memory dysfunction and decreases levels of biomarkers of oxidative stress induced by lipopolysaccharide in rats

Pistacia lentiscus L. is a well-known medicinal plant that has been used for its antioxidant, anti-inflammatory, neuroprotective, and hepatoprotective effects. However, the neuroprotective effect of Pistacia lentiscus oil (PLo) of has not been reported. The present study was designed to examine the neuroprotective and hepatoprotective effects of PLo aigainst lipopolysaccharide (LPS)-induced memory impairment and oxidative damage in rats. Twenty-four adult male Wistar rats were equally divided into three groups. The first group was kept as a control. In the second group, LPS was given at the single dose of 1 mg/kg intraperitoneally (i.p.). In the third group, PLo (3.3 mL/kg; per orally (p.o.)) was administered daily for 15 days, and challenged with LPS (1 mg/kg; i.p. injection two h before behavioral test). Thereafter, memory was assessed using spatial object recognition test. Cholinesterase activity and oxidative stress response were estimated in brain tissues and liver. PLo attenuated LPS-induced memory impairment in spatial object recognition test (p < 0.05). LPS treatment caused significant oxidative damage via induction of lipid peroxidation and reductions antioxidant defense system potency in the brain tissue and liver. Moreover, LPS increased brain activity of acetylcholinesterase and butyrylcholinesterase activity in the liver. The present results suggest that the beneficial effects of PLo on memory impairment of LPS-treated rats may be due to its protective effects against oxidative stress damage presumably via its antioxidant property.

Memory enhancing effect of Nigella Sativa hydro-alcoholic extract on lipopolysaccharide-induced memory impairment in rats

In this study, the effects of Nigella Sativa (NS) hydro-alcoholic extract on lipopolysaccharide (LPS)-induced learning and memory impairments, hippocampal cytokine levels, and brain tissues oxidative damage were investigated in rats. The rats were grouped and treated: (1) control (saline), (2) LPS (1 mg/kg i.p.), and (3-5) 100, 200, or 400 mg/kg NS hydro-alcoholic extract 30 min before LPS injection. The treatment was started since 6 days before the behavioral experiments and continued during the behavioral tests (LPS injection 2 h before each behavioral experiment). Finally, the brains were removed for biochemical assessments. In Morris water maze (MWM) test, LPS increased the escape latency and traveled path compared to control group, whereas all doses of NS hydro-alcoholic extract decreased them compared to LPS group. In passive avoidance (PA) test, the latency to enter the dark compartment in LPS group was shorter than control group while in all treated groups it was longer than LPS group. LPS increased tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), malondialdehyde (MDA), and nitric oxide (NO) metabolites, and decreased thiol content, superoxide dismutase (SOD), and catalase (CAT) in the hippocampal tissues compared to control group while NS hydro-alcoholic extract decreased MDA and NO metabolites and increased thiol content, SOD, and CAT compared to LPS group. Findings of the current study indicated that the hydro-alcoholic extract of NS improved the LPS-induced learning and memory impairments induced by LPS in rats by improving hippocampal cytokine levels and brain tissues oxidative damage.