Apoptosis and necroptosis of mouse hippocampal and parenchymal astrocytes, microglia and neurons caused by Angiostrongylus cantonensis infection

Exploration of the Molecular Mechanism by Which Caveolin-1 Regulates Changes in Blood-Brain Barrier Permeability Leading to Eosinophilic Meningoencephalitis

Angiostrongylus cantonensis, a zoonotic parasite, can invade the human central nervous system (CNS) and cause acute eosinophilic meningitis or eosinophilic meningoencephalitis. Mice infected with A. cantonensis show elevated levels of pro-inflammatory cytokines, plasminogen activators, and matrix metalloproteinase-9, resulting in disruption of the blood-brain barrier (BBB) and immune cell infiltration into the CNS. Caveolin-1 (Cav-1) regulates the permeability of the BBB, which affects immune cells and cerebrospinal fluid. This intricate interaction ultimately fuels the progression of brain damage and edema. This study aims to investigate the regulatory role of Cav-1 in the pathogenesis of meningoencephalitis induced by A. cantonensis infection. We investigated pathological alterations by triphenyl-tetrazolium chloride, brain water content, BBB permeability, Western blot analysis, and gelatin zymography in BALB/c mice after A. cantonensis. The study evaluates the critical role of Cav-1 regulation through the TLR4/MyD88 signaling pathway, modulates tight junction proteins, influences BBB permeability, and contributes to brain damage in A. cantonensis-induced meningoencephalitis.

Angiostrongylus cantonensis induces energy imbalance and dyskinesia in mice by reducing the expression of melanin-concentrating hormone

BACKGROUND

Infection with Angiostrongylus cantonensis (AC) in humans or mice can lead to severe eosinophilic meningitis or encephalitis, resulting in various neurological impairments. Developing effective neuroprotective drugs to improve the quality of life in affected individuals is critical.

METHODS

We conducted a Gene Ontology enrichment analysis on microarray gene expression (GSE159486) in the brains of AC-infected mice. The expression levels of melanin-concentrating hormone (MCH) were confirmed through real-time quantitative PCR (RT-qPCR) and immunofluorescence. Metabolic parameters were assessed using indirect calorimetry, and mice's energy metabolism was evaluated via pathological hematoxylin and eosin (H&E) staining, serum biochemical assays, and immunohistochemistry. Behavioral tests assessed cognitive and motor functions. Western blotting was used to measure the expression of synapse-related proteins. Mice were supplemented with MCH via nasal administration.

RESULTS

Postinfection, a marked decrease in Pmch expression and the encoded MCH was observed. Infected mice exhibited significant weight loss, extensive consumption of sugar and white fat tissue, reduced movement distance, and decreased speed, compared with the control group. Notably, nasal administration of MCH countered the energy imbalance and dyskinesia caused by AC infection, enhancing survival rates. MCH treatment also increased the expression level of postsynaptic density protein 95 (PSD95) and microtubule-associated protein-2 (MAP2), as well as upregulated transcription level of B cell leukemia/lymphoma 2 (Bcl2) in the cortex.

CONCLUSIONS

Our findings suggest that MCH improves dyskinesia by reducing loss of synaptic proteins, indicating its potential as a therapeutic agent for AC infection.

Doxycycline cotherapy with albendazole relieves neural function damage in C57BL/6 and BALB/c mice infected with Angiostrongylus cantonensis

BACKGROUND

We investigated the effects of combination therapy albendazole and doxycycline in Angiostrongylus cantonensis-infected mice during early and late treatment.

MATERIALS AND METHODS

C57BL/6 and BALB/c mice were divided into five groups: (i) uninfected, (ii) infected with A. cantonensis, (iii) infected + 10 mg/kg albendazole, (iv) infected + 25mg/kg doxycycline, and (v) infected + 10 mg/kg albendazole + 25 mg/kg doxycycline. We administered drugs in both early treatments started at 7-day post infections (dpi) and late treatments (14 dpi) to A. cantonensis-infected C57BL/6 and BALB/c mice. To assess the impact of these treatments, we employed the Morris water maze test to evaluate spatial learning and memory abilities, and the rotarod test to measure motor coordination and balance in C57BL/6 mice. Additionally, we monitored the expression of the cytokine IL-33 and GFAP in the brain of these mice using western blot analysis.

RESULTS

In this study, A. cantonensis infection was observed to cause extensive cerebral angiostrongyliasis in C57BL/6 mice. This condition significantly affected their spatial learning and memory abilities, as assessed by the Morris water maze test, as well as their motor coordination, which was evaluated using the rotarod test. Early treatment with albendazole led to favorable recovery outcomes. Both C57BL/6 and BALB/c mice express IL-33 and GFAP after co-therapy. The differences of levels and patterns of IL-33 and GFAP expression in mice may be influenced by the balance between pro-inflammatory and anti-inflammatory signals within the immune system.

CONCLUSIONS

Combination therapy with anthelmintics and antibiotics in the early stage of A. cantonensis infection, in C57BL/6 and BALB/c mice resulted in the death of parasites in the brain and reduced the subsequent neural function damage and slowed brain damage and neurobehavior impairment. This study suggests a more effective and novel treatment, and drug delivery method for brain lesions that can decrease the neurological damage of angiostrongyliasis patients.

Efficacy of artemether against toxocariasis in mice: parasitological and immunopathological changes in brain, liver, and lung

Toxocariasis is a zoonosis that represents a serious threat to public health particularly in tropical and subtropical areas. Currently, albendazole, the most effective drug for treating visceral toxocariasis, shows moderate efficacy against the larvae in tissues and has some adverse effects. Artemether is an antiparasitic drug mainly used in the treatment of malaria and showed effectiveness against numerous helminthic infections. Besides, it possesses potent anti-inflammatory, antiapoptotic, antifibrotic, and neuroprotective properties. Thus, the study's aim was to investigate artemether's effects in comparison with albendazole on the therapeutic outcome of experimental toxocariasis. For this aim, 140 laboratory-bred mice were divided into four main groups: uninfected control, treatment control, albendazole-treated, and artemether-treated groups. The treatment regimens were started at the 15th dpi (early treatment), and at the 35th dpi (late treatment). The effectiveness of treatment was determined by brain larval count, histopathological, immunohistochemical, and biochemical examination. Artemether showed more effectiveness than albendazole in reducing brain larval counts, markers of brain injury including NF-κB, GFAP, and caspase-3, the diameter and number of hepatic granulomas, hepatic oxidative stress, hepatic IL-6, and TG2 mRNA, and pulmonary inflammation and fibrosis. The efficacy of artemether was the same when administered early or late in the infection. Finally, our findings illustrated that artemether might be a promising therapy for T. canis infection and it could be a good substitution for albendazole in toxocariasis treatment.

Necroptosis in CNS diseases: Focus on astrocytes

In the last few years, necroptosis, a recently described type of cell death, has been reported to play an important role in the development of various brain pathologies. Necroptosis is a cell death mechanism that has morphological characteristics similar to necrosis but is mediated by fundamentally different molecular pathways. Necroptosis is initiated by signaling through the interaction of RIP1/RIP3/MLKL proteins (receptor-interacting protein kinase 1/receptor-interacting protein kinase 3/mixed lineage kinase domain-like protein). RIPK1 kinase is usually inactive under physiological conditions. It is activated by stimulation of death receptors (TNFR1, TNFR2, TLR3, and 4, Fas-ligand) by external signals. Phosphorylation of RIPK1 results in the formation of its complex with death receptors. Further, complexes with the second member of the RIP3 and MLKL cascade appear, and the necroptosome is formed. There is enough evidence that necroptosis plays an important role in the pathogenesis of brain ischemia and neurodegenerative diseases. In recent years, a point of view that both neurons and glial cells can play a key role in the development of the central nervous system (CNS) pathologies finds more and more confirmation. Astrocytes play complex roles during neurodegeneration and ischemic brain damage initiating both impair and protective processes. However, the cellular and molecular mechanisms that induce pathogenic activity of astrocytes remain veiled. In this review, we consider these processes in terms of the initiation of necroptosis. On the other hand, it is important to remember that like other types of programmed cell death, necroptosis plays an important role for the organism, as it induces a strong immune response and is involved in the control of cancerogenesis. In this review, we provide an overview of the complex role of necroptosis as an important pathogenetic component of neuronal and astrocyte death in neurodegenerative diseases, epileptogenesis, and ischemic brain damage.

Different phenotypes of microglia in animal models of Alzheimer disease

Microglia are immune-competent cells that are critically involved in maintaining normal brain function. A prominent characteristic of Alzheimer disease (AD) is microglial proliferation and activation concentrated around amyloid plaques in the brain. Recent research has revealed numerous microglial phenotypes related to aging and AD, apart from the traditional M1 and M2 types. Redox signalling modulates the acquisition of the classical or alternative microglia activation phenotypes. The numerous microglial functions can be achieved through these multiple phenotypes, which are associated with distinct molecular signatures.

Improvements of cognitive functions in mice heavily infected by Angiostrongylus cantonensis after treatment with albendazole, dexamethasone, or co-therapy

Angiostrongylus cantonensis, the causative agent of human eosinophilic meningitis and eosinophilic meningoencepalitis, has been reported to cause cognitive impairments in the host. To determine whether drug treatment improves the cognitive functions, BALB/c mice infected with 50 third-stage larvae were treated with albendazole, dexamethasone, or co-therapy since day 7 or 14 post-infection for one or two weeks. Abilities of spatial memory and learning of these animals were assessed with the Morris water maze. Our results showed that body weight was significant higher then infected group in the albendazole and combined therapy groups. Significantly lower worm recovery rates were found in mice treated with the same groups. The mice treated with dexamethasone since day 7 for 14 day had significant longer time in the remaining groups were found in forced swimming test. The animals treated with albendazole and combined therapy since day 7 for 14 days was demonstrated to have significantly shorter latencies to the platform in learning memory on day 3 and 4. Mice in these two groups were demonstrated to have significantly higher sores in spatial memory tests. These results indicate that treatment with albendazole or combined therapy may be more efficient in preventing brain damages and depression as well as preserving their capabilities in learning and memory. Therefore, administration of albendazole alone or combined with dexamethasone should have higher efficacies than dexamethasone alone in treatment of BALB/c mice infected with a heavy dose of 50 third-stage larvae of A. cantonensis.

Regulated necrosis, a proinflammatory cell death, potentially counteracts pathogenic infections

Since the discovery of cell apoptosis, other gene-regulated cell deaths are gradually appreciated, including pyroptosis, ferroptosis, and necroptosis. Necroptosis is, so far, one of the best-characterized regulated necrosis. In response to diverse stimuli (death receptor or toll-like receptor stimulation, pathogenic infection, or other factors), necroptosis is initiated and precisely regulated by the receptor-interacting protein kinase 3 (RIPK3) with the involvement of its partners (RIPK1, TRIF, DAI, or others), ultimately leading to the activation of its downstream substrate, mixed lineage kinase domain-like (MLKL). Necroptosis plays a significant role in the host's defense against pathogenic infections. Although much has been recognized regarding modulatory mechanisms of necroptosis during pathogenic infection, the exact role of necroptosis at different stages of infectious diseases is still being unveiled, e.g., how and when pathogens utilize or evade necroptosis to facilitate their invasion and how hosts manipulate necroptosis to counteract these detrimental effects brought by pathogenic infections and further eliminate the encroaching pathogens. In this review, we summarize and discuss the recent progress in the role of necroptosis during a series of viral, bacterial, and parasitic infections with zoonotic potentials, aiming to provide references and directions for the prevention and control of infectious diseases of both human and animals.

In silico prediction of flavan-3-ol as a bioactive compound of Calophyllum macrophyllum as a potential drug against angiostrongylus eosinophilic meningitis

Background and Aim:

Angiostrongylus eosinophilic meningitis is caused by larvae of the rat lungworm Angiostrongylus cantonensis. It manifests as meningitis, radiculitis, cranial nerve abnormalities, and encephalitis, which can be fatal. A flavan-3-ol compound isolated from the bark of Calophyllum macrophyllum Scheff. has several medicinal properties, including antioxidant, anti-inflammatory, antidiabetic, and antibacterial activities. This compound is stronger than other types of flavan-3-ols such as catechin. This study aimed to identify the hydroxylation pattern of this flavan-3-ol compound and evaluated its potential as an anti-meningitis drug, using an in silico approach through pharmacophore and molecular docking methods.

Materials and Methods:

Pharmacokinetic and toxicological data were analyzed and supported by the server http://www.swissadme.ch/index.php and https://tox-new.charite.de/protox_II/index.php. The hydroxylation pattern of the flavan-3-ol compound was identified using shear reagents (MeOH, NaOH, NaOAc, HCl, and AlCl₃). The CviR receptor (pdb id.3QP5) was used in the in silico approach, and seven ligands were downloaded from PubChem in “SMILES” format.

Results:

The spectroscopic analysis conducted using the shear reagents confirmed that the flavan-3-ol compound has a “p-diOH” pattern on the cinnamoyl ring. Pharmacophore analysis revealed this compound “hit” with pharmacophore features, and molecular docking analysis showed that this compound has a strong affinity with both receptors.

Conclusion:

The flavan-3-ol compound is a potential drug candidate for meningitis caused by pathogenic bacteria and the worm A. cantonensis. This result was supported by the pharmacokinetic profile, which had a very low toxicity level to the host. However, further investigation is required to confirm the data in vitro and in vivo.

Synaptic loss and progression in mice infected with Angiostrongylus cantonensis in the early stage

Background

Angiostrongylus cantonensis is also known as rat lungworm. Infection with this parasite is a zoonosis that can cause eosinophilic meningitis and/or eosinophilic meningoencephalitis in humans and may lead to fatal outcomes in severe cases. In this study, we explored the mechanisms of the impairments in the cognitive functions of mice infected with A. cantonensis.

Methods

In infected mice with different infective intensities at different timepoint postinfection, loss and recovery of cognitive functions such as learning and memory abilities were determined. Neuronal death and damage to synaptic structures were analyzed by Western blotting and IHC in infected mice with different infection intensities at different timepoint postinfection.

Results

The results of behavioral tests, pathological examinations, and Golgi staining showed that nerve damage caused by infection in mice occurred earlier than pathological changes of the brain. BDNF was expressed on 14 day post-infection. Cleaved caspase-3 increased significantly in the late stage of infection. However, IHC on NeuN indicated that no significant changes in the number of neurons were found between the infected and uninfected groups.

Conclusions

The synaptic loss caused by the infection of A. cantonensis provides a possible explanation for the impairment of cognitive functions in mice. The loss of cognitive functions may occur before severe immunological and pathological changes in the infected host.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12974-022-02436-8.

Actions of Klotho on hippocampal neuronal cells

Klotho gene was originally recognized as a putative aging-suppressor and its prominent age-regulating effects are mostly attributed to the modulation of mineral homeostasis in the kidney. However, recent studies link alterations in hippocampal Klotho expression with cognitive impairment and neurodegenerative diseases. This suggests that hippocampal neurons require Klotho for health and proper functionality. Klotho protects against neuronal dysfunction and regulates several intracellular signaling pathways including oxidative stress response, inflammation, DNA damage, autophagy, endoplasmic reticulum stress response, and multiple types of cell death. Specifically, this chapter covers the current knowledge as to how Klotho protein affects the hippocampal neuronal cells, with special attention paid to underlying molecular mechanisms, and thus influences hippocampal development, hippocampal-dependent cognition, behavior, and motor skills as well as mediates neurodegenerative processes.

Novel insights into RIPK1 as a promising target for future Alzheimer's disease treatment

Alzheimer's disease (AD) is an intractable neurodegenerative disease showing a clinical manifestation with memory loss, cognitive impairment and behavioral dysfunction. The predominant pathological characteristics of AD include neuronal loss, β-amyloid (Aβ) deposition and hyperphosphorylated Tau induced neurofibrillary tangles (NFTs), while considerable studies proved these could be triggered by neuronal death and neuroinflammation. Receptor-interacting protein kinase 1 (RIPK1) is a serine/threonine kinase existed at the cross-point of cell death and inflammatory signaling pathways. Emerging investigations have shed light on RIPK1 for its potential role in AD progression. The present review makes a bird's eye view on the functions of RIPK1 and mainly focus on the underlying linkages between RIPK1 and AD from comprehensive aspects including neuronal death, Aβ and Tau, inflammasome activation, BBB rupture, AMPK/mTOR, mitochondrial dysfunction and O-glcNAcylation. Moreover, the discovery of RIPK1 inhibitors, ongoing clinical trials along with future RIPK1-targeted therapeutics are also reviewed.

CX3CL1 Recruits NK Cells Into the Central Nervous System and Aggravates Brain Injury of Mice Caused by Angiostrongylus cantonensis Infection

Background

Angiostrongylus cantonensis (A. cantonensis), is a food-borne zoonotic parasite that can cause central nervous system (CNS) injury characterized by eosinophilic meningitis. However, the pathogenesis of angiostrongylosis remains elusive. Natural killer cells (NK cells) are unique innate lymphocytes important in early defense against pathogens. The aim of this study was to investigate the role of NK cells in A. cantonensis infection and to elucidate the key factors that recruit NK cells into the CNS.

Methods

Mouse model of A. cantonensis infection was established by intragastric administration of third-stage larvae. The expression of cytokines and chemokines at gene and protein levels was analyzed by qRT-PCR and ELISA. Distribution of NK cells was observed by immunohistochemistry and flow cytometry. NK cell-mediated cytotoxicity against YAC-1 cells was detected by LDH release assay. The ability of NK cells to secrete cytokines was determined by intracellular flow cytometry and ELISA. Depletion and adoptive transfer of NK cells in vivo was induced by tail vein injection of anti-asialo GM1 rabbit serum and purified splenic NK cells, respectively. CX₃CL1 neutralization experiment was performed by intraperitoneal injection of anti-CX₃CL1 rat IgG.

Results

The infiltration of NK cells in the CNS of A. cantonensis-infected mice was observed from 14 dpi and reached the peak on 18 and 22 dpi. Compared with uninfected splenic NK cells, the CNS-infiltrated NK cells of infected mice showed enhanced cytotoxicity and increased IFN-γ and TNF-α production ability. Depletion of NK cells alleviated brain injury, whereas adoptive transfer of NK cells exacerbated brain damage in A. cantonensis-infected mice. The expression of CX₃CL1 in the brain tissue and its receptor CX₃CR1 on the CNS-infiltrated NK cells were both elevated after A. cantonensis infection. CX₃CL1 neutralization reduced the percentage and absolute number of the CNS-infiltrated NK cells and relieved brain damage caused by A. cantonensis infection.

Conclusions

Our results demonstrate that the up-regulated CX₃CL1 in the brain tissue recruits NK cells into the CNS and aggravates brain damage caused by A. cantonensis infection. The findings improve the understanding of the pathogenesis of angiostrongyliasis and expand the therapeutic intervention in CNS disease.

TNF-α Triggers RIP1/FADD/Caspase-8-Mediated Apoptosis of Astrocytes and RIP3/MLKL-Mediated Necroptosis of Neurons Induced by Angiostrongylus cantonensis Infection

Angiostrongylus cantonensis (AC) can cause severe eosinophilic meningitis or encephalitis in non-permissive hosts accompanied by apoptosis and necroptosis of brain cells. However, the explicit underlying molecular basis of apoptosis and necroptosis upon AC infection has not yet been elucidated. To determine the specific pathways of apoptosis and necroptosis upon AC infection, gene set enrichment analysis (GSEA) and protein-protein interaction (PPI) analysis for gene expression microarray (accession number: GSE159486) of mouse brain infected by AC revealed that TNF-α likely played a central role in the apoptosis and necroptosis in the context of AC infection, which was further confirmed via an in vivo rescue assay after treating with TNF-α inhibitor. The signalling axes involved in apoptosis and necroptosis were investigated via immunoprecipitation and immunoblotting. Immunofluorescence was used to identify the specific cells that underwent apoptosis or necroptosis. The results showed that TNF-α induced apoptosis of astrocytes through the RIP1/FADD/Caspase-8 axis and induced necroptosis of neurons by the RIP3/MLKL signalling pathway. In addition, in vitro assay revealed that TNF-α secretion by microglia increased upon LSA stimulation and caused necroptosis of neurons. The present study provided the first evidence that TNF-α was secreted by microglia stimulated by AC infection, which caused cell death via parallel pathways of astrocyte apoptosis (mediated by the RIP1/FADD/caspase-8 axis) and neuron necroptosis (driven by the RIP3/MLKL complex). Our research comprehensively elucidated the mechanism of cell death after AC infection and provided new insight into targeting TNF-α signalling as a therapeutic strategy for CNS injury.

Chemoprevention of DMH-Induced Early Colon Carcinogenesis in Male BALB/c Mice by Administration of Lactobacillus Paracasei DTA81

We evaluated the effects of the probiotic candidate Lactobacillus paracasei DTA81 (DTA81) on liver oxidative stress, colonic cytokine profile, and gut microbiota in mice with induced early colon carcinogenesis (CRC) by 1,2-dimethylhydrazine (DMH). Animals were divided into four different groups (n = 6) and received the following treatments via orogastric gavage for 8 weeks: Group skim milk (GSM): 300 mg/freeze-dried skim milk/day; Group L. paracasei DTA81 (DTA81): 3 × 10⁹ colony-forming units (CFU)/day; Group Lactobacillus rhamnosus GG (LGG): 3 × 10⁹ CFU/day; Group non-intervention (GNI): 0.1 mL/water/day. A single DMH dose (20 mg/kg body weight) was injected intraperitoneally (i.p), weekly, in all animals (seven applications in total). At the end of the experimental period, DTA81 intake reduced hepatic levels of carbonyl protein and malondialdehyde (MDA). Moreover, low levels of the pro-inflammatory cytokines Interleukin-6 (IL-6) and IL-17, as well as a reduced expression level of the proliferating cell nuclear antigen (PCNA) were observed in colonic homogenates. Lastly, animals who received DTA81 showed an intestinal enrichment of the genus Ruminiclostridium and increased concentrations of caecal acetic acid and total short-chain fatty acids. In conclusion, this study indicates that the administration of the probiotic candidate DTA81 can have beneficial effects on the initial stages of CRC development.

Mitochondrial dynamics in Angiostrongylus cantonensis-infected mouse brain

Angiostrongylus cantonensis is one of the most widespread parasites causing central nervous system (CNS) diseases in mammals. Since the mitochondrion is an essential cell organelle responsible for both physiological and pathological processes, its dysfunction might lead to inflammation and multiple disorders. In this study we aimed to investigate the changes in mitochondrial dynamics that occur in the mouse brain upon infection with A. cantonensis, using molecular biology techniques such as polymerase chain reaction (PCR), western blot analysis, transmission electron microscopy (TEM), and different staining methods. Here, we show that mouse brain infected with A. cantonensis exhibits altered mitochondrial dynamics, including fission, fusion, and biogenesis. Additionally, we demonstrate that caspases and B-cell lymphoma 2 (BCL-2) were significantly upregulated in A. cantonensis-infected brain. These results are indicative of the occurrence of apoptosis during A. cantonensis infection, which was further confirmed by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining. These findings suggest the change in mitochondrial dynamics in A. cantonensis-infected brain, providing another point of view on the pathogenesis of meningoencephalitis caused by A. cantonensis infection.

BALB/c mice infected with Angiostrongylus cantonensis: A new model for demyelination in the brain

In this study, we present a new model for demyelination of the central nervous system (CNS). BALB/c mice were infected with Angiostrongylus cantonensis and analyzed 7, 14, and 21 days postinfection. Neurological scale evaluation, magnetic resonance imaging (MRI), histology, real-time quantitative polymerase chain reaction, and western blotting were all performed on days 7, 14, and 21. The results showed that the neurological functions and weight of A. cantonensis-infected mice decreased markedly after 21 days of infection. MRI showed subdural effusion and white high signals in the corpus callosum in both T1WI and T2WI, while hematoxylin and eosin and luxol fast blue staining showed hemorrhage and demyelination in the corpus callosum. Transmission electron microscopy revealed that the ultrastructure of the myelin sheath in the corpus callosum was dispersed or disintegrated. The percentage of myelinated axons was significantly decreased, and the g-ratio was lower than that in the normal group. Both protein and mRNA levels of myelin basic protein decreased markedly at 21 days postinfection. Immunofluorescence revealed that the number of CC1 positive cells in the corpus callosum also decreased, which confirmed the damage of A. cantonensis to oligodendrocytes. Our experiments confirmed that A. cantonensis infection caused demyelination in the CNS of BALB/c mice after 21 days, and its clinical manifestations and pathological changes were similar to those of multiple sclerosis and other CNS demyelination models. Thus, mice infected with A. cantonensis could be used as a new model to study acute demyelination of the CNS.

Angiostrongylus cantonensis causes cognitive impairments in heavily infected BALB/c and C57BL/6 mice

Background

Parasitic infections may cause significant effects on behavior, learning, and memory of the host. In the brain of mice heavily infected with Angiostrongylus cantonensis, severe damage has been observed in the hippocampus. This component has been considered to have associations with spatial learning and memory in humans and vertebrates. This study was designed to determine the impairments in behavior, learning, and memory in BALB/c and C57BL/6 mice heavily infected with the parasite.

Methods

Each mouse was inoculated with 50 third-stage larvae of A. cantonensis. After infection, daily changes in weight and dietary consumption, worm recoveries and survival rates were determined. The forced swimming test, open field test, and Morris water maze test were employed to evaluate depression- and anxiety-like behavior as well as impairments in spatial learning and memory, respectively.

Results

The worm recovery rate in the BALB/c mice was significantly lower than that of C57BL/6 mice from day 14 post-infection. The survival rate in infected BALB/c mice decreased to 0% by day 25 whereas those with swim-training survived three more days. On day 42, the C57BL/6 mice had a survival rate of 85.7% in the swimming group and 70% in the non-swimming group. Significant differences were found in weight between infected and non-infected BALB/c and C57BL/6 mice from day 13 and day 12, respectively with corresponding changes in their dietary consumption. Depression-like behavior was found in the infected BALB/c mice but not in C57BL/6 mice. However, anxiety-like behavior was found to occur only in C57BL/6 mice. Impaired spatial learning and memory were also found in the two strains of mice which occurred from day 14 post-infection.

Conclusions

Results of this study indicate that A. cantonensis causes depression, anxiety, and impairments in spatial learning and memory in heavily infected mice. Moreover, significantly higher severity was observed in the Th-2 dominant BALB/c mice.

Microglia dependent BDNF and proBDNF can impair spatial memory performance during persistent inflammatory pain

Inflammatory pain is commonly associated with cognitive impairment. However, its molecular mechanisms are poorly understood. Thus, this study was conducted to investigate the molecular mechanisms of behavioral changes associated with inflammatory pain. Briefly, 36 Wistar rats were randomly divided into two main groups: CFA group treated with 100 μL of Complete Freunds' Adjuvant (CFA) and CFA + Minocycline group treated with 100 μL of CFA+40 mg/kg/day of minocycline). After that, each group was divided into three subgroups based on different time points of the study. The pain was induced using CFA and subsequent behavioral changes (i.e., hyperalgesia and learning and spatial memory) were analyzed by the Morris Water Maze (MWM) task and Radiant Heat. Then, the cellular and molecular changes were assessed using Western Blotting, Immunohistochemistry, and Terminal deoxynucleotidyl transferase dUTP Nick End Labeling (TUNEL) techniques. Results of the study indicated that CFA-induced pain impaired spatial learning and memory functions. Studying the cellular changes showed that persistent inflammatory pain increased the microglial activity in CA1 and Dentate Gyrus (DG) regions. Furthermore, an increase was observed in the percentage of TUNEL-positive cells. Also, pro-Brain-Derived Neurotrophic Factor (BDNF)/BDNF ratio, Caspase3, and Receptor-Interacting Protein kinase 3 (RIP3) levels increased in the rats' hippocampus following induction of persistent inflammatory pain. These changes were reversed following the cessation of pain as well as the injection of minocycline. Taking together, the results of the current study for the first time revealed that an increase in the microglia dependent proBDNF/BDNF ratio following persistent inflammatory pain leads to cell death of the CA1 and DG neurons that subsequently causes a cognitive deficit in the learning and spatial memory functions.

Angiostrongylus cantonensis Galectin-1 interacts with Annexin A2 to impair the viability of macrophages via activating JNK pathway

BACKGROUND

Angiostrongylus cantonensis can cause severe symptoms of central nervous system infections. In the host, this parasite localizes in the blood and cerebrospinal fluid, and its secreted components can impact immune responses. Our previous study demonstrated that immune responses were inhibited in A. cantonensis-infected mice immunized with Ac-Galectin-1 (AcGal-1). However, the mechanisms by which AcGal-1 regulates the immune responses remain unclear. Macrophages are innate immune cells that rapidly respond to infection. The direct impact of AcGal-1 on macrophages may affect the immune responses.

METHODS

AcGal-1 protein was purified by nickel ion affinity chromatography. The effect of AcGal-1 on the apoptosis of macrophages was detected using CCK-8 assay, flow cytometry and western blot. Macrophage membrane proteins bound to AcGal-1 were obtained using the His-tag-based pull-down assay and identified via mass spectrometry. Co-localization of AcGal-1 and the macrophage membrane protein Annexin A2 was observed by immunofluorescence microscopy, and their interaction was validated by co-immunoprecipitation experiments. SiRNA-mediated knockdown of Annexin A2 was used to determine if AcGal-1-induced macrophage apoptosis required interaction with Annexin A2. The phosphorylation level of apoptotic signal pathway protein was detected by phospho-antibody microarray and western blot.

RESULTS

Our study showed that AcGal-1 caused apoptosis of the macrophages. AcGal-1 increased the expression of apoptosis proteins caspase-3, caspase-9, Bax, but reduced the expression of anti-apoptosis protein Bcl-2. AcGal-1 interacted with the membrane protein Annexin A2, and knockdown of Annexin A2 expression increased Bcl-2 but decreased Bax levels in AcGal-1-treated cells. Moreover, AcGal-1 increased JNK phosphorylation and the inhibition of JNK phosphorylation in AcGal-1-treated cells decreased the expression of caspase-3, -9, Bax and almost restored Bcl-2 to the level observed in control cells.

CONCLUSIONS

AcGal-1 can induce the apoptosis of macrophages by binding to Annexin A2 and activating JNK downstream the apoptotic signaling pathway.

Mesenchymal stem cells combined with albendazole as a novel therapeutic approach for experimental neurotoxocariasis

Neurotoxocariasis (NT) is a serious condition that has been linked to reduced cognitive function, behavioural alterations and neurodegenerative diseases. Unfortunately, the available drugs to treat toxocariasis are limited with unsatisfactory results, because of the initiation of treatment at late chronic stages after the occurrence of tissue damage and scars. Therefore, searching for a new therapy for this important disease is an urgent necessity. In this context, cytotherapy is a novel therapeutic approach for the treatment of many diseases and tissue damages through the introduction of new cells into the damaged sites. They exert therapeutic effects by their capability of renewal, differentiation into specialized cells, and being powerful immunomodulators. The most popular cell type utilized in cytotherapy is the mesenchymal stem cells (MSCs) type. In the current study, the efficacy of MSCs alone or combined with albendazole was evaluated against chronic brain insults induced by Toxocara canis infection in an experimental mouse model. Interestingly, MSCs combined with albendazole demonstrated a healing effect on brain inflammation, gliosis, apoptosis and significantly reduced brain damage biomarkers (S100B and GFAP) and T. canis DNA. Thus, MSCs would be protective against the development of subsequent neurodegenerative diseases with chronic NT.

Necroptosis and Caspase-2-Mediated Apoptosis of Astrocytes and Neurons, but Not Microglia, of Rat Hippocampus and Parenchyma Caused by Angiostrongylus cantonensis Infection

Infection with the roundworm Angiostrongylus cantonensis is the main cause of eosinophilic meningitis worldwide. The underlying molecular basis of the various pathological outcomes in permissive and non-permissive hosts infected with A. cantonensis remains poorly defined. In the present study, the histology of neurological disorders in the central nervous system (CNS) of infected rats was assessed by using hematoxylin and eosin staining. Quantitative reverse transcription polymerase chain reaction (RT-qPCR), western blot and immunofluorescence (IF) were used in evolutions of the transcription and translation levels of the apoptosis-, necroptosis-, autophagy-, and pyroptosis-related genes. The distribution of apoptotic and necroptotic cells in the rat hippocampus and parenchyma was further detected using flow cytometry, and the features of the ultrastructure of the cells were examined by transmission electron microscopy (TEM). The inflammatory response upon CNS infection with A. cantonensis evolved, as characterized by the accumulation of a small number of inflammatory cells under the thickened meninges, which peaked at 21 days post-infection (dpi) and returned to normal by 35 dpi. The transcription levels and translation of caspase-2, caspase-8, RIP1 and RIP3 increased significantly at 21 and 28 dpi but decreased sharply at 35 dpi compared to those in the normal control group. However, the changes in the expression of caspase-1, caspase-3, caspase-11, Beclin-1 and LC3B were not obvious, suggesting that apoptosis and necroptosis but not autophagy or pyroptosis occurred in the brains of infected animals at 21 and 28 dpi. The results of RT-qPCR, western blot analysis, IF, flow cytometry and TEM further illustrated that necroptosis and caspase-2-mediated apoptosis occurred in astrocytes and neurons but not in microglia in the parenchyma and hippocampus of infected animals. This study provides the first evidence that neuronal and astrocytic necroptosis and caspase-2-mediated apoptosis are induced by A. cantonensis infection in the parenchymal and hippocampal regions of rats at 21 and 28 dpi but these processes are negligible at 35 dpi. These findings enhance our understanding of the pathogenesis of A. cantonensis infection and provide new insights into therapeutic approaches targeting the occurrence of cell death in astrocytes and neurons in infected patients.

Trichostatin A, a Histone Deacetylase Inhibitor, Alleviates Eosinophilic Meningitis Induced by Angiostrongylus cantonensis Infection in Mice

Histone deacetylase inhibitor (HDACi) has been used in the treatment of neurodegenerative or autoimmune diseases. Angiostrongyliasis cantonensis caused by Angiostrongylus cantonensis infection is an emerging zoonosis of human eosinophilic meningitis or meningoencephalitis. Progressive neuronal apoptosis is the pathological basis of behavioral dysfunctions in angiostrongyliasis cantonensis. Neurological defects after anthelmintic treatment for angiostrongyliasis cantonensis are still common. In this study, we examined the effects of trichostatin A (TSA), a HDACi, on eosinophilic meningitis induced by A. cantonensis in mice. Intragastric administration of TSA significantly ameliorated brain injury and decreased cognitive impairments in mice at 15 days post-infection. TSA administration effectively reduced the inflammatory factor levels of iNOS, TNF-α, IL-5, IL-6, and IL-13 in infected mice. TSA treatment counteracted apoptosis with reduced expression levels of cleaved caspase-3, -4, -6, and RIP3 in A. cantonensis infected mice. In addition, TSA administration reduced total HDAC activity and increased the acetylation of histone H3 and H4 in the brain tissue of infected mice. The underlying mechanism of TSA on eosinophilic meningitis might be associated with decreased NF-κB p65 nuclear accumulation by inhibiting IκB phosphorylation. Furthermore, a co-expressive network of NF-κB p65 with 22 other genes was constructed according to our previous transcriptomic data in infected mice. We identified the correlations in the gene expression of NF-κB p65 with Lrp10, Il12rb1, Nfkbia, Ube2n, and Ube2d1 in infected mice after TSA administration. Thus, TSA has a protective effect on the progression of eosinophilic meningitis induced by A. cantonensis in mice.

Significant apoptosis rather autophagy predominates in astrocytes caused by Toxocara canis larval excretory-secretory antigens

BACKGROUND/PURPOSE

Toxocariasis is a worldwide parasitic zoonosis and mainly caused by Toxocara canis. Humans can be infected by accidental ingestion of T. canis embryonated ova through contacting with contaminated food, water, or encapsulated larvae in paratenic hosts' viscera or meat. Since humans are the paratenic host of T. canis, the wandering and neuroinvasive larvae can cause mechanical tissue damage and the excretory-secretory antigens (TcES Ag) might induce neuroinflammatory responses in the brain. Human cerebral toxocariasis (CT) has been reported to cause several neurological symptoms and may develop into neurodegenerative diseases. However, the roles of astrocytes involved in the pathogenesis of CT remained largely unclear.

METHODS

This study intended to investigate the cytotoxic effects of TcES Ag on astrocytes as assessed by apoptosis and autophagy expression.

RESULTS

Our results showed TcES Ag treatment reduced cell viability and caused morphological changes. Expressions of autophagy associated proteins including Beclin 1, phosphor-mTOR and LC3-Ⅱ were not significantly changed; however, p62 as well as the cell survival protein, mTOR, was concomitantly decreased in TcES Ag treatment. Significantly accelerated cleaved caspase-3 and cytochrome c expression as well as enhanced caspase-9 and caspase-8 activation were found in astrocytes with TcES Ag treatment. Caspase-3 activity and apoptotic cells numbers were also increased as detected by fluorescence microscopy.

CONCLUSION

We concluded that TcES Ag may trigger astrocytes apoptosis predominantly through intrinsic and extrinsic pathways rather autophagy, revealing a novel role of astrocytes in the pathogenesis of CT.

Schisandra chinensis Fructus and Its Active Ingredients as Promising Resources for the Treatment of Neurological Diseases

Neurological diseases (NDs) are a leading cause of death worldwide and tend to mainly affect people under the age of 50. High rates of premature death and disability caused by NDs undoubtedly constrain societal development. However, effective therapeutic drugs and methods are very limited. Schisandra chinensis Fructus (SCF) is the dry ripe fruit of Schisandra chinensis (Turcz.) Baill, which has been used in traditional Chinese medicine for thousands of years. Recent research has indicated that SCF and its active ingredients show a protective role in NDs, including cerebrovascular diseases, neurodegenerative diseases, or depression. The key neuroprotective mechanisms of SCF and its active ingredients have been demonstrated to include antioxidation, suppression of apoptosis, anti-inflammation, regulation of neurotransmitters, and modulation of brain-derived neurotrophic factor (BDNF) related pathways. This paper summarizes studies of the role of SCF and its active ingredients in protecting against NDs, and highlights them as promising resources for future treatment. Furthermore, novel insights on the future challenges of SCF and its active ingredients are offered.