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.

Curative effects and mechanisms of AG1296 and LY294002 co-therapy in Angiostrongylus cantonensis-induced neurovascular unit dysfunction and eosinophilic meningoencephalitis.

BACKGROUND: Co-therapy with albendazole and steroid is commonly used in patients with eosinophilic meningoencephalitis caused by Angiostrongylus cantonensis infections. However, anthelminthics often worsen symptoms, possibly due to the inflammatory reaction to antigens released by dying worms. Therefore, the present study was to investigate the curative effects and probable mechanisms of the platelet-derived growth factor receptor-beta (PDGFR-ß) inhibitor AG1296 (AG) and the phosphoinositide 3-kinase inhibitor (PI3K) LY294002 (LY) in A. cantonensis-induced neurovascular unit dysfunction and eosinophilic meningoencephalitis. METHODS: Western blots were used to detect matrix protein degradation and the expressions of PDGFR-ß/PI3K signaling pathway. The co-localization of PDGFR-ß and vascular smooth muscle cells (VSMCs), and metalloproteinase-9 (MMP-9) and VSMCs on the blood vessels were measured by confocal laser scanning immunofluorescence microscopy. Sandwich enzyme-linked immunosorbent assays were used to test S100B, interleukin (IL)-6, and transforming growth factor beta in the cerebrospinal fluid to determine their possible roles in mouse resistance to A. cantonensis. RESULTS: The results showed that AG and LY cotherapy decreased the MMP-9 activity and inflammatory reaction. Furthermore, S100B, IL-6 and eosinophil counts were reduced by inhibitor treatment. The localization of PDGFR-ß and MMP-9 was observed in VSMCs. Furthermore, we showed that the degradation of the neurovascular matrix and blood-brain barrier permeability were reduced in the mouse brain. CONCLUSIONS: These findings demonstrate the potential of PDGFR-ß inhibitor AG and PI3K inhibitor LY co-therapy as anti-A. cantonensis drug candidates through improved neurovascular unit dysfunction and reduced inflammatory response.

Calycosin attenuates Angiostrongylus cantonensis-induced parasitic meningitis through modulation of HO-1 and NF-κB activation.

Angiostrongylus cantonensis causes a form of parasitic meningitis in humans. Albendazole (ABZ) kills nematode larvae in the brain. However, dead larvae can trigger a severe inflammatory response, resulting in brain damage. Accumulating evidence suggests that calycosin represents a potential anti-inflammatory therapeutic candidate. In this study, we investigated the combined effects of ABZ and calycosin in angiostrongyliasis caused by A. cantonensis in BALB/c mice. Inflammatory mediators (such as phospho-nuclear factor-κB, cyclooxygenase-2, matrix metalloproteinase-9, tumour necrosis factor-α and interleukin-1ß) are associated with the development of meningitis and immune inflammatory reactions. We found that A. cantonensis significantly induces inflammatory mediator production and increases the blood­brain barrier (BBB) permeability. However, co-administration of both ABZ and calycosin markedly suppressed meningitis and inflammatory mediator production and decreased the BBB permeability compared to treatment with a single drug. Furthermore, calycosin and ABZ plus calycosin treatment facilitated production of the antioxidant haem oxygenase-1 (HO-1). Moreover, co-therapy with ABZ and calycosin failed to mitigate angiostrongyliasis in the presence of tin-protoporphyrin IX, an HO-1-specific inhibitor. This finding suggests that the beneficial effects of ABZ plus calycosin treatment on the regulation of inflammation are mediated by the modulation of HO-1 activation. The present results provide new insights into the treatment of human angiostrongyliasis using co-therapy with ABZ and calycosin.

Heme oxygenase-1 modulates brain inflammation and apoptosis in mice with angiostrongyliasis.

The rat nematode lungworm Angiostrongylus cantonensis undergoes obligatory intracerebral migration in its hosts and causes eosinophilic meningitis or meningoencephalitis. Heme oxygenase 1 (HO-1) has several cytoprotective properties such as anti-oxidative, anti-inflammatory, and anti-apoptotic effects. HO-1 in brain tissues was induced in A. cantonensis-infected group and showed positive modulation in cobalt protoporphyrin (CoPP)-treated groups. Assay methods for the therapeutic effect include western blot analysis, enzyme-linked immunosorbent assay, gelatin zymography, blood-brain barrier permeability evaluation and eosinophil count in cerebrospinal fluid. The combination of albendazole (ABZ) and CoPP significantly decreased pro-inflammatory cytokines, tumor necrosis factor-α, interleukin (IL)-1ß, IL-5, and IL-33 but significantly increased anti-inflammatory cytokines IL-10 and transforming growth factor-ß. In addition, worm recovery, matrix metalloproteinase-9, BBB permeability, and eosinophil counts were decreased in the ABZ and CoPP co-treated groups. Induction of HO-1 with CoPP strongly inhibited the protein levels of caspase-3 and increased the induction of annexin-V and B-cell leukemia 2. Thus, co-treatment with ABZ and CoPP prevented A. cantonensis-induced eosinophilic meningoencephalitis and its anti-apoptotic effect by promoting HO-1 signaling prior to BBB dysfunction. HO-1 induction might be a therapeutic modality for eosinophilic meningoencephalitis.

Peroxisome-Proliferator Activator Receptor γ in Mouse Model with Meningoencephalitis Caused by Angiostrongylus cantonensis.

Peroxisome-proliferator activator receptor γ (PPARγ) has an anti-inflammatory role that inhibits the nuclear factor-κB (NF-κB) pathway and regulates the expressions of pro-inflammatory proteins, whereas its role in parasitic meningoencephalitis remains unknown. In this study we investigated the role of PPARγ and related mechanisms in eosinophilic meningoencephalitis caused by the rat lungworm Angiostrongylus cantonensis. We observed increased protein NF-κB expression in mouse brain tissue using GW9662, which is the specific antagonist of PPARγ, in a mouse model of angiostrongyliasis. Then we investigated NF-κB-related downstream proteins, such as COX-2, NOSs, and IL-1ß, with Western blot or enzyme-linked immunosorbent assay and found that the protein expression was upregulated. The results of gelatin zymography also showed that the MMP-9 activities were upregulated. Treatment with GW9662 increased the permeability of the blood-brain barrier and the number of eosinophils in cerebrospinal fluid. These results suggested that in angiostrongyliasis, PPARγ may play an anti-inflammation role in many inflammatory mediators, including NOS-related oxidative stress, cytokines, and matrix metalloproteinase cascade by decreasing the NF-κB action.

Matrix metalloproteinases activation in Toxocara canis induced pulmonary pathogenesis.

BACKGROUND: Toxocara canis, a source of visceral larva migrans, causes toxocariasis and induces respiratory symptoms. The reasons by which the pulmonary pathological alteration in the lungs infected with T. canis remain unclear. METHODS: The involvement of the pulmonary pathological alteration by histology, enzyme activity, and Western blot analysis in the lungs of BALB/c mice after the infection of 2000 embryonated eggs. RESULTS: The pathological effects gradually increased after the infection culminated in severe leukocyte infiltration and hemorrhage from days 4-14 post-inoculation. Gelatin zymography using substrate showed that the relative activity of matrix metalloproteinase (MMP) -9 and MMP-2 significantly increased in T. canis-infected mice. Western blot analysis indicated that the MMPs protein level of fibronectin monomer significantly increased in T. canis-infected mice compared with that in uninfected control. T. canis larvae mainly initiated leukocyte infiltration and hemorrhage in the lungs. CONCLUSION: These phenomena subsequently induced the activities of MMPs in parallel with the pathological changes in early stage pulmonary inflammation. In conclusion, T. canis larval migration activated the MMPs and caused pulmonary pathogenesis.

Regulation of Proinflammatory Enzymes by Peroxisome Proliferator-Activated Receptor Gamma in Astroglia Infected with Toxoplasma gondii.

Peroxisome proliferator-activated receptor gamma (PPARγ) regulates neuroinflammation, and its agonists act as neuroprotective agents. This study aims to investigate the correlation between PPARγ and proinflammatory enzyme expression in astroglia infected with Toxoplasma gondii tachyzoite in vitro. Our results showed that matrix metalloprotease (MMP)-2, MMP-9, cyclooxygenase-2 (COX-2), prostaglandin (PGE)-2, inducible nitric-oxide synthase (iNOS), and nitric oxide (NO) were significantly increased in T. gondii-infected astroglia. Furthermore, the expression levels of MMP-2, MMP-9, COX-2, PGE-2, iNOS, and NO were significantly decreased by rosiglitazone-a PPARγ agonist. By contrast, the treatment with GW9662, a PPARγ antagonist, efficiently increased the expression levels of MMP-2, MMP-9, COX-2, PGE-2, iNOS, and NO. These results suggested that the treatment with rosiglitazone offers a potential strategy for controlling the inflammatory factors in T. gondii infection.

Angiostrongylus cantonensis infection induces MMP-9 and causes tight junction protein disruption associated with Purkinje cell degeneration.

Angiostrongylus cantonensis causes a human central nervous system (CNS) infection characterized by eosinophilic meningitis or meningoencephalitis. Individuals infected with A. cantonensis exhibit unbalanced walking. The mechanism of extensive neurological impairments of hosts caused by A. cantonensis larvae remains unclear. Tight junction proteins (e.g., claudin-5 and zonula occludens-1) are the most important regulators of paracellular permeability and cellular adhesion. In a previous study, we found that increased matrix metalloproteinase-9 (MMP-9) activity may be associated with blood-CNS barrier disruption and/or the degeneration of Purkinje cells in eosinophilic meningitis caused by A. cantonensis. In the present study, the co-localization of MMP-9 and tight junction proteins on the degeneration of Purkinje cells was measured via confocal laser scanning immunofluorescence microscopy. The statistical evidence indicated that MMP-9 correlated between tight junction protein disruption and Purkinje cell degeneration at 20 days post-infection with A. cantonensis. In conclusion, Purkinje cell degeneration is highly correlated with tight junction protein disruption via the MMP-9 activation pathway.

Proteasome serves as pivotal regulator in Angiostrongylus cantonensis-induced eosinophilic meningoencephalitis.

Proteasome primarily degrades the unneeded or damaged proteins by proteolysis. Disruption of the brain barrier and its resulting meningoencephalitis caused by Angiostrongylus cantonensis are important pathological events in non-permissive hosts. In this study, the results showed upregulated proteasome during A. cantonensis infection. Occludin degradation and matrix metalloproteinase-9 (MMP-9) activity were significantly increased in infected mice than in uninfected mice. Moreover, confocal immunoflourescence microscopy showed that occludin was co-localized with MMP-9. The infected-mice were treated with proteasomal activity inhibitor MG132 by 1.5 and 3.0 mg/kg/day, which resulted in significantly reduced protein levels of phosphorylated IκBα (P<0.05) compared with the untreated control. The phosphorylated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) showed similar result. In addition, MMP-9 activity and occludin degradation were reduced because of MG132 treatment. These results suggested that the proteasome in A. cantonensis infection degraded phosphorylated IκBα, modulated phosphorylated NF-κB, and then regulated the activation of MMP-9 and occludin degradation. Proteasome alterations were presented in eosinophilic meningitis of BALB/c mice and may contribute to the pathophysiology of eosinophilic meningitis by increasing occludin degradation. This molecule would serve as pivotal regulator in A. cantonensis-induced eosinophilic meningoencephalitis.

Matrix metalloproteinase-2 and matrix metalloproteinase-9 in mice with ocular toxocariasis.

In ocular toxocariasis, Toxocara canis-induced inflammatory reaction can lead to eye destruction and granuloma, which is formed by immune cell infiltration and concurrent extensive remodeling tissue. Herein, the histomorphology of granuloma and proteinase production in the eye of T. canis-infected BALB/c mice were investigated. Pathological effects substantially increased after the infection culminated in a severe leukocyte infiltration and granuloma formation from days 4 to 56 post-inoculation. The matrix metalloproteinase (MMP)-2 and MMP-9 activities remarkably increased, compared with those of uninfected control, by gelatin zymography and Western blot analysis in ocular toxocariasis. Granuloma formation had a remarkably positive correlation with MMP-2 and MMP-9 levels. We suggested that T. canis larvae and leukocytes infiltrated from blood vessel both migrated into corpus adiposum orbitae. Activated leukocytes secreted MMP-2 and MMP-9, leading to fibronectin degradation. The imbalance of MMP-2/TIMP-2 and MMP-9/TIMP-1 may play a role in inflammatory cell infiltration and extracellular matrix degradation, forming granuloma, in ophthalmological pathogenesis of T. canis infection.

Resveratrol relieves Angiostrongylus cantonensis - Induced meningoencephalitis by activating sirtuin-1.

Resveratrol, a natural herbal compound found in high levels in grapes and red wine, is frequently used as activator of sirtuin-1. This study investigated the potential function of sirtuin-1 in regulating angiostrongyliasis meningoencephalitis in resveratrol-treated mice. Mice were subjected to meningoencephalitis to study the protective effect of resveratrol against meningoencephalitis and investigate the effects of sirtuin-1 activation on brain. Results demonstrated that sirtuin-1 level decreased in mice with meningoencephalitis and significantly increased in resveratrol-treated mice. Moreover, resveratrol treatment significantly reduced eosinophil counts, p65, Interferon-γ, interleukin (IL)-5, IL-33, and tumor necrosis factor-α levels, matrix metalloproteinase-9 activity, claudin-5 degradation, and blood-brain barrier permeability. By contrast, the anti-inflammatory factor IL-10 was significantly increased in resveratrol-treated mice. Resveratrol treatment was partially beneficial in controlling the pathological processes of angiostrongyliasis meningoencephalitis. The results demonstrate the neuroprotective and anti-inflammatory effects of resveratrol against Angiostrongylus cantonensis-induced eosinophilic meningoencephalitis in mice. Treatment with sirtuin-1 agonist was given within a therapeutic window after A. cantonensis infection.

Naringenin inhibits migration of lung cancer cells via the inhibition of matrix metalloproteinases-2 and -9.

Lung cancer is among the most common causes of cancer-related mortality. It has a high mortality rate and resistance to chemotherapy due to its high metastatic potential. Naringenin, a bioactive compound identified in several fruits, displays anti-inflammatory and antitumor effects. Furthermore, naringenin mitigates the migration of several human cancer cell types. However, the effects of naringenin on lung cancer remain unclear. The current study investigated the mechanisms of naringenin on the migration of lung cancer A549 cells. The results indicate that significant alteration in A549 cell proliferation was observed in response to naringenin (0-300 µM) treatment for 24 and 48 h. Furthermore, a dose-dependent migration inhibition of A549 in the presence of naringenin was observed by healing and transwell migration assays. In addition, a zymography assay revealed that naringenin exhibited a concentration-dependent inhibition of matrix metalloproteinase (MMP)-2 and -9 activities. Furthermore, naringenin also inhibited the activities of AKT in a dose-dependent manner. These observations indicated that naringenin inhibited the migration of lung cancer A549 cells through several mechanisms, including the inhibition of AKT activities and reduction of MMP-2 and -9 activities.

Lumbrokinase attenuates myocardial ischemia-reperfusion injury by inhibiting TLR4 signaling.

Lumbrokinase, a novel antithrombotic agent, purified from the earthworm Lumbricus rubellus, has been clinically used to treat stroke and cardiovascular diseases. However, inflammatory responses associated with the cardioprotective effect of lumbrokinase remain unknown. In this study, the signaling pathways involved in lumbrokinase-inhibited expressions of inflammation mediators were investigated in rats subjected to myocardial ischemia-reperfusion (I-R) injury. The left main coronary artery of anesthetized rats was subjected to 1h occlusion and 3h reperfusion. The animals were treated with/without lumbrokinase and the severities of I-R-induced arrhythmias and infarction were compared. Lumbrokinase inhibited I-R-induced arrhythmias and reduced mortality, as well as decreased the lactate dehydrogenase levels in carotid blood. Lumbrokinase also inhibited the enhancement of I-R induced expressions of cyclooxygenase (COX)-2, inducible nitric oxide synthase (iNOS), and matrix metalloproteinase (MMP)-9 through toll-like receptor 4 (TLR4) signaling pathway. Moreover, our results demonstrated that stimulation with lumbrokinase decreases the phosphorylation of JNK, IκB, and NF-κB. These findings suggested that lumbrokinase is a potent cardioprotective drug in rats with I-R injury. The cardioprotective effects of lumbrokinase may be correlated with its inhibitory effect on the I-R-induced expressions of COX-2, iNOS and MMP-9, mediated by TLR4 signaling through JNK and NF-κB pathways.

Fibronectin changes in eosinophilic meningitis with blood-CSF barrier disruption.

Fibronectin, which is present at relatively low levels in healthy central nervous systems (CNS), shows increased levels in meningitis. In this study, fibronectin processing was correlated with the increased permeability of the blood-cerebrospinal fluid (CSF) barrier as well as with the formation of eosinophil infiltrates in angiostrongyliasis meningitis. The immunohistochemistry results show matrix metalloproteinase-9 (MMP-9) is localized in the choroid plexus epithelium. Coimmunoprecipitation demonstrated fibronectin strongly binds MMP-9. Furthermore, treatment with the MMP-9 inhibitor GM6001 significantly inhibited fibronectin processing, reduced the blood-CSF barrier permeability, and decreased the eosinophil counts. The decreased fibronectin processing in CSF implies decreased cellular invasion of the subarachnoid space across the blood-CSF barrier. Therefore, increased fibronectin processing may be associated with barrier disruption and participate in the extravasation and migration of eosinophils into the CNS during experimental parasitic infection.

Matrix metalloproteinase-9 leads to blood-brain barrier leakage in mice with eosinophilic meningoencephalitis caused by Angiostrongylus cantonensis.

Blood-brain barrier (BBB) disruption is associated with tight junction protein degradation, basal membrane disruption, and astrocyte damage. This study aims to investigate the role of matrix metalloproteinase (MMP)-9 in BBB disruption during Angiostrongylus cantonensis infection. We used mice infected with A. cantonensis, in which parasite-induced eosinophilia and inflammation might induce MMP-9 elevation. MMP-9 could cause claudin-5 degradation in endothelium tight junction, collagen type IV degradation in basal membranes, and S100B degradation in astrocytes of wild-type mice. BBB permeability was significantly attenuated in MMP-9 knockout mice than in wild-type mice in angiostrongyliasis meningoencephalitis. Immune cell aggregates were also more attenuated in the brains of MMP-9 knockout mice than in the brains of wild-type mice. Results suggest that MMP-9 activities are significant in BBB disruption in angiostrongyliasis meningoencephalitis. This study improves understanding of molecular mechanisms that underlie brain invasion by A. cantonensis, which is a key step in the pathogenesis of meningoencephalitis, and can offer a new strategy to reduce mortality.

A fatal case of Naegleria fowleri meningoencephalitis in Taiwan.

After bathing at a hot spring resort, a 75-year-old man presented to the emergency department because of seizure-like attack with loss of conscious. This is the first case of primary amebic meningoencephalitis (PAM) caused by Naegleria fowleri in Taiwan. PAM was diagnosed based on detection of actively motile trophozoites in cerebrospinal fluid using a wet-mount smear and the Liu's stain. The amoebae were further confirmed by PCR and gene sequencing. In spite of administering amphotericin B treatment, the patient died 25 days later.

Induction of matrix metalloproteinase-2 and -9 via Erk1/2-NF-κB pathway in human astroglia infected with Toxoplasma gondii.

Matrix metalloproteinase (MMP)-2 and MMP-9 can cleave fibronectin, allowing leukocyte migration to the site of Toxoplasma gondii infection during toxoplasmic encephalitis. The aim of this study was to investigate the association between extracellular signal-regulated kinase (Erk)1/2-nuclear factor (NF)-κB pathway and MMP-2/-9 expression in astroglia infected with T. gondii tachyzoite in vitro. Our results showed that phosphorylated (p)-Erk1/2 transiently increased 1h post-infection (PI) and p-NF-κB significantly increased from 1h PI to 12h PI in cell homogenates. NF-κB was bound directly to oligonucleotides containing putative NF-κB binding sites for the MMP-9 promoter. Additionally, expression of p-NF-κB, MMP-2, and MMP-9 was significantly decreased by MG132, an indirect NF-κB inhibitor. Treatment with PD98059, an Erk kinase inhibitor, efficiently reduced p-Erk1/2, p-NF-κB, MMP-2, and MMP-9 expression. These results suggest that suppression of the Erk1/2-NF-κB signaling pathway causes reductions in MMP-2 and MMP-9 activities in astroglia response to T. gondii infection. Thus, inhibiting this signaling intermediate involved in MMP-2 and MMP-9 expression may be a potential method for controlling inflammatory development of T. gondii-induced encephalitis.

Matrix metalloproteinase-9 leads to claudin-5 degradation via the NF-κB pathway in BALB/c mice with eosinophilic meningoencephalitis caused by Angiostrongylus cantonensis.

The epithelial barrier regulates the movement of ions, macromolecules, immune cells and pathogens. The objective of this study was to investigate the role of the matrix metalloproteinase (MMP)-9 in the degradation of tight junction protein during infection with rat nematode lungworm Angiostrongylus cantonensis. The results showed that phosphorylation of IκB and NF-κB was increased in mice with eosinophilic meningoencephalitis. Treatment with MG132 reduced the phosphorylation of NF-κB and the activity of MMP-9, indicating upregulation of MMP-9 through the NF-κB signaling pathway. Claudin-5 was reduced in the brain but elevated in the cerebrospinal fluid (CSF), implying that A. cantonensis infection caused tight junction breakdown and led to claudin-5 release into the CSF. Degradation of claudin-5 coincided with alteration of the blood-CSF barrier permeability and treatment with the MMP inhibitor GM6001 attenuated the degradation of claudin-5. These results suggested that degradation of claudin-5 was caused by MMP-9 in angiostrongyliasis meningoencephalitis. Claudin-5 could be used for the pathophysiologic evaluation of the blood-CSF barrier breakdown and tight junction disruption after infection with A. cantonensis.

Matrix metalloproteinase-2 and -9 lead to fibronectin degradation in astroglia infected with Toxoplasma gondii.

Toxoplasma gondii is a zoonotic parasite and its infection in human can induce toxoplasmic encephalitis in immune disorders. In this study, astroglia were infected with the TS-4 strain of T. gondii tachyzoite in vitro to investigate the changes of matrix metalloproteinase (MMP)-2, MMP-9 and their substrate fibronectin. MMP-2 and MMP-9 were significantly increased at 1 h, 6 h and 12 h post-infection (PI) in the cell homogenates, and increased at 6 h, 12 h, 24 h and 48 h PI in the cell-cultured supernatants. Fibronectin degradation also occurred at the same time points. In addition, immunocytochemistry showed that MMP-2 and MMP-9 localized in the cytoplasm, and confocal scanning laser microscopy revealed co-labeled patterns of MMP-2 and MMP-9 with fibronectin. MMP-2 and MMP-9 interacted with fibronectin, respectively. These results suggest that MMP-2 and MMP-9 induction from astroglia may contribute to extracellular matrix (ECM) degradation occurring in toxoplasmosis. Thus, we hypothesize that MMP-2 and MMP-9 cleave fibronectin and may contribute to the astroglia reaction and leukocyte migration to the sites of T. gondii replication during toxoplasmic encephalitis.

Apoptosis in meningoencephalitis of Angiostrongylus cantonensis-infected mice.

A hallmark of eosinophilic meningoencephalitis is infiltration of leukocytes into brain parenchyma and subarachnoid space infected by Angiostrongylus cantonensis. Apoptosis, a process that eliminates useless cells and counterbalances tissue homeostasis, is important for homeostasis of the immune system. In this study, we investigated the characteristics of cell death induced in BABL/c mice infected with A. cantonensis. We observed increased expression of the apoptotic proteins, caspase-3, caspase-8, caspase-9, and cytochrome c, and decreased expression of anti-apoptotic proteins, B-cell leukemia 2 and inhibitor of apoptosis protein 1. On immunohistochemistry, apoptotic proteins were localized within the leukocytes infiltrate. A terminal deoxynucleotidyl transferase-mediated deoxyuridine 5-triphosphate nick-end labeling assay to detect DNA fragmentation confirmed these observations. The infiltration of leukocytes present in the brain parenchyma and subarachnoid space in vivo may also express these apoptotic regulatory molecules, which demonstrates the capacity of these cells to undergo apoptosis.