Modulation of amoebic hepatic abscess by the parasympathetic system

Acetylcholine Upregulates Entamoeba histolytica Virulence Factors, Enhancing Parasite Pathogenicity in Experimental Liver Amebiasis

Entamoeba histolytica is an invasive enteric protozoan, whose infections are associated to high morbidity and mortality rates. However, only less than 10% of infected patients develop invasive amebiasis. The ability of E. histolytica to adapt to the intestinal microenvironment could be determinant in triggering pathogenic behavior. Indeed, during chronic inflammation, the vagus nerve limits the immune response through the anti-inflammatory reflex, which includes acetylcholine (ACh) as one of the predominant neurotransmitters at the infection site. Consequently, the response of E. histolytica trophozoites to ACh could be implicated in the establishment of invasive disease. The aim of this study was to evaluate the effect of ACh on E. histolytica virulence. Methods include binding detection of ACh to plasma membrane, quantification of the relative expression of virulence factors by RT-PCR and western blot, evaluation of the effect of ACh in different cellular processes related to E. histolytica pathogenesis, and assessment of the capability of E. histolytica to migrate and form hepatic abscesses in hamsters. Results demonstrated that E. histolytica trophozoites bind ACh on their membrane and show a clear increase of the expression of virulence factors, that were upregulated upon stimulation with the neurotransmitter. ACh treatment increased the expression of L220, Gal/GalNAc lectin heavy subunit (170 kDa), amebapore C, cysteine proteinase 2 (ehcp-a2), and cysteine proteinase 5 (ehcp-a5). Moreover, erythrophagocytosis, cytotoxicity, and actin cytoskeleton remodeling were augmented after ACh treatment. Likewise, by assessing the formation of amebic liver abscess, we found that stimulated trophozoites to develop greater hamster hepatic lesions with multiple granulomas. In conclusion, ACh enhanced parasite pathogenicity by upregulating diverse virulence factors, thereby contributing to disease severity, and could be linked to the establishment of invasive amebiasis.

Morphological changes during the formation of amoebic liver abscess in vagotomized hamsters

Amoebic liver abscess (ALA) is the main extra-intestinal complication caused by Entamoeba histolytica. Given the histological features of ALA in hamsters and the importance of the vagus nerve in the immune response, the aim of this study was to identify and analyze the major changes in ALA that are caused by a vagotomy. The changes found are related to inflammatory foci and abscess size, the type of collagen formed, and the number of trophozoites in lesions. Male hamsters were divided into three groups: Intact animals (IA) and those undergoing a false operation (SHAM) or a subdiaphragmatic vagotomy (VAG). In each group, E. histolytica trophozoites or culture medium (CM) were inoculated in hamsters by the intrahepatic route, and then euthanized at 6h, 12h, 24h, 48h, 4d or 7d post-infection. Initially the growth of the abscess was more rapid in the VAG group, but at day 7 it was faster in the IA and SHAM groups. VAG animals showed a higher quantity of type III collagen than the IA and SHAM groups. A larger number of amoebic trophozoites/mm² was observed up to day 4 in VAG hamsters (23.3±2.19) compared to IA (14.6±0.23) and SHAM (6.13±0.87) animals. This parameter decreased by day 7 in VAG (13.4±0.87) with respect to IA (24.7±1.47) and SHAM (21.7±1.48). The results show that a subdiaphragmatic vagotomy influenced the development of ALA in hamsters, suggesting a modification of the morphological structure of damaged hepatic tissue.

Entamoeba histolytica L220 induces the in vitro activation of macrophages and neutrophils and is modulated by neurotransmitters

The neuroimmunoregulation of inflammation has been well characterized. Entamoeba histolytica provokes an inflammatory response in the host in which macrophages and neutrophils are the first line of defense. The aim of this study was to analyze the effect of the 220 kDa lectin of Entamoeba histolytica on stimulation of human macrophages and neutrophils, especially the secretion of cytokines and the relation of these to neurotransmitters. Human cells were interacted with L220, epinephrine, nicotine, esmolol and vecuronium bromide. The concentrations of IL-1β, IFN-γ, TNF-α and IL-10 were determined by ELISA at, 4 h of interaction. L220 has a cytokine stimulating function of macrophages and neutrophils for secretion of IL-1β, and IL-10 only by macrophages, which was modulated by the effect of vecuronium on cholinergic receptors in this immune cells.

Adrenergic regulation during acute hepatic infection with Entamoeba histolytica in the hamster: involvement of oxidative stress, Nrf2 and NF-KappaB

Oxidative stress and transcriptional pathways of nuclear factor erythroid 2-related factor 2 (Nrf2) and nuclear factor kappa-B (NF-κB) are critically involved in the etiopathology of amebic liver abscess (ALA). In this work, we studied the relationship between the adrenergic nervous system and ALA in the hamster. ALA was visible at 12 h of infection. While 6-hydroxidopamine (6-OHDA) decreased infection, propranolol (β-adrenergic blocker) treatment was associated with less extensive liver damage, and phentolamine treatment (α-adrenergic blocker) significantly reduced ALA compared to 6-OHDA and propranolol. Serum enzymatic activities of alanine aminotransferase (ALT) and γ-glutamyl transpeptidase (γ-GTP) were increased at 12 h post-infection. Chemical denervation and α and β-adrenergic blockers decreased ALT to normal levels, while 6-OHDA and propranolol showed a trend to decrease γ-GTP but phentolamine significantly reduced γ-GTP. Amebic infection increased oxidized glutathione (GSSG) and decreased both reduced glutathione (GSH) and the GSH/GSSG ratio. Propranolol and 6-OHDA showed a tendency to decrease GSSG. However, GSH, GSSG and GSH/GSSG returned to normal levels with phentolamine. Furthermore, amebic infection increased pNF-κB and interleukin-1β (IL-1β), and showed a tendency to decrease hemoxigenase-1 (HO-1), but not Nrf2. Chemical denervation showed a trend to decrease pNF-κB and IL-1β, and neither Nrf2 nor HO-1 increased significantly. In addition, NF-κB and IL-1β were attenuated by propranolol and phentolamine treatments, although phentolamine showed significant overexpression of Nrf2 and HO-1. This suggests that the adrenergic system may be involved in oxidative stress and in modulation of the Nrf2 and NF-κB pathways during ALA development.

Modulation of innate immune response by the vagus nerve in experimental hepatic amebiasis in rats

The parasympathetic nervous system has a crucial role in immunomodulation of the vagus nerve, its structure provides a pathogen detection system, and a negative feedback to the immune system after the pathogenic agent has been eliminated. Amebiasis is a disease caused by the protozoan parasite Entamoeba histolytica, considered the third leading cause of death in the world. The rats are used as a natural resistance model to amoebic liver infection. The aim of this study is to analyze the interaction of Entamoeba histolytica with neutrophils, macrophages, and NK cells in livers of intact and vagotomized rats. Six groups were studied (n = 4): Intact (I), Intact + amoeba (IA), Sham (S), Sham + amoeba (SA), Vagotomized (V) and Vagotomized + amoeba (VA). Animals were sacrificed at 8 h post-inoculation of E. histolytica. Then, livers were obtained and fixed in 4% paraformaldehyde. Tissue liver slides were stained with H-E, PAS and Masson. The best development time for E. histolytica infection was at 8 h. Amoeba was identified with a monoclonal anti-220 kDa E. histolytica lectin. Neutrophils (N) were identified with rabbit anti-human neutrophil myeloperoxidase, macrophages (Mɸ) with anti-CD68 antibody and NK cells (NK) with anti-NK. Stomachs weight and liver glycogen were higher in V. Collagen increased in VA, whereas vascular and neutrophilic areas were decreased. There were fewer N, Mɸ, NK around the amoeba in the following order IA > SA > VA (p < 0.05 between IA and VA). In conclusion, these results suggest that the absence of parasympathetic innervation affects the participation of neutrophils, macrophages and NK cells in the innate immune response, apparently by parasympathetic inhibition on the cellular functions and probably for participation in sympathetic activity.

Vagotomy induces deregulation of the inflammatory response during the development of amoebic liver abscess in hamsters

BACKGROUND

The parasympathetic nervous system modulates the immune response in the abdominal-pelvic gut through the vagus nerve, which releases acetylcholine. This endogenous ligand acts on α7 nicotinic receptors expressed on immune cells.

OBJECTIVE

To study the mechanism of the production and regulation of cytokines in parasympathectomized and control hamsters during the development of amoebic liver abscesses (ALA) caused by Entamoeba histolytica.

METHODOLOGY

Six- to 8-week-old male hamsters with and without vagotomy were used in a model of ALA. The animals were infected with trophozoites (350,000; HM1:IMSS strain) via the intrahepatic route and sacrificed at 6, 12, and 24 h and at 2, 4, and 7 days postinfection. Immune parameters were recorded at each time point using morphometric techniques including immunofluorescence and immunohistochemistry assays. These parameters included signal transducer and activator of transcription 3 (STAT3) levels, pro- and anti-inflammatory cytokine levels, and nuclear factor-κB (NFκB) activation in neutrophils and macrophages.

RESULTS

Compared to the control groups, the vagotomized (VAG) hamsters showed a significant increase in NFκB activation in neutrophils and macrophages, and higher levels of interleukin (IL)-1β, IL-6, interferon-γ, and tumor necrosis factor-α. VAG hamsters showed an increase in the expression of IL-8 and phosphorylated STAT3 during the first 24 h postinfection as well as slightly increased levels of transforming growth factor-β on days 2-7 postinfection. No significant differences were demonstrated in the levels of IL-10.

CONCLUSIONS

These results suggest that the vagus nerve plays an important role in the regulation of inflammation during ALA formation.

Amoebicidal Activity of Essential Oil of Dysphania ambrosioides (L.) Mosyakin & Clemants in an Amoebic Liver Abscess Hamster Model

Amebiasis is a parasitic disease that extends worldwide and is a public health problem in developing countries. Metronidazole is the drug recommended in the treatment of amebiasis, but its contralateral effects and lack of continuity of treatment induce low efficiency, coupled with the appearance of resistant amoebic strains. Therefore, the search of new compounds with amoebicidal activity is urgent and important. In this study, we evaluated the in vitro and in vivo antiamoebic activity of the essential oil Dysphania ambrosioides (L.) Mosyakin & Clemants. It exhibited an IC₅₀ = 0.7 mg/mL against trophozoites. The oral administration of essential oil (8 mg/kg and 80 mg/kg) to hamster infected with Entamoeba histolytica reverted the infection. Ascaridole was identified as the main component of essential oil of D. ambrosioides. The identification of amoebicidal activity of Ascaridole gives support to the traditional use. Further studies with Ascaridole will be carried out to understand the mechanism involved.

Localization of extratemporal seizure with noninvasive dense-array EEG. Comparison with intracranial recordings

A 13-year-old girl presented with refractory seizures since the age of 5 years. Clinical exam and MRI studies were normal. Ictal EEG discharges suggested possible left posterior quadrant distribution but were not well localized with standard methods. A seizure was recorded during 128-channel EEG video long-term monitoring prior to invasive recordings. Applying a source analysis method, seizure onset and propagation patterns were calculated and displayed on an MRI model. The onset was localized to the left inferior posterior occipital cortex, followed by propagation to the right, then left, posterior cerebral hemispheres, and finally to the left superior-medial parietal lobe. These patterns were replicated closely on subsequent invasive recordings. Surgery was based on intracranial findings and she is seizure-free 30 months after resection. Noninvasive dense-array EEG, used in conjunction with realistic source analysis methods, may have the potential to assist in localizing seizure onsets when standard methods fail.