Sequential expression of the neuropeptides substance P and somatostatin in granulomas associated with murine cysticercosis

Increased iron uptake in the bladder wall of racemose cysts of Taenia solium

Racemose neurocysticercosis is an aggressive infection caused by the aberrant expansion and proliferation of the bladder wall of the Taenia solium cyst within the subarachnoid spaces of the human brain. The parasite develops and proliferates in a microenvironment with low concentrations of growth factors and micronutrients compared to serum. Iron is important for essential biological processes, but its requirement for racemose cyst viability and proliferation has not been studied. The presence of iron in the bladder wall of racemose and normal univesicular T. solium cysts was determined using Prussian blue staining. Iron deposits were readily detected in the bladder wall of racemose cysts but were not detectable in the bladder wall of univesicular cysts. Consistent with this finding, the genes for two iron-binding proteins (ferritin and melanotransferrin) and ribonucleotide reductase were markedly overexpressed in the racemose cyst compared to univesicular cysts. The presence of iron in the bladder wall of racemose cysts may be due to its increased metabolic rate due to proliferation.

Proliferative cells in racemose neurocysticercosis have an active MAPK signalling pathway and respond to metformin treatment

Racemose neurocysticercosis is an aggressive infection caused by the aberrant expansion of the cyst form of Taenia solium within the subarachnoid spaces of the human brain and spinal cord, resulting in the displacement of the surrounding host tissue and chronic inflammation. We previously demonstrated that the continued growth of the racemose bladder wall is associated with the presence of mitotically active cells but the nature and control of these proliferative cells are not well understood. Here, we demonstrated by immunofluorescence that the racemose cyst has an active mitogen-activated protein kinases (MAPK) signalling pathway that is inhibited after treatment with metformin, which reduces racemose cell proliferation in vitro, and reduces parasite growth in the murine model of Taenia crassiceps cysticercosis. Our findings indicate the importance of insulin receptor-mediated activation of the MAPK signalling pathway in the proliferation and growth of the bladder wall of the racemose cyst and its susceptibility to metformin action. The antiproliferative action of metformin may provide a new therapeutic approach against racemose neurocysticercosis.

Identification and culture of proliferative cells in abnormal Taenia solium larvae: Role in the development of racemose neurocysticercosis

Racemose neurocysticercosis is an aggressive disease caused by the aberrant expansion of the cyst form of Taenia solium within the subarachnoid spaces of the human brain and spinal cord resulting in a mass effect and chronic inflammation. Although expansion is likely caused by the proliferation and growth of the parasite bladder wall, there is little direct evidence of the mechanisms that underlie these processes. Since the development and growth of cysts in related cestodes involves totipotential germinative cells, we hypothesized that the expansive growth of the racemose larvae is organized and maintained by germinative cells. Here, we identified proliferative cells expressing the serine/threonine-protein kinase plk1 by in situ hybridization. Proliferative cells were present within the bladder wall of racemose form and absent from the homologous tissue surrounding the vesicular form. Cyst proliferation in the related model species Taenia crassiceps (ORF strain) occurs normally by budding from the cyst bladder wall and proliferative cells were concentrated within the growth buds. Cells isolated from bladder wall of racemose larvae were established in primary cell culture and insulin stimulated their proliferation in a dose-dependent manner. These findings indicate that the growth of racemose larvae is likely due to abnormal cell proliferation. The different distribution of proliferative cells in the racemose larvae and their sensitivity to insulin may reflect significant changes at the cellular and molecular levels involved in their tumor-like growth. Parasite cell cultures offer a powerful tool to characterize the nature and formation of the racemose form, understand the developmental biology of T. solium, and to identify new effective drugs for treatment.

Host immune responses during Taenia solium Neurocysticercosis infection and treatment

Taenia solium cysticercosis and taeniasis (TSCT), caused by the tapeworm T. solium, is a foodborne and zoonotic disease classified since 2010 by WHO as a neglected tropical isease. It causes considerable impact on health and economy and is one of the leading causes of acquired epilepsy in most endemic countries of Latin America, Sub-Saharan Africa, and Asia. There is some evidence that the prevalence of TSCT in high-income countries has recently increased, mainly due to immigration from endemic areas. In regions endemic for TSCT, human cysticercosis can manifest clinically as neurocysticercosis (NCC), resulting in epileptic seizures and severe progressive headaches, amongst other neurological signs and/or symptoms. The development of these symptoms results from a complex interplay between anatomical cyst localization, environmental factors, parasite's infective potential, host genetics, and, especially, host immune responses. Treatment of individuals with active NCC (presence of viable cerebral cysts) with anthelmintic drugs together with steroids is usually effective and, in the majority, reduces the number and/or size of cerebral lesions as well as the neurological symptoms. However, in some cases, treatment may profoundly enhance anthelmintic inflammatory responses with ensuing symptoms, which, otherwise, would have remained silent as long as the cysts are viable. This intriguing silencing process is not yet fully understood but may involve active modulation of host responses by cyst-derived immunomodulatory components released directly into the surrounding brain tissue or by the induction of regulatory networks including regulatory T cells (Treg) or regulatory B cells (Breg). These processes might be disturbed once the cysts undergo treatment-induced apoptosis and necrosis or in a coinfection setting such as HIV. Herein, we review the current literature regarding the immunology and pathogenesis of NCC with a highlight on the mobilization of immune cells during human NCC and their interaction with viable and degenerating cysticerci. Moreover, the immunological parameters associated with NCC in people living with HIV/AIDS and treatments are discussed. Eventually, we propose open questions to understand the role of the immune system and its impact in this intriguing host-parasite crosstalk.

The Therapeutic Potential of Targeting Substance P/NK-1R Interactions in Inflammatory CNS Disorders

The inflammatory responses of resident central nervous system (CNS) cells are now known to play a critical role in the initiation and progression of an array of infectious and sterile neuroinflammatory disorders such as meningitis, encephalitis, Parkinson's disease, Alzheimer's disease and multiple sclerosis (MS). Regulating glial inflammatory responses in a timely manner is therefore critical in preserving normal CNS functions. The neuropeptide substance P is produced at high levels within the CNS and its selective receptor, the neurokinin 1 receptor (NK-1R), is abundantly expressed by neurons and is present on glial cell types including microglia and astrocytes. In addition to its functions as a neurotransmitter in the perception of pain and its essential role in gut motility, this tachykinin is widely recognized to exacerbate inflammation at peripheral sites including the skin, gastrointestinal tract and the lungs. Recently, a number of studies have identified a role for substance P and NK-1R interactions in neuroinflammation and described the ability of this neuropeptide to alter the immune functions of activated microglia and astrocytes. In this review article, we describe the expression of substance P and its receptor by resident CNS cells, and we discuss the ability of this neuropeptide to exacerbate the inflammatory responses of glia and immune cells that are recruited to the brain during neurodegenerative diseases. In addition, we discuss the available data indicating that the NK-1R-mediated augmentation of such responses appears to be detrimental during microbial infection and some sterile neurodegenerative disorders, and propose the repurposed use of NK-1R antagonists, of a type that are currently approved as anti-emetic and anti-anxiolytic agents, as an adjunct therapy to ameliorate the inflammatory CNS damage in these conditions.

Regulation of immunity by Taeniids: lessons from animal models and in vitro studies

Taeniidae is the largest family of the Cyclophyllidea order of parasites despite being composed of just two genera: Taenia spp and Echinococcus spp. These parasites are flatworms with a terrestrial life cycle, having an immature or larval stage called metacestode, which develops into the mature form within the intestine of the primary host after being consumed in raw or poorly cooked meat. Consumed eggs hatch into oncospheres, penetrate the intestinal walls and are transported via the bloodstream to later develop into metacestodes within the muscles and internal organs of secondary and sometimes primary hosts, thereby initiating the cycle again. Larval stages of both Taenia spp and Echinococcus spp are well known to produce tissue-dwelling, long-lasting infections; in this stage, these parasites can reach centimetres (macroparasites) and both genera may cause life-threatening diseases in humans. Establishing such long-term infections requires an exceptional ability to modulate host immunity for long periods of time. In this review, we analyse the immunoregulatory mechanisms induced by these tapeworms and their products, mainly discussing the importance of taeniid strategies to successfully colonize their hosts, such as antigen-presenting cell phenotype manipulation and the consequent induction of T-cell anergy, among others.

Substance P and Antagonists of the Neurokinin-1 Receptor in Neuroinflammation Associated with Infectious and Neurodegenerative Diseases of the Central Nervous System

This review addresses the role that substance P (SP) and its preferred receptor neurokinin-1 (NK1R) play in neuroinflammation associated with select bacterial, viral, parasitic, and neurodegenerative diseases of the central nervous system. The SP/NK1R complex is a key player in the interaction between the immune and nervous systems. A common effect of this interaction is inflammation. For this reason and because of the predominance in the human brain of the NK1R, its antagonists are attractive potential therapeutic agents. Preventing the deleterious effects of SP through the use of NK1R antagonists has been shown to be a promising therapeutic strategy, as these antagonists are selective, potent, and safe. Here we evaluate their utility in the treatment of different neuroinfectious and neuroinflammatory diseases, as a novel approach to clinical management of CNS inflammation.

Somatostatin negatively regulates parasite burden and granulomatous responses in cysticercosis

Cysticercosis is an infection of tissues with the larval cysts of the cestode, Taenia   solium. While live parasites elicit little or no inflammation, dying parasites initiate a granulomatous reaction presenting as painful muscle nodules or seizures when cysts are located in the brain. We previously showed in the T. crassiceps murine model of cysticercosis that substance P (SP), a neuropeptide, was detected in early granulomas and was responsible for promoting granuloma formation, while somatostatin (SOM), another neuropeptide and immunomodulatory hormone, was detected in late granulomas; SOM's contribution to granuloma formation was not examined. In the current studies, we used somatostatin knockout (SOM^−/−) mice to examine the hypothesis that SOM downmodulates granulomatous inflammation in cysticercosis, thereby promoting parasite growth. Our results demonstrated that parasite burden was reduced 5.9-fold in SOM^−/− mice compared to WT mice (P < 0.05). This reduction in parasite burden in SOM^−/− mice was accompanied by a 95% increase in size of their granulomas (P < 0.05), which contained a 1.5-fold increase in levels of IFN-γ and a 26-fold decrease in levels of IL-1β (P < 0.05 for both) compared to granulomas from WT mice. Thus, SOM regulates both parasite burden and granulomatous inflammation perhaps through modulating granuloma production of IFN-γ and IL-1β.

Substance P causes seizures in neurocysticercosis

Neurocysticercosis (NCC), a helminth infection of the brain, is a major cause of seizures. The mediators responsible for seizures in NCC are unknown, and their management remains controversial. Substance P (SP) is a neuropeptide produced by neurons, endothelial cells and immunocytes. The current studies examined the hypothesis that SP mediates seizures in NCC. We demonstrated by immunostaining that 5 of 5 brain biopsies from NCC patients contained substance P (SP)-positive (+) cells adjacent to but not distant from degenerating worms; no SP+ cells were detected in uninfected brains. In a rodent model of NCC, seizures were induced after intrahippocampal injection of SP alone or after injection of extracts of cysticercosis granuloma obtained from infected wild type (WT), but not from infected SP precursor-deficient mice. Seizure activity correlated with SP levels within WT granuloma extracts and was prevented by intrahippocampal pre-injection of SP receptor antagonist. Furthermore, extracts of granulomas from WT mice caused seizures when injected into the hippocampus of WT mice, but not when injected into SP receptor (NK1R) deficient mice. These findings indicate that SP causes seizures in NCC, and, suggests that seizures in NCC in humans may be prevented and/or treated with SP-receptor antagonists.

Substance P signaling contributes to granuloma formation in Taenia crassiceps infection, a murine model of cysticercosis

Cysticercosis is an infection with larval cysts of the cestode Taenia solium. Through pathways that are incompletely understood, dying parasites initiate a granulomatous reaction that, in the brain, causes seizures. Substance P (SP), a neuropeptide involved in pain-transmission, contributes to inflammation and previously was detected in granulomas associated with dead T. crassiceps cysts. To determine if SP contributes to granuloma formation, we measured granuloma-size and levels of IL-1β, TNF-α, and IL-6 within granulomas in T. crassiceps-infected wild type (WT) mice and mice deficient in SP-precursor (SPP) or the SP-receptor (neurokinin 1, NK1). Granuloma volumes of infected SPP- and NK1-knockout mice were reduced by 31 and 36%, respectively, compared to WT mice (P < .05 for both) and produced up to 5-fold less IL-1β, TNF-α, and IL-6 protein. Thus, SP signaling contributes to granuloma development and proinflammatory cytokine production in T. crassiceps infection and suggests a potential role for this mediator in human cystercercosis.

Genome-wide analyses of gene expression during mouse endochondral ossification

Background

Endochondral ossification is a complex process involving a series of events that are initiated by the establishment of a chondrogenic template and culminate in its replacement through the coordinated activity of osteoblasts, osteoclasts and endothelial cells. Comprehensive analyses of in vivo gene expression profiles during these processes are essential to obtain a complete understanding of the regulatory mechanisms involved.

Methodology/Principal Findings

To address these issues, we completed a microarray screen of three zones derived from manually segmented embryonic mouse tibiae. Classification of genes differentially expressed between each respective zone, functional categorization as well as characterization of gene expression patterns, cytogenetic loci, signaling pathways and functional motifs both confirmed reported data and provided novel insights into endochondral ossification. Parallel comparisons of the microdissected tibiae data set with our previously completed micromass culture screen further corroborated the suitability of micromass cultures for modeling gene expression in chondrocyte development. The micromass culture system demonstrated striking similarities to the in vivo microdissected tibiae screen; however, the micromass system was unable to accurately distinguish gene expression differences in the hypertrophic and mineralized zones of the tibia.

Conclusions/Significance

These studies allow us to better understand gene expression patterns in the growth plate and endochondral bones and provide an important technical resource for comparison of gene expression in diseased or experimentally-manipulated cartilages. Ultimately, this work will help to define the genomic context in which genes are expressed in long bones and to understand physiological and pathological ossification.

Absence of the SP/SP receptor circuitry in the substance P-precursor knockout mice or SP receptor, neurokinin (NK)1 knockout mice leads to an inhibited cytokine response in granulomas associated with murine Taenia crassiceps infection

Neurocysticercosis, caused by the cestode Taenia solium, is the most common parasitic infection of the human central nervous system that leads to seizures. Taenia crassiceps cysticercosis in mice is an experimental model for Taenia solium cysticercosis. Similar to the human infection, live parasites cause little or no granulomatous inflammation. Dying parasites initiate a granulomatous reaction. The neuropeptide, substance P (SP), stimulates T-helper (TH) 1 cytokine production. In the current studies, we determined whether absence of SP/SP receptor circuitry in the SP-precursor, preprotachykinin, knockout or SP-receptor, neurokinin (NK) 1, knockout mice affected granuloma cytokine production. We hence compared the levels of Th1 cytokines interleukin (IL)-2 and interferon (IFN)-gamma, and levels of Th2/immunoregulatory cytokines IL-4 and IL-10, by enzyme-linked immunosorbent assay in T. crassiceps-induced granulomas derived from infected C57BL/6 wild type (WT) versus SP-precursor knockout and NK1 knockout mice. We found that mean levels of IL-2, IFN-gamma, IL-4, and IL-10 in infected WT-derived granulomas were significantly higher than those of granulomas derived from infected SP-precursor knockout or the NK1 receptor (NKIR)knockout mice. Levels of Th2/immunoregulatory cytokines, IL-4 and IL-10 were higher in early stage granulomas (histologically-staged on basis of evidence of parasite remnants) versus late stage granulomas (no parasite-remnants) of both knockouts, whereas the reverse was noted in WT-derived granulomas. These study established that the absence of an SP/SP receptor circuitry in the SP precursor knockout mice or NK1 receptor knockout mice led to an inhibited cytokine response.

Neurocysticercosis: Current knowledge and advances

Neurocysticercosis is the most common cause of acquired seizures worldwide. Most cases of this larval stage infection of the pork tapeworm Taenia solium occur in the developing world, although increasing numbers of cases are being recognized in the United States, particularly among Hispanic immigrants. The ability of the pathogen to persist for years within the host is the subject of immunologic and biochemical investigation. The major presenting symptom is seizures, although symptoms of obstructive hydrocephalus occur if cysts are located near the ventricles or in the subarachnoid spaces. Diagnosis is dependent on clinical, radiologic, and serologic data. Therapy with antiparasitic agents, especially albendazole, is effective in large burden disease or disease within sensitive neuraxis sites (the ventricles, the subarachnoid spaces). When patients with radiologically enhancing disease are given cysticidal therapy, there appears to be a reduction in seizure recurrences. Surgery is indicated for disease in selected anatomic sites. Long-term prevention requires attention to pork husbandry and general sanitation, including the potential use of mass human chemotherapy and porcine vaccination.

Treatment of neurocysticercosis: current status and future research needs

Here we put forward a roadmap that summarizes important questions that need to be answered to determine more effective and safer treatments. A key concept in management of neurocysticercosis is the understanding that infection and disease due to neurocysticercosis are variable and thus different clinical approaches and treatments are required. Despite recent advances, treatments remain either suboptimal or based on poorly controlled or anecdotal experience. A better understanding of basic pathophysiologic mechanisms including parasite survival and evolution, nature of the inflammatory response, and the genesis of seizures, epilepsy, and mechanisms of anthelmintic action should lead to improved therapies.

Neurocysticercosis

Since international travel has become widespread, clinicians increasingly have been confronted with the diagnosis of symptomatic and incidental neurocysticercosis. The difficulty with managing this disease lies in its varied clinical presentations. The treatment of neurocysticercosis depends upon anatomic locations, stages of cysts, and overall cyst burden. Despite recent clinical and laboratory advances, experts are divided on many key management questions. This article reviews the pathophysiology and experimental data underlying treatment recommendations for this emerging and complex condition.

PROINFLAMMATORY CYTOKINES IN GRANULOMAS ASSOCIATED WITH MURINE CYSTICERCOSIS ARE NOT THE CAUSE OF SEIZURES

Neurocysticercosis is a parasitic infection of the human central nervous system caused by the cestode Taenia solium. The most common clinical manifestations of neurocysticercosis are seizures. Taenia crassiceps cysticercosis in mice has been used as an experimental model for T. solium cysticercosis. Granulomas surrounding murine cysticerci have striking immunopathological resemblance to human neurocysticercosis; early stage granulomas were able to induce seizures in a rodent model. To assess the role of proinflammatory cytokines in early stage granulomas, we isolated RNA from murine cysticercal granulomas and checked for cytokine expression by reverse transcriptase-polymerase chain reaction (RT-PCR) and/or ribonuclease (RNase) protection assays. Cytokine expression was compared with histological stages. Interleukin (IL)-1alpha, IL-1beta, IL-1 receptor antagonist, and tumor necrosis factor (TNF-alpha) were the major cytokines detected in all granulomas. Signals for IL-12, IL-18, and IL-6 RNA were not consistently detected and, when detected, were barely demonstrable. Expression of migration inhibitory factor (MIF), IL-6, IL-1alpha, TNF-alpha, and IL-18 was not significantly different between early and late-stage granulomas. Expression of IL-1beta, IL-1 receptor antagonist, and IL-12 p40 were higher in late, compared with early, stages. Thus, we demonstrated a broad range of cytokines in these granulomas. However, we did not document preferential expression of any proinflammatory cytokines in early stage granulomas. Thus, proinflammatory cytokines are not responsible for the seizures in the rodent model of neurocysticercosis.

ArrayVigil: a methodology for statistical comparison of gene signatures using segregated-one-tailed (SOT) Wilcoxon's signed-rank test

Due to versatile diagnostic and prognostic fidelity molecular signatures or fingerprints are anticipated as the most powerful tools for cancer management in the near future. Notwithstanding the experimental advancements in microarray technology, methods for analyzing either whole arrays or gene signatures have not been firmly established. Recently, an algorithm, ArraySolver has been reported by Khan for two-group comparison of microarray gene expression data using two-tailed Wilcoxon signed-rank test. Most of the molecular signatures are composed of two sets of genes (hybrid signatures) wherein up-regulation of one set and down-regulation of the other set collectively define the purpose of a gene signature. Since the direction of a selected gene's expression (positive or negative) with respect to a particular disease condition is known, application of one-tailed statistics could be a more relevant choice. A novel method, ArrayVigil, is described for comparing hybrid signatures using segregated-one-tailed (SOT) Wilcoxon signed-rank test and the results compared with integrated-two-tailed (ITT) procedures (SPSS and ArraySolver). ArrayVigil resulted in lower P values than those obtained from ITT statistics while comparing real data from four signatures.

ArraySolver: an algorithm for colour-coded graphical display and Wilcoxon signed-rank statistics for comparing microarray gene expression data

The massive surge in the production of microarray data poses a great challenge for proper analysis and interpretation. In recent years numerous computational tools have been developed to extract meaningful interpretation of microarray gene expression data. However, a convenient tool for two-groups comparison of microarray data is still lacking and users have to rely on commercial statistical packages that might be costly and require special skills, in addition to extra time and effort for transferring data from one platform to other. Various statistical methods, including the t-test, analysis of variance, Pearson test and Mann-Whitney U test, have been reported for comparing microarray data, whereas the utilization of the Wilcoxon signed-rank test, which is an appropriate test for two-groups comparison of gene expression data, has largely been neglected in microarray studies. The aim of this investigation was to build an integrated tool, ArraySolver, for colour-coded graphical display and comparison of gene expression data using the Wilcoxon signed-rank test. The results of software validation showed similar outputs with ArraySolver and SPSS for large datasets. Whereas the former program appeared to be more accurate for 25 or fewer pairs (n < or = 25), suggesting its potential application in analysing molecular signatures that usually contain small numbers of genes. The main advantages of ArraySolver are easy data selection, convenient report format, accurate statistics and the familiar Excel platform.