STAT3-dependent transactivation of miRNA genes following Toxoplasma gondii infection in macrophage

Toxoplasma gondii infection regulates apoptosis of host cells via miR-185/ARAF axis

BACKGROUND

Toxoplasmosis is a zoonosis with a worldwide presence that is caused by the intracellular parasite Toxoplasma gondii. Active regulation of apoptosis is an important immune mechanism by which host cells resist the growth of T. gondii or avoid excessive pathological damage induced by this parasite. Previous studies found that upregulated expression of microRNA-185 (miR-185) during T. gondii infection has a potential role in regulating the expression of the ARAF gene, which is reported to be associated with cell proliferation and apoptosis.

METHODS

The expression levels of miR-185 and the ARAF gene were evaluated by qPCR and Western blot, respectively, in mice tissues, porcine kidney epithelial cells (PK-15) and porcine alveolar macrophages (3D4/21) following infection with the T. gondii ToxoDB#9 and RH strains. The dual luciferase reporter assay was then used to verify the relationship between miR-185 and ARAF targets in PK-15 cells. PK-15 and 3D4/21 cell lines with stable knockout of the ARAF gene were established by CRISPR, and then the apoptosis rates of the cells following T. gondii infection were detected using cell flow cytometry assays. Simultaneously, the activities of cleaved caspase-3, as a key apoptosis executive protein, were detected by Western blot to evaluate the apoptosis levels of cells.

RESULTS

Infection with both the T. gondii ToxoDB#9 and RH strains induced an increased expression of miR-185 and a decreased expression of ARAF in mice tissues, PK-15 and 3D4/21 cells. MiR-185 mimic transfections showed a significantly negative correlation in expression levels between miR-185 and the ARAF gene. The dual luciferase reporter assay confirmed that ARAF was a target of miR-185. Functional investigation revealed that T. gondii infection induced the apoptosis of PK-15 and 3D4/21 cells, which could be inhibited by ARAF knockout or overexpression of miR-185. The expression levels of cleaved caspase-3 protein were significantly lower in cells with ARAF knockout than in normal cells, which were consistent with the results of the cell flow cytometry assays.

CONCLUSIONS

Toxoplasma gondii infection could lead to the upregulation of miR-185 and the downregulation of ARAF, which was not related to the strain of T. gondii and the host cells. Toxoplasma gondii infection could regulate the apoptosis of host cells via the miR-185/ARAF axis, which represents an additional strategy used by T. gondii to counteract host-cell apoptosis in order to maintain survival and reproduce in the host cells.

The interplay between toxoplasmosis and host miRNAs: Mechanisms and consequences

Toxoplasmosis is one of the highly prevalent zoonotic diseases worldwide caused by the parasite Toxoplasma gondii (T. gondii). The infection with T. gondii could pass unidentified in immunocompetent individuals; however, latent cysts remain dormant in their digestive tract, but they could be shed and excreted with feces infesting the environment. However, active toxoplasmosis can create serious consequences, particularly in newborns and infected persons with compromised immunity. These complications include ocular toxoplasmosis, in which most cases cannot be treated. Additionally, it caused many stillbirths and miscarriages. Circulating miRNAs are important regulatory molecules ensuring that the normal physiological role of various organs is harmonious. Upon infection with T. gondii, the tightly regulated miRNA profile is disrupted to favor the parasite's survival and further participate in the disease pathogenesis. Interestingly, this dysregulated profile could be useful in acute and chronic disease discrimination and in providing insights into the pathomechanisms of the disease. Thus, this review sheds light on the various roles of miRNAs in signaling pathways regulation involved in the pathogenesis of T. gondii and provides insights into the application of miRNAs clinically for its diagnosis and prognosis.

A Systematic Review of Apicomplexa Looking into Epigenetic Pathways and the Opportunity for Novel Therapies

Interest in host epigenetic changes during apicomplexan infections increased in the last decade, mainly due to the emergence of new therapies directed to these alterations. This review aims to carry out a bibliometric analysis of the publications related to host epigenetic changes during apicomplexan infections and to summarize the main studied pathways in this context, pointing out those that represent putative drug targets. We used four databases for the article search. After screening, 116 studies were included. The bibliometric analysis revealed that the USA and China had the highest number of relevant publications. The evaluation of the selected studies revealed that Toxoplasma gondii was considered in most of the studies, non-coding RNA was the most frequently reported epigenetic event, and host defense was the most explored pathway. These findings were reinforced by an analysis of the co-occurrence of keywords. Even though we present putative targets for repurposing epidrugs and ncRNA-based drugs in apicomplexan infections, we understand that more detailed knowledge of the hosts' epigenetic pathways is still needed before establishing a definitive drug target.

Exosomal miRNA-21 from Toxoplasma gondii-infected microglial cells induces the growth of U87 glioma cells by inhibiting tumor suppressor genes

Toxoplasma gondii is an intracellular protozoan parasite that can modulate the microenvironment of infected hosts and is known to be associated with the incidence of brain tumor growth. In this study, we suggested that the exosomal microRNA-21 derived from Toxoplasma infection would contribute to the growth of brain tumors. Exosomes of BV2 microglial cells infected with Toxoplasma were characterized and confirmed internalization to U87 glioma cells. Exosomal miRNA expression profiles were analyzed using microRNA array and miR-21A-5p associated with Toxoplasma and tumor sorted. We also examined the mRNA level of tumor-associated genes in U87 glioma cells by changing the level of miR-21 within exosomes and the effects of exosomes on the proliferation of human U87 glioma cells. Expression of miRNA-21 was increased and anti-tumorigenic genes (FoxO1, PTEN, and PDCD4) were decreased in exosomes within T. gondii-infected U87 glioma cells. Toxoplasma-infected BV2-derived exosomes induced proliferation of U87 glioma cells. The exosomes induced the growth of U87 cells in a mouse tumor model. We suggest that the increased exosomal miR-21 from Toxoplasma-infected BV2 microglial cells may play an important role as a cell growth promotor of U87 glioma cells through a down-regulation of anti-tumorigenic genes.

High-concentration atropine induces corneal epithelial cell apoptosis via miR-30c-1/SOCS3

Atropine is an anticholinergic drug widely used in the field of ophthalmology, but its abuse can cause cytotoxicity to the cornea, resulting in blurred vision. This study used cultured human corneal epithelial cells (HCECs) to investigate the mechanism of high-concentration atropine-induced cytotoxicity. HCECs were treated with different concentrations of atropine. The expression levels of microRNA (miR)-30c-1 and suppressor of cytokine signaling 3 (SOCS3) were manipulated in HCECs treated with 0.1% atropine. Cell counting kit-8 assay and flow cytometry were used to assess the viability and apoptosis of HCECs. The relationship between miR-30c-1 and SOCS3 was obtained from an online database and validated using a dual-luciferase reporter assay and RNA immunoprecipitation method. The effect of atropine on the Janus kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) signaling pathway was also investigated. High-concentration atropine inhibited the viability of HCECs and promoted their apoptosis. Moreover, atropine reduced miR-30c-1 expression and increased SOCS3 expression in a dose-dependent manner. It was found that miR-30c-1 targeted SOCS3. Overexpression of miR-30c-1-reduced atropine-induced HCEC cytotoxicity, whereas upregulation of SOCS3 reversed the effects of miR-30c-1 overexpression. High-concentration atropine inhibited activation of the JAK2/STAT3 signaling pathway via miR-30c-1/SOCS3. High-concentration atropine induces HCEC apoptosis by regulating the miR-30c-1/SOCS3 axis and JAK2/STAT3 signaling pathway.

Toxoplasmosis in Human and Animals Around the World. Diagnosis and Perspectives in the One Health Approach

Toxoplasmosis is a unique health disease that significantly affects the health of humans, domestic animals, wildlife and is present in ecosystems, including water, soil and food. Toxoplasma gondii is one of the best-adapted parasites in the word. This parasite is able to persist for long periods in its hosts, in different geographic regions of the word. This review summarizes the current literature of these themes, focusing on: (1) toxoplasmosis, a zoonotic infection; (2) One health approach and toxoplasmosis; (3) human toxoplasmosis; (4) animal toxoplasmosis; (5) toxoplasmosis diagnosis, as immunological, parasitological and molecular diagnosis; (6) T. gondii outbreaks caused by infected meat, milk and dairy products, as well as, vegetables and water consume; (7) studies in experimental models; (8) genetic characterization of T. gondii strains; (9) extracellular vesicles and miRNA; and (10) future perspectives on T. gondii and toxoplasmosis. The vast prevalence of toxoplasmosis in both humans and animals and the dispersion and resistence of T. gondii parasites in environment highlight the importance of the one health approach in diagnostic and control of the disease. Here the different aspects of the one health approach are presented and discussed.

The Core Human MicroRNAs Regulated by Toxoplasma gondii

BACKGROUND

Toxoplasma gondii (T. gondii) is an intracellular zoonotic protozoan parasite known to effectively modulate the host system for its survival. A large number of microRNAs (miRNAs) regulated by different strains of T. gondii in diverse types of host cells/tissues/organs have been reported across multiple studies.

OBJECTIVE

We aimed to decipher the complexity of T. gondii regulated spectrum of miRNAs to derive a set of core miRNAs central to different strains of T. gondii infection in diverse human cell lines.

METHODS

We first assembled miRNAs hat are regulated by T. gondii altered across the various assortment of infections and time points of T. gondii infection in multiple cell types. For these assembled datasets, we employed specific criteria to filter the core miRNAs regulated by T. gondii. Subsequently, accounting for the spectrum of miRNA-mRNA target combinations, we applied a novel confidence criterion to extract their core experimentally-validated mRNA targets in human cell systems.

RESULTS

This analysis resulted in the extraction of 74 core differentially regulated miRNAs and their 319 high-confidence mRNA targets. Based on these core miRNA-mRNA pairs, we derived the central biological processes perturbed by T. gondii in diverse human cell systems. Further, our analysis also resulted in the identification of novel autocrine/paracrine signalling factors that could be associated with host response modulated by T. gondii.

CONCLUSION

The current analysis derived a set of core miRNAs, their targets, and associated biological processes fine-tuned by T. gondii for its survival within the invaded cells.

MicroRNAs: master regulators in host-parasitic protist interactions

MicroRNAs (miRNAs) are a group of small non-coding RNAs present in a wide diversity of organisms. MiRNAs regulate gene expression at a post-transcriptional level through their interaction with the 3' untranslated regions of target mRNAs, inducing translational inhibition or mRNA destabilization and degradation. Thus, miRNAs regulate key biological processes, such as cell death, signal transduction, development, cellular proliferation and differentiation. The dysregulation of miRNAs biogenesis and function is related to the pathogenesis of diseases, including parasite infection. Moreover, during host-parasite interactions, parasites and host miRNAs determine the probability of infection and progression of the disease. The present review is focused on the possible role of miRNAs in the pathogenesis of diseases of clinical interest caused by parasitic protists. In addition, the potential role of miRNAs as targets for the design of drugs and diagnostic and prognostic markers of parasitic diseases is also discussed.

Global MicroRNAs Expression Profile Analysis Reveals Possible Regulatory Mechanisms of Brain Injury Induced by Toxoplasma gondii Infection

Toxoplasma gondii (T. gondii) is an obligate intracellular parasitic protozoan that can cause toxoplasmosis in humans and other endotherms. T. gondii can manipulate the host gene expression profile by interfering with miRNA expression, which is closely associated with the molecular mechanisms of T. gondii-induced brain injury. However, it is unclear how T. gondii manipulates the gene expression of central nervous system (CNS) cells through modulation of miRNA expression in vivo during acute and chronic infection. Therefore, high-throughput sequencing was used to investigate expression profiles of brain miRNAs at 10, 25, and 50 days post-infection (DPI) in pigs infected with the Chinese I genotype T. gondii strain in this study. Compared with the control group 87, 68, and 135 differentially expressed miRNAs (DEMs) were identified in the infected porcine brains at 10, 25, and 50 DPI, respectively. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that a large number significantly enriched GO terms and KEGG pathways were found, and were mostly associated with stimulus or immune response, signal transduction, cell death or apoptosis, metabolic processes, immune system or diseases, and cancers. miRNA–gene network analysis revealed that the crucial connecting nodes, including DEMs and their target genes, might have key roles in the interactions between porcine brain and T. gondii. These results suggest that the regulatory strategies of T. gondii are involved in the modulation of a variety of host cell signaling pathways and cellular processes, containing unfolded protein response (UPR), oxidative stress (OS), autophagy, apoptosis, tumorigenesis, and inflammatory responses, by interfering with the global miRNA expression profile of CNS cells, allowing parasites to persist in the host CNS cells and contribute to pathological damage of porcine brain. To our knowledge, this is the first report on miRNA expression profile in porcine brains during acute and chronic T. gondii infection in vivo. Our results provide new insights into the mechanisms underlying T. gondii-induced brain injury during different infection stages and novel targets for developing therapeutic agents against T. gondii.

Liquid Biopsy for Promising Non-invasive Diagnostic Biomarkers in Parasitic Infections

BACKGROUND

Liquid biopsy refers to the sampling and molecular analysis of body fluids such as blood, saliva, and urine in contrast to conventional tissue biopsies. Liquid biopsy approach can offer powerful non-invasive biomarkers (circulating markers) for diagnosis and monitoring treatment response of a variety of diseases, including parasitic infections.

METHODS

In this review, we concentrate on cell-free DNA (cfDNA), microRNA (miRNA), and exosomes in the published literature.

RESULTS

Considering the high prevalence and severity of parasitic infections worldwide, circulating biomarkers can provide a new insight into the diagnosis and prognosis of parasites in the near future. Moreover, identifying and characterizing parasite- or host-derived circulating markers are important for a better understanding of the pathogenesis of parasite infection and host-parasite relationship at the molecular level. Profiling of biomarkers for parasitic diseases is a promising potential field, though further studies and optimization strategies are required, both in vitro and in vivo.

CONCLUSION

In this review, we discuss three approaches in the liquid biopsy including circulating cfDNA, miRNAs, and exosomes for diagnosis and evaluation of parasites and summarize circulating biomarkers in non-invasive samples during parasitic infections.

The NF-κB Pathway: Modulation by Entamoeba histolytica and Other Protozoan Parasites

Protozoan parasites have led to worldwide devastation because of their ability to cause infectious diseases. They have evolved as successful pathogens in part because of their remarkable and sophisticated ways to evade innate host defenses. This holds true for both intracellular and extracellular parasites that deploy multiple strategies to circumvent innate host defenses for their survival. The different strategies protozoan parasites use include hijacking the host cellular signaling pathways and transcription factors. In particular, the nuclear factor-κB (NF-κB) pathway seems to be an attractive target for different pathogens owing to their central role in regulating prompt innate immune responses in host defense. NF-κB is a ubiquitous transcription factor that plays an indispensable role not only in regulating immediate immune responses against invading pathogens but is also a critical regulator of cell proliferation and survival. The major immunomodulatory components include parasite surface and secreted proteins/enzymes and stimulation of host cells intracellular pathways and inflammatory caspases that directly or indirectly interfere with the NF-κB pathway to thwart immune responses that are directed for containment and/or elimination of the pathogen. To showcase how protozoan parasites exploits the NF-κB signaling pathway, this review highlights recent advances from Entamoeba histolytica and other protozoan parasites in contact with host cells that induce outside-in and inside-out signaling to modulate NF-κB in disease pathogenesis and survival in the host.

The Role of microRNAs in the Infection by T. gondii in Humans

MicroRNAs are molecules belonging to an evolutionarily conserved family of small non-coding RNAs, which act on post-transcriptional gene regulation, causing messenger RNA (mRNA) degradation or inhibiting mRNA translation into proteins. These molecules represent potential biomarkers for diagnosis, non-invasive prognosis, and monitoring the development of the disease. Moreover, they may provide additional information on the pathophysiology of parasitic infections and guide strategies for treatment. The Apicomplexan parasite Toxoplasma gondii modifies the levels of microRNAs and mRNAs in infected host cells by modulating the innate and adaptive immune responses, facilitating its survival within the host. Some studies have shown that microRNAs are promising molecular markers for developing diagnostic tools for human toxoplasmosis. MicroRNAs can be detected in human specimens collected using non-invasive procedures. changes in the circulating host microRNAs have been associated with T. gondii infection in mice and ocular toxoplasmosis in humans. Besides, microRNAs can be amplified from samples using sensitive and molecular-specific approaches such as real-time PCR. This review presents recent findings of the role that microRNAs play during T. gondii infection and discuss their potential use of these small nuclei acid molecules to different approaches such as laboratory diagnosis, modulation of cell and tissue infected as other potential applications in human toxoplasmosis.

Transcriptomics analysis of Toxoplasma gondii-infected mouse macrophages reveals coding and noncoding signatures in the presence and absence of MyD88

BACKGROUND

Toxoplasma gondii is a globally distributed protozoan parasite that establishes life-long asymptomatic infection in humans, often emerging as a life-threatening opportunistic pathogen during immunodeficiency. As an intracellular microbe, Toxoplasma establishes an intimate relationship with its host cell from the outset of infection. Macrophages are targets of infection and they are important in early innate immunity and possibly parasite dissemination throughout the host. Here, we employ an RNA-sequencing approach to identify host and parasite transcriptional responses during infection of mouse bone marrow-derived macrophages (BMDM). We incorporated into our analysis infection with the high virulence Type I RH strain and the low virulence Type II strain PTG. Because the well-known TLR-MyD88 signaling axis is likely of less importance in humans, we examined transcriptional responses in both MyD88+/+ and MyD88-/- BMDM. Long noncoding (lnc) RNA molecules are emerging as key regulators in infection and immunity, and were, therefore, included in our analysis.

RESULTS

We found significantly more host genes were differentially expressed in response to the highly virulent RH strain rather than with the less virulent PTG strain (335 versus 74 protein coding genes for RH and PTG, respectively). Enriched in these protein coding genes were subsets associated with the immune response as well as cell adhesion and migration. We identified 249 and 83 non-coding RNAs as differentially expressed during infection with RH and PTG strains, respectively. Although the majority of these are of unknown function, one conserved lncRNA termed mir17hg encodes the mir17 microRNA gene cluster that has been implicated in down-regulating host cell apoptosis during T. gondii infection. Only a minimal number of transcripts were differentially expressed between MyD88 knockout and wild type cells. However, several immune genes were among the differences. While transcripts for parasite secretory proteins were amongst the most highly expressed T. gondii genes during infection, no differentially expressed parasite genes were identified when comparing infection in MyD88 knockout and wild type host BMDM.

CONCLUSIONS

The large dataset presented here lays the groundwork for continued studies on both the MyD88-independent immune response and the function of lncRNAs during Toxoplasma gondii infection.

Human microRNAs in host-parasite interaction: a review

MicroRNAs (miRNAs) are a group of small noncoding RNA molecules with significant capacity to regulate the gene expression at the post-transcriptional level in a sequence-specific manner either through translation repression or mRNA degradation triggering a fine-tuning biological impact. They have been implicated in several processes, including cell growth and development, signal transduction, cell proliferation and differentiation, metabolism, apoptosis, inflammation, and immune response modulation. However, over the last few years, extensive studies have shown the relevance of miRNAs in human pathophysiology. Common human parasitic diseases, such as Malaria, Leishmaniasis, Amoebiasis, Chagas disease, Schistosomiasis, Toxoplasmosis, Cryptosporidiosis, Clonorchiasis, and Echinococcosis are the leading cause of death worldwide. Thus, identifying and characterizing parasite-specific miRNAs and their host targets, as well as host-related miRNAs, are important for a deeper understanding of the pathophysiology of parasite-specific diseases at the molecular level. In this review, we have demonstrated the impact of human microRNAs during host-parasite interaction as well as their potential to be used for diagnosis and prognosis purposes.

Delayed IL-12 production by macrophages during Toxoplasma gondii infection is regulated by miR-187

Toxoplasma gondii is an important zoonotic protozoan worldwide which infects most of warm-blooded mammals and birds, including human, and cause toxoplasmosis. As an intracellular parasite, T. gondii must evade host immune surveillance, such as IL-12 and IFN-γ, in order to survive and multiply in macrophages and other host cells. By delaying IL-12 secretion of host macrophages within 24 h after infection, T. gondii ensures not only self-survival but also the establishment of chronic infection of host cells. MicroRNA plays an important role in regulating gene transcription and translation. The mechanisms of IL-12 production during T. gondii infection are still unknown. Thus, understanding how the parasites manipulate IL-12 production by host macrophage is critical for the effective prevention and therapy of T. gondii infection. In the present study, regulation of delayed macrophage IL-12 production during T. gondii infection was explored. We found that the production of IL-12 after T. gondii infection was inhibited during the first 24 h and then resumed. The expression pattern of miR-187 production was consistent with the production pattern of IL-12 during T. gondii infection. The downregulation of miR-187 promoted Akt and P65 phosphorylation and delayed IL-12 production at late stage (after 24 h) of T. gondii infection. Dual-luciferase reporter assay indicated that MiR-187 targeted the NFKBIZ gene. Our results suggested that the delayed IL-12 production in mouse macrophages during T. gondii infection was regulated by miR-187.

Systems and Synthetic microRNA Biology: From Biogenesis to Disease Pathogenesis

MicroRNAs (miRNAs) are approximately 22-nucleotide-long, small non-coding RNAs that post-transcriptionally regulate gene expression. The biogenesis of miRNAs involves multiple steps, including the transcription of primary miRNAs (pri-miRNAs), nuclear Drosha-mediated processing, cytoplasmic Dicer-mediated processing, and loading onto Argonaute (Ago) proteins. Further, miRNAs control diverse biological and pathological processes via the silencing of target mRNAs. This review summarizes recent findings regarding the quantitative aspects of miRNA homeostasis, including Drosha-mediated pri-miRNA processing, Ago-mediated asymmetric miRNA strand selection, and modifications of miRNA pathway components, as well as the roles of RNA modifications (epitranscriptomics), epigenetics, transcription factor circuits, and super-enhancers in miRNA regulation. These recent advances have facilitated a system-level understanding of miRNA networks, as well as the improvement of RNAi performance for both gene-specific targeting and genome-wide screening. The comprehensive understanding and modeling of miRNA biogenesis and function have been applied to the design of synthetic gene circuits. In addition, the relationships between miRNA genes and super-enhancers provide the molecular basis for the highly biased cell type-specific expression patterns of miRNAs and the evolution of miRNA-target connections, while highlighting the importance of alterations of super-enhancer-associated miRNAs in a variety of human diseases.

Identification of Host Proteins Interacting with Toxoplasma gondii SAG1 by Yeast Two-Hybrid Assay

Toxoplasma gondii is one of the most successful human pathogens. To eliminate the infection, identification of receptors or binding partners from humans is indeed urgent. T. gondii surface antigen is the ultimate component involved during the attachment of parasite into host cell. However, mechanism of invasion between SAG and host-cell membrane remains unclear. Yeast two-hybrid experiment was used to identify the binding partners from cDNA human library by using T. gondii SAG1 as bait. Mated yeast cells were plated on DDO/X plates to confirm only prey plasmid that expressing interacting protein was selected. We detected 39 clones interacted with SAG1 based on a series of the selection procedures. After colony PCR, only 29 clones were positive and subsequently sent for sequencing. The yeast plasmids for true positive clones were rescued by transformation into E. coli TOP 10F' cells. Twenty-two clones were further examined by small-scale Y2H experiment. The results indicated that a strong interaction existed between Homo sapiens lysine-rich coil-coiled and SAG1 protein, which could activate the expressions of the reporter genes in diploid yeast. Co-immunoprecipitation experiment result indicated the binding between this prey and SAG1 protein was significant (Mann-Whitney U test, Z = - 1.964, P = 0.05). H. sapiens lysine-rich coil-coiled protein was found to be interacted with SAG1. This prey protein may serve as the potential drug target in vaccination study.

Impact of Toxoplasma gondii Infection on Host Non-coding RNA Responses

As an intracellular microbe, Toxoplasma gondii must establish a highly intimate relationship with its host to ensure success as a parasite. Many studies over the last decade-and-a-half have highlighted how the host reshapes its immunoproteome to survive infection, and conversely how the parasite regulates host responses to ensure persistence. The role of host non-protein-coding RNA during infection is a vast and largely unexplored area of emerging interest. The potential importance of this facet of the host-parasite interaction is underscored by current estimates that as much as 80% of the host genome is transcribed into non-translated RNA. Here, we review the current state of knowledge with respect to two major classes of non-coding RNA, microRNA (miRNA) and long non-coding RNA (lncRNA), in the host response to T. gondii infection. These two classes of regulatory RNA are known to have profound and widespread effects on cell function. However, their impact on infection and immunity is not well-understood, particularly for the response to T. gondii. Nevertheless, numerous miRNAs have been identified that are upregulated by Toxoplasma, and emerging evidence suggests a functional role during infection. While the field of lncRNA is in its infancy, it is already clear that Toxoplasma is also a strong trigger for this class of regulatory RNA. Non-coding RNA responses induced by T. gondii are likely to be major determinants of the host's ability to resist infection and the parasite's ability to establish long-term latency.

Comparison of splenocyte microRNA expression profiles of pigs during acute and chronic toxoplasmosis

BACKGROUND

Toxoplasma gondii is an obligate intracellular parasite that infects humans and other warm-blooded animals. Previous quantitative proteomic analyses of infected host cells revealed that the expression of many host proteins is modulated by T. gondii infection. However, at present limited data are available on the differentially expressed miRNAs (DEMs) associated with the pathology and host immune responses induced by acute and chronic infection with T. gondii in pigs in vivo. In this study, high-throughput sequencing was used to investigate expression profiles of spleen miRNAs at 10, 25 and 50 days post-infection (DPI) in pigs infected with Chinese I genotype strain T. gondii isolated from a dead pig.

RESULTS

When compared to the control group, 34, 6 and 86 DEMs were found in spleens of infected pigs at 10, 25 and 50 DPI, respectively. Gene Ontology (GO) enrichment analysis of the target genes of DEMs showed that no GO terms were enriched at 25 DPI, whereas 28 and 241 GO terms, of which two and 215 were sample-specific, were significantly enriched at 10 and 50 DPI, respectively. The top 20 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways of the target genes of DEMs included signal transduction, immune system, metabolism and diseases. miRNA-gene network analysis revealed that the DEMs played important roles in the host immune response to T. gondii infection by modulating expression levels of cellular immunity-related cytokines and immune-related C-type lectins.

CONCLUSION

Our results not only showed that host miRNA expression is altered by T. gondii but also revealed differences in the regulation of key biological processes and pathways involved in host responses to acute versus chronic T. gondii infection. This will aid future research into miRNA-target interactions during T. gondii infection in pigs and the development of novel therapies against T. gondii.

Expression profile of microRNAs in porcine alveolar macrophages after Toxoplasma gondii infection

BACKGROUND

Toxoplasma gondii is an apicomplexan protozoan parasite that can cause serious clinical illnesses in both humans and animals. microRNAs (miRNAs) are non-protein-coding RNAs that can regulate the expression of target genes. A previous study found that many miRNAs were differentially expressed after T. gondii infection and exert significant effects and revealed that both host survival and the virulence of different strains can be regulated by different miRNAs. Macrophages play an important role in T. gondii infection, but few studies have investigated the relationship between miRNAs and porcine alveolar macrophages infected with T. gondii.

METHODS

Porcine alveolar macrophages (3D4-21) were infected with the RH (Type I) and Me49 (Type II) strains of T. gondii for 12 h and 24 h and then harvested. miRNA libraries were generated using the NEBNext® Multiplex Small RNA Library Prep Set for Illumina® (NEB, USA), and the miRNA expression levels were estimated based on transcripts per million reads (TPM).

RESULTS

Our study generated six miRNA expression profiles from macrophages infected with RH and Me49 compared with the control groups. The comparison of the T. gondii-infected and uninfected samples identified 81 differentially expressed miRNAs, including 36 novel miRNAs and 45 mature miRNAs. The target genes of these differentially expressed miRNAs were predicted using miRanda software, and ssc-miR-127 and ssc-miR-143-3p were predicted to regulate nitric oxide synthase 1 (NOS1) and nitric oxide synthase 3 (NOS3), respectively, which play essential roles in synthesizing nitric oxide (NO) by oxidizing L-arginine. These genes were differentially expressed in both the RH- and Me49-infected groups. A KEGG enrichment analysis indicated that the predicted target genes were involved in multiple signaling pathways, including FcγR-mediated phagocytosis, the AMPK signaling pathway, the mTOR signaling pathway, and the FcγRI signaling pathway, all of which are indispensable for the normal functioning of porcine alveolar macrophages.

CONCLUSIONS

Our results provide data on the miRNA profile of porcine alveolar macrophages infected with T. gondii. To our knowledge, this study provides the first demonstration of the relationship between miRNA and macrophages of swine origin. Understanding the functions of these regulated miRNAs will aid the investigation of T. gondii infectious diseases, and the differentially expressed miRNAs might be candidate drug targets for T. gondii infection in pigs.

MicroRNA expression profile of HCT-8 cells in the early phase of Cryptosporidium parvum infection

Background

Cryptosporidium parvum is an important zoonotic parasitic disease worldwide, but the molecular mechanisms of the host–parasite interaction are not fully understood. Noncoding microRNAs (miRNAs) are considered key regulators of parasitic diseases. Therefore, we used microarray, qPCR, and bioinformatic analyses to investigate the intestinal epithelial miRNA expression profile after Cryptosporidium parvum infection.

Results

Twenty miRNAs were differentially expressed after infection (four upregulated and 16 downregulated). Further analysis of the differentially expressed miRNAs revealed that many important cellular responses were triggered by Cryptosporidium parvum infection, including cell apoptosis and the inflammatory and immune responses.

Conclusions

This study demonstrates for the first time that the miRNA expression profile of human intestinal epithelium cells is altered by C. parvum infection. This dysregulation of miRNA expression may contribute to the regulation of host biological processes in response to C. parvum infection, including cell apoptosis and the immune responses. These results provide new insight into the regulatory mechanisms of host miRNAs during cryptosporidiosis, which may offer potential targets for future C. parvum control strategies.

Electronic supplementary material

The online version of this article (10.1186/s12864-018-5410-6) contains supplementary material, which is available to authorized users.

Inhibition of MicroRNA-23b Attenuates Immunosuppression During Late Sepsis Through NIK, TRAF1, and XIAP

Background

microRNA-23b (miR-23b) is a multiple functional miRNA. We hypothesize that miR-23b plays a role in the pathogenesis of sepsis. Our study investigated the effect of miR-23b on sepsis-induced immunosuppression.

Methods

Mice were treated with miR-23b inhibitors by tail vein injection 2 days after cecal ligation puncture (CLP)-induced sepsis. Apoptosis in spleens and apoptotic signals were investigated, and survival was monitored. T-cell immunoreactivities were examined during late sepsis. Nuclear factor κB (NF-κB)-inducing kinase (NIK), tumor necrosis factor (TNF)-receptor associated factor 1 (TRAF1), and X-linked inhibitor of apoptosis protein (XIAP), the putative targets of miR-23b, were identified by a dual-luciferase reporter assay.

Results

miR-23b expression is upregulated and sustained during sepsis. The activation of the TLR4/TLR9/p38 MAPK/STAT3 signal pathway contributes to the production of miR-23b in CLP-induced sepsis. miR-23b inhibitor decreased the number of spleen cells positive by terminal deoxynucleotidyl transferase dUTP nick-end labeling and improved survival. miR-23b inhibitor restored the immunoreactivity by alleviating the development of T-cell exhaustion and producing smaller amounts of immunosuppressive interleukin 10 and interleukin 4 during late sepsis. We demonstrated that miR-23b mediated immunosuppression during late sepsis by inhibiting the noncanonical NF-κB signal and promoting the proapoptotic signal pathway by targeting NIK, TRAF1, and XIAP.

Conclusions

Inhibition of miR-23b reduces late-sepsis-induced immunosuppression and improves survival. miR-23b might be a target for immunosuppression.

miR-20a inhibition using locked nucleic acid (LNA) technology and its effects on apoptosis of human macrophages infected by Toxoplasma gondii RH strain

Toxoplasma gondii is a ubiquitous and infectious parasite that multiplies in any nucleated cell of warm-blooded animals and humans worldwide. This parasite has intricate mechanisms to reciprocate host-cell apoptosis to exist in the host cell. So far, the details of the parasite interactions with host cells are not well known. MicroRNAs (miRNAs) are one of the small noncoding RNAs that are now considered as a key mechanism of gene regulation. They are important in physiological and pathological processes such as apoptosis. In this study a Real Time quantitative PCR technique was used to evaluate the levels of miR-20a of miRNAs family in human macrophage during T. gondii infection to determine the role of miR-20a in apoptosis. Then, the inhibition of miR-20a function through interaction with transfection of Locked Nucleic Acid (LNA) antisense oligomer was studied. Furthermore, it was examined whether miR-20a is involved in apoptosis of human macrophages with T. gondii infected cells using flow cytometry. We found that miR-20a expression is up-regulated in human macrophages following T. gondii infection. After LNA anti miR-20a oligomer transfection, miR-20a inhibition was evaluated by quantitative reverse transcriptase polymerase chain reaction. Flow cytometry results showed that LNA anti-miR20a oligomer increased apoptosis. In agreement with this result, we found that specific LNA oligonucleotides prevent the functional activity of miR-20a and promotion of human macrophages apoptosis with T. gondii infection by inhibition of this miRNAs gene. Also, the results support the concept that LNA oligomer antisense may be used as a therapeutic implement for blocking detrimental miRNAs overexpressed in infections.

Regulation and biological roles of the multifaceted miRNA-23b (MIR23B)

MicroRNAs (miRNAs) are important short endogenous non-coding RNAs that have critical biological roles by acting as post-transcriptional regulators of gene expression. Chromosomal region 9q22.32 encodes the miR-23b/27b/24-1 cluster and produces miR-23b, which is a pleiotropic modulator in many developmental processes and pathological conditions. Expression of miR-23b is actively suppressed and induced in response to many different stimuli. We discuss the biological functions and transcriptional regulation of this multifaceted miRNA in different tumor types, during development, upon viral infection, as well as in various clinical disorders, immune responses, as well as cardiovascular and thyroid functions. The combined body of work suggests that miR-23b expression is modulated by a diverse array of stimuli in cells from different lineages and participates in multiple gene regulatory feedback loops. Elevation of miR-23b levels appears to instruct cells to limit their proliferative and migratory potential, while promoting the acquisition of specialized phenotypes or protection from invading viruses and parasites. In contrast, loss of miR-23b can deregulate normal tissue homeostasis by removing constraints on cell cycle progression and cell motility. Collectively, the findings on miR-23b indicate that it is a very potent post-transcriptional regulator of growth and differentiation during development, multiple cancers and other biological processes. Understanding the regulation and activity of miR-23b has significant diagnostic value in many biological disorders and may identify cellular pathways that are amenable to therapeutic intervention.

Modulation of host immune responses to Toxoplasma gondii by microRNAs

To survive successfully, Toxoplasma counteracts the strictly regulated host innate response to downregulate inflammation that could be deleterious for the parasite. MicroRNAs are vital regulators of both innate and adaptive immunity, controlling the maintenance and development of immune progenitors as well as the differentiation and the functions of host mature immune cells. Thus, the complexity of mechanisms underlying the connection between Toxoplasma and host immunity has led to investigations of miRNAs as additional key molecular players. The knowledge acquired from these studies will be useful for aiding the discovery of new targets for diagnosis or therapeutic approaches for toxoplasmosis and insight into the interaction between host and parasite.

STAT3 activation in infection and infection-associated cancer

The Janus kinase/signal transducers and activators for transcription (JAK/STAT) pathway plays crucial roles in regulating apoptosis, proliferation, differentiation, and the inflammatory response. The JAK/STAT families are composed of four JAK family members and seven STAT family members. STAT3 plays a key role in inducing and maintaining a pro-carcinogenic inflammatory microenvironment. Recent evidence suggests that STAT3 regulates diverse biological functions in pathogenesis of diseases, such as infection and cancer. In the current review, we will summarize the research progress of STAT3 activation in infection and cancers. We highlight our recent study on the novel role of STAT3 in Salmonella infection-associated colon cancer. Infection with bacterial AvrA-expressing Salmonella activates the STAT3 pathway, which induces the β-catenin signals and enhances colonic tumorigenesis. STAT3 may be a promising target in developing prevention and treatment for infectious diseases and infection-associated cancers.

p53-mediated miR-18 repression activates HSF2 for IGF-IIR-dependent myocyte hypertrophy in hypertension-induced heart failure

Hypertension-induced cardiac hypertrophy and attenuated cardiac function are the major characteristics of early stage heart failure. Cardiomyocyte death in pathological cardiac conditions is the primary cause of heart failure and mortality. Our previous studies found that heat shock factor 1 (HSF1) protected cardiomyocytes from death by suppressing the IGF-IIR signaling pathway, which is critical for hypertensive angiotensin II-induced cardiomyocyte apoptosis. However, the role of heat shock factor 2 (HSF2) in hypertension-induced cardiac hypertrophy is unknown. We identified HSF2 as a miR-18 target for cardiac hypertrophy. p53 activation in angiotensin II (ANG II)-stimulated NRVMs is responsible for miR-18 downregulation both in vitro and in vivo, which triggers HSF2 expression and the activation of IGF-IIR-induced cardiomyocyte hypertrophy. Finally, we provide genetic evidence that miR-18 is required for cardiomyocyte functions in the heart based on the gene transfer of cardiac-specific miR-18 via adenovirus-associated virus 2 (AAV2). Transgenic overexpression of miR-18 in cardiomyocytes is sufficient to protect against dilated cardiomyopathy during hypertension-induced heart failure. Our results demonstrated that the p53-miR-18-HSF2-IGF-IIR axis was a critical regulatory pathway of cardiomyocyte hypertrophy in vitro and in vivo, suggesting that miR-18 could be a therapeutic target for the control of cardiac functions and the alleviation of cardiomyopathy during hypertension-induced heart failure.

Co-Expression Network and Pathway Analyses Reveal Important Modules of miRNAs Regulating Milk Yield and Component Traits

Co-expression network analyses provide insights into the molecular interactions underlying complex traits and diseases. In this study, co-expression network analysis was performed to detect expression patterns (modules or clusters) of microRNAs (miRNAs) during lactation, and to identify miRNA regulatory mechanisms for milk yield and component traits (fat, protein, somatic cell count (SCC), lactose, and milk urea nitrogen (MUN)) via miRNA target gene enrichment analysis. miRNA expression (713 miRNAs), and milk yield and components (Fat%, Protein%, lactose, SCC, MUN) data of nine cows at each of six different time points (day 30 (D30), D70, D130, D170, D230 and D290) of an entire lactation curve were used. Four modules or clusters (GREEN, BLUE, RED and TURQUOISE) of miRNAs were identified as important for milk yield and component traits. The GREEN and BLUE modules were significantly correlated (|r| > 0.5) with milk yield and lactose, respectively. The RED and TURQUOISE modules were significantly correlated (|r| > 0.5) with both SCC and lactose. In the GREEN module, three abundantly expressed miRNAs (miR-148a, miR-186 and miR-200a) were most significantly correlated to milk yield, and are probably the most important miRNAs for this trait. DDR1 and DDHX1 are hub genes for miRNA regulatory networks controlling milk yield, while HHEX is an important transcription regulator for these networks. miR-18a, miR-221/222 cluster, and transcription factors HOXA7, and NOTCH 3 and 4, are important for the regulation of lactose. miR-142, miR-146a, and miR-EIA17-14144 (a novel miRNA), and transcription factors in the SMAD family and MYB, are important for the regulation of SCC. Important signaling pathways enriched for target genes of miRNAs of significant modules, included protein kinase A and PTEN signaling for milk yield, eNOS and Noth signaling for lactose, and TGF β, HIPPO, Wnt/β-catenin and cell cycle signaling for SCC. Relevant enriched gene ontology (GO)-terms related to milk and mammary gland traits included cell differentiation, G-protein coupled receptor activity, and intracellular signaling transduction. Overall, this study uncovered regulatory networks in which miRNAs interacted with each other to regulate lactation traits.

Identification of a TNF-α inducer MIC3 originating from the microneme of non-cystogenic, virulent Toxoplasma gondii

Toxoplasma gondii is an opportunistic parasite with avirulent cystogenic and highly virulent non-cystogenic isolates. Although non-cystogenic strains are considered the most virulent, there are also marked genetic and virulence differences among these strains. Excretory-secretory antigens (ESAs) of T. gondii are critical for the invasion process and the immune response of the host. To better understand the differences in virulence between non-cystogenic T. gondii isolates, we studied ESAs of the RH strain (Type I), and the very prevalent in China, but less virulent TgCtwh3 strain (Chinese 1). ESAs of RH and TgCtwh3 triggered different levels of TNF-α production and macrophage M1 polarization. Using iTRAQ analysis, 27 differentially expressed proteins originating from secretory organelles and surface were quantified. Of these proteins, 11 microneme-associated proteins (MICs), 6 rhoptry proteins, 2 dense granule proteins and 5 surface proteins were more abundant in RH than in TgCtwh3. The protein-protein correlation network was employed to identify the important functional node protein MIC3, which was upregulated 5-fold in RH compared with TgCtwh3. MIC3 was experimentally confirmed to evoke a TNF-α secretory response, and it also induced macrophage M1 polarization. This result suggests that MIC3 is a potentially useful immunomodulator that induces TNF-α secretion and macrophage M1 polarization.

MicroRNA profiling of the intestinal tissue of Kazakh sheep after experimental Echinococcus granulosus infection, using a high-throughput approach

Cystic echinococcosis (CE), caused by infection with the larval stage of the cestode Echinococcus granulosus, is a chronic zoonosis, to which sheep are highly susceptible. Previously, we found that Kazakh sheep with different MHC haplotypes differed in CE infection. Sheep with haplotype MHCMvaIbc-SacIIab-Hin1Iab were resistant to CE infection, while their counterparts without this haplotype were not. MicroRNAs (miRNAs), a class of small non-coding RNAs, are key regulators of gene expression at the post-transcriptional level and play essential roles in fundamental biological processes such as development and metabolism. To identify microRNA controlling resistance to CE in the early stage of infection, microRNA profiling was conducted in the intestinal tissue of sheep with resistant and non-resistant MHC haplotypes after peroral infection with E. granulosus eggs. A total of 351 known and 186 novel miRNAs were detected in the resistant group, against 353 known and 129 novel miRNAs in the non-resistant group. Among these miRNAs, 83 known miRNAs were significantly differentially expressed, including 75 up-regulated and 8 down-regulated miRNAs. Among these known microRNAs, miR-21-3p, miR-542-5p, miR-671, miR-134-5p, miR-26b, and miR-27a showed a significantly higher expression in CE-resistant sheep compared to the CE-non-resistant library, with the FC > 3. Functional analysis showed that they were NF-kB pathway-responsive miRNAs, which are involved in the inflammation process. The results suggest that these microRNAs may play important roles in the response of intestinal tissue to E. granulosus.

The role of STAT3 in autophagy

Autophagy is an evolutionarily conserved process in eukaryotes that eliminates harmful components and maintains cellular homeostasis in response to a series of extracellular insults. However, these insults may trigger the downstream signaling of another prominent stress responsive pathway, the STAT3 signaling pathway, which has been implicated in multiple aspects of the autophagic process. Recent reports further indicate that different subcellular localization patterns of STAT3 affect autophagy in various ways. For example, nuclear STAT3 fine-tunes autophagy via the transcriptional regulation of several autophagy-related genes such as BCL2 family members, BECN1, PIK3C3, CTSB, CTSL, PIK3R1, HIF1A, BNIP3, and microRNAs with targets of autophagy modulators. Cytoplasmic STAT3 constitutively inhibits autophagy by sequestering EIF2AK2 as well as by interacting with other autophagy-related signaling molecules such as FOXO1 and FOXO3. Additionally, the mitochondrial translocation of STAT3 suppresses autophagy induced by oxidative stress and may effectively preserve mitochondria from being degraded by mitophagy. Understanding the role of STAT3 signaling in the regulation of autophagy may provide insight into the classic autophagy model and also into cancer therapy, especially for the emerging targeted therapy, because a series of targeted agents execute antitumor activities via blocking STAT3 signaling, which inevitably affects the autophagy pathway. Here, we review several of the representative studies and the current understanding in this particular field.

Macrophage autophagy regulated by miR-384-5p-mediated control of Beclin-1 plays a role in the development of atherosclerosis

Macrophages play an essential and complicated role in the pathogenesis of atherosclerosis. However, the regulation of macrophage autophagy as well as it role in the development of atherosclerosis is unclear. MicroRNA-384-5p (miR-384-5p) is a new miRNA that attracted attention very recently, while its effects on Beclin-1 and cell autophagy has not been reported. Here, we studied macrophage autophagy in ApoE (-/-) mice suppled with high-fat diet (HFD), a mouse model for atherosclerosis (simplified as HFD mice). We analyzed the levels of Beclin-1 and the levels of miR-384-5p in the purified F4/80+ macrophages from mouse aorta. Prediction of the binding between miR-384-5p and 3'-UTR of Beclin-1 mRNA was performed by bioinformatics analyses and confirmed by a dual luciferase reporter assay. We found that HFD mice developed atherosclerosis in 12 weeks, while the control ApoE (-/-) mice that had received normal diet (simplified as NOR mice) did not. Compared to NOR mice, HFD mice had significantly lower levels of macrophage autophagy, and significantly higher levels of macrophage death, resulting from decreases in Beclin-1. The decreases in Beclin-1 in macrophages were due to HFD-induced increases in miR-384-5p, which suppressed the translation of Bectlin-1 mRNA via 3'-UTR binding. Together, our study suggests that upregulation of miR-384-5p by HFD may impair the Beclin-1-mediated protection of macrophages through autophagy to accelerate the development of atherosclerosis.

MicroRNAs in the Host-Apicomplexan Parasites Interactions: A Review of Immunopathological Aspects

MicroRNAs (miRNAs), a class of small non-coding regulatory RNAs, have been detected in a variety of organisms ranging from ancient unicellular eukaryotes to mammals. They have been associated with numerous molecular mechanisms involving developmental, physiological and pathological changes of cells and tissues. Despite the fact that miRNA-silencing mechanisms appear to be absent in some Apicomplexan species, an increasing number of studies have reported a role for miRNAs in host-parasite interactions. Host miRNA expression can change following parasite infection and the consequences can lead, for instance, to parasite clearance. In this context, the immune system signaling appears to have a crucial role.

MiRNA profiling of whole trabecular bone: identification of osteoporosis-related changes in MiRNAs in human hip bones

Background

MicroRNAs (miRNAs) are important regulators of gene expression, with documented roles in bone metabolism and osteoporosis, suggesting potential therapeutic targets. Our aim was to identify miRNAs differentially expressed in fractured vs nonfractured bones. Additionally, we performed a miRNA profiling of primary osteoblasts to assess the origin of these differentially expressed miRNAs.

Methods

Total RNA was extracted from (a) fresh femoral neck trabecular bone from women undergoing hip replacement due to either osteoporotic fracture (OP group, n = 6) or osteoarthritis in the absence of osteoporosis (Control group, n = 6), matching the two groups by age and body mass index, and (b) primary osteoblasts obtained from knee replacement due to osteoarthritis (n = 4). Samples were hybridized to a microRNA array containing more than 1900 miRNAs. Principal component analysis (PCA) plots and heat map hierarchical clustering were performed. For comparison of expression levels, the threshold was set at log fold change > 1.5 and a p-value < 0.05 (corrected for multiple testing).

Results

Both PCA and heat map analyses showed that the samples clustered according to the presence or absence of fracture. Overall, 790 and 315 different miRNAs were detected in fresh bone samples and in primary osteoblasts, respectively, 293 of which were common to both groups. A subset of 82 miRNAs was differentially expressed (p < 0.05) between osteoporotic and control osteoarthritic samples.

The eight miRNAs with the lowest p-values (and for which a validated miRNA qPCR assay was available) were assayed, and two were confirmed: miR-320a and miR-483-5p. Both were over-expressed in the osteoporotic samples and expressed in primary osteoblasts. miR-320a is known to target CTNNB1 and predicted to regulate RUNX2 and LEPR, while miR-483-5p down-regulates IGF2. We observed a reduction trend for this target gene in the osteoporotic bone.

Conclusions

We identified two osteoblast miRNAs over-expressed in osteoporotic fractures, which opens novel prospects for research and therapy.

Electronic supplementary material

The online version of this article (doi:10.1186/s12920-015-0149-2) contains supplementary material, which is available to authorized users.

microRNA-17-5p Modulates Bacille Calmette-Guerin Growth in RAW264.7 Cells by Targeting ULK1

To explore the potential roles of miRNAs in controlling the survival of mycobacteria in macrophages, miR-17-5p in the regulation of Bacillus Calmette-Guérin(BCG)growth in the macrophage RAW264.7 cells was interrogated. Our results reveal that an infection of BCG shows a time-dependent up-regulation of miR-17-5p in RAW264.7 cells in early phase; importantly, excessive expression of miR-17-5p in these cells exhibits an increased propagation of intracellular BCG. Mechanistically, the Unc-51 like autophagy activating kinase 1 (ULK1), an initial molecular of autophagy are identified as novel target of miR-17-5p, the miR-17-5p is capable of targeting down-regulating the expression of ULK1 protein. In addition, an overexpression of miR-17-5p in RAW264.7 cells is correlated with repression of ULK1 and the autophagosome related proteins LC3I/II. These results imply that miR-17-5p may be able to arrest the maturation of mycobacterial phagosomes in part by targeting ULK1, subsequently reduces the ability of host cells to kill intracellular BCG.

Autophagic digestion of Leishmania major by host macrophages is associated with differential expression of BNIP3, CTSE, and the miRNAs miR-101c, miR-129, and miR-210

BACKGROUND

Autophagy participates in innate immunity by eliminating intracellular pathogens. Consequently, numerous microorganisms have developed strategies to impair the autophagic machinery in phagocytes. In the current study, interactions between Leishmania major (L. m.) and the autophagic machinery of bone marrow-derived macrophages (BMDM) were analyzed.

METHODS

BMDM were generated from BALB/c mice, and the cells were infected with L. m. promastigotes. Transmission electron microscopy (TEM) and electron tomography were used to investigate the ultrastructure of BMDM and the intracellular parasites. Affymetrix chip analyses were conducted to identify autophagy-related messenger RNAs (mRNAs) and microRNAs (miRNAs). The protein expression levels of autophagy related 5 (ATG5), BCL2/adenovirus E1B 19 kDa protein-interacting protein 3 (BNIP3), cathepsin E (CTSE), mechanistic target of rapamycin (MTOR), microtubule-associated proteins 1A/1B light chain 3B (LC3B), and ubiquitin (UB) were investigated through western blot analyses. BMDM were transfected with specific small interfering RNAs (siRNAs) against autophagy-related genes and with mimics or inhibitors of autophagy-associated miRNAs. The infection rates of BMDM were determined by light microscopy after a parasite-specific staining.

RESULTS

The experiments demonstrated autophagy induction in BMDM after in vitro infection with L. m.. The results suggested a putative MTOR phosphorylation-dependent counteracting mechanism in the early infection phase and indicated that intracellular amastigotes were cleared by autophagy in BMDM in the late infection phase. Transcriptomic analyses and specific downregulation of protein expression with siRNAs suggested there is an association between the infection-specific over expression of BNIP3, as well as CTSE, and the autophagic activity of BMDM. Transfection with mimics of mmu-miR-101c and mmu-miR-129-5p, as well as with an inhibitor of mmu-miR-210-5p, demonstrated direct effects of the respective miRNAs on parasite clearance in L. m.-infected BMDM. Furthermore, Affymetrix chip analyses revealed a complex autophagy-related RNA network consisting of differentially expressed mRNAs and miRNAs in BMDM, which indicates high glycolytic and inflammatory activity in the host macrophages.

CONCLUSIONS

Autophagy in L. m.-infected host macrophages is a highly regulated cellular process at both the RNA level and the protein level. Autophagy has the potential to clear parasites from the host. The results obtained from experiments with murine host macrophages could be translated in the future to develop innovative and therapeutic antileishmanial strategies for human patients.

Plasma microRNAs are promising novel biomarkers for the early detection of Toxoplasma gondii infection

Background

MicroRNAs (miRNAs) have been shown to be present in plasma, which are remarkably stable, and have been suggested as disease biomarkers. Toxoplasma gondii (T. gondii) is a protozoan parasite that is infective to a wide range of animals and human beings. Previous studies have found that the parasite generated a large number of miRNAs during proliferation and it is known that the spectrum of miRNA expression in the infected hosts is pathogen-specific. To date, there are no reports regarding the application of microRNAs as biomarkers for the early detection of T. gondii infection.

Methods

In this study, we investigated the expression patterns of 414 murine miRNAs and tested their expression levels in the plasma after T. gondii infection by real-time PCR, with an ultimate purpose of identifying infection-related miRNAs. Three miRNAs in particular, exhibiting prominently elevated expressions, were further validated in a large number of infected mice. The Toxoplasma infection-specific miRNAs were confirmed by comparing their expression levels with those of mice infected with Plasmodium berghei, P. yoelii, P. chabaudi, Cryptosporidium parvum, Mouse hepatitis virus, and Staphylococcus aureus.

Results

Among the 414 miRNA candidates identified by a real-time PCR array, 71 were found to be up-regulated in the plasma of T. gondii infected mice. Three of those miRNAs (mmu-miR-712-3p, mmu-miR-511-5p and mmu-miR-217-5p) were prominently expressed in mice infected by both the RH and ME49 strains of T. gondii. Additionally, the elevated expression of these miRNAs was Toxoplasma-specific.

Conclusions

The levels of the three miRNAs, mmu-miR-712-3p, mmu-miR-511-5p and mmu-miR-217-5p miRNAs, were found specifically up-regulated in plasma of mice after T. gondii infection.

Activated microglia contribute to neuronal apoptosis in Toxoplasmic encephalitis

BACKGROUND

A plethora of evidence shows that activated microglia play a critical role in the pathogenesis of the central nervous system (CNS). Toxoplasmic encephalitis (TE) frequently occurs in HIV/AIDS patients. However, knowledge remains limited on the contributions of activated microglia to the pathogenesis of TE.

METHODS

A murine model of reactivated encephalitis was generated in a latent infection with Toxoplasma gondii induced by cyclophosphamide. The neuronal apoptosis in the CNS and the profile of pro-inflammatory cytokines were assayed in both in vitro and in vivo experiments.

RESULTS

Microglial cells were found to be activated in the cortex and hippocampus in the brain tissues of mice. The in vivo expression of interleukin-6 (IL-6), interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and inducible nitric oxide synthase (iNOS) were up-regulated in TE mice, and accordingly, the neuronal apoptosis was significantly increased. The results were positively correlated with those of the in vitro experiments. Additionally,apoptosis of the mouse neuroblastoma type Neuro2a (N2a) remarkably increased when the N2a was co-cultured in transwell with microglial cells and Toxoplasma tachyzoites. Both in vivo and in vitro experiments showed that minocycline (a microglia inhibitor) treatment notably reduced microglial activation and neuronal apoptosis.

CONCLUSIONS

Activated microglia contribute to neuronal apoptosis in TE and inhibition of microglia activation might represent a novel therapeutic strategy of TE.

Toxoplasma gondii inhibits apoptosis via a novel STAT3-miR-17-92-Bim pathway in macrophages

In order to accomplish their life cycles, intracellular pathogens, including the apicomplexan Toxoplasma gondii, subvert the innate apoptotic response of infected host cells. However, the precise mechanisms of parasite interference with the apoptotic pathway remain unclear. MicroRNAs (miRNAs) regulate gene expression at the posttranscriptional level. Using T. gondii strain TgCtwh3, which was isolated from felids and possesses the predominant genotype China 1 (ToxoDB(#)9) in China, we analyzed the miRNA expression profile of human macrophages challenged with TgCtwh3. The results showed that miR-17-92 miRNA expression was significantly increased and Bim was decreased in TgCtwh3-infected cells. Database analysis of miR-17-92 miRNAs revealed the potential binding sites in the 3'UTR of Bim, one of the crucial effectors of pro-apoptosis. Furthermore, we demonstrated that the promoter of the miR-17-92 gene cluster which encodes miRNAs was transactivated through the promoter binding of the STAT3 following TgCtwh3 infection. Taken together, we describe a novel STAT3-miR-17-92-Bim pathway, thus providing a mechanistic explanation for inhibition of apoptosis of host cells following Toxoplasma infection.