MicroRNA-155 is required for Mycobacterium bovis BCG-mediated apoptosis of macrophages

miRNA-Mediated Fine Regulation of TLR-Induced M1 Polarization

Macrophage polarization to the M1 spectrum is induced by bacterial cell wall components through stimulation of Toll-like family (TLR) receptors. By orchestrating the expression of relevant mediators of the TLR cascade, as well as associated pathways and feedback loops, macrophage polarization is coordinated to ensure an appropriate immune response. This is central to the successful control of pathogens and the maintenance of health. Macrophage polarization is known to be modulated at both the transcriptional and post-transcriptional levels. In recent years, the miRNA-based post-transcriptional regulation of M1 polarization has received increasing attention from the scientific community. Comparative studies have shown that TLR stimulation alters the miRNA profile of macrophages and that macrophages from the M1 or the M2 spectrum differ in terms of miRNAs expressed. Simultaneously, miRNAs are considered critical post-transcriptional regulators of macrophage polarization. In particular, miRNAs are thought to play a regulatory role in the switch between the early proinflammatory response and the resolution phase. In this review, we will discuss the current state of knowledge on the complex interaction of transcriptional and post-transcriptional regulatory mechanisms that ultimately determine the functionality of macrophages.

MicroRNA-155, a double-blade sword regulator of innate tuberculosis immunity

Tuberculosis (TB) is a chronic, life-threatening disease caused by unusual facultative intracellular bacteria, Mycobacterium tuberculosis. This bacterium has unique resistance to many antimicrobial agents and has become a major global health concern due to emerging multidrug-resistant strains. Additionally, it has developed multiple schemes to exploit host immune signaling and establish long-term survival within host tissues. Thus, understanding the pathways that govern the crosstalk between the bacterium and the immune system could provide a new avenue for therapeutic interventions. MicroRNAs (miRs) are short, noncoding, and regulator RNA molecules that control the expression of cellular genes by targeting their mRNAs post-transcriptionally. MiR-155 is one of the most crucial miR in shaping the host immune defenses against M. tuberculosis. MiR-155 is remarkably downregulated in patients with clear clinical TB symptoms in comparison with latently infected patients and/or healthy individuals, thereby implicating its role in controlling M. tuberculosis infection. However, functional probing of miR-155 suggests dual effects in regulating the host's innate defenses in response to mycobacterial infection. This review provides comprehensive knowledge and future perspectives regarding complex signaling pathways that mediated miR-155 expression during M. tuberculosis infections. Moreover, miR-155-targeting signaling orchestrates inflammatory mediators' production, apoptosis, and autophagy.

Mycobacterium tuberculosis: Pathogenesis and therapeutic targets

Tuberculosis (TB) remains a significant public health concern in the 21st century, especially due to drug resistance, coinfection with diseases like immunodeficiency syndrome (AIDS) and coronavirus disease 2019, and the lengthy and costly treatment protocols. In this review, we summarize the pathogenesis of TB infection, therapeutic targets, and corresponding modulators, including first-line medications, current clinical trial drugs and molecules in preclinical assessment. Understanding the mechanisms of Mycobacterium tuberculosis (Mtb) infection and important biological targets can lead to innovative treatments. While most antitubercular agents target pathogen-related processes, host-directed therapy (HDT) modalities addressing immune defense, survival mechanisms, and immunopathology also hold promise. Mtb's adaptation to the human host involves manipulating host cellular mechanisms, and HDT aims to disrupt this manipulation to enhance treatment effectiveness. Our review provides valuable insights for future anti-TB drug development efforts.

Differential Expression of miR-146 and miR-155 in Active and Latent Tuberculosis Infection

Background

Tuberculosis (TB) is one of the leading causes of death worldwide. Besides, one-third of the world population is infected with Mycobacterium tuberculosis (MTB) while staying clinically asymptomatic; the situation is called latent TB infection (LTBI). MiR-21, miR-31, miR-146a, and miR-155 play an important role in many immune and inflammatory pathways. In the present study the expression levels of MiR-21, miR-31, miR-146a, and miR-155 in peripheral blood mononuclear cells (PBMCs) from patients with active TB, latently infected individuals (LTBI), and healthy controls (HC) were investigated. Participants were recruited at the Bouali Hospital, Zahedan University of Medical Sciences, Zahedan, Iran from 2010 to 2011.

Methods

PBMCs were stimulated with PPD before RNA extraction. TaqMan RT-qPCR assay was used to analyze the expression levels of miRNAs.

Results

The results indicated no significant differences in the expression of miR-21 and miR-31 between different groups; however, in patients with active TB, the expression of miR-21 (P=0.03) and miR-31 (P=0.04) were significantly increased after stimulation with PPD compared to the unstimulated condition. The expression of miR-146 in response to PPD in both LTBI (P=0.02) and TB (P=0.03) groups compared to the HC group was increased. No significant differences were found in the expression level of miR-155 in response to PPD between LTBI and HC groups. However, the fold change was significantly higher in the TB group in comparison with the HC (P=0.03) and LTBI (P=0.05) groups.

Conclusion

The results confirm the main role of miR-146 and miR-155 in TB infection and suggest a role for miR-146 and miR-155 as infection and activation markers in tuberculosis infection, respectively.

Saliva microRNA Profile in Children with and without Severe SARS-CoV-2 Infection

Severe acute respiratory syndrome corona virus 2 (SARS-CoV-2) may impair immune modulating host microRNAs, causing severe disease. Our objectives were to determine the salivary miRNA profile in children with SARS-CoV-2 infection at presentation and compare the expression in those with and without severe outcomes. Children <18 years with SARS-CoV-2 infection evaluated at two hospitals between March 2021 and February 2022 were prospectively enrolled. Severe outcomes included respiratory failure, shock or death. Saliva microRNAs were quantified with RNA sequencing. Data on 197 infected children (severe = 45) were analyzed. Of the known human miRNAs, 1606 (60%) were measured and compared across saliva samples. There were 43 miRNAs with ≥2-fold difference between severe and non-severe cases (adjusted p-value < 0.05). The majority (31/43) were downregulated in severe cases. The largest between-group differences involved miR-4495, miR-296-5p, miR-548ao-3p and miR-1273c. These microRNAs displayed enrichment for 32 gene ontology pathways including viral processing and transforming growth factor beta and Fc-gamma receptor signaling. In conclusion, salivary miRNA levels are perturbed in children with severe COVID-19, with the majority of miRNAs being down regulated. Further studies are required to validate and determine the utility of salivary miRNAs as biomarkers of severe COVID-19.

MicroRNAs induced by Listeria monocytogenes and their role in cells

Listeria monocytogenes (Lm) causes abortions at high rates and threatens newborns' lives. Also, the elderly and immunocompromised individuals are particularly vulnerable neurologically. The bacterium exerts its pathogenesis intracellularly by manipulating cell organs. It manipulates nucleus elements, microRNAs (miRNAs), in order to increase survival and evade immunity. miRNAs are small non-coding RNAs that degrade gene expression post-transcriptionally. Any alteration to the expression of miRNAs affects various cascades in cells, especially immunity-related responses. Thus, utilizing miRNAs as a novel therapeutic agent not only restricts infection but enhances immunity reactions. This review provides an overview of miRNAs in listeriosis, their role in cells, and their prospects as therapy.

Different modalities of host cell death and their impact on Mycobacterium tuberculosis infection

Mycobacterium tuberculosis (Mtb) is the pathogen that causes tuberculosis (TB), a leading infectious disease of humans worldwide. One of the main histopathological hallmarks of TB is the formation of granulomas comprised of elaborately organized aggregates of immune cells containing the pathogen. Dissemination of Mtb from infected cells in the granulomas due to host and mycobacterial factors induces multiple cell death modalities in infected cells. Based on molecular mechanism, morphological characteristics, and signal dependency, there are two main categories of cell death: programmed and nonprogrammed. Programmed cell death (PCD), such as apoptosis and autophagy, is associated with a protective response to Mtb by keeping the bacteria encased within dead macrophages that can be readily phagocytosed by arriving in uninfected or neighboring cells. In contrast, non-PCD necrotic cell death favors the pathogen, resulting in bacterial release into the extracellular environment. Multiple types of cell death in the PCD category, including pyroptosis, necroptosis, ferroptosis, ETosis, parthanatos, and PANoptosis, may be involved in Mtb infection. Since PCD pathways are essential for host immunity to Mtb, therapeutic compounds targeting cell death signaling pathways have been experimentally tested for TB treatment. This review summarizes different modalities of Mtb-mediated host cell deaths, the molecular mechanisms underpinning host cell death during Mtb infection, and its potential implications for host immunity. In addition, targeting host cell death pathways as potential therapeutic and preventive approaches against Mtb infection is also discussed.

MicroRNAs as immune regulators and biomarkers in tuberculosis

Tuberculosis (TB), which is caused by Mycobacterium tuberculosis (Mtb), is one of the most lethal infectious disease worldwide, and it greatly affects human health. Some diagnostic and therapeutic methods are available to effectively prevent and treat TB; however, only a few systematic studies have described the roles of microRNAs (miRNAs) in TB. Combining multiple clinical datasets and previous studies on Mtb and miRNAs, we state that pathogens can exploit interactions between miRNAs and other biomolecules to avoid host mechanisms of immune-mediated clearance and survive in host cells for a long time. During the interaction between Mtb and host cells, miRNA expression levels are altered, resulting in the changes in the miRNA-mediated regulation of host cell metabolism, inflammatory responses, apoptosis, and autophagy. In addition, differential miRNA expression can be used to distinguish healthy individuals, patients with TB, and patients with latent TB. This review summarizes the roles of miRNAs in immune regulation and their application as biomarkers in TB. These findings could provide new opportunities for the diagnosis and treatment of TB.

Immune regulation and emerging roles of noncoding RNAs in Mycobacterium tuberculosis infection

Tuberculosis, caused by Mycobacterium tuberculosis, engenders an onerous burden on public hygiene. Congenital and adaptive immunity in the human body act as robust defenses against the pathogens. However, in coevolution with humans, this microbe has gained multiple lines of mechanisms to circumvent the immune response to sustain its intracellular persistence and long-term survival inside a host. Moreover, emerging evidence has revealed that this stealthy bacterium can alter the expression of demic noncoding RNAs (ncRNAs), leading to dysregulated biological processes subsequently, which may be the rationale behind the pathogenesis of tuberculosis. Meanwhile, the differential accumulation in clinical samples endows them with the capacity to be indicators in the time of tuberculosis suffering. In this article, we reviewed the nearest insights into the impact of ncRNAs during Mycobacterium tuberculosis infection as realized via immune response modulation and their potential as biomarkers for the diagnosis, drug resistance identification, treatment evaluation, and adverse drug reaction prediction of tuberculosis, aiming to inspire novel and precise therapy development to combat this pathogen in the future.

Cromileptes altivelis microRNA Transcriptome Analysis upon Nervous Necrosis Virus (NNV) Infection and the Effect of cal-miR-155 on Cells Apoptosis and Virus Replication

MicroRNAs (miRNAs) could regulate various biological processes. Nervous necrosis virus (NNV) is one of the primary germs of the Humpback grouper (Cromileptes altivelis), a commercial fish of great importance for Asian aquaculture. However, there is limited available information on the host-virus interactions of C. altivelis. miRNAs have been shown to play key roles in the host response to infection by a variety of pathogens. To better understand the regulatory mechanism of miRNAs, we constructed miRNA transcriptomes and identified immune-related miRNAs of C. altivelis spleen in response to NNV infection. Reads from the three libraries were mapped onto the Danio rerio reference genome. As a result, a total of 942 mature miRNAs were determined, with 266 known miRNAs and 676 novel miRNAs. Among them, thirty-two differentially expressed miRNAs (DEmiRs) were identified compared to the PBS control. These DEmiRs were targeted on 895 genes, respectively, by using miRanda v3.3a. Then, 14 DEmiRs were validated by qRT-PCR and showed consistency with those obtained from high-throughput sequencing. In order to study the relationship between viral infection and host miRNA, a cell line from C. altivelis brain (CAB) was used to examine the expressions of five known DEmiRs (miR-132-3p, miR-194a, miR-155, miR-203b-5p, and miR-146) during NNV infection. The results showed that one miRNA, cal-miRNA-155, displayed significantly increased expression in response to the virus infection. Subsequently, it was proved that overexpression of cal-miR-155 enhanced cell apoptosis with or without NNV infection and inhibited virus replication in CAB cells. Oppositely, the cal-miRNA-155 inhibitor markedly suppressed apoptosis in CAB cells. The results of the apoptosis-related genes mRNA expression also showed the regulation of cal-miR-155 on the apoptosis process in CAB cells. These findings verify that miR-155 might exert a function as a pro-apoptotic factor in reply to NNV stimulation in CAB cells and help us further study the molecular mechanisms of the pathogenesis of NNV in C. altivelis.

Progressive Host-Directed Strategies to Potentiate BCG Vaccination Against Tuberculosis

The pursuit to improve the TB control program comprising one approved vaccine, M. bovis Bacille Calmette-Guerin (BCG) has directed researchers to explore progressive approaches to halt the eternal TB pandemic. Mycobacterium tuberculosis (M.tb) was first identified as the causative agent of TB in 1882 by Dr. Robert Koch. However, TB has plagued living beings since ancient times and continues to endure as an eternal scourge ravaging even with existing chemoprophylaxis and preventive therapy. We have scientifically come a long way since then, but despite accessibility to the standard antimycobacterial antibiotics and prophylactic vaccine, almost one-fourth of humankind is infected latently with M.tb. Existing therapeutics fail to control TB, due to the upsurge of drug-resistant strains and increasing incidents of co-infections in immune-compromised individuals. Unresponsiveness to established antibiotics leaves patients with no therapeutic possibilities. Hence the search for an efficacious TB immunization strategy is a global health priority. Researchers are paving the course for efficient vaccination strategies with the radically advanced operation of core principles of protective immune responses against M.tb. In this review; we have reassessed the progression of the TB vaccination program comprising BCG immunization in children and potential stratagems to reinforce BCG-induced protection in adults.

Andrographolide Suppresses Pyroptosis in Mycobacterium tuberculosis-Infected Macrophages via the microRNA-155/Nrf2 Axis

Tuberculosis (TB) remains a leading threat to public health worldwide with Mycobacterium tuberculosis (Mtb) infections causing long-term abnormal and excessive inflammatory responses, which in turn lead to lung damage and fibrosis, and ultimately death. Host-directed therapy (HDT) has been shown to be an effective anti-TB strategy in the absence of effective anti-TB drugs. Here, we used an in vitro macrophage model of Mtb infection to evaluate the effects of andrographolide (Andro), extracted from Andrographis paniculata, on pyroptosis in Mtb-infected macrophages. We evaluated the molecular mechanisms underlying these outcomes. These evaluations revealed that Andro downregulated the expression of proinflammatory miR-155-5p, which then promoted the expression of Nrf2 to suppress pyroptosis in Mtb-infected macrophages. Further study also demonstrated that siNrf2 could attenuate the inhibitory effect of Andro on TXNIP, validating our mechanistic studies. Thus, our data suggest that Andro may be a potential candidate adjuvant drug for anti-TB therapy as it inhibits pyroptosis in Mtb-infected macrophages, potentially improving clinical outcomes.

MicroRNAs as Regulators of Phagocytosis

MicroRNAs (miRNAs) are short non-coding RNAs that regulate gene expression and thus act as important regulators of cellular phenotype and function. As their expression may be dysregulated in numerous diseases, they are of interest as biomarkers. What is more, attempts of modulation of some microRNAs for therapeutic reasons have been undertaken. In this review, we discuss the current knowledge regarding the influence of microRNAs on phagocytosis, which may be exerted on different levels, such as through macrophages polarization, phagosome maturation, reactive oxygen species production and cytokines synthesis. This phenomenon plays an important role in numerous pathological conditions.

Pathophysiology of Atherosclerosis

Atherosclerosis is the main risk factor for cardiovascular disease (CVD), which is the leading cause of mortality worldwide. Atherosclerosis is initiated by endothelium activation and, followed by a cascade of events (accumulation of lipids, fibrous elements, and calcification), triggers the vessel narrowing and activation of inflammatory pathways. The resultant atheroma plaque, along with these processes, results in cardiovascular complications. This review focuses on the different stages of atherosclerosis development, ranging from endothelial dysfunction to plaque rupture. In addition, the post-transcriptional regulation and modulation of atheroma plaque by microRNAs and lncRNAs, the role of microbiota, and the importance of sex as a crucial risk factor in atherosclerosis are covered here in order to provide a global view of the disease.

MicroRNA-155 expression with Brucella infection in vitro and in vivo and decreased serum levels of MicroRNA-155 in patients with brucellosis

Infection with Brucella is characterized by the inhibition of host immune responses. MicroRNA-155 (miR-155) has been implicated in the immune response to many diseases. In this study, its expression during Brucella 16M infection of macrophages and mice was analyzed. Expression of miR-155 was significantly induced in macrophages at 24 h post infection. Further, an analysis of infected mice showed that miR-155 was inhibited at 7 and 14 days but induced at 28 days. Interestingly, this trend in induction or inhibition was reversed at 7 and 14 days in 16M△virB-infected mice. This suggested that decreased expression of miR-155 at an early stage of infection was dependent on intracellular replication. In humans with brucellosis, serum levels of miR-155 were significantly decreased compared to those in individuals without brucellosis and healthy volunteers. Significant correlations were observed between serum level of miR-155 and serum anti-Brucella antibody titers and the sweating symptom. This effect suggests that Brucella interferes with miR-155-regulated immune responses via a unique mechanism. Taken together, data from this study indicate that Brucella infection affects miR-155 expression and that human brucellosis patients show decreased serum levels of miR-155.

miRNA-Mediated Priming of Macrophage M1 Differentiation Differs in Gram-Positive and Gram-Negative Settings

A proper regulation of macrophage polarization is essential for the organism's health and pathogen control. Differentiation control is known to occur at the transcriptional as well as the posttranscriptional levels. The mechanisms involved, however, have not yet been fully elucidated. In this study, we co-cultured macrophages with viable Gram-positive and Gram-negative bacteria to mimic macrophage differentiation to the M1-like type in an inflammatory milieu. We found that Gram-positive stimulation resulted in increased expressions of miR-7a-5p, miR-148a-3p, miR-155-5p, and miR-351-5p. Of note, these miRNAs were found to target inhibitory mediators of the Rac1-PI3K-Akt pathway and the MyD88-dependent pathway. In contrast, Gram-negative stimulation-induced downregulation of miR-9-5p, miR-27b-3p, miR-93-5p, and miR-106b-5p is known to target key members of the Rac1-PI3K-Akt pathway and the MyD88-dependent pathway. These results, taken together, point to a fine-tuning of macrophage polarization by TLR-induced changes in macrophage miRNA profiles. Here, the miRNA-mediated priming of M1 differentiation seems to differ in the Gram-positive and Gram-negative settings in terms of the mechanism and miRNAs involved.

Mycobacterium tuberculosis ESAT6 modulates host innate immunity by downregulating miR-222-3p target PTEN

Tuberculosis (TB) remains a major cause of mortality and morbidity worldwide, and it is instant to discover novel anti-TB drugs due to the rapidly growing drug-resistance TB. Mycobacterium tuberculosis (Mtb) secreted effector ESAT6 plays a critical role in modulation miRNAs to regulate host defense mechanisms during Mtb infection, it can be a possible target for new tuberculosis drugs. The non-tuberculous mycobacteria Mycobacterium smegmatis (M. smegmatis) and Mtb have high gene homology but no pathogenicity. We used ESAT6 to interfere with macrophages or mice infected by M. smegmatis and determined that it enhanced the survival rate of bacteria and regulated miR-222-3p target PTEN. Expression of miR-222-3p reduced and PTEN enhanced with the progression of macrophages infected by M. smegmatis with ESAT6 co-incubation. MiR-222-3p overexpression diminished M. smegmatis survival and upregulated proinflammatory cytokines. VO-Ohpic trihydrate (PTEN inhibitor) reduced M. smegmatis survival and upregulated proinflammatory cytokines in vivo and in vitro, and VO-Ohpic trihydrate reversed the tissue damage of mouse organs caused by ESAT6. These results uncover an ESAT6 dependent role for miR-222-3p and its target PTEN in regulating host immune responses to bacterial infection and may provide a potential site for the development of anti-tuberculosis drugs that specifically antagonize the virulence of ESAT6.

Circ_0001490/miR-579-3p/FSTL1 axis modulates the survival of mycobacteria and the viability, apoptosis and inflammatory response in Mycobacterium tuberculosis-infected macrophages

BACKGROUND

Macrophages play an important role in the host immune response against mycobacterial infection, and this process is regulated by various factors, including circular RNAs (circRNAs). We intended to explore the role of circ_0001490 in tuberculosis (TB) using Mycobacterium tuberculosis (M.tb)-infected THP-1 macrophages.

METHODS

Real-time quantitative polymerase chain reaction (RT-qPCR) and Western blot assay were conducted to measure RNA and protein expression, respectively. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was conducted to analyze the viability of THP-1 macrophages. Flow cytometry was performed to analyze the apoptosis rate of THP-1 macrophages. Enzyme-linked immunosorbent assay (ELISA) was conducted to assess the release of inflammatory cytokines. Colony-forming unit (CFU) assay was conducted to analyze the survival of M.tb in THP-1 macrophages. Intermolecular target interaction was verified by dual-luciferase reporter assay and RNA immunoprecipitation (RIP) assay.

RESULTS

Circ_0001490 expression was down-regulated in the serum samples of TB patients and M.tb-infected THP-1 macrophages. Circ_0001490 overexpression suppressed M.tb survival and promoted the viability and inflammatory response of THP-1 macrophages. Circ_0001490 interacted with microRNA-579-3p (miR-579-3p), and circ_0001490 overexpression-induced protective effects in M.tb-infected THP-1 macrophages were largely overturned by the overexpression of miR-579-3p. miR-579-3p interacted with the 3' untranslated region (3'UTR) of follistatin-like protein 1 (FSTL1). FSTL1 silencing largely overturned miR-579-3p knockdown-induced effects in M.tb-infected THP-1 macrophages. Circ_0001490 acted as miR-579-3p sponge to up-regulate FSTL1 in THP-1 macrophages.

CONCLUSION

In conclusion, our results demonstrated that circ_0001490 suppressed M.tb survival and promoted the viability and inflammatory response of M.tb-infected THP-1 macrophages partly by regulating miR-579-3p/FSTL1 axis.

Pre-existing mycobacterial infection modulates Candida albicans-driven pyroptosis

Active tuberculosis patients are at high risk of coinfection with opportunistic fungal pathogen Candida albicans. However, the molecular mechanisms that orchestrate pathogenesis of Mycobacterium tuberculosis (Mtb)-C. albicans coinfection remain elusive. In the current study, we utilize a mouse model to demonstrate that Mtb promotes a macrophage environment that is conducive for C. albicans survival. Mtb-dependent protein kinase Cζ-WNT signalling axis induces expression of an E3 ubiquitin ligase, constitutive photomorphogenesis protein 1 (COP1). A secondary infection of C. albicans in such Mtb-infected macrophages causes COP1 to mediate the proteasomal degradation of interferon regulatory factor 9 (IRF9), a cardinal factor that we identified to arbitrate an inflammatory programmed cell death, pyroptosis. In vivo experiments mimicking a pre-existing Mtb infection demonstrate that inhibition of pyroptosis in mice results in increased C. albicans burden and aberrant lung tissue architecture, leading to increased host mortality. Together, our study reveals the crucial role of pyroptosis regulation for manifesting a successful C. albicans-Mtb coinfection.

Optimization of BCG Therapy Targeting Neutrophil Extracellular Traps, Autophagy, and miRNAs in Bladder Cancer: Implications for Personalized Medicine

Bladder cancer (BC) is the ninth most common cancer and the thirteenth most common cause of mortality worldwide. Bacillus Calmette Guerin (BCG) instillation is a common treatment option for BC. BCG therapy is associated with the less adversary effects, compared to chemotherapy, radiotherapy, and other conventional treatments. BCG could inhibit the progression and recurrence of BC by triggering apoptosis pathways, arrest cell cycle, autophagy, and neutrophil extracellular traps (NETs) formation. However, BCG therapy is not efficient for metastatic cancer. NETs and autophagy were induced by BCG and help to suppress the growth of tumor cells especially in the primary stages of BC. Activated neutrophils can stimulate autophagy pathway and release NETs in the presence of microbial pathogenesis, inflammatory agents, and tumor cells. Autophagy can also regulate NETs formation and induce production of reactive oxygen species (ROS) and NETs. Moreover, miRNAs are important regulator of gene expression. These small non-coding RNAs are also considered as an essential factor to control the levels of tumor development. However, the interaction between BCG and miRNAs has not been well-understood yet. Therefore, the present study discusses the roles of miRNAs in regulations of autophagy and NETs formation in BCG therapy in the treatment of BC. The roles of autophagy and NETs formation in BC treatment and efficiency of BCG are also discussed.

MicroRNA-142-3p inhibits autophagy and promotes intracellular survival of Mycobacterium tuberculosis by targeting ATG16L1 and ATG4c

BACKGROUND

Mycobacterium tuberculosis (M. tuberculosis), which parasitizes host macrophages and lead to cellular immunologic responses, such as autophagy and apoptosis. Several studies had indicated that autophagy played important roles in alleviating intracellular survival of M. tuberculosis by accelerating the maturation of phagosome. Previously, we found miR-142-3p was significantly down-regulated in the macrophages after infection with M. tuberculosis. However, the role of miR-142-3p in the regulation of autophagy and M. tuberculosis survival is elusive.

METHODS

Bioinformatics analysis was used to obtain target genes of miR-142-3p; the binding sites of ATG16L1 and ATG4c were further confirmed with dual luciferase reporter assay; RAW264.7 cells were infected with H37Ra and the expression of miR-142-3p was measured by qRT-PCR; the autophagic marker protein was detected by western blot as well as immunofluorescence microscopy and transmission electron microscopes analysis.

RESULTS

Overexpression of miR-142-3p significantly inhibited H37Ra-induced activation of autophagy, blocked the maturation of phagosome in macrophages and promoted M. tuberculosis survival in macrophages. Furthermore, miR-142-3p negatively-regulated expression of ATG16L1 and ATG4c by directly targeting its 3'-UTR, and meaningfully abated the level of autophagy.

CONCLUSION

These findings suggested that miR-142-3p inhibited M. tuberculosis-induced activation of autophagy and promoted H37Ra survival in RAW264.7 cells by targeting ATG16L1 and ATG4c.

Inhibition of the miR-155 and protein prenylation feedback loop alleviated acute graft-versus-host disease through regulating the balance between T helper 17 and Treg cells

MicroRNA-155(miR-155) and protein prenylation have been reported to participate in acute graft-versus-host disease (aGVHD) through modulating T lymphocyte differentiation, however the mechanism remains elusive. In this study, we found that the expression of miR-155 and protein prenyltransferases in peripheral blood T lymphocytes of aGVHD mice was significantly increased. Suppression of miR-155 by antagomir-155 could remarkably reduce prenyltransferases mRNA and protein expression in T lymphocytes of aGVHD mice. Conversely, prenyltransferase inhibitors significantly reduced the level of miR-155. Inhibition of this feedback loop of miR-155 and protein prenylation in aGVHD mice led to improved survival and lower aGVHD histopathology scores and significantly induced T cell deficient differentiation towards T helper 17 (Th17) cells and titled differentiation towards CD4⁺CD25^hi regulatory T (Treg) cells. Furthermore, the immunoregulatory effects and protection from aGVHD of prenyltransferase inhibitors could be reversed by the addition of miR-155. The dual treatment of prenylation inhibitors and antagomir-155 showed synergistic effects on T polarization and protection from aGVHD. Consistent with the in vivo changes, inhibition of this feedback loop of miR-155 and protein prenylation affected Th17 and Treg cell polarization in vitro. Our data suggest that miR-155 and protein prenylation may constitute a feedback loop that amplifies immune and inflammatory responses in subjects with aGVHD, and they may serve as potential targets for aGVHD prophylaxis and treatment.

Targeted RNA-Seq Reveals the M. tuberculosis Transcriptome from an In Vivo Infection Model

Simple Summary

High-throughput sequencing techniques such as RNA-seq allow a more detailed characterization of the gene expression profile during in vivo infections. However, using this strategy for intracellular pathogens such as Mycobacterium tuberculosis (Mtb) entails technical limitations. Some authors have resorted to flow cytometers to separate infected cells or significantly increase sequencing depth to obtain pathogens’ gene expression. However, these options carry additional expenses in specialized equipment. We propose an experimental protocol based on differential cell lysis and a probe-based ribosomal depletion to determine the gene expression of Mtb and its host during in vivo infection. This method allowed us to increase the number of observed expressed genes from 13 using a traditional RNA-seq approach to 702. In addition, we observed the expression of genes essential for establishing the infection, codifying proteins such as PE-PGRS, lipoproteins lppN and LpqH, and three ncRNAs (small RNA MTS2823, transfer-messenger RNA RF00023, and ribozyme RF00010). We believe our method represents a valuable alternative to current RNA-seq approaches to study host–pathogen interactions and will help explore host–pathogen mechanisms in tuberculosis and other similar models of intracellular infections.

Abstract

The study of host-pathogen interactions using in vivo models with intracellular pathogens like Mycobacterium tuberculosis (Mtb) entails technical limitations, such as: (i) Selecting an efficient differential lysis system to enrich the pathogen cells; (ii) obtaining sufficient high-quality RNA; and (iii) achieving an efficient rRNA depletion. Thus, some authors had used flow cytometers to separate infected cells or significantly increase the sequencing depth of host–pathogen RNA libraries to observe the pathogens’ gene expression. However, these options carry additional expenses in specialized equipment typically not available for all laboratories. Here, we propose an experimental protocol involving differential cell lysis and a probe-based ribosomal depletion to determine the gene expression of Mtb and its host during in vivo infection. This method increased the number of observed pathogen-expressed genes from 13 using the traditional RNA-seq approach to 702. After eliminating rRNA reads, we observed that 61.59% of Mtb sequences represented 702 genes, while 38.41% represented intergenic regions. Some of the most expressed genes codified for IS1081 (Rv2512c) transposase and eight PE-PGRS members, such as PGRS49 and PGRS50. As expected, a critical percent of the expressed genes codified for secreted proteins essential for infection, such as PE68, lppN, and LpqH. Moreover, three Mtb ncRNAs were highly expressed (small RNA MTS2823, transfer-messenger RNA RF00023, and ribozyme RF00010). Many of the host-expressed genes were related to the inflammation process and the expression of surfactant proteins such as the Sftpa and Sftpc, known to bind Mtb to alveolar macrophages and mi638, a microRNA with no previous associations with pulmonary diseases. The main objective of this study is to present the method, and a general catalog of the Mtb expressed genes at one point of the in vivo infection. We believe our method represents a different approach to the existing ones to study host–pathogen interactions in tuberculosis and other similar intracellular infections, without the necessity of specialized equipment.

Epigenetic code during mycobacterial infections: therapeutic implications for tuberculosis

Epigenetics involves changing the gene function without any change in the sequence of the genes. In the case of tuberculosis (TB) infections, the bacilli, Mycobacterium tuberculosis (M.tb), uses epigenetics as a tool to protect itself from the host immune system. TB is a deadly disease-causing maximum death per year due to a single infectious agent. In the case of TB, there is an urgent need for novel host-directed therapies which can effectively target the survival and long-term persistence of the bacteria without developing drug resistance in the bacterial strains while also reducing the duration and toxicity associated with the mainstream anti-TB drugs. Recent studies have suggested that TB infection has a significant effect on the host epigenome thereby manipulating the host immune response in the favor of the pathogen. M.tb alters the activation status of key genes involved in the immune response against TB to promote its survival and subvert the antibacterial strategies of the host. These changes are reversible and can be exploited to design very efficient host-directed therapies to fight against TB. This review has been written with the purpose of discussing the role of epigenetic changes in TB pathogenesis and the therapeutic approaches involving epigenetics, which can be utilized for targeting the pathogen.

MicroRNA-155 Modulates Macrophages' Response to Non-Tuberculous Mycobacteria through COX-2/PGE2 Signaling

Non-tuberculous mycobacteria (NTM) have been recognized as a causative agent of various human diseases, including severe infections in immunocompromised patients, such as people living with HIV. The most common species identified is the Mycobacterium avium-intracellulare complex (MAI/MAC), accounting for a majority of infections. Despite abundant information detailing the clinical significance of NTM, little is known about host–pathogen interactions in NTM infection. MicroRNAs (miRs) serve as important post-transcriptional regulators of gene expression. Using a microarray profile, we found that the expression of miR-155 and cyclo-oxygenase 2 (COX-2) is significantly increased in bone-marrow-derived macrophages from mice and human monocyte-derived macrophages from healthy volunteers that are infected with NTM. Antagomir against miR-155 effectively suppressed expression of COX-2 and reduced Prostaglandin E₂(PGE2) secretion, suggesting that COX-2/PGE2 expression is dependent on miR-155. Mechanistically, we found that inhibition of NF-κB activity significantly reduced miR-155/COX-2 expression in infected macrophages. Most importantly, blockade of COX-2, E-prostanoid receptors (EP2 and EP4) enhanced killing of MAI in macrophages. These findings provide novel mechanistic insights into the role of miR-155/COX-2/PGE2 signalling and suggest that induction of these pathways enhances survival of mycobacteria in macrophages. Defining host–pathogen interactions can lead to novel immunomodulatory therapies for NTM infections which are difficult to treat.

Monocyte and Macrophage miRNA: Potent Biomarker and Target for Host-Directed Therapy for Tuberculosis

The end TB strategy reinforces the essentiality of readily accessible biomarkers for early tuberculosis diagnosis. Exploration of microRNA (miRNA) and pathway analysis opens an avenue for the discovery of possible therapeutic targets. miRNA is a small, non-coding oligonucleotide characterized by the mechanism of gene regulation, transcription, and immunomodulation. Studies on miRNA define their importance as an immune marker for active disease progression and as an immunomodulator for innate mechanisms, such as apoptosis and autophagy. Monocyte research is highly advancing toward TB pathogenesis and biomarker efficiency because of its innate and adaptive response connectivity. The combination of monocytes/macrophages and their relative miRNA expression furnish newer insight on the unresolved mechanism for Mycobacterium survival, exploitation of host defense, latent infection, and disease resistance. This review deals with miRNA from monocytes, their relative expression in different disease stages of TB, multiple gene regulating mechanisms in shaping immunity against tuberculosis, and their functionality as biomarker and host-mediated therapeutics. Future collaborative efforts involving multidisciplinary approach in various ethnic population with multiple factors (age, gender, mycobacterial strain, disease stage, other chronic lung infections, and inflammatory disease criteria) on these short miRNAs from body fluids and cells could predict the valuable miRNA biosignature network as a potent tool for biomarkers and host-directed therapy.

The Roles of Host Noncoding RNAs in Mycobacterium tuberculosis Infection

Tuberculosis remains a major health problem. Mycobacterium tuberculosis, the causative agent of tuberculosis, can replicate and persist in host cells. Noncoding RNAs (ncRNAs) widely participate in various biological processes, including Mycobacterium tuberculosis infection, and play critical roles in gene regulation. In this review, we summarize the latest reports on ncRNAs (microRNAs, piRNAs, circRNAs and lncRNAs) that regulate the host response against Mycobacterium tuberculosis infection. In the context of host-Mycobacterium tuberculosis interactions, a broad and in-depth understanding of host ncRNA regulatory mechanisms may lead to potential clinical prospects for tuberculosis diagnosis and the development of new anti-tuberculosis therapies.

DGCR8 deficiency impairs macrophage growth and unleashes the interferon response to mycobacteria

The mycobacterial cell wall glycolipid trehalose-6,6-dimycolate (TDM) activates macrophages through the C-type lectin receptor MINCLE. Regulation of innate immune cells relies on miRNAs, which may be exploited by mycobacteria to survive and replicate in macrophages. Here, we have used macrophages deficient in the microprocessor component DGCR8 to investigate the impact of miRNA on the response to TDM. Deletion of DGCR8 in bone marrow progenitors reduced macrophage yield, but did not block macrophage differentiation. DGCR8-deficient macrophages showed reduced constitutive and TDM-inducible miRNA expression. RNAseq analysis revealed that they accumulated primary miRNA transcripts and displayed a modest type I IFN signature at baseline. Stimulation with TDM in the absence of DGCR8 induced overshooting expression of IFNβ and IFN-induced genes, which was blocked by antibodies to type I IFN. In contrast, signaling and transcriptional responses to recombinant IFNβ were unaltered. Infection with live Mycobacterium bovis Bacille Calmette-Guerin replicated the enhanced IFN response. Together, our results reveal an essential role for DGCR8 in curbing IFNβ expression macrophage reprogramming by mycobacteria.

MicroRNAs in the interaction between host-bacterial pathogens: A new perspective

Gene expression regulation plays a critical role in host-pathogen interactions, and RNAs function is essential in this process. miRNAs are small noncoding, endogenous RNA fragments that affect stability and/or translation of mRNAs, act as major posttranscriptional regulators of gene expression. miRNA is involved in regulating many biological or pathological processes through targeting specific mRNAs, including development, differentiation, apoptosis, cell cycle, cytoskeleton organization, and autophagy. Deregulated microRNA expression is associated with many types of diseases, including cancers, immune disturbances, and infection. miRNAs are a vital section of the host immune response to bacterial-made infection. Bacterial pathogens suppress host miRNA expression for their benefit, promoting survival, replication, and persistence. The role played through miRNAs in interaction with host-bacterial pathogen has been extensively studied in the past 10 years, and knowledge about these staggering molecules' function can clarify the complicated and ambiguous interactions of the host-bacterial pathogen. Here, we review how pathogens prevent the host miRNA expression. We briefly discuss emerging themes in this field, including their role as biomarkers in identifying bacterial infections, as part of the gut microbiota, on host miRNA expression.

MicroRNA research: The new dawn of Tuberculosis

Tuberculosis (TB) is global, one of the most fatal communicable diseases and leading cause of worldwide mortality. One-third of the global population is latently affected by Mtb (Mycobacterium tuberculosis) due to its ability to circumvent the host's immune response for its own survival. MicroRNAs (miRNAs) are small, non-coding RNAs which function at the post-transcriptional level and are critical in fine-tuning immune responses regulating the repertoire of genes expressed in immune cells. Recent studies have established their crucial role against TB. Furthermore, the differential expression pattern of miRNAs has revealed the potential role of miRNAs as biomarkers which could be utilized to differentiate between healthy controls and active TB patients or between active and latent TB. The recent advancements made in the field of miRNA regulation of the host responses against TB, as well as the potential of miRNAs as biomarkers for TB diagnosis are discussed here in this review.

MicroRNA-23a-3p Down-Regulation in Active Pulmonary Tuberculosis Patients with High Bacterial Burden Inhibits Mononuclear Cell Function and Phagocytosis through TLR4/TNF-α/TGF-β1/IL-10 Signaling via Targeting IRF1/SP1

The aim of this study is to explore the role of microRNAs (miR)-21/23a/146a/150/155 targeting the toll-like receptor pathway in active tuberculosis (TB) disease and latent TB infection (LTBI). Gene expression levels of the five miRs and predicted target genes were assessed in peripheral blood mononuclear cells from 46 patients with active pulmonary TB, 15 subjects with LTBI, and 17 non-infected healthy subjects (NIHS). THP-1 cell lines were transfected with miR-23a-3p mimics under stimuli with Mycobacterium TB-specific antigens. Both miR-155-5p and miR-150-5p gene expressions were decreased in the active TB group versus the NIHS group. Both miR-23a-3p and miR-146a-5p gene expressions were decreased in active TB patients with high bacterial burden versus those with low bacterial burden or control group (LTBI + NIHS). TLR2, TLR4, and interleukin (IL)10 gene expressions were all increased in active TB versus NIHS group. MiR-23a-3p mimic transfection reversed ESAT6-induced reduction of reactive oxygen species generation, and augmented ESAT6-induced late apoptosis and phagocytosis, in association with down-regulations of the predicted target genes, including tumor necrosis factor (TNF)-α, TLR4, TLR2, IL6, IL10, Notch1, IL6R, BCL2, TGF-β1, SP1, and IRF1. In conclusion, the down-regulation of miR-23a-3p in active TB patients with high bacterial burden inhibited mononuclear cell function and phagocytosis through TLR4/TNF-α/TGF-β1/IL-10 signaling via targeting IRF1/SP1.

The role of non-coding RNA on macrophage modification in tuberculosis infection

Tuberculosis (TB), a serious disease caused by Mycobacterium tuberculosis (Mtb), remains the world's top infectious killer. It is well-established that TB can circumvent the host's immune response for long-term survival. Macrophages serve as the major host cells for TB growth and persistence and their altered functions are critical for the response of the host defense against TB exposure (elimination, latency, reactivation, and bacillary dissemination). Noncoding RNAs are crucial posttranscriptional regulators of macrophage discrimination. Therefore, this review highlights the regulatory mechanism underlying the relationship between noncoding RNAs and macrophages in TB infection, which may facilitate the identification of potential therapeutic targets and effective diagnosis biomarkers for TB disease.

Tuberculosis-Associated MicroRNAs: From Pathogenesis to Disease Biomarkers

Tuberculosis (TB) caused by Mycobacterium tuberculosis is one of the most lethal infectious diseases with estimates of approximately 1.4 million human deaths in 2018. M. tuberculosis has a well-established ability to circumvent the host immune system to ensure its intracellular survival and persistence in the host. Mechanisms include subversion of expression of key microRNAs (miRNAs) involved in the regulation of host innate and adaptive immune response against M. tuberculosis. Several studies have reported differential expression of miRNAs during active TB and latent tuberculosis infection (LTBI), suggesting their potential use as biomarkers of disease progression and response to anti-TB therapy. This review focused on the miRNAs involved in TB pathogenesis and on the mechanism through which miRNAs induced during TB modulate cell antimicrobial responses. An attentive study of the recent literature identifies a group of miRNAs, which are differentially expressed in active TB vs. LTBI or vs. treated TB and can be proposed as candidate biomarkers.

MiRNAs in tuberculosis: Their decisive role in the fate of TB

Tuberculosis (TB) is one of the most lethal global infectious diseases. Despite the availability of much higher levels of technology in health and medicine, tuberculosis still remains a serious global health problem. Mycobacterium tuberculosis has the capacity for prolonged survival inside macrophages by exploiting host metabolic and energy pathways and perturbing autophagy and apoptosis of infected cells. The mechanism(s) underlying this process are not completely understood but evidence suggests that mycobacteria subvert the host miRNA network to enable mycobacterial survival. We present here a comprehensive review on the role of miRNAs in TB immune escape mechanisms and the potential for miRNA-based TB therapeutics. Further validation studies are required to (i) elucidate the precise effect of TB on host miRNAs, (ii) determine the inhibition of mycobacterial burden using miRNA-based therapies and (iii) identify novel miRNA biomarkers that may prove useful in TB diagnosis and treatment monitoring.

MiR-155 promotes interleukin-1β-induced chondrocyte apoptosis and catabolic activity by targeting PIK3R1-mediated PI3K/Akt pathway

Osteoarthritis (OA) is a common joint disease characterized by progressive cartilage degradation, in which elevated chondrocyte apoptosis and catabolic activity play an important role. MicroRNA-155 (miR-155) has recently been shown to regulate apoptosis and catabolic activity in some pathological circumstances, yet, whether and how miR-155 is associated with OA pathology remain unexplored. We report here that miR-155 level is significantly up-regulated in human OA cartilage biopsies and also in primary chondrocytes stimulated by interleukin-1β (IL-1β), a pivotal pro-catabolic factor promoting cartilage degradation. Moreover, miR-155 inhibition attenuates and its overexpression promotes IL-1β-induced apoptosis and catabolic activity in chondrocytes in vitro. We also demonstrate that the PIK3R1 (p85α regulatory subunit of phosphoinositide 3-kinase (PI3K)) is a target of miR-155 in chondrocytes, and more importantly, PIK3R1 restoration abrogates miR-155 effects on chondrocyte apoptosis and catabolic activity. Mechanistically, PIK3R1 positively regulates the transduction of PI3K/Akt pathway, and a specific Akt inhibitor reverses miR-155 effects on promoting chondrocyte apoptosis and catabolic activity, phenocopying the results obtained via PIK3R1 knockdown, hence establishing that miR-155 promotes chondrocyte apoptosis and catabolic activity through targeting PIK3R1-mediated PI3K/Akt pathway activation. Altogether, our study discovers novel roles and mechanisms of miR-155 in regulating chondrocyte apoptosis and catabolic activity, providing an implication for therapeutically intervening cartilage degradation and OA progression.

Multifaceted Roles of microRNAs in Host-Bacterial Pathogen Interaction

MicroRNAs (miRNAs) are a well-characterized class of small noncoding RNAs that act as major posttranscriptional regulators of gene expression. Accordingly, miRNAs have been associated with a wide range of fundamental biological processes and implicated in human diseases. During the past decade, miRNAs have also been recognized for their role in the complex interplay between the host and bacterial pathogens, either as part of the host response to counteract infection or as a molecular strategy employed by bacteria to subvert host pathways for their own benefit. Importantly, the characterization of downstream miRNA targets and their underlying mechanisms of action has uncovered novel molecular factors and pathways relevant to infection. In this article, we review the current knowledge of the miRNA response to bacterial infection, focusing on different bacterial pathogens, including Salmonella enterica, Listeria monocytogenes, Mycobacterium spp., and Helicobacter pylori, among others.

Soluble PTX3 of Human Umbilical Cord Blood-Derived Mesenchymal Stem Cells Attenuates Hyperoxic Lung Injury by Activating Macrophage Polarization in Neonatal Rat Model

Therapeutic treatment of various inflammation-related diseases using mesenchymal stem cells (MSCs) has increased in recent years because of the paracrine action of these cells but shows several limitations. First, MSC-based therapies exhibit varying efficacies; thus, biomarkers should be determined to identify who may benefit from these candidate therapeutic agents. Second, the mechanism underlying the therapeutic effects is poorly understood. To evaluate the effects of human umbilical cord blood-derived MSCs (UCB-MSCs) on macrophages, the macrophage cell line NR8383 stimulated with lipopolysaccharide (LPS) was cocultured by UCB-MSCs. We found that UCB-MSCs mediated changes in macrophage polarization towards M2 from M1 macrophages. To identify the paracrine action underlying the anti-inflammation effect of UCB-MSCs, the secretion of UCB-MSCs exposed to LPS-stimulated NR8383 cells was tested using a biotin label-based 507 antibody array. Among the secreted proteins, we selected pentraxin-related protein PTX3/tumor necrosis factor-inducible gene 14 protein (PTX3) to investigate its association with UCB-MSCs in macrophage polarization. We found that human PTX3 was secreted from UCB-MSCs under inflammation condition and reinforced the M2 macrophage marker via the Dectin-1 receptor by activating MSK1/2 phosphorylation signaling in NR8383 cells. Accordingly, knockdown of PTX3 in UCB-MSCs significantly attenuated their therapeutic effects in a neonatal hyperoxic lung injury resulting in reduced survival, lung alveolarization, M2 marker expression, Dectin-1 levels, anti-inflammatory cytokines, and improved M1 marker expression and inflammatory cytokines compared to control MSC-injected rats. UCB-MSCs show therapeutic potential by controlling macrophage polarization. Interestingly, higher PTX3 levels in UCB-MSCs induced greater improvement in the therapeutic effects than lower PTX3 levels. Collectively, PTX3 is a potential marker with critical paracrine effects for predicting the therapeutic potential of MSC therapy in inflammatory diseases; quality control assessments using PTX3 may be useful for improving the therapeutic effects of UCB-MSCs.

Biomarkers for Detecting Resilience against Mycobacterial Disease in Animals

Paratuberculosis and bovine tuberculosis are two mycobacterial diseases of ruminants which have a considerable impact on livestock health, welfare, and production. These are chronic "iceberg" diseases which take years to manifest and in which many subclinical cases remain undetected. Suggested biomarkers to detect infected or diseased animals are numerous and include cytokines, peptides, and expression of specific genes; however, these do not provide a strong correlation to disease. Despite these advances, disease detection still relies heavily on dated methods such as detection of pathogen shedding, skin tests, or serology. Here we review the evidence for suitable biomarkers and their mechanisms of action, with a focus on identifying animals that are resilient to disease. A better understanding of these factors will help establish new strategies to control the spread of these diseases.

MicroRNAs as the actors in the atherosclerosis scenario

Atherosclerosis is considered as the most common cardiovascular disease and a leading cause of global mortality, which develops through consecutive steps. Various cellular and molecular biomarkers such as microRNAs are identified to be involved in atherosclerosis progression. MicroRNAs are a group of endogenous, short, non-coding RNAs, which are able to bind to specific sequences on target messenger RNAs and thereby modulate gene expression post-transcriptionally. MicroRNAs are key players in wide range of biological processes; thus, their expression level is regulated in pathophysiological conditions. Ample evidences including in vitro and in vivo studies approved a critical role of microRNAs in epigenetic and the sequential processes of atherosclerosis from risk factors to plaque formation, progression, and rupture. Based on these findings, miRNAs seems to be promising candidates for therapeutic approach. This review summarizes the role of miRNAs in atherosclerosis development, epigenetic, and therapy. Moreover, the application of exosomes in miRNA delivery, and/or their prognostic and diagnostic values are also discussed.

miR-155 promotes macrophage pyroptosis induced by Porphyromonas gingivalis through regulating the NLRP3 inflammasome

OBJECTIVE

The aim of this study is to detect pyroptosis in macrophages stimulated with Porphyromonas gingivalis and elucidate the mechanism by which P. gingivalis induces pyroptosis in macrophages.

METHODS

The immortalized human monocyte cell line U937 was stimulated with P. gingivalis W83. Flow cytometry was carried out to detect pyroptosis in macrophages. The expression of miR-155 was detected by real-time PCR and inhibited using RNAi. Suppressor of cytokine signaling (SOCS) 1, cleaved GSDMD, caspase (CAS)-1, caspase-11, apoptosis-associated speck-like protein (ASC), and NOD-like receptor protein 3 (NLRP3) were detected by Western blotting, and IL-1β and IL-18 were detected by ELISA.

RESULTS

The rate of pyroptosis in macrophages and the expression of miR-155 increased upon stimulation with P. gingivalis and pyroptosis rate decreased when miR-155 was silenced. GSDMD-NT, CAS-11, CAS-1, ASC, NLRP3, IL-1β, and IL-18 levels increased, but SOCS1 decreased in U937 cells after stimulated with P. gingivalis. These changes were weakened in P. gingivalis-stimulated U937 macrophages transfected with lentiviruses carrying miR-155 shRNA compared to those transfected with non-targeting control sequence. However, there was no significant difference in ASC expression between P. gingivalis-stimulated shCont and shMiR-155 cells.

CONCLUSIONS

Porphyromonas gingivalis promotes pyroptosis in macrophages during early infection. miR-155 is involved in this process through regulating the NLRP3 inflammasome.

MiR-140 modulates the inflammatory responses of Mycobacterium tuberculosis-infected macrophages by targeting TRAF6

This study aimed to examine miR‐140 expression in clinical samples from tuberculosis (TB) patients and to explore the molecular mechanisms of miR‐140 in host‐bacterial interactions during Mycobacterium tuberculosis (M tb) infections. The miR‐140 expression and relevant mRNA expression were detected by quantitative real‐time PCR (qRT‐PCR); the protein expression levels were analysed by ELISA and western blot; M tb survival was measured by colony formation unit assay; potential interactions between miR‐140 and the 3′ untranslated region (UTR) of tumour necrosis factor receptor‐associated factor 6 (TRAF6) was confirmed by luciferase reporter assay. MiR‐140 was up‐regulated in the human peripheral blood mononuclear cells (PBMCs) from TB patients and in THP‐1 and U937 cells with M tb infection. Overexpression of miR‐140 promoted M tb survival; on the other hand, miR‐140 knockdown attenuated M tb survival. The pro‐inflammatory cytokines including interleukin 6, tumour necrosis‐α, interleukin‐1β and interferon‐γ were enhanced by M tb infection in THP‐1 and U937 cells. MiR‐140 overexpression reduced these pro‐inflammatory cytokines levels in THP‐1 and U937 cells with M tb infection; while knockdown of miR‐140 exerted the opposite actions. TRAF6 was identified to be a downstream target of miR‐140 and was negatively modulated by miR‐140. TRAF6 overexpression increased the pro‐inflammatory cytokines levels and partially restored the suppressive effects of miR‐140 overexpression on pro‐inflammatory cytokines levels in THP‐1 and U937 cells with M tb infection. In conclusion, our results implied that miR‐140 promoted M tb survival and reduced the pro‐inflammatory cytokines levels in macrophages with M tb infection partially via modulating TRAF6 expression.

miR-155-5p Promotes Dorsal Root Ganglion Neuron Axonal Growth in an Inhibitory Microenvironment via the cAMP/PKA Pathway

Sensory dysfunction post spinal cord injury causes patients great distress. Sciatic nerve conditioning injury (SNCI) has been shown to restore sensory function after spinal cord dorsal column injury (SDCL); however, the underlying mechanism of this recovery remains unclear. We performed a microarray assay to determine the associated miRNAs that might regulate the process of SNCI promoting SDCL repair. In total, 13 miRNAs were identified according to our inclusion criteria, and RT-qPCR was used to verify the microarray results. Among the 13 miRNAs, the miR-155-5p levels were decreased at 9 h, 3 d, 7 d, 14 d, 28 d, 2 m and 3 m timepoints in the SDCL group, while the SNCI group had a smaller decrease. Thus, miR-155-5p was chosen for further study after a literature review and an analysis with the TargetScan online tool. Specifically, miR-155-5p targets PKI-α, and the expression pattern of PKI-α was opposite that of miR-155-5p in both the SDCL and SNCI groups. Interestingly, miR-155-5p could promote dorsal root ganglion (DRG) neuron axon growth via the cAMP/PKA pathway and in a TNF-α, IL-1β or MAG inhibitory microenvironment in vitro. Furthermore, miR-155-5p could regulate the cAMP/PKA pathway and promote sensory conduction function recovery post dorsal column injury as detected by NF-200 immunohistochemistry, somatosensory-evoked potentials, BBB scale and tape removal test. Collectively, our results demonstrated that miR-155-5p participates in the molecular mechanism by which SNCI promotes the repair of SDCL and that upregulated miR-155-5p can repair SDCL by enhancing DRG neuron axon growth via the cAMP/PKA pathway. These findings suggest a novel treatment target for spinal cord injury.

MiR-21-5p regulates mycobacterial survival and inflammatory responses by targeting Bcl-2 and TLR4 in Mycobacterium tuberculosis-infected macrophages

To date, very little is known about the role of microRNA-21-5p (miR-21-5p) in Mycobacterium tuberculosis (M.tb)-infected macrophages. Here, we show that M.tb infection of RAW264.7 and THP-1 cells increases the expression of miR-21-5p. MiR-21-5p enhances M.tb survival and apoptosis, and attenuates the secretion of inflammatory cytokines, including interleukin (IL)-1β, IL-6, and tumor necrosis factor-α in M.tb-infected macrophages. Dual-luciferase reporter assay revealed that the 3'-UTR of B-cell lymphoma 2 (Bcl-2) or toll-like receptor 4 (TLR4) is a direct target of miR-21-5p. Enforced expressions of Bcl-2 or TLR4 partially attenuate the suppressive effects of miR-21-5p on cell viability and inflammatory cytokines, and effectively decrease bacterial burden. Therefore, the present study highlights a novel role for miR-21-5p in regulation of mycobacterial survival and inflammatory responses by targeting Bcl-2 and TLR4 in M.tb-infected macrophages.

Differential Targeting of c-Maf, Bach-1, and Elmo-1 by microRNA-143 and microRNA-365 Promotes the Intracellular Growth of Mycobacterium tuberculosis in Alternatively IL-4/IL-13 Activated Macrophages

Mycobacterium tuberculosis (Mtb) can subvert the host defense by skewing macrophage activation toward a less microbicidal alternative activated state to avoid classical effector killing functions. Investigating the molecular basis of this evasion mechanism could uncover potential candidates for host directed therapy against tuberculosis (TB). A limited number of miRNAs have recently been shown to regulate host-mycobacterial interactions. Here, we performed time course kinetics experiments on bone marrow-derived macrophages (BMDMs) and human monocyte-derived macrophages (MDMs) alternatively activated with IL-4, IL-13, or a combination of IL-4/IL-13, followed by infection with Mtb clinical Beijing strain HN878. MiR-143 and miR-365 were highly induced in Mtb-infected M(IL-4/IL-13) BMDMs and MDMs. Knockdown of miR-143 and miR-365 using antagomiRs decreased the intracellular growth of Mtb HN878, reduced the production of IL-6 and CCL5 and promoted the apoptotic death of Mtb HN878-infected M(IL-4/IL-13) BMDMs. Computational target prediction identified c-Maf, Bach-1 and Elmo-1 as potential targets for both miR-143 and miR-365. Functional validation using luciferase assay, RNA-pulldown assay and Western blotting revealed that c-Maf and Bach-1 are directly targeted by miR-143 while c-Maf, Bach-1, and Elmo-1 are direct targets of miR-365. Knockdown of c-Maf using GapmeRs promoted intracellular Mtb growth when compared to control treated M(IL-4/IL-13) macrophages. Meanwhile, the blocking of Bach-1 had no effect and blocking Elmo-1 resulted in decreased Mtb growth. Combination treatment of M(IL-4/IL-13) macrophages with miR-143 mimics or miR-365 mimics and c-Maf, Bach-1, or Elmo-1 gene-specific GapmeRs restored Mtb growth in miR-143 mimic-treated groups and enhanced Mtb growth in miR-365 mimics-treated groups, thus suggesting the Mtb growth-promoting activities of miR-143 and miR-365 are mediated at least partially through interaction with c-Maf, Bach-1, and Elmo-1. We further show that knockdown of miR-143 and miR-365 in M(IL-4/IL-13) BMDMs decreased the expression of HO-1 and IL-10 which are known targets of Bach-1 and c-Maf, respectively, with Mtb growth-promoting activities in macrophages. Altogether, our work reports a host detrimental role of miR-143 and miR-365 during Mtb infection and highlights for the first time the role and miRNA-mediated regulation of c-Maf, Bach-1, and Elmo-1 in Mtb-infected M(IL-4/IL-13) macrophages.

MicroRNA-155 promotes pro-inflammatory functions and augments apoptosis of monocytes/macrophages during Vibrio anguillarum infection in ayu, Plecoglossus altivelis

Upon recognition of pathogen-associated molecular patterns by pattern-recognition receptors, immune cells are recruited, and multiple antibacterial/viral signaling pathways are activated, leading to the production of immune-related cytokines, chemokines, and interferons along with further activation of the adaptive immune response. MicroRNAs (miRs) play essential roles in regulating such immune signaling pathways, as well as the biological activities of immune cells; however, knowledge regarding the roles of miRs in the immune-related function of monocytes/macrophages (MO/MΦ) remains limited in teleosts. In the present study, we addressed the effects of miR-155 on Vibrio anguillarum-infected MO/MΦ. Our results showed that miR-155 augmented MO/MΦ expression of proinflammatory cytokines and attenuated the expression of anti-inflammatory cytokines. Additionally, the phagocytosis and bacteria-killing abilities of these cells were boosted by miR-155 administration, which also promoted M1-type polarization but inhibited M2-type polarization. Furthermore, the V. anguillarum-infection-induced apoptosis was also enhanced by miR-155 mimic transfection, which might have been due to excessive inflammation or the accumulation of reactive oxygen species. These results represent the first report providing a detailed account of the regulatory roles of miR-155 on MO/MΦ functions in teleosts and offer insight into the evolutionary history of miR-155-mediated regulation of host immune responses.

The role of epigenetics, bacterial and host factors in progression of Mycobacterium tuberculosis infection

Tuberculosis (TB) infection caused by Mycobacterium tuberculosis (Mtb) is still a persistent global health problem, particularly in developing countries. The World Health Organization (WHO) reported a mortality rate of about 1.8 million worldwide due to TB complications in 2015. The Bacillus Calmette-Guérin (BCG) vaccine was introduced in 1921 and is still widely used to prevent TB development. This vaccine offers up to 80% protection against various forms of TB; however its efficacy against lung infection varies among different geographical settings. Devastatingly, the development of various forms of drug-resistant TB strains has significantly impaired the discovery of effective and safe anti-bacterial agents. Consequently, this necessitated discovery of new drug targets and novel anti-TB therapeutics to counter infection caused by various Mtb strains. Importantly, various factors that contribute to TB development have been identified and include bacterial resuscitation factors, host factors, environmental factors and genetics. Furthermore, Mtb-induced epigenetic changes also play a crucial role in evading the host immune response and leads to bacterial persistence and dissemination. Recently, the application of GeneXpert MTB/RIF^® to rapidly diagnose and identify drug-resistant strains and discovery of different molecular markers that distinguish between latent and active TB infection has motivated and energised TB research. Therefore, this review article will briefly discuss the current TB state, highlight various mechanisms employed by Mtb to evade the host immune response as well as to discuss some modern molecular techniques that may potentially target and inhibit Mtb replication.

Cell death at the cross roads of host-pathogen interaction in Mycobacterium tuberculosis infection

Tuberculosis (TB) continues to be the leading cause of death by any single infectious agent, accounting for around 1.7 million annual deaths globally, despite several interventions and support programs by national and international agencies. With the development of drug resistance in Mycobacterium tuberculosis (M. tb), there has been a paradigm shift in TB research towards host-directed therapy. The potential targets include the interactions between host and bacterial proteins that are crucial for pathogenesis. Hence, collective efforts are being made to understand the molecular details of host-pathogen interaction for possible translation into host-directed therapy. The present review focuses on 'host cell death modalities' of host-pathogen interaction, which play a crucial role in determining the outcome of TB disease progression. Several cell death modalities that occur in response to mycobacterial infection have been identified in human macrophages either as host defences for bacterial clearance or as pathogen strategies for multiplication and dissemination. These cell death modalities include apoptosis, necrosis, pyroptosis, necroptosis, pyronecrosis, NETosis, and autophagy. These processes are highly overlapping with several mycobacterial proteins participating in more than one cell death pathway. Until now, reviews in M. tb and host cell death have discussed either focusing on host evasion strategies, apoptosis, autophagy, and necrosis or describing all these forms with limited discussions of their role in host-pathogen interactions. Here, we present a comprehensive review of various mycobacterial factors modulating host cell death pathways and the cross-talk between them. Besides this, we have discussed the networking of host cell death pathways including the interference of host miRNA during M. tb infection with their respective targets. Through this review, we present the host targets that overlap across several cell death modalities and the technical limitations of methodology in cell death research. Given the compelling need to discover alternative drug target(s), this review identifies these overlapping cell death factors as potential targets for host-directed therapy.

miRNAs reshape immunity and inflammatory responses in bacterial infection

Pathogenic bacteria cause various infections worldwide, especially in immunocompromised and other susceptible individuals, and are also associated with high infant mortality rates in developing countries. MicroRNAs (miRNAs), small non-coding RNAs with evolutionarily conserved sequences, are expressed in various tissues and cells that play key part in various physiological and pathologic processes. Increasing evidence implies roles for miRNAs in bacterial infectious diseases by modulating inflammatory responses, cell penetration, tissue remodeling, and innate and adaptive immunity. This review highlights some recent intriguing findings, ranging from the correlation between aberrant expression of miRNAs with bacterial infection progression to their profound impact on host immune responses. Harnessing of dysregulated miRNAs in bacterial infection may be an approach to improving the diagnosis, prevention and therapy of infectious diseases.

Changes in production of tiny cellular RNAs in response to bacterial infection could guide the development of better diagnostics and therapies. MicroRNAs regulate other genes by binding to messenger RNA strands and controlling their translation into proteins. Xikun Zhou, Min Wu and colleagues of the University of North Dakota have now reviewed current knowledge about how microRNA levels shift during infection with various bacterial pathogens. These microRNAs can modulate the immune response as well as pathways that influence metabolic activity and cell survival. Increasing studies have indicated that shifts in microRNA levels in response to different infections could provide a potential bacterial ‘fingerprint’ for achieving accurate diagnosis. With deeper insight into how different microRNAs influence infection, it might one day day become possible to target these molecules with ‘antisense’ or ‘agonist’ drugs that modulate their activity.

MicroRNA-27b Modulates Inflammatory Response and Apoptosis during Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis poses a significant global health threat. MicroRNAs play an important role in regulating host anti-mycobacterial defense; however, their role in apoptosis-mediated mycobacterial elimination and inflammatory response remains unclear. In this study, we explored the role of microRNA-27b (miR-27b) in murine macrophage responses to M. tuberculosis infection. We uncovered that the TLR-2/MyD88/NF-κB signaling pathway induced the expression of miR-27b and miR-27b suppressed the production of proinflammatory factors and the activity of NF-κB, thereby avoiding an excessive inflammation during M. tuberculosis infection. Luciferase reporter assay and Western blotting showed that miR-27b directly targeted Bcl-2-associated athanogene 2 (Bag2) in macrophages. Overexpression of Bag2 reversed miR-27b-mediated inhibition of the production of proinflammatory factors. In addition, miR-27b increased p53-dependent cell apoptosis and the production of reactive oxygen species and decreased the bacterial burden. We also showed that Bag2 interacts with p53 and negatively regulates its activity, thereby controlling cell apoptosis and facilitating bacterial survival. In summary, we revealed a novel role of the miR-27b/Bag2 axis in the regulation of inflammatory response and apoptosis and provide a potential molecular host defense mechanism against mycobacteria.