Anti-inflammatory effects of miR-21 in the macrophage response to peritonitis

RNA interference-based therapies for atherosclerosis: Recent advances and future prospects

Atherosclerosis represents a pathological state that affects the arterial system of the organism. This chronic, progressive condition is typified by the accumulation of atheroma within arterial walls. Modulation of RNA molecules through RNA-based therapies has expanded the range of therapeutic options available for neurodegenerative diseases, infectious diseases, cancer, and, more recently, cardiovascular disease (CVD). Presently, microRNAs and small interfering RNAs (siRNAs) are the most widely employed therapeutic strategies for targeting RNA molecules, and for regulating gene expression and protein production. Nevertheless, for these agents to be developed into effective medications, various obstacles must be overcome, including inadequate binding affinity, instability, challenges of delivering to the tissues, immunogenicity, and off-target toxicity. In this comprehensive review, we discuss in detail the current state of RNA interference (RNAi)-based therapies.

Extracellular vesicles from hiPSC-NSCs can prevent peripheral inflammation-induced cognitive dysfunction with inflammasome inhibition and improved neurogenesis in the hippocampus

Extracellular vesicles (EVs) released by human induced pluripotent stem cell-derived neural stem cells (hiPSC-NSCs) are enriched with miRNAs and proteins capable of mediating robust antiinflammatory activity. The lack of tumorigenic and immunogenic properties and ability to permeate the entire brain to incorporate into microglia following intranasal (IN) administrations makes them an attractive biologic for curtailing chronic neuroinflammation in neurodegenerative disorders. We tested the hypothesis that IN administrations of hiPSC-NSC-EVs can alleviate chronic neuroinflammation and cognitive impairments induced by the peripheral lipopolysaccharide (LPS) challenge. Adult male, C57BL/6J mice received intraperitoneal injections of LPS (0.75 mg/kg) for seven consecutive days. Then, the mice received either vehicle (VEH) or hiPSC-NSC-EVs (~ 10 × 109 EVs/administration, thrice over 6 days). A month later, mice in all groups were investigated for cognitive function with behavioral tests and euthanized for histological and biochemical studies. Mice receiving VEH after LPS displayed deficits in associative recognition memory, temporal pattern processing, and pattern separation. Such impairments were associated with an increased incidence of activated microglia presenting NOD-, LRR-, and pyrin domain containing 3 (NLRP3) inflammasomes, elevated levels of NLRP3 inflammasome mediators and end products, and decreased neurogenesis in the hippocampus. In contrast, the various cognitive measures in mice receiving hiPSC-NSC-EVs after LPS were closer to naive mice. Significantly, these mice displayed diminished microglial activation, NLRP3 inflammasomes, proinflammatory cytokines, and a level of neurogenesis matching age-matched naïve controls. Thus, IN administrations of hiPSC-NSC-EVs are an efficacious approach to reducing chronic neuroinflammation-induced cognitive impairments.

DnaJ-induced miRNA-146a negatively regulates the expression of IL-8 in macrophages

As a member of the damage-associated molecular patterns, heat shock proteins (HSPs) are widely recognized for their role in initiating innate immune responses. These highly conserved proteins are expressed ubiquitously in both prokaryotes and eukaryotes. In this study, our aim was to investigate how DnaJ, a HSP40 homolog derived from Pseudomonas aeruginosa (P. aeruginosa), influences the regulation of IL-8 expression in macrophages. Treatment with DnaJ served as a stimulus, inducing a more robust expression of IL-8 compared to other HSP homologs, including DnaK, GroEL, and HtpG. This effect was achieved through the activation of the NF-κB signaling pathway. Interestingly, DnaJ treatment also significantly increased the expression of microRNA-146a (miR-146a), which appears to play a role in modulating the expression of innate defense genes. As a consequence, pre-treatment with DnaJ led to a reduction in the extent of IL-8 induction in response to P. aeruginosa treatment. Notably, this reduction was counteracted by transfection of a miR-146a inhibitor, highlighting the involvement of miR-146a in P. aeruginosa-mediated induction of IL-8 expression. Therefore, this study uncovers the role of DnaJ in triggering the expression of miR-146a, which, in turn, modulates the excessive expression of IL-8 induced by P. aeruginosa infection.

The miRNA neuroinflammatory biomarkers in COVID-19 patients with different severity of illness

INTRODUCTION

The expression of specific miRNAs and their mRNA targets are changed in infectious disease. The aim of this study was to analyze the expression of pro-neuroinflammatory miRNAs, anti-neuroinflammatory miRNAs, and their mRNA targets in the serum of COVID-19 patients with different grades.

METHODS

COVID-19 patients with different grades were enrolled in this study and the expression of pro-neuroinflammatory miRNAs, anti-neuroinflammatory miRNAs, and their target mRNAs was analyzed by q-PCR.

RESULTS

The relative expression of anti- neuroinflammatory miRNAs (mir-21, mir-124, and mir-146a) was decreased and the relative expression of their target mRNAs (IL-12p53, Stat3, and TRAF6) was increased. Also, the relative expression of pro-neuroinflammatory miRNAs (mir-326, mir-155, and mir-27b) was increased and the relative expression of their target mRNA (PPARS, SOCS1, and CEBPA) was decreased in COVID-19 patients with increase of disease grade. A negative significant correlation was seen between mir-21 and IL-12p53 mRNA, mir-124 and Stat3 mRNA, mir-146a and TRAF6 mRNA, mir-27b and PPARS mRNA, mir-155 and SOCS1 mRNA, and between mir-326 and CEBPA mRNA in COVID-19 patients (P<0.05).

CONCLUSIONS

This study showed that the relative expression of anti- neuroinflammatory miRNAs was decreased and the relative expression of their targeted mRNAs was increased in COVID-19 patients from asymptomatic to critical illness. Also, this study showed that the relative expression of pro-neuroinflammatory miRNAs was increased and the relative expression of their targeted mRNA was decreased in COVID-19 patients from asymptomatic to critical illness.

MicroRNAs in Macrophages: Regulators of Activation and Function

Macrophages are sentinels of the innate immune system that maintain tissue homeostasis and contribute to inflammatory responses. Their broad scope of action depends on both functional heterogeneity and plasticity. Small noncoding RNAs called microRNAs (miRNAs) contribute to macrophage function as post-transcriptional inhibitors of target gene networks. Genetic and pharmacologic studies have uncovered genes regulated by miRNAs that control macrophage cellular programming and macrophage-driven pathology. miRNAs control proinflammatory M1-like activation, immunoregulatory M2-like macrophage activation, and emerging macrophage functions in metabolic disease and innate immune memory. Understanding the gene networks regulated by individual miRNAs enhances our understanding of the spectrum of macrophage function at steady state and during responses to injury or pathogen invasion, with the potential to develop miRNA-based therapies. This review aims to consolidate past and current studies investigating the complexity of the miRNA interactome to provide the reader with a mechanistic view of how miRNAs shape macrophage behavior.

Expression profile of microRNAs related with viral infectivity, inflammatory response, and immune activation in people living with HIV

Objective

To evaluate the serum expression of microRNAs (miRNAs) with ability to modulate the human immunodeficiency (HIV) replication or inflammatory status in people living with HIV (PLWH).

Methods

Forty healthy controls and two groups of PLWH were evaluated: (a) Group 1 (n = 30), patients with detectable viral load at inclusion, analyzed before receiving antiretroviral therapy (ART) and 12 months after initiating it; (b) Group 2 (n = 55), PLWH with prolonged undetectable viral load. Intestinal barrier disruption (I-FABP) and bacterial translocation (16S rDNA) markers, inflammatory markers such as interleukin (IL)-6 and sCD163, immune activation and expression of specific miRNAs were evaluated.

Results

Serum concentrations of I-FABP, 16S rDNA, IL-6, sCD163 and activated T lymphocytes were increased in PLWH. Serum miR-34a was overexpressed at inclusion and remained elevated after ART. The expression of the remaining miRNAs that modulate HIV infectivity (miR-7, mir-29a, miR-150, and miR-223) was similar in PLWH and controls. Related to miRNAs implicated in inflammation (miR-21, miR-155, and miR-210), significant overexpression were observed in miR-21 and miR-210 levels in untreated PLWH, but levels were restored in those patients treated for a long period.

Conclusion

A sustained overexpression of miR-34a was detected even after prolonged HIV controlled replication. miR-21 and miR-210 can be considered new markers of inflammation with high sensitivity to its modifications.

Role of MicroRNAs, Aptamers in Neuroinflammation and Neurodegenerative Disorders

Exploring the microRNAs and aptamers for their therapeutic role as biological drugs has expanded the horizon of its applicability against various human diseases, explicitly targeting the genetic materials. RNA-based therapeutics are widely being explored for the treatment and diagnosis of multiple diseases, including neurodegenerative disorders (NDD). Latter includes microRNA, aptamers, ribozymes, and small interfering RNAs (siRNAs), which control the gene expression mainly at the transcriptional strata. One RNA transcript translates into different protein types; hence, therapies targeted at the transcriptional sphere may have prominent and more extensive effects than alternative therapeutics. Unlike conventional gene therapy, RNAs, upon delivery, can either altogether abolish or alter the synthesis of the protein of interest, therefore, regulating their activities in a controlled and diverse manner. NDDs like Alzheimer's disease, Parkinson's disease, Huntington's disease, multiple sclerosis, Prion disease, and others are characterized by deposition of misfolded protein such as amyloid-ß, tau, α-synuclein, huntingtin and prion proteins. Neuroinflammation, one of the perquisites for neurodegeneration, is induced during neurodegenerative pathogenesis. In this review, we discuss microRNAs and aptamers' role as two different RNA-based approaches for their unique ability to regulate protein production at the transcription level, hence offering many advantages over other biologicals. The microRNA acts either by alleviating the malfunctioning RNA expression or by working as a replacement to lost microRNA. On the contrary, aptamer act as a chemical antibody and forms an aptamer-target complex.

Suppression of Hepatic PPARα in Primary Biliary Cholangitis Is Modulated by miR-155

Background: PPARα is a ligand-activated transcription factor that shows protective effects against metabolic disorders, inflammation and apoptosis. Primary biliary cholangitis and primary sclerosing cholangitis result in the intrahepatic accumulation of bile acids that leads to liver dysfunction and damage. Small, non-coding RNAs such as miR-155 and miR-21 are associated with silencing PPARα. Methods: The expression of miR-155, miR-21 and PPARα were evaluated using real-time PCR on liver tissue, as well as on human hepatocytes (HepG2) or cholangiocytes (NHCs) following exposure to lipopolysaccharide (LPS), glycodeoxycholic acid (GCDCA), lithocholic acid (LCA) and/or ursodeoxycholic acid (UDCA). Results: A reduction of PPARα in primary biliary cholangitis (PBC) livers was associated with miR-21 and miR-155 upregulation. Experimental overexpression of either miR-155 or miR-21 inhibited PPARα in hepatocytes, whereas, in cholangiocytes, only miR-21 suppressed PPARα. Both GCDCA and LCA induced the cell type-specific upregulation of miR-155 or miR-21. In HepG2, LPS-induced miR-155 expression was blocked by a cotreatment with UDCA and was associated with PPARα upregulation. In NHC cells, the expression of miR-21 was induced by LPS but did not affect PPARα expression. Conclusions: Hepatic PPARα expression is reduced in PBC livers as a likely result of miR-155 overexpression. UDCA effectively reduced both baseline and LPS-induced miR-155 expression, thus preventing the suppression of PPARα.

Non-Coding RNAs as Novel Regulators of Neuroinflammation in Alzheimer's Disease

Alzheimer’s disease (AD) is one of the most common causes of dementia. Although significant breakthroughs have been made in understanding the progression and pathogenesis of AD, it remains a worldwide problem and a significant public health burden. Thus, more efficient diagnostic and therapeutic strategies are urgently required. The latest research studies have revealed that neuroinflammation is crucial in the pathogenesis of AD. Non-coding RNAs (ncRNAs), including long noncoding RNAs (lncRNAs), microRNAs (miRNAs), circular RNAs (circRNAs), PIWI-interacting RNAs (piRNAs), and transfer RNA-derived small RNAs (tsRNAs), have been strongly associated with AD-induced neuroinflammation. Furthermore, several ongoing pre-clinical studies are currently investigating ncRNA as disease biomarkers and therapeutic interventions to provide new perspectives for AD diagnosis and treatment. In this review, the role of different types of ncRNAs in neuroinflammation during AD are summarized in order to improve our understanding of AD etiology and aid in the translation of basic research into clinical practice.

Proficiency of Extracellular Vesicles From hiPSC-Derived Neural Stem Cells in Modulating Proinflammatory Human Microglia: Role of Pentraxin-3 and miRNA-21-5p

Extracellular vesicles (EVs) shed by human-induced pluripotent stem cell (hiPSC)-derived neural stem cells (hNSC-EVs) have shown potent antiinflammatory properties in a mouse macrophage assay and a mouse model of acute neuroinflammation. They can also quickly permeate the entire brain after intranasal administration, making them attractive as an autologous or allogeneic off-the-shelf product for treating neurodegenerative diseases. However, their ability to modulate activated human microglia and specific proteins and miRNAs mediating antiinflammatory effects of hNSC-EVs are unknown. We investigated the proficiency of hNSC-EVs to modulate activated human microglia and probed the role of the protein pentraxin 3 (PTX3) and the miRNA miR-21-5p within hNSC-EVs in mediating the antiinflammatory effects. Mature microglia generated from hiPSCs (iMicroglia) expressed multiple microglia-specific markers. They responded to lipopolysaccharide (LPS) or interferon-gamma challenge by upregulating tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) mRNA expression and protein release. iMicroglia also exhibited proficiency to phagocytose amyloid-beta (Aβ). The addition of hNSC-EVs decreased TNF-α and IL-1β mRNA expression and the release of TNF-α and IL-1β by LPS-stimulated iMicroglia (proinflammatory human Microglia). However, the antiinflammatory activity of hNSC-EVs on LPS-stimulated microglia was considerably diminished when the PTX3 or miR-21-5p concentration was reduced in EVs. The results demonstrate that hNSC-EVs are proficient for modulating the proinflammatory human microglia into non-inflammatory phenotypes, implying their utility to treat neuroinflammation in neurodegenerative diseases. Furthermore, the role of PTX3 and miR-21-5p in the antiinflammatory activity of hNSC-EVs provides a new avenue for improving the antiinflammatory effects of hNSC-EVs through PTX3 and/or miR-21-5p overexpression.

Pathogenic role of microRNAs in atherosclerotic ischemic stroke: Implications for diagnosis and therapy

Ischemic stroke resulting from atherosclerosis (particularly in the carotid artery) is one of the major subtypes of stroke and has a high incidence of death. Disordered lipid homeostasis, lipid deposition, local macrophage infiltration, smooth muscle cell proliferation, and plaque rupture are the main pathological processes of atherosclerotic ischemic stroke. Hepatocytes, macrophages, endothelial cells and vascular smooth muscle cells are the main cell types participating in these processes. By inhibiting the expression of the target genes in these cells, microRNAs play a key role in regulating lipid disorders and atherosclerotic ischemic stroke. In this article, we listed the microRNAs implicated in the pathology of atherosclerotic ischemic stroke and aimed to explain their pro- or antiatherosclerotic roles. Our article provides an update on the potential diagnostic use of miRNAs for detecting growing plaques and impending clinical events. Finally, we provide a perspective on the therapeutic use of local microRNA delivery and discuss the challenges for this potential therapy.

Correlation analysis of serum miR-21 and miR-210 with hs-CRP, TNF-α, IL-6, and ICAM-1 in patients with sepsis after burns

BACKGROUND

The aim of this study was to explore expression levels and clinical values of miR-21 and miR-210 in patients with sepsis after burns.

METHODS

One hundred and twenty-eight burn patients who were treated in Binzhou Medical University Hospital were selected as research objects, among which 69 complicated with sepsis were in an observation group and 59 complicated with infection were in a control group. MiR-21 and miR-210 expression in the patients' serum was detected by RT-PCR. Serum inflammatory cytokines were detected by an enzyme-linked immunosorbent assay (ELISA). Correlation analysis was used for the correlations of the miR-21 and miR-210 with the cytokines. Receiver operating characteristic (ROC) curves were plotted to analyze the diagnostic values of the miR-21 and miR-210 for sepsis after burns and their predictive values for the poor prognosis of sepsis patients.

RESULTS

MiR-21 expression reduced remarkably and miR-210 expression rose remarkably in the serum of patients with sepsis after burns. According to the analysis of the ROC curves, both of the miR-21 and miR-210 had relatively high diagnostic sensitivity for the disease, but the diagnostic value of their combined detection was higher. Contents of hs-CRP, TNF-α, IL-6, and ICAM-1 in serum were remarkably higher in the observation group than those in the control group. According to the correlation analysis, miR-21 was negatively correlated with the expression of the four cytokines, while miR-210 was positively correlated with that. The predictive value of miR-21 for the prognosis of sepsis patients was not high, but miR-210 had a certain predictive value, and their combined detection had a higher value.

CONCLUSION

In serum of patients with sepsis after burns, miR-21 expression reduces remarkably and miR-210 expression rises. The miR-21 and miR-210 are related to the degree of inflammatory responses in septic patients, and their combined detection has a certain value for diagnosing the disease and predicting its prognosis.

miR-21 differentially regulates IL-1β and IL-10 expression in human decidual cells infected with streptococcus B

Intrauterine infections caused by bacteria like group B streptococcus (GBS) and the subsequent activation of the maternal inflammatory response have been long suspected to be the underlying cause of preterm labor. The inflammatory network triggered by maternal decidua has been widely described and includes the secretion of pro- and anti-inflammatory cytokines as IL-1β and IL-10; however, the mechanisms that regulate their secretion have not been completely elucidated. MicroRNAs (miRNAs) are critical modulators of the inflammatory response by regulating cytokine expression in several cell types. Here, we explored the role of miR-21 in the expression of IL-1β and IL-10 in human decidual stromal cells (DSCs) exposed in vitro to GBS. We observed that IL1B and IL10 expression at the mRNA level was increased in DSCs after GBS infection. IL-10 but not IL-1β secretion was detected in the culture supernatants. We found a higher miR-21 expression (22-fold) in infected DSCs as compared with non-infected cells. miR-21 functional analysis revealed that DSCs transfected with an antagomiR vs. miR-21 significantly increased the secretion of IL-1β but decreased that of IL-10 in DSCs cells infected with GBS. Our results suggest that miR-21 participates in balancing the inflammatory response in infected decidua through at least IL-1β and IL-10 regulation. This is the first study attributing a functional role of miR-21 in the regulation of key molecules involved in the inflammatory response in infected DSCs, providing new insights into the epigenetic control of human decidual inflammation.

Respiratory Effects of Exposure to Aerosol From the Candidate Modified-Risk Tobacco Product THS 2.2 in an 18-Month Systems Toxicology Study With A/J Mice

Smoking cessation is the most effective measure for reducing the risk of smoking-related diseases. However, switching to less harmful products (modified-risk tobacco products [MRTP]) can be an alternative to help reduce the risk for adult smokers who would otherwise continue to smoke. In an 18-month chronic carcinogenicity/toxicity study in A/J mice (OECD Test Guideline 453), we assessed the aerosol of Tobacco Heating System 2.2 (THS 2.2), a candidate MRTP based on the heat-not-burn principle, compared with 3R4F cigarette smoke (CS). To capture toxicity- and disease-relevant mechanisms, we complemented standard toxicology endpoints with in-depth systems toxicology analyses. In this part of our publication series, we report on integrative assessment of the apical and molecular exposure effects on the respiratory tract (nose, larynx, and lungs). Across the respiratory tract, we found changes in inflammatory response following 3R4F CS exposure (eg, antimicrobial peptide response in the nose), with both shared and distinct oxidative and xenobiotic responses. Compared with 3R4F CS, THS 2.2 aerosol exerted far fewer effects on respiratory tract histology, including adaptive tissue changes in nasal and laryngeal epithelium and inflammation and emphysematous changes in the lungs. Integrative analysis of molecular changes confirmed the substantially lower impact of THS 2.2 aerosol than 3R4F CS on toxicologically and disease-relevant molecular processes such as inflammation, oxidative stress responses, and xenobiotic metabolism. In summary, this work exemplifies how apical and molecular endpoints can be combined effectively for toxicology assessment and further supports findings on the reduced respiratory health risks of THS 2.2 aerosol.

MicroRNA 21 Elicits a Pro-inflammatory Response in Macrophages, with Exosomes Functioning as Delivery Vehicles

MicroRNAs can regulate inflammatory responses by modulating macrophage polarization. Although microRNA miR-21 is linked to crucial processes involved in inflammatory responses, its precise role in macrophage polarization is controversial. In this study, we investigated the functional relevance of endogenous miRNA-21 and the role of exosomes. RAW 264.7 macrophages were transfected with miR-21 plasmid, and the inflammatory response was evaluated by flow cytometry, phagocytosis, and real-time PCR analysis of inflammatory cytokines. To understand the signaling pathways' role, the cells were treated with inhibitors specific for PI3K or NFĸB. Exosomes from transfected cells were used to study the paracrine action of miR-21 on naive macrophages. Overexpression of miR-21 resulted in significant upregulation of pro-inflammatory cytokines, pushing the cells towards a pro-inflammatory phenotype, with partial involvement of PI3K and NFĸB signal pathways. The cells also secreted miR-21 rich exosomes, which, on delivery to naive macrophages, caused them to exhibit pro-inflammatory activity. The presence of miR-21 inhibitor quenched the inflammatory response. This study validates the pro-inflammatory property of miR-21 with a tendency to foster an inflammatory milieu. Our findings also reinforce the dual importance of exosomal miR-21 as a biomarker and therapeutic target in inflammatory conditions.

Macrophage-Derived MicroRNA-21 Drives Overwhelming Glycolytic and Inflammatory Response during Sepsis via Repression of the PGE2/IL-10 Axis

Myeloid cells are critical for systemic inflammation, microbial control, and organ damage during sepsis. MicroRNAs are small noncoding RNAs that can dictate the outcome of sepsis. The role of myeloid-based expression of microRNA-21 (miR-21) in sepsis is inconclusive. In this study, we show that sepsis enhanced miR-21 expression in both peritoneal macrophages and neutrophils from septic C57BL/6J mice, and the deletion of miR-21 locus in myeloid cells (miR-21^Δmyel mice) enhanced animal survival, decreased bacterial growth, decreased systemic inflammation, and decreased organ damage. Resistance to sepsis was associated with a reduction of aerobic glycolysis and increased levels of the anti-inflammatory mediators PGE₂ and IL-10 in miR-21^Δmyel in vivo and in vitro. Using blocking Abs and pharmacological tools, we discovered that increased survival and decreased systemic inflammation in septic miR-21^Δmyel mice is dependent on PGE₂/IL-10-mediated inhibition of glycolysis. Together, these findings demonstrate that expression of miR-21 in myeloid cells orchestrates the balance between anti-inflammatory mediators and metabolic reprogramming that drives cytokine storm during sepsis.

[The miRNA neuroinflammatory biomarkers in COVID-19 patients with different severity of illness]

INTRODUCTION

The expression of specific miRNAs and their mRNA targets are changed in infectious disease. The aim of this study was to analyze the expression of pro-neuroinflammatory miRNAs, anti- neuroinflammatory miRNAs, and their mRNA targets in the serum of COVID-19 patients with different grades.

METHODS

COVID-19 patients with different grades were enrolled in this study and the expression of pro-neuroinflammatory miRNAs, anti-neuroinflammatory miRNAs, and their target mRNAs was analyzed by q-PCR.

RESULTS

The relative expression of anti- neuroinflammatory miRNAs (mir-21, mir-124, and mir-146a) was decreased and the relative expression of their target mRNAs (IL-12p53, Stat3, and TRAF6) was increased. Also, the relative expression of pro-neuroinflammatory miRNAs (mir-326, mir-155, and mir-27b) was increased and the relative expression of their target mRNA (PPARS, SOCS1, and CEBPA) was decreased in COVID-19 patients with increase of disease grade. A negative significant correlation was seen between mir-21 and IL-12p53 mRNA, mir-124 and Stat3 mRNA, mir-146a and TRAF6 mRNA, mir-27b and PPARS mRNA, mir-155 and SOCS1 mRNA, and between mir-326 and CEBPA mRNA in COVID-19 patients (P<0.05).

CONCLUSIONS

This study showed that the relative expression of anti- neuroinflammatory miRNAs was decreased and the relative expression of their targeted mRNAs was increased in COVID-19 patients from asymptomatic to critical illness. Also, this study showed that the relative expression of pro-neuroinflammatory miRNAs was increased and the relative expression of their targeted mRNA was decreased in COVID-19 patients from asymptomatic to critical illness.

Size changes in miR‑21 knockout mice: Geometric morphometrics on teeth, alveolar bone and mandible

MicroRNA‑21 (miR‑21) is a small non‑coding RNA that is differentially expressed during tooth development, particularly during amelogenesis. Although orthodontic tooth movement and the innate immune response are impaired, miR‑21 knockout mice demonstrate no obvious skeletal phenotype. However, the consequence of miR‑21 knockout on tooth phenotype and corresponding alveolar bone is unknown. The current study utilized landmark‑based geometric morphometrics to identify anatomical dissimilarities of the three lower and upper molars, and the corresponding alveolar bone, in miR‑21 knockout and wild‑type control mice. The anatomical structures were visualized by microcomputer tomography. A total of 36 and 38 landmarks were placed on mandibular and maxillary molars, respectively. For the alveolar bone, 16 landmarks were selected on both anatomical sites. General Procrustes analysis revealed significantly smaller molars and dimensions of the alveolar bone in the mandible of the miR‑21 knockout mice when compared with wild‑type controls (P=0.03 and P=0.04, respectively). The overall dimension of the mandible was reduced by the lack of miR‑21 (P=0.02). In the maxilla, the dimension of the alveolar bone was significant (P=0.02); however, this was not observed in the molars (P=0.36). Based on principal component analysis, no changes in shape for any of the anatomical sites were observed. Dental and skeletal jaw length were calculated and no prognathism was identified. However, the fluctuating asymmetry of the molars in the mandible and the maxilla was reduced in the miR‑21 knockout mice by 38 and 27%, respectively. Taken together, the results of the present study revealed that the molars in the mandible and the dimension of the respective alveolar bone were smaller in miR‑21 mice compared with wild‑type littermates, suggesting that miR‑21 influences tooth development.

Dexmedetomidine suppresses the development of abdominal aortic aneurysm by downregulating the mircoRNA‑21/PDCD 4 axis

Abdominal aortic aneurysm (AAA) is a pathological state with permanent dilation, which indicates a fatal potential for aortic rupture. It has been reported that dexmedetomidine (Dex) and microRNA (miR)-21 are involved in the progression of AAA. Thus, the present study aimed to investigate the joint effects of these factors on AAA treatment. For this purpose, rat models of AAA were established with enzyme perfusion and the rats were then injected with Dex. Alterations in the abdominal aorta in rats with AAA were recorded. miR-21 expression in the rats with AAA was determined. Inflammatory factor expression was detected by western blot analysis. Subsequently, a dual-luciferase reporter gene assay was performed to verify the targeting association between miR-21 and programmed cell death protein 4 (PDCD4). Additionally, AAA-related indices and inflammatory responses were examined by an injection of a combination of antagomiR (ant)-miR-21 and Dex or lentivirus-PDCD4-short hairpin RNA. It was found that Dex markedly alleviated the development of AAA and downregulated the expression of inflammatory factors and matrix metalloproteinase in rats with AAA. The high expression of miR-21, which targets PDCD4, was observed in the rats with AAA. However, ant-miR-21 induced AAA development and inflammatory responses. Additionally, the inhibition of PDCD4 reduced AAA development and inflammatory responses. On the whole, the present study demonstrates that Dex inhibits AAA development by downregulating the miR-21/PCDP4 axis. The findings of the present study may provide novel insight for the treatment of AAA. These findings may provide a reference for the future treatment of AAA and may provide theoretical guidance for the early prevention and development of AAA.

Retinoic acid abrogates LPS-induced inflammatory response via negative regulation of NF-kappa B/miR-21 signaling

CONTEXT

Macrophages are essential components of the immune system, with significant roles in inflammation modulation. They can be activated into pro-inflammatory M1 or anti-inflammatory M2 phenotypes, depending on their micro-environment. Molecular factors that modulate macrophage polarization are hot targets for therapeutic strategies to counter chronic inflammatory pathological conditions.

OBJECTIVE

The current study aimed to elucidate the molecular mechanisms by which Retinoic acid (RA), a potent immunomodulator, suppresses LPS-induced inflammatory response in macrophages.

MATERIALS AND METHODS

RAW 264.7 macrophages were treated with RA and/or LPS, and analyzed for inflammatory genes and miR-21 by PCR. The roles of miR-21 and NF-ĸB signaling pathway were also assessed by knock-down experiments, immunofluorescence, and ChIP assays.

RESULTS

Pretreatment with RA quenched the LPS-induced inflammatory responses, including phagocytosis, ROS generation, and NO production. RA shifted the polarization away from the M1 state by negative regulation of IKKα/β, p65, and miR-21. RA hindered the phosphorylation of IKKα/β, translocation of p65 into the nucleus, and the subsequent upregulation of miR-21. Knock-in and knock-down experiments showed that miR-21 is central for the polarization shift toward the pro-inflammatory M1 state.

CONCLUSION

miR-21 is involved in the LPS-induced pro-inflammatory profile of macrophages and that RA negatively regulates the inflammatory response by targeting NF-ĸB/miR-21 signaling. Our data exposes RA's potential as a pharmacological agent to manipulate miR-21 and counteract hyper-inflammatory response.

Fasciola hepatica hijacks host macrophage miRNA machinery to modulate early innate immune responses

Fasciola hepatica, a global worm parasite of humans and their livestock, regulates host innate immune responses within hours of infection. Host macrophages, essential to the first-line defence mechanisms, are quickly restricted in their ability to initiate a classic protective pro-inflammatory immune response. We found that macrophages from infected animals are enriched with parasite-derived micro(mi)RNAs. The most abundant of these miRNAs, fhe-miR-125b, is released by the parasite via exosomes and is homologous to a mammalian miRNA, hsa-miR-125b, that is known to regulate the activation of pro-inflammatory M1 macrophages. We show that the parasite fhe-miR-125b loads onto the mammalian Argonaut protein (Ago-2) within macrophages during infection and, therefore, propose that it mimics host miR-125b to negatively regulate the production of inflammatory cytokines. The hijacking of the miRNA machinery controlling innate cell function could be a fundamental mechanism by which worm parasites disarm the early immune responses of their host to ensure successful infection.

Mycobacterium tuberculosis Limits Host Glycolysis and IL-1β by Restriction of PFK-M via MicroRNA-21

Increased glycolytic metabolism recently emerged as an essential process driving host defense against Mycobacterium tuberculosis (Mtb), but little is known about how this process is regulated during infection. Here, we observe repression of host glycolysis in Mtb-infected macrophages, which is dependent on sustained upregulation of anti-inflammatory microRNA-21 (miR-21) by proliferating mycobacteria. The dampening of glycolysis by miR-21 is mediated through targeting of phosphofructokinase muscle (PFK-M) isoform at the committed step of glycolysis, which facilitates bacterial growth by limiting pro-inflammatory mediators, chiefly interleukin-1β (IL-1β). Unlike other glycolytic genes, PFK-M expression and activity is repressed during Mtb infection through miR-21-mediated regulation, while other less-active isoenzymes dominate. Notably, interferon-γ (IFN-γ), which drives Mtb host defense, inhibits miR-21 expression, forcing an isoenzyme switch in the PFK complex, augmenting PFK-M expression and macrophage glycolysis. These findings place the targeting of PFK-M by miR-21 as a key node controlling macrophage immunometabolic function.

MicroRNA-21-5p targets PDCD4 to modulate apoptosis and inflammatory response to Clostridium perfringens beta2 toxin infection in IPEC-J2 cells

Clostridium perfringens (C. perfringens), a toxin-producing enteric pathogen, causes a variety of intestinal infections in humans and animals. C. perfringens beta2 (CPB2) toxin has been considered to be a strong virulence factor for C. perfringens infectious enteric diseases (CPED). Altered levels and functions of microRNA-21-5p (miR-21-5p) have been associated with apoptosis and inflammation response in pathological processes. However, little is known about its functional mechanism in CPED. Here, we found that miR-21-5p expressed in multiple tissues of pig, had a highest level in jejunum, and significantly upregulated in intestinal porcine epithelial cells (IPEC-J2) exposed to CPB2 toxin. Noteworthily, transfection of CPB2-treated IPEC-J2 cells with miR-21-5p mimic increased cell viability and Bcl2 expression, as well as reduced cytotoxicity, apoptosis rates and Bax level. Moreover, overexpression of miR-21-5p significantly suppressed the levels of interleukin (IL)-6, IL-8, TNF-α, IL-1β and nuclear factor-kappa B (NF-κB p65) activity induced by CPB2 toxin, whereas that of the IL-10 was increased in IPEC-J2 cells. On the contrary, transfection of miR-21-5p inhibitor promoted CPB2-induced cell apoptosis and inflammation. Furthermore, we validated that programmed cell death 4 (PDCD4) was strikingly downregulated in CPB2-treated IPEC-J2 cells. PDCD4 exhibited opposing effects to those of miR-21-5p mimic on IPEC-J2 cells, and restoration of PDCD4 expression counteracted the suppressive effect of miR-21-5p on CPB2-induced apoptosis and inflammatory response. Collectively, our findings demonstrated that miR-21-5p was involved in regulating the immune response triggered by CPB2 toxin and contributed to protective effects in CPB2-induced CPED cell model by targeting PDCD4.

miR-21 mediates nickel nanoparticle-induced pulmonary injury and fibrosis

We and other groups have demonstrated that exposure to nickel nanoparticles (Nano-Ni) results in severe and persistent lung inflammation and fibrosis, but the underlying mechanisms remain unclear. Here, we propose that miR-21 may play an important role in Nano-Ni-induced lung inflammation, injury, and fibrosis. Our dose- and time-response studies demonstrated that exposure of C57BL/6J (WT) mice to Nano-Ni resulted in upregulation of miR-21, proinflammatory cytokines, and profibrotic mediators. Histologically, exposure to Nano-Ni caused severe pulmonary inflammation and fibrosis. Based on the dose- and time-response studies, we chose a dose of 50 µg of Nano-Ni per mouse to compare the effects of Nano-Ni on WT with those on miR-21 KO mouse lungs. At day 3 post-exposure, Nano-Ni caused severe acute lung inflammation and injury that were reflected by increased neutrophil count, CXCL1/KC level, LDH activity, total protein concentration, MMP-2/9 protein levels and activities, and proinflammatory cytokines in the BALF or lung tissues from WT mice, which were confirmed histologically. Although Nano-Ni had similar effects on miR-21 KO mice, the above-mentioned levels were significantly lower than those in WT mice. Histologically, lungs from WT mice exposed to Nano-Ni had infiltration of a large number of polymorphonuclear (PMN) cells and macrophages in the alveolar space and interstitial tissues. However, exposure of miR-21 KO mice to Nano-Ni only caused mild acute lung inflammation and injury. At day 42 post-exposure, Nano-Ni caused extensive pulmonary fibrosis and chronic inflammation in the WT mouse lungs. However, exposure of miR-21 KO mice to Nano-Ni only caused mild lung fibrosis and chronic lung inflammation. Our results also showed that exposure to Nano-Ni caused upregulation of TGF-β1, phospho-Smad2, COL1A1, and COL3A1 in both WT and miR-21 KO mouse lungs. However, levels were significantly lower in miR-21 KO mice than in WT mice, except TGF-β1, which was similar in both kinds of mice. Decreased expression of Smad7 was observed in WT mouse lungs, but not in miR-21 KO mice. Our results demonstrated that knocking out miR-21 ameliorated Nano-Ni-induced pulmonary inflammation, injury, and fibrosis, suggesting the important role of miR-21 in Nano-Ni-induced pulmonary toxicity.

Extracellular vesicles from human iPSC-derived neural stem cells: miRNA and protein signatures, and anti-inflammatory and neurogenic properties

Grafting of neural stem cells (NSCs) derived from human induced pluripotent stem cells (hiPSCs) has shown promise for brain repair after injury or disease, but safety issues have hindered their clinical application. Employing nano-sized extracellular vesicles (EVs) derived from hiPSC-NSCs appears to be a safer alternative because they likely have similar neuroreparative properties as NSCs and are amenable for non-invasive administration as an autologous or allogeneic off-the-shelf product. However, reliable methods for isolation, characterization and testing the biological properties of EVs are critically needed for translation. We investigated signatures of miRNAs and proteins and the biological activity of EVs, isolated from hiPSC-NSCs through a combination of anion-exchange chromatography (AEC) and size-exclusion chromatography (SEC). AEC and SEC facilitated the isolation of EVs with intact ultrastructure and expressing CD9, CD63, CD81, ALIX and TSG 101. Small RNA sequencing, proteomic analysis, pathway analysis and validation of select miRNAs and proteins revealed that EVs were enriched with miRNAs and proteins involved in neuroprotective, anti-apoptotic, antioxidant, anti-inflammatory, blood-brain barrier repairing, neurogenic and Aβ reducing activities. Besides, EVs comprised miRNAs and/or proteins capable of promoting synaptogenesis, synaptic plasticity and better cognitive function. Investigations using an in vitro macrophage assay and a mouse model of status epilepticus confirmed the anti-inflammatory activity of EVs. Furthermore, the intranasal administration of EVs resulted in the incorporation of EVs by neurons, microglia and astrocytes in virtually all adult rat and mouse brain regions, and enhancement of hippocampal neurogenesis. Thus, biologically active EVs containing miRNAs and proteins relevant to brain repair could be isolated from hiPSC-NSC cultures, making them a suitable biologic for treating neurodegenerative disorders.

P2X7 Receptor-Dependent microRNA Expression Profile in the Brain Following Status Epilepticus in Mice

The ionotropic ATP-gated P2X7 receptor is an important contributor to inflammatory signaling cascades via the release of Interleukin-1β, as well as having roles in cell death, neuronal plasticity and the release of neurotransmitters. Accordingly, there is interest in targeting the P2X7 receptor for the treatment of epilepsy. However, the signaling pathways downstream of P2X7 receptor activation remain incompletely understood. Notably, recent studies showed that P2X7 receptor expression is controlled, in part, by microRNAs (miRNAs). Here, we explored P2X7 receptor-dependent microRNA expression by comparing microRNA expression profiles of wild-type (wt) and P2X7 receptor knockout mice before and after status epilepticus. Genome-wide microRNA profiling was performed using hippocampi from wt and P2X7 receptor knockout mice following status epilepticus induced by intra-amygdala kainic acid. This revealed that the genetic deletion of the P2X7 receptor results in distinct patterns of microRNA expression. Specifically, we found that in vehicle-injected control mice, the lack of the P2X7 receptor resulted in the up-regulation of 50 microRNAs and down-regulation of 35 microRNAs. Post-status epilepticus, P2X7 receptor deficiency led to the up-regulation of 44 microRNAs while 13 microRNAs were down-regulated. Moreover, there was only limited overlap among identified P2X7 receptor-dependent microRNAs between control conditions and post-status epilepticus, suggesting that the P2X7 receptor regulates the expression of different microRNAs during normal physiology and pathology. Bioinformatic analysis revealed that genes targeted by P2X7 receptor-dependent microRNAs were particularly overrepresented in pathways involved in intracellular signaling, inflammation, and cell death; processes that have been repeatedly associated with P2X7 receptor activation. Moreover, whereas genes involved in signaling pathways and inflammation were common among up- and down-regulated P2X7 receptor-dependent microRNAs during physiological and pathological conditions, genes associated with cell death seemed to be restricted to up-regulated microRNAs during both physiological conditions and post-status epilepticus. Taken together, our results demonstrate that the P2X7 receptor impacts on the expression profile of microRNAs in the brain, thereby possibly contributing to both the maintenance of normal cellular homeostasis and pathological processes.

microRNAs: key modulators of disease-modifying therapies in multiple sclerosis

There is a high level of heterogeneity in symptom manifestations and response to disease-modifying therapies (DMTs) in multiple sclerosis (MS), an immune-based neurodegenerative disease with ever-increasing prevalence in recent decades. Because of unknown aspects of the etiopathology of MS and mechanism of action of DMTs, the reason for this variability is undetermined, and much remains to be understood. Traditionally, physicians consider switching to other DMTs based on the exacerbation of symptoms and/or change in the results of magnetic resonance imaging and biochemical factors. Therefore, identifying biological treatment response markers that help us recognizing non-responders rapidly and subsequently choosing another DMTs is necessary. microRNAs (miRNAs) are micromanagers of gene expression which have been profiled in different samples of MS patients, highlighting their role in pathogenetic of MS. Recent studies have investigated expression profiling of miRNAs after treatment with DMTs to clarify possible DMTs-mediated mechanism and obtaining response to therapy biomarkers. In this review, we will discuss the modulation of miRNAs by DMTs in cells and pathways involved in MS.

Characterization of miRNAs in Cultured Atlantic Salmon Head Kidney Monocyte-Like and Macrophage-Like Cells

Macrophages are among the first cells to respond to infection and disease. While microRNAs (miRNAs) are involved in the process of monocyte-to-macrophage differentiation in mammals, less is known in teleost fish. Here, Atlantic salmon head kidney leukocytes (HKLs) were used to study the expression of miRNAs in response to in vitro culture. The morphological analysis of cultures showed predominantly monocyte-like cells on Day 1 and macrophage-like cells on Day 5, suggesting that the HKLs had differentiated from monocytes to macrophages. Day 5 HKLs also contained a higher percentage of phagocytic cells. Small RNA sequencing and qPCR analysis were applied to examine the miRNA diversity and expression. There were 370 known mature Atlantic salmon miRNAs in HKLs. Twenty-two miRNAs (15 families) were downregulated while 44 miRNAs (25 families) were upregulated on Day 5 vs. Day 1. Mammalian orthologs of many of the differentially expressed (DE) miRNAs are known to regulate macrophage activation and differentiation, while the teleost-specific miR-2188, miR-462 and miR-731 were also DE and are associated with immune responses in fish. In silico predictions identified several putative target genes of qPCR-validated miRNAs associated with vertebrate macrophage differentiation. This study identified Atlantic salmon miRNAs likely to influence macrophage differentiation, providing important knowledge for future functional studies.

Multi-omics systems toxicology study of mouse lung assessing the effects of aerosols from two heat-not-burn tobacco products and cigarette smoke

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Multi-omics systems toxicology study, comprising five omics data modalities.

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Multi-Omics Factor Analysis and multi-modality functional network interpretation.

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Cigarettes smoke (CS) induced complex immunoregulatory interactions across molecular layers.

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Aerosols from two heat-not-burn tobacco products had less impact on lungs than CS.

Cigarette smoke (CS) causes adverse health effects and, for smoker who do not quit, modified risk tobacco products (MRTPs) can be an alternative to reduce the risk of developing smoking-related diseases. Standard toxicological endpoints can lack sensitivity, with systems toxicology approaches yielding broader insights into toxicological mechanisms. In a 6-month systems toxicology study on ApoE^−/− mice, we conducted an integrative multi-omics analysis to assess the effects of aerosols from the Carbon Heated Tobacco Product (CHTP) 1.2 and Tobacco Heating System (THS) 2.2—a potential and a candidate MRTP based on the heat-not-burn (HnB) principle—compared with CS at matched nicotine concentrations. Molecular exposure effects in the lungs were measured by mRNA/microRNA transcriptomics, proteomics, metabolomics, and lipidomics. Integrative data analysis included Multi-Omics Factor Analysis and multi-modality functional network interpretation. Across all five data modalities, CS exposure was associated with an increased inflammatory and oxidative stress response, and lipid/surfactant alterations. Upon HnB aerosol exposure these effects were much more limited or absent, with reversal of CS-induced effects upon cessation and switching to CHTP 1.2. Functional network analysis revealed CS-induced complex immunoregulatory interactions across the investigated molecular layers (e.g., itaconate, quinolinate, and miR-146) and highlighted the engagement of the heme–Hmox–bilirubin oxidative stress axis by CS. This work exemplifies how multi-omics approaches can be leveraged within systems toxicology studies and the generated multi-omics data set can facilitate the development of analysis methods and can yield further insights into the effects of toxicological exposures on the lung of mice.

Evaluation of the clinical value of circulating miR-101, miR-187 and miR-21 in neonatal sepsis diagnosis and prognosis

Background

Neonatal sepsis is considered as a complicated syndrome, which requires urgent intervention to avoid the unfavorable outcome. Thus, biomarkers that can either distinguish sepsis early or predict sepsis outcome are of critical need. Therefore, the aim of the current study was to investigate the clinical value of miR-187, miR-101, and miR-21 on neonatal sepsis diagnosis and prediction of prognosis. Fifty neonates with sepsis, 30 neonates with SIRS, and 20 healthy neonates were selected. Relative expression levels of the selected miRNAs were quantified by qRT-PCR. Serum CRP and PCT were analyzed.

Results

miR-101 and miR-187 expression levels were elevated in septic neonates compared with SIRS neonates and normal controls. The AUC of miR-101, miR-187, and PCT to predict sepsis diagnosis were 0.908, 789, and 0.856, respectively. miR-21 expression levels in non-survivors were significantly higher than in survivors. The AUC of miR-21, a score of neonatal acute physiology (SNAP-II), and PCT to detect the predictive mortality value were 0.793, 0.781, and 0.635, respectively. Survival analysis revealed that high miR-21 expression levels were related to low survival rates. miR-21 and SNAP II were independent risk factors for sepsis mortality, and the AUC of the two combined variables’ predictive probabilities was 0.926 and yielded a specificity of 91.2% and a sensitivity of 81.3%, which was higher than that of either miR-21 or SNAP II.

Conclusion

miR-101 might function as a hopeful diagnostic biomarker for neonatal sepsis. Additionally, miR-21 gained attention to be a valuable predictor for sepsis prognosis especially if combined with SNAP II.

miR-21-5p Under-Expression in Patients with Obstructive Sleep Apnea Modulates Intermittent Hypoxia with Re-Oxygenation-Induced-Cell Apoptosis and Cytotoxicity by Targeting Pro-Inflammatory TNF-α-TLR4 Signaling

The purpose of this study is to explore the anti-inflammatory role of microRNAs (miR)-21 and miR-23 targeting the TLR/TNF-α pathway in response to chronic intermittent hypoxia with re-oxygenation (IHR) injury in patients with obstructive sleep apnea (OSA). Gene expression levels of the miR-21/23a, and their predicted target genes were assessed in peripheral blood mononuclear cells from 40 treatment-naive severe OSA patients, and 20 matched subjects with primary snoring (PS). Human monocytic THP-1 cell lines were induced to undergo apoptosis under IHR exposures, and transfected with miR-21-5p mimic. Both miR-21-5p and miR-23-3p gene expressions were decreased in OSA patients as compared with that in PS subjects, while TNF-α gene expression was increased. Both miR-21-5p and miR-23-3p gene expressions were negatively correlated with apnea hypopnea index and oxygen desaturation index, while TNF-α gene expression positively correlated with apnea hypopnea index. In vitro IHR treatment resulted in decreased miR-21-5p and miR-23-3p expressions. Apoptosis, cytotoxicity, and gene expressions of their predicted target genes—including TNF-α, ELF2, NFAT5, HIF-2α, IL6, IL6R, EDNRB, and TLR4—were all increased in response to IHR, while all were reversed with miR-21-5p mimic transfection under IHR condition. The findings provide biological insight into mechanisms by which IHR-suppressed miRs protect cell apoptosis via inhibit inflammation, and indicate that over-expression of the miR-21-5p may be a new therapy for OSA.

Metformin shows anti-inflammatory effects in murine macrophages through Dicer/microribonucleic acid-34a-5p and microribonucleic acid-125b-5p

AIMS/INTRODUCTION

Metformin, a widely prescribed antidiabetic agent, has been shown to exhibit anti-inflammatory effects in obese and type 2 diabetes patients, but the mechanism is not well elucidated. Microribonucleic acids (miRNAs) are a group of small non-coding ribonucleic acids that participate in many biological and pathological processes. The aim of the present study was to investigate whether Dicer, a key miRNA biogenesis enzyme, and miRNAs in macrophages are implicated in the anti-inflammatory effects of metformin.

MATERIALS AND METHODS

Enzyme-linked immunosorbent assay and reverse transcription quantitative polymerase chain reaction were carried out to verify the anti-inflammatory effects of metformin. miRNA microarray was applied to detect the expression profile of miRNA. Western-blotting, enzyme-linked immunosorbent assay and reverse transcription quantitative polymerase chain reaction were used to examine the role Dicer and miRNAs play in the anti-inflammatory effects of metformin.

RESULTS

In parallel with the suppression of interleukin-6 and tumor necrosis factor-α production in resting and lipopolysaccharide-stimulated macrophages, metformin could induce an increase in Dicer and most miRNAs. When Dicer was knocked down, the anti-inflammatory effects of metformin were significantly attenuated. Additionally, the upregulation of miRNA (miR)-34a-5p and miR-125b-5p by metformin were also blunted in Dicer knockdown macrophages. Furthermore, inhibition of miR-34a-5p and miR-125b-5p could impair the suppressive action of metformin on pro-inflammatory factors production, whereas overexpression of the two miRNAs mimicked the anti-inflammatory effects of metformin.

CONCLUSIONS

Metformin might show anti-inflammatory effects in macrophages through the induction of Dicer and the subsequent upregulation of miR-34a-5p and miR-125b-5p.

Regulation of JAK/STAT signal pathway by miR-21 in the pathogenesis of juvenile idiopathic arthritis

BACKGROUND

Overexpression of the components of the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signalling pathway is the key factor of the pathogenic mechanisms underlying systemic juvenile idiopathic arthritis (sJIA). The study aims to investigate the association between miR-21 and the JAK/STAT signal pathway in JIA.

METHODS

Total RNA was extracted from peripheral blood mononuclear cells (PBMCs) in active JIA patients. The relative expressions of miR-21, STAT3 and suppressor of cytokine signalling 3 in PBMCs were measured by real-time polymerase chain reaction and their expressions were measured by western blotting and dual-luciferase reported assay. Rheumatoid arthritis fibroblast-like synovial cell (RASF) was stimulated to become to osteoclasts using macrophage colony-stimulating factor (M-CSF) and factors that can impact on their differentiation ability were identified through the transfection of LV3-miR-21. The expression of STAT3/p-STAT3 was measured by western blot, and the levels of interleukin (IL)-17A, p65, matrix metalloproteinases (MMP)-3, MMP-4 and receptor activator of nuclear factor-κB after the LV3-miR-21 transfection were tested by enzyme-linked immunosorbent assay. Finally, the miR-21 targeted STAT3 gene was detected by the dual-luciferase reported assay.

RESULTS

The expression of miR-21 was significantly lower in JIA patients than in healthy control (P < 0.05). The level of STAT3 was increased in PBMCs of JIA group compared with control group (P < 0.05). Furthermore, the expression levels of miR-21 in sJIA and polyarticular JIA groups were negatively correlated with STAT3 (r = - 0.5854/r = - 0.6134, P < 0.05). The expression of STAT3 changed little in PBMCS after the stimulation of IL-6 and not in RASFs with transfection of LV3-miR-21. The expression of p-STAT3 decreased after the stimulation of IL-6 in RASFs transfected by LV3-miR-21 (P < 0.05). RASFs were induced into osteoclasts using M-CSF. The number of osteoclasts as determined by tartrate-resistant acid phosphatase staining was significantly lower in group miR-21 mimics as compared with the negative control group (P < 0.05).

CONCLUSIONS

We showed that expression of miR-21 was significantly lower in JIA patients compared with healthy control. MiR-21 might affect the JAK/STAT signal pathway by suppressing the expression of STAT3 and phosphorylation of STAT3. MiR-21 could inhibit the production of osteoclasts induced from RASFs by M-CSF.

Emodin protects against lipopolysaccharide-induced inflammatory injury in HaCaT cells through upregulation of miR-21

Background/aim: Pressure ulcers are a disastrous health issue in which inflammation is involved. Emodin possesses biological properties in inflammation. Our study investigated functions of emodin in lipopolysaccharide (LPS)-treated HaCaT cells. Methods: LPS was used to induce cell inflammation. MTT and flow cytometry were applied for cell viability and apoptosis assays, respectively. Moreover, apoptotic proteins were detected by western blot. Similarly, inflammatory factors and signalling related proteins were also determined by western blot. Results: Emodin increased cell viability and diminished apoptosis in LPS-treated HaCaT cells. Moreover, cleaved-PARP, cleaved-caspase-3 and cleaved-caspase-9 were all downregulated by emodin. Furthermore, inflammatory factors IL-1β, IL-6, Cox-2 and iNOS were inhibited by emodin in LPS-treated cells. In addition, emodin decreased phosphorylation of p65 and IκBα and the level of PTEN while enhanced phosphorylation of PI3K and AKT. Importantly, emodin increased expression of miR-21 suppressed by LPS and miR-21 downregulation negated the protective functions of emodin. Conclusions: Emodin promoted cell growth presented by increasing viability and blocking apoptosis process with inflammation inhibition. The protective activity of emodin was mediated by miR-21 up-regulation.

LincRNA Cox-2 Regulates Lipopolysaccharide-Induced Inflammatory Response of Human Peritoneal Mesothelial Cells via Modulating miR-21/NF-κB Axis

Postoperative peritoneal adhesion (PPA) is a common postoperative complication caused by any peritoneal inflammatory process. This study aimed to identify the biological function of large intergenic non-coding RNAs (lincRNAs) Cox-2 in the inflammation reaction of adhesion formation. The Cox-2 expression in peritoneal adhesion tissues and normal tissues was detected. The human peritoneal mesothelium cells (HPMCs) were treated with lipopolysaccharide (LPS) to induce inflammatory injury. The effect of Cox-2 suppression on cell viability, apoptosis and inflammatory factors of LPS induced HPMCs injury were explored. The regulatory correlation between Cox-2 and miR-21, as well as the targeted genes of miR-21 were identified. Meanwhile, the regulatory mechanism of Cox-2/miR-21 axis on NF-κB pathway was explored. It indicated that Cox-2 was highly expressed in peritoneal adhesion tissues compared with that in normal tissues. Suppression of Cox-2 ameliorated LPS induced HMPCs injury as cell viability was promoted, and cell apoptosis and the production of inflammatory factors were inhibited. And suppression of Cox-2 reversed the LPS induced HPMCs injury by regulation of miR-21 negatively. miR-21 was negatively correlated with TLR4, and TLR4 was predicted as target gene of miR-21. Furthermore, the suppression of miR-21 on LPS induced HPMCs injury was reversed by knockdown of TLR4, which could inhibited the activation of NF-κB pathway axis. It suggested that the effect of Cox-2 on LPS induced HPMCs injury was achieved by negatively regulation of miR-21 and targeted TLR4 through NF-κB pathway axis. The findings may provide a new insight into preventing postoperative peritoneal adhesion.

The predictive value of microRNA-21 for sepsis risk and its correlation with disease severity, systemic inflammation, and 28-day mortality in sepsis patients

Background

This study aimed to investigate the value of microRNA (miR)‐21 for predicting sepsis risk and its correlation with inflammation, disease severity as well as 28‐day mortality in sepsis patients.

Methods

Totally, 219 sepsis patients and 219 healthy controls (HCs) were recruited. Plasma samples were obtained from sepsis patients within 24 hours after admission and from HCs at the enrollment to detect miR‐21 expressions by real‐time quantitative polymerase chain reaction. Besides, the clinical characteristics of sepsis patients were recorded and the 28‐day mortality of sepsis patients was evaluated.

Results

MiR‐21 expression was decreased in sepsis patients compared with HCs, and further receiver operating characteristic (ROC) curve analysis revealed that miR‐21 was of a good value in predicting sepsis risk (area under the curve [AUC]: 0.801, 95% CI: 0.758‐0.844). Besides, miR‐21 expression was negatively associated with acute pathologic and chronic health evaluation II (APACHE II) and sequential organ failure assessment (SOFA) score in sepsis patients. Furthermore, miR‐21 expression was negatively correlated with serum creatinine, C‐reactive protein, tumor necrosis factor‐α, interleukin (IL)‐1β, IL‐6, and IL‐17, while positively correlated with albumin in sepsis patients. However, there was no correlation of miR‐21 expression with white blood cell, smoke, or comorbidities in sepsis patients. Additionally, ROC curve analysis displayed that miR‐21 exhibited a poor predictive value for 28‐day mortality risk in sepsis patients (AUC: 0.588, 95% CI: 0.505‐0.672).

Conclusion

MiR‐21 might serve as a potential biomarker for the development and progression of sepsis, while not for prognosis prediction in sepsis patients.

MicroRNA delivery through nanoparticles

MicroRNAs (miRNAs) are attracting a growing interest in the scientific community due to their central role in the etiology of major diseases. On the other hand, nanoparticle carriers offer unprecedented opportunities for cell specific controlled delivery of miRNAs for therapeutic purposes. This review critically discusses the use of nanoparticles for the delivery of miRNA-based therapeutics in the treatment of cancer and neurodegenerative disorders and for tissue regeneration. A fresh perspective is presented on the design and characterization of nanocarriers to accelerate translation from basic research to clinical application of miRNA-nanoparticles. Main challenges in the engineering of miRNA-loaded nanoparticles are discussed, and key application examples are highlighted to underline their therapeutic potential for effective and personalized medicine.

Gastrodin combined with rhynchophylline inhibits cerebral ischaemia-induced inflammasome activation via upregulating miR-21-5p and miR-331-5p

BACKGROUND

The protective effects of gastrodin and rhynchophylline in ischaemic injury have been reported. However, the underlying mechanism and the effect of the combination of these two drugs in ischaemic injury remain unclear. Herein, we aimed to explore the effects of the combination of gastrodin and rhynchophylline on ischaemia-induced inflammasome activation as well as the underlying mechanism.

METHODS

Middle cerebral artery occlusion (MCAO) mice and oxygen glucose deprivation (OGD)-treated BV2 cells were used as in vivo and in vitro models of ischaemia, respectively. Cerebral injury was determined by TTC staining, H&E staining and neurological deficit scores. The effects of the combination of gastrodin and rhynchophylline on inflammasome activation were measured by the MTT assay, Western blotting and ELISA. The expression of miR-21-5p and miR-331-5p was measured by qRT-PCR. The potential binding between miR-21-5p and TXNIP and between miR-331-5p and TRAF6 was analysed with Targetscan and a luciferase assay.

RESULTS

MCAO-induced tissue infarction, neurological deficits, inflammasome activation, and downregulation of miR-21-5p and miR-331-5p were all mitigated by the combination of gastrodin and rhynchophylline. In OGD-treated BV2 cells, the combination of gastrodin and rhynchophylline also alleviated inflammasome activation and restored the expression of miR-21-5p and miR-331-5p. TXNIP and TRAF6 were confirmed to be targets of miR-21-5p and miR-331-5p, respectively. Moreover, OGD-induced inflammasome activation was attenuated by the overexpression of either miR-331-5p or miR-21-5p and was further attenuated by the overexpression of both. Finally, we demonstrated that a miR-21-5p inhibitor and/or a miR-331-5p inhibitor counteracted the protective effects of gastrodin and/or rhynchophylline.

CONCLUSIONS

The combination of gastrodin and rhynchophylline exerts neuroprotective effects by preventing ischaemia-induced inflammasome activation via upregulating miR-21-5p and miR-331-5p.

MicroRNA-21 deficiency attenuated atherogenesis and decreased macrophage infiltration by targeting Dusp-8

BACKGROUND AND AIMS

Atherosclerosis is a chronic inflammatory disorder mediated by macrophage activation. MicroRNA-21 (miR-21) is a key regulator in the macrophage inflammatory response. However, the functional role of miR-21 in atherogenesis is far from clear.

METHODS AND RESULTS

Here, we report that miR-21 is significantly upregulated in mouse atherosclerotic plaques and peripheral monocytes from patients with coronary artery disease. Compared with miR-21^+/+apoE^-/- mice (apoE^-/- mice), miR-21^-/-apoE^-/- (double knockout, DKO) mice showed less atherosclerotic lesions, reduced presence of macrophages, decreased smooth muscle cells(SMC) and collagen content in the aorta. We further explored the role of miR-21 in macrophage activation in vitro. Bone marrow-derived macrophages (BMDMs) from DKO mice not only exhibit impaired function of migration induced by chemokine (C-C motif) ligand 2 (CCL2) but also a weakened macrophage-endothelium interaction activated by tumor necrosis factor-α (TNF-α). However, atherogenic inflammatory cytokine secretion was not affected by miR-21 in vitro or in vivo. Additionally, miR-21 knockdown in BMDMs directly derepressed the expression of dual specificity protein phosphatase 8 (Dusp-8), a previously validated miR-21 target in cardiac fibroblasts, which negatively regulates mitogen-activated protein kinase (MAPK) signaling, particularly the p38-and c-Jun N-terminal kinase (JNK)-related signaling pathways.

CONCLUSIONS

These data demonstrate that inhibition of miR-21 may restrict the formation of atherosclerotic plaques partly by regulating macrophage migration and adhesion, while, reduced SMCs and collagen content in plaques may lead to a less stable phenotype with the progression of atherosclerosis. Thus, the absence of miR-21 reduces atherosclerotic lesions but may not represent all benefit in atherosclerosis development.

MicroRNAs in Neuroinflammation: Implications in Disease Pathogenesis, Biomarker Discovery and Therapeutic Applications

The central nervous system can respond to threat via the induction of an inflammatory response. Under normal circumstances this response is tightly controlled, however uncontrolled neuroinflammation is a hallmark of many neurological disorders. MicroRNAs are small non-coding RNA molecules that are important for regulating many cellular processes. The ability of microRNAs to modulate inflammatory signaling is an area of ongoing research, which has gained much attention in recent years. MicroRNAs may either promote or restrict inflammatory signaling, and either exacerbate or ameliorate the pathological consequences of excessive neuroinflammation. The aim of this review is to summarize the mode of regulation for several important and well-studied microRNAs in the context of neuroinflammation, including miR-155, miR-146a, miR-124, miR-21 and let-7. Furthermore, the pathological consequences of miRNA deregulation during disorders that feature neuroinflammation are discussed, including Multiple Sclerosis, Alzheimer’s disease, Parkinson’s disease, Prion diseases, Japanese encephalitis, Herpes encephalitis, ischemic stroke and traumatic brain injury. There has also been considerable interest in the use of altered microRNA signatures as biomarkers for these disorders. The ability to modulate microRNA expression may even serve as the basis for future therapeutic strategies to help treat pathological neuroinflammation.

Serum miR-21 expression correlates with radiographic progression but also low bone mineral density in patients with ankylosing spondylitis: a cross-sectional study

Increased expressions of miR-21 have been detected in ankylosing spondylitis (AS) patients. The current study was performed to examine the serum miR-21 expression with radiographic severity in AS patients, which was determined based on the modified New York (NY) criteria for sacroiliac joints assessment and modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS) system for spine involvement. Bone mineral density at lumbar 1–4 and femoral neck were examined by dual-energy absorptiometry (DXA). Serum miR-21 expressions were determined by quantitative real-time PCR, and receiver operating characteristic curve analysis was performed to identify the diagnostic value of miR-21 expression levels regarding the NY criteria. Elevated levels of serum miR-21 expressions were detected in AS patients compared with healthy controls. AS patients with modified NY grade 4 showed significantly higher miR-21 expression than grade 3 and grade 2. AS patients with spinal syndesmophytes had significantly higher serum miR-21 expressions than non-syndesmophyte patients. Increased miR-21 expressions were significantly related to the disease radiographic severity. In addition, serum miR-21 expressions were negatively associated with lumbar 1–4 and femoral neck bone mineral density. In summary, serum miR-21 expressions were related to structural damage and radiological progression in AS, indicating that miR-21 may act as a switch between inflammation and new bone information and regulate different signal ways between lesioned enthesis and trabecular bone.

Phenotypic Effects of Wild-Type and Mutant SOD1 Expression in N9 Murine Microglia at Steady State, Inflammatory and Immunomodulatory Conditions

Accumulation of mutated superoxide dismutase 1 (mSOD1) in amyotrophic lateral sclerosis (ALS) involves injury to motor neurons (MNs), activation of glial cells and immune unbalance. However, neuroinflammation, besides its detrimental effects, also plays beneficial roles in ALS pathophysiology. Therefore, the targeting of microglia to modulate the release of inflammatory neurotoxic mediators and their exosomal dissemination, while strengthening cell neuroprotective properties, has gained growing interest. We used the N9 microglia cell line to identify phenotype diversity upon the overexpression of wild-type (WT; hSOD1WT) and mutated G93A (hSOD1G93A) protein. To investigate how each transduced cell respond to an inflammatory stimulus, N9 microglia were treated with lipopolysaccharide (LPS). Glycoursodeoxycholic acid (GUDCA) and dipeptidyl vinyl sulfone (VS), known to exert neuroprotective properties, were tested for their immunoregulatory properties. Reduced Fizz1, IL-10 and TLR4 mRNAs were observed in both transduced cells. However, in contrast with hSOD1WT-induced decreased of inflammatory markers, microglia transduced with hSOD1G93A showed upregulation of pro-inflammatory (TNF-α/IL-1β/HMGB1/S100B/iNOS) and membrane receptors (MFG-E8/RAGE). Importantly, their derived exosomes were enriched in HMGB1 and SOD1. When inflammatory-associated miRNAs were evaluated, increased miR-146a in cells with overexpressed hSOD1WT was not recapitulated in their exosomes, whereas hSOD1G93A triggered elevated exosomal miR-155/miR-146a, but no changes in cells. LPS stimulus increased M1/M2 associated markers in the naïve microglia, including MFG-E8, miR-155 and miR-146a, whose expression was decreased in both hSOD1WT and hSOD1G93A cells treated with LPS. Treatment with GUDCA or VS led to a decrease of TNF-α, IL-1β, HMGB1, S100B and miR-155 in hSOD1G93A microglia. Only GUDCA was able to increase cellular IL-10, RAGE and TLR4, together with miR-21, while decreased exosomal miR-155 cargo. Conversely, VS reduced MMP-2/MMP-9 activation, as well as upregulated MFG-E8 and miR-146a, while producing miR-21 shuttling into exosomes. The current study supports the powerful role of overexpressed hSOD1WT in attenuating M1/M2 activation, and that of hSOD1G93A in switching microglia from the steady state into a reactive phenotype with low responsiveness to stimuli. This work further reveals GUDCA and VS as promising modulators of microglia immune response by eliciting common and compound-specific molecular mechanisms that may promote neuroregeneration.

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 microRNAs in newborn brain development and hypoxic ischaemic encephalopathy

Neonates can develop hypoxic-ischaemic encephalopathy (HIE) due to lack of blood supply or oxygen, resulting in a major cause of death and disability among term newborns. However, current definitive treatment of therapeutic hypothermia, will only benefit one out of nine babies. Furthermore, the mechanisms of HIE and therapeutic hypothermia are not fully understood. Recently, microRNAs (miRNAs) have become of interest to many researchers due to their important role in post-transcriptional control and deep evolutionary history. Despite this, role of miRNAs in newborns with HIE remains largely unknown due to limited research in this field. Therefore, this review aims to understand the role of miRNAs in normal brain development and HIE pathophysiology with reliance on extrapolated data from other diseases, ages and species due to current limited data. This will provide us with an overview of how miRNAs in normal brain development changes after HIE. Furthermore, it will indicate how miRNAs are affected specifically or globally by the various pathophysiological events. In addition, we discuss about how drugs and commercially available agents can specifically target certain miRNAs as a mechanism of action and potential safety issue with off-target effects. Improving our understanding of the role of miRNAs on the cellular response after HIE would enhance the success of effective diagnosis, prognosis, and treatment of newborns with HIE.

Inflammatory cells and their non-coding RNAs as targets for treating myocardial infarction

Myocardial infarction triggers infiltration of several types of immune cells that coordinate both innate and adaptive immune responses. These play a dual role in post-infarction cardiac remodeling by initiating and resolving inflammatory processes, which needs to occur in a timely and well-orchestrated way to ensure a reestablishment of normalized cardiac functions. Thus, therapeutic modulation of immune responses might have benefits for infarct patients. While such strategies have shown great potential in treating cancer, applications in the post-infarction context have been disappointing. One challenge has been the complexity and plasticity of immune cells and their functions in cardiac regulation and healing. The types appear in patterns that are temporally and spatially distinct, while influencing each other and the surrounding tissue. A comprehensive understanding of the immune cell repertoire and their regulatory functions following infarction is sorely needed. Processes of cardiac remodeling trigger additional genetic changes that may also play critical roles in the aftermath of cardiovascular disease. Some of these changes involve non-coding RNAs that play crucial roles in the regulation of immune cells and may, therefore, be of therapeutic interest. This review summarizes what is currently known about the functions of immune cells and non-coding RNAs during post-infarction wound healing. We address some of the challenges that remain and describe novel therapeutic approaches under development that are based on regulating immune responses through non-coding RNAs in the aftermath of the disease.

Mesenchymal Stromal Cell-Derived Extracellular Vesicles Attenuate Dendritic Cell Maturation and Function

Mesenchymal stromal cells (MSCs) are potent regulators of immune responses largely through paracrine signaling. MSC secreted extracellular vesicles (MSC-EVs) are increasingly recognized as the key paracrine factors responsible for the biological and therapeutic function of MSCs. We report the first comprehensive study demonstrating the immunomodulatory effect of MSC-EVs on dendritic cell (DC) maturation and function. MSC-EVs were isolated from MSC conditioned media using differential ultracentrifugation. Human monocyte-derived DCs were generated in the absence or presence of MSC-EVs (20 ug/ml) then subjected to phenotypic and functional analysis in vitro. MSC-EV treatment impaired antigen uptake by immature DCs and halted DC maturation resulting in reduced expression of the maturation and activation markers CD83, CD38, and CD80, decreased secretion of pro-inflammatory cytokines IL-6 and IL-12p70 and increased production of anti-inflammatory cytokine TGF-β. MSC-EV treated DCs also demonstrated a diminished CCR 7 expression after LPS stimulation, coupled with a significantly reduced ability to migrate toward the CCR7-ligand CCL21, although they were still able to stimulate allogeneic T cell proliferation in vitro. Through microRNA profiling we have identified 49 microRNAs, which were significantly enriched in MSC-EVs compared to their parent MSCs. MicroRNAs with known effect on DC maturation and functions, including miR-21-5p, miR-142-3p, miR-223-3p, and miR-126-3p, were detected within the top 10 most enriched miRNAs in MSC-EVs, with MiR-21-5p as the third highest expressed miRNA in MSC-EVs. In silico analysis revealed that miR-21-5p targets the CCR7 gene for degradation. To verify these observations, DCs were transfected with miR-21-5p mimics and analyzed for their ability to migrate toward the CCR7-ligand CCL21 in vitro. MiR-21-5p mimic transfected DCs showed a clear trend of reduced CCR7 expression and a significantly decreased migratory ability toward the CCL21. Our findings suggest that MSC-EVs are able to recapitulate MSC mediated DC modulation and MSC-EV enclosed microRNAs may represent a novel mechanism through which MSCs modulate DC functions. As MSCs are currently used in clinical trials to treat numerous diseases associated with immune dysregulation, such as graft-versus-host disease and inflammatory bowel disease, our data provide novel evidence to inform potential future application of MSC-EVs as a cell-free therapeutic agent.

MicroRNA-21 in the Pathogenesis of Traumatic Brain Injury

MicroRNAs (miRNAs), an abundant class of small noncoding RNA molecules, which regulate gene expression by functioning as post-transcriptional regulatory factors, have been identified as key components of traumatic brain injury (TBI) progression. MicroRNA-21 (miR-21) is a recently identified typical miRNA that is involved in the signaling pathways of inflammation, neuronal apoptosis, reactive gliosis, disruption of blood brain barrier, angiogenesis and recovery process induced by physical exercises in TBI. Hence, miR-21 is now considered as a potential therapeutic target of TBI. We review the correlative literature and research progress regarding the roles of miR-21 in TBI in this article.

MicroRNA-21 down-regulates inflammation and inhibits periodontitis

Periodontitis is one of the most prevalent inflammatory diseases, characterized by gingival inflammation and alveolar bone loss. MicroRNAs (MiRNAs) are important regulators of inflammation and involved in periodontitis pathogenesis. In this work, we studied the roles of microRNA-21 (miR-21) in periodontitis. MiR-21 is up-regulated in both periodontitis patients and the mice that induced with periodontitis. We tested the roles of miR-21 in the macrophages challenged by periodontitis pathogen Porphyromonas gingivalis (P. gingivalis) lipopolysaccharide (LPS). MiR-21 expression is up-regulated in P. gingivalis LPS-stimulated macrophages. MiR-21 mimic inhibits the pro-inflammatory cytokine production by macrophages, while miR-21 deficiency elevates the production of pro-inflammatory cytokines. Moreover, absence of miR-21 promotes activation of nuclear factor-κB (NF-κB) in P. gingivalis LPS- stimulated cells. In a murine periodontitis model, ligation induced exacerbated gingival inflammation and alveolar bone loss in miR-21 deficient mice than their wild-type littermates. These results demonstrated the anti-inflammatory function of miR-21 in vitro and in vivo, indicating miR-21 could be an interventional target for the control of periodontitis.