MicroRNA-146a gene transfer ameliorates senescence and senescence-associated secretory phenotypes in tendinopathic tenocytes

OBJECTIVE

Tendinopathy is influenced by multiple factors, including chronic inflammation and aging. Senescent cells exhibit characteristics such as the secretion of matrix-degrading enzymes and pro-inflammatory cytokines, collectively known as senescence-associated secretory phenotypes (SASPs). Many of these SASP cytokines and enzymes are implicated in the pathogenesis of tendinopathy. MicroRNA-146a (miR-146a) blocks senescence by targeting interleukin-1β (IL-1β) receptor-associated kinase 4 (IRAK-4) and TNF receptor-associated factor 6 (TRAF6), thus inhibiting NF-κB activity. The aims of this study were to (1) investigate miR-146a expression in tendinopathic tendons and (2) evaluate the role of miR-146a in countering senescence and SASPs in tendinopathic tenocytes.

METHODS

MiR-146a expression was assessed in human long head biceps (LHB) and rat tendinopathic tendons by in situ hybridization. MiR-146a over-expression in rat primary tendinopathic tenocytes was achieved by lentiviral vector-mediated precursor miR-146a transfer (LVmiR-146a). Expression of various senescence-related markers was analyzed by quantitative reverse transcription polymerase chain reaction (qRT-PCR), immunoblotting and immunofluorescence. MiR-146a expression showed a negative correlation with the severity of tendinopathy in human and rat tendinopathic tendons (p<0.001).

RESULTS

Tendinopathic tenocyte transfectants overexpressing miR-146a exhibited downregulation of various senescence and SASP markers, as well as the target molecules IRAK-4 and TRAF6, and the inflammatory mediator phospho-NF-κB. Additionally, these cells showed enhanced nuclear staining of high mobility group box 1 (HMGB1) compared to LVmiR-scramble-transduced controls in response to IL-1β stimulation.

CONCLUSIONS

We demonstrate that miR-146a expression is negatively correlated with the progression of tendinopathy. Moreover, its overexpression protects tendinopathic tenocytes from SASPs and senescence through the IRAK-4/TRAF6/NF-kB pathway.

ApoE enhances mitochondrial metabolism via microRNA-142a/146a-regulated circuits that suppress hematopoiesis and inflammation in hyperlipidemia

Apolipoprotein E (ApoE) is recognized for its pleiotropic properties that suppress inflammation. We report that ApoE serves as a metabolic rheostat that regulates microRNA control of glycolytic and mitochondrial activity in myeloid cells and hematopoietic stem and progenitor cells (HSPCs). ApoE expression in myeloid cells increases microRNA-146a, which reduces nuclear factor κB (NF-κB)-driven GLUT1 expression and glycolytic activity. In contrast, ApoE expression reduces microRNA-142a, which increases carnitine palmitoyltransferase 1a (CPT1A) expression, fatty acid oxidation, and oxidative phosphorylation. Improved mitochondrial metabolism by ApoE expression causes an enrichment of tricarboxylic acid (TCA) cycle metabolites and nicotinamide adenine dinucleotide (NAD+) in macrophages. The study of mice with conditional ApoE expression supports the capacity of ApoE to foster microRNA-controlled immunometabolism. Modulation of microRNA-146a and -142a in the hematopoietic system of hyperlipidemic mice using RNA mimics and antagonists, respectively, improves mitochondrial metabolism, which suppresses inflammation and hematopoiesis. Our findings unveil microRNA regulatory circuits, controlled by ApoE, that exert metabolic control over hematopoiesis and inflammation in hyperlipidemia.

MicroRNA-146a Promotes Embryonic Stem Cell Differentiation towards Vascular Smooth Muscle Cells through Regulation of Kruppel-like Factor 4

OBJECTIVE

Vascular smooth muscle cell (VSMC) differentiation from stem cells is one source of the increasing number of VSMCs that are involved in vascular remodeling-related diseases such as hypertension, atherosclerosis, and restenosis. MicroRNA-146a (miR-146a) has been proven to be involved in cell proliferation, migration, and tumor metabolism. However, little is known about the functional role of miR-146a in VSMC differentiation from embryonic stem cells (ESCs). This study aimed to determine the role of miR-146a in VSMC differentiation from ESCs.

METHODS

Mouse ESCs were differentiated into VSMCs, and the cell extracts were analyzed by Western blotting and RT-qPCR. In addition, luciferase reporter assays using ESCs transfected with miR-146a/mimic and plasmids were performed. Finally, C57BL/6J female mice were injected with mimic or miR-146a-overexpressing ESCs, and immunohistochemistry, Western blotting, and RT-qPCR assays were carried out on tissue samples from these mice.

RESULTS

miR-146a was significantly upregulated during VSMC differentiation, accompanied with the VSMC-specific marker genes smooth muscle-alpha-actin (SMαA), smooth muscle 22 (SM22), smooth muscle myosin heavy chain (SMMHC), and h1-calponin. Furthermore, overexpression of miR-146a enhanced the differentiation process in vitro and in vivo. Concurrently, the expression of Kruppel-like factor 4 (KLF4), predicted as one of the top targets of miR-146a, was sharply decreased in miR-146a-overexpressing ESCs. Importantly, inhibiting KLF4 expression enhanced the VSMC-specific gene expression induced by miR-146a overexpression in differentiating ESCs. In addition, miR-146a upregulated the mRNA expression levels and transcriptional activity of VSMC differentiation-related transcription factors, including serum response factor (SRF) and myocyte enhancer factor 2c (MEF-2c).

CONCLUSION

Our data support that miR-146a promotes ESC-VSMC differentiation through regulating KLF4 and modulating the transcription factor activity of VSMCs.

Repression of miR-146a in predicting poor treatment outcome in triple-negative breast cancer

OBJECTIVES

In the era of precision medicine, the highly aggressive and heterogenous triple-negative breast cancer (TNBC) is still characterized by limited options to support personalized prognosis and guide therapeutic interventions. Thereafter, the aim of the present study has been the thorough evaluation of miR-146a as a novel molecular indicator of TNBC prognosis and treatment outcome, utilizing four independent TNBC cohorts.

DESIGN & METHODS

miR-146a levels were clinically evaluated in our screening (n = 122) and three external validation TNBC cohorts (de Rinaldis et al. 2013, n = 114; Jézéquel et al. 2015, n = 107; TCGA, n = 180). Analysis of miR-146a and validated gene targets was performed in Jézéquel et al. and TCGA validation cohorts. Patients' survival, recurrence and metastasis were determined as clinical endpoints for the survival analysis. Internal validation was performed by bootstrap analysis and clinical net benefit was evaluated by decision curve analysis.

RESULTS

Reduction of miR-146a is strongly associated with patients' poor survival and can predict post-treatment disease early-recurrence, independently of tumor size, lymph node status, histological grade and patients' age. The analysis of the external validation cohorts corroborated the unfavorable nature of miR-146a repression regarding patients' survival and, strikingly, unveiled the ability of miR-146a to predict TNBC metastasis. Combined assessment of miR-146a levels and lymph node status resulted in superior risk-stratification of TNBC patients and higher clinical benefit regarding disease prognosis and post-treatment outcome. Ultimately, miR-146a was negatively associated with EGFR and SOX2 expression in TNBC.

CONCLUSIONS

miR-146a evaluation could ameliorate personalized prognosis and support precision medicine decisions in TNBC.

MiR-146a in ALS: Contribution to Early Peripheral Nerve Degeneration and Relevance as Disease Biomarker

Amyotrophic lateral sclerosis (ALS) is characterized by the progressive, irreversible loss of upper and lower motor neurons (UMNs, LMNs). MN axonal dysfunctions are emerging as relevant pathogenic events since the early ALS stages. However, the exact molecular mechanisms leading to MN axon degeneration in ALS still need to be clarified. MicroRNA (miRNA) dysregulation plays a critical role in the pathogenesis of neuromuscular diseases. These molecules represent promising biomarkers for these conditions since their expression in body fluids consistently reflects distinct pathophysiological states. Mir-146a has been reported to modulate the expression of the NFL gene, encoding the light chain of the neurofilament (NFL) protein, a recognized biomarker for ALS. Here, we analyzed miR-146a and Nfl expression in the sciatic nerve of G93A-SOD1 ALS mice during disease progression. The miRNA was also analyzed in the serum of affected mice and human patients, the last stratified relying on the predominant UMN or LMN clinical signs. We revealed a significant miR-146a increase and Nfl expression decrease in G93A-SOD1 peripheral nerve. In the serum of both ALS mice and human patients, the miRNA levels were reduced, discriminating UMN-predominant patients from the LMN ones. Our findings suggest a miR-146a contribution to peripheral axon impairment and its potential role as a diagnostic and prognostic biomarker for ALS.

Effects of acupuncture on the miR-146a-mediated IRAK1/TRAF6/NF-κB signaling pathway in rats with sarcopenia induced by D-galactose

Background

Sarcopenia during aging is closely linked to sterile, low-grade, chronic inflammation. However, considering the increasingly aging global population, the effectiveness of existing treatments for sarcopenia is not exact, and acupuncture, as an effective anti-inflammatory therapy, has the potential to treat it.

Methods

Fifty Sprague-Dawley rats were randomly allocated into five groups, including Control group, D-galactose (D-gal) group, D-gal + acupuncture (DA) group, D-gal + non-acupoint (DN) group and D-gal amino acid mixture (DAA) group. An aging rat was model constructed using D-gal for 12 weeks. Rats in the control group received 0.9% physiological saline daily. Treatment groups were acupunctured or given amino acid mixture interventions daily, and lasted for last 4 consecutive weeks. The effects of acupuncture were evaluated by the hematoxylin and eosin staining (H&E), transmission electron microscopic (TEM) examination and terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assays. The anti-inflammatory mechanism of acupuncture was studied by using the expressions of microRNA-146a (miR-146a) mediated nuclear factor-kappa B (NF-κB) signaling pathway-related proteins were detected by immunofluorescence, western blotting, quantitative real-time polymerase chain reaction (PCR) and enzyme-linked immunosorbent assay (ELISA).

Results

Rats injected by D-galactose (D-gal) revealed apparent skeletal muscle atrophy with significantly reduced cross-sectional area and fiber diameter. In contrast, acupuncture treatment alleviated these hallmarks of skeletal muscle atrophy and mitigated the mitochondrial aberrations and skeletal muscle apoptosis in D-gal rats. In addition, acupuncture also downgraded the overexpression of inflammatory factors in skeletal muscle, influenced miR-146a and the target genes level, and inhibited NF-κB nuclear translation in D-gal rats.

Conclusions

Acupuncture may ameliorate skeletal muscle atrophy, and its effects may be associated with the control of mitochondrial function regulation and the suppression of inflammation.

Effects of crocin on T-bet/GATA-3 ratio, and miR-146a and miR-106a expression levels in lung tissue of ovalbumin-sensitized mice

Objectives

Although various studies have revealed the beneficial effects of crocin (derived from saffron), such as anti-inflammatory, anti-cancer, antioxidant, and immune modulator, however, its exact mechanism is unknown. The present study aimed to investigate the effect of crocin on the expression ratio of T-bet/GATA-3 as an indicator of altered immune responses in the lung tissue of ovalbumin (OVA)-sensitized mice. In addition, the effect of crocin on the expression level of miR-146a and miR-106a in the lung tissue OVA-sensitized mice was investigated.

Materials and Methods

Mice were randomly divided into five groups (n=6): Control; OVA, OVA + Crocin 25, OVA + Cro 50, and OVA + Cro100 groups. Crocin was administrated intraperitoneally at doses of 25, 50, and 100 mg/kg for five consecutive days. One day after asthma induction, animals were euthanized, and lungs were sampled for pathological and gene expression analysis.

Results

OVA-sensitization led to increased inflammation and histopathological changes in the lung tissue of mice. In addition, GATA-3 expression increased (P<0.001) and T-bet expression decreased (P<0.001) in OVA-sensitized groups. The T-bet/GATA3 ratio was also reduced markedly in asthma groups (P<0.001). Furthermore, increased expression of miR-146a and miR-106a levels was evident in the lung tissue of OVA-sensitized mice (P<0.001 for both). Intervention with high concentrations of crocin (50 and 100 mg/kg) significantly reduced airway inflammation, GATA-3 expression, miR-146a expression, and miR-106a expression and corrected the T-bet/GATA-3 ratio (P<0.05 to P<0.001).

Conclusion

Treatment with crocin led to a decrease in the severity of lung inflammation in OVA-sensitized mice, which is probably through the reduction of the T-bet/GATA-3 ratio, and mir-146a and mir-106a expression level.

miR-146a promotes M2 macrophage polarization and accelerates diabetic wound healing by inhibiting the TLR4/NF-κB axis

We tried to unveil the clinical significance of miR-146a as a biomarker in M2 macrophage polarization in diabetic wound healing. Initially, we found reduced miR-146a in macrophages of diabetic patients. Next, dual-luciferase assay verified that toll-like receptor 4 (TLR4) was a target gene of miR-146 and was negatively regulated by miR-146. Moreover, after ectopic expression and depletion experiments of miR-146 and/or TLR4, lipopolysaccharide-induced inflammatory response of macrophages was detected. The results revealed that overexpression of miR-146a promoted the M2 macrophage polarization by suppressing the TLR4/nuclear factor-kappaB (NF-κB) axis, so as to enhance wound healing in diabetic ulcers. Further, mouse models with diabetic ulcers were established to investigate the effects of miR-146a on diabetic wound healing in vivo, which revealed that miR-146a promoted wound healing in diabetic ulcers by inhibiting the TLR4/NF-κB axis. In conclusion, we demonstrate that miR-146a can induce M2 macrophage polarization to enhance wound healing in diabetic ulcers by inhibiting the TLR4/NF-κB axis.

microRNA-146a-5p, Neurotropic Viral Infection and Prion Disease (PrD)

The human brain and central nervous system (CNS) harbor a select sub-group of potentially pathogenic microRNAs (miRNAs), including a well-characterized NF-kB-sensitive Homo sapiens microRNA hsa-miRNA-146a-5p (miRNA-146a). miRNA-146a is significantly over-expressed in progressive and often lethal viral- and prion-mediated and related neurological syndromes associated with progressive inflammatory neurodegeneration. These include ~18 different viral-induced encephalopathies for which data are available, at least ~10 known prion diseases (PrD) of animals and humans, Alzheimer’s disease (AD) and other sporadic and progressive age-related neurological disorders. Despite the apparent lack of nucleic acids in prions, both DNA- and RNA-containing viruses along with prions significantly induce miRNA-146a in the infected host, but whether this represents part of the host’s adaptive immunity, innate-immune response or a mechanism to enable the invading prion or virus a successful infection is not well understood. Current findings suggest an early and highly interactive role for miRNA-146a: (i) as a major small noncoding RNA (sncRNA) regulator of innate-immune responses and inflammatory signaling in cells of the human brain and CNS; (ii) as a critical component of the complement system and immune-related neurological dysfunction; (iii) as an inducible sncRNA of the brain and CNS that lies at a critical intersection of several important neurobiological adaptive immune response processes with highly interactive associations involving complement factor H (CFH), Toll-like receptor pathways, the innate-immunity, cytokine production, apoptosis and neural cell decline; and (iv) as a potential biomarker for viral infection, TSE and AD and other neurological diseases in both animals and humans. In this report, we review the recent data supporting the idea that miRNA-146a may represent a novel and unique sncRNA-based biomarker for inflammatory neurodegeneration in multiple species. This paper further reviews the current state of knowledge regarding the nature and mechanism of miRNA-146a in viral and prion infection of the human brain and CNS with reference to AD wherever possible.

MicroRNA-146a overexpression alleviates intestinal ischemia/reperfusion-induced acute lung injury in mice

Previous studies have shown that microRNAs (miRs), such as miR-146a play an important role in the pathogenesis of intestinal ischemia/reperfusion (I/R)-induced injury; however, the role of miR-146a in intestinal I/R-induced acute lung injury has not been elucidated. An intestinal I/R-induced injury mouse model was established in the present study by clamping the superior mesenteric artery and expression levels of miR-146a in intestinal and lung tissue samples were evaluated using reverse transcription-quantitative PCR (RT-qPCR). Intestinal and lung histopathological characteristics in mice with intestinal I/R-induced injury were assessed by hematoxylin and eosin staining, and mRNA and protein expression levels in intestinal and lung tissue samples were evaluated using RT-qPCR and western blotting, respectively. miR-146a expression was significantly downregulated in the intestinal and lung tissue samples of mice with intestinal I/R-induced injury. Intestinal I/R injury-induced histopathological changes in the lung and intestines, and pulmonary edema in mice transduced with an adenoviral miR-146a-overexpression vector (the miR-146a overexpression group) were alleviated. mRNA expression levels of TNF-α, IL-1β, IFN-γ and TGF-β1, and protein expression levels of TNF receptor-associated factor 6, phosphorylated-p65 NF-κB, cleaved caspase-3 and cleaved caspase-9 in lung and intestinal tissue samples were downregulated in I/R-miR-146a-overexpressing mice, compared with those from the I/R-negative control group. Thus, the present study identified that pre-treatment with the miR-146a overexpression vector alleviated intestinal I/R-induced acute lung injury in mice.

MicroRNA-146a downregulates interleukin-13 and inhibits the proliferation of human periodontal ligament stem cells

OBJECTIVE

This study was carried out to investigate the interaction between microRNA-146a and interleukin-13 (IL-13) in periodontitis.

DESIGN

The expression levels of microRNA-146a and IL-13 in periodontal ligament stem cells (PDLSCs) derived from periodontitis-affected teeth and healthy teeth were detected by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR). A microRNA-146a mimic was transfected into PDLSCs, and proliferation and IL-13 expression were detected via a cell counting kit-8 (CCK-8) assay and western blot, respectively.

RESULTS

microRNA-146a was downregulated and IL-13 was upregulated in PDLSCs derived from periodontitis-affected teeth compared to that in PDLSCs derived from healthy teeth. microRNA-146a and IL-13 were negatively correlated in periodontitis-derived PDLSCs but not in those derived from healthy teeth. The former also exhibited significantly enhanced cell proliferation. Overexpression of microRNA-146a inhibited proliferation of PDLSCs derived from both periodontitis-affected teeth and healthy teeth while downregulating IL-13.

CONCLUSIONS

microRNA-146a may improve periodontitis by downregulating IL-13 and inhibiting the proliferation of human PDLSCs.

Serum exosomal microRNA-146a as a novel diagnostic biomarker for acute coronary syndrome

Background

Circulating microRNAs (miRNAs) have emerged as potential biomarkers for cardiovascular diseases. However, few studies have focused on the role of exosomal miRNAs in acute coronary syndrome (ACS). The purpose of this study was to explore weather serum exosomal microRNA-146a (exo-miR-146a) could be used as a novel diagnostic biomarker for ACS and to investigate its relationship with inflammatory response.

Methods

A total of 63 ACS patients and 25 patients with normal coronary arteries (Control) were enrolled respectively. The serum exosomes were isolated and then identified by transmission electron microscopy (TEM), western blot, and nanoparticle tracking analysis (NTA). The expression levels of exo-miR-146a in serum were detected by real-time quantitative polymerase chain reaction (RT-qPCR) and the expression levels of interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in serum were assessed by enzyme-linked immunosorbent assay (ELISA). Spearman’s correlation analysis was used to appraise the potential factors related to serum exo-miR-146a and receiver operating characteristic (ROC) curve analysis was applied for predicting the accuracy of ACS via the area under curve (AUC).

Results

Exosomes isolated from serum were of typical cup-like shape, with 50-150 nm diameter, and expressed CD9, CD63, CD81, and HSP70. The expression levels of serum exo-miR-146a, IL-1β, IL-6, and TNF-α were significantly increased in ACS patients compared with the control group, Spearman′s correlation analysis indicated that exo-miR-146a expression was markedly positively correlated with IL-1β, IL-6, and TNF-α. The ROC curve analyses revealed that exo-miR-146a could distinguish ACS patients from their normal controls.

Conclusions

The serum exo-miR-146a may be used as a novel diagnostic biomarker for ACS patients, and it is also associated with inflammatory response.

Elevation of miR-146a Inhibits BTG2/BAX Expression to Ameliorate Postoperative Cognitive Dysfunction Following Probiotics (VSL#3) Treatment

It has been reported that the gut microbiome modulates postoperative cognitive dysfunction (POCD), and that administration of probiotics (VSL#3) may effectively relieve POCD. In this study, we aimed to identify the underlying mechanism of VSL#3 in POCD. A mouse model of POCD was constructed in adult male C57BL/6 mice, which were then treated with VSL#3. VSL#3 exerted a protective role against POCD and resultant neuronal apoptosis. The expression of miR-146a was found to be downregulated in hippocampal tissues of POCD mice, while VSL#3 could restore its expression. Loss- and gain-function approaches were conducted to determine the roles of microRNA (miR)-146a, B-cell translocation gene 2 (BTG2), and Bcl-2-associated X protein (Bax) in post-operative effects on cognitive function and neuronal apoptosis. The levels of reactive oxygen species (ROS), malondialdehyde (MDA), and superoxide dismutase (SOD) were measured to determine oxidative stress in brain tissue. The dual-luciferase reporter gene assay identified that miR-146a could target BTG2 and negatively regulate its expression. BTG2 knockdown suppressed neuronal apoptosis and contributed to shortened time of latency, prolonged time of mice spent in the target quadrant, and reduced oxidative stress through downregulating Bax expression. Finally, VSL#3 treatment upregulated the expression of miR-146a to block BTG2/Bax axis and consequently inhibited neuronal apoptosis and reduced oxidative stress in POCD mice. Taken together, the study suggested that miR-146a-mediated suppression of BTG2/Bax contributed to the protective role of probiotics treatment against POCD.

Treatment of diabetic peripheral neuropathy with engineered mesenchymal stromal cell-derived exosomes enriched with microRNA-146a provide amplified therapeutic efficacy

Diabetic peripheral neuropathy (DPN) is one of the most prevalent chronic complications of diabetes mellitus with no effective treatment. We recently demonstrated that mesenchymal stromal cell (MSC)-derived exosomes (exo-naïve) alleviate neurovascular dysfunction and improve functional recovery. MicroRNA (miRNA), one of the exosomal cargos, downregulates inflammation-related genes, resulting in suppression of pro-inflammatory gene activation. In the present study, we developed engineered MSC-exosomes loaded with miR-146a (exo-146a) and compared the therapeutic effects of exo-146a with exo-naïve in diabetic (db/db) mice with DPN. Exo-146a possesses a high loading capacity, robust ability to accumulate in peripheral nerve tissues upon systemic administration, and evokes substantially enhanced therapeutic efficacy on neurological recovery compared with exo-naïve. Treatment of DPN in diabetic mice with exo-146a for two weeks significantly increased and decreased nerve conduction velocity, and thermal and mechanical stimuli threshold, respectively, whereas it took four weeks of exo-naive treatment to achieve these improvements. Compared with exo-naïve, exo-146a significantly suppressed the peripheral blood inflammatory monocytes and the activation of endothelial cells via inhibiting Toll-like receptor (TLR)-4/NF-κB signaling pathway. These data provide a proof-of-concept about both the feasibility and efficacy of the exosome-based gene therapy for DPN. The translation of this approach to the clinic has the potential to improve the prospects for people who suffer from DPN.

MicroRNA-146a switches microglial phenotypes to resist the pathological processes and cognitive degradation of Alzheimer's disease

Alzheimer's disease (AD) is the most prevalent neurodegenerative disease and currently has no effective treatment. Mainstream research on the mechanisms and therapeutic targets of AD is focused on the two most important hallmarks, Aβ and Tau, but the results from clinical studies are not encouraging. Abnormal microglial polarization is a clear typical pathological feature in the progression of AD. Microglia can be neuroprotective by degrading and removing Aβ and Tau. However, under AD conditions, microglia transform into a pro-inflammatory phenotype that decreases the phagocytic activity of microglia, damages neurons and promotes the pathology of AD. We previously reported that a miR-146a polymorphism is associated with sporadic AD risk, and the nasal administration of miR-146a mimics reduced cognitive impairment and the main pathological features of AD. However, it is not clear by what mechanism miR-146a resists the pathological process of AD. In this study, we discovered that microglia-specific miR-146a overexpression reduced cognitive deficits in learning and memory, attenuated neuroinflammation, reduced Aβ levels, ameliorated plaque-associated neuritic pathology, and prevented neuronal loss in APP/PS1 transgenic mice. In addition, we found that miR-146a switched the microglial phenotype, reduced pro-inflammatory cytokines and enhanced phagocytic function to protect neurons in vitro and in vivo. Moreover, transcriptional analysis confirmed that miR-146a opposed the pathological process of AD mainly through neuroinflammation-related pathways. In summary, our results provide sufficient evidence for the mechanism by which miR-146a opposes AD and strengthen the conclusion that miR-146a is a promising target for AD and other microglia-related diseases.

Knockdown of miR-146a in regulatory T cells suppresses heart transplantation rejection in mice by increasing autophagy

Clinical trials of regulatory T cells (Tregs) have shown that adoptive transfer of Tregs has great promise for the treatment of rejection. However, strategies to improve Treg function are needed in order to enhance their efficacy and reduce the number of Tregs required for adoptive transfer. Autophagy is a process for degrading intracellular components, and it mediates cell death, lymphocyte homeostasis, and Treg function. Studies have shown that the survival and function of Tregs with disrupted autophagy are defective. We found that the autophagic status of Tregs was compromised during acute rejection, allowing us to enhance Treg autophagy by regulating microRNA-146a (miR-146a), which is highly expressed in Tregs and is implicated in their function and metabolism. MiR-146a antagomir-mediated miR-146a knockdown promoted Treg autophagy, as evaluated by Western blot analysis. Further, we evaluated whether altering autophagy affects Treg function in both an in vitro cell coculture model and a heart transplantation model in mice. An increase in autophagy enhanced the inhibitory effects of Tregs on CD4⁺ T cells and dendritic cells (DCs) in vivo and in vitro. In addition, adoptive transfer of highly autophagic Tregs treated with miR-146a antagomir significantly alleviated rejection. Collectively, these data provide a new method that uses miR-146a knockdown to increase Treg efficacy by increasing autophagy.

MicroRNA-146a regulates the production of cytokines in lymphocytes stimulated by Porphyromonas gingivalis lipopolysaccharide

OBJECTIVES

This study aimed to investigate the effects of microRNA-146a (miR-146a) on the production of cytokines in lymphocytes stimulated by Porphyromonas gingivalis (P.gingivalis) lipopolysaccharide (LPS).

METHODS

Lymphocytes were harvested from mouse spleen and cultured in vitro. The cells were treated with P. gingivalis LPS, miR-146a mimic, or miR-146a inhibitor. Scramble RNA served as the negative control of mimic and inhibitor. The production of inflammatory cytokines was detected by quantitative real-time polymerase chain reaction and enzyme-linked immunosorbent assay.

RESULTS

Compared with non-LPS-stimulated group, P. gingivalis LPS could increase the levels of interleukin (IL)-1β, IL-6, receptor activator NF-κB ligand (RANKL), and IL-10 (P<0.05) and decrease the mRNA level of osteoprotectin (OPG) (P<0.05). However, it did not significantly change the secretion of OPG. Compared with the negative control group, miR-146a mimic upregulated the levels of IL-10 and OPG (P<0.05), downregulated IL-1β, IL-6, and RANKL (P<0.05). Meanwhile, miR-146a inhibitor had a reverse effect on these cytokines (P<0.05) in P.gingivalis LPS-treated-lymphocytes.

CONCLUSIONS

MiR-146a can provide a suitable microenvironment for bone formation by preventing the inflammatory effects of P.gingivalis LPS through the inhibition of IL-1β, IL-6, and RNAKL, thereby enhancing IL-10 and OPG.

Correlations between microRNA-146a and immunoglobulin and inflammatory factors in Guillain-Barré syndrome

Objective

To study correlations between expression of microRNA-146a (miR-146a) and immunoglobulin and inflammatory cytokines in serum of patients with Guillain–Barré syndrome (GBS).

Methods

Eighty-four patients with GBS were selected as the experimental group and 50 healthy individuals as controls. Reverse transcription-PCR was used to detect expression of miR-146a in peripheral blood of all participants. Immunoturbidometric assay was used to detect immunoglobulins (Ig)G, IgA, and IgM in peripheral blood of all participants. The levels of interleukin-6 (IL-6), C-reactive protein (CRP), and tumor necrosis factor α (TNF-α) were measured by ELISA in peripheral blood. The expression of miR-146a was compared between the two groups and Pearson correlation analysis was used to analyze correlations between miR-146a and immunoglobulin and inflammatory factors.

Results

Expression of miR-146a was higher in the GBS group than in controls. Expression of IL-6, CRP, TNF-α, and IgG was significantly higher in the GBS group than in controls. miR-146a was significantly and positively correlated with IL-6, CRP, TNF-α, and IgG but not with IgA and IgM.

Conclusion

The expression profile of miR-146a in patients with GBS differs from that in healthy individuals. Thus, miR-146a may participate in the pathogenesis of GBS by regulating immune and inflammatory responses.

Gastrointestinal (GI)-Tract Microbiome Derived Neurotoxins and their Potential Contribution to Inflammatory Neurodegeneration in Alzheimer's Disease (AD)

The human gastrointestinal (GI)-tract microbiome is a rich, complex and dynamic source of microorganisms that possess a staggering diversity and complexity. Importantly there is a significant variability in microbial complexity even amongst healthy individuals-this has made it difficult to link specific microbial abundance patterns with age-related neurological disease. GI-tract commensal microorganisms are generally beneficial to human metabolism and immunity, however enterotoxigenic forms of microbes possess significant potential to secrete what are amongst the most neurotoxic and pro-inflammatory biopolymers known. These include toxic glycolipids such as lipopolysaccharide (LPS), enterotoxins, microbial-derived amyloids and small non-coding RNA. One major microbial species of the GI-tract microbiome, about ~100-fold more abundant than Escherichia coli in deep GI-tract regions is Bacteroides fragilis, an anaerobic, rod-shaped Gram-negative bacterium. B. fragilis can secrete: (i) a particularly potent, pro-inflammatory and unique LPS subtype (BF-LPS); and (ii) a zinc-metalloproteinase known as B. fragilis-toxin (BFT) or fragilysin. Ongoing studies indicate that BF-LPS and/or BFT disrupt paracellular-and transcellular-barriers by cleavage of intercellular-proteins resulting in 'leaky' barriers. These barriers: (i) become defective and more penetrable with aging and disease; and (ii) permit entry of microbiome-derived neurotoxins into the systemic-circulation from which they next transit the blood-brain barrier and gain access to the CNS. Here LPS accumulates and significantly alters homeostatic patterns of gene expression. The affinity of LPS for neuronal nuclei is significantly enhanced in the presence of amyloid beta 42 (Aβ42) peptides. Recent research on the appearance of the brain thanatomicrobiome at the time of death and the increasing likelihood of a complex brain microbiome are reviewed and discussed. This paper will also highlight some recent advances in this extraordinary research area that links the pro-inflammatory exudates of the GI-tract microbiome with innate-immune disturbances and inflammatory-signaling within the CNS with reference to Alzheimer's disease (AD) wherever possible.

Inhibition of microRNA-146a attenuated heart failure in myocardial infarction rats

The aim of the present study was to determine the roles of microRNA (miR)-146a on myocardial infarction (MI)-induced heart failure and cardiac remodeling. Experiments were carried out in Sprague-Dawley rats treated with ligation of left coronary artery to induce heart failure, and in primary neonatal rat cardiac fibroblasts (CFs) and cardiomyocytes treated with angiotensin (Ang) II. Four weeks after MI, rats were injected with miR-146a antagomiR or agomiR via tail vein. After 2 weeks of injection, the rats were killed. In MI rats, left ventricle (LV) ejection fraction and fractional shortening were reduced, and LV volumes in diastole and systole were increased, which were reversed by miR-146a antagomiR, and further exacerbated after miR-146a agomiR treatment. Administration of miR-146a antagomiR improved the decreases of LV ±dp/dt_max and LV systolic pressure (LVSP), and the increase in LV end-diastolic pressure (LVEDP) of MI rats, but miR-146a agomiR deteriorated the LV ±dp/dt_max, LVSP and LVEDP. The increases in the levels of atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), collagen I and collagen III in the heart, and ST2 and norepinephrine in the serum of MI rats were inhibited by miR-146a antagomiR, but aggravated after miR-146a agomiR treatment. The increases of collagen I and collagen III levels induced by Ang II in CFs, and the increases of ANP and BNP levels induced by Ang II in cardiomyocytes were inhibited by miR-146a antagomiR, but aggravated by miR-146a agomiR. These results demonstrated that inhibition of miR-146a improved cardiac dysfunction and cardiac remodeling in heart failure rats.

Protective effect and mechanism of microRNA-146a on ankle fracture

The present study investigated the expression and role of microRNA-146a (miR-146a) on ankle fracture, and explored the underlying mechanism. miR-146a levels in the blood of patients with ankle fracture was measured using reverse transcription-quantitative PCR (RT-qPCR). Expression of pro-inflammatory factors in the peripheral blood of ankle fracture patients was also detected using ELISA. Oxidative stress biomarkers including malondialdehyde (MDA), superoxide dismutase (SOD) and catalase (CAT) were additionally investigated. The role of miR-146a in ankle fracture was investigated in vitro where MG-63 cells were transfected with miR-146a mimic or miR-146a inhibitor for 2 h, then treated with 1 µg/ml bradykinin for 24 h. An MTT assay was then performed to assess cell viability and pro-inflammatory factors were detected via RT-qPCR and western blot analysis. Finally, activation of the TNF receptor associated factor 6 (TRAF6)/NF-κB pathway was determined via western blotting and RT-qPCR. The results demonstrated that miR-146a was significantly downregulated in the blood of patients with ankle fracture. The protein levels of tumor necrosis factor (TNF-α), interleukin (IL)-1β and IL-6 were significantly upregulated in patients with ankle fracture. In addition, MDA content significantly increased, and SOD and CAT activity significantly decreased in patients with ankle fracture. In vitro experiments demonstrated that miR-146a overexpression significantly enhanced cell viability. miR-146a mimic suppressed BK-induced upregulation of TNF-α, IL-1β, IL-6 and MDA, and increased SOD and CAT activity. Finally, miR-146a mimic inhibited activation of the TRAF6/NF-κB pathway whilst miR-146a inhibitor had the opposite effect. In conclusion, miR-146a may be a potential therapeutic target for the treatment of ankle fracture by inhibiting the inflammatory response and attenuating oxidative stress.

Genetic variants of microRNA-146a gene: an indicator of systemic lupus erythematosus susceptibility, lupus nephritis, and disease activity

Genetic variations of microRNA encoding genes influence various sorts of diseases by modifying the expression or activity of microRNAs. MicroRNA 146a is an epigenetic regulator of immune response through controlling the type I interferon (IFN) and nuclear factor kappa B (NF-κB) pathways. Genetic variations of microRNA 146a impact the susceptibility to systemic lupus erythematosus (SLE) and its clinical presentations. This study aimed to investigate the polymorphisms of microRNA-146a gene (rs2431697 and rs57095329) in patients with SLE and its association with disease activity. Sixty-five patients with SLE and 40 apparently healthy controls were enrolled in this study. Patients were subjected to history taking, clinical examination, and disease activity evaluation by SLEDAI score. The microRNA-146a variants were determined by allele discrimination real-time PCR method in all participants. We found a statistically significant association between rs2431697 T allele and SLE (P-value < 0.05), but there was no significant association between rs57095329 and SLE. The T/T genotype of microRNA-146a rs2431697 was associated with lupus nephritis, higher disease activity, and autoantibodies production. The microRNA-146a rs2431697 T allele could be a potential risk factor that contributes to SLE susceptibility, development of lupus nephritis, and disease activity.

Association of miR-146a polymorphism rs2910164 and type 2 diabetes risk: a meta-analysis

OBJECTIVE

Circulating miR-146a is aberrantly expressed in patients with type 2 diabetes (T2D), probably resulting from gene polymorphisms. However, the role of polymorphism rs2910164 in T2D pathogenesis remains controversial. Thus, we designed a meta-analysis to investigate the association between rs2910164 and T2D.

METHODS

PubMed and Embase were searched for eligible papers in English published through September 2, 2019. Random or fixed effect models were used to determine risk estimates according to heterogeneities.

RESULTS

Four studies, involving 2,069 patients and 1,950 controls, were included. Odds ratios (ORs) and 95% confidence intervals (95% CIs) were used to pool the effect size. The pooled ORs and 95% CIs were 1.501 (0.887-2.541), 1.102 (0.931-1.304), 1.276 (0.900-1.811), 1.204 (0.878-1.652), 1.238 (0.880-1.740), and 1.350 (0.904-2.016) under the homozygote, heterozygote (CG vs. GG and CC vs. CG), dominant, allele, and recessive models, respectively. Heterogeneity was detected in most genetic models, with subgroup analyses performed by ethnicity, genotyping method, and disease duration. The co-dominant model was determined to be the most appropriate genetic model.

CONCLUSIONS

Our findings suggested that polymorphism rs2910164 is not correlated with T2D susceptibility. However, the results should be interpreted with caution because of confounding factors.

Vesicular Transport of Encapsulated microRNA between Glial and Neuronal Cells

Exosomes (EXs) and extracellular microvesicles (EMVs) represent a diverse assortment of plasma membrane-derived nanovesicles, 30–1000 nm in diameter, released by all cell lineages of the central nervous system (CNS). They are examples of a very active and dynamic form of extracellular communication and the conveyance of biological information transfer essential to maintain homeostatic neurological functions and contain complex molecular cargoes representative of the cytoplasm of their cells of origin. These molecular cargoes include various mixtures of proteins, lipids, proteolipids, cytokines, chemokines, carbohydrates, microRNAs (miRNA) and messenger RNAs (mRNA) and other components, including end-stage neurotoxic and pathogenic metabolic products, such as amyloid beta (Aβ) peptides. Brain microglia, for example, respond to both acute CNS injuries and degenerative diseases with complex reactions via the induction of a pro-inflammatory phenotype, and secrete EXs and EMVs enriched in selective pathogenic microRNAs (miRNAs) such as miRNA-34a, miRNA-125b, miRNA-146a, miRNA-155, and others that are known to promote neuro-inflammation, induce complement activation, disrupt innate–immune signaling and deregulate the expression of neuron-specific phosphoproteins involved in neurotropism and synaptic signaling. This communication will review our current understanding of the trafficking of miRNA-containing EXs and EMVs from astrocytes and “activated pro-inflammatory” microglia to target neurons in neurodegenerative diseases with an emphasis on Alzheimer’s disease wherever possible.

Lysine-Specific Demethylase 1 Affects the Progression of Papillary Thyroid Carcinoma via HIF1α and microRNA-146a

CONTEXT

Lysine-specific demethylase 1 (LSD1) stabilizes hypoxia-inducible factor 1α (HIF1α) to advance tumor progression, while HIF1α functions as a transcription factor to increase the expression of microRNA-146a (miR-146a).

OBJECTIVE

We aim to investigate whether LSD1 affects the development of papillary thyroid carcinoma (PTC) via HIF1α and miR-146a.

DESIGN

In vitro assays were performed with Nthy-ori 3-1, BHP5-16, BCPAP, K1, and BHP2-7 cell lines. In vivo assays were conducted with established xenograft tumors in nude mice.

SETTING

This study was conducted at our lab.

PATIENTS AND MATERIALS

PTC tissues and corresponding adjacent normal tissues were obtained from 45 patients hospitalized in Sun Yat-Sen Memorial Hospital. Assays were conducted using Nthy-ori 3-1, BHP5-16, BCPAP, K1, and BHP2-7 cell lines, as well as 50 male BALB/c nude mice.

INTERVENTION

Cells were transfected with sh-LSD1, sh-GABPA, oe-LSD1, oe-HIF1α, miR-146a mimic, and miR-146a inhibitor. In addition, K1 cells expressing lv-oe-LSD1, lv-miR-146a inhibitor, lv-oe-LSD1 or miR-146a inhibitor were injected into the right side of the mice. LSD1 gene and protein expression patterns were analyzed in 45 clinical PTC tissue samples.

MAIN OUTCOME MEASURE

Expression of LSD1, HIF1α, miR-146a, and GA-binding protein transcription factor alpha (GABPA), as well as their effects on PTC.

RESULTS

LSD1 was highly expressed in clinical PTC tissues. LSD1 stabilized HIF1α and inhibited the degradation of its ubiquitin proteasome. HIF1α was enriched in the promoter region of miR-146a, an upregulated miRNA in PTC. HIF1α increased miR-146a expression to promote PTC progression in vitro, which was achieved by inhibiting GABPA, a target gene of miR-146a. LSD1 upregulated miR-146a to enhance the development and metastasis of PTC in nude mice.

CONCLUSION

Our results show that LSD1 functions as an oncogene in PTC by upregulating HIF1α and miR-146a, elucidating an understanding of undefined mechanisms associated with tumor progression in PTC.

MicroRNA-146a Is a Wide-Reaching Neuroinflammatory Regulator and Potential Treatment Target in Neurological Diseases

Progressive functional deterioration and loss of neurons underlies neurological diseases and constitutes an important cause of disability and death worldwide. The causes of various types of neurological diseases often share several critical nerve-related cellular mechanisms and pathological features, particularly the neuroinflammatory response in the nervous system. A rapidly growing body of evidence indicates that various microRNAs play pivotal roles in these processes in neurological diseases and might be viable therapeutic targets. Among these microRNAs, microRNA-146a (miR-146a) stands out due to the rapid increase in recent literature on its mechanistic involvement in neurological diseases. In this review, we summarize and highlight the critical role of miR-146a in neurological diseases. MiR-146a polymorphisms are associated with the risk of neurological disease. Alterations in miR-146a expression levels are crucial events in the pathogenesis of numerous neurological diseases that are spatially and temporally diverse. Additionally, the target genes of miR-146a are involved in the regulation of pathophysiological processes in neurological diseases, particularly the neuroinflammatory response. In summary, miR-146a mainly plays a critical role in neuroinflammation during the progression of neurological diseases and might be a prospective biomarker and therapeutic target. Understanding the mechanisms by which miR-146a affects the neuroinflammatory response in different neurological injuries, different cell types, and even different stages of certain neurological diseases will pave the way for its use as a therapeutic target in neurodegenerative diseases.

Effect and mechanism of miR-146a on malignant biological behaviors of lung adenocarcinoma cell line

The aim of the present study was to assess the expression of microRNA-146a (miR-146a) in human lung adenocarcinoma cells, its effect on cellular behaviors, and the underlying molecular mechanisms. Reverse transcription-quantitative PCR (RT-qPCR) was used to measure miR-146a expression in the human normal lung epithelial cell line, BEAS-2B, and human lung adenocarcinoma cell lines, A549, PC-9 and H1299, to determine whether miR-146a acts as an oncogene or anti-oncogene. miR-146a mimics were transfected into target cells to observe the proliferation, apoptosis, invasion and migration of human lung adenocarcinoma cells. The target genes of miR-146a were predicted using bioinformatics analysis, and binding sites were validated by dual-luciferase reporter assay. Target gene expression at the mRNA and protein levels was measured by RT-qPCR and western blot analysis, respectively. The expression levels of miR-146a in human lung adenocarcinoma cell lines were lower than its expression in BEAS-2B (P<0.01). A549 cell line is a EGFR wild-type lung adenocarcinoma cell line, which is also the most widely studied in NSCLC, and therefore this was chosen as the target cell line for further investigation. Overexpression of miR-146a in A549 cells can inhibit cell proliferation (P<0.05), promote apoptosis (P<0.05), and reduce the cells' migratory ability (P<0.01). Bioinformatics prediction indicated that interleukin-1 receptor-associated kinase 1 (IRAK1) and TNF receptor associated factor 6 (TRAF6) are the target genes of miR-146a. Dual-luciferase reporter assay showed that miR-146a could specifically bind to 3′-untranslated regions of IRAK1 and TRAF6. The protein and mRNA levels of IRAK1 and TRAF6 were significantly downregulated after miR-146a overexpression in A549 cells (P<0.01). The results of this study demonstrated that the expression of miR-146a in human lung adenocarcinoma cells was significantly lower than in normal lung epithelial cells, indicating that miR-146a acts as an anti-oncogene. miR-146a suppresses the proliferation and migration of human lung adenocarcinoma cells by downregulating the expression of IRAK1 and TRAF6.

Silencing of microRNA-146a alleviates the neural damage in temporal lobe epilepsy by down-regulating Notch-1

This study aimed to evaluate the specific regulatory roles of microRNA-146a (miRNA-146a) in temporal lobe epilepsy (TLE) and explore the related regulatory mechanisms. A rat model of TLE was established by intraperitoneal injection of lithium chloride-pilocarpine. These model rats were injected intracerebroventricularly with an miRNA-146a inhibitor and Notch-1 siRNA. Then, neuronal damage and cell apoptosis in the cornu ammonis (CA) 1 and 3 regions of the hippocampus were assessed. SOD and MDA levels in the hippocampus were detected by chromatometry, and IL-1β, IL-6, and IL-18 levels were detected by ELISA. Then, we evaluated the expression levels of caspase-9, GFAP, Notch-1, and Hes-1 in the hippocampus. The interaction between Notch-1 and miRNA-146a was assessed by a dual luciferase reporter gene assay. A rat model of TLE was successfully established, which exhibited significantly increased miRNA-146a expression in the hippocampus. Silencing of miRNA-146a significantly alleviated the neuronal damage and cell apoptosis in the CA1 and CA3 regions of the hippocampus in TLE rats and decreased MDA, IL-1β, IL-6, and IL-18 levels and increased SOD levels in the hippocampus of TLE rats. In addition, silencing of miRNA-146a significantly decreased the expression levels of caspase-9, GFAP, Notch-1, and Hes-1 in the hippocampus of TLE rats. Notch-1 was identified as a target of miRNA-146a and silencing of Notch-1 aggravated the neuronal damage in the CA1 and CA3 regions. Silencing of miRNA-146a alleviated the neuronal damage in the hippocampus of TLE rats by down-regulating Notch-1.

MicroRNA-146a protects against myocardial ischaemia reperfusion injury by targeting Med1

BACKGROUND

Myocardial ischaemia reperfusion injury (MIRI) is a difficult problem in clinical practice, and it may involve various microRNAs. This study investigated the role that endogenous microRNA-146a plays in myocardial ischaemia reperfusion and explored the possible target genes.

METHODS

MIRI models were established in microRNA-146a deficient (KO) and wild type (WT) mice. MicroRNA-146a expression was evaluated in the myocardium of WT mice after reperfusion. The heart function, area of myocardium infarction and in situ apoptosis were compared between the KO and WT mice. Microarray was used to explore possible target genes of microRNA-146a, while qRT-PCR and dual luciferase reporter assays were used for verification. Western blotting was performed to detect the expression levels of the target gene and related signalling molecules. A rescue study was used for further testing.

RESULTS

MicroRNA-146a was upregulated 1 h after reperfusion. MicroRNA-146a deficiency decreased heart function and increased myocardial infarction and apoptosis. Microarray detected 19 apoptosis genes upregulated in the KO mice compared with the WT mice. qRT-PCR and dual luciferase verified that Med1 was one target gene of microRNA-146a. TRAP220, encoded by Med1 in the KO mice, was upregulated, accompanied by an amplified ratio of Bax/Bcl2 and increased cleaved caspase-3. Inhibition of microRNA-146a in H9C2 cells caused increased TRAP220 expression and more apoptosis under the stimulus of hypoxia and re-oxygenation, while knockdown of the increased TRAP220 expression led to decreased cell apoptosis.

CONCLUSIONS

MicroRNA-146a exerts a protective effect against MIRI, which might be partially mediated by the target gene Med1 and related to the apoptosis signalling pathway.

MicroRNA-146a protects against intracerebral hemorrhage by inhibiting inflammation and oxidative stress

The present study aimed to investigate the role of microRNA-146a (miR-146a) in intracerebral hemorrhage (ICH), and to further assess its underlying mechanism. An ICH rat model was established in the current study and 1 h following ICH induction, rats were treated with or without an miR-146a mimic. A total of 3 days following ICH induction, rat neurological score, brain water content and neuronal apoptosis were measured via flow cytometry. Levels of pro-inflammatory cytokines tumor necrosis factor-α and interleukin-1β were detected via ELISA and certain biomarkers of oxidative stress, including malondialdehyde, superoxide dismutase and glutathione peroxidase, were also determined in current study. The expression of genes and proteins were detected in current study via reverse transcription-quantitative polymerase chain reaction and western blotting, respectively. MicroRNA.org software and a dual luciferase reporter assay were used to confirm the association between miR-146a and TRAF6. The results of the current study revealed that miR-146a was significantly downregulated in ICH rats, and its overexpression reduced neurological damage and brain edema, as evidenced by decreased neurological scores and brain water content. Results from further analyses demonstrated that the overexpression of miR-146a inhibited neuronal apoptosis, reduced pro-inflammatory cytokine production and prevented oxidative stress in ICH rats. In addition, it was revealed that the upregulation of miR-146a repressed the TRAF6/NF-κB pathway in the brain tissue of ICH rats. TRAF6 was also determined to be a target of miR-146a. In conclusion, these data indicated that miR-146a protects against ICH by inhibiting inflammation and oxidative stress.

Multiple roles of microRNA-146a in immune responses and hepatocellular carcinoma

MicroRNAs (miRNAs/miRs), consisting of ~22 nucleotides of single-stranded RNA, participate in post-transcriptional gene regulation by binding to the 3′-untranslated region (UTR) of mRNAs, repressing their translation and promoting their degradation. Studies have shown that certain miRNAs play a key role in the control of various cellular activities, such as inhibiting inflammation, modulating cell differentiation and suppressing cancer growth. The role of miR-146a in the immune response and in the pathogenesis of hepatocellular carcinoma (HCC) has also been investigated. Although some studies have shown that increased miR-146a levels are associated with HCC, others have revealed that miR-146a suppresses cancer cell proliferation, invasion and metastasis. Toll-like receptor 4 (TLR4) signaling has an important role in regulating innate and adaptive immune responses. In addition, TLR4 is functionally expressed in HCC cells and promotes HCC cell proliferation, which can be regulated by miR-146a. The present review focuses on the recent progress in analyzing the multiple roles of miR-146a in mediating the TLR4 pathway and adaptive immune response. Finally, the function of miR-146a in the pathogenesis of HCC is also discussed.

Human Neutrophil Elastase Induces MUC5AC Overexpression in Chronic Rhinosinusitis Through miR-146a

Background

The pathogenesis of chronic rhinosinusitis (CRS) is not yet clear. microRNAs are widely involved in a number of physiological and pathological processes, of which microRNA-146a (miR-146a) plays an important role in innate immunity, inflammatory response, and other pathophysiological processes. Mucins (MUCs) are important components of secreted mucus, of which MUC5AC is the major MUC secreted in the normal airway.

Objective

This study was performed to examine human neutrophil elastase (HNE)-induced MUC5AC overexpression in CRS via miR-146a.

Methods

miR-146a, HNE, epidermal growth factor receptor (EGFR), and MUC5AC expression in the sinonasal mucosa were determined using quantitative real-time polymerase chain reaction (qRT-PCR). EGFR, phosphorylated EGFR (pEGFR), and MUC5AC expression were determined in primary cultures of human nasal epithelial cells (HNECs). We examined the expression of miR-146a, MUC5AC, EGFR, and pEGFR by transfecting HNECs with miR-146a mimics and negative control (NC). Moreover, dual-luciferase reporter gene assays were used to validate EGFR as an hsa-miR-146a target gene.

Results

miR-146a was significantly downregulated, and HNE, EGFR, and MUC5AC were upregulated in CRS patients both with and without nasal polyps. In the in vitro cell experiment, MUC5AC was significantly downregulated after use of an EGFR-specific inhibitor (AG1478). Upon addition of miR-146a inhibitor, miR-146a was downregulated, while MUC5AC was upregulated. MUC5AC was suppressed in normal primary HNECs by miR-146a mimic and pEGFR was downregulated. The results of dual-luciferase reporter assays showed that the luciferase activities were markedly inhibited in the pGL3-EGFR-3′ UTR+miR-146a mimic group compared with the pGL3+ miR-146a mimic group, suggesting that EGFR is a target gene for miR-146a.

Conclusion

In HNE-induced CRS, miR-146a downregulates the expression of MUC5AC by inhibiting the activation of EGFR, and EGFR is a target gene of miR-146a.

MicroRNA-146a inhibits NF-κB activation and pro-inflammatory cytokine production by regulating IRAK1 expression in THP-1 cells

MicroRNA (miR)-146a levels are reduced in peripheral blood mononuclear cells of patients with systemic lupus erythematosus (SLE); however, its function is not well understood. The present study investigated the role of miR-146a in the regulation of lipopolysaccharide (LPS)-induced inflammation in THP-1 cells. A miR-146a mimic and an inhibitor were used to overexpress and downregulate miR-146a expression, respectively. Reverse transcription-quantitative PCR and western blot analyses were performed to evaluate interleukin (IL)-1 receptor-associated kinase 1 (IRAK1) expression, and western blot analysis was applied to assess nuclear factor-κB activation by analyzing p65 subunit levels in the nucleus. To investigate the effects of miR-146a on LPS-induced inflammation, IL-6 and tumor necrosis factor-α (TNF-α) levels were also measured using ELISA. The results of the present study revealed thatmiR-146a overexpression significantly reduced IRAK1 expression, reduced p65 levels in the nucleus and reduced IL-6 and TNF-α levels in the supernatant of the cell culture medium of THP-1 cells following LPS treatment. Luciferase assays confirmed IRAK1 to be a direct target of miR-146a in THP-1 cells. In conclusion, miR-146a may regulate IRAK1 expression and inhibit the activation of inflammatory signals and secretion of pro-inflammatory cytokines. The present study revealed, at least in part, the mechanisms by which miR-146a regulate the inflammatory response in SLE.

MicroRNA-146a improves sepsis-induced cardiomyopathy by regulating the TLR-4/NF-κB signaling pathway

The aim of the current study was to investigate the regulatory effect of miR-146a on the toll-like receptor 4 (TLR-4)/NF-κB pathway and therefore inflammation in septic cardiomyopathy. A total of 60 healthy male Sprague Dawley rats were equally divided into a control, LPS, miR-146a agonist and miR-146a inhibitor group. Blood samples were collected from rats 24 h after intraperitoneal lipopolysaccharide injection and myocardial tissues were subsequently collected. After hematoxylin and eosin staining of rat myocardial tissues, the degree of inflammatory cell infiltration and myocardial damage was observed. The content of certain myocardial injury markers were also observed, including cardiac troponin I (cTnI), B-type natriuretic peptide (BNP), creatine kinase myocardial bound (CK-MB) and myoglobin (Mb). Western blot analysis was performed to detect the expression of NF-κB/TLR-4, tumor necrosis factor (TNF-α) and intercellular adhesion molecule-1 (ICAM-1) in myocardial tissues. Reverse transcription-quantitative (RT-q) PCR was used to detect the expression of miR-146a, TNF-α, interleukin (IL)-1α and IL-1β mRNA in myocardial tissues. In the LPS group, myocardial interstitial tissue edema occurred, with enlarged and loosely arranged cardiomyocytes. Compared with the sepsis model group, myocardial interstitial tissue edema was relieved in the miR-146a agonist group, but was aggravated in the miR-146a inhibition group. The serum levels of cTnI, BNP, CK-MB, Mb, NF-κB, TLR-4, TNF-α and ICAM-1 in the sepsis model group were higher than those in the control group. In the miR-146a agonist group, levels of myocardial injury markers were lower than those in the sepsis model group, but were higher in the miR-146a inhibition group. The results of RT-qPCR demonstrated that the expression of miR-146a, TNF-α, IL-1α and IL-1β in the sepsis model group were upregulated compared with the control group. In addition, miR-146a expression in the miR-146a agonist group and the miR-146a inhibition group was increased, but TNF-α, IL-1α and IL-1β mRNA was downregulated. miR-146a may regulate the TLR-4/NF-κB signaling pathway via negative feedback mechanisms, leading to the improvement of the inflammatory response and cardiac dysfunction in sepsis-induced cardiomyopathy.

MicroRNA-146a regulates the transformation from liver fibrosis to cirrhosis in patients with hepatitis B via interleukin-6

The aim of the present study was to measure the expression of microRNA (miR)-146a in liver tissues, peripheral blood mononuclear cells (PMBC) and serum from patients with Hepatitis B and either liver fibrosis or cirrhosis, as well as to determine the regulatory mechanism of miR-146a. A total of 36 patients with Hepatitis B and liver fibrosis and 25 patients with hepatitis B and liver cirrhosis admitted to Linyi People's Hospital (Shandong, China) between June 2012 and February 2016 were included in the present study. Reverse transcription-quantitative polymerase chain reaction was performed to determine the expression of miR-146a and interleukin (IL)-6 mRNA in the liver tissue, PBMCs and serum. Western blotting was used to assess the expression of IL-6 in liver tissues and PBMCs. An enzyme-linked immunosorbent assay was conducted to measure IL-6 levels in serum. To identify the direct interaction between IL-6 and miR-146a, a dual luciferase reporter assay was performed. IL-6 mRNA expression in liver tissues, PBMCs and serum from patients with liver cirrhosis was significantly higher than that from patients with liver fibrosis (P<0.05). Furthermore, IL-6 expression in liver tissues and PBMCs from patients with liver cirrhosis was enhanced and levels of IL-6 protein in the serum of patients with liver cirrhosis were significantly elevated compared with patients with liver fibrosis (P<0.05). By contrast, levels of miR-146a in liver tissues, PBMCs and serum from patients with liver cirrhosis were significantly downregulated (P<0.05) compared with patients with liver fibrosis. miR-146a regulated the expression of IL-6 by binding to its 3'-untranslated region. Thus, in the transformation from liver fibrosis to cirrhosis, the upregulation of IL-6 in liver tissues, PBMCs and serum may be associated with the downregulation of miR-146a. miR-146a directly targets IL-6, which may regulate the occurrence and immune responses of Hepatitis B.

Plasma microRNA-21, microRNA-146a and IL-13 expression in asthmatic children

Childhood asthma represents a worldwide problem, involving genetic, immune defense and environmental components. MicroRNAs (miRs) are non-coding, single-stranded RNAs involved in immune regulation. The aim was to evaluate clinical potential of plasma miR-21 and miR-146a involved in T helper differentiation in childhood asthma and non-asthmatic controls. Group 1 consisted of 27 asthmatic children receiving inhaled corticosteroids (ICSs), which was compared to group 2 with 21 healthy control children. All patients were assessed by pulmonary function tests. miR-21 and miR-146a expression levels were determined by real-time quantitative PCR, and IL-13 was measured using ELISA. Group 1 showed significant up-regulation of plasma miR-21 and miR-146a levels with mean values 42.6-fold and 4.7-fold higher than average expression, respectively, in group 2. miR-21 levels positively correlated with IL-13 levels and eosinophil percentage, while miR-146a only correlated to eosinophil percentage. There was a linear association between each of miR-21 and miR-146a expression and FEV1 (forced expiratory volume in the first second), miR-21 and miR-146a are up-regulated in asthmatic children. miR-21 served as a better asthma biomarker. Association between both markers and FEV1 points to their role in determining asthma outcome following ICS treatment. miR-21 and miR-146a play a role in eosinophilic endotypic classification of asthma.

Nanoparticle-microRNA-146a-5p polyplexes ameliorate diabetic peripheral neuropathy by modulating inflammation and apoptosis

Nontoxic and nonimmunogenic nanoparticles play an increasingly important role in the application of pharmaceutical nanocarriers. The pathogenesis of diabetic peripheral neuropathy (DPN) has been extensively studied. However, the role of microRNAs in DPN remains to be clarified. We verified in vitro that miR-146a-5p mimics inhibited the expression of proinflammatory cytokines and apoptosis. Then, we explored the protective effect of nanoparticle-miRNA-146a-5p polyplexes (nano-miR-146a-5p) on DPN rats. We demonstrated that nano-miR-146a-5p improved nerve conduction velocity and alleviated the morphological damage and demyelination of the sciatic nerve of DPN rats. The expression of the inflammatory cytokines, caspase-3, and cleaved caspase-3 in the sciatic nerve was inhibited by nano-miR-146a-5p. Additionally, nano-miR-146a-5p increased the expression of myelin basic protein. These results all indicated that nano-miR-146a-5p had a protective effect on peripheral nerves in the DPN rat model, which may occur through the regulation of the inflammatory response and apoptosis.

Assessment of microRNA-146a in generalized aggressive periodontitis and its association with disease severity

BACKGROUND AND OBJECTIVE

MicroRNA-146a (miR-146a) is a small noncoding RNA that plays a critical role in the negative regulation of the innate immune response, and the dysregulation of miR-146a has been associated with several inflammatory disorders. In generalized aggressive periodontitis (GAgP) the degree of clinical inflammation appears to be similar to that of chronic periodontitis, and, in this situation, age of onset and family history are important additional criteria for diagnosis. This study was performed to evaluate the level of miR-146a expressed in gingival tissues of patients with GAgP and its association with disease severity.

MATERIAL AND METHODS

Gingival samples from 18 patients with GAgP and 10 healthy subjects were collected and the level of miR-146a and its targets, including necrosis factor-alpha, interleukin-1beta, and interleukin-6, were assessed using real-time PCR. Clinical parameters, including probing depth and clinical attachment loss, were measured and their correlations with the level of miR-146a were determined.

RESULTS

Our results demonstrated an elevation in the level of miR-146a expressed in patients with GAgP compared with healthy controls (P < .001), which was directly associated with disease severity (P < .05). Overexpression of miR-146a was accompanied by a reduction in the levels of pro-inflammatory cytokines.

CONCLUSIONS

Our findings suggest that there is an association between miR-146a and GAgP and imply that miR-146a may serve as an indicator of periodontal disease severity. However, further studies and additional information are required to confirm this relationship and the precise role of miR-146a in the development and/or progression of periodontitis.

Endothelial stem cells attenuate cardiac apoptosis via downregulating cardiac microRNA-146a in a rat model of coronary heart disease

Coronary artery disease (CAD) is one of the main causes of hospitalization worldwide and has high morbidity. It has previously been demonstrated that stem cells serve an important role in improving myocardial function. MicroRNA (miRNA)-146a downregulation has been reported to inhibit vascular smooth muscle cell apoptosis in a rat model of coronary heart disease. The aim of the present study was to investigate the mechanisms underlying the effects of endothelial stem cell (ESC)-derived paracrine factors and cardiac miRNAs in CAD. Acute myocardial infarction was induced in 20 rats. Autologous ESCs (n=10; experimental group) or PBS (n=10; control group) were injected in the border zone. Reverse transcription-quantitative polymerase chain reaction, ELISA and immunohistochemistry assays were performed to analyze the therapeutic effects of ESCs in rats with coronary heart disease rats. Serum interleukin (IL)-1, IL-17 and tumor necrosis factor-α were reduced in the experimental group compared with control rats, as was the number of circulating proatherogenic cells. The results demonstrated that ESC transplantation markedly downregulated miRNA-146a expression and decreased apoptosis in the myocardium compared with the control group. Rats in the experimental group also had higher levels of vascular endothelial growth factor compared with the control group. In addition, it was demonstrated that miRNA-146 knockdown reduced cardiac apoptosis and increased VEGF expression. Furthermore, the infarct area in the border zone or rats with CAD was reduced in the experimental group compared with the control group. In conclusion, these results suggest that ESC transplantation may improve cardiac function via downregulating miR-146a, which may be have potential as a treatment for CAD.

miRNA-146a attenuates inflammation in an in vitro spinal cord injury model via inhibition of TLR4 signaling

The present study evaluated the anti-inflammatory effect of microRNA (miR)-146a in a spinal cord injury (SCI) rat model and in vitro model, and explored possible underlying mechanisms of this effect. miR-146a expression was analyzed using reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Tumor necrosis factor (TNF)-α, interleukin (IL)-1β and IL-6 content was measured using ELISA kits. Inducible nitric oxide synthase (iNOS), prostaglandin E2 (PGE2), Toll-like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88) and phosphorylated (p)-nuclear factor (NF)-κB were measured using western blotting. In the SCI rat model, miR-146a expression was downregulated. In the in vitro model, downregulation of miR-146a increased inflammation, enhanced iNOS and PGE2 protein expression and induced TLR4, MyD88 and NF-κB expression. Overexpression of miR-146a reduced inflammation, iNOS and PGE2 protein expression, and suppressed TLR4, MyD88 and NF-κB expression in the in vitro SCI model. The inhibition of TLR4 attenuated the proinflammatory effects of anti-miR-146a in the in vitro SCI model. The results indicate that miR-146a reduces inflammation in an SCI model through the TLR4-NF-κB signaling pathway. The present study demonstrated that miR-146a may be a promising therapeutic agent for SCI.

MicroRNA-21 and microRNA-146a negatively regulate the secondary inflammatory response of microglia after intracerebral hemorrhage

BACKGROUND

A secondary inflammatory response is the most important mechanism of injury after intracerebral hemorrhage (ICH). Previous studies found microRNAs (miRs) expressed abnormally in the perihematomal tissue and blood of patients with ICH and demonstrated that miRs were related to pathophysiological changes and prognosis after ICH, and the development of inflammation.

METHODS

We induced a microglial inflammatory response by lipopolysaccharide (LPS) to construct a microglial inflammatory model. MiR-21/miR-146a overexpression adenovirus was used to infect microglia to increase miR-21/miR-146a expression. MiR-21, miR-146a, IRAK1, MMP-9, TNF-α, TIMP3 and other inflammatory factors were analyzed. Then, miR-21/miR-146a overexpression adenovirus was injected into rats with ICH to modulate the expression. Inflammation, brain edema, and neurological scores were assessed.

RESULTS

For in vitro and vivo experiments, overexpression of miR-21/miR-146a decreased the expression of IL-1β, IL-6, IL-8, IRAK1, MMP-9 and TNF-α, meanwhile increased the expression of TIMP3 significantly (P<0.001), compared with the negative control group. Additionally, miR-21 and miR-146a reduced brain edema and improved the neurological function in ICH rats.

CONCLUSION

Our study proved that miR-21 and miR-146a could negatively regulate the inflammatory response of microglia after ICH and provided a new theoretical basis for the treatment of secondary inflammatory injury after ICH in humans.

microRNA-146a is involved in rSjP40-inhibited activation of LX-2 cells by targeting Smad4 expression

Previous studies have demonstrated that the recombinant Schistosoma japonicum protein P40 (rSjP40) could inhibit activation of hepatic stellate cells (HSCs) through the TGF-β1/Smads signaling pathway. Since multiple microRNAs could play essential roles in HSC activation and in the process of hepatic fibrosis through targeting Smads, we attempted to seek the potential microRNAs that could be involved in rSjP40-induced inhibition of HSC activation. Using the method of quantitative real-time PCR, we found that rSjP40 could induce miR-146a expression in LX-2 cells. The down-regulated expression levels of Smad4 and α-SMA in LX-2 cells induced by rSjP40 were partially restored by an miR-146a inhibitor. miR-146a can be involved in rSjP40-induced inhibition of HSC activation through targeting Smad4. These findings provide us a new idea to explore the potential mechanisms by which rSjP40 could regulate the process of hepatic fibrosis.

Microglial SMAD4 regulated by microRNA-146a promotes migration of microglia which support tumor progression in a glioma environment

Glioma tumors constitute a significant portion of microglial cells, which are known to support tumor progression. The present study demonstrates that transforming growth factor-β (TGFβ) signaling pathway in microglia in a glioma environment is involved in tumor progression and pathogenesis. It has been shown that the TGFβ level is elevated in higher grades of gliomas and its signaling pathway regulates tumor progression through phosphorylation of SMAD2 and SMAD3, which form a complex with SMAD4 to regulate target gene transcription. In an in vitro cell line-based model increased protein levels of pSMAD2/3, total SMAD2/3 and SMAD4 were observed in murine BV2 microglia cultured in glioma conditioned medium (GCM), indicative of the activated TGFβ signaling pathway in microglia associated with glioma environment. Immunofluorescence labeling further revealed the expression of SMAD4 in microglial and non-microglial cells of human glioblastomas tissue in vivo. Functional analysis through shRNA-mediated stable knockdown of SMAD4 in microglia revealed the downregulation of the expression of matrix metalloproteinase 9 (MMP9), which has been shown to be involved in tumor progression and cell migration. Further, knockdown of SMAD4 in microglia decreased the migration of microglial cells towards GCM, indicating that SMAD4 promotes microglial migration in glioma environment. In addition, SMAD4 has been shown to be post-transcriptionally regulated by microRNA-146a, which was downregulated in microglia treated with GCM. Overexpression of miR-146a resulted in decreased expression of SMAD4 together with tumor supportive gene MMP9 in microglia, and subsequently suppressed microglial migration towards GCM, possibly through regulation of SMAD4. On the other hand, the cell viability assay revealed decreased viability of glioma cells when they were treated with conditioned medium derived from SMAD4 knockdown microglia or miR-146a overexpressed microglia as compared to glioma cells treated with the medium from control microglial cells. Taken together, the present study suggests that microglial SMAD4 which is epigenetically regulated by miR-146a promotes microglial migration in gliomas and glioma cell viability.

MicroRNA-146a: A Comprehensive Indicator of Inflammation and Oxidative Stress Status Induced in the Brain of Chronic T2DM Rats

Objective: It was demonstrated that inflammation and oxidative stress induced by hyperglycemia were closely associated with alteration of miR-146a. Here, we investigated the role of miR-146a in mediating inflammation and oxidative stress in the brain of chronic T2DM rats.

Methods: The chronic T2DM (cT2DM) models were induced by intraperitoneal administration of STZ (35 mg/kg) after being fed a high-fat, high-sugar diet for 6 weeks. H&E staining was conducted to observe the morphological impairment of the rat hippocampus. The expressions of inflammatory mediators (COX-2, TNF-α, IL-1β) and antioxidant proteins (Nrf2, HO-1) were measured by western blot. The levels of MDA and SOD were detected by the respective activity assay kit. The levels of p22phox and miR-146a were examined by quantitative real-time PCR (qRT-PCR). The expressions of IRAK1, TRAF6 and NF-κB p65 were measured by western blot and qRT-PCR. Pearson correlation analysis was performed to investigate the correlations between miR-146a and inflammatory mediators as well as oxidative stress indicators.

Results: The expression of miR-146a was negatively correlated with inflammation and oxidative stress status. In the brain tissues of cT2DM rats, it was observed that the expressions of inflammatory mediators (COX-2, TNF-α, IL-1β) and oxidative stress indicators including MDA and p22phox were elevated, which were negatively correlated with the expression of miR-146a. While, the antioxidant proteins (Nrf2, HO-1, SOD) levels decreased in the brain of cT2DM rats, which were positively correlated with the miR-146a level. The expressions of NF-κB p65 and its specific modulators (IRAK1&TRAF6) were elevated in the brain of cT2DM rats, which might be inhibited by miR-146a.

Conclusion: Our results implied that increased inflammation and oxidative stress status were associated with brain impairment in cT2DM rats, which were negatively correlated with miR-146a expression. Thus, miR-146a may serve as a negative comprehensive indicator of inflammation and oxidative stress status in the brain of chronic T2DM rats.

Involvement of microRNA-146a in the Inflammatory Response of S tatus Epilepticus Rats

BACKGROUND

Status epilepticus (SE), is characterized by high mortality and morbidity, which can cause neuronal injury, neuronal death and alteration of neuronal networks, Recently, inflammation was shown to play a significant role in SE pathogenesis. And miRNA-146a has been shown to be involved in inflammation and to inhibit inflammatory cytokines through NF-κB pathway. In our study, we investigated the relationship between inflammation and miR-146a expression.

METHOD

The SE rat model was induced by lithium-pilocarpine. Hematoxylin and eosin staining (H&E) was performed to observe the histopathology of the rat hippocampus. The expression of COX-2, TNF-α, IL-6 and IL-1β were respectively measured by Western blot and Bio-Plex ProTM Assays. The miR-146a expression in hippocampus tissue was measured by Quantitative real-time PCR.

RESULTS

microRNA-146a was highly expressed in the hippocampus of SE rats coupled with increased level of inflammatory cytokines than the normal group. And TQ can attune the expression of inflammatory cytokines, meanwhile, miR-146a was lower in TQ group. The expression of miRNA-146a were positively correlated with the level of inflammatory reaction.

CONCLUSION

TQ may alleviate the inflammatory reaction by inhibiting the NF-κB signaling pathway. Our study shows that miRNA-146a was involved in the inflammatory response and indicated inflammation severity in SE rats. Therefore, miRNA-146a may serve as a potential biomarker or a therapeutic target in SE.

Lung injury caused by paraquat poisoning results in increased interleukin-6 and decreased microRNA-146a levels

The aim of the present study was to investigate the expression of microRNA (miR)-146a in the pulmonary macrophages, peripheral blood mononuclear cells and serum of patients with lung injury caused by paraquat poisoning, as well as the underlying mechanism of its regulation in the disease. A total of 26 patients with lung injury caused by paraquat poisoning were included in the present study. In addition, 33 healthy subjects were included as the control group. The expression levels of interleukin (IL)-6 mRNA and miR-146a was determined by reverse transcription-quantitative polymerase chain reaction (RT-qPCR). Western blotting was used to measure IL-6 protein expression, while enzyme-linked immunosorbent assay was also performed to determine the secretion of IL-6 protein. A dual-luciferase reporter assay was conducted to examine whether IL-6 mRNA is a direct target of miR-146a. Patients with lung injury caused by paraquat poisoning exhibited higher IL-6 mRNA and protein levels as compared with those in healthy subjects. In addition, miR-146a expression in patients with paraquat poisoning-induced lung injury was significantly reduced in comparison with that in healthy subjects. Notably, the overexpression of miR-146a by mimic transfection downregulated the expression of IL-6 in pulmonary macrophages. The results of dual-luciferase reporter assay demonstrated that IL-6 mRNA was a direct target of miR-146a. Therefore, the present study demonstrated that increased expression of IL-6 in patients with lung injury caused by paraquat poisoning is associated with decreased expression of miR-146a. Furthermore, miR-146a may regulate the occurrence and immune response of lung injury caused by paraquat poisoning and this process is possibly achieved via IL-6, an important cytokine that mediates inflammation.

Microbiome-Mediated Upregulation of MicroRNA-146a in Sporadic Alzheimer's Disease

The first indication of a potential mechanistic link between the pathobiology of the human gastrointestinal (GI)-tract microbiome and its contribution to the pathogenetic mechanisms of sporadic Alzheimer's disease (AD) came a scant 4 years ago (1). Ongoing research continues to strengthen the hypothesis that neurotoxic microbial-derived components of the GI tract microbiome can cross aging GI tract and blood-brain barriers and contribute to progressive proinflammatory neurodegeneration, as exemplified by the AD-process. Of central interest in these recent investigations are the pathological roles played by human GI tract resident Gram-negative anaerobic bacteria and neurotropic viruses-two prominent divisions of GI tract microbiome-derived microbiota-which harbor considerable pathogenic potential. It is noteworthy that the first two well-studied microbiota-the GI tract abundant Gram-negative bacteria Bacteroides fragilis and the neurotropic herpes simplex virus-1 both share a final common pathway of NF-κB (p50/p65) activation and microRNA-146a induction with ensuing pathogenic stimulation of innate-immune and neuroinflammatory pathways. These appear to strongly contribute to the inflammation-mediated amyloidogenic neuropathology of AD. This communication: (i) will review recent research contributions that have expanded our understanding of the nature of the translocation of microbiome-derived neurotoxins-across biophysiological barriers; (ii) will assess multiple-recent investigations of the induction of the proinflammatory pathogenic microRNA-146a by these two prominent classes of human microbiota; and (iii) will discuss the role of molecular neurobiology and mechanistic contribution of polymicrobial infections to AD-type neuropathological change.

Inositol-Requiring Enzyme 1-Mediated Downregulation of MicroRNA (miR)-146a and miR-155 in Primary Dermal Fibroblasts across Three TNFRSF1A Mutations Results in Hyperresponsiveness to Lipopolysaccharide

Tumor necrosis factor (TNF)-receptor-associated periodic fever syndrome (TRAPS) is a rare monogenic autoinflammatory disorder characterized by mutations in the TNFRSF1A gene, causing TNF-receptor 1 (TNFR1) misfolding, increased cellular stress, activation of the unfolded protein response (UPR), and hyperresponsiveness to lipopolysaccharide (LPS). Both microRNA (miR)-146a and miR-155 provide negative feedback for LPS-toll-like receptor 2/4 signaling and cytokine production, through regulation of nuclear factor kappa B (NF-κB). In this study, we hypothesized that proinflammatory cytokine signaling in TRAPS downregulates these two miRs, resulting in LPS-induced hyperresponsiveness in TRAPS dermal fibroblasts (DFs), irrespective of the underlying genetic mutation. Primary DF were isolated from skin biopsies of TRAPS patients and healthy controls (HC). TNFR1 cell surface expression was measured using immunofluorescence. DF were stimulated with LPS, interleukin (IL)-1β, thapsigargin, or TNF, with and without inositol-requiring enzyme 1 (IRE1) inhibitor (4u8C), following which miR-146a and miR-155 expression was measured by RT-qPCR. IL-1β, IL-6, and TNF secretion was measured by enzyme-linked immunosorbent assays, and baseline expression of 384 different miRs was assessed using microfluidics assays. TNFR1 was found to be expressed on the surface of HC DF but expression was deficient in all samples with TRAPS-associated mutations. HC DF showed significant dose-dependent increases in both miR-146a and miR-155 expression levels in response to LPS; however, TRAPS DF failed to upregulate either miR-146a or miR-155 under the same conditions. This lack of miR-146a and miR-155 upregulation was associated with increased proinflammatory cytokine production in TRAPS DF in response to LPS challenge, which was abrogated by 4u8C. Incubation of HC DF with IL-1β led to downregulation of miR-146a and miR-155 expression, which was dependent on IRE1 enzyme. We observed global dysregulation of hundreds of other miRs at baseline in the TRAPS DF. In summary, these data suggest a mechanism whereby IL-1β, produced in response to activation of the UPR in TRAPS DF, downregulates miR-146a and miR-155, by inducing IRE1-dependent cleavage of both these miRs, thereby impairing negative regulation of NF-κB and increasing proinflammatory cytokine production.

MicroRNA-146a Overexpression Impairs the Positive Selection during T Cell Development

MicroRNAs play crucial roles in modulating immune system. miR-146a, a potent feedback suppressor of NF-κB signaling, was shown to limit the innate immune response and myelopoiesis in a knockout mouse model. Here, we observed high lymphopoiesis demonstrated as mild splenomegaly and severe lymphadenopathy in a miR-146a transgenic mouse model. Overexpression of miR-146a resulted in enhanced proliferation and reduced apoptosis of T cells. More activated CD4⁺ T cells or effector memory T cells were observed in transgenic mice even under physiological conditions. Importantly, as one of the key steps to generate central tolerance, the positive selection of thymocytes is impaired in transgenic mice, resulting in more CD4⁺CD8⁺ double-positive thymocytes but fewer CD4⁺CD8⁻ and CD4⁻CD8⁺ single-positive thymocytes. The maturation of selected CD4⁻CD8⁺ thymocytes was also impaired, leading to more severe loss of CD4⁻CD8⁺ than CD4⁺CD8⁻ thymocytes in thymus of transgenic mice. Gene expression profiling analysis identified nine positive selection-associated genes, which were downregulated in transgenic mice, including genes encoding major histocompatibility complex class I/II molecules, IL-7 receptor α chain, and Gimap4, whose downregulation may contribute to the impairment of positive selection. Gimap4 was verified as a novel target of miR-146a. These findings further extend our understanding of the function of miR-146a in T cell biology and identify a novel regulatory mechanism underlying the positive selection during T cell development.

Circulating MiR-146a May be a Potential Biomarker of Coronary Heart Disease in Patients with Subclinical Hypothyroidism

BACKGROUND/AIMS

Subclinical hypothyroidism (SCH) plays a crucial role in the development and progression of coronary heart disease (CHD). However, any associated changes in the circulating microRNAs (miRNAs) levels and slightly elevated thyroid stimulating hormone (TSH) levels in CHD patients are unknown. miR-146a is a well known miRNA associated with inflammatory autoimmune diseases. Here, we evaluated miR-146a expression in patients, with the goal of re-evaluating the effect of SCH on CHD.

METHODS

A total of 192 study subjects who underwent coronary angiography for either suspected or confirmed CHD were enrolled in 3 groups: CHD with SCH, CHD alone, and healthy controls. The circulating levels of miR-146a were quantified using qRT-PCR.

RESULTS

Levels of miR-146a were positively correlated with CHD severity, as indicated by the Gensini score (r=0.354). The relative expression of miR-146a in the CHD+SCH, CHD and healthy control groups was 2.223±0.827, 1.588±0.726 and 0.632±0.309, respectively. Plasma TSH levels were positively correlated with miR-146a levels (r=0.321). According to multivariate logistic regression analyses, miR-146a levels were associated with the incidence of CHD in patients with SCH. For diagnosing CHD, the area under the ROC curve (AUC) of miR-146a and TSH was 0.779 and 0.752, respectively. When the TSH and miR-146a levels were combined to form a composite panel, the AUC of the panel was 0.858.

CONCLUSION

Plasma miR-146a levels correlated with the severity of coronary atherosclerosis and increased with TSH slightly elevated in patients with CHD. Thus, miR-146a may have good predictive value for CHD among individuals with elevated TSH levels.