MicroRNA-206 regulates surfactant secretion by targeting VAMP-2

Streptococcus gordonii-Induced miRNAs Regulate CCL20 Responses in Human Oral Epithelial Cells

The mechanisms through which oral commensal bacteria mitigates uncontrolled inflammatory responses of the oral mucosa remain unknown. Here, we show that representative oral bacterial species normally associated with oral health [S. gordonii (Sg), V. parvula (Vp), A. naeslundii (An), C. sputigena (Cs), and N. mucosa (Nm)] enhanced differential chemokine responses in oral epithelial cells (OECs), with some bacteria (An, Vp, and Nm) inducing higher chemokine levels (CXCL1, CXCL8) than others (Sg, Cs). Although all bacterial species (except Cs) increased CCL20 mRNA levels consistent with protein elevations in cell lysates, only An, Vp, and Nm induced higher CCL20 secretion, similar to the effect of the oral pathogen F. nucleatum (Fn). In contrast, most CCL20 remained associated with OECs exposed to Sg and negligible amounts released into the cell supernatants. Consistently, Sg attenuated An-induced CCL20. MiR-4516 and miR-663a were identified as Sg-specifically induced miRNAs modulating validated targets of chemokine-associated pathways. Cell transfection with miR-4516 and miR-663a decreased An- and Fn-induced CCL20. MiRNA upregulation and attenuation of An-induced CCL20 by Sg were reversed by catalase. Up-regulation of both miRNAs was specifically enhanced by oral streptococci H2O2-producers. These findings suggest that CCL20 levels produced by OECs in response to bacterial challenge are regulated by Sg-induced miR-4516 and miR-663a in a mechanism that involves hydrogen peroxide. This type of molecular mechanism could partly explain the central role of specific oral streptococcal species in balancing inflammatory and antimicrobial responses given the critical role of CCL20 in innate (antimicrobial) and adaptive immunity (modulates Th17 responses).

Interplay between C-type lectin receptors and microRNAs in cellular homeostasis and immune response

C-type lectin receptors (CLRs) belong to the family of pattern recognition receptors (PRRs). They have a critical role to play in the regulation of a range of physiological functions including development, respiration, angiogenesis, inflammation, and immunity. CLRs can recognize distinct and conserved exogenous pathogen-associated as well as endogenous damage-associated molecular patterns. These interactions set off downstream signaling cascades, leading to the production of inflammatory mediators, activation of effector immune cells as well as regulation of the developmental and physiological homeostasis. CLR signaling must be tightly controlled to circumvent the excessive inflammatory burden and to maintain the cellular homeostasis. Recently, MicroRNAs (miRNAs) have been shown to be important regulators of expression of CLRs and their downstream signaling. The delicate balance between miRNAs and CLRs seems crucial in almost all aspects of multicellular life. Any dysregulations in the miRNA-CLR axes may lead to tumorigenesis or inflammatory diseases. Here, we present an overview of the current understanding of the central role of miRNAs in the regulation of CLR expression, profoundly impacting upon homeostasis and immunity, and thus, development of therapeutics against immune disorders.

Temporal dynamics of miRNAs in human DLPFC and its association with miRNA dysregulation in schizophrenia

Brain development is dependent on programmed gene expression, which is both genetically and epigenetically regulated. Post-transcriptional regulation of gene expression by microRNAs (miRNAs) is essential for brain development. As abnormal brain development is hypothesized to be associated with schizophrenia, miRNAs are an intriguing target for this disorder. The aims of this study were to determine the temporal dynamics of miRNA expression in the human dorsolateral prefrontal cortex (DLPFC), and the relationship between miRNA's temporal expression pattern and dysregulation in schizophrenia. This study used next-generation sequencing to characterize the temporal dynamics of miRNA expression in the DLPFC of 109 normal subjects (second trimester-74 years of age) and miRNA expression changes in 34 schizophrenia patients. Unlike mRNAs, the majority of which exhibits a wave of change in fetuses, most miRNAs are preferentially expressed during a certain period before puberty. It is noted that in schizophrenia patients, miRNAs normally enriched in infants tend to be upregulated, while those normally enriched in prepuberty tend to be downregulated, and the targets of these miRNAs are enriched for genes encoding synaptic proteins and those associated with schizophrenia. In addition, miR-936 and miR-3162 were found to be increased in the DLPFC of patients with schizophrenia. These findings reveal the temporal dynamics of miRNAs in the human DLPFC, implicate the importance of miRNAs in DLPFC development, and suggest a possible link between schizophrenia and dysregulation of miRNAs enriched in infancy and prepuberty.

miR-206 regulates alveolar type II epithelial cell Cx43 expression in sepsis-induced acute lung injury

The present study investigated the relationship between connexin 43 (Cx43) expression in alveolar type II epithelial cells (ATII) and alveolar air-blood barrier permeability, and the effect of microRNA-206 (miR-206) on the expression of Cx43 in sepsis-induced acute lung injury. For the in vivo study, rats were divided into the sham, caecum ligation and perforation (CLP), CLP+Cx43 inhibitors (Cx43-In) and CLP+miR-206 analogs (miR-206-Mi) groups. CLP method was used to prepare an acute lung injury model of sepsis. Following successful modeling, lung tissue was collected for hematoxylin and eosin (HE) staining, and the wet to dry weight ratio (W/D) and protein content in bronchoalveolar lavage fluid (BALF) were detected. Cx43 expression in lung tissue was determined by immunohistochemistry and western blot analysis. Additionally, miR-206 and Cx43 expression levels in lung tissue were detected by reverse transcription-quantitative polymerase chain reaction. Rat ATII cells were cultured in Transwells plates to form monolayers, then treated with Cx43 mRNA inhibitors or miR-206 analogs. The cell monolayers were then stimulated with lipopolysaccharide and their permeability was evaluated by detecting fluorescein-labeled dextran at the lower chamber of the Transwells. The dual luciferase reporter gene assay was used to investigate whether miR-206 targeted the 3′ untranslated region of Cx43 mRNA to regulate Cx43 expression, thereby regulating the permeability of the alveolar air-blood barrier. Results demonstrated that the CLP method induced damage to the alveolar structure, thickened the alveolar wall, caused hyperemia and hemorrhage in the pulmonary interstitium and caused infiltration of inflammatory cells. Edema in the pulmonary interstitium and alveolar space, exudation of neutrophilic granulocyte and pink edema fluid in alveolar cavities were also observed. W/D ratio, the BALF protein content, and expression of Cx43mRNA and Cx43 were increased significantly, whilst miR-206 expression decreased compared with the control group. The lung tissue inflammatory response was attenuated, and the W/D ratio and BALF protein content decreased in the Cx43-In and miR-206-Mi groups compared with the CLP group. Moreover, Cx43 mRNA and protein expression were decreased significantly in the Cx43-In and miR-206-Mi groups. In addition, the dual luciferase reporter gene assay determined that the untranslated region of Cx43 mRNA had a complementary sequence to miR-206. Of note, Cx43 mRNA expression in the miR-206-Mi group was not significantly decreased in vitro. In conclusion, the increase in ATII cell Cx43 expression during sepsis-induced acute lung injury resulted in an increase in the permeability of the alveolar air-blood barrier. miR-206 targeted the Cx43 mRNA 3′untranslated region to downregulate Cx43 expression, which further improved the permeability of the alveolar air-blood barrier.

The role of miR-431-5p in regulating pulmonary surfactant expression in vitro

Background

Pulmonary surfactant is the complex mixture of lipid and protein that covers the alveolar surface. Pulmonary surfactant deficiency is one of the main causes of neonatal respiratory distress. Recent studies showed that miRNA plays an important role in lung development, but research into miR-431 regulation of pulmonary surfactant are sparse. In this study, we explored the regulatory role of miR-431-5p in the expression of pulmonary surfactant and identified its potential target gene, Smad4.

Methods

The bioinformatics tool TargetScan was used to predict the targets of miR-431. The expression of miR-431-5p was achieved via transfection of miR-431-5p mimics, an miR-431-5p inhibitor and corresponding negative control. The level of miR-431-5p was determined using quantitative real-time PCR. The CCK8 assay was conducted to confirm cell growth 12 h after transfection with miR-431-5p mimics, inhibitor or NC. Smad4 and surfactant-associated proteins in A549 were analyzed using western blot and quantitative real-time PCR.

Results

Smad4 was validated as a target of miR-431 in A549 cells. Overexpression of miR-431 accelerated A549 proliferation and inhibited A549 apoptosis. The mRNA and protein levels for the surfactant proteins (SP-A, SP-B, SP-C and SP-D) were found to be differentially expressed in A549 cells over- or under-expressing miR-431-5p.

Conclusion

Our results show that miR-431-5p is critical for pulmonary surfactant expression and that its regulation is closely related to the TGF-β/Smad4 pathway. These results will help us to study the pathophysiological mechanism of lung developmental diseases.