Macrophages demonstrate a high level of plasticity, with the ability to undergo dynamic transition between M1 and M2 polarized phenotypes. The role of miRNAs in regulating macrophage polarization has been largely undefined. In this study, we found that microRNA let-7c is expressed at a higher level in M-BMM (M2 macrophages) than in GM-BMM (M1 macrophages). let-7c levels are also greater in alveolar macrophages from fibrotic lungs as compared to those from normal lungs. let-7c expression was decreased when M-BMM converted to GM-BMM whereas increased when GM-BMM converted to M-BMM. LPS stimulation reduced let-7c expression in M-BMM. We found that overexpression of let-7c in GM-BMM diminished M1 phenotype expression while promoting polarization to the M2 phenotype. In contrast, knockdown of let-7c in M-BMM promoted M1 polarization, and diminished M2 phenotype expression. We found that let-7c targets C/EBP-δ, a transcriptional factor that plays an important role in inflammatory response. Furthermore, we found that let-7c regulates bactericidal and phagocytic activities of macrophages, two functional phenotypes implicated in macrophage polarization. Our data suggest that the microRNA let-7c plays an important role in regulating macrophage polarization.

Renal fibrosis is a final stage of many forms of kidney disease and leads to impairment of kidney function. The molecular pathogenesis of renal fibrosis is currently not well-understood. microRNAs (miRNAs) are important players in initiation and progression of many pathologic processes including diabetes, cancer, and cardiovascular disease. However, the role of miRNAs in kidney injury and repair is not well-characterized. In the present study, we found a unique miRNA signature associated with unilateral ureteral obstruction (UUO)-induced renal fibrosis. We found altered expression in UUO kidneys of miRNAs that have been shown to be responsive to stimulation by transforming growth factor (TGF)-β1 or TNF-α. Among these miRNAs, miR-21 demonstrated the greatest increase in UUO kidneys. The enhanced expression of miR-21 was located mainly in distal tubular epithelial cells. miR-21 expression was upregulated in response to treatment with TGF-β1 or TNF-α in human renal tubular epithelial cells in vitro. Furthermore, we found that blocking miR-21 in vivo attenuated UUO-induced renal fibrosis, presumably through diminishing the expression of profibrotic proteins and reducing infiltration of inflammatory macrophages in UUO kidneys. Our data suggest that targeting specific miRNAs could be a novel therapeutic approach to treat renal fibrosis.

Excessive extracellular matrix production by fibroblasts in response to tissue injury contributes to fibrotic diseases, such as idiopathic pulmonary fibrosis (IPF). Epithelial-mesenchymal transition, involving transition of alveolar epithelial cells (AECs) to pulmonary fibroblasts, appears to be an important contributory process to lung fibrosis. Although aberrant expression of microRNAs (miRs) is involved in a variety of pathophysiologic processes, the role of miRs in fibrotic lung diseases is less well understood. In the present study, we found that miR-200a, miR-200b, and miR-200c are significantly down-regulated in the lungs of mice with experimental lung fibrosis. Levels of miR-200a and miR-200c were reduced in the lungs of patients with IPF. miR-200 had greater expression in AECs than in lung fibroblasts, and AECs from mice with experimental pulmonary fibrosis had diminished expression of miR-200. We found that the miR-200 family members inhibit transforming growth factor-β1-induced epithelial-mesenchymal transition of AECs. miR-200 family members can reverse the fibrogenic activity of pulmonary fibroblasts from mice with experimental pulmonary fibrosis and from patients with IPF. Indeed, the introduction of miR-200c diminishes experimental pulmonary fibrosis in mice. Thus, the miR-200 family members participate importantly in fibrotic lung diseases and suggest that restoring miR-200 expression in the lungs may represent a novel therapeutic approach in treating pulmonary fibrotic diseases.

Background:The role of miRNAs in macrophage polarization has not been well defined. Results: miR-125a-5p promotes M2, while it suppresses M1 macrophage polarization. Conclusion: miR-125a-5p is an important regulator of the differential activation of macrophages. Significance: Delineation of the role of miR-125a-5p in macrophage polarization provides insights into miRNA regulation of inflammation, tissue repair and tumor progression.

(miRNA) is closely associated with a number of pathophysiologic processes. However, the role of miRNAs in chronic hypoxia-induced pulmonary vascular remodeling and PH has not been well characterized. In this study, we found increased expression of miR-21 in distal small arteries in the lungs of hypoxia-exposed mice. Putative miR-21 targets, including bone morphogenetic protein receptor (BMPR2), WWP1, SATB1, and YOD1, were downregulated in the lungs of hypoxia-exposed mice and in human pulmonary artery smooth muscle cells (PASMCs) overexpressing miR-21. We found that sequestration of miR-21, either before or after hypoxia exposure, diminished chronic hypoxia-induced PH and attenuated hypoxia-induced pulmonary vascular remodeling, likely through relieving the suppressed expression of miR-21 targets in the lungs of hypoxia-exposed mice. Overexpression of miR-21 enhanced, whereas downregulation of miR-21 diminished, the proliferation of human PASMCs in vitro and the expression of cell proliferation associated proteins, such as proliferating cell nuclear antigen, cyclin D1, and Bcl-xL. Our data suggest that miR-21 plays an important role in the pathogenesis of chronic hypoxia-induced pulmonary vascular remodeling and also suggest that miR-21 is a potential target for novel therapeutics to treat chronic hypoxia associated pulmonary diseases. pulmonary hypertension; micro-ribonucleic acid; smooth muscle cell CHRONIC HYPOXIA OCCUR FREQUENTLY in a number of pulmonary disorders, such as chronic obstructive pulmonary disease, obstructive sleep apnea, and diffuse interstitial fibrosis (42,49,54). Persistent hypoxia causes vascular structural remodeling, leading to pulmonary hypertension (PH) that results in right ventricle (RV) hypertrophy and ultimately RV failure (42,49,54). The response of PH due to vascular remodeling to current therapies is limited. Thus there is a pressing need to identify novel targets for developing more effective approaches to treat PH.Chronic hypoxia-induced vascular remodeling occurs in all three layers of the pulmonary small arterial wall (49). In the adventitia, there is increased accumulation of pulmonary artery adventitial fibroblasts (PAAFbs) and excessive deposition of extracellular matrix (ECM) proteins (45,46,48,50,53). In the media, hypertrophy and hyperplasia of pulmonary arterial smooth muscle cells (PASMCs) represent one of the major pathological features (32, 49). Chronic hypoxia also induces endothelial cell proliferation that promotes intimal thickening (33).Many contributing molecular mechanisms have been identified in chronic hypoxia-induced vascular remodeling. Chronic hypoxia has dramatic impacts on transcriptome in the resident cells of the pulmonary vascular wall (49). Upregulation of hypoxia inducible factor-1, a transcriptional factor that mediates responses to hypoxia in cells, is a characteristic finding in pulmonary vascular cells isolated during chronic hypoxia (15,17). Furthermore, elevated expression in a number of mitogenic and vasoconstrictive small molecules, cyto...

The expression of smooth muscle actin-α (SMA-α) by fibroblasts defines phenotypic transition to myofibroblasts and is a primary contributor to contractile force generation by these differentiated cells. Although the regulation of SMA-α expression has been the focus of many studies, there is presently only limited information concerning miRNA regulation of lung myofibroblast differentiation and the involvement of these miRNAs in pulmonary fibrosis. To determine the role of miR-145 in regulating lung myofibroblast differentiation and pulmonary fibrosis. Wild-type and miR-145(-/-) mice were studied. Lung fibrosis models and cell culture systems were employed. miR-145 mimics or inhibitors were transfected into pulmonary fibroblasts. Fibrogenic and contractile activities of lung fibroblasts were determined. We found that miR-145 expression is upregulated in TGF-β1-treated lung fibroblasts. miR-145 expression is also increased in the lungs of patients with idiopathic pulmonary fibrosis as compared to in normal human lungs. Overexpression of miR-145 in lung fibroblasts increased SMA-α expression, enhanced contractility, and promoted formation of focal and fibrillar adhesions. In contrast, miR-145 deficiency diminished TGF-β1 induced SMA-α expression. miR-145 did not affect the activity of TGF-β1, but promoted the activation of latent TGF-β1. miR-145 targets KLF4, a known negative regulator of SMA-α expression. Finally, we found that miR-145(-/-) mice are protected from bleomycin-induced pulmonary fibrosis. miR-145 plays an important role in the differentiation of lung myofibroblasts. miR-145 deficiency is protective against bleomycin-induced lung fibrosis, suggesting that miR-145 may be a potential target in the development of novel therapies to treat pathological fibrotic disorders.

Pancreatic cancer is a malignant neoplasm with a high mortality rate. Therapeutic agents that activate TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis have shown promising efficacy, but many pancreatic cancers are resistant to TRAIL therapy. Epigenetic regulation plays important roles in tumor pathogenesis and resistance, and a recent study indicated that the long non-coding RNA HOX transcript antisense RNA (HOTAIR) is overexpressed in pancreatic cancer. However, the role of HOTAIR in pancreatic cancer resistance to anticancer agents is unknown. The present study determined the role of HOTAIR in pancreatic cancer TRAIL resistance and investigated the underlying molecular mechanisms. We observed that TRAIL-resistant pancreatic cancer cells had higher levels of HOTAIR expression, whereas TRAIL-sensitive pancreatic cancer cells had lower HOTAIR levels. Overexpressing HOTAIR in TRAIL-sensitive cells attenuated TRAIL-induced apoptosis, and shRNA-mediated HOTAIR knockdown in TRAIL-resistant PANC-1 cells sensitized them to TRAIL-induced apoptosis. These results support a causative effect of HOTAIR on TRAIL sensitivity. Mechanistically, we found that increased HOTAIR expression inhibited the expression of the TRAIL receptor death receptor 5 (DR5), whereas HOTAIR knockdown increased DR5 expression. We further demonstrated that HOTAIR regulates DR5 expression via the epigenetic regulator enhancer of zeste homolog 2 (EZH2) and that EZH2 controls histone H3 lysine 27 trimethylation on the gene. Taken together, these results demonstrate that high HOTAIR levels increase the resistance of pancreatic cancer cells to TRAIL-induced apoptosis via epigenetic regulation of DR5 expression. Our study therefore supports the notion that targeting HOTAIR function may represent a strategy to overcome TRAIL resistance in pancreatic cancer.

Vascular smooth muscle cells (VSMCs) are the predominant cell type in the arterial wall. These cells play a critical role in maintaining vascular homeostasis including vasoconstriction and vasodilatation through active contraction and relaxation. Dysregulation of VSMC function alters the response of blood vessels to mechanical stress, contributing to the pathogenesis of vascular diseases, particularly atherosclerosis and hypertension. The stiffness of VSMCs is a major regulator of vascular function. Previous studies suggest that intracellular Ca 2+ controls the stiffness of VSMCs by a mechanism involving myosin contractile apparatus. More recent studies highlight important functions of cytoskeletal α-smooth muscle actin (α-SMA), α5β1 integrin, and integrin-mediated cell-extracellular matrix (ECM) interactions in Ca 2+ -dependent regulation of VSMC stiffness and adhesion to the ECM, providing novel insights into the mechanism of calcium action.