SREBP2 promotes the viability, proliferation, and migration and inhibits apoptosis in TGF-ß1-induced airway smooth muscle cells by regulating TLR2/NF-κB/NFATc1/ABCA1 regulatory network.

Asthma is a respiratory disease with complex pathogenesis. Sterol-responsive element-binding proteins 2 (SREBP2) was found to bind to promoter sequences of ABCA1 to suppress ABCA1 promoter activity. This study aimed to explore the expression level of SREBP2 and ATP-binding cassette transporter A1 (ABCA1), and their effects on the development of airway smooth muscle cells (ASMCs) in asthma. ASMCs were treated with different concentrations of TGF-ß1 (0, 0.5, 1, 5 and 10 ng/mL). Short hairpin SREBP2 (shSREBP2), SREBP2, shABCA1 or ABCA1 were transfected into ASMCs. Cell viability, proliferation, apoptosis, migration, and the expression of SREBP2, ABCA1 and related pathway proteins were detected by MTT assay, Brdu staining, flow cytometer, Transwell assay, qRT-PCR, and Western blotting, respectively. The results showed that TGF-ß1 increased the viability, proliferation, migration and inhibited apoptosis in ASMCs. Moreover, TGF-ß1 also decreased the expression of ABCA1, cleaved caspase-3, cleaved PARP, E-cadherin, and increased the expression of vimentin, TLR2, p-p65 and NFATc1. SREBP2 knockdown alleviated these TGF-ß1-induced changes. SREBP2 overexpression inhibited ABCA1 expression and apoptosis, and promoted cell migration and the expression of TLR2, p-p65, NFATc1 in ASMCs. ABCA1 overexpression alleviated these SREBP2-induced promoting and inhibition effects. In conclusion, SREBP2 activates TLR2/NF-κB/NFATc1 regulatory network and promotes TGF-ß1-induced cell movement through inhibiting ABCA1 expression.

TGF-ß1/SMOC2/AKT and ERK axis regulates proliferation, migration, and fibroblast to myofibroblast transformation in lung fibroblast, contributing with the asthma progression.

BACKGROUND: Asthma is a common chronic respiratory disease that influences 300 million people all over the world. However, the pathogenesis of asthma has not been fully elucidated. It has been reported that transforming growth factor-ß (TGF-ß) can activate myofibroblasts. Moreover, the fibroblast to myofibroblast transformation (FMT) can be triggered by TGF-ß, which is a major mediator of subepithelial fibrosis. Secreted modular calcium-binding protein 2 (SMOC2) is a member of cysteine (SPARC) family and is involved in the progression of multiple diseases. However, its role in asthma remains poorly understood. RT-qPCR evaluated the expression of SMOC2. Bromodeoxyuridine assay and wound-healing assay detected the proliferation and migration of lung fibroblasts, respectively. IF staining was performed to assess the expression of α-smooth muscle actin (α-SMA). Western blot analysis detected the levels of proteins. Flow cytometry was utilized for determination of the number of myofibroblasts. RESULTS: We found the expression of SMOC2 was upregulated by the treatment of TGF-ß1 in lung fibroblasts. In addition, SMOC2 promoted the proliferation and migration of lung fibroblasts. More importantly, SMOC2 accelerated FMT of lung fibroblasts. Furthermore, SMOC2 was verified to control the activation of AKT and ERK. Rescue assays showed that the inhibition of AKT and ERK pathway reversed the promoting effect of SMOC2 overexpression on proliferation, migration and FMT in lung fibroblasts. CONCLUSIONS: This work demonstrated that SMOC2 modulated TGF-ß1-induced proliferation, migration and FMT in lung fibroblasts and may promote asthma, which potentially provided a novel therapeutic target for the management of asthma.

Crocin Improves Endothelial Mitochondrial Dysfunction via GPx1/ROS/KCa3.1 Signal Axis in Diabetes.

Mitochondrial dysfunction contributes to excessive reactive oxygen species (ROS) generation, which is a dramatic cause to promote endothelial dysfunction in diabetes. It was previously demonstrated that crocin protected the endothelium based on its diverse medicinal properties, but its effect on the mitochondrion and the potential mechanism are not fully understood. In this study, mitochondrial function was analyzed during the process of excessive ROS generation in high glucose (HG)-cultured human umbilical vein endothelial cells (HUVECs). The role played by KCa3.1 was further investigated by the inhibition and/or gene silence of KCa3.1 in this process. In addition, nicotinamide adenine dinucleotide phosphate (NADPH)-oxidase 2 (NOX2), superoxide dismutase 1 (SOD1), and glutathione peroxidase 1 (GPx1) were also detected in this study. Our data showed that crocin improved mitochondrial dysfunction and maintained normal mitochondrial morphology by enhancing the mitochondrial membrane potential (MMP), mitochondrial mass, and mitochondrial fusion. Furthermore, KCa3.1 was confirmed to be located in the mitochondrion, and the blockade and/or silencing of KCa3.1 improved mitochondrial dysfunction and reduced excessive ROS generation but did not affect NOX2 and/or the SOD1 system. Intriguingly, it was confirmed that KCa3.1 expression was elevated by ROS overproduction in the endothelium under HG and/or diabetes conditions, while crocin significantly suppressed this elevation by promoting GPx1 and subsequently eliminating ROS generation. In addition, crocin enhanced CD31, thrombomodulin (TM), and p-/t-endothelial nitric oxide synthase (eNOS) expressions as well as NO generation and decreased vascular tone. Hence, crocin improved mitochondrial dysfunction through inhibiting ROS-induced KCa3.1 overexpression in the endothelium, which in turn reduced more ROS generation and final endothelial dysfunction in diabetes.