Insect molting and metamorphosis are regulated by two hormones: 20-hydroxyecdysone (20E) and juvenile hormone (JH). The hormone 20E regulates gene transcription via the nuclear receptor EcR to promote metamorphosis, whereas JH regulates gene transcription via its intracellular receptor methoprene-tolerant (Met) to prevent larval–pupal transition. However, the function and mechanism of Met in various insect developments are not well understood. We propose that Met1 plays a key role in maintaining larval status not only by promoting JH-responsive gene transcription but also by repressing 20E-responsive gene transcription in the Lepidopteran insect Helicoverpa armigera. Met1 protein is increased during feeding stage and decreased during molting and metamorphic stages. Met1 is upregulated by JH III and a low concentration of 20E independently, but is downregulated by a high concentration of 20E. Knockdown of Met1 in larvae causes precocious pupation, decrease in JH pathway gene expression, and increase in 20E pathway gene expression. Met1 interacts with heat shock protein 90 and binds to JH response element to regulate Krüppel homolog 1 transcription in JH III induction. Met1 interacts with ultraspiracle protein 1 (USP1) to repress 20E transcription complex EcRB1/USP1 formation and binding to ecdysone response element. These data indicate that JH via Met1 regulates JH pathway gene expression and represses 20E pathway gene expression to maintain the larval status.
Wen-Li Zhao, Chun-Yan Liu, Wen Liu, Di Wang, Jin-Xing Wang and Xiao-Fan Zhao
Sarah X Zhang, Joshua J Wang, Guoquan Gao, Kyoungmin Parke and Jian-xing Ma
It has been shown that the balance between vascular endothelial growth factor (VEGF), a major angiogenic stimulator, and pigment epithelium-derived factor (PEDF), a potent angiogenic inhibitor, is critical for the regulation of vascular permeability and angiogenesis. However, the regulation of the balance is largely unclear. The present study demonstrated that there is a reciprocal interaction between VEGF and PEDF in the retina. PEDF significantly decreased VEGF expression in both retinal capillary endothelial cells (RCEC) and Müller cells. This PEDF effect was confirmed in the retina of rats with oxygen-induced retinopathy. Silencing of the PEDF gene by siRNA in Müller cells resulted in a significant upregulation of VEGF expression at both the RNA and protein levels, suggesting that PEDF is an endogenous negative regulator of VEGF. The further study of the mechanism showed that PEDF inhibited hypoxia-induced increases in VEGF promoter activity, HIF-1 nuclear translocation and mitogen activated protein kinase phosphorylation. These results suggest that PEDF inhibits VEGF expression at the transcriptional level. In addition, PEDF effectively inhibited VEGF binding to RCEC. Moreover, in vitro receptor-binding assay demonstrated that PEDF competed with VEGF for binding to VEGF receptor 2, which may represent a new mechanism for PEDF activity. On the other hand, VEGF significantly downregulated PEDF expression in RCEC, but not in retinal Müller cells, suggesting a VEGF receptor-mediated process. These results suggest that the reciprocal regulation between VEGF and PEDF may play a role in angiogenic control. The decrease in PEDF levels in the retina is at least partially responsible for the increase in VEGF expression and subsequent vascular leakage and neovascularization in diabetes.
Sarah X Zhang, Joshua J Wang, Azar Dashti, Kenneth Wilson, Ming-Hui Zou, Luke Szweda, Jian-Xing Ma and Timothy J Lyons
Oxidized and/or glycated low-density lipoprotein (LDL) may mediate capillary injury in diabetic retinopathy. The mechanisms may involve pro-inflammatory and pro-oxidant effects on retinal capillary pericytes. In this study, these effects, and the protective effects of pigment epithelium-derived factor (PEDF), were defined in a primary human pericyte model. Human retinal pericytes were exposed to 100 μg/ml native LDL (N-LDL) or heavily oxidized glycated LDL (HOG-LDL) with or without PEDF at 10–160 nM for 24 h. To assess pro-inflammatory effects, monocyte chemoattractant protein-1 (MCP-1) secretion was measured by ELISA, and nuclear factor-κB (NF-κB) activation was detected by immunocytochemistry. Oxidative stress was determined by measuring intracellular reactive oxygen species (ROS), peroxynitrite (ONOO−) formation, inducible nitric oxide synthase (iNOS) expression, and nitric oxide (NO) production. The results showed that MCP-1 was significantly increased by HOG-LDL, and the effect was attenuated by PEDF in a dose-dependent manner. PEDF also attenuated the HOG-LDL-induced NF-κB activation, suggesting that the inhibitory effect of PEDF on MCP-1 was at least partially through the blockade of NF-κB activation. Further studies demonstrated that HOG-LDL, but not N-LDL, significantly increased ONOO− formation, NO production, and iNOS expression. These changes were also alleviated by PEDF. Moreover, PEDF significantly ameliorated HOG-LDL-induced ROS generation through up-regulation of superoxide dismutase 1 expression. Taken together, these results demonstrate pro-inflammatory and pro-oxidant effects of HOG-LDL on retinal pericytes, which were effectively ameliorated by PEDF. Suppressing MCP-1 production and thus inhibiting macrophage recruitment may represent a new mechanism for the salutary effect of PEDF in diabetic retinopathy and warrants more studies in future.
Yingdi Yuan, Xinguo Cao, Jiaojiao Hu, Jingyun Li, Dan Shen, Lianghui You, Xianwei Cui, Xing Wang, Yahui Zhou, Yao Gao, Lijun Zhu, Pengfei Xu, Chenbo Ji, Xirong Guo and Juan Wen
Obesity is a major risk factor for metabolic diseases, while adipocyte differentiation is closely related to obesity occurrence. Long noncoding RNAs (lncRNAs) are a unique class of transcripts in regulation of various biological processes. Using lncRNA microarray, we found lncRNA AC092159.2 was highly expressed in differentiated HPA-v and located ~247 bp upstream of the TMEM18, which was associated with BMI and obesity. We aimed to explore the role of AC092159.2 in adipogenesis and the underlying mechanisms. The effects of AC092159.2 gain- and loss-of-function on HPA-v adipogenesis were determined with lentivirus and siRNA-mediated cell transduction, respectively. Lipid accumulation was evaluated by oil red O staining; the expression of AC092159.2, TMEM18 and several adipogenesis makers in HPA-v were analyzed by qPCR/Western blot. We found that the expression of AC092159.2 gradually increased during HPA-v differentiation, and its expression in omental adipose tissue was positively related with BMI among 48 human subjects. Overexpression of AC092159.2 promoted adipocytes differentiation while knockdown of it led to an adipogenic defect. Moreover, the expression of AC092159.2 and TMEM18 were positively correlated during adipogenic differentiation. AC092159.2 overexpression boosted TMEM18 expression while AC092159.2 knockdown restrained TMEM18 expression. Further rescue experiments showed that TMEM18 knockdown partially restrained adipogenic differentiation in AC092159.2 overexpressed HPA-v and adipogenic defect caused by AC092159.2 knockdown could be rescued by TMEM18 overexpression. Luciferase reporter assays revealed that AC092159.2 had a transcriptional activation effect on TMEM18. We concluded that lncRNA AC092159.2 promoted human adipocytes differentiation possibly by regulating TMEM18.