Resistin is an adipocytokine leading to insulin resistance. Endotoxin/lipopolysaccharide (LPS) has been reported to decrease the expression of resistin mRNA and protein in both lean and db/db obese mice, although the underlying mechanism remains unclear. Several models such as ex vivo culture of adipose tissues, primary rat adipocytes and 3T3-L1 adipocytes were used to further characterize the effect of LPS on the expression of resistin. LPS attenuated both the resistin mRNA and protein in a time- and dose-dependent manner. In the presence of actinomycin D, LPS failed to reduce the half-life of resistin mRNA, suggesting a transcriptional mechanism. The lipid A fraction is crucial for the inhibition of resistin expression induced by LPS. Pharmacological intervention of c-Jun N-terminal kinase (JNK) reversed the inhibitory effect of LPS. LPS down-regulated CCAAT/enhancer-binding protein α (C/EBP-α; CEBPA) and peroxisome proliferator-activated receptor γ (PPAR-γ; PPARG), while activation of C/EBP-α or PPAR-γ by either over-expressing these transcriptional factors or by rosiglitazone, an agonist of PPAR-γ, blocked the inhibitory effect of LPS on resistin. C/EBP homologous protein (CHOP-10; DDIT3) was up-regulated by LPS, while a CHOP-10 antisense oligonucleotide reversed the decrement of resistin protein induced by LPS. Taken together, these results suggest that LPS inhibits resistin expression through a unique signaling pathway involving toll-like receptor 4, JNK, CHOP-10 and C/EBP-α/PPAR-γ.
Xinxin Xiang, Wenjiao An, Changtao Jiang, Jing Zhao, Xian Wang, Guang Sun, Yin Li and Weizhen Zhang
Yan-hui Bai, Yong Lv, Wei-qun Wang, Guang-li Sun and Hao-hao Zhang
Human corneal fibroblasts (HCFs) are implicated in corneal neovascularization (CRNV). The mechanisms underlying the inflammatory response in HCFs and the development of CRNV were explored in this study. Alkali burns were applied to the corneas of rats to establish a CRNV model. The expression of long noncoding RNA (lncRNA) nuclear enriched abundant transcript 1 (NEAT1) and mRNA and protein levels of nuclear factor kappa B (NF-κB)- activating protein (NKAP) were examined by quantitative real-time (qRT-PCR) and Western blot methods, respectively. Lipopolysaccharide (LPS) is used to stimulate HCFs for inflammatory response. The level of inflammation factors in HCF supernatant was detected using an enzyme-linked immunosorbent assay (ELISA). Binding and interactions between NEAT1 and miRNA 1246 (miR-1246) were determined by RNA immunoprecipitation (RIP) and RNA pull-down assays in HCFs. Compared with the control group (n = 6), NEAT1 was upregulated in the corneas of the CRNV rat model (n = 6). The expression of NEAT1 in HCFs was upregulated by LPS. Downregulation of NEAT1 suppressed the secretion of tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). NEAT1 could bind and interact with miR-1246. LPS regulated the expression of NKAP and NF-κB signaling via the NEAT1/miR-1246 pathway. Downregulation of NEAT1 in vivo inhibited CRNV progression in the CRNV rat model. The lncRNA NEAT1 induced secretion of inflammatory factors, mediated by NF-κB, by targeting miR-1246, thereby promoting CRNV progression.
Yingkai Sun, Rui Wang, Shaoqian Zhao, Wen Li, Wen Liu, Lingyun Tang, Zhugang Wang, Weiqing Wang, Ruixin Liu, Guang Ning, Jiqiu Wang and Jie Hong
Browning of white adipose tissue has been proven to be a potential target to fight against obesity and its metabolic commodities, making the exploration of molecules involved in browning process important. Among those browning agents reported recently, FGF21 play as a quite promising candidate for treating obesity for its obvious enhancement of thermogenic capacity in adipocyte and significant improvement of metabolic disorders in both mice and human. However, whether other members of fibroblast growth factor (FGF) family play roles in adipose thermogenesis and obese development is still an open question. Here, we examined the mRNA expression of all FGF family members in three adipose tissues of male C57BL/6 mice and found that FGF9 is highly expressed in adipose tissue and decreased under cold stress. Furthermore, FGF9 treatment inhibited thermogenic genes in the process of beige adipocytes differentiation from stromal vascular fraction (SVF) in a dose-dependent manner. Similar results were obtained with FGF9 overexpression. Consistently, knockdown of FGF9 in SVF cells by using lentiviral shRNA increased thermogenic genes in differentiated beige adipocytes. RNA sequencing analysis revealed a significant increment of hypoxia-inducible factor (HIF) pathway in the early stage of beige adipocytes differentiation under FGF9 treatment, which was validated by real-time PCR. FGF9 expression was increased in subcutaneous WAT of obese human and mice. This study shows that adipose-derived FGF9 play as an inhibitory role in the browning of white adipocytes. Activation of hypoxia signaling at early stage of adipose browning process may contribute to this anti-thermogenic effect of FGF9.