α-Naphthoflavone Increases Lipid Accumulation in Mature Adipocytes and Enhances Adipocyte-Stimulated Endothelial Tube Formation

Abstract

The aryl hydrocarbon receptor (AhR) is a ligand-activated factor that regulates biological effects associated with obesity. The AhR agonists, such as environmental contaminants 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and β-naphthoflavone (BNF), inhibit preadipocyte differentiation and interfere with the functions of adipose tissue, whereas the antagonist may have opposite or protective effects in obesity. This study investigated the effects of α-naphthoflavone (α-NF), an AhR antagonist, on adipogenesis- and angiogenesis-associated factors in mature adipocytes and on cross-talk of mature adipocytes with endothelial cells (ECs). Besides, the roles of the AhR on lipid accumulation and on secretion of vascular endothelial growth factor were also determined by introducing siRNA of AhR. Differentiated 3T3-L1 cells were treated with α-naphthoflavone (α-NF) (1–5 μM) for 16 h. Lipid accumulation and the expressions of AhR-associated factors in the cells were determined. The interaction between adipocytes and ECs was investigated by cultivating ECs with conditioned medium (CM) from α-NF-treated mature adipocytes, followed by the determination of endothelial tube formation. The results showed that α-NF significantly increased triglyceride (TG) accumulation in mature adipocytes, which was associated with increased expression of hormone-sensitive lipase (HSL), estrogen receptor (ER), as well as decreased expression of AhR, AhR nuclear translocator (ARNT), cytochrome P4501B1 (CYP1B1), and nuclear factor erythroid-2-related factor (NRF-2) proteins. In addition, CM stimulated formation of tube-like structures in ECs, and α-NF further enhanced such stimulation in association with modulated the secretions of various angiogenic mediators by mature adipocytes. Similarly, increased TG accumulation and vascular endothelial growth factor (VEGF) secretion were observed in AhR-knockout cells. In conclusion, α-NF increased TG accumulation in mature adipocytes and enhanced mature adipocyte-stimulated tube formation in ECs, suggesting that the AhR may suppress obesity-induced adverse effects, and α-NF abolished the protective effects of the AhR.

Long-term in vivo polychlorinated biphenyl 126 exposure induces oxidative stress and alters proteomic profile on islets of Langerhans

“…In this context, we previously showed that in vivo inhalatory PCB126 exposure enhanced AhR expression in the adipose tissues 13 , and here we suppose that both reductions on periepididimal and retroperitoneal fat depots detected in PCB126 exposed rats may be due to direct activation of AhR in the adipocytes. This hypothesis is based on recent data showing that AhR null mice exhibited increased fat mass when fed a standard, low or high fat diet 27 ; transgenic mice with constitutively activated AhR present decreased adipose tissue deposits associated with elevation of peripheral fat mobilization 28 ; and in vitro ligand-activated AhR inhibits the lipid synthesis, adipocyte differentiation, and secretion of adypocyte proliferating mediators 14 29 30 31 . On the other hand, AhR activation induces inflammation in adipose tissue, contributing to obesity 27 28 32 33 34 .…”

Suppression of Lipid Accumulation by Indole-3-Carbinol Is Associated with Increased Expression of the Aryl Hydrocarbon Receptor and CYP1B1 Proteins in Adipocytes and with Decreased Adipocyte-Stimulated Endothelial Tube Formation

“…The AhR ligands, such as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), β-naphthoflavone (BNF), and polychlorinated biphenyl, activate the transcription of xenobiotic metabolizing enzymes CYP1A and CYP1B [ 17 ]. On the other hand, the AhR negatively regulates adipocyte differentiation [ 13 , 18 ], and TCDD suppresses adipocyte differentiation [ 19 , 20 ], whereas the AhR antagonist α-naphthoflavone (ANF) increases lipid accumulation in mature adipocytes [ 21 ]. I3C is a naturally occurring AhR agonist that exhibits antiobesity activities, such as the reduction of body and WAT weights in high-fat-diet-induced obese mice and the inhibition of adipocyte differentiation by activating the silent mating type information regulation 2 homolog 1 and subsequently downregulating the expression of PPARγ2, C/EBPα, and aP2, factors crucial for differentiation [ 12 , 22 ].…”

“…TCDD increased the expression of lipolysis-associated factors in treated mice, and this increase is related to the TCDD-induced wasting syndrome [ 28 , 29 ]. On the other hand, we previously reported that the AhR antagonist ANF reduced the expression of the AhR in association with increased TG accumulation in adipocytes [ 21 ]. Therefore, we hypothesize that I3C reduces lipid accumulation in adipocytes by inducing AhR expression and then reducing lipogenesis and increasing lipolysis responses in 3T3-L1 adipoyctes.…”

Effects of Caffeine, Paracetamol and Βnaphthoflavone on the Lipid Content and Differentiation of Human Adipose Derived Mesenchymal Stem Cells in Vitro

“…Synthetic flavonoid α-Naphthoflavone is classified as an ahR antagonist and has been shown to promote adipogenesis and lipid accumulation in 3T3-L1 cells in vitro (Wang et al, 2015).Inversely,utilizingahR agonists such as β-Naphthoflavone (BNF) are hypothesized to have an opposite effect and effectively inhibit or minimize lipid accumulation. BNF has been shown to be an effective inducer of important detoxifying enzymes such as CYP1A1 through the translocation of ahR receptor bound to BNF (Yoshinari et al, 2006).…”