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Inflammation stimulates hypoxia‐inducible factor‐1α regulatory activity in 3T3‐L1 adipocytes with conditioned medium from lipopolysaccharide‐activated RAW 264.7 macrophages
Author(s) -
LopezPascual Amaya,
LorenteCebrián Silvia,
MorenoAliaga María J.,
Martinez J. Alfredo,
GonzálezMuniesa Pedro
Publication year - 2019
Publication title -
journal of cellular physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.529
H-Index - 174
eISSN - 1097-4652
pISSN - 0021-9541
DOI - 10.1002/jcp.26763
Subject(s) - adipose tissue , lipopolysaccharide , tumor necrosis factor alpha , medicine , inflammation , adipose tissue macrophages , endocrinology , hypoxia inducible factors , downregulation and upregulation , adipocyte , chemistry , gene knockdown , hypoxia (environmental) , white adipose tissue , biology , biochemistry , apoptosis , oxygen , gene , organic chemistry
Obesity is a multifactorial, chronic, inflammatory disease that involves different processes, such as adipose tissue hypoxia. The aim of the current study was to characterize the effects of conditioned medium (CM) from lipopolysaccharide (LPS)‐activated macrophages on the regulation of hypoxia‐inducible factor 1α (HIF‐1α)‐related genes in murine adipocytes. For the in vitro analyses, 3T3‐L1 murine adipocytes (9 days postdifferentiation) were incubated either in CM (25% medium of RAW 264.7 murine macrophages with 24 hr 500 ng/ml LPS), LPS at 500 ng/ml, or hypoxia (Hx; 1% O 2 , 94% N 2 , 5% CO 2 ) for 24 hr. For the in vivo experiments, mice were fed a high‐fat diet. Both epididymal white adipose tissue (eWAT) and adipocytes in CM showed upregulation of Glut1 , Mcp1 , Il10 , Tnf , and Il1b . The secretion of IL‐6, TNF‐α, and MCP‐1 was also increased in CM‐treated adipocytes. Moreover, increased levels of HIF‐1α subunit and nuclear factor kappa B p65 were found after CM treatment, linking Hx, and inflammation. HIF‐1α directly bound vascular endothelial growth factor A ( Vegfa ) and uncoupling protein 2 ( Ucp2 ) genes, up‐ and downregulating its expression, respectively. Furthermore, the oxygen consumption rate was 30% lower in CM. The siRNA knockdown of mammalian target of rapamycin ( Mtor ) reversed the induction of HIF‐1α found in CM. The macrophage infiltration simulated through CM seems to be a similar environment to an abnormally enlarged eWAT. We have evidenced that HIF‐1α plays a regulatory role in the expression of Vegfa and Ucp2 in CM. Finally, the inhibition of the mTOR pathway prevented the HIF‐1α activation induced by CM. The involvement of HIF‐1α under proinflammatory conditions provides insight into the origins of Hx in obesity.