Macrophage-conditioned medium inhibits differentiation-induced Rb phosphorylation in 3T3-L1 preadipocytes

Yarmo, Michelle N.; Landry, Anne; Molgat, André S.D.; Gagnon, AnneMarie; Sorisky, Alexander

doi:10.1016/j.yexcr.2008.10.036

Cited by 30 publications

(32 citation statements)

References 35 publications

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“…We have reported that MacCM from mouse J774 and human THP-1 macrophage cell lines inhibit the differentiation of mouse 3T3-L1 and human primary preadipocytes into adipocytes (4,5,40). Conditioned medium from human monocytederived macrophages and from human adipose tissue macrophages is similarly anti-adipogenic (15,17).…”

Section: Discussionmentioning

confidence: 99%

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Preadipocyte apoptosis is prevented by macrophage-conditioned medium in a PDGF-dependent manner

Molgat

Gagnon²,

Sorisky³

2009

American Journal of Physiology-Cell Physiology

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Molgat AS, Gagnon A, Sorisky A. Preadipocyte apoptosis is prevented by macrophage-conditioned medium in a PDGF-dependent manner. Am J Physiol Cell Physiol 296: C757-C765, 2009. First published February 18, 2009 doi:10.1152/ajpcell.00617.2008.-Obesity is associated with macrophage accumulation and inflammation in adipose tissue. Macrophage-secreted factors have been reported to inhibit the differentiation of preadipocytes into adipocytes and to modulate adipogenic extracellular matrix gene expression. To enlarge our understanding of macrophages and the scope of their interactions with preadipocytes, we investigated their effect on preadipocyte survival. Acute exposure of 3T3-L1 preadipocytes to J774A.1 macrophage-conditioned medium (MacCM) stimulated platelet-derived growth factor receptor (PDGFR) tyrosine phosphorylation by 4.1-fold. There were significant increases in the phosphocontent of downstream PDGFR targets Akt and ERK1/2 (5.3-fold and 2.4-fold, respectively) that were inhibited by PDGF immunoneutralization or by the selective PDGFR inhibitor imatinib. Serum-free J774A.1-MacCM or RAW264.7-MacCM completely prevented 3T3-L1 preadipocyte apoptosis normally induced by serum deprivation. Addition of PDGF alone to serum-free control medium was sufficient to prevent 3T3-L1 preadipocyte apoptosis. Inhibition of PDGFR activation by MacCM, either by addition of imatinib or by PDGF immunodepletion of MacCM, effectively disrupted the prosurvival effect. In summary, our data indicate that MacCM promotes preadipocyte survival in a PDGFdependent manner.platelet-derived growth factor; obesity; macrophage OBESITY, defined as an increase in adiposity, results from a chronic positive energy balance. Expansion of adipose tissue occurs through the formation of new adipocytes, via the differentiation of stromal precursor preadipocytes, and the enlargement of existing adipocytes (9). Deficiency in the number of preadipocytes, or their capacity to differentiate, may lead to excessively hypertrophied and dysfunctional adipocytes that overproduce immune cell chemoattractant proteins (7,13,14). Concomitantly, the population of adipose tissue macrophages rises due to monocyte infiltration. This abnormal cellular remodeling of adipose tissue is associated with low-grade inflammation and insulin resistance (38,39).Paracrine communication among macrophages, adipocytes, and preadipocytes is believed to contribute to obesity-associated adipose tissue dysfunction (12). We and others have reported that macrophages produce anti-adipogenic factors that restrain the differentiation of preadipocytes into adipocytes (4,5,15,17,33,40). Macrophage-secreted factors have also been observed to have variable effects on preadipocyte proliferation (17,23). Apoptosis, the other key preadipocyte fate pertinent to adipose tissue remodeling (11, 21, 28), has not been evaluated with respect to potential macrophage paracrine interactions.The precise identity of the macrophage products influencing preadipocyte responses is not known. Here, we demonstrate th...

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Section: Discussionmentioning

confidence: 99%

“…We and others have reported that macrophages produce anti-adipogenic factors that restrain the differentiation of preadipocytes into adipocytes (4,5,15,17,33,40). Macrophage-secreted factors have also been observed to have variable effects on preadipocyte proliferation (17,23).…”

mentioning

confidence: 98%

Preadipocyte apoptosis is prevented by macrophage-conditioned medium in a PDGF-dependent manner

Molgat

Gagnon²,

Sorisky³

2009

American Journal of Physiology-Cell Physiology

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“…For HA-FOXO3a localization assay, the ␣-HA-fluorescein clone 3F10 (Roche Applied Science) was added (2 g/ml) in combination with secondary antibody. ␣-c/EBP␤ immunofluorescence was performed as described (19).…”

Section: Methodsmentioning

confidence: 99%

Regulation of Adipocyte Differentiation by Distinct Subcellular Pools of Protein Kinase B (PKB/Akt)

Maiuri

Stambolic

2010

Journal of Biological Chemistry

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The phosphatidylinositol 3-kinase (PI3K)-protein kinase B (PKB)/Akt-PTEN signal transduction pathway orchestrates a variety of fundamental cell processes and its deregulation is implicated in many human diseases. Although the importance of this pathway to many cellular functions is well established, the mechanisms by which it achieves context-specific physiological outcomes in response to a variety of stimuli, using a relatively limited pool of effectors, remain largely unknown. Spatial restriction of signaling events is one means by which cells coordinate specific responses using common molecules. To investigate the subcellular location-specific roles of the major PI3K effector PKB/Akt in various cell processes, we have developed a novel experimental system employing cellular compartment-directed PKB/Akt pseudosubstrate inhibitors. Subcellular location-restricted PKB/Akt inhibition in the 3T3L1 adipocyte differentiation model revealed that nuclear and plasma membrane, but not cytoplasmic, PKB/Akt activity is required for terminal adipocyte differentiation. Nuclear and plasma membrane pools of PKB/Akt were found to contribute to distinct stages of adipocyte differentiation, revealing that PKB/Akt activity impacts multiple points of this program. Our work establishes the use of localized pseudosubstrate PKB/Akt inhibitors as an effective method for the dissection of PKB/Akt signaling.The phosphatidylinositol 3-kinase (PI3K) 2 -protein kinase B (PKB)/Akt-phosphatase and tensin homolog (PTEN) pathway is an evolutionarily conserved signaling cascade implicated in the regulation of several fundamental cell processes including cell proliferation, survival, motility and size, glucose metabolism, and differentiation. Appropriate execution of PI3K-PKB/ Akt-PTEN signaling is of critical importance to the proper functioning of cells and organisms, exemplified by the variety of developmental defects associated with disruption of its constituents in model organisms (1). Moreover, the components of the pathway are frequent targets of mutations associated with cancer and other human diseases (2).Upon activation in response to a variety of cellular stimuli, PI3K phosphorylates the D3 position of the phosphoinositide PI(4,5)P 2 , leading to the generation of the second messenger PI(3,4,5)P 3 at the plasma membrane. PI(3,4,5)P 3 acts as a docking site for pleckstrin homology (PH) domain containing proteins such as PKB/Akt and its activating kinase, 3-phosphoinositide-dependent kinase 1 (3). Upon recruitment to PI(3,4,5)P 3 and activation-specific phosphorylation by 3-phosphoinositide-dependent kinase 1, as well as additional phosphorylation by mammalian target of rapamycin complex 2 (mTORC2) (4), fully activated PKB/Akt executes a wide spectrum of cellular responses acting through a variety of intracellular substrates (5). The role of this signaling pathway in the process of adipocyte differentiation has been demonstrated by genetic disruption of PKB/Akt in mice, which results in impaired adipogenesis (6), as well as cell culture...

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“…The conditioned culture medium, collected from mature adipocytes (ACM) 24 h after isolation (12,21), was concentrated in a speed vacuum system (Vacufuge, Eppendorf) and kept at 220°C for further determination of aldosterone, corticosterone, angiotensin II, and hydrogen peroxide (H 2 O 2 ) levels.…”

Section: Conditioned Culture Mediummentioning

confidence: 99%

Adipocyte-Specific Mineralocorticoid Receptor Overexpression in Mice Is Associated With Metabolic Syndrome and Vascular Dysfunction: Role of Redox-Sensitive PKG-1 and Rho Kinase

et al. 2016

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Mineralocorticoid receptor (MR) expression is increased in adipose tissue from obese individuals and animals.We previously demonstrated that adipocyte-MR overexpression (Adipo-MROE) in mice is associated with metabolic changes. Whether adipocyte MR directly influences vascular function in these mice is unknown. We tested this hypothesis in resistant mesenteric arteries from Adipo-MROE mice using myography and in cultured adipocytes. Molecular mechanisms were probed in vessels/vascular smooth muscle cells and adipose tissue/adipocytes and focused on redox-sensitive pathways, Rho kinase activity, and protein kinase G type-1 (PKG-1) signaling. Adipo-MROE versus control-MR mice exhibited reduced vascular contractility, associated with increased generation of adipocyte-derived hydrogen peroxide, activation of vascular redox-sensitive PKG-1, and downregulation of Rho kinase activity. Associated with these vascular changes was increased elastin content in Adipo-MROE. Inhibition of PKG-1 with Rp-8-Br-PET-cGMPS normalized vascular contractility in Adipo-MROE. In the presence of adipocyte-conditioned culture medium, anticontractile effects of the adipose tissue were lost in Adipo-MROE mice but not in control-MR mice. In conclusion, adipocyte-MR upregulation leads to impaired contractility with preserved endothelial function and normal blood pressure.Increased elasticity may contribute to hypocontractility. We also identify functional cross talk between adipocyte MR and arteries and describe novel mechanisms involving redox-sensitive PKG-1 and Rho kinase. Our results suggest that adipose tissue from Adipo-MROE secrete vasoactive factors that preferentially influence vascular smooth muscle cells rather than endothelial cells. Our findings may be important in obesity/ adiposity where adipocyte-MR expression/signaling is amplified and vascular risk increased.

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Macrophage-conditioned medium inhibits differentiation-induced Rb phosphorylation in 3T3-L1 preadipocytes

Cited by 30 publications

References 35 publications

Preadipocyte apoptosis is prevented by macrophage-conditioned medium in a PDGF-dependent manner

Preadipocyte apoptosis is prevented by macrophage-conditioned medium in a PDGF-dependent manner

Regulation of Adipocyte Differentiation by Distinct Subcellular Pools of Protein Kinase B (PKB/Akt)

Adipocyte-Specific Mineralocorticoid Receptor Overexpression in Mice Is Associated With Metabolic Syndrome and Vascular Dysfunction: Role of Redox-Sensitive PKG-1 and Rho Kinase

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