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Microparticles release by adipocytes act as "find-me" signals to promote macrophage migration.

Eguchi A, Mulya A, Lazic M, Radhakrishnan D, Berk MP, Povero D, Gornicka A, Feldstein AE - PLoS ONE (2015)

Bottom Line: The release of MPs was highly regulated and dependent on caspase 3 and Rho-associated kinase.Further analysis identified these MPs as a central chemoattractant in vitro and in vivo.In addition, intravenously transplanting circulating MPs from the ob/ob mice lead to activation of monocytes in circulation and adipose tissue of the wild type mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, University of California San Diego (UCSD), La Jolla, California, United States of America.

ABSTRACT
Macrophage infiltration of adipose tissue during weight gain is a central event leading to the metabolic complications of obesity. However, what are the mechanisms attracting professional phagocytes to obese adipose tissue remains poorly understood. Here, we demonstrate that adipocyte-derived microparticles (MPs) are critical "find-me" signals for recruitment of monocytes and macrophages. Supernatants from stressed adipocytes stimulated the attraction of monocyte cells and primary macrophages. The activation of caspase 3 was required for release of these signals. Adipocytes exposed to saturated fatty acids showed marked release of MPs into the supernatant while common genetic mouse models of obesity demonstrate high levels of circulating adipocyte-derived MPs. The release of MPs was highly regulated and dependent on caspase 3 and Rho-associated kinase. Further analysis identified these MPs as a central chemoattractant in vitro and in vivo. In addition, intravenously transplanting circulating MPs from the ob/ob mice lead to activation of monocytes in circulation and adipose tissue of the wild type mice. These data identify adipocyte-derived MPs as novel "find me" signals that contributes to macrophage infiltration associated with obesity.

No MeSH data available.


Related in: MedlinePlus

Obesity is associated with increased levels of circulating MPs and increased adipose activity of Rho associated kinase and caspase 3Annexin V positive MPs from (A) ob control or ob/ob mice. Blood was collected by cardiac puncture and PFP was obtained as detailed in methods section. Annexin V positive MPs were analyzed by flow cytometry (n = 5 each group). (B) Dynamic light scattering analysis and Transmission Electron Microscopy of isolated circulating MPs. (C) Western blot analysis of perilipin A levels in MPs isolated from mouse PFP in WT mice on a regular chow diet and ob/ob mice (n = 3 each group). Perilipin A abundance in MPs isolated from mouse PFP correlated to: (D) total mouse body weights and (E) weight of extracted mouse epididymal fat pads. (F) Western blots of p-MYPT1, total MYPT1/2, cleaved (active) caspase 3, total caspase 3, and actin levels in subcutaneous and epididymal adipose tissue lysates from ob control or ob/ob mice. Quantification of Western blots of (G) cleaved caspase 3 and (H) p-MYPT in ob control and ob/ob mice adipose tissues normalized to actin levels. Values represent mean ± S.E.M. *P < 0.05; ***P < 0.001 compared to respective controls.
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pone.0123110.g005: Obesity is associated with increased levels of circulating MPs and increased adipose activity of Rho associated kinase and caspase 3Annexin V positive MPs from (A) ob control or ob/ob mice. Blood was collected by cardiac puncture and PFP was obtained as detailed in methods section. Annexin V positive MPs were analyzed by flow cytometry (n = 5 each group). (B) Dynamic light scattering analysis and Transmission Electron Microscopy of isolated circulating MPs. (C) Western blot analysis of perilipin A levels in MPs isolated from mouse PFP in WT mice on a regular chow diet and ob/ob mice (n = 3 each group). Perilipin A abundance in MPs isolated from mouse PFP correlated to: (D) total mouse body weights and (E) weight of extracted mouse epididymal fat pads. (F) Western blots of p-MYPT1, total MYPT1/2, cleaved (active) caspase 3, total caspase 3, and actin levels in subcutaneous and epididymal adipose tissue lysates from ob control or ob/ob mice. Quantification of Western blots of (G) cleaved caspase 3 and (H) p-MYPT in ob control and ob/ob mice adipose tissues normalized to actin levels. Values represent mean ± S.E.M. *P < 0.05; ***P < 0.001 compared to respective controls.

Mentions: To further gain insight into the potential role of adipocyte-derived MPs in recruitment of macrophages to adipose tissue during obesity, we used common genetic murine model of obesity and insulin resistance. Three-months old ob/ob mice showed a marked increase in circulating MPs compared to ob control mice (Fig 5A). Furthermore, MPs extracted from platelet free plasma (PFP) of ob/ob mice were similar to the isolated MPs from stressed 3T3-L1 adipocytes both in size (approximately 90–500 nm range; Fig 5B) and in appearance as observed by electron microscopy (Fig 5B). Since we revealed that adipocyte-derived MP release is increased in stressed adipocytes and adipocyte-derived MP were enriched in perilipin A, we next assessed for the presence of perilipin A in the circulation as a plausible indicator of AT as a source of circulating MPs. Perilipin A is known for its roles as a central gatekeeper of the adipocyte lipid storehouse and a marker of adipocyte differentiation [31, 32]. Furthermore, perilipin is not known to be a secretory protein. We observed that expression of perilipin A was detected in circulating MPs isolated from ob/ob mice (Fig 5C), showing a significant positive correlation of perilipin A levels in circulating MPs with total body weights (Fig 5D; P<0.01, R = 0.94) and epididymal fat pad weights (Fig 5E; P<0.0001, R = 0.993). These changes were associated with increased abundance of cleaved/ active caspase 3 in subcutaneous and epididymal adipose tissue of ob/ob mice compared to ob control (Fig 5F and 5G). In addition, we observed increased phosphorylated myosine phosphatase targeting protein-1 (p-MYPT1) in the same adipose tissues suggested increased Rho-associated kinase activity (Fig 5F–5H). These results suggest that adipocyte-specific MPs might be novel mediators of macrophage recruitment to adipose tissue during weight gain (S3A Fig) and adipose tissue expansion (S3B Fig) associated with macrophage infiltration (S3C Fig) and also identify potential therapeutic targets for inhibition of MP release by adipocytes.


Microparticles release by adipocytes act as "find-me" signals to promote macrophage migration.

Eguchi A, Mulya A, Lazic M, Radhakrishnan D, Berk MP, Povero D, Gornicka A, Feldstein AE - PLoS ONE (2015)

Obesity is associated with increased levels of circulating MPs and increased adipose activity of Rho associated kinase and caspase 3Annexin V positive MPs from (A) ob control or ob/ob mice. Blood was collected by cardiac puncture and PFP was obtained as detailed in methods section. Annexin V positive MPs were analyzed by flow cytometry (n = 5 each group). (B) Dynamic light scattering analysis and Transmission Electron Microscopy of isolated circulating MPs. (C) Western blot analysis of perilipin A levels in MPs isolated from mouse PFP in WT mice on a regular chow diet and ob/ob mice (n = 3 each group). Perilipin A abundance in MPs isolated from mouse PFP correlated to: (D) total mouse body weights and (E) weight of extracted mouse epididymal fat pads. (F) Western blots of p-MYPT1, total MYPT1/2, cleaved (active) caspase 3, total caspase 3, and actin levels in subcutaneous and epididymal adipose tissue lysates from ob control or ob/ob mice. Quantification of Western blots of (G) cleaved caspase 3 and (H) p-MYPT in ob control and ob/ob mice adipose tissues normalized to actin levels. Values represent mean ± S.E.M. *P < 0.05; ***P < 0.001 compared to respective controls.
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pone.0123110.g005: Obesity is associated with increased levels of circulating MPs and increased adipose activity of Rho associated kinase and caspase 3Annexin V positive MPs from (A) ob control or ob/ob mice. Blood was collected by cardiac puncture and PFP was obtained as detailed in methods section. Annexin V positive MPs were analyzed by flow cytometry (n = 5 each group). (B) Dynamic light scattering analysis and Transmission Electron Microscopy of isolated circulating MPs. (C) Western blot analysis of perilipin A levels in MPs isolated from mouse PFP in WT mice on a regular chow diet and ob/ob mice (n = 3 each group). Perilipin A abundance in MPs isolated from mouse PFP correlated to: (D) total mouse body weights and (E) weight of extracted mouse epididymal fat pads. (F) Western blots of p-MYPT1, total MYPT1/2, cleaved (active) caspase 3, total caspase 3, and actin levels in subcutaneous and epididymal adipose tissue lysates from ob control or ob/ob mice. Quantification of Western blots of (G) cleaved caspase 3 and (H) p-MYPT in ob control and ob/ob mice adipose tissues normalized to actin levels. Values represent mean ± S.E.M. *P < 0.05; ***P < 0.001 compared to respective controls.
Mentions: To further gain insight into the potential role of adipocyte-derived MPs in recruitment of macrophages to adipose tissue during obesity, we used common genetic murine model of obesity and insulin resistance. Three-months old ob/ob mice showed a marked increase in circulating MPs compared to ob control mice (Fig 5A). Furthermore, MPs extracted from platelet free plasma (PFP) of ob/ob mice were similar to the isolated MPs from stressed 3T3-L1 adipocytes both in size (approximately 90–500 nm range; Fig 5B) and in appearance as observed by electron microscopy (Fig 5B). Since we revealed that adipocyte-derived MP release is increased in stressed adipocytes and adipocyte-derived MP were enriched in perilipin A, we next assessed for the presence of perilipin A in the circulation as a plausible indicator of AT as a source of circulating MPs. Perilipin A is known for its roles as a central gatekeeper of the adipocyte lipid storehouse and a marker of adipocyte differentiation [31, 32]. Furthermore, perilipin is not known to be a secretory protein. We observed that expression of perilipin A was detected in circulating MPs isolated from ob/ob mice (Fig 5C), showing a significant positive correlation of perilipin A levels in circulating MPs with total body weights (Fig 5D; P<0.01, R = 0.94) and epididymal fat pad weights (Fig 5E; P<0.0001, R = 0.993). These changes were associated with increased abundance of cleaved/ active caspase 3 in subcutaneous and epididymal adipose tissue of ob/ob mice compared to ob control (Fig 5F and 5G). In addition, we observed increased phosphorylated myosine phosphatase targeting protein-1 (p-MYPT1) in the same adipose tissues suggested increased Rho-associated kinase activity (Fig 5F–5H). These results suggest that adipocyte-specific MPs might be novel mediators of macrophage recruitment to adipose tissue during weight gain (S3A Fig) and adipose tissue expansion (S3B Fig) associated with macrophage infiltration (S3C Fig) and also identify potential therapeutic targets for inhibition of MP release by adipocytes.

Bottom Line: The release of MPs was highly regulated and dependent on caspase 3 and Rho-associated kinase.Further analysis identified these MPs as a central chemoattractant in vitro and in vivo.In addition, intravenously transplanting circulating MPs from the ob/ob mice lead to activation of monocytes in circulation and adipose tissue of the wild type mice.

View Article: PubMed Central - PubMed

Affiliation: Department of Pediatrics, University of California San Diego (UCSD), La Jolla, California, United States of America.

ABSTRACT
Macrophage infiltration of adipose tissue during weight gain is a central event leading to the metabolic complications of obesity. However, what are the mechanisms attracting professional phagocytes to obese adipose tissue remains poorly understood. Here, we demonstrate that adipocyte-derived microparticles (MPs) are critical "find-me" signals for recruitment of monocytes and macrophages. Supernatants from stressed adipocytes stimulated the attraction of monocyte cells and primary macrophages. The activation of caspase 3 was required for release of these signals. Adipocytes exposed to saturated fatty acids showed marked release of MPs into the supernatant while common genetic mouse models of obesity demonstrate high levels of circulating adipocyte-derived MPs. The release of MPs was highly regulated and dependent on caspase 3 and Rho-associated kinase. Further analysis identified these MPs as a central chemoattractant in vitro and in vivo. In addition, intravenously transplanting circulating MPs from the ob/ob mice lead to activation of monocytes in circulation and adipose tissue of the wild type mice. These data identify adipocyte-derived MPs as novel "find me" signals that contributes to macrophage infiltration associated with obesity.

No MeSH data available.


Related in: MedlinePlus