Urokinase-type plasminogen activator and macrophages are required for skeletal muscle hypertrophy in mice

2007 ◽  
Vol 293 (4) ◽  
pp. C1278-C1285 ◽  
Author(s):  
Dana M. DiPasquale ◽  
Ming Cheng ◽  
William Billich ◽  
Sharon A. Huang ◽  
Nico van Rooijen ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Plasminogen Activator ◽  
Mechanical Loading ◽  
Muscle Hypertrophy ◽  
Compensatory Hypertrophy ◽  
Wild Type ◽  
Adult Skeletal Muscle ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Macrophage Accumulation

Adult skeletal muscle possesses remarkable potential for growth in response to mechanical loading; however, many of the cellular and molecular mechanisms involved remain undefined. The hypothesis of this study was that the extracellular serine protease, urokinase-type plasminogen activator (uPA), is required for muscle hypertrophy, in part by promoting macrophage accumulation in muscle subjected to increased mechanical loading. Compensatory muscle hypertrophy was induced in mouse plantaris (PLT) muscles by surgical ablation of synergist muscles. Following synergist ablation, PLT muscles in wild-type mice demonstrated edema and infiltration of neutrophils and macrophages but an absence of overt muscle fiber damage. Sham procedures resulted in no edema or accumulation of inflammatory cells. In addition, synergist ablation was associated with a large increase in activity of uPA in the PLT muscle. uPA-null mice demonstrated complete abrogation of compensatory hypertrophy associated with reduced macrophage accumulation, indicating that uPA is required for hypertrophy. Macrophages isolated from wild-type PLT muscle during compensatory hypertrophy expressed uPA and IGF-I, both of which may contribute to hypertrophy. To determine whether macrophages are required for muscle hypertrophy, clodronate liposomes were administered to deplete macrophages in wild-type mice; this resulted in reduced muscle hypertrophy. Decreased macrophage accumulation was associated with reduced cell proliferation but did not alter signaling through the mammalian target of rapamycin pathway. These data indicate that uPA and macrophages are required for muscle hypertrophy following synergist ablation.

The urokinase-type plasminogen activator receptor is not required for skeletal muscle inflammation or regeneration

2007 ◽  
Vol 293 (3) ◽  
pp. R1152-R1158 ◽  
Author(s):  
Scott C. Bryer ◽  
Timothy J. Koh
Keyword(s):  
Skeletal Muscle ◽  
Plasminogen Activator ◽  
Muscle Regeneration ◽  
Inflammatory Cells ◽  
Wild Type ◽  
Neutrophil Accumulation ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Plasminogen Activator Receptor

The hypothesis of this study was the urokinase-type plasminogen activator receptor (uPAR) is required for accumulation of inflammatory cells in injured skeletal muscle and for efficient muscle regeneration. Expression of uPAR was elevated at 1 and 3 days after cardiotoxin-induced muscle injury in wild-type mice before returning to baseline levels. Neutrophil accumulation peaked 1 day postinjury in muscle from both wild-type (WT) and uPAR null mice, while macrophage accumulation peaked between 3 and 5 days postinjury, with no differences between strains. Histological analyses confirmed efficient muscle regeneration in both wild-type and uPAR null mice, with no difference between strains in the formation or growth of regenerating fibers, or recovery of normal morphology. Furthermore, in vitro experiments demonstrated that chemotaxis is not different between WT and uPAR null macrophages. Finally, fusion of cultured satellite cells into multinucleated myotubes was not different between cells isolated from WT and uPAR null mice. These results demonstrate that uPAR is not required for the accumulation of inflammatory cells or the regeneration of skeletal muscle following injury, suggesting uPA can act independently of uPAR to regulate events critical for muscle regeneration.

Expression and Characterization of Clustered Charge-to-Alanine Mutants of Low Mr Single-Chain Urokinase-Type Plasminogen Activator

1994 ◽  
Vol 71 (01) ◽  
pp. 134-140 ◽  
Author(s):  
S Ueshima ◽  
P Holvoet ◽  
H R Lijnen ◽  
L Nelles ◽  
V Seghers ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Solvent Accessibility ◽  
Site Directed Mutagenesis ◽  
Clot Lysis ◽  
Wild Type ◽  
Single Chain ◽  
Charged Amino Acids ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Pharmacokinetic Properties

SummaryIn an effort to modify the fibrinolytic and/or pharmacokinetic properties of recombinant low M r single-chain urokinase-type plasminogen activator (rscu-PA-32k), mutants were prepared by site-directed mutagenesis of clusters of charged amino acids with the highest solvent accessibility. The following mutants of rscu-PA-32k were prepared: LUK-2 (Lys 212, Glu 213 and Asp 214 to Ala), LUK-3 (Lys 243 and Asp 244 to Ala), LUK-4 (Arg 262, Lys 264, Glu 265 and Arg 267 to Ala), LUK-5 (Lys 300, Glu 301 and Asp 305 to Ala) and LUK-6 (Arg 400, Lys 404, Glu 405 and Glu 406 to Ala).The rscu-PA 32k moictic3 were expressed in High Five Ttichoplasiani cells, and purified to humugciicily from the conditioned cell culture medium, with recoveries of 0.8 to 3.7 mg/1. The specific fibrinolytic activities (220,000 to 300,000 IU/mg), the rates of plasminogen activation by the single-chain moieties and the rates of conversion In lwo chain moieties by plasmin were comparable for mutant and wild-type rscu PA 32k moieties, with the exception of LUK-5 which was virtually inactive. Equi-effective lysis (50% in 2 h) of 60 pi 125I-fibrin labeled plasma clots submerged in 0.5 ml normal human plasma was obtained with 0.7 to 0.8 μg/ml of wild-type or mutant rscu-PA-3?.k, except with LUK-5 (no significant lysis with 16 pg/ml). Following bolus injection in hamsters, all rscu-PA-32k moieties had a comparably rapid plasma clearance (1.3 to 2.7 ml/min), as a result of a short initial half-life (1.4 to 2.5 min). In hamsters with pulmonary embolism, continuous intravenous infusion over 60 min at a dose of 1 mg/kg, resulted in 53 to 72% clot lysis with the mutants, but only 23% with LUK-5, as compared to 36% for wild-type rscu-PA-32k.These data indicate that clustered charge-to-alanine mutants of rscu-PA-32k, designed to eliminate charged regions with the highest solvent accessibility, do not have significantly improved functional, fibrinolytic or pharmacokinetic properties.

Urokinase-dependent plasminogen activation is required for efficient skeletal muscle regeneration in vivo

Blood ◽  
2001 ◽  
Vol 97 (6) ◽  
pp. 1703-1711 ◽  
Author(s):  
Frederic Lluı́s ◽  
Josep Roma ◽  
Mònica Suelves ◽  
Maribel Parra ◽  
Gloria Aniorte ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Plasminogen Activator ◽  
Muscle Regeneration ◽  
Plasminogen Activators ◽  
Skeletal Muscle Regeneration ◽  
Plasminogen Activation ◽  
Wild Type ◽  
Type Plasminogen Activator ◽  
Deficient Mice

Plasminogen activators urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA) are extracellular proteases involved in various tissue remodeling processes. A requirement for uPA activity in skeletal myogenesis was recently demonstrated in vitro. The role of plasminogen activators in skeletal muscle regeneration in vivo in wild-type, uPA-deficient, and tPA-deficient mice is investigated here. Wild-type and tPA−/− mice completely repaired experimentally damaged skeletal muscle. In contrast, uPA−/− mice had a severe regeneration defect, with decreased recruitment of blood-derived monocytes to the site of injury and with persistent myotube degeneration. In addition, uPA-deficient mice accumulated fibrin in the degenerating muscle fibers; however, the defibrinogenation of uPA-deficient mice resulted in a correction of the muscle regeneration defect. A similar severe regeneration deficit with persistent fibrin deposition was also reproducible in plasminogen-deficient mice after injury, suggesting that fibrinolysis by uPA-mediated plasminogen activation plays a fundamental role in skeletal muscle regeneration. In conclusion, the uPA-plasmin system is identified as a critical component of the mammalian skeletal muscle regeneration process, possibly because it prevents intramuscular fibrin accumulation and contributes to the adequate inflammatory response after injury. These studies demonstrate the requirement of an extracellular proteolytic cascade during muscle regeneration in vivo.

Urokinase-type plasminogen activator receptor is associated with the development of adipose tissue

2010 ◽  
Vol 104 (12) ◽  
pp. 1124-1132 ◽  
Author(s):  
Hiroyuki Matsuno ◽  
Eri Kawashita ◽  
Kiyotaka Okada ◽  
Hidetaka Suga ◽  
Shigeru Ueshima ◽  
...  
Keyword(s):  
Adipose Tissue ◽  
Plasminogen Activator ◽  
Adipocyte Differentiation ◽  
Cellular Adhesion ◽  
Wild Type ◽  
Tissue Mass ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Plasminogen Activator Receptor

SummaryUrokinase-type plasminogen activator receptor (uPAR) plays a role in cellular responses which include cellular adhesion, differentiation, proliferation and migration. The aim of this study was to clarify the role of uPAR on the development of adipose tissue. To clarify the role of uPAR on adipogenesis, we examined the effect of uPAR overexpression and uPAR deficiency on the adipocyte differentiation. Adipocyte differentiation was induced by incubation of 3T3-L1 cells with differentiation media containing insulin, dexamethasone, and 1-methyl-3-isobutylxanthin. uPAR overexpression by transfection of uPAR expression vector induced adipocyte differentiation. In addition, we examined the difference in adipocyte differentiation of mesenchymal stem cells from wild-type mice and uPAR knockout (uPAR-/-) mice. The uPAR deficiency attenuated differentiation media-induced adipocyte differentiation. Moreover, we found that the inhibition of phosphatidylinositol 3-kinase (PI3K) pathway attenuated uPAR overexpression-induced adipocyte differentiation, and uPAR overexpression induced the activation of Akt. We also found that an increase of the adipose tissue mass in uPAR-/- mice was less than that observed in wild-type mice. The present results suggest that uPAR plays a pivotal role in the development of adipose tissue through PI3K/Akt pathway.

Urokinase-type plasminogen activator and plasminogen mediate activation of macrophage phagocytosis during liver repair in vivo

2012 ◽  
Vol 107 (04) ◽  
pp. 749-759 ◽  
Author(s):  
Naoyuki Kawao ◽  
Nobuo Nagai ◽  
Yukinori Tamura ◽  
Yoshitaka Horiuchi ◽  
Katsumi Okumoto ◽  
...  
Keyword(s):  
Plasminogen Activator ◽  
Golgi Complex ◽  
Border Region ◽  
Primary Role ◽  
Wild Type ◽  
Macrophage Phagocytosis ◽  
Type Plasminogen Activator ◽  
Cellular Debris ◽  
Urokinase Type Plasminogen Activator ◽  
Liver Repair

SummaryUrokinase-type plasminogen activator (u-PA) and plasminogen play a primary role in liver repair through the accumulation of macrophages and alteration of their phenotype. However, it is still unclear whether u-PA and plasminogen mediate the activation of macrophage phagocytosis during liver repair. Herein, we investigated the morphological changes in macrophages that accumulated at the edge of damaged tissue induced by a photochemical reaction or hepatic ischaemia-reperfu-sion in mice with u-PA (u-PA−/− ) or plasminogen (Plg−/− ) gene deficiency by using transmission electron and fluorescence microscopy. In wild-type mice, the macrophages aligned at the edge of the damaged tissue and extended a large number of long pseudopodia. These macrophages clearly engulfed cellular debris and showed well-developed organelles, including lysosome-like vacuoles, nuclei, and Golgi complexes. In wild-type mice, the distribution of the Golgi complex in these macrophages was biased towards the direction of the damaged tissue, indicating the extension of their pseudopodia in this direction. Conversely, in u-PA−/− and Plg−/− mice, the macrophages located at the edge of the damaged tissue had few pseudopodia and less developed organelles. The Golgi complex was randomly distributed in these macrophages in u-PA−/− mice. Furthermore, interferon γ and IL-4 were expressed at a low level at the border region of the damaged tissue in u-PA−/− mice. Our data provide novel evidence that u-PA and plasminogen are essential for the phagocytosis of cellular debris by macrophages during liver repair. Furthermore, u-PA plays a critical role in the induction of macrophage polarity by affecting the microenvironment at the edge of damaged tissue.

scholarly journals Urokinase-type plasminogen activator increases hepatocyte growth factor activity required for skeletal muscle regeneration

Blood ◽  
2009 ◽  
Vol 114 (24) ◽  
pp. 5052-5061 ◽  
Author(s):  
Thomas H. Sisson ◽  
Mai-Huong Nguyen ◽  
Bi Yu ◽  
Margaret L. Novak ◽  
Richard H. Simon ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Growth Factor ◽  
Hepatocyte Growth Factor ◽  
Muscle Regeneration ◽  
Wild Type ◽  
Blocking Antibody ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Hepatocyte Growth ◽  
Pai 1

Abstract The plasminogen system plays a crucial role in the repair of a variety of tissues, including skeletal muscle. We hypothesized that urokinase-type plasminogen activator (uPA) promotes muscle regeneration by activating hepatocyte growth factor (HGF), which, in turn, stimulates proliferation of myoblasts required for regeneration. In our studies, levels of active HGF and phosphorylation of the HGF receptor c-met were increased after muscle injury in wild-type mice. Compared with wild-type animals, mice deficient in uPA (uPA−/−) had markedly reduced HGF levels and c-met activation after muscle damage. This reduced HGF activity in uPA−/− animals was associated with decreased cell proliferation, myoblast accumulation, and new muscle fiber formation. On the other hand, HGF activity was enhanced at early time points in PAI-1−/− mice compared with wild-type mice and the PAI-1−/− animals exhibited accelerated muscle fiber regeneration. Furthermore, administration of exogenous uPA rescued HGF levels and muscle regeneration in uPA−/− mice, and an HGF-blocking antibody reduced HGF activity and muscle regeneration in wild-type mice. We also found that uPA promotes myoblast proliferation in vitro through its proteolytic activity, and this process was inhibited by an HGF-blocking antibody. Together, our findings demonstrate that uPA promotes muscle regeneration through HGF activation and subsequent myoblast proliferation.

scholarly journals COX-2 inhibitor reduces skeletal muscle hypertrophy in mice

2009 ◽  
Vol 296 (4) ◽  
pp. R1132-R1139 ◽  
Author(s):  
Margaret L Novak ◽  
William Billich ◽  
Sierra M. Smith ◽  
Kunal B. Sukhija ◽  
Thomas J. McLoughlin ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Cell Proliferation ◽  
Muscle Hypertrophy ◽  
Muscle Growth ◽  
Muscular Activity ◽  
Compensatory Hypertrophy ◽  
Cell Nuclei ◽  
Skeletal Muscle Hypertrophy ◽  
Cox 2 ◽  
Macrophage Accumulation

Anti-inflammatory strategies are often used to reduce muscle pain and soreness that can result from high-intensity muscular activity. However, studies indicate that components of the acute inflammatory response may be required for muscle repair and growth. The hypothesis of this study was that cyclooxygenase (COX)-2 activity is required for compensatory hypertrophy of skeletal muscle. We used the synergist ablation model of skeletal muscle hypertrophy, along with the specific COX-2 inhibitor NS-398, to investigate the role of COX-2 in overload-induced muscle growth in mice. COX-2 was expressed in plantaris muscles during compensatory hypertrophy and was localized mainly in or near muscle cell nuclei. Treatment with NS-398 blunted the increases in mass and protein content in overloaded muscles compared with vehicle-treated controls. Additionally, the COX-2 inhibitor decreased activity of the urokinase type plasminogen activator, macrophage accumulation, and cell proliferation, all of which are required for hypertrophy after synergist ablation. Expression of insulin-like growth factor-1 and phosphorylation of Akt, mammalian target of rapamycin, and p70S6K were increased following synergist ablation, but were not affected by NS-398. Additionally, expression of atrogin-1 was reduced during hypertrophy, but was also not affected by NS-398. These results demonstrate that COX-2 activity is required for skeletal muscle hypertrophy, possibly through facilitation of extracellular protease activity, macrophage accumulation, and cell proliferation.

Leukocyte urokinase plasminogen activator receptor and PSGL1 play a role in endogenous arterial fibrinolysis

2009 ◽  
Vol 102 (12) ◽  
pp. 1212-1218 ◽  
Author(s):  
Xufang Bai ◽  
Jeffrey Weitz ◽  
Peter Gross
Keyword(s):  
Plasminogen Activator ◽  
High Speed ◽  
Wild Type ◽  
Urokinase Plasminogen Activator Receptor ◽  
Activated Platelets ◽  
Upa Receptor ◽  
Type Plasminogen Activator ◽  
Urokinase Type Plasminogen Activator ◽  
Plasminogen Activator Receptor ◽  
Deficient Mice

SummaryFibrin is an integral component of arterial thrombi. Using a mouse model of arteriolar thrombosis, high-speed fluorescence microscopy reveals that, within minutes, the fibrin content of thrombi rapidly increases and then decreases.The decrease in fibrin coincides with leukocyte binding to the thrombi, a process mediated by the interaction of leukocyte P-selectin glycoprotein ligand-1 (PSGL-1) with P-selectin on the surface of activated platelets. Because leukocytes possess urokinase-type plasminogen activator (uPA) activity,we used mice deficient in uPA or the uPA receptor (uPAR) to explore the contribution of leukocyte associated uPA to the loss of fibrin from these thrombi. Fibrin loss in both uPA-deficient mice and uPAR-deficient mice was reduced compared with that in wild-type controls.Transfusion of leukocytes from wild-type mice into uPAR-deficient mice restored fibrin loss to levels similar to that in wild-type mice. In contrast, transfusion of leukocytes from mice deficient in uPAR or PSGL-1 did not enhance fibrin loss. Thus, fibrin loss from microarteriolar thrombi is mediated, at least in part, by leukocyte-associated uPA in a process that requires leukocyte uPAR and PSGL-1.

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