α2-Antiplasmin is associated with macrophage activation and fibrin deposition in a macrophage activation syndrome mouse model

Macrophage activation syndrome (MAS) is a life-threatening condition, characterized by cytopenia, multi-organ dysfunction, and coagulopathy associated with excessive activation of macrophages. In this study, we investigated the roles of alpha2-antiplasmin (α2AP) in the progression of MAS using fulminant MAS mouse model induced by toll-like receptor-9 agonist (CpG) and D-(+)-galactosamine hydrochloride (DG). α2AP deficiency attenuated macrophage accumulation, liver injury, and fibrin deposition in the MAS model mice. Interferon-γ (IFN-γ) is associated with macrophage activation, including migration, and plays a pivotal role in MAS progression. α2AP enhanced the IFN-γ-induced migration, and tissue factor production. Additionally, we showed that fibrin-induced macrophage activation and tumor necrosis factor-α production. Moreover, the blockade of α2AP by neutralizing antibodies attenuated macrophage accumulation, liver injury, and fibrin deposition in the MAS model mice. These data suggest that α2AP may regulate IFN-γ-induced responses and be associated with macrophage activation and fibrin deposition in the MAS progression.

Plasminogen activator inhibitor-1 is involved in glucocorticoid-induced decreases in angiogenesis during bone repair in mice

INTRODUCTION

Glucocorticoids delay fracture healing and induce osteoporosis. Angiogenesis plays an important role in bone repair after bone injury. Plasminogen activator inhibitor-1 (PAI-1) is the principal inhibitor of plasminogen activators and an adipocytokine that regulates metabolism. However, the mechanisms by which glucocorticoids delay bone repair remain unclear.

MATERIALS AND METHODS

Therefore, we herein investigated the roles of PAI-1 and angiogenesis in glucocorticoid-induced delays in bone repair after femoral bone injury using PAI-1-deficient female mice intraperitoneally administered dexamethasone (Dex).

RESULTS

PAI-1 deficiency significantly attenuated Dex-induced decreases in the number of CD31-positive vessels at damaged sites 4 days after femoral bone injury in mice. PAI-1 deficiency also significantly ameliorated Dex-induced decreases in the number of CD31- and endomucin-positive type H vessels and CD31-positive- and endomucin-negative vessels at damaged sites 4 days after femoral bone injury. Moreover, PAI-1 deficiency significantly mitigated Dex-induced decreases in the expression of vascular endothelial growth factor as well as hypoxia inducible factor-1α, transforming growth factor-β1, and bone morphogenetic protein-2 at damaged sites 4 days after femoral bone injury.

CONCLUSION

The present results demonstrate that Dex-reduced angiogenesis at damaged sites during the early bone-repair phase after femoral bone injury partly through PAI-1 in mice.

Roles of Plasminogen Activator Inhibitor-1 in Heterotopic Ossification Induced by Achilles Tenotomy in Thermal Injured Mice

Heterotopic ossification (HO) is the process by which ectopic bone forms at an extraskeletal site. Inflammatory conditions induce plasminogen activator inhibitor 1 (PAI-1), an inhibitor of fibrinolysis, which regulates osteogenesis. In the present study, we investigated the roles of PAI-1 in the pathophysiology of HO induced by trauma/burn treatment using PAI-1-deficient mice. PAI-1 deficiency significantly promoted HO and increased the number of alkaline phosphatase (ALP)-positive cells in Achilles tendons after trauma/burn treatment. The mRNA levels of inflammation markers were elevated in Achilles tendons of both wild-type and PAI-1-deficient mice after trauma/burn treatment and PAI-1 mRNA levels were elevated in Achilles tendons of wild-type mice. PAI-1 deficiency significantly up-regulated the expression of Runx2, Osterix, and type 1 collagen in Achilles tendons 9 weeks after trauma/burn treatment in mice. In in vitro experiments, PAI-1 deficiency significantly increased ALP activity and mineralization in mouse osteoblasts. Moreover, PAI-1 deficiency significantly increased ALP activity and up-regulated osteocalcin expression during osteoblastic differentiation from mouse adipose-tissue-derived stem cells, but suppressed the chondrogenic differentiation of these cells. In conclusion, the present study showed that PAI-1 deficiency promoted HO in Achilles tendons after trauma/burn treatment partly by enhancing osteoblast differentiation and ALP activity in mice. Endogenous PAI-1 may play protective roles against HO after injury and inflammation.

Serum brain natriuretic peptide levels may be a useful marker for early diagnosis of cardiomyopathy secondary to neuroblastoma: A case report

Cardiomyopathy is a rare but serious complication associated with neuroblastoma. The brain natriuretic peptide level led to a diagnosis of secondary dilated cardiomyopathy before the worsening of heart failure symptoms.

Plasminogen deficiency exacerbates skeletal muscle loss during mechanical unloading in developing mice

Mechanical-unloading-induced skeletal muscle atrophy results in physical frailty and disability. Elucidating its mechanism is required to establish effective countermeasures for this muscle adaptation. First, we analyzed the proteome profile in the gastrocnemius (Gast) and soleus muscles of space-flown mice raised under microgravity or artificial 1-g for 30 days, and found that the expression levels of fibrinolysis-related proteins were significantly elevated in the mechanical-unloaded muscles. Next, we investigated the roles of the fibrinolytic system in skeletal muscle atrophy induced by mechanical unloading on the ground. Eight-week-old male mice with plasminogen gene deficiency (Plg-/-) and their wild-type littermates were divided into control and hindlimb-suspended groups and were raised for 21 days. Plasminogen deficiency significantly enhanced the decrease in muscle mass at the lower limbs of mice following hindlimb unloading, and the Gast muscle atrophy was more prominent in Plg-/- mice. In addition, plasminogen deficiency significantly increased the expression of autophagy-related markers, beclin1 mRNA and LC3B protein, in the mechanical-unloaded Gast muscles, but did not affect the increase in the gene expression of ubiquitin ligases, atrogin-1 and MuRF1. Neither plasminogen deficiency nor hindlimb unloading affected the Akt/mechanistic target of rapamycin pathway in the Gast muscles. These results suggested that plasminogen deficiency might accelerate protein breakdown via the autophagy-lysosome, but not the ubiquitin-proteasome, system in the mechanical-unloaded Gast muscles. In conclusion, we first showed that plasminogen deficiency exacerbated the Gast muscle atrophy in hindlimb-unloaded mice. Plasminogen and the fibrinolysis system might play some protective roles against muscle atrophy induced by mechanical unloading in developing mice.NEW & NOTEWORTHY The expression levels of fibrinolysis-related proteins, including plasminogen, were significantly elevated in the gastrocnemius (Gast) and soleus muscles of mice following 30-day microgravity exposure. Plasminogen deficiency exacerbated atrophy of the Gast, but not the soleus, muscles in mice following 21-day hindlimb suspension. It was also suggested that protein breakdown via the autophagy-lysosome system was accelerated in the Gast muscles. Plasminogen might play some protective roles against muscle atrophy induced by mechanical unloading in developing mice.

A Community-Based Intervention to Enhance Subjective Well-Being in Older Adults: Study Design and Baseline Participant Profiles

Promoting subjective well-being is a crucial challenge in aging societies. In 2022, we launched a community-based intervention trial (the Chofu-Digital-Choju Movement). This initiative centered on fostering in-person and online social connections to enhance the subjective well-being of older adults. This paper describes the study design and baseline survey. This quasi-experimental study involved community-dwelling older adults aged 65-84 years in Chofu City, Tokyo, Japan. A self-administered questionnaire was distributed to 3742 residents (1681 men and 2061 women), and a baseline survey was conducted in January 2022. We assessed subjective well-being (primary outcome); psychosocial, physical, and dietary factors; and the use of information and communication technology variables (secondary outcomes) among the participants. After the intervention involving online classes, community hubs, and community events, a 2-year follow-up survey will be conducted to evaluate the effects of the intervention, comparing the intervention group (participants) with the control group (non-participants). We received 2503 questionnaires (66.9% response rate); of these, the analysis included 2343 questionnaires (62.6% valid response rate; mean age, 74.4 (standard deviation, 5.4) years; 43.7% male). The mean subjective well-being score was 7.2 (standard deviation, 1.9). This study will contribute to the development of a prototype subjective well-being strategy for older adults.

Urokinase-type plasminogen activator promotes corneal epithelial migration and nerve regeneration

Urokinase-type plasminogen activator (uPA) is a serine protease that plays a central role in the pericellular fibrinolytic system, mediates the degradation of extracellular matrix proteins and activation of growth factors, and contributes to the regulation of various cellular processes including cell migration and adhesion, chemotaxis, and angiogenesis. The corneal epithelium responds rapidly to injury by initiating a wound healing process that involves cell migration, cell proliferation, and tissue remodeling. It is innervated by sensory nerve endings that play an important role in the maintenance of corneal epithelial homeostasis and in the wound healing response. We here investigated the role of uPA in corneal nerve regeneration and epithelial resurfacing after corneal injury with the use of uPA-deficient mice. Both the structure of the corneal epithelium and the pattern of corneal innervation in uPA-/- mice appeared indistinguishable from those in uPA+/+ mice. Whereas the cornea was completely resurfaced by 36-48 h after epithelial scraping in uPA+/+ mice, however, such resurfacing required at least 72 h in uPA-/- mice. Restoration of epithelial stratification was also impaired in the mutant mice. Fibrin zymography revealed that the expression of uPA increased after corneal epithelial scraping and returned to basal levels in association with completion of re-epithelialization in wild-type animals. Staining of corneal whole-mount preparations for βIII-tubulin also revealed that the regeneration of corneal nerves after injury was markedly delayed in uPA-/- mice compared with uPA+/+ mice. Our results thus demonstrate an important role for uPA in both corneal nerve regeneration and epithelial migration after epithelial debridement, and they may provide a basis for the development of new treatments for neurotrophic keratopathy.

Utility of the Total Thrombus-Formation Analysis System as a Tool for Evaluating Thrombogenicity and Monitoring Antithrombotic Therapy in Pediatric Fontan Patients

BACKGROUND

There is no consensus regarding thromboprophylaxis after Fontan procedure, and novel tools to assess thrombogenicity are needed to establish optimal thromboprophylaxis. The Total Thrombus-formation Analysis System (T-TAS) was developed for the quantitative analysis of thrombus formation using microchips with thrombogenic surfaces. This prospective study evaluated the utility of T-TAS in the assessment of thrombogenicity in pediatric Fontan patients.

METHODS AND RESULTS

The participants included 20 consecutive Fontan patients who underwent cardiac catheterization and 30 healthy controls. Blood samples collected without and with antithrombotic therapy (aspirin or aspirin and warfarin) were used for T-TAS to compute the area under the curve (AUC) in the atheroma (AR₁₀-AUC₃₀) and platelet (PL₁₈-AUC₁₀) chips. A higher AUC indicates higher thrombogenicity. T-TAS values showed that patients in the Fontan group without antithrombotic therapy had lower thrombogenicity than those in the control group [PL₁₈-AUC₁₀, median (interquartile range) 356 (313-394) vs. 408 (392-424); AR₁₀-AUC₃₀, median (interquartile range) 1270 (1178-1351) vs. 1382 (1338-1421)]. Aspirin and warfarin therapies significantly decreased PL₁₈-AUC₁₀ and AR₁₀-AUC₃₀, respectively, compared with those of patients without antithrombotic therapy (P < 0.001 for each comparison). Subgroup analysis divided by low (< 9 mmHg) or high (≥ 9 mmHg) central venous pressure (CVP) showed that CVP affects the reduction in AR₁₀-AUC₃₀ with antithrombotic therapy.

CONCLUSIONS

T-TAS may be a useful tool for monitoring thrombogenicity and antithrombotic therapy in Fontan patients.

Effects of Enzamin, a Microbial Product, on Alterations of Intestinal Microbiota Induced by a High-Fat Diet

In the human intestinal tract, there are more than 100 trillion microorganisms classified into at least 1000 different species. The intestinal microbiota contributes to the regulation of systemic physiologic functions and the maintenance of homeostasis of the host. It has been reported that the alteration of the intestinal microbiota is involved in metabolic syndromes, including type II diabetes and dyslipidemia, inflammatory bowel disease, allergic disease, and cancer growth. It has been reported that a microbial product from Paenibacillus polymyxa AK, which was named Enzamin, ameliorated adipose inflammation with impaired adipocytokine expression and insulin resistance in db/db mice. In order to investigate the effect of Enzamin on the intestinal microbiota and inflammation induced by obesity, mice were fed with a high-fat diet and 1% Enzamin for 4 weeks. Enzamin improved the Firmicutes-to-Bacteroidetes ratio and altered the intestinal microbiota in mice fed the high-fat diet. In addition, Enzamin suppressed the decreased expression of claudin-4 and the increased serum LPS level in mice fed with the high-fat diet. Modulating the intestinal microbiota with Enzamin may cause a decrease in serum LPS level. Based on these results, Enzamin may improve inflammation and metabolic disorders by regulating the intestinal microbiota in obese mice.

Torsion of wandering spleen after Fontan operation in a patient with situs inversus: a rare complication

Torsion of wandering spleen after the Fontan operation with situs inversus is rare.Here, we report the case of a 6-year-old girl with a single ventricle and complete situs inversus who developed torsion of wandering spleen due to splenomegaly caused by post-operative haemodynamics of the Fontan operation. The platelet count was suggested to be useful in predicting splenic torsion.

Role of Macrophages and Plasminogen Activator Inhibitor-1 in Delayed Bone Repair Induced by Glucocorticoids in Mice

Glucocorticoids delay fracture healing and induce osteoporosis. However, the mechanisms by which glucocorticoids delay bone repair have yet to be clarified. Plasminogen activator inhibitor-1 (PAI-1) is the principal inhibitor of plasminogen activators and an adipocytokine that regulates metabolism. We herein investigated the roles of macrophages in glucocorticoid-induced delays in bone repair after femoral bone injury using PAI-1-deficient female mice intraperitoneally administered with dexamethasone (Dex). Dex significantly decreased the number of F4/80-positive macrophages at the damaged site two days after femoral bone injury. It also attenuated bone injury-induced decreases in the number of hematopoietic stem cells in bone marrow in wild-type and PAI-1-deficient mice. PAI-1 deficiency significantly weakened Dex-induced decreases in macrophage number and macrophage colony-stimulating factor (M-CSF) mRNA levels at the damaged site two days after bone injury. It also significantly ameliorated the Dex-induced inhibition of macrophage phagocytosis at the damaged site. In conclusion, we herein demonstrated that Dex decreased the number of macrophages at the damaged site during early bone repair after femoral bone injury partly through PAI-1 and M-CSF in mice.

Role of plasminogen activator inhibitor-1 in muscle wasting induced by a diabetic state in female mice

Muscle wasting is a complication in patients with diabetes and leads to a reduced quality of life. However, the detailed mechanisms of diabetes-induced muscle wasting remain unknown. Plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor that suppresses plasminogen activator activity, is involved in the pathophysiology of various diseases, including diabetes. In the present study, we examined the role of endogenous PAI-1 in the decrease in muscle mass and the impaired grip strength induced by the diabetic state by employing streptozotocin (STZ)-treated PAI-1-deficient female mice. The analyses of skeletal muscles and grip strength were performed in PAI-1-deficient and wild-type mice 4 weeks after the induction of a diabetic state by STZ administration. PAI-1 deficiency did not affect muscle mass in the lower limbs measured by quantitative computed tomography or tissue weights of the tibialis anterior, gastrocnemius and soleus muscles of female mice with or without STZ treatment. On the other hand, PAI-1 deficiency significantly aggravated grip strength decreased by STZ in female mice. PAI-1 deficiency did not affect the mRNA levels of Pax7, MyoD, myogenin or myosin heavy chain in either the tibialis anterior or soleus muscles of female mice with or without STZ treatment. In conclusion, we revealed for the first time that PAI-1 deficiency aggravates grip strength impaired by the diabetic state in female mice, although it did not affect diabetes-decreased muscle mass.

Alpha2-antiplasmin deficiency affects depression and anxiety-like behavior and apoptosis induced by stress in mice

OBJECTIVES

Depression is a psychiatric disorder that affects about 10% of the world's population and is accompanied by anxiety. Depression and anxiety are often caused by various stresses. However, the etiology of depression and anxiety remains unknown. It has been reported that alpha2-antiplasmin (α2AP) not only inhibits plasmin but also has various functions such as cytokine production and cell growth. This study aimed to determine the roles of α2AP on the stress-induced depression and anxiety.

METHODS

We investigated the mild repeated restraint stress-induced depressive and anxiety-like behavior in the α2AP^+/+ and α2AP^-/- mice using the social interaction test (SIT), sucrose preference test (SPT), and elevated plus maze (EPM).

RESULTS

The stresses such as the mild repeated restraint stress suppressed α2AP expression in the hippocampus of mice, and the treatment of fluoxetine (selective serotonin reuptake inhibitor [SSRI]) recovered the stress-caused α2AP suppression. We also showed that α2AP deficiency promoted the mild restraint stress-stimulated depression-like behavior such as social withdrawal and apathy and apoptosis in mice. In contrast, α2AP deficiency attenuated the mild restraint stress induced the anxiety-like behavior in mice.

CONCLUSIONS

α2AP affects the pathogenesis of depression and anxiety induced by stress.

α2-antiplasmin positively regulates endothelial-to-mesenchymal transition and fibrosis progression in diabetic nephropathy

BACKGROUND

Diabetic nephropathy (DN), is microvascular complication of diabetes causes to kidney dysfunction and renal fibrosis. It is known that hyperglycemia and advanced glycation end products (AGEs) produced by hyperglycemic condition induce myofibroblast differentiation and endothelial-to-mesenchymal transition (EndoMT), and exacerbate fibrosis in DN. Recently, we demonstrated that α2-antiplasmin (α2AP) is associated with inflammatory response and fibrosis progression.

METHODS

We investigated the role of α2AP on fibrosis progression in DN using a streptozotocin-induced DN mouse model.

RESULTS

α2AP deficiency attenuated EndoMT and fibrosis progression in DN model mice. We also showed that the high glucose condition/AGEs induced α2AP production in fibroblasts (FBs), and the reduction of receptor for AGEs (RAGE) by siRNA attenuated the AGEs-induced α2AP production in FBs. Furthermore, the bloackade of α2AP by the neutralizing antibody attenuated the high glucose condition-induced pro-fibrotic changes in FBs. On the other hand, the hyperglycemic condition/AGEs induced EndoMT in vascular endothelial cells (ECs), the FBs/ECs co-culture promoted the high glucose condition-induced EndoMT compared to ECs mono-culture. Furthermore, α2AP promoted the AGEs-induced EndoMT, and the blockade of α2AP attenuated the FBs/ECs co-culture-promoted EndoMT under the high glucose condition.

CONCLUSIONS

The high glucose conditions induced α2AP production, and α2AP is associated with EndoMT and fibrosis progression in DN. These findings provide a basis for clinical strategies to improve DN.

α2-Antiplasmin as a potential regulator of the spatial memory process and age-related cognitive decline

α2-Antiplasmin (α2AP), a principal physiological plasmin inhibitor, is mainly produced by the liver and kidneys, but it is also expressed in several parts of the brain, including the hippocampus and cerebral cortex. Our previous study demonstrated that α2AP knockout mice exhibit spatial memory impairment in comparison to wild-type mice, suggesting that α2AP is necessary for the fetal and/or neonatal development of the neural network for spatial memory. However, it is still unclear whether α2AP plays a role in the memory process. The present study demonstrated that adult hippocampal neurogenesis and remote spatial memory were enhanced by the injection of an anti-α2AP neutralizing antibody in WT mice, while the injection of α2AP reduced hippocampal neurogenesis and impaired remote spatial memory, suggesting that α2AP is a negative regulator in memory processing. The present study also found that the levels of α2AP in the brains of old mice were higher than those in young mice, and a negative correlation between the α2AP level and spatial working memory. In addition, aging-dependent brain oxidative stress and hippocampal inflammation were attenuated by α2AP deficiency. Thus, an age-related increase in α2AP might cause cognitive decline accompanied by brain oxidative stress and neuroinflammation. Taken together, our findings suggest that α2AP is a key regulator of the spatial memory process, and that it may represent a promising target to effectively regulate healthy brain aging.

PAI-1 is involved in delayed bone repair induced by glucocorticoids in mice

Glucocorticoid (GC) treatments induce osteoporosis and chronic GC treatments have been suggested to induce delayed bone repair; however, the mechanisms by which GC induces delayed bone repair remain unclear. We herein investigated the roles of plasminogen activator inhibitor-1 (PAI-1) in GC-induced effects on bone repair after femoral bone injury using female mice with a PAI-1 deficiency and their wild-type counterparts. Dexamethasone (Dex) increased plasma PAI-1 levels as well as PAI-1 mRNA levels in the adipose tissues and muscles of wild-type mice. PAI-1 deficiency significantly blunted Dex-induced delayed bone repair in mice. Moreover, PAI-1 deficiency significantly blunted Runx2 mRNA levels suppressed by Dex as well as Dex-induced osteoblast apoptosis at the damaged site 7 days after bone injury in mice. On the other hand, PAI-1 deficiency did not affect adipogenic gene expression enhanced by Dex at the damaged site 7 days after bone injury in mice. In conclusion, we herein showed for the first time that PAI-1 is involved in delayed bone repair after bone injury induced by GC in mice. PAI-1 may influence early stage osteoblast differentiation and apoptosis during the osteoblastic restoration phase of the bone repair process.

α2AP is associated with the development of lupus nephritis through the regulation of plasmin inhibition and inflammatory responses

Introduction

Lupus nephritis (LN) is a common complication of systemic lupus erythematosus (SLE), which is a chronic autoimmune disease. However, the detailed mechanisms underlying this disorder have remained unclear. Alpha2‐antiplasmin (α2AP) is known to perform various functions, such as plasmin inhibition and cytokine production, and to be associated with immune and inflammatory responses.

Methods

We investigated the roles of α2AP in the pathogenesis of LN using a pristane‐induced lupus mouse model.

Results

The levels of plasmin‐α2AP complex and α2AP were elevated in the lupus model mice. In addition, α2AP deficiency attenuated the pristane‐induced glomerular cell proliferation, mesangial matrix expansion, collagen production, fibrin deposition, immunoglobulin G deposition, and proinflammatory cytokine production in the model mice. We also showed that interferon‐γ (IFN‐γ), which is an essential inducer of LN, induced α2AP production through the c‐Jun N‐terminal kinase (JNK) pathway in fibroblasts. In addition, plasmin attenuated the IFN‐γ‐induced proinflammatory cytokine production through the AMPK pathway in macrophages, and α2AP eliminated these effects. Furthermore, we showed that α2AP induced proinflammatory cytokine production through the ERK1/2 and JNK pathways in macrophages.

Conclusion

α2AP regulates the inflammatory responses through plasmin inhibition and proinflammatory cytokine production and is associated with the development of LN. Our findings may be used to develop a novel therapeutic approach for SLE.

Plasminogen activator inhibitor-1 is involved in interleukin-1β-induced matrix metalloproteinase expression in murine chondrocytes

Objectives: Interleukin (IL)-1β and matrix metalloproteinases (MMPs) play important roles in the pathogenesis of osteoarthritis. On the other hand, plasminogen activator inhibitor-1 (PAI-1), an inhibitor of fibrinolysis, exerts functions in the pathogenesis of various diseases. However, the functional roles of PAI-1 in the chondrocytes have been still remained unknown.Methods: In the present study, we investigated the roles of PAI-1 in the effects of IL-1β on the chondrocytes using wild-type and PAI-1-deficient mice.Results: IL-1β significantly elevated PAI-1 mRNA levels in the chondrocytes from wild-type mice. PAI-1 deficiency significantly blunted the mRNA levels of TGF-β and IL-6 enhanced by IL-1β in murine chondrocytes. Moreover, PAI-1 deficiency significantly decreased the mRNA levels of MMP-13, -3 and -9 as well as MMP-13 activity enhanced by IL-1β in the chondrocytes. In addition, PAI-1 deficiency significantly reversed type II collagen mRNA levels suppressed by IL-1β in the chondrocytes. On the other hand, active PAI-1 treatment significantly enhanced the mRNA levels of MMP-13, -3 and -9 as well as decreased type II collagen mRNA levels in the chondrocytes from wild-type mice.Conclusion: We first demonstrated that PAI-1 is involved in MMP expression enhanced by IL-1β in murine chondrocytes. PAI-1 might be crucial for the cartilage matrix degradation and the impaired chondrogenesis by IL-1β in mice.

Plasminogen activator inhibitor-1 deficiency suppresses osteoblastic differentiation of mesenchymal stem cells in mice

Plasminogen activator inhibitor-1 (PAI-1) is known as an inhibitor of fibrinolytic system. Previous studies suggest that PAI-1 is involved in the pathogenesis of osteoporosis induced by ovariectomy, diabetes, and glucocorticoid excess in mice. However, the roles of PAI-1 in early-stage osteogenic differentiation have remained unknown. In the current study, we investigated the roles of PAI-1 in osteoblastic differentiation of mesenchymal stem cells (MSCs) using wild-type (WT) and PAI-1-deficient (PAI-1 KO) mice. PAI-1 mRNA levels were increased with time during osteoblastic differentiation of MSCs or mesenchymal ST-2 cells. However, the increased PAI-1 levels declined at the mineralization phase in the experiment using MC3T3-E1 cells. PAI-1 deficiency significantly blunted the expression of osteogenic gene, such as osterix and alkaline phosphatase enhanced by bone morphogenetic protein (BMP)-2 in bone marrow-derived MSCs (BM-MSCs), adipose-tissue-derived MSCs (AD-MSCs), and bone marrow stromal cells of mice. Moreover, a reduction in endogenous PAI-1 levels by small interfering RNA significantly suppressed the expression of osteogenic gene in ST-2 cells. Plasmin did not affect osteoblastic differentiation of AD-MSCs induced by BMP-2 with or without PAI-1 deficiency. PAI-1 deficiency and a reduction in endogenous PAI-1 levels did not affect the phosphorylations of receptor-specific Smads by BMP-2 and transforming growth factor-β in AD-MSCs and ST-2 cells, respectively. In conclusion, we first showed that PAI-1 is crucial for the differentiation of MSCs into osteoblasts in mice.

Effect of Heat Shock on the Expression of Urokinase-Type Plasminogen Activator Receptor in Human Umbilical Vein Endothelial Cells

We investigated the effect of heat shock on the fibrinolytic potential of human umbilical vein endothelial cells (HUVECs) in culture. When cultured at 43° C, the mRNA for heat shock protein 70 (HSP70) was dramatically induced within 120 min with a maximal induction of more than 90-fold compared with that in HUVECs cultured at 37° C. The level of urokinase-type plasminogen activator (u-PA) receptor (u-PAR) mRNA increased up to 2.2-fold in response to heat shock, which was associated with the increased u-PA binding and cell-surface u-PA activity determined by adding exogenous u-PA to acid-treated HUVECs. The increased u-PAR mRNA returned to normal level when HUVECs were further incubated at 37° C for 180 min, and this decline was not affected in the presence of actinomycin D. Though the secreted antigens for tissue-type plasminogen activator (t-PA) and type 1 plasminogen activator inhibitor (PAI-1) in the conditioned medium (CM) of HUVECs were simultaneously increased at 43° C during this period, the increase in the levels of t-PA (about 26.6-fold at 120 min) was greater than that of PAI-1 (1.8-fold at 120 min). The fibrinolytic activity of CM obtained from HUVECs at 43° C was significantly enhanced up to 3-fold, indicating that heat shock induced hyperfibrinolytic states in HUVECs. The secretion of u-PA into CM was also enhanced by heat shock. These results suggested that human endothelial cells respond to hyperthermia by inducing HSP70 followed by hyperfibrinolytic states with the enhanced expression of u-PAR as well as that of t-PA and u-PA.

Comparative Fibrinolytic Properties of Staphylokinase and Streptokinase in Animal Models of Venous Thrombosis

The thrombolytic and pharmacokinetic properties of staphylokinase were compared with those of streptokinase in hamsters with a pulmonary embolus produced from human plasma or from hamster plasma, and in rabbits with a jugular vein blood clot produced from rabbit blood. In both models, a continuous intravenous infusion of staphylokinase and streptokinase over 60 min in hamsters or over 4 h in rabbits, induced dose-dependent progressive clot lysis in the absence of significant systemic activation of the fibrinolytic system. The results of thrombolytic potency (clot lysis at 30 min after the end of the infusion, in percent, versus dose administered, in mg/kg) were fitted with an exponentially transformed sigmoidal function and the maximal percent clot lysis (c), the maximal rate of lysis (z = ¼ac · e b ) and the dose at which the maximal rate of lysis is achieved (b) were determined. In hamsters with a pulmonary embolus produced from human plasma, streptokinase had a somewhat higher thrombolytic potency than staphylokinase, as revealed by a higher z value (2,100 ± 1,100% lysis per mg/kg streptokinase administered versus 1,100 ± 330% lysis per mg/kg for staphylokinase). In hamsters with a pulmonary embolus produced from hamster plasma, staphylokinase had a somewhat higher thrombolytic potency than streptokinase (z = 1,600 ± 440 versus 1,200 ± 370% lysis per mg/kg). Staphylokinase had a higher thrombolytic potency than streptokinase in rabbits, as revealed by a higher z-value (950 ± 350% lysis per mg/kg staphylokinase administered versus 330 ± 39% lysis per mg/kg for streptokinase) and a lower b-value (0.035 ± 0.010 mg/kg staphylokinase versus 0.091 ± 0.008 mg/kg for streptokinase). The plasma clearance following bolus injection of staphylokinase or streptokinase in hamsters or rabbits was comparably rapid (1.1 to 1.4 ml/min in hamsters and 14 to 15 ml/min in rabbits) as a result of a short initial half-life (1.8 to 1.9 min in hamsters and 1.7 to 2.0 min in rabbits). These results in two quantitative rodent models of thrombolysis suggest that staphylokinase is a potent thrombolytic agent with an in vivo thrombolytic potency that is comparable to that of streptokinase. Further investigation of the thrombolytic potential of staphylokinase seems to be warranted.

Plasminogen Activator and Plasminogen Activator Inhibitor Associated with Granulomatous Inflammation: A Study with Murine Leprosy

Plasminogen activator that is associated with the development of hypersensitivity granulomas (gPA) was partially purified from a saline soluble fraction of murine lepromas elicited in “resistant” mice, C57BL/6N. The gPA was shown to consist of two subspecies (23,000 and 48,000 in molecular weight) with essentially identical enzymologic properties. The gPA was found to be a relatively heat stable weakly alkaline serine proteinase with trypsin-like characteristics in the specificity for synthetic substrates and proteinase inhibitors. It showed a high affinity for H- D-Ile-Pro-Arg-pNA (Km = 1.4 × 10-4 M) H-D-Val-Leu-Lys- pNA (Km = 5.2 × 10-4 M), and L-pyroGlu-Gly-Arg-pNA (Km = 9.3 × 10-4 M). The gPA did not demonstrate antigenic cross reaction with urokinase-type or tissue-type plasminogen activator.

Two distinct enzymatic regulators of the gPA were also demonstrated in the saline soluble fraction of the hypersensitivity granulomas. The gPA and its regulation are assumed to be correlated with macrophage activation in the hypersensitivity granulomas

Comparative Study of the Activity of High and Low Molecular Weight Urokinase in the Presence of Fibrin

The fibrinolytic or thrombolytic activity of low molecular weight urokinase (LMW-UK) and high molecular weight urokinase (HMW-UK) is not significantly different when measured in a bovine fibrin plate method, in a circulating plasma system containing a 125I-labelled human fibrin clot, or on 125I-fibrin films in culture plates using normal or α2-antiplasmin depleted human plasma.

In a human fibrin plate method however HMW-UK was found to be more active than LMW-UK. In a purified system on human 125I-fibrin films the activation of native or modified human plasminogen by HMW-UK was also found to be more effective than by LMW-UK.

Using a clot lysis test system we did not observe a different inhibition of LMW-UK and HMW-UK upon incubation in human plasma. This is in contrast with previous reports that HMW-UK is inhibited more rapidly in human plasma than LMW-UK.

In a purified system the inhibition rate of LMW-UK and HMW-UK by α2-antiplasmin is the same (rate constants at 25ΰC of 167 ± 9 M−1s−1 and 171 ± 5 M−1s−1 respectively).

The clinical trials available at present used doses of urokinase which were in excess of those required to obtain a maximal fibrinolytic effect. This might explain why in these trials no difference was observed between the thrombolytic effect of LMW-UK and HMW-UK, while in vitro HMW-UK appeared to be more effective. However, one should always be careful to extrapolate in vitro observations as such to the in vivo situation encountered during thrombolytic therapy.

Low Molecular Weight Trypsin-Plasmin Inhibitors Isolated from Papain Treated Urinary Trypsin Inhibitor

Papain treatment of human urinary trypsin inhibitor (UTI67; mol. wt. 43,000 by SDS-polyacrylamide gel electrophoresis, specific activity 1,897 U/mg protein) produced four new protease inhibitors, which were highly purified by gel chromatography on Sephadex G-100 and isoelectric focusing. The purified inhibitors (UTI26, UTI9-I, UTI9-II, and UTI9-III) were shown to be homogeneous by polyacrylamide disc gel electrophoresis, and had apparent molecular weights of 26,000, 9,000, 9,000, and 9,800, respectively, by sodium dodecyl sulfate gel electrophoresis. During enzymatic degradation of UTI67, the amino acid compositions changed to more basic, and the isoelectric point increased from pH 2.0 (UTI67) to pHs 4.4, 5.2, 6.6, and 8.3 (UTI26, UTI9-I, UTI9-II, and UTI9-III), respectively. Both the parent and degraded inhibitors had anti-plasmin activity as well as antitrypsin and anti-chymotrypsin activities. Much higher anti-plasmin/anti-trypsin and anti-plasmin/anti-chymotrypsin activities were observed in the degraded inhibitors than in the parent UTI67. They competitively inhibited human plasmin with Ki values of 1.13 X 10-7 - 2.12 X 10-6 M (H-D-Val-Leu-Lys-pNA substrate). The reactions were very fast and the active site of the inhibitors to plasmin was thought to be different from that to trypsin or chymotrypsin.

Characterization and Targeting of the Murine α2-Antiplasmin Gene

α2-Antiplasmin (α2-AP) is the main physiological plasmin inhibitor in mammalian plasma. As a first step toward the generation of α2-AP deficient mice, the murine α2-AP 1 gene was characterized and a targeting vector for homologous recombination in embryonic stem (ES) cells constructed. Alignment of nucleotide sequences obtained from genomic subclones allowed location of exons 2 through 10 of the α2-AP 1gene, but failed to identify the 5’ boundary of exon 1. Compared to the human gene, exons 2 through 9 in the murine gene have identical size and intron-exon boundaries obeying the GT/AG rule. The 5’ boundary of exon 10 is identical in both genes while the 3’ non-coding region is 64 bp longer in the human gene. Introns 2,3,6 and 8 have similar sizes in the mouse and human genes; intron 1 is 6-fold smaller, introns 5, 7 and 9 are 2- to 3-fold smaller, whereas intron 4 is about 2-fold larger in the mouse gene. Compared to the human 5’ flanking sequence, an insertion of a simple repeat region with sequence (TGG)n has occurred. The open reading frame of the mouse α2-AP gene encodes a 491-amino acid protein comprising the experimentally determined NH2-terminus of the mature protein Val-Asp-Leu-Pro-Gly-.

A targeting vector, ppPNT.α2-AP, was constructed by introducing a homologous sequence of 8.3 kb in total in the parental pPNT vector. In pPNT.α2-AP, the neomycin resistance expression cassette replaces a 7 kb genomic fragment comprising exon 2 through part of exon 10 (including the stop codon), which represents the entire sequence encoding the mature protein, including the fibrin-binding domain, the reactive site peptide bond and the plasmin(ogen)-binding region. Electroporation of 129R1 embryonic stem (ES) cells with the linearized vector pPNT.α2-AP yielded three targeted clones with correct homologous recombination at the 5’- and 3’-ends, as confirmed by Southern blot analysis of purified genomic DNA with appropriate restriction enzymes and probes. These targeted clones will be used to generate α2-AP deficient mice.

Comparison of the Relative Fibrinogenolytic, Fibrinolytic and Thrombolytic Properties of Tissue Plasminogen Activator and Urokinase in Vitro

The relative fibrinogenolytic, fibrinolytic and thrombolytic properties of human tissue plasminogen activator and human urokinase were compared in purified systems, in whole human plasma and in a system composed of a radioactive human blood clot (¹²⁵I-fibrinogen) hanging in circulating human plasma. The human tissue plasminogen activator was highly purified from the culture fluid of a human melanoma cell line.

In purified systems composed of fibrinogen or fibrin, plasminogen and α₂-antiplasmin as well as in whole plasma, tissue plasminogen activator digested fibrin without degrading fibrinogen significantly. Urokinase did not have this specific fibrinolytic effect.

In the circulating plasma system, the degree of fibrinolysis was proportional to the amount of activator added, tissue plasminogen activator being about 10 times more efficient than urokinase. In addition, tissue plasminogen activator appeared to cause negligible fibrinogen degradation. Tissue plasminogen activator still induced significant thrombolysis at a concentration of 10 IU per ml whereas no effect of urokinase was observed at 20 IU per ml. Infusion of 100 IU (1 (μg) of tissue plasminogen activator per ml resulted in moderate activation of the fibrinolytic system as judged from a decrease of plasminogen and α₂-antiplasmin to 40-50 percent. Nevertheless, extensive fibrinolysis (50 to 80 percent of radioactivity released after 12 hrs) and only very limited fibrinogenolysis were observed. An equivalent amount of urokinase (100 IU per ml) only induced approximately 15 percent lysis in 12 hrs. At higher concentrations of urokinase (260 IU per ml or more) extensive activation of the fibrinolytic system was obtained as evidenced by a depletion of plasminogen, α₂-antiplasmin and fibrinogen. This was associated with extensive fibrinolysis (approximately 60 percent after 12 hrs). It is concluded that human tissue plasminogen activator is a more specific and effective fibrinolytic-thrombolytic agent than human urokinase.

Recombinant Variants of Tissue-Type Plasminogen Activator Containing Amino Acid Substitutions in the Finger Domain

Tissue-type plasminogen activator (t-PA) is a fibrin-specific agent which has been used to treat acute myocardial infarction. In an attempt to clarify the determinants for its rapid clearance in vivo and high affinity for fibrin clots, we produced five variants containing amino acid substitutions in the finger domain, at amino acid residues 7–9, 10–14, 15–19, 28–33, and 37–42. All the variants had a prolonged half-life and a decreased affinity for fibrin of various degrees. The 37–42 variant demonstrated about a 6-fold longer half-life with a lower affinity for fibrin. Human plasma clot lysis assay estimated the fibrinolytic activity of the 37–42 variant to be 1.4-fold less effective than that of the wild-type rt-PA. In a rabbit jugular vein clot lysis model, doses of 1.0 and 0.15 mg/kg were required for about 70% lysis in the wild-type and 37–42 variant, respectively. Fibrinogen was degraded only when the wild-type rt-PA was administered at a dose of 1.0 mg/kg. These findings suggest that the 37–42 variant can be employed at a lower dosage and that it is a more fibrin-specific thrombolytic agent than the wild-type rt-PA.

In Vitro and in Vivo Measurement of Total Antiplasmin Activity

Total antiplasmin was measured in vitro and in vivo. In the former case, rabbit plasma was mixed with various concentrations of Urokinase (UK) and the least concentration for appearance of fibrinolytic activity was estimated. This concentration was multiplied by the plasma volume of the rabbit to give the in vitro total antiplasmin. The mean value for 14 rabbits was 4,068.6 units.

In order to estimate the total antiplasmin in vivo, UK solution was infused into rabbits. The infusion speed was multiplied by the time of the first appearance of fibrinolytic activity to give the total antiplasmin, although when the infusion speed was low, fibrinolytic activity did not appear during infusion. The mean in vivo total antiplasmin calculated for 6 cases where the infusion speed was high and fibrinolytic activity was observed, was 28,699.8 units, i.e. about 7 (range, 3-11) times the in vitro value.

Roles of plasminogen in the alterations in bone marrow hematopoietic stem cells during bone repair

We previously revealed that stromal cell-derived factor-1 (SDF-1) is involved in the changes in the number of bone marrow stem cells during the bone repair process in mice. Moreover, we reported that plasminogen (Plg) deficiency delays bone repair and the accumulation of macrophages at the site of bone damage in mice. We investigated the roles of Plg in the changes in bone marrow stem cells during bone repair. We analyzed the numbers of hematopoietic stem cells (HSC) and mesenchymal stem cells (MSCs) within bone marrow from Plg-deficient and wild-type mice after a femoral bone injury using flow cytometric analysis. Plg deficiency significantly blunted a decrease in the number of HSCs after bone injury in mice, although it did not affect an increase in the number of MSCs. Plg deficiency significantly blunted the number of SDF-1- and Osterix- or SDF-1- and alkaline phosphatase-double-positive cells in the endosteum around the lesion as well as matrix metalloprotainase-9 (MMP-9) activity and mRNA levels of SDF-1 and transforming growth factor–β (TGF-β) elevated by bone injury. TGF-β signaling inhibition significantly blunted a decrease in the number of HSCs after bone injury. The present study showed that Plg is critical for the changes in bone marrow HSCs through MMP-9, TGF-β, and SDF-1 at the damaged site during bone repair in mice.

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We investigated the roles of plasminogen in bone marrow stem cell changes after bone injury in mice.

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Plasminogen deficiency blunted a decrease in the number of HSCs after bone injury.

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Plasminogen deficiency blunted the expression of SDF-1, TGF-β and MMP-9 at the damaged site.

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TGF-β signaling inhibition blunted a decrease in the number of HSCs after bone injury.

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Plasminogen is involved in HSC change through TGF-β and SDF-1 at the damaged site during bone repair.

Role of Macrophages and Plasminogen Activator Inhibitor-1 in Delayed Bone Repair in Diabetic Female Mice

Delayed fracture healing is a clinical problem in diabetic patients. However, the mechanisms of diabetic delayed bone repair remain unknown. Here, we investigate the role of macrophages in diabetic delayed bone repair after femoral bone injury in streptozotocin (STZ)-treated and plasminogen activator inhibitor-1 (PAI-1)-deficient female mice. STZ treatment significantly decreased the numbers of F4/80-positive cells (macrophages) but not granulocyte-differentiation antigen-1-positive cells (neutrophils) at the damaged site on day 2 after femoral bone injury in mice. It significantly decreased the messenger RNA (mRNA) levels of macrophage colony-stimulating factor, inducible nitric oxide synthase (iNOS), interleukin (IL)-6, and CD206 at the damaged site on day 2 after bone injury. Moreover, STZ treatment attenuated a decrease in the number of hematopoietic stem cells in bone marrow induced by bone injury. On the other hand, PAI-1 deficiency significantly attenuated a decrease in the number of F4/80-positive cells induced by STZ treatment at the damaged site on day 2 after bone injury in mice. PAI-1 deficiency did not affect the mRNA levels of iNOS and IL-6 in F4/80- and CD11b-double-positive cells from the bone marrow of the damaged femurs decreased by diabetes in mice. PAI-1 deficiency significantly attenuated the phagocytosis of macrophages at the damaged site suppressed by diabetes. In conclusion, we demonstrated that type 1 diabetes decreases accumulation and phagocytosis of macrophages at the damaged site during early bone repair after femoral bone injury through PAI-1 in female mice.

Role of plasminogen activator inhibitor-1 in glucocorticoid-induced muscle change in mice

We recently revealed that plasminogen activator inhibitor-1 (PAI-1), a serine protease inhibitor, is involved in diabetes, osteoporosis and muscle wasting induced by glucocorticoid (GC) treatment in mice. In the present study, we investigated the detailed mechanisms by which GC induces muscle wasting through PAI-1 in vivo and in vitro. PAI-1 deficiency suppressed the mRNA levels of atrogin1 and muscle RING-Finger Protein 1 (MuRF1), ubiquitin ligases leading to muscle degradation, elevated by GC treatment in the gastrocnemius muscle of mice. In vitro study revealed that active PAI-1 treatment augmented the increase in atrogin1 mRNA levels enhanced by dexamethasone (Dex) in mouse myoblastic C2C12 cells. Moreover, a reduction in endogenous PAI-1 level by siRNA suppressed the mRNA levels of atrogin1 and MuRF1 enhanced by Dex in C2C12 cells. In contrast, a reduction in endogenous PAI-1 levels and active PAI-1 did not affect the phosphorylations of Akt and p70S6 kinase nor myogenic differentiation with or without Dex in C2C12 cells. In addition, PAI-1 deficiency blunted IGF-1 mRNA levels decreased by GC treatment in the gastrocnemius muscle of mice, although neither active PAI-1 nor a reduction in endogenous PAI-1 levels affected the levels of IGF-1 mRNA in C2C12 cells in the presence of Dex. In conclusion, our data suggest that paracrine PAI-1 is involved in GC-induced muscle wasting through the enhancement of muscle degradation in mice.

Determination of a factor VIII-interactive region within plasmin responsible for plasmin-catalysed activation and inactivation of factor VIII(a)

Plasmin, an active form of plasminogen, activates and inactivates factor VIII (FVIII) by limited proteolysis. We have previously identifiedly sine-binding site-independent plasmin-interactive sites on the FVIII A2 domain responsible for cleavages at Arg336 and Arg372, together with lysine-binding site-dependent plasmin sites on the light chain responsible for cleavage at Lys36. We have now characterised FVIII-interactive regions on plasmin. SDS-PAGE analysis demonstrated that a monoclon al antibody (mAb) against kringle (K)5-catalytic domain (K5-CD) of plasmin significantly blocked plasmin-catalysed cleavages at Arg336 and Arg372. K5-CD fragment and this mAb blocked plasmincatalysed activation and inactivation of FVIII(a). Anti-K1–2–3 and anti-K4 mAbs blocked plasmin-catalysed cleavages at Lys36, and K1–2–3 and K4 fragments inhibited plasmin-catalysed inactivation of A11–336 FVIIIa. The K5-CD preferentially bound to the A2 domain (Kd app ; 52 nM), whilst the K1–2–3 and K4 bound to the light chain (Kd app; 75 and 106 nM, respectively) in ELISA. Binding was attributed to the A2 484–509 region and A3 1690–1705/1804–1818 region, respectively. 6-aminohexanoic acid, a lysine analogue, significantly inhibited the light chain/K1–2–3 (and K4) binding by ∼90%, whilst A2/K5-CD binding was moderated by only ∼35%. Furthermore, an anti-CD antibody blocked plasmin-catalysed cleavage by inhibiting the A2/K5-CD interaction. These data demon strate that the K5-CD of plasmin (and plasminogen) interacts with the A2 domain independent of lysine-binding site, whilst interactions of K1–2–3 and K4 with the light chain are lysine-binding site-dependent. Interactions between the K5-CD and A2 likely constitute the major regulatory mechanism for activation and inactivation of FVIII(a) mediated by cleavage at Arg372 and Arg336.

Plasmin Generation Plays different Roles in the Formation and Removal of Arterial and Venous Thrombus in Mice

The role of plasminogen (Plg) and α2-antiplasmin (α2-AP) in vascular thrombolysis in vivo was investigated in mice deficient in plasminogen (Plg−/−) or α2-AP (α2-AP−/−) or their wild type (PAI-1+/+, α2AP+/+). A thrombus was induced in the murine carotid artery or the internal jugular vein by endothelial injury. Blood flow was continuously monitored for 90 min and for 6 h 30 min after the initiation of endothelial injury. The times to occlusion by the developing thrombus in the carotid artery and the jugular vein of wild type mice were 12 ± 1.8 and 7.2 ± 1.9 min, respectively. The arterial thrombus formation in α2AP−/− mice was indistinguishable from the one in wild type mice, whereas the time to occlusion in Plg−/− was significantly shortened to 5.9 ± 1.7 min. Vascular patency after spontaneous reperfusion was markedly improved in α2-AP−/− mice. On the contrary, arterial patency in Plg−/− mice was aggravated. In venous thrombus formation, the time to occlusion in α2-AP−/− mice was significantly prolonged (27.1 ± 5.2 min), whereas in Plg−/− it was slightly shortened to 6.5 ± 2.5 min. Vascular patency after spontaneous reperfusion was also improved in α2-AP−/− mice, but not in Plg−/− mice. Histological observations using SEM indicated that fibrin nets were firmly fixed on the injured area in Plg−/− mice, but not in α2-AP−/− mice. The tail bleeding time was not different in any type of mice. However, re-bleeding time using a template bleeding device was significantly prolonged in α2-AP−/− as compared with that of wild type mice. In conclusion, lack of plasminogen markedly reduces the antithrombotic activities in vivo, whereas α2-AP plays a more important role in the formation and removal of venous thrombus in mice. Consequently, the inhibition of α2-AP could be a useful tool for the therapy of venous thrombosis and the prevention of re-thrombus formation.

Suppression of argatroban-induced endogenous thrombolysis by PKSI-527, and antibodies to TPA and UPA, evaluated in a rat arterial thrombolysis model

We have previously confirmed, using a rat mesenteric arteriole thrombolysis model, that thrombin inhibition induces endogenous thrombolysis in vivo. In addition, we have shown that thrombin-activatable fibrinolysis inhibitor (TAFI) plays a role in the down regulation of endogenous thrombolysis. However, the mechanism of endogenous thrombolysis or spontaneous plasmin generation in vivo remains unclear.

It has been shown in an in vitro system that plasma kallikrein activates pro-urokinase (pro uPA) and/or plasminogen, resulting in plasmin generation. These findings suggest that spontaneous fibrinolysis might be mediated by tPA and plasma kallikrein-dependent uPA. The aim of the present study was to examine whether these mechanisms play a dominant role in endogenous thrombolysis in vivo, using our rat mesenteric arterial thrombolysis model.

Argatroban infusion enhanced endogenous thrombolysis. PKSI-527, anti uPA and anti tPA IgGs suppressed argatroban-induced thrombolysis. Also, the antibody IgG preparations suppressed endogenous thrombolysis in the absence of argatroban. In the presence of PKSI-527, anti tPA IgG was more effective than anti uPA IgG in suppressing argatroban-induced thrombolysis. The results suggested that both tPA and plasma kallikrein-mediated uPA activation and tPA release contribute to endogenous fibrinolytic or thrombolytic mechanisms.

Differential Role of Components of the Fibrinolytic System in the Formation and Removal of Thrombus Induced by Endothelial Injury

The role of fibrinolytic system components in thrombus formation and removal in vivo was investigated in groups of six mice deficient in urokinase-type plasminogen activator (u-PA), tissue-type plasminogen activator (t-PA), or plasminogen activator inhibitor-1 (PAI-1) (u-PA-/-, t-PA-/- or PAI-1-/-, respectively) or of their wild type controls (u-PA+/+, t-PA+/+ or PAI-1+/+). Thrombus was induced in the murine carotid artery by endothelial injury using the photochemical reaction between rose bengal and green light (540 nm). Blood flow was continuously monitored for 90 min on day 0 and for 20 min on days 1, 2 and 3. The times to occlusion after the initiation of endothelial injury in u-PA+/+, t-PA+/+ or PAI-1+/+ mice were 9.4 ± 1.3, 9.8 ± 1.1 or 9.7 ± 1.6 min, respectively. u-PA-/- and t-PA-/- mice were indistinguishable from controls, whereas that of PAI-1-/- mice were significantly prolonged (18.4 ± 3.7 min). Occlusion persisted for the initial 90 min observation period in 10 of 18 wild type mice and was followed by cyclic reflow and reocclusion in the remaining 8 mice. At day 1, persistent occlusion was observed in 1 wild type mouse, 8 mice had cyclic reflow and reocclusion and 9 mice had persistent reflow. At day 2, all injured arteries had persistent reflow. Persistent occlusion for 90 min on day 0 was observed in 3 u-PA-/-, in all t-PA-/- mice at day 1 and in 2 of the t-PA-/-mice at day 2 (p <0.01 versus wild type mice). Persistent patency was observed in all PAI-1-/- mice at day 1 and in 5 of the 6 u-PA-/- mice at day 2 (both p <0.05 versus wild type mice). In conclusion, t-PA increases the rate of clot lysis after endothelial injury, PAI-1 reduces the time to occlusion and delays clot lysis, whereas u-PA has little effect on thrombus formation and spontaneous lysis.

Lack of tPA Significantly Affects Antithrombotic Therapy by a GPIIb/IIIa Antagonist, but not by a Thrombin Inhibitor in Mice

The interaction of fibrinolytic components with platelets or coagulation factors after endothelial injury, was investigated in mouse deficient in tissue type plasminogen activator (tPA –/–), or urokinase (uPA –/–) and in their wild type control (tPA +/+, uPA +/+). A thrombus was induced in the murine carotid artery using the photochemical reaction. Blood flow was continuously monitored and the time needed before the vessel became completely obstructed was within 11 min in all types of mice. When GR144053, a platelet glycoprotein IIb/IIIa antagonist, or argatroban, a thrombin inhibitor, was applied, the time required to occlusion was prolonged in a dose-dependent manner in all types of mice. However, when GR144053 was injected in tPA –/– mice, the most significant changes were observed: that is the estimated ED50 was 14.8 times higher than the one in tPA +/+ mice. On the other hand, when argatroban was injected in tPA –/– mice, the estimated ED50 was not changed. Platelet aggregation, haemostasis tests and bleeding times were not significantly different among the different types of mice. In conclusion, the antithrombotic effect of platelet inhibition by a GPIIb/IIIa antagonist, is severely affected by the absence or presence of tPA-production. Thus, the lack of tPA significantly reduces the antithrombotic efficacy.

Function of Tissue-type Plasminogen Activator Releaser on Vascular Endothelial Cells and Thrombolysis In Vivo

The effect of monosodium[2-(6-hydroxynaphthalen-2-yl)-6-methylpyrimidin-4-yloxy]acetate dihydrate (JTV-926) on fibrinolysis was investigated in vitro and in vivo. JTV-926 released tissue-type plasminogen activator (t-PA) from human vascular endothelial cells in a dose-dependent manner. The thrombolytic effect of JTV-926 was studied using three animal thrombosis models; a photo-irradiation-induced mouse carotid artery thrombosis model, a photo-irradiation-induced rat femoral artery thrombosis model and a thrombin-induced rat venous thrombosis model. In the mouse thrombosis model, t-PA deficient mice (t-PA−/−mice) and their wild-type (t-PA+/+) were used. JTV-926 was injected as a bolus 30 min after the interruption of blood flow by an occlusion thrombi. Blood flow was continuously monitored for 180 min after intravenous administration of JTV-926 (1 mg/kg). Although the recanalization rate of the occluded artery was 37.5% in t-PA +/+ mice with the vehicle control, it increased to 75% in t-PA+/+ mice after JTV-926 administration. However, when JTV-926 was administrated in t-PA−/−mice, vascular recanalization was not observed in any arteries. In the photo-irradiation-induced rat femoral artery thrombosis model, intra-duodenal administration of JTV-926 induced thrombolysis. Moreover, in the thrombin-induced rat venous thrombosis model, the dose-dependent thrombolysis was also observed by oral administration of JTV-926. It was suggested that JTV-926 revealed a sufficient thrombolytic effect through the absorption from the intestine. Thus, a newly synthesized compound, JTV-926 induced t-PA release from vascular endothelial cells and effective thrombolysis in vivo.

Transcriptional Regulation of Urokinase-type Plasminogen Activator Receptor by Cyclic AMP in PL-21 Human Myeloid Leukemia Cells: Comparison with the Regulation by Phorbol Myristate Acetate

We investigated the effect of dibutyryl cyclic AMP (Bt2-cAMP) on urokinase-type plasminogen activator receptor (uPAR) expression in human PL-21 myeloid leukemia cells and compared it with the effect of phorbol myristate acetate (PMA). Flow cytometric analysis clearly demonstrated that Bt2-cAMP and PMA both induced the cell surface expression of uPAR. Northern analysis and nuclear run-on assay revealed that cAMP and PMA activated the uPAR gene transcription and both additively increased the uPAR mRNA level. However, actinomycin-D decay experiment showed that PMA, but not cAMP, prolonged the uPAR mRNA half-life. Furthermore, inhibition of the ongoing protein synthesis with cycloheximide abrogated completely the PMA-induced uPAR mRNA accumulation but only partially the induction by PMA plus cAMP, whereas the induction by cAMP alone was rather amplified, indicating that the de novo protein synthesis is necessary in the induction by PMA but not in the induction by cAMP and that the cAMP pathway may be dominant in uPAR gene expression in the PL-21 cells as compared to the PMA pathway. These results suggest that cAMP induces the uPAR expression exclusively through activating the gene transcription in which a preexisting transcriptional factor may be involved, whereas PMA transcriptionally and post-transcriptionally regulates the uPAR gene expression.

Effect of staphylokinase-derived nonadecapeptide on the activation of plasminogen

Staphylokinase (SAK) expresses plasminogen activator (PA) activity by forming a complex with plasmin. The interaction between the plasmin-SAK complex and plasminogen was investigated using synthesized peptides, which were constructed according to the amino acid sequence of the SAK molecule.A synthetic nonadecapeptide (SAK22–40) corresponding to Glu22-Leu40 by the SAK molecule enhanced the activation of Glu-plasminogen by the plasmin-SAK complex.Analysis of IAsys resonant mirror biosensor showed that SAK22–40 bound to Glu-plasminogen.This binding was completely inhibited by IgG against the B-chain in the plasminogen molecule. But, this binding was not inhibited by IgG against lysine-binding sites (LBS) of the A-chain in the plasminogen molecule. The substitution of Lys35 with Ala in SAK22–40 did not enhance the activation of Glu-plasminogen by the plasmin-SAK complex. When SAK22–40 was administrated in a mouse thrombosis model, earlier recanalization was observed than in mice with vehicle administration. Thus, a newly synthesized peptide, SAK22–40 enhanced Glu-plasminogen activation and induced effective thrombolysis.

Plasminogen activator inhibitor-1 deficiency enhances subchondral osteopenia after induction of osteoarthritis in mice

BACKGROUND

Subchondral osteopenia is important for the pathophysiology of osteoarthritis (OA). Although previous studies suggest that plasminogen activator inhibitor-1 (PAI-1), an inhibitor of fibrinolysis, is related to bone metabolism, its role in OA remains unknown. We therefore investigated the roles of PAI-1 in the subchondral bone in OA model mice.

METHODS

Wild type (WT) and PAI-1-deficient (KO) mice were ovariectomized (OVX), and then destabilization of the medial meniscus (DMM) surgery was performed.

RESULTS

DMM and OVX significantly decreased the trabecular bone mineral density of the subchondral bone evaluated by quantitative computed tomography in PAI-1 KO mice. The effects of OVX and/or PAI-1 deficiency on the OARSI score for the evaluation of the progression of knee degeneration were not significant. PAI-1 deficiency significantly augmented receptor activator nuclear factor κB ligand mRNA levels enhanced by IL-1β in mouse primary osteoblasts, although it did not affect osteoblast differentiation. Moreover, PAI-1 deficiency significantly increased osteoclast formation from mouse bone marrow cells.

CONCLUSION

We showed that PAI-1 deficiency accelerates the subchondral osteopenia after induction of OA in mice. PAI-1 might suppress an enhancement of bone resorption and subsequent subchondral osteopenia after induction of OA in mice.

α2-antiplasmin modulates bone formation by negatively regulating osteoblast differentiation and function

α2-antiplasmin (α2AP) is known to be a physiological inhibitor of plasmin. Previously, we showed that α2AP displays various functions, such as promotion of extracellular matrix production, cell growth, and cell differentiation that are not promoted by its function as a plasmin inhibitor. We herein investigated the role of α2AP in bone formation by examining calcein incorporation after its injection in α2AP-deficient mice. We found that α2AP deficiency enhanced the bone formation rate in mice. We also found that the osteocalcin expression and alkaline phosphatase activity were elevated in the femur and serum of the α2AP-deficient mice. Intriguingly, α2AP deficiency promoted osteoblast (OB) differentiation of primary calvarial OBs. In contrast, α2AP attenuated OB differentiation of mouse osteoblastic the MC3T3-E1 cells. Furthermore, α2AP attenuated Wnt-3a-induced β-catenin expression and low‑density lipoprotein receptor-related protein 6 activation in the MC3T3-E1 cells. These results suggest that α2AP negatively affects OB differentiation and function by inhibiting the Wnt/β-catenin pathway. These findings provide a basis for clinical strategies to improve various bone disorders.

Plasminogen deficiency is associated with improved glucose tolerance, and lower DPP-4 activity

Plasminogen (Plg), which is the inactive form of plasmin, deficiency enhanced insulin secretion, and was associated with improved oral glucose tolerance in mice. Additionally, Plg deficiency was associated with lower dipeptidyl peptidase-4 (DPP-4) activity, and enhanced glucagons-like peptide-1 (GLP-1) expression. Plg may regulate the DPP-4 activity and the glucose metabolism.

Association of Nonalcoholic Fatty Liver Disease and Venous Thromboembolism in Women With Endometrial Cancer

OBJECTIVE

Recent studies have demonstrated that surgical menopause results in a significantly increased risk of nonalcoholic fatty liver disease (NAFLD) in women with endometrial cancer. In addition, venous thromboembolism (VTE) is known to be one of the major prognostic factors for decreased survival in endometrial cancer. Given the fact that coagulation factors are produced in the liver, the correlation between NAFLD and VTE was examined in endometrial cancer.

METHODS

A retrospective study was conducted to examine patients with endometrial cancer who underwent surgical staging including oophorectomy between 2000 and 2013 (n = 714). Cumulative risk of VTE was examined based on the NAFLD status. A Cox proportional hazard regression model was used to determine the independent risk predictors of VTE.

RESULTS

Venous thromboembolism and NAFLD were seen in 57 (8.0%) and 181 (25.4%) cases, respectively. Two-year cumulative risks of VTE and NAFLD were 7.9% and 19.3%, respectively. In univariate analysis, VTE was significantly associated with decreased disease-free survival (2-year rate, 43.6% vs 91.4%, P < .001) and overall survival (65.8% vs 96.8%, P < .001), whereas NAFLD was associated with decreased risk of VTE (1.7% vs 10.4%, P < .001). In multivariate analysis controlling for clinicopathological factors, NAFLD remained an independent predictor of decreased risk of VTE (hazard ratio [HR]: 0.24, 95% confidence interval [CI]: 0.07-0.79, P = .02). Thrombocytosis (HR: 2.30, 95% CI: 1.22-4.35, P = .01), cancer antigen 125 ≥ 35 (HR: 3.81, 95% CI: 1.78-8.17, P < .001), and recurrent disease (HR: 4.57, 95% CI: 1.97-10.6, P < .001) remained as independent predictors of increased risk of VTE.

CONCLUSION

Our results suggest that NAFLD may be associated with decreased VTE risk in women with endometrial cancer.

Hypofibrinolytic Activity after Total Joint Replacement

Tissue-type plasminogen activator (t-PA), tissue-type plasminogen activator inhibitor (t-PAI), and other factors (platelets, fibrinogen, fibrinogen degrada tion products, antithrombin-III, plasminogen, and α2-plasmin inhibitor [α2-PI]) related to the fibrinolytic system were studied in 21 patients undergoing total joint replacement.

Seventeen of the 21 patients revealed an impaired fibrinolytic activity from the first to seventh postoperative day and a subsequent return to the preopera tive level by the fourteenth postoperative day. There were accompanying increases in the level of α2-PI and in the t-PAI/t-PA ratio, and there was decrease in plas minogen level. Such hypofibrinolytic states may be related to a higher incidence of postoperative thrombosis in total joint replacement patients.