Plasminogen is an important regulator in the pathogenesis of a murine model of asthma

RATIONALE: Asthma is a syndrome whose common pathogenic expression is inflammation of the airways. Plasminogen plays an important role in cell migration and is also implicated in tissue remodeling, but its role in asthma has not been defined. OBJECTIVES: To test whether plasminogen is a critical component in the development of asthma. METHODS: We used a mouse model of ovalbumin-induced pulmonary inflammation in Plg(+/+), Plg(+/-), and Plg(-/-) mice. MEASUREMENTS AND MAIN RESULTS: The host responses measured included lung morphometry, and inflammatory mediators and cell counts were assessed in bronchoalveolar lavage fluid. Bronchoalveolar lavage demonstrated a marked increase in eosinophils and lymphocytes in ovalbumin-treated Plg(+/+) mice, which were reduced to phosphate-buffered saline-treated control levels in Plg(+/-) or Plg(-/-) mice. Lung histology revealed peribronchial and perivascular leukocytosis, mucus production, and increased collagen deposition in ovalbumin-treated Plg(+/+) but not in Plg(+/-) or Plg(-/-) mice. IL-5, tumor necrosis factor-alpha, and gelatinases, known mediators of asthma, were detected in bronchoalveolar lavage fluid of ovalbumin-treated Plg(+/+) mice, yet were reduced in Plg(-/-) mice. Administration of the plasminogen inhibitor, tranexamic acid, reduced eosinophil and lymphocyte numbers, mucus production, and collagen deposition in the lungs of ovalbumin-treated Plg(+/+) mice. CONCLUSIONS: The decreased inflammation in the lungs of Plg(-/-) mice and its blockade with a plasminogen inhibitor indicate that plasminogen plays an important role in orchestrating the asthmatic response and suggests that plasminogen may be a therapeutic target for the treatment of asthma.     

Vegfb gene knockout mice display reduced pathology and synovial angiogenesis in both antigen-induced and collagen-induced models of arthritis

OBJECTIVE: To determine the role of vascular endothelial growth factor B (VEGF-B) in 2 mouse models of arthritis, antigen-induced arthritis (AIA) and collagen-induced arthritis (CIA). METHODS: For AIA studies, monarticular AIA was induced by methylated bovine serum albumin (mBSA) priming of Vegfb gene knockout (Vegfb(-/-)) and wild-type (Vegfb(+/+)) mice, followed by intraarticular injection of mBSA or saline control 8 days later. CIA was induced in Vegfb(-/-) and Vegfb(+/+) mice by intradermal injection of chick type II collagen in adjuvant. Arthritis was monitored in both models using defined criteria (clinical and histologic). Angiogenesis was measured by synovial vessel density in diseased and control joints. RESULTS: In AIA studies, Vegfb(+/+) mice displayed significant knee joint swelling and synovial inflammation 7 days after intraarticular injection of antigen. Synovial inflammation was associated with angiogenesis, since vessel density in AIA synovium was significantly higher in arthritic than in control joints from the same animal. Knee joint swelling, synovial inflammation, and inflammation-associated vessel density in arthritic joints were reduced in Vegfb(-/-) mice compared with arthritic joints from Vegfb(+/+) mice. Similarly, in CIA, both disease incidence and mean clinical severity scores were significantly reduced in Vegfb(-/-) mice compared with Vegfb(+/+) mice. Mean histologic severity scores and mean synovial vessel density were reduced in diseased joints from Vegfb(-/-) mice when compared with diseased joints from Vegfb(+/+) mice. CONCLUSION: The reduction in inflammation-associated synovial angiogenesis in Vegfb(-/-) mice implicates VEGF-B in pathologic vascular remodeling in inflammatory arthritis. VEGF-B may be an attractive target in the design of anti-angiogenic therapies for rheumatoid arthritis.     

Role of macrophages in Staphylococcus aureus-induced arthritis and sepsis

OBJECTIVE: A model of hematogenously induced Staphylococcus aureus arthritis was used to analyze the role of macrophages in this highly destructive condition. In this model, the majority of cells in the cartilage-synovial junction that participate in the destructive process are macrophages. METHODS: To assess the role of monocytes/macrophages in staphylococcal arthritis, mice were inoculated with S aureus or given phosphate buffered saline as control. Mice were rendered monocytopenic by administration of etoposide, a drug that selectively depletes the monocyte/macrophage population. RESULTS: Throughout the course of infection, the etoposide-treated mice exhibited a significantly less severe arthritis than the control animals. These data were confirmed by histopathologic analysis of the joints. The down-regulation of development of arthritis was accompanied by decreased serum levels of the proinflammatory cytokines tumor necrosis factor alpha and interleukin-6. In contrast, infection-triggered mortality was increased in the etoposide-treated mice as compared with the control animals. Notably, the monocytopenic mice exhibited elevated bacterial burden in the blood and kidneys on days 3 and 7 after inoculation with staphylococci. CONCLUSION: This study indicates a dual role of mononuclear phagocytes in the pathogenesis of S aureus-induced infection. On the one hand, absence of macrophages leads to a favorable outcome concerning the severity of arthritic lesions, but on the other hand, the clearance of bacteria by monocytes/macrophages is decreased, resulting in poor survival.     

Pancreas recovery following cerulein-induced pancreatitis is impaired in plasminogen-deficient mice

BACKGROUND & AIMS: The plasminogen (plg) system participates in tissue repair in several organs, but its role in pancreas repair remains poorly characterized. To understand better the role of plg in pancreas recovery following injury, we examined the course of cerulein-induced pancreatitis in plg-deficient and -sufficient mice. METHODS: Pancreatitis was induced by cerulein administration (50 microg/kg, 7 intraperitoneal injections). Mice were killed either at the acute phase (7 hours after the first cerulein injection) or during recovery (at 2, 4, and 7 days). In pancreatic sections, we examined pancreatic morphology, trypsin activation, inflammatory cell infiltration, acinar cell death, cell proliferation, extracellular matrix deposition, activation of stellate cells (PSCs), and components of the plg and metalloproteinase systems. RESULTS: In plg-sufficient mice, pancreatic plg levels and plasmin activity increased during the acute phase and remained elevated during recovery. Pancreatitis resolved in plg-sufficient mice within 7 days. Pancreas recovery involved reorganization of the parenchyma structure, removal of necrotic debris, cell proliferation, transient activation of PSCs, and moderate deposition of extracellular matrix proteins. Acute pancreatitis (7 hours) was indistinguishable between plg-deficient and -sufficient mice. In contrast, pancreas recovery was impaired in plg-deficient mice. Plg deficiency led to disorganized parenchyma, extensive acinar cell loss, poor removal of necrotic debris, reduced cell proliferation, and fibrosis. Fibrosis was characterized by deposition of collagens and fibronectin, persistent activation of PSCs, and up-regulation of pancreatic transforming growth factor beta1. CONCLUSIONS: Plg/plasmin deficiency leads to features similar to those found in chronic pancreatitis such as parenchymal atrophy and fibrosis.     

Rapid systemic bone resorption during the course of Staphylococcus aureus-induced arthritis

Bacterial arthritis is the most rapidly progressing destructive joint disease in humans. To evaluate bone resorption and formation, mice were injected with Staphylococcus aureus and killed after 3 and 14 days. Both total and trabecular bone mineral density were, compared with those in uninfected controls, already significantly reduced 3 days after bacterial inoculation. Serum levels of type I collagen fragments were significantly increased and osteocalcin levels decreased in mice infected with S. aureus, compared with those in noninfected mice, 3 and 14 days after bacterial inoculation. This study shows that there is a rapid and easily measurable systemic bone resorption during S. aureus-induced arthritis.     

The regulation of liver regeneration by the plasmin/alpha 2-antiplasmin system

BACKGROUND/AIMS: The regeneration after liver injury is regulated by the release and activation of several growth factors. The role of the plasmin/alpha(2)-antiplasmin (alpha(2)-AP) system in liver regeneration was investigated. METHODS: CCl(4) was injected intraperitoneally into the mice deficient (-/-) in fibrinolytic factors: alpha(2)-AP-/-, plasminogen (Plg) -/-, and Plg-/-.alpha(2)-AP-/-, and wild-type (WT) mice. The liver tissue was examined for its microscopic appearance, fibrinolytic activity, and fibronectin levels. RESULTS: In the gene deficient and WT mice, the livers exhibited the same extent of necrosis 2 days after the CCl(4) injection. The livers of the WT mice normalized after 7 days, and the alpha(2)-AP-/- mice normalized after 5 days. In contrast, the livers of the Plg-/- and Plg-/-.alpha(2)-AP-/- mice remained in the damaged state until 14 days after the liver injury. The injection of anti-alpha(2)-AP antibody in the WT mice improved the regeneration after the liver injury, and the injection of tranexamic acid in the alpha(2)-AP-/- mice reduced. CONCLUSIONS: These results suggest that the plasmin/alpha(2)-AP system played an important role in hepatic repair via clearance from the injury area.     

Plasminogen deficiency leads to impaired remodeling after a toxic injury to the liver

Cellular proliferation and tissue remodeling are central to the regenerative response after a toxic injury to the liver. To explore the role of plasminogen in hepatic tissue remodeling and regeneration, we used carbon tetrachloride to induce an acute liver injury in plasminogen-deficient (Plg(o)) mice and nontransgenic littermates (Plg(+)). On day 2 after CCl(4), livers of Plg(+) and Plg(o) mice had a similar diseased pale/lacy appearance, followed by restoration of normal appearance in Plg(+) livers by day 7. In contrast, Plg(o) livers remained diseased for as long as 2.5 months, with a diffuse pale/lacy appearance and persistent damage to centrilobular hepatocytes. The persistent centrilobular lesions were not a consequence of impaired proliferative response in Plg(o) mice. Notably, fibrin deposition was a prominent feature in diseased centrilobular areas in Plg(o) livers for at least 30 days after injury. Nonetheless, the genetically superimposed loss of the Aalpha fibrinogen chain (Plg(o)/Fib(o) mice) did not correct the abnormal phenotype. These data show that plasminogen deficiency impedes the clearance of necrotic tissue from a diseased hepatic microenvironment and the subsequent reconstitution of normal liver architecture in a fashion that is unrelated to circulating fibrinogen.     

Deletion of the gene encoding CD59a in mice increases disease severity in a murine model of rheumatoid arthritis

OBJECTIVE: To investigate the roles of CD59a in the protection of joint tissue in the context of murine antigen-induced arthritis (AIA). METHODS: AIA was triggered in CD59a-deficient (CD59a(-/-)) mice and in CD59a-sufficient (CD59a(+/+)) controls; the course and severity of disease were compared between groups. The effects on arthritis of restoring CD59 to the joint in CD59a(-/-) mice by use of a membrane-targeted recombinant CD59 were also explored. RESULTS: Disease, as assessed clinically by measurement of joint swelling on day 1 (P < 0.0001), day 2 (P < 0.01), and day 7 (P < 0.02) and histologically from indicators of joint damage on day 21 (P < 0.02), was significantly enhanced in CD59a(-/-) mice compared with CD59a(+/+) wild-type controls. Membrane attack complex (MAC) deposition in the arthritic joints of CD59a(-/-) mice was also increased compared with that in the joints of CD59a(+/+) controls. Restitution of CD59 activity in joints of CD59a(-/-) mice was attempted with soluble recombinant rat CD59 (sCD59) or with a novel membrane-targeted rat CD59 derivative (sCD59-APT542). Strong immunohistochemical staining of the synovial membrane and subsynovial tissue was apparent in sCD59-APT542-injected joints, but not in joints injected with untargeted sCD59. Intraarticular administration of sCD59-APT542 markedly ameliorated disease severity in CD59a(-/-) mice, knee swelling was significantly reduced over the time course of the disease, and joint damage, assessed histologically, was significantly milder on day 21 (P < 0.05). CONCLUSION: These data firmly implicate the MAC of complement as a major effector of joint damage in the murine AIA model of rheumatoid arthritis (RA), and they provide a rationale for the inhibition of MAC assembly as a therapeutic strategy for RA.     

Plasminogen enhances virulence of group A streptococci by streptokinase-dependent and streptokinase-independent mechanisms

Interactions between host plasminogen (Plg) and streptokinase (SK) secreted by group A streptococci (GAS) have been hypothesized to promote bacterial invasion of tissues. The virulence of GAS strain UMAA2616, after being subcutaneously inoculated into mice, was studied. Skin lesions and mortality were observed after inoculation of 7x106 cfu. Coadministration of human Plg with UMAA2616 markedly increased virulence. SK-deficient UMAA2616 (UMAA2616-SK(-)) was generated. Mean skin-lesion area and mortality, after bacterial inoculation (3x105 cfu), were significantly greater with UMAA2616 in the presence of human Plg than with UMAA2616-SK(-) in the presence of human Plg (P=.0001). Human Plg also enhanced UMAA2616-SK(-) virulence. Exogenous human Plg enhanced the virulence of MGAS166, a human clinical isolate. These findings suggest that SK-Plg interactions are an important determinant of GAS invasiveness in vivo and that both SK and host Plg activators appear to promote virulence of GAS by catalyzing plasmin formation.     

Vaccination with nontoxic mutant toxic shock syndrome toxin 1 protects against Staphylococcus aureus infection

To investigate whether vaccination with nontoxic mutant toxic shock syndrome toxin 1 (mTSST-1) can protect against Staphylococcus aureus infection, mice were vaccinated with mTSST-1 and challenged with viable S. aureus. Survival in the mTSST-1-vaccinated group was higher, and bacterial counts in organs were significantly lower than those of control mice. Passive transfer of mTSST-1-specific antibodies also provided protection against S. aureus-induced septic death. Interferon (IFN)-gamma production in the serum samples and spleens from vaccinated mice was significantly decreased compared with that in controls, whereas interleukin-10 titers were significantly higher in vaccinated mice. IFN-gamma and tumor necrosis factor-alpha production in vitro were significantly inhibited by serum samples from mTSST-1-immunized mice but not from control mice. These results suggest that vaccination with mTSST-1 devoid of superantigenic properties provides protection against S. aureus infection and that the protection might be mediated by TSST-1-neutralizing antibodies as well as by the down-regulation of IFN-gamma production.     

Experimental protection of mice against lethal Staphylococcus aureus infection by novel bacteriophage phi MR11

The protective effects of bacteriophages were assessed against experimental Staphylococcus aureus infection in mice. Of the S. aureus phages isolated in the study, phi MR11 was representatively used for all testing, because its host range was the most broad and it carries no genes for known toxins or antibiotic resistance. Intraperitoneal injections (8 x 10(8) cells) of S. aureus, including methicillin-resistant bacteria, caused bacteremia and eventual death in mice. In contrast, subsequent intraperitoneal administration of purified phi MR11 (MOI > or = 0.1) suppressed S. aureus-induced lethality. This lifesaving effect coincided with the rapid appearance of phi MR11 in the circulation, which remained at substantial levels until the bacteria were eradicated. Inoculation with high-dose phi MR11 alone produced no adverse effects attributable to the phage. These results uphold the efficacy of phage therapy against pernicious S. aureus infections in humans and suggest that phi MR11 may be a potential prototype for gene-modified, advanced therapeutic S. aureus phages.     

Plasminogen activator inhibitor type-1 deficiency attenuates murine antigen-induced arthritis

OBJECTIVE: To examine the role of plasminogen activator inhibitor type-1 (PAI-1), the major fibrinolytic inhibitor, in vivo during murine antigen-induced arthritis (AIA). METHODS: AIA was induced in PAI-1-deficient mice and control wild-type mice. Arthritis severity was evaluated by technetium 99m (99mTc) uptake in the knee joints and by histological scoring. Intra-articular fibrin deposition was examined by immunohistochemistry and synovial fibrinolysis quantitated by tissue D-dimer measurements and zymograms. RESULTS: Joint inflammation, quantitated by 99mTc uptake, was significantly reduced in PAI-1(-/-) mice on day 7 after arthritis onset (P<0.01). Likewise, synovial inflammation, evaluated by histological scoring, was significantly decreased in PAI-1-deficient mice on day 10 after arthritis onset (P<0.001). Articular cartilage damage was significantly decreased in PAI-1(-/-) mice, as shown by histological grading of safranin-O staining on day 10 after arthritis onset (P<0.005). Significantly decreased synovial accumulation of fibrin was observed by day 10 in arthritic joints of PAI-1(-/-) mice (P<0.005). Accordingly, the synovial tissue content of D-dimers, the specific fibrin degradation products generated by plasmin, were increased in PAI-1(-/-) mice (P<0.02). Finally, as expected, PA activity was increased in synovial tissues from PAI-1(-/-) mice, as shown by zymographic analysis. CONCLUSIONS: These results indicate that deficiency of PAI-1 results in increased synovial fibrinolysis, leading to reduced fibrin accumulation in arthritic joints and reduced severity of AIA.     

Plasminogen deficiency attenuates postnatal erythropoiesis in male C57BL/6 mice through decreased activity of the LH-testosterone axis

Novel roles for the serine protease plasmin have been implicated recently in physiological and pathological processes. However, whether plasmin is involved in erythropoiesis is not known. In the present study, we studied the consequences of plasminogen deficiency on erythropoiesis in plasminogen-deficient (Plg knockout [KO]) mice. Erythroid differentiation was attenuated in male Plg KO mice and resulted in erythroblastic accumulation within the spleen and bone marrow, with increased apoptosis in the former, erythrocytosis, and splenomegaly, whereas similar erythropoietic defect was less prominent in female Plg KO mice. In addition, erythrocyte lifespan was shorter in both male and female Plg KO mice. Erythropoietin levels were compensatory increased in both male and female Plg KO mice, and resulted in a higher frequency of burst-forming units-erythroid within the spleen and bone marrow. Surprisingly, we found that male Plg KO mice, but not their female counterparts, exhibited normochromic normocytic anemia. The observed sex-linked erythropoietic defect was attributed to decreased serum testosterone levels in Plg KO mice as a consequence of impaired secretion of the pituitary luteinizing hormone (LH) under steady-state condition. Surgical castration causing testosterone deficiency and stimulating LH release attenuated erythroid differentiation and induced anemia in wild-type animals, but did not further decrease the hematocrit levels in Plg KO mice. In addition, complementation of LH using human choriogonadotropin, which increases testosterone production, improved the erythropoietic defect and anemia in Plg KO mice. The present results identify a novel role for plasmin in the hormonal regulation of postnatal erythropoiesis by the LH-testosterone axis.     

Trabecular bone mass and bone formation are preserved after limb immobilisation in p53 null mice

OBJECTIVES: To determine whether disruption of the p53 gene leads to preservation of trabecular bone volume (BV) after limb immobilisation. MATERIALS AND METHODS: Tibias of immobilised hind limbs of p53 gene knockout (p53(-/-)) and wild-type (p53(+/+)) mice were compared. Right knee joints of 8 week old mice were immobilised in full extension for 7 days. Trabecular structure and bone formation were similar in the p53(-/-) and p53(+/+) control groups. RESULTS: Immobilisation significantly reduced BV to 77% of the control in p53(+/+) mice, but no change was noted in p53(-/-) mice. After immobilisation, bone formation rate was significantly reduced in p53(+/+) but not in p53(-/-) mice. In bone marrow cell cultures the numbers of alkaline phosphatase positive colony forming units-fibroblastic and mineralised nodules were significantly reduced by immobilisation in p53(+/+) but not in p53(-/-) mice. Immobilisation enhanced p53 mRNA expression in marrow cells of p53(+/+) mice and increased terminal dUTP nick end labelling positive osteocytes and marrow cells in p53(+/+) but not in p53(-/-) mice. Lack of p53 in immobilised mice was associated with preservation of trabecular bone mass and bone formation and suppression of significant apoptosis of marrow cells. CONCLUSION: Disruption of the p53 gene preserves trabecular bone mass and leads to bone formation after limb immobilisation.     

Plasmin activity is required for myogenesis in vitro and skeletal muscle regeneration in vivo

Plasmin, the primary fibrinolytic enzyme, has a broad substrate spectrum and is implicated in biologic processes dependent upon proteolytic activity, such as tissue remodeling and cell migration. Active plasmin is generated from proteolytic cleavage of the zymogen plasminogen (Plg) by urokinase-type plasminogen activator (uPA) and tissue-type plasminogen activator (tPA). Here, we have investigated the role of plasmin in C2C12 myoblast fusion and differentiation in vitro, as well as in skeletal muscle regeneration in vivo, in wild-type and Plg-deficient mice. Wild-type mice completely repaired experimentally damaged skeletal muscle. In contrast, Plg(-/-) mice presented a severe regeneration defect with decreased recruitment of blood-derived monocytes and lymphocytes to the site of injury and persistent myotube degeneration. In addition, Plg-deficient mice accumulated fibrin in the degenerating muscle fibers; however, fibrinogen depletion of Plg-deficient mice resulted in a correction of the muscular regeneration defect. Because we found that uPA, but not tPA, was induced in skeletal muscle regeneration, and persistent fibrin deposition was also reproducible in uPA-deficient mice following injury, we propose that fibrinolysis by uPA-dependent plasmin activity plays a fundamental role in skeletal muscle regeneration. In summary, we identify plasmin as a critical component of the mammalian skeletal muscle regeneration process, possibly by preventing intramuscular fibrin accumulation and by contributing to the adequate inflammatory response after injury. Finally, we found that inhibition of plasmin activity with alpha2-antiplasmin resulted in decreased myoblast fusion and differentiation in vitro. Altogether, these studies demonstrate the requirement of plasmin during myogenesis in vitro and muscle regeneration in vivo.     

Apoptosis and p53 expression in chondrocytes relate to degeneration in articular cartilage of immobilized knee joints

OBJECTIVE: We have reported that articular cartilage showed early stage degeneration at 7 and 14 days after immobilization, moderate degeneration at 28 days, and severe degeneration at 42 days in rabbits. To test whether apoptosis occurs in association with p53 expression in chondrocytes during the process of articular cartilage degeneration, we investigated the degree of cartilage degeneration, the frequency of apoptotic cells, and the levels of p53 mRNA in rabbits and mice after knee immobilization. METHODS: Right knees of male Japanese white rabbits were immobilized in full extension with fiberglass casts for up to 42 days. Similarly, right knees of male p53 wild-type [p53 (+/+)] and p53 null [p53 (-/-)] mice were immobilized in full extension with bandage tape for up to 84 days. Apoptotic cells were confirmed by TUNEL staining on the sections of knee joints. Total RNA of articular chondrocytes obtained from Day 0 or immobilized knees was analyzed semiquantitatively by RT-PCR using specific primers for p53. RESULTS: Articular cartilage degenerated after immobilization of p53 (+/+) mouse knees, but not after immobilization of p53 (-/-) knees. Apoptotic cells were observed in articular cartilage in the femur and tibia of rabbits and p53 (+/+) mice after immobilization. However, only a few apoptotic cells were observed at the same sites in p53 (-/-) mice. In RT-PCR analysis, the levels of p53 mRNA obtained from immobilized groups were significantly higher than those of Day 0 groups in rabbit and p53 (+/+) mouse knees. CONCLUSION: Apoptosis and p53 expression in chondrocytes relate to degeneration in articular cartilage of immobilized knee joints.     

Alpha(2)-antiplasmin gene deficiency in mice does not affect neointima formation after vascular injury

The hypothesis that alpha(2)-antiplasmin (alpha(2)-AP), the main physiological plasmin inhibitor, plays a role in neointima formation was tested with use of a vascular injury model in wild-type (alpha(2)-AP(+/+)) and alpha(2)-AP-deficient (alpha(2)-AP(-/-)) mice. The neointimal and medial areas were similar 1 to 3 weeks after electric injury of the femoral artery in alpha(2)-AP(+/+) and alpha(2)-AP(-/-) mice, resulting in comparable intima/media ratios (eg, 0.43+/-0.12 and 0.42+/-0.11 2 weeks after injury). Nuclear cell counts in cross-sectional areas of the intima of the injured region were also comparable in arteries from alpha(2)-AP(+/+) and alpha(2)-AP(-/-) mice (78+/-19 and 69+/-8). Fibrin deposition was not significantly different in arteries of both genotypes 1 day after injury, and no mural thrombosis was detected 1 week after injury. Fibrinolytic activity in femoral arterial sections, as monitored by fibrin zymography, was higher in alpha(2)-AP(-/-) mice 1 week after injury (P<0.001) but was comparable in both genotypes 2 and 3 weeks after injury. Staining for elastin did not reveal significant degradation of the internal elastica lamina in either genotype. Immunocytochemical analysis revealed a comparable distribution pattern of alpha-actin-positive smooth muscle cells in both genotypes. These findings indicate that the endogenous fibrinolytic system of alpha(2)-AP(+/+) mice is capable of preventing fibrin deposition after vascular injury and suggest that alpha(2)-AP does not play a major role in smooth muscle cell migration and neointima formation in vivo.     

Differential role of interleukin-6 in lung inflammation induced by lipoteichoic acid and peptidoglycan from Staphylococcus aureus

Lipoteichoic acids (LTA) and peptidoglycans (PepG) are major components of the cell walls of gram-positive bacteria that trigger inflammatory responses in vitro. To study the in vivo effects of LTA and PepG from Staphylococcus aureus in lungs and to determine the role of interleukin (IL)-6 herein, these compounds were intranasally administered to IL-6 gene deficient (IL-6(-/-)) and wild type (IL-6(+/+)) mice. In IL-6(+/+) mice, LTA and PepG induced acute pulmonary inflammation in a dose-dependent way, characterized by neutrophilic influx and IL-6 production in the bronchoalveolar lavage fluid. Endogenously produced IL-6 attenuated inflammation induced by 10 microg LTA, as reflected by enhanced neutrophil influx, and increased tumor necrosis factor-alpha, macrophage inflammatory protein-1-alpha, and cytokine-induced neutrophil chemoattractant (KC) release into bronchoalveolar lavage fluid of IL-6(-/-) mice, compared with IL-6(+/+) mice. By contrast, pulmonary inflammation induced by 100 microg LTA was similar (neutrophil influx) or even tended to be attenuated (cytokine and chemokine release) in IL-6(-/-) mice. Endogenous IL-6 increased inflammation induced by PepG, as reflected by decreased neutrophil influx into lungs of IL-6(-/-) mice, compared with IL-6(+/+) mice. These data suggest that IL-6 plays an anti-inflammatory role during LTA-induced pulmonary inflammation, which is dependent on the severity of the inflammatory challenge, and a proinflammatory role in peptidoglycan-induced acute lung inflammation. Thus, the contribution of IL-6 to lung inflammation may vary with the stimulus used.     

The effects of intrinsic pathway protease deficiencies on plasminogen-deficient mice

Plasminogen (Plg)-deficient mice experience wasting and have decreased longevity due to disseminated fibrin deposition. We generated mice with combined deficiencies of Plg and coagulation factor IX (fIX) or XI (fXI) to determine the effects on the Plg null phenotype. Mice lacking Plg and fIX (Plg(-/-)/fIX-/-) have lower mortality at age 6 months than Plg(-/-)/fIX+/+ mice (15% and 67%, respectively) and less severe wasting, consistent with the importance of fIX in fibrin formation. In contrast, combined Plg and fXI deficiency (Plg(-/-)/fXI-/-) reduces life span (more than 90% mortality at 6 months) and is associated with leukocyte infiltration of the lungs and pulmonary fibrosis. These abnormalities are not seen in Plg-/- or Plg(-/-)/fIX-/- animals. Activated fXI is thought to function primarily as a fIX activator; however, our observation suggests that fXI may have functions in regulation of inflammation or tissue repair distinct from its role in coagulation.