Plasminogen activator inhibitor type I may contribute to transient, non-specific changes in immunity in the subacute phase of murine tuberculosis

A Narrative Review on Plasminogen Activator Inhibitor-1 and Its (Patho)Physiological Role: To Target or Not to Target?

Plasminogen activator inhibitor-1 (PAI-1) is the main physiological inhibitor of plasminogen activators (PAs) and is therefore an important inhibitor of the plasminogen/plasmin system. Being the fast-acting inhibitor of tissue-type PA (tPA), PAI-1 primarily attenuates fibrinolysis. Through inhibition of urokinase-type PA (uPA) and interaction with biological ligands such as vitronectin and cell-surface receptors, the function of PAI-1 extends to pericellular proteolysis, tissue remodeling and other processes including cell migration. This review aims at providing a general overview of the properties of PAI-1 and the role it plays in many biological processes and touches upon the possible use of PAI-1 inhibitors as therapeutics.

The thrombomodulin lectin-like domain does not change host responses to tuberculosis

Tuberculosis (TB), caused by Mycobacterium (M.) tuberculosis, is a devastating infectious disease causing many deaths world-wide. Thrombomodulin (TM) is a multidomain glycoprotein expressed on all vascular endothelial cells. We here studied the role of the lectin-like domain of TM, responsible for a variety of anti-inflammatory properties of TM, during TB. We compared the extent of TM-expression in human lung tissue of TB and control patients. The, the role of the lectin-like domain of TM was investigated by comparing mice lacking this domain (TMLeD/LeD mice) with wild-type (WT) mice during experimental lung TB induced by infection with M. tuberculosis via the airways. Lungs were harvested for analyses at two, six and 29 weeks after infection. Lung TM-expression was downregulated in TB patients, which was not related to changes in the amount of endothelium in infected lungs. TMLeD/LeD mice showed unaltered mycobacterial loads in lungs, liver and spleen during experimental TB. Additionally, lung histopathology and cytokine concentrations were largely similar in TMLeD/LeD and WT mice, while total leukocyte counts were increased in lungs of TMLeD/LeD mice after 29 weeks of infection. Mortality did not occur in either group. The lectin-like domain of TM does not play an important role in the host response to M. tuberculosis infection in mice.

Lavandula angustifolia Mill. Essential Oil Exerts Antibacterial and Anti-Inflammatory Effect in Macrophage Mediated Immune Response to Staphylococcus aureus

Different studies described the antibacterial properties of Lavandula angustifolia (Mill.) essential oil and its anti-inflammatory effects. Besides, no data exist on its ability to activate human macrophages during the innate response against Staphylococcus aureus. The discovery of promising regulators of macrophage-mediated inflammatory response, without side effects, could be useful for the prevention of, or as therapeutic remedy for, various inflammation-mediated diseases. This study investigated, by transcriptional analysis, how a L. angustifolia essential oil treatment influences the macrophage response to Staphylococcus aureus infection. The results showed that the treatment increases the phagocytic rate and stimulates the containment of intracellular bacterial replication by macrophages. Our data showed that this stimulation is coupled with expression of genes involved in reactive oxygen species production (i.e., CYBB and NCF4). Moreover, the essential oil treatment balanced the inflammatory signaling induced by S. aureus by repressing the principal pro-inflammatory cytokines and their receptors and inducing the heme oxygenase-1 gene transcription. These data showed that the L. angustifolia essential oil can stimulate the human innate macrophage response to a bacterium which is responsible for one of the most important nosocomial infection and might suggest the potential development of this plant extract as an anti-inflammatory and immune regulatory coadjutant drug.

A new murine model to study musculoskeletal tuberculosis (short communication)

Musculoskeletal tuberculosis (TB) is a severe extrapulmonary manifestation of chronic Mycobacterium (M.) tuberculosis infection. Considering increasing incidence, multi-drug resistance and associated treatment difficulties, more preclinical research is needed. In this study we developed a murine model for musculoskeletal TB. Mice, intranasally infected with M. tuberculosis, were sacrificed after ten months. Mycobacterial growth was detected in lung and femur homogenates. Ziehl-Neelsen staining of paraffin-embedded femurs showed acid-fast rods in the myelum and Magnetic Resonance Imaging demonstrated osteomyelitis and macronodular tuberculomas. This new murine model of musculoskeletal TB might be of value to further investigate immunologic and radiologic responses.

The endothelial protein C receptor and activated protein C play a limited role in host defense during experimental tuberculosis

The protein C (PC) system is an important regulator of both coagulation and inflammation. Activated PC (APC), together with its receptor the endothelial protein C receptor (EPCR), has anticoagulant and anti-inflammatory properties. During tuberculosis (TB), a devastating chronic pulmonary disease caused by Mycobacterium (M.) tuberculosis, both a local inflammatory reaction characterised by the recruitment of mainly mononuclear cells and the formation of pulmonary granulomas as well as activation of coagulation occurs as part of the host immune response. We investigated the role of EPCR and APC in a mouse model of TBusing mice overexpressing EPCR (Tie2-EPCR), mice deficient for EPCR (EPCR-/-), mice treated with APC-inhibiting antibodies and mice overexpressing APC (APChigh) and compared them with wild-type (WT) mice. Blood and organs were harvested to quantify bacterial loads, cellular influxes, cytokines, histopathology and coagulation parameters. Additionally observation studies were performed. Lung EPCR expression was upregulated during experimental TB. No significant differences in bacterial growth were seen between WT and Tie2-EPCR mice. However, Tie2-EPCR mice had decreased pulmonary coagulation activation, displayed an increased influx of macrophages 2 and 6 weeks after infection, but no increase in other proinflammatory markers. On the other hand, in EPCR-/--mice coagulation activation was decreased 6 weeks post-infection, with little impact on other inflammation markers. APC-overexpression or treatment with anti-(A)PC antibodies displayed minimal effects during experimental TB. In conclusion, EPCR and APC play a limited role in the host response during experimental pulmonary TB.