Plasminogen activator inhibitor-1 deficiency augments visceral mesothelial organization, intrapleural coagulation, and lung restriction in mice with carbon black/bleomycin-induced pleural injury.

Local derangements of fibrin turnover and plasminogen activator inhibitor (PAI)-1 have been implicated in the pathogenesis of pleural injury. However, their role in the control of pleural organization has been unclear. We found that a C57Bl/6j mouse model of carbon black/bleomycin (CBB) injury demonstrates pleural organization resulting in pleural rind formation (14 d). In transgenic mice overexpressing human PAI-1, intrapleural fibrin deposition was increased, but visceral pleural thickness, lung volumes, and compliance were comparable to wild type. CBB injury in PAI-1(-/-) mice significantly increased visceral pleural thickness (P < 0.001), elastance (P < 0.05), and total lung resistance (P < 0.05), while decreasing lung compliance (P < 0.01) and lung volumes (P < 0.05). Collagen, α-smooth muscle actin, and tissue factor were increased in the thickened visceral pleura of PAI-1(-/-) mice. Colocalization of α-smooth muscle actin and calretinin within pleural mesothelial cells was increased in CBB-injured PAI-1(-/-) mice. Thrombin, factor Xa, plasmin, and urokinase induced mesothelial-mesenchymal transition, tissue factor expression, and activity in primary human pleural mesothelial cells. In PAI-1(-/-) mice, D-dimer and thrombin-antithrombin complex concentrations were increased in pleural lavage fluids. The results demonstrate that PAI-1 regulates CBB-induced pleural injury severity via unrestricted fibrinolysis and cross-talk with coagulation proteases. Whereas overexpression of PAI-1 augments intrapleural fibrin deposition, PAI-1 deficiency promotes profibrogenic alterations of the mesothelium that exacerbate pleural organization and lung restriction.

4-Hydroxy-2-nonenal enhances tissue factor activity in human monocytic cells via p38 mitogen-activated protein kinase activation-dependent phosphatidylserine exposure.

OBJECTIVE: 4-hydroxy-2-nonenal (HNE) is one of the major aldehydes formed during lipid peroxidation and is believed to play a role in the pathogenesis of atherosclerosis. The objective of the present study is to investigate the effect of HNE on tissue factor (TF) procoagulant activity expressed on cell surfaces. APPROACH AND RESULTS: TF activity and antigen levels on intact cells were measured using factor Xa generation and TF monoclonal antibody binding assays, respectively. Exposure of phosphatidylserine on the cell surface was analyzed using thrombin generation assay or by binding of a fluorescent dye-conjugated annexin V. 2',7'-dichlorodihydrofluorescein diacetate was used to detect the generation of reactive oxygen species. Our data showed that HNE increased the procoagulant activity of unperturbed THP-1 cells that express traces of TF antigen, but had no effect on unperturbed endothelial cells that express no measurable TF antigen. HNE increased TF procoagulant activity but not TF antigen of both activated monocytic and endothelial cells. HNE treatment generated reactive oxygen species, activated p38 mitogen-activated protein kinase, and increased the exposure of phosphatidylserine at the outer leaflet in THP-1 cells. Treatment of THP-1 cells with an antioxidant, N-acetyl cysteine, suppressed the above HNE-induced responses and negated the HNE-mediated increase in TF activity. Blockade of p38 mitogen-activated protein kinase activation inhibited HNE-induced phosphatidylserine exposure and increased TF activity. CONCLUSIONS: HNE increases TF coagulant activity in monocytic cells through a novel mechanism involving p38 mitogen-activated protein kinase activation that leads to enhanced phosphatidylserine exposure at the cell surface.

Marginal zone B cells produce 'natural' atheroprotective IgM antibodies in a T cell-dependent manner.

AIMS: The adaptive immune response plays an important role in atherosclerosis. In response to a high-fat/high-cholesterol (HF/HC) diet, marginal zone B (MZB) cells activate an atheroprotective programme by regulating the differentiation and accumulation of 'poorly differentiated' T follicular helper (Tfh) cells. On the other hand, Tfh cells activate the germinal centre response, which promotes atherosclerosis through the production of class-switched high-affinity antibodies. We therefore investigated the direct role of Tfh cells and the role of IL18 in Tfh differentiation in atherosclerosis. METHODS AND RESULTS: We generated atherosclerotic mouse models with selective genetic deletion of Tfh cells, MZB cells, or IL18 signalling in Tfh cells. Surprisingly, mice lacking Tfh cells had increased atherosclerosis. Lack of Tfh not only reduced class-switched IgG antibodies against oxidation-specific epitopes (OSEs) but also reduced atheroprotective natural IgM-type anti-phosphorylcholine (PC) antibodies, despite no alteration of natural B1 cells. Moreover, the absence of Tfh cells was associated with an accumulation of MZB cells with substantially reduced ability to secrete antibodies. In the same manner, MZB cell deficiency in Ldlr-/- mice was associated with a significant decrease in atheroprotective IgM antibodies, including natural anti-PC IgM antibodies. In humans, we found a positive correlation between circulating MZB-like cells and anti-OSE IgM antibodies. Finally, we identified an important role for IL18 signalling in HF/HC diet-induced Tfh. CONCLUSION: Our findings reveal a previously unsuspected role of MZB cells in regulating atheroprotective 'natural' IgM antibody production in a Tfh-dependent manner, which could have important pathophysiological and therapeutic implications.

Factor VIIa bound to endothelial cell protein C receptor activates protease activated receptor-1 and mediates cell signaling and barrier protection.

Recent studies have shown that factor VIIa (FVIIa) binds to the endothelial cell protein C receptor (EPCR), a cellular receptor for protein C and activated protein C, but the physiologic significance of this interaction is unclear. In the present study, we show that FVIIa, upon binding to EPCR on endothelial cells, activates endogenous protease activated receptor-1 (PAR1) and induces PAR1-mediated p44/42 mitogen-activated protein kinase (MAPK) activation. Pretreatment of endothelial cells with FVIIa protected against thrombin-induced barrier disruption. This FVIIa-induced, barrier-protective effect was EPCR dependent and did not involve PAR2. Pretreatment of confluent endothelial monolayers with FVIIa before thrombin reduced the development of thrombin-induced transcellular actin stress fibers, cellular contractions, and paracellular gap formation. FVIIa-induced p44/42 MAPK activation and the barrier-protective effect are mediated via Rac1 activation. Consistent with in vitro findings, in vivo studies using mice showed that administration of FVIIa before lipopolysaccharide (LPS) treatment attenuated LPS-induced vascular leakage in the lung and kidney. Overall, our present data provide evidence that FVIIa bound to EPCR on endothelial cells activates PAR1-mediated cell signaling and provides a barrier-protective effect. These findings are novel and of great clinical significance, because FVIIa is used clinically for the prevention of bleeding in hemophilia and other bleeding disorders.

Lipoprotein receptor-related protein 1 regulates collagen 1 expression, proteolysis, and migration in human pleural mesothelial cells.

The low-density lipoprotein receptor-related protein 1 (LRP-1) binds and can internalize a diverse group of ligands, including members of the fibrinolytic pathway, urokinase plasminogen activator (uPA), and its receptor, uPAR. In this study, we characterized the role of LRP-1 in uPAR processing, collagen synthesis, proteolysis, and migration in pleural mesothelial cells (PMCs). When PMCs were treated with the proinflammatory cytokines TNF-α and IL-1ß, LRP-1 significantly decreased at the mRNA and protein levels (70 and 90%, respectively; P < 0.05). Consequently, uPA-mediated uPAR internalization was reduced by 80% in the presence of TNF-α or IL-1ß (P < 0.05). In parallel studies, LRP-1 neutralization with receptor-associated protein (RAP) significantly reduced uPA-dependent uPAR internalization and increased uPAR stability in PMCs. LRP-1-deficient cells demonstrated increased uPAR t(1/2) versus LRP-1-expressing PMCs. uPA enzymatic activity was also increased in LRP-1-deficient and neutralized cells, and RAP potentiated uPA-dependent migration in PMCs. Collagen expression in PMCs was also induced by uPA, and the effect was potentiated in RAP-treated cells. These studies indicate that TNF-α and IL-1ß regulate LRP-1 in PMCs and that LRP-1 thereby contributes to a range of pathophysiologically relevant responses of these cells.

Cystine 186-cystine 209 disulfide bond is not essential for the procoagulant activity of tissue factor or for its de-encryption.

Tissue factor (TF) on cell surfaces resides mostly in a cryptic state. It is not entirely clear how cryptic TF differs from procoagulantly active TF and how deencryption occurs. Here, we critically evaluated the importance of cystine 186-cystine 209 (Cys186-Cys209) bond formation for TF procoagulant activity and its de-encryption. Chinese hamster ovary cells transfected with TF(C186S), TF(C209S), or TF(C186S/C209S) expressed little procoagulant activity at the cell surface. TF monoclonal antibody and activated factor VII (FVIIa) binding studies showed that little TF protein was present at the cell surface in cells expressing mutant TF. Similar data were obtained in human umbilical vein endothelial cells (HUVECs) transduced to express TF(C186S), TF(C209S), or TF(C186S/C209S). Analysis of TF activity in HUVECs expressing similar levels of wild-type TF and TF(C186S/C209S) showed that TF mutant in the presence of saturating concentrations of FVIIa exhibited similar coagulant activity as that of wild-type TF. More importantly, treatment of HUVECs expressing TF(C186S/C209S) with HgCl(2) or ionomycin increased the cell-surface TF activity to the same extent as that of the wild-type TF. Our data provide clear evidence that TF lacking the Cys186-Cys209 bond is coagulantly active once it is complexed with FVIIa, and TF de-encryption does not require Cys186-Cys209 disulfide bond formation.

Tissue factor in COVID-19-associated coagulopathy.

Evidence of micro- and macro-thrombi in the arteries and veins of critically ill COVID-19 patients and in autopsies highlight the occurrence of COVID-19-associated coagulopathy (CAC). Clinical findings of critically ill COVID-19 patients point to various mechanisms for CAC; however, the definitive underlying cause is unclear. Multiple factors may contribute to the prothrombotic state in patients with COVID-19. Aberrant expression of tissue factor (TF), an initiator of the extrinsic coagulation pathway, leads to thrombotic complications during injury, inflammation, and infections. Clinical evidence suggests that TF-dependent coagulation activation likely plays a role in CAC. Multiple factors could trigger abnormal TF expression and coagulation activation in patients with severe COVID-19 infection. Proinflammatory cytokines that are highly elevated in COVID-19 (IL-1ß, IL-6 and TNF-α) are known induce TF expression on leukocytes (e.g. monocytes, macrophages) and non-immune cells (e.g. endothelium, epithelium) in other conditions. Antiphospholipid antibodies, TF-positive extracellular vesicles, pattern recognition receptor (PRR) pathways and complement activation are all candidate factors that could trigger TF-dependent procoagulant activity. In addition, coagulation factors, such as thrombin, may further potentiate the induction of TF via protease-activated receptors on cells. In this systematic review, with other viral infections, we discuss potential mechanisms and cell-type-specific expressions of TF during SARS-CoV-2 infection and its role in the development of CAC.

Identification of human immune cell subtypes most responsive to IL-1ß-induced inflammatory signaling using mass cytometry.

IL-1ß is a key mediator of the cytokine storm linked to high morbidity and mortality from COVID-19, and IL-1ß blockade with anakinra and canakinumab during COVID-19 infection has entered clinical trials. Using mass cytometry of human peripheral blood mononuclear cells, we identified effector memory CD4+ T cells and CD4-CD8low/-CD161+ T cells, specifically those positive for the chemokine receptor CCR6, as the circulating immune subtypes with the greatest response to IL-1ß. This response manifested as increased phosphorylation and, thus, activation of the proinflammatory transcription factor NF-κB and was also seen in other subsets, including CD11c+ myeloid dendritic cells, classical monocytes, two subsets of natural killer cells (CD16-CD56brightCD161- and CD16-CD56dimCD161+), and lineage- (Lin-) cells expressing CD161 and CD25. IL-1ß also induced a rapid but less robust increase in the phosphorylation of the kinase p38 as compared to that of NF-κB in most of these immune cell subsets. Prolonged IL-1ß stimulation increased the phosphorylation of the transcription factor STAT3 and to a lesser extent that of STAT1 and STAT5 across various immune cell types. IL-1ß-induced production of IL-6 likely led to the activation of STAT1 and STAT3 at later time points. Interindividual heterogeneity and inhibition of STAT activation by anakinra raise the possibility that assays measuring NF-κB phosphorylation in response to IL-1ß in CCR6+ T cell subtypes could identify those patients at higher risk of cytokine storm and most likely to benefit from IL-1ß-neutralizing therapies.

Cardiac resynchronization therapy reduces expression of inflammation-promoting genes related to interleukin-1ß in heart failure.

AIMS: In light of recent data regarding inflammatory signalling pathways in cardiovascular disease and the recently demonstrated impact of pharmacologic inhibition of interleukin-1ß (IL-1ß) in heart failure, the primary aim was to assess the physiologic effects of cardiac resynchronization therapy (CRT) on the expression of systemic inflammatory, immune-modulatory, metabolic, and apoptotic genes in peripheral blood mononuclear cells (PBMCs) of patients with heart failure. METHODS AND RESULTS: We used RNA sequencing (RNA-Seq) and reverse transcription quantitative real-time polymerase chain reaction (RT-qPCR) to identify gene expression changes in PBMCs in response to CRT. In total, 27 patients were analysed: 12 with heart failure undergoing CRT, 6 with heart failure undergoing standard implanted cardioverter defibrillators, and 9 with coronary artery disease but not heart failure. In CRT patients (median age 65.5 years, interquartile range 63.0-66.8 years, 33% female), RNA-Seq analysis identified 40 genes, including multiple genes associated with the IL-1ß pathway, with significant correlations (false discovery rate < 0.05) with four key CRT response measures. CRT was associated with suppression of PBMC expression of IL-1ß (1.80-fold decrease, P = 0.047), FOS proto-oncogene (FOS) (3.25-fold decrease, P = 0.01), dual specificity phosphatase 1 (DUSP1) (2.05-fold decrease, P = 0.001), and early growth response 1 (EGR1) (7.38-fold decrease, P = 0.03), and suppression was greater in responders vs. non-responders (P = 0.03 for IL-1ß, P = 0.02 for FOS, P = 0.02 for DUSP1, and P = 0.11 for EGR1). Baseline FOS and DUSP-1 levels were greater in responders vs. non-responders (6.15-fold higher, FOS, P = 0.002; 2.60-fold higher, DUSP1, P = 0.0001). CRT responders but not non-responders showed higher baseline gene expression of FOS (P = 0.04) and DUSP1 (P = 0.06) compared with control patients without heart failure. Baseline serum high-sensitivity C-reactive protein levels were 3.47-fold higher in CRT responders vs. non-responders (P = 0.008). CONCLUSION: Treatment of heart failure with CRT resulted in decreased PBMC expression of genes linked to inflammation. Moreover, CRT responders had higher expression of these inflammatory genes prior to CRT and greater suppression of these genes after CRT compared with non-responders.

Post-transcriptional, post-translational and pharmacological regulation of tissue factor pathway inhibitor.

: Tissue factor (TF) pathway inhibitor (TFPI) is an endogenous natural anticoagulant that readily inhibits the extrinsic coagulation initiation complex (TF-FVIIa-Xa) and prothrombinase (FXa, FVa and calcium ions). Alternatively, spliced TFPI isoforms (α, ß and δ) are expressed by vascular and extravascular cells and regulate thrombosis and haemostasis, as well as cell signalling functions of TF complexes via protease-activated receptors (PARs). Proteolysis of TFPI plays an important role in regulating physiological roles of the TF pathway in host defense and possibly haemostasis. Elimination of TFPI inhibition has therefore been proposed as an approach to improve haemostasis in haemophilia patients. In this review, we focus on posttranscription and translational modification of TFPI and its function in thrombosis and how pharmacological inhibitors and endogenous proteases interfere with TFPI and alter haemostasis.

Association of D-dimer with Plaque Characteristics and Plasma Biomarkers of Oxidation-Specific Epitopes in Stable Subjects with Coronary Artery Disease.

D-dimer has emerged as a biomarker of cardiovascular event risk, yet pathophysiological factors associated with plasma D-dimer levels in stable coronary artery disease (CAD) subjects are poorly understood. In 106 stable CAD subjects undergoing intravascular ultrasound with virtual histology (IVUS-VH), we measured D-dimer, lipoprotein(a) (Lp(a)), plasminogen, biomarkers reflecting oxidation-specific epitopes (OSE) such as oxidized phospholipids on apolipoprotein B-100 (OxPL-apoB), OxPL on plasminogen (OxPL-PLG), and autoantibodies to phosphorylcholine-BSA [PC-BSA] and a malondialdehyde [MDA] mimotope. In univariate analysis, D-dimer was positively associated with Lp(a), OxPL-apoB, OxPL-PLG, and coronary artery calcium, and inversely associated with autoantibodies to OSE and plaque fibrosis. D-dimer levels > 500 ng/ml also showed positive association with plaque necrosis. After multivariate analysis, D-dimer remained significantly associated with Lp(a) and plaque calcium. While further studies are needed, results provide evidence that plasma D-dimer levels are associated with levels of OxPLs and IVUS-VH indices linked to plaque erosion and rupture.

Possibility of membrane modification as a mechanism of antimony resistance in Leishmania donovani.

Resistance to antimonials has become a clinical threat in the treatment of visceral leishmaniasis (VL). Unravelling the resistance mechanism needs attention to circumvent the problem of drug resistance. In one of the resistant isolates, we earlier identified a gene (PG1) implicated in antimony resistance whose localization in the present study was confirmed on the pellicular plasma membrane of the parasite thereby indicating towards membrane modification as a mechanism of resistance in this resistant isolate.

Effect of additive selection on calculated aluminum content of parenteral nutrient solutions.

PURPOSE: The quantity of aluminum in common ingredients used to compound parenteral nutrient (PN) solutions was calculated to quantify the actual aluminum content, and opportunities to modify the aluminum content by changing the manufacturer of the ingredients were explored. METHODS: A retrospective evaluation of a random sample of 10 neonatal, 10 pediatric, and 10 adult patients who received PN solutions was performed to quantify the aluminum content in these solutions on the basis of the ingredients used at the authors' institution. A recalculation was performed using the lowest aluminumcontaining ingredients to determine the potential for aluminum minimization in each PN solution. RESULTS: Various manufacturers produce each ingredient required to make PN solutions. Significant variation exists among manufacturers, vial size, and concentrations. Statistically significant differences in the mean aluminum content of PN solutions before and after aluminum minimization were found to exist within each sample of patients. Among the neonatal PN solutions, aluminum content was significantly reduced from a mean +/- S.D. of 84.16 +/- 47.61 to 33.6 +/- 16.69 mug/kg/day. The pediatric PN solutions had a significant decline in aluminum content from a mean +/- S.D. of 16.24 +/- 3.66 to 6.84 +/- 2.66 mug/kg/day. Aluminum content in the high-risk adult PN solutions significantly decreased from a mean +/- S.D. of 4.58 +/- 2.06 to 2.31 +/- 0.63 mug/kg/day. CONCLUSION: There is wide variability in the aluminum concentration of injectable products used in the compounding of PN solutions. Selecting products with low aluminum concentration may substantially reduce the amount of the element administered to patients.

Inactivation of factor VIIa by antithrombin in vitro, ex vivo and in vivo: role of tissue factor and endothelial cell protein C receptor.

Recent studies have suggested that antithrombin (AT) could act as a significant physiologic regulator of FVIIa. However, in vitro studies showed that AT could inhibit FVIIa effectively only when it was bound to tissue factor (TF). Circulating blood is known to contain only traces of TF, at best. FVIIa also binds endothelial cell protein C receptor (EPCR), but the role of EPCR on FVIIa inactivation by AT is unknown. The present study was designed to investigate the role of TF and EPCR in inactivation of FVIIa by AT in vivo. Low human TF mice (low TF, ∼ 1% expression of the mouse TF level) and high human TF mice (HTF, ∼ 100% of the mouse TF level) were injected with human rFVIIa (120 µg kg(-1) body weight) via the tail vein. At varying time intervals following rFVIIa administration, blood was collected to measure FVIIa-AT complex and rFVIIa antigen levels in the plasma. Despite the large difference in TF expression in the mice, HTF mice generated only 40-50% more of FVIIa-AT complex as compared to low TF mice. Increasing the concentration of TF in vivo in HTF mice by LPS injection increased the levels of FVIIa-AT complexes by about 25%. No significant differences were found in FVIIa-AT levels among wild-type, EPCR-deficient, and EPCR-overexpressing mice. The levels of FVIIa-AT complex formed in vitro and ex vivo were much lower than that was found in vivo. In summary, our results suggest that traces of TF that may be present in circulating blood or extravascular TF that is transiently exposed during normal vessel damage contributes to inactivation of FVIIa by AT in circulation. However, TF's role in AT inactivation of FVIIa appears to be minor and other factor(s) present in plasma, on blood cells or vascular endothelium may play a predominant role in this process.

Role of tissue factor in Mycobacterium tuberculosis-induced inflammation and disease pathogenesis.

Tuberculosis (TB) is a chronic lung infectious disease characterized by severe inflammation and lung granulomatous lesion formation. Clinical manifestations of TB include hypercoagulable states and thrombotic complications. We previously showed that Mycobacterium tuberculosis (M.tb) infection induces tissue factor (TF) expression in macrophages in vitro. TF plays a key role in coagulation and inflammation. In the present study, we investigated the role of TF in M.tb-induced inflammatory responses, mycobacterial growth in the lung and dissemination to other organs. Wild-type C57BL/6 and transgenic mice expressing human TF, either very low levels (low TF) or near to the level of wild-type (HTF), in place of murine TF were infected with M.tb via aerosol exposure. Levels of TF expression, proinflammatory cytokines and thrombin-antithrombin complexes were measured post M.tb infection and mycobacterial burden in the tissue homogenates were evaluated. Our results showed that M.tb infection did not increase the overall TF expression in lungs. However, macrophages in the granulomatous lung lesions in all M.tb-infected mice, including low TF mice, showed increased levels of TF expression. Conspicuous fibrin deposition in the granuloma was detected in wild-type and HTF mice but not in low TF mice. M.tb infection significantly increased expression levels of cytokines IFN-γ, TNF-α, IL-6 and IL-1ß in lung tissues. However, no significant differences were found in proinflammatory cytokines among the three experimental groups. Mycobacterial burden in lungs and dissemination into spleen and liver were essentially similar in all three genotypes. Our data indicate, in contrast to that observed in acute bacterial infections, that TF-mediated coagulation and/or signaling does not appear to contribute to the host-defense in experimental tuberculosis.

Tissue factor encryption and decryption: facts and controversies.

Tissue factor (TF)-initiated coagulation plays a critical role in both hemostasis and thrombosis. It is generally believed that most of the tissue factor expressed on cell surfaces is maintained in a cryptic, i.e., coagulantly inactive state and an activation step (decryption) is required for the expression of maximum TF procoagulant activity. However, what exactly constitutes cryptic or procoagulant TF, molecular differences between these two forms and mechanisms that are responsible for transformation from one to the other form are not entirely clear and remain highly controversial, thus are a matter of ongoing debate. This brief review discusses pertinent literature on TF encryption/decryption with specific emphasis on the role of membrane phospholipids and reduction/oxidation of the TF Cys186-Cys209 disulfide bond in regulating TF activity at cell surfaces.

Tissue factor: mechanisms of decryption.

It is generally believed that only a small fraction of the tissue factor (TF) found on cell surfaces is active whereas the vast majority is cryptic in coagulation. It is unclear how cryptic TF differs from the coagulant active TF or potential mechanisms involved in transformation of cryptic TF to the coagulant active form. Exposure of phosphatidylserine (PS) in response to various chemical or pathophysiological stimuli has been considered as the most potent inducer of TF decryption. In addition to PS, TF self-association and association with specialized membrane domains may also play a role in TF decryption. It has been suggested recently that protein disulfide isomerase regulates TF decryption through its oxidoreductase activity by targeting Cys186-Cys209 disulfide bond in TF extracellular domain or regulating the PS equilibrium at the plasma membrane. However, this hypothesis requires further validation to become an accepted mechanism. In this article, we critically review literature on TF encryption/decryption with specific emphasis on recently published data and provide our perspective on this subject.

Mycobacterium tuberculosis infection and tissue factor expression in macrophages.

A number of earlier studies reported the occurrence of thrombotic complications, particularly disseminated intravascular coagulation and deep vein thrombosis, in tuberculosis (TB) patients. The aberrant expression of tissue factor (TF), the primary activator of coagulation cascade, is known to be responsible for thrombotic disorders in many diseases including bacterial infections. Further, expression of TF by cells of the monocyte/macrophage lineage is also shown to contribute to the development and progression of local and systemic inflammatory reactions. In the present study, we have investigated whether Mycobacterium tuberculosis (Mtb) infection induces TF expression in macrophages, and various host and pathogenic factors responsible for TF expression. We have tested the effect of live virulent Mtb H37Rv, gamma-irradiated Mtb H37Rv (γ-Mtb) and various components derived from Mtb H37Rv on TF expression in macrophages. The data presented in the manuscript show that both live virulent Mtb and γ-Mtb treatments markedly increased TF activity in macrophages, predominantly in the CD14(+) macrophages. Detailed studies using γ-Mtb showed that the increased TF activity in macrophages following Mtb treatment is the result of TF transcriptional activation. The signaling pathways of TF induction by Mtb appears to be distinct from that of LPS-induced TF expression. Mtb-mediated TF expression is dependent on cooperation of CD14/TLR2/TLR4 and probably yet another unknown receptor/cofactor. Mtb cell wall core components, mycolyl arabinogalactan peptidoglycan (mAGP), phosphatidylinositol mannoside-6 (PIM6) and lipomannan (LM) were identified as factors responsible for induction of TF in the order of mAGP>PIM6>LM. A direct contact between bacteria and macrophage and not Mtb-released soluble factors is critical for TF induction by Mtb. In summary, our data show that Mtb induces TF expression in macrophages and Mtb signaling pathways that elicit TF induction require cooperation of multiple receptors, co-receptors/co-factors including Toll-like receptors. The importance of TF in granuloma formation and containment of Mtb is discussed.

Translation of open reading frame in kinetoplast DNA minicircles of clinical isolates of L. donovani.

Till today, it remains an enigma whether the open reading frames said to be transcribed in minicircle sequences are indeed translated into protein products or not. We establish a protein-coding gene in minicircle variable region of kinetoplast DNA from clinical isolates of Leishmania donovani. The protein was expressed as an N-tagged green fluorescent protein (GFP) fusion protein in leishmanial expression system. Fluorescence microscopy of the transfectants carrying recombinant GFP construct showed the protein to be localized on the plasmalemma of the parasite. This shows that the minicircle transcript is indeed translated into a protein product in the parasite cell and further points toward probable biological function of minicircles in kinetoplastids.

Prokaryotic expression, purification, and polyclonal antibody production against a novel drug resistance gene of Leishmania donovani clinical isolate.

Diseases produced by protozoan parasites are one of the main causes of morbidity and mortality around the world, affecting millions of people. Among these, leishmaniasis has become the second most common cause of death and the problem is further complicated by the expansion of parasite resistance to the conventional drugs. The high rate of therapeutic failure thus calls for new rational approaches to develop alternative drugs. Understanding resistance mechanisms may help identify new targets for drug development. So we present here the cloning, expression, purification, and antibody production of a gene implicated in imparting resistance to pentavalent antimony (SbV) in clinical isolates of kala azar with a view to gain insight into the novel mechanism of its drug resistance.