Biomedical subjects

Kumkum Ganguly

Publications and source records attributed to Kumkum Ganguly.

9 recordsLinked to original sources

PubMed2007

The glycocalyx protects erythrocyte-bound tissue-type plasminogen activator from enzymatic inhibition.

Coupling tissue-type plasminogen activator (tPA) to carrier red blood cells (RBC) prolongs its intravascular life span and permits its use for thromboprophylaxis. Here, we studied the susceptibility of RBC/tPA to PA inhibitors including plasminogen activator inhibitor-1 (PAI-1) that constrain its activity and may reduce the duration of its effect. Despite lesser spatial and diffusional limitations, soluble tPA was far less effective than RBC/tPA in dissolving clots formed in vitro from blood of wild-type (WT) mice (40 versus 80% lysis at equal doses of tPA). Furthermore, after i.v. injection, soluble tPA lost activity faster in transgenic mice expressing a high level of PAI-1 than in WT mice, whereas the activity of RBC/tPA was unaffected. PAI-1 inactivated soluble tPA at equimolar ratios in vitro, but it had no effect on the amidolytic or fibrinolytic activity of RBC/tPA. RBC/tPA was also more resistant than soluble tPA to in vitro inhibition by other serpins (alpha2-macroglobulin and alpha1-antitrypsin) and pathologically high levels of glucose. However, coupling to RBC did not protect a truncated tPA mutant, Retavase, from plasma inhibitors. Chemical removal of the RBC glycocalyx negated tPA protection from inhibitors: tPA coupled to glycocalyx-stripped RBC bound twice as much 125I-PAI-1 as did tPA coupled to naive RBC, and susceptibility of the bound tPA to inhibition by PAI-1 was restored. Thus, the RBC glycocalyx protects RBC-coupled tPA against inhibition. Resistance to high levels of inhibitors in vivo contributes to the potential utility of RBC/tPA for thromboprophylaxis.

Animals↗

PubMed2006

Human complement receptor type 1-directed loading of tissue plasminogen activator on circulating erythrocytes for prophylactic fibrinolysis.

Plasminogen activators (PAs) are not used for thromboprophylaxis due to rapid clearance, bleeding, and extravascular toxicity. We describe a novel strategy that overcomes these limitations. We conjugated tissue-type PA (tPA) to a monoclonal antibody (mAb) against complement receptor type 1 (CR1) expressed primarily on human RBCs. Anti-CR1/tPA conjugate, but not control conjugate (mIgG/tPA), bound to human RBCs (1.2 x 10(3) tPA molecules/cell at saturation), endowing them with fibrinolytic activity. In vitro, RBC-bound anti-CR1/tPA caused 90% clot lysis versus 20% by naive RBCs. In vivo, more than 40% of anti-CR1/(125)I-tPA remained within the circulation ( approximately 90% bound to RBCs) 3 hours after injection in transgenic mice expressing human CR1 (TgN-hCR1) versus less than 10% in wild-type (WT) mice, without RBC damage; approximately 90% of mIgG/(125)I-tPA was cleared from the circulation within 30 minutes in both WT and TgN-hCR1 mice. Anti-CR1/tPA accelerated lysis of pulmonary emboli and prevented stable occlusive carotid arterial thrombi from forming after injection in TgN-hCR1 mice, but not in WT mice, whereas soluble tPA and mIgG/tPA were ineffective. Anti-CR1/tPA caused 20-fold less rebleeding in TgN-hCR1 mice than the same dose of tPA. CR1-directed immunotargeting of PAs to circulating RBCs provides a safe and practical means to deliver fibrinolytics for thromboprophylaxis in settings characterized by a high imminent risk of thrombosis.

Animals↗

PubMed2005

Fibrin affinity of erythrocyte-coupled tissue-type plasminogen activators endures hemodynamic forces and enhances fibrinolysis in vivo.

Plasminogen activators (PAs; e.g., tissue-type, tPA) coupled to red blood cells (RBCs) display in vivo features useful for thromboprophylaxis: prolonged circulation, minimal extravasation, and preferential lysis of nascent versus preexisting clots. Yet, factors controlling the activity of RBC-bound PAs in vivo are not defined and may not mirror the profile of soluble PAs. We tested the role of RBC/PA binding to fibrin in fibrinolysis. RBC/tPA and RBC/tPA variant with low fibrin affinity (rPA) bound to and lysed plasminogen-containing fibrin clots in vitro comparably. In contrast, when coinjected in mice with fibrin emboli lodging in pulmonary vasculature, only RBC/tPA accumulated in lungs, which resulted in a more extensive fibrinolysis versus RBC/rPA (p < 0.01). Reconciling this apparent divergence between in vitro and in vivo behaviors, RBC/tPA, but not RBC/rPA perfused over fibrin in vitro at physiological shear stress bound to fibrin clots and caused greater fibrinolysis versus RBC/rPA (p < 0.001). These results indicate that because of high fibrin affinity, RBC/tPA binding to clots endures hemodynamic stress, which enhances fibrinolysis. Behavior of RBC/PAs under hemodynamic pressure is an important predictor of their performance in vivo.

Animals↗

PubMed2005

Endothelial targeting of a recombinant construct fusing a PECAM-1 single-chain variable antibody fragment (scFv) with prourokinase facilitates prophylactic thrombolysis in the pulmonary vasculature.

Means to prevent thrombus extension and local recurrence remain suboptimal, in part because of the limited effectiveness of existing thrombolytics. In theory, plasminogen activators could be used for this purpose if they could be anchored to the vascular lumen by targeting stably expressed, noninternalized determinants such as platelet-endothelial-cell adhesion molecule 1 (PECAM-1). We designed a recombinant molecule fusing low-molecular-weight single-chain prourokinase plasminogen activator (lmw-scuPA) with a single-chain variable fragment (scFv) of a PECAM-1 antibody to generate the prodrug scFv/lmw-scuPA. Cleavage by plasmin generated fibrinolytically active 2-chain lmw-uPA. This fusion protein (1) bound specifically to PECAM-1-expressing cells; (2) was rapidly cleared from blood after intravenous injection; (3) accumulated in the lungs of wild-type C57BL6/J, but not PECAM-1 null mice; and (4) lysed pulmonary emboli formed subsequently more effectively than lmw-scuPA, thereby providing support for the concept of thromboprophylaxis using recombinant scFv-fibrinolytic fusion proteins that target endothelium.

Animals↗

PubMed2004

Blood clearance and activity of erythrocyte-coupled fibrinolytics.

Conjugating tissue-type plasminogen activator (tPA) to red blood cells (RBCs) endows it with features useful for thromboprophylaxis. However, the optimal intensity and duration of thromboprophylaxis vary among clinical settings. To assess how the intrinsic properties of a plasminogen activator (PA) affect functions of the corresponding RBC/PA conjugate, we coupled equal amounts of tPA or Retavase (rPA; a variant with an extended circulation time, lower fibrin affinity, and greater susceptibility to PA inhibitors). Conjugation to RBC markedly prolonged the circulation of each PA in rats and mice, without detrimental effects on carrier RBC. The initial blood clearance of RBC/tPA was faster than RBC/rPA, yet it exerted greater fibrinolytic activity, in part due to greater resistance of tPA and RBC/tPA to plasma inhibitors versus rPA and RBC/rPA observed in vitro. Soluble and RBC-coupled tPA and rPA exerted the same amidolytic activity, yet RBC/tPA lysed fibrin clots more effectively than RBC/rPA, notwithstanding comparable fibrinolytic activity of their soluble counterparts. Conjugation to RBC suppressed rPA's ability to be activated by fibrin, whereas the fibrin activation of RBC-coupled tPA was not hindered. Therefore, the functional profile of RBC/PA is influenced by: pharmacokinetic features provided by carrier RBC (e.g., prolonged circulation), intrinsic PA features (e.g., clearance rate, resistance to inhibitors), and changes imposed by conjugation to RBC (e.g., loss of cofactor stimulation). These factors, different from those guiding the design of soluble PA for lysis of existing clots, can be exploited in the rational design of RBC/PA tailored for specific prophylactic indications.

Animals↗

PubMed2004

Triflupromazine: a microbicide non-antibiotic compound.

The antipsychotic phenothiazine triflupromazine, possessing a methyl-thio substituent at position 10 and a fluorine moiety at position 2, exhibited significant antibacterial activity against 279 strains of Gram-positive and Gram-negative bacteria. The minimum inhibitory concentration (MIC) of the drug, according to the agar dilution method, was between 2 and 50 microg/ml for Staphylococcus aureus, and 5 and 100 microg/ml for shigellae and vibrios. Triflupromazine, when injected intraperitoneally into Swiss albino mice at a concentration of 30 microg/mouse (20 g), manifested a significant protection to the mice (p<0.001) when they were challenged with 50 median lethal dose (MLD) of Salmonella typhimurium NCTC 74. Moreover, there was a statistically significant reduction in the number of viable bacteria in organ homogenates and blood of mice treated with this phenothiazine compound.

Animals↗

PubMed2003

Antimicrobial potentiality of a new non-antibiotic: the cardiovascular drug oxyfedrine hydrochloride.

Ten cardiovascular drugs, having diverse pharmacological action, were screened for possible antimicrobial property against known eight sensitive bacteria, belonging to Gram positive and Gram negative types. Although five drugs failed to show antimicrobial activity and three had moderate antimicrobial action, oxyfedrine HCl and dobutamine were seen to possess pronounced antimicrobial property. Oxyfedrine was further tested in vitro against 471 strains of bacteria from two Gram positive and fourteen Gram negative genera. The minimum inhibitory concentration (MIC) of oxyfedrine was determined by agar dilution method, which ranged from 50-200 microg/ml in most of the strains, while some strains were inhibited at even lower concentrations. In animal experiments, this compound was capable of offering significant protection to Swiss strain of white mice, challenged with 50 median lethal dose (MLD) of a virulent strain of Salmonella typhimurium at concentrations of 15, 30 and 60 microg/mouse. The in vivo results were highly significant according to chi-square test.

Animals↗

PubMed2003

Amlodipine: a cardiovascular drug with powerful antimicrobial property.

Ten cardiovascular drugs were procured in pure form from their manufacturers in India and screened for antimicrobial property against fifteen known bacteria belonging to both gram-positive and gram-negative types. These bacteria were inhibited by the common antibiotics at 1-5 mg ml(-1) level through our earlier studies. Since most of the bacteria were moderate to highly responsive to amlodipine, this compound was further tested in vitro against 504 bacteria comprising 4 genera of gram-positive and 15 genera of gram-negative bacteria. Most of these were inhibited by the drug at 50-200 microg ml(-1) level and few strains were sensitive even at lower concentrations (10 microg ml(-1)). The bacteria could be arranged in the decreasing order of sensitivity towards amlodipine in the following manner: Staphylococcus aureus, Vibrio cholerae, Vibrio parahemolyticus, Shigella spp., Salmonella spp., Bacillus spp., whereas Escherichia coli, Klebsiella spp. and Pseudomonas aeruginosa were found to be resistant to the lower concentrations of the drug. Amlodipine was found to be bactericidal in nature when its mode of action was studied against S. aureus 6571, V. cholerae 14035 and Sh boydii 8 NCTC 254/66. The antibacterial activity of amlodipine could also be confirmed in vivo. When it was given to Swiss strain of white mice at different dosages (30 and 60 microg/mouse), it could significantly protect the animals challenged with 50 MLD of Salmonella typhimurium NCTC 74. According to Chi square test the in vivo data were highly significant (p<0.001).

Amlodipine↗

PubMedDate not supplied

Pronounced inhibitory effect of chlorcyclizine (CCZ) in experimental hepatocarcinoma.

Thepiperazine chlorcyclizine HCl (CCZ), possessing significant antimetabolic as well as virucidal and virustatic activities against the human immunodeficiency virus (HIV) and other retroviruses, was selected to determine its anticarcinogenic potential The anticancer activity of CCZ was evaluated against procarcinogen n-diethylnitrosamine (NDA)-initiated hepatocarcinogenesis, which was subsequently promoted by phenobarbital (PB) in male Sprague-Dawley rats. The anticancer efficacy of CCZ was monitored by estimating some potential markers of neoplastic and preneoplastic hepatic conditions, e.g., glutathione (GSH), glutathione-S-transferase (GST) and gamma-glutamyl transpeptidase (gammaGTP). CCZ exhibited antineoplastic activity on a long-term therapeutic basis. Furthermore, this drug restricted the exponential increase of the antioxidant markers in the hyperplastic nodule and the surrounding liver tissues in comparison with the carcinogen-controlled rats during the entire period of treatment. A decrease in the number of nodules was observed in the CCZ-treated group.

Animals↗