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Biomedical subjects

A Banerjee

Publications and source records attributed to A Banerjee.

At least 289 records · Page 16Linked to original sources
PubMed1995

Interleukin-8 increases endothelial permeability independent of neutrophils.

Interleukin-8 (IL-8) has been associated with a variety of hyperinflammatory states and adverse clinical events. Circulating IL-8 levels correlate with the severity of tissue trauma, and excessive elevations of IL-8 are associated with postinjury adult respiratory distress syndrome and multiple organ failure. While IL-8 is a potent neutrophil (PMN) chemoattractant and activator and enhances PMN transendothelial migration, it also acts to inhibit PMN adhesion to stimulated endothelial cells (ECs). We hypothesized that IL-8 could interact directly with ECs to increase permeability independent of PMNs. Human umbilical vein ECs (HUVECs) were cultured on collagen-coated micropore filters, and integrity of the EC monolayer measured by albumin flux across the filter. Cytochalasin D was used as a positive control. IL-8 induced increased permeability at a concentration of 1000 ng/mL. This effect was abrogated by preincubation of HUVECs with a protein synthesis inhibitor (cycloheximide). These data suggest a role for IL-8 in promoting endothelial leak independent of PMNs, via a mechanism involving protein synthesis.

Cell Membrane Permeability↗
PubMed1995

Early neutrophil sequestration after injury: a pathogenic mechanism for multiple organ failure.

Polymorphonuclear neutrophils (PMNs) play a pivotal role in the inflammation that precedes multiple organ failure (MOF). In a rat model of MOF, PMNs become primed for enhanced superoxide anion (O2-) release and CD11b expression, sequester in end organs, and produce organ failure. Therefore, we hypothesized that circulating PMNs harvested in the first 24 hours after injury from trauma patients at risk for MOF would (1) exhibit a primed O2- release, (2) upregulate CD11b expression, and (3) show evidence of sequestration in tissues. Extracellular PMN O2- release and CD11b receptor expression were measured at 3, 6, 12, and 24 hours after injury in 33 torso trauma patients with Injury Severity Scores > 15; eight patients (24%) developed MOF. Healthy adults served as controls. PMNs after injury were primed for enhanced in vitro O2- release at 3, 6, 12, and 24 hours after injury, indicating prior in vivo priming. CD11b expression was also increased at 6, 12, and 24 hours after injury. Circulating PMN numbers increased sharply at 3 hours after injury, before decreasing dramatically at 6 and 12 hours, suggesting end organ sequestration. At 12 hours after injury, declines in circulating PMNs were significantly greater in MOF than in non-MOF patients (p < 0.05). These data indicate that PMNs are quickly mobilized into the circulation after injury and then primed for enhanced O2- release and CD11b expression. PMN priming appears to be a necessary preamble to PMN sequestration in patients with major torso trauma. Upregulation of PMN function, accompanied by subsequent end organ sequestration, may represent an important early event in the pathogenesis of MOF after injury.

Adult↗
PubMed1995

Postinjury neutrophil priming and activation states: therapeutic challenges.

Both hyperactivity and hypoactivity of neutrophils (PMNs) have been implicated in the pathogenesis of postinjury multiple organ failure. In this paper, the cellular and molecular mechanisms involved in the regulation of PMN O2- production are reviewed. In addition, relevant research laboratory techniques for measuring both intracellular and extracellular O2- release are outlined. In a pilot study PMN O2- release in response to a battery of PMN agonists was determined, and four functional states of the NADPH were defined: resting, primed, activated, and unresponsive. PMNs from normal adult volunteers are in the resting state. In contrast, PMNs from patients with severe torso trauma are primed and activated in the first 24 h postinjury, but, after 48 h, become unresponsive to both receptor-dependent (platelet activating factor and N-formyl-methyl-leucyl-phenylalanine) and receptor-independent (phorbol 12-myristate 13-acetate) activation. The ability to identify at-risk patients and provide a rationale for ameliorating PMN-mediated tissue injury in patients with hyperinflammation syndromes are discussed. In addition, the importance of identifying patients with PMNs that are unresponsive, and the necessity for increasing PMN function in these patients in order to reduce the risk of sepsis, are also discussed.

Humans↗
PubMed1995

Gut phospholipase A2 mediates neutrophil priming and lung injury after mesenteric ischemia-reperfusion.

Intestinal ischemia-reperfusion (I/R) provokes polymorphonuclear neutrophil (PMN)-mediated lung injury via a process characterized by circulating PMN priming, pulmonary PMN sequestration, and increased microvascular leak in the lung. We found in rats subjected to intestinal I/R (ischemia 45 min and reperfusion 6 h) that 1) intestinal phospholipase A2 (PLA2) was activated during ischemia, 2) circulating PMN priming (assessed by superoxide production with N-formyl-Met-Leu-Phe) occurred after 1 h reperfusion, and 3) exaggerated 125I-labeled albumin lung leak occurred after 2 h reperfusion, compared with sham-treated animals (P < 0.05). Treatment with a PLA2 inhibitor, quinacrine, within 15 min of reperfusion reversed the exaggerated gut PLA2 activity and abrogated subsequent PMN priming and lung leak (P < 0.05). However, when quinacrine was administered after 2 h of reperfusion, circulating PMN priming and lung leak continued to evolve despite suppression of intestinal PLA2 activity. We conclude that intestinal PLA2 activation may be a prerequisite for the sequelae of circulating PMN priming and pulmonary microvascular leak observed after intestinal I/R.

Animals↗
PubMed1995

Quantifying oxidative injury in the liver.

Oxidative injury is a mechanism common to both ischemia-reperfusion (IR) and leukocyte-mediated injury. Reperfused tissue beds and elaborated mediators can activate a cascade of intercellular and interorgan injuries that often precipitates multiple organ failure. Initiation of lung injury by gut IR is a case in point, but concomitant liver injury may have been overlooked because of the absence of comparably sensitive physiological markers. In this study, we explore the hypothesis that occurrence of portally derived oxidant-induced liver dysfunction may be detected with both sensitivity and specificity. We simulated pure oxidative injury to the liver and separated the contributions from secondary systemic oxidation. Both tissue and plasma indicators were evaluated, each reflecting aspects of oxidation, membrane integrity, and metabolic function. Tissue markers readily detect oxidative liver injury, but systemic 3-hydroxybutyrate (3-OHB) concentration and ketone body ratio (KBR) are the most sensitive. Comparison of 3-OHB concentrations against the corresponding KBR can be used to distinguish adjustments within a physiological range from the transition into injury.

3-Hydroxybutyric Acid↗
PubMed1995

Role of bradykinin in cardiac functional protection after global ischemia-reperfusion in rat heart.

We have reported that cardiac preconditioning against ischemia-reperfusion (IR) can be induced by transient ischemia (TI) and alpha 1-adrenoreceptor stimulation, both mediated by protein kinase C (PKC) (Mitchell, M., X. Meng, C. Parker, E. Brew, A. Harken, and A. Banerjee. Circ. Res. 76: 73-81, 1995). Our study objective was to explore the mechanism of endogenous preconditioning and address the role of PKC activation in bradykinin-mediated cardiac functional protection. Isolated rat heart was used to assess the effects of exogenous bradykinin, TI, selective B2-receptor blocker, and PKC antagonism on cardiac functional recovery after a global IR injury. Final recovery of developed pressure was improved in hearts treated with bradykinin and TI compared with controls. Bradykinin- and TI-mediated preconditioning was eliminated with coinfusion of the B2-receptor antagonist. Further evaluation of bradykinin-mediated preconditioning revealed that PKC blockade also eliminated functional protection. Immunofluorescent stains of bradykinin-treated hearts demonstrated translocation and activation of specific PKC isoforms in the preconditioned heart. We conclude that TI-mediated preconditioning involves intrinsic cardiac bradykinin receptor stimulation. Bradykinin, through the B2 receptor, initiates a series of intracellular events culminating in the activation of PKC.

Animals↗
PubMed1995

Dysfunction of cGMP-mediated pulmonary vasorelaxation in endotoxin-induced acute lung injury.

Endothelial-dependent and -independent cGMP-mediated mechanisms of pulmonary vasorelaxation were studied in endotoxin-induced acute lung injury in the rat. Concentration-response curves were generated (10(-9) to 10(-6) M) for acetylcholine (ACh), A23187, and sodium nitroprusside (SNP) and for 8-bromoguanosine 3',5'-cyclic monophosphate (8-BrcGMP) (10(-9) to 10(-4) M) in isolated pulmonary arterial rings preconstricted with phenylephrine 6 h after endotoxin treatment (20 mg/kg ip). Endotoxin treatment produced significantly increased lung neutrophil accumulation (myeloperoxidase assay, 28 +/- 6 units/g lung tissue vs. 1.8 +/- 1 in controls) and lung leakage (lung/blood 125I-labeled albumin ratio, 0.06 +/- 0.01 vs. 0.028 +/- 0.01 in controls) as well as histological evidence of pulmonary vascular endothelial damage. The concentration-response curves demonstrated that pulmonary vasorelaxation by mechanisms that require generation of cGMP by either endothelial-dependent (both receptor-dependent, ACh, and receptor-independent, A23187) or endothelial-independent (SNP) pathways were significantly impaired after endotoxin treatment. Relaxation by stimulation with the cGMP analogue 8-BrcGMP was not different from control. Pulmonary vascular smooth muscle is able to relax in response to cGMP after endotoxin treatment, but relaxation by endothelial-dependent and -independent pathways that require generation of cGMP is significantly impaired.

Acetylcholine↗
PubMed1995

Preconditioning of isolated rat heart is mediated by protein kinase C.

Catecholamines have been implicated in the phenomenon of ischemic preconditioning. We have previously demonstrated that ischemic preconditioning against postischemic mechanical dysfunction in the isolated rat heart is mediated by the alpha 1-adrenergic receptor. The purpose of this study was to delineate the signal transduction of preconditioning distal to the alpha 1-adrenergic receptor. Our results suggest that (1) transient ischemia and alpha 1-adrenergic receptor-induced preconditioning is inhibited by protein kinase C (PKC) antagonists, (2) functional protection against global ischemia/reperfusion injury can be induced by infusion of diacylglycerol, the second messenger of the alpha 1-adrenergic pathway, and (3) transient ischemia and alpha 1-adrenergic preconditioning are both characterized by similar translocation of PKC-delta to the sarcolemma of myocardium. These findings suggest that PKC is an effector of preconditioning in the isolated rat heart.

Animals↗
PubMed1995

Rapid Mycobacterium species assignment and unambiguous identification of mutations associated with antimicrobial resistance in Mycobacterium tuberculosis by automated DNA sequencing.

OBJECTIVE: To develop and demonstrate the utility of automated DNA sequencing strategies for rapid and unambiguous identification of Mycobacterium species and mutations associated with antimicrobial resistance in Mycobacterium tuberculosis. DESIGN AND SPECIMENS: A 360-base pair segment of the gene (hsp65) encoding a 65-kd heat shock protein was characterized from 91 isolates assigned to 24 Mycobacterium species by traditional biochemical techniques. Areas of seven genes recently shown to contain mutations associated with antimicrobial resistance in M tuberculosis strains were also sequenced in a sample of 128 resistant organisms. Early positive BACTEC 460 cultures and acid-fast, bacterium-positive sputum specimens from patients with tuberculosis were also studied. RESULTS: Automated DNA sequencing identified species-specific polymorphism in the target segment of hsp65, successfully identified organisms to the species level in smear-positive sputum samples, and unambiguously characterized seven genes associated with antimicrobial resistance in M tuberculosis. CONCLUSIONS: Rapid identification of M tuberculosis and other Mycobacterium species is possible by automated DNA sequencing of a portion of hsp65. The technique is also feasible for analysis of some smear-positive sputum specimens. Unambiguous characterization of target segments of genes harboring mutations associated with antimicrobial resistance in M tuberculosis is possible from primary patient specimens. Taken together, the data demonstrate the feasibility of mycobacterial species identification and potential to identify mutations associated with antimicrobial resistance in less than 48 hours.

Alleles↗
PubMed1995

CD4+ T-cell responses to recombinant hsp65 and hsp18 of M. leprae and their trypsin-digested fragments in leprosy: diversity in HLA-DR restriction.

Mycobacterium leprae heat-shock proteins hsp65 and hsp18 have received immense attention as major T-cell target antigens in leprosy. Both of these hsps and their tryptic fragments were characterized for their ability to stimulate CD4+ T cells derived from polar leprosy cases and healthy contacts. The optimal digestion of hsps with trypsin yielded four fragments of hsp65--TDB65-1 (24 kDa), TDB65-2 (18 kDa), TDB65-3 (17 kDa), TDB65-4 (14 kDa)-- and three of hsp18--TDB18-1 (10 kDa), TDB18-2 (5 kDa), TDB18-3 (3 kDa). While all of these tryptic fragments and undigested hsps triggered CD4+ T cells from tuberculoid (TT) leprosy patients and healthy contacts (SI > 2), only two fragments--TDB65-2 and TDB18-3--were found to be stimulatory in anergic lepromatous (LL) leprosy patients (SI = 5.27 and 3.0, respectively). Blocking studies using allele-specific anti-DR monoclonal antibodies revealed multiple HLA-Dr restriction, with DR2 providing the strongest restriction in both TT as well as LL leprosy. These findings indicate that M. leprae hsps and their trypsin-digested fragments are promiscuous and recognizable in the context of diverse HLA alleles, of which DR2 is the most efficient restriction element. The 18-kDa fragment of hsp65 and the 3-kDa fragment of hsp18 are the most versatile fragments that could elicit in vitro proliferation in both polar forms of leprosy.

Antibodies, Monoclonal↗