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Direct and indirect effects of E. coli lipopolysaccharide on isolated human polymorphonuclear granulocytes and mixed
1Institute of Physiology, University of Oslo, Norway.
Abstract:
Polymorphonuclear neutrophil granulocytes (PMN) may contribute to the lung injury induced by nonpulmonary infections with gram-negative bacteria. The direct effect of E. coli lipopolysaccharide (LPS) on isolated human PMN or mixed leukocytes (ML), as well as the priming effect of preincubating cells with LPS, was examined in assays measuring the maximal rate of oxygen consumption (OC), cell chemiluminescence (CHML), and aggregation (AGG). LPS, 1-10 micrograms/ml, caused no acute response in PMN or ML suspended in Fisher's-HEPES medium with BSA (FHA), but increased both CHML and AGG of cells suspended in autologous plasma. Preincubation in FHA with LPS, 1 microgram/ml, for more than 15 min increased the OC of PMN activated with zymosan-activated plasma (ZAP) or n-formyl-methionyl-leu-cyl-phenylalanine (FMLP) by more than 100%. A similar increase in the CHML of such cells was seen after FMLP, but not after ZAP. ZAP, however, primed the CHML response of the cells to subsequent activation with FMLP more than did preincubation with LPS. Previous exposure to both agents had an additive effect. Preincubation of PMN with LPS decreased the time interval from addition of phorbol myristate acetate (PMA) to peak OC response, but less so than previous activation with FMLP. Neither agent affected the maximal rate of OC after addition of PMA. LPS also increased the PMN aggregation induced by ZAP and FMLP, but not by PMA. Cells preincubated with LPS, 0.01 microgram/ml, increased their CHML in response to FMLP if suspended in Krebs-Ringer balanced salt solution, but not if suspended in FHA. Such preincubation had no effect on OC of similarly activated cells in any of the media.
Insights
Escherichia coli lipopolysaccharide (LPS) primes human polymorphonuclear neutrophils (PMN) to enhance oxygen consumption and chemiluminescence. This priming effect, crucial for understanding lung injury from gram-negative bacterial infections, depends on the suspension medium and activation agents.
Area of Science:
- Immunology
- Cellular Biology
- Pathophysiology
Background:
- Polymorphonuclear neutrophil granulocytes (PMN) play a role in lung injury caused by gram-negative bacterial infections.
- Gram-negative bacteria release lipopolysaccharide (LPS), a potent immune stimulant.
- Understanding PMN responses to LPS is critical for managing sepsis-induced lung injury.
Purpose of the Study:
- To investigate the direct and priming effects of Escherichia coli lipopolysaccharide (LPS) on human PMN and mixed leukocytes (ML).
- To assess how LPS affects PMN oxygen consumption (OC), chemiluminescence (CHML), and aggregation (AGG).
- To determine the influence of different media and activation agents on LPS-induced PMN responses.
Main Methods:
- Isolated human PMN and ML were incubated with varying concentrations of LPS.
- Assays measured maximal oxygen consumption (OC), cell chemiluminescence (CHML), and aggregation (AGG).
- Cells were suspended in autologous plasma, Fisher's-HEPES medium with BSA (FHA), or Krebs-Ringer balanced salt solution and activated with zymosan-activated plasma (ZAP), n-formyl-methionyl-leu-cyl-phenylalanine (FMLP), or phorbol myristate acetate (PMA).
Main Results:
- LPS alone did not induce an acute response in PMN/ML in FHA but increased CHML and AGG in autologous plasma.
- Preincubation with LPS (1 µg/ml) in FHA significantly enhanced PMN OC (>100%) and CHML upon activation with FMLP or ZAP.
- LPS preincubation also increased PMN aggregation induced by ZAP and FMLP, and reduced the time to peak OC with PMA.
Conclusions:
- LPS acts as a priming agent for human PMN, enhancing their functional responses like oxygen consumption and aggregation.
- The priming effect of LPS is dependent on the suspension medium and the specific activating stimulus used.
- These findings highlight LPS's role in modulating PMN function, potentially contributing to inflammatory lung injury.