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Sodium arachidonate induced in vitro polymorphonuclear leukocyte aggregation
Abstract:
Human polymorphonuclear leukocytes (PMNs) aggregated to sodium arachidonate (AA) in a dose dependent manner. Other agents such as epinephrine, or ADP were unable to initiate aggregation. The cells released lactate dehydrogenase (LDH) during aggregation, and electron microscopy demonstrated distinct morphologic changes in PMNs aggregated with AA. Indomethacin enhanced AA induced aggregation, whereas 1-methylimidazole inhibited aggregation and LDH release. Preincubation with cytochalasin B (CTB) did not enhance AA induced aggregation, nor did it reduce LDH release. Also, the effects of indomethacin or 1-methylimidazole on AA induced aggregation were unaltered by the presence of CTB. The results indicate that 1) LDH release occurs as a function of the aggregation process rather than a non-specific effect, 2) competition between cyclooxygenase and lipoxygenase occurs and 3) shifting this competition in favor of lipoxygenase enhances the PMN aggregation process.
Insights
Human polymorphonuclear leukocytes (PMNs) aggregate in response to arachidonic acid (AA), releasing lactate dehydrogenase (LDH). Modulating cyclooxygenase and lipoxygenase pathways impacts this aggregation process.
Area of Science:
- Immunology
- Cell Biology
- Biochemistry
Background:
- Human polymorphonuclear leukocytes (PMNs) play crucial roles in inflammatory responses.
- Arachidonic acid (AA) is a key fatty acid involved in cellular signaling and inflammation.
Purpose of the Study:
- To investigate the mechanism of PMN aggregation induced by sodium arachidonate (AA).
- To elucidate the role of cyclooxygenase and lipoxygenase pathways in AA-induced PMN aggregation and lactate dehydrogenase (LDH) release.
Main Methods:
- Dose-dependent aggregation assays using human PMNs and sodium arachidonate.
- Assessment of lactate dehydrogenase (LDH) release as a marker of cell integrity.
- Electron microscopy to visualize morphologic changes in aggregated PMNs.
- Pharmacological modulation using indomethacin (cyclooxygenase inhibitor) and 1-methylimidazole (lipoxygenase inhibitor).
- Investigation of cytochalasin B (CTB) effects on aggregation and LDH release.
Main Results:
- Sodium arachidonate induced dose-dependent PMN aggregation, unlike epinephrine or ADP.
- PMNs released LDH during AA-induced aggregation, with observed morphologic changes.
- Indomethacin enhanced AA-induced aggregation, while 1-methylimidazole inhibited it and LDH release.
- Cytochalasin B did not affect AA-induced aggregation or LDH release, nor did it alter the effects of indomethacin or 1-methylimidazole.
Conclusions:
- Lactate dehydrogenase (LDH) release is intrinsically linked to the PMN aggregation process induced by AA.
- A competitive interaction exists between cyclooxygenase and lipoxygenase pathways in regulating PMN aggregation.
- Shifting this balance towards lipoxygenase activity potentiates PMN aggregation.