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Hypoxia reoxygenation-induced injury of cultured pulmonary microvessel endothelial cells
M E Wiles1, H B Hechtman, N M Morel
1Microvascular Research Laboratory, Boston University, Massachusetts 02215.
Abstract:
Polymorphonuclear leukocyte (PMN) sequestration within the pulmonary microvasculature is known to occur in association with ischemia/reoxygenation (I/R). This sequestration is dependent on eicosanoids and reactive oxygen species. PMN sequestration within the lungs suggests that pulmonary microvascular endothelial cells (MECs) may in part regulate the I/R response. Simulating I/R, we examined the effect of hypoxia/reoxygenation (H/R) on pulmonary MECs in vitro, with and without PMNs. Significant cellular injury, assessed by 51Cr release, occurred upon reoxygenation of MECs (P < .01). Addition of PMNs to the H/R-injured monolayers did not increase MEC injury. Reoxygenation of MECs also resulted in increased thromboxane (Tx) B2 production compared to controls (P < .01). Inhibition of Tx secretion by aspirin reduced H/R-induced PMN adhesion to MECs (P < .01). Furthermore, H/R-induced increases in PMN-MEC adhesion were prevented by allopurinol and superoxide dismutase (P < .01). These data suggest that the pulmonary response to H/R is mediated by MEC generation of reactive oxygen radical species and Tx, which promotes increased PMN adhesion.
Insights
Pulmonary microvascular endothelial cells (MECs) generate reactive oxygen species and thromboxane during hypoxia/reoxygenation (H/R). This response increases polymorphonuclear leukocyte (PMN) adhesion, contributing to lung injury during ischemia/reoxygenation (I/R).
Area of Science:
- Pulmonary vascular biology
- Cellular injury mechanisms
- Inflammatory responses
Background:
- Polymorphonuclear leukocyte (PMN) sequestration in lung microvasculature is linked to ischemia/reoxygenation (I/R).
- Eicosanoids and reactive oxygen species mediate this PMN sequestration.
- Pulmonary microvascular endothelial cells (MECs) may play a role in regulating the I/R response.
Purpose of the Study:
- To investigate the effects of hypoxia/reoxygenation (H/R) on pulmonary MECs in vitro.
- To determine the role of MECs and PMNs in the pulmonary response to simulated I/R.
- To elucidate the mechanisms by which H/R affects MECs and PMN adhesion.
Main Methods:
- Cultured pulmonary MECs were subjected to hypoxia/reoxygenation (H/R) in vitro.
- Cellular injury was assessed using 51Cr release assay.
- Thromboxane B2 production was measured.
- PMN adhesion to MECs was quantified.
- Effects of aspirin, allopurinol, and superoxide dismutase on PMN adhesion were evaluated.
Main Results:
- Reoxygenation of MECs after hypoxia caused significant cellular injury.
- PMNs did not exacerbate H/R-induced MEC injury.
- H/R increased thromboxane B2 production by MECs.
- Inhibition of thromboxane secretion reduced H/R-induced PMN adhesion.
- Allopurinol and superoxide dismutase prevented H/R-induced increases in PMN-MEC adhesion.
Conclusions:
- Pulmonary MECs generate reactive oxygen species and thromboxane during H/R.
- These mediators promote PMN adhesion to MECs.
- MEC-derived mediators play a significant role in the pulmonary response to H/R and potentially I/R injury.