Korean J Med.
1999 Feb;56(2):174-181.
The effect of cytokines and endotoxin on the nitric oxide production and its relation to mitochondrial aconitase activity in cultured rat lung microvascular endothelial cells
- Affiliations
-
- 1Departments of Internal Medicine and Microbiology, Yonsei University College of Medicine, Seoul, Korea.
- 2Division of Respiratory, Critical Care and Occupational Pulmonary Medicine.
- 3Department of Medicine, Veterans Affair Medical Center and University of Utah School of Medicine, Salt Lake City, Utah 84132, U.S.A.
Abstract
OBJECTIVE
Both constitutive and inducible forms of nitric oxide synthase exist in endothelial
cells. Disorders that produce acute lung injury frequently release endotoxin and cytoknes,
such as interferon(IFNgamma) and tumor necrosis factor (TNFalpha). Endotoxin and these cytokines
likely act as important mediators of cell injury. Because nitric oxide (NO) avidly reacts with
iron, it may affect the activity of key enzymes, such as mitochondrial aconitase, which contain
an iron-sulfur structure as a prosthetic group.
METHOD: We studied the effect of IFNgamma, TNFalpha and E. coli lipopolysaccharide(LPS)
on NO production and mitochondrial aconitase activity in cultured rat lung microvascular endothelial cells(RLMVC).
RESULT: Exposing RLMVC for 24 hours to IFNgamma(500 U/mL), TNFalpha(300 U/mL) and LPS(5 microgram/mL)
significantly increases nitrite production to 20+/-1 micrometer compared to 0.07 micrometer in control
cells(P<0.05, n=4). Cytokine treatment also reduced mitochondrial aconitase activity from
196+/-8 to 102+/-34 nmole/min/mg of cell protein(P<0.05, n=4).
Treatment with the inhibitor of nitric oxide synthase N-monomethyl-L-arginine(NMMA) (0.5 mM) not
only significantly blunted the cytokine-mediated increase in nitrite formation (3+/-0.5 micrometer vs
20+/-1 micrometer with cytokines, P<0.05, n=4), but also prevented the cytokine-mediated drop in
aconitase activity (161+/- 24 vs. 196+/-8 nmole/min/mg of cell protein, NS).
CONCLUSION
Exposing RLMVC to IFNgamma, TNFalpha and E. coli LPS substantially decreases
mitochondrial aconitase activity. Nitric oxide appears to mediate this effect. Our results
suggest that the excessive production of NO by endothelial cells, in response to cytokines and
endotoxin, may inhibit the function of the endothelial cell itself.