Nitric oxide production in PMN

EFFECTS OF HYPEROXIA AND NITRIC OXIDE ON ENDOGENOUS NITRIC OXIDE PRODUCTION IN POLYMORPHONUCLEAR LEUKOCYTES

T Hoehn, A Gratopp, K Raehse, P Koehne

Background and Aims:

Exposure towards hyperoxia and nitric oxide (NO)occur frequently during the treatment of neonatal hypoxic pulmonary failure. Toanalyse the response of neonatal polymorphonuclear neutrophils (PMN) tohyperoxia and NO in vitro.

Methods:

Neonatal cord blood was exposed to100% oxygen, NO 20ppm plus 100% oxygen, and NO 20ppm for 30 minutes. Flowcytometry was used to quantify production of nitric oxide by measurement of theintracellular dye DAF-2 DA.

Results:

DAF-2 DA signals followingequilibration with room air were used as controls. Exposure to 100% oxygenincreased NO production significantly when compared to NO 20ppm plus 100% oxygen(p=0,031) and to NO 20ppm alone (p=0,006).

Conclusions:

Exposure ofhuman PMN cells to hyperoxia induces intracellular upregulation of endogenousNO production, whereas exposure to exogenous NO does not. Hyperoxia - whether incombination with NO or not – can lead to NO-induced apoptosis. This needs to betaken into account in the treatment of clinical conditions requiring highinspiratory concentrations of oxygen and/or inhaled NO.