Inhaled nitric oxide augments nitric oxide transport on sickle cell hemoglobin without affecting oxygen affinity
Mark T. Gladwin, Alan N. Schechter, James H. Shelhamer, Lewis K. Pannell, Deirdre A. Conway, Borys W. Hrinczenko, James S. Nichols, Margaret E. Pease-Fye, Constance T. Noguchi, Griffin P. Rodgers, Frederick P. Ognibene
Mark T. Gladwin, Alan N. Schechter, James H. Shelhamer, Lewis K. Pannell, Deirdre A. Conway, Borys W. Hrinczenko, James S. Nichols, Margaret E. Pease-Fye, Constance T. Noguchi, Griffin P. Rodgers, Frederick P. Ognibene
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Inhaled nitric oxide augments nitric oxide transport on sickle cell hemoglobin without affecting oxygen affinity

Abstract

Nitric oxide (NO) inhalation has been reported to increase the oxygen affinity of sickle cell erythrocytes. Also, proposed allosteric mechanisms for hemoglobin, based on S-nitrosation of β-chain cysteine 93, raise the possibilty of altering the pathophysiology of sickle cell disease by inhibiting polymerization or by increasing NO delivery to the tissue. We studied the effects of a 2-hour treatment, using varying concentrations of inhaled NO. Oxygen affinity, as measured by P50, did not respond to inhaled NO, either in controls or in individuals with sickle cell disease. At baseline, the arterial and venous levels of nitrosylated hemoglobin were not significantly different, but NO inhalation led to a dose-dependent increase in mean nitrosylated hemoglobin, and at the highest dosage, a significant arterial-venous difference emerged. The levels of nitrosylated hemoglobin are too low to affect overall hemoglobin oxygen affinity, but augmented NO transport to the microvasculature seems a promising strategy for improving microvascular perfusion.

Authors

Mark T. Gladwin, Alan N. Schechter, James H. Shelhamer, Lewis K. Pannell, Deirdre A. Conway, Borys W. Hrinczenko, James S. Nichols, Margaret E. Pease-Fye, Constance T. Noguchi, Griffin P. Rodgers, Frederick P. Ognibene

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Chemiluminescent detection of NO released from hemoglobin reacted in I3–...
Chemiluminescent detection of NO released from hemoglobin reacted in I3– before and after dose escalation of inhaled NO. NO signal is measured in millivolts (y-axis), and time is measured in seconds (x-axis). (a) Sample measurements before NO inhalation are shown. The first 2 peaks are from 200 μL of water collected from the G25 column immediately before use. The following 4 peaks are from 200 μL of lysed desalted hemoglobin from the venous (v) and arterial (a) blood injected in duplicate in alternating sequence. An arterial-venous difference is not appreciated, and the signal is very low (0.0035% moles NO per moles heme subunit; calculated by dividing the area under the curve [after subtraction from G25 water] from each injection by the concentration of hemoglobin in the sample, multiplied by 100). (b) The signal obtained after breathing 40 ppm NO gas for 1 hour. The venous (0.014%) and arterial (0.011%) nitrosylated hemoglobin levels have risen. (c) The signal obtained after breathing 60 ppm NO gas for 1 hour exhibits a difference between the arterial (0.02%) nitrosylated hemoglobin level and the venous (0.014%), although this difference was not observed in all patients studied. (d) Inhalation of 80 ppm NO further increased the arterial-venous difference (arterial 0.024% and venous 0.017%). This difference was observed in all 3 individuals studied.