title: Nitroprusside inhibits calcium-induced impairment of red blood cell deformability.
abstract: BACKGROUND
  Red blood cell (RBC) deformation is critical for microvascular perfusion and oxygen delivery to tissues. Abnormalities in RBC deformability have been observed in aging, sickle cell disease, diabetes, and preeclampsia. Although nitric oxide (NO) prevents decreases in RBC deformability, the underlying mechanism is unknown.
  
  
  METHODS
  As an experimental model, we used ionophore A23187-mediated calcium influx in RBCs to reduce their deformability and investigated the role of NO donor sodium nitroprusside (SNP) and KCa3.1 (Gardos) channel blockers on RBC deformability (measured as elongation index [EI] by microfluidic ektacytometry). RBC intracellular Ca(2+) and extracellular K(+) were measured by inductively coupled plasma mass spectrometry and potassium ion selective electrode, respectively.
  
  
  RESULTS
  SNP treatment of RBCs blocked the Ca(2+) (approx. 10 μmol/L)-induced decrease in RBC deformability (EI 0.34 ± 0.02 vs. 0.09 ± 0.01, control vs. Ca(2+) loaded, p < 0.001; and EI 0.37 ± 0.02 vs. 0.30 ± 0.01, SNP vs. SNP plus Ca(2+) loaded) as well as Ca(2+) influx and K(+) efflux. The SNP effect was similar to that observed after pharmacologic blockade of the KCa3.1 channel (with charybdotoxin or extracellular medium containing isotonic K(+) concentration). In RBCs from KCa3.1(-/-) mice, 10 μmol/L Ca(2+) loading did not decrease cellular deformability. A preliminary attempt to address the molecular mechanism of SNP protection suggests the involvement of cell surface thiols.
  
  
  CONCLUSIONS
  Our results suggest that nitroprusside treatment of RBCs may protect them from intracellular calcium increase-mediated stiffness, which may occur during microvascular perfusion in diseased states, as well as during RBC storage.
authors.affiliation: Department of Anesthesiology/Critical Care Medicine, The Johns Hopkins Hospital; Molecular Dynamics Section, National Institute on Aging, National Institutes of Health; The Solomon H. Snyder Department of Neuroscience, Johns Hopkins University School of Medicine, Baltimore, Maryland.
authors.forename: Viachaslau
authors.initials: V
authors.lastname: Barodka
authors.forename: Joy G
authors.initials: JG
authors.lastname: Mohanty
authors.forename: Asif K
authors.initials: AK
authors.lastname: Mustafa
authors.forename: Lakshmi
authors.initials: L
authors.lastname: Santhanam
authors.forename: Aoibhinn
authors.initials: A
authors.lastname: Nyhan
authors.forename: Anil K
authors.initials: AK
authors.lastname: Bhunia
authors.forename: Gautam
authors.initials: G
authors.lastname: Sikka
authors.forename: Daniel
authors.initials: D
authors.lastname: Nyhan
authors.forename: Dan E
authors.initials: DE
authors.lastname: Berkowitz
authors.forename: Joseph M
authors.initials: JM
authors.lastname: Rifkind
mesh_terms: D000818:Animals; D001782:Blood Donors; D000001:Calcimycin / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism*; D061207:Calcium Ionophores / Q000494:pharmacology; D018999:Charybdotoxin / Q000494:pharmacology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004907:Erythrocyte Deformability / Q000187:drug effects*; D006801:Humans; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels / Q000037:antagonists & inhibitors* / Q000235:genetics; D019807:Iodoacetic Acid / Q000494:pharmacology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009498:Neurotoxins / Q000494:pharmacology; D009569:Nitric Oxide / Q000378:metabolism; D020030:Nitric Oxide Donors / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology
chemical_list: D061207:Calcium Ionophores; D004791:Enzyme Inhibitors; D051660:Intermediate-Conductance Calcium-Activated Potassium Channels; C496925:Kcnn4 protein, mouse; D009498:Neurotoxins; D020030:Nitric Oxide Donors; D018999:Charybdotoxin; D009599:Nitroprusside; D009569:Nitric Oxide; D000001:Calcimycin; D011188:Potassium; D002118:Calcium; D019807:Iodoacetic Acid