Erythrocytic bioactivation of nitrite and its potentiation by far-red light

Abstract

BackgroundNitrite is reduced by heme-proteins and molybdenum-containing enzymes to form the important signaling molecule nitric oxide (NO), mediating NO signaling. Substantial evidence suggests that deoxygenated hemoglobin within red blood cells (RBCs) is the main erythrocytic protein responsible for mediating nitrite-dependent NO signaling. In other work, infrared and far red light have been shown to have therapeutic potential that some attribute to production of NO. Here we explore whether a combination of nitrite and far red light treatment has an additive effect in NO-dependent processes, and whether this effect is mediated by RBCs.Methods and resultsUsing photoacoustic imaging in a rat model as a function of varying inspired oxygen, we found that far red light (660 nm, five min. exposure) and nitrite feeding (three weeks in drinking water at 100 mg/L) each separately increased tissue oxygenation and vessel diameter, and the combined treatment was additive. We also employed inhibition of human platelet activation measured by flow cytometry to assess RBC-dependent nitrite bioactivation and found that far red light dramatically potentiates platelet inhibition by nitrite. Blocking RBC-surface thiols abrogated these effects of nitrite and far-red light. RBC-dependent production of NO was also shown to be enhanced by far red light using a chemiluminescence-based nitric oxide analyzer. In addition, RBC-dependent bioactivation of nitrite led to prolonged lag times for clotting in platelet poor plasma that was enhanced by exposure to far red light.ConclusionsOur results suggest that nitrite leads to the formation of a photolabile RBC surface thiol-bound species such as an S-nitrosothiol or heme-nitrosyl (NO-bound heme) for which far red light enhances NO signaling. These findings expand our understanding of RBC-mediated NO production from nitrite. This pathway of NO production may have therapeutic potential in several applications including thrombosis, and, thus, warrants further study.

Impaired Fibrinolysis in Patients with Isolated Aortic Stenosis is Associated with Enhanced Oxidative Stress

“…This methodological difference might justify why oxidative stress has a crucial effect on impaired fibrinolysis in AS despite the various demographic and laboratory determinants of prolonged lysis time between these assays (Siudut et al manuscript in review). The assay by Pieters et al that was introduced in 2019 and supported by the International Society on Thrombosis and Hemostasis Subcommittee has been used in a few studies [ 23 , 25 , 26 ] and is known to be more sensitive to endogenous PAI-1 levels, especially in both hypofibrinolytic and/or hyperfibrinolytic conditions [ 27 ]. On the other hand, the Lys50 assay has been previously applied in studies investigating fibrinolytic capacity in patients with metabolic syndrome, including diabetes mellitus [ 24 ].…”

“…The oxidative modification of the plasma proteins was assessed based on carbonyl content, using 2,4-dinitrophenylhydrazine (DNPH; AppliChem, Darmstadt, Germany), as reported previously [ 25 ]. Briefly, DNPH reacts with protein carbonyls (PC), forming a Schiff base to form the corresponding hydrazone.…”

Carbonic anhydrase II does not regulate nitrite‐dependent nitric oxide formation and vasodilation

“…Our current finding that deletion of CAII gene did not affect the effects of nitrite on platelet activation and vasodilation provides further evidence that CAII is not responsible for nitrite bioactivation in red blood cells, vessel walls, and circulation. Moreover, inhibition of erythrocytic CAII by its inhibitor, dorzolamide, had no significant effect on NO production from RBCs, which further excludes the role of CAII and supports that deoxygenated haemoglobin within red blood cells is the main erythrocytic protein responsible for mediating nitrite-dependent NO signalling (Liu et al, 2015;Wajih et al, 2019). It should be noted that CAII inhibitors are used in a wide variety of clinical conditions to treat hypertension-related diseases (Swenson, 2014), which is incompatible with the role of CAII mediating NO formation as well.…”

Estimation of the influence of photobiomodulation on the endothelial function in patients with arterial hypertension under the conditions of hyperuricemia

“…Таким чином, гемоглобін виступає у ролі нітроредуктази, яка приймає участь у гіпоксичний вазодилятації. У 2019 році у спільному дослідженні провідних наукових центрів США був виявлений ефект біоактивації гемоглобіну еритроцитів світловим випромінюванням з довжиною хвилі 660 нм з наступним вивільненням NO [9]. У пацієнтів з гіпертензією без підвищення рівня сечової кислоти після проведення антигіпертензивної терапії відбулося зниження лише швидкості пульсової хвилі.…”