High affinity histamine-binding and antihistaminic activity of the salivary nitric oxide-carrying heme protein (nitrophorin) of Rhodnius prolixus.

Abstract

Summal'yThe salivary glands of Rhodnius prolixus contain a nitrosyl-heme protein, named nitrophorin, that releases the vasodilatory and antiplatelet compound nitric oxide (NO). Because imidazole compounds such as histamine can interact with Fe(III) heme proteins, we investigated whether such substances could interact with Rhodnius nitrophorins. Both imidazole and histamine, but not histidine can produce full change of the difference spectra of the Soret band in the 1-3 #M concentration range (at a heme protein concentration of 0.4 #M). The apparent Ko.5 for the binding of histamine with the heme protein is below 1 #M. Furthermore, the complex histamine-heme protein does not dissociate after molecular sieving chromatography. To investigate whether histamine could displace NO from the native nitrosyl nitrophorins, histamine was added to the native heme proteins, leading to displacement of the bound NO as observed by changes in the absorption spectra as well as by the production of nitrite. Finally, the antihistamine effect of the heme protein was demonstrated by its inhibition of the histamine-provoked contractures of the guinea pig ileum. It is concluded that histamine, a common autacoid found at the site of injury and exposure to antigenic substances such as the site of feeding by hematophagous arthropods, can be scavenged by the nitrosyl nitrophorin of R. prolixus, which, in return, will release the vasodilatory and platelet inhibiting NO to counteract the host hemostatic response.

Exploring the sialome of the blood-sucking bug Rhodnius prolixus

“…Several distinct nitrophorins (NP), which are hemecontaining lipocalins, carry nitric oxide (NO) from the salivary glands to the injured tissue, causing vasodilation and further inhibiting platelet aggregation Champagne et al, 1995). These NP also bind histamine with high affinity (Ribeiro and Walker, 1994;Andersen et al, 1998), and one, NP2, also inhibits the Xase complex of the intrinsic pathway of the blood coagulation cascade Zhang et al, 1998;Isawa et al, 2000). An additional lipocalin, biogenic amine binding protein (BABP), removes serotonin and adrenergic mediators of vasoconstriction (Andersen et al, 2003).…”

Effect of the N-Terminus on Heme Cavity Structure, Ligand Equilibrium, Rate Constants, and Reduction Potentials of Nitrophorin 2 from Rhodnius prolixus

“…WEFT-NOESY and HMQC spectra were obtained on a Bruker DRX-500 spectrometer operating at 500.03 MHz proton Larmor frequency and a Bruker DRX-600 spectrometer operating at 600.13 MHz. The 1 H- 13 C HMQC experiments were recorded using a 5 mm inverse-detection probe with decoupling during acquisition. A recycle time of 200 ms and refocusing time of 2.5 ms (J = 200) were used.…”

Recognition of Anionic Phospholipid Membranes by an Antihemostatic Protein from a Blood-Feeding Insect

“…Also, all NPs are capable of binding a molecule of histamine in the distal pocket after release of NO. It is thought that this process may serve an antiïnflammatory function during feeding (16).…”