Ruthenium complexes as nitric oxide scavengers: a potential therapeutic approach to nitric oxide‐mediated diseases

• Published in: British journal of pharmacology Vol. 122; no. 7; pp. 1441 - 1449
• Main Authors: Fricker, S. P., Slade, Elizabeth, Powell, N. A., Vaughan, O. J., Henderson, G. R., Murrer, B. A., Megson, I. L., Bisland, S. K., Flitney, F. W.
• Format: Journal Article
• Language: English
• Published: Oxford, UK Blackwell Publishing Ltd 01-12-1997; Nature Publishing
• Subjects: Animals; Arteries - drug effects; Arteries - physiology; Biological and medical sciences; Blood Pressure - drug effects; Cardiovascular system; Cell Culture Techniques; Dose-Response Relationship, Drug; endotoxaemia; Endotoxemia - chemically induced; Hemodynamics - drug effects; hypotension; Hypotension - chemically induced; Hypotension - metabolism; Immunomodulators; Lipopolysaccharides - adverse effects; Male; Medical sciences; Mice; Miscellaneous; Nitric Oxide - metabolism; Nitric oxide scavengers; nitric oxide synthase; Nitric Oxide Synthase - drug effects; Nitric Oxide Synthase - metabolism; Nitric Oxide Synthase Type II; Organometallic Compounds - pharmacology; Penicillamine - analogs & derivatives; Penicillamine - pharmacology; Pharmacology. Drug treatments; Rats; Rats, Wistar; Ruthenium; ruthenium(III) polyaminocarboxylates; S-Nitroso-N-Acetylpenicillamine; vascular hyporeactivity; Vasodilator Agents - pharmacology; Intraperitoneal administration; Rat; Smooth muscle; Cellular immunity; Free radical; Blood vessel; Established cell line; Vasoconstrictor agent; Oxygen; Rodentia; Cardioprotective agent; Antioxidant; Muscle contraction; In vitro; Radical scavenger; Biological activity; Artery; In vivo; Vertebrata; Immunostimulant agent; Mammalia; Animal; Nitric oxide; Non specific immunity; Circulatory system; Inflammatory cell; Macrophage; Ruthenium complex
• ISSN: 0007-1188; 1476-5381
• DOI: 10.1038/sj.bjp.0701504

1
Ruthenium(III) reacts with nitric oxide (NO) to form stable ruthenium(II) mononitrosyls. Several Ru(III) complexes were synthesized and a study made of their ability to bind NO, in vitro and also in several biological systems following expression of the inducible isoform of nitric oxide synthase (iNOS). Here we report on the properties of two, related polyaminocarboxylate‐ruthenium complexes: potassium chloro[hydrogen(ethylenedinitrilo)tetraacetato]ruthenate (=JM1226; CAS no.14741‐19‐6) and aqua[hydrogen(ethylenedinitrilo)tetraacetato]ruthenium (=JM6245; CAS no.15282‐93‐6).
2
Binding of authentic NO by aqueous solutions of JM1226 yielded a product with an infrared (IR) spectrum characteristic of an Ru(II)‐NO adduct. A compound with a similar IR spectrum was obtained after reacting JM1226 with S‐nitroso‐N‐acetylpenicillamine (SNAP).
3
The effect of JM1226 or JM6245 on nitrite (NO2−) accumulation in cultures of macrophages (RAW 264 line) 18 h after stimulating cells with lipolysaccharide (LPS) and interferon‐γ (IFNγ) was studied. Activation of RAW264 cells increased NO2− levels in the growth medium from (mean±1 s.e.mean) 4.9±0.5  μM to 20.9±0.4 μM. This was blocked by actinomycin D (10 μM) or cycloheximide (5 μM). The addition of JM1226 or JM6245 (both 100 μM) to activated RAW264 cells reduced NO2− levels to 7.6±0.2 μM and 8.8±0.6 μM, respectively. NG‐methyl‐L‐arginine (L‐NMMA; 250 μM) similarly reduced NO2− levels, to 6.1±0.2 μM.
4
The effect of JM1226 or JM6245 on NO‐mediated tumour cell killing by LPS+IFNγ‐activated macrophages (RAW 264) was studied in a co‐culture system, using a non‐adherent murine mastocytoma (P815) line as the ‘target’ cell. Addition of JM1226 or JM6245 (both 100 μM) to the culture medium afforded some protection from macrophage‐mediated cell killing: target cell viability increased from 54.5±3.3% to 93.2±7.1% and 80.0±4.6%, respectively (n=6).
5
Vasodilator responses of isolated, perfused, pre‐contracted rat tail arteries elicited by bolus injections (10 μl) of SNAP were attenuated by the addition of JM1226 or JM6245 (10−4 M) to the perfusate: the ED50 increased from 6.0 μM (Krebs only) to 1.8 mM (Krebs+JM6245) and from 7 μM (Krebs only) to 132 μM (Krebs+JM1226). Oxyhaemoglobin (5 μM) increased the ED50 value for SNAP from 8 μM to 200 μM.
6
Male Wistar rats were injected with bacterial LPS (4 mg kg−1; i.p.) to induce endotoxaemia. JM1226 and JM6245 (both 100 μM) fully reversed the hyporesponsiveness to phenylephrine of tail arteries isolated from animals previously (24 h earlier) injected with LPS. Blood pressure recordings were made in conscious LPS‐treated rats using a tail cuff apparatus. A single injection of JM1226 (100 mg kg−1, i.p.) administered 20 h after LPS (4 mg kg−1, i.p.) reversed the hypotension associated with endotoxaemia.
7
The results show that JM1226 and JM6245 are able to scavenge NO in biological systems and suggest a role for these compounds in novel therapeutic strategies aimed at alleviating NO‐mediated disease states.