Antihypertensive and antibacterial investigations of novel nitric oxide donor compounds

Hills, Daniel; Mohseni, Maria; Dowler, Jan; Greenwood, Iain; Fielder, Mark; Pearson, Russell; Perumal, Dhaya

Abstract

Nitric oxide, being a free radical, has a unique biological chemistry that since its elucidation as a signalling molecule in the cardiovascular system has been implicated in diverse biological functions ranging from insulin secretion, nociception and angiogenesis. Both cardiovascular disease, exacerbated by hypertension, and antibiotic-resistant bacterial infections are major yet avoidable public health concerns. Aberrant NO may factor into these pathologies and exogenous NO may provide an alternative therapeutic strategy.

Twelve novel nitric oxide donor molecules of the furoxan class were developed through heterocyclic synthetic chemistry. These compounds have had their NO release characterised via the Griess spectrophotometric assay and have been investigated for both novel antibacterial activity and vasodilatory effects.

Direct toxicity was explored using an optimised MTT assay to assess cell viability post incubation in three bacterial species: Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa. Vasodilatory potential of the compounds was studied using rat thoracic aorta removed from humanely killed rats by cervical dislocation. The vessels were precontracted with an α-1 receptor agonist and dose-dependent relaxation was monitored through isometric tension changes.

Results demonstrate that these compounds elicit a toxic effect against all three bacteria which was enhanced in the presence of S-nitrosoglutathione, despite having negligible toxicity itself. This would indicate that NO indeed has an antimicrobial effect, either directly via biofilm inhibition or quorum sensing disruption or through interaction with such bacterial metabolites as superoxide to form cytotoxic agents such as peroxynitrite. The precise nature of this toxicity is under investigation. NO has also been detected from activated neutrophils through iNOS and the proposal that exogenous NO can enhance neutrophil-mediated bacterial death in vitro will be examined more closely using these compounds.

Isometric tension data show that three quarters of the compounds produced strong, sustained relaxation of contracted aorta, and two in particular caused almost complete reversal of contraction in concentrations of 250 and 350 nM respectively. Molecular inhibition studies will be employed to determine whether these compounds act solely via the sGC-cGMP pathway, and regional explorations using renal, pulmonary and mesenteric arteries will test for vessel selectivity. These compounds have the potential for clinical applications.

Citation

Hills, D., Mohseni, M., Dowler, J., Greenwood, I., Fielder, M., Pearson, R., & Perumal, D. (2014). Antihypertensive and antibacterial investigations of novel nitric oxide donor compounds. Nitric Oxide: Biology and Chemistry, 42, 126. https://doi.org/10.1016/j.niox.2014.09.082

• Journal Article Type: Article
• Online Publication Date: Nov 24, 2014
• Publication Date: Nov 15, 2014
• Deposit Date: Jun 8, 2023
• Journal: Nitric Oxide
• Print ISSN: 1089-8603
• Publisher: Elsevier
• Peer Reviewed: Not Peer Reviewed
• Volume: 42
• Pages: 126
• DOI: https://doi.org/10.1016/j.niox.2014.09.082
• Keywords: Cancer Research; Clinical Biochemistry; Physiology; Biochemistry; Nitric oxide; Furoxan; Antibacterial; Antihypertensive; Aorta; Neutrophil