Antibacterial activity of resazurin-based compounds against Neisseria gonorrhoeae in vitro and in vivo.

Neisseria gonorrhoeae is the cause of the second most common sexually transmitted bacterial infection, with ca. 80 million new cases of gonorrhoea reported annually. The recent emergence of clinical isolates resistant to the last monotherapy against this bacterium, the cephalosporins, illustrates the need for new antigonococcal agents. Here we have characterised a new group of antimicrobials based on the compound resazurin that exhibits robust activity against N. gonorrhoeae in vitro. Resazurin inhibits the growth of a broad range of N. gonorrhoeae isolates, including those resistant to multiple antibiotics. Furthermore, treatment of human endometrial cells infected with N. gonorrhoeae with resazurin significantly reduces the number of intracellular bacteria. Whilst resazurin exhibited potent in vitro antimicrobial activity, in vivo resazurin did not limit the colonisation of mice with N. gonorrhoeae following vaginal infection. The ineffectiveness of resazurin in vivo is likely due to its interaction with serum albumin, which completely diminishes its antimicrobial activity. However, treatment of mice with a resazurin analogue (resorufin pentyl ether) that maintains its antimicrobial activity in the presence of serum albumin approached a significant decrease in the percentage of mice vaginally colonised. This treatment also decreased vaginal colonisation by N. gonorrhoeae over time. Together, these data suggest that resazurin derivatives have potential for the treatment of gonorrhoea.

Lovastatin inhibits oxidized L-A-phosphatidylcholine B-arachidonoyl-gamma-palmitoyl (ox-PAPC)-stimulated interleukin-8 mRNA and protein synthesis in human aortic endothelial cells by depleting stores of geranylgeranyl pyrophosphate.

Human aortic endothelial cells (HAEC) exposed to 50 microg/ml oxidized L-A-phosphatidylcholine B-arachidonoyl-gamma-palmitoyl (ox-PAPC) for 6h increased in interleukin-8 mRNA and protein levels. Preincubation of HAEC with the 3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) inhibitor, (20 microM), significantly inhibited ox-PAPC-stimulated interleukin-8 mRNA and protein levels. Mevalonate (200 microM) reversed the inhibition of ox-PAPC-stimulated mRNA and protein levels by lovastatin, indicating the inhibitory effect of lovastatin was due to inhibition of mevalonate synthesis. Addition of the geranylgeraniol (GGOL, 10 microM) but not farnesol (FOL, 10 microM), reversed the inhibitory effect of lovastatin on interleukin-8 mRNA and protein levels stimulated by ox-PAPC, indicating that lovastatin exerted its effect by inhibiting stores of geranylgeranyl pyrophosphate (GGPP) which are necessary for geranylgeranylation of proteins. These results suggest a new mechanism for lovastatin in preventing atherosclerosis by inhibiting the inflammatory response that takes place in the vascular wall.