Memantine Promotes Bactericidal Effect of Neutrophils Against Infection with Pseudomonas aeruginosa and Its Drug-Resistant Strain, by Improving Reactive Oxygen Species Generation

Pseudomonas aeruginosa is an opportunistic pathogen, which usually presents multiple antibiotic resistance. Host-directed therapy involves modulating the host defense system and the interplay between innate and adaptive immunity is a new strategy for designing anti-infection drugs. Memantine (MEM), a drug used to treat Alzheimer's disease, has a good inhibitory effect on neonatal mice with Escherichia coli-associated bacteremia and meningitis; however, the inhibitory effect and mechanisms of MEM against P. aeruginosa infection remain unclear. Here, we investigated whether MEM could inhibit P. aeruginosa infection and explored the potential mechanisms. MEM significantly promoted the bactericidal effect of neutrophils against P. aeruginosa and its drug-resistant strain. The combination index of MEM and amikacin (AMK) was <1. In vivo experiments showed that the bacteremia and inflammation severities in the MEM-treated group were less than those in the untreated group, and the bacterial load in the organs was significantly less than that in the control group. Combining MEM with the reactive oxygen species (ROS) inhibitor, N-acetyl-l-cysteine, weakened the anti-infective effect of MEM. MEM increased the expression of NADPH p67phox and promoted neutrophilic ROS production. Deleting the p67phox gene significantly weakened the effects of MEM on ROS generation and improving bactericidal effect of neutrophils. In conclusion, MEM promoted the bactericidal effect of neutrophils against P. aeruginosa and its drug-resistant strain, and had a synergistic antibacterial effect when combined with AMK. MEM may exert its anti-infective effects by promoting neutrophilic bactericidal activity via increasing the expression level of p67phox and further stimulating ROS generation.