Inhibitory Effects of 2-Benzoylamino-Benzoic Acid Analogues on Superoxide Anion and Elastase Release in Human Neutrophils

Neutrophils are known to play important roles in a host's defenses against invasion by microorganisms and in the pathogenesis of various diseases such as rheumatoid arthritis, ischemia-reperfusion injury, chronic obstructive pulmonary disease, and asthma. In response to diverse stimuli, activated neutrophils secrete a series of cytotoxins, such as the superoxide anion, a precursor of other reactive oxygen species, and granule proteases. Suppression of the extensive or inappropriate activation of neutrophils using drugs has been proposed as a way to ameliorate these inflammatory diseases. Despite this, there are only a few currently available agents that directly modulate neutrophil proinflammatory responses in clinical practice. Therefore, the research and development of new generation anti-inflammatory drugs continue as important targets. In a search for new anti-inflammatory agents, the effects of new synthetic compounds, 2-benzoylamino-benzoic acid analogues, on superoxide anion and elastase release by human neutrophils will be tested in this project. In the meantime, we will explore the novel mechanism of the potential candidates and evaluate their potentials as the lead compounds for the drug development in this field. In the preliminary experiments, we have examined fifty-six analogues of 2-benzoylamino-benzoic acid on the generation of superoxide and the release of elastase in formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP)-activated human neutrophils. Among these compounds, 1a and 5a showed potent and specific inhibition of superoxide anion generation in FMLP-activated human neutrophils. On the other hand, 9f, 9g, 9h, 9i and 9j showed potent and specific inhibition of elastase release in FMLP-activated human neutrophils. These inhibitory effects were not due to cytoxicity because culturing with these compounds did not cause lactate dehydrogenase release. Moreover, our preliminary results suggest that 1a and 5a are cAMP-elevating agents and 9f, 9g, 9h, 9i and 9j are direct inhibitors of human neutrophil elastase. Certainly, the mechanisms of action of these compounds will be further investigated in this project. On the basis of these preliminary findings, we therefore propose a three-year project to conduct studies in the following aspects: (i) to examine the pharmacological activities of 2-benzoylamino-benzoic acid analogues on generation of superoxide anion and release of elastase in human neutrophils; (ii) to investigate the respective roles of cAMP, calcium, PI3K, and MAPK signal transduction pathways in mediating the effects of 2-benzoylamino-benzoic acid analogues; (iii) to establish the structure activities relationships of 2-benzoylamino-benzoic acid analogues in neutrophil functions. These studies will provide new insight into the pharmacological functions of 2-benzoylamino-benzoic acid analogues and support the hypothesis that 2-benzoylamino-benzoic acid analogues may have the potential to protect against the progression of inflammatory diseases.

Project ID:PC9609-4321
External Project ID:NSC96-2628-B182-004-MY3