Novel Anti‐inflammatories: Effect of Amidation Inhibitors on Inflammatory Pathways in Macrophages

Abstract

Chronic inflammation is responsible for numerous life‐threatening diseases. Substance P (SP), a pro‐inflammatory peptide, is synthesized by the post‐translational amidation of its glycine‐extended precursor (SP‐Gly). SP has been implicated in chronic inflammation along with inducible nitric oxide synthase (iNOS) and the cytokine TNF‐α. In primary mouse macrophages exogenous SP stimulates production of iNOS and cytokines, including TNF‐α, and enhances other stimulators such as the endotoxin LPS. Drugs designed to interfere with TNF‐α signaling have been shown to be an effective treatment for chronic inflammatory diseases. Therefore, elucidation of signaling pathways involving TNF‐α are of great importance to understanding and treating these diseases. We have previously shown that a prototypical amidation inhibitor, 4‐ phenyl‐3‐butenoic acid (PBA), and the ester of the highly potent amidation inhibitor, N‐acetyl‐(L)‐phenylalanylacrylic acid (NAPAA), are effective against chronic and acute rat models of inflammation, respectively. We report the effects of these amidation inhibitors on the activities of SP, SP‐Gly and LPS in inflammatory pathways in a commonly used macrophage‐like mouse cell line, RAW 264.7. We report that SP but not SP‐Gly stimulates TNF‐α production from RAW 264.7 macrophages, that PBA inhibits this SP stimulation and that NAPAA inhibits LPS stimulation of iNOS activity.