PPM-18 is a chemically synthesized naphthoquinone derivative and an anti-inflammatory agent that inhibits the expression of inducible NO synthase (iNOS). NOS catalyzes the oxidation of the amino acid L-arginine to form NO. As an important cellular signaling molecule, NO has been implicated in modulating vascular tone, airway tone, insulinsecretion, and peristalsis. It has also been shown that NO is involved in angiogenesis and neural development and can function as a retrograde neurotransmitter
In vitro: Pretreatment of rat alveolar macrophages with PPM-18 (0.1-10 μM) significantly inhibited nitrite production, iNOS mRNA accumulation and iNOS protein expression. PPM-18 did not affect the enzymic activities of iNOS and other constitutive NOS forms directly. PPM-18 (10 μM) inhibited the LPS-induced increase in nuclear transcription factor κB (NF-κB) p65 and p50 in nucleus.. PPM-18 significantly decreased LPS-induced the production of tumour necrosis factor α [1]. PPM-18 inhibited NF-κB activation with an IC50 of 5 μM [3].
In vivo: In rats, intravenously pretreatment with PPM-18 (15 mg/kg) maintained a significantly higher mean arterial pressure compared with LPS-treated controls. PPM-18 protected mice against LPS-induced lethal toxicity. In mice, PPM-18 (5 or 15 mg/kg) dose-dependently decreased the lethality. In the mouse model of sepsis, PPM-18 exhibited as a potent inhibitor of iNOS expression by blocking the binding of NF-κB to promoter and exerted a beneficial effect [1].
References:
[1] YU M S, LIN J F W U T L, KUO C S. Inhibition of nitric oxide synthase expression by PPM-18, a novel anti-inflammatory agent, in vitro and in vivo[J]. Biochemical Journal, 1997, 328(2): 363-369.
[2] Beck K F, Eberhardt W, Frank S, et al. Inducible NO synthase: role in cellular signalling[J]. Journal of Experimental Biology, 1999, 202(6): 645-653.
[3] Davis, M. E.,Grumbach, I.M.,Fukai, T., et al. Shear stress regulates endothelial nitric-oxide synthase promoter activity through nuclear factor κB binding.The Journal of Biological Chemisty 279(1), 163-168 (2004).