Thalidomide as a Nitric Oxide Synthase Inhibitor and Its Structural Development

Abstract

Thalidomide has been found to exhibit weak nitric oxide synthase (NOS)-inhibitory activity. Structural development studies of thalidomide showed that some N-2,6-dimethylphenylhomophthalimide analogs possess NOS-inhibiting activity.Key words thalidomide; nitric oxide synthase (NOS); inhibitor; structural development Thalidomide (1) is a hypnotic/sedative drug that was withdrawn from the market because of its severe teratogenicity. [2][3][4] In spite of this, research into thalidomide was not halted, and the drug has since been established to be effective for the treatment of various diseases, including leprosy, myeloma and AIDS. [3][4][5] Although thalidomide affects production of various cytokines, the prevailing hypothesis was that the effectiveness of thalidomide in these diseases is elicited entirely through regulation of tumor necrosis factor (TNF)-a production.We have been engaged in structural development studies of thalidomide, and have demonstrated that thalidomide is in fact a multi-target drug. Our studies resulted in the creation of TNF-a production regulators (including bi-directional ones, as well as pure inhibitors and enhancers), 3,4,[6][7][8] androgen antagonists, 3,4,9,10) peptidase inhibitors, 4,[11][12][13][14][15] glucosidase inhibitors, 16,17) thymidine phosphorylase inhibitors 18) and cyclooxygenase inhibitors. 19,20) Nevertheless, not all of the beneficial pharmacological effects elicited by thalidomide can be fully interpreted in terms of the above activities, indicating the existence of other target molecules/phenomena. We suspected that nitric oxide synthase (NOS) might be another target molecule of thalidomide, because the drug is effective against diabetes and has hypoglycemic effect, whereas NO acts as disease-progressing factor.The family of nitric oxide synthases (NOS), which includes neuronal NOS (nNOS), endothelial NOS (eNOS) and inducible NOS (iNOS), 21) catalyzes the conversion of L-arginine to L-citrulline and nitric oxide (NO), an important cellular messenger molecule which has been implicated in both physiological and pathophysiological functions. In this paper, we describe evaluation of the NOS-inhibitory activity of thalidomide and its analogs.First we investigated NOS-inhibitory activity of thalidomide (1). Inhibitory activity was assayed by monitoring nitrite/nitrate production using Ichimori's protocol with a little modifications. 22,23) Although the quantitative values differed from experiment to experiment, the results were basically reproducible, and average inhibition rate are presented in Table 1. In the assay system, the IC 50 value of N G -nitro-L-arginine methyl ester (NNA, 2), which is a well-known analog of the endogenous NOS substrate, L-arginine, was determined to be 10 mM. The assay was performed in triplicate, and repeated at least three times. The result showed that thalidomide at 1 mM inhibits NOS by about 23% (Table 1). Although the NOS-inhibitory activity of thalidomide was weak, one or more of the thalidomide metabolites or decomposition products mig...

Effect of Thalidomide on Endotoxin-Induced Decreases in Activity and Expression of Hepatic Cytochrome P450 3A2

“…These results may be supported by the previous studies demonstrating that NOSinhibitory activity of thalidomide in vitro is weak. 26) Second, we examined the effects of thalidomide on the constitutive expression and endotoxin-induced down-regulation of CYP3A2 using Western blot analysis. This experiment revealed that thalidomide had no effect on the constitutive expression of CYP3A2, and the degree of the decreased protein levels of CYP3A2 was greater in endotoxin plus thalidomide-treated rats than that in endotoxin-treated rats, which can be agreed well with the results obtained from the antipyrine clearance experiment.…”

“…[17][18][19][20][21] There are interesting reports suggesting that thalidomide improves endotoxin-or alcohol-induced liver injury, 22,23) and prolongs the survival rate following the experimental sepsis induced by endotoxin or bacterial challenge in rats. 24,25) Shimazawa et al 26) have reported that thalidomide and its analogs have NO synthase (NOS)-inhibitory activity in vitro, but the activity of thalidomide is weak. Enomoto et al 27) reported that thalidomide abolishes the endotoxin-induced increase in CD14 expression in Kupffer cells in vitro.…”

Thalidomide as a Multi‐Template for Development of Biologically Active Compounds

“…Figure 8. LXR antagonistic activities of PP2P (7), PP50 (23), and 5CPPSS-50 (8) measured by means of reporter gene assay. Various concentration of the test compounds were added in the presence of 0.1 lM T0901317.…”

“…These findings suggested that thalidomide 1 is a multi-target drug, and this, in turn, implied the possible usefulness of thalidomide 1 as a template for development of various kinds of medicaments. In fact, various biologically active compounds, such as TNF-a production regulators (including bi-directional ones, pure inhibitors, and pure enhancers) [7,8], androgen antagonists [9 -11], aminopeptidase inhibitors [12 -15], a-glucosidase inhibitors [16 -18], thymidine phosphorylase inhibitors [19], cyclooxygenase (COX) inhibitors [20 -22], nitric oxide synthase (NOS) inhibitors [23,24], histone deacetylase (HDAC) inhibitors [25 -27], anti-angiogenic agents [28,29], tubulin polymerization inhibitors [30 -32], cell differentiation inducers [33], and liver X receptor (LXR) antagonists [34,35] have been developed based on the structure of thalidomide 1 ( Fig. 2 and 3).…”

“…3, i.e. TNF-a productionregulating activity [36,37], COX-inhibiting activity [20], NOS-inhibiting activity [23], and anti-angiogenic activity [29]. In addition, thalidomide 1 is a labile compound both metabolically and chemically.…”