Inhibition of LDL oxidation and inflammasome assembly by nitroaliphatic derivatives. Potential use as anti-inflammatory and anti-atherogenic agents.

We have previously shown the antioxidant and anti-inflammatory properties of several para-substituted arylnitroalkenes. Since oxidative stress and inflammation are key processes that drive the initiation and progression of atherosclerosis, in the present work the antioxidant, anti-inflammatory and anti-atherogenic properties of an extended library of aryl-nitroaliphatic derivatives, including several newly designed nitroalkanes, was explored. The antioxidant capacity of the nitroaliphatic compounds, measured using the oxygen radical absorbance capacity assay (ORAC) showed that the p-methylthiophenyl-derivatives were about three times more effective than Trolox to prevent fluorescein oxidation, independently of the presence or the absence of the double bond next to the nitro group. The peroxyl radical scavenger capacity of the p-dimethylaminophenyl-derivatives was even higher, being the reduced form of these compounds even more active. In fact, while the antioxidant capacity of 1-dimethylamino-4-(2-nitro-1Z-ethenyl)benzene and 1-dimethylamino-4-(2-nitro-1Z-propenyl)benzene was 4.2 ±â€¯0.1 and 5.4 ±â€¯0.1 Trolox Eq/mol, respectively; ORAC values obtained with the ethyl and the propyl derivatives were 10 ±â€¯1 and 13 ±â€¯2 Trolox Eq/mol, respectively. The p-dimethylamino-derivatives, especially the nitroalkanes, were also able to prevent LDL oxidation mediated by peroxyl radicals. Oxygen consumption due to the oxidation of fatty acids was delayed in the presence of the dimethylamino substituted compounds, only the alkanes interrupted the chain of lipid oxidations decreasing the rate of oxygen consumption. Although the formation of foam cells in the presence of oxidized-LDL (oxLDL) remained unaffected, the molecules containing the dimethylamino moiety were able to decrease the expression of IL-1ß in LPS/INF-γ challenged macrophages.

Analgesic and Anti-Inflammatory Properties of Arylnitroalkenes.

In a recent work, we described the design and synthesis of arylnitroalkenes, able to scavenge macrophagederived oxidants, in particular peroxynitrite and peroxynitrite derived radicals. Four compounds emerged as potential leads, 1,1-dimethylamino-4-(2-nitro-1Z-ethenyl)benzene (1), 1,1-dimethylamino-4-(2-nitro-1Z-propenyl)benzene (2), 5- (2-nitro-1Z-ethenyl)benzo[d][1,3]dioxol (3), and 5-(2-nitro-1Z-ethenyl)benzo[d][1,3]dioxol (4). In the present work, the possibility of the preclinical validation of these molecules as anti-inflammatory and analgesic was explored in appropriate in vivo mouse models. Compounds 1, 2 and 4, administered orally as a single dose (30 µmol kg-(1)) to the mice showed anti-inflammatory and analgesic properties similar to classic nonsteroidal anti-inflammatory agents. The pharmacological effects were consistent with the inhibitory effect observed on prostaglandin endoperoxide H synthase (PGHS). In fact, both PGHS-1 and PGHS-2 were inhibited by the compounds, with compound 2 being more specific as PGHS-2 inhibitor with a specificity index superior to 70%. Conversely to classical nonsteroidal anti-inflammatory drugs, compound 2 inhibited peroxidase half reaction of the enzyme (IC50 2.3 µM) while the cyclooxygenase activity of hrPGHS-2 remained unchanged. In vitro experiments were reinforced by docking and molecular dynamics simulations showing arylnitroalkene moiety located in the region of the peroxidase active site, competing with the peroxide intermediate. The absence of toxicity and mutagenicity of the compounds was also demonstrated.

Arylnitroalkenes as scavengers of macrophage-generated oxidants.

Oxygen and nitrogen derived molecules mediated oxidation and nitration have been involved in several pathological conditions. Conversely, nitric oxide and hydrogen peroxide are important signalization intermediates, whose concentrations are tightly regulated by specialized enzyme repertoires and should remain undisturbed by the addition of exogenous antioxidant molecules, as already demonstrated by intervention studies with antioxidant vitamins. Our goal was to develop specific antioxidants able to scavenge peroxynitrite anion, as well the radicals derived from the homolytic decomposition of its conjugated acid, nitrogen dioxide and hydroxyl radical. Fourteen substituted nitroalkenes, seven 4-substituted 1-(2-nitro-1Z-ethenyl)benzene, and seven 4-substituted (2-nitro-1Z-propenyl)benzene, with different stereochemical and electronic characteristics were synthesized and tested. Compounds with the electron donor group N,N-dimethylamino showed the highest reaction rates against peroxynitrite, and also reacted with its homolytic decomposition products, OH and NO2. While 1,1-dimethylamino-4-(2-nitro-1Z-ethenyl)benzene came up as a lead for future developments without the risk of interfering with signalization pathways, since it was highly specific for peroxynitrite and peroxynitrite derived radicals, its methylated analogous 1,1-dimethylamino-4-(2-nitro-1Z-propenyl)benzene was less specific and also reacted with NO and O2(-), the biological precursor of H2O2.