Inhibition of rat liver microsomal lipid peroxidation by N-acyldehydroalanines: an in vitro comparative study

Concise synthesis and voltammetric studies of dielsiquinone, a cytotoxic azaanthraquinone

We have developed a concise synthesis of dielsiquinone 1, a potent cytotoxic agent related to anthraquinones. Electrochemical studies have shown that dielsiquinone is reduced to a semiquinone radical that does not react with O2 to generate toxic reactive oxygen species. These results strongly suggest that 1 should be less cardiotoxic than anthracyclines used in clinic and may therefore provide the basis for the development of safer anticancer drugs.

Human cytochrome P450's are pro-oxidants in iron/ascorbate-initiated microsomal lipid peroxidation

We have examined the effect of human cytochrome P450's (1A1,1A2,3A4,2A6,2B6,2D6,2E1) on ascorbate/iron-induced lipid peroxidation. Using microsomes prepared from human lymphoblastic cells enriched in recombinant cytochrome P450 isoenzymes, we have shown that the degree of peroxidation is a function of the amount of P450 present rather than the presence of any specific isoenzyme. Incorporated P450 increased the amount of peroxidation products by up to 2.1-fold compared to the control microsomes with no P450. It is therefore concluded that cytochrome P450's play a significant role in ascorbate/iron peroxidation.

Radioprotective effects of the immunostimulating lauroylpeptide LtriP (RP 56142)

The lipopeptide lauroyl-L-Ala-gamma-D-Glu-L,L-A2pm (LtriP) increased the resistance of mice to the lethal effect of gamma-ray irradiation. The radioprotective effect was dependent on the doses of LtriP and of radiation. Maximum survival was observed when the lipopeptide was injected on two successive days before irradiation. This activity seems to be related to immunostimulating functions, since the non-immunostimulating analog lauroyl-L-Ala-gamma-D-Glu-D,D-A2pm-Gly, containing D,D-diaminopimelic acid, was not radioprotective. The protective activity might result from an induction of cytokines, such as IL-1, TNF and M-CSF, since LtriP induced the mRNA expression and the secretion of these immunomodulators.

Effects of N-acyl dehydroalanines on phorbol ester-elicited tumor development and other events in mouse skin

The free radical scavengers N-acyl dehydroalanines (AD compounds) were examined for their effect on several 12-O-tetradecanoylphorbol-13-acetate (TPA) elicited events in mouse skin. The induction of oxidant production by TPA in isolated mouse epidermal cells was reduced by approximately 70% by 1 mM paramethoxyphenyl-acetyl dehydroalanine (AD5) and 80% by 1 mM parasulfoxyphenyl-acetyl dehydroalanine (AD19). These AD compounds also completely suppressed the TPA-dependent stimulation of prostaglandin E2 synthesis in primary cultures of epidermal cells. Single and multiple topical applications on the dorsal skin of SENCAR mice of either AD5 or AD 19 inhibited TPA-induced epidermal hyperplasia but failed to inhibit epidermal ornithine decarboxylase induction. When used with TPA on initiated mice, AD19 did not inhibit papilloma formation; however, after 40 weeks of promotion, the carcinoma incidence was reduced by 50% in the AD19 group. These results suggest that reactive oxygens may be more important to the conversion of benign to malignant tumors than in the initial development of the benign tumors.

Increase in the survival time of mice exposed to ionizing radiation by a new class of free radical scavengers

N-acyl dehydroalanines react with and scavenge mainly superoxide radical (O-2.) and hydroxyl radical (HO.). The ortho-methoxyphenylacetyl dehydroalanine derivative, indexed as AD-20, protects mice against damage resulting from total body X-irradiation, as measured by the increase in their survival time. AD-20 increases the LD50 at 30 days from 6.1 to 7.3 Gy in animals exposed to a wide range of X-rays (6 to 10 Gy). The dose reduction factor (D R F) of AD-20 is 1.20. We postulate that such radioprotective effect may result from its free radical scavenging activity.

AD 5, a dehydroalanine derivative, decreases the amount of reactive oxygen species formed during nitrofurantion microsomal metabolism

N-acyl dehydroalanines have been shown to react with and scavenge oxygen derived free radicals. One of those compounds, the AD-5 (N-(paramethoxyphenylacetyl) dehydroalanine) has been examined for its ability to decrease the amount of reactive oxygen species which appeared when liver microsomes (isolated from rats pretreated with phenobarbital) are incubated in the presence of Nitrofurantoin (NF). This molecule was used as a model compound in order to stimulate the production of superoxide anion and hydrogen peroxide, as well as to enhance the oxidation of NADPH and the oxygen uptake. These two later parameters were not modified when adding AD-5 to microsomes incubated in the presence of NF. However, in such conditions the amount of both and hydrogen peroxide was decreased. These effects were dose-dependent. These data suggest that AD 5 inhibits the building up of superoxide and consequently the production of hydrogen peroxide. We postulate that AD-5 acting as an oxygen derived free radical scavenger, can be used to inhibit the oxidative injury induced by nitrofurantoin and other redox cycling drugs.