Louis Levy

Effect of N-acetylcysteine on some aspects of cyclophosphamide-induced toxicity and immunosuppression.

Abstract Cyclophosphamide (CPA)-induced bladder toxicity and lethality were inhibited by N -acetylcysteine (NAC) when given systemically at a 4 : 1 ratio prior to CPA. This dose of NAC did not affect the production or the formation of free alkylating agents from CPA in vivo or in vitro . The immunosuppressive effect of CPA against T cell response systems, such as graft vs host reaction, antibody to sheep red blood cells and (PHA) phytohemagglutin stimulation was unaffected by NAC. It is concluded that the metabolic products of CPA for cytotoxicity as expressed as cystitis and lethality are different from the alkylating agents, which appear to affect immunological phenomena.

Effect of cyclophosphamide on a local graft-versus-host reaction in the rat: Influence of sex, disease and different dosage regimens

A new pharmacological method for screening potential immunosuppressive drugs, the local graft-versus-host reaction in rats, has been used to evaluate the efficacy of cyclophosphamide applied at varous times in the development of this reaction.This drug was relatively ineffective when applied to the F1 hybrid recipient of the graft cells (splenic lymphocytes) prior to grafting, rather more effective when given only to the parental donor prior to harvesting the graft cells, and most effective when given to the recipient either immediately after the graft or after a delay of three days.Biliary and hepatic metabolites of cyclophosphamide diminished the competence of parental lymphocytes to evoke the graft response. By contrast, cyclophosphamide itself was devoid of such activity in vitro. Non-enzymic decomposition (hydroxylation) of cyclophosphamide with the Udenfriend system (Fe++, ascorbate, EDTA) efficiently generated in vitro graft-deactivating agents.Fortified liver preparations from normal female rats formed alkylating metabolites at a much slower rate, and adjuvant-arthritic male rats were less capable of generating graft deactivating cyclophosphamide metabolites in vitro, than liver preparations from normal male rats. However cyclophosphamide appeared to be no less effective in normal female or arthritic male rats in vivo, than in normal male rats, in controlling the graft-versus-host response. This lack of correlation between rates of hepatic cyclophosphamide metabolism and evident bioefficacy as an immunosuppressive drug is discussed, with special reference to similar findings by Sladek concerning rates of bioactivation and anti-tumor efficacy.

The antiinflammatory action of some compounds with antioxidant properties.

Current concepts of the inflammatory process include the formation of oxidation products which have the ability to damage tissue. In a few selected inflammation models which included irritant and immunologic stimulus, some representative compounds with antioxidant activity were studied. A diverse set of responses were obtained, but consistently DPPD and ethoxyquin exhibited antiinflammatory activity. Although it cannot be categorically stated that antioxidant capability leads to antiinflammatory activity, it appears that these data provide a theoretical basis for modulating the inflammatory process.

Binding of Dapsone and Monoacetyldapsone by Human Plasma Proteins

Summary Binding of dapsone and monoacetyldapsone to human plasma proteins has been investigated by means of an ultrafiltration technique. When binding was studied in vivo or in vitro at therapeutic concentrations of the drugs, dapsone was 70 to 80% bound, and monoacetyldapsone 98 to 100%. Rapid and slow acetylators of dapsone bind both compounds to the same degree. Protein binding of monoacetyldapsone may well account for the limited excretion of this compound in the urine. The contribution of protein binding to the long plasma half-lives of these compounds must be evaluated in the light of future studies.

Minimal Inhibitory Concentration of Dapsone for Mycobacterium leprae in Rats

To define the minimal inhibitory concentration (MIC) of dapsone (DDS) for Mycobacterium leprae in rats, we determined the relationship between dietary and plasma levels of DDS in uninfected male and female Lewis rats. This knowledge was applied to the design of experiments using rats inoculated in the footpads with M. leprae. The MIC for DDS in male and female rats, respectively, was 1.5 to 4.0 ng and 1.8 to 3.0 ng of DDS/ml of plasma, even though the sexes exhibited markedly different concentrations of DDS when receiving the same dietary level of DDS. These values for the MIC of DDS for M. leprae in rats are nearly identical to the previously determined MIC of DDS for M. leprae in mice.

Characteristics of the binding of dapsone and monoacetyldapsone by serum albumin.

Summary The characteristics of binding of DDS and MADDS by HSA and of DDS by MPA have been studied by means of an equilibrium dialysis technique and analyzed by means of the Scatchard relationship. The plot of v/A vs v for each of the three studies yielded a straight line, suggesting only one species of binding site. Each molecule of HSA was found to possess one binding site for MADDS. Each molecule of MPA and HSA possessed 1/2 binding site for DDS, suggesting that DDS behaved as a bivalent molecule, and that one molecule of DDS was bound to two albumin molecules. The binding constant of HSA binding of MADDS was 10 times greater than the constant of HSA binding of DDS. The binding constants for DDS binding by both HSA and MPA were the same.

Mechanism by Which Hydnocarpic Acid Inhibits Mycobacterial Multiplication

Recent work in this laboratory has shown that hydnocarpic acid (HA), a principal constituent of chaulmoogra oil, inhibits multiplication in vitro of a number of mycobacterial species. This activity of HA was not shared by several straight-chain fatty acids and by dihydrochaulmoogric acid. A study of the interaction of HA with biotin has been undertaken, based on a structural analogy between biotin and the cyclopentenyl fatty acid. The multiplication of a strain of Mycobacterium intracellulare susceptible to 2 μg of HA/ml was measured turbidimetrically in Dubos medium, in the presence and absence of biotin and several other compounds. Biotin and, to a lesser extent, adenine plus guanine, palmitic acid, and linoleic acid antagonized growth inhibition by HA. Desthiobiotin, thioctic acid, and succinic acid did not block inhibition of bacterial multiplication by HA. HA may act by blocking the coenzymatic activity of biotin, or it may inhibit microbial biotin synthesis. Resumption of multiplication of M. intracellulare after a period of inhibition by HA in broth culture was found to be accompanied by reduction of the effective concentration of the drug; this could have resulted from metabolism of HA or production of an antagonist to HA by the organisms. Also, those organisms that multiplied in the presence of HA were found to represent HA-resistant mutants of M. intracellulare.

Activity of Derivatives and Analogs of Dapsone Against Mycobacterium leprae

Of 25 dapsone derivatives and analogs screened for activity against Mycobacterium leprae in the mouse footpad system, only 7 were active. All seven were metabolized to or contaminated with dapsone.

Death of Mycobacterium leprae in mice, and the additional effect of dapsone administration.

Summary If the assumptions be valid that the lag phase of bacterial multiplication is constant when M. leprae are repeatedly harvested from untreated mice and passed to other mice of the same inbred strain, and that those M. leprae capable of multiplying in the mouse foot pad do so always at the same rate, then the results of these experiments may be interpreted to show that once the peak of bacterial multiplication has been reached, death of M. leprae ensues. Death of M. leprae appears to have occurred in mice during DDS treatment at the same rate as in the untreated mice, but the lag phase of bacterial growth was uniformly prolonged as a result of treatment.

Recovery of the murine mononuclear phagocytic system following chronic exposure to cadmium

Consistent with our previously reported findings, chronic ingestion of cadmium chloride in drinking water by mice caused a decrease in the rate of circulation clearance of 51Cr-labeled sheep red blood cells (E) and IgG-coated E (E-IgG) due to a decrease in the localization of E and E-IgG in the liver. These decreases reached their nadirs after 15 weeks of cadmium ingestion and remained relatively constant for up to one year during continued ingestion of cadmium. Replacement of the drinking water containing cadmium with regular tap water resulted within 8 days in an improvement in the ability of the mice to clear E and E-IgG. Mice also had a decreased ability to develop delayed-type hypersensitivity reactions while being given cadmium; this abnormality also returned toward normal after withdrawal of cadmium. The return of these two responses toward control levels occurred while there was still a large organ burden of cadmium that was not measurably different from that at cessation of cadmium ingestion.