Safety evaluation of 5-hydroxytryptophan and S-(2-aminoethyl)isothiouronium bromide hydrobromide on rodent lungs

OBJECTIVES

During the past few decades, various compounds have been researched for their potential as radioprotectants, and many of them were found to be safe and effective in several preclinical models. However, many of these compounds were found to have serious adverse effects when evaluated in clinical settings, thereby making them unsuitable for human applications. 5-hydroxytryptophan (5-HTP) and S-(2-aminoethyl) isothiouronium bromide hydrobromide (AET) act in a synergistic fashion to promote radioprotection. The present study primarily emphasizes the safety of fixed dose of 5-HTP + AET in the lungs of C57BL/6 mice, a well-known model used in drug safety studies.

MATERIALS AND METHODS

Post-administration of the combination of HTP+AET at specific time points, blood and bronchoalveolar lavage fluid (BALF) were collected for the analysis of inflammatory and oxidative stress markers of the lungs. Thereafter, the mice were sacrificed and the lungs were dissected out, weighed, and fixed in formalin for histopathological studies.

RESULTS

The inflammatory biomarkers: tumor necrosis factor-alpha and interleukin-10 and oxidative stress biomarkers: 8-isoprostane and 8-hydroxy-2'-deoxyguanosine were found to have normal levels in blood and BALF in both control and treatment groups, which was further supported by normal histological findings. In addition, other endpoints such as food and water intake were found to be within normal limits.

CONCLUSION

The present safety study reflects that the combination has no adverse effects on the lungs of the experimental mouse. Further, evaluation in higher mammals including nonhuman primates is essential prior to validation of the safety of the combination in humans.

THE EHRLICH ASCITES CARCINOMA AS A TOOL FOR THE RAPID EVALUATION OF THE EFFICACY OF RADIOPROTECTIVE COMPOUNDS AT THE CELLULAR LEVEL

A simple, rapid quantitative method for biologically evaluating radioprotective compounds at the cellular level has been developed by means of Ehrlich mouse ascites tumor cells. The cells were irradiated in vitro and subsequently grown in vivo and the radioprotective compound was evaluated by its ability to prevent mitotic arrest and loss of proliferative capacity in the cells. Results statistically significant at the 1% level were available in 48 hours when groups of 15 mice per sample were compared. L-Cysteine was found to be a better protector than 2-aminoethylisothiouronium bromide hydrobomide or 2-mercaptoethylamine and also increased the protection of cells irradiated under anaerobic conditions.

Characterization of the complement sensitivity of paroxysmal nocturnal hemoglobinuria erythrocytes

The affected erythrocytes of paroxysmal nocturnal hemoglobinuria (PNH II and PNH III cells) are abnormally sensitive to complement-mediated lysis. Normal human erythrocytes chemically modified by treatment with 2-amino-ethylisothiouronium bromide (AET) have been used as models for PNH cells inasmuch as they also exhibit an enhanced susceptibility to complement. To investigate the bases for the greater sensitivity of these abnormal cells to complement-mediated lysis, we compared binding of C3 and constituents of the membrane attack complex to normal, PNH II, PNH III, and AET-treated cells after classical pathway activation by antibody and fluid-phase activation by cobra venom factor complexes. When whole serum complement was activated by antibody, there was increased binding of C3 and C9 to PNH II, PNH III, and AET-treated cells, although the binding of these complement components to PNH II and PNH III cells was considerably greater than their binding to the AET-treated cells. In addition, all of the abnormal cell types showed a greater degree of lysis per C9 bound than did the normal erythrocytes. PNH III and AET-treated cells were readily lysed by fluid-phase activation of complement, whereas normal and PNH II erythrocytes were not susceptible to bystander lysis. The greater hemolysis of PNH III and AET-treated cells in this reactive lysis system was due to a quantitative increase in binding of constituents of the membrane attack complex. This more efficient binding of the terminal components after fluid-phase activation of whole serum complement was not mediated by cell-bound C3 fragments. These investigations demonstrate that the molecular events that characterize the enhanced susceptibility of PNH II, PNH III, and AET-treated erythrocytes to complement-mediated lysis are heterogeneous.

Use of a modified procedure for treating small amounts of red blood cells with 2-aminoethylisothiouronium bromide

Kell null red blood cell samples can be prepared using 2-aminoethylisothiouronium bromide (AET). This article describes a modification whereby only three drops of a 5% red blood cell suspension may be AET treated. This procedure has been used routinely in the authors' laboratory for more than a year. One patient's serum contained anti-Kpb plus anti-C and anti-D. Tests with panel cells pretreated with AET made it possible to identify underlying Rh antibodies without using a panel of genetic Kpb negative red blood cells. Of 24 red blood cell eluates from patient sample with warm autoantibodies, one had specificity within the Kell blood group system. This small volume AET-treatment method is a quick screen for the differentiation of a Kell-related specificity from a non-Kell specificity of both warm autoantibodies and alloantibodies to high-incidence antigens.

A further example of the low frequency antigen Pta

The third Pt(a+) family is described and it has been shown that the red cell antigen is denatured when treated with proteolytic enzymes, but unaffected by neuraminidase and 2-aminoethylisothiouronium bromide treatment.

Rosette forming T-lymphocyte levels in the peripheral blood of cattle affected with squamous cell carcinoma of horn

The level of thymus-derived lymphocytes was assessed by determining the per cent of cells which formed non-immune rosettes with 2-Aminoethyl isothiouronium bromide treated sheep erythrocytes in the peripheral blood of 20 (14 bullocks and 6 cows) histopathologically confirmed cases of bovine squamous cell carcinoma of horn (horn cancer) and an equal number of age-matched control animals. A significantly marked (P less than 0.01) depression in the per cent erythrocyte-rosette forming cell count was observed in horn cancer affected bullocks and cows as compared to the values in unaffected control animals. The decrease in the level of these cells was comparatively more marked in animals which were clinically in advanced stages of the disease.

A comparative study of procedures for sheep erythrocyte-human-T-lymphocyte rosette formation

A comparative study of several published methods for sheep red blood cell-T-lymphocyte rosette formation was performed. Maximum SRBC-rosette formation occurred with AET treated SRBC in medium supplemented with 20% FCS or with untreated SRBC in 100% FCS. Prolongation of the 4 degrees C incubation period from 4 to 18 h enchanced rosette formation. Fluorescein diacetate staining significantly increased calculated percentage of rosette formation. Fluorescein diacetate staining significantly increased calculated percentage of rosette-forming lyphocytes by allowing accurate indentification of the central lymphocytes in morulas.

A case of small-cell Sézary's syndrome with null-cell features

A case of the small-cell variant of Sézary's syndrome (SS) is reported in which the SS cells lacked the surface-marker characteristics of both T- and B-cells. In particular, the SS cells failed to form E-rosettes even with a sensitive technique using 2-amino-ethylisothiouronium bromide (AET)-treated sheep red blood cells. The significance of these findings is briefly considered in relation to the existing literature.

Effects of reducing and oxidizing agents on the action of bleomycin

The effects of reducing agents, such as 2-mercaptoethanol, dithiothreitol, L-ascorbic acid, or sodium borohydride, and oxidizing agents, such as hydrogen peroxide or dehydroascorbic acid, on the in vitro action of bleomycin were investigated. After the incubation of DNA with a low concentration of bleomycin and a reducing or oxidizing agent, single strand breaks were mainly caused in the DNA molecules. The degradation of DNA was largely prevented by the removal of oxygen, or by the addition of divalent cations or of S-(2-aminoethyl)isothiuronium bromide hydrobromide, a radical scavenger, to the incubation mixture. Preincubation of bleomycin with these reducing or oxidizing agents reduced the DNA-degrading activity of the antibiotic. However, this reduction in activity was observed even in the absence of oxygen, or in preincubation mixture supplemented with radical scavenger.

Lesions in Escherichia coli cell walls caused by the action of mouse complement

Characteristic lesions formed by mouse complement were visible in electron micrographs of Escherichia coli cell walls treated with aminoethylisothiouronium bromide and then incubated with normal mouse serum in vitro. However, lesions could not be detected in E. coli cell walls recovered from the blood of normal mice after intravenous injection.

Lesions were not produced by either heated or complement deficient mouse sera in any of the experiments.

After incubation with normal or complement deficient mouse serum E. coli cell walls were surrounded by a layer probably made up of complement components and immunoglobulins. This layer was less evident when the sera had been heated at 56° for 1 hour.

Numerous lesions formed by the in vivo action of guinea-pig complement were found in E. coli cell walls recovered from the animal after intravenous injection.