Effects Of Ricin Research Articles

The Possible Protective Effect of Alpha-Lipoic Acid against Acute Ricin-Induced Nephrotoxicity in Adult Male Albino Rats

Background: Ricin toxin is considered one of the most potent plant-derived toxins. It induces rapid and irreversible toxic effects through many mechanisms with special concern to inhibition of protein synthesis and oxidative stress resulting in cell death. Moreover, ricin could be used as a terrorist weapon which indicates the importance of finding a specific treatment. Alpha lipoic acid (ALA) possesses almost all characters of an ideal antioxidant; thereby it is suggested to be used against ricin toxicity. Aim of the work: The current study aimed at investigating the acute toxic effects of ricin on the kidneys of adult male albino rats and to appraise the possible protective effect of ALA in altering ricin-induced nephrotoxicity. Material & Methods: the present study was carried out on 60 adult male albino rats; they were divided into four groups. Group I: ten rats were intraperitoneally injected by 0.9% saline. Group II:tenrats were intraperitoneally injected by 100 mg/kg ALA. Group III: twentyrats were subcutaneously injected once with 25 µg/kg body weight of ricin solution. Group IV: twenty rats were injected by 100 mg/kg ALA, 15 minutes prior to single injection of 25 μg/kg body weight of ricin solution, and then reinjected with the same dose of ALA immediately after ricin injection. Survival time, renal function tests, renal malondialdehyde (MDA), renal superoxide dismutase (SOD) and catalase enzyme activities were recorded. Kidney samples were used for electron microscopic examination. Results: Ricin induced nephrotoxicity with significant increase of renal function tests, renal MDA and catalase activity with significant decrease of SOD. Also, the kidney samples of ricin-treated animals revealed focal ultrastructural changes in renal corpuscles, proximal and distal convoluted tubules. On the other hand, most of ricin-induced injuries were much improved after administration of ALA together with ricin. Conclusion: Ricin produces oxidative nephrotoxic effects that markedly improved by the effective antioxidant properties of alpha lipoic acid.

A novel biological-based assay for the screening of neutralizing antibodies to ricin.

A novel approach to screen hybridomas producing antibodies directed against ricin was developed. Anti-ricin antibodies were produced and characterized based on protection of Sp2/mIL6 myeloma cells and in vivo studies demonstrating neutralization of the toxic effects of ricin in mice. During the production of hybridomas, cells were plated in media supplemented with hypoxanthine, aminopterin, and thymidine supplement (HAT), HAT + ricin, or ricin. Three hybridomas, designated HRF4, HHRD7 and HHRD9, were selected from the media supplemented with ricin and were shown to produce antibodies directed against ricin. Intraperitoneal injection of hybridoma supernatant containing anti-ricin antibodies combined with 0.5 microg ricin (a toxic dosage) protected Balb/C mice from the deleterious effects of the ricin. Hybridoma, HHRD9, did not contain high titre antibodies to ricin but appeared to neutralize the toxic effects of ricin in mice.

Time- and concentration-dependent production of superoxide anion, nitric oxide, DNA damage and cellular death by ricin in the J774A.1 macrophage cells.

The time- and concentration-dependent effects of ricin on some biomarkers of cellular toxicity, including production of superoxide anion (O2-), nitric oxide (NO), and DNA single strand breaks (SSB), as well as cellular death, have been examined in the J774A.1 macrophage cell cultures. Various concentrations of ricin have been added to various cell cultures, and the cells were incubated for 12, 24, 36, and 48 hours. Following 12 hour incubation, ricin did not cause significant increases in any of those biomarkers. However, time- and concentration-dependent increases were observed in the induction of all the biomarkers after incubation for 24-48 hours. Approximately twofold increases in the production of O2- were observed after incubation with 1 and 10 ng/mL of ricin for 24 and 36-48 hours, respectively. The concentrations of ricin that caused approximately twofold increases in the rate of DNA-SSB are 10 and 1-10 ng/mL after 24 and 36-48 hours incubation, respectively. Approximately twofold increases in NO production were only observed after incubation of the cultures with 1-10 ng/mL of ricin for 36-48 hours. Fifty percent reductions in cellular viability were also observed with ricin concentrations of 10-100, 10, and 1-10 ng/mL, after incubation for 24, 36, and 48 hours, respectively.

Effects of ricin on the ability of the rabbit aorta to relax to relaxant agents

Effects of ricin on the ability of the rabbit aorta to relax to relaxant agents

The effects of ricin on the sympathetic vascular neuroeffector system of the rabbit.

Ricin is a toxic lectin that inhibits protein synthesis. Because ricin decreases arterial pressure and causes cardiovascular collapse, its effects on the vascular neuroeffector system were investigated. Rabbits were given either of two doses of ricin, and then norepinephrine (NE) release from aorta to transmural stimulation, NE uptake into aorta, NE content of aorta, monoamine oxidase activity, and catechol-O-methyl transferase activity in aorta were determined 18 hours, 4 days or 7 days later. Norepinephrine uptake and enzyme activities in the aorta were not altered by ricin administration. Norepinephrine release and content of aorta were increased at most time periods following ricin administration, significantly so for NE content at 4 days and for release at 18 hours following the lower dose of ricin. We conclude that the mechanisms involved in the release of NE from sympathetic nerves in the vasculature are not impaired by ricin administration, but rather show changes that indicate increased compensatory activity.

Ricin-induced hepatic lipid peroxidation, glutathione depletion, and DNA single-strand breaks in mice

The ability of ricin, the glycoprotein toxin from the castor bean ( Ricinus communis), to stimulate oxidative stress was investigated. Following the i.p. administration of 25 μg ricin/kg or the vehicle to female CF-1 mice, the effects of ricin on hepatic lipid peroxidation, nonprotein sulfhydryl (reduced glutathoine) content and DNA single-strand breaks were determined at 0, 12, 24, 36, 48 and 72 hr post-treatment. Hepatic lipid peroxidation significantly increased 3.4-, 3.8-, and 3.0-fold relative to control values at 24, 36, and 48 hr post-treatment, respectively. Hepatic nonprotein sulfhydryl concentrations decreased significantly to approximately 51%, 61% and 65% of control values, at 24, 36, and 48 hr, respectively. The incidence of hepatic DNA single-strand breaks increased by 2.9-, 2.8-, and 2.4- fold relative to the zero time values at 24, 36, and 48 hr after treatment with ricin, respectively. No significant differences were observed in either lipid peroxidation or nonprotein sulfhydryl concentrations at 12 or 27 hr post-treatment. Decreases in liver and intestinal weight to body weight ratios were observed in ricin-treated animals, while no changes were observed in spleen and kidney weight to body weight ratios. These results indicate that in the liver of mice, ricin induces an oxidative stress which is maximal at approximately 36 hr post-treatment.

Selective cytotoxic effects of a ricin A chain immunotoxin made with the monoclonal antibody SWA11 recognising a human small cell lung cancer antigen

The potential of mouse monoclonal antibodies for recognising different antigens associated with human small cell lung cancer (SCLC) to form active immunotoxins was assessed by an indirect in vitro screening assay. The screening agent used was a conjugate made by linking ricin A chain to a sheep anti-mouse IgG Fab' fragment via a disulphide bond. The monoclonal antibodies SWA11 and SWA20 both mediated the toxic effects of ricin A chain against the HC12 classic SCLC cell line in dose-dependent fashion. The SWA11 antibody was the more effective; in combination with the screening agent at a concentration of 1 x 10(-7) M, it inhibited the incorporation of [3H] leucine into HC12 cells by 94% compared with only 44% inhibition in the case of SWA20. An immunotoxin made by the direct chemical conjugation of ricin A chain to SWA11 exhibited selective toxic effects upon HC12 cells in tissue culture inhibiting the incorporation of [3H] leucine by 50% at a concentration (IC50) of 6.2 x 10(-10) M and by 98% at 1 x 10(-7) M. SWA11-ricin A chain had an IC50 of 4.4 x 10(-10) M against the NCI-H69 classic SCLC cell line but showed no cytotoxic activity against the human lung adenocarcinoma cell line NCI-H23 at a concentration of 1 x 10(-8) M.

Increasing cytostatic effects of ricin A chain and Staphylococcus aureus enterotoxin A through in vitro hydrophobization with fatty acid residues.

In order to impart an ability for receptor-independent transmembrane transfer to water-soluble proteins, it has been suggested that they be hydrophobized by lipid groups (fatty acids, etc.). To this end, systems of reversed micelles of surfactants in organic solvents were used as reaction media for protein modification. It was shown that after introduction of a hydrophobic anchor (stearic acid residue) the toxic effect of ricin A-chain (in the absence of B-chain) on intact cells became very close to that of the native toxin. As a result of stearic acid acylation, the activity of Staphylococcal enterotoxin A increased by nearly 1.5-2 orders. The observed phenomena can be explained by receptor-independent intracellular translocation of the hydrophobized toxins.

Ultrastructural observations of non-selective effects of ricin treatment (RCA-120) in the rat dorsal root ganglion

The effects of ricin (RCA-120) on non-injected dorsal root ganglion (DRG) cells, sharing the same DRG as the injected ones, were studied after ricin injections into the tibial nerve and B-HRP injections into the peroneal nerve. Numerous DRG cells containing B-HRP reaction product and exhibiting signs of advanced degeneration were observed. The findings suggest that ricin may be released from dying injected DRG neurons and taken up by adjacent non-injected DRG cells, which subsequently degenerate.

Ricin and alpha-sarcin alter the conformation of 60S ribosomal subunits at neighboring but different sites.

The effects of ricin and alpha-sarcin separately or in combination on the conformation of rat liver ribosomes were investigated by measuring the relative accessibility of individual ribosomal proteins to N-ethylmaleimide after 80S ribosomes were treated with these toxins. By using a double-labelling technique in which ribosomes were incubated with the toxins and then treated with 3H-labelled or 14C-labelled N-ethylmaleimide, it was found that labelling of protein L14 was specifically reduced by treatment with ricin, and that of proteins L3 and L4 by treatment with alpha-sarcin, suggesting that the toxins alter the conformation of ribosomes in the vicinity of these proteins. When ribosomes were treated with both ricin and alpha-sarcin, the extent of labelling of protein L3 was reduced compared to that observed after treatment with alpha-sarcin alone. These results are discussed in relation to previous observations showing that these three proteins are neighbours in the 60S ribosomal subunit and probably play important roles in protein biosynthesis, and in the actions of ricin and alpha-sarcin on 28S rRNA.

Effects of ricin, a protein toxin, on glucose absorption by rat small intestine. Biochemical studies on oral toxicity of ricin. II.

The effects of ricin, a proteinous toxin from castor bean seeds, on glucose absorption by rat small intestine have been examined by the everted sac method. Glucose absorption was affected by ricin poisoning at 1 h after oral administration, and the inhibition reached the maximum at 5h, whereas very slight impairment of glucose absorption was observed at 5h after intraperitoneal injection of ricin. The dose required for 50% impairment of glucose absorption was 10mg ricin/kg body weight of rat when determined at 5 h after oral administration. This inhibition of glucose absorption was found only when ricin or ricin B-chain had been in contact with the mucosal membrane of the small intestine of the normal rats. The inhibition was prevented by the presence of a galactose-containing sugar, lactose. The effect of ricin on glucose absorption under physiological conditions was analyzed in situ, and the increase in blood glucose level was inhibited in ricin-intoxicated rats. These results suggest that ricin, especially its B-chain, interacts primarily with the intestinal mucosa and inhibits sugar absorption of the rat small intestine. It was also inferred that ricin B-chain is cytotoxic to the epithelial absorptive cells of the small intestine, but that impairment of sugar absorption by the small intestine alone is not the direct cause of death of animals following oral administration of ricin.

Deficient cytidine monophospho-N-acetylneuraminic acid: glycoprotein sialyltransferase activity in a clone of KB cells with altered cell fusion ability.

Lines of KB cells resistant to Sendai virus-induced cytolysis have been isolated and characterized (Toyama, S., Toyama, Su., and Uetake, H. (1977) Virology 76, 503-515). This study is concerned with the nature of this mutation. Plasma membrane fractions from Sil cells were found to have decreased amount of sialic acid and the same amount of galactose as compared to the membranes from parental KB cells. Sil cells exhibited an increase in sensitivity to toxic effects of ricin and a decrease in sensitivity to wheat germ agglutinin. Binding of wheat germ agglutinin to Sil cells was markedly decreased. Several membrane glycoproteins of Sil cells migrated slightly faster than the corresponding bands of wild type membrane when examined by gel electrophoresis in sodium dodecyl sulfate. Sil cells had decreased sialyltransferase activity that catalyzed the transfer of sialic acid residues from CMP-N-acetylneuraminic acid to glycoprotein acceptors containing Gal beta 1 leads to 3GalNAc alpha 1 leads to O-Ser(Thr) chain. The decreased enzyme activity could not be accounted for by the presence of inhibitors, altered pH optimum, or increased sialidase or CMP-sialic acid hydrolase activities. These results indicate that a molecular basis for the Sil cell phenotype might be the deficiency of sialyltransferase.

Effects of ricin on the ribosomal sites involved in the interaction of the elongation factors.

The effects of ricin on the different steps of the elongation cycle of protein synthesis in a rabbit reticulocyte cell-free system are studied in this paper. The toxin most probably acts by catalytically inactivating the ribosomes, since a single molecule of the toxin can inactivate 300 ribosomes for poly(U)-directed phenylalanine incorporation. The effect of the toxin on the ribosome is irreversible. Ricin specifically inhibits elongation-factor-1-dependent aminoacyl-tRNA binding to ribosomes but has no effect on the non-enzymic binding of aminoacyl-tRNA. Ricin also inhibits formation of the complex elongation-factor-2 - ribosome - nucleotide with GTP, GDP or GMP-P(CH2)P. However, the toxin has no effect on translocation. These apparently conflicting results are discussed in this study.