Neutrophil mediated inflammatory lung damage following single Sub lethal inhalation exposure to plant protein toxin abrin in mice.

Abrin, a highly toxic plant protein found in the seeds of Abrus precatorius plant. To date, there is no antidote against abrin intoxication. Abrin is toxic by all routes of exposure, but inhalation exposure is the most toxic of all routes. Present study was conducted to evaluate the acute inhalation toxicity of aerosolized abrin in BALB/c mice. Animals were exposed to 0.2 and 0.8LC50 doses of aerosolized abrin and evaluated at 1 and 3 day post toxin exposure. Bronchoalveolar fluid from lungs was used for evaluation of markers for lung injury. Abrin inhalation exposure caused rise in LDH activity, protein content, increase in ß-glucuronidase and myeloperoxidase activity. Increase in CRP activity, MMP-9 expression and recruitment of CD11b + inflammatory cells in lungs was also observed which was associated with severe inflammation and lung damage. Histopathological findings support the lung damage after abrin exposure. Our results indicate lung injury after single aerosol inhalation exposure, associated with excessive inflammation, oxidative stress, pulmonary edema followed by lung damage. These results could supplement treatment strategies and planning for therapeutic approaches against aerosolized abrin inhalation exposure.

Inhibitory effect of Abrus abrin-derived peptide fraction against Dalton's lymphoma ascites model.

Peptides derived from larger molecules that are important modulators in cancer regression are becoming leads for development of therapeutic drugs. It has been reported that Abrus abrin, isolated from the seeds of Abrus precatorius, showed in vitro and in vivo antitumor properties by the induction of apoptosis. The present study was designed to evaluate the in vivo therapeutic effectiveness of abrin-derived peptide (ABP) fraction in Dalton's lymphoma (DL) mice model. The lethal dose (LD(50)) of ABP was found to be 2.25 mg/kg body weight and further the acute toxicity was determined with sublethal doses in normal mice. The acute toxicity like body weight, peripheral blood cell count, lympho-hematological and biochemical parameters remained unaffected till 200 microg/kg body weight of ABP. The sublethal doses of ABP showed very significant growth inhibitory properties in vivo DL mice model. There were 24%, 70.8% and 89.7% reductions in DL cell survival in 25, 50 and 100 microg/kg body weight of ABP, respectively. Analysis of the growth inhibitory mechanism in DL cells revealed nuclear fragmentation, and condensation with the appearance of the sub-G(0)/G(1) peak is indicative of apoptosis. Further, the Western blotting showed that apoptosis was mediated by the reduction in the ratio of Bcl-2 and Bax protein expression, and activation of caspase-3 through the release of cytochrome c in DL cells. Kaplan-Meier survival analysis showed an effective antitumor response (104.6 increase in life span (ILS) %) with a dose of 100 microg/kg body weight.

Enzymatic activity of toxic and non-toxic type 2 ribosome-inactivating proteins.

Ribosome-inactivating proteins (RIPs) display adenine polynucleotide glycosylase activity on different nucleic acid substrates, which at the ribosomal level is responsible for the arrest of protein synthesis. Some type 2 RIPs, namely ricin and related proteins, are extremely toxic to mammalian cells and animals whilst other type 2 RIPs (non-toxic type 2 RIPs) display three to four logs less toxicity. We studied whether a correlation exists between toxicity on cells and enzymatic activity on nucleic acids. All type 2 RIPs differ in their depurinating activity on the different substrates with differences of up to one to two logs. The toxicity of type 2 RIPs is independent of their enzymatic activity on nucleic acids or on ribosomes.

A characterization of abrin A from the seeds of the Abrus precatorius plant.

Abrin A was purified from the seeds of the Abrus precatorius plant and its physical and biological properties were studied. The biological properties of abrin A were found to be similar to the better studied Abrus protein, abrin C, in that it is toxic to cell-free protein synthesis and binds D-galactose. Abrin A contains carbohydrate moieties including both neutral and amine sugars but no metals, similar to the other two Abrus proteins (abrin C and the Abrus agglutinin). Amino acid compositions of the subunits of abrin A indicated that it consists of two different subunits of comparable size. Furthermore, one of the subunits showed microheterogeneity suggesting that abrin A is a mixture of isolectins. A comparative study of abrin A and abrin C based on compositions and tryptic maps reveals them to be closely related. The evidence suggests that the two abrins may have the same mechanisms of toxic action. Far-ultraviolet circular dichroic studies of abrin A show it to contain 47% beta-pleated sheet and 10% alpha-helix, again similar to the other two Abrus proteins.