Known Hepatoprotectors Act as Antioxidants and Immune Stimulators in Stressed Mice: Perspectives in Animal Health Care.

BACKGROUND: Oxygen is involved in a variety of physiological reactions in aerobic organisms, such as those produced in the electron transport chain, hydroxylation, and oxygenation. Reactive oxygen species (ROS) are naturally formed as byproducts from these previously reactions involving the O2 molecule; they are made up of superoxide anion (O2-), hydroxyl radical (HO-), hydrogen peroxide (H2O2), nitric oxide (NO), peroxyl (ROO-), and reactive aldehyde (ROCH). Under certain environmental stress conditions, ROS are accumulated causing cellular damage but also triggering the overexpression of several enzyme classes such as superoxide dismutases (SOD), catalases (CAT) and glutathione peroxidases (GPx), which represent an important intrinsic antioxidant defence line. Liver is a key organ in vertebrates including farm animals and human. The oxidative stress plays an important role in systemic malfunctions including hepatic, renal and immunological, disorders. METHODS: This review presents a brief update about the relationship of oxidative stress with hepatic, renal and immunological malfunctions in stressed organisms. Cellular and exogenous hepatoprotective compounds share also the ability to scavenge ROS acting as antioxidants and in many cases as stimulators of immune response in stressed organisms. We present the effect of some hepatoprotectors on the hepatic, renal and immunological function in stressed mice by the jointed evaluation of biological and oxidative stress markers. CONCLUSION: Hepatoprotective effect of several exogenous compounds is very associated with their antioxidant capacity. This fact is relevant for keeping oxidant/antioxidant balance in the respective organs, but also for maintaining the physiological status of the whole organism.

Role of tryptophan residues in toxicity of Cry1Ab toxin from Bacillus thuringiensis.

Bacillus thuringiensis produces insecticidal proteins (Cry protoxins) during the sporulation phase as parasporal crystals. During intoxication, the Cry protoxins must change from insoluble crystals into membrane-inserted toxins which form ionic pores. The structural changes of Cry toxins during oligomerization and insertion into the membrane are still unknown. The Cry1Ab toxin has nine tryptophan residues; seven are located in domain I, the pore-forming domain, and two are located in domain II, which is involved in receptor recognition. Eight Trp residues are highly conserved within the whole family of three-domain Cry proteins, suggesting an essential role for these residues in the structural folding and function of the toxin. In this work, we analyzed the role of Trp residues in the structure and function of Cry1Ab toxin. We replaced the Trp residues with phenylalanine or cysteine using site-directed mutagenesis. Our results show that W65 and W316 are important for insecticidal activity of the toxin since their replacement by Phe reduced the toxicity against Manduca sexta. The presence of hydrophobic residue is important at positions 117, 219, 226, and 455 since replacement by Cys affected either the crystal formation or the insecticidal activity of the toxin in contrast to replacement by Phe in these positions. Additionally, some mutants in positions 219, 316, and 455 were also affected in binding to brush border membrane vesicles (BBMV). This is the first report that studies the role of Trp residues in the activity of Cry toxins.