ABSTRACT
Strongly pronounced argyrosis caused by adding AgCl to the feed of laboratory rats efficiently mimics the deficiency of ceruloplasmin (CP) ferroxidase activity. Bringing the concentration of AgCl in the feedstuff of lactating rats to 250 mg % and keeping their progeny (Ag-rats) for 3 months on the same silver-containing feed provided the serum iron content 1.4 times lower than that in the control group. Besides, the ferroxidase activity of CP dropped to zero. In CP purified from sera of Ag-rats two copper ions were substituted with two silver ions. Using rat models of both post-hemorrhagic and hemolytic anemia we showed that the deficiency of CP ferroxidase activity in Ag-rats affects the iron content in serum, though does not prevent the recovery of hemoglobin level accompanied by exhaustion of iron caches in liver and spleen. When apo-lactoferrin (apo-LF) was administered to Ag-rats suffering from either post-hemorrhagic or hemolytic anemia, both hemoglobin and serum iron were restored more rapidly than in the control animals. In independent experiments Ag-rats were compared with those fed on regular diet and the former displayed a prolonged 3-day stabilization of hypoxia-inducible factors 1 and 2 alpha (HIF-1a and HIF-2a) along with an increased serum concentration of erythropoietin. Introduction to Ag-rats of active CP separately or together with apo-LF reduced that effect to 1 day only. It is concluded that saturation of apo-LF with iron, provided by active CP, can strongly affect its protective capacity.
Subject(s)
Anemia/drug therapy , Ceruloplasmin/metabolism , Diet , Hemorrhage/drug therapy , Lactoferrin/pharmacology , Silver Compounds/administration & dosage , Acute Disease , Anemia/chemically induced , Animals , Ceruloplasmin/antagonists & inhibitors , Ceruloplasmin/deficiency , Female , Hemorrhage/chemically induced , Iron/metabolism , Lactoferrin/administration & dosage , Rats , Rats, Wistar , Silver Compounds/pharmacologyABSTRACT
Streptococcus pyogenes (group A Streptococcus; GAS) is an important gram-positive extracellular bacterial pathogen responsible for a number of suppurative infections. This micro-organism has developed complex virulence mechanisms to avoid the host's defenses. We have previously reported that SDSC from GAS type M22 causes endothelial-cell dysfunction, and inhibits cell adhesion, migration, metabolism, and proliferation in a dose-dependent manner, without affecting cell viability. This work aimed to isolate and characterize a component from GAS type M22 supernatant that suppresses the proliferation of endothelial cells (EA.hy926). In the process of isolating a protein possessing antiproliferative activity we identified arginine deiminase (AD). Further study showed that this enzyme is most active at pH 6.8. Calculating Km and Vmax gave the values of 0.67 mmol·L(-1) and 42 s(-1), respectively. A distinctive feature of AD purified from GAS type M22 is that its optimum activity and the maximal rate of the catalytic process is close to neutral pH by comparison with enzymes from other micro-organisms. AD from GAS type M22 suppressed the proliferative activity of endothelial cells in a dose-dependent mode. At the same time, in the presence of AD, the proportion of cells in G0/G1 phase increased. When l-Arg was added at increasing concentrations to the culture medium containing AD (3 µg·mL(-1)), the enzyme's capacity to inhibit cell proliferation became partially depressed. The proportion of cells in phases S/G2 increased concomitantly, although the cells did not fully recover their proliferation activity. This suggests that AD from GAS type M22 has potential for the suppression of excessive cell proliferation.
