Molecular machinery providing copper bioavailability for spermatozoa along the epididymial tubule in mouse

Progressive functional maturation of spermatozoa is completed during the transit of these cells through the epididymis, a tubule structure connecting a testicle to a vas deferens. Epididymal epithelial cells by means of their secretory and absorptive functions determine a highly specialized luminal microenvironment containing multiple organic and inorganic components. The latter include copper ions, which due to their redox properties are indispensable for critical homeostatic processes occurring in spermatozoa floating in different part of epididymis but can be potentially toxic. Main purpose of our study was to determine epididymal region-dependent expression and localization of copper transporters ensuring a tight control of copper concentration in epididymal fluid. We also aimed at identifying proteins responsible for copper uptake by spermatozoa and verifying whether this process is coordinated with copper supply to superoxide dismutase 1 (SOD1), a copper-dependent antioxidant enzyme. Our study identifies two ATPases-ATP7A, ATP7B and Slc31a1, major copper importers/exporters depending on their differential expression on epididymal polarized epithelial cells of the caput, corpus, and cauda. Next, ceruloplasmin seems to be a chief protein transporting copper in the epididymal fluid and providing this biometal to spermatozoa. The entry of copper to germ cells is mediated by Slc31a1 and is correlated with both expressions of copper chaperone for superoxide dismutase (CCS), copper chaperone directly providing copper ions to SOD1 and with the expression and activity of the latter. Our results outline a network of cooperating copper binding proteins expressed in epididymal epithelium and in spermatozoa that orchestrate bioavailability of this microelement for gametes and protect them against copper toxicity.

Intracellular iron status as a hallmark of mammalian cell susceptibility to oxidative stress: a study of L5178Y mouse lymphoma cell lines differentially sensitive to H(2)O(2)

The redox properties of iron make this metal a key participant in oxygen-mediated toxicity. Accordingly, L5178Y (LY) mouse lymphoma cell lines, which display a unique inverse cross-sensitivity to ionizing radiation (IR) and hydrogen peroxide (H(2)O(2)), are a suitable model for the study of possible differences in the constitutive control of intracellular iron availability. We report here that the level of iron in the cytosolic labile iron pool (LIP), ie, potentially active in the Fenton reaction, is more than 3-fold higher in IR-resistant, H(2)O(2)-sensitive (LY-R) cells than in IR-sensitive, H(2)O(2)-resistant (LY-S) cells. This difference is associated with markedly greater content of ferritin H-subunits (H-Ft) in LY-S than in LY-R cells. Our results show that different expression of H-Ft in LY cells is a consequence of an up-regulation of H-Ft mRNA in the LY-S mutant cell line. In contrast, posttranscriptional control of iron metabolism mediated by iron-responsive element-iron regulatory proteins (IRPs) interaction is similar in the 2 cell lines, although IRP1 protein levels in iron-rich LY-R cells are twice those in iron-deficient LY-S cells. In showing that LY cell lines exhibit 2 different patterns of intracellular iron regulation, our results highlight both the role of high LIP in the establishment of pro-oxidant status in mammalian cells and the antioxidant role of ferritin. (Blood. 2000;95:2960-2966)

Antibacterial system generated by lactoferrin in mice in vivo is primarily a killing system

A single dose of bovine lactoferrin (BLF) was given intravenously (i.v.) to CFW mice 24 hours (h) prior to the i.v. injection of the E. coli lethal dose (LD100). BLF strongly accelerated the clearance rate of E. coli from the blood as well as its killing rate in the liver, lungs, spleen and kidney. The highest clearing and killing rate was found 5 h after E. coli LD100 injection. The most intensive killing in the organs examined was found in the lungs and kidney. Analysis of organs of i.v. BLF-stimulated mice which survived up to day 30 after the infection by E. coli showed that not all animals were definitely pathogen-free. It was concluded that the defense system generated by BLF in mice in vivo is primarily a bacteria-killing one. The participation and cooperation of reticulo-endothelial (RE)-macrophages and granulocytes in the phagocytosis and killing of E. coli may thus be related to the protective activity of LF.

Protective effect of tissue ferritins in experimental Escherichia coli infection of mice in vivo

The effect of ferritins from horse (FH) and bovine (FB) spleen and murine liver (FM) on the survival rate of CFW mice lethally infected with Escherichia coli (strain 8440-78 K 80/B) was evaluated. Ferritins given intravenously 24 h before intravenous inoculation of bacteria, protected mice most effectively from death due to infection. The effect was dose dependent. At 500 micrograms of ferritin per mouse, the maximum survival rates were 86% (FH), 81% (FM) and 79% (FB), while only 5% of the control mice survived up to the 30th day. The survival rates of animals injected with bovine serum albumin (BSA) and heat-inactivated FB were 8 and 25%, respectively. Intraperitoneal injection of FB was as effective as intravenous in enhancing the resistance of mice against bacteria. These data provide evidence for the beneficial role of tissue ferritins in nonspecific antibacterial resistance.

Lactoferrin can protect mice against a lethal dose of Escherichia coli in experimental infection in vivo

Experiments were undertaken to demonstrate and partially explain the protective effect of bovine lactoferrin (LB) when administered intravenously to mice 24 h before a challenge with a lethal dose of Escherichia coli. About 70% of mice pretreated with LB survived challenge. The survival rates in control mice treated with E. coli alone and pretreated with bovine serum albumin (BSA), were 4 and 8%, respectively. Human lactoferrin (LH) had almost the same protective effect as LB. Sufficient amounts of ferric ions were given to mice, in single and multiple doses, for full serum transferrin saturation 30 min before or after E. coli administration. The multiple dose of ferric ions did not change considerably the survival rate of mice pretreated with LB. In contrast, a single dose of ferric ions gradually decreased the survival rate of the mice after the first week of experiment. From day 14 this decrease was statistically significant in all groups of mice treated with a single dose of ferric ions when compared with mice pretreated only with LB, and the difference ranged from 25 to 35% on day 30. The possible mechanism(s) of protective effect of LB and role of iron ions are discussed.