Pathogenesis of diquat-induced liver necrosis in selenium-deficient rats: Assessment of the roles of lipid peroxidation and selenoprotein P

Abstract

A dose of diquat below the amount injurious to selenium-replete animals causes lipid peroxidation and massive liver necrosis in selenium-deficient rats. The current study was undertaken to characterize the lipid peroxidation with respect to the liver injury and to correlate the presence of several selenoproteins with the protective effect of selenium. Lipid peroxidation was assessed by measurement of F2 isoprostanes. Diquat caused an increase in liver and plasma F2 isoprotanes. A gradient of these compounds was detected across the liver in some animals, indicating that this organ was a source of some of the plasma F2 isoprostanes. A time-course experiment showed that liver F2 isoprostane concentration increased before plasma alanine transaminase (ALT) levels rose. Selenium-deficient rats were injected with selenium doses from 2 to 50 micrograms/kg and studied 12 hours later. A dose of 10 micrograms/kg or more prevented diquat-induced lipid peroxidation and liver injury. This dose increased plasma selenoprotein P substantially, and a dose-response was present. Liver cellular and plasma glutathione peroxidase activities remained below 2% of their values in control rats for all selenium doses. In selenium-deficient rats given diquat, hepatic lipid peroxidation precedes hepatic necrosis and could therefore be an important mechanism of the necrosis. Selenoprotein P levels were increased by selenium injections, which protected against diquat injury, but glutathione peroxidase activity was not increased. This is consistent with selenoprotein P being the mediator of the selenium effect.

A complex DNA-repeat structure within the Selenoprotein P promoter contains a functionally relevant polymorphism and is genetically unstable under conditions of mismatch repair deficiency

“…First, we found a homozygous allele pattern representing the known (TC) 5 (T) 17 as confirmed by cycle sequencing of subcloned PCR products (Panel A, Figure 2). In addition, a second allele, four nucleotides smaller in size, was seen (Panel C, Figure 2).…”

“…A 132 bp fragment of the SeP promoter, containing a TC (5) repeat followed by a T (17) repeat, was amplified using the forward primer 5'-CTAACAAAGGTCACACTGTG-3' labelled with ABI-FAM (Applied Biosystems, Weiterstadt, Germany) at the 5' end and the reverse primer 5'-GCTGAGCCAGCGAA-TAA-3'. PCR was performed in a volume of 50 ml containing 100 ng genomic DNA, 10 mM Tris (pH 8.4), 50 mM KCl, 1.5 mM MgCl 2 , 0.25 mM dNTPs, 5 pmol of each primer, and 0.5 units of Taq polymerase (Amersham, Braunschweig, Germany).…”

“…Two different internal deletion constructs, construct TC3 containing a (TC) 3 -repeat instead of the wildtype (TC) 5 -repeat, and construct T13 containing a (T) 13 -repeat instead of the wildtype (T) 17 -repeat were generated from the wildtype vector by polymerase chain reaction based site-directed mutagenesis (Quik Change 1 sitedirected mutagenesis kit, Stratagene, La Jolla, CA, USA). Mutated sequences were confirmed by cycle sequencing.…”

“…The initial proposal that SeP acts as a selenium storage and transport protein due to its high content of selenocysteine residues and high plasma levels 4 has not yet been confirmed. Recent studies suggest a function of SeP in antioxidative cell defense systems as it protects against diquat toxicity 5 and neutralises peroxinitrite. 6,7 Recently, 1850 bp of the gene promoter region were characterised and inhibitory regulation of SeP European Journal of Human Genetics (2002) 10, 499 ± 504 promoter activity, mRNA and protein expression by different cytokines like interleukin 1b, tumour necrosis factor a, transforming growth factor b 1 and interferon g has been demonstrated.…”

Biotransfer Possibilities of Selenium from Plants Used in Phytoremediation

“…Selenium absorption by the animal from Se-enriched plant material may vary for many reasons, including type of animal, quantity and Se concentration of plant mixture provided, duration of feeding, and tissue or animal organ evaluated (Feng et al, 1999;Yeh et al, 1997;Burk et al, 1995;Levander and Burk, 1994). Selenium absorption by animals from plant products containing Se has prompted research for increasing Se intake into humans (Finley and Penland, 1998).…”