PubMed · 4248916
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C A Greene, V Sudhakar Rao. 1970. Current concepts--status epilepticus.. https://pubmed.ncbi.nlm.nih.gov/4248916/
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To create new, effective reagents for affinity modification of restriction-modification (R-M) enzymes, a regioselective method for reactive dialdehyde group incorporation into oligonucleotides, based on insertion of a 1-beta-D-galactopyranosylthymine residue, has been developed. We synthesized DNA duplex analogs of the substrates of the Eco RII and Mva I R-M enzymes that contained a galactose or periodate-oxidized galactose residue as single substituents either in the center of the Eco RII (Mva I) recognition site or in the flanking nucleotide sequence. The dependence of binding, cleavage and methylation of these substrate analogs on the modified sugar location in the duplex was determined. Cross-linking of the reagents to the enzymes under different conditions was examined. M. Eco RII covalent attachment to periodate-oxidized substrate analogs proceeded in a specific way and to a large extent depended on the location of the reactive dialdehyde group in the substrate. The yield of covalent attachment to a DNA duplex with a dialdehyde group in the flanking sequence with Eco RII or Mva I methylases was 9-20% and did not exceed 4% for R. Eco RII.
Membrane lipid peroxidation is known to produce various aldehydic compounds which cause a wide range of biological effects including heart disease, aging, and cancer. To investigate the effect of lipid peroxidation products on the expression of glutathione S-transferases (GSTs), which catalyze the conjugation of reactive chemicals with glutathione and play an important role in protecting cells, normal rat liver epithelial cells (RL34) were exposed to a variety of aldehydic compounds. We found that the GST activity in RL34 cells was induced by alpha,beta-unsaturated aldehydes, such as acrolein (1.3-fold), crotonaldehyde (1.3-fold), 4-hydroxy-2-hexenal (HHE) (1.4-fold), and 4-hydroxy-2-nonenal (HNE) (1.7-fold). The induction of GST activity by HNE was time-dependent, reaching a plateau after 16 h. The immunoblot analysis using the polyclonal antibodies against GST isozymes demonstrated that GST-P (pi-class), a well-known tumor marker, was significantly induced 16 h after the HNE treatment. Also, immunostaining for the presence of GST-P confirmed the enhanced expression of GST-P in the cytoplasm of the cells. Northern blot analysis revealed that the HNE treatment of RL34 cells for 1 h enhanced the expression of GST-P mRNA, which returned to the control level after 16 h. These data suggest that the induction of GST-P by HNE may represent an important cellular defense mechanism against oxidative injury.
In Alzheimer's disease (AD) the microtubule-associated protein tau is excessively phosphorylated in degenerating neurons, but the mechanisms underlying the increased phosphorylation are unknown. Recent findings suggest that oxidative stress, and membrane lipid peroxidation in particular, contributes to the neurodegenerative process in AD. We now report that following exposure of cultured rat hippocampal neurons to 4-hydroxynonenal (HNE), an aldehydic product of membrane lipid peroxidation, tau is resistant to dephosphorylation. Immunocytochemical and Western blot analyses using phosphorylation-sensitive tau antibodies showed that HNE treatment causes a moderate increase in basal levels of tau phosphorylation, and prevents tau dephosphorylation by alkaline phosphatase in neurons pretreated with the phosphatase inhibitor okadaic acid. Studies with anti-HNE antibodies showed that HNE binds directly to tau, and that HNE immunoreactivity localizes to cell bodies and axons, cell compartments that contain tau. These data suggest a role for HNE in altered tau phosphorylation and neurofibrillary degeneration in AD.