Plasminogen activator inhibitor-2 (PAI-2

We have identified specific iron (Fe) chelators of the pyridoxal isonicotinoyl hydrazone (PIH) class that are far more effective ligands than desferrioxamine (DFO; Richardson et al, Blood 86:4295, 1995; Richardson and Milnes, Blood 89:3025, 1997). In the present study, we have compared the effect of DFO and one of the most active chelators (2-hydroxy-1-naphthylaldehyde isonicotinoyl hydrazone; 311) on molecular targets involved in proliferation. This was performed to further understand the mechanisms involved in the antitumor activity of Fe chelators. Ligand 311 was far more active than DFO at increasing Fe release from SK-N-MC neuroepithelioma and BE-2 neuroblastoma cells and preventing Fe uptake from transferrin. Like DFO, 311 increased the RNA-binding activity of the iron-regulatory proteins (IRPs). However, despite the far greater Fe chelation efficacy of 311 compared with DFO, a similar increase in IRP-RNA binding activity occurred after 2 to 4 hours of incubation with either chelator, and the binding activity was not inhibited by cycloheximide. These results suggest that, irrespective of the Fe chelation efficacy of a ligand, an increase IRP-RNA binding activity occurred via a time-dependent step that did not require protein synthesis. Further studies examined the effect of 311 and DFO on the expression of p53-transactivated genes that are crucial for cell cycle control and DNA repair, namely WAF1,GADD45, and mdm-2. Incubation of 3 different cell lines with DFO or 311 caused a pronounced concentration- and time-dependent increase in the expression of WAF1 and GADD45 mRNA, but not mdm-2 mRNA. In accordance with the distinct differences in Fe chelation efficacy and antiproliferative activity of DFO and 311, much higher concentrations of DFO (150 μmol/L) than 311 (2.5 to 5 μmol/L) were required to markedly increase GADD45 and WAF1 mRNA levels. The increase in GADD45 and WAF1 mRNA expression was seen only after 20 hours of incubation with the chelators and was reversible after removal of the ligands. In contrast to the chelators, the Fe(III) complexes of DFO and 311 had no effect on increasing GADD45 and WAF1 mRNA levels, suggesting that Fe chelation was required. Finally, the increase in GADD45 and WAF1 mRNAs appeared to occur by a p53-independent pathway in SK-N-MC and K562 cells, because these cell lines lack functional p53. Our results suggest that GADD45 and WAF1 may play important roles in the cell cycle arrest observed after exposure to these chelators.

A novel alphavirus was isolated from the louse Lepidophthirus macrorhini, collected from southern elephant seals, Mirounga leonina, on Macquarie Island, Australia. The virus displayed classic alphavirus ultrastructure and appeared to be serologically different from known Australasian alphaviruses. Nearly all Macquarie Island elephant seals tested had neutralizing antibodies against the virus, but no virus-associated pathology has been identified. Antarctic Division personnel who have worked extensively with elephant seals showed no serological evidence of exposure to the virus. Sequence analysis illustrated that the southern elephant seal (SES) virus segregates with the Semliki Forest group of Australasian alphaviruses. Phylogenetic analysis of known alphaviruses suggests that alphaviruses might be grouped according to their enzootic vertebrate host class. The SES virus represents the first arbovirus of marine mammals and illustrates that alphaviruses can inhabit Antarctica and that alphaviruses can be transmitted by lice.The genus Alphavirus in the family Togoviridae represents a group of enveloped, plus-strand viruses comprising over 40 known members. Alphaviruses are classified as arboviruses since they are maintained in nature by a biological transmission cycle between susceptible vertebrate hosts and hematophagous arthropods, usually ticks or mosquitoes. Alphaviruses have been grouped by geographic distribution into Old and New World viruses (28). The New World alphaviruses, which include Venezuelan equine encephalitis (VEE), eastern equine encephalitis (EEE), and western equine encephalitis (WEE) viruses are pathogenic for humans, horses, and certain bird species (26,28). The Old World alphaviruses are associated with rheumatic disease in humans and include the Australian Ross River (RR) and Barmah Forest viruses, the Asian/African chikungunya virus, the African o'nyong-nyong virus, and the European Ockelbo virus, which is a subtype of Sindbis virus (28). Weaver et al. (39) hypothesized that alphaviruses may have originated a few thousand years ago in the New World, possibly through recombination with plant viruses (9), and spread to the Old World via bird migration. Recently, two fish alphaviruses have been described, salmon pancreas disease virus (40) and rainbow trout sleeping disease virus (37), suggesting either aquatic origins for alphaviruses or an invasion of the marine environment by terrestrial alphaviruses.Macquarie Island is located some 2,000 km south (54°30'S, 159°E) off the Australian mainland. The island has been a rich source of tick-borne arboviruses. A flavivirus of penguins (22) has been identified on Macquarie Island, as have flaviviruses, bunyaviruses, and orbiviruses, whose enzootic hosts are also likely to be birds (3, 23, 33). The island is also home to about 12% of the world's population of southern elephant seals (Mirounga leonina), roughly 78,000 animals (16), which are known to be infested with the blood-sucking louse Lepidophthirus macrorhini (25). The Macquarie Island elepha...