Cyotoxins

About

Background: Nitric oxide (•NO) is a free radical involved in numerousphysiological and pathological processes in mammals. NO is producedendogenously by a family of enzymes known as NO synthases (NOS). NO ischemically unreactive towards most bioorganic compounds, but it can rapidly andspontaneously auto-oxidize to yield the highly reactive species, N2O3, whichcovalently modifies (nitrosates) free thiol and amino groups. High levels of NOsynthesis and nitrosation are generally associated with immune response againstbacteria and viruses. Recently we showed that nonpolar molecules of •NO and O2are absorbed from aqueous solution and concentrated in a small volume ofhydrophobic cores of various proteins. Within such “micelles” catalysis of •NOoxidation and formation of nitrosating N2O3 occurs. We also demonstrated thathydrophobic derivatives of 5-aminonaphtalenesulfonamides (ANSA) can beefficiently solubilized by various proteins and suppress their enzymaticactivity upon nitrosation. Protein inactivation occurs due to irreversiblecross-linking between the functional amino acid side chains and thearyldiazonium cation, which forms upon nitrosation of the NH2 group of ANSA inthe protein hydrophobic interior.  Description of Project: Many bacteria (if not all) produce significant amountsof NO endogenously. They are also persistently attacked by exogenous NOproduced by macrophages during immune response. Additionally, tumor cells arecharacterized by the increased level of NOS expression and •NO production.Based on these observation, we propose that our ANSA derivatives willpreferentially target bacterial or tumor cells in the diseased organism. Ourpreliminary data show that hydrophobic ANSAs posses a strong cytotoxic effecttowards both gram negative and positive bacteria and also prostate tumor celllines. This effect depends on the level of NO that is produced endogenously orprovided via external sources such as activated macrophages, NO-donors, oraqueous NO solution. To further increase the specificity of ANSA towardsinfectious bacteria or cancer cells, various peptides have been covalentlyattached to the NH2 group of ANSA. Blocking of the NH2 group with the peptidylligand will prevent it from being converted into the aryldiazonium cation uponreaction with N2O3. Thus the peptide will keep ANSA inactive and nontoxic evenin the presence of •NO. Cleavage of such a peptide by proteases specificallyexpressed by bacteria or in tumors activates ANSA cytotoxicity. Applications: Treatment of bacterial, viral or fungal infections Treatment of resistant strains of pathogens Treatment of tumors Destruction of specific cytotoxins or enzymes.