Polyamine modification by acrolein exclusively produces 1,5-diazacyclooctanes: a previously unrecognized mechanism for acrolein-mediated oxidative stress

Abstract

Acrolein, a toxic unsaturated aldehyde generated as a result of oxidative stress, readily reacts with a variety of nucleophilic biomolecules. Polyamines, which produced acrolein in the presence of amine oxidase, were then found to react with acrolein to produce 1,5-diazacyclooctane, a previously unrecognized but significant downstream product of oxidative stress. Although diazacyclooctane formation effectively neutralized acrolein toxicity, the diazacyclooctane hydrogel produced through a sequential diazacyclooctane polymerization reaction was highly cytotoxic. This study suggests that diazacyclooctane formation is involved in the mechanism underlying acrolein-mediated oxidative stress.

Imino [4+4] cycloaddition products as exclusive and biologically relevant acrolein-amine conjugates are intermediates of 3-formyl-3,4-dehydropiperidine (FDP), an acrolein biomarker

“…40 Our studies strongly suggested that the 2,6,9-triazabicyclononanes and 1,5-diazacyclooctanes, such as 1 and 2, were the exclusive acrolein-amine conjugates; however, we were surprised to find that the production of the 3-formyl-3,4-dehydropiperidine (FDP) conjugates, which are now widely used as biomarkers of the oxidative stress, were nearly undetectable in our hands in these reaction mixtures. [38][39][40] This paper reports further evidence of the facile and quantitative production of 1,5-diazacyclooctanes 3 (Scheme 1c) from biologically relevant amines other than polyamines, that is, sphingosine and noradrenaline, through a hydroxyl-mediated [4+4] cycloaddition mechanism. We examined the stabilities of three eight-membered heterocycles, namely, 2,6,9-triazabicyclononane 1 (derived from an aliphatic amine) and 1,5-diazacyclooctanes 2 and 3 (derived from either polyamine or noradrenaline derivatives).…”

“…The 1,5-diazacyclooctane derivatives were found to be the exclusive products, based on the characteristic 1 H NMR spectrum and the high-resolution MS traces. 40,41 The separation and direct analysis of the equilibrium mixtures 4a and 4b were difficult; therefore, the structure was unambiguously determined by reducing the compounds using LiAlH 4 (5, quantitative yield). The reaction proceeded smoothly in an aqueous PBS buffer solution with an efficiency comparable to that observed in organic solvents.…”

“…40 The nucleophilic amino group substitutions on the imino nitrogen (highlighted by the blue atom in Scheme 1b) accelerated and stabilized the resulting 1,5-diazacyclooctane. discovery of the polyamine reactivity described in Scheme 1b revealed a new mechanism underlying the acrolein-mediated oxidative stress: an excess of acrolein produced under oxidative stress conditions or during the combustion of organic materials mediated a sequential imino [4+4] polymerization with polyamines to yield a very toxic diazacyclooctane hydrogel (Scheme 1b).…”

“…9 Our research program, which explores the novel reactivities of N-alkyl unsaturated imines, [35][36][37] recently determined, by chance, that the imines derived from N-alkyl amines and acrolein participated in the previously unknown 'head-to-tail' [4+4] dimerization (Scheme 1). [38][39][40] Thus, the reaction of acrolein with general aliphatic amines, for example, alkyl, benzyl, or allyl amines, which are abundant among biomolecules, smoothly provided the 2,6,9-triazabicyclo[3.3.1]nonane derivatives 1 in quantitative yields (Scheme 1a). 38,39 The reaction proceeded through a formal [4+4] reaction of the intermediary imines, followed by the addition of an extra amine at the aminoacetal carbons.…”

1,5‐Diazacyclooctanes, as Exclusive Oxidative Polyamine Metabolites, Inhibit Amyloid‐β(1‐40) Fibrillization

“…22, 23, 24, 25 We demonstrated that these compounds are produced in much higher amounts and efficiency than the oxidative stress marker, FDP, which thus far has only been detected under standard analytical conditions. This likely suggests that acrolein reacts with polyamines to exclusively produce the eight‐membered heterocycles as initial acrolein‐modified intermediates.…”