Polyamines and their metabolites as diagnostic markers of human diseases

Abstract

Polyamines, putrescine, spermidine and spermine, are ubiquitous in living cells and are essential for eukaryotic cell growth. These polycations interact with negatively charged molecules such as DNA, RNA, acidic proteins and phospholipids and modulate various cellular functions including macromolecular synthesis. Dysregulation of the polyamine pathway leads to pathological conditions including cancer, inflammation, stroke, renal failure and diabetes. Increase in polyamines and polyamine synthesis enzymes is often associated with tumor growth, and urinary and plasma contents of polyamines and their metabolites have been investigated as diagnostic markers for cancers. Of these, diacetylated derivatives of spermidine and spermine are elevated in the urine of cancer patients and present potential markers for early detection. Enhanced catabolism of cellular polyamines by polyamine oxidases (PAO), spermine oxidase (SMO) or acetylpolyamine oxidase (AcPAO), increases cellular oxidative stress and generates hydrogen peroxide and a reactive toxic metabolite, acrolein, which covalently incorporates into lysine residues of cellular proteins. Levels of protein-conjuagated acrolein (PC-Acro) and polyamine oxidizing enzymes were increased in the locus of brain infarction and in plasma in a mouse model of stroke and also in the plasma of stroke patients. When the combined measurements of PC-Acro, interleukin 6 (IL-6), and C-reactive protein (CRP) were evaluated, even silent brain infarction (SBI) was detected with high sensitivity and specificity. Considering that there are no reliable biochemical markers for early stage of stroke, PC-Acro and PAOs present promising markers. Thus the polyamine metabolites in plasma or urine provide useful tools in early diagnosis of cancer and stroke.

Keywords: Acrolein; Cancer; Diacetylspemine; Diagnostic marker; Polyamine metabolites; Stroke.

Fig. 1.. Polyamine metabolism and regulation in mammalian cells. The biosynthetic enzymes are indicated by yellow ovals, catabolic enzymes in aquablue ovals, and hypusine modification enzymes in green ovals. Inhibition is indicated by broken red lines and stimulation by solid blue lines. ODC: ornithine decarboxylase; SAMDC: S-adenosylmethionine decarboxylase; SPDS: spermidine synthase; SPMS: spermine synthase, SSAT1: spermidine/spermine N¹-acetyltransferase; AcPAO: acetylpolyamine oxidase; SMO: spermine oxidase; eIF5A: eukaryotic initiation factor 5A; eIF5A (Lys): eIF5A lysine form; eIF5A (Dhp): eIF5A deoxyhypusine form; eIF5A (Hpu): eIF5A hypusine form; DHS: deoxyhypusine synthase; DOHH: deoxyhypusine hydroxylase; Az: antizyme; AzI: antizyme inhibitor.

Fig. 2.. Generation of acrolein and protein-conjugated acrolein by polyamine oxidase reactions. Acrolein generated by SMO, AcPAO or BSAO reacts with ε-amino group of lysine residues of proteins to form FDP-lysine containing adducts. BSAO: bovine serum amine oxidase; FDP-Lys: N-(3-formyl-3,4-dehydropiperidino)lysine.

Fig. 3.. Correlation between brain infarction and PC-Acro in PIT model mice. (A) Infarction volume at 24 h after the induction of infarction, the level of PC-Acro estimated by Western blotting using anti-FDP-Lys antibody, and polyamine levels at the locus of brain infarction and at the corresponding locus in normal mice are shown. (B) Increase in PC-Acro and polyamines in plasma of PIT model mice with brain infarction is shown. *p<0.05, **p<0.01, ***p<0.001. Data were adapted from Saiki et al. (2009).