(A). Homogenates of hearts subjected to ischemia ex vivo were separated by IEF/SDS 2-D gel and probed with a mixture of phospho-serine/threonine antibodies. Using a Langendorff apparatus, hearts were perfused with oxygenated Kreb-Henseleit buffer alone as control, with 50mM ethanol for 10 minutes, with 1μM εPKC agonist (ψεRACK) for 10 minutes (C), or with 1μM εPKC antagonist (εV1-2) for 5 minutes followed by 10 minutes of perfusion together with 50mM ethanol. The hearts were then subjected to a 30 minute period of no-flow ischemia before homogenization. Treatment with ethanol and ψεRACK induced a leftward shift of ALDH2 as compared to control, which was blocked with εV1-2 treatment. Blots were probed with anti-ALDH2 or anti-phospho Ser and Thr (5). (B). ALDH2 activity correlates with cardiac protection from ischemic injury (B). Measurements of ALDH activities in normoxic and ischemic hearts treated with ethanol (EtOH; 50mM), εPKC agonist (ψεRACK) or εPKC antagonist (εV1-2) in the presence of ethanol using the Langendorf apparatus (5). Ischemic hearts were also treated with the ALDH2 inhibitor, cyanamide (CYA) in the presence or absence of ethanol, εPKC agonist and antagonist, and the ALDH2 desensitizer, nitroglycerin (GTN). Shown is ALDH2 activity (μmoles of NADH/min/mg protein) as a function of infarct size, measured by TTC staining from corresponding heart samples derived from the same studies as in Table 1. Linear regression yielded a high inverse correlation of R² = 0.95.

(A).In vitro metabolism of 4HNE (200μM) by ALDH2 (arbitrary units) is lost within one minute of incubation with the substrate; (5), presumably due to 4HNE-induced ALDH2 inactivation (18). HNE-induced ALDH2 inactivation is blocked by Alda-1 (20μM; n=3) as compared with vehicle control (n=3). (B) The protection of ALDH2 from HNE-induced inactivation by Alda-1 correlates with a 34% reduction in 4HNE levels (n=4; p<0.05).

(A). Activation of wild type, heterozygotes and homozygotes mutants of ALDH2 by Alda-1 (100 μM). Enzymatic activity of recombinant ALDH2 proteins (20μg each) are presented as percent of control [n=3, **p<0.01 vs. control; (5)]. Alda-1 reduces cardiac damage in an ex vivo model of ischemia and reperfusion injury (B). Top: Ex vivo cardiac ischemia model protocol. Myocardial infarct size, induced by 35 minutes ischemia followed by 60 minutes of reperfusion after 10 minutes pretreatment with Alda-1 (20 μM) or vehicle control using Langendorff apparatus, as in Fig. 1B, 2B [n=7, *p<0.01; (5)]. Representative cross-sectional slices derived from a single heart stained by TTC without (control) and with Alda-1 treatment (n=7). Infarct area is indicated by the light pink color and marked with dotted lines. Alda-1 reduces cardiac damage in an in vivo model of acute myocardial infarction (C). Top: In vivo cardiac ischemia model protocol. Reduction of infarct size by pretreatment of Alda-1 (8.5mg/kg) before LAD ligation was also determined in vivo (n=7, **p<0.01; SOM, Fig. S6A, B). Shown is TTC staining of representative cross-sectional slices (seven rats per group).