Discovery of novel regulators of aldehyde dehydrogenase isoenzymes

Over the past three years we have been involved in high-throughput screening in an effort to discover novel small molecular modulators of aldehyde dehydrogenase (ALDH) activity. In particular, we have been interested in both the activation and inhibition of the three commonly studied isoenzymes, ALDH1A1, ALDH2 and ALDH3A1, as their distinct, yet overlapping substrate specificities, present a particularly difficult challenge for inhibitor discovery and design. Activation of ALDH2 has been shown to benefit cardiovascular outcome following periods of ischemia and renewed interest in specific inhibition of ALDH2 has application for alcohol aversion therapy, and more recently, in cocaine addiction. In contrast, inhibition of either ALDH1A1 or ALDH3A1 has application in cancer treatments where the isoenzymes are commonly over-expressed and serve as markers for cancer stem cells. We are taking two distinct approaches for these screens: in vitro enzyme activity screens using chemical libraries and virtual computational screens using the structures of the target enzymes as filters for identifying potential inhibitors, followed by in vitro testing of their ability to inhibit their intended targets. We have identified selective inhibitors of each of these three isoenzymes with inhibition constants in the high nanomolar to low micromolar range from these screening procedures. Together, these inhibitors provide proof for concept that selective inhibition of these broad specificity general detoxication enzymes through small molecule discovery and design is possible.