Compounds that confer thermal stress resistance and extended lifespan

Abstract

The observation that long-lived and relatively healthy animals can be obtained by simple genetic manipulation prompts the search for chemical compounds that have similar effects. Since aging is the most important risk factor for many socially and economically important diseases, the discovery of a wide range of chemical modulators of aging in model organisms could prompt new strategies for attacking age-related disease such as diabetes, cancer and neurodegenerative disorders [Collins, J.J., Evason, K., Kornfeld, K., 2006. Pharmacology of delayed aging and extended lifespan of Caenorhabditis elegans. Exp. Gerontol.; Floyd, R.A., 2006. Nitrones as therapeutics in age-related diseases. Aging Cell 5, 51-57; Gill, M.S., 2006. Endocrine targets for pharmacological intervention in aging in Caenorhabditis elegans. Aging Cell 5, 23-30; Hefti, F.F., Bales, R., 2006. Regulatory issues in aging pharmacology. Aging Cell 5, 3-8]. Resistance to multiple types of stress is a common trait in long-lived genetic variants of a number of species; therefore, we have tested compounds that act as stress response mimetics. We have focused on compounds with antioxidant properties and identified those that confer thermal stress resistance in the nematode Caenorhabditis elegans. Some of these compounds (lipoic acid, propyl gallate, trolox and taxifolin) also extend the normal lifespan of this simple invertebrate, consistent with the general model that enhanced stress resistance slows aging.

Figure 1. Survival during Acute Thermal Stress of C. elegans Treated with Antioxidant Compounds

3-day-old adult hermaphrodite worms were treated with compound or control vehicle (water, DMSO, or ethanol) for 24 hr on agar plates then dispensed using a COPAS Biosort wormsorter 1 worm per well into a 384 well plate. Survival of individuals at 35°C was measured via SYTOX-Green fluorescent staining every 30 min for 20 hr. All curves have n > 50. * Drug treatment varied significantly from vehicle control (p-value <0.001).

Figure 1. Survival during Acute Thermal Stress of C. elegans Treated with Antioxidant Compounds

3-day-old adult hermaphrodite worms were treated with compound or control vehicle (water, DMSO, or ethanol) for 24 hr on agar plates then dispensed using a COPAS Biosort wormsorter 1 worm per well into a 384 well plate. Survival of individuals at 35°C was measured via SYTOX-Green fluorescent staining every 30 min for 20 hr. All curves have n > 50. * Drug treatment varied significantly from vehicle control (p-value <0.001).

Figure 2. Survivorship during Normal Aging of C. elegans Treated with Antioxidants

3-day-old adult hermaphrodite worms were added to plates containing either compound or vehicle control. Worms were transferred to fresh compound-containing agar plates every 2–3 days. Survival was scored by means of touch provoked movement and pumping of the pharynx. Kaplan-Meier survival curves were generated using the GraphPad Prism version 2, GraphPad Software Inc., San Diego Ca.

Figure 3. Effect of Antioxidant Treatment on Stress Gene Expression

3-day-old adult hermaphrodite worms were added to plates containing compound or DMSO vehicle control. After 24 hr, worms were mounted on slides and immobilized with levamisole. GFP expression was scored at 24 on up to 20 randomly selected worms and fluorescence quantified (mean±SEM). The data were analyzed by 1 way ANOVA in GraphPad Prism^™ and were subject to Bonferroni’s multiple comparison test. (*= p<.05).

Figure 4. Average Daily Fertility of C. elegans Treated with 1mM lipoic acid

Young adult worms were transferred to compound or vehicle control plates each day during the fertile period. Progeny was counted for 11 worms per condition. Comparisons were made using one-way ANOVA test in GraphPad Prism^™. 48 hr fertility totals are 260 ± 16 and 194 ± 25 for DMSO and 1mM lipoic acid respectively (p-value <0.05).