A pharmacological network for lifespan extension in Caenorhabditis elegans

Abstract

One goal of aging research is to find drugs that delay the onset of age-associated disease. Studies in invertebrates, particularly Caenorhabditis elegans, have uncovered numerous genes involved in aging, many conserved in mammals. However, which of these encode proteins suitable for drug targeting is unknown. To investigate this question, we screened a library of compounds with known mammalian pharmacology for compounds that increase C. elegans lifespan. We identified 60 compounds that increase longevity in C. elegans, 33 of which also increased resistance to oxidative stress. Many of these compounds are drugs approved for human use. Enhanced resistance to oxidative stress was associated primarily with compounds that target receptors for biogenic amines, such as dopamine or serotonin. A pharmacological network constructed with these data reveal that lifespan extension and increased stress resistance cluster together in a few pharmacological classes, most involved in intercellular signaling. These studies identify compounds that can now be explored for beneficial effects on aging in mammals, as well as tools that can be used to further investigate the mechanisms underlying aging in C. elegans.

Keywords: aging; dopamine; drugs; oxidative stress; pharmaceutical; serotonin.

Figure 1

Overview of screening strategy and results. (a) Schematic shows screening strategy and results, with numbers of compounds in parentheses. (b) Q-Q plot showing lifespan P value-distribution for animals treated with DMSO (black) or compounds (red). Dashed line shows expected P value distribution due to chance. (c) In silico modeling of control data shows the probability of detecting a given increase in lifespan using the numbers of animals employed in the screen (n) (average, 41 (red line); range in >90% of experiments, 30–58). (d) Pie charts show the fraction of compounds belonging to different pharmacological classes in the Pharmacologically Active Compounds (LOPAC) library (Library) and among compounds that increased lifespan (Hits).

Figure 2

Numerous compounds increase Caenorhabditis elegans lifespan. (a) Bars show the number of compounds that increased lifespan by different percentages. The range of percent lifespan extension is indicated at the top of each bar and the number of compounds at the bottom. (b) Survival curves from representative experiments show the percent of animals alive on different days [red, compound-treated; black, vehicle-treated (DMSO)]. Percent lifespan increase is shown for each compound (red) with asterisks indicating significant increases (***, P < 0.0001). For number of animals used and exact P values see Table S2 (Supporting information).

Figure 3

Many compounds protect Caenorhabditis elegans from oxidative stress. Animals were exposed to individual compounds or the vehicle control (DMSO) (blue) for 5 days and then to paraquat for 24 h before survival was determined. Of 57 compounds that increased lifespan, 33 (red) caused a significant increase in the percentage of live animals compared to the control and 3 (purple) caused a significant decrease whereas the others (black) had no significant effect. P value and false discovery rate are indicated. Shown are average values from four experiments. For values and cohort sizes see Table 3 (Supporting information). Error bars indicate SEM. Asterisks indicate compounds whose names are abbreviated: N−(2−[4−(4−Chlorophenyl)*, N−(2−[4−(4−Chlorophenyl)piperazin−1−yl]ethyl)−3−methoxybenzamide 3,4−DIC **, 3,4−Dichloroisocoumarin 7−Cyclopentyl***, 7-Cyclopentyl-5-(4-phenoxy)phenyl-7H-pyrrolo[2,3-d]pyrimidin-4-ylamine, (R,R)-THC****, (R,R)−cis−Diethyltetrahydro−2,8−chrysenediol, 4−Phenyl−3-*****, 4−Phenyl−3−furoxancarbonitrile.

Figure 4

Correlation between effects of compounds on lifespan and stress resistance. (a) A graph compares the effects of different compounds on C. elegans lifespan versus resistance to oxidative stress induced by paraquat. Values indicate percent change in lifespan (X-axis) or survival (stress resistance) (Y-axis) relative to controls. Each dot represents a single compound whose pharmacological class is indicated by a color, as noted below. (b) A graph like that shown in a) in which all the compounds have been grouped as either ‘biogenic amine’ targeting or ‘other’. Correlations and P value are indicated.

Figure 5

Pharmacological network for lifespan extension. Shown is a network generated by connecting compounds (circles) and their respective protein targets (squares). Arrows indicate agonist action, and T’s indicate antagonist action. For compounds (circles), the node size is proportional to the compound’s effect on lifespan whereas the size of protein nodes is fixed. Induction of stress resistance is indicated by a red ring around compounds, with the thickness of the ring proportional to the effect magnitude. Nodes (compounds and targets) and connections between nodes are colored according to pharmacology, as indicated in the key below. See the Fig. 3 legend for names of compounds that are abbreviated.