Mechanisms Of Life Span Extension By 2,5-dimethyl-celecoxib In Drosophila

The demographic shift towards population aging in almost all countries underpins the current search for antiaging therapies.Among various interventions,drugs that affect life span offer great promise as no genetic modifications are involved,and they can be used in a time-and dose-dependent manner.2,5-Dimethyl-celecoxib(DMC)is a derivative of celecoxib and,in mice,faithfully mimics a number of its positive effects on antitumor.Moreover,it shows inhibition of both IIS and TOR signaling in a mouse model of inherited dilated cardiomyopathy.Therefore,DMC may be a potential antiaging drug.The effects of DMC on life span have not yet been tested,so we assayed its action using the fruit fly Drosophila melanogaster.The results are shown below.1.DMC extends Drosophila life span.We tested a range of doses(0.05,0.2,0.5,2,and 10μM)and found positive effects on life span at the intermediate doses 0.2 μM(increased mean life span up to 4.8%in females and 11%in males)and 0.5 μM(increased mean life span up to 10,2%in females and 9.1%in males)but no effect below and above these concentrations.In addition,DMC can elicit beneficial effects on total life span whether treatment is restricted to early(in the first 20 days)or later life(42 day onward).2.The effect of DMC on physiological function and stress tolerance.DMC significantly improved the vertical climbing speed in males and fertility in females.It also improved gut barrier function and reduced the intestinal flora in old flies.In addition,the tolerance to heat stress and starvation in females and males was increased after treated by DMC,DMC-treated flies also possessing higher energy stores in the form of triacylglycerol.3.DMC extends life span beyond the maximum achieved by dietary restriction.DMC had no effect on food consumption in Drosophila,nor did it have any effect on body mass of either sex after 10 days’ DMC-treatment,which is a known correlate of DR.Furthermore,DMC extended life span of both male and female flies on both DR diet and fully fed diet.Thus,DMC appears to act via a different mechanism to the life span extension by DR.4.Intact insulin signaling is required for DMC to modify life span.DMC administration caused a reduction in phosphorylation of T308-Akt to approximately half the level as found in controls.In PDK1 and Akt knockdown flies,we found a significant increase in starvation resistance and life span,similar to what is known for other long-lived IIS mutant flies.Treatment with DMC failed to improve starvation tolerance and life span further in PDK1 and Akt knockdown flies.In addition,DMC also failed to increase life span and starvation tolerance in FOXO deletion mutant flies.5.The role of TOR signaling in the life-extending effect of DMC.We found a decrease in phosphorylation of the translational repressor 4E-BP,which lies downstream of TOR,in DMC-treated flies.DMC did not extend the life span of 4E-BP null mutant flies.Knockdown of S6K significantly increased Drosophila starvation resistance and life span,and DMC failed to extend them further.These results indicate that normal levels of TOR pathway outputs are required for the effects of DMC on starvation tolerance and longevity in Drosophila.6.The role of autophagy signaling in the life-extending effect of DMC.DMC increased the autophagosomes in Drosophila midgut epithelial cells,and upregulated the transcription levels of autophagy-related genes atgl,atg5,and atg8a.For both atg1-RNAi and atg5-RNAi flies,we found no significant effect on starvation tolerance,but adding DMC significantly improved it.Knockdown of atgl and atg5 significantly decreased Drosophila life span,but DMC partially rescued their impaired lifespan.These data show that while DMC treatment of control flies appears to increase autophagy in the gut,its life-span-extending properties are not blocked by atg knockdown.7.Co-administration of DMC and rapamycin do not produce additive effects on life span.Using concentrations of DMC and rapamycin that maximized life span when independently administered,we saw no evidence for an additive effect of the two drugs on life span in either sex,and the combined effect appeared to be less than the two administered separately.