(a–c) Dose response effects on the median lifespan of select C. briggsae strains after treatment with chemicals that exhibited strong positive effects on the C. elegans strains. Dosing was performed only on strains that failed to respond positively in the initial tests (single dose experiments), as we did not attempt to identify peak responses, instead we only sought to identify whether positive effects could be obtained by altering doses. Chemical doses were chosen to center around the effective dose identified for C. elegans strains and were sometimes expanded after preliminary rounds of testing. ThT exhibited a positive effect on strain JU1348 at 25 μM, but was profoundly toxic to all strains at and above 100 μM
The amyloid dye Thioflavin T emerged as the superstar when age researchers in 3 independent laboratories tested 10 already-promising pro-longevity chemicals across a range of distinctive strains and species of tiny nematode worms known as Caenorhabditis. The project, dubbed the Caenorhabditis Intervention Testing Program (CITP), also tackled reproducibility, which has been a lingering problem in age research. Initial results from the project are published in Nature Communications.
“The goal of the CITP is to identify pro-longevity chemicals that are effective across diverse genetic distances making them excellent candidates for trials in more complex animals, including mammals,” said Prof. Gordon Lithgow, PhD, Buck Institute for Research on Aging. Lithgow runs the Buck lab that in 2011 showed that Thioflavin T extended lifespan in healthy nematode worms by >50% and slowed the disease process in worms engineered to mimic aspects of Alzheimer’s disease. “Running experiments in 3 discrete laboratories allowed us to demonstrate the reproducibility of our study with Thioflavin T,” he said. “But it’s important to note that some of our other compounds did not pass this stringent test – getting feedback on the ‘fails’ also furthers the larger effort.”
CITP researchers from the Buck, Rutgers University and the University of Oregon characterized the lifespans of 22 Caenorhabditis strains spanning three species. Thioflavin T was found to be the most robust pro-longevity chemical, as it extended the lifespan of all strains tested. In addition, researchers found that 6 out of the 10 pro-longevity chemicals significantly extended lifespan in at least 1 strain of Caenorhabditis. 3 dietary restriction mimetics were mainly effective across strains of C. elegans but showed more variable responses in other species. “Nearly 100,000 worms were individually monitored during this initial project,” said Mark Lucanic, PhD, a postdoc, Lithgow lab.
“The genetic differences between the 3 species of Caenorhabditis were vast – they were comparable to the differences between mice and humans,” said Patrick Phillips, PhD, professor in the Department of Biology at the University of Oregon in Eugene. “Aging is a variable process. Identifying compounds that promote longevity across all of those species increases the odds that we are hitting pathways common to many animals, including humans. These are the ones that warrant further exploration.”
The CITP also provided a standard protocol for doing compound screening in the simple animals. “By documenting in unprecedented detail everything we do in the lab, we were able to get close to seeing identical results across the 3 labs,” said Monica Driscoll, PhD. “We hope that researchers will capture more details of their experimental protocols and that journals will remove limits on how much methodology can be included in publications. Detailing ‘how’ this work is done is just as important as explaining the ‘what’ of our results.”
Reproducibility is considered a cornerstone of experimental science – one that has an economic impact. One study has estimated the cost of flawed or irreproducible research at $28 billion per year in the U.S. alone, with 65% of the expense incurred by the pharmaceutical industry. Lithgow says problems with reproducibility have also cost the field of age research, which has long battled to distinguish itself from a cloud of pseudoscience based on false claims which promise elixirs of health and longevity.
The CITP is an independent, yet complementary effort to the Intervention Testing Program (ITP) undertaken by the National Institutes on Aging. That project set rigorous standards for testing pro-longevity interventions in genetically diverse mice. The shining star of that project was the FDA-approved drug rapamycin. “While mouse studies are an essential part of pre-clinical research, they are also expensive to do,” said Lithgow, noting that some of the ITP interventions failed to show effects on aging. “Our hope is that the CITP will yield robust and reproducible candidates that will help fuel success in higher organisms, including humans, where these compounds might be candidates for drugs to combat chronic diseases.”
Lithgow said CITP researchers hope to study features that more closely relate to human health during their next round of compound screening of Caenorhabditis, possibly including neuronal activity and muscle strength. He also said that the project welcomes suggestions of potential drug candidates from others in the field.
http://www.buckinstitute.org/buck-news/longevity-promoting-superstar-gets-revealed-caenorhabditis-reproducibility-project http://www.nature.com/articles/ncomms14256
Recent Comments