Quercetin enhances motility in aged and heat-stressed Caenorhabditis elegans nematodes by modulating both HSF-1 activity, and insulin-like and p38-MAPK signalling

Abstract

Quercetin is a yellow pigment that is found in many common dietary plants, and that protects against oxidative stress, inflammation, and arteriosclerosis. It has also been suggested to prolong the lifespan of, and enhance heat-stress tolerance in nematodes; thus, the present study investigated its effects on both the nematode life- and health span by assessing its capacity to promote nematode motility after aging and/or heat stress, as well as the mechanisms underlying these effects. The results of the conducted analyses showed that quercetin feeding prolonged lifespan, suppressed age-related motility retardation, improved motility recovery after heat stress, and decreased the production of both intercellular and mitochondrial reactive oxygen species in the analysed Caenorhabditis elegans strains, likely by modulating the insulin-like signalling (ILS) pathway and p38-mitogen-activated protein kinase (MAPK) pathway. In particular, the transcription factors DAF-16 and SKN-1 were found to mediate the observed quercetin-induced effects, consistent with their previously demonstrated roles as regulators of aging. Furthermore, we demonstrated, for the first time, that quercetin induced heat-stress tolerance in C. elegans by modulating HSF-1 expression and/or activity. Thus, the present study provides valuable insights into the mechanisms by which quercetin inhibit aging and enhance heat-stress tolerance via ILS and MAPK pathway in C. elegans.

Fig 1. Quercetin induced life span extension.

Survival rate analysis was generated for N2 wild-type Caenorhabditis elegans nematodes every 2 days and presented relative to that calculated on day 0. n = 60/group. ++P < 0.01, +++P < 0.005 vs CT (dDW) and **P < 0.01, ***P < 0.005 vs CT (DMSO) according to the conducted log-rank test. All assays were conducted at least three times independently.

Fig 2. Quercetin suppressed age-related retardation.

Movement counts were generated for (A) N2, (B) e1370, (C) hx546, (D) mgDf50, (E) tm850, (F) ag1, (G) tm676, (H) tm4241, and (I) sy441 Caenorhabditis elegans nematodes every 3 days from day 0 until (A, B, E–I) day 9 or (C, D) day 12, and presented relative to that calculated on day 0. Data are presented as the mean ± SEM, n = 10/group. +++P < 0.005 vs CT (dDW) and *P < 0.05, ***P < 0.005 vs CT (DMSO) according to the conducted Tukey’s HSD. All assays were conducted at least three times independently.

Fig 3. Quercetin increased heat stress tolerance.

Movement counts were generated to assess the motility-recovery rate of (A) N2, (B) e1370, (C) hx546, (D) mgDf50, (E) tm850, (F) ag1, (G) tm676, (H) tm4241, and (I) sy441 Caenorhabditis elegans nematodes at (A–C, E–H) 6 h and (D, I) 12 h intervals after heat stress. Data are presented as the mean ± SEM, n = 10/group. +P < 0.01, +++P < 0.005 vs CT (dDW) and *P < 0.05, **P < 0.01 vs CT (DMSO) according to the conducted Tukey’s HSD. All assays were conducted at least three times independently.

Fig 4. Quercetin decreased mitochondrial- and intercellular ROS.

(A) Mitochondrial and (B) cellular ROS levels in (a) control (CT), and Caenorhabditis elegans nematodes treated with (b) Q50 mM, and (c) Q500 mM quercetin. (d) Analysis of data presented in (a–c). Scale bars, 200 μm. Data are presented as the mean ± SEM. *P < 0.05, ***P < 0.005 according to the conducted Tukey’s HSD. All assays were conducted at least three times independently.

Fig 5. Quercetin changed expression of genes.

The mRNA expression levels of the analysed genes are shown relative to that of the selected reference gene (actin). Data are presented as the mean ± SEM. *P < 0.05, ***P < 0.005 according to the conducted Tukey’s HSD. Assays were conducted at least three times independently.

Fig 6. Effects of quercetin on signalling pathways in Caenorhabditis elegans.

Signalling pathways shown to be modulated by quercetin in this study. Solid lines indicate relatedness, hashed lines indicate partial relatedness.