Molecular mechanisms of resistance to human pathogenic bacteria in Caenorhabditis elegans by MEV-1 mediated oxidative stress

Flavonol glycoside complanatoside A requires FOXO/DAF-16, NRF2/SKN-1, and HSF-1 to improve stress resistances and extend the life span of Caenorhabditis elegans

Aging is associated with the increased risk of most age-related diseases in humans. Complanatoside A (CA) is a flavonoid compound isolated from the herbal medicine Semen Astragali Complanati. CA was reported to have potential anti-inflammatory and anti-oxidative activities. In this study, we investigated whether CA could increase the stress resistance capability and life span of Caenorhabditis elegans. Our results showed that CA could extend the longevity of C. elegans in a dosage-dependent manner, while 50 μM of CA has the best effect and increased the life span of C. elegans by about 16.87%. CA also improved the physiological functions in aging worms, such as enhanced locomotor capacity, and reduced the accumulation of the aging pigment. CA could also reduce the accumulation of toxic proteins (α-synuclein and β-amyloid) and delay the onset of neurodegenerative disorders, such as Alzheimer’s disease and Parkinson’s disease, in models of C. elegans. Further investigation has revealed that CA requires DAF-16/FOXO, SKN-1, and HSF-1 to extend the life span of C. elegans. CA could increase the antioxidation and detoxification activities regulated by transcription factor SKN-1 and the heat resistance by activating HSF-1 that mediated the expression of the chaperone heat shock proteins. Our results suggest that CA is a potential antiaging agent worth further research for its pharmacological mechanism and development for pharmaceutical applications.

Coix seed oil prolongs lifespan and enhances stress resistance in Caenorhabditis elegans

Coix seed oil (CSO) has many beneficial effects, but there is limited research on its influence on the processes and mechanisms related to senescence. Here, we used Caenorhabditis elegans as an in vivo model to investigate CSO's bioeffects on longevity. CSO (1 mg/mL) significantly extended the mean lifespan of C. elegans by over 22.79% and markedly improved stress resistance. Gene-specific mutant studies showed that the CSO-mediated increase in life expectancy was dependent on mev-1, hsf-1 and daf-16, but not daf-2. Furthermore, CSO significantly upregulated stress-inducible genes, including daf-16 and its downstream genes (sod-3, hsp-16.2 and gst-4). In addition, four major fatty acids, linoleic, oleic, palmitic and stearic, played leading roles in C. elegans' extended lifespan. Thus, CSO increased the life expectancy of, and enhanced the stress resistance in, C. elegans mainly through daf-16 and its downstream genes, but not through the insulin/insulin-like growth factor 1 signaling pathway.

Lonicera japonica extends lifespan and healthspan in Caenorhabditis elegans

Lonicera japonica (LJ) is widely used as the local medicine to improve body and prevent ills in China, but mechanisms of its healthy beneficial effects remain largely unclear. Here, we evaluated the anti-aging and healthspan promoting activities of 75% ethanol extract of LJ (LJ-E) in the animal model Caenorhabditis elegans. Our results showed that LJ-E (500 μg/mL) treatment enhanced the mean lifespan of worms by over 21.87% and significantly improved age-associated physiological functions in C. elegans. The 500 μg/mL concentration of LJ-E enhanced the survival rates under oxidative and thermal stresses, and decreased reactive oxygen species (ROS) levels and fat accumulation in the worms. Gene-specific mutant studies showed that LJ-E-mediated lifespan extension was dependent on mev-1, daf-2, daf-16, and hsf-1, but not eat-2 genes. LJ-E could upregulate stress-inducible genes, viz., hsp-16.2, sod-3 and mtl-1. Moreover, we found that the D1086.10 protein interacted with superoxide dismutase (SOD)-3 by functional protein association networks analysis according to RNA-sequencing results. It was confirmed that D1086.10 was needed to promote longevity, and positively regulated expression of sod-3 by using D1086.10 mutants. Furthermore, LJ-E significantly delayed amyloid β-protein induced paralysis in CL4176 strain. Given the important role of autophagy in aging and protein homeostasis, we observed that LJ-E could remarkably increase the mRNA expression of autophagy gene bec-1 in CL4176 strain, and decrease expression of autophagy substrate p62 protein by more than 40.0% in BC12921 strain. Finally, we found that combination composed of three major compounds (54 μg/mL chlorogenic acid, 15 μg/mL 1,5-dicaffeoylquinic acid and 7.5 μg/mL 1,3-dicaffeoylquinic acid) of 500 μg/mL LJ-E could significantly delay paralysis in CL4176 worms caused by Aβ toxicity, comparable to that of LJ-E. Overall, our study may have important implications in using Lonicera japonica to promote healthy aging and have a potency to design therapeutics for age-related diseases.

Contrasting invertebrate immune defense behaviors caused by a single gene, the Caenorhabditis elegans neuropeptide receptor gene npr-1

Background

The invertebrate immune system comprises physiological mechanisms, physical barriers and also behavioral responses. It is generally related to the vertebrate innate immune system and widely believed to provide nonspecific defense against pathogens, whereby the response to different pathogen types is usually mediated by distinct signalling cascades. Recent work suggests that invertebrate immune defense can be more specific at least at the phenotypic level. The underlying genetic mechanisms are as yet poorly understood.

Results

We demonstrate in the model invertebrate Caenorhabditis elegans that a single gene, a homolog of the mammalian neuropeptide Y receptor gene, npr-1, mediates contrasting defense phenotypes towards two distinct pathogens, the Gram-positive Bacillus thuringiensis and the Gram-negative Pseudomonas aeruginosa. Our findings are based on combining quantitative trait loci (QTLs) analysis with functional genetic analysis and RNAseq-based transcriptomics. The QTL analysis focused on behavioral immune defense against B. thuringiensis, using recombinant inbred lines (RILs) and introgression lines (ILs). It revealed several defense QTLs, including one on chromosome X comprising the npr-1 gene. The wildtype N2 allele for the latter QTL was associated with reduced defense against B. thuringiensis and thus produced an opposite phenotype to that previously reported for the N2 npr-1 allele against P. aeruginosa. Analysis of npr-1 mutants confirmed these contrasting immune phenotypes for both avoidance behavior and nematode survival. Subsequent transcriptional profiling of C. elegans wildtype and npr-1 mutant suggested that npr-1 mediates defense against both pathogens through p38 MAPK signaling, insulin-like signaling, and C-type lectins. Importantly, increased defense towards P. aeruginosa seems to be additionally influenced through the induction of oxidative stress genes and activation of GATA transcription factors, while the repression of oxidative stress genes combined with activation of Ebox transcription factors appears to enhance susceptibility to B. thuringiensis.

Conclusions

Our findings highlight the role of a single gene, npr-1, in fine-tuning nematode immune defense, showing the ability of the invertebrate immune system to produce highly specialized and potentially opposing immune responses via single regulatory genes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2603-8) contains supplementary material, which is available to authorized users.