ORIGINAL RESEARCH article

Front. Pharmacol., 11 June 2021

Sec. Ethnopharmacology

Volume 12 - 2021 | https://doi.org/10.3389/fphar.2021.618123

Proteomic Analysis of Red Ginseng on Prolonging the Life Span of Male Drosophila melanogaster

  • 1. School of Pharmaceutical Sciences, Jilin University, Changchun, China

  • 2. Institute of Special Animal and Plant Sciences, Chinese Academy of Agricultural Sciences, Changchun, China

Abstract

Ginseng (Panax ginseng C. A. Mey.) is a traditional medicine that has been utilized for over 2000 years in Asia and shows varied pharmacological effects. Red ginseng (RG) is steamed and dried ginseng root and is considered to be more effective. Heating inactivates its catabolic enzymes and increases the activities of RG, which can improve the immune system, alleviate fatigue, and has anti-inflammatory effects and antioxidant activity. In addition, RG has a good anti-aging effect, but its mechanism is unclear. Senescence, a side-effect of normal developmental and metabolic processes, is a gradual decline in physiological integrity and function of the body. Senescence is usually associated with a variety of diseases, including neurodegenerative diseases and diabetes. Research on anti-aging and the prolongation of life span has always been a focus topic. In this study, we investigated the molecular mechanism of RG that results in prolonged the life span for male Drosophila melanogaster. Isobaric tag for relative and absolute quantitation (iTRAQ) was used to identify protein changes in an old male D. melanogaster treated with RG. The differential proteins were verified by qRT-PCR and western blotting. The results showed that 12.5 mg/ml RG prolonged its life span significantly. iTRAQ results showed that, compared to the control group, 32 upregulated proteins and 62 downregulated proteins displayed significantly differential expression in the RG group. In this study, we explored the pathways that RG may participate in that extend the life span of D. melanogaster, and the results showed that the PI3K/AKT/FoxO pathway was involved. In addition, 4E-BP increased and participated in the regulation of life span.

Introduction

Senescence is a gradual decline in the physiological integrity and function of the body, including molecules, cells, tissue structure, and function, as well as homeostasis (He and Jasper, 2014). Senescence is usually associated with various diseases, such as neurodegenerative diseases, diabetes, cardiovascular diseases, and cerebrovascular diseases. Research on anti-aging and the prolongation of life span has always been a point of focus.

Ginseng (Panax ginseng C. A. Mey.) is a traditional medicine that has been utilized for over 2000 years in Asia and has varied pharmacological effects (Wisniewski et al., 2009; Wu et al., 2017). The ancient Chinese Meteria Medica ShenNong BenCao Jing recorded that ginseng could be taken for a long time and prolong life. Modern pharmacological studies have shown that ginseng extract enhances the activity of superoxide dismutase in aged rats (Ramesh et al., 2012). In addition, ginseng has been shown to be cardioprotective because of its antioxidative, anti-arrhythmic, and calcium channel-antagonistic activities (Yuan 2015). Red ginseng (RG) is steamed and dried ginseng root, which is considered more effective. Heating inactivates its catabolic enzymes and increases the activities of RG, which can improve the immune system and alleviate fatigue and has anti-inflammatory effects and antioxidant activity; it allows effective coping with the metabolic dysfunction of senescent cells and functional decline (Wu et al., 2017; Ham et al., 2019). Furthermore, RG can protect the brain and spinal cord from neurodegeneration and extend the life span of Drosophila melanogaster (Wisniewski et al., 2009; Kim 2013; Liu et al., 2018).

D. melanogaster is an excellent model for research on senescence due to its short life span and easy maintenance (Allocca et al., 2018). In our previous experiments, we fed D. melanogaster RG, and the results showed that RG extended the life span of D. melanogaster in both males and females (Liu et al., 2018; Hou et al., 2020). However, the mechanism by which RG extends the life span of male D. melanogaster has not been elucidated. In this study, an isobaric tag for relative and absolute quantitation (iTRAQ) was used to identify protein changes in senile male D. melanogaster treated with RG and is the first study to reveal the changes in signaling pathways.

Materials and Methods

Materials

Red ginseng (6 years) was purchased from Changchun City (Jilin Province, China) and pulverized into a powder. The panaxoside content was determined by high-performance liquid chromatography method (Zhang et al., 2018), and the contents were (all in mg/g) Re 1.470, Rg1 1.836, Rf 1.01, Rb1 5.21, Rc 4.447, Rb2 3.211, Rb3 0.317, and Rd 4.453 (Figure 1).

FIGURE 1

Red Ginseng Prolongs the Life Span of Male D. melanogaster

D. melanogaster (wild type) were a gift from Jilin Agricultural University (Changchun, China). All male D. melanogaster were housed in an artificial climate incubator at 25°C and 60% humidity with 12 h alternating dark and light phases. New eclosion D. melanogaster were separated by sex and males were subsequently divided into six groups (n = 60 each). D. melanogaster of the control group were fed a basic diet of water, agar, corn extract, sucrose, extra yeast powder, and propionic acid, and D. melanogaster of the RG group were fed basic diet supplemented with RG at a final concentration of 10.0, 12.5, 15.0, 17.5, or 20.0 mg/ml. The food was changed every 2–3 days. Survival was recorded at 8:00 AM for both the control and RG groups. D. melanogaster that died unnaturally were eliminated (accidental death), and the D. melanogaster that died naturally were removed from the cage. The test was repeated three times. All animals were handled in strict accordance with good animal practice according to the Animal Ethics Procedures and Guidelines of the People’s Republic of China, and the study was approved by The Animal Administration and Ethics Committee of Institute of Special Animal and Plant Sciences, Chinese Academy of Agricultural Sciences.

Climbing Ability Test

The male D. melanogaster of the control and RG groups were tested at the age of 36 days. The test was repeated three times. The locomotor activity of D. melanogaster was measured by climbing ability. D. melanogaster were placed into culture tubes (Diameter, 2.5 cm; Height, 12 cm). D. melanogaster was tapped down to the bottom of tube and then the maximum height that the D. melanogaster climbed up the tube was measured over 15 s (Iliadi and Boulianne 2010; Minois et al., 2001).

Protein Preparation

The male D. melanogaster of the control and RG group were anesthetized at the age of 36 days. Liquid nitrogen was added to the samples (The male D. melanogaster body) and ground into a fine powder. Then, the powder was dissolved in SDT buffer (4% sodium dodecyl sulfate, 0.1 M; dithiothreitol, 100 mM; Tris-HCl, pH 7.6). The protein content was tested using a BCA protein assay (Thermo Fisher Scientific, United States). Protein digestion was performed according to the filter-aided proteome preparation procedure (Wisniewski et al., 2009). The peptides were desalted on MILI-SPE Extraction disk cartridge (C18-SD), lyophilized, and 40 µL dissolution buffer was added.

Isobaric Tag for Relative and Absolute Quantitation Labeling

Each peptide mixture (100 μg) was labeled with the iTRAQ reagent-8 plex Multiplex Kit (AB SCIEX United Kingdom. Limited, United Kingdom). The peptide mixture of control-male-1 was labeled as a 113 tag. Control-male-2 was labeled as a 114 tag, and control-male-3 was labeled as a 115 tag. RG-male-1 was labeled as a 116 tag, RG-male-2 as a 117 tag, and RG-male-3 as a 118 tag.

LC-MS/MS Analysis

Each peptide mixture was analyzed by nano LC-MS/MS coupled to an EASY nLC (Thermo Fisher Scientific). The sample was loaded into the column (Thermo Scientific Acclaim PepMap100, 100 μm × 2 cm, nanoViper C18) by an automatic sampler and connected to an analytical column (Thermo Scientific EASY Column, 10 cm, ID75 μm, 3 μm, C18-A2) in buffer A (0.1% formic acid) and buffer B (84% acetonitrile and 0.1% formic acid) at a flow rate of 300 nL/min. LC-MS/MS analysis was performed on a Q Exactive mass spectrometer (Thermo Scientific). The mass spectrometer was detected in positive ion mode, and the precursor ions scanning range was 300–1,800 m/z. The automatic gain control (AGC) target was set to 1e6 and maximum inject time (IT) to 50 ms. Survey scans were acquired at a resolution of 70,000 at m/z 200 and the resolution for HCD spectra was set to 17,500 at m/z 200, and an isolation width of 2 m/z. Normalized collision energy was 30 eV, and the underfill ratio was defined as 0.1% (Liu et al., 2017; Yu et al., 2017). Raw mass spectrometry data were submitted to China National Genomics Data Center (CNCB-NGDC, https://bigd.big.ac.cn/omix/) BioProject accession number under PRJCA004725.

Proteomic Analysis

The mass spectrometry data were noted and quantified using the MASCOT engine (version 2.2; Matrix Science, London, United Kingdom) and Proteome Discoverer 1.4 (Thermo Fisher Scientific). The selected database was UniProt D. melanogaster 42524 20180327. fasta. The following options were used to identify proteins: peptide mass tolerance = ±20 ppm; fragment mass tolerance = 0.1 Da; enzyme = trypsin; max missed cleavages = 2; fixed modification: carbamidomethyl (C), iTRAQ4/8plex (N-term), iTRAQ4/8plex (K); and variable modification: xidation (M), iTRAQ4/8plex (Y); database pattern = decoy. The selection criteria for differential proteins were set as fold-change with a comparison >1.2 or <0.83, combined with an unadjusted p < 0.05. The Blast2GO program (https://www.blast2go.com/) was used to annotate the functions of the differentially expressed proteins. The Kyoto Encyclopedia of Genes and Genomes (KEGG) database was used to analyze the pathway enrichment of significant proteins (Liu et al., 2017; Yu et al., 2017).

qRT-PCR

The identified differentially expressed proteins were examined at the transcriptional level by qRT-PCR. Glyceraldehyde-3-phosphate dehydrogenase (GAPDH; Proteintech, United States) was used as an internal reference. D. melanogaster from the control and RG group were euthanized at the age of 36 days. The test was repeated three times. Total RNA was extracted using the Total RNA Extraction Kit (UNIQ-10 Trizol, SK1321, Shanghai, China), and cDNA was synthesized using the Thermo Fisher Scientific cDNA Synthesis kit (EP0733). The 2−ΔΔCT method was used to analyze RNA expression. Primer sequences for qRT-PCR are shown in Table 1.

TABLE 1

<GenePrimer sequences
GAPDHF 5' CCT​ATG​ACG​AAA​TCA​AGG​CTA​A 3'
R 5' GCT​GAA​GAA​GTC​GGT​GGA​GA 3'
CG9286F 5' TGC​CCA​GGG​AAT​CTC​TCA​A 3'
R 5' GCA​CAG​AGG​TGA​TTC​CAA​AGA​T 3'
Vir-1F 5' CGA​CTG​GCG​ACT​CTG​ATG​AT 3'
R 5' AAT​GGT​GGA​AGT​GGT​GTT​GG 3'
CG10472F 5' TTC​GGT​CAA​GAA​CCT​GAA​CAT​C 3'
R 5' TTGGGCTCGGCAATCTGT 3'
RhebF 5' AAA​ACT​GCT​CGA​CGT​AAT​GGG 3'
R 5' CCC​ACG​GAC​TCG​TTC​TGT​TT 3'
Ent2F 5' GAG​TTA​CCG​CAC​CCA​TTT​CA 3'
R 5' AGGTCGCCGCCAAAGTT 3'
ND-MLRQF 5' TCA​CTT​GGA​ATC​GCA​CAT​CA 3'
R 5' TAG​TTT​TGG​AAT​AAT​CCC​TCA​CAG 3'
Rab4F 5' GAT​CGT​ACT​ATC​GCG​GAG​CA 3'
R 5' GCA​TCA​TTC​AGC​CAG​TTT​GTC 3'
PathF 5' ACA​ATC​CGC​ATC​CAA​CAA​CC 3'
R 5' GCA​ATT​TCG​GCA​AAG​GTC​AT 3'
MuskelinF 5' GCC​AGC​AGG​GCT​ATT​TGA​GT 3'
R 5' TTG​CCA​GGC​TTT​ATG​TCG​C 3'
FK506-bp2F 5' AAA​AGG​TCA​CGG​TCC​ACT​ACA​C 3'
R 5' AAC​TGG​GCA​ACT​CCC​TCA​TC 3'
AkhF 5' GAA​TCC​CAA​GAG​CGA​AGT​CC 3'
R 5' CCC​TGC​TGT​GTC​TCG​AAA​AA 3'
HgoF 5' TTC​GAT​GAT​CGG​GAT​GTA​AAG 3'
R 5' GGA​CAA​GTG​AGC​ACG​GTA​AAA 3'
CASKF 5' GGA​CAT​CGG​TGC​GAA​TGA​GTA 3'
R 5' GCT​GCC​GTC​GTA​ATC​TGC​TAT 3'
CG31674F 5' GGT​GGT​CGG​GAC​ATA​CTC​AA 3'
R 5' GTA​AGA​TCG​GCT​ACC​GCA​AC 3'
LpinF 5' TGGAGCGTCGCAACCTAA 3'
R 5' GGCTTCTTCTCGCCCTGA 3'
BcDNA:RH44935F 5' GTG​GCT​ACA​AGG​TGC​CTG​AAT 3'
R 5' GTA​CTT​GGC​CAT​TTC​CAC​CTC 3'
TrpF 5' AGG​GCA​CGG​ACA​AGT​TCA​A 3'
R 5' TAT​GCT​CCA​GCA​GGA​TCA​CC 3'
HppyF 5' CAC​AGT​CAC​CAC​AAT​GCC​AAT​A 3'
R 5' GGT​TCC​CGA​GCC​AAT​CTT​T 3'
Chchd2F 5' TCA​TGG​ATT​GAC​CTC​GCT​GTT 3'
R 5' TGG​AGA​TGG​TGG​CTC​TGC​TT 3'
Dmel\CG5510F 5' CTGTTCGGCGACGGATTT 3'
R 5' GCT​GAG​ATA​TGG​ATG​TTG​GTG​G 3'

Primer sequences.

Western Blotting

The significant proteins were validated using western blotting. Male D. melanogaster from the control and RG group were euthanized at the age of 36 days. The test was repeated three times. Total protein was extracted from D. melanogaster with lysis buffer (Beyotime, Haimen, China) and Bullet Blender (NY, United States). Protein concentration was tested using the BCA protein assay reagent. GAPDH was used as the loading control. Samples were separated by 12% SDS-PAGE (Bio-Rad, Hercules, CA, United States) and transferred to polyvinylidene difluoride membranes (Millipore, United States). Membranes were blocked with 5% w/v nonfat dry milk (BD Biosciences, United States) and incubated with primary antibodies at 4°C overnight. The membranes were washed with Tris-buffered saline-Tween and incubated with horseradish peroxidase-labeled secondary antibodies (Proteintech, United States) for 1.5 h at 25°C. Finally, the enhanced chemiluminescence kit (GE Healthcare, United States) was used to visualize the immunobands. The protein bands were scanned using an imaging densitometer.

Statistical Analyses

SAS software (version 9.2) was used for statistical analysis. Fisher’s LSD (least significant difference) was used for the analysis of life span and climbing ability test data. The data of qRT-PCR and Western blotting were analyzed using t-test. A p value of less than 0.05 was considered statistically significant.

Result

Red Ginseng on Prolongs the Life Span of Male D. melanogaster

The male D. melanogaster in the RG group were fed RG at concentrations of 10.0, 12.5, 15.0, 17.5, or 20.0 mg/ml. The life spans of male D. melanogaster treated with 12.5 mg/ml RG and 15.0 mg/ml RG were significantly extended compared with the control group, while the life spans of male D. melanogaster treated with 20.0 mg/ml RG decreased (Figure 2). These results indicated that RG could prolong the life span of male D. melanogaster within the appropriate dose range, while an overdose of RG had a negative impact on the life span.

FIGURE 2

Climbing Ability Test

The male D. melanogaster of the control and RG groups were tested at the age of 36 days. Climbing activity had already been successfully used to evaluate the rate of aging in D. melanogaster. The male D. melanogaster treated with 12.5 mg/ml and 15.0 mg/ml RG had better climbing activity compared with the control group (Figure 3). These results indicated that RG could slow down the rate of aging.

FIGURE 3

Identification of Significantly Changed Proteins

To investigate the effects of RG on male D. melanogaster life span, we treated male D. melanogaster with 12.5 mg/ml RG and used iTRAQ to identify protein changes. Using a threshold of >1.2 or <0.83 (p < 0.05), a total of 94 proteins were found to be differentially expressed between the RG and control groups. Of these, the expression of 32 proteins increased and the expression of 62 proteins decreased in the experimental group (Table 2). Clustering heatmaps and volcano plots showed significant changes in protein expression (Figures 4A,B).

TABLE 2

EntryProtein IDGene nameRG/ControlpChange
1Q6IJ59HDC158111.7350260.031516984Up
2Q2XYE0CG83431.4802315.98782E-05Up
3Q4V509CG104451.4061390.049010132Up
4Q27279Su(fu)1.3835910.010438172Up
5Q9VFR0CG92861.3598720.003587151Up
6Q7JYV3CG123741.3558480.020600274Up
7Q960S8Unr1.349770.021517929Up
8Q9VNI8Hpr11.3165670.025014078Up
9Q4V5T1CG146611.3007250.032815710Up
10Q8MRN5CG58391.2969390.005629237Up
11Q8SZ36Vir-11.2933050.026735257Up
12Q86NQ5CG87731.2895290.013560964Up
13Q8MR67CG104721.2783580.028262384Up
14A0A0B4KFH1Muskelin1.2761120.046799449Up
15Q95TG5Svil1.2644270.016375094Up
16Q9GQR6Stai1.2456080.039443523Up
17Q9VND8Rheb1.2450720.014024349Up
18Q7JZN0Sec61beta1.2432140.025590847Up
19A1Z6I7BubR11.2424690.020906239Up
20Q9VEH4Dmel\CG143251.2385430.010173205Up
21A8JV30Dmel\CG343271.2332420.005286876Up
22Q9VMB6Ent21.2266650.01309915Up
23Q8SYJ2ND-MLRQ1.2231820.025171248Up
24Q9VYY3Uba51.2223870.001308629Up
25Q9VIU8Dmel\CG101321.2179110.016758497Up
26Q7KY04Rab41.2120450.029160556Up
27Q8SYU2RpL7-like1.2111140.031963084Up
28M9WDW1Lds-RA1.2107290.007067795Up
29Q9VT04Path1.2074970.012074239Up
30Q9VNX8CG74141.2054460.00520136Up
31P40301Prosalpha21.2015620.026267051Up
32Q8MS69Dmel\CG95961.2013650.043806106Up
33A8YPP4CG302960.8329420.015104015Down
34Q9VS47Anon-WO0118547.3490.832330.037428812Down
35Q4V5Y8CG133090.831390.00628201Down
36Q9VSN0Zasp660.8298110.011645056Down
37Q29QY40.8296440.023284602Down
38Q9VLP2Dmel\CG77810.8236220.023643643Down
39P48375FK506-bp20.8232030.013030252Down
40Q9VND4Dmel\CG146710.8135420.032412725Down
41P61855Akh0.8135330.000702961Down
42B3DNM30.8134450.023169705Down
43Q8MR80EG:BACR42I17.20.8115680.033391311Down
44A0A0B4JCT6Kank0.8101750.039877023Down
45G2J5Y4CG8446-RE0.8101380.000136072Down
46Q9VKJ0Hgo0.80880.002827784Down
47Q9U5V9Su(p)0.8048790.040446674Down
48Q24407ATPsynCf60.8040150.007844585Down
49O61345Peng0.8038250.020630303Down
50Q9VZ34Dmel\CG20760.8033810.048727204Down
51O76877BcDNA:LD036130.8031760.032438469Down
52Q24210CASK0.801120.041871672Down
53Q6AWS3CG316740.7988070.026233971Down
54Q709R6Bocks0.7987350.02187602Down
55Q7JRA7CG150960.7937070.039789077Down
56Q9W078Cpr62Bb0.7907970.033351008Down
57Q8SZM0Cpr92F0.7899620.000668051Down
58K7ZE33PUG0.7813020.002310275Down
59Q9VSN3Cpr66D0.7811550.000250163Down
60Q7K5J8Cpr57A0.7787780.031569703Down
61Q8SZA8Fdx20.7729510.000578374Down
62Q9VFX3BcDNA:RE531270.7729180.041415202Down
63E5DK16Lpin0.7642130.026655127Down
64A0A0B4K6X5Dmel\CG430930.7634550.007419164Down
65Q9VZ01BcDNA:RH449350.760590.004836408Down
66Q7JZZ3CG133210.7512250.046743486Down
67M9NDL7Reps0.7499730.004348601Down
68P19334trp0.7477940.03200816Down
69Q9W4D2Rnp4F0.7476630.011693647Down
70Q9XZS3CG133640.7429110.023862935Down
71Q9VJ22BEST:GH098760.7418740.011097374Down
72E1UIM5CG136750.7415440.042732988Down
73Q9VS21Dmel\CG158290.7390490.044600699Down
74Q9VKU5Dmel\CG61440.7361710.014459095Down
75A0A0B4LFQ3Hppy0.7307290.002866597Down
76M9PE69Dmel\CG437400.7257640.016526142Down
77Q8MYR7PI4KIIIalpha0.7132360.006458911Down
78Q4V5K3CG156530.6838020.002240457Down
79M9PH94Caz0.6785289.17871E-05Down
80Q9VCQ9Dmel\CG67330.6723570.019442633Down
81Q8T043CG3409-RA0.6618670.036690684Down
82Q9VAD3Vps13B0.6576830.008481404Down
83Q9VQF9Snapin0.6495710.035362079Down
84Q6IJB6HDC153030.6377370.032958939Down
85Q8SXL8Cln30.633770.005102953Down
86A0A0B4K891CG89630.6258730.014196561Down
87Q8T412CG107490.603930.017466337Down
88A9UN96CG182590.5697430.047419921Down
89Q8MZ62CG51030.5598210.044463531Down
90Q9V8I2CG51890.5540820.025951457Down
91Q6NP21CG121240.5511030.038401808Down
92Q9VX77Chchd20.5336660.000874477Down
93C1C5B1cact-RB0.4613010.034408467Down
94Q9VCC2Dmel\CG55100.4021570.028519357Down

Identification of differential proteins in male D. melanogaster.

p value <0.05 was considered statistically significant.

FIGURE 4

Bioinformatics Analysis of Significantly Changed Proteins

The significantly changed proteins were analyzed by the Blast2GO program and Fisher’s exact test (p < 0.05). The enriched GO terms were from the following three categories: cellular component, molecular function, and biological process. The biological process category was significantly enriched in GO for proteins involved in lipid homeostasis, positive regulation of TOR signaling, and regulation of cellular ketone metabolic process. The molecular function category was significantly enriched in GO for structural constituents of the chitin-based larval cuticle, protein disulfide oxidoreductase activity, and prostaglandin-E synthase activity. The cellular component category was significantly enriched in GO for the extrinsic component of the endoplasmic reticulum membrane, molybdopterin synthase complex, and translocation complex (Figure 4C). Significantly changed proteins were analyzed by KEGG. The identified pathways were protein processing in the endoplasmic reticulum, oxidative phosphorylation, and the mTOR signaling pathway.

Validation of Significantly Changed Proteins by qRT-PCR

The mRNA levels of these differentially expressed proteins were tested by qRT-PCR. The mRNA level changes of CG9286, CG10472, FK506-bp2, Akh, hgo, CG31674, Lpin, BcDNA:RH44935, hppy, and Chchd2 were consistent with the changes analyzed by iTRAQ. No significant changes were evident in the levels of trp and Dmel\CG5510 between the control and RG groups (Figure 5).

FIGURE 5

Validation of Proteins by Western Blotting

Expression of hppy, Lpin, Ent2, Rheb, and FK506-bp2 was tested by western blotting. The altered expressions of hppy, Lpin, Ent2, Rheb, and FK506-bp2 between the control and RG groups were consistent with the changes analyzed by iTRAQ. The expression of hppy, Lpin, and FK506-bp2 was downregulated and the expression of Ent2 and Rheb was upregulated (Figure 6).

FIGURE 6

Effect of Hppy, Rheb, and Lpin on the PI3K/AKT/FoxO Pathway

The differentially expressed proteins hppy, Rheb, and Lpin participated in the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT)/forkhead box O (FoxO) signaling pathway and regulated the life span of D. melanogaster. We tested the changes of PI3K, AKT, p-AKT, mTOR, p-mTOR, S6K, 4E-BP, and FoxO proteins using western blotting. The expression of PI3K, AKT, and p-AKT was decreased in the RG group (p < 0.05), and the expression of mTOR and p-mTOR did not change significantly. The expression of 4E-BP and FoxO increased significantly (p < 0.05) and S6K did not change (Figures 7, 8).

FIGURE 7

FIGURE 8

Discussion

Red ginseng prolongs the life span of D. melanogaster, but the mechanism has not been elucidated. In this study, iTRAQ was used to identify protein changes in senile (36 days old) male D. melanogaster. The iTRAQ examination revealed that a total of 94 proteins were differentially expressed in the RG group. Of these, the expression of 32 proteins increased and the expression of 62 proteins decreased. qRT-PCR revealed variations in the mRNA levels of CG9286, CG10472, FK506-bp2, Akh, hgo, CG31674, Lpin, BcDNA: RH44935, hppy, and Chchd2, which were consistent with the iTRAQ results. No significant changes were seen in the levels of trp and Dmel\CG5510 between the control and RG groups. The mRNA expression of vir-1, Rheb, Ent2, ND-MLRQ, Rab4, path, muskelin, and CASK after qRT-PCR detection were not consistent with iTRAQ results (Figure 4). This inconsistency in changes may be because mRNA is regulated by many regulatory factors during translation. The altered expression of hppy, Lpin, Ent2, Rheb, and FK506-bp2 found in western blotting were consistent with the results of iTRAQ.

The differentially expressed protein hppy, which is homologous to human MAP4K3, regulates various signaling pathways, including the mTOR pathway (Lam et al., 2010). The mTOR pathway plays an important role in the process of Drosophila senescence. A decrease in MAP4K3 level can reduce the activity of mTOR (Bryk et al., 2010). S6 protein kinase (S6K) and translation inhibitor (4E-BP) are targets of mTOR activity, and MAP4K3 also regulates the activity of S6K and 4E-BP (Weichhart 2018). The effect of 4E-BP on extending life span has been shown in Drosophila before (Hay 2011). In our study, western blotting results showed that the expression of hppy in male D. melanogaster was decreased after RG treatment. The expression of mTOR, p-mTOR, and S6K did not change. The expression of 4E-BP increased significantly (p < 0.05). The findings indicated that the decreased expression of hppy upregulated the expression of 4E-BP, directly inhibited protein synthesis, and participated in the regulation of life extension. In addition, MAP4K3 can also activate the JNK pathway and induce cell apoptosis. Based on these results, the decreased expression of hppy may inhibit the JNK pathway (Lam et al., 2010).

The differentially expressed protein Rheb, a homolog of Ras GTPase, participates in the PI3K/AKT/mTOR signaling pathway and upregulates Rheb activated mTOR activity (Karassek et al., 2010). Inhibiting mTOR activity and reducing protein synthesis can prolong the life span of organisms, including yeast, D. melanogaster, nematodes, and mice (Alic and Partridge 2011). However, long-term inhibition of mTOR activity can lead to inhibition of wound healing, anemia, proteinuria, pneumonia, and hypercholesterolemia (Lamming et al., 2012). The balance of the mTOR pathway is essential for cell health. In this study, the results showed that the expression of Rheb in male D. melanogaster was increased after RG treatment, and the expression of PI3K, AKT, and p-AKT was decreased in the RG group (p < 0.05). The expression of p-mTOR increased slightly in the RG group, but the difference was not significant (p > 0.05). Inactivation of AKT directly activates the FoxO family of proteins, which reduces oxidative stress, repairs DNA damage, and inhibits premature aging and cellular senescence (Zhang et al., 2011). Therefore, we tested the changes of FoxO protein, and the results showed that the expression of FoxO was increased (p < 0.05). The findings indicated that RG prolonged the life span of male D. melanogaster by regulating the PI3K/AKT/FoxO pathway. The mTOR pathway remained relatively balanced and was not overactivated. In addition, Rheb can reduce reactive oxygen species (ROS) and oxidative damage independently of the mTOR pathway (Ashraf et al., 2019). On feeding D. melanogaster RG, Rheb may reduce the oxidative damage and prolong the life span.

The differentially expressed protein Lpin, a homolog of human lipin, is a lipid protein regulated by the mTOR pathway. Aging is accompanied by the accumulation of Lpin (Romic et al., 2017). The expression of Lpin can be decreased by inhibiting mTOR and upregulating the expression of 4E-BP (Guo et al., 2019; Reue and Wang, 2019). The iTRAQ, qRT-PCR, and western blotting results showed that the expression of Lpin was decreased and 4E-BP was increased. The decreased expression of Lpin indicated that there was no excessive accumulation of lipids in the senile flies.

The differentially expressed protein Fk506-bp2 changed significantly, which is a binding protein. Fk506-bp2 is sensitive to oxidative stress and easily decomposes with the ryanodine receptor (Kreko-Pierce et al., 2016). The results showed that the expression of FK506-bp2 decreased, which may reduce the sensitivity to oxidative stress and oxidative damage.

The differentially expressed protein CG31674 is an oxidoreductase involved in oxidative stress (Yi et al., 2007; Fernandez-Ayala et al., 2010). Our results showed that the expression of CG31674 decreased. It was speculated that the activity of the redox reaction and oxidative damage may have decreased. Oxidative damage can induce aging. Significant prolongation of a healthy life span requires a reduction of all aging processes of an organism (Avril, et al., 1984).

Red ginseng prolonged the life span of male D. melanogaster through a complex biological process and may be used as a potential anti-aging drug. The iTRAQ examination revealed that a total of 94 proteins were differentially expressed in the RG group. Many proteins do not have primary antibodies and western blotting confirmatory experiments were not executed. In addition, D. melanogaster is a model organism and non-mammal. We will continue to study RG’s effect on prolonging life span and PI3K/AKT/FoxO pathway in mammals.

Conclusion

In this study, we explored the pathways that RG may participate in when extending the life span of D. melanogaster, and the results showed that the PI3K/AKT/FoxO pathway was involved. In addition, 4E-BP expression increased and participated in the regulation of life span.

Statements

Data availability statement

Raw mass spectrometry data were submitted to China National Genomics Data Center (CNCB-NGDC, https://bigd.big.ac.cn/omix/) under BioProject accession number PRJCA004725.

Author contributions

JP conceived and designed the experiments. WH performed the experiments, analyzed the data, and contributed reagents/materials/analysis tools. WH and JP wrote the paper.

Funding

This work was supported by grants from the Jilin Science andTechnology Development Plan (No. 20180101261JC), the Central Public-Interest Scientific Institution Basal Research Fund (No. 1610342020008), the Jilin Provincial Department of Science and Technology China (No.20190201160JC), and the Jilin Province Development and Reform Commission (No. 2019C052-10).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Summary

Keywords

red ginseng, anti-Aging, isobaric tag for relative and absolute quantitation, proteome, drosophila

Citation

Hou W and Pei J (2021) Proteomic Analysis of Red Ginseng on Prolonging the Life Span of Male Drosophila melanogaster. Front. Pharmacol. 12:618123. doi: 10.3389/fphar.2021.618123

Received

16 October 2020

Accepted

14 April 2021

Published

11 June 2021

Volume

12 - 2021

Edited by

Javier Echeverria, University of Santiago, Chile

Reviewed by

Paul Chazot, Durham University, United Kingdom

Yu Chiang Hung, Kaohsiung Chang Gung Memorial Hospital, Taiwan

Updates

Copyright

*Correspondence: Jin Pei,

This article was submitted to Ethnopharmacology, a section of the journal Frontiers in Pharmacology

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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