[Lycopene ameliorates D-galactose-induced hepatic senescence in CD-1 female mice through fibroblast growth factor 21/mitochondrial dynamics mediation]

Abstract

Objective: Evaluation of whether lycopene(LYC)ameliorates D-galactose-induced liver senescence and its associated molecular mechanisms.

Methods: Forty-five 2-month-old female CD-1 mice were acclimatized and fed for 1 week and randomly divided into 3 groups(15 mice/group): Control group receiving 0.9% physiological saline(intraperitoneally injected, i. p. ) plus basal chow diet; D-galactose group injected with 150 mg/kg D-galactose(i. p) plus basal chow diet; D-galactose+LYC group receiving 150 mg/kg D-galactose(i. p) plus 0.03% LYC(W/W, mixed with standard diet) for consecutive 8 weeks. Mouse senescence associated-beta-galactosidase(SA-β-gal) staining and enzyme-linked immunoassay(ELISA) kit were used to detect the SA-β-gal content in liver tissues, and western blots detected the protein expression of P21 and P53 in liver tissues, which were significantly higher than those in the control group, it was determined that the modeling of senescent mice was successful. The kit was used to determine glutamate pyruvate transaminase(GPT), glutamic oxaloacetic transaminase(GOT), alkaline phosphatase(ALP) activities in serum, hydrogen peroxide(H_2O_2), total antioxidant capacity(T-AOC) and malondialdehyde(MDA) activities in liver tissue. ELISA kits were used to detect the levels of fibroblast growth factor 21(FGF21), interleukin 6(IL-6), interleukin 8(IL-8) and interleukin 10(IL-10) in mouse liver tissues; immunofluorescence was used to detect the levels of reactive oxygen species(ROS) in liver tissues; immunohistochemistry was used to detect mito-fusion 2(MFN2) and tumor necrosis factor-α(TNF-α) in liver tissues. Transmission electron microscopy was used to observe the morphology of liver mitochondria; western blots were used to detect the expression of mito-fusion 1(MFN1) and fission 1(FIS1).

Results: Compared with the control group, hepatic SA-β-gal content was elevated(P<0.01) and P21 and P53 protein expression levels were up-regulated(P<0.01) in the D-galactose group, successful modelling in senescent mice. Serum GPT(P<0.05), GOT(P<0.01) and ALP(P<0.05) activities were significantly up-regulated; T-AOC activity was down-regulated(P<0.05), MDA(P<0.05) and H_2O_2(P<0.01) contents were elevated, and the level of ROS was up-regulated; the mitochondria of mouse livers in the D-galactose group were disrupted and swollen in the double membrane structure, as observed by transmission electron microscopy; the level of FGF21 was down-regulated(P<0.05), the protein expression of the fission gene FIS1 was down-regulated(P<0.01), the proteins of the mito-fusion genes MFN1 and MFN2 were up-regulated(P<0.05); the expression of the pro-inflammatory factors TNF-α, IL-6(P<0.01), and IL-8(P<0.05) was up-regulated in the liver tissue and down-regulated expression of anti-inflammatory factor IL-10(P<0.01) in liver tissue. Compared with the D-galactose group, the hepatic SA-β-gal content in the D-galactose + lycopene group was reduced(P<0.01), and the protein expression levels of P21 and P53 proteins were down-regulated(P<0.01); the activities of GPT(P<0.05), GOT(P<0.05), and ALP(P<0.01) were significantly down-regulated in serum; the activity of T-AOC was up-regulated(P<0.01), reduced MDA(P<0.01) and H_2O_2(P<0.01) contents as well as down-regulated ROS levels; improved mitochondrial bilayer membrane structure in lycopene-intervened group as observed by transmission electron microscopy; up-regulated FGF21 levels(P<0.05), the protein expression of the fission gene FIS1 was up-regulated(P<0.01) and that of the mito-fusion genes MFN1 and MFN2 was down-regulated(P<0.05); the expression of the pro-inflammatory factors TNF-α, IL-6(P<0.05), IL-8(P<0.05) was down-regulated and the expression of the anti-inflammatory factor IL-10 was up-regulated(P<0.05) in liver tissue.

Conclusion: Lycopene ameliorated D-galactose-induced hepatic senescence and hepatic impairment, which may be associated with its activation of hepatic FGF21 signaling and enhancement of mitochondrial function.

Keywords: D-galactose; fibroblast growth factor 21(FGF21); liver senescence; lycopene; mitochondrion.