Lacticaseibacillus paracasei E6 improves vinorelbine-induced immunosuppression in zebrafish through its metabolites acetic acid and propionic acid

doi:10.12122/j.issn.1673-4254.2025.02.14

Abstract

Abstract:

Objective To explore the mechanism of Lacticaseibacillus paracasei E6 for improving vinorelbine-induced immunosuppression in zebrafish. Methods The intestinal colonization of L. paracasei E6 labeled by fluorescein isothiocyanate (FITC) in zebrafish was observed under fluorescence microscope. In a zebrafish model of vinorelbine-induced immunosuppression, the immunomodulatory activity of L. paracasei E6 was assessed by analyzing macrophage and neutrophil counts in the caudal hematopoietic tissue (CHT), the number of T-lymphocyte, and the expressions of interleukin-12 (IL-12) and interferon-γ (IFN-γ). The contents of short-chain fatty acids (SCFAs) in L. paracasei E6 fermentation supernatant and the metabolites of L. paracasei E6 in zebrafish were detected by LC-MS/MS-based targeted metabolomics. The immunomodulatory effects of the SCFAs including sodium acetate, sodium propionate and sodium butyrate were evaluated in the zebrafish model of immunosuppression. Results After inoculation, green fluorescence of FITC-labeled L. paracasei E6 was clearly observed in the intestinal ball, midgut and posterior gut regions of zebrafish. In the immunocompromised zebrafish model, L. paracasei E6 significantly alleviated the reduction of macrophage and neutrophil counts in the CHT, increased the fluorescence intensity of T-lymphocytes, and promoted the expressions of IL-12 and IFN-γ. Compared with MRS medium, L. paracasei E6 fermentation supernatant showed significantly higher levels of acetic acid, propionic acid and butyric acid, which were also detected in immunocompromised zebrafish following treatment with L. paracasei E6. Treatment of the zebrafish model with sodium acetate and sodium propionate significantly increased macrophage and neutrophil counts in the CHT and effectively inhibited vinorelbine-induced reduction of thymus T cells. Conclusion L. paracasei E6 can improve vinorelbine-induced immunosuppression in zebrafish through its SCFA metabolites acetic acid and propionic acid.

Key words: Lactobacillus paracei E6, metabolites, short-chain fatty acids, vinorelbine, immunosuppression

XU Xinzhu, Lina GUO, Kangdi ZHENG, Yan MA, Shuxian LIN, Yingxi HE, Wen SHENG, Suhua XU, Feng QIU. Lacticaseibacillus paracasei E6 improves vinorelbine-induced immunosuppression in zebrafish through its metabolites acetic acid and propionic acid[J]. Journal of Southern Medical University, 2025, 45(2): 331-339.

Figures/Tables 7

Tab.1 Sequences of the primers for qRT-PCR

Gene	Forward (5'—3')	Reverse (5'—3')
β-actin	TCGAGCAGGAGATGGGAACC	CTCGTGGATACCGCAAGATTC
IL-2	AACTCCTACAAGCCCAGCAC	ACACTCGGTCGTCAAACGAA
INF-γ	GCCTGGGGAGTATGTTTGCT	CAGGAAGATGGGGTGTGCAT

Fig.1 Colonization of L. paracasei E6 in the intestinal tract of zebrafish.

Fig.2 L. paracasei E6 improves vinorelbine-induced immunosuppression in zebrafish. A: L. paracasei E6 inhibits vinorelbine-induced reduction of macrophage count in the caudal hematopoietic tissue (CHT; dashed box) of zebrafish (left). Macrophage counts are shown in the diagram on the right. B: L. paracasei E6 inhibits vinorelbine-induced reduction of neutrophil counts in the CHT (dashed box) in zebrafish. *P<0.05, ***P<0.001.

Fig.4 Effect ofL. paracasei E6 on mRNA expression levels of IL-12 and IFN-γ in zebrafish. **P<0.01, ***P<0.001

Tab.2 Short-chain fatty acids (SCFAs) detected in culture supernatant of L. paracasei E6 (Mean±SD, n=3)

SCFAs	Concentration(ng/mL)
SCFAs	MRS	Culture supernatant
Acetic acid	354.70±5.03	33576.01±200.71***
Propionic acid	-	74.65±1.70***
Isobutyric acid	-	-
Butyric acid	-	33.40±2.29***
2-Methylbutyric acid	-	-
Isovaleric acid	-	-
Valeric acid	-	-
2, 2-Dimethylbutanoic acid	-	-
2-Ethyl butyric acid	-	-
3, 3-Dimethylbutanoic acid	-	-
2-Methylvaleric acid	-	-
3-Methylvaleric acid	-	-
4-Methylvaleric acid	-	-
Caproic acid	-	-

Fig.5 SCFAs produced by the metabolism of L. paracasei E6 in zebrafish. *P<0.05, **P<0.01, ***P<0.001.

Fig.6 Effects of SCFAs (sodium acetate, sodium propionate, and sodium butyrate) on vinorelbine-induced immunosuppression in zebrafish. A: Effects of sodium acetate, sodium propionate, and sodium butyrate on vinorelbine-induced reduction of macrophage number in the CHT (dashed box) of zebrafish. B: Effects of sodium acetate, sodium propionate, and sodium butyrate on vinorelbine-induced reduction of neutrophil number in the CHT (dashed box) of zebrafish. ***P<0.001.

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