Heat-inactivated Lacticaseibacillus paracasei N1115 alleviates the damage due to brain function caused by long-term antibiotic cocktail exposure in mice

Abstract

Critical development period of intestinal microbiota occurs concurrently with brain development, and their interaction is influenced by the microbiota-gut-brain axis. This study examined how antibiotics exposure affected gut microbiota and brain development and analyzed the possible benefits of heat-inactivated Lacticaseibacillus paracasei N1115 (N1115). Thirty neonatal male mice were randomly divided into three groups and treated with sterilized water (control), an antibiotic cocktail (Abx), or antibiotics plus heat-inactivated N1115 (Abx + N1115) for 84 days. We found that while the mRNA levels of GABA_Aα1, GABA_b1, and glucocorticoid receptor (GR) in the hippocampus and brain-derived neurotrophic factor (BDNF), GABA_Aα1, GABA_b1, and nerve growth factor (NGF) in the prefrontal cortex were higher, the mRNA levels of 5-HT_1A were lower in the Abx group. The Abx + N1115 group had lower mRNA levels of GABA_Aα1, GABA_b1, and GR in the hippocampus and BDNF, GABA_b1, and NGF in the prefrontal cortex than the Abx group. The latency period was longer in the Morris water maze test while longer rest time was seen in tail suspension test in the Abx group than the control and Abx + N1115 groups. In the open field test, the moving time and distance of the Abx group were reduced. Further, the alpha-diversity indexes of the Abx and Abx + N1115 groups were significantly lower than the control. Further, long-term exposure to antibiotics disrupted the intestinal microbiota as evidenced by decreased Bacteroides, Firmicutes, and Lactobacillus, and increased Proteobacteria and Citrobacter. However, N1115 significantly decreased the abundance of Citrobacter when compared with those in the Abx group. These results indicate that antibiotics can substantially damage the intestinal microbiota and cognitive function, causing anxiety and depression, which can be alleviated by heat-inactivated N1115 via modulation of the microbiota-gut-brain axis.

Keywords: Antibiotic; Cognitive function; Microbiota–gut–brain axis; Paraprobiotic.

Fig. 1

A protocol of experiment groups and treatment. The control group was gavaged with distilled water, and the Abx and Abx + N1115 groups were gavaged with the antibiotics cocktail. After two hours, the Abx + N1115 group was gavaged with 10⁹ CFU per mouse of heated-inactivated N1115, while other groups were gavaged with distilled water. All the mice were gavaged until PND21, and the behavioral experiments were carried out from PND76 to 84, and sacrificed at PND84

Fig. 2

The effect of long-term intervention of antibiotics and heat-inactivated N1115 on intestinal tissue, serum cytokines and corticosterone. (n = 6). Pathological results of a colonic crypts and b ileal villi. level of c TNF-α, d IL-1, e IL-6, f IL-10, g corticosterone in serum. *P < 0.05, **P < 0.01, ***P < 0.001

Fig. 3

The effect of long-term intervention of antibiotics and heat-inactivated N1115 on brain function related molecular mRNA expressions of the hippocampus. (n = 6, GR of the control group n = 5). a BDNF, b GABA_Aα1, c GABA_b1, d 5-HT_1A, e NGF, f GR, g MR. *P < 0.05, **P < 0.01, ***P < 0.001

Fig. 4

The effect of long-term intervention of antibiotics and heat-inactivated N1115 on brain function related molecular mRNA expressions of the prefrontal cortex. (n = 6, MR of the Abx + N1115 group and MR of the control group n = 5). a BDNF, b GABA_Aα1, c GABA_b1, d 5-HT_1A, e NGF, g GR, f MR. *P < 0.05, **P < 0.01, ***P < 0.001

Fig. 5

The effect of long-term intervention of antibiotics and heat-inactivated N1115 on behavioral test. (n = 6). Changes of a latency on training days and b latency on test day on Morris water maze test, and the maximum latency is 60s. Changes of c rest time on tail suspension test and d horizontal score, e vertical score, f moving time and g moving distance on open field test. *P < 0.05, **P < 0.01, ***P < 0.001

Fig. 6

The effects of long-term intervention of antibiotics and heat-inactivated N1115 on α diversity of gut microbiota. (n = 5). a ACE index and b Chao1 index estimate the community richness of microbiota. c Shannon index and d Simpson index estimate the community diversity of microbiota. e PD-whole tree is a diversity index which is calculated based on the phylogenetic tree. The larger the value means the higher the community diversity. *P < 0.05, **P < 0.01, ***P < 0.001

Fig. 7

The effects of long-term intervention of antibiotics and heat-inactivated N1115 on structure of gut microbiota. a The PCoA analysis based on the weighted UniFrac distance. b Microbiota composition at the phylum and c genus levels. rare taxa (< 1%) are classifed into others