Effect of Lactobacillus casei on peripheral and central nervous inflammation in depressed offspring rats induced by maternal separation

Abstract

Objective To observe the effect of Lactobacillus casei(L.casei) on the depression-like behaviors of offspring rats induced by maternal separation (MS), and explore the potential action mechanism of probiotics to improve central nervous inflammation in depression-like behaviors. Methods MS stress was used to establish a depressed animal model in offspring.Female SD rats were randomly divided into control group (CON), MS group, and MS+L.casei group, with 8 animals in each group.The female rats and their offspring in the control group did not undergo MS intervention after delivery, while those in the MS group were separated 3 h each day, for 14 consecutive days after normal delivery.The offspring of the MS+L.casei group was given intervention of 8×108 CFU/(kg·d)L.casei gavage for 4 weeks.Source preference test (SPT) and forced swimming test (FST) were used to evaluate the changes in depressive behaviors of the offspring rats.ELISA was employed to determine the levels of TNF-α, IL-6, IL-1 β and IL-10 in serum and hippocampus tissue.Real-time fluorescence quantitative PCR was applied to detect the mRNA expression levels of indoleamine 2, 3-dioxygenase-1(IDO1) and 5-HT mRNA in hippocampus. Results Compared with the CON group, the offspring in the MS group had significantly reduced percentage of source preference (P < 0.05), prolonged immobility time during forced swimming (P < 0.05), and decreased number of grid crossings in spontaneous activity test (though no statistical difference), indicating that the offspring rats had obvious depression-like behaviors after MS.L.casei treatment improved the behavioral changes of offspring rats caused by MS stress, with significantly increased percentage of source preference (P < 0.05) and shortened immobility time of forced swimming (P < 0.05).Compared with the conditions in the MS group, L.casei reduced the levels of IL-6, IL-1 β and TNF-α(P < 0.01) and increased that of IL-10(P < 0.05) in the hippocampus and peripheral blood, and decreased mRNA level of IDO1 and enhanced 5-HT mRNA level in hippocampus (P < 0.01) in the offspring rats of the MS+L.casei group. Conclusion MS stress induces depression-like behavior in offspring rats.L.casei inhibits the hippocampal expression of IDO1 and enhances that of 5-HT by regulating inflammatory factors in hippocampus and peripheral blood, and thus, improves depression-like behavior.

Keywords

• maternal separation
• serum
• hippocampus
• inflammatory cytokines
• indoleamine 2
• 3-dioxygenase-1
• depression