Probiotic Strains Alleviate Lipopolysaccharide-Induced Depressive-Like Symptoms via Attenuation of Neuroinflammatory Signaling in Rats

Abstract

A growing body of evidence has linked mental health to the gut microbiome. This has led to the investigation of the gastrointestinal tract  as a possible source of novel treatments and probiotic supplements for depressive disorders. Thus, this study aims to evaluate the  antidepressant effect of a multi-strain probiotics against lipopolysaccharide (LPS)-induced depression in rats. Twentyfour male Wistar  rats were randomly grouped into four groups of 6 animals each. Groups 1 and 2 received vehicle (distilled water, 10 mL/kg), group 3  received a probiotic cocktail (10 mL/kg), while group 4 received fluoxetine (10 mg/kg). All treatments were administered orally for seven consecutive days. One hour after treatment on day seven, LPS (0.85 mg/kg, i.p.) was given to all the animals except group 1 animals.  Twenty-four hours later, all the animals were subjected to behavioural tests [Forced Swim Test (FST), Sucrose Splash Test (SST), and Open  Field Test (OFT)]. Thereafter, the animals were sacrificed, and brain samples were collected for bioassay of central pro-inflammatory  mediators; tumour necrosis factor-alpha (TNF-α), interleukin-6, and interleukin-17 (IL-6 and IL-17) using enzyme-linked immunosorbent  assay. The LPS significantly increased immobility of rats in the FST and decreased grooming in the SST which is indicative of depressive- like behaviours. These behaviours were significantly attenuated by probiotics compared to control. LPS caused marked increase in TNF-α,  IL-6, and IL-17 concentration in the hippocampus. The elevated cytokine levels were attenuated by pretreatment with probiotics. Therefore, probiotics exhibited antidepressant-like activity which may be due to the inhibition of neuroinflammatory signalling pathways.