Abstract
Probiotic administration is a potential strategy against enteric pathogen infection in either clinical treatment or animal nutrition industry, but the administration duration of probiotics varied and the underlying mechanisms remain unclear. A strain (YC) affiliated to Pediococcus pentosaceus, a commonly used probiotic, was isolated from fish gut and the potential role of YC against Aeromonas hydrophila was detected in zebrafish. We found that 3- or 4-week YC administration (YC3W or YC4W) increased the resistance against A. hydrophila while 1- or 2-week treatment (YC1W or YC2W) did not. To determine the possible reason, intestinal microbiota analysis and RNAseq were conducted. The results showed that compared with CON and YC1W, YC4W significantly increased the abundance of short-chain fatty acids (SCFAs) producing bacteria and elevated the gene expression of nlrp3. Higher butyrate content and enhanced expression of IL1β were subsequently found in YC4W. To identify the causal relationship between butyrate and the higher pathogen resistance, different concentrations of sodium butyrate (SB) were supplemented. The results suggested that 10 mmol/kg SB addition mirrored the protective effect of YC4W by increasing the production of IL-1β. Furthermore, the increased IL-1β raised the percentage of intestinal neutrophils, which endued the zebrafish with A. hydrophila resistance. In vivo knockdown of intestinal il1b eliminated the anti-infection effect. Collectively, our data suggested that the molecular mechanism of probiotics determined the administration duration, which is vital for the efficiency of probiotics. Promoting host inflammation by probiotic pretreatment is one potential way for probiotics to provide their protective effects against pathogens.
Highlights
Probiotic supplementation is commonly used to protect the host against enteropathogenic bacteria in human or animals and the mechanisms of different probiotics varied [1]
We found that 4-week but not 1-week YC administration increased the level of intestinal butyrate and subsequently increased the production of IL-1b via NLRP3 inflammasome activation, which contributed to the higher resistance against A. hydrophila of zebrafish
The results indicated that zebrafish of YC4W and YC3W had a significantly higher survival rate compared with CON on the seventh day post A. hydrophila challenge while zebrafish from YC2W and YC1W showed no significant difference with CON (Figure 1D)
Summary
Probiotic supplementation is commonly used to protect the host against enteropathogenic bacteria in human or animals and the mechanisms of different probiotics varied [1]. Probiotics increased the host resistance against pathogen infection and could be attributed to host immunomodulation-independent and immunomodulation-dependent types [2]. It has been reported that some probiotic strains including Lactobacillus and Bacillus directly inhibit pathogen adhesion by producing bacteriocin or interfering quorum sensing [7, 8], while others could modulate the gut microbiota shift to a healthier status to protect the host. Faecalibacterium prausnitzii ameliorated gut dysbiosis by increasing the abundance of short-chain fatty acids (SCFA)-producing bacteria [11]. All these researches suggested that regulating the intestinal microbiota is an effective way of probiotics to protect the host
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