Divergent responses to peptidoglycans derived from different E. coli serotypes influence inflammatory outcome in trout, Oncorhynchus mykiss, macrophages

Abstract

BackgroundPathogen-associated molecular patterns (PAMPs) are structural components of pathogens such as lipopolysaccharide (LPS) and peptidoglycan (PGN) from bacterial cell walls. PAMP-recognition by the host results in an induction of defence-related genes and often the generation of an inflammatory response. We evaluated both the transcriptomic and inflammatory response in trout (O. mykiss) macrophages in primary cell culture stimulated with DAP-PGN (DAP; meso-diaminopimelic acid, PGN; peptidoglycan) from two strains of Escherichia coli (PGN-K12 and PGN-O111:B4) over time.ResultsTranscript profiling was assessed using function-targeted cDNA microarray hybridisation (n = 36) and results show differential responses to both PGNs that are both time and treatment dependent. Wild type E. coli (K12) generated an increase in transcript number/diversity over time whereas PGN-O111:B4 stimulation resulted in a more specific and intense response. In line with this, Gene Ontology analysis (GO) highlights a specific transcriptomic remodelling for PGN-O111:B4 whereas results obtained for PGN-K12 show a high similarity to a generalised inflammatory priming response where multiple functional classes are related to ribosome biogenesis or cellular metabolism. Prostaglandin release was induced by both PGNs and macrophages were significantly more sensitive to PGN-O111:B4 as suggested from microarray data.ConclusionResponses at the level of the transcriptome and the inflammatory outcome (prostaglandin synthesis) highlight the different sensitivity of the macrophage to slight differences (serotype) in peptidoglycan structure. Such divergent responses are likely to involve differential receptor sensitivity to ligands or indeed different receptor types. Such changes in biological response will likely reflect upon pathogenicity of certain serotypes and the development of disease.

Effect of β glucan dietary levels on immune response and hematology of channel catfish Ictalurus punctatus juveniles

“…Fish cage culture is a highly efficient intensive system that is a potentially stressful environment due to overcrowding, inducing fish susceptibility to pathogen infection due to immune system alterations, which may result in fish disease (Villamil et al, 2003). In recent years, immunostimulants have been included in the feed of cultured fish in order to improve their immune system (Meena et al, 2013;De et al, 2014;Vaseeharan & Thaya, 2014;Yang et al, 2016), stress resistance, antioxidant activity (Zhao et al, 2012;Guzmán-Villanueva et al, 2014;Zanuzzo et al, 2015;Zeng et al, 2016), inflammatory response (Boltaña et al, 2011), and resistance to bacterial (Bonaldo et al, 2009;Meshram et al, 2015), virus (Parmar et al, 2012) and parasite infections (Jaafar et al, 2011). Glucans are polysaccharides with different primary molecular structures that vary depending on their source, which have different implications on their immunostimulant activity (Akramienė et al, 2007); glucans are commonly found ___________________ Corresponding editor: Jesús Ponce-Palafox in mushrooms, algae, yeast, cereals and cell walls of bacteria (Ringø et al, 2011;Meena et al, 2013).…”

Use of bacterial subcellular components as immunostimulants in fish aquaculture

“…Conversely, rainbow trout macrophages stimulated with PGN induced the expression of Myd88, IRAK and a TNF‐activated factor (TRAF6), suggesting the involvement of TLR in PGN‐mediated inflammatory responses in trout (Boltaña et al . ). However, although knowledge regarding the TLR‐mediated fish innate immune response is increasing, further investigation is necessary to determine the underlying effects upon recognition and activation of the fish immune response by PAMP‐associated immunostimulants.…”

Gut feelings of safety: tolerance to the microbiota mediated by innate immune receptors

“…Likewise, in contrast to LPS from other Salmonella species, LPS from S. typhimurium moderately enhances proliferation of Tregs . Furthermore, PGN originating from distinct strains of E. coli has been found to induce distinct transcriptional responses in trout macrophages . Thus, intestinal PRRs have the potential to specifically recognize microbe safety signals of certain species of bacteria.…”