Aeromonas sobria Induces Proinflammatory Cytokines Production in Mouse Macrophages via Activating NLRP3 Inflammasome Signaling Pathways

Abstract

Aeromonas sobria, a common conditional pathogenic bacteria, is widely distributed in the environment and causes gastroenteritis in humans or septicemia in fish. Of all Aeromonas species, A. sobria is the most frequently isolated from human infections especially in immunocompromised subjects. Innate immunity is the first protection system of organism to resist non-specific pathogens invasion; however, the immune response process of hosts against A. sobria infection re\mains unexplored. The present study established an A. sobria infection model using primary mouse peritoneal macrophages (PMφs). The adherence and cytotoxicity of A. sobria on PMφs were determined by May-Grünwald Giemsa staining and LDH release measurement. Pro-inflammatory cytokine expression levels were measured using qPCR, western blotting, and ELISA methods. We also investigated the levels of ASC oligomerization and determined the roles of active caspase-1 in IL-1β secretion through inhibition assays and explored the activated pattern recognition receptors through immunofluorescence. We further elucidated the roles of activated inflammasome in regulating the host’s inflammatory response through inhibition combined with ELISA assays. Our results showed that A. sobria induced lytic cell death and LDH release, whereas it had no adhesive properties on PMφs. A. sobria triggered various proinflammatory cytokine transcription level upregulation, and IL-1β occupied the highest levels. The pro-IL-1β protein expression levels increased in a dose-dependent manner with MOI ranging from 1 to 100. This process was regulated by ASC-dependent inflammasome, which cleavage pro-IL-1β into active IL-1β p17 with activated caspase-1 p20. Meanwhile, the expression levels of NLRP3 receptor significantly increased, location analysis revealed puncta-like surrounding nuclear, and inhibition of NLRP3 inflammasome downregulated caspase-1 activation and IL-1β secretion. Blocking of NLRP3 inflammasome activation through K+ efflux and cathepsin B or caspase approaches downregulated A. sobria–induced proinflammatory cytokine production. Overall, these data indicated that A. sobria induced proinflammatory cytokine production in PMφs through activating NLRP3 inflammasome signaling pathways.

Gut microbiota-derived metabolites mediate the neuroprotective effect of melatonin in cognitive impairment induced by sleep deprivation

“…The increase in opportunistic pathogens is one of the possible consequences of dysbiosis of the intestinal microbiota, which can destabilize intestinal tight junction proteins, leading to disruption of the intestinal integrity barrier and an increase in permeability, called leaky gut [ 15 , 16 ]. Aeromonas , an opportunistic pathogen, can induce intestinal inflammation and cause extraintestinal inflammatory responses [ 17 , 18 ]. Breakage of the intestinal barrier can lead to the entry of large numbers of microorganisms or microbial constituents, such as lipopolysaccharide (LPS), into circulation, thus causing systemic inflammation [ 19 ].…”

A. caviae infection triggers IL-1β secretion through activating NLRP3 inflammasome mediated by NF-κB signaling pathway partly in a TLR2 dependent manner

“…A. hydrophila caused mitochondrial dysfunction, produced mtROS release, translocated mtDNA to cytoplasm, activated caspase-1/IL-1β, and induced IL-1β production [ 16 ]. IL-1β also functioned against A. dhakensis infection in the spleen and head kidney of Piaractus mesopotamicus at the initial stage [ 10 ], as well as A. sobria infection in primary mouse macrophages via activating NLRP3 inflammasome [ 8 ]. In our study, mice in vivo infection assays demonstrated that A. caviae infection-induced IL-1β release in murine serum.…”

“…Studies so far revealed that the infection with A. hydrophila [ 6 ], A. veronii [ 7 ], A. sobria [ 8 ], A. salmonicida [ 9 ] and A. dhakensis [ 10 ] would induce a series of inflammatory response with elevated IL-1β, TNF-α, IL-6, IL-8 and so on. IL-1β was a potent cytokine that functioned in host-response and the resistance to pathogens [ 11 ].…”

“…Mature caspase-1 will cleave the pro-IL-1β to IL-1β p17 and serves as the second signal. Previous study reported that A. sobria led to NLRP3 inflammasome assembling and IL-1β enhancement in PMs [ 8 ]. IL-1β and NLRP3 inflammasome were weakened in Hepatitis B virus infection through NF-κB and ROS in Kupffer cells [ 19 ].…”

“…The IL-1β secretion during Aeromonas spp . infection is well studied in A. hydrophila [ 6 ], A. veronii [ 7 ] and A. sobria [ 8 ], and less reports focused on the IL-1β secretion in A. caviae . Macrophages played vital roles in host innate immunity in response to pathogens invasion.…”