Dynamic interplay of immune response, metabolome, and microbiota in cows during high-grain feeding: insights from multi-omics analysis

This study explores the dynamics of immune gene expression, ruminal metabolome, and gut microbiota in cows due to the duration of high-grain feeding, shedding light on host response and microbial dynamics in parallel. Cows consumed forage for a week, then gradually transitioned to a high-grain diet, which they consumed for 4 weeks. Immune response was evaluated in ruminal papillae by expression of genes related to the nuclear factor-kappaB (NFkB) pathway and correlated with the microbiota. Rumen metabolome was evaluated with high-performance liquid chromatography coupled with mass spectrometry and anion-exchange chromatography. Rumen and fecal microbiota were evaluated with 16S rRNA gene amplicon sequencing. In the rumen, expression of inflammation-associated genes increased with the duration on high grain, indicating activation of pro-inflammatory cascades; microbial diversity decreased with a high-grain diet but stabilized after week 3 on high grain. Changes in microbial relative abundance and metabolite enrichment were observed throughout the 4 weeks on high grain, with increments in propionogenic taxa (i.e., Succinivibrionaceae). Metabolite enrichment analysis showed that at the start of high-grain feeding, simple carbohydrates were enriched; then, these were substituted by their fermentation products. There were correlations between certain ruminal bacterial taxa (i.e., Ruminococcaceae UCG-005) and expression of genes of the NFkB pathway, suggesting the influence of these taxa on host immune response. In feces, microbial diversity and several Ruminococcaceae members initially declined but recovered by weeks 3 and 4. Overall, despite the stabilization of microbial diversity, changes in microbial relative abundance and proinflammatory genes were observed throughout high-grain feeding, suggesting that cows need more than 4 weeks to fully adjust once consuming a high-grain diet.IMPORTANCEDespite the stepwise diet transition typically assumed to serve for animal adaptation, expression of signaling receptors, mediators, and downstream targets of nuclear factor-kappaB pathway were found throughout the 4 weeks on high grain, which correlated with changes in the rumen microbial profile. In addition, although microbial diversity recovered in the feces and stabilized in the rumen in week 3 on high grain, we observed changes in microbial relative abundance throughout the 4 weeks on high grain, suggesting that cows need more than 4 weeks to adjust once consuming this diet. Findings are particularly important to consider when planning experiments involving dietary changes.

Role of interferons in LPS hypersensitivity

The innate immune response to Gram-negative bacteria depends mainly on the ability of the host to respond to the LPS component. Consequently, the state of LPS sensitivity at the time of infection and the numbers of invading bacteria ( i.e. the amounts of LPS) are primary factors determining the innate responses provoked by Gram-negative pathogens. LPS sensitivity increases following treatment of mice with live or killed micro-organisms. Two types of sensitization have been recognized, strong, IFN-γ-dependent and moderate IFN-γ-independent. IL-12 and IL-18 are intimately involved in the induction of IFN-γ by bacteria. We showed that Gram-negative bacteria induce IFN-γ in mice also by an IFN-β-dependent pathway that requires IL-18 and is independent of IL-12 signaling. This pathway is STAT4 dependent, the activation of which is directly linked to IFN-β. Further, IFN-β can be replaced by IFN-α. While different components of Gram-negative bacteria induce IL-12 and IL-18, LPS seems to be the only component in these bacteria capable of inducing IFN-β. Therefore, the IFN-β pathway of IFN-γ induction, unlike the IL-12 pathway, proceeds only in LPS responder mice. The IFN-α/β-dependent pathway is expected to play a role whenever IFN-α or IFN-β, and IL-18 are produced concomitantly during infection.

Heat shock protein profiles on the protein and gene expression levels in olive flounder kidney infected with Streptococcus parauberis

Heat shock proteins (HSPs) have been observed in cells exposed to a variety of stresses, including infectious pathogens. This study used a label-free, quantitative proteomic approach and transcriptional gene expression analysis to investigate infection-related HSP proteins and their encoding genes in whole kidneys from olive flounder (Paralichthys olivaceus). During Streptococcus parauberis infection in the flounder, the genes encoding Hsp10, Hsp40A4, Hsp40B6, Hsp40B11, Hsp60, Hsp70, glucose regulated protein 78 (Grp78), Hsp90α, Hsp90β and Grp94 were induced, and the protein levels of Hsp60, Hsp70, Hsp90α, Hsp90β and Grp94 were differentially regulated over time. Subsequent results also revealed that Hsp60, Hsp70, Hsp90α, Hsp90β and Grp94 appear to be the dominant and critical HSPs in olive flounder during bacterial infection. This is the first estimation of the differential involvement of HSPs in the immune response of olive flounder exposed to bacterial infection.

Propionibacterium acnes-killed attenuates the inflammatory response and protects mice from sepsis by modulating inflammatory factors

Background

Sepsis is a systemic inflammation associated with infection caused by pathogenic micro-organisms with high mortality rates.

Objective

In this study, we investigated the protective effect of Propionibacterium acnes-killed against polymicrobial sepsis induced by cecal ligation and puncture.

Methods

The mice were treated by intramuscular route in 1, 3, 5, and 7 days before the cecal ligation and puncture induction. The control group animals received vehicle (saline solution 0.9%) and the animals of the treated group received the P. acnes-killed (0.4 mg/animal). After anesthesia, midline laparotomy was performed with exposure of cecum followed by ligature and one transverse perforation of the same, with a 18 G needle, for induction of lethal sepsis. After surgery, the cecum of the animals was replaced into the peritoneal cavity, and it was closed with a 4.0 nylon suture. The survival of animals subjected to lethal sepsis was evaluated after cecal ligation and puncture induction. Six hours after the induction of sepsis, neutrophil migration, the number of bacteria, TNF-α, MCP-1, IL-6, and IL-10 were performed in the peritoneal lavage.

Results

Prophylactic treatment with P. acnes-killed increased the survival of the animals, followed by a significant decrease in the TNF-α, IL-10, and MCP-1 levels, 6 h after cecal ligation and puncture. Furthermore, P. acnes-killed administration reduced the number of bacteria in the peritoneal cavity with increased migration of leukocytes, especially neutrophils.

Conclusion

P. acnes-killed promoted increased survival rate of animals with sepsis, in part attributed to its immunomodulatory properties against pathogenic microorganisms, as well as better control of infection by reducing bacterial counts.

TLR9-dependent and independent pathways drive activation of the immune system by Propionibacterium acnes

Propionibacterium acnes is usually a relatively harmless commensal. However, under certain, poorly understood conditions it is implicated in the etiology of specific inflammatory diseases. In mice, P. acnes exhibits strong immunomodulatory activity leading to splenomegaly, intrahepatic granuloma formation, hypersensitivity to TLR ligands and endogenous cytokines, and enhanced resistance to infection. All these activities reach a maximum one week after P. acnes priming and require IFN-γ and TLR9. We report here the existence of a markedly delayed (1-2 weeks), but phenotypically similar TLR9-independent immunomodulatory response to P. acnes. This alternative immunomodulation is also IFN-γ dependent and requires functional MyD88. From our experiments, a role for MyD88 in the IFN-γ-mediated P. acnes effects seems unlikely and the participation of the known MyD88-dependent receptors, including TLR5, Unc93B-dependent TLRs, IL-1R and IL-18R in the development of the alternative response has been excluded. However, the crucial role of MyD88 can partly be attributed to TLR2 and TLR4 involvement. Either of these two TLRs, activated by bacteria and/or endogenously generated ligands, can fulfill the required function. Our findings hint at an innate immune sensitizing mechanism, which is potentially operative in both infectious and sterile inflammatory disorders.

All-trans retinoic acid induces TLR-5 expression and cell differentiation and promotes flagellin-mediated cell functions in human THP-1 cells

Toll-like receptor 5 (TLR-5), which is expressed on macrophages and dendritic cells (DCs), is a crucial cell surface molecule that senses microbial-associated molecular patterns and initiates host innate immune responses upon infection with invaders that express flagellin. Little information is known about the induction factors and mechanisms of TLR-5 expression. In this study, we demonstrate that all-trans retinoic acid (ATRA) significantly up-regulated TLR-5 expression in human macrophage THP-1 cells by co-activating NF-κB and the RARα receptor and inducing the differentiation of CD11b(-)CD11c(-) THP-1 cells to CD11b(+)CD11c(low) cells. Furthermore, when stimulated with flagellin, ATRA-induced THP-1 cells expressed multiple cytokines, including TNF-α, IL-1beta, and IL-12p40, and several co-stimulatory molecules, such as CD40, CD80, CD86, and MHC class I and II. We also showed that when ATRA-induced THP-1 cells were stimulated with flagellin, the cells displayed an allostimulatory capacity rather than phagocytic activity. Taken together, our findings suggest that ATRA is a crucial immunostimulatory cofactor that induces the activation of macrophages and their subsequent differentiation into dendritic-like cells.

Unraveling the lethal synergism betweenTrypanosoma cruzi infection and LPS: A role for increased macrophage reactivity

Various infections sensitize to lethal shock by promoting hyperactivation of macrophages to LPS stimulation. Although macrophages are thought to be deactivated upon contact with apoptotic cells during Trypanosoma cruzi infection, T. cruzi infection also sensitizes mice to endotoxemia. Herein, we studied the mechanisms of sensitization to endotoxemia in T. cruzi-infected mice in order to solve the paradox. Live (but not fixed) trypomastigotes from various stocks sensitized mice to endotoxemia. Mice deficient in glycolipid recognition (TLR2(-/-) and CD1d(-/-)) were sensitized by infection to challenge with LPS. Infected mice hyperproduced TNF and IL-10 upon LPS challenge. Infected TNF-R1(-/-), macrophage migration inhibitory factor (MIF)(-/-) and IFN-gamma(-/-) mice were lethally sensitized, but infected TNF-R1(-/-) mice administered anti-MIF survived shock with LPS. Macrophages from infected mice hyperproduced TNF in response to LPS stimulation and displayed increased expression of TLR4 compared to non-infected controls. Treatment with the PGE(2) synthesis inhibitor acetylsalicylic acid (AAS) in vivo reduced parasitemia and enhanced LPS-stimulated production of TNF by macrophages, but the effect was less in infected mice than in normal mice. Nevertheless, AAS treatment did not increase the susceptibility of infected mice to sublethal shock with LPS. Our results point to independent MIF and TNF/TNF-R1 lethal pathways and suggest a role for hyperactivated macrophages in T. cruzi-sensitized LPS-induced shock.

Stage of primary infection with lymphocytic choriomeningitis virus determines predisposition or resistance of mice to secondary bacterial infections

We investigated the effect of a primary non-lethal infection with lymphocytic choriomeningitis virus (LCMV) on the course and outcome of a secondary infection with the Gram-negative Salmonella enterica serovar Typhimurium or the Gram-positive Listeria monocytogenes in mice. We found that at each stage of the viral infection the susceptibility of mice to bacterial super-infections changes dramatically and depends also on whether the secondary infection is a Gram-positive or Gram-negative one. The study shows that the outcome of the secondary infection is determined by a delicate balance between the overproduction of and the hypersensitivity to inflammatory cytokines (TNF-alpha and IFN-gamma), as well as by the changes in blood leukocytes occurring in mice in the course of viral infection.

Lethal effect and apoptotic DNA fragmentation in response of D-GalN-treated mice to bacterial LPS can be suppressed by pre-exposure to minute amount of bacterial LPS: Dual role of TNF receptor 1

AIM: To investigate whether induction of tolerance of mice to lipopolysaccharide (LPS) was able to inhibit apoptotic reaction in terms of characteristic DNA fragmentation and protect mice from lethal effect.

METHODS: Experimental groups of mice were pretreated with non-lethal amount of LPS (0.05 μg). Both control and experimental groups simultaneously were challenged with LPS plus D-GalN for 6-7 h. The evaluations of both DNA fragmentations from the livers and the protection efficacy against lethality to mice through induction of tolerance to LPS were conducted.

RESULTS: In the naive mice challenge with LPS plus D-GalN resulted in complete death in 24 h, whereas a characteristic apoptotic DNA fragmentation was exclusively seen in the livers of mice receiving LPS in combination with D-GalN. The mortality in the affected mice was closely correlated to the onset of DNA fragmentation. By contrast, in the mice pre-exposed to LPS, both lethal effect and apoptotic DNA fragmentation were suppressed when challenged with LPS/D-GalN. In addition to LPS, the induction of mouse tolerance to TNF also enabled mice to cross-react against death and apoptotic DNA fragmentation when challenged with TNF and/or LPS in the presence of D-GalN. Moreover, this protection effect by LPS could last up to 24 h. TNFR1 rather than TNFR2 played a dual role in signaling pathway of either induction of tolerance to LPS for the protection of mice from mortality or inducing morbidity leading to the death of mice.

CONCLUSION: The mortality of D-GalN-treated mice in response to LPS was exceedingly correlated to the onset of apoptosis in the liver, which can be effectively suppressed by brief exposure of mice to a minute amount of LPS. The induced tolerance status was mediated not only by LPS but also by TNF. The developed tolerance to either LPS or TNF can be reciprocally cross-reacted between LPS and TNF challenges, whereas the signaling of induction of tolerance and promotion of apoptosis was through TNFR1, rather than TNFR2.

Enhanced resistance to Gram-positive bacterium and increased susceptibility to bacterial endotoxin in mice sensitized withPropionibacterium acnes: involvement of Toll-like receptor

Mice sensitized with Propionibacterium acnes showed an enhanced resistance against infection with Listeria monocytogenes in contrast to the increased susceptibility to LPS-induced endotoxin shock. The enhanced protection to L. monocytogenes was mediated by activated innate immunity but not by generation of Listeria-specific acquired immunity. After infection with L. monocytogenes, the elimination of bacteria was observed earlier in accordance with a higher level of endogenous cytokine production in P. acnes-sensitized mice than in control mice. Peritoneal cells from P. acnes-sensitized mice produced a larger amount of IL-12p70 and nitric oxide after stimulation with heat-killed L. monocytogenes or peptidoglycan purified from Staphylococcus aureus. RT-PCR analysis showed that the expression of TLR2 but not TLR1, TLR4 nor TLR6 was induced by injection of P. acnes in peritoneal cells. These results indicated that P. acnes-sensitization could induce the activation of innate immunity against L. monocytogenes through increased recognition of bacterial components by TLR2.

Differential contribution of Toll-like receptors 4 and 2 to the cytokine response to Salmonella enterica serovar Typhimurium and Staphylococcus aureus in mice

The contribution of murine Toll-like receptors 2 and 4 (TLR2 and -4, respectively) to cytokine induction by heat-killed bacteria was analyzed in vitro and in vivo. Gram-negative bacteria induced cytokines primarily via TLR4; the contribution of TLR2 was only minor. Neither TLR4 nor, surprisingly, TLR2 was required in the MyD88-dependent response to Staphylococcus aureus.

Beneficial or deleterious effects of a preexisting hypersensitivity to bacterial components on the course and outcome of infection

Priming with heat-killed Propionibacterium acnes enhances the sensitivity of mice to lipopolysaccharide (LPS) and other biologically active bacterial components. We show that P. acnes priming has protective and deleterious effects on a subsequent serovar Typhimurium infection. It may result in a complete protection or prolonged survival, or it may accelerate mortality of the infected mice, depending on the number of serovar Typhimurium bacteria administered and on the degree of LPS hypersensitivity at the time of infection. Both effects of P. acnes-induced hypersensitivity are mediated by gamma interferon (IFN-gamma) and are based on a differential activation of the innate immune mechanisms which recognize and react against the LPS present in infecting bacteria. In P. acnes-primed mice null for LPS-binding protein (LBP(-/-) mice), the impaired LPS recognition, due to the absence of LBP, resulted in a higher resistance to serovar Typhimurium infection. A similar P. acnes priming of mice had a protective, but no deleterious effect on a subsequent L. monocytogenes infection. This effect was IFN-gamma dependent but independent of LBP.

Differences in innate defense mechanisms in endotoxemia and polymicrobial septic peritonitis

Loss, reduction, or enhancement of the ability to respond to bacterial lipopolysaccharide (LPS) has no influence on survival of mice in a model of postoperative polymicrobial septic peritonitis induced by cecal ligation and puncture (CLP). This was demonstrated by using either mice with a defective Tlr4 gene, which encodes the critical receptor molecule for LPS responses, or mice deficient for LPS binding protein (LBP) or mice sensitized to LPS by Propionibacterium acnes. Though interleukin-12 (IL-12) and gamma interferon (IFN-gamma) play an important role in the sensitivity to LPS as well as in the resistance to several infections, loss of these cytokine pathways does not affect survival after CLP. Thus, neutralization of neither endogenous IL-12 nor IFN-gamma altered mortality. In addition, IFN-gamma receptor-deficient mice demonstrated the same sensitivity to CLP as mice with a functional IFN-gamma receptor. However, administration of IFN-gamma at the time of operation or pretreatment of both IFN-gamma-sensitive and IFN-gamma-resistant mice with IL-12 significantly enhanced mortality. This indicates that in the present infection model activation of innate defense mechanisms is not dependent on LPS recognition and does not require endogenous IL-12 or IFN-gamma function. Indeed, exogenous application of these two mediators had deleterious effects.