TLR22-mediated activation of TNF-α-caspase-1/IL-1β inflammatory axis leads to apoptosis of Aeromonas hydrophila-infected macrophages

Correlation analysis between IL-1R/TLRs pathway and superficial dermatomycosis

OBJECTIVE

This study explored the correlation between interleukin-1 receptor/Toll-like receptor (IL-1R/TLRs)-mediated inflammatory signaling pathways and the severity of superficial dermatomycosis.

METHODS

From May 2020 to August 2022, 76 patients with superficial dermatomycosis (infected group) and 52 patients without infection (non-infected group) were enrolled. The indicators related to IL-1R/TLRs pathway were analyzed, and the diagnostic value of the combined detection of each index for superficial dermatomycosis and disease severity was analyzed. The correlation between each index and the severity of infection was analyzed.

RESULTS

IL-1β, TLR4, IL-6, and TNF-α in the infected group were higher than those in the non-infected group (P < 0.05). The AUC of IL-1R/TLRs combined detection in the group diagnosed with a superficial dermatomycosis was higher than that of each single detection (P < 0.05). IL-1β, TLR4, IL-6, and TNF-α in the severe group were higher than those in the mild group (P < 0.05). IL-1β, TLR4, IL-6, and TNF-α were positively correlated with the degree of infection (P < 0.05). The AUC of IL-1R/TLRs combined detection was higher than that of each single test (P < 0.05). IL-1β ≥ 2.87 ng/L, TLR4 ≥ 3.12 ng/L, IL-6 ≥ 4.58 ng/L, TNF-α ≥ 70.53 ng/L were the influencing factors of severe superficial dermatomycosis (P < 0.05).

CONCLUSION

IL-1R/TLRs pathway is related to the severity of superficial dermatomycosis, and the collective identification of each indicator provides diagnostic insight into infection severity.

Effect of Vietnamese coriander Powder on Growth, Body Composition, Hematology, and Immune-Related Gene Expression in Nile Tilapia

Dietary supplementation of plant herbs into aquafeed is recommended for intensive and sustainable aquaculture practices. This study has investigated the effect of Persicaria odorata (PO) leaf powder on growth, feed utilization, whole-body composition, hematology, and immune-related gene expression in Nile tilapia (Oreochromis niloticus). Fish (∼7.77 ± 0.01 g/fish) were randomly allocated into four treatment groups, each with three replicates. They were fed with dietary supplementation of PO at concentrations of 0, 15, 30, and 50 g/kg (termed PO0-PO50) for 10 weeks. Results indicated that the final body weight, weight gain, and specific growth rate were significantly higher at all PO supplementation levels compared to the control, with the highest value in the PO30 group. Similarly, the protein efficiency ratio and protein productive value in all PO groups were significantly higher than those of the control group. Red blood cells, white blood cells, and hemoglobin levels showed quadratic increases in the PO groups. In addition, total protein, globulin, and high-density lipoprotein cholesterol were linearly and quadratically increased with increasing PO levels, but alanine aminotransferase activity was linearly and quadratically decreased. Furthermore, dietary PO supplementation linearly decreased triglyceride and lipoprotein cholesterol levels, with the lowest levels found in the PO15 group. The expression of genes related to immunity showed that dietary supplementation of PO significantly increased the expression of proinflammatory factors (IL-1β and TNF-α), anti-inflammatory (IL-10 and TGF-β), and HSP70. In addition, glucose and cortisol levels decreased in all PO-supplemented groups, with the lowest levels found in the PO50 and PO30 groups, respectively. These findings showed that a dietary intervention with PO could improve growth, feed utilization, hematological parameters, upregulating genes related to immunity, and decreasing stress markers in Nile tilapia. Consequently, the utilization of PO at a dosage of 30 g/kg could contribute to the sustainable development of the aquaculture sector.

Differentially Expressed Genes and Alternative Splicing Analysis Revealed the Difference in Virulence to American Eels (Anguilla rostrata) Infected by Edwardsiella anguillarum and Aeromonas hydrophila

Edwardsiella anguillarum and Aeromonas hydrophila are two common bacterial pathogens affecting cultivated eels, and the differences in their virulence remain unclear. In this study, after two groups of American eels (Anguilla rostrata) were administered the LD50 dose of E. anguillarum and A. hydrophila, respectively, the histopathology of the liver, trunk kidney, and spleen, as well as transcriptomic RNA sequencing (RNA-seq) analysis of the spleen, was examined at three time points: pre-infection (Con group) and post-infection at 36 h (Ea_36 group, Ah_36 group) and 60 h (Ea_60 group, Ah_60 group). The results showed that the differences in pathological changes were characterized by severe hepatocyte edema at 36 h post-infection (hpi) and hepatocyte atrophy at 60 hpi in the livers of eels infected by A. hydrophila, in contrast to the severe atrophy of glomeruli in the trunk kidneys and numerous bacterial nodules in the spleens of eels infected by E. anguillarum. The RNA-seq results revealed 906 and 77 typical differentially expressed genes (DEGs) in eels infected with E. anguillarum and A. hydrophila, respectively, compared to the control eels. The DEGs between the infected and control groups were predominantly annotated in GO terms related to binding, catalytic activity, membrane part, cell part, and cellular process, as well as in KEGG pathways associated with human diseases and organismal systems. The GO enrichment analysis showed 83 and 146 differential GO terms, along with 32 and 78 differential KEGG pathways in two comparisons of Ea_36 vs Con versus Ah_36 vs Con and Ea_60 vs Con versus Ah_60 vs Con, respectively. Furthermore, the analysis of differential alternative splicing genes (DASs) showed 1244 and 1341 DASs out of 12,907 and 12,833 AS genes, respectively, in the comparisons of Ea_36 vs Ah_36 and Ea_60 vs Ah_60. These DASs were enriched in two common KEGG pathways: "NOD-like receptor signaling pathway" and "necroptosis" which shared 11 hub DASs. Finally, analysis of protein-protein interactions revealed that 91 of 412 cross DASs between Ea_36 vs Ah_36 and Ea_60 vs Ah_60 potentially play an essential role in the difference in virulence of E. anguillarum and A. hydrophila in American eels, with 12 encoded proteins being particularly notable. Together, this study is the first to report a comparative pathogenicity and RNA-seq analysis of E. anguillarum and A. hydrophila in American eels, shedding new light on our understanding of the differences in virulence as revealed by pathological changes, DEGs, and DASs, contributing to more effective control strategies to prevent outbreaks of bacterial infections.

Activation of ARP2/3 and HSP70 Expression by Lipoteichoic Acid: Potential Bidirectional Regulation of Apoptosis in a Mastitis Inflammation Model

Mastitis typically arises from bacterial invasion, where host cell apoptosis significantly contributes to the inflammatory response. Gram-positive bacteria predominantly utilize the virulence factor lipoteichoic acid (LTA), which frequently leads to chronic breast infections, thereby impacting dairy production and animal husbandry adversely. This study employed LTA to develop models of mastitis in cow mammary gland cells and mice. Transcriptomic analysis identified 120 mRNAs associated with endocytosis and apoptosis pathways that were enriched in the LTA-induced inflammation of the Mammary Alveolar Cells-large T antigen (MAC-T), with numerous differential proteins also concentrated in the endocytosis pathway. Notably, actin-related protein 2/3 complex subunit 3 (ARPC3), actin-related protein 2/3 complex subunit 4 (ARPC4), and the heat shock protein 70 (HSP70) are closely related. STRING analysis revealed interactions among ARPC3, ARPC4, and HSP70 with components of the apoptosis pathway. Histological and molecular biological assessments confirmed that ARPC3, ARPC4, and HSP70 were mainly localized to the cell membrane of mammary epithelial cells. ARPC3 and ARPC4 are implicated in the mechanisms of bacterial invasion and the initiation of inflammation. Compared to the control group, the expression levels of these proteins were markedly increased, alongside the significant upregulation of apoptosis-related factors. While HSP70 appears to inhibit apoptosis and alleviate inflammation, its upregulation presents novel research opportunities. In conclusion, we deduced the development mechanism of ARPC3, ARPC4, and HSP70 in breast inflammation, laying the foundation for further exploring the interaction mechanism between the actin-related protein 2/3 (ARP2/3) complex and HSP70.

β-Catenin Elicits Drp1-Mediated Mitochondrial Fission Activating the Pro-Apoptotic Caspase-1/IL-1β Signalosome in Aeromonas hydrophila-Infected Zebrafish Macrophages

Canonical Wnt signaling plays a major role in regulating microbial pathogenesis. However, to date, its involvement in A. hydrophila infection is not well known. Using zebrafish (Danio rerio) kidney macrophages (ZKM), we report that A. hydrophila infection upregulates wnt2, wnt3a, fzd5, lrp6, and β-catenin (ctnnb1) expression, coinciding with the decreased expression of gsk3b and axin. Additionally, increased nuclear β-catenin protein accumulation was observed in infected ZKM, thereby suggesting the activation of canonical Wnt signaling in A. hydrophila infection. Our studies with the β-catenin specific inhibitor JW67 demonstrated β-catenin to be pro-apoptotic, which initiates the apoptosis of A. hydrophila-infected ZKM. β-catenin induces NADPH oxidase (NOX)-mediated ROS production, which orchestrates sustained mitochondrial ROS (mtROS) generation in the infected ZKM. Elevated mtROS favors the dissipation of the mitochondrial membrane potential (ΔΨm) and downstream Drp1-mediated mitochondrial fission, leading to cytochrome c release. We also report that β-catenin-induced mitochondrial fission is an upstream regulator of the caspase-1/IL-1β signalosome, which triggers the caspase-3 mediated apoptosis of the ZKM as well as A. hydrophila clearance. This is the first study suggesting a host-centric role of canonical Wnt signaling pathway in A. hydrophila pathogenesis wherein β-catenin plays a primal role in activating the mitochondrial fission machinery, which actively promotes ZKM apoptosis and helps in containing the bacteria.

Molecular characterization of a teleost-specific toll-like receptor 22 (tlr22) gene from yellow catfish (Pelteobagrus fulvidraco) and its transcriptional change in response to poly I:C and Aeromonas hydrophila stimuli

Toll-like receptors (TLRs) are a class of pattern recognition receptors (PRRs) that can recognize pathogen-associated molecular patterns (PMPs) and play important roles in the innate immune system in vertebrates. In this study, we identified a teleost-specific tlr22 gene from yellow catfish (Pelteobagrus fulvidraco) and its immune roles in response to different pathogens were also determined. The open reading frame (ORF) of the tlr22 was 2892 bp in length, encoding a protein of 963 amino acids. Multiple protein sequences alignment, secondary and three-dimensional structure analyses revealed that TLR22 is highly conserved among different fish species. Phylogenetic analysis showed that the phylogenetic topology was divided into six families of TLR1, TLR3, TLR4, TLR5, TLR7 and TLR11, and TLR22 subfamily was clustered into TLR11 family. Meanwhile, synteny and gene structure comparisons revealed functional and evolutionary conservation of the tlr22 gene in teleosts. Furthermore, tlr22 gene was shown to be widely expressed in detected tissues except barbel and eye, with highest expression level in liver. The transcription of tlr22 was significantly increased in spleen, kidney, liver and gill tissues at different timepoints after Poly I:C infection, suggesting TLR22 plays critical roles in defensing virus invasion. Similarly, the transcription of tlr22 was also dramatically up-regulated in spleen, kidney and gill tissues with different patterns after Aeromonas hydrophila infection, indicating that TLR22 is also involved in resisting bacteria invasion. Our findings will provide a solid basis for the investigation the immune functions of tlr22 gene in teleosts, as well as provide useful information for disease control and treatment for yellow catfish.

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

Aeromonas caviae, an important food-borne pathogen, induces serious invasive infections and inflammation. The pro-inflammatory IL-1β functions against pathogenic infections and is elevated in various Aeromonas infection cases. However, the molecular mechanism of A. caviae-mediated IL-1β secretion remains unknown. In this study, mouse macrophages (PMs) were used to establish A. caviae infection model and multiple strategies were utilized to explore the mechanism of IL-1β secretion. IL-1β was elevated in A. caviae infected murine serum, PMs lysates or supernatants. This process triggered NLRP3 levels upregulation, ASC oligomerization, as well as dot gathering of NLRP3 and speck-like signals of ASC in the cytoplasm. MCC950 blocked A. caviae mediated IL-1β release. Meanwhile, NLRP3 inflammasome mediated the release of IL-1β in dose- and time-dependent manners, and the release of IL-1β was dependent on active caspase-1, as well as NLRP3 inflammasome was activated by potassium efflux and cathepsin B release ways. A. caviae also enhanced TLR2 levels, and deletion of TLR2 obviously decreased IL-1β secretion. What’s more, A. caviae resulted in NF-κB p65 nuclear translocation partly in a TLR2-dependent manner. Blocking NF-κB using BAY 11-7082 almost completely inhibited NLRP3 inflammasome first signal pro-IL-1β expression. Blocking TLR2, NF-κB, NLRP3 inflammasome significantly downregulated IL-1β release and TNF-α and IL-6 levels. These data illustrate that A. caviae caused IL-1β secretion in PMs is controlled by NLRP3 inflammasome, of which is mediated by NF-κB pathway and is partially dependent on TLR2, providing basis for drugs against A. caviae.

Aeromonas hydrophila inhibits autophagy triggering cytosolic translocation of mtDNA which activates the pro-apoptotic caspase-1/IL-1β-nitric oxide axis in headkidney macrophages

The molecular mechanisms underlying Aeromonas hydrophila-pathogenesis are not well understood. Using head kidney macrophages (HKM) of Clarias gariepinus, we previously reported the role of ER-stress in A. hydrophila-induced pathogenesis. Here, we report that PI3K/PLC-induced cytosolic-Ca²⁺ imbalance induces the expression of pro-apoptotic ER-stress marker, CHOP in A. hydrophila-infected HKM. CHOP promotes HKM apoptosis by inhibiting AKT activation and enhancing JNK signaling. Elevated mitochondrial ROS (mtROS) was recorded which declined significantly by ameliorating ER-stress and in the presence of ER-Ca²⁺ release modulators (2-APB and dantrolene) and mitochondrial-Ca²⁺ uptake inhibitor, Ru360, together suggesting the role of ER-mitochondrial Ca²⁺ dynamics in mtROS generation. Inhibiting mtROS production reduced HKM death implicating the pro-apoptotic role of mtROS in A. hydrophila-pathogenesis. The expression of autophagic proteins (LC3B, beclin-1, and atg 5) was suppressed in the infected HKM. Our results with autophagy-inducer rapamycin demonstrated that impaired autophagy favored the cytosolic accumulation of mitochondrial DNA (mtDNA) and the process depended on mtROS levels. Enhanced caspase-1 activity and IL-1β production was detected and transfection studies coupled with pharmacological inhibitors implicated mtROS/mtDNA axis to be crucial for activating the caspase-1/IL-1β cascade in infected HKM. RNAi studies further suggested the involvement of IL-1β in generating pro-apoptotic NO in A. hydrophila-infected HKM. Our study suggests a novel role of ER-mitochondria cross-talk in regulating A. hydrophila pathogenesis. Based on our observations, we conclude that A. hydrophila induces ER-stress and inhibits mitophagy resulting in mitochondrial dysfunction which leads to mtROS production and translocation of mtDNA into cytosol triggering the activation of caspase-1/IL-1β-mediated NO production, culminating in HKM apoptosis.

Immunoprotective Effects of Two Histone H2A Variants in the Grass Carp Against Flavobacterium columnare Infection

In teleost fish, the nucleotide polymorphisms of histone H2A significantly affect the resistance or susceptibility of zebrafish to Edwardsiella piscicida infection. Whether histone H2A variants can enhance the resistance of grass carp to Flavobacterium columnare infection remains unclear. Here, the effects of 7 previously obtained variants (gcH2A-1~gcH2A-7) and 5 novel histone H2A variants (gcH2A-11, gcH2A-13~gcH2A-16) in response to F. columnare infection were investigated. It was found that these histone H2A variants could be divided into type I and II. Among them, 5 histone H2A variants had no any effects on the F. columnare infection, however 7 histone H2A variants had antibacterial activity against F. columnare infection. The gcH2A-4 and gcH2A-11, whose antibacterial activity was the strongest in type I and II histone H2A variants respectively, were picked out for yeast expression. Transcriptome data for the samples from the intestines of grass carp immunized with the engineered Saccharomyces cerevisiae expressing PYD1, gcH2A-4 or gcH2A-11 revealed that 5 and 12 immune-related signaling pathways were significantly enriched by gcH2A-4 or gcH2A-11, respectively. For the engineered S. cerevisiae expressing gcH2A-4, NOD-like receptor and Toll-like receptor signaling pathways were enriched for up-regulated DEGs. Besides NOD-like receptor and Toll-like receptor signaling pathways, the engineered S. cerevisiae expressing gcH2A-11 also activated Cytosolic DNA-sensing pathway, RIG-I-like receptor signaling pathway and C-type lectin receptor signaling pathway. Furthermore, grass carp were immunized with the engineered S. cerevisiae expressing PYD1, gcH2A-4 or gcH2A-11 for 1 month and challenged with F. columnare. These grass carp immunized with gcH2A-4 or gcH2A-11 showed lower mortality and fewer numbers of F. columnare than did the control group. All these results suggest that gcH2A-4 and gcH2A-11 play important roles in evoking the innate immune responses and enhancing disease resistance of grass carp against F. columnare infection.