Prostaglandin E2 promotes nitric oxide synthase 2, platelet-activating factor receptor, and matrix metalloproteinase-2 expression in Escherichia coli-challenged ex vivo endometrial explants via the prostaglandin E2 receptor 4/protein kinase a signaling pathway

Prostaglandin E2 accumulation is closely associated with S. aureus-infected bovine endometritis

S. aureus isolated from bacterial bovine endometritis is common in epidemiological reports, but is often ignored as a subclinical pathogenic microorganism. In a previous study, we showed that live S. aureus (LSA) and heat killed S. aureus (HK-SA) induce different inflammatory responses in bovine endometrial tissue, and possibly being associated with the accumulation of prostaglandin E2 (PGE2). Thus, in this study, we varied PGE2 concentrations using inhibitors or agonists in HK-SA-treated bovine endometrial tissues. The results demonstrated that PGE2 has a positive relationship with IL-6, TNF-α, and damage-associated molecular patterns (DAMPs; e.g., HMGB-1 and HABP-1) expression and tissues damage, and is regulated by the EP4-p38 MAPK pathway. We concluded that lipoproteins of S. aureus are associated with PGE2 generation. To further explore the relationship between LSA and PGE2 accumulation, we used the S. aureus strain SA113 lipoprotein knockout (SA113Δlpl) to infect bovine endometrial epithelial cells (BECs). LSA decreased PGE2, cAMP, EP4, IL-6, IL-8, cAMP secretion, and the MAPK and PKA signaling pathways when infected with SA113Δlpl, as compared with SA113-infected groups. Moreover, the adhesion and invasion of BECs were similarly downregulated when lipoproteins in S. aureus were knocked out. The results of this study show that PGE2 is involved in both HK-SA- and LSA-induced inflammatory responses in the bovine endometrium. We suggest that S. aureus infection is associated with bovine endometritis, and although HK-SA and LSA induce different inflammatory responses, the strategy of decreasing PGE2 accumulation is helpful in reducing the inflammation stage caused by S. aureus.

PGE2 functions in ovoviviparous teleost black rockfish (Sebastes schlegelii): evolutionary status between parturition and ovulation†

Fish have evolved various reproductive strategies including oviparity, viviparity, and ovoviviparity, which undoubtedly affect the survival of the whole species continuity. As the final step in reproduction, parturition in viviparous vertebrate and ovulation in oviparous teleost seem to share a similar mechanism, when prostaglandins (PGs) act as the trigger to launch the whole process. In the present study, ovoviviparous teleost black rockfish (Sebastes schlegelii) is employed as the research object. Intraperitoneal injection showed that PGE2 (500 μg/kg) could activate the delivery reactions in perinatal black rockfish. RNA-seq data of ovary in perinatal period revealed transcriptional change in cell junction, inflammation, and apoptosis, which is related to mammal parturition and teleost ovulation. Further results proved the positive correlation between ptger EP2 and previous mentioned pathways. Subsequent experiment proved that PGE2 was able to induce the ovulation and spawning in unfertilized individuals, which had a bilayer follicular structure compared to monolayer follicular in perinatal period black rockfish. Both unfertilized and perinatal ovary matrix could response to PGE2 stimulation. In conclusion, the function of PGE2 in activating both parturition and ovulation in a relatively different pathways conserved with viviparity or oviparity provided novel evidence of the evolutionary status of ovoviviparous vertebrates.

Liriodendrin exerts protective effects against chronic endometritis in rats by modulating gut microbiota composition and the arginine/nitric oxide metabolic pathway

BACKGROUND

Chronic endometritis (CE), a gynecological disease, is characterized by inflammation. Liriodendrin is reported to exhibit anti-inflammatory properties. However, the therapeutic effects of liriodendrin on CE and the underlying molecular mechanisms have not been elucidated. This study aimed to investigate the therapeutic effects of liriodendrin on CE in rats and the underlying mechanisms.

METHODS

A CE rat model was established and administered with liriodendrin for 21 days. The serum levels of inflammatory cytokines were examined using enzyme-linked immunosorbent assay. The uterine mRNA levels of cytokines were examined using quantitative real-time polymerase chain reaction analysis. The activation of the Toll-like receptor 4 (TLR4)/NF-κB pathway was investigated using western blotting analysis. The effects of liriodendrin on intestinal flora and serum metabolites were examined using 16S rRNA sequencing and untargeted serum metabolomics, respectively. The protein and mRNA levels of arginase-2 (Arg-2) and the nitric oxide (NO) metabolic pathway-related factors were assessed. Molecular docking was performed to explore the interaction between liriodendrin and Arg-2.

RESULTS

Liriodendrin alleviated the CE-induced pathological changes in the uterus, modulated the serum levels of inflammatory cytokines, and downregulated the mRNA and protein levels of TLR4/NF-κB pathway-related factors. Treatment with liriodendrin mitigated the CE-induced upregulation of Firmicutes/Bacteroidetes ratio and Lachnospiraceae abundance and downregulation of Ruminococcaceae abundance. Serum metabolomic analysis revealed that liriodendrin regulated the biosynthesis of choline metabolism pathway-related factors. Liriodendrin suppressed the CE-induced upregulation of Arg-2 and downregulation of inducible nitric oxide synthase (iNOS) expression, and NO levels by directly binding to the amino acid residues of Arg-2 through hydroxyl bonds.

CONCLUSIONS

Liriodendrin exerted therapeutic effects on CE in rats through the alleviation of inflammation by modulating the gut microbiota structure, directly downregulating Arg-2, and regulating the arginine/NO metabolic pathway.

Anti-inflammatory effects of the prostaglandin D2/prostaglandin DP1 receptor and lipocalin-type prostaglandin D2 synthase/prostaglandin D2 pathways in bacteria-induced bovine endometrial tissue

Dairy cows often develop different degrees of endometritis after calving and this is attributed to pathogenic bacterial infections such as by Escherichia coli and Staphylococcus aureus. Infection of the bovine endometrium causes tissue damage and increases the expression of prostaglandin D2 (PGD2), which exerts anti-inflammatory effects on lung inflammation. However, the roles of PGD2 and its DP1 receptor in endometritis in cows remain unclear. Here, we examined the anti-inflammatory roles of the lipocalin-type prostaglandin D2 synthase (L-PGDS)/PGD2 and DP1 receptor regulatory pathways in bovine endometritis. We evaluated the regulatory effects of PGD2 on inflammation and tissue damage in E. coli- and S. aureus-infected bovine endometrial cells cultured in vitro. We found that the secretion of pro-inflammatory cytokines interleukin (IL)-6, IL-1β, and tumour necrosis factor (TNF)-α as well as expression of matrix metalloproteinase (MMP)-2, platelet-activating factor receptor (PAFR), and high mobility group box (HMGB)-1 were suppressed after DP1 receptor agonist treatment. In contrast, IL-6, IL-1β, and TNF-α release and MMP-2, PAFR, and HMGB-1 expression levels were increased after treatment of bovine endometrial tissue with DP1 receptor antagonists. DP1-induced anti-inflammatory effects were dependent on cellular signal transduction. The L-PGDS/PGD2 pathway and DP1 receptor induced anti-inflammatory effects in bovine endometrium infected with S. aureus and E. coli by inhibiting the mitogen-activated protein kinase and nuclear factor-κB signalling pathways, thereby reducing tissue damage. Overall, our findings provide important insights into the pathophysiological roles of PGD2 in bovine endometritis and establish a theoretical basis for applying prostaglandins or non-steroidal anti-inflammatory drugs for treating endometrial inflammatory infertility in bovines.

Infectious Inflammatory Processes and the Role of Bioactive Agent Released from Imino-Chitosan Derivatives Experimental and Theoretical Aspects

The paper focuses on the development of a multifractal theoretical model for explaining drug release dynamics (drug release laws and drug release mechanisms of cellular and channel-type) through scale transitions in scale space correlated with experimental data. The mathematical model has been developed for a hydrogel system prepared from chitosan and an antimicrobial aldehyde via covalent imine bonds. The reversible nature of the imine linkage points for a progressive release of the antimicrobial aldehyde is controlled by the reaction equilibrium shifting to the reagents, which in turn is triggered by aldehyde consumption in the inhibition of the microbial growth. The development of the mathematical model considers the release dynamic of the aldehyde in the scale space. Because the release behavior is dictated by the intrinsic properties of the polymer–drug complex system, they were explained in scale space, showing that various drug release dynamics laws can be associated with scale transitions. Moreover, the functionality of a Schrödinger-type differential equation in the same scale space reveals drug release mechanisms of channels and cellular types. These mechanisms are conditioned by the intensity of the polymer–drug interactions. It was demonstrated that the proposed mathematical model confirmed a prolonged release of the aldehyde, respecting the trend established by in vitro release experiments. At the same time, the properties of the hydrogel recommend its application in patients with intrauterine adhesions (IUAs) complicated by chronic endometritis as an alternative to the traditional antibiotics or antifungals.

Live S. aureus and heat-killed S. aureus induce different inflammation-associated factors in bovine endometrial tissue in vitro

Staphylococcus aureus is majorly involved in bovine mastitis; however, it weakly induces pro-inflammatory factors in mammary gland epithelial cells. We aimed to clarify the involvement of S. aureus in other inflammation types and its relationship with inflammatory factor secretion in bovine endometritis. We used live S. aureus (LSA)- and heat-killed S. aureus (HK-SA)-treated bovine endometrial tissue in vitro. The HK-SA-treated group showed significantly higher IL-6, IL-1β, TNF-α, CXCL1/2 and TLR2 expression than the LSA-infected group. Contrastingly, the LSA-infected group showed significantly higher PTGS2, mPGES-1, and EP4 expression than the HK-SA treated group. There was no significant between-group difference in hyaluronan-binding protein 1 expression, which suggested similar inflammatory responses. H&E results indicated that LSA and HK-SA induced shedding of endometrial gland epithelial cells. The LSA-infected group showed higher high-mobility group box 1 protein expression than the HK-SA treated groups, which indicated differences in signaling pathway activation. Further, the LSA-treated group had higher JNK and p38 MAPK levels while the HK-SA-treated group had higher IκB-α levels. There was no significant between-group difference in the ERK signaling pathway. Our findings indicate that the pathogen-associated molecular patterns (PAMPs) of S. aureus activate pro-inflammatory factor expression via the TLR2-ERK-NF-κB signaling pathway. Contrastingly, LSA induced PGE₂ accumulation via the TLR2/MAPKs signaling pathway. This is the first report that S. aureus and the PAMPs of S. aureus activate different signaling pathways and that LSA mainly induce PGE₂ accumulation rather than cytokine secretion.

Activation of alpha7 nicotinic acetylcholine receptor protects bovine endometrial tissue against LPS-induced inflammatory injury via JAK2/STAT3 pathway and COX-2 derived prostaglandin E2

Bovine endometritis is one of the major postpartum diseases associated with infertility and subfertility, decreasing the benefit of dairy industry. It is important to develop alternate therapies for endometritis in the context of drug residues in the milk and hormone disorder in the estrous cycle. α7 nicotine acetylcholine receptor has been identified as the core of 'cholinergic anti-inflammatory pathway (CAP)', which is a potential drug target to inflammatory diseases. However, there has been still no study on its anti-inflammatory effects and mechanism on lipopolysaccharide (LPS)-induced bovine endometritis. This study aimed to demonstrate the underlying anti-inflammatory effects and mechanism of α7-nACh receptor on LPS-induced inflammation in bovine endometrial tissues cultured in vitro. The results suggested that activation of α7-nACh receptor significantly suppressed the mRNA expression levels of interleukin 1β (IL-1β), IL-6, IL-8, and tumor necrosis factor alpha (TNF-α) in bovine endometrial tissues. Western blot and enzyme-linked immunosorbent assay (ELISA) detection results showed that activation of α7-nACh receptor inhibited LPS-induced phosphorylation of Janus kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3). Moreover, α7-nACh receptor agonist decreased the expression of cyclooxygenase 2 (COX-2) and microsomal prostaglandin E synthase-1(mPGES-1), as well as prostaglandin E₂ (PGE₂) secretion. Interestingly, in COX-2 inhibition experiment, activation of α7-nACh receptor increased COX-2 expression and PGE₂ production, compared with COX-2 inhibitor treatment. In conclusion, activation of the cholinergic system through α7-nACh receptor agonist has suppressed inflammation of bovine endometrial tissues via JAK2/STAT3 pathway and potential COX-2-derived PGE₂.

Strategies for Optimizing the Production of Proteins and Peptides with Multiple Disulfide Bonds

Bacteria can produce recombinant proteins quickly and cost effectively. However, their physiological properties limit their use for the production of proteins in their native form, especially polypeptides that are subjected to major post-translational modifications. Proteins that rely on disulfide bridges for their stability are difficult to produce in Escherichia coli. The bacterium offers the least costly, simplest, and fastest method for protein production. However, it is difficult to produce proteins with a very large size. Saccharomyces cerevisiae and Pichia pastoris are the most commonly used yeast species for protein production. At a low expense, yeasts can offer high protein yields, generate proteins with a molecular weight greater than 50 kDa, extract signal sequences, and glycosylate proteins. Both eukaryotic and prokaryotic species maintain reducing conditions in the cytoplasm. Hence, the formation of disulfide bonds is inhibited. These bonds are formed in eukaryotic cells during the export cycle, under the oxidizing conditions of the endoplasmic reticulum. Bacteria do not have an advanced subcellular space, but in the oxidizing periplasm, they exhibit both export systems and enzymatic activities directed at the formation and quality of disulfide bonds. Here, we discuss current techniques used to target eukaryotic and prokaryotic species for the generation of correctly folded proteins with disulfide bonds.

TLR2/4 promotes PGE2 production to increase tissue damage in Escherichia coli-infected bovine endometrial explants via MyD88/p38 MAPK pathway

Prostaglandin E2 (PGE₂), a lipid mediator, is released by several cell types including endometrial cells and plays a central role in bacterial infection of the endometrium during inflammation. PGE₂ production accumulated in Escherichia coli (E. coli) -infected bovine endometrial tissue, which increased E. coli-infected endometrial tissue damage. However, the mechanisms of PGE₂ accumulation in the E. coli-infected endometrium during inflammation-associated endometrial tissue damage remain unclear. This study was conducted to investigate the role of Toll-like receptors (TLRs) 2 and 4 in increased PGE₂ production in E. coli-infected endometrial tissue. E. coli and TLR2/4 agonists significantly induced cyclooxygenase-2 and microsomal prostaglandin E synthase-1 expression and PGE₂ synthesis detected by RT-PCR, Western blot, and ELISA in the endometrial tissue. The expression and synthesis were dramatically decreased by TLR4, myeloid differentiation factor88 (MyD88), and p38 mitogen-activated protein kinase (MAPK) inhibitors in E. coli-infected endometrial tissue. These inhibitors also significantly decreased proinflammatory factor (interleukin-6 and tumor necrosis factor-α) and damage-associated molecular pattern (high mobility group box-1 and hyaluronan-binding protein-1) release and tissue damage measured by double-label immunofluorescence in E. coli-infected endometrial explants. Our work provides in vitro evidence that TLR2/4-MyD88/p38 MAPK promotes PGE₂ synthesis and E. coli-infected endometrial tissue damage, which may be useful for improving PGE₂-based therapies for endometritis.

Water-separated part of Chloranthus serratus alleviates lipopolysaccharide- induced RAW264.7 cell injury mainly by regulating the MAPK and Nrf2/HO-1 inflammatory pathways

Background

Chloranthus serratus (Chloranthaceae) has been used to treat bruises, rheumatoid and bone pain. However, the anti-inflammatory mechanisms of C. serratus in vitro have not been fully elucidated. The present study aimed to explore the anti-inflammatory activity and potential mechanisms of C. serratus’s separated part of water (CSSPW) in lipopolysaccharide (LPS)-induced RAW264.7 cells.

Methods

The concentrations of CSSPW were optimized by CCK-8 method. Nitric oxide (NO) content was detected by one-step method. The levels of inflammatory cytokines were determined by enzyme-linked immunosorbent assay (ELISA). Gene expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) was detected by real-time quantitative PCR (qPCR). Immunofluorescence and DCFH-DA fluorescent probes were used to detect p65 nuclear translocation and reactive oxygen species (ROS) content, respectively. Western blotting was used to assay the protein expression of mitogen-activated protein kinases (MAPK), nuclear factor-kappa B (NF-κB) and nuclear transcription factor E2 related factor 2/haem oxygenase-1 (Nrf2/HO-1) pathways.

Results

The final concentrations of 15 ng/mL, 1.5 μg/mL and 150 μg/mL were selected as low, medium and high doses of CSSPW, respectively. CSSPW treatment significantly reduced the generation of NO, tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6), prostaglandinE₂ (PGE₂), iNOS mRNA and COX-2 mRNA in response to LPS stimulation. Furthermore, the protein expression of the MAPK and NF-κB pathways was suppressed by CSSPW treatment, as well as p65 nuclear translocation and ROS production. In contrast, the protein expression of the Nrf2/HO-1 pathway was markedly upregulated.

Conclusions

CSSPW exerts its anti-inflammatory effect via downregulating the production of pro-inflammatory mediators, inhibiting the activation of NF-κB and MAPK pathways, as well as activating Nrf2/HO-1 pathway in LPS-induced RAW264.7 cells.

EP2/4 Receptors Promote the Synthesis of PGE2 Increasing Tissue Damage in Bovine Endometrial Explants Induced by Escherichia coli

The bovine uterine is easily contaminated with bacteria during coitus or parturition. A previous study suggested that prostaglandin E₂ (PGE₂) promoted Escherichia coli-infected bovine endometrial tissue inflammatory damage via cyclooxygenase-2 (COX-2) and microsomal prostaglandin E synthase-1 (mPGES-1). However, it remains unclear which PGE₂ receptors regulate the proinflammatory effect of PGE₂ In this study, we evaluated the effect of PGE₂ and its mediated receptors on E. coli-infected endometrium explants isolated from the bovine uterus. The E. coli-infected bovine endometrial explants were cultured in vitro, and the study used EP2/4 receptor agonists to investigate the responses of COX-2, mPGES-1, PGE₂, proinflammatory factors, and damage-associated molecular patterns (DAMPs). The expression of COX-2, mPGES-1, PGE₂, proinflammatory factors, and DAMPs was significantly increased after infection with E. coli; however, the high expression levels caused by E. coli were reduced following treatment with COX-2 and mPGES-1 inhibitors. In addition, the expression levels of COX-2, mPGES-1, PGE₂, proinflammatory factors, and DAMPs were higher in treatment with EP2/4 receptor agonists in E. coli-infected endometrium explants, and their promotable effects were effectively blocked by EP2/4 receptor antagonists. These findings provide evidence that PGE₂ may promote the progress of inflammation in endometrial explants infected with E. coli in bovines. Furthermore, EP2/4 may be involved in a positive feedback loop for COX-2 and mPGES-1 expression, and this may be responsible for the proinflammatory reaction of PGE₂ in E. coli-infected uteri of bovines. SIGNIFICANCE STATEMENT: PGE₂ promoted E. coli-infected bovine endometrial tissue damage via COX-2 and mPGES-1. However, this proinflammatory effect of PGE₂ depends on which receptors are affected by PGE₂, and this remains unclear. In this study, it was investigated that EP2 and EP4 may be involved in a positive feedback loop for COX-2 and mPGES-1 expression, and this may be responsible for the proinflammatory reaction of PGE₂ in E. coli-infected uteri of bovines.