Gas6 negatively regulates the Staphylococcus aureus-induced inflammatory response via TLR signaling in the mouse mammary gland

Ferroptosis is involved in Staphylococcus aureus-induced mastitis through autophagy activation by endoplasmic reticulum stress

Cell death caused by severe Staphylococcus aureus (S. aureus) infection is a fatal threat to humans and animals. However, whether ferroptosis, an iron-dependent form of cell death, is involved in S. aureus-induced cell death and its role in S. aureus-induced diseases are unclear. Using a mouse mastitis model and mammary epithelial cells (MMECs), we investigated the role of ferroptosis in the pathogenesis of S. aureus infection. The results revealed that S. aureus-induced ferroptosis in vivo and in vitro as demonstrated by dose-dependent increases in cell death; the level of malondialdehyde (MDA), the final product of lipid peroxidation; and dose-dependent decrease the production of the antioxidant glutathione (GSH). Treatment with typical inhibitors of ferroptosis, including ferrostatin-1 (Fer-1) and deferiprone (DFO), significantly inhibited S. aureus-induced death in MMECs. Mechanistically, treatment with S. aureus activated the protein kinase RNA-like ER kinase (PERK)-eukaryotic initiation factor 2, α subunit (eIF2α)-activating transcription factor 4 (ATF4)-C/EBP homologous protein (CHOP) pathway, which subsequently upregulated autophagy and promoted S. aureus-induced ferroptosis. The activation of autophagy degraded ferritin, resulting in iron dysregulation and ferroptosis. In addition, we found that excessive reactive oxygen species (ROS) production induced ferroptosis and activated endoplasmic reticulum (ER) stress, manifesting as elevated p-PERK-p-eIF2α-ATF4-CHOP pathway protein levels. Collectively, our findings indicate that ferroptosis is involved in S. aureus-induced mastitis via ER stress-mediated autophagy activation, implying a potential strategy for the prevention of S. aureus-associated diseases by targeting ferroptosis. In conclusion, the ROS-ER stress-autophagy axis is involved in regulating S. aureus-induced ferroptosis in MMECs. These findings not only provide a new potential mechanism for mastitis induced by S. aureus but also provide a basis for the treatment of other ferroptotic-related diseases.

Development and challenges of antimicrobial peptide delivery strategies in bacterial therapy: A review

The escalating global prevalence of antimicrobial resistance poses a critical threat, prompting concerns about its impact on public health. This predicament is exacerbated by the acute shortage of novel antimicrobial agents, a scarcity attributed to the rapid surge in bacterial resistance. This review delves into the realm of antimicrobial peptides, a diverse class of compounds ubiquitously present in plants and animals across various natural organisms. Renowned for their intrinsic antibacterial activity, these peptides provide a promising avenue to tackle the intricate challenge of bacterial resistance. However, the clinical utility of peptide-based drugs is hindered by limited bioavailability and susceptibility to rapid degradation, constraining efforts to enhance the efficacy of bacterial infection treatments. The emergence of nanocarriers marks a transformative approach poised to revolutionize peptide delivery strategies. This review elucidates a promising framework involving nanocarriers within the realm of antimicrobial peptides. This paradigm enables meticulous and controlled peptide release at infection sites by detecting dynamic shifts in microenvironmental factors, including pH, ROS, GSH, and reactive enzymes. Furthermore, a glimpse into the future reveals the potential of targeted delivery mechanisms, harnessing inflammatory responses and intricate signaling pathways, including adenosine triphosphate, macrophage receptors, and pathogenic nucleic acid entities. This approach holds promise in fortifying immunity, thereby amplifying the potency of peptide-based treatments. In summary, this review spotlights peptide nanosystems as prospective solutions for combating bacterial infections. By bridging antimicrobial peptides with advanced nanomedicine, a new therapeutic era emerges, poised to confront the formidable challenge of antimicrobial resistance head-on.

Hexadecanamide alleviates Staphylococcus aureus-induced mastitis in mice by inhibiting inflammatory responses and restoring blood-milk barrier integrity

Subacute ruminal acidosis (SARA) has been demonstrated to promote the development of mastitis, one of the most serious diseases in dairy farming worldwide, but the underlying mechanism is unclear. Using untargeted metabolomics, we found hexadecanamide (HEX) was significantly reduced in rumen fluid and milk from cows with SARA-associated mastitis. Herein, we aimed to assess the protective role of HEX in Staphylococcus aureus (S. aureus)- and SARA-induced mastitis and the underlying mechanism. We showed that HEX ameliorated S. aureus-induced mastitis in mice, which was related to the suppression of mammary inflammatory responses and repair of the blood-milk barrier. In vitro, HEX depressed S. aureus-induced activation of the NF-κB pathway and improved barrier integrity in mouse mammary epithelial cells (MMECs). In detail, HEX activated PPARα, which upregulated SIRT1 and subsequently inhibited NF-κB activation and inflammatory responses. In addition, ruminal microbiota transplantation from SARA cows (S-RMT) caused mastitis and aggravated S. aureus-induced mastitis, while these changes were reversed by HEX. Our findings indicate that HEX effectively attenuates S. aureus- and SARA-induced mastitis by limiting inflammation and repairing barrier integrity, ultimately highlighting the important role of host or microbiota metabolism in the pathogenesis of mastitis and providing a potential strategy for mastitis prevention.

Genomic and Phenotypic Udder Evaluation for Dairy Cattle Selection: A Review

The traditional point of view regarding dairy cattle selection has been challenged by recent genomic studies indicating that livestock productivity prediction can be redefined based on the evaluation of genomic and phenotypic data. Several studies that included different genomic-derived traits only indicated that interactions among them or even with conventional phenotypic evaluation criteria require further elucidation. Unfortunately, certain genomic and phenotypic-derived traits have been shown to be secondary factors influencing dairy production. Thus, these factors, as well as evaluation criteria, need to be defined. Owing to the variety of genomic and phenotypic udder-derived traits which may affect the modern dairy cow functionality and conformation, a definition of currently important traits in the broad sense is indicated. This is essential for cattle productivity and dairy sustainability. The main objective of the present review is to elucidate the possible relationships among genomic and phenotypic udder evaluation characteristics to define the most relevant traits related to selection for function and conformation in dairy cattle. This review aims to examine the potential impact of various udder-related evaluation criteria on dairy cattle productivity and explore how to mitigate the adverse effects of compromised udder conformation and functionality. Specifically, we will consider the implications for udder health, welfare, longevity, and production-derived traits. Subsequently, we will address several concerns covering the application of genomic and phenotypic evaluation criteria with emphasis on udder-related traits in dairy cattle selection as well as its evolution from origins to the present and future prospects.

Ginsenoside Rb1 Mitigates Escherichia coli Lipopolysaccharide-Induced Endometritis through TLR4-Mediated NF-κB Pathway

Endometritis is the inflammatory response of the endometrial lining of the uterus and is associated with low conception rates, early embryonic mortality, and prolonged inter-calving intervals, and thus poses huge economic losses to the dairy industry worldwide. Ginsenoside Rb1 (GnRb1) is a natural compound obtained from the roots of Panax ginseng, having several pharmacological and biological properties. However, the anti-inflammatory properties of GnRb1 in lipopolysaccharide (LPS)-challenged endometritis through the TLR4-mediated NF-κB signaling pathway has not yet been researched. This study was planned to evaluate the mechanisms of how GnRb1 rescues LPS-induced endometritis. In the present research, histopathological findings revealed that GnRb1 ameliorated LPS-triggered uterine injury. The ELISA and RT-qPCR assay findings indicated that GnRb1 suppressed the expression level of pro-inflammatory molecules (TNF-α, IL-1β and IL-6) and boosted the level of anti-inflammatory (IL-10) cytokine. Furthermore, the molecular study suggested that GnRb1 attenuated TLR4-mediated NF-κB signaling. The results demonstrated the therapeutic efficacy of GnRb1 in the mouse model of LPS-triggered endometritis via the inhibition of the TLR4-associated NF-κB pathway. Taken together, this study provides a baseline for the protective effect of GnRb1 to treat endometritis in both humans and animals.

STAT1/SOCS1/3 Are Involved in the Inflammation-Regulating Effect of GAS6/AXL in Periodontal Ligament Cells Induced by Porphyromonas gingivalis Lipopolysaccharide In Vitro

Periodontitis involves chronic inflammation of the tissues around the teeth caused by plaque and the corresponding immune response. Growth arrest-specific protein 6 (GAS6) and AXL receptor tyrosine kinase (AXL) are known to be involved in inflammatory diseases, while signal transducer and activator of transcription-1 (STAT1) and suppressor of cytokine signaling (SOCS) are related to inflammatory processes. Moreover, miRNA34a directly targets AXL to regulate the AXL expression. However, the specific roles of GAS6 and AXL in periodontitis remain unclear. This study was designed to explore the effect and mechanism of AXL on the expression of inflammatory cytokines induced by Porphyromonas gingivalis lipopolysaccharide (P. gingivalis LPS) in human periodontal ligament cells (hPDLCs). The effects of different concentrations of P. gingivalis LPS on the expression of GAS6/AXL in hPDLCs were observed. Additionally, the effect of LPS on AXL was investigated by transfection of the miRNA34a inhibitor. AXL was knocked down or overexpressed to observe the release of inflammatory cytokines interleukin- (IL-) 8 and IL-6. The results showed that the expression levels of GAS6 and AXL decreased after P. gingivalis LPS infection. Transfection of a miR-34a inhibitor to hPDLCs demonstrated a role of miR-34a in the downregulation of AXL expression induced by LPS. Moreover, AXL knockdown or overexpression influencing the expression of IL-8 and IL-6 was investigated under LPS stimulation. AXL knockdown decreased the expression of STAT1 and SOCS1/3. Overall, these results demonstrate that AXL inhibits the expression of LPS-induced inflammatory cytokines in hPDLCs and that STAT1 and SOCS1/3 are involved in the regulation of inflammation by GAS6/AXL.

14-O-[(4,6-Diamino-pyrimidine-2-yl) thioacetyl] mutilin inhibits α-hemolysin and protects Raw264.7 cells from injury induced by methicillin-resistant S. aureus

A new pleuromutilin derivative, 14-O-[(4,6-Diaminopyrimidine-2-yl) thioacetyl] mutilin (DPTM), has been synthesized and proven to be a potent agent against Gram-positive pathogens, especially for Staphylococcus aureus (S. aureus). However, its pharmacological activities against α-hemolysin (Hla), a major virulence factor produced by S. aureus, and inflammations related to S. aureus are still unknown. In the present study, we investigated the DPTM inhibition activities against methicillin-resistant S. aureus (MRSA) Hla and protective efficacy of Raw264.7 cells from injury induced by MRSA. The results showed that DPTM with sub-inhibitory concentrations significantly inhibited Hla on the hemolysis of rabbit erythrocytes and down-regulated the gene expressions of Hla and agrA with a dose-dependent fashion. In Raw264.7 cells infected with MRSA, DPTM efficiently attenuated the productions of lactate dehydrogenase (LDH), nitric oxide (NO) and pro-inflammatory cytokines, as well as the express levels of nuclear factor-kappaB (NF-κB), nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, DPTM inhibited the translocation of p-65 to nucleus in RAW264.7 cells infected by MRSA.

Wuzi-Yanzong prescription alleviates spermatogenesis disorder induced by heat stress dependent on Akt, NF-κB signaling pathway

Akt and nuclear factor kappa B (NF-κB) signaling pathways are involved in germ cell apoptosis and inflammation after testicular heat stress (THS). We observed that after THS induced by the exposure of rat testes to 43 °C for 20 min, their weight decreased, the fraction of apoptotic testicular germ cells significantly increased, and the proliferation of germ cells was inhibited. In addition, THS lowered serum testosterone (T) level, whereas the levels of follicle stimulating hormone and luteinizing hormone were not significantly changed. The ultrastructure of the seminiferous tubules became abnormal after THS, the structure of the blood-testis barrier (BTB) became loose, and the Sertoli cells showed a trend of differentiation. The level of phosphorylated Akt was reduced, whereas the amount of phosphorylated NF-κB p65 was augmented by THS. Wuzi-Yanzong (WZYZ), a classic Chinese medicine prescription for the treatment of male reproductive dysfunctions, alleviated the changes induced by THS. In order to determine the mechanism of action of WZYZ, we investigated how this preparation modulated the levels of T, androgen receptor (AR), erythropoietin (EPO), EPO receptor, and Tyro-3, Axl, and Mer (TAM) family of tyrosine kinase receptors. We found that WZYZ activated the Akt pathway, inhibited the Toll-like receptor/MyD88/NF-κB pathway, and repaired the structure of BTB by regulating the levels of T, AR, TAM receptors, and EPO. In conclusion, these results suggest that WZYZ activates the Akt pathway and inhibits the NF-κB pathway by acting on the upstream regulators, thereby improving spermatogenesis deficit induced by THS.

MerTK inhibits the activation of the NLRP3 inflammasome after subarachnoid hemorrhage by inducing autophagy

The NLR family pyrin domain-containing 3 (NLRP3) multiprotein complex is associated with neuroinflammation and poor prognosis after subarachnoid hemorrhage (SAH). Accumulating evidence shows that Mer tyrosine kinase (MerTK) alleviates inflammatory responses via a negative feedback mechanism. However, the contribution and function of MerTK in SAH remain to be determined. In this study, we explored the role of MerTK during microglial NLRP3 inflammasome activation and evaluated its contribution to the outcome of SAH in mice. Activating MerTK with growth arrest-specific 6 (Gas6) alleviated brain edema, neuronal degeneration and neurological deficits after SAH by regulating neuroinflammation. Gas6 did not change the mRNA levels of Nlrp3 or Casp1 but decreased the protein expression of NLRP3, cleaved caspase1 (p20), interleukin-1β and interleukin-18. Furthermore, Gas6 increased the expression of Beclin1, the ratio of LC3-II/LC3-I and the level of autophagic flux. Inhibiting autophagy with 3-MA reversed the inhibition of NLRP3 inflammasome activation and diminished the neuroprotective effects of Gas6. Thus, MerTK activation may exert protective effects by limiting neuroinflammation and promoting neurological recovery after SAH via autophagy induction.

Genes associated with somatic cell count index in Brown Swiss cattle

Subclinical mastitis (SM) is one of the most common diseases of cows in milk production herds caused by contagious and/or environmental pathogens. Since there are no visible abnormalities in the milk or udder, the detection of SM requires special diagnostic tests. Somatic cell count (SCC) is the most common test used to detect changes in milk due to the inflammatory process. Previously, we developed somatic cell count index (SCCI), a new method for the accurate prediction of milk yield losses caused by elevated SCC. The aim of this study was to identify new candidate genetic markers for SCCI in the Slovenian population of Brown Swiss (BS) cattle. For that purpose, we analyzed samples of BS cows, which were genotyped using single-nucleotide polymorphism (SNP) microarray ICBF International Dairy and Beef v3 (ICBF, Ireland) for a total of 53,262 SNP markers. After quality control, the set of 18,136 SNPs was used in association analysis. Our association analysis revealed that 130 SNPs were associated with SCCI, which were used for haplotype and overlap analysis. Haplotypes generated from the genotyped data for those 130 SNPs revealed 10 haplotype blocks among 22 SNPs. Additionally, all 130 SNPs, mastitis-related quantitative trait loci, and protein-coding genes are shown on the bovine genome. Overlap analysis shows that the majority of significantly associated SNPs (70) are intergenic, while 60 SNPs are mapped within, upstream, or downstream of the protein-coding genes. However, those genes can serve as strong candidate genes for the marker-assisted selection programs in our and possibly other populations of cattle.

Mangiferin Inhibits Apoptosis and Autophagy Induced by Staphylococcus aureus in RAW264.7 Cells

Purpose

Staphylococcus aureus (S. aureus) is an important bacterial pathogen, which creates infective inflammation to human being and animals. Mangiferin (MG) is one of the natural flavonoids with anti-inflammatory, anti-bacterial, and anti-oxidative properties. However, the anti-apoptosis and anti-autophagy of MG are unknown. Hence, this study was aimed to research the inhibition of MG on S. aureus-induced apoptosis and autophagy in RAW264.7 cells.

Methods

The RAW264.7 cells were pretreated with MG, or pretreated with SP600125 or anisomycin synchronously, and then infected with S. aureus (MOI=100:1). The viability and proliferation status of RAW264.7 cells were detected by MTT and EdU assay. The relative expression of TNF-α, IL-6 and IL-10 protein was tested with ELISA. The levels of Bax, Bcl-2, caspase-3, c-Jun N-terminal kinase (JNK), extracellular-regulated protein kinase (ERK), p38, LC3, Beclin-1, p62, phosphorylated JNK, phosphorylated p38 and phosphorylated ERK in cells were detected by Western blotting. The apoptosis rate of RAW264.7 cells was analyzed by flow cytometric assay.

Results

The study showed that MG significantly attenuated RAW264.7 cells apoptosis and autophagy caused by S. aureus. MG alleviated S. aureus-induced apoptosis by down-regulating the protein level of active caspase-3 and Bax and up-regulating the level of Bcl-2. MG also inhibited S. aureus-induced autophagy via decreasing the protein level of LC3-II/LC3-I and Beclin-1 or increasing the protein expression of p62. This protective role was dependent on the up-regulation of JNK signal pathway, which was confirmed by using JNK agonist and inhibitor.

Conclusion

Our results demonstrated that MG might protect RAW264.7 cells from S. aureus-induced apoptosis and autophagy via inhibiting JNK/Bax-dependent signal pathway. Therefore, MG may be a potential agent against pathological cell damage induced by S. aureus infection.

Gas6 Inhibits Toll-Like Receptor-Mediated Inflammatory Pathways in Mouse Microglia via Axl and Mer

Background: Microglia are well known key regulators of neuroinflammation which feature in multiple neurodegenerative disorders. These cells survey the CNS and, under inflammatory conditions, become "activated" through stimulation of toll-like receptors (TLRs), resulting in changes in morphology and production and release of cytokines. In the present study, we examined the roles of the related TAM receptors, Mer and Axl, and of their ligand, Gas6, in the regulation of microglial pro-inflammatory TNF-α production and microglial morphology. Methods: Primary cultures of murine microglia of wild-type (WT), Mer^-/- and Axl^-/- backgrounds were stimulated by the TLR4 agonist, lipopolysaccharide (LPS) with or without pre-treatment with Gas6. Gene expression of TNF-α, Mer, and Axl was examined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), and enzyme-linked immunosorbent assay (ELISA) was used to measure TNF-α release from microglia. Immunofluorescence staining of β-actin and the microglial marker Iba1 was performed to reveal microglial morphological changes, with cellular characteristics (area, perimeter, Feret's diameter, minimum Feret, roundness, and aspect ratio) being quantified using ImageJ software. Results: Under basal conditions, TNF-α gene expression was significantly lower in Axl^-/- microglia compared to WT cells. However, all microglial cultures robustly responded to LPS stimulation with the upregulation of TNF-α expression to similar degrees. Furthermore, Mer receptor expression was less responsive to LPS stimulation when in Axl knockout cells. The presence of Gas6 consistently inhibited the LPS-induced upregulation of TNF-α in WT, Mer^-/- and Axl^-/- microglia. Moreover, Gas6 also inhibited LPS-induced changes in the microglial area, perimeter length, and cell roundness in wild-type cells. Conclusion: Gas6 can negatively regulate the microglial pro-inflammatory response to LPS as well as via stimulation of other TLRs, acting through either of the TAM receptors, Axl and Mer. This finding indicates an interaction between TLR and TAM receptor signaling pathways and reveals an anti-inflammatory role for the TAM ligand, Gas6, which could have therapeutic potential.

MerTK negatively regulates Staphylococcus aureus induced inflammatory response via SOCS1/SOCS3 and Mal

OBJECTIVE

Staphylococcus aureus (S. aureus), one of Gram-positive pathogen, is frequently associated with acute lung inflammation. The central feature of S. aureus acute lung inflammation are pulmonary dysfunctioning and impeded host defence response, which cause failure in inflammatory cytokines homeostasis and leads to serious tissue damage. However, the role of the Mer receptor tyrosine kinase (MerTK) in the lung following S. aureus infection remains elusive. Here, we investigate whether MerTK alleviates S. aureus induced uncontrolled inflammation through negatively regulating toll-like receptor 2 and 6 (TLR2/ TLR6) via suppressor of cytokine signalling 1, 3 (SOCS1/SOCS3).

METHODS AND RESULTS

We found in mice lung tissues and RAW 264.7 macrophages upon S. aureus infection activates TLR2 and TLR6 driven mitogen-activated protein kinases (MAPKs) and nuclear factor kappa B (NF-κB) signalling pathways, resulting in production of inflammatory cytokines including tumour necrosis factor-α (TNF-α), interleukin 1β (IL-1β), interleukin 6 (IL-6). Furthermore, S. aureus-infection groups showed a significant up-regulation of MerTK which serves as mediator of SOCS1 and SOCS3. Subsequently, through feedback mechanism SOCS1/3 degrade Mal, resulting in inhibition of downstream TLR mediated inflammatory pathways. Moreover, MerTK^-/- mice lung tissues and silencing MerTK in RAW 264.7 inhibited the S. aureus-induced activation of MerTK, which significantly upregulated the phosphorylation of crucial protein in MAPKs (ERK, JNK, p38) and NF-κB (IĸBα, p65) signalling pathways, as well as the production of pro-inflammatory cytokines.

CONCLUSION

Collectively, these findings indicate the important role of MerTK in self-regulatory resolution of S. aureus-induced inflammatory pathways and cytokines through intrinsic SOCS1 and SOCS3 repressed feedback on TLR2, TLR6 both in vivo and in vitro.