Dioscin Improves Pyroptosis in LPS-Induced Mice Mastitis by Activating AMPK/Nrf2 and Inhibiting the NF-κB Signaling Pathway

Role of AMPK-regulated autophagy in retinal pigment epithelial cell homeostasis: A review

The retinal pigment epithelium (RPE) is a regularly arranged monolayer of cells in the outermost layer of the retina. It is crucial for transporting nutrients and metabolic substances in the retina and maintaining the retinal barrier. RPE dysfunction causes diseases related to vision loss. Thus, understanding the mechanisms involved in normal RPE function is vital. Adenosine monophosphate-activated protein kinase (AMPK) is an RPE energy sensor regulating various signaling and metabolic pathways to maintain cellular energetic homeostasis. AMPK activation is involved in multiple signaling pathways regulated by autophagy in the RPE, thereby protecting the cells from oxidative stress and slowing RPE degeneration. In this review, we attempt to broaden the understanding of the pathogenesis of RPE dysfunction by focusing on the role and mechanism of AMPK regulation of autophagy in the RPE. The correlation between RPE cellular homeostasis and role of AMPK was determined by analyzing the structure and mechanism of AMPK and its signaling pathway in autophagy. The protective effect of AMPK-regulated autophagy on the RPE for gaining insights into the regulatory pathways of RPE dysfunction has been discussed.

Hesperetin regulates the intestinal flora and inhibits the TLR4/NF-κB signaling axis to protect the blood-milk barrier and prevent mastitis

The World Health Organization recommends breastfeeding for 6 months, but mastitis, a common disease during lactation, presents a major obstacle to fulfilling this recommendation. Maternal nutrient intake during lactation has been shown to be related to mastitis. Therefore, this study aimed to explore the effect of hesperetin, a phytonutrient, on mastitis. The oral administration of hesperetin to lipopolysaccharide (LPS)-induced mastitis mice alleviated their pathological damage, reduced the secretion of pro-inflammatory cytokines, and maintained the integrity of their blood-milk barrier. Moreover, our results showed that oral administration of hesperetin regulates the composition of the intestinal flora of mice. Fecal microbial transplantation (FMT) from the mice of hesperetin group alleviated LPS-induced mastitis in recipient mice. In additional, hesperetin attenuated the inflammatory response and increased the expression of tight junction proteins (TJs) in LPS-stimulated mouse mammary epithelial cells (mMECs). Through network pharmacological analysis and further research, we demonstrated hesperetin inhibits the expression of TLR4 and the activation of NF-κB signaling. In conclusion, hesperetin protects the blood-milk barrier and improve mastitis by regulating intestinal flora and inhibiting the activation of TLR4/NF-κB signaling axis. This study provides a theoretical basis for lactating females to consume hesperetin as a supplement to prevent mastitis and maintain mammary health.

dCas9-guided demethylation of the AKT1 promoter improves milk protein synthesis in a bovine mastitis mammary gland epithelial model induced by using Staphylococcus aureus

Mastitis is among the main factors affecting milk quality and yield. Although DNA methylation is associated with mastitis, its role in mastitis remains unclear. In this study, a bovine mastitis mammary epithelial cells (BMMECs) model was established via Staphylococcus aureus infection of bovine mammary gland epithelial cells (BMECs). Bisulfite sequencing PCR was used to determine the methylation status of the AKT1 promoter in BMMECs. We found that the degree of the AKT1 promoter methylation in BMMECs was significantly greater than that in BMECs, and the expression levels of genes related to milk protein synthesis were significantly decreased. We used the pdCas9-C-Tet1-SgRNA 2.0 system to regulate the methylation status of the AKT1 promoter. High-efficiency sgRNAs were screened and dCas9-guided AKT1 promoter demethylation vectors were constructed. Following transfection with the vectors, the degree of methylation of the AKT1 promoter was significantly reduced in BMMECs, while AKT1 protein levels increased. When the methylation level of the AKT1 promoter decreased, the synthesis of milk proteins and the expression levels of genes related to milk protein synthesis increased significantly. The viability of the BMMECs was enhanced. Taken together, these results indicate that demethylation guided by the pdCas9-C-Tet1-SgRNA 2.0 system on the AKT1 promoter can reactivate the expression of AKT1 and AKT1/mTOR signaling pathway-related proteins by reducing the AKT1 promoter methylation level and promoting the recovery milk protein expression in BMMECs, thereby alleviating the symptoms of mastitis.

Erythropoietin alleviates astrocyte pyroptosis by targeting the miR-325-3p/Gsdmd axis in rat spinal cord injury

BACKGROUND

Neuroinflammation plays an important role in spinal cord injury (SCI), and an increasing number of studies have focused on the role of astrocytes in neuroinflammation. Pyroptosis is an inflammation-related form of programmed cell death, and neuroinflammation induced by astrocytes in the form of pyroptosis has been widely reported in many central nervous system diseases. Recent studies have found that erythropoietin has significant anti-inflammatory and neuroprotective effects in SCI; however, it has not been reported whether erythropoietin can reduce neuroinflammation by inhibiting neural cell pyroptosis in SCI.

METHODS

A GEO dataset (GSE153720) was used to analyse the expression of pyroptosis-related genes in sham astrocytes and astrocytes 7 days, 1 month and 3 months after SCI. TargetScan and miRDB databases were used to predict the miRNA that could bind to the 3'UTR of rat Gsdmd. Primary rat spinal astrocytes were used for in vitro experiments, and the modified version of Allen's method was used to establish the rat SCI model. Western blotting, quantitative real-time polymerase chain reaction, flow cytometry, immunofluorescence, lactate dehydrogenase release assay and propidium iodide staining were used to detect the pyroptosis phenotype. A dual luciferase reporter gene assay was used to verify that miR-325-3p can bind to the 3'UTR of Gsdmd.

RESULTS

We found that pyroptosis-related genes mediated by the canonical NLRP3 inflammasome were highly expressed in astrocytes in an SCI animal model by bioinformatic analysis. We also observed that erythropoietin could reduce astrocyte pyroptosis in vivo and in vitro. In addition, we predicted miRNAs that regulate Gsdmd, the pyroptosis executor, and verified that erythropoietin inhibits astrocyte pyroptosis in SCI through the miR-325-3p/Gsdmd axis.

CONCLUSIONS

We demonstrated that erythropoietin can inhibit astrocyte pyroptosis through the miR-325-3p/Gsdmd axis. This study is expected to provide a new mechanism for erythropoietin in the treatment of SCI and a more reliable theoretical basis for clinical research.

Catalpol ameliorates LPS-induced inflammatory response by activating AMPK/mTOR signaling pathway in rat intestinal epithelial cells

Intestinal inflammation is a common clinical intestinal disease. Catalpol, a natural iridoid compound, has been shown to have anti-inflammatory, anti-oxidant and anti-apoptotic functions, but the mechanism of its protection against intestinal inflammation is still unclear. This study investigated the protective effect and potential mechanism of catalpol on the lipopolysaccharide (LPS)-induced inflammatory response of intestinal epithelial cell-6 (IEC-6). The results showed that catalpol could inhibit LPS-induced inflammatory response by dose-dependently reducing the release of inflammatory factors, such as tumor necrosis (TNF)-α, interleukin (IL)-1β and IL-6, and inhibiting the nuclear factor kappa-B (NF-κB) signaling pathway. Catalpol ameliorated cellular oxidative stress by reducing reactive oxygen species (ROS) and malondialdehyde (MDA) levels and increasing superoxide dismutase (SOD) and glutathione peroxidase (GSH-PX) expression. Meanwhile, catalpol also inhibited cell apoptosis, decreased the expression of B-cell lymphoma 2 (Bcl-2) - associated X (Bax), caspase 3 and caspase 9, and increased the expression of Bcl-2. This study found that catalpol activates AMP-activated protein kinase (AMPK) signaling pathway and inhibit mammalian target of rapamycin (mTOR) phosphorylationthe. In a further study, after inhibiting AMPK with dorsomorphin, the anti-inflammatory effects of catalpol were significantly reduced. Therefore, catalpol ameliorates LPS-induced inflammatory response by activating AMPK/mTOR signaling pathway in IEC-6 cells.

Mammary Epithelial Cell-Derived Exosomal miR-221-3p Regulates Macrophage Polarization by Targeting Igf2bp2 during Mastitis

Mastitis affects the milk quality and yield and is the most expensive disease in dairy cows. Elucidation of the pathogenesis of mastitis is of great importance for disease control. As a medium of intercellular communication, exosomes play key roles in various inflammatory diseases by regulating macrophage polarization. However, the molecular factors in exosomes that mediate the intercellular communication between mammary epithelial cells and macrophages during mastitis remain to be further explored. In this study, we isolated and identified mammary epithelial cell-derived exosomes from a lipopolysaccharide (LPS)/lipoteichoic acid (LTA)-induced mastitis cell model, and we demonstrated that exosomes from LPS/LTA-stimulated mammary epithelial cells promote M1-type macrophage polarization in vivo and in vitro. Based on the results of high-throughput sequencing, we constructed a differential miRNA (microRNA) expression profile of exosomes and demonstrated that miR-221-3p was highly expressed. Furthermore, in vivo and in vitro experiments, combined with coculture experiments and fluorescence tracing, showed that high miR-221-3p expression promoted M1-type macrophage polarization, demonstrating the transcellular role of miR-221-3p. Mechanistically, dual luciferase reporter gene assays and rescue assays showed that miR-221-3p regulated macrophage polarization by targeting Igf2bp2. The results of this study will deepen our understanding of the pathogenesis of mastitis, and the molecular regulatory axis that was established in this study is expected to be a target for mastitis treatment.

Maslinic acid alleviates LPS-induced mice mastitis by inhibiting inflammatory response, maintaining the integrity of the blood-milk barrier and regulating intestinal flora

Mastitis occurs frequently in breastfeeding women and not only affects the women's health but also hinders breastfeeding. Maslinic acid is a type of pentacyclic triterpenoid widely found in olives that has good anti-inflammatory activity. This study aims to discuss the protective function of maslinic acid against mastitis and its underlying mechanism. For this, mice models of mastitis were established using lipopolysaccharide (LPS). The results revealed that maslinic acid reduced the pathological lesions in the mammary gland. In addition, it reduced the generation of pro-inflammatory factors and enzymes (IL-6, IL-1β, TNF-α, iNOS, and COX2) in both mice mammary tissue and mammary epithelial cells. The high-throughput 16S rDNA sequencing of intestinal flora showed that in mice with mastitis, maslinic acid treatment altered β-diversity and regulated microbial structure by increasing the abundance of probiotics such as Enterobacteriaceae and downregulating harmful bacteria such as Streptococcaceae. In addition, maslinic acid protected the blood-milk barrier by maintaining tight-junction protein expression. Furthermore, maslinic acid downregulated mammary inflammation by inhibiting the activation of NLRP3 inflammasome, AKT/NF-κB, and MAPK signaling pathways. Thus, in a mice model of LPS-induced mastitis, maslinic acid can inhibit the inflammatory response, protect the blood-milk barrier, and regulate the constitution of intestinal flora.

San Huang Xiao Yan recipe modulates the HMGB1-mediated abnormal inflammatory microenvironment and ameliorates diabetic foot by activating the AMPK/Nrf2 signalling pathway

BACKGROUND

Diabetic foot (DF) is one of the serious complications of diabetes and lacks of therapeutic drugs. Abnormal and chronic inflammation promoting foot infection and wound healing delay are the main pathogenesis of DF. The traditional prescription San Huang Xiao Yan Recipe (SHXY) has been used in the clinical treatment of DF for several decades as approved hospital experience prescription and showed remarkable therapeutic effect, but the mechanisms by which SHXY treats DF are still unclear.

PURPOSE

Objectives of this study were to investigate SHXY anti-inflammatory effect on DF and explore the molecular mechanism for SHXY.

METHODS

We detected the effects of SHXY on DF in C57 mouse and SD rat DF models. Animal blood glucose, weight and wound area were detected every week. Serum inflammatory factors were detected by ELISA. H&E and Masson's trichrome were used to observe tissue pathology. Single-cell sequencing data reanalysis revealed the role of M1 macrophages in DF. Venn analysis showed the co-target genes between DF M1 macrophages and compound-disease network pharmacology. Western blotting was used to explored target protein expression. Meanwhile, RAW264.7 cells were treated with drug-containing serum of SHXY to further unravel the roles of target proteins during high glucose-induced inflammation in vitro. The Nrf2 inhibitor ML385 was used on RAW 264.7 cells to further explore the relationship between Nrf2, AMPK and HMGB1. The main components of SHXY were analysed by HPLC. Finally, the treatment effect of SHXY on DF were detected on rat DF model.

RESULTS

In vivo, SHXY can ameliorate inflammatory, accelerate wound healing and upregulate expression of Nrf2, AMPK and downregulate of HMGB1. Bioinformatic analysis showed that M1 macrophages were the main inflammatory cell population in DF. Moreover, the Nrf2 downstream proteins HO-1 and HMGB1 were potential DF therapeutic targets for SHXY. In vitro, we also found that SHXY increased AMPK and Nrf2 protein levels and downregulated HMGB1 expression in RAW264.7 cells. Inhibiting the expression of Nrf2 impaired the inhibition effect of SHXY on HMGB1. SHXY promoted Nrf2 translocation into the nucleus and increased the phosphorylation of Nrf2. SHXY also inhibited HMGB1 extracelluar release under high glucose. In rat DF models, SHXY also exhibited significant anti-inflammatory effect.

CONCLUSION

The SHXY activated AMPK/Nrf2 pathway to suppress abnormal inflammation on DF via inhibiting HMGB1 expression. These findings provide novel insight into the mechanisms by which SHXY treats DF.

Diosgenin alleviates the inflammatory damage and insulin resistance in high glucose‑induced podocyte cells via the AMPK/SIRT1/NF‑κB signaling pathway

Diabetic nephropathy (DN) is the predominant cause of end-stage renal disease globally. Diosgenin (DSG) has been reported to play a protective role in podocyte injury in DN. The present study aimed to explore the role of DSG in DN, as well as its mechanism of action in a high glucose (HG)-induced in vitro model of DN in podocytes. Cell viability, apoptosis, inflammatory response and insulin-stimulated glucose uptake were evaluated using Cell Counting Kit-8, TUNEL, ELISA and 2-deoxy-D-glucose assay, respectively. In addition, the expression of AMP-activated protein kinase (AMPK)/sirtuin 1 (SIRT1)/NF-κB signaling-related proteins in podocyte cells was measured using western blotting. The results indicated that DSG enhanced the viability of podocytes after HG exposure, but inhibited inflammatory damage and attenuated insulin resistance. Moreover, DSG induced the activation of the AMPK/SIRT1/NF-κB signaling pathway. Furthermore, treatment with compound C, an inhibitor of AMPK, counteracted the protective effects of DSG on HG-induced podocyte cells. Therefore, DSG may be a potential therapeutic compound for the treatment of diabetic nephropathy.

Caffeic acid, but not ferulic acid, inhibits macrophage pyroptosis by directly blocking gasdermin D activation

Regulated pyroptosis is critical for pathogen elimination by inducing infected cell rupture and pro-inflammatory cytokines secretion, while overwhelmed pyroptosis contributes to organ dysfunction and pathological inflammatory response. Caffeic acid (CA) and ferulic acid (FA) are both well-known antioxidant and anti-inflammatory phenolic acids, which resemble in chemical structure. Here we found that CA, but not FA, protects macrophages from both Nigericin-induced canonical and cytosolic lipopolysaccharide (LPS)-induced non-canonical pyroptosis and alleviates LPS-induced mice sepsis. It significantly improved the survival of pyroptotic cells and LPS-challenged mice and blocked proinflammatory cytokine secretion. The anti-pyroptotic effect of CA is independent of its regulations in cellular lipid peroxidation, mitochondrial function, or pyroptosis-associated gene transcription. Instead, CA arrests pyroptosis by directly associating with gasdermin D (GSDMD) and blocking its processing, resulting in reduced N-GSDMD pore construction and less cellular content release. In LPS-induced septic mice, CA inhibits GSDMD activation in peritoneal macrophages and reduces the serum levels of interleukin-1β and tumor necrosis factor-α as the known pyroptosis inhibitors, disulfiram and dimethyl fumarate. Collectively, these findings suggest that CA inhibits pyroptosis by targeting GSDMD and is a potential candidate for curbing the pyroptosis-associated disease.

Sulforaphane prevents LPS-induced inflammation by regulating the Nrf2-mediated autophagy pathway in goat mammary epithelial cells and a mouse model of mastitis

BACKGROUND

Mastitis not only deteriorates the composition or quality of milk, but also damages the health and productivity of dairy goats. Sulforaphane (SFN) is a phytochemical isothiocyanate compound with various pharmacological effects such as anti-oxidant and anti-inflammatory. However, the effect of SFN on mastitis has yet to be elucidated. This study aimed to explore the anti-oxidant and anti-inflammatory effects and potential molecular mechanisms of SFN in lipopolysaccharide (LPS)-induced primary goat mammary epithelial cells (GMECs) and a mouse model of mastitis.

RESULTS

In vitro, SFN downregulated the mRNA expression of inflammatory factors (tumor necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6), inhibited the protein expression of inflammatory mediators (cyclooxygenase-2 (COX2), and inducible nitric oxide synthase (iNOS)) while suppressing nuclear factor kappa-B (NF-κB) activation in LPS-induced GMECs. Additionally, SFN exhibited an antioxidant effect by increasing Nrf2 expression and nuclear translocation, up-regulating antioxidant enzymes expression, and decreasing LPS-induced reactive oxygen species (ROS) production in GMECs. Furthermore, SFN pretreatment promoted the autophagy pathway, which was dependent on the increased Nrf2 level, and contributed significantly to the improved LPS-induced oxidative stress and inflammatory response. In vivo, SFN effectively alleviated histopathological lesions, suppressed the expression of inflammatory factors, enhanced immunohistochemistry staining of Nrf2, and amplified of LC3 puncta LPS-induced mastitis in mice. Mechanically, the in vitro and in vivo study showed that the anti-inflammatory and anti-oxidative stress effects of SFN were mediated by the Nrf2-mediated autophagy pathway in GMECs and a mouse model of mastitis.

CONCLUSIONS

These results indicate that the natural compound SFN has a preventive effect on LPS-induced inflammation through by regulating the Nrf2-mediated autophagy pathway in primary goat mammary epithelial cells and a mouse model of mastitis, which may improve prevention strategies for mastitis in dairy goats.

Semaglutide alleviates inflammation-Induced endothelial progenitor cells injury by inhibiting MiR-155 expression in macrophage exosomes

The low-grade inflammatory state in obesity can damage vascular endothelial cells and lead to several cardiovascular diseases. Macrophage exosomes improve glucose tolerance and insulin sensitivity in obese mice, and yet it is unclear how it relates to endothelial cell injury. Firstly, lipopolysaccharide (LPS)-induced macrophage exosomes were co-cultured with endothelial progenitor cells (EPCs) to examine the function of EPCs and the level of inflammatory factors. Secondly, macrophages were transfected with MicroRNA-155 (miR-155) miR-155 mimics and inhibitors, and their secreted exosomes were co-cultured with EPCs to detect EPCs function and inflammatory factor levels. Then, EPCs were transfected with miR-155 mimics and inhibitors to clarify the effect of miR-155 on EPCs function and inflammatory factors. Finally, macrophages were intervened using semaglutide, and their secreted exosomes were co-cultured with EPCs to test EPCs function, inflammatory factor levels and macrophages miR-155 expression. LPS-induced macrophage exosomes reduced the cellular activity, migratory capacity and tube-forming ability of EPCs and rendered EPCs in an inflammatory state. LPS-induced microphage exosomes significantly upregulated miR-155 expression. miR-155 high expression exacerbated the pro-inflammatory nature of macrophage exosomes and inhibited the cell viability of EPCs. In contrast, inhibition of miR-155 expression showed the opposite result, suppressing inflammation and increasing the cell viability of EPCs. Semaglutide improved the cell viability of EPCs and also inhibited the expression of inflammatory factors in EPCs as well as miR-155 in exosomes. Semaglutide improves the function and inflammatory status of EPCs may via inhibition of LPS-induced macrophage expression of miR-155 in exosomes.

Dioscin alleviates the progression of osteoarthritis: an in vitro and in vivo study

Osteoarthritis (OA) is a common joint disease and is the main cause of physical disability in the elderly. Currently, there is no adequate therapeutic strategy to reverse the progression of OA. Many natural plant extracts have received attention in the treatment of OA due to their potential anti-inflammatory properties, and reduced incidence of adverse events. Dioscin (Dio), a natural steroid saponin, has been demonstrated to inhibit the release of inflammatory cytokines in mouse and rat models of various diseases, and has a protective effect in chronic inflammatory diseases. However, whether Dio alleviates OA progression remains to be explored. In this research, our purposes were to investigate the therapeutic potential of Dio in OA. The results demonstrated that Dio exerted anti-inflammatory effects by repressing NO, PGE₂, iNOS and COX-2. Moreover, the application of Dio could repress IL-1β-induced overexpression of matrix metalloproteinases (MMPs, including MMP1, MMP3, and MMP13) and ADAMTS-5, and improve the synthesis of collagen II and aggrecan, which contribute to the maintenance of chondrocyte matrix homeostasis. The underlying mechanism involved the inhibition of the MAPK and NF-κB signaling pathways by Dio. Furthermore, the treatment of Dio significantly improved the pain behaviors of rat OA models. The in vivo study revealed that Dio could ameliorate cartilage erosion and degradation. These results collectively indicate that Dio can be used as a promising and effective agent for the therapy of OA.

Sulforaphane Suppresses H2O2-Induced Oxidative Stress and Apoptosis via the Activation of AMPK/NFE2L2 Signaling Pathway in Goat Mammary Epithelial Cells

Oxidative stress in high-yielding dairy goats adversely affects lactation length, milk quality, and the economics of dairy products. During the lactation period, goat mammary epithelial cells (GMECs) are often in a state of disordered metabolic homeostasis primarily caused by the overproduction of reactive oxygen species (ROS). Sulforaphane (SFN), an electrophilic compound that is enriched in broccoli, is a promising antioxidant agent for future potential clinical applications. The objective of the present study was to investigate the function of SFN on hydrogen peroxide (H₂O₂)-induced oxidative damage in primary GMECs and the underlying molecular mechanisms. Isolated GMECs in triplicate were pretreated with SFN (1.25, 2.5, and 5 μM) for 24 h in the absence or presence of H₂O₂ (400 μM) for 24 h. The results showed that SFN effectively enhanced superoxide dismutase (SOD) activity, elevated the ratio of glutathione (GSH)/glutathione oxidized (GSSG), and reduced H₂O₂-induced ROS and malondialdehyde (MDA) production and cell apoptosis. Mechanically, SFN-induced nuclear factor erythroid 2-related factor 2 (NRF2/NFE2L2) translocation to the nucleus through the activation of the adenosine monophosphate-activated protein kinase (AMPK) signaling pathway coupled with inhibition of the caspase apoptotic pathway. In addition, GMECs were transfected with NFE2L2 small interfering RNA (NFE2L2 siRNA) for 48 h and/or treated with SFN (5 μM) for 24 h before being exposed to H₂O₂ (400 μM) for 24 h. We found that knockdown of NFE2L2 by siRNA abrogated the preventive effect of SFN on H₂O₂-induced ROS overproduction and apoptosis. Taken together, sulforaphane suppressed H₂O₂-induced oxidative stress and apoptosis via the activation of the AMPK/NFE2L2 signaling pathway in primary GMECs.

Effects of natural products on skin inflammation caused by abnormal hormones secreted by the adrenal gland

The cortex of adrenal gland produces glucocorticoid, mineralocorticoid, and androgen. The medulla of adrenal gland secrets catecholamines. These hormones play an important role in regulating blood pressure, metabolism, and homeostasis of glucose or electrolytes. Hypersecretion or hyposecretion by the adrenal gland will cause a complex cascade of hormone effects and lead to diseases, including Addison's disease, Cushing's syndrome, and congenital adrenal cortical hyperplasia. Skin is the largest organ of body. It provides protection and acts as a barrier against external damage factors like infectious organisms, chemicals, and allergens. Endocrinologic disorders often induce cutaneous abnormalities. According to the previous evidences, natural products have the potential properties for attenuating skin disorders and improving dermatologic symptoms by inhibiting inflammation through MAPK or PI3K/AKT-dependent NF-κB pathways. The natural products may also promote skin wound healing by inhibiting the production of matrix metalloproteinase-9. We systematically searched the relevant articles from databases, including PubMed, Embase, and Cochrane library databases, to review the effects of natural products on skin disorders. This article summarized the effects of natural products on skin inflammation caused by abnormal hormone secreted by adrenal gland. And the published papers indicated that natural products might be a potential source for treating skin diseases.

Role of Transcription Factor Nrf2 in Pyroptosis in Spinal Cord Injury by Regulating GSDMD

Spinal cord injury (SCI) is a prevalent disease that debilitates millions of people. Nuclear factor E2-related factor 2 (Nrf2) is an important regulator of SCI. The current study sought to elaborate on the effects of Nrf2 on gasdermin D (GSDMD)-mediated microglia pyroptosis to repair SCI. The SCI rat model was established via the percussion of the T10 spinal cord and in vitro SCI model was established on BV-2 cells via lipopolysaccharide (LPS)/adenosine triphosphate (ATP) treatment. Nrf2 expression in SCI rats and BV-2 cells was overexpressed via pcDNA3.1-Nrf2 injection. Functional assays were carried out to evaluate SCI rat pathological injury, BV-2 cell viability, the release of lactate dehydrogenase (LDH), and pyroptotic factors. The binding relations of Nrf2 and microRNA (miR)-146a and miR-146a and GSDMD were verified. BV-2 pyroptosis was analyzed after the combined experiment of miR-146a-inhibitor and pcDNA3.1-GSDMD. Our experiments revealed that Nrf2 was downregulated in SCI, and Nrf2 overexpression relieved SCI pathological injury, promoted BV-2 cell viability, inhibited the release of LDH, and repressed pyroptosis. Mechanically, Nrf2 bound to the miR-146a promoter and promoted miR-146a expression, and miR-146a targeted GSDMD transcription. Rescue experiments revealed that miR-146a knockdown or GSDMD overexpression annulled the inhibitory function of Nrf2 overexpression in LPS/ATP-induced microglia pyroptosis. Overall, our findings initially highlighted that Nrf2 inhibited GSDMD-mediated microglia pyroptosis and accelerated SCI repair by repressing miR-146a.

Dioscin Protects against Cisplatin-Induced Acute Kidney Injury by Reducing Ferroptosis and Apoptosis through Activating Nrf2/HO-1 Signaling

Acute kidney injury (AKI) is a clinical syndrome with high morbidity and mortality worldwide, and there is currently no effective means to prevent it. Dioscin is naturally present in the dioscoreaceae plants and has antioxidant and anti-inflammatory effects. Here, we found that dioscin is protective against cisplatin-induced AKI. Pathological and ultrastructural observations revealed that dioscin reduced renal tissue lesions and mitochondrial damage. Furthermore, dioscin markedly suppressed reactive oxygen species and malondialdehyde levels in the kidneys of AKI rats and increased the contents of glutathione and catalase. In addition, dioscin dramatically reduced the number of apoptotic cells and the expression of pro-apoptotic proteins in rat kidneys and human renal tubular epithelial cells (HK2). Conversely, the protein levels of anti-ferroptosis including GPX4 and FSP1 in vivo and in vitro were significantly enhanced after dioscin treatment. Mechanistically, dioscin promotes the entry of Nrf2 into the nucleus and regulates the expression of downstream HO-1 to exert renal protection. However, the nephroprotective effect of dioscin was weakened after inhibiting Nrf2 in vitro and in vivo. In conclusion, dioscin exerts a reno-protective effect by decreasing renal oxidative injury, apoptosis and ferroptosis through the Nrf2/HO-1 signaling pathway, providing a new insight into AKI prevention.

Metformin antagonizes nickel-refining fumes-induced cell pyroptosis via Nrf2/GOLPH3 pathway in vitro and in vivo

Nickel compounds, an international carcinogen in the industrial environment, increased the risk of lung inflammation even lung cancer in Ni refinery workers. Metformin has displayed the intense anti-inflammation and anti-cancer properties through regulating pyroptosis. This study was designed to explore whether Nickel-refining fumes (NiRF) can induce cell pyroptosis and how AMPK/CREB/Nrf2 mediated the protection afforded by metformin against Ni particles-induced lung impairment. Our results represented that Ni fumes exposure evoked pyroptosis via GOLPH3 and induced oxidative stress, while, metformin treatment alleviated Ni particles-mediated above changes. Moreover, nuclear factor erythroid 2-related factor 2 (Nrf2) involved in the protection of metformin, and the deficiency of Nrf2 attenuated the beneficial protection. We also determined that Nrf2 was a downstream molecule of AMPK/CREB pathway. Furthermore, male C57BL/6 mice were administered with Ni at a dose of 2 mg/kg by non-exposed endotracheal instillation and metformin (100, 200 and 300 mg/kg) via oral gavage for 4 weeks. The results indicated that NiRF promoted GOLPH3 and pyroptosis by stimulating NLRP3, caspase-1, N-GSDMD, IL-18 and IL-1β expression. However, various doses of metformin reduced GOLPH3 and the above protein levels of pyroptosis, also improved AMPK/CREB/Nrf2 expression. In summary, we found that metformin suppressed NiRF-connected GOLPH3-prompted pyroptosis via AMPK/CREB/Nrf2 signaling pathway to confer pulmonary protection.

Linear ubiquitination of LKB1 activates AMPK pathway to inhibit NLRP3 inflammasome response and reduce chondrocyte pyroptosis in osteoarthritis

Background

Osteoarthritis (OA) is the most common chronic disease. It is characterized by high levels of clinical heterogeneity and low inflammation. Therefore, elucidation of the mechanisms that regulate gene expression is critical for developing effective OA therapies. This study aimed to explore the role of LKB1/AMPK in the progression of OA.

Methods

Anterior cruciate ligament transection (ACLT) was performed on Sprague Dawley (SD) rats right knee to construct OA model, followed by AICAR [AMP-activated protein kinase (AMPK) activator] treatment. The level changes [AMPK, IL-10, IL-13, IL-1β, TNF-α, IL-6, ASC, Caspase-1, Ki67, and hibit Nod-like receptor protein 3 (NLRP3)] and the degree of tissue injury were assessed by western blot, Immunohistochemical (IHC), Enzyme-linked immunosorbent assay (ELISA), Hematoxylin-eosin staining (HE), Immunofluorescence (IF), Terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay, and Safranin O and Fast Green staining (S-O). Human chondrocytes were induced by LPS to construct a cellular inflammatory model, and then transfected with oe-AMPK or oe-HOIL-1-interacting protein (HOIP). Cell viability/apoptotic and intracellular content of AMPK, HOIP, IL-1β, IL-10, IL-13, TNF-α, IL-6, ASC, NLRP3 and Caspase-1 were measured by western blot, ELISA, CCK-8, IF, flow cytometry and TUNEL assays.

Results

After AICAR treatment with OA rats, the expression of p-AMPK, IL-10, IL-13, Ki67 and Bcl-2 increased, the level of NLRP3 inflammasome, TNF-α, IL-6, Bax and Caspase-3 levels were decreased, and tissue damage and apoptosis were significantly alleviated. After transfected with oe-LKB1, chondrocyte activity and LKB1 linear ubiquitination were enhanced, and the level of HOIP, p-AMPK, IL-10 and IL-13 were increased. In contrast, NLRP3 inflammasome (ASC, NLRP3, Caspase-1, IL-1β, and cleaved Caspase-1), TNF-α, and IL-6 levels decreased, apoptosis rate and TUNEL positive rate were attenuated.

Conclusion

LKB1/AMPK pathway significantly ameliorated NLRP3 inflammasome response and chondrocyte injury. Activation of AMPK pathway by linear ubiquitination of LKB1 may be a potential target for OA treatment.

The translational potential of this article

This study highlights the importance of the LKB1/AMPK pathway in NLRP3 inflammatory body response and chondrocyte injury. Activation of LKB1 by modulating linear ubiquitination may be a potential target for OA treatment.

AMPK and NRF2: Interactive players in the same team for cellular homeostasis?

NRF2 (Nuclear factor E2 p45-related factor 2) is a stress responsive transcription factor lending cells resilience against oxidative, xenobiotic, and also nutrient or proteotoxic insults. AMPK (AMP-activated kinase), considered as prime regulator of cellular energy homeostasis, not only tunes metabolism to provide the cell at any time with sufficient ATP or building blocks, but also controls redox balance and inflammation. Due to observed overlapping cellular responses upon AMPK or NRF2 activation and common stressors impinging on both AMPK and NRF2 signaling, it is plausible to assume that AMPK and NRF2 signaling may interdepend and cooperate to readjust cellular homeostasis. After a short introduction of the two players this narrative review paints the current picture on how AMPK and NRF2 signaling might interact on the molecular level, and highlights their possible crosstalk in selected examples of pathophysiology or bioactivity of drugs and phytochemicals.

HucMSC-Ex carrying miR-203a-3p.2 ameliorates colitis through the suppression of caspase11/4-induced macrophage pyroptosis

BACKGROUND

Inflammatory bowel disease (IBD) is a kind of chronic, idiopathic, and recurrent inflammation, associated with dysregulated intestinal mucosal immunity. Caspase (casp) 11/4-induced macrophage pyroptosis contributes to the development of inflammation, while human umbilical cord mesenchymal stem cell-secreted exosomes (hucMSC-Ex) play a reparative role in IBD.

OBJECTIVE

The present study focused on the treatment of IBD with hucMSC-Ex and its regulatory mechanism via the casp11/4 pathway.

METHODS

BALB/c mice were used to establish a dextran sulfate sodium (DSS)-induced colitis model, and hucMSC-Ex was administered intravenously to estimate its therapeutic effect. In vitro, RAW264.7 cells line, THP-1 cells line, and mouse peritoneal macrophages (MPMs) were stimulated with lipopolysaccharides (LPS) to activate an inflammatory environment of pyroptosis, followed by repairing with hucMSC-Ex. MicroRNA mimics and inhibitors were provided to verify the role of miR-203a-3p.2 from hucMSC-Ex in inflammation. The results were analyzed by Western blot, RT-qPCR、ELISA, and LDH secretion.

RESULTS

HucMSC-Ex inhibited the activation of casp11 and reduced the secretion of interleukin (IL)-1β, IL-6, and casp11, which relieved macrophage pyroptosis to alleviate murine colitis. A consistent outcome was revealed in the cell experiments, where hucMSC-Ex contributed to a decreased casp11/4 expression, and lactate dehydrogenase (LDH) release, as a marker of cell damage. Moreover, miR-203a-3p.2 from hucMSC-Ex functioned as an effective mediator in the interaction with casp4 in THP-1 macrophage pyroptosis.

CONCLUSION

HucMSC-Ex ameliorates colitis through the suppression of casp11/4-induced macrophage pyroptosis, and hucMSC-Ex carrying miR-203a-3p.2 inhibits casp4-induced macrophage pyroptosis in an inflammatory environment.

Inhibiting Ferroptosis: A Novel Approach for Ulcerative Colitis Therapeutics

Ulcerative colitis (UC) is a recurrent and persistent nonspecific inflammatory bowel disease (IBD) that greatly affects human survival and social wealth. Despite the advances in the treatment of UC, there is still a high demand for novel therapeutic strategies for UC patients. Cell death is critical to the development and progression of UC. Understanding how intestinal cells die and how to prevent damage to intestinal cells is of great interest for the diagnosis and early treatment of UC. Ferroptosis, a novel form of regulated cell death (RCD) manifested by iron accumulation, lipid peroxidation, and excessive reactive oxygen species (ROS) production, has been shown to contribute to the development and progression of UC. Inhibitors of ferroptosis have been validated in models of UC. Here, we reviewed the mechanisms of initiation and control of ferroptosis and summarize the therapeutic activity of ferroptosis inhibitors in models of UC. We further discussed the possibility of inhibiting ferroptosis as a novel therapeutic target for UC. These findings revealed novel mechanisms to protect the colonic mucosa and highlighted the importance of ferroptosis in the disease process.

Buformin alleviates sepsis-induced acute lung injury via inhibiting NLRP3-mediated pyroptosis through an AMPK-dependent pathway

BACKGROUND

NOD-like receptor family pyrin domain containing 3 (NLRP3)-mediated macrophage pyroptosis plays an important role in sepsis-induced acute lung injury (ALI). Inhibition of pyroptosis may be a way to alleviate inflammation as well as tissue damage triggered after lipopolysaccharide (LPS) stimulation. The aim of the present study was to explore whether buformin (BF), a hypoglycemic agent, could alleviate sepsis-induced ALI by inhibiting pyroptosis.

METHODS

Wildtype C57BL/6 mice were randomly divided into control group, BF group, LPS group and LPS+BF group. BF group and LPS+BF group were pretreated with BF at a dose of 25 mg/kg, and the changes were observed. In addition, BF was used to interfere with THP-1 cells. The therapeutic effect of BF has been verified by intraperitoneal injection of BF in vivo after LPS stimulation.

RESULTS

Inflammation and injury was significantly reduced in BF pretreated mice, and the indexes related to pyroptosis were suppressed. The phosphorylation of AMP-activated protein kinase (AMPK) in lung tissues of mice in the BF and LPS+BF groups was significantly higher. In THP-1 cells, the AMPK inhibitor, Compound C was added to demonstrate that BF worked via AMPK to inhibit NLRP3 inflammasome. It was further demonstrated that BF up-regulated autophagy, which in turn promoted NLRP3 inflammasome degradation. On the other hand, BF decreased NLRP3 mRNA level by increasing nuclear factor-erythroid 2 related factor 2 (Nrf2). And BF showed a therapeutic effect after LPS challenge.

CONCLUSION

Our study confirmed that BF inhibited NLRP3-mediated pyroptosis in sepsis-induced ALI by up-regulating autophagy and Nrf2 protein level through an AMPK-dependent pathway. This provides a new strategy for clinical mitigation of sepsis-induced ALI.

Dioscin promotes autophagy by regulating the AMPK-mTOR pathway in ulcerative colitis

BACKGROUND

Dioscin is reported to alleviate the dextran sodium sulfate (DSS)-induced ulcerative colitis (UC) in mice. Autophagy plays an anti-inflammatory role in UC. We herein aimed to explore the biological functions of dioscin in autophagy in UC.

METHODS

To explore the effects of dioscin on UC progression, a DSS-induced mouse model of UC was established. Body weight, disease activity index and macroscopic damage index scores were recorded for seven days. Hematoxylin & Eosin (HE) staining was used to stain colon sections and an BX53 microscope was prepared to observe pathological changes. The activities of glutathione, superoxidative dismutase, and malondialdehyde were determined by commercially available kits. Western blotting was performed to measure the protein levels of p-AMPK/AMPK, p-mTOR/mTOR and autophagy-related genes.

RESULTS

The DSS-induced colitis and oxidative stress in mice were ameliorated after dioscin treatment. Dioscin promoted the phosphorylation of AMPK to inhibit mTOR activation and facilitated autophagy in DSS-induced mice model of UC.

CONCLUSION

Dioscin promotes autophagy by promoting the phosphorylation of AMPK to inhibit mTOR activation in ulcerative colitis.

Inhibition of Gasdermin D-Mediated Pyroptosis Attenuates the Severity of Seizures and Astroglial Damage in Kainic Acid-Induced Epileptic Mice

Objective: Our study aimed to explore whether gasdermin D (GSDMD)-mediated pyroptosis is involved in the mechanism of kainic acid-induced seizures.

Methods: C57BL/6 mice were randomly divided into sham and epilepsy groups. The epilepsy group was intrahippocampally injected with kainic acid to induce status epilepticus (SE), and the sham group was injected with an equal volume of saline. Dimethyl fumarate (DMF) was used as the GSDMD N-terminal fragments (GSDMD-N) inhibitor and suspended in 0.5% sodium carboxymethyl cellulose (CMC) for orally administration. The epilepsy group was divided into SE + CMC and SE + DMF groups. In the SE + DMF group, DMF was orally administered for 1 week before SE induction and was continued until the end of the experiment. An equal volume of CMC was administered to the sham and SE + CMC groups. Recurrent spontaneous seizures (SRSs) were monitored for 21 days after SE. Western blot analysis and immunofluorescent staining was performed.

Results: The expression of GSDMD increased at 7–21 days post-SE, and GSDMD-N expression was significantly elevated 7 days after SE in both ipsilateral and contralateral hippocampus. GSDMD-positive cells were co-labeled with astrocytes, but not neurons or microglia. Astroglial damage occurs following status epilepticus (SE). Damaged astrocytes showed typical clasmatodendrosis in the CA1 region containing strong GSDMD expression at 7–21 days post-SE, accompanied by activated microglia. In the SE + DMF group, the expression of GSDMD-N was significantly inhibited compared to that in the SE + CMC group. After administration of DMF, SRSs at 7–21 days after SE were significantly decreased, and the number of clasmatodendritic astrocytes, microglia, and the expression of inflammatory factors such as IL-1β and IL-18 were significantly attenuated.

Conclusion: GSDMD-mediated pyroptosis is involved in the mechanism of kainic acid-induced seizures. Our study provides a new potential therapeutic target for seizure control.

Phenols and terpenoids: natural products as inhibitors of NLRP3 inflammasome in cardiovascular diseases

Inflammatory infiltration has been implicated in the pathogenesis of cardiovascular diseases (CVDs). The NLRP3 inflammasome is involved in the development of several types of CVDs, including myocardial infarction, myocardial ischemia-reperfusion damage, heart failure, atrial fibrillation, and hypertension. Inhibiting the activity of NLRP3 inflammasome can inhibit the progress of CVDs. However, there is no NLRP3 inflammasome inhibitor in clinic, and it is very important to find a safe and effective NLRP3 inhibitor. Phenols and terpenoids are naturally natural products that have many anti-inflammatory effects in CVDs by modulating the NLRP3 inflammatory pathway. Thus, 20 natural products from phenols and terpenoids for the treatment of cardiovascular disease based on the inhibition of NLRP3 inflammasome were summarized and screened. Docking results showed salvianolic acid B and ellagic acid in phenols, and oridonin and triptolide in terpenoids had a better binding activity with NLRP3, which can provide theoretical support for finding novel NLRP3 inflammasome inhibitors or lead compounds in the future.

Phytic Acid Maintains the Integrity of the Blood-Milk Barrier by Regulating Inflammatory Response and Intestinal Flora Structure

The destruction of the blood-milk barrier (BMB) caused by the mammary inflammatory response (MIR) is one of the main reasons that hinders breastfeeding. To relieve the inflammatory response and maintain BMB, we found that phytic acid (PA) has good anti-inflammatory activity. Therefore, we focused on researching the influence and mechanism of PA on BMB and MIR. We constructed a mammary inflammatory response model using lipopolysaccharide (LPS) in vivo, and we used mammary epithelial cells (mMECs) to construct a cell inflammatory response model in vitro. The results showed that PA alleviated mammary tissue damage and reduced the production of inflammatory mediators (such as IL-1β and iNOS) in mammary tissue and mMECs. PA also maintained the integrity of the BMB in mice by increasing the expression of tight junction proteins. 16S rDNA high-throughput sequencing showed that PA significantly ameliorated the intestinal flora of model mice. Mechanism studies showed that PA exerted an anti-MIR effect by inhibiting the AKT/NF-κB signaling pathway. In summary, our study found that PA maintains the integrity of BMB by regulating the inflammatory response and intestinal flora structure.

Pyrroloquinoline quinone ameliorates diabetic cardiomyopathy by inhibiting the pyroptosis signaling pathway in C57BL/6 mice and AC16 cells

Purpose

Diabetic cardiomyopathy (DCM), a common complication of diabetes mellitus and is characterized by myocardial hypertrophy and myocardial fibrosis. Pyrroloquinoline quinone (PQQ), a natural nutrient, exerts strong protection against various myocardial diseases. Pyroptosis, a type of inflammation-related programmed cell death, is vital to the development of DCM. However, the protective effects of PQQ against DCM and the associated mechanisms are not clear. This study aimed to investigate whether PQQ protected against DCM and to determine the underlying molecular mechanism.

Methods

Diabetes was induced in mice by intraperitoneal injection of streptozotocin, after which the mice were administered PQQ orally (10, 20, or 40 mg/kg body weight/day) for 12 weeks. AC16 human myocardial cells were divided into the following groups and treated accordingly: control (5.5 mmol/L glucose), high glucose (35 mmol/L glucose), and HG + PQQ groups (1 and 10 nmol/L PQQ). Cells were treated for 24 h.

Results

PQQ reduced myocardial hypertrophy and the area of myocardial fibrosis, which was accompanied by an increase in antioxidant function and a decrease in inflammatory cytokine levels. Moreover, myocardial hypertrophy—(ANP and BNP), myocardial fibrosis—(collagen I and TGF-β1), and pyroptosis-related protein levels decreased in the PQQ treatment groups. Furthermore, PQQ abolished mitochondrial dysfunction and the activation of NF-κB/IκB, and decreased NLRP3 inflammation-mediated pyroptosis in AC16 cells under high-glucose conditions.

Conclusion

PQQ improved DCM in diabetic mice by inhibiting NF-κB/NLRP3 inflammasome-mediated cell pyroptosis. Long-term dietary supplementation with PQQ may be greatly beneficial for the treatment of DCM.

Graphical abstract

Diagram of the underlying mechanism of the effects of PQQ on DCM. PQQ inhibits ROS generation and NF-κB activation, which stimulates activation of the NLRP3 inflammasome and regulates the expression of caspase-1, IL-1β, and IL-18. The up-regulated inflammatory cytokines trigger myocardial hypertrophy and cardiac fibrosis and promote the pathological process of DCM.

Cancer Chemopreventive Role of Dietary Terpenoids by Modulating Keap1-Nrf2-ARE Signaling System—A Comprehensive Update

ROS, RNS, and carcinogenic metabolites generate excessive oxidative stress, which changes the basal cellular status and leads to epigenetic modification, genomic instability, and initiation of cancer. Epigenetic modification may inhibit tumor-suppressor genes and activate oncogenes, enabling cells to have cancer promoting properties. The nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that in humans is encoded by the NFE2L2 gene, and is activated in response to cellular stress. It can regulate redox homoeostasis by expressing several cytoprotective enzymes, including NADPH quinine oxidoreductase, heme oxygenase-1, UDP-glucuronosyltransferase, glutathione peroxidase, glutathione-S-transferase, etc. There is accumulating evidence supporting the idea that dietary nutraceuticals derived from commonly used fruits, vegetables, and spices have the ability to produce cancer chemopreventive activity by inducing Nrf2-mediated detoxifying enzymes. In this review, we discuss the importance of these nutraceuticals in cancer chemoprevention and summarize the role of dietary terpenoids in this respect. This approach was taken to accumulate the mechanistic function of these terpenoids to develop a comprehensive understanding of their direct and indirect roles in modulating the Keap1-Nrf2-ARE signaling system.

The protective effect of quercetin on macrophage pyroptosis via TLR2/Myd88/NF-κB and ROS/AMPK pathway

AIMS

Pyroptosis is a pro-inflammatory form of programmed cell death, which plays a vital role in the development of inflammatory diseases. As a natural flavonoid, quercetin has been shown to possess anti-inflammatory activity, but its effects on macrophage pyroptosis is still unclear. Therefore, this study aims to investigate the effects of quercetin on macrophage pyroptosis and the underlying mechanism.

MATERIAL AND METHODS

LPS/ATP treatment was used to induce THP-1 macrophage pyroptosis. Cell counting kit-8 (CCK-8) assay was used to evaluate cell viability. Scanning electron microscope (SEM) was used to detect cell morphology. Hoechst/propidium iodide (PI) staining and lactate dehydrogenase (LDH) assay were performed to evaluate the cell membrane integrity. The expression of key components and effectors of nod-like receptors3 (NLRP3) inflammasome were examined by real-time PCR and western blot. Immunofluorescence staining was used to detect reactive oxygen species (ROS) level and P65 nuclear translocation.

KEY FINDINGS

Our results showed that quercetin prevented THP-1 macrophage pyroptosis by reducing the expression of NLRP3 and cleaved-caspase1, as well as IL-1β and N-GSDMD in a concentration dependent manner. Quercetin suppressed NLRP3 inflammasome activation by inhibiting ROS overproduction. Moreover, quercetin inhibited the phosphorylation of P65 and its translocation from cytoplasm into nuclear. In addition, we found that quercetin suppressed the increase of TLR2/Myd88 and p-AMPK induced by LPS/ATP, while both TLR2 and AMPK agonist weakened the inhibitory effect of quercetin on the activity of NLRP3 inflammasome and alleviated the protective effect on macrophages pyroptosis.

SIGNIFICANCE

Quercetin possesses a protective effect on macrophages pyroptosis via TLR2/Myd88/NF-κB and ROS/AMPK pathway.

Lactobacillus rhamnosus GR-1 Prevents Escherichia coli-Induced Apoptosis Through PINK1/Parkin-Mediated Mitophagy in Bovine Mastitis

Escherichia coli is one of the most important pathogens that cause clinical mastitis in dairy cattle worldwide and lead to severe economic losses. Antibiotics are often used to treat this inflammatory disease; however, antimicrobial resistance and environmental pollution cannot be ignored. Probiotic is the best alternative; however, its mechanisms of action to prevent mastitis remain unclear. Moreover, the role of probiotics in regulating mitophagy, a selective autophagy that maintains mitochondrial quality, needs to be explored. E. coli infection induced NOD-like receptor family member pyrin domain-containing protein 3 (NLRP3) inflammasome assembly, Caspase-1 activation, and apoptosis in MAC-T cells. Infection also resulted in mitochondrial damage and subsequent increase in reactive oxygen species (ROS) production. Moreover, inhibition of ROS release by scavenger N-acetyl-L-cysteine (NAC) abrogated the importance of ROS in NLRP3 assembly and apoptosis in MAC-T cells. Pretreatment with Lactobacillus rhamnosus GR-1 (LGR-1), a probiotic, alleviated E. coli-induced NLRP3 inflammasome activation and apoptosis via ROS inhibition. Besides, E. coli infection inhibited mitophagy while LGR-1 pretreatment augmented PINK1/Parkin–mediated mitophagy activation, which further blocked ROS generation. To explore the effect of LGR-1 in vivo, a mouse mastitis model was established. The results showed that LGR-1 pretreatment had preventive and protective effects on E. coli induced mastitis, and could reduce cytokines levels such as IL-1β and TNF-α. In accordance with the results in vitro, E. coli can inhibit mitophagy and activate NLRP3 inflammasome and apoptosis, while LGR-1 can weaken the effect of E. coli. Taken together, our data indicated that LGR-1 pretreatment induced PINK1/Parkin-mediated mitophagy that eliminated damaged mitochondria and reduced ROS production and NLRP3 inflammasome activation, which subsequently decreased E. coli-induced apoptosis. To conclude, our study suggests that therapeutic strategies aiming at the upregulation of mitophagy under E. coli-induced mastitis may preserve mitochondrial function and provide theoretical support for the application of probiotics in bovine mastitis.

Evodiamine Relieve LPS-Induced Mastitis by Inhibiting AKT/NF-κB p65 and MAPK Signaling Pathways

Evodiamine, an alkaloid component in the fruit of Evodia, has been shown to have biological functions such as antioxidant and anti-inflammatory. But whether evodiamine plays an improvement role on mastitis has not been studied. To investigate the effect and mechanism of evodiamine on lipopolysaccharide (LPS)-induced mastitis was the purpose of this study. In animal experiments, the mouse mastitis model was established by injecting LPS into the canals of the mammary gland. The results showed that evodiamine could significantly relieve the pathological injury of breast tissue and the production of pro-inflammatory cytokines and inhibit the activation of inflammation-related pathways such as AKT, NF-κB p65, ERK1/2, p38, and JNK. In cell experiments, the mouse mammary epithelial cells (mMECs) were incubated with evodiamine for 1 h and then stimulated with LPS. Next, pro-inflammatory mediators and inflammation-related signal pathways were detected. As expected, our results showed that evodiamine notably ameliorated the inflammatory reaction and inhibit the activation of related signaling pathways of mMECs. All the results suggested that evodiamine inhibited inflammation by inhibiting the phosphorylation of AKT, NF-κBp65, ERK1/2, p38, and JNK thus the LPS-induced mastitis was ameliorated. These findings suggest that evodiamine maybe a potential drug for mastitis because of its anti-inflammatory effects.