Milk fat globule epidermal growth factor 8 attenuates acute lung injury in mice after intestinal ischemia and reperfusion

Alveolar-capillary endocytosis and trafficking in acute lung injury and acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is associated with high morbidity and mortality but lacks specific therapeutic options. Diverse endocytic processes play a key role in all phases of acute lung injury (ALI), including the initial insult, development of respiratory failure due to alveolar flooding, as a consequence of altered alveolar-capillary barrier function, as well as in the resolution or deleterious remodeling after injury. In particular, clathrin-, caveolae-, endophilin- and glycosylphosphatidyl inositol-anchored protein-mediated endocytosis, as well as, macropinocytosis and phagocytosis have been implicated in the setting of acute lung damage. This manuscript reviews our current understanding of these endocytic pathways and subsequent intracellular trafficking in various phases of ALI, and also aims to identify potential therapeutic targets for patients with ARDS.

Sestrin2 reduces ferroptosis via the Keap1/Nrf2 signaling pathway after intestinal ischemia-reperfusion

Sestrins are metabolic regulators that respond to stress by reducing the levels of reactive oxygen species (ROS) and inhibiting the activity of target of rapamycin complex 1 (mTORC1). Previous research has demonstrated that Sestrin2 mitigates ischemia-reperfusion (IR) injury in the heart, liver, and kidneys. However, its specific role in intestinal ischemia-reperfusion (IIR) injury remains unclear. To elucidate the role of Sestrin2 in IIR injury, we conducted an experimental study using a C57BL/6J mouse model of IIR. We noticed an increase in the levels of Sestrin2 expression and indicators associated with ferroptosis. Our study revealed that manipulating Sestrin2 expression in Caco-2 cells through overexpression or knockdown resulted in a corresponding decrease or increase, respectively, in ferroptosis levels. Furthermore, our investigation revealed that Sestrin2 alleviated ferroptosis caused by IIR injury through the activation of the Keap1/Nrf2 signal pathway. This finding highlights the potential of Sestrin2 as a therapeutic target for alleviating IIR injury. These findings indicated that the modulation of Sestrin2 could be a promising strategy for managing prolonged IIR injury.

hUC-MSCs-derived MFGE8 ameliorates locomotor dysfunction via inhibition of ITGB3/ NF-κB signaling in an NMO mouse model

Neuromyelitis optica (NMO) is a severe autoimmune inflammatory disease of the central nervous system that affects motor function and causes relapsing disability. Human umbilical cord-derived mesenchymal stem cells (hUC-MSCs) have been used extensively in the treatment of various inflammatory diseases, due to their potent regulatory roles that can mitigate inflammation and repair damaged tissues. However, their use in NMO is currently limited, and the mechanism underlying the beneficial effects of hUC-MSCs on motor function in NMO remains unclear. In this study, we investigate the effects of hUC-MSCs on the recovery of motor function in an NMO systemic model. Our findings demonstrate that milk fat globule epidermal growth 8 (MFGE8), a key functional factor secreted by hUC-MSCs, plays a critical role in ameliorating motor impairments. We also elucidate that the MFGE8/Integrin αvβ3/NF-κB signaling pathway is partially responsible for structural and functional recovery, in addition to motor functional enhancements induced by hUC-MSC exposure. Taken together, these findings strongly support the involvement of MFGE8 in mediating hUC-MSCs-induced improvements in motor functional recovery in an NMO mouse model. In addition, this provides new insight on the therapeutic potential of hUC-MSCs and the mechanisms underlying their beneficial effects in NMO.

A novel opsonic eCIRP inhibitor for lethal sepsis

Sepsis is a life-threatening inflammatory condition partly orchestrated by the release of various damage-associated molecular patterns such as extracellular cold-inducible RNA-binding protein (eCIRP). Despite advances in understanding the pathogenic role of eCIRP in inflammatory diseases, novel therapeutic strategies to prevent its excessive inflammatory response are lacking. Milk fat globule-epidermal growth factor-VIII (MFG-E8) is critical for the opsonic clearance of apoptotic cells, but its potential involvement in the removal of eCIRP was previously unknown. Here, we report that MFG-E8 can strongly bind eCIRP to facilitate αvβ3-integrin-dependent internalization and lysosome-dependent degradation of MFG-E8/eCIRP complexes, thereby attenuating excessive inflammation. Genetic disruption of MFG-E8 expression exaggerated sepsis-induced systemic accumulation of eCIRP and other cytokines, and consequently exacerbated sepsis-associated acute lung injury. In contrast, MFG-E8-derived oligopeptide recapitulated its eCIRP binding properties, and significantly attenuated eCIRP-induced inflammation to confer protection against sepsis. Our findings suggest a novel therapeutic approach to attenuate eCIRP-induced inflammation to improve outcomes of lethal sepsis.

Cellular mechanisms underlying the impairment of macrophage efferocytosis

The phagocytosis and clearance of dying cells by macrophages, a process termed efferocytosis, is essential for both maintaining homeostasis and promoting tissue repair after infection or sterile injury. If not removed in a timely manner, uncleared cells can undergo secondary necrosis, and necrotic cells lose membrane integrity, release toxic intracellular components, and potentially induce inflammation or autoimmune diseases. Efferocytosis also initiates the repair process by producing a wide range of pro-reparative factors. Accumulating evidence has revealed that macrophage efferocytosis defects are involved in the development and progression of a variety of inflammatory and autoimmune diseases. The underlying mechanisms of efferocytosis impairment are complex, disease-dependent, and incompletely understood. In this review, we will first summarize the current knowledge about the normal signaling and metabolic processes of macrophage efferocytosis and its importance in maintaining tissue homeostasis and repair. We then will focus on analyzing the molecular and cellular mechanisms underlying efferocytotic abnormality (impairment) in disease or injury conditions. Next, we will discuss the potential molecular targets for enhanced efferocytosis in animal models of disease. To provide a balanced view, we will also discuss some deleterious effects of efferocytosis.

MFG-E8 Knockout Aggravated Nonalcoholic Steatohepatitis by Promoting the Activation of TLR4/NF-κB Signaling in Mice

Nonalcoholic steatohepatitis (NASH) is the common liver disease characterized by hepatic steatosis, inflammation, and fibrosis; there are no approved drugs to treat this disease because of incomplete understanding of pathophysiological mechanisms of NASH. Milk fat globule-epidermal growth factor-factor 8 (MFG-E8), a multifunctional glycoprotein, has shown anti-inflammation and antifibrosis. Here, MFG-E8 was shown to play a key role in NASH progression. Using methionine and choline deficient (MCD) diet-fed mice, we found MFG-E8 knockout exacerbated hepatic damage and steatosis as indicated by increased plasma transaminases activities and hepatic histopathologic change, higher hepatic triglycerides (TGs), and lipid accumulation. Moreover, liver fibrosis and inflammation elicited by MCD were aggravated in MFG-E8 knockout mice. Mechanistically, MFG-E8 knockout facilitated activation of hepatic toll-like receptor 4 (TLR4)/nuclear factor kappa B (NF-κB) signaling pathway in MCD-fed mice. In vitro experiment, the TLR4 specific antagonist TAK-242 rescued palmitic acid- (PA-) primed lipid formation and inflammation in MFG-E8 knockout primary murine hepatocytes. These findings indicated that MFG-E8 is involved in the progression of NASH and the possible mechanism by which MFG-E8 knockout exacerbated NASH in mice is associated with activation of the TLR4/NF-κB signaling pathway.

Chondroprotective Effects of Periodontal Ligament Derived Stem Cells Conditioned Medium on Articular Cartilage After Impact Injury

Paracrine factors secreted in the conditioned media of periodontal ligament derived stem cells (PDLSCs) have been shown to downregulate inflammatory effects of IL-1β on chondrocytes wherein milk fat globule-epidermal growth factor 8 (MFG-E8) is one of the PDLSCs highly secretory proteins. Therefore, the objective of this study was to investigate the ability of PDLSC conditioned media (CM) and MFG-E8 to reduce the inflammatory effects of impact injury on porcine talar articular cartilage (AC) and IL-1β on chondrocytes, respectively. Stem cells were isolated from human periodontal ligaments. the MFG-E8 content in CM collected at 5% and 20% oxygen was measured by ELISA assay and compared across subcultures and donors. AC samples were divided into three groups: control, impact, and impact+CM. Chondrocytes were isolated from pig knees and were divided into three groups: control, IL-1β, and IL-1β+MFG-E8. Gene expression data was analyzed by RT-PCR. It was found that impact load and IL-1β treatment upregulated IL-1β, TNF-α, ADAMTS-4, and ADAMTS-5 gene expression in AC and chondrocytes, respectively. PDLSCs-CM prevented the upregulation of all four genes due to impact whereas MFG-E8 prevented upregulation of IL-1β, ADAMTS-4, and ADAMTS-5 in chondrocytes, but it did not prevent TNF-α upregulation. There were no significant differences in MFG-E8 content in CM among oxygen levels, passage numbers, or donors. The findings suggested that MFG-E8 is an effective anti-inflammatory agent contributing to the chondroprotective effects of PDLSCs-CM on acutely injured articular cartilage. Thus, introducing PDLSCs-CM to sites of acute traumatic AC injury could prevent the development of post-traumatic osteoarthritis.

Prostaglandin D2 Attenuates Lipopolysaccharide-Induced Acute Lung Injury through the Modulation of Inflammation and Macrophage Polarization

Acute lung injury (ALI) is a well-known respiratory disease and a leading cause of death worldwide. Despite advancements in the medical field, developing complete treatment strategies against this disease is still a challenge. In the current study, the therapeutic role of prostaglandin D2 (PGD2) was investigated on lipopolysaccharide (LPS)-induced lung injury in mice models and RAW264.7 macrophages through anti-inflammatory, histopathology, immunohistochemistry, and TUNEL staining. The overproduction of cytokines by RAW264.7 macrophages was observed after stimulation with LPS. However, pretreatment with PGD2 decreased the production of cytokines. The level of inflammatory markers was significantly restored in the PGD2 treatment group (TNF-α = 58.6 vs. 78.5 pg/mL; IL-1β = 29.3 vs. 36.6 pg/mL; IL-6 = 75.4 vs. 98.2 pg/mL; and CRP = 0.84 vs. 1.14 ng/mL). The wet/dry weight ratio of the lungs was quite significant in the disease control (LPS-only treatment) group. Moreover, the histological changes as determined by haematoxylin and eosin (H&E) staining clearly showed that PGD2 treatment maintains the lung tissue architecture. The iNOS expression pattern was increased in lung tissues of LPS-treated animals, whereas, in mice treated with PGD2, the expression of iNOS protein decreased. Flow cytometry data demonstrated that LPS intoxication enhanced apoptosis, which significantly decreased with PGD2 treatment. In conclusion, all these observations indicate that PGD2 provides an anti-inflammatory response in RAW264.7 macrophages and in ALI, and they suggest a therapeutic potential in lung pathogenesis.

Potential influences of expression levels of MFGE8 and HMGB1 on the intestinal mucosal barrier function and inflammatory response after blunt abdominal injury in rats

Purpose:

To explore the influence of milk fat globule-EGF factor 8 protein (MFGE8) on blunt abdominal injury in Sprague Dawley (SD) rats through the RhoA/ROCK signaling pathway.

Methods:

The blunt abdominal injury model was generated in SD rats. A total of 44 rats was randomly assigned into three groups. Rat blunt abdominal injury was assessed by the abbreviated injury scale (AIS). The rats were sacrificed for observing the morphology of the abdominal cavity and intestines. Hematoxylin and eosin staining was performed to visualize the pathological changes of rat intestines. Positive expressions of MFGE8 and high mobility group box 1 (HMGB1) in rat intestines were examined by immunohistochemical staining. Protein levels were determined by Western blot. Serum levels of tumor necrosis factor α (TNF-α), IL-1β, IL-6 and malondialdehyde (MDA) were measured by enzyme linked immunosorbent assay (ELISA).

Results:

Blunt abdominal injury resulted in inflammatory response of intestinal tissues, increased serum levels of TNF-α, IL-1β, IL-6 and MDA, upregulation of HMGB1, RhoA and ROCK2, and downregulation of MFGE8 in rats, which were significantly alleviated by intervention of rhMFGE8.

Conclusions:

MFGE8 protects the intestinal mucosal barrier function after blunt abdominal injury in rats by downregulating HMGB1. Moreover, it alleviates inflammatory response and oxidative stress caused by blunt abdominal injury in rats through downregulating RhoA and ROCK.

Effects of RGD-grafted phosphatidylserine-containing liposomes on the polarization of macrophages and bone tissue regeneration

Phosphatidylserine-containing liposomes (PSLs) can mimic the anti-inflammatory effects of apoptotic cells by binding to the phosphatidylserine receptors of macrophages. MGF-E8, a bridge molecule between phosphatidylserine and macrophages, can promote M2 polarization by activating macrophage integrin with its arginine-glycine-aspartic acid (RGD) motif. In this study, to mimic MGF-E8, PSLs presenting RGD peptide (RGD-PSLs) were prepared, and their immunomodulatory effects on macrophages and the bone tissue regeneration of rat calvarial defects were investigated. RGD peptides enhanced the phagocytosis of PSLs by macrophages, especially when the PSLs contained 3% RGD. RGD-PSLs were also more effective than PSLs for the suppression of lipopolysaccharide-induced gene expression of proinflammatory cytokines (i.e., IL-1β, IL-6, and TNF-α) as well as CD86 (M1 marker) expression. Furthermore, RGD promoted PSL-induced M2 polarization: 3%-RGD-PSLs significantly enhanced the mRNA expression of Arg-1, FIZZ1, and YM-1, as well as CD206 (M2 marker) expression. In a calvarial defect model, a significant increase in M2 with a decrease in M1 macrophages was observed with 3%-RGD-PSL treatment compared with the effects of PSLs alone. Finally, new bone formation was also accelerated by 3%-RGD-PSLs. Thus, these results suggest that the intensive immunomodulatory effect of RGD-PSLs led to the enhancement of bone tissue regeneration.

Human adrenomedullin and its binding protein attenuate tissue injury and inflammation following hepatic ischemia reperfusion in rabbits

Background

Liver injury caused by ischemia reperfusion (I/R) during surgical procedures, such as liver resection or liver transplantation, is a major cause of liver damage and graft failure. The current method of treatment is mostly preventative (i.e., ischemic preconditioning). While a number of pharmacological modalities have been studied to reduce hepatic I/R injury, none have been entirely successful. It has been demonstrated that the administration of adrenomedullin (AM) in combination with AM-binding protein (AM/AMBP-1) exerts significant protective effects in various pathological conditions. In an effort to develop AM/AMBP-1 as a novel therapeutic for hepatic I/R injury, the present study examined the effect of a low dose of human AM, which does not induce hypotension, in combination with human AMBP-1 in a rabbit model of hepatic I/R (i.e., non-rodent species).

Methods

Ischemia of 70% of the liver was induced by placing a microvascular clip across the hilum of the left and median lobes for 60 min. The clip was then removed to commence reperfusion. At 15 min following clip removal (i.e., reperfusion), human AM/AMBP-1 was administered intravenously via the ear marginal vein continuously for 30 min. At 20 h, blood and tissue samples were collected for various measurements.

Results

The serum levels of liver enzymes (alanine aminotransferase and aspartate aminotransferase) and lactate dehydrogenase, were elevated following hepatic I/R. The administration of AM/AMBP-1 significantly decreased these levels by 58, 44, 41%, respectively. Hepatic I/R increased the direct and total bilirubin levels, whereas treatment with human AM/AMBP-1 decreased these levels by 60% and 69%, respectively. Treatment with AM/AMBP-1 also inhibited interleukin-6 gene expression by 95%. There were no changes in tumor necrosis factor-α (TNF-α) gene expression and myeloperoxidase activity (MPO), lactate and Suzuki scores after treatment. The treatment, however, reduced apoptosis post-hepatic I/R in the ischemic portion of the liver.

Conclusion

Additional experiments with AM and AMBP-1 alone are needed to completely interpret the experimental results in this non-rodent species of hepatic I/R injury. The present study suggests that human AM/AMBP-1 may be developed as a novel therapeutic to attenuate hepatic I/R associated inflammation and liver injury.

Long non-coding RNA (lncRNA): A potential therapeutic target in acute lung injury

Acute Lung Injury (ALI) and its severe form Acute Respiratory Distress Syndrome (ARDS) are the major cause of ICU death worldwide. ALI/ARDS is characterized by severe hypoxemia and inflammation that leads to poor lung compliance. Despite many advances in understanding and management, ALI/ARDS is still causing significant morbidity and mortality. Long non-coding RNA (lncRNA) is a fast-growing topic in lung inflammation and injury. lncRNA is a class of non-coding RNA having a length of more than 200 nucleotides. It has been a center of research for understanding the pathophysiology of various diseases in the past few years. Multiple studies have shown that lncRNAs are abundant in acute lung injury/injuries in mouse models and cell lines. By targeting these long non-coding RNAs, many investigators have demonstrated the alleviation of ALI in various mouse models. Therefore, lncRNAs show great promise as a therapeutic target in ALI. This review provides the current state of knowledge about the relationship between lncRNAs in various biological processes in acute lung injury and its use as a potential therapeutic target.

Anti-Inflammatory Effects of Conditioned Medium of Periodontal Ligament-Derived Stem Cells on Chondrocytes, Synoviocytes, and Meniscus Cells

Osteoarthritis (OA) is the most common type of arthritis, afflicting millions of people in the world. Elevation of inflammatory mediators and enzymatic matrix destruction is often associated with OA. Therefore, the objective of this study was to investigate the effects of conditioned medium from periodontal ligament-derived stem cells (PDLSCs) on inflammatory and catabolic gene expressions of chondrocytes, synoviocytes, and meniscus cells under in vitro inflammatory condition. Stem cells were isolated from human periodontal ligaments. Conditioned medium was collected and concentrated 20 × . Chondrocytes, synoviocytes, and meniscus cells were isolated from pig knees and divided into four experimental groups: serum-free media, serum-free media+interleukin-1β (IL-1β) (10 ng/mL), conditioned media (CM), and CM+IL-1β. Protein content and extracellular vesicle (EV) miRNAs of CM were analyzed by liquid chromatography-tandem mass spectrometry and RNA sequencing, respectively. It was found that the IL-1β treatment upregulated the expression of IL-1β, tumor necrosis factor-α (TNF-α), MMP-13, and ADAMTS-4 genes in the three cell types, whereas PDLSC-conditioned medium prevented the upregulation of gene expression by IL-1β in all three cell types. This study also found that there was consistency in anti-inflammatory effects of PDLSC CM across donors and cell subcultures, while PDLSCs released several anti-inflammatory factors and EV miRNAs at high levels. OA has been suggested as an inflammatory disease in which all intrasynovial tissues are involved. PDLSC-conditioned medium is a cocktail of trophic factors and EV miRNAs that could mediate different inflammatory processes in various tissues in the joint. Introducing PDLSC-conditioned medium to osteoarthritic joints could be a potential treatment to prevent OA progression by inhibiting inflammation.

Relationship Between Milk Fat Globule-Epidermal Growth Factor 8 and Intestinal Cytokines in Infants Born Preterm

OBJECTIVES

To investigate the relationships between dietary intake and fecal concentrations of milk fat globule-epidermal growth factor 8 (MFG-E8), and between fecal concentrations of MFG-E8 and markers of intestinal inflammation in infants born preterm.

STUDY DESIGN

Fecal samples were collected daily and enteral feedings were sampled weekly. MFG-E8 in enteral feedings and feces, and cytokine concentrations in feces were quantified by enzyme-linked immunosorbent assay.

RESULTS

Milk MFG-E8 concentrations were significantly greater in unfortified mother's own milk (MOM) and MOM with human milk fortifier than either donor human milk or preterm formula. MFG-E8 concentrations in fecal samples were positively correlated with MFG-E8 concentrations in respective milks. High MFG-E8 exposure (≥60 mL/kg/day of feedings that include MOM or MOM with human milk fortifier) was associated with lower concentrations of proinflammatory cytokines (interleukin-8, tumor necrosis factor-α, and monocyte chemoattractant protein-1) and higher concentrations of the anti-inflammatory cytokine interleukin-4 in feces, compared with low MFG-E8 exposure.

CONCLUSIONS

Infants born preterm who were fed MOM had greater concentrations of MFG-E8 and lower concentrations of proinflammatory cytokines in fecal samples than other diets or no feedings. These data further support the protective role of MOM, possibly because of MFG-E8, against intestinal inflammation.

Milk fat globule EGF factor 8 restores mitochondrial function via integrin-medicated activation of the FAK-STAT3 signaling pathway in acute pancreatitis

Acute pancreatitis (AP) remains a significant clinical challenge. Mitochondrial dysfunction contributes significantly to the pathogenesis of AP. Milk fat globule EGF factor 8 (MFG-E8) is an opsonizing protein, which has many biological functions via binding to αvβ3/5 integrins. Ligand-dependent integrin-FAK activation of STAT3 was reported to be of great importance for maintaining a normal mitochondrial function. However, MFG-E8's role in AP has not been evaluated.

METHODS

Blood samples were acquired from 69 healthy controls and 134 AP patients. Serum MFG-E8 levels were measured by ELISA. The relationship between serum concentrations of MFG-E8 and disease severity were analyzed. The role of MFG-E8 was evaluated in experimental models of AP.

RESULTS

Serum concentrations of MFG-E8 were lower in AP patients than healthy controls. And serum MFG-E8 concentrations were negatively correlated with disease severity in AP patients. In mice, MFG-E8 administration decreased L-arginine-induced pancreatic injury and mortality. MFG-E8's protective effects in experimental AP were associated with improvement in mitochondrial function and reduction in oxidative stress. MFG-E8 knockout mice suffered more severe pancreatic injury and greater mitochondrial damage after l-arginine administration. Mechanistically, MFG-E8 activated the FAK-STAT3 pathway in AP mice. Cilengitide, a specific αvβ3/5 integrin inhibitor, abolished MFG-E8's beneficial effects in AP. PF00562271, a specific FAK inhibitor, blocked MFG-E8-induced STAT3 phosphorylation. APTSTAT3-9R, a specific STAT3 antagonist, also eliminated MFG-E8's beneficial effects under such a condition.

CONCLUSIONS

MFG-E8 acts as an endogenous protective mediator in the pathogenesis of AP. MFG-E8 administration protects against AP possibly by restoring mitochondrial function via activation of the integrin-FAK-STAT3 signaling pathway. Targeting the action of MFG-E8 may present a potential therapeutic option for AP.

Nervilifordin F alleviates intestinal ischemia/reperfusion-induced acute lung injury via inhibiting inflammasome and mTOR pathway

Acute lung injury (ALI) is a life-threatening disorder with high rates of morbidity and mortality. Up to now, there are still no effective drugs for its therapies due to the complexity of its etiology and pathogenesis. In this present study, we investigated the protective effect of Nervilifordin F (NF) on ALI induced by intestinal ischemia/reperfusion (II/R) and its related mechanism. Firstly, the ALI model rats were induced through II/R, and treated with NF. Then, the pathological and cytokine level changes in the lung tissue of ALI rats were evaluated by hematoxylin and eosin and enzyme-linked immunosorbent assay (ELISA). The related genes expression level of mammalian target of rapamycin (mTOR) pathway and inflammasome were measured by real-time quantitative polymerase chain reaction (RT-qPCR), western blot and immunohistochemistry. Finally, the NF-protein complexes were predicted by SYBYL-X 2.0. The results indicated that NF can significant reduces the levels of tumor necrosis factor-alpha (TNF-α), interleukin (IL)-6 and IL-1β, and inhibits the expression of inflammasome related genes (such as toll-like receptor 4 (TLR4), p65, NOD-like receptor protein 3 (NLRP3) and Caspase 1), thereby reduce inflammation in II/R-induced ALI rats. Moreover, NF can activate the expression of FK506 binding protein 25 (FKBP25) and down-regulate the expression of mTOR and p70 ribosomal protein S6 kinase 1 (p70S6K). In addition, molecular docking results showed that NF can be combined well with p70S6K, TLR4, mTOR and NLRP3, which further verified the inhibitory effect of NF on ALI inflammation. Therefore, the findings indicate that NF can alleviates II/R-induced inflammation of ALI rats by inhibiting inflammasome related genes and mTOR pathway, which expected to use as a potential drug for the treatment of ALI.

MiR-23a-5p exacerbates intestinal ischemia-reperfusion injury by promoting oxidative stress via targeting PPAR alpha

MiR-23a-5p is involved in the occurrence and development of some serious diseases, but its effects on intestinal ischemia-reperfusion (II/R) injury is unclear. In this research, the hypoxia/reoxygenation (H/R) model on IEC-6 cells and II/R model in mice were used. The data showed that the ROS level in model group was significantly increased compared with control group. The level of intestinal MPO was increased and serum SOD was decreased in mice compared with sham group. Moreover, the expression levels of miR-23a-5p in model groups were obviously increased in vitro and in vivo, while the expression levels of PPARα, FOXO3α, PGC-1α, Nrf2, CAT, NQO1, HO-1 and SOD2 were significantly decreased. The double luciferase reporter gene assay showed that there was binding site between miR-23a-5p and PPARα. When miR-23a-5p was inhibited or PPARα gene was overexpressed, H/R-caused cell damage was alleviated and ROS level was decreased compared with NC group. PPARα expression level was increased, accompanied by the increased levels of FOXO3α, PGC-1α, Nrf2, CAT, NQO1, HO-1 and SOD2. After enhancing miR-23a-5p expression or silencing PPARα gene, H/R-caused cell damage was further aggravated compared with NC group, and ROS level was increased associated with the decreased levels of FOXO3α, PGC-1α, Nrf2, CAT, NQO1, HO-1 and SOD2. Our study demonstrated that miR-23a-5p exacerbated II/R injury by promoting oxidative stress via targeting PPARα, which should be considered as one new drug target to treat II/R injury.

NLRP3 Inflammasome Activation in Lung Vascular Endothelial Cells Contributes to Intestinal Ischemia/Reperfusion-Induced Acute Lung Injury

Intestinal ischemia/reperfusion (I/R) injury is a life-threatening complication that leads to inflammation and remote organ damage. The NLRP3 inflammasome regulates the caspase-1-dependent release of IL-1β, an early mediator of inflammation after I/R injury. In this study, we investigated the role of the NLRP3 inflammasome in mice with intestinal I/R injury. Deficiency of NLRP3, ASC, caspase-1/11, or IL-1β prolonged survival after intestinal I/R injury, but neither NLRP3 nor caspase-1/11 deficiency affected intestinal inflammation. Intestinal I/R injury caused acute lung injury (ALI) characterized by inflammation, reactive oxygen species generation, and vascular permeability, which was markedly improved by NLRP3 deficiency. Bone marrow chimeric experiments showed that NLRP3 in non-bone marrow-derived cells was the main contributor to development of intestinal I/R-induced ALI. The NLRP3 inflammasome in lung vascular endothelial cells is thought to be important to lung vascular permeability. Using mass spectrometry, we identified intestinal I/R-derived lipid mediators that enhanced NLRP3 inflammasome activation in lung vascular endothelial cells. Finally, we confirmed that serum levels of these lipid mediators were elevated in patients with intestinal ischemia. To our knowledge, these findings provide new insights into the mechanism underlying intestinal I/R-induced ALI and suggest that endothelial NLRP3 inflammasome-driven IL-1β is a novel potential target for treating and preventing this disorder.

Hydrogen-Rich Saline Attenuates Acute Lung Injury Induced by Limb Ischemia/Reperfusion via Down-Regulating Chemerin and NLRP3 in Rats

Limb ischemia/reperfusion (LI/R) injury is associated with high morbidity and mortality. The hypothesis of this study is that hydrogen-rich solution could attenuateacute lung injury and improve mortality via chemerin and NLRP3 after LI/R in rats. A rat model of LI/R was performed by clamping the bilateral femoral arteries for 3 h followed by reperfusion. Hydrogen-rich saline (HRS) was administered intraperitoneally (10 mL/kg or 2.5 mL/kg) when the atraumatic micro clips were released. The rats were euthanized at 2 h after reperfusion and then the arterial blood and lung specimens were harvested for further analyses. Meanwhile, survival rate was observed. The results showed that HRS improved the survival rate and attenuated pulmonary edema, injury, and apoptosis. HRS also decreased the levels of tumor necrosis factor-α, interleukin-6, myeloperoxidase and malondialdehyde, and increased the activity of superoxide dismutase in serum and lung after the LI/R event. HRS downregulated the expression of chemerin and NLRP3 in lung. The study demonstrated that chemerin and NLRP3 could serve as important response factors that were involved in the lung injury following LI/R. HRS could significantly attenuate LI/R-mediated acute lung injury, at least in part, by inhibiting the activated chemerin/NLRP3 signaling pathway.

Inhibition of a triggering receptor expressed on myeloid cells-1 (TREM-1) with an extracellular cold-inducible RNA-binding protein (eCIRP)-derived peptide protects mice from intestinal ischemia-reperfusion injury

BACKGROUND

Intestinal ischemia-reperfusion injury results in morbidity and mortality from both local injury and systemic inflammation and acute lung injury. Extracellular cold-inducible RNA-binding protein is a damage associated molecular pattern that fuels systemic inflammation and potentiates acute lung injury. We recently discovered a triggering receptor expressed on myeloid cells-1 serves as a novel receptor for extracellular cold-inducible RNA-binding protein. We developed a 7-aa peptide, named M3, derived from the cold-inducible RNA-binding protein, which interferes with cold-inducible RNA-binding protein's binding to a triggering receptor expressed on myeloid cells-1. Here, we hypothesized that M3 protects mice against intestinal ischemia-reperfusion injury.

METHODS

Intestinal ischemia was induced in C57BL/6 mice via clamping of the superior mesenteric artery for 60 minutes. At reperfusion, mice were treated intraperitoneally with M3 (10 mg/kg body weight) or normal saline vehicle. Mice were killed 4 hours after reperfusion and blood and lungs were collected for various analysis. A 24-hours survival after intestinal ischemia-reperfusion was assessed.

RESULTS

Serum levels of organ injury markers aspartate aminotransferase, alanine aminotransferase, lactate dehydrogenase, and lactate were increased with intestinal ischemia-reperfusion, while treatment with M3 significantly decreased their levels. Serum, intestinal, and lung levels of proinflammatory cytokines and chemokines were also increased by intestinal ischemia-reperfusion, and treatment with M3 significantly reduced these values. Intestinal ischemia-reperfusion caused significant histological intestinal and lung injuries, which were mitigated by M3. Treatment with M3 improved the survival from 40% to 80% after intestinal ischemia-reperfusion.

CONCLUSION

Inhibition of triggering receptor expressed on myeloid cells-1 by an extracellular cold-inducible RNA-binding protein-derived small peptide (M3) decreased inflammation, reduced lung injury, and improved survival in intestinal ischemia-reperfusion injury. Thus, blocking the extracellular cold-inducible RNA-binding protein-triggering receptor expressed on myeloid cells-1 interaction is a promising therapeutic avenue for mitigating intestinal ischemia-reperfusion injury.

Breast Milk Lipids and Fatty Acids in Regulating Neonatal Intestinal Development and Protecting against Intestinal Injury

Human breast milk is the optimal source of nutrition for infant growth and development. Breast milk fats and their downstream derivatives of fatty acids and fatty acid-derived terminal mediators not only provide an energy source but also are important regulators of development, immune function, and metabolism. The composition of the lipids and fatty acids determines the nutritional and physicochemical properties of human milk fat. Essential fatty acids, including long-chain polyunsaturated fatty acids (LCPUFAs) and specialized pro-resolving mediators, are critical for growth, organogenesis, and regulation of inflammation. Combined data including in vitro, in vivo, and human cohort studies support the beneficial effects of human breast milk in intestinal development and in reducing the risk of intestinal injury. Human milk has been shown to reduce the occurrence of necrotizing enterocolitis (NEC), a common gastrointestinal disease in preterm infants. Preterm infants fed human breast milk are less likely to develop NEC compared to preterm infants receiving infant formula. Intestinal development and its physiological functions are highly adaptive to changes in nutritional status influencing the susceptibility towards intestinal injury in response to pathological challenges. In this review, we focus on lipids and fatty acids present in breast milk and their impact on neonatal gut development and the risk of disease.

Pretreatment with dexmedetomidine alleviates lung injury in a rat model of intestinal ischemia reperfusion

The aim of the present study was to investigate the antioxidant mechanisms of dexmedetomidine against lung injury during intestinal ischemia reperfusion (IIR) in rats. The model of IIR-induced acute lung injury was established by occluding the superior mesenteric artery (SMA) for 1 h and reperfusing for 2 h using Sprague-Dawley rats. Pathological examination was used to assess the extent of the lung injury. Oxidative stress was evaluated by measuring malondialdehyde, myeloperoxidase and superoxide dismutase in the lung and plasma. The proinflammatory cytokines tumor necrosis factor-α and interleukin-6 were determined via an enzyme-linked immunosorbent assay. The mRNA and protein expression of nuclear factor-erythroid 2 related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) were determined using a reverse transcription-quantitative polymerase chain reaction and western blotting. Pretreatment with dexmedetomidine significantly inhibited the oxidative stress response and proinflammatory factor release caused by IIR compared with the normal saline group (MDA and SOD in lung and plasma, P<0.05; MPO, IL-1β and TNF-α in lung and plasma, P<0.05). Dexmedetomidine improved pulmonary pathological changes in IIR rats compared with the normal saline group. Investigations into the molecular mechanism revealed that dexmedetomidine increased the expression levels of Nrf2 and HO-1 via activating α2 adrenergic receptors compared with the normal saline group. The antagonism of α2 adrenergic receptors may reverse the protective effect of dexmedetomidine on lung injury during IIR, including decreasing the expression levels of Nrf2 and HO-1, elevating the oxidative stress response and increasing the proinflammatory factor release. In conclusion, pretreatment with dexmedetomidine demonstrated protective effects against lung injury during IIR via α2 adrenergic receptors. The Nrf2/HO-1 signaling pathway may serve a function in the protective effect of dexmedetomidine.

Irisin reverses intestinal epithelial barrier dysfunction during intestinal injury via binding to the integrin αVβ5 receptor

Disruption of the gut barrier results in severe clinical outcomes with no specific treatment. Metabolic disorders and destruction of enterocytes play key roles in gut barrier dysfunction. Irisin is a newly identified exercise hormone that regulates energy metabolism. However, the effect of irisin on gut barrier function remains unknown. The therapeutic effect of irisin on gut barrier dysfunction was evaluated in gut ischemia reperfusion (IR). The direct effect of irisin on gut barrier function was studied in Caco‐2 cells. Here, we discovered that serum and gut irisin levels were decreased during gut IR and that treatment with exogenous irisin restored gut barrier function after gut IR in mice. Meanwhile, irisin decreased oxidative stress, calcium influx and endoplasmic reticulum (ER) stress after gut IR. Moreover, irisin protected mitochondrial function and reduced enterocyte apoptosis. The neutralizing antibody against irisin significantly aggravated gut injury, oxidative stress and enterocyte apoptosis after gut IR. Further studies revealed that irisin activated the AMPK‐UCP 2 pathway via binding to the integrin αVβ5 receptor. Inhibition of integrin αVβ5, AMPK or UCP 2 abolished the protective role of irisin in gut barrier function. In conclusion, exogenous irisin restores gut barrier function after gut IR via the integrin αVβ5‐AMPK‐UCP 2 pathway.

SIRT3-mediated deacetylation of PRDX3 alleviates mitochondrial oxidative damage and apoptosis induced by intestinal ischemia/reperfusion injury

Background

Hydrogen peroxide (H₂O₂)-induced mitochondrial oxidative damage is critical to intestinal ischemia/reperfusion (I/R) injury, and PRDX3 is an efficient H₂O₂ scavenger that protects cells from mitochondrial oxidative damage and apoptosis. However, the function of PRDX3 in intestinal I/R injury is unclear. The aim of this study was to investigate the precise mechanism underlying the involvement of PRDX3 in intestinal I/R injury.

Methods

An intestinal I/R model was established in mice with superior mesenteric artery occlusion, and Caco-2 cells were subjected to hypoxia/reoxygenation (H/R) for the in vivo simulation of I/R.

Results

PRDX3 expression was decreased during intestinal I/R injury, and PRDX3 overexpression significantly attenuated H/R-induced mitochondrial oxidative damage and apoptosis in Caco-2 cells. The level of acetylated PRDX3 was clearly increased both in vivo and in vitro. The inhibition of SIRTs by nicotinamide (NAM) increased the level of acetylated PRDX3 and impaired the antioxidative activity of PRDX3. Furthermore, NAM did not increase the acetylation of PRDX3 in sirtuin-3 (SIRT3)-knockdown Caco-2 cells. Importantly, PRDX3 acetylation was increased in mice lacking SIRT3, and this effect was accompanied by serious mitochondrial oxidative damage, apoptosis and remote organ damage after intestinal I/R injury. We screened potential sites of PRDX3 acetylation in the previously reported acetylproteome through immunoprecipitation (IP) experiments and found that SIRT3 deacetylates K253 on PRDX3 in Caco-2 cells. Furthermore, PRDX3 with the lysine residue K253 mutated to arginine (K253R) increased its dimerization in Caco-2 cells after subjected to 12 h hypoxia and followed 4 h reoxygenation. Caco-2 cells transfected with the K253R plasmid exhibited notably less mitochondrial damage and apoptosis, and transfection of the K253Q plasmid abolished the protective effect of PRDX3 overexpression. Analysis of ischemic intestines from clinical patients further verified the correlation between SIRT3 and PRDX3.

Conclusions

PRDX3 is a key protective factor for intestinal I/R injury, and SIRT3-mediated PRDX3 deacetylation can alleviate intestinal I/R-induced mitochondrial oxidative damage and apoptosis.

Impact of Intermittent Hypoxia on Sepsis Outcomes in a Murine Model

Sleep apnea has been associated with a variety of diseases, but its impact on sepsis outcome remains unclear. This study investigated the effect of intermittent hypoxia [IH]–the principal feature of sleep apnea–on murine sepsis. 5-week-old male C57BL6 mice were assigned to groups receiving severe IH (O2 fluctuating from room air to an O2 nadir of 5.7% with a cycle length of 90 seconds), mild IH (room air to 12%, 4 minutes/cycle), or room air for 3 weeks. Sepsis was induced by cecal ligation and puncture and survival was monitored. Sepsis severity was evaluated by murine sepsis scores, blood bacterial load, plasma tumor necrosis factor-α [TNF-α]/interleukin-6 [IL-6] levels and histopathology of vital organs. Compared with normoxic controls, mice subjected to severe IH had earlier mortality, a lower leukocyte count, higher blood bacterial load, higher plasma TNF-α and IL-6 levels, more severe inflammatory changes in the lung, spleen and small intestine. Mice subjected to mild IH did not differ from normoxic controls, except a higher IL-6 level after sepsis induced. The adverse impact of severe IH was reversed following a 10-day normoxic recovery. In conclusion, severe IH, not mild IH, contributed to poorer outcomes in a murine sepsis model.

Synovial fluid and plasma levels of milk fat globule-epidermal growth factor 8 are inversely correlated with radiographic severity of knee osteoarthritis

Objective

Mounting evidence demonstrates that inflammation plays an important role in the pathogenesis of osteoarthritis (OA). Milk fat globule–epidermal growth factor 8 (MFG-E8) is an important glycoprotein that is involved in anti-inflammatory responses. The present study was performed to assess the MFG-E8 levels in plasma and synovial fluid and explore the association between radiographic severity and MFG-E8 levels in patients with knee OA.

Methods

This study involved 138 healthy controls and 142 patients with knee OA. The MFG-E8 levels in plasma and synovial fluid were evaluated by enzyme-linked immunosorbent assay. The Kellgren and Lawrence classification was used for OA grading.

Results

The plasma MFG-E8 level was significantly lower in patients with knee OA than in healthy controls. The synovial fluid MFG-E8 level was significantly lower than the plasma level in patients with knee OA. More importantly, the MFG-E8 levels in synovial fluid and plasma were significantly and inversely associated with radiographic severity among patients with knee OA.

Conclusions

These results demonstrate that the levels of MFG-E8 in synovial fluid and plasma are inversely correlated with the radiographic severity of knee OA.

MFG-E8/integrin β3 signaling contributes to airway inflammation response and airway remodeling in an ovalbumin-induced murine model of asthma

Asthma is the most common chronic childhood disease worldwide, characterized by airway remodeling and chronic inflammation, orchestrated primarily by Th2 cytokines. The aim of the current study was to explore the influences of milk fat globule epidermal growth factor 8 (MFG-E8)/integrin β3 signaling involved in airway inflammation and remodeling in asthma. BALB/c mice were sensitized by intraperitoneal injection of ovalbumin (OVA), followed by OVA nebulization. The levels of MFG-E8 expression were declined markedly in the OVA-induced allergy murine model. In addition, administration of MFG-E8 strongly reduced the accumulation of T-helper type 2 (Th2)-associated cytokines (such as interleukin-4, -5, and -13) as well as chemokine CCL11 (eotaxin) in bronchoalveolar lavage fluid and tissues in the OVA-sensitized mice. Moreover, MFG-E8 remarkably repressed the total immunoglobulin E and OVA-specific immunoglobulin E in serum in OVA-challenged mice. Meanwhile, treatment with recombinant murine MFG-E8 noticeably prevented inflammatory cell infiltration into the airways, as showed by a marked decrease in the numbers of total immune cells, eosinophils, neutrophils, macrophages, and lymphocytes in the bronchoalveolar lavage fluid in response to OVA challenge. Importantly, MFG-E8 apparently alleviated OVA-driven airway remodeling, which were evidenced by declined secretion of important mediators of airway remodeling, including transforming growth factor-β1, matrix metalloproteinase 9, ADAM8, and vascular endothelial growth factor, and reduced airway collagen deposition and inhibited goblet cell hyperplasia in OVA-induced asthma in mice. Mechanistically, integrin 3 contributes to the protective effect of MFG-E8 in inhibiting airway inflammation and remodeling in OVA-driven features of allergic asthma. Overall, MFG-E8, as a candidate molecule to evaluate airway inflammation and remodeling, could be a potential target for the management and prevention of asthma exacerbations, suggesting that MFG-E8/integrin β3 signaling may serve as a promising therapeutic agent for childhood asthma.

Inhibition of ubiquitin-activating enzyme protects against organ injury after intestinal ischemia-reperfusion

Intestinal ischemia-reperfusion (I/R) occurs in various clinical settings, such as transplantation, acute mesenteric arterial occlusion, trauma, and shock. I/R injury causes severe systemic inflammation, leading to multiple organ dysfunction associated with high mortality. The ubiquitin proteasome pathway has been indicated in the regulation of inflammation, particularly through the NF-κB signaling pathway. PYR-41 is a small molecular compound that selectively inhibits ubiquitin-activating enzyme E1. A mouse model of intestinal I/R injury by clamping the superior mesenteric artery for 45 min was performed to evaluate the effect of PYR-41 treatment on organ injury and inflammation. PYR-41 was administered intravenously at the beginning of reperfusion. Blood and organ tissues were harvested at 4 h after reperfusion. PYR-41 treatment improved the morphological structure of gut and lung after I/R, as judged by hematoxylin and eosin staining. It also reduced the number of apoptotic terminal deoxynucleotidyl transferase dUTP nick end-labeling-positive cells and caspase-3 activity in the organs. PYR-41 treatment decreased the expression of proinflammatory cytokines IL-6 and IL-1β as well as chemokines keratinocyte chemoattractant and macrophage inflammatory protein-2 in the gut and lung, which leads to inhibition of neutrophils infiltrating into these organs. The serum levels of IL-6, aspartate aminotransferase, and lactate dehydrogenase were reduced by the treatment. The IκB degradation in the gut increased after I/R was inhibited by PYR-41 treatment. Thus, ubiquitination may be a potential therapeutic target for treating patients suffering from intestinal I/R. NEW & NOTEWORTHY Excessive inflammation contributes to organ injury from intestinal ischemia-reperfusion (I/R) in many clinical conditions. NF-κB signaling is very important in regulating inflammatory response. In an experimental model of gut I/R injury, we demonstrate that administration of a pharmacological inhibitor of ubiquitination process attenuates NF-κB activation, leading to reduction of inflammation, tissue damage, and apoptosis in the gut and lungs. Therefore, ubiquitination process may serve as a therapeutic target for treating patients with intestinal I/R injury.

Knockdown of TNF‑α alleviates acute lung injury in rats with intestinal ischemia and reperfusion injury by upregulating IL‑10 expression

Intestinal ischemia and reperfusion (II/R) injury often triggers severe injury in remote organs, with the lungs being considered the main target. Excessive elevation of proinflammatory cytokines is a major contributor in the occurrence and development of II/R-induced acute lung injury (ALI). Therefore, the present study aimed to investigate whether blocking tumor necrosis factor-α (TNF-α) expression could protect the lungs from injury following II/R, and to explore the possible underlying mechanism involving interleukin-10 (IL-10). Briefly, II/R was induced in rats by 40 min occlusion of the superior mesenteric artery and celiac artery, followed by 8, 16 or 24 h of reperfusion. Subsequently, lentiviral vectors containing TNF-α short hairpin (sh)RNA were injected into the right lung tissues, in order to induce TNF-α knockdown. The severity of ALI was determined according to lung injury scores and lung edema (lung wet/dry weight ratio). The expression levels of TNF-α were analyzed by quantitative polymerase chain reaction (qPCR), western blotting and immunofluorescence (IF) staining. IL-10 expression, in response to TNF-α knockdown, was detected in lung tissues by qPCR and IF. The results detected marked inflammatory responses, and increased levels of lung wet/dry weight ratio and TNF-α expression, in the lungs of II/R rats. Conversely, treatment with TNF-α shRNA significantly alleviated the severity of ALI and upregulated the expression levels of IL-10 in lung tissues. These findings suggested that TNF-α RNA interference may exert a protective effect on II/R-induced ALI via the upregulation of IL-10. Therefore, TNF-α knockdown may be considered a potential strategy for the prevention or treatment of ALI induced by II/R in future clinical trials.

Neutralization of Osteopontin Ameliorates Acute Lung Injury Induced by Intestinal Ischemia-Reperfusion

Intestinal ischemia-reperfusion (I/R) is associated with acute respiratory distress syndrome. Osteopontin (OPN), a glycoprotein secreted from immune-reactive cells, plays a deleterious role in various inflammatory diseases. Considering OPN as a pro-inflammatory molecule, we hypothesize that the treatment with its neutralizing antibody (anti-OPN Ab) protects mice against intestinal I/R-induced acute lung injury (ALI). Intestinal I/R was induced in mice by superior mesenteric artery occlusion with a vascular clip. After 45 min of occlusion, the clip was removed and anti-OPN Ab (25 μg/mouse) or normal IgG isotype control (25 μg/mouse) was immediately administrated intravenously. Blood, small intestine, and lung tissues were collected at 4 h after reperfusion for various analyses. After intestinal I/R, mRNA and protein levels of OPN were significantly induced in the small intestine, lungs, and blood relative to sham-operated animals. Compared with the IgG control group, treatment of anti-OPN Ab significantly reduced plasma levels of pro-inflammatory cytokine and chemokine (IL-6 and MIP-2) and organ injury markers (AST, ALT, and LDH). The histological architecture of the gut and lung tissues in anti-OPN Ab-treated intestinal I/R-induced mice showed significant improvement versus the IgG control mice. The lung inflammation measured by the levels of IL-6, IL-1β, and MIP-2 was also significantly downregulated in the anti-OPN Ab-treated mice as compared with the IgG control mice. Besides, the lung MPO and neutrophil infiltration in anti-OPN Ab-treated mice showed significant reduction as compared with the IgG control animals. In conclusion, we have demonstrated beneficial outcomes of anti-OPN Ab treatment in protecting against ALI, implicating a novel therapeutic potential in intestinal I/R.

Deficiency in milk fat globule-epidermal growth factor-factor 8 exacerbates organ injury and mortality in neonatal sepsis

INTRODUCTION

Neonatal sepsis is a systemic inflammation occurring in neonates because of a proven infection within the first 28days of birth. It is the third leading cause of morbidity and mortality in the newborns. The mechanism(s) underlying the systemic inflammation in neonatal sepsis has not been completely understood. We hypothesize that the deficiency of milk fat globule-epidermal growth factor-factor 8 (MFG-E8), a protein commonly found in human milk, could be responsible for the increased inflammatory response leading to morbidity and mortality in neonatal sepsis.

METHODS

Male and female newborn mice aged 5-7days were injected intraperitoneally with 0.9mg/g body weight cecal slurry (CS). At 10h after CS injection, they were euthanized, and blood, lungs and gut tissues were obtained for further analyses. Control newborn mice underwent similar procedures with the exception of the CS injection. In duplicate newborn mice after CS injection, they were returned to their respective cages with their mothers and were closely monitored for 7days and survival rate recorded.

RESULTS

At 10h after CS injection, serum LDH in the MFG-E8 knockout (KO) newborn mice was significantly increased by 58% and serum IL-6, IL-1β and TNF-α in the MFG-E8KO newborn mice were also significantly increased by 56%, 65%, and 105%, respectively, from wild type (WT) newborn mice. There were no significant difference between WT control and MFG-E8 control newborn mice. The lung architecture was severely damaged and a significant 162% increase in injury score was observed in the CS MFG-E8KO newborn mice. The MPO, TUNEL staining, and cytokine levels in the lungs and the intestine in CS MFG-E8KO newborn mice were significantly increased from CS WT newborn mice. Similarly, intestinal integrity was also compromised in the CS MFG-E8KO newborn mice. In a survival study, while the mortality rate within 7days was only 29% in the CS WT newborn mice, 80% of the CS MFG-E8KO newborn mice died during the same time period with the majority of mortality occurring within 48h.

CONCLUSION

The deficiency in MFG-E8 caused increases in inflammation, tissue injury, neutrophil infiltration and apoptosis, which led to morbidity and mortality in murine neonatal sepsis. These studies suggest that MFG-E8 has a protective role in fighting against neonatal sepsis.

Lactadherin orthologs inhibit migration of human, porcine and murine intestinal epithelial cells

Lactadherin was originally described due to its appearance in milk, but is abundantly expressed especially by professional and nonprofessional phagocytes. The proteins has been shown to have a multitude of bioactive effects, including inhibition of inflammatory phospholipases, induction of effero‐ and phagocytosis, prevent rotavirus induced gastroenteritis, and modulate intestinal homeostasis by regulating epithelial cell migration. The level of expression seems to be important in a row of serious pathologies linked to the intestinal epithelial barrier function, vascular‐ and autoimmune disease. This study examines the ability of lactadherin to modulate migration of intestinal epithelium. A cell exclusion assay is used to quantify the ability of human, bovine and murine lactadherin orthologs to affect migration of primary small intestine epithelium cells. Previous reports show that recombinant murine lactadherin stimulate rat small intestine cell migration. The present study could not confirm this. Conversely, 10 μg/ml lactadherin inhibits migration. Therefore, as lactadherins enteroprotective properties is well established using in vivo models we conclude that the protective effects are linked to lactadherins ability operate as an opsonin, or other modulating effects, and not a direct lactadherin‐cell induction of migration. Thus, the molecular mechanism behind the enteroprotective role of lactadherin remains to be established.

Interleukin‑6 RNA knockdown ameliorates acute lung injury induced by intestinal ischemia reperfusion in rats by upregulating interleukin‑10 expression

Acute lung injury (ALI) is a common complication following intestinal ischemia/reperfusion (II/R) injury and contributes to the associated high mortality rate. However, the underlying mechanism is poorly understood and treatments are limited. RNA interference (RNAi) has been demonstrated to provide a promising disease treatment strategy both in vitro and in vivo. Therefore, the present study aimed to test whether blocking the proinflammatory cytokine IL‑6 by RNAi may protect the lungs from remote organ injury following II/R, and to investigate the potential underlying mechanisms. A total of 176 adult healthy male Sprague‑Dawley rats were randomly divided into sham, II/R, negative‑control and IL‑6‑short hairpin (sh)RNA groups. The rats underwent II/R injury with occlusion of the superior mesenteric artery and coeliac artery to induce ischemia for 40 min, and were subsequently reperfused for 0‑48 h. The negative‑control group received a control lentiviral vector containing scrambled or non‑specific sequences, and the IL‑6‑shRNA groups were administered with a vector containing an IL‑6 shRNA sequence to affect RNAi‑mediated knockdown of IL‑6. ALI severity was determined by lung edema (lung wet/dry ratio) and histological analysis (lung injury scores). IL‑6 localization, and mRNA and protein expression levels, were detected by immunofluorescence, reverse transcription‑quantitative polymerase chain reaction and western blot analysis, respectively. IL‑10 expression induced by IL‑6 knockdown in lung tissues was additionally detected. IL‑6 RNAi was revealed to significantly reduce the expression of IL‑6, which was associated with upregulated IL‑10 expression in lung tissues. Consequently, the severities of ALI and edema induced by II/R were substantially improved. In conclusion, the present study demonstrated that IL‑6 RNAi may protect the lung from ALI induced by II/R, and that this protective role may be associated with upregulation of IL‑10. These findings may contribute to the development of an IL‑6‑RNAi‑based therapeutic strategy for the treatment of II/R‑induced ALI.

Treatment with milk fat globule epidermal growth factor-factor 8 (MFG-E8) reduces inflammation and lung injury in neonatal sepsis

BACKGROUND

Sepsis remains one of the leading causes of infant death worldwide. It is characterized by uncontrolled inflammatory responses due to proven bacterial infection. Despite improvement in supportive care and the availability of effective antibiotics, no specific therapy targeting the dysregulated inflammatory response is available for neonatal sepsis. Milk fat globule epidermal growth factor-factor 8 (MFG-E8) is a secretory glycoprotein abundantly present in human milk. MFG-E8 suppresses the systemic inflammatory responses in adult murine injury models by improving the clearance of dying cells. We hypothesized that exogenous administration of recombinant mouse MFG-E8 could inhibit the exaggerated inflammatory response and lung injury in a murine model of neonatal sepsis.

METHODS

Neonatal sepsis was induced in 5- to 7-day-old male and female C57BL6 mice using an intraperitoneal injection of cecal slurry. At 1 hour after sepsis induction, a single dose of 40 μg/kg recombinant mouse MFG-E8 or vehicle was administered via retro-orbital injection. All neonates were returned to their mothers as a group. At 10 hours after cecal slurry injection, pups were killed and blood and lung tissues were collected. Control mice underwent a similar procedure with the exception of cecal slurry intraperitoneal injection.

RESULTS

Serum lactate dehydrogenase, IL-1β, and IL-6 were significantly increased 10 hours after cecal slurry injection. Treatment with recombinant mouse MFG-E8 decreased these levels by 30%, 56%, and 37%, respectively. Lung morphology was significantly compromised in the vehicle group after cecal slurry injection, whereas the recombinant mouse MFG-E8-treated groups demonstrated a 48% improvement in the lung injury score. Lung IL-6 and MIP-2 protein levels were significantly reduced with recombinant mouse MFG-E8 treatment. Lung neutrophil infiltration as observed by Gr-1 staining and, TUNEL-positive cells were also significantly reduced with recombinant mouse MFG-E8 treatment.

CONCLUSION

Treatment with recombinant mouse MFG-E8 attenuated inflammation and lung injury in murine neonatal sepsis. Thus, MFG-E8 could be developed as a possible therapy for neonatal sepsis.

Milk fat globule-epidermal growth factor-factor VIII attenuates sepsis-induced acute kidney injury

BACKGROUND

Acute kidney injury (AKI) is most commonly caused by sepsis in critically ill patients, and it is associated with high morbidity and mortality. The pathophysiology of sepsis-induced AKI is generally accepted to include direct inflammatory injury, endothelial cell dysfunction, and apoptosis. Milk fat globule-epidermal growth factor-factor VIII (MFG-E8) is a secretory glycoprotein with a known role in the enhancement of apoptotic cell clearance and regulation of inflammation. We hypothesize that administration of recombinant mouse MFG-E8 (rmMFG-E8) can protect mice from kidney injuries caused by sepsis.

METHODS

Sepsis was induced in 8-wk-old male C57BL/6 mice by cecal ligation and puncture (CLP). rmMFG-E8 or phosphate-buffered saline (vehicle) was injected intravenously at a dosage of 20 μg/kg body weight at time of CLP (n = 5-8 mice per group). After 20 h, serum and renal tissue were harvested for various analyses. The renal injury markers blood urea nitrogen (BUN) and creatinine were determined by enzymatic and chemical reactions, respectively. The gene expression analysis was carried out by real-time quantitative polymerase chain reaction.

RESULTS

At 20 h after CLP, serum levels of BUN and creatinine were both significantly increased in the vehicle group compared with the sham group, whereas the mice treated with rmMFG-E8 had a significant reduction in BUN and creatinine levels by 28% and 24.1%, respectively (BUN: 197.7 ± 23.6 versus 142.3 ± 20.7 mg/dL; creatinine: 0.83 ± 0.12 versus 0.63 ± 0.06 mg/dL; P < 0.05). Expressions of novel biomarkers of renal tissue injury neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 were also significantly downregulated by 58.2% and 95%, respectively, after treatment with rmMFG-E8. Proinflammatory cytokine interleukin-6 and tumor necrosis factor-α messenger RNA (mRNA) were significantly reduced by 50.8% and 50.3%, respectively, in rmMFG-E8-treated mice compared with vehicle-treated mice. The mRNA levels of the chemokines keratinocyte chemoattractant and macrophage inhibitory protein-2 were reduced by 85.1% and 78%, respectively, in mice treated with rmMFG-E8 compared with the vehicle mice. In addition, the expression of intercellular cell adhesion molecule-1 and platelet endothelial cell adhesion molecule-1 (PECAM-1/CD31) mRNA was downregulated by 35.6% and 77.8%, respectively, in rmMFG-E8-treated mice compared with the vehicle animals (P < 0.05).

CONCLUSIONS

Treatment with rmMFG-E8 reduces renal tissue injury induced by sepsis through inhibiting the production of proinflammatory cytokines and chemokine, as well as through the activation of endothelial cells. Thus, MFG-E8 may have a therapeutic potential for treating AKI induced by sepsis.

Cigarette smoke attenuates phagocytic ability of macrophages through down-regulating Milk fat globule-EGF factor 8 (MFG-E8) expressions

Chronic obstructive pulmonary disease (COPD) is one of the most common inflammatory diseases resulting from habitual smoking. Impaired clearance of apoptotic cell by airway macrophages contributes to lung inflammation. Milk fat globule-EGF factor 8 (MFG-E8), as a link between apoptotic cells and phagocytes, facilitates clearance of apoptotic cells and attenuates inflammation. We sought to investigate altered expression and potential role of MFG-E8 in COPD. In this study, apoptosis was increased and the level of MFG-E8 was decreased while HMGB1 expression was increased in lung tissues of CS-exposed mice. Compared with CS-exposed WT mice, more apoptotic cells were accumulated in lung tissues of CS-exposed MFG-E8 deficiency mice. Exposure of a range of macrophages to cigarette smoke extract (CSE) resulted in decreased MFG-E8 expression. Administration of rmMFG-E8 ameliorated phagocytic ability of RAW264.7 cells and suppressed inflammatory response induced by CS-exposure. 10% CSE stimulation suppressed Rac1 membrane localization in RAW264.7 cells which was restored by administration of rmMFG-E8. MFG-E8 deficiency diminished uptake of apoptotic thymocytes by peritoneal macrophages upon CSE exposure. Overall, the findings in current work provide a novel target for diagnosing and treating COPD.

MFG-E8-derived peptide attenuates adhesion and migration of immune cells to endothelial cells

Milk fat globule-epidermal growth factor-factor 8 (MFG-E8) plays an immunomodulatory role in inflammatory diseases. MFG-E8-derived short peptide (MSP68) greatly reduces neutrophil infiltration and injury in the lung during sepsis. In this study, we examined the effect of MSP68 on chemotaxis of various immune cells and its regulatory mechanism. Bone marrow-derived neutrophils (BMDNs) from C57BL/6 mice, human monocyte THP-1 cell line, and human T lymphocyte Jurkat cell line were used for adhesion and migration assays using a Transwell method in the presence of MSP68. Treatment with MSP68 significantly inhibited the BMDN and THP-1 cell but not Jurkat cell adhesion on the TNF-α-stimulated pulmonary artery endothelial cell (PAEC) monolayer dose-dependently. MSP68 also significantly reduced BMDN adhesion on VCAM-1-coated wells dose dependently. Surface plasmon resonance (SPR) analysis revealed that MSP68 efficiently recognized integrin α₄β₁ (receptor for VCAM-1) at the dissociation constant (K_D) of 1.53 × 10^-7 M. These findings implicate that MSP68 prevents neutrophil adhesion to the activated endothelial cells by interfering with the binding between integrin α₄β₁ on neutrophils and VCAM-1 on endothelial cells. Moreover, MSP68 significantly attenuated the migration of BMDN and THP-1 cells but not Jurkat cells to their chemoattractants. Pretreatment with MSP68 inhibited the transmigration of BMDNs across the PAECs toward chemoattractants, fMLP, MIP-2, and complement fragment 5a (C5a) dose-dependently. Finally, we identified that the activation of p38 MAPK in BMDNs by fMLP was inhibited by MSP68. Thus, MSP68 attenuates extravasation of immune cells through the endothelial cell lining into inflamed tissue, implicating MSP68 to be a novel, therapeutic agent for inflammatory diseases caused by excessive immune cell infiltration.

Protective effects of ethyl pyruvate on lipopolysaccharide‑induced acute lung injury through inhibition of autophagy in neutrophils

Among a number of clinical factors, bacterial infection is one of the most common causes of acute lung injury (ALI), a serious complication that carries a high risk of mortality (~40%). During the process of ALI, intense local and systemic inflammation is elicited, which exacerbates the injury. Neutrophil infiltration into airspace is observed in early stage of ALI, and is required for the full development of ALI through an array of mechanisms, including the release of granule contents and the production of pro‑inflammatory cytokines, due to the overactivation of complement and cytokines. The present study noted that ethyl pyruvate alleviated ALI in lipopolysaccharide (LPS)‑induced ALI mice. Increased autophagy in neutrophils from ALI mice was observed, while ethyl pyruvate diminished autophagy in neutrophils and constrained granule release, and therefore myeloperoxidase (MPO) in bronchoalveolar lavage fluid and the production of proinflammatory cytokines. Using neutrophil cells, it was identified that autophagy was required for neutrophil activation and granule release, and that ethyl pyruvate caused neutrophil autophagy, leading to the restriction of granule release, and thus contributing to the mitigation of ALI. If autophagy was obviated through knockdown of key regulator of autophagy Atg5, the effects of ethyl pyruvate on granule release by neutrophils disappeared. Taken together, the results demonstrated that ethyl pyruvate alleviates ALI through inhibition of autophagy‑induced granule release by neutrophils, and this mechanism suggested a novel potential therapeutic target in autophagy regulation for ALI.

Elevated serum milk fat globule-epidermal growth factor 8 levels in type 2 diabetic patients are suppressed by overweight or obese status

Inflammation is the most important link between obesity and type 2 diabetes (T2D). Although milk fat globule-epidermal growth factor 8 (MFG-E8) is a key mediator in anti-inflammatory responses, its role in obesity and diabetes is not yet completely understood. We aimed to measure MFG-E8 serum levels and to explore the role of MFG-E8 in obesity and T2D. Fasting serum MFG-E8 levels were quantified by enzyme-linked immunosorbent assay for 168 individuals, whose oral glucose tolerance test was conducted, and levels of inflammatory factors, including tumor necrosis factor-α (TNF-α) and C-reactive protein, were measured. The participants were subdivided into 66 newly diagnosed T2D individuals, 44 impaired glucose tolerance (IGT) subjects and 58 healthy controls. Their characteristics were further classified as lean or nonlean for investigation. MFG-E8 levels were significantly higher in T2D subjects than in healthy controls (P = 0.028). Decreased levels of MFG-E8 were found in overweight or obese individuals, compared to those in lean subjects, in both the T2D and IGT groups (P < 0.001). Interestingly, MFG-E8 levels showed a negative correlation with body mass index (BMI) and TNF-α levels in the total population and the T2D subgroup. Further, BMI and TNF-α concentrations were found to be independent predictors of MFG-E8 levels in all subjects. MFG-E8 levels are elevated in T2D but suppressed by increased adipose tissues, thereby allowing inflammatory factors to rise to high levels. MFG-E8 may serve as a potential biomarker for obesity and T2D in the clinical setting. © 2017 IUBMB Life, 69(2):63-71, 2017.

Mfge8 regulates enterocyte lipid storage by promoting enterocyte triglyceride hydrolase activity

The small intestine has an underappreciated role as a lipid storage organ. Under conditions of high dietary fat intake, enterocytes can minimize the extent of postprandial lipemia by storing newly absorbed dietary fat in cytoplasmic lipid droplets. Lipid droplets can be subsequently mobilized for the production of chylomicrons. The mechanisms that regulate this process are poorly understood. We report here that the milk protein Mfge8 regulates hydrolysis of cytoplasmic lipid droplets in enterocytes after interacting with the αvβ3 and αvβ5 integrins. Mice deficient in Mfge8 or the αvβ3 and αvβ5 integrins accumulate excess cytoplasmic lipid droplets after a fat challenge. Mechanistically, interruption of the Mfge8-integrin axis leads to impaired enterocyte intracellular triglyceride hydrolase activity in vitro and in vivo. Furthermore, Mfge8 increases triglyceride hydrolase activity through a PI3 kinase/mTORC2-dependent signaling pathway. These data identify a key role for Mfge8 and the αvβ3 and αvβ5 integrins in regulating enterocyte lipid processing.

Milk fat globule-EGF factor 8 suppresses the aberrant immune response of systemic lupus erythematosus-derived neutrophils and associated tissue damage

Abnormal features of the systemic lupus erythematosus (SLE)-derived neutrophils, promoted aberrant immune response, have inspired new studies of the induction of autoimmunity and the development of organ damage in SLE. In this study, we explore the effect of milk fat globule-EGF factor 8 (MFG-E8) on the aberrant nitrification features in pristane-induced lupus. SLE patients and mice with pristane-induced lupus develop autoantibodies associated with MFG-E8 overproduction. However, the deletion of MFG-E8 leads to uncontrolled early pulmonary and peritoneal inflammation and tissue damage in mice with pristane-induced lupus. Consistent with these findings, MFG-E8-deficient mice that are exposed to pristane show enhanced neutrophil accumulation and increased neutrophil death, including apoptosis, necrosis and NETosis, as well as impaired phagocytosis of macrophages. The consequences are the expansion of diffuse pulmonary hemorrhage, increased anti-nuclear antibody, anti-dsDNA antibody and anti-neutrophil cytoplasmic antibody levels, and enhanced immune complexes deposition and neutrophil extracellular traps (NETs) formation in the lung and kidney tissues of MFG-E8-deficient mice exposed to pristane. In patients with SLE and mice with pristane-induced lupus, neutrophil accumulation is elevated, which depends on higher expression of the surface receptor CXCR2. After pretreatment with recombinant MFG-E8, the surface expression of CXCR2 on neutrophil is downregulated, and the MFG-E8 deletion increase CXCR2 expression by ~40%. These studies indicate that MFG-E8 reduces neutrophil migration and NETosis via downregulating surface CXCR2 expression in parallel with its role in the phagocytosis of apoptotic neutrophils, suggesting that MFG-E8 may serve as a therapeutic agent for attenuating the early inflammatory responses of SLE and protect patients from lupus-related damage.

Milk fat globule-epidermal growth factor-factor VIII-derived peptide MSP68 is a cytoskeletal immunomodulator of neutrophils that inhibits Rac1

BACKGROUND

Prolonged neutrophil infiltration leads to exaggerated inflammation and tissue damage during sepsis. Neutrophil migration requires rearrangement of their cytoskeleton. Milk fat globule-epidermal growth factor-factor VIII-derived short peptide 68 (MSP68) has recently been shown to be beneficial in sepsis-induced tissue injury and mortality. We hypothesize that MSP68 inhibits neutrophil migration by modulating small GTPase Rac1-dependent cytoskeletal rearrangements.

METHODS

Bone marrow-derived neutrophils (BMDNs) or whole lung digest isolated neutrophils were isolated from 8 to 10 wk old C57BL/6 mice by Percoll density gradient centrifugation. The purity of BMDN was verified by flow cytometry with CD11b/Gr-1 staining. Neutrophils were stimulated with N-formylmethionine-leucine-phenylalanine (f-MLP) (10 nM) in the presence or absence of MSP68 at 10 nM or cecal ligation and puncture (CLP) was used to induce sepsis, and MSP68 was administered at 1 mg/kg intravenously. Cytoskeletal organization was assessed by phalloidin staining, followed by analysis using fluorescence microscopy. Activity of the Rac1 GTPase in f-MLP or CLP-activated BMDN in the presence or absence of MSP68 was assessed by GTPase enzyme-linked immunosorbent assay. Mitogen-activated protein (MAP) kinase activity was determined by western blot densitometry.

RESULTS

BMDN treatment with f-MLP increased cytoskeletal remodeling as revealed by the localization of filamentous actin to the periphery of the neutrophil. By contrast, cells pretreated with MSP68 had considerably reduced filamentous actin polymerization. Cytoskeletal spreading is associated with the activation of the small GTPase Rac1. We found BMDN-treated with f-MLP or that were exposed to sepsis by CLP had increased Rac1 signaling, whereas the cells pretreated with MSP68 had significantly reduced Rac1 activation (P < 0.05). MAP kinases related to cell migration including pp38 and pERK were upregulated by treatment with f-MLP. Upregulation of these MAP kinases was also significantly reduced after pretreatment with MSP68 (P < 0.05).

CONCLUSIONS

MSP68 downregulates actin cytoskeleton-dependent, Rac1-MAP kinase-mediated neutrophil motility. Thus, MSP68 is a novel therapeutic candidate for regulating inflammation and tissue damage caused by excessive neutrophil migration in sepsis.

Role of milk fat globule-epidermal growth factor 8 in osteoimmunology

Milk fat globule-epidermal growth factor 8 (MFG-E8) is a glycoprotein that is abundantly expressed in various tissues and has a pivotal role in the phagocytic clearance of apoptotic cells. However, MFG-E8 has also gained significant attention because of its wide range of functions in autoimmunity, inflammation and tissue homeostasis. More recently, MFG-E8 has been identified as a critical regulator of bone homeostasis, being expressed in both, osteoblasts and osteoclasts. In addition, it was shown that MFG-E8 fulfils an active role in modulating inflammatory processes, suggesting an anti-inflammatory role of MFG-E8 and proposing it as a novel therapeutic target for inflammatory diseases. This concise review focusses on the expression and regulation of MFG-E8 in the context of inflammatory bone diseases, highlights its role in the pathophysiology of osteoimmune diseases and discusses the therapeutic potential of MFG-E8.

B7H3 ameliorates LPS-induced acute lung injury via attenuation of neutrophil migration and infiltration

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are characterized by an excessive inflammatory response within the lungs and severely impaired gas exchange resulting from alveolar-capillary barrier disruption and pulmonary edema. The costimulatory protein B7H3 functions as both a costimulator and coinhibitor to regulate the adaptive and innate immune response, thus participating in the development of microbial sepsis and pneumococcal meningitis. However, it is unclear whether B7H3 exerts a beneficial or detrimental role during ALI. In the present study we examined the impact of B7H3 on pulmonary inflammatory response, polymorphonuclear neutrophil (PMN) influx, and lung tissue damage in a murine model of lipopolysaccharide (LPS)-induced direct ALI. Treatment with B7H3 protected mice against LPS-induced ALI, with significantly attenuated pulmonary PMN infiltration, decreased lung myeloperoxidase (MPO) activity, reduced bronchoalveolar lavage fluid (BALF) protein content, and ameliorated lung pathological changes. In addition, B7H3 significantly diminished LPS-stimulated PMN chemoattractant CXCL2 production by inhibiting NF-κB p65 phosphorylation, and substantially attenuated LPS-induced PMN chemotaxis and transendothelial migration by down-regulating CXCR2 and Mac-1 expression. These results demonstrate that B7H3 substantially ameliorates LPS-induced ALI and this protection afforded by B7H3 is predominantly associated with its inhibitory effect on pulmonary PMN migration and infiltration.

Functional Role of Milk Fat Globule-Epidermal Growth Factor VIII in Macrophage-Mediated Inflammatory Responses and Inflammatory/Autoimmune Diseases

Inflammation involves a series of complex biological processes mediated by innate immunity for host defense against pathogen infection. Chronic inflammation is considered to be one of the major causes of serious diseases, including a number of autoimmune/inflammatory diseases, cancers, cardiovascular diseases, and neurological diseases. Milk fat globule-epidermal growth factor 8 (MFG-E8) is a secreted protein found in vertebrates and was initially discovered as a critical component of the milk fat globule. Previously, a number of studies have reported that MFG-E8 contributes to various biological functions including the phagocytic removal of damaged and apoptotic cells from tissues, the induction of VEGF-mediated neovascularization, the maintenance of intestinal epithelial homeostasis, and the promotion of mucosal healing. Recently, emerging studies have reported that MFG-E8 plays a role in inflammatory responses and inflammatory/autoimmune diseases. This review describes the characteristics of MFG-E8-mediated signaling pathways, summarizes recent findings supporting the roles of MFG-E8 in inflammatory responses and inflammatory/autoimmune diseases, and discusses MFG-E8 targeting as a potential therapeutic strategy for the development of anti-inflammatory/autoimmune disease drugs.

Molecular Mechanisms Underlying the Regulation of the MFG-E8 Gene Promoter Activity in Physiological and Inflammatory Conditions

Milk fat globule-EGF factor 8 (MFG-E8) is expressed by macrophages and plays an important role in attenuating inflammation and maintaining tissue homeostasis. Previously, we and others found that lipopolysaccharide (LPS) inhibits MFG-E8 gene expression in macrophages. Here, we characterized the 5'-flanking region of the mouse MFG-E8 gene. To functionally analyze the upstream regulatory region of the MFG-E8 gene, a series of luciferase reporter gene constructs containing deleted or mutated regulatory elements were prepared. Using the luciferase assay, we revealed that Sp1 binding motifs within the proximal promoter region were necessary for full activity of the MFG-E8 promoter, whereas AP-1 like binding sequence at -372 played a role in governing the promoter activity at a homeostatic level. With chromatin immunoprecipitation assay, we showed that Sp1 and c-Jun physically interact with the MFG-E8 promoter region in vivo. In addition, Sp1 was found to regulate the MFG-E8 promoter activity positively and c-Jun negatively. Furthermore, we demonstrated that LPS inhibited MFG-E8 promoter activity via targeting Sp1 and AP-1-like motifs in the 5'-flanking region. Collectively, our data indicate that Sp1 and AP-1-related factors are involved in the regulation of MFG-E8 gene transcription by targeting their binding sites in the 5'-flanking region under physiological and inflammatory states.

Milk Fat Globule-Epidermal Growth Factor 8 (MFG-E8) Is a Novel Anti-inflammatory Factor in Rheumatoid Arthritis in Mice and Humans

Milk fat globule-epidermal growth factor 8 (MFG-E8) is an anti-inflammatory glycoprotein that mediates the clearance of apoptotic cells and is implicated in the pathogenesis of autoimmune and inflammatory diseases. Because MFG-E8 also controls bone metabolism, we investigated its role in rheumatoid arthritis (RA), focusing on inflammation and joint destruction. The regulation of MFG-E8 by inflammation was assessed in vitro using osteoblasts, in arthritic mice and in patients with RA. K/BxN serum transfer arthritis (STA) was applied to MFG-E8 knock-out mice to assess its role in the pathogenesis of arthritis. Stimulation of osteoblasts with lipopolysaccharide (LPS) and tumor necrosis factor (TNF)-α downregulated the expression of MFG-E8 by 30% to 35%. MFG-E8-deficient osteoblasts responded to LPS with a stronger production of pro-inflammatory cytokines. In vivo, MFG-E8 mRNA levels were 52% lower in the paws of collagen-induced arthritic (CIA) mice and 24% to 42% lower in the serum of arthritic mice using two different arthritis models (CIA and STA). Similarly, patients with RA (n = 93) had lower serum concentrations of MFG-E8 (-17%) compared with healthy controls (n = 140). In a subgroup of patients who had a moderate to high disease activity (n = 21), serum concentrations of MFG-E8 rose after complete or partial remission had been achieved (+67%). Finally, MFG-E8-deficient mice subjected to STA exhibited a stronger disease burden, an increased number of neutrophils in the joints, and a more extensive local and systemic bone loss. This was accompanied by an increased activation of osteoclasts and a suppression of osteoblast function in MFG-E8-deficient mice. Thus, MFG-E8 is a protective factor in the pathogenesis of RA and subsequent bone loss. Whether MFG-E8 qualifies as a novel biomarker or therapeutic target for the treatment of RA is worth addressing in further studies.