P38 MAPK Pharmacological Inhibitor SB203580 Alleviates Total Parenteral Nutrition-Induced Loss of Intestinal Barrier Function but Promotes Hepatocyte Lipoapoptosis

Comprehensive review of milk fat globule membrane proteins across mammals and lactation periods in health and disease

Milk fat globule membrane (MFGM) is a three-layer membrane-like structure encasing natural milk fat globules (MFGs). MFGM holds promise as a nutritional supplement because of the numerous physiological functions of its constituent protein. This review summarizes and compares the differences in MFGM protein composition across various species, including bovines, goats, camels, mares, and donkeys, and different lactation periods, such as colostrum and mature milk, as assessed by techniques such as proteomics and mass spectrometry. We also discuss the health benefits of MFGM proteins throughout life. MFGM proteins promote intestinal development, neurodevelopment, and glucose and lipid metabolism by upregulating tight junction protein expression, brain function-related genes, and glucose and fatty acid biosynthesis processes. We focus on the mechanisms underlying these beneficial effects of MFGM proteins. MFGM proteins activate key substances in in signaling pathways, such as the phosphatidylinositol 3-kinase/protein kinase B, mitogen-activated protein kinase, and myosin light chain kinase signaling pathways. Overall, the consumption of MFGM proteins plays an essential role in conferring health benefits, some of which are important throughout the mammalian life cycle.

Potent anti-inflammatory activity of the lectin-like domain of TNF in joints

In view of the crucial role of tumor necrosis factor (TNF) in joint destruction, TNF inhibitors, including neutralizing anti-TNF antibodies and soluble TNF receptor constructs, are commonly used therapeutics for the treatment of arthropathies like rheumatoid arthritis (RA). However, not all patients achieve remission; moreover, there is a risk of increased susceptibility to infection with these agents. Spatially distinct from its receptor binding sites, TNF harbors a lectin-like domain, which exerts unique functions that can be mimicked by the 17 residue solnatide peptide. This domain binds to specific oligosaccharides such as N'N'-diacetylchitobiose and directly target the α subunit of the epithelial sodium channel. Solnatide was shown to have anti-inflammatory actions in acute lung injury and glomerulonephritis models. In this study, we evaluated whether the lectin-like domain of TNF can mitigate the development of immune-mediated arthritis in mice. In an antigen-induced arthritis model, solnatide reduced cell influx and release of pro-inflammatory mediators into the joints, associated with reduction in edema and tissue damage, as compared to controls indicating that TNF has anti-inflammatory effects in an acute model of joint inflammation via its lectin-like domain.

Operation of the Atypical Canonical Bone Morphogenetic Protein Signaling Pathway During Early Human Odontogenesis

Bone morphogenetic protein (BMP) signaling plays essential roles in the regulation of early tooth development. It is well acknowledged that extracellular BMP ligands bind to the type I and type II transmembrane serine/threonine kinase receptor complexes to trigger the BMP signaling pathway. Then, the receptor-activated Smad1/5/8 in cytoplasm binds to Smad4, the central mediator of the canonical BMP signaling pathway, to form transfer complexes for entering the nucleus and regulating target gene expression. However, a recent study revealed the functional operation of a novel BMP-mediated signaling pathway named the atypical BMP canonical signaling pathway in mouse developing tooth, which is Smad1/5/8 dependent but Smad4 independent. In this study, we investigated whether this atypical BMP canonical signaling is conserved in human odontogenesis. We showed that pSMAD1/5/8 is required for the expression of Msh homeobox 1 (MSX1), a well-defined BMP signaling target gene, in human dental mesenchyme, but the typical BMP canonical signaling is in fact not operating in the early human developing tooth, as evidenced by the absence of pSMAD1/5/8-SMAD4 complexes in the dental mesenchyme and translocation of pSMAD1/5/8, and the expression of MSX1 induced by BMP4 is mothers against decapentaplegic homolog 4 (SMAD4)-independent in human dental mesenchymal cells. Moreover, integrative analysis of RNA-Seq data sets comparing the transcriptome profiles of human dental mesenchymal cells with and without SMAD4 knockdown by siRNA displays unchanged expression profiles of pSMAD1/5/8 downstream target genes, further affirming the functional operation of the atypical canonical BMP signaling pathway in a SMAD1/5/8-dependent but SMAD4-independent manner in the dental mesenchyme during early odontogenesis in humans.

Role of the p38MAPK signaling pathway in hippocampal neuron autophagy in rats with chronic intermittent hypoxia

This study explored the role of the p38 mitogen-activated protein kinase (MAPK) signaling pathway in hippocampal neuron autophagy in rats with chronic intermittent hypoxia (CIH). Male Sprague-Dawley rats were randomly divided to normoxic control (CON), CIH (optimal modeling time was determined prior by measuring the expression of several proteins after 2-, 4-, and 6-wk intermittent hypoxia), solvent (CIH+Veh), or p38MAPK inhibitor (CIH+SB203580) groups. DMSO and SB203580 were injected intraperitoneally 30 min before hypoxia in CIH+Veh and CIH+SB203580 group rats, respectively. Rat learning and memory were evaluated via the Morris water maze test. Ultrastructural changes in the hippocampal CA1 region autophagic vesicles and neurons were observed under transmission electron and light microscopy. Hippocampal microtubule-associated proteins were detected by western blot. Morris water maze test showed that CIH+SB203580 group rats spent significantly more time on the platform quadrant and crossed the platform more times than CIH+Veh group rats (P < 0.01). Hematoxylin-eosin (HE) staining showed greater rat cell damage in the CIH+SB group than in the CIH and CIH+Veh groups. Western blot analysis showed that CIH+SB group rats had significantly lower p-p38MAPK/p38MAPK, LC3I, and p62 expression and higher beclin-1 expression than CIH+Veh group rats (P < 0.01). Electron microscopy showed that CIH+SB203580 group rats had several small hippocampal neuron autophagic vesicles. On immunofluorescence analyses, it showed a higher LC3II expression in CIH+SB203580 group rats than in CIH+Veh group rats (P < 0.01). These results indicate that inhibition of the CIH p38MAPK signaling pathway can activate autophagy and protect hippocampal neurons in rats.NEW & NOTEWORTHY The pathophysiological processes related to autophagy obstructive sleep apnea-hypopnea syndrome (OSAHS) are unclear. This study clarified that the inhibition of the p38MAPK signaling pathway could further activate autophagy in hippocampal nerve cells, thus reducing nerve cell injury.

Antifibrotic effects of eupatilin on TGF-β1-treated human vocal fold fibroblasts

Vocal fold scarring is a major cause of dysphonia. Vocal fold fibroblasts (VFFs) and the TGF-β signaling pathway play important roles in scar formation. Eupatilin, a chromone derivative of the Artemisia species, is a traditional folk remedy for wound healing. However, until recently, few studies investigated the therapeutic effects of eupatilin. We investigated the antifibrogenic effects of eupatilin on TGF-β1-treated human vocal fold fibroblasts (hVFFs). The optimal concentration of eupatilin was determined by a cell viability assay. Western blotting was used to measure the expression of alpha-smooth muscle actin during myofibroblast differentiation, fibronectin (FN), collagen type I (Col I), and collagen type III (Col III) extracellular matrix proteins, and Smad2, Smad3, and p38 in the fibrotic pathway. Measurements were made before and after eupatilin treatment. Eupatilin at 100 nM was shown to be safe for use in hVFFs. TGF-β1 induced hVFFs to proliferate and differentiate into myofibroblasts and increased Col III and FN synthesis in a time- and dose-dependent manner. Eupatilin suppressed TGF-β1-induced hVFF proliferation and differentiation into myofibroblasts through the Smad and p38 signaling pathways. Furthermore, eupatilin inhibited TGF-β1-induced FN, Col I, and Col III synthesis in hVFFs. Our in vitro findings show that eupatilin effectively suppressed TGF-β1-induced fibrotic changes in hVFFs via the Smad and p38 signaling pathways. Thus, eupatilin may be considered a novel therapeutic agent for the treatment of vocal fold fibrosis.

Inhibition of p38 MAPK Mitigates Lung Ischemia Reperfusion Injury by Reducing Blood-Air Barrier Hyperpermeability

Background: Lung ischemia reperfusion injury (LIRI) is a complex pathophysiological process activated by lung transplantation and acute lung injury. The p38 mitogen-activated protein kinase (MAPK) is involved in breakdown of the endothelial barrier during LIRI, but the mechanism is still unclear. Therefore, we investigated the function of p38 MAPK in LIRI in vivo and in vitro.

Methods: Sprague–Dawley rats were subjected to ischemia reperfusion with or without pretreatment with a p38 MAPK inhibitor. Lung injury was assessed using hematoxylin and eosin staining, and pulmonary blood–air barrier permeability was evaluated using Evans blue staining. A rat pulmonary microvascular endothelial cell line was infected with lentiviral expressing short hairpin (sh)RNA targeting p38 MAPK and then cells were subjected to oxygen/glucose deprivation and reoxygenation (OGD/R). Markers of endothelial destruction were measured by western blot and immunofluorescence.

Results:In vivo LIRI models showed structural changes indicative of lung injury and hyperpermeability of the blood–air barrier. Inhibiting p38 MAPK mitigated these effects. Oxygen/glucose deprivation and reoxygenation promoted hyperpermeability of the endothelial barrier in vitro, but knockdown of p38 MAPK attenuated cell injury; maintained endothelial barrier integrity; and partially reversed injury-induced downregulation of permeability protein AQP1, endothelial protective protein eNOS, and junction proteins ZO-1 and VE-cadherin while downregulating ICAM-1, a protein involved in destroying the endothelial barrier, and ET-1, a protein involved in endothelial dysfunction.

Conclusion: Inhibition of p38 MAPK alleviates LIRI by decreasing blood–air hyperpermeability. Blocking p38 MAPK may be an effective treatment against acute lung injury.

Perspective: Prospects for Nutraceutical Support of Intestinal Barrier Function

Impairment of intestinal barrier function is linked to certain pathologies and to aging, and can be a cause of bacterial infections, systemic and hepatic inflammation, food allergies, and autoimmune disorders. The formation and maintenance of intestinal tight junctions is supported by glucagon-like peptide-2 (GLP-2), which via insulin-like growth factor I activity boosts phosphoinositide 3-kinase/Akt/mammalian target of rapamycin complex 1 (PI3K/Akt/mTORC1) signaling in enterocytes. 5'-AMP-activated protein kinase (AMPK) activity as well as estrogen receptor-β (ERβ) activity are also protective in this regard. Conversely, activation of mitogen-activated protein kinases (MAPKs) and cellular Src (c-Src) under inflammatory conditions can induce dissociation of tight junctions. Hence, nutraceuticals that promote GLP-2 secretion from L cells-effective pre/probiotics, glycine, and glutamine-as well as diets rich in soluble fiber or resistant starch, can support intestinal barrier function. AMPK activators-notably berberine and the butyric acid produced by health-promoting microflora-are also beneficial in this regard, as are soy isoflavones, which function as selective agonists for ERβ. The adverse impact of MAPK and c-Src overactivation on the intestinal barrier can be combatted with various antioxidant measures, including phycocyanobilin, phase 2-inducer nutraceuticals, and N-acetylcysteine. These considerations suggest that rationally designed functional foods or complex supplementation programs could have clinical potential for supporting and restoring healthful intestinal barrier function.

Dihydroartemisinin attenuates alcoholic fatty liver through regulation of lipin-1 signaling

Alcoholic liver disease (ALD) is generated from excessive alcohol consumption, characterized by hepatic steatosis. Mechanistically, excessive hepatic lipid accumulation was attributed to the aberrant lipin-1 signaling during the development of alcoholic steatosis in rodent species and human. Dihydroartemisinin (DHA) has been recently identified to relieve hepatocytes necrosis and prevent from hepatic steatosis in alcohol-induced liver diseases; however, the role of DHA in ALD has not been elucidated completely. Therefore, this study was aimed to further identify the potential mechanisms of pharmacological effects of DHA on ALD. Results demonstrated that DHA regulated the expression and nucleocytoplasmic shuttling of lipin-1 in mice with chronic ethanol exposure. Results confirmed that the disruption of lipin-1 signaling abolished the suppression of DHA on alcohol-induced hepatic steatosis. Interestingly, DHA also significantly improved liver injury, and inflammation mediated by lipin-1 signaling in chronic alcohol-fed mice. in vivo experiments further consolidated the concept that DHA protected against hepatocyte lipoapoptosis dependent on the regulation of nucleocytoplasmic shuttling of lipin-1 signaling, resulting in attenuated ratio of Lpin1 β/α. Obvious increases in cell apoptosis were observed in alcohol-treated lipin1β-overexpressed mice. Although DHA attenuated cell apoptosis, overexpression of lipin-1β neutralized DHA action. DHA ameliorated activation of endoplasmic reticulum stress through inhibiting activation of JNK and CHOP, which was abrogated by overexpression of lipin-1β. In summary, DHA significantly improved liver injury, steatosis and hepatocyte lipoapoptosis in chronic alcohol-fed mice via regulation of lipin-1 signaling.

The TNF-derived TIP peptide activates the epithelial sodium channel and ameliorates experimental nephrotoxic serum nephritis

In mice, the initial stage of nephrotoxic serum-induced nephritis (NTN) mimics antibody-mediated human glomerulonephritis. Local immune deposits generate tumor necrosis factor (TNF), which activates pro-inflammatory pathways in glomerular endothelial cells (GECs) and podocytes. Because TNF receptors mediate antibacterial defense, existing anti-TNF therapies can promote infection; however, we have previously demonstrated that different functional domains of TNF may have opposing effects. The TIP peptide mimics the lectin-like domain of TNF, and has been shown to blunt inflammation in acute lung injury without impairing TNF receptor-mediated antibacterial activity. We evaluated the impact of TIP peptide in NTN. Intraperitoneal administration of TIP peptide reduced inflammation, proteinuria, and blood urea nitrogen. The protective effect was blocked by the cyclooxygenase inhibitor indomethacin, indicating involvement of prostaglandins. Targeted glomerular delivery of TIP peptide improved pathology in moderate NTN and reduced mortality in severe NTN, indicating a local protective effect. We show that TIP peptide activates the epithelial sodium channel(ENaC), which is expressed by GEC, upon binding to the channel's α subunit. In vitro, TNF treatment of GEC activated pro-inflammatory pathways and decreased the generation of prostaglandin E2 and nitric oxide, which promote recovery from NTN. TIP peptide counteracted these effects. Despite the capacity of TIP peptide to activate ENaC, it did not increase mean arterial blood pressure in mice. In the later autologous phase of NTN, TIP peptide blunted the infiltration of Th17 cells. By countering the deleterious effects of TNF through direct actions in GEC, TIP peptide could provide a novel strategy to treat glomerular inflammation.

Modulation of Intestinal Epithelial Permeability by Plasma from Patients with Crohn's Disease in a Three-dimensional Cell Culture Model

Intestinal epithelial barrier is affected by multiple factors, such as tumour necrosis factor-α (TNF-α). Plasma concentration of TNF-α is higher in patients with Crohn’s disease (CD) than healthy controls (HC) and correlates positively with disease activity. This study aimed to determine the effect of plasma from active, inactive CD patients on intestinal barrier function and to investigate the underlying mechanism. Plasma samples were collected from CD patients and HC. 3D Caco-2 cysts were treated with plasma or TNF-α, with or without pre-incubation of adalimumab (a monoclonal antibody that antagonizes TNF-α) or JNK inhibitor SP600125. The results demonstrated that exposure of the cysts to plasma from CD patients resulted in enhanced paracellular permeability in a disease activity-dependent manner. Compared to HC, active CD plasma decreased ZO-1 and OCCLUDIN expression on mRNA and protein levels, and led to an increased JNK phosphorylation. Pre-incubation with adalimumab or SP600125 ameliorated TJ disruption and barrier dysfunction induced by plasma from CD patients. These results indicate that plasma from CD patients is able to induce epithelial barrier disruption, in part through TNF-α induced TJs modulation. The data also demonstrate an involvement of MAPK pathway, in particular the JNK isoform, in CD patient plasma-induced barrier dysfunction.

Neuronal MAP kinase p38α inhibits c-Jun N-terminal kinase to modulate anxiety-related behaviour

Modulation of behavioural responses by neuronal signalling pathways remains incompletely understood. Signalling via mitogen-activated protein (MAP) kinase cascades regulates multiple neuronal functions. Here, we show that neuronal p38α, a MAP kinase of the p38 kinase family, has a critical and specific role in modulating anxiety-related behaviour in mice. Neuron-specific p38α-knockout mice show increased levels of anxiety in behaviour tests, yet no other behavioural, cognitive or motor deficits. Using CRISPR-mediated deletion of p38α in cells, we show that p38α inhibits c-Jun N-terminal kinase (JNK) activity, a function that is specific to p38α over other p38 kinases. Consistently, brains of neuron-specific p38α-knockout mice show increased JNK activity. Inhibiting JNK using a specific blood-brain barrier-permeable inhibitor reduces JNK activity in brains of p38α-knockout mice to physiological levels and reverts anxiety behaviour. Thus, our results suggest that neuronal p38α negatively regulates JNK activity that is required for specific modulation of anxiety-related behaviour.

Milk Fat Globule Membrane Inhibits NLRP3 Inflammasome Activation and Enhances Intestinal Barrier Function in a Rat Model of Short Bowel

BACKGROUND

The milk fat globule membrane (MFGM) contains various bioactive components which have been shown to maintain gut barrier integrity. This study aimed to evaluate the protective effects of MFGM on intestinal barrier function and its possible mechanisms in a rat model of short bowel syndrome (SBS).

MATERIALS AND METHODS

Five-week-old male Sprague-Dawley rats were divided into 3 groups (n = 8 per group), consisting of Sham group and rats submitted to massive small-bowel resection then supplemented with either water (SBS) or 1.5g/kg/d MFGM (SBS+MFGM) by daily gavage. Rats were sacrificed on day 15 postoperation. Intestinal adaptation, gut permeability, bacterial translocation (BT), expression of tight junction proteins, mucin 1 (MUC1), and nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing protein 3 (NLRP3) pathway in the ileum were evaluated.

RESULTS

Both SBS+MFGM and SBS groups exhibited lower body weight and higher ileum villus height than Sham group, but no difference was detected between each other. SBS group had significantly higher intestinal permeability and BT rate than other groups (P < .05). Compared with SBS rats, SBS+MFGM group showed higher expression of tight junction proteins and MUC1, lower expression of NLRP3 and caspase-1 in the ileum, as well as lower interleukin (IL)-1β but higher IL-18 levels in ileum tissue.

CONCLUSIONS

Supplementation of MFGM helps to modulate NLRP3 inflammasome activation and enhances gut barrier integrity in rats after massive small-bowel resection, which provides experimental support for potential applications of MGFM in intestinal barrier dysfunction, although further studies are needed.

Fish oil-derived lipid emulsion induces RIP1-dependent and caspase 8-licensed necroptosis in IEC-6 cells through overproduction of reactive oxygen species

BACKGROUND

Excessive cell death of enterocytes has been demonstrated to be partially associated with the intravenously-administrated lipid emulsions (LEs) during parenteral nutrition (PN) support. However, as a new generation of LE, the effect of fish oil-derived lipid emulsion (FOLE) on the death of enterocytes remains elusive.

METHODS

Intestinal epithelial cells (IEC-6 cell line) were treated with FOLE (0.25-1%) for 24 h. Cell survival was measured by CCK-8 assay, and morphological changes were monitored by time-lapse live cell imaging. The expression of receptor-interacting protein 1/3 (RIP1/3) and caspase 8 was assessed by westernblot, and the formation of necrosome (characterized by the assembly of RIP1/3 complex along with the dissociation of caspase 8) was examined by immunoprecipitation. Additionally, the production of intracellular reactive oxygen species (ROS) was detected by using a ROS detection kit with an oxidation-sensitive probe (DCFH-DA).

RESULTS

FOLE dose-dependently induced non-apoptotic, but programmed necroctic cell death (necroptosis) within 4-8 h after treatment. The assembly of RIP1/3 complex along with the dissociation of caspase 8 from RIP1 was observed in FOLE-treated cells. Moreover, FOLE-induced cell death was significantly alleviated by inhibiting RIP1, and was further aggravated by inhibiting caspase 8. In addition, prior to cell death the accumulation of intracellular ROS was significantly increased in FOLE-treated cells (increased by approximately 5-fold versus control, p < 0.001), which could be attenuated by inhibiting RIP1 (decreased by approximately 35% versus FOLE, p < 0.05).

CONCLUSIONS

FOLE induces RIP1-dependent and caspase 8-licensed necroptosis through overproduction of ROS in vitro. Our findings may provide novel insights into the clinical applications of FOLE during PN support.

Resveratrol Attenuates Cognitive Deficits of Traumatic Brain Injury by Activating p38 Signaling in the Brain

BACKGROUND Traumatic brain injury (TBI) is characterized by cognitive deficits, which was associated with brain oxidative stress and apoptosis. Resveratrol (RSV) is an anti-apoptotic and anti-oxidative. This study aimed to investigate neuroprotective effects and involved molecular mechanisms in TBI. MATERIAL AND METHODS RSV and p38 inhibitor were administrated to TBI rats. Cognitive deficits were evaluated by Morris water maze assay. Reactive oxygen species (ROS) and apoptosis were detected in rat brains by fluorescent staining. Western blotting was used to assess the phosphorylation of p38 and the expression levels of Nrf2, HO1, and activated caspase-3. RESULTS RSV administration attenuated cognitive deficits of TBI rats. The ROS generation and apoptosis in the brain of TBI rats were suppressed by RSV treatment. Moreover, RSV treatment recovered activation of p38/Nrf2/HO1 signaling pathway. The co-administration of p38 inhibitor impaired RSV's attenuating effects on cognitive deficits, brain apoptosis, and ROS generation. CONCLUSIONS RSV attenuated cognitive deficits of TBI by inhibiting oxidative stress-mediated apoptosis via targeting p38/Nrf2 signaling.

p38α MAPK antagonizing JNK to control the hepatic fat accumulation in pediatric patients onset intestinal failure

The p38α mitogen-activated protein kinase (MAPK) has been related to gluconeogenesis and lipid metabolism. However, the roles and related mechanisms of p38α MAPK in intestinal failure (IF)-associated liver steatosis remained poor understood. Here, our experimental evidence suggested that p38α MAPK significantly suppressed the fat accumulation in livers of IF patients mainly through two mechanisms. On the one hand, p38α MAPK increased hepatic bile acid (BA) synthesis by upregulating the expression of the rate-limiting enzyme cholesterol 7-α-hydroxylase (CYP7A1) and peroxisome proliferator-activated receptor γ coactivator-1α (PGC-1α), which in turn activated the transcription of the CYP7A1. On the other hand, p38α MAPK promoted fatty acid (FA) β-oxidation via upregulating peroxisome proliferator-activated receptor alpha (PPARα) and its transcriptional target genes carnitine palmitoyltransferase 1A (CPT1A) and peroxisomal acyl-coenzyme aoxidase 1 (ACOX1). Dual luciferase assays indicated that p38α MAPK increased the transcription of PPARα, PGC-1α and CYP7A1 by upregulating their promoters’ activities. In addition, in vitro and in vivo assays indicated p38α MAPK negatively regulates the hepatic steatosis by controlling JNK activation. In conculsion, our findings demonstrate that hepatic p38α MAPK functions as a negative regulator of liver steatosis in maintaining BA synthesis and FAO by antagonizing the c-Jun N-terminal kinase (JNK).