Differential roles of JNK, ERK1/2, and p38 mitogen-activated protein kinases on endothelial cell tissue repair functions in response to tumor necrosis factor-α

JAKinibs prevent persistent, IFNγ-autonomous endothelial cell inflammation and immunogenicity

The adhesion and subsequent activation of T cells is a critical step in local inflammatory responses, particularly of alloreactive leukocytes in rejection of transplanted donor tissue. Interferon (IFN)γ is an adaptive cytokine that promotes endothelial cell (EC) expression of pro-adhesive factors and costimulatory molecules. We recently reported that IFNγ-induced endothelial cell antigen-presenting capacity was protracted after cytokine withdrawal. This study sought to determine what intracellular signaling mediates this chronic endothelial activation by IFNγ. The durability of interferon signaling in human aortic endothelial activation was tested. Pro-adhesive and costimulatory gene expression, phenotype, secretome, and Janus kinase (JAK)/STAT phosphorylation in human primary endothelial cells were measured under chronic and transient IFNγ stimulation, with various JAK inhibitors. IFNγ reporter cells were tested for STAT1 transcriptional activity with JAK inhibition and suppressors of cytokine signaling (SOCS) overexpression, under continuous and priming conditions. The consequences of even short exposure to IFNγ were long-lasting and broad, with sustained elevation of adhesion molecules and chemokines up to 48 h later. JAK/STAT and interferon response factor expression were likewise durable, dependent on new transcription but autonomous of continuous IFNγ. Persistent STAT new transcription and JAK signaling in the endothelium was required to maintain a pro-adhesive and proimmunogenic phenotype after IFNγ withdrawal since both could be prevented by cycloheximide but only by JAKinibs with potency against JAK2. Finally, the suppressor of cytokine signaling SOCS1 failed to emerge in primed endothelial cells, which likely accounted for prolonged inflammatory gene expression. The results reveal a sustained JAK-dependent perturbation of endothelial function and suggest that JAKinibs may have therapeutic benefits in dampening vascular inflammation and allogeneic leukocyte activation.NEW & NOTEWORTHY The central question investigated in this study is why vascular endothelium remains inflamed and what underlying signaling is responsible. The new results show that the resolution of endothelial-controlled inflammation may be impaired or delayed because Janus kinase (JAK)/STAT activation is maintained autonomous of interferon (IFN)γ presence, and the late phase negative regulator suppressors of cytokine signaling (SOCS)1 fails to be induced.

Late phase endothelial cell inflammation is characterized by interferon response genes and driven by JAK/STAT, not NFκB

Chronic vascular inflammation underlies many diseases, including atherosclerosis, autoimmune vasculitides and transplant rejection. The resolution of inflammation is critical for proper healing and restoration of homeostasis, but the timing and signaling mechanisms involved in the return to a non-inflamed state are not well understood. Pro-adhesive gene expression, phenotype and secretome of human endothelial cells was measured in primary human aortic endothelium under chronic TNFα stimulation, and after short-term TNFα priming followed by withdrawal. The effects of NFκB, MAPK and JAK1/2 inhibitors on TNFα-induced gene expression were tested. The majority of inducible TNFα effectors, such as E-selectin, VCAM-1 and most chemokines, required continuous exposure for reinforcement of the altered phenotype, and were NFκB dependent. However, 3 h priming with TNFα induced late phase STAT activation and interferon response genes after 18 h, as well as enhanced ICAM-1, BST2 and CXCR3 ligand expression. Chronic activation was autonomous of continuous TNFα, and could be blocked by the JAK1/2 inhibitor ruxolitinib. The results demonstrate that NFκB is not a significant driver of the later phase of endothelial cell activation by TNFα, but that sustained inflammation is JAK1/2-dependent and characterized by adaptive chemokines.

The role of TrkA in the promoting wounding-healing effect of CD271 on epidermal stem cells

CD271, a receptor of nerve growth factor (NGF), affects the biological properties of epidermal stem cells (eSCs) which are essential for skin wound closure. Tropomyosin-receptor kinase A (TrkA), another receptor of NGF, combined with CD271 has been involved with nervous system and skin keratinocytes. However, the exact role of TrkA combined with CD271 in eSCs during skin wound closure is still unclear. This study aimed to reveal the role of TrkA in the promoting wounding-healing effect of CD271 on eSCs. We obtained CD271-vo (over-expression of CD271) eSCs by lentiviral infection. K252a was used to inhibit TrkA expression. Full-thickness skin mouse wound closure model (5 mm in diameter) was used to detect the ability of CD271 over-expressed/TrkA-deficient during wound healing. The biological characteristics of eSCs and their proliferation and apoptosis were detected using immunohistochemistry and western blot. The expressions of protein kinase B (pAkt)/Akt, phosphorylated extracellular-signal-related kinase (pERK)/ERK1/2, and c-Jun N-terminal kinase (pJNK)/JNK were also detected by western blot. We found that over-expression of CD271 promoted the biological functions of eSCs. Interestingly, over-expression of CD271 in the absence of TrkA neither promoted eSCs' migration and proliferation nor promoted wound healing in a mouse model. In addition, we observed the reduced expression of pAkt/Akt and pERK/ERK1/2 following TrkA inhibition in vitro. Our studies demonstrated that the role of TrkA in the promoting wounding-healing effect of CD271 on eSCs.

Attenuation of TNF-α-Induced Inflammatory Injury in Endothelial Cells by Ginsenoside Rb1 via Inhibiting NF-κB, JNK and p38 Signaling Pathways

It is currently believed that inflammation plays a central role in the pathophysiology of atherosclerosis. Oxidative stress and redox-sensitive transcription factors are implicated in the process. Ginsenoside Rb1, a major active ingredient in processed Radix notoginseng, has attracted widespread attention because of its potential to improve cardiovascular function. However, the effects of ginsenoside Rb1 on tumor necrosis factor-α (TNF-α)-induced vascular endothelial cell injury and the underlying molecular mechanisms have never been studied. This study showed that TNF-α-induced oxidative stress, inflammation and apoptosis in human umbilical vein endothelial cells (HUVECs) could be attenuated by ginsenoside Rb1 pretreatment. Using JC-1, Annexin V/PI and TUNEL staining, and a caspase-3 activity assay, we found that Rb1 provided significant protection against TNF-α-induced cell death. Furthermore, Rb1 pretreatment could inhibit TNF-α-induced ROS and MDA production; increase the activities of SOD, CAT, and GSH-Px; and decrease the levels of IL-1β, IL-6, VCAM-1, ICAM-1, VEGF, MMP-2 and MMP-9. Importantly, the cytoprotective effects of Rb1 were correlated with NF-κB signaling pathway inhibition. Additionally, we found that Rb1 may suppress the NF-κB pathway through p-38 and JNK pathway activation, findings supported by the results of our experiments involving anisomycin (AM), a JNK and p38 activator. In conclusion, this study showed that ginsenoside Rb1 protects HUVECs from TNF-α-induced oxidative stress and inflammation by inhibiting JNK and p38. This inhibition suppressed NF-κB signaling and down-regulated the expression of inflammatory factors and apoptosis-related proteins.

Resveratrol attenuates ICAM-1 expression and monocyte adhesiveness to TNF-α-treated endothelial cells: evidence for an anti-inflammatory cascade mediated by the miR-221/222/AMPK/p38/NF-κB pathway

Resveratrol, an edible polyphenolic phytoalexin, improves endothelial dysfunction and attenuates inflammation. However, the mechanisms have not been thoroughly elucidated. Therefore, we investigated the molecular basis of the effects of resveratrol on TNF-α-induced ICAM-1 expression in HUVECs. The resveratrol treatment significantly attenuated the TNF-α-induced ICAM-1 expression. The inhibition of p38 phosphorylation mediated the reduction in ICAM-1 expression caused by resveratrol. Resveratrol also decreased TNF-α-induced IκB phosphorylation and the phosphorylation, acetylation, and translocation of NF-κB p65. Moreover, resveratrol induced the AMPK phosphorylation and the SIRT1 expression in TNF-α-treated HUVECs. Furthermore, TNF-α significantly suppressed miR-221/-222 expression, which was reversed by resveratrol. miR-221/-222 overexpression decreased p38/NF-κB and ICAM-1 expression, which resulted in reduced monocyte adhesion to TNF-α-treated ECs. In a mouse model of acute TNF-α-induced inflammation, resveratrol effectively attenuated ICAM-1 expression in the aortic ECs of TNF-α-treated wild-type mice. These beneficial effects of resveratrol were lost in miR-221/222 knockout mice. Our data showed that resveratrol counteracted the TNF-α-mediated reduction in miR-221/222 expression and decreased the TNF-α-induced activation of p38 MAPK and NF-κB, thereby suppressing ICAM-1 expression and monocyte adhesion. Collectively, our results show that resveratrol attenuates endothelial inflammation by reducing ICAM-1 expression and that the protective effect was mediated partly through the miR-221/222/AMPK/p38/NF-κB pathway.

The effect of ethyl acetate extract from persimmon leaves on Alzheimer's disease and its underlying mechanism

BACKGROUND

Alzheimer's disease (AD) is one of the most prevalent neurodegenerative disorders characterized by neuronal loss in the brain and cognitive impairment. AD is now considered to be the third major cause of death in developed countries, after cardiovascular disease and cancer. Persimmon leaves are used as a popular folk medicine to treat hypertension, angina and internal haemorrhage in Cyangbhina, and it has been reported that ethyl acetate extract of persimmon leaves (EAPL) displays a potential therapeutic effect on neurodegenerative diseases.

HYPOTHESIS/PURPOSE

This study was designed to investigate the effects of EAPL on AD, to clarify the possible mechanism by which EAPL exerts its beneficial effects and prevents AD, and to determine the major constituents involved.

STUDY DESIGN

AD model was established by bilateral injection of Aβ1-42 into the hippocampus of rats. The cognitive performance was determined by the Morris water maze and step-down tests. Superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), malondialdehyde (MDA), apoptosis, total and phosphorylated c-Jun NH2-terminal kinase (JNK/p-JNK), caspase-3, Bax and Bcl-2 were determined. In addition, a sensitive and reliable LC-QTOF-MS method was applied to identify the major compounds present in EAPL.

RESULTS

EAPL at doses of 200mg/kg, 400mg/kg could markedly reduce the latency, significantly increase the time in the first quadrant and number of the target crossing times in Morris water maze test, markedly increase the latency and reduce the number of errors in the step-down test, significantly inhibit the reductions in SOD and GSH-Px activities, and increase the level of MDA. In addition, EAPL treatment attenuated neuronal apoptosis in the hippocampus, reduced the expression of p-JNK, caspase-3, and the relative ratio of Bax/Bcl-2. Meanwhile, 32 constituents were identified by LC-QTOF-MS/MS assays.

CONCLUSION

The results indicate that EAPL has a potent protective effect on cognitive deficits induced by Aβ in rats and this effect appears to be associated with the regulation of the antioxidative defense system and the mechanism of mitochondrial-mediated apoptosis. Furthermore, analysis of the LC-MS data suggests that flavonoids and triterpenoids may be responsible for the potential biological effects of EAPL.

Human amniotic epithelial stem cells promote wound healing by facilitating migration and proliferation of keratinocytes via ERK, JNK and AKT signaling pathways

Wound healing is a highly orchestrated physiological process consisting in a complex interaction of cellular and biochemical events. Human amniotic epithelial stem cells (HAESCs) have been shown to be an attractive resource for wound healing because they are primitive stem cells. However, the exact effects of amnion-derived stem cells on the migration or proliferation of keratinocytes and their potential mechanism are not fully understood. We have found that HAESCs accelerate the migration of keratinocytes and induce a remarkable increase in the activity of phospho-ERK, phospho-JNK, and phospho-AKT, the blockade of which by their specific inhibitors significantly inhibits migration induced by HAESC-conditioned medium (CM). Furthermore, the co-culture of keratinocytes with HAESCs up-regulates the expression levels of cell proliferation proteins Cyclin D1, Cyclin D3 and Mdm2. In vivo animal experiments have shown that HAESC-CM improves wound healing, whereas blockade with ERK, JNK and AKT inhibitors significantly impairs wound healing. Taken together, these results reveal, for the first time, that HAESCs promote wound healing by facilitating the migration and proliferation of keratinocytes via ERK, JNK and AKT signaling pathways and might be a potential therapy in skin wound healing.

ROS-Induced JNK and p38 Signaling Is Required for Unpaired Cytokine Activation during Drosophila Regeneration

Upon apoptotic stimuli, epithelial cells compensate the gaps left by dead cells by activating proliferation. This has led to the proposal that dying cells signal to surrounding living cells to maintain homeostasis. Although the nature of these signals is not clear, reactive oxygen species (ROS) could act as a signaling mechanism as they can trigger pro-inflammatory responses to protect epithelia from environmental insults. Whether ROS emerge from dead cells and what is the genetic response triggered by ROS is pivotal to understand regeneration of Drosophila imaginal discs. We genetically induced cell death in wing imaginal discs, monitored the production of ROS and analyzed the signals required for repair. We found that cell death generates a burst of ROS that propagate to the nearby surviving cells. Propagated ROS activate p38 and induce tolerable levels of JNK. The activation of JNK and p38 results in the expression of the cytokines Unpaired (Upd), which triggers the JAK/STAT signaling pathway required for regeneration. Our findings demonstrate that this ROS/JNK/p38/Upd stress responsive module restores tissue homeostasis. This module is not only activated after cell death induction but also after physical damage and reveals one of the earliest responses for imaginal disc regeneration.

Regenerative biology pursues to unveil the genetic networks triggered by tissue damage. Regeneration can occur after damage by cell death or by injury. We used the imaginal disc of Drosophila in which we genetically activated apoptosis or physically removed some parts and monitored the capacity to repair the damage. We found that dying cells generate a burst of reactive oxygen species (ROS) necessary to activate JNK and p38 signaling pathways in the surrounding living cells. The action of these pathways is necessary for the activation of the cytokines Unpaired (Upd). Eventually, Upd will turn on the JAK/STAT signaling pathway to induce regenerative growth. Thus, we present here a module of signals that depends on oxidative stress and that, through the p38-JNK interplay, will activate cytokine-dependent regeneration.

Astragaloside IV inhibits platelet-derived growth factor-BB-stimulated proliferation and migration of vascular smooth muscle cells via the inhibition of p38 MAPK signaling

Astragaloside IV (AS-IV), the major active component extracted from Astragalus membranaceus, has been demonstrated to exhibit protective effects on the cardiovascular, immune, digestive and nervous systems; thus, has been widely used in traditional Chinese medicine. Abnormal proliferation and migration of vascular smooth muscle cells (VSMCs) is closely associated with the initiation and progression of cardiovascular diseases, including atherosclerosis and restenosis. However, the effects of AS-IV on VSMCs remain unknown. For the first time, the present study demonstrated that AS-IV markedly suppressed platelet-derived growth factor (PDGF)-BB-stimulated cellular proliferation and migration of HDMEC-a human dermal VSMCs (HDVSMCs). Further investigation into the underlying molecular mechanisms demonstrated that the administration of AS-IV attenuated the PDGF-BB-stimulated switch of HDVSMCs into a proliferative phenotype. Furthermore, AS-IV inhibited the PDGF-BB-induced expression of cell cycle-associated proteins, as well as the upregulation of matrix metalloproteinase (MMP)2, but not MMP9. In addition, AS-IV was shown to downregulate the activation of p38 mitogen-activated protein kinase (MAPK) signaling induced by PDGF-BB in HDVSMCs. Therefore, the observations of the present study indicate that AS-IV inhibits PDGF-BB-stimulated VSMC proliferation and migration, possibly by inhibiting the activation of the p38 MAPK signaling pathway. Thus, AS-IV may be useful for the treatment of vascular diseases.

Effect of vascular endothelial cells on the pathogenesis of inflammatory bowel disease

Inflammatory bowel disease (IBD), including Crohn's disease (CD) and ulcerative colitis (UC), are a group of chronic recurrent intestinal autoimmune diseases characterized by intestinal chronic intestinal inflammation. The important characteristics of persistent intestinal inflammation in IBD are the aggregation of inflammatory cells and the release of inflammatory factors in the intestinal mucosa. Functional alternations of immune cells and intestinal microvascular endothelial cells play an important role in the mucosal immunity and intestinal function. Moreover, alternation of the structure and function of microvascular endothelial cells can regulate the migration of immune cells, blood supply and homeostasis of intestinal tissue. Endothelial cells in newly formed vessels can induce tissue injury by regulating the recruitment of blood cells and inflammatory mediators to maintain the inflammatory reaction.