MKP-7, a negative regulator of JNK, regulates VCAM-1 expression through IRF-1

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.

MKP-3 suppresses LPS-induced inflammatory responses in HUVECs via inhibition of p38 MAPK/NF-κB pathway

Endothelial cell dysfunction and inflammatory responses play critical roles in the development of atherosclerosis. Recent data on the processes underlying atherogenesis indicate the substantial role of endotoxins (lipopolysaccharides; LPS) of the intestinal microflora in the initiation and progression of atherosclerosis. Mitogen-activated protein (MAP) kinase phosphatase-3 (MKP-3) is a cytoplasmic dual-specificity protein phosphatase that specifically binds to and inactivates MAP kinases in mammalian cells, but its biological function in endothelial cell dysfunction and inflammatory responses remains largely unknown. The aim of the present study was to investigate the role of MKP-3 in endotoxin-induced endothelial inflammation by western blotting, quantitative polymerase chain reaction, and immunofluorescence. The results of our study demonstrated that MKP-3 overexpression markedly inhibited the adhesion of human monocytic THP-1 cells to human umbilical vein endothelial cells (HUVECs) by downregulating the expression of vascular cell adhesion protein 1 (VCAM-1) and pro-inflammatory cytokines. In contrast, MKP-3-encoding gene knockdown by small interfering RNA (siRNA) exacerbated LPS-induced endothelial dysfunction. Additionally, we found that MKP-3 overexpression inhibited LPS-induced p38 MAPK phosphorylation and decreased the nuclear translocation of nuclear factor kappa B (NF-κB) after LPS treatment, suggesting its implication in the LPS/Toll-like receptor 4 (TLR4)/p38/NF-κB pathway. Overall, these observations suggest that MKP-3 plays a protective role in endothelial dysfunction and may be a therapeutic target.

A Novel STAT3-Mediated GATA6 Pathway Contributes to tert-Butylhydroquinone- (tBHQ-) Protected TNFα-Activated Vascular Cell Adhesion Molecule 1 (VCAM-1) in Vascular Endothelium

The activation of vascular cell adhesion molecule 1 (VCAM-1) in vascular endothelial cells has been well considered implicating in the initiation and processing of atherosclerosis. Oxidative stress is mechanistically involved in proatherosclerotic cytokine-induced VCAM-1 activation. tert-Butylhydroquinone (tBHQ), a synthetic phenolic antioxidant used for preventing lipid peroxidation of food, possesses strongly antioxidant capacity against oxidative stress-induced dysfunction in various pathological process. Here, we investigated the protective role of tBHQ on tumor necrosis factor alpha- (TNFα-) induced VCAM-1 activation in both aortic endothelium of mice and cultured human vascular endothelial cells and uncovered its potential mechanisms. Our data showed that tBHQ treatment significantly reversed TNFα-induced activation of VCAM-1 at both transcriptional and protein levels. The mechanistic study revealed that inhibiting neither nuclear factor (erythroid-derived 2)-like 2 (Nrf2) nor autophagy blocked the beneficial role of tBHQ. Alternatively, tBHQ intervention markedly alleviated TNFα-increased GATA-binding protein 6 (GATA6) mRNA and protein expressions and its translocation into nucleus. Further investigation indicated that tBHQ-inhibited signal transducer and activator of transcription 3 (STAT3) but not mitogen-activated protein kinase (MAPK) pathway contributed to its protective role against VCAM-1 activation via regulating GATA6. Collectively, our data demonstrated that tBHQ prevented TNFα-activated VCAM-1 via a novel STAT3/GATA6-involved pathway. tBHQ could be a potential candidate for the prevention of proatherosclerotic cytokine-caused inflammatory response and further dysfunctions in vascular endothelium.

Dynamics of Dual Specificity Phosphatases and Their Interplay with Protein Kinases in Immune Signaling

Dual specificity phosphatases (DUSPs) have a well-known role as regulators of the immune response through the modulation of mitogen-activated protein kinases (MAPKs). Yet the precise interplay between the various members of the DUSP family with protein kinases is not well understood. Recent multi-omics studies characterizing the transcriptomes and proteomes of immune cells have provided snapshots of molecular mechanisms underlying innate immune response in unprecedented detail. In this study, we focus on deciphering the interplay between members of the DUSP family with protein kinases in immune cells using publicly available omics datasets. Our analysis resulted in the identification of potential DUSP-mediated hub proteins including MAPK7, MAPK8, AURKA, and IGF1R. Furthermore, we analyzed the association of DUSP expression with TLR4 signaling and identified VEGF, FGFR, and SCF-KIT pathway modules to be regulated by the activation of TLR4 signaling. Finally, we identified several important kinases including LRRK2, MAPK8, and cyclin-dependent kinases as potential DUSP-mediated hubs in TLR4 signaling. The findings from this study have the potential to aid in the understanding of DUSP signaling in the context of innate immunity. Further, this will promote the development of therapeutic modalities for disorders with aberrant DUSP signaling.

Deletion of interferon-regulatory factor-1 results in cognitive impairment

Interferon-regulatory factor (IRF)-1-dependent genes in neurons play a role in ischemic neuronal death; however, the roles of IRF-1 in dementia are not well investigated. Therefore, we assessed the effect of IRF-1 on cognitive function using a vascular cognitive impairment mouse model created by chronic cerebral hypoperfusion. Male 10-week-old C57BL/6 (wild-type; WT) and IRF-1-knockout (IRF-1KO) mice were used in this study. A chronic cerebral hypoperfusion mouse model was generated by bilateral common carotid artery stenosis (BCAS) treatment. After 6 weeks of BCAS, the mice were subjected to the Morris water maze test five times a day for 5 days. In the Morris water maze task, escape latency was significantly prolonged in sham-operated IRF-1KO mice compared with sham-operated WT mice. However, BCAS treatment cancelled such difference in spatial learning between WT and IRF-1KO mice. BCAS treatment decreased CBF, but no significant difference was observed between the two strains after BCAS. Sham-operated IRF-1KO mice showed a decrease in mRNA expression of caspase-1 and an increase in IRF-2 expression in the hippocampus. Expression of angiotensin II type 2 (AT₂) receptor, which induces better cognitive function, is regulated by IRF-1; however, no obvious difference in AT₂ receptor expression was observed between the two strains even after BCAS. These results suggest that IRF-1 has a protective effect on cognitive decline in a normal condition; however, there was no obvious effect on cognition after chronic cerebral hypoperfusion treatment.

D-chiro-inositol enriched Fagopyrum tataricum (L.) Gaench extract alleviates mitochondrial malfunction and inhibits ER stress/JNK associated inflammation in the endothelium

ETHNOPHARMACOLOGICAL RELEVANCE

Tartary buckwheat is a food medicine dual-use crop with healing effects on cardiovascular diseases and type2 diabetes. It has been proposed that endothelial dysfunction is the initial lesion in these diseases and it's associated with mitochondrial dysfunction, endoplasmic reticulum (ER) stress and inflammation. D-chiro-inositol (DCI) is a bioactive compound of Tartary buckwheat and is always deficit in type2 diabetes. However, it remains unknown whether DCI-enriched Tartary buckwheat extract can ameliorate mitochondrial dysfunction, ER stress and inflammation in the endothelium.

MATERIAL AND METHODS

Endothelial cells were treated with palmitic acid (PA) and mice were fed with high fat diet (HFD). The effects of DCI-enriched Tartary buckwheat bran extract (TBBE) on superoxide anion generation, dynamin-related protein 1 (Drp1), mitofusin2 (Mfn2), inositol-requiring enzyme-1α (IRE1α) and Jun n-terminal kinase (JNK) activation and inflammation in the endothelium against lipotoxicity were investigated.

RESULTS

In endothelial cells, TBBE significantly inhibited oxidative stress. Meanwhile, in HFD-fed mice and PA-induced cells, TBBE regulated Drp1 phosphorylation and inhibited its activation, implying the protective effect of TBBE on mitochondrial morphology. As a result, TBBE protected mitochondrial function. Additionally, TBBE inhibited ER stress and reduced the production of IL-6 and VCAM-1, associated with JNK pathway, thereby inhibiting the caspase-3 activation in vivo and in vitro.

CONCLUSIONS

Taken together, this study indicated the beneficial role of TBBE in endothelial inflammation, with emphasis on mitochondrial dysfunction, ER stress and JNK activation.

Dual specificity phosphatase DUSP6 promotes endothelial inflammation through inducible expression of ICAM-1

Tumor necrosis factor (TNF)-α activates a diverse array of signaling pathways in vascular endothelial cells (ECs), leading to the inflammatory phenotype that contributes to the vascular dysfunction and neutrophil emigration in patients with sepsis. To date, it is not well understood what key regulator might coordinate signaling pathways to achieve inflammatory response in TNF-α-stimulated ECs. This study investigated the role of dual specificity phosphatase-6 (DUSP6) in the regulation of endothelial inflammation. Using knockout mice, we found that DUSP6 is important for TNF-α-induced endothelial intercellular adhesion molecule-1 (ICAM-1) expression in aorta and in vein. Moreover, genetic deletion of Dusp6 in pulmonary circulation significantly alleviated the susceptibility of mice to lung injury caused by neutrophil recruitment during experimental sepsis induced by TNF-α or lipopolysaccharide (LPS). The role of DUSP6 was further investigated in primary human umbilical vein endothelial cells (HUVECs). Employing RNAi approach in which endogenous DUSP6 was ablated, we showed a critical function of DUSP6 to facilitate TNF-α-induced ICAM-1 expression and endothelial leukocyte interaction. Interestingly, DUSP6-promoted endothelial inflammation is independent of extracellular signaling-regulated kinase (ERK) signaling. On the other hand, inducible DUSP6 leads to activation of canonical nuclear factor (NF)-κB-mediated transcription of ICAM-1 gene in TNF-α-stimulated human ECs. These results are the first to demonstrate a positive role of DUSP6 in endothelial inflammation-mediated pathological process and the underlying mechanism through which DUSP6 promotes NF-κB signaling in the inflamed ECs. Our findings suggest that manipulation of DUSP6 holds great potential for the treatment of acute inflammatory diseases.

Inhibitory effect of trans-caryophyllene (TC) on leukocyte-endothelial attachment

trans-Caryophyllene (TC) is a major component found in the essential oils of many spices and foods/medicinal plants. It is a natural sesquiterpene and has been the subject of numerous studies. However, the effects of TC on vascular inflammation remain unknown. In this study, we reported that TC treatment in human umbilical vein endothelial cells (HUVECs) prevented attachment of monocytic leukemia cell line THP-1 cells to endothelial cells. In addition, in vivo results indicate that TC inhibited macrophage infiltration to the aortic surface and reduced total serum levels of cholesterol and triglycerides. Importantly, administration of TC could inhibit the induction of vascular cell adhesion molecule-1 (VCAM-1) both in vitro and in vivo. Notably, our data indicate that the inhibitory effects of TC on the expression of VCAM-1 are mediated by the JAK2/STAT1/IRF-1 pathway. TC is a specific agonist of the type 2 cannabinoid receptor (CB2R). Importantly, we further verified that the inhibitory effects of TC on the expression of IRF-1 and VCAM-1 are dependent on activation of CB2R. Inhibition of CB2R by either specific inhibitors or RNA interference abolished the inhibitory effects of TC on the expression of IRF-1 and VCAM-1. Our results suggest that TC might have a capacity to suppress the development of atherosclerosis.

Thiram activates NF-kappaB and enhances ICAM-1 expression in human microvascular endothelial HMEC-1 cells

Thiram (TMTD) is a fungicidal and bactericidal agent used as antiseptic, seed disinfectant and animal repellent. In the light of known properties, thiram is considered to be used as an inhibitor of angiogenesis and/or inflammation. Since angiogenesis requires the growth of vascular endothelial cells we have used microvascular endothelial cell line HMEC-1 to elucidate the effect of thiram on normal and stimulated cells. We cultured HMEC-1 cells in the presence of thiram at low concentration (0.5 µg/mL or 2 µg/mL) (0.2 µM or 0.8 µM) or TNF-α (10 ng/mL) alone, and thiram together with TNF-α. TNF-α was used as a cytokine that triggers changes characteristic for inflammatory state of the cell. We carried out an in vitro study aimed at assessing generation of reactive oxygen species (ROS), activation of NF-κB, and expression of cell adhesion molecules ICAM-1, VCAM-1, PECAM-1. It was found that TMTD produced ROS and activated NF-κB. Activation of NF-κB was concurrent with an increase in ICAM-1 expression on the surface of HMEC-1 cells. ICAM-1 reflects intensity of inflammation in endothelial cell milieu. The expression of VCAM-1 and PECAM-1 on these cells was not changed by thiram. It was also found that stimulation of the HMEC-1 cells with the pro-inflammatory cytokine TNF-α caused activation of ICAM-1 and VCAM-1 expression with concomitant decrease of PECAM-1 cell surface expression above the control levels. Treatment with thiram and TNF-α changed cellular response compared with effects observed after treatment with TNF-α alone, i.e. further increase of ICAM-1 expression and impairment of the TNF-α effect on PECAM-1 and VCAM-1 expression. This study demonstrated that thiram acts as a pro-oxidant, and elicits in endothelial cell environment effects characteristic for inflammation. However, when it is present concurrently with pro-inflammatory cytokine TNF-α interferes with its action.

Discovery of Novel DUSP16 Phosphatase Inhibitors through Virtual Screening with Homology Modeled Protein Structure

Recently, dual-specificity phosphatase 16 (DUSP16) emerged as a promising therapeutic target protein for the development of anti-atherosclerosis and anticancer medicines. The present study was undertaken to identify the novel inhibitors of DUSP16 based on the structure-based virtual screening. We have been able to find seven novel inhibitors of DUSP16 through the drug design protocol involving homology modeling of the target protein, docking simulations between DUSP16 and its putative inhibitors with the modified scoring function, and in vitro enzyme assay. These inhibitors revealed good potency, with IC50 values ranging from 1 to 22 µM, and they were also screened computationally for having desirable physicochemical properties as drug candidates. Therefore, they deserve consideration for further development by structure-activity relationship studies to optimize the inhibitory activity against DUSP16. Structural features relevant to the stabilization of the newly identified inhibitors in the active site of DUSP16 are addressed in detail.