Activation of spleen tyrosine kinase is required for TNF-α-induced endothelin-1 upregulation in human aortic endothelial cells

Thioredoxin reductase as a pharmacological target

Thioredoxin reductases (TrxRs) belong to the pyridine nucleotide disulfide oxidoreductase family enzymes that reduce thioredoxin (Trx). The couple TrxR and Trx is one of the major antioxidant systems that control the redox homeostasis in cells. The thioredoxin system, comprised of TrxR, Trx and NADPH, exerts its activities via a disulfide-dithiol exchange reaction. Inhibition of TrxR is an important clinical goal in all conditions in which the redox state is perturbed. The present review focuses on the most critical aspects of the cellular functions of TrxRs and their inhibition mechanisms by metal ions or chemicals, through direct targeting of TrxRs or their substrates or protein interactors. To update the involvement of overactivation/dysfunction of TrxRs in various pathological conditions, human diseases associated with TrxRs genes were critically summarized by publicly available genome-wide association study (GWAS) catalogs and literature. The pieces of evidence presented here justify why TrxR is recognized as one of the most critical clinical targets and the growing current interest in developing molecules capable of interfering with the functions of TrxR enzymes.

Innate Immune Signaling and Its Role in Metabolic and Cardiovascular Diseases

The innate immune system is an evolutionarily conserved system that senses and defends against infection and irritation. Innate immune signaling is a complex cascade that quickly recognizes infectious threats through multiple germline-encoded cell surface or cytoplasmic receptors and transmits signals for the deployment of proper countermeasures through adaptors, kinases, and transcription factors, resulting in the production of cytokines. As the first response of the innate immune system to pathogenic signals, inflammatory responses must be rapid and specific to establish a physical barrier against the spread of infection and must subsequently be terminated once the pathogens have been cleared. Long-lasting and low-grade chronic inflammation is a distinguishing feature of type 2 diabetes and cardiovascular diseases, which are currently major public health problems. Cardiometabolic stress-induced inflammatory responses activate innate immune signaling, which directly contributes to the development of cardiometabolic diseases. Additionally, although the innate immune elements are highly conserved in higher-order jawed vertebrates, lower-grade jawless vertebrates lack several transcription factors and inflammatory cytokine genes downstream of the Toll-like receptors (TLRs) and retinoic acid-inducible gene-I (RIG-I)-like receptors (RLRs) pathways, suggesting that innate immune signaling components may additionally function in an immune-independent way. Notably, recent studies from our group and others have revealed that innate immune signaling can function as a vital regulator of cardiometabolic homeostasis independent of its immune function. Therefore, further investigation of innate immune signaling in cardiometabolic systems may facilitate the discovery of new strategies to manage the initiation and progression of cardiometabolic disorders, leading to better treatments for these diseases. In this review, we summarize the current progress in innate immune signaling studies and the regulatory function of innate immunity in cardiometabolic diseases. Notably, we highlight the immune-independent effects of innate immune signaling components on the development of cardiometabolic disorders.

Inhibition of spleen tyrosine kinase signaling protects against acute lung injury through blockade of NADPH oxidase and IL-17A in neutrophils and γδ T cells respectively in mice

Acute lung injury (ALI) is one of the most serious complications in critically ill patients which often leads to morbidity and mortality. ALI characterized by severe inflammation of lungs occurs due to uncontrolled inflammatory immune response. However, the immunological mechanism(s) are far from being understood. The spleen tyrosine kinase (SYK), a key component of immune receptor signaling, plays a critical role in the modulation of inflammatory signaling in different immune cells. However, its role in ALI remains to be explored. Therefore, in this study, we investigated the effect of R406, a SYK inhibitor in lipopolysaccharide (LPS)-induced ALI mouse model. LPS led to increased SYK expression in neutrophils and gamma delta (γδ) T cells. This was associated with increased neutrophilic airway inflammation, vascular permeability, myeloperoxidase activity in the lung with upregulated expression of NADPH oxidase (NOX2)/MCP-1/TNF-α in neutrophils and IL-17A in γδ T cells/lung. Pulmonary inflammation was associated with higher mortality in mice with ALI. Inhibition of SYK signaling using R406 in the lung led to blockade of neutrophilic airway inflammation, vascular permeability, pro-inflammatory cytokine release and oxidative stress in innate immune cells, i.e. γδ T cells and neutrophils and the lung. R406 administered LPS group had better survival rate than LPS group. This suggests that SYK upregulation in γδ T cells and neutrophils plays an important role in inflammatory process during ALI. In conclusion, R406 exhibited a great potential to block the LPS-induced airway inflammation and mortality which could be developed as a potential future therapy in ALI.

Innate Immune Signaling in Nonalcoholic Fatty Liver Disease and Cardiovascular Diseases

The physiological significance of innate immune signaling lies primarily in its role in host defense against invading pathogens. It is becoming increasingly clear that innate immune signaling also modulates the development of metabolic diseases, especially nonalcoholic fatty liver disease and cardiovascular diseases, which are characterized by chronic, low-grade inflammation due to a disarrangement of innate immune signaling. Notably, recent studies indicate that in addition to regulating canonical innate immune-mediated inflammatory responses (or immune-dependent signaling-induced responses), molecules of the innate immune system regulate pathophysiological responses in multiple organs during metabolic disturbances (termed immune-independent signaling-induced responses), including the disruption of metabolic homeostasis, tissue repair, and cell survival. In addition, emerging evidence from the study of immunometabolism indicates that the systemic metabolic status may have profound effects on cellular immune function and phenotypes through the alteration of cell-intrinsic metabolism. We summarize how the innate immune system interacts with metabolic disturbances to trigger immune-dependent and immune-independent pathogenesis in the context of nonalcoholic fatty liver disease, as representative of metabolic diseases, and cardiovascular diseases.

Levistilide A Ameliorates NLRP3 Expression Involving the Syk-p38/JNK Pathway and Peripheral Obliterans in Rats

Background

Inflammation is one of the most important pathogeneses of thromboangiitis obliterans (TAO). The NLRP3 inflammasome plays a vital role in the body's immune response and disease development. It can be activated by numerous types of pathogens or danger signals. As the core of the inflammatory response, the NLRP3 inflammasome may provide a new target for the treatment of various inflammatory diseases. Levistilide A (LA) is a phthalide dimer isolated from umbelliferous plants. Its pharmacological effect is largely unknown. This study revealed the effects of LA on endothelial cell activation, NLRP3, IL-1β, TNF-α, IL-32, and CCL-2, VCAM-1, MCP-1, and the spleen tyrosine kinase (Syk)--p38/JNK signaling axis and its effect on vasculitis in rats.

Results

LA inhibited endothelial activation and the expression of IL-1β, TNF-α, IL-32, CCL-2, VCAM-1, and MCP-1. LA directly obstructed Syk phosphorylation and activity in a dose-dependent manner, inhibited the activity of p38 and JNK, and reduced the expression of NLRP3 in human umbilical vein endothelial cells and vascular tissue of rats with vasculitis.

Conclusion

LA suppressed NLRP3 gene expression by blocking the Syk--p38/JNK pathway and reduced damage to the rats' limbs in the thromboangiitis obliterans model.

Diacerein inhibits the pro-atherogenic & pro-inflammatory effects of IL-1 on human keratinocytes & endothelial cells

We investigated IL-1-induced regulation of genes related to inflammation and atherogenesis in human keratinocytes and endothelial cells, and if ‘diacerein’, an oral IL-1 inhibiting drug currently approved for use in osteoarthritis, would reverse IL-1’s effects on these cells. Primary human keratinocytes and coronary artery endothelial cells were treated with either IL-1α or IL-1β, with and without diacerein. Using PCR-array, we assessed differential gene-expression regulated by IL-1 and diacerein. We identified 34 pro-atherogenic genes in endothelial cells and 68 pro-inflammatory genes in keratinocytes significantly (p<0.05) regulated at least 2-fold by IL-1, in comparison to control. Diacerein completely or partially reversed this regulation on almost all genes. Using ELISA, we confirmed diacerein’s ability to reverse IL-1-driven gene-regulation of 11 selected factors, at the protein level. The results support a novel idea that diacerein acts as an inhibitor of the pro-atherogenic and pro-inflammatory effects of IL-1. Diacerein may have therapeutic applications to diminish IL-1-induced skin inflammation in psoriasis and attenuate IL-1-induced development of atherosclerosis. Further investigation into diacerein’s effect on skin inflammation, atherogenesis and cardiovascular risk in animal models or humans is warranted.

Tumor-Host Cell Interactions in Ovarian Cancer: Pathways to Therapy Failure

Although most ovarian cancer patients are highly responsive to chemotherapy, they frequently present with recurrent metastatic lesions that result in poor overall survival, a situation that has not changed in the last 20 years. This review discusses new insights into the regulation of ovarian cancer chemoresistance with a focus on the emerging role of immune and other host cells. Here, we summarize the complex molecular pathways that regulate the interaction between tumor and host cells, discuss the limitations of current in vitro and in vivo models for translational studies, and present perspectives for the development of innovative therapies.

A spleen tyrosine kinase inhibitor attenuates the proliferation and migration of vascular smooth muscle cells

Background

Pathologic vascular smooth muscle cell (VSMC) proliferation and migration after vascular injury promotes the development of occlusive vascular disease. Therefore, an effective chemical agent to suppress aberrant proliferation and migration of VSMCs can be a potential therapeutic modality for occlusive vascular disease such as atherosclerosis and restenosis. To find an anti-proliferative chemical agent for VSMCs, we screened an in-house small molecule library, and the selected small molecule was further validated for its anti-proliferative effect on VSMCs using multiple approaches, such as cell proliferation assays, wound healing assays, transwell migration assays, and ex vivo aortic ring assay.

Results

Among 43 initially screened small molecule inhibitors of kinases that have no known anti-proliferative effect on VSMCs, a spleen tyrosine kinase (Syk) inhibitor (BAY61-3606) showed significant anti-proliferative effect on VSMCs. Further experiments indicated that BAY61 attenuated the VSMC proliferation in both concentration- and time-dependent manner, and it also significantly suppressed the migration of VSMCs as assessed by both wound healing assays and transwell assays. Additionally, BAY61 suppressed the sprouting of VSMCs from endothelium-removed aortic rings.

Conclusion

The present study identified a Syk kinase inhibitor as a potent VSMC proliferation and migration inhibitor and warrants further studies to elucidate its underlying molecular mechanisms, such as its primary target, and to validate its in vivo efficacy as a therapeutic agent for restenosis and atherosclerosis.

A respiratory chain controlled signal transduction cascade in the mitochondrial intermembrane space mediates hydrogen peroxide signaling

Reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) govern cellular homeostasis by inducing signaling. H2O2 modulates the activity of phosphatases and many other signaling molecules through oxidation of critical cysteine residues, which led to the notion that initiation of ROS signaling is broad and nonspecific, and thus fundamentally distinct from other signaling pathways. Here, we report that H2O2 signaling bears hallmarks of a regular signal transduction cascade. It is controlled by hierarchical signaling events resulting in a focused response as the results place the mitochondrial respiratory chain upstream of tyrosine-protein kinase Lyn, Lyn upstream of tyrosine-protein kinase SYK (Syk), and Syk upstream of numerous targets involved in signaling, transcription, translation, metabolism, and cell cycle regulation. The active mediators of H2O2 signaling colocalize as H2O2 induces mitochondria-associated Lyn and Syk phosphorylation, and a pool of Lyn and Syk reside in the mitochondrial intermembrane space. Finally, the same intermediaries control the signaling response in tissues and species responsive to H2O2 as the respiratory chain, Lyn, and Syk were similarly required for H2O2 signaling in mouse B cells, fibroblasts, and chicken DT40 B cells. Consistent with a broad role, the Syk pathway is coexpressed across tissues, is of early metazoan origin, and displays evidence of evolutionary constraint in the human. These results suggest that H2O2 signaling is under control of a signal transduction pathway that links the respiratory chain to the mitochondrial intermembrane space-localized, ubiquitous, and ancient Syk pathway in hematopoietic and nonhematopoietic cells.

Angiotensin II induces endothelin-1 expression in human hepatic stellate cells

BACKGROUND

Both angiotensin (Ang)-II and endothelin-1 (ET-1) are involved in the pathogenesis of liver fibrosis. Activated hepatic stellate cells (HSCs) are considered a key effector of liver fibrosis.

AIMS

To explore the effect of Ang-II on ET-1 expression in cultured human HSCs and the underlying mechanisms.

METHODS

Human HSCs were treated with Ang-II in different concentrations (0.1, 0.5, 1, 5, or 10 nM) for different lengths of time (0.5, 1, 2, 4, or 6 h) with or without transcription inhibitor actinomycin D, Ang-II type 1 (AT1) receptor blocker losartan, AT2 receptor blocker PD123177, or different kinase inhibitors.

RESULTS

Ang-II increased the ET-1 mRNA level in a statistically significant dose- and time-dependent manner within 4 h, which led to dose-dependent up-regulation of the ET-1 protein level. Actinomycin D (1 mg/ml), losartan (50 μM), and phosphatidylinositol-3 kinase inhibitor LY294002 (50 μM) abolished the promoting effect of Ang-II on ET-1 expression. Ang-II (10 nM) significantly increased the expression of α-smooth muscle actin and type I collagen in HSCs, which was abolished by losartan, LY294002, ET A receptor blocker BQ123, and ET-1 siRNA, but not PD123177 and ET B receptor blocker BQ788.

CONCLUSIONS

Ang-II induces ET-1 expression in human HSCs via the AT1 receptor by the PI3 K/Akt signaling pathway. The ET-1/ET A receptor axis could mediate the promoting effects of Ang-II on HSCs' transdifferentiation into myofibroblast-like cells. This is the first evidence of crosstalk between the Ang-II/AT1 axis and the ET-1 system in regard to the pathogenesis of liver fibrosis.

TWIST interacts with endothelin-1/endothelin A receptor signaling in osteosarcoma cell survival against cisplatin

Both TWIST and the endothelin-1 (ET-1)/endothelin A receptor (ETAR) signaling are important in osteosarcoma (OS) progression. In the present study, the interaction between TWIST and ET-1/ETAR signaling in OS cells was investigated, and the impact of the functional interaction on OS cell survival against chemotherapy agent-induced apoptosis was assessed. TWIST was overexpressed and knocked down in Saos-2 and MG-63 OS cells, respectively. In Saos-2 cells, overexpression of TWIST significantly decreased ET-1 mRNA and protein expression levels, cell survival against cisplatin and phosphorylation of Akt at serine 473 (ser473), which was abolished by the selective phosphatidylinositol 3-kinase (PI3K) inhibitor, LY294002, or the selective ETAR inhibitor, BQ123. In MG-63 cells, knockdown of TWIST significantly increased ET-1 expression, cell survival against cisplatin and phosphorylation of Akt at ser473. However, exogenous ET-1 only partially rescued cell survival against cisplatin-induced apoptosis in the cells in which TWIST had been knocked down in the presence of LY294002. In conclusion, we have demonstrated that TWIST significantly, although only partially, decreases OS cell survival against cisplatin by downregulating ET-1/ETAR signaling via inhibition of the PI3K/Akt pathway. To the best of our knowledge, the present study has provided the first evidence of a functional interaction between TWIST and ET-1/ETAR signaling in OS cells. This finding adds novel insights into the molecular mechanisms underlying OS progression, cell survival and chemoresistance.

Mycophenolic acid regulates spleen tyrosine kinase to repress tumour necrosis factor-alpha-induced monocyte chemotatic protein-1 production in cultured human aortic endothelial cells

Atherosclerosis develops from cascades of inflammatory processes. Spleen tyrosine kinase (Syk) and monocyte chemotatic protein-1 (MCP-1) play important roles in the pathogenesis of atherosclerosis. Mycophenolic acid (MPA) has an anti-inflammatory effect. We have investigated whether MPA regulates Syk to repress tumour necrosis factor-α (TNF-α)-induced MCP-1 production in cultured human aortic endothelial cells. Expression of MCP-1 mRNA and its protein were measured by real time RT-PCR and ELISA, respectively. Reactive oxygen species (ROS) production were measured using 2'7'-dichlorofluorescein diacetate. Activation of AP-1 and NF-κB were assessed by electrophoretic mobility shift assay. Tyrosine phosphorylation of Syk was examined by Western blot analysis. TNF-α increased MCP-1 at both mRNA and protein levels. TNF-α-induced MCP-1 mRNA expression was inhibited by N-acetylcysteine (NAC), Syk inhibitor, Syk-siRNA and MPA. TNF-α-induced MCP-1 protein production was also inhibited by Syk inhibitor and MPA. TNF-α increased DNA binding activity of AP-1 and NF-κB, whereas both AP-1 and NF-κB decoy oligodeoxynucleotides downregulated TNF-α-induced MCP-1 mRNA expression. TNF-α increased ROS generation, which was inhibited by NAC and MPA, but not by Syk inhibitor. TNF-α increased tyrosine phosphorylation of Syk, which was attenuated by NAC and MPA. MPA and Syk inhibitor attenuated TNF-α-induced DNA binding activity of NF-κB and AP-1. TNF-α induced MCP-1 expression via activation of AP-1 and NF-κB. AP-1 and NF-κB were mediated through ROS, followed by Syk. MPA exerts anti-inflammatory effect by inhibiting MCP-1 expression via suppression of ROS and Syk.