CLI-095 decreases atherosclerosis by modulating foam cell formation in apolipoprotein E-deficient mice

PTX3 Protects Intestinal Mucosal Barrier Damage in Sepsis Through Toll-Like Receptor Signaling Pathway

This study aims to confirm the protective effect of Pentraxin 3 (PTX3) on intestinal mucosal barrier damage in sepsis in animal and cell models and explore its mechanism. Analysis of the GSE147775 gene set revealed that the level of PTX3 was upregulated in the lipopolysaccharide (LPS)-induced rat sepsis model. The mice sepsis model was established by cecal ligation perforation (CLP), and the cell inflammation model was induced by LPS. Cell apoptosis and the expression of apoptosis-related protein were detected by flow cytometry and Western blotting. The PTX3 level was significantly upregulated in the mice sepsis model. Intestinal mucosal barrier damage was aggravated and inflammatory factor expression was upregulated after PTX3 downregulation in sepsis mice. After upregulation of PTX3, intestinal mucosal barrier damage was alleviated and inflammatory factor expression was decreased in sepsis mice. Further data mining suggested that the anti-inflammatory effect of PTX3 might be realized through inhibition of the toll-like receptor (TLR) signaling pathway. Moreover, compared with the LPS group, downregulation of PTX3 increased cell apoptosis and the levels of BCL2-associated X (Bax), myeloperoxidase (MPO), tumor necrosis factor-alfa (TNF-α), interleukin 1 beta (IL-1β), and interferon-gamma (IFN-γ), and decreased the levels of B-cell lymphoma-2 (Bcl-2), zona occludens (ZO)-1, and occludin. On the contrary, overexpression of PTX3 reduced cell apoptosis and the levels of Bax, MPO, TNF-α, IL-1β, and IFN-γ. Moreover, downregulation of PTX3 reversed the inhibitive effects on cell apoptosis and inflammation and promotive effects on the levels of Zo-1 and occludin induced by CLI-095 (a TLR signaling pathway inhibitor). In the CLP-induced mice sepsis model and LPS-induced cell inflammation model, PTX3 inhibits inflammatory response and reduces intestinal mucosal barrier damage through the TLR signaling pathway.

Linear ubiquitination modification of NR6A1 by LUBAC inhibits RIPK3 kinase activity and attenuates apoptosis of vascular smooth muscle cells

Nuclear receptor subfamily 6 group A member 1 (NR6A1) is involved in promoting the apoptotic process of vascular smooth muscle cells (VSMCs) which is a critical process involved in atherosclerosis, but the action mechanism remains to be determined. Therefore, we studied the underlying mechanisms by which NR6A1 accelerated VSMC apoptosis in atherosclerosis. An atherosclerosis model has been established in apolipoprotein E-deficient rats with a high-fat diet for 12 weeks, which was characterized by pathological aortic plaques, increased lipid deposition and collagen content in aortic tissues, and high cholesterol and triglycerides levels in the serum. NR6A1 was experimentally shown to increase at protein level rather than messenger RNA level in atherosclerotic rats. Immunofluorescence exhibited the main location of NR6A1 in the cell nucleus of rat aortic tissues. By performing ectopic expression experiments, NR6A1 was demonstrated to suppress the viability and expedite the apoptosis of VSMCs, corresponding to augmented caspase-3, caspase-8, and caspase-9 activities. It was further unraveled that NR6A1 could activate receptor-interacting serine/threonine-protein kinase 3 (RIPK3) by inducing its phosphorylation. Conversely, RIPK3 inhibitor GSK872 undermined the proapoptotic effect of NR6A1 on VSMCs. The co-immunoprecipitation assay identified that linear ubiquitin chain assembly complex (LUBAC) can be pulled down by NR6A1. Furthermore. LUBAC inhibited the expression of NR6A1 by promoting its linear ubiquitination, thereby dephosphorylating RIPK3 and consequently inhibiting the VSMC apoptosis. Overall, LUBAC-induced linear ubiquitination of NR6A1 can potentially arrest the apoptosis of VSMCs in atherosclerosis by downregulating RIPK3 and attenuating caspase activity. This finding suggests promising athero-protective targets by limiting VSMC apoptosis.

Pro-inflammatory mediators released by activated monocytes promote aortic valve fibrocalcific activity

Background

Calcific aortic valve disease (CAVD) is the most prevalent heart valve disorder in the elderly. Valvular fibrocalcification is a characteristic pathological change. In diseased valves, monocyte accumulation is evident, and aortic valve interstitial cells (AVICs) display greater fibrogenic and osteogenic activities. However, the impact of activated monocytes on valular fibrocalcification remains unclear. We tested the hypothesis that pro-inflammatory mediators from activated monocytes elevate AVIC fibrogenic and osteogenic activities.

Methods and results

Picro-sirius red staining and Alizarin red staining revealed collagen and calcium depositions in cultured human AVICs exposed to conditioned media derived from Pam3CSK4-stimulated monocytes (Pam3 CM). Pam3 CM up-regulated alkaline phosphatase (ALP), an osteogenic biomarker, and extracellular matrix proteins collagen I and matrix metalloproteinase-2 (MMP-2). ELISA analysis identified high levels of RANTES and TNF-α in Pam3 CM. Neutralizing RANTES in the Pam3 CM reduced its effect on collagen I and MMP-2 production in AVICs while neutralizing TNF-α attenuated the effect on AVIC ALP production. In addition, Pam3 CM induced NF-κB and JNK activation. While JNK mediated the effect of Pam3 CM on collagen I and MMP-2 production, NF-κB was critical for the effect of Pam3 CM on ALP production in AVICs.

Conclusions

This study demonstrates that activated monocytes elevate the fibrogenic and osteogenic activities in human AVICs through a paracrine mechanism. TNF-α and RANTES mediate the pro-fibrogenic effect of activated monocytes on AVICs through activation of JNK, and TNF-α also activates NF-κB to elevate AVIC osteogenic activity. The results suggest that infiltrated monocytes elevate AVIC fibrocalcific activity to promote CAVD progression.

The Transcription Factor SUB1 Is a Master Regulator of the Macrophage TLR Response in Atherosclerosis

Toll-like receptor 2 and 4 (TLR2, TLR4) signaling is implicated in atherosclerotic plaque formation. The two-stage master regulator Virtual Inference of Protein-activity by Enriched Regulon (VIPER) analysis of macrophage TLR2 and TLR4 signature genes integrated with coexpression network genes derived from 371 patient-derived carotid specimens identifies activated RNA polymerase II transcriptional coactivator p15 (SUB1/Sub1, PC4) as a master regulon in the atherogenic TLR response. It is found that TLR2 and TLR4 signaling is proinflammatory and proatherosclerotic in chow-fed apolipoprotein E-deficient (ApoE^-/- ) mice. Through transgenic myeloid-specific Sub1 knockout in ApoE^-/- mice, it is discovered that these proatherosclerotic effects of TLR2 and TLR4 signaling are mediated by Sub1. Sub1 knockout in macrophages enhances anti-inflammatory M2 macrophage polarization and cholesterol efflux. Irradiated low density lipoprotein receptor-deficient (Ldlr^-/- ) mice transplanted with Sub1^-/- murine bone marrow display reduced atherosclerosis. Promoter analysis reveals Sub1-dependent activation of interferon regulatory factor 1 (Irf1) transcription in a casein kinase 2 (Ck2)-dependent manner, and Sub1-knockout macrophages display decreased Irf1 expression. Artificial Irf1 overexpression in Sub1-knockout macrophages enhances proinflammatory M1 skewing and lowers cholesterol clearance. In conclusion, the TLR master regulon Sub1, and its downstream effect on the transcription factor Irf1, promotes a proinflammatory M1 macrophage phenotype and enhances atherosclerotic burden in vivo.

Pharmacological inhibition of EZH2 by GSK126 decreases atherosclerosis by modulating foam cell formation and monocyte adhesion in apolipoprotein E-deficient mice

Histone modifications play an important role in the occurrence and development of atherosclerosis in human and atherosclerosis-prone mice. Histone methylation in macrophages, monocytes and endothelial cells markedly influence the progression of atherosclerosis. However, it remains unclear whether treatment with a histone methyltransferase enhancer of zeste homolog 2 (EZH2) inhibitor may suppress atherosclerosis. The present study aimed to determine the effects of the EZH2 inhibitor, GSK126, on the suppression and regression of atherosclerosis in apolipoprotein E-deficient mouse models. In vitro, it was found that pharmacological inhibition of EZH2 by GSK126 markedly reduced lipid transportation and monocyte adhesion during atherogenesis, predominantly through increasing the expression levels of ATP-binding cassette transporter A1 and suppressing vascular cell adhesion molecule 1 in human THP-1 cells. In vivo, it was found that atherosclerotic plaques in GSK126-treated mice were significantly decreased when comparing with the vehicle-treated animals. These results indicated that the GSK126 has the ability to attenuate the progression of atherosclerosis by reducing macrophage foam cell formation and monocyte adhesion in cell and mouse models. In conclusion, the present study provided new insights into the molecular mechanism behind the action of GSK126 and suggested its therapeutic potential for the treatment of atherosclerosis.

Reformulating Small Molecules for Cardiovascular Disease Immune Intervention: Low-Dose Combined Vitamin D/Dexamethasone Promotes IL-10 Production and Atheroprotection in Dyslipidemic Mice

The targeting of proinflammatory pathways has a prophylactic and therapeutic potential on atherosclerotic cardiovascular diseases (CVD). An alternative/complementary strategy is the promotion of endogenous atheroprotective mechanisms that are impaired during atherosclerosis progression, such as the activity of tolerogenic dendritic cells (tolDC) and regulatory T cells (Treg). There is a need to develop novel low cost, safe and effective tolDC/Treg-inducing formulations that are atheroprotective and that can be of easy translation into clinical settings. We found that apolipoprotein E-deficient (ApoE^–/–) mice treated with a low-dose combined formulation of Vitamin D and Dexamethasone (VitD/Dexa), delivered repetitively and subcutaneously (sc) promoted interleukin-10 (IL-10) production by dendritic cells and other antigen presenting cells in the lymph nodes draining the site of injection and the spleens. Expectedly, the treatment also increased the numbers of IL-10-producing CD4⁺ T cells. Concomitantly, the frequency of IFNγ-producing CD4⁺ and CD8⁺ T cells in the spleen, and the IFNγ response of splenocytes to polyclonal stimulation ex vivo were lower after VitD/Dexa treatment, indicating a reduced proatherogenic Th1 response. Interestingly, VitD/Dexa-treated mice had smaller atherosclerotic lesions, with reduced lipid content and lower inflammatory infiltrate of macrophages and T cells in the aortic root. No hypolipidemic or antioxidant effect could be detected, suggesting that a dominantly immunomodulatory mechanism of atheroprotection was engaged under the low-dose sc VitD/Dexa conditions used. Finally, no evidence of clinical, biochemical or immune toxicity was observed in treated ApoE^–/– mice and, most importantly, C57BL/6 mice latently infected with Leishmania parasites and treated with an identical VitD/Dexa dose/scheme showed no clinical or microbiological signs of disease reactivation, suggesting the absence of general immunosuppression. Altogether, these results indicate that a non-toxic, non-immunosuppressive, low-dose of VitD/Dexa, administered subcutaneously and repetitively, exerts atheroprotective effects in dyslipidemic mice, apparently due to the induction of an IL-10-producing network of lymphoid and myeloid immune cells. These well known, widely available, and inexpensive small molecules can be easily co-formulated into a simple and accessible agent with a potential use as a prophylactic or therapeutic immune intervention for CVD and other chronic inflammatory diseases.

Vasculoprotective Effects of Vildagliptin. Focus on Atherogenesis

Vildagliptin is a representative of Dipeptidyl Peptidase-4 (DPP-4) inhibitors, antihyperglycemic drugs, approved for use as monotherapy and combination therapy in type 2 diabetes mellitus. By inhibiting enzymatic decomposition, DPP-4 inhibitors increase the half-life of incretins such as GLP-1 (Glucagon-like peptide-1) and GIP (Gastric inhibitors polypeptide) and prolong their action. Some studies present results suggesting the anti-sclerotic and vasculoprotective effects of vildagliptin reaching beyond glycemic control. Vildagliptin is able to limit inflammation by suppression of the NF-κB (nuclear factor kappa-light-chain-enhancer of activated B cells) signaling pathway and proinflammatory agents such as TNF-α (tumor necrosis factor α), IL-1β (Interleukin-1β), and IL-8 (Interleukin 8). Moreover, vildagliptin regulates lipid metabolism; attenuates postprandial hypertriglyceridemia; and lowers serum triglycerides, apolipoprotein B, and blood total cholesterol levels. This DPP-4 inhibitor also reduces macrophage foam cell formation, which plays a key role in atheromatous plaque formation and stability. Vildagliptin reduces vascular stiffness via elevation of nitric oxide synthesis, improves vascular relaxation, and results in reduction in both systolic and diastolic blood pressure. Treatment with vildagliptin lowers the level of PAI-1 presenting possible antithrombotic effect. By affecting the endothelium, inflammation, and lipid metabolism, vildagliptin may affect the development of atherosclerosis at its various stages. The article presents a summary of the studies assessing vasculoprotective effects of vildagliptin with special emphasis on atherogenesis.

Targeting Foam Cell Formation in Atherosclerosis: Therapeutic Potential of Natural Products

Foam cell formation and further accumulation in the subendothelial space of the vascular wall is a hallmark of atherosclerotic lesions. Targeting foam cell formation in the atherosclerotic lesions can be a promising approach to treat and prevent atherosclerosis. The formation of foam cells is determined by the balanced effects of three major interrelated biologic processes, including lipid uptake, cholesterol esterification, and cholesterol efflux. Natural products are a promising source for new lead structures. Multiple natural products and pharmaceutical agents can inhibit foam cell formation and thus exhibit antiatherosclerotic capacity by suppressing lipid uptake, cholesterol esterification, and/or promoting cholesterol ester hydrolysis and cholesterol efflux. This review summarizes recent findings on these three biologic processes and natural products with demonstrated potential to target such processes. Discussed also are potential future directions for studying the mechanisms of foam cell formation and the development of foam cell-targeted therapeutic strategies.

EDA fibronectin-TLR4 axis sustains megakaryocyte expansion and inflammation in bone marrow fibrosis

The fibronectin EDA isoform sustains bone marrow fibrosis, binding to TLR4 on megakaryocytes and inducing NF-κB activation and IL-6 release. In primary myelofibrosis patients, the bone marrow fibrosis correlates with increased levels of fibronectin EDA isoform in plasma.

The fibronectin EDA isoform (EDA FN) is instrumental in fibrogenesis but, to date, its expression and function in bone marrow (BM) fibrosis have not been explored. We found that mice constitutively expressing the EDA domain (EIIIA^+/+), but not EDA knockout mice, are more prone to develop BM fibrosis upon treatment with the thrombopoietin (TPO) mimetic romiplostim (TPO^high). Mechanistically, EDA FN binds to TLR4 and sustains progenitor cell proliferation and megakaryopoiesis in a TPO-independent fashion, inducing LPS-like responses, such as NF-κB activation and release of profibrotic IL-6. Pharmacological inhibition of TLR4 or TLR4 deletion in TPO^high mice abrogated Mk hyperplasia, BM fibrosis, IL-6 release, extramedullary hematopoiesis, and splenomegaly. Finally, developing a novel ELISA assay, we analyzed samples from patients affected by primary myelofibrosis (PMF), a well-known pathological situation caused by altered TPO signaling, and found that the EDA FN is increased in plasma and BM biopsies of PMF patients as compared with healthy controls, correlating with fibrotic phase.

ATF4 Involvement in TLR4 and LOX-1-Induced Host Inflammatory Response to Aspergillus fumigatus Keratitis

Purpose

Activating transcription factor 4 (ATF4) is induced by various stressors. Here, we investigated the expression of ATF4 in the host inflammatory response to Aspergillus fumigatus (A. fumigatus) keratitis.

Methods

A. fumigatus keratitis mouse models developed by intrastromal injection as well as corneal epithelium scratching were examined daily with a slit lamp microscope for corneal opacification and ulceration. Subsequent in vitro experimentation was carried out in human corneal epithelial cells (HCECs) as well as THP-1 macrophages infected with A. fumigatus. Inhibitors, including CLI-095, Poly (I), SCH772984, and SP600125, were used to assess the role of proteins like toll-like receptor 4 (TLR4), lectin-type oxidized LDL receptor 1 (LOX-1), extracellular signal-regulated kinases (ERK1/2), and c-Jun N-terminal kinase (JNK) in ATF4 expression as a response to A. fumigatus infection. This assessment was made in both mouse models and HCECs using western blot.

Results

Compared to the controls, ATF4 was increased in corneas from two kinds of A. fumigatus keratitis models at 3 days after infection. ATF4 expression was upregulated with A. fumigatus conidia both in HCECs and THP-1 macrophages 16 hours after stimulation. Furthermore, ATF4 expression in response to A. fumigatus infection was shown to be dependent on TLR4 and LOX-1 expression, and ERK1/2 and JNK contributed to the expression of ATF4 in response to A. fumigatus.

Conclusion

Our results clearly indicate that ATF4 was involved in the host antifungal immune response to A. fumigatus keratitis; expression was found to be dependent on TLR4, LOX-1 expression, and MAPKs pathway.

DFMG reverses proliferation and migration of vascular smooth muscle cells induced by co-culture with injured vascular endothelial cells via suppression of the TLR4-mediated signaling pathway

7-Difluoromethoxy-5,4′-dimethoxy-genistein (DFMG) is a novel chemical compound synthesized using genistein. Previous studies have indicated that DFMG can reverse the apoptosis of vascular endothelial cells (VECs) by regulating the mitochondrial apoptosis pathway. The present study aimed to investigate the activity and molecular mechanism underlying DFMG-mediated protection of vascular smooth muscle cell (VSMCs) using a non-contact co-culture model established by using Transwell insert. Secretion of interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) were measured by ELISA. Proliferation and migration of VSMCs were assessed using a Cell Counting kit-8 and wound healing assays, respectively. Toll-like receptor 4 (TLR4) mRNA and protein levels were detected by reverse transcription-quantitative polymerase chain reaction and western blotting analyses, respectively. In the present study, lysophosphatidylcholine (LPC) significantly increased the secretion of IL-6 and TNF-α in VECs. VECs treated with LPC markedly increased proliferation and migration of VSMCs, which were inhibited by DFMG. Transfection of either TLR4 short hairpin RNA (shRNA) or TLR4 cDNA in VECs inhibited and increased proliferation and migration of VSMCs, respectively. Furthermore, transfection of VECs with TLR4 shRNA suppressed the proliferation and migration of VSMCs induced by co-culture with injured VECs, which was further enhanced by treatment with DFMG. By contrast, transfection of VECs with TLR4 cDNA enhanced proliferation and migration of VSMCs and this effect was inhibited by treatment with DFMG. Taken together, the results of the present study demonstrated that DFMG can reverse proliferation and migration of VSMCs induced by co-culture with injured VECs via suppression of the TLR4-mediated signaling pathway.

HMGB1 binding heptamer peptide improves survival and ameliorates brain injury in rats after cardiac arrest and cardiopulmonary resuscitation

Excessive inflammatory response produced after cardiac arrest and cardiopulmonary resuscitation (CA/CPR) is one of major causes of cerebral injury. High mobility group box 1 (HMGB1) is a pro-inflammatory cytokine and its role in brain injury after CA/CPR is unclear. Herein we investigated whether blocking HMGB1 signaling could ease brain injury after CA/CPR. Male Sprague-Dawley rats (n=181) were subjected to 8-min Asphyxia CA model or Sham operation. The ELISA data revealed both resuscitated patients and animals had elevated HMGB1 level in sera, compared with the healthy volunteers or Sham operative rats, respectively (P<0.01). Rats successfully resuscitated from CA were then randomly treated with either membrane permeable (TAT-fused) HMGB1 binding heptamer peptide (HBHP) or Scramble peptide. Results showed that HBHP treatment markedly improved 7-day survival rate, reduced neurological deficit scores, and prevented neuronal and dendrite loss in hippocampal CA1 region. Moreover, HBHP inhibited the activation of microglia and astrocytes and downregulated the mRNA and protein expressions of proinflammatory factors. We finally blocked toll-like receptor-4 (TLR4, one of HMGB1 receptors) with a specific antagonist TAK-242 before CA induction to confirm the detrimental effect of HMGB1 signaling and found blocking TLR4 could also attenuate the neuronal degeneration, as well as reduce NF-κB-mediated inflammatory signaling. Our findings indicate that CA/CPR can induce HMGB1 release to serum, while blocking HMGB1 signaling with peptide may improve the survival and attenuate post-resuscitation brain injury in the rat model of CA/CPR. TLR4 antagonist may also offer neuroprotective effects through weakening HMGB1-mediated proinflammatory reactions.

Lipopolysaccharide induced vascular smooth muscle cells proliferation: A new potential therapeutic target for proliferative vascular diseases

Vascular smooth muscle cells (VSMCs) proliferation is involved in vascular atherosclerosis and restenosis. Recent studies have demonstrated that lipopolysaccharide (LPS) promotes VSMCs proliferation, but the signalling pathways which are involved are not completely understood. The purpose of this review was to summarize the existing knowledge of the role and molecular mechanisms involved in controlling VSMCs proliferation stimulated by LPS and mediated by toll-like receptor 4 (TLR4) signalling pathways. Moreover, the potential inhibitors of TLR4 signalling for VSMCs proliferation in proliferative vascular diseases are discussed.

Atorvastatin attenuates p‑cresyl sulfate‑induced atherogenesis and plaque instability in ApoE knockout mice

p-cresyl sulfate (PCS) is a protein-bound uremic toxin retained in the blood of patients with chronic kidney disease (CKD) As atherosclerosis is a primary cardiovascular complication for patients with CKD, the aim of the present study was to investigate the mechanisms underlying the aggravation of atherosclerosis by PCS. In addition, the effect of atorvastatin was assessed in reversing the effects of PCS. PCS was revealed to promote the initiation and progression of atherosclerosis. Following treatment with atorvastatin, apolipoprotein E knockout mice demonstrated a reduction in PCS-induced atherogenesis and plaque vulnerability. In addition, atorvastatin decreased the protein expression levels of vascular cell adhesion molecule-1 and intercellular cell adhesion molecule-1, and the interaction between leukocytes and endothelia. The plasma lipid profiles of mice were not significantly affected by gavage of low-dose atorvastatin. The results of the present study indicate that PCS promotes plaque growth and instability by enhancing leukocyte-endothelium interaction, and that these effects may be attenuated by atorvastatin treatment.