Targeting HDAC6 attenuates nicotine-induced macrophage pyroptosis via NF-κB/NLRP3 pathway.

BACKGROUND AND AIMS: During the development of atherosclerosis, nicotine activates macrophage inflammation. However, whether nicotine induces macrophage pyroptosis and the underlying mechanisms remain unclear. This study aimed to investigate the role of histone deacetylase 6 (HDAC6) in nicotine-induced macrophage pyroptosis. METHODS: For the in vivo study, nicotine was administered to 8-week-old ApoE-/- mice fed a high-fat diet (HFD) for 12 weeks. TUNEL/CD68 and Caspase-1/CD68 staining was used to assess macrophage pyroptosis in plaque. For the in vitro study, Western blotting, lactic dehydrogenase activity (LDH), coimmunoprecipitation, chromatin immunoprecipitation and immunofluorescence were used to evaluate pyroptosis and related signaling pathway in RAW264.7 cells. RESULTS: A high-fat diet and nicotine upregulated macrophage pyroptosis in atherosclerotic lesions. Nicotine promoted pyroptosis in RAW264.7 cells, as evidenced by increased expression of cleaved Caspase1, NLRP3, IL-1ß, IL-18, and elevated LDH release. Inhibition of HDAC6 suppressed nicotine-induced pyroptosis, which is partly mediated by p65 acetylation and NLRP3 transcription. Silencing p65 or NLRP3 resulted in decreased pyroptosis in RAW264.7 cells. CONCLUSIONS: Nicotine induces macrophage pyroptosis in atherosclerosis through HDAC6/NF-κB/NLRP3 signaling pathway.

Nicotine Modulates CTSS (Cathepsin S) Synthesis and Secretion Through Regulating the Autophagy-Lysosomal Machinery in Atherosclerosis.

OBJECTIVE: Increased CTSS (cathepsin S) has been reported to play a critical role in atherosclerosis progression. Both CTSS synthesis and secretion are essential for exerting its functions. However, the underlying mechanisms contributing to CTSS synthesis and secretion in atherosclerosis remain unclear. Approach and Results: In this study, we showed that nicotine activated autophagy and upregulated CTSS expression in vascular smooth muscle cells and in atherosclerotic plaques. Western blotting and immunofluorescent staining showed that nicotine inhibited the mTORC1 (mammalian target of rapamycin complex 1) activity, promoted the nuclear translocation of TFEB (transcription factor EB), and upregulated the expression of CTSS. Chromatin immunoprecipitation-qualificative polymerase chain reaction, electrophoretic mobility shift assay, and luciferase reporter assay further demonstrated that TFEB directly bound to the CTSS promoter. mTORC1 inhibition by nicotine or rapamycin promoted lysosomal exocytosis and CTSS secretion. Live cell assays and IP-MS (immunoprecipitation-mass spectrometry) identified that the interactions involving Rab10 (Rab10, member RAS oncogene family) and mTORC1 control CTSS secretion. Nicotine promoted vascular smooth muscle cell migration by upregulating CTSS, and CTSS inhibition suppressed nicotine-induced atherosclerosis in vivo. CONCLUSIONS: We concluded that nicotine mediates CTSS synthesis and secretion through regulating the autophagy-lysosomal machinery, which offers a potential therapeutic target for atherosclerosis treatment.

The interaction between STAT3 and nAChRα1 interferes with nicotine-induced atherosclerosis via Akt/mTOR signaling cascade.

During atherosclerosis development, nicotine and its α1 nicotinic acetylcholine receptors (nAChRα1) activate atherogenic inflammation. However, the effect of signal transducer and activator of transcription 3 (STAT3)-related inflammatory pathways in nicotine-induced atherosclerosis has been poorly studied. This study investigated the transcriptional mechanism of STAT3 in nicotine/nAChRα1-induced atherosclerosis. In vivo, ApoE-/- mice were used to establish an atherosclerotic model. Plaque area and composition were assessed by oil red O staining and immunohistochemistry. In vitro, vascular smooth muscle cells and macrophages were used to investigate cell migration, proliferation, inflammation and related signaling pathways by Transwell migration assay, EdU assay, immunofluorescence, western blotting, coimmunoprecipitation and chromatin immunoprecipitation. nAChRα1 knockdown significantly decreases the nicotine-induced upregulation of p-STAT3, p-Akt and p-mTOR in vitro, while nAChRα1 overexpression has the opposite effects. The inhibition of STAT3 attenuated nicotine-induced atherosclerosis, by reducing the proliferation and migration of vascular smooth muscle cells and inflammation in macrophages. Moreover, there is a direct interaction between STAT3 and nAChRα1 that modulates STAT3 nuclear translocation and its binding to the Akt promoter region upon nicotine exposure. Taken together, STAT3 and nAChRα1 blockade attenuates nicotine-induced atherosclerosis by reducing the migration and proliferation of vascular smooth muscle cells and inflammation in macrophages via the Akt/mTOR pathway.

Clinical Efficacy and Safety of Combination Therapy with Amlodipine and Olmesartan or an Olmesartan/Hydrochlorothiazide Compound for Hypertension: A Prospective, Open-Label, and Multicenter Clinical Trial in China.

BACKGROUND: Amlodipine (AML) is the initial therapy most commonly prescribed for patients with hypertension in China. However, AML monotherapy is often less effective in achieving blood pressure (BP) control than other agents. OBJECTIVE: We performed a clinical study to evaluate efficacy and safety of a combination therapy with AML, olmesartan (OLM), or an OLM/hydrochlorothiazide (HCTZ) compound for Chinese patients with mild-to-moderate hypertension. METHODS: In the clinical trial, patients were initially treated with OLM 20 mg/d combined with AML 5 mg/d. Then OLM was uptitrated to 40 mg/d or changed to an OLM/HCTZ (20/12.5 mg/d) compound if the patients did not reach the target of seated diastolic BP <90 mm Hg (<80 mm Hg in patients with diabetes) after 8 weeks. RESULTS: The overall response rate of the combination therapy was 59.2% (95% CI, 54.23%-63.97%) at Week 2 and gradually increased to 97.1% (95% CI, 94.93%-98.47%) at the end of the study (Week 16). CONCLUSIONS: The combination therapy with OLM or OLM/HCTZ was well tolerated. The total incidence of adverse events was 42.9% (n = 176). Most of the adverse events were mild in severity (39.5%; n = 162) and not associated with the drugs (33.2%). In conclusion, combination therapy with AML, OLM, or OLM/HCTZ can significantly lower BP safely and achieve a high BP control rate in patients with mild-to-moderate hypertension in China. ClinicalTrial.org identifier: ChiCTR-ONC-12001963.

Nicotine promotes atherosclerosis development in apolipoprotein E-deficient mice through α1-nAChR.

α1 Nicotinic acetylcholine receptor (α1nAChR) is an important nicotine receptor that is widely distributed in vascular smooth muscle cells, macrophages, and endothelial cells. However, the role of α1nAChR in nicotine-mediated atherosclerosis remains unclear. The administration of nicotine for 12 weeks increased the area of the atherosclerotic lesion, the number of macrophages infiltrating the plaques, and the circulating levels of inflammatory cytokines, such as interleukin-6 and tumor necrosis factor-α, in apolipoprotein E-deficient (ApoE-/- ) mice fed a high-fat diet. Nicotine also increased α1nAChR, calpain-1, matrix metalloproteinase-2 (MMP-2), and MMP-9 expression in the aortic tissue. Silencing of α1nAChR with an adenoassociated virus decreased the atherosclerotic size, lesion macrophage content, and circulating levels of inflammatory cytokines and suppressed α1nAChR, calpain-1, MMP-2, and MMP-9 expression in the nicotine group. In vitro, nicotine-induced α1nAChR, calpain-1, MMP-2, and MMP-9 expression in mouse vascular smooth muscle cells (MOVAS) and macrophages (RAW264.7), and enhanced the migration and proliferation of these cells. The silencing of α1nAChR inhibited these effects of nicotine MOVAS and RAW264.7 cells. Thus, we concluded that nicotine promoted the development of atherosclerosis partially by inducing the migration and proliferation of vascular smooth muscle cells and macrophages and inducing an inflammatory reaction. The effect of nicotine on atherogenesis may be mediated by α1nAChR-induced activation of the calpain-1/MMP-2/MMP-9 signaling pathway.

Cysteine Protease Cathepsins in Atherosclerotic Cardiovascular Diseases.

Atherosclerotic cardiovascular disease (ASCVD) is an inflammatory disease characterized by extensive arterial wall matrix protein degradation. Cysteine protease cathepsins play a pivotal role in extracellular matrix (ECM) remodeling and have been implicated in the development and progression of atherosclerosis-based cardiovascular diseases. An imbalance in expression between cathepsins (such as cathepsins S, K, L, C) and their inhibitor cystatin C may favor proteolysis of ECM in the pathogenesis of cardiovascular disease such as atherosclerosis, aneurysm formation, restenosis, and neovascularization. New insights into cathepsin functions have been made possible by the generation of knockout mice and by the application of specific inhibitors. Inflammatory cytokines regulate the expression and activities of cathepsins in cultured vascular cells and macrophages. In addition, evaluations of the possibility of cathepsins as a diagnostic tool revealed that the circulating levels of cathepsin S, K, and L, and their endogenous inhibitor cystatin C could be promising biomarkers in the diagnosis of coronary artery disease, aneurysm, adiposity, peripheral arterial disease, and coronary artery calcification. In this review, we summarize the available information regarding the mechanistic contributions of cathepsins to ASCVD.

Stimulation of Alpha7 Nicotinic Acetylcholine Receptor Attenuates Nicotine-Induced Upregulation of MMP, MCP-1, and RANTES through Modulating ERK1/2/AP-1 Signaling Pathway in RAW264.7 and MOVAS Cells.

Vagus nerve stimulation through alpha7 nicotine acetylcholine receptors (α7-nAChR) signaling had been demonstrated attenuation of inflammation. This study aimed to determine whether PNU-282987, a selective α7-nAChR agonist, affected activities of matrix metalloproteinase (MMP) and inflammatory cytokines in nicotine-treatment RAW264.7 and MOVAS cells and to assess the underlying molecular mechanisms. RAW264.7 and MOVAS cells were treated with nicotine at different concentrations (0, 1, 10, and 100 ng/ml) for 0-120 min. Nicotine markedly stimulated the phosphorylation of extracellular signal-regulated kinase1/2 (ERK1/2) and c-Jun in RAW264.7 cells. Pretreatment with U0126 significantly suppressed phosphorylation of ERK1/2 and further attenuated nicotine-induced activation of c-Jun and upregulation of MMP-2, MMP-9, monocyte chemotactic protein- (MCP-) 1, and regulated upon activation normal T cell expressed and secreted (RANTES). Similarly, nicotine treatment also increased phosphorylation of c-Jun and expressions of MMP-2, MMP-9, MCP-1, and RANTES in MOVAS cells. When cells were pretreated with PNU-282987, nicotine-induced activations of ERK1/2 and c-Jun in RAW264.7 cells and c-Jun in MOVAS cells were effectively inhibited. Furthermore, nicotine-induced secretions of MMP-2, MMP-9, MCP-1, and RANTES were remarkably downregulated. Treatment with α7-nAChR agonist inhibits nicotine-induced upregulation of MMP and inflammatory cytokines through modulating ERK1/2/AP-1 signaling in RAW264.7 cells and AP-1 in MOVAS cells, providing a new therapeutic for abdominal aortic aneurysm.

Cathepsin S Activity Controls Injury-Related Vascular Repair in Mice via the TLR2-Mediated p38MAPK and PI3K-Akt/p-HDAC6 Signaling Pathway.

OBJECTIVE: Cathepsin S (CatS) participates in atherogenesis through several putative mechanisms. The ability of cathepsins to modify histone tail is likely to contribute to stem cell development. Histone deacetylase 6 (HDAC6) is required in modulating the proliferation and migration of various types of cancer cells. Here, we investigated the cross talk between CatS and HADC6 in injury-related vascular repair in mice. APPROACH AND RESULTS: Ligation injury to the carotid artery in mice increased the CatS expression, and CatS-deficient mice showed reduced neointimal formation in injured arteries. CatS deficiency decreased the phosphorylation levels of p38 mitogen-activated protein kinase, Akt, and HDAC6 and toll-like receptor 2 expression in ligated arteries. The genetic or pharmacological inhibition of CatS also alleviated the increased phosphorylation of p38 mitogen-activated protein kinase, Akt, and HDAC6 induced by platelet-derived growth factor BB in cultured vascular smooth muscle cells (VSMCs), and p38 mitogen-activated protein kinase inhibition and Akt inhibition decreased the phospho-HDAC6 levels. Moreover, CatS inhibition caused decrease in the levels of the HDAC6 activity in VSMCs in response to platelet-derived growth factor BB. The HDAC6 inhibitor tubastatin A downregulated platelet-derived growth factor-induced VSMC proliferation and migration, whereas HDAC6 overexpression exerted the opposite effect. Tubastatin A also decreased the intimal VSMC proliferation and neointimal hyperplasia in response to injury. Toll-like receptor 2 silencing decreased the phosphorylation levels of p38 mitogen-activated protein kinase, Akt, and HDAC6 and VSMC migration and proliferation. CONCLUSIONS: This is the first report detailing cross-interaction between toll-like receptor 2-mediated CatS and HDAC6 during injury-related vascular repair. These data suggest that CatS/HDAC6 could be a potential therapeutic target for the control of vascular diseases that are involved in neointimal lesion formation.

Nicotine-induced upregulation of VCAM-1, MMP-2, and MMP-9 through the α7-nAChR-JNK pathway in RAW264.7 and MOVAS cells.

The ability of nicotine to induce aortic aneurysms has been shown in animal models; however, its underlying mechanisms remain elusive. In the present experiment, both the RAW264.7 and MOVAS cell lines were employed to examine the nicotine-induced modulation of VCAM-1, MMP-2, and MMP-9 expressions in macrophages and vascular smooth muscle cells. Our results showed that nicotine concentrations of both 0.5 and 5 ng/ml induced VCAM-1, MMP-2, and MMP-9 upregulation, while a concentration of 50 ng/ml had a slight inhibitory effect and a concentration of 500 ng/ml showed a significant inhibitory effect. When cells were pretreated with either SP600125 (JNK inhibitor) or PNU-282987 (α7-nAChR agonist) prior to nicotine exposure, the nicotine-induced upregulation of VCAM-1, MMP-2, MMP-9, and p-JNK was suppressed, with a joint treatment producing a more significant inhibitory effect. Moreover, PNU-282987 had a comparable inhibitory effect on VCAM-1, MMP-2, and MMP-9 expressions and JNK activation via phosphorylation as did SP600125. In conclusion, nicotine-induced VCAM-1, MMP-2, and MMP-9 expressions occur in a dose-dependent fashion in both of the cell lines tested. Furthermore, the nicotine exposure equivalent to plasma levels found in regular smokers can augment VCAM-1, MMP-2, and MMP-9 expressions through the α7-nAChR-JNK pathway.

Pathogenesis of abdominal aortic aneurysms: role of nicotine and nicotinic acetylcholine receptors.

Inflammation, proteolysis, smooth muscle cell apoptosis, and angiogenesis have been implicated in the pathogenesis of abdominal aortic aneurysms (AAAs), although the well-defined initiating mechanism is not fully understood. Matrix metalloproteinases (MMPs) such as MMP-2 and -9 and other proteinases degrading elastin and extracellular matrix are the critical pathogenesis of AAAs. Among the risk factors of AAAs, cigarette smoking is an irrefutable one. Cigarette smoke is practically involved in various aspects of the AAA pathogenesis. Nicotine, a major alkaloid in tobacco leaves and a primary component in cigarette smoke, can stimulate the MMPs expression by vascular SMCs, endothelial cells, and inflammatory cells in vascular wall and induce angiogenesis in the aneurysmal tissues. However, for the inflammatory and apoptotic processes in the pathogenesis of AAAs, nicotine seems to be moving in just the opposite direction. Additionally, the effects of nicotine are probably dose dependent or associated with the exposure duration and may be partly exerted by its receptors--nicotinic acetylcholine receptors (nAChRs). In this paper, we will mainly discuss the pathogenesis of AAAs involving inflammation, proteolysis, smooth muscle cell apoptosis and angiogenesis, and the roles of nicotine and nAChRs.

Allopurinol attenuates oxidative stress and cardiac fibrosis in angiotensin II-induced cardiac diastolic dysfunction.

AIMS: Oxidative stress and fibrosis is implicated in cardiac remodeling and failure. We tested whether allopurinol could decrease myocardial oxidative stress and attenuate cardiac fibrosis and left ventricular diastolic dysfunction in angiotensin II (AngII)-induced hypertensive mice. METHODOLOGY: We used 8-week-old male C57BL/6J mice, in which angiotensin II was subcutaneously infused for 4 weeks to mimic cardiac remodeling and fibrosis. They were treated with either normal saline or allopurinol in daily doses, which did not lower blood pressure. RESULTS: Allopurinol improved diastolic dysfunction in angiotensin II-induced hypertensive mice, which was associated with the amelioration of cardiac fibrosis. However, allopurinol showed no effect on the increased systolic blood pressure by angiotensin II infusion. The ratio of reduced glutathione (GSH) to oxidized glutathione (GSSG) [GSH/GSSG] was decreased and malondialdehyde levels were increased in the hearts of AngII-treated mice. Allopurinol also inhibited both the decrease in the GSH/GSSG ratio and the increase in malondialdehyde levels in the heart. Infusion of AngII-induced upregulation of transfer growth factor (TGF)-ß1, Smad3 expression and downregulation of Smad7 expression. Treatment with allopurinol reduced cardiac levels of TGF-ß1, Smad3, and increased Smad7 expression. CONCLUSIONS: These results suggest that allopurinol prevents pathological remodeling of the heart in AngII-induced hypertensive mice. The antioxidative effect of allopurinol contributes to the regression of AngII-induced cardiac diastolic dysfunction. These effects of allopurinol to prevent cardiac fibrosis are mediated at least partly through modulation of the TGF-ß1/Smad signaling pathway.

IL-8 reduces VCAM-1 secretion of smooth muscle cells by increasing p-ERK expression when 3-D co-cultured with vascular endothelial cells.

OBJECTIVE: The goal of this study was to investigate the crosstalk between vascular endothelial cells (ECs) and smooth muscle cells (SMCs) using a three-dimensional (3-D) co-culture model. In addition, the role of IL-8 in this crosstalk was investigated. METHODS: A 3-D co-culture model was constructed using a Transwell chamber system and type I collagen gel. Human umbilical artery smooth muscle cells (HUASMCs) were suspended in the gel and added to the upper compartment of the Transwell. Human umbilical vein endothelial cells (HUVECs) were then grown on the surface of the gel. The growth of HUASMCs was tested with a CFDA SE cell proliferation kit. IL-8 and other bioactive substances were investigated by ELISA and real-time PCR. The alteration of p-ERK expression related to the change in IL-8 levels was also examined by Western blot analysis. RESULTS: The proliferation rate of HUASMCs in the 3-D co-culture model was 0.679 ± 0.057. Secretion and transcription of VEGF, t-PA, NO and VCAM-1 in the 3-D co-culture model were different than in single (2-D) culture. When 3-D co-cultured, IL-8 released by HUVECs was significantly increased (2.35 ± 0.16 fold) (P﹤0.05) and the expression of VCAM-1 from HUASMCs was reduced accordingly (0.55±0.09 fold). In addition, increasing or decreasing the level of IL-8 changed the level of p-ERK and VCAM-1 expression. The reduction of VCAM-1, resulting from increased IL-8, could be blocked by the MEK inhibitor, PD98059. CONCLUSION: Crosstalk between HUVECs and HUASMCs occurred and was probably mediated by IL-8 in this 3-D co-culture model.

Passive cigarette smoking induces inflammatory injury in human arterial walls.

BACKGROUND: Epidemiological studies have shown that both active and passive cigarette smoking increase the risk of atherosclerosis. But very little is known about the biological processes induced by passive cigarette smoking that contribute to atherosclerosis. We observe the expression of a few of biological and inflammatory markers in human arterial walls in vitro which were treated with the second-hand smoke solution (sidestream whole, SSW), and discuss the possible mechanism of inflammatory injury induced by second-hand smoke. METHODS: The biological markers (platelet endothelial cell adhesion molecule-1, PECAM-1; alpha-smooth muscle actin, alpha-SMA; collagen IV, Col IV) and inflammatory markers (vascular cell adhesion molecule-1, VCAM-1; monocyte chemoattractant protein-1, MCP-1; interleukin-8, IL-8) of human aortal wall were tested by immunofluorescence staining. The levels of MCP-1 and IL-8 mRNA expression were detected by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: No distinct difference was observed between SSW and the control group on the expression of biological markers as assessed by the light microscope. But the inflammatory markers VCAM-1, MCP-1 and IL-8 on the subendothelial layer and smooth muscle cell layers, which are near the endothelium of arterial wall, were strongly stained in the SSW group compared with the control group. Their fluorescence intensities in the 1:40 SSW group (VCAM-1: 0.35 +/- 0.04, MCP-1: 0.34 +/- 0.05, IL-8: 0.37 +/- 0.05) and the 1:20 SSW group (VCAM-1: 0.40 +/- 0.04, MCP-1: 0.52 +/- 0.09, IL-8: 0.51 +/- 0.07) were significantly stronger than the control group (VCAM-1: 0.12 +/- 0.04, MCP-1: 0.06 +/- 0.02, IL-8: 0.24 +/- 0.03) by semi-quantitative analysis of immunofluorescence (P < 0.001 vs control). MCP-1 mRNA expression in the 1:40 SSW (0.15 +/- 0.04) and the 1:20 SSW (0.19 +/- 0.06) group was significantly higher than in the control group (0.09 +/- 0.03) (P < 0.05, P < 0.01 vs control); IL-8 mRNA expression in the 1:40 SSW (0.64 +/- 0.12) and 1:20 SSW (0.72 +/- 0.13) groups was also significantly higher than that in the control group (0.49 +/- 0.13) (P < 0.05, P < 0.01 vs control) by RT-PCR. CONCLUSIONS: It is implied that a second-hand smoke solution induces the inflammatory reaction of the arterial wall by release of inflammatory factors even though there is no distinct structural change on the arterial walls under light microscope, indicating that passive cigarette smoking is related to inflammatory injury in human arterial wall and could be closely related to the early inflammatory stage of atherosclerosis.

Neuregulin-1 promotes cardiomyocyte differentiation of genetically engineered embryonic stem cell clones.

Embryonic stem (ES) cell-derived cardiomyocytes (ESCMs) must be specifically purified in order to prevent teratoma formation, and this confusing issue has hampered their clinical application. We therefore investigated a technique to generate pure labeled ESCMs for possible use in cardiac repair. We generated transgenic ES cell lines expressing enhanced green fluorescent protein (EGFP) under the transcriptional control of the alpha-cardiac myosin heavy chain (alpha-MHC) promoter. Differentiated EGFP-positive ES cells displayed characteristics of CMs. Furthermore, neuregulin-1 (NRG-1) upregulated the expression of the cardiac-restricted transcription factors Nkx2.5 and GATA-4, as well as differentiated CM factors (alpha-MHC, beta-MHC). Immunohistochemistry demonstrated that NRG-1 increased expression of cardiac-specific troponin T in the beating foci of the embryoid bodies. This work revealed a potential method for specifically labeling and enriching ESCMs by combining genetically-engineered ES cell clones and exogenous growth factor treatment.