Selective inhibition of histone deacetylase 8 improves vascular hypertrophy, relaxation, and inflammation in angiotensin II hypertensive mice
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The dysregulation of histone deacetylase (HDAC) protein expression or its enzyme activity is implicated in a variety of diseases. Cardiac HDAC6 and HDAC8 enzyme activity induced by deoxycorticosterone acetate (DOCA) hypertension was attenuated by sodium valproate, a pan-HDAC inhibitor. However, the HDAC6-selective inhibitor, tubastatin A, did not attenuate angiotensin II-induced hypertension. The purpose of this study was to investigate whether PCI34051, an HDAC8-selective inhibitor, can modulate angiotensin II-induced hypertension and its regulatory mechanism.
An angiotensin II-regulated mouse model was used in this study. Animals received vehicle or PCI34051 (3 mg·kg − 1·day− 1) via intraperitoneal injection. Systolic blood pressure was measured by the tail-cuff method. Blood vessel thickness was measured following hematoxylin and eosin staining, VCAM-1 immunohistochemistry was performed in the aortas, and mRNA expression of renin-angiotensin system components, inflammation markers, and NADPH oxidase (Nox) was determined by RT-PCR. The effect of PCI34051 on vasorelaxation was studied in rat aortic rings, and its effect on nitric oxide (NO) production was determined using DAF-FM DA, a fluorescent dye, in human umbilical vascular endothelial cells (HUVECs).
PCI34051 administration reduced systolic blood pressure via downregulation of angiotensin II receptor type 1 (AT1) mRNA expression. PCI34051 treatment attenuated vascular hypertrophy by decreasing E2F3 and GATA6 mRNA expression. Vascular relaxation after PCI34051 treatment was more dependent on vascular endothelial cells and it was blocked by an NO synthase (NOS) inhibitor. In addition, NO production increased in HUVECs after PCI34051 treatment; this was decreased by the NOS inhibitor. The expression of inflammatory molecules and adhesion molecules VCAM-1 and ICAM-1 decreased in the aortas of angiotensin II-infused mice after PCI34051 administration. However, PCI34051 did not affect Nox or its regulatory subunits.
PCI34051 lowered high blood pressure through modulation of arterial remodeling, vasoconstriction, and inflammation in an angiotensin II-induced hypertension model. We suggest that HDAC8 could be a potential therapeutic target for hypertension.
KeywordsPCI34051 Hypertension Arterial remodeling Vascular relaxation Inflammation
- Ang II
Angiotensin II receptor blocker
Angiotensin II receptor type I
- DAF-FM DA
Endothelial cell basal medium
Hematoxylin and eosin
Human umbilical vascular endothelial cells
Half-maximal inhibitory concentration
Intercellular adhesion molecule-1
Interleukin-1 beta iNOS: inducible nitric oxide synthase
NG-nitro-L-arginine methyl ester
Monocyte chemoattractant protein-1
Nicotinamide adenine dinucleotide phosphate
Platelet endothelial cell adhesion molecule
Tumor necrosis factor-α
Vascular cell adhesion molecule-1
Continuously high blood pressure causes multiple complications, including stroke, hypertensive retinopathy, myocardial infarction, heart failure, and chronic renal failure [1, 2]. High blood pressure is known as a silent killer because there are no symptoms and therefore it can go untreated for long periods of time. It is known that the control rate is no more than 40% even when hypertensive patients receive two or more antihypertensive drugs . Inflammatory responses are involved in the pathophysiology of hypertension . Recent evidence has revealed inflammation in the vessel structure of animal models of hypertension .
Angiotensin II is a vasoconstrictor, causing vascular inflammation in arteries as well as in the kidneys and heart [6, 7]. It increases the expression of adhesion molecules, cytokines, and chemokines in endothelial cells and vascular smooth muscle cells . Vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), and platelet endothelial cell adhesion molecule (PECAM) may be implicated in hypertension . However, soluble E-selectin has been significantly associated with blood pressure . In contrast, soluble VCAM-1 (sVCAM-1) is elevated in older men with uncomplicated essential hypertension . Recent evidence showed that expression of VCAM-1 is positively correlated with coronary lesion severity in atherosclerotic patients . In addition, VCAM-1 was reported to be a biochemical marker of left ventricular mass in patients with uncomplicated hypertension .
The renin-angiotensin system (RAS) is the most important and well-known hormone system for controlling hypertension. Angiotensin-converting enzyme (ACE) converts angiotensin I to angiotensin II. Angiotensin II acts through angiotensin II receptor type 1 (AT1), which leads to vasoconstriction and inflammation . An angiotensin II receptor blocker (ARB) reduces high blood pressure and inflammation by interfering with AT1 binding. Currently, ACE inhibitors and ARBs are widely used as hypertension treatments in clinical trials.
Hypertension is caused by increased resistance of blood vessels. Blood vessels are mainly composed of smooth muscle cells and endothelial cells. Endothelial cells secret substances that relax blood vessels, such as nitric oxide (NO), and substances that contract blood vessels, for example, endothelin-1. Vascular smooth muscle cells control blood pressure mainly through vascular contraction and relaxation. Contraction of smooth muscle cells is mainly due to changes in calcium concentration. Phosphorylation of myosin light chains is effected by myosin light chain kinase (MLCK), and arterial smooth muscle contracts through Ca2+/MLCK pathways [15, 16].
Histone deacetylases (HDACs) and their inhibitors have been extensively studied in cancer and they are now attracting attention in cardiovascular disease research . HDACs are classified into class I (HDAC1, 2, 3, and 8), class IIa (HDAC4, 5, 7, and 9), class IIb (HDAC6 and 10), class III (sirtuins1-7), and class IV (HDAC11), based on their sequence. HDAC inhibitors have been shown to be effective in cardiac hypertrophy, fibrosis, heart failure, and restenosis [18, 19, 20]. Furthermore, the HDAC inhibitor, valproic acid, attenuated blood pressure in spontaneously hypertensive rats and deoxycorticosterone acetate (DOCA)- induced hypertensive rats [21, 22]. However, there was no use of isoform-specific HDAC inhibitors in these reports. We have published a study showing that HDAC6 and 8 enzyme activities are increased in the hearts of DOCA hypertensive rats . We demonstrated that the HDAC6-selective inhibitor, tubastatin A, did not affect high blood pressure in an angiotensin II-induced hypertensive mouse model. Therefore, we hypothesized that HDAC8 may have a role in hypertension. To provide evidence supporting this hypothesis, we decided to investigate the effect of the HDAC8-selective inhibitor, PCI34051, on blood pressure in angiotensin II-induced hypertensive mice.
Animal model and blood pressure measurement
Angiotensin II (Ang II) was obtained from EMD Millipore (Billerica, MA, USA). PCI34051 was purchased from Selleckchem (Houston, TX, USA). CD-1 male mice (aged 8 weeks) were purchased from Orient Bio Company (Gyeonggi-do, South Korea). All animal experiments were approved by the Animal Experiment Committee of the Chonnam National University Medical School (CNU IACUC-H-2017-70) and carried out in accordance with the Guide for the Care and Use of Laboratory Animals (US National Institutes of Health Publication, 8th edition, 2011). Mice were anesthetized with ketamine (120 mg/kg) and xylazine (6.21 mg/kg), and a 1 cm incision was made in the back. Ang II (1.3 mg·kg−1·day−1, n=8 per group) was infused via an ALZET® osmotic pump as described previously. Ang II was dissolved in 0.9% NaCl solution. The sham control mice received dimethyl sulfoxide vehicle (DMSO; n=8). PCI34051 (3 mg·kg−1·day−1) was administered to the mice (n=8 per group) by intraperitoneal injection from the eighth to the fourteenth day after Ang II infusion began. Blood pressure was measured three times a week in conscious animals by the tail-cuff method. Systolic blood pressure was determined on the fourteenth day after Ang II infusion began.
Hematoxylin and eosin (H&E) staining
Aorta tissues were fixed in 4% paraformaldehyde at 25°C, embedded in paraffin, and cut into 3 μm thick sections. The tissue slides were deparaffinized three times with xylene and hydrated using serially diluted ethanol. After dipping in tap water for 2 min, the slides were stained with Gill’s hematoxylin V for 5 min, washed in tap water for 5 min, and in 95% ethanol for 2 min. The slides were stained using Eosin Y for 1 min, dehydrated with ethanol and xylene, and mounted using Canada balsam. The aortic wall thickness was measured using NIS Elements Software (Nikon, Japan).
Aorta tissues were fixed in 4% paraformaldehyde at 25°C, embedded in paraffin, and cut into 3-μm-thick sections. After deparaffinization in xylene, the tissues were subjected to antigen retrieval using 10 mM citrate-phosphate buffer (pH 6.0) and incubated in 3% H2O2 for 10 min. To remove non-specific binding, an Avidin/Biotin blocking kit (Abcam, USA) was used, and the sections were then blocked with 1% bovine serum albumin in PBS for 10 min. Sections were incubated overnight with mouse monoclonal VCAM-1 antibody (1:50, Santa Cruz) at 4°C and washed in PBS before being incubated with prediluted biotinylated pan- specific universal secondary antibody (R.T.U. VECTASTAIN kit) for 30 min at 25°C. Tissues were washed with PBS, incubated in streptavidin/peroxidase complex for 5 min, and again washed with PBS. The tissues were incubated in DAB (peroxidase substrate kit, SK-4100) for 7 min. Sections were stained with hematoxylin for 30 s and washed and mounted. Images were captured using a fluorescent microscope (Eclipse 80i, Nikon, Japan).
Isometric tension measurement
The vasoconstriction-relaxation study was performed as described previously. Male Sprague- Dawley rats were purchased from Orient Bio (Gyeonggi-do, South Korea). Briefly, thoracic aortas were excised and immersed in ice-cold modified Krebs solution. The aortas were cleaned of all connective tissue, soaked in Krebs-bicarbonate solution, and cut into four ring segments (3.5 mm in length). Each aortic ring was suspended in a water-jacketed organ bath(6 ml) maintained at 37°C and aerated with a mixture of 95% O2 and 5% CO2. Each ring was connected to an isometric force transducer (Danish Myo Technology, Skejbyparken, Aarhus N, Denmark). Rings were stretched to an optimal resting tension of 2.0 ×g or 1.0 ×g, which was maintained throughout the experiment. Each ring was equilibrated in the organ bath solution for 90 min before measuring the contractile response after the addition of 50 mM KCl. To determine the effect of PCI34051 on the maintenance of vascular tension in rat endothelium-intact or endothelium-denuded aortic rings, vascular contractions were induced using the thromboxane A2 agonist, U46619 (30 nM, 20 min). When each contraction reached a plateau, increasing concentrations of PCI34051 (0.003 - 3 μM) were added cumulatively to elicit vascular relaxation.
In the second experiment, we investigated the inhibition of the relaxation response by treating endothelium-intact aortic rings with NG-nitro-L-arginine methyl ester (L-NAME, 10 and 100 μM) for 30 min. After U46619 treatment, increasing concentrations of PCI34051 (0.003 - 1 μM) were added cumulatively to the aortic rings.
Human umbilical vein endothelial cells (HUVECs) were obtained from Gibco (Waltham, MA, USA). HUVECs were grown in endothelial cell basal medium (EBM) with an EGM-2 bullet kit (Lonza, Walkersville, MD) and maintained at 37°C under 5% CO2. The cells were subcultured when they reached approximately 90% confluency. Cells were used from passages five to seven. The vascular smooth muscle cells (VSMCs) were isolated from rat aortas as described previously . VSMCs were maintained in low glucose with Dulbecco’s modified Eagle medium (DMEM) containing 10% fetal bovine serum. VSMCs were used from passages five to nine.
Western blot analysis
VSMCs were lysed with RIPA buffer (150 mM NaCl; 1% Triton X-100; 1% sodium deoxycholate; 50 mM Tris-HCl, pH 7.5; 2 mM EDTA; 1 mM PMSF; 1 mM DTT; 1 mM Na3VO4; and 5 mM NaF) containing a protease inhibitor cocktail. The proteins were subjected to 10% SDS-PAGE and transferred on to polyvinylidene difluoride (PVDF) membranes. The membranes were blocked with 5% skim milk in Tris-buffered saline with Tween® 20 (TBST) buffer (20 mM Tris, 200 mM NaCl, and 0.04% Tween® 20) for 1 h at 25 °C. The membranes were incubated overnight at 4 °C with HDAC8 antibody (Santa Cruz) and then incubated with anti-mouse horseradish-peroxidase-conjugated secondary antibody (1:5000) for 1 h at 25 °C. The protein bands were visualized using Immobilon Western detection reagents (EMD Millipore). Bio-ID software was used to quantify the protein expression (Vilber Lourmat, Eberhardzell, Germany).
DAF-FM imaging of NO
The production of NO was estimated using a NO-sensitive fluorescence probe, 4-amino-5- methylamino-2′,7′-difluorofluorescein diacetate (DAF-FM DA, Cayman). HUVECs were seeded on coverslips in 12-well plates. Cells were serum-starved with EBM for 16 h, and were treated with PCI34051 (1 μM) or L-NAME (250 μM) for 24 h and then incubated with DAF-FM DA (2.5 μM) at 37°C for 30 min. Cells were fixed using 70% ethanol for 45 min, washed three times with PBS, and mounted using Prolong Gold antifade reagent with DAPI (Invitrogen, USA).
Reverse transcription polymerase chain reaction
Primers for the reverse transcription polymerase chain reaction (RT-PCR)
(mouse or rat)
Primer sequence (5′ to 3′)
Fluorogenic HDAC enzyme activities
To evaluate the HDAC enzyme inhibitory activity of PCI34051, we determined the activities of HDAC1, HDAC2, HDAC3, and HDAC8 using enzyme assay kits (BPS Bioscience, San Diego, CA, USA) according to the manufacturer’s protocols. HDAC activities were measured using a fluorometer (Spectra Max GEMINI XPS, Molecular Devices, Sunnyvale, CA, USA) at excitation and emission wavelengths of 350 nm and 460 nm, respectively. To test the inhibitory activity of PCI34051, concentrations of 0.001, 0.003, 0.01, 0.03, 0.1, 0.3, 1, and 3 μM were used. For the half-maximal inhibitory concentration (IC50) calculations, every data point was normalized to the vehicle (100% activity). The normalized data were fitted using a Hill nonlinear curve (OriginPro 9.0). The “Find X from Y” function in OriginPro 9.0 was used to determine the IC50 values (50% activity).
Statistical analysis was performed using one-way analysis of variance (ANOVA) followed by the Bonferroni post-hoc test to compare the treatment groups (GraphPad Prism, version 5.0; GraphPad Software, La Jolla, CA, USA). Data are presented as the mean ± SEM. A value of P < 0.05 was considered statistically significant.
HDAC8-selective inhibitor PCI34051 reduces blood pressure through down-regulation of AT1 in Ang II-induced hypertensive mice
IC50 [μM] values for PCI34051
PCI34051 reduces aortic wall thickness in Ang II-induced hypertensive mice
PCI34051 increases vascular relaxation in rat aortic rings and NO production in HUVECs
We investigated whether vascular relaxation was related to the NO signaling system. We confirmed that pretreatment of the aortic rings with L-NAME (100 μM), a NOS inhibitor, prevented blood vessel relaxation by PCI34051 (Fig. 3b). Endothelial NO synthase (eNOS) synthesizes NO in vascular endothelium . To explore whether blood vessel relaxation by PCI34051 is related to NO generation, we studied the effect of PCI34051 on NO production in HUVECs using a NO-sensitive fluorescent dye, DAF-FM. As shown by the increase in green fluorescence in Fig. 3c, PCI34051 treatment induced NO synthesis. Pretreatment with L-NAME reduced the amount of NO generated by PCI34051 in HUVECs.
PCI34051 attenuates inflammation in Ang II-induced hypertensive mice
PCI34051 reduces adhesion molecules in Ang II-induced hypertensive mice
PCI34051 does not affect NADPH oxidase (Nox) in Ang II-induced hypertensive mice
In the present study, we demonstrated that PCI34051, an HDAC8-selective inhibitor, lowered systolic blood pressure, reduced aortic wall thickness, increased vascular relaxation, and inhibited inflammation in a mouse model of Ang II-induced hypertension.
Although there are reports that HDAC inhibitors lower blood pressure  in various diseases including essential hypertension, high-fat diet-induced hypertension , and Cushing’s syndrome , in many circumstances we do not know which isoform of HDAC is involved. Initially, in a cell-free system, we observed that PCI34051 selectively inhibits HDAC8 enzyme activity, but not the activities of HDAC1, HDAC2, or HDAC3.
Ang II causes hypertension through effects on the AT1 receptor, leading to vascular contraction . It is well known that ARBs act by selectively blocking the binding of Ang II to the AT1 receptor . In the present study, we observed that PCI34051 administration significantly decreased systolic blood pressure in Ang II-infused mice by decreasing AT1 mRNA expression. However, blood pressure was not fully returned to control levels by PCI34051 administration, implying that other HDACs may be involved, in addition to HDAC8.
There have been reports that drugs such as calcium-calmodulin-dependent kinase II inhibitor (KN-93) and HDAC inhibitor (MC1568) are effective in reducing Ang II-induced vascular hypertrophy [24, 46]. In the present study, the HDAC8-selective inhibitor, PCI34051, was also effective in partially reducing the vascular hypertrophy induced by Ang II. In our previous research , GATA6 transcription factor directly increased the size of vascular smooth muscle cells. E2F3 is well known as a transcription factor that regulates cell proliferation . Our results show that the inhibitory effect of PCI34051 on vascular hypertrophy may be due to its inhibition of GATA6 and E2F3 expression, as a decrease in the mRNA expression of these transcription factors was seen in the Ang II-infused mice after PCI34051 administration.
The most interesting finding is that PCI34051 relaxes blood vessels in rat aortic rings. The blood vessel relaxation by PCI34051 is particularly dependent on endothelial cells and is effected through the NO signaling system. Indeed, we demonstrated that PCI34051 treatment induced NO production in HUVECs and that this could be blocked by a NOS inhibitor.
This result suggests that HDAC8 activity is closely related to vascular contraction and relaxation. In contrast to our results, Lee et al reported that a pan-HDAC inhibitor, CG200745, had little effect on vascular relaxation in DOCA-induced hypertension . However, in agreement with our results, SAHA, a pan-HDAC inhibitor, or trichostatin A (TSA) caused a dose-dependent relaxation of the phenylephrine-induced vascular contraction of mouse aortas or the Ang II-induced contraction of rat aortas [49, 50]. Long-term treatment with TSA inhibited Ang II-induced contraction in spontaneously hypotensive rats . Some researchers have used pan-HDAC inhibitors, so we cannot be sure which HDACs have an effect on vascular relaxation.
Ang II induces vascular inflammation by inducing proinflammatory cytokines . The HDAC8-selective inhibitor decreased the expression of the proinflammatory cytokines, TNFα, IL-1β, and MCP-1, and suppressed inflammation, suggesting that these two effects may be linked. Adhesion molecules are also implicated in inflammation. ICAM-1 and VCAM-1 mediate adhesion of leukocytes to the endothelium. sICAM-1, sVCAM-1, P-selectin, and E- selectin levels have been seen to be higher in hypertensive patients . In addition, the expression of VCAM-1 was increased in the aortas and mesenteric resistance arteries of Ang II-induced hypertensive mice . Our current study shows that treatment with an HDAC8- 18 selective inhibitor suppresses the increased expression of VCAM-1 and ICAM-1 in Ang II- induced hypertension. Furthermore, immunohistochemistry demonstrated that VCAM-1 protein was highly expressed in the endothelium of aorta tissues in Ang II-infused mice compared to that in control mice. Our findings suggest that HDAC8 activity may well be responsible for vascular inflammation.
Ang II regulates ROS through upregulation of Nox . Angiotensin II-induced ROS can cause vasoconstriction, inflammation, and vascular remodeling through activation of multiple pathways. In our study, Ang II increased the aortic expression of Nox1 and Nox2 mRNA but did not affect the expression of Nox4. The HDAC8-selective inhibitor did not decrease Nox1 and Nox2 expression. This result implies that HDACs other than HDAC8 modulate Nox expression. Cardiac Nox1, Nox2, and Nox4 mRNA levels significantly increased in SHR hypertensive rats compared to that in Wistar Kyoto (WKY) control rats . Gallic acid, which inhibits HDAC5, HDAC7, HDAC8, and HDAC9, ameliorated Nox2 mRNA and protein levels in SHR . Manea et al. reported that SAHA decreased the aortic expression of Nox1, Nox2, and Nox4 in diabetic mice by regulation of HDAC1 and HDAC2 . In contrast, increased expression of HDAC3, HDAC4, and HDAC5 is associated with induction of Nox2 and Nox4 in pulmonary arterial hypertension, which was decreased by the HDAC inhibitor, valproic acid . The results of the above study show that the expression of Nox varies depending on the type of disease; for example, arterial hypertension, pulmonary hypertension, or diabetes. The pan-HDAC inhibitor was more effective in reducing the expression of Nox than an HDAC isoform-specific inhibitor.
We demonstrated that an HDAC8-selective inhibitor lowered blood pressure, inhibited vascular hypertrophy and inflammation, and relaxed blood vessels in an Ang II-induced hypertension model. The HDAC8-selective inhibitor contributed to blood pressure reduction by inhibiting a component of the RAS or regulating NO signaling pathways. We suggest that HDAC8 may be a therapeutic target for hypertension.
This study is supported by the Korean Society of Hypertension (2017).
Availability of data and materials
The raw data supporting the findings presented in this study will be available from the corresponding author upon request.
HJK designed the research; YR, YMS, SS, GRK, SYC, performed the experiments; HJK, YR, YMS, MHJ performed data analysis and interpreted the data; HJK wrote the paper. All authors read and approved the final manuscript.
Ethics approval and consent to participate
All animal experiments were approved by the Animal Experiment Committee of the Chonnam National University Medical School (CNU IACUC-H-2017-70) and carried out in accordance with the Guide for the Care and Use of Laboratory Animals (US National Institutes of Health Publication, 8th edition, 2011).
Consent for publication
The authors declare that they have no competing interest.
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- 54.De Ciuceis C, Amiri F, Brassard P, Endemann DH, Touyz RM, Schiffrin EL. Reduced vascular remodeling, endothelial dysfunction, and oxidative stress in resistance arteries of angiotensin II-infused macrophage colony-stimulating factor-deficient mice: evidence for a role in inflammation in angiotensin-induced vascular injury. Arterioscler Thromb Vasc Biol. 2005;25:2106–13.CrossRefPubMedGoogle Scholar
- 57.Manea SA, Antonescu ML, Fenyo IM, Raicu M, Simionescu M, Manea A. Epigenetic regulation of vascular NADPH oxidase expression and reactive oxygen species production by histone deacetylase- dependent mechanisms in experimental diabetes. Redox Biol. 2018;16:332–43.CrossRefPubMedPubMedCentralGoogle Scholar
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