MRP1-Dependent Extracellular Release of Glutathione Induces Cardiomyocyte Ferroptosis After Ischemia-Reperfusion

BACKGROUND

The membrane components of cardiomyocytes are rich in polyunsaturated fatty acids, which are easily oxidized. Thus, an efficient glutathione-based lipid redox system is essential for maintaining cellular functions. However, the relationship between disruption of the redox system during ischemia-reperfusion (IR), oxidized lipid production, and consequent cell death (ferroptosis) remains unclear. We investigated the mechanisms underlying the disruption of the glutathione-mediated reduction system related to ferroptosis during IR and developed intervention strategies to suppress ferroptosis.

METHODS

In vivo fluctuations of both intra- and extracellular metabolite levels during IR were explored via microdialysis and tissue metabolome analysis. Oxidized phosphatidylcholines were assessed using liquid chromatography high-resolution mass spectrometry. The areas at risk following IR were assessed using triphenyl-tetrazolium chloride/Evans blue stain.

RESULTS

Metabolomic analysis combined with microdialysis revealed a significant release of glutathione from the ischemic region into extracellular spaces during ischemia and after reperfusion. The release of glutathione into extracellular spaces and a concomitant decrease in intracellular glutathione concentrations were also observed during anoxia-reperfusion in an in vitro cardiomyocyte model. This extracellular glutathione release was prevented by chemical inhibition or genetic suppression of glutathione transporters, mainly MRP1 (multidrug resistance protein 1). Treatment with MRP1 inhibitor reduced the intracellular reactive oxygen species levels and lipid peroxidation, thereby inhibiting cell death. Subsequent in vivo evaluation of endogenously oxidized phospholipids following IR demonstrated the involvement of ferroptosis, as levels of multiple oxidized phosphatidylcholines were significantly elevated in the ischemic region 12 hours after reperfusion. Inhibition of the MRP1 transporter also alleviated intracellular glutathione depletion in vivo and significantly reduced the generation of oxidized phosphatidylcholines. Administration of MRP1 inhibitors significantly attenuated infarct size after IR injury.

CONCLUSIONS

Glutathione was released continuously during IR, primarily in an MRP1-dependent manner, and induced ferroptosis. Suppression of glutathione release attenuated ferroptosis and reduced myocardial infarct size following IR.

De-escalation of oxygen-therapy and medication in patients with chronic thromboembolic pulmonary hypertension after balloon pulmonary angioplasty

INTRODUCTION

There is no consensus on the adjustment of home oxygen therapy (HOT) and pulmonary hypertension (PH)-specific medications after balloon pulmonary angioplasty (BPA) in patients with chronic thromboembolic pulmonary hypertension (CTEPH). We aimed to examine the status of de-escalation/discontinuation of HOT and PH-specific medications post-BPA and clarify its effect on hemodynamics, biomarkers, and long-term outcomes.

METHODS AND RESULTS

From November 2012 to May 2018, 135 consecutive CTEPH patients who underwent BPA at a single university hospital were enrolled (age, 63.5 ± 13.5 years; World Health Organization functional class [WHO-FC] II/III/IV, 34/92/9). The mean pulmonary arterial pressure decreased from 37.7 ± 11.3 to 20.4 ± 5.1 mmHg 1-year post-BPA (p<0.01). The proportion of patients who required HOT and combination medical therapy (≥2 PH-specific medications) decreased 1-year post-BPA (from 58.5% to 7.4% and from 40.0% to 10.4%, respectively). Baseline factors influencing the requirement of HOT and combination medical therapy post-BPA were almost identical (i.e., lower exercise capacity and pulmonary diffusion capacity, and worse hemodynamics). Regardless of their discontinuation, the improved hemodynamics, functional capacity (WHO-FC), and biomarkers (B-type natriuretic peptide and high-sensitivity troponin T) were almost maintained, and no adverse 1-year clinical outcomes (all-cause death and PH-related hospitalization) were observed.

CONCLUSIONS

Most CTEPH patients discontinued HOT and PH-specific combination medical therapy post-BPA, which was not associated with the deterioration of hemodynamics, functional capacity, or biomarkers. No long-term adverse outcomes were observed.

RNF213-Associated Vascular Disease: A Concept Unifying Various Vasculopathies

The ring finger protein 213 gene (RNF213) encodes a 590 kDa protein that is thought to be involved in angiogenesis. This gene was first recognized as a vasculopathy-susceptibility locus through genome-wide association studies undertaken in a Japanese population, demonstrating that heterozygotes for RNF213 p.Arg4810Lys (c.14429G>A, rs112735431) had a greatly increased risk of moyamoya disease. The association of RNF213 p.Arg4810Lys as a susceptibility variant of moyamoya disease was reproduced in Korean and Chinese individuals and, later, in Caucasians. Variants of the RNF213 gene have been linked to a number of vascular diseases such as moyamoya disease, intracranial major artery stenosis, pulmonary arterial hypertension, and peripheral pulmonary artery stenosis, and have also been associated with co-occurrent diseases and vascular disease in different organs. Based on the findings that we have reported to date, our paper proposes a new concept of “RNF213-associated vascular disease” to unify these conditions with the aim of capturing patients with multiple diseases but with a common genetic background. This concept will be highly desirable for clarifying all of the diseases in the RNF213-associated vascular disease category by means of global epidemiological investigations because of the possibility of such diseases appearing asymptomatically in some patients.

Impact of additional selexipag on prostacyclin infusion analogs in patients with pulmonary arterial hypertension

The effective therapy for pulmonary arterial hypertension (PAH) with inadequate clinical response is scarce except for lung transplantation when prostacyclin infusion is ineffective. The purpose of this study is to investigate the efficacy and safety of selexipag in addition to the infusion of prostacyclin. Nine patients [median 38 (36–49) years of age; 78% female] with PAH whose clinical response was inadequate despite the use of prostacyclin infusion analogs, were evaluated. Addition of selexipag significantly improved hemodynamics and no serious adverse events were observed. Selexipag with prostacyclin infusion analogs can be an effective therapeutic strategy for the PAH patients with inadequate clinical response.

MITOL/MARCH5 determines the susceptibility of cardiomyocytes to doxorubicin-induced ferroptosis by regulating GSH homeostasis

MITOL/MARCH5 is an E3 ubiquitin ligase that plays a crucial role in the control of mitochondrial quality and function. However, the significance of MITOL in cardiomyocytes under physiological and pathological conditions remains unclear. First, to determine the significance of MITOL in unstressed hearts, we assessed the cellular changes with the reduction of MITOL expression by siRNA in neonatal rat primary ventricular cardiomyocytes (NRVMs). MITOL knockdown in NRVMs induced cell death via ferroptosis, a newly defined non-apoptotic programmed cell death, even under no stress conditions. This phenomenon was observed only in NRVMs, not in other cell types. MITOL knockdown markedly reduced mitochondria-localized GPX4, a key enzyme associated with ferroptosis, promoting accumulation of lipid peroxides in mitochondria. In contrast, the activation of GPX4 in MITOL knockdown cells suppressed lipid peroxidation and cell death. MITOL knockdown reduced the glutathione/oxidized glutathione (GSH/GSSG) ratio that regulated GPX4 expression. Indeed, the administration of GSH or N-acetylcysteine improved the expression of GPX4 and viability in MITOL-knockdown NRVMs. MITOL-knockdown increased the expression of the glutathione-degrading enzyme, ChaC glutathione-specific γ-glutamylcyclotransferase 1 (Chac1). The knockdown of Chac1 restored the GSH/GSSG ratio, GPX4 expression, and viability in MITOL-knockdown NRVMs. Further, in cultured cardiomyocytes stressed with DOX, both MITOL and GPX4 were reduced, whereas forced-expression of MITOL suppressed DOX-induced ferroptosis by maintaining GPX4 content. Additionally, MITOL knockdown worsened vulnerability to DOX, which was almost completely rescued by treatment with ferrostatin-1, a ferroptosis inhibitor. In vivo, cardiac-specific depletion of MITOL did not produce obvious abnormality, but enhanced susceptibility to DOX toxicity. Finally, administration of ferrostatin-1 suppressed exacerbation of DOX-induced myocardial damage in MITOL-knockout hearts. The present study demonstrates that MITOL determines the cell fate of cardiomyocytes via the ferroptosis process and plays a key role in regulating vulnerability to DOX treatment. (288/300).

Time-Series Transcriptome Analysis Reveals the miR-27a-5p-Ppm1l Axis as a New Pathway Regulating Macrophage Alternative Polarization After Myocardial Infarction

BACKGROUND

Timely differentiation of monocytes into M2-like macrophages is important in the cardiac healing process after myocardial infarction (MI), but molecular mechanisms governing M2-like macrophage differentiation at the transcriptional level after MI have not been fully understood.Methods and Results:A time-series microarray analysis of mRNAs and microRNAs in macrophages isolated from the infarcted myocardium was performed to identify the microRNAs involved in regulating the process of differentiation to M2-like macrophages. Correlation analysis revealed 7 microRNAs showing negative correlations with the progression of polarity changes towards M2-like subsets. Next, correlation coefficients for the changes in expression of mRNAs and miRNAs over time were calculated for all combinations. As a result, miR-27a-5p was extracted as a possible regulator of the largest number of genes in the pathway for the M2-like polarization. By selecting mouse mRNAs and human mRNAs possessing target sequences of miR-27a-5p and showing expression patterns inversely correlated with that of miR-27a-5p, 8 potential targets of miR-27a-5p were identified, includingPpm1l. Using the mouse bone marrow-derived macrophages undergoing differentiation into M2-like subsets by interleukin 4 stimulation, we confirmed that miR-27a-5p suppressed M2-related genes by negatively regulatingPpm1lexpression.

CONCLUSIONS

Ppm1land miR-27a-5p may be the key molecules regulating M2-like polarization, with miR-27a-5p inhibiting the M2-like polarization through downregulation ofPpm1lexpression.

Triple oral combination therapy with macitentan, riociguat, and selexipag for pulmonary arterial hypertension

Background:

The evidence regarding triple oral combination therapy for patients with pulmonary arterial hypertension (PAH) is scarce. This study was performed to investigate the effectiveness and safety of triple oral combination therapy with macitentan, riociguat, and selexipag.

Methods:

Among consecutive patients with PAH who were referred to our hospital from 2009 to 2020, those who underwent triple oral combination therapy using macitentan, riociguat, and selexipag were retrospectively analyzed. Hemodynamic and echocardiographic assessments and Kaplan–Meier analyses of all-cause death and initiation of prostacyclin infusion were conducted.

Results:

Twenty-six patients underwent this combination therapy. These patients were predominantly female (73.1%) with a median age of 38 years at baseline and nine patients were taking some PAH medications at baseline. The median time from initiation of the first PAH drug to the third PAH drug in treatment naïve patients was 24 days (interquartile range, 12–47 days). Four patients (15.0%) discontinued taking any of the three vasodilators because of adverse events, and 17 patients (65.4%) reached the maximum dose of all three drugs. The mean pulmonary arterial pressure, pulmonary vascular resistance, and cardiac output improved by 29%, 65%, and 82%, respectively (median observation period: 441 days) and similar improvements were observed in treatment-naïve patients at baseline. The survival rate and prostacyclin infusion-free rate since administration of all three vasodilators was 93.3% and 74.6% at 3 years, respectively. When patients were divided by risk stratification, the prostacyclin-free rate at 3 years was 92.9% in low-/intermediate-risk patients and 55.0% in high-risk patients.

Conclusion:

Triple oral combination therapy with macitentan, riociguat, and selexipag sufficiently improved clinical parameters and was well tolerated in patients with PAH. This combination could be a particularly promising strategy in patients with low/intermediate risk and possibly even in half of patients with high risk. Further studies are needed to validate these findings.

The reviews of this paper are available via the supplemental material section.

TNFRSF13B c.226G>A (p.Gly76Ser) as a Novel Causative Mutation for Pulmonary Arterial Hypertension

Background

Recently, some studies reported the pulmonary artery hypertension (PAH)–associated genes. However, a majority of patients with familial or sporadic PAH lack variants in the known pathogenic genes. In this study, we investigated the new causative gene variants associated with PAH.

Methods and Results

Whole‐exome sequencing in 242 Japanese patients with familial or sporadic PAH identified a heterozygous substitution change involving c.226G>A (p.Gly76Ser) in tumor necrotic factor receptor superfamily 13B gene (TNFRSF13B) in 6 (2.5%) patients. TNFRSF13B controls the differentiation of B cell and secretion of inflammatory cytokines and may be involved in vascular inflammation. In silico structural analysis simulation demonstrated the structural instability of the N‐terminal region of the protein synthesized from TNFRSF13B p.Gly76Ser variant. These suggest that the TNFRSF13B p.Gly76Ser variant may be involved in the development of PAH via aberrant inflammation in pulmonary vessels.

Conclusions

TNFRSF13B p.Gly76Ser variant is a candidate of novel causative gene variant for PAH.

Clinical Significance of Guanylate Cyclase Stimulator, Riociguat, on Right Ventricular Functional Improvement in Patients with Pulmonary Hypertension

BACKGROUND

Riociguat is a soluble guanylate cyclase stimulator that improves hemodynamics in patients with pulmonary hypertension (PH). Accumulating evidence implicates the additional effect of riociguat on the increase in cardiac output. However, its mechanisms have not been fully understood. This study aimed to investigate whether riociguat could ameliorate right ventricular (RV) contraction as well as hemodynamics.

METHODS

We studied 45 patients with pulmonary arterial hypertension (14) or chronic thromboembolic pulmonary hypertension (31) and evaluated hemodynamics, using right-sided heart catheterization, before and after the administration of riociguat. RV function was assessed by echocardiography, including speckle-tracking echocardiography.

RESULTS

Riociguat significantly improved the WHO functional class and reduced the mean pulmonary arterial pressure and vascular resistance. In addition, the cardiac index increased. RV remodeling was ameliorated after riociguat administration as assessed by the echocardiographic parameters, such as RV diameter and RV area index. RV function, including RV fractional area change and RV global longitudinal strain, also significantly improved, and their improvement was even observed in patients with mild PH after pulmonary endarterectomy or balloon pulmonary angioplasty. Furthermore, covariance analysis revealed that RV global longitudinal strain and RV fractional area change improved after riociguat administration, even with the same mean pulmonary arterial pressure, implicating the improvement of RV contractile function by riociguat, regardless of RV loading.

CONCLUSIONS

Riociguat not only improved the hemodynamics of patients with PH but also ameliorated the echocardiographic parameters with RV function. RV strain could detect the subtle improvement in mild PH, and riociguat may have a benefit even after intervention, as assessed by speckle-tracking echocardiography.

Regional Right Ventricular Abnormalities Implicate Distinct Pathophysiological Conditions in Patients With Chronic Thromboembolic Pulmonary Hypertension

Background

Right ventricular (RV) dysfunction is a prognostic factor for cardiovascular disease. However, its mechanism and pathophysiology remain unknown. We investigated RV function using RV‐specific 3‐dimensional (3D)‐speckle‐tracking echocardiography (STE) in patients with chronic thromboembolic pulmonary hypertension. We also assessed regional wall motion abnormalities in the RV and chronological changes during balloon pulmonary angioplasty (BPA).

Methods and Results

Twenty‐nine patients with chronic thromboembolic pulmonary hypertension who underwent BPA were enrolled and underwent right heart catheterization and echocardiography before, immediately after, and 6 months after BPA. Echocardiographic assessment of RV function included both 2‐dimensional‐STE and RV‐specific 3D‐STE. Before BPA, global area change ratio measured by 3D‐STE was significantly associated with invasively measured mean pulmonary artery pressure and pulmonary vascular resistance (r=0.671 and r=0.700, respectively). Dividing the RV into the inlet, apex, and outlet, inlet area change ratio showed strong correlation with mean pulmonary artery pressure and pulmonary vascular resistance before BPA (r=0.573 and r=0.666, respectively). Only outlet area change ratio was significantly correlated with troponin T values at 6 months after BPA (r=0.470), and its improvement after BPA was delayed compared with the inlet and apex regions. Patients with poor outlet area change ratio were associated with a delay in RV reverse remodeling after treatment.

Conclusions

RV‐specific 3D‐STE analysis revealed that 3D RV parameters were novel useful indicators for assessing RV function and hemodynamics in pulmonary hypertension and that each regional RV portion presents a unique response to hemodynamic changes during treatment, implicating that evaluation of RV regional functions might lead to a new guide for treatment strategies.

Efficacy and outcomes of balloon pulmonary angioplasty in elderly vs non-elderly chronic thromboembolic pulmonary hypertension patients

Introduction

Balloon pulmonary angioplasty (BPA) has been reported as an effective and safe treatment for patients with chronic thromboembolic pulmonary hypertension (CTEPH). However, its safety and efficacy in elderly patients remains unknown.

Purpose

We investigated the effect of BPA on hemodynamics and respiratory parameters, functional capacity, and short- and long-term outcome in elderly patients.

Methods

From November 2012 to May 2018, 141 consecutive CTEPH patients who underwent BPA in a single university hospital were enrolled (age: 65 [54.5–74] years old, WHO functional class [WHO-FC] II/III/IV; 35/96/10). Patients were divided into two groups according to the age; elderly (≥75 years, N=32) and young groups (&lt;75 years, N=109). Hemodynamics (right-sided heart catheterization), biomarkers (brain natriuretic peptide), respiratory function (spirometry and diffusion capacity measurement), and functional capacity (6-minute walk distance [6MWD] and WHO-FC) were evaluated at baseline and 1-year post BPA. Procedure-related complications (in hospital death, use of percutaneous cardiopulmonary support [PCPS], and pulmonary injury) and all cause death during the follow up period were also assessed.

Results

At baseline, although elderly group had less severe hemodynamics (mPAP: 33.1±6.7 vs 39.0±11.8 mmHg, p&lt;0.05), they had poor exercise capacity and reduced pulmonary diffusion capacity, compared with young group (6MWD: 264.6±101.3 vs 369.7±105.2 m, %DLco: 42.0±12.0 vs 50.2±12.7%, all p&lt;0.05). BPA improved hemodynamics, biomarkers, exercise capacity, and pulmonary diffusion capacity in both elderly and young groups (all p&lt;0.05). There was no in-hospital death or use of PCPS in both groups, although the incidence of pulmonary injury was higher in elderly group (14.3% vs 5.3%, p&lt;0.01). Under the normalized hemodynamics 1-year after BPA in both groups, exercise capacity and pulmonary diffusion capacity were worse in the elderly group than young groups (p&lt;0.01). The incidence of all-cause death in the follow up period was higher in elderly group, all of which were due to non-pulmonary hypertension (PH)-related death (p&lt;0.01).

Conclusion

BPA was effective in improving hemodynamics and respiratory parameters and functional capacity, in associated with no critical complication, regardless of the age. Elderly patients who were treated with BPA were associated with higher incidence of non-PH-related death.

Changes of mean PAP in the two groups

Funding Acknowledgement

Type of funding source: None

A novel causative gene variant, TNFRSF13B p.Gly76Ser, in patients with pulmonary arterial hypertension

Background

Pulmonary artery hypertension (PAH) is a poor prognostic disease. Some causative genes were reported as the PAH-associated genes. However, the pathogenetic variants in PAH-associated genes have not been identified in majority of patients with idiopathic PAH.

Purpose

Our aim was to investigate the new causative gene variants associated with PAH.

Methods

We performed whole-exome sequencing in 272 patients with idiopathic/heritable PAH. Structural analysis simulation was performed to define how the candidate gene variant affected the structure of protein.

Results

We identified the heterozygous substitution change of c.226G&gt;A (p.Gly76Ser, rs146436713) in tumor necrotic factor receptor superfamily 13B gene (TNFRSF13B) (NM_012452.2) in 6 (2.2%) patients with idiopathic/heritable PAH, although the allele frequency of this rare variant is 0% in Integrative Japanese Genome Variation Database (control population database). Two of the six cases were blood relatives, although they did not have the known causative gene variants of PAH. One of these two relatives died of right heart failure despite the combination medical therapy, and her pathological anatomy demonstrated intimal thickening and medial hypertrophy in the pulmonary arteries, formation of plexiform lesions (Heath-Edwards classification grade V). Time-lapse images from structural analysis simulation showed the instability of N-terminal in the protein, which regulates the vascular inflammation, synthesized from TNFRSF13B p.Gly76Ser variant (Figure), suggesting that p.Gly76Ser variant may be involved in the development of PAH via aberrant inflammation in pulmonary vessels.

Conclusions

TNFRSF13B p.Gly76Ser variant is a candidate of causative gene variant for PAH.

Structural analysis of proteins

Funding Acknowledgement

Type of funding source: None

De-escalation/discontinuation of oxygen-therapy and medication is feasible and safe in chronic thromboembolic pulmonary hypertension patients treated with balloon pulmonary angioplasty

Introduction

There has been increasing evidence of the efficacy of balloon pulmonary angioplasty (BPA) in improving the hemodynamics, exercise capacity, and biomarkers of patients with chronic thromboembolic pulmonary hypertension (CTEPH). However, there is no consensus on the adjustment of home oxygen therapy (HOT) and pulmonary hypertension (PH)-specific medications after BPA in patients with CTEPH.

Purpose

We aimed to examine the current status of the de-escalation/discontinuation of HOT and PH-specific medications post-BPA, and clarify its effect on subsequent hemodynamics, biomarkers, and long-term clinical outcomes.

Methods and results

From November 2012 to July 2019, 134 consecutive CTEPH patients who underwent BPA at a single university hospital were enrolled (age; 63.6±13.4 years, female; n=87 [64.9%], WHO functional class [WHO-FC] II/III/IV; 33/92/9). Hemodynamic data, functional capacity (6-minute walk distance and WHO-FC), biomarkers (brain natriuretic peptide [BNP] and high-sensitivity troponin T [hs-TropT]), and respiratory function were evaluated at baseline, immediately and 1 year post-BPA. Clinical outcomes (all-cause death and heart failure [HF] admission) were also assessed during the follow up period. The total number of sessions was 6.3±2.0, and the number of target vessels was 14.3±2.0. Mean pulmonary arterial pressure decreased from 37.8±11.2 to 20.4±5.1 mmHg 1-year after BPA (p&lt;0.01). The proportion of patients who required HOT (at rest or on exertion) and combination medical therapy (≥2 PH-specific medications) decreased 1 year post-BPA (from 59.0% to 7.5%, and from 41.8% to 10.4%, respectively; Figure). Among 79 patients who required HOT during daytime, 64 patients (81.0%) discontinued HOT just after BPA completion. Among 56 patients who required combination medical therapy, 29 (51.8%) discontinued combination therapy. Baseline factors influencing the continuation of HOT and combination medical therapy post-BPA were almost identical (i.e. lower exercise capacity and pulmonary diffusion capacity, and worse hemodynamics). Results showed that discontinuation of HOT and combination medical therapy did not affect the maintenance of improved hemodynamics and levels of BNP and hs-TropT, and no adverse clinical outcomes (all-cause death and HF hospitalization) were observed during 1 year post-BPA.

Conclusions

Most CTEPH patients discontinued HOT and PH-specific combination medical therapy after BPA, which was not associated with the deterioration of hemodynamics, functional capacity, or biomarkers. No adverse long-term outcomes were observed. De-escalation/discontinuation of HOT and PH-specific combination medical therapy after BPA is feasible and safe for patients with CTEPH.

De-escalation of HOT and medical therapy

Funding Acknowledgement

Type of funding source: None

MerTK Expression and ERK Activation Are Essential for the Functional Maturation of Osteopontin-Producing Reparative Macrophages After Myocardial Infarction

Background We previously reported that osteopontin plays an essential role in accelerating both reparative fibrosis and clearance of dead cells (efferocytosis) during tissue repair after myocardial infarction (MI) and galectin-3^hiCD206⁺ macrophages is the main source of osteopontin in post-MI heart. Interleukin-10- STAT3 (signal transducer and activator of transcription 3)-galectin-3 axis is essential for Spp1 (encoding osteopontin) transcriptional activation in cardiac macrophages after MI. Here, we investigated the more detailed mechanism responsible for functional maturation of osteopontin-producing macrophages. Methods and Results In post-MI hearts, Spp1 transcriptional activation occurred almost exclusively in MerTK (Mer tyrosine kinase)⁺ galectin-3^hi macrophages. The induction of MerTK on galectin-3^hi macrophages is essential for their functional maturation including efferocytosis and Spp1 transcriptional activity. MerTK⁺galectin-3^hi macrophages showed a strong activation of both STAT3 and ERK (extracellular signal-regulated kinase). STAT3 inhibition suppressed the differentiation of osteopontin-producing MerTK⁺galectin-3^hi macrophages, however, STAT3 activation was insufficient at inducing Spp1 transcriptional activity. ERK inhibition suppressed Spp1 transcriptional activation without affecting MerTK or galectin-3 expression. Concomitant activation of ERK is required for transcriptional activation of Spp1. In Il-10 knockout enhanced green fluorescent protein-Spp1 knock-in mice subjected to MI, osteopontin-producing macrophages decreased but did not disappear entirely. Interleukin-10 and macrophage colony-stimulating factor synergistically activated STAT3 and ERK and promoted the differentiation of osteopontin-producing MerTK⁺galectin-3^hi macrophages in bone marrow-derived macrophages. Coadministration of anti-interleukin-10 plus anti-macrophage colony-stimulating factor antibodies substantially reduced the number of osteopontin-producing macrophages by more than anti-interleukin-10 antibody alone in post-MI hearts. Conclusions Interleukin-10 and macrophage colony-stimulating factor act synergistically to activate STAT3 and ERK in cardiac macrophages, which in turn upregulate the expression of galectin-3 and MerTK, leading to the functional maturation of osteopontin-producing macrophages.

Pharmacokinetics of a single inhalation of hydrogen gas in pigs

The benefits of inhaling hydrogen gas (H2) have been widely reported but its pharmacokinetics have not yet been sufficiently analyzed. We developed a new experimental system in pigs to closely evaluate the process by which H2 is absorbed in the lungs, enters the bloodstream, and is distributed, metabolized, and excreted. We inserted and secured catheters into the carotid artery (CA), portal vein (PV), and supra-hepatic inferior vena cava (IVC) to allow repeated blood sampling and performed bilateral thoracotomy to collapse the lungs. Then, using a hydrogen-absorbing alloy canister, we filled the lungs to the maximum inspiratory level with 100% H2. The pig was maintained for 30 seconds without resuming breathing, as if they were holding their breath. We collected blood from the three intravascular catheters after 0, 3, 10, 30, and 60 minutes and measured H2 concentration by gas chromatography. H2 concentration in the CA peaked immediately after breath holding; 3 min later, it dropped to 1/40 of the peak value. Peak H2 concentrations in the PV and IVC were 40% and 14% of that in the CA, respectively. However, H2 concentration decay in the PV and IVC (half-life: 310 s and 350 s, respectively) was slower than in the CA (half-life: 92 s). At 10 min, H2 concentration was significantly higher in venous blood than in arterial blood. At 60 min, H2 was detected in the portal blood at a concentration of 6.9-53 nL/mL higher than at steady state, and in the SVC 14-29 nL/mL higher than at steady state. In contrast, H2 concentration in the CA decreased to steady state levels. This is the first report showing that inhaled H2 is transported to the whole body by advection diffusion and metabolized dynamically.

P6009Poor outcomes in pulmonary arterial hypertension as a member of RNF213-associated vascular diseases

Background

A variant of c.14429G>A (p.Arg4810Lys, rs112735431) in the ring finger protein 213 gene (RNF213; NM_001256071.2) has been recently identified as a risk allele for pulmonary arterial hypertension (PAH), suggesting that PAH can be added as a new member of RNF213-associated vascular diseases including Moyamoya disease and peripheral pulmonary stenosis.

Purpose

Our aim was to identify the clinical features and outcomes of PAH patients with RNF213 p.Arg4810Lys variant.

Methods

Whole-exome sequencing was performed in 139 idiopathic (or possibly heritable) PAH patients. Hemodynamics and prognosis were evaluated in the patients with RNF213 p.Arg4810Lys variant and the patients with bone morphogenic protein receptor type 2 (BMPR2) mutations.

Results

The RNF213 p.Arg4810Lys variant was identified in a heterozygous state in 11 patients (7.9%). Time-course changes in hemodynamics after combination therapy in the patients with the RNF213 p.Arg4810Lys variant were significantly poorer compared with those in BMPR2 mutation carriers (n=36) (comparison of changes in mean pulmonary arterial pressure, P=0.007). The event-free rate of death or lung transplantation was significantly poorer in RNF213 p.Arg4810Lys variant carriers than in BMPR2 mutation carriers (5-year event-free rate since the introduction of prostaglandin I2 infusion, 0% vs. 93%, P<0.001) (Figure).

Time to death or lung transplantation

Conclusions

PAH patients with the RNF213 p.Arg4810Lys variant were associated with a poor reactivity to vasodilator drugs and poor clinical outcomes even in the recent era. Earlier consideration of lung transplantation might be required for RNF213 p.Arg4810Lys variant carriers developing PAH. Documentation of the RNF213 p.Arg4810Lys variant, as well as already known pathogenic genes, can provide clinically relevant information for therapeutic strategies, leading to a personalized approach for the treatment of PAH.

IL (Interleukin)-10-STAT3-Galectin-3 Axis Is Essential for Osteopontin-Producing Reparative Macrophage Polarization After Myocardial Infarction

BACKGROUND

Both osteopontin (OPN) and galectin-3 have been implicated in phagocytic clearance of dead cells and reparative fibrosis during wound healing. CD206⁺ macrophages are involved in tissue repair through phagocytosis and fibrosis after myocardial infarction (MI). However, the relationship among OPN, galectin-3, and macrophage polarization in the context of MI remains unclear.

METHODS

The time course of Spp1 (encoding OPN) expression in the heart after MI showed a strong activation of Spp1 on day 3 after MI. To identify where in the body and in which cells the transcriptional activity of Spp1 increased after MI, we analyzed EGFP (enhanced green fluorescent protein)- Spp1 knockin reporter mice on day 3 after MI.

RESULTS

The transcriptional activity of Spp1 increased only in CD206⁺ macrophages in the infarct myocardium, and most of CD206⁺ macrophages have strong transcriptional activation of Spp1 after MI. The temporal expression pattern of Lgal3 (encoding galectin-3) in cardiac macrophages after MI was similar to that of Spp1, and OPN is almost exclusively produced by galectin-3^hiCD206⁺ macrophages. Although both interleukin (IL)-4 and IL-10 were reported to promote CD206⁺ macrophage-mediated cardiac repair after MI, IL-10- but not IL-4-stimulated CD11b⁺Ly6G^- cells could differentiate into OPN-producing galectin-3^hiCD206⁺ macrophages and showed enhanced phagocytic ability. Inhibition of STAT3 tyrosine phosphorylation suppressed IL-10-induced expression of intracellular galectin-3 and transcriptional activation of Spp1. Knockdown of galectin-3 suppressed their ability to differentiate into OPN-producing cells, but not STAT3 activation. The tyrosine phosphorylation of STAT3 and the appearance rate of galectin-3^hiCD206⁺ cells on cardiac CD11b⁺Ly6G^- cells in Spp1 knockout mice were the same as those in wild-type mice. Spp1 knockout mice showed vulnerability to developing post-MI left ventricular chamber dilatation and the terminal deoxynucleo-tidyltransferase 2'-Deoxyuridine-5'-triphosphate nick-end labeling (TUNEL)-positive cells in the infarcted myocardium after MI remained higher in number in Spp1 knockout mice than in wild-type mice.

CONCLUSIONS

OPN is almost exclusively produced by galectin-3^hiCD206⁺ macrophages, which specifically appear in the infarct myocardium after MI. The IL-10-STAT3-galectin-3 axis is essential for OPN-producing reparative macrophage polarization after myocardial infarction, and these macrophages contribute to tissue repair by promoting fibrosis and clearance of apoptotic cells. These results suggest that galectin-3 may contribute to reparative fibrosis in the infarct myocardium by controlling OPN levels.

Poor outcomes in carriers of the RNF213 variant (p.Arg4810Lys) with pulmonary arterial hypertension

BACKGROUND

A variant of c.14429G>A (p.Arg4810Lys, rs112735431) in the ring finger protein 213 gene (RNF213; NM_001256071.2) has been recently identified as a risk allele for pulmonary arterial hypertension (PAH). PAH can be added as a new member of RNF213-associated vascular diseases, which include Moyamoya disease and peripheral pulmonary stenosis. Our aim was to identify the clinical features and outcomes of PAH patients with this variant.

METHODS

Whole-exome sequencing was performed in 139 idiopathic (or possibly heritable) PAH patients.

RESULTS

The RNF213 p.Arg4810Lys variant was identified in a heterozygous state in 11 patients (7.9%). Time-course changes in hemodynamics after combination therapy in the patients with the RNF213 p.Arg4810Lys variant were significantly poorer compared with those carrying the bone morphogenic protein receptor type 2 (BMPR2) mutation (n = 36) (comparison of changes in mean pulmonary arterial pressure, p = 0.007). The event-free rate of death or lung transplantation was significantly poorer in RNF213 p.Arg4810Lys variant carriers than in BMPR2 mutation carriers (5-year event-free rate since the introduction of prostaglandin I₂ infusion, 0% vs 93%, respectively; p < 0.001).

CONCLUSIONS

Idiopathic PAH patients with the RNF213 p.Arg4810Lys variant are associated with poor clinical outcomes even in recent times. Earlier consideration of lung transplantation might be required for RNF213 p.Arg4810Lys variant carriers who are developing PAH. Documentation of the RNF213 p.Arg4810Lys variant, as well as already known pathogenic genes, such as BMPR2, can provide clinically relevant information for therapeutic strategies, leading to a personalized approach for the treatment of PAH.

Abstract 873: Acetate Protects the Heart Against Ischemic Injury by Alternating TCA Cycle-related Metabolites and AMP-activated Protein Kinase

Introduction: Acetate is preferentially taken up in the heart, and converted into acetyl-CoA by acetyl-CoA synthetase2 (AceCS2), which is abundant in the mitochondria of cardiomyocytes, resulting in activation of AMPK through an elevation of AMP/ATP ratio. In this context, we investigated the effects of acetate on myocardial ischemic injury in isolated cardiomyocytes and in vivo mouse hearts.

Methods and Results: In isolated cardiomyocytes, 13 C-labelled metabolites were analyzed using capillary electrophoresis-electrospray ionization mass spectroscopy (CE-ESI-MS) in order to determine the fate of exogenously administered 13 C-acetate. The oxygen consumption rate (OCR) was evaluated using a flux analyzer. A variety of 13 C-labelled intermediates in the TCA cycle increased 10 minutes after administration of 13 C-acetate followed by a subsequent increase in OCR. The OCR elevation was sustained more than 2 hours after acetate injection. The acetate-induced OCR elevation was partially blocked by the glycolysis inhibitor 2-Deoxyglucose (2-DG), carnitine palmitoyl transferase1A (CPT-1A) inhibitor (etomoxir), and mitochondrial pyruvate carrier (MPC) inhibitor (UK5099). The acetate-induced OCR elevation was also blocked by AMP-activated protein kinase (AMPK) inhibitor (compound C). These findings indicated that acetate caused an elevation in mitochondrial function through activation of various metabolic pathways, which may be related to activation of the AMPK pathway. Next, left anterior descending artery-ligated hearts were processed with focused microwave and analyzed by CE-MS and matrix-assisted laser desorption/ionization imaging mass spectrometry in order to examine the region-specific metabolite changes at the early phase of ischemia. Nicotinamide adenine dinucleotide (NADH) elevation in the ischemic core region was suppressed by acetate administration. Furthermore, acetate inhibited cardiac remodeling in a protective manner several weeks after myocardial ischemia when viewed by cardiac ultrasound.

Conclusion: Acetate caused an increase in OCR via both a significant elevation in TCA cycle metabolites and activation of AMPK pathway, and may have a protective effect on myocardial ischemic injury.

Abstract 640: Indigo Naturalis, a Promising Herbal Medicine for Ulcerative Colitis, Can Induce Experimental Pulmonary Arterial Hypertension via Aryl Hydrocarbon Pathway

Background: Indigo naturalis is a Chinese herbal medicine, whose dramatical effects for treatment of ulcerative colitis have been reported. However, some patients who took indigo naturalis developed pulmonary arterial hypertension (PAH), which is a poor prognostic disease with right ventricular (RV) failure and progressive remodeling of pulmonary vessels.

Aims: We examined the reproducibility in experimental animals and elucidate the mechanisms for indigo naturalis to induce PAH.

Methods and Results: Rats with 12-week intake of low-dose indigo naturalis (60 mg/kg body weight; corresponding to therapeutic dose for patients) did not induce PAH. However, RV and pulmonary vessel remodeling were identified in rats fed with high-dose indigo naturalis (600 mg/kg body weight) for 12 weeks. Significantly elevated RV systolic pressure was identified in rats administered with vascular endothelial growth factor-2 receptor blocker (Sugen 5416) and fed with indigo naturalis for 8 weeks compared to that of rats fed with normal diet (38.6 [38.2, 40.0] mmHg) vs. 31.9 [31.4, 34.6] mmHg, p < 0.001). Indigo, a major compound of indigo naturalis, also induced mild PAH. Indigo works as a ligand of aryl hydrocarbon receptor (AhR), and the mRNA levels of CYP1A1, downstream of AhR signal, were elevated in lungs. Rats with indigo naturalis and AhR antagonist gavage developed less pulmonary vessel remodeling than rats without AhR antagonist.

Conclusions: The combination of Sugen 5416 and indigo naturalis can be a novel unique approach to generate rat PAH model without a hypoxic chamber. The effects of indigo naturalis to PAH might be mediated at least in part through activation of AhR-CYP1A1 pathway.

Impact of catheter-induced iatrogenic coronary artery dissection with or without postprocedural flow impairment: A report from a Japanese multicenter percutaneous coronary intervention registry

Despite the ever-increasing complexity of percutaneous coronary intervention (PCI), the incidence, predictors, and in-hospital outcomes of catheter-induced coronary artery dissection (CICAD) is not well defined. In addition, there are little data on whether persistent coronary flow impairment after CICAD will affect clinical outcomes. We evaluated 17,225 patients from 15 participating hospitals within the Japanese PCI registry from January 2008 to March 2016. Associations between CICAD and in-hospital adverse cardiovascular events were evaluated using multivariate logistic regression. Outcomes of patients with CICAD with or without postprocedural flow impairment (TIMI flow ≤ 2 or 3, respectively) were analyzed. The population was predominantly male (79.4%; mean age, 68.2 ± 11.0 years); 35.6% underwent PCI for complex lesions (eg. chronic total occlusion or a bifurcation lesion.). CICAD occurred in 185 (1.1%), and its incidence gradually decreased (p < 0.001 for trend); postprocedural flow impairment was observed in 43 (23.2%). Female sex, complex PCI, and target lesion in proximal vessel were independent predictors (odds ratio [OR], 2.18; 95% confidence interval [CI], 1.53–3.10; OR, 2.19; 95% CI, 1.58–3.04; and OR, 1.55; 95% CI, 1.06–2.28, respectively). CICAD was associated with an increased risk of in-hospital adverse events (composite of new-onset cardiogenic shock and new-onset heart failure) regardless of postprocedural flow impairment (OR, 10.9; 95% CI, 5.30–22.6 and OR, 2.27; 95% CI, 1.20–4.27, respectively for flow-impaired and flow-recovered CICAD). In conclusion, CICAD occurred in roughly 1% of PCI cases; female sex, complex PCI, and proximal lesion were its independent risk factors. CICAD was associated with adverse in-hospital cardiovascular events regardless of final flow status. Our data implied that the appropriate selection of PCI was necessary for women with complex lesions.

The clinical value of assessing right ventricular diastolic function after balloon pulmonary angioplasty in patients with chronic thromboembolic pulmonary hypertension

Chronic thromboembolic pulmonary hypertension (CTEPH) has a poor prognosis because of the associated progressive right heart failure. Accurate evaluation of right ventricular (RV) function would thus be useful to predict prognosis. However, the significance of RV diastolic function remains unclear. We aimed to identify which echocardiographic measures are most accurate, and potentially useful, in assessing RV diastolic function in patients with CTEPH, and to study the effects of balloon pulmonary angioplasty (BPA) on them. We enrolled 53 CTEPH patients who underwent BPA. Echocardiographic parameters, including two-dimensional speckle-tracking echocardiography, were compared to the hemodynamic parameters measured by right heart catheterization before and after BPA. RV strain rate during early diastole (SR_E), tricuspid e' and right atrial area (RAA) were ameliorated after BPA, concomitant with a decrease in the time constant of the RV pressure curve during diastole (tau), indicating the improvement of RV diastolic function. Among them, SR_E had the strongest correlation with tau (r = - 0.39, p < 0.001). Furthermore, the receiver operating characteristic analyses revealed that E/SR_E (AUC 0.704) and inferior vena cava diameter (AUC 0.726) had a stronger association with higher mean right atrial pressure than RAA (AUC 0.632). In contrast, RAA had a stronger correlation with 6 min-walk distances than SR_E (r = - 0.39, p < 0.001 vs. r = 0.30, p = 0.005). Taken together, echocardiographic assessment of RV diastolic function might be associated with hemodynamics as well as exercise tolerance in patients with CTEPH, indicating its benefits in evaluating the therapeutic effects of BPA.

Possible Involvement of Hypotension in Postprandial Headache: A Case Series

BACKGROUND

It is commonly known that headaches are induced by intake of specific food, drink, and/or additive. In addition, some patients experience postprandial headache independent of ingestion of specific items. Currently, information on the pathophysiology underlying this particular type of headache is scarce.

CASE REPORTS

We report two cases in which headaches were observed after each meal. Postprandial hypotension was demonstrated in both cases. Tonometry-based continuous blood pressure measurement during head-up tilt revealed sympathetic dysfunction. In one patient, meta-iodobenzylguanidine (MIBG) myocardial scintigraphy detected cardiac sympathetic denervation, and diagnosis of pure autonomic failure was made. In both cases, treatment of postprandial hypotension was effective in relieving postprandial headache.

DISCUSSION

The possibility of postprandial hypotension should be explored in patients with headache that occurs after meal. To this end, tonometry-based blood pressure measurement and MIBG myocardial scintigraphy may be useful diagnostic investigations. Treating postprandial hypotension may be effective in alleviating the symptoms.

Durability of Flexible Molded Polyurethane Foams

In recent years, we have developed highly resilient (HR) flexible molded foams with superb durability, resilience and vibration characteristics, and we have reported that these improvements were based on control of cross link degree of polymer, morphology and mobility of hard and soft segments. This paper describes factors that dominantly influence the durability and the mechanism of fatigue by investigation of cross linking by covalent and hydrogen-bonds and the morphology of hard/soft segments. In this study, we use molded foams with different durabilities. These are TDI-based high performance/conventional HR, MDI-based high-performance/conventional HR, and hot molded foams.

On the whole, a small apparent viscosity coefficient, which is calculated from vibration characteristics of the foam, and a higher cross link degree of foam polymer make static and dynamic durability of flexible molded foam better. Mobility of the soft segment, estimated by solid state NMR, also dominates dynamic durability. Accordingly, hydrogen-bonds of the hard segment contribute against creep as a cross link point in static/dynamic durability test, and tight hydrogen-bonds of hot molded foam are durable against rupture or rebonding by water molecules in the wet compression set oven.

The drop in cross link degree of foam polymer was not observed during vibration durability test. Accordingly, the mechanism of fatigue could be the change of state in hydrogen-bonds or tangling of polymer-chains, or relatively macro rupture.

A 12 month in vivo study on the response of bone to a hydroxyapatite–polymethylmethacrylate cranioplasty composite

We investigated the osteoconductivity and biocompatibility in vivo of a new hydroxyapatite-polymethylmethacrylate (HA-PMMA) composite developed for use as an implant material for cranioplasty, which is expected to have the good osteoconductivity of HA together with the strength and ease of handling of PMMA. The HA-PMMA composites were implanted in eight full-grown beagles and then 6, 12, 24 weeks and 1 year after implantation, the animals were sacrificed and the implanted materials removed along with the surrounding tissues. Extirpated specimens were studied using an optical microscope and micro-computed tomography (micro-CT). Fibrous connective tissue was prominent in the interface of the composite at 6 weeks. New bone formation was seen around the implant, 12 and 24 weeks after operation. At 1 year, new bone filled in the interface of the HA-PMMA composite and adhered to the surrounding autogenous bone. Mixing HA and PMMA did not interfere with the osteoconductivity of the HA component. In micro-CT findings, the new bone growing on the HA-PMMA composite could be seen attaching preferentially to HA particles exposed at the composite surface, rather than the PMMA. This study demonstrated that this HA-PMMA composite is a good candidate for cranial bone implants due to its good osteoconductivity and biocompatibility.

Adenosine receptor antagonists cancelled the ischemic tolerance phenomenon in gerbil

Pretreatment of the brain with sublethal ischemia has been reported to induce neuronal resistance to otherwise lethal ischemia, a phenomenon designated as ischemic tolerance. The protective mechanisms of the phenomenon are not known yet, however, recent experimental data suggest the involvement of adenosine receptor activation in the acquisition of tolerance. In this study, the effect of theophylline, a non-selective adenosine receptor antagonist, and 8-cyclopentyl-1,3-dipropylxanthine (DPCPX), an adenosine A1 receptor antagonist, were investigated to ascertain if these drugs could cancel the protective effect of ischemic tolerance in the gerbil. DPCPX or theophylline was administered at 3 h after a short preconditioning ischemia, and 21 h later animals were subjected to lethal ischemia of 5 min duration. DPCPX at a dose of 1.0 mg/kg (i.p) and theophylline at a dose of 20 mg/kg (i.p) significantly reduced the protective effect of preconditioning in the CA1 hippocampal neurons. These findings suggest the involvement of adenosine receptor activation for the development of ischemic tolerance phenomenon.

Chromatographic separation of a small subunit (PsbW/PsaY) and its assignment to Photosystem I reaction center

By using a hydroxyapatite column, the five major Photosystem I (PSI) subunits (PsaA,-B,-C,-D,-E) solubilized by sodium dodecyl sulfate (SDS) were fractionated from a spinach PSI reaction center preparation. Another small (5-6 kDa) polypeptide was also separated, and purified to homogeneity. Mass spectroscopy yielded its molecular weight to be 5942 +/- 10. This polypeptide had an N-terminal sequence homologous to those of previously reported 5-kDa subunits from spinach and wheat and a 6.1-kDa subunit of Chlamydomonas, which had all been assigned to Photosystem II (PSII) and designated as PsbW. However, we found similar 5-kDa polypeptides with highly conserved N-terminal sequences ubiquitously in PSI particles from other plants including Daikon (Raphanus sativus, Japanese radish), Chingensai (Brassica parachinensis, Chinese cabbage), parsley and Shungiku (Chrysanthemum coronarium, Garland chrysanthemum) as well. Preparations of spinach PSI particles prepared by using a mild detergent (digitonin) had this 5-kDa subunit, while PSII particles did not. Moreover, a bare-bone PSI reaction center preparation consisting of PsaA/B alone had a more than stoichiometric amount of this 5-kDa polypeptide. A mechanically (without detergent) fractionated stroma thylakoid preparation from Phytolacca americana, which lacked other PSII subunits, also contained this 5-kDa subunit. Thus, we propose that this 5-kDa polypeptide, previously designated as a PSII subunit (PsbW), is an integral subunit of PSI as well.

Cellular roles in relapse processes of experimentally-moved rat molars

This histological study was designed to clarify the relapse processes of rat molars following orthodontic tooth movement by the Waldo method. An elastic band was inserted between the upper first and second molars, and removed either 7 or 21 days later. The relapse processes of first molars were examined at 1 or 4 days after completing the 7-day-insertion and at 5 or 10 days after the end of the 21-day-insertion. At the end of the 7-day-insertion period, the mean interdental space was 158 microns, but decreased rapidly, reaching 44 microns by 1 day after removal, and 16 microns by day 4. In the periodontal ligament (PDL) compressed by elastic band insertion, partial hyalinization and/or mineralization occurred. The stretched PDL consisted of irregularly-distributed, thin principal fibres, approximately 2.4 microns in diameter. On days 1 and 4 after removal, osteoclasts, macrophage-like cells and fibroblast-like cells were localized around hyalinized tissues, but thick principal fibres, approximately 3.8 microns in diameter, were regularly distributed throughout the PDL proper. The mean interdental space after the 21-day-insertion was 536 microns, but this had decreased to 108 microns by day 5, and 71 microns by day 10. On day 5 after removal, numerous osteoclasts were evenly distributed in the compressed PDL, while thick principal fibres, approximately 3.5 microns, were present in the stretched PDL. These results suggest that, during relapse of experimentally-moved rat molars, (i) rapid remodelling of the PDL and surrounding alveolar bones is the main cause of tooth relapse and (ii) hyalinized and/or mineralized tissues occurred by compression are rapidly resorbed by osteoclasts, macrophage-like cells and fibroblast-like cells.

Persistent primitive hypoglossal artery complicated by atrial septal defect and congenital intrahepatic shunts

During early embryogenesis, anastomoses are formed between the carotid artery and the basilar or the vertebral artery, and subsequently, these anastomoses regress. In some cases, these anastomoses remain as persistent carotid-basilar or carotid-vertebral anastomoses. Atrial septal defect (ASD), a communication between the atria at the septal level, is a congenital heart anomaly. Intrahepatic venous shunts between the portal and hepatic veins are very rare and only some are considered congenital. We present the first case report of a patient with an ASD, a persistent primitive hypoglossal artery, and congenital portahepatic shunts.

Activation of cytosolic phospholipase A2 by platelet-derived growth factor is essential for cyclooxygenase-2-dependent prostaglandin E2 synthesis in mouse osteoblasts cultured with interleukin-1

The synthesis of prostaglandins (PGs) is regulated by the arachidonic acid release by phospholipase A2 (PLA2) and its conversion to PGs by cyclooxygenase (COX). In the present study, we examined the regulation of PG synthesis by interleukin (IL)-1alpha in primary mouse osteoblastic cells isolated from mouse calvaria. Although IL-1alpha greatly enhanced cox-2 mRNA expression and its protein levels, PGE2 was not produced until 24 h. When arachidonic acid was added to osteoblastic cells precultured with IL-1alpha for 24 h, PGE2 was produced within 10 min. Of several growth factors tested, platelet-derived growth factor (PDGF) specifically initiated the rapid synthesis of PGE2, which was markedly suppressed by a selective inhibitor of cox-2 (NS-398). In mouse osteoblastic cells, cytosolic PLA2 (cPLA2) mRNA and its protein were constitutively expressed and increased approximately 2-fold by IL-1alpha, but secretory PLA2 mRNA was not detected. PDGF rapidly stimulated PLA2 activity, which was blocked completely by a cPLA2 inhibitor (arachidonyltrifluoromethyl ketone). The PDGF-induced cPLA2 activation was accompanied by phosphorylation of its protein. These results indicate that cox-2 induction by IL-1alpha is not sufficient, but cPLA2 activation by PDGF is crucial for IL-1alpha-induced PGE2 synthesis in mouse osteoblasts.

Expression of c-fos-like protein in the rat brain after injection of interleukin-1-beta into the gingiva

Expression of the c-fos proto-oncogene in the rat brain was examined by immunostaining for fos, the nuclear protein product of the c-fos gene, after injection of interleukin-1-beta (IL-1 beta) into the gingiva of an incisor. The distribution pattern of labelled cells was compared with that induced by tooth pulp stimulation. Neurons that express fos-immunoreactivity (fos-IR) appeared in several regions in the neuraxis 1.5 h after IL-1 beta injection, peaked at 2 h, and then declined. Labelled cells were found bilaterally in regions that contribute to pain-relay and pain-inhibition. The distribution of labelled cells almost matched the pattern induced by noxious tooth pulp stimulation. In indomethacin-pretreated animals, no neurons expressing fos-IR were found in nuclei associated with relay of nociception nor in nuclei contributing to inhibition of nociception. The results suggest that a small amount of IL-1 beta at the site of periodontal disease can induce fos-IR in brain neurons through increased prostaglandin production.

Continuously applied compressive pressure induces bone resorption by a mechanism involving prostaglandin E2 synthesis

In previous research, we devised a specific culture chamber to examine the effect of continuously applied compressive pressure (CCP) on bone formation and resorption. The chamber was infused with compressed mixed gases with different O2 and CO2 composition to maintain the pO2, pCO2, and pH in the culture medium under pressures of +0.5 atm (1.5 atm total) to +2.0 atm (3.0 atm total) at the same levels as those at the ordinary pressure (1 atm). Using the specific culture chamber, we demonstrated that CCP greatly suppressed the differentiation of mouse osteoblast-like MC3T3-E1 cells. The inhibition by CCP appeared to be mediated by prostaglandin E2 (PGE2). In the present study, we examined the effect of CCP on osteoclastic bone resorption. CCP treatment of mouse bone marrow culture markedly increased both the PGE2 production and the number of tartrate-resistant acid phosphatase (TRACP)-positive mononuclear cells (possibly precursors of multinucleated osteoclasts). An autoradiographic study using [125I]-salmon calcitonin showed clearly that those TRACP-positive cells had calcitonin receptors. The CCP effect was the greatest at +1.0 atm (2.0 atm total). Isobutylmethylxanthine potentiated the production of TRACP-positive cells induced by CCP. Adding indomethacin completely inhibited both the TRACP-positive cell formation and the PGE2 production induced by CCP. CCP also increased the release of 45Ca from prelabeled mouse calvaria during later stages (2-6 days) of the 6-day culture period. CCP markedly increased PGE2 but not interleukin 1 in the culture media of mouse calvaria. These results indicate that, besides inhibiting osteoblast differentiation, CCP stimulates bone resorption by generating new osteoclasts through a mechanism involving PGE2 production.

Effect of a continuously applied compressive pressure on mouse osteoblast-like cells (MC3T3-E1) in vitro

Bone metabolism is often affected by a variety of mechanical forces, but the cytological basis of their action is not known. In this study, we examined the effect of a continuously applied compressive pressure (CCP) on the growth and differentiation of clonal mouse osteoblast-like cells (MC3T3-E1) cultured in a specifically devised culture chamber. The gas phase of the chamber was maintained at a pressure of 2 atmospheres (atm) above ambient (3 atm total, 3.1 kg/cm2; 3.0 x 10(5) Pa) by continuously infusing a compressed mixed gas (O2: N2:CO2 = 7.0%:91.3%:1.7%). The pO2, pCO2, and pH in the culture medium at 37 degrees C under 3 atm were maintained at the same levels as those under 1 atm. MC3T3-E1 cells were cultured in alpha-minimal essential medium containing 10% fetal bovine serum under either 3 atm in the CCP culture chamber or 1 atm in an ordinary CO2 incubator. Alkaline phosphatase activity, a marker of osteoblasts, was greatly suppressed by the CCP treatment. The inhibition of alkaline phosphatase activity was rapidly restored when the cells were transferred to an ordinary CO2 incubator under 1 atm, indicating that the inhibition of alkaline phosphatase activity by CCP is reversible. Cell growth was not altered under CCP. The CCP treatment greatly increased the production and secretion of prostaglandin E2 (PGE2). Adding either conditioned medium from the CCP culture or exogenous PGE2 to the control culture under 1 atm suppressed alkaline phosphatase activity dose-dependently. The CCP treatment also suppressed collagen synthesis and calcification. These results suggest that CCP causes the cells to produce and secrete PGE2, which, in turn, inhibits differentiation of osteoblasts and the concomitant calcification.