The efficacy of a PCSK9 inhibitor for the plaque stabilization in the non-culprit lesion of ACS patients by using near-infrared intravascular ultrasonography

Background and purpose

In acute coronary syndrome (ACS) patients, major cardiovascular events during follow-up were equally attributable to recurrence at the site of culprit lesions and to non-culprit lesions, and mostly occurred within one year. Recent studies showed that Proprotein convertase subtilisin kexin type 9 (PCSK9) inhibitor significantly reduces the risk of cardiovascular events. However, the rigorous effects of PCSK9 inhibitor in patients with ACS, especially for the stabilization of plaque in the non-culprit lesions has not been identified. The purpose of this study was to evaluate the efficacy of a PCSK9 inhibitor for the plaque stabilization in the non-culprit lesion of ACS patients.

Methods

We retrospectively analyzed the 10 ACS patients (STEMI:5 cases, NSTEMI:1 case, and UAP:4 cases) who had non-culprit lesions and were injected with a PCSK9 inhibitor. We analyzed 11 non-culprit lesions before and after PSCK9 injections by using a near-infrared intravascular ultrasonography (NIRS-IVUS).

Results

The follow up intervals were 229.4±82.9 days. Major cardiovascular events did not occur in all patients. The serum low-density lipoprotein (LDL) cholesterol levels were significantly decreased form 128±36.7 mg/dl to 26.7±7.4 mg/dl (P<0.01; Figure 1A). There were no significant changes in percent atheroma volume before and after PCSK9 injections. However, the max lipid core burden index (LCBI) were significantly improved from 392.5±155.8 to 209.4±116 (P<0.01; Figure 1B). Although the lesion characteristics did not change in the images, by IVUS, the LCBI of the lesion was significantly decreased after PCSK9 injections. This study suggested that NIRS-IVUS had the possibility of detection for the slight changes in the plaque characteristics, which could not be detected by only an IVUS.

Conclusion

This study suggested that the plaque morphology can be altered by the aggressive lipid lowering therapy by using a PCSK9 inhibitor, and NIRS-IVUS can detect these plaque stabilizations of non-culprit lesion in ACS patients.

The authors have no financial conflicts of interest to disclose concerning the presentation.

Figure 1

Funding Acknowledgement

Type of funding source: None

Prognostic value of cardiac 123I-metaiodobenzylguanidine imaging for predicting cardiac events after transcatheter aortic valve replacement

Background

In patients with aortic valve stenosis (AS), cardiac sympathetic nervous (CSN) dysfunction and its improvement after TAVR have been reported; however, the prognostic impact of CSN function remains unclear. This study investigated the prognostic value of cardiac 123I-metaiodobenzylguanidine (MIBG) imaging for the prediction of cardiac events after transcatheter aortic valve replacement (TAVR).

Methods

This study was a single-center prospective observational study that enrolled patients with AS or failed surgical bioprostheses between July 2017 and May 2019. MIBG scintigraphy was performed before and after TAVR to evaluate the delayed heart–mediastinum ratio (d-H/M). Patients were classified into three pairs of groups based on the baseline and post-TAVR d-H/M (≥2.0 or <2.0) and on the presence of TAVR-related improvement of d-H/M. The study endpoints were major adverse cardiac events (MACE), including all-cause death, myocardial infarction, and hospitalization due to heart failure. The association of d-H/M with MACE following TAVR was based on a Cox proportional hazards ratio model adjusted for multiple prognostic variables.

Results

Of 187 consecutive patients who underwent TAVR, 111 (31 men; median age: 86 years) were evaluated. Over a median follow-up of 366 days, 16 (14.4%) patients had MACE. The incidence of MACE was significantly lower in patients with d-H/M improvement and/or the high post-TAVR d-H/M (≥2.0). Post-TAVR d-H/M had significant impacts on MACE, with an adjusted hazard ratio of 1.326 (95% confidence interval, 0.139–2.515; p=0.027).

Conclusions

Both d-H/M improvement and high post-TAVR d-H/M were associated with better prognosis in patients who underwent TAVR. Cardiac MIBG imaging was useful for predicting cardiac events after TAVR.

Funding Acknowledgement

Type of funding source: None

P932Structural changes in left ventricle after transcatheter aortic valve implantation

Background

Transcatheter aortic valve implantation (TAVI) has improved prognosis and quality of life of patients with severe aortic stenosis (AS) who had been considered inoperable or at high risk for surgical aortic valve replacement reflecting their age, frailty, and comorbidities. However, less is known about changes in cardiac geometry after TAVI procedure, and predictors of them.

Purpose

To clarify changes in cardiac geometry after TAVI, and their predictors.

Methods

We retrospectively analyzed patients with severe AS who underwent TAVI in our institute between May 2016 and June 2018. Of the 117 consecutive patients enrolled to this study, 12 patients died before six-month follow up, and finally 88 patients received follow up exams including echocardiography at six months after TAVI procedure.

Results

The analysis of echocardiographic data at the baseline and the six-month follow up of the 88 patients (age 86.2±4.0 years, male 19.3%, STS-PROM 6.76±3.28%, peak aortic jet velocity 4.67±0.75m/s) revealed that left ventricular end-diastolic volume index (LVEDVi) (from 80.1±20.9ml/m2to 74.2±15.9ml/m2, p=0.011), and left ventricular mass index (LVMi) (from 116.0±32.7g/m2to 93.6±25.6g/m2, p<0.001) had improved in six months after TAVI procedure. The difference of LVEDVi (ΔLVEDVi: six-month LVEDVi–baseline LVEDVi) and the difference of LVMi (ΔLVMi: six-month LVMi – baseline LVMi) were significantly higher in the patients with chronic atrial fibrillation compared to the rest (ΔLVEDVi: +7.7±8.7ml/m2 vs −7.2±18.1ml/m2, p=0.024; ΔLVMi: +7.1±11.5g/m2 vs −25.3±33.5g/m2, p=0.008). In echocardiographic data, ΔLVEDVi and ΔLVMi both had positive correlation between baseline E/e' ratio (ΔLVEDVi: r=0.224, p=0.048; ΔLVMi: r=0.240, p=0.034), and negative correlation between baseline LVEDVi (ΔLVEDVi: r=−0.674, p<0.001; ΔLVMi: r=−0.312, p=0.003), LVMi (ΔLVEDVi: r=−0.422, p<0.001; ΔLVMi: r=−0.699, p<0.001), peak aortic jet velocity (ΔLVEDVi: r=−0.257, p=0.016; ΔLVMi: r=−0.376, p<0.001), and mean transaortic pressure gradient (ΔLVEDVi: r=−0.269, p=0.011; ΔLVMi: r=−0.403, p<0.001).

Conclusion

TAVI resulted in reverse remodeling and regression of hypertrophy in left ventricle. And these improvement were grater in patients with more advanced left ventricular remodeling and hypertrophy, and higher severity of AS at the baseline, however, less in patients with chronic atrial fibrillation and worse diastolic dysfunction.

P1221Effect of transcatheter aortic valve implantation on cardiac sympathetic nervous function assessed by 123I-metaiodobenzylguanidine scintigraphy in patients with severe aortic stenosis

Background

Cardiac sympathetic nervous (CSN) function assessed by 123I-metaiodobenzylguanidine (MIBG) scintigraphy is associated with poor prognosis in patients with heart failure.

Purpose

The aim of this study was to investigate the effects of transcatheter aortic valve implantation (TAVI) on CSN function in patients with severe aortic stenosis (AS) using MIBG scintigraphy.

Methods

This was a single-center prospective observational study that enrolled patients between July 2017 and July 2018. Among 77 registered patients who scheduled to undergo TAVI, 35 patients (7 men; mean age: 87 years) were evaluated. The MIBG scintigraphy was performed at baseline and 6 months after TAVI procedure to evaluate the heart-mediastinum ratio (H/M) and washout rate (WR). The MIBG parameter changes were compared with B-type natriuretic peptide (BNP) levels and echocardiographic parameters, including aortic valve area (AVA), peak velocity (Vmax), mean pressure gradient (PG), and left ventricular ejection fraction (LVEF).

Results

All patients successfully underwent TAVI with improved BNP level (388±341 pg/mL vs. 167±118 pg/mL, p<0.001). The AVA, Vmax, mean PG and LVEF improved after TAVI (0.6±0.2 cm2 vs. 1.6±0.5 cm2, p<0.001; 4.6±0.8 m/s vs. 2.1±0.3 m/s, p<0.001; 54±20 mmHg vs. 9±3 mmHg, p<0.001; 58±11% vs. 63±9%, p=0.01, respectively). In the MIBG imaging, the delayed H/M significantly increased (2.5±0.6 vs. 2.6±0.7, p=0.03), and the WR decreased (32±8% vs. 29±8%, p=0.047) after TAVI. There was a correlation between the changes in the MIBG parameters and the change in mean PG from baseline to 6 months (delayed H/M: r=0.391, p=0.02; WR: r=0.347, p=0.04). Multivariate logistic regression analysis showed that baseline mean PG was an independent predictor of improved both delayed H/M and WR (odds ratio=1.062; 95% confidence interval: 1.009–1.137; p=0.042).

Conclusions

TAVI can improve the CSN function in patients with AS. Such CSN improvement was related with hemodynamic changes.

Acknowledgement/Funding

None

A case of pulmonary alveolar microlithiasis with an intragenetic deletion in SLC34A2 detected by a genome-wide SNP study

A case of pulmonary alveolar microlithiasis occurring in an inbred family is presented. A genome-wide analysis of the patient's genomic DNA using a high-density single nucleotide polymorphism (SNP) array revealed a small intragenetic mutation at SLC34A2. The results suggest that the high-density SNP array has the power to identify a recessive disease gene(s) even in the analysis of only a single inbred patient.

IL-4-producing CD8+ T cells may be an immunological hallmark of chronic GVHD

Chronic graft-versus-host disease (cGVHD) occurs in approximately 60-80% of those who survive over 100 days after allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, the pathophysiology of cGVHD is poorly understood. To gain more insight into the immunological mechanism of cGVHD, we examine cytokine production of peripheral blood T cells from 19 patients in the chronic phase of allo-HSCT. The percentage of IFN-gamma-producing CD8(+) T cells among CD8(+) T cells was significantly higher in patients with or without cGVHD than in normal control subjects (P<0.001). On the other hand, the percentage of IL-4-producing CD8(+) T cells among CD8(+) T cells was significantly higher in patients with cGVHD (mean 3.3%; range 1.3-8.2%) than in patients without cGVHD (mean 1.2%; range 0.8-1.7%) and normal control subjects (mean 1.1%; range 0.1-1.6%) (both P<0.001). By contrast, the percentage of IL-4-producing CD4(+) T cells was not different among patients with and without cGVHD and normal controls. These findings suggest that IL-4-producing CD8(+) T cells may be an immunological marker of cGVHD.

Intra-arterial steroid-injection therapy for steroid-refractory acute graft-versus-host disease with the evaluation of angiography

We treated three patients with steroid-refractory acute graft-versus-host disease (aGVHD) with intra-arterial steroid-injection therapy (IAST). Two patients with gut aGVHD received IAST into both superior and inferior mesenteric arteries, while one patient with liver aGVHD received IAST into the proper hepatic artery. The volume of stools and the bilirubin level improved soon after IAST. Angiography of the superior and inferior mesenteric arteries was performed in the two patients with steroid-refractory gut aGVHD, and identical abnormal findings were obtained. IAST might be an earlier option for steroid-refractory aGVHD.

Blood dendritic cells are decreased in acute graft-versus-host disease

The recipients of allogeneic hematopoietic stem cell transplantation (allo-HSCT) often develop acute graft-versus-host disease (aGVHD), which is closely related to morbidity and mortality. However, the essential part of the immune responses elicited in aGVHD remains largely unknown. We attempt to determine if peripheral blood dendritic cells (PBDCs) are altered in aGVHD, and find that the number of PBDCs (both myeloid and lymphoid DCs) is significantly decreased. Immunohistochemical staining of the biopsied skin from patients with aGVHD demonstrates that a number of fascin(+) cells with dendritic projections infiltrate the dermis of the skin. Based on these findings, we hypothesize that the PBDCs are recruited to the affected tissues and may thus play important roles in immune responses elicited in aGVHD.

A patient with type I CD36 deficiency whose myocardium accumulated 123I-BMIPP after 4 years

A 73-year-old man with aortic regurgitation was examined by 123I-alpha-methyl-p-iodophenylpentadecanoic acid (BMIPP) myocardial single photon emission computed tomography (SPECT) in 1995. Myocardial accumulation was not evident on either the early or the delayed image obtained 15 minutes and 3 hours, respectively, after injecting 123I-BMIPP. Flow cytometric analysis of CD36 expression in monocytes and platelets identified a type I CD36 deficiency. The patient was hospitalized for severe heart failure in 1999. Upon admission, the cardiothoracic ratio on chest X-rays was 73%, and the left ventricular end-diastolic diameter on echocardiograms was enlarged to 77 mm. On the second day, we performed 123I-BMIPP myocardial SPECT. Myocardial accumulation was evident in the delayed, but not in the early image. We repeated 123I-BMIPP myocardial SPECT on the 10th day after admission. Myocardial accumulation was evident on both early and delayed images. 99mTc-tetrofosmin myocardial SPECT was immediately performed after 123I-BMIPP myocardial SPECT to distinguish myocardial from pooling images in the left ventricle, but, because the images from both 99Tc-tetrofosmin and 123I-BMIPP myocardial SPECT were idential, we considered that the 123I-BMIPP myocardial SPECT images reflected the actual myocardial condition. The CD36 molecule transports long-chain fatty acid (LCFA) on the myocardial membrane, but 123I-BMIPP scintigraphy does not show any myocardial accumulation in patients with type I CD36 deficiency, indicating that myocardial LCFA uptake occurs through CD36 on the human myocardial membrane. Even though our patient had type I CD36 deficiency, BMIPP was uptaken by the myocardium during heart failure, suggesting a variant pathway on the human myocardial membrane for LCFA uptake.

[Unusual changes detected by iodine-123 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid myocardial single photon emission computed tomography in the process of acute myocardial infarction: a case report]

Iodine-123 15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid myocardial single photon emission computed tomography(iodine-123 BMIPP myocardial SPECT) is useful for the diagnosis and evaluation of ischemic myocardial disease or cardiomyopathy. Changes in fatty acid metabolism in the post-myocardial ischemic state were evaluated using iodine-123 BMIPP myocardial SPECT. A 77-year-old woman was hospitalized for treatment of acute myocardial infarction. Emergency coronary angiography showed severe stenosis with delayed filling of contrast medium in the middle portion of the left anterior descending artery, so primary percutaneous transluminal coronary angioplasty was performed successfully. On the second day, iodine-123 BMIPP uptake was decreased slightly on the early imaging in the apico-anterior region, and increased slightly on the delayed imaging. On the seventh day, iodine-123 BMIPP uptake was decreased moderately or markedly in the apico-anterior region on the early imaging, and decreased markedly on the delayed imaging. Iodine-123 BMIPP myocardial SPECT subsequently became almost normalized. These unusual dynamic changes In iodine-123 BMIPP myocardial SPECT imaging may reflect metabolic changes of fatty acids in the ischemic state, the size of the triacylglycerol pool, and the degree of turnover in the triacylglycerol pool.

Uncommon and dynamic changes detected by 123I-15-(p-iodophenyl)-3-R,S-methylpentadecanoic acid myocardial single photon emission computed tomography in a stunned myocardium induced by coronary microvascular spasm

A 55-yr-old man underwent surgery. Soon after the procedure was finished, the patient complained of chest pain, and the electrocardiogram showed increase in the ST-segment in some leads. Emergency angiography showed normal coronary arteries, but there was asynergy in the left ventricle, and delayed filling of contrast medium was observed in the LCA. An intracoronary infusion of isosorbide dinitrate did not improve the delayed filling of contrast medium or ST segment increase in the electrocardiogram. Soon after nicorandil was injected into the LCA, the patient's symptoms, electrocardiogram, and delayed filling of contrast medium dramatically improved. On the second day, initial imaging by 123I-BMIPP myocardial SPECT showed a moderate increase in tracer uptake in the apico-anteroseptal region and a moderate decrease in tracer uptake in the lateral region, in which the first left ventriculography showed akinesis, and delayed imaging revealed a moderate increase in tracer uptake in the apical region and a high washout of 123I-BMIPP in the anteroseptal and lateral regions. On the sixth day, initial imaging by 123I-BMIPP myocardial SPECT showed a moderate decrease in tracer uptake in the apical and lateral regions and a mild decrease in tracer uptake in the anteroseptal region, and delayed imaging revealed a moderate increase in tracer uptake in the apical region and a high washout of 123I-BMIPP in the anteroseptal and lateral regions. By the 30th day, 123I-BMIPP myocardial SPECT had normalized. We consider that these dynamic changes in 123I-BMIPP myocardial SPECT imaging may reflect metabolic changes in fatty acids in the ischemic state, the size of the triacylglycerol pool, and the degree of turnover in the triacylglycerol pool.

[Clinical usefulness of 123I-BMIPP myocardial SPECT in collagen disease]

This study was designed to evaluate the clinical usefulness of 123I-BMIPP myocardial SPECT for detecting cardiac involvement in patients with collagen disease. We studied 12 patients with systemic lupus erythematosus (SLE), 8 with progressive systemic sclerosis (PSS), 6 with polymyositis/dermatomyositis (PM/DM) and 3 with allergic granulomatosis and angiitis (AGA). A 111 MBq of 123I-BMIPP was intravenously injected at rest, and SPECT images were obtained at 15 min after the injection. Seven of 12 SLE, 6 of 8 PSS, 3 of 6 PM/DM and all 3 AGA patients showed an abnormal tracer uptake. The left ventricular ejection fraction was inversely correlated with a BMIPP abnormality. The regional wall motion abnormality was reduced in regions with reduced tracer uptake. These findings suggest that 123I-BMIPP imaging could be useful for assessment of cardiac involvement in patients with collagen disease.

[Clinical usefulness of delayed exercise images on 99mTc-Tetrofosmin myocardial SPECT in the diagnosis of vasospastic angina pectoris]

This study was designed to evaluate the clinical usefulness of delayed exercise images in 99mTc-tetrofosmin (TF) myocardial SPECT in the diagnosis of vasospastic angina pectoris. We studied 30 patients with vasospastic angina, 10 of 30 patients (group A) had both effort and rest angina, 20 of 30 patients (group B) had rest angina. A 370 MBq of TF was intravenously injected at peak exercise, and initial (EX-I) and delayed exercise (EX-D) images were obtained at 30 min and 180 min after the injection. An additional 740 MBq of TF was intravenously reinjected after EX-D image acquisition, and rest images were obtained 30 min after the reinjection. The left ventricular wall was divided into 9 segments. Regional myocardial uptakes of TF were scored by 4-point defect score (0 = normal, 1 = mildly reduced, 2 = moderately reduced, and 3 = severely reduced). Total defect score (TDS) was calculated from the sum of defect scores in 9 segments. Reverse redistribution (RR) was defined as increase of more than 2 in TDS on EX-D images. In group A, 4 of 10 cases (40%) showed decreased uptake on EX-I images, 6 of 10 cases (60%) revealed RR on EX-D images, and none of the patients showed decreased uptake on rest images. In group B, no one showed decreased uptake on EX-I and rest images, 11 of 20 cases (55%) revealed RR on EX-D images. The mean +/- SD of TDS were 2.9 +/- 3.4, 5.1 +/- 4.5, 0.5 +/- 0.5 on EX-I, EX-D, rest images in group A, and serially 0.4 +/- 0.5, 3.3 +/- 3.6, 0.4 +/- 0.5 in group B. Regional wall motion abnormality was reduced in regions with RR. RR on EX-D images may reflect ischemic damaged but viable myocardium in vasospastic angina. The clinical usefulness of exercise-rest TF imaging in detection of organic coronary artery disease has been well established. Therefore, exercise-rest TF imaging with additional delayed exercise image could evaluate not only organic coronary artery disease but also coronary artery vasospasm.

[Impairment of septal uptake and washout on 123I-BMIPP myocardial SPECT after pacemaker implantation: report of two cases]

Case 1 involved a 62-year-old woman with complete atrioventricular block and case 2 involved a 70-year-old woman with sick sinus syndrome. In both cases, echocardiography, 123I-15-(p-iodophenyl)-3-R,S-methyl pentadecanoic acid (BMIPP) and 99mTc-tetrofosmin myocardial single photon emission computed tomographic (SPECT) findings were normal. Coronary arteriography and left ventriculography also revealed normal in both cases. After pacemaker implantation (DDD-type in case 1 and VVI-type in case 2), both patient's electrocardiograms revealed left bundle branch block-type conduction disturbance, and echocardiography showed asynchronous hypokinesia in the septal region. One year later, although both patient's ATP loading tetrofosmin SPECT were normal, BMIPP SPECT showed reduced uptake and increased washout in the septal region. These findings suggest that these changes of BMIPP SPECT might be caused by left bundle branch block-type conduction disturbance after pacemaker implantation.

[Bone marrow transplantation-associated thrombotic microangiopathy manifested by visual disturbance]

In October 1996, a 26-year-old woman was given a diagnosis of acute myeloblastic leukemia, FAB subtype M1. Treatment with combined chemotherapy achieved a complete remission (CR). In May 1997, the patient received an allogenic bone marrow transplant (BMT) from an HLA-identical sibling donor. Cyclosporine (CsA) and short-term methotrexate were given for graft-versus-host disease (GVHD) prophylaxis. Successful engraftment was obtained and signs of acute or chronic GVHD never developed. Five months after BMT, the patient experienced low-grade fever and blurred vision. Retinal examination demonstrated intraretinal hemorrhages, cotton-wool spots, and retinal detachments, which were presumably attributable to multiple thrombosis of retinal microvessels. The patient also exhibited hemolytic anemia with red cell fragmentation, thrombocytopenia, elevated lactate dehydrogenase, and renal impairment, and was thus given a diagnosis of BMT-associated thrombotic microangiopathy (BMT-TM). Discontinuation of CsA and administration of ticlopidine and prednisolone induced successful recovery from BMT-TM. Three months after the onset of BMT-TM, however, the patient experienced generalized clonic-tonic seizures with consciousness loss. Single-photon-emission computed tomography revealed blood-flow disturbances in the brain, suggesting the recurrence of microthrombosis. Accordingly, multiple transfusions of fresh frozen plasma were administered together with dipyridamole and aspirin. The patient gradually recovered and remained asymptomatic through the following 13 months. Currently, early diagnosis of BMT-TM is considered to be difficult. We suggest that careful examination of the ocular base may be useful for the early detection of BMT-TM.

[Two cases of microvascular vasospastic angina usefulness of 99mTc-tetrofosmin myocardial SPECT in clinical diagnosis]

Case 1 involved a 52-year-old man with angina chest pain at rest and case 2 involved a 63-year-old woman with chest oppression at rest. An electrocardiogram (ECG) showed negative T wave in III and aVF leads in case 1, and complete atrioventricular block and ST segment depression in II, III, aVF, and V5-6 leads in case 2. In both cases, 99mTc-tetrofosmin myocardial SPECT showed reduced uptake in the inferior and posterior wall. Although bath patients' left coronary arteriographies were normal, right coronary arteriographies revealed severely delayed filling of contrast medium without significant narrowing of epicardial coronary arteries, suggesting microembolism or microvascular vasospasm. An intracoronary infusion of isosorbide dinitrate did not improve the delayed filling of contrast medium or ST segment depression on ECG. Soon after intracoronary infusion of diltiazem in case 1 and nicorandil in case 2, coronary arterial flows were normalized, chest symptoms disappeared, and ECG findings were normalized. The next day, both patients' 99mTc-tetrofosmin myocardial SPECT showed normal uptake. These findings suggest that myocardial ischemia in these cases might be explained as having been caused by microvascular spasm.

NF-kappaB activation is required for human endothelial survival during exposure to tumor necrosis factor-alpha but not to interleukin-1beta or lipopolysaccharide

In the presence of a protein synthesis inhibitor, cycloheximide, tumor necrosis factor-alpha (TNF-alpha), interleukin 1-beta (IL-1beta), or lipopolysaccharide (LPS) induces human umbilical vein endothelial cells (HUVECs) to undergo apoptosis, suggesting that constitutive or inducible cytoprotective pathways are required for cell survival. We studied the correlation between nuclear factor-kappaB (NF-kappaB) activation and cell death induced by TNF-alpha, IL-1beta, or LPS. Adenovirus-mediated overexpression of a dominant-negative IkappaBalpha (inhibitor of kappaB) mutant blocked NF-kappaB activation by gel shift assay and blocked induction of vascular cell adhesion molecule-1 protein by TNF-alpha, IL-1beta, and LPS, a NF-kappaB-dependent response. In cells overexpressing the IkappaBalpha mutant, TNF-alpha induced cell death, whereas IL-1beta or LPS did not. We conclude that cell survival following TNF-alpha stimulation is NF-kappaB-dependent but that a constitutive or inducible NF-kappaB-independent pathway(s) protects IL-1beta- or LPS-treated HUVECs from cell death.

Lipopolysaccharide-induced NF-kappaB activation in human endothelial cells involves degradation of IkappaBalpha but not IkappaBbeta

We studied the signal transduction pathways involved in NF-kappaB activation and the induction of the cytoprotective A20 gene by lipopolysaccharide (LPS) in human umbilical vein endothelial cells (HUVEC). LPS induced human A20 mRNA expression with a maximum level 2 h after stimulation. The proteasome inhibitor N-acetyl-leucinyl-leucinyl-norleucinal-H (ALLN) and the tyrosine kinase inhibitor herbimycin A (HMA) blocked A20 mRNA expression and partially inhibited NF-kappaB DNA-binding activity induced by LPS treatment. LPS induced IkappaBalpha degradation at 30-60 min after treatment, but did not induce IkappaBbeta degradation up to 120 min. In contrast, TNF-alpha rapidly induced IkappaBalpha degradation within 5 min and IkappaBbeta degradation within 15 min. Cycloheximide did not prevent LPS-induced IkappaBalpha degradation, indicating that newly synthesized proteins induced by LPS were not involved in LPS-stimulated IkappaBalpha degradation. LPS-induced IkappaBalpha degradation was inhibited by ALLN, confirming that ALLN inhibits NF-kappaB activation by preventing IkappaBalpha degradation. Of note, HMA also inhibited LPS-induced IkappaBalpha degradation. However, tyrosine phosphorylation of IkappaBalpha itself was not elicited by LPS stimulation, suggesting that tyrosine phosphorylation of a protein(s) upstream of IkappaBalpha is required for subsequent degradation. We conclude that in HUVEC, LPS induces NF-kappaB-dependent genes through degradation of IkappaBalpha, not IkappaBbeta, and propose that this degradation is induced in part by HMA-sensitive kinase(s) upstream of IkappaBalpha.

Generation and characterization of monoclonal antibodies to alveolar type II cell lamellar body membrane

Monoclonal antibodies against the limiting membrane of alveolar type II cell lamellar bodies were obtained after immunization of mice with a membrane fraction prepared from lamellar bodies isolated from rat lungs. The specificity of the antibodies was investigated with Western blot analysis, indirect immunofluorescence, and electron-microscopic immunogold studies of freshly isolated or cultured alveolar type II cells, alveolar macrophages, and rat lung tissue. One of the monoclonal antibodies identified, MAb 3C9, recognized a 180-kDa lamellar body membrane (lbm180) protein. Immunogold labeling of rat lung tissue with MAb 3C9 demonstrated that lbm180 protein is primarily localized at the lamellar body limiting membrane and is not found in the lamellar body contents. Most multivesicular bodies of type II cells were also labeled, as were some small cytoplasmic vesicles. Golgi complex labeling and plasma membrane labeling were weak. The appearance of lbm180 protein by immunofluorescence in fetal rat lung cryosections correlated with the biogenesis of lamellar bodies. The lbm180 protein decreased with time in type II cells cultured on plastic. The lbm180 protein is an integral membrane protein of lamellar bodies and was also found in the pancreas and the pancreatic betaHC9 cell line but not in the rat brain, liver, kidney, stomach, or intestine. The present study provides evidence that the lbm180 protein is a lung lamellar body and/or multivesicular body membrane protein and that its antibody, MAb 3C9, will be a valuable reagent in further investigations of the biogenesis and trafficking of type II cell organelles.

Monocyte-derived macrophages prime peripheral T cells to undergo apoptosis by cell-cell contact via ICAM-1/LFA-1-dependent mechanism

We designed the present study to clarify the mechanism of superantigen-induced apoptosis of human mature T cells and to elucidate the pivotal roles of monocyte-derived macrophages in induction of T cell apoptosis. Exposure of unfractionated human peripheral blood mononuclear cells to SEA, SEB or PHA elicited apoptosis in T cells after 5-day culture. In purified T cell preparations, SEB was unable to induce apoptosis, but was inductive when the purified T cells were cocultured with monocyte-derived macrophages adhering to plastic culture dishes. Placing the T cells in the insert wells which physically separated them from the adhering macrophages resulted in a complete loss of SEB-induced apoptosis. The addition of blocking antibodies against LFA-1, ICAM-1 and CD2 to the cocultures significantly inhibited the SEB-induced T cell apoptosis. We concluded therefore that direct contact of macrophages with T cells is critical in SEB-induced T cell apoptosis, and that adhesion molecules such as LFA-1/ICAM-1 and CD2 may be involved in the mechanism of this effect.

Pathways for uptake of fluorescently labeled liposomes by alveolar type II cells in culture

Isolated alveolar type II cells are shown in real time to internalize 1-palmitoyl-2-[12-[(7 nitro-2-1,3-benzoxadiazol-4-yl)amino]dodecanoyl] phosphatidyl choline (C12-NBD-PC)-labeled liposomes in an intact manner with the use of fluorescence microscopy. Cells isolated from rat lungs, cultured on plastic for 24 h, are exposed at 37 degrees C to liposomes on the microscope stage, using a microperfusion system. Liposomes composed of a self-quenching concentration of fluorophore (25 mol% C12-NBD-PC) do not dequench at the level of the plasma membrane; rather, they appear to fuse with intracellular lipids primarily in vesicular structures consistent with lamellar bodies. Temperature and energy dependence of this uptake mechanism is demonstrated by the lack of uptake of maximally fluorescent liposomes (15 mol% C12-NBD-PC) at 4 degrees C or when depleted of ATP. Inhibition of the coated-pit endocytic pathway by hypertonic media reduces fluorescent lipid uptake by 50%, suggesting a separate, clathrin-independent endocytic pathway for intact internalization of liposomes by type II cells. Uptake is inhibited by cytochalasin D by 49%, suggesting a dependence on action, and by 88% with combined cytochalasin D and hypertonicity, or nearly the same level as ATP depletion. The evidence is consistent with the existence of two separate endocytic pathways for lipids in type II cells: one clathrin dependent and the other actin dependent.

The lactose permease meets Frankenstein

The lactose permease (lac) of Escherichia coli is a paradigm for membrane transport proteins. Encoded by the lacY gene, the permease has been solubilized, purified to homogeneity, reconstituted into phospholipid vesicles and shown to catalyse the coupled translocation of beta-galactosides and H+ with a stoichiometry of unity. Circular dichroism and other spectroscopic approaches demonstrate that the purified permease is about 80% helical. Based on hydropathy analysis of the primary amino-acid sequence, a secondary structure has been proposed in which the protein has 12 hydrophobic domains in alpha-helical conformation that traverse the membrane in zigzag fashion connected by hydrophilic loops. A variety of other approaches are consistent with the model and demonstrate that both the N and C termini are on the inner surface of the membrane, and studies on an extensive series of lac permease/alkaline phosphatase fusion proteins provide exclusive support for the topological predictions of the 12-helix motif. This presentation concentrates on the use of site-directed fluorescence spectroscopy to study structure-function relationships in the permease.

Gene expression of monocyte chemoattractant protein-1 in human monocytes is regulated by cell density through protein tyrosine kinase and protein kinase C

The present study investigated the signal transduction pathways leading to the gene expression for monocyte chemoattractant protein-1 (MCP-1) in human monocytes. By Northern blot analysis, MCP-1 mRNA was undetectable in freshly isolated monocytes, but was induced and reached a maximal level at 4 h during culture. The level of accumulated mRNA altered with cell density of the monocytes and was highest at a density of 1 x 10(6) cells/ml. Nuclear run-on assay demonstrated that this cell density-dependent expression of MCP-1 mRNA was regulated at the transcriptional level, and protein tyrosine kinase (PTK) inhibitors, genistein and herbimycin A, completely abrogated this gene transcription. Immunoblot analysis for phosphotyrosine in whole cell lysates demonstrated gradual increases in tyrosine phosphorylation of 55-, 60-, and 70-kDa proteins during culture. Cell density regulated tyrosine phosphorylation of 70-kDa protein in parallel with alterations in MCP-1 mRNA expression. The protein kinase C (PKC) inhibitor H-7 also abrogated the gene transcription and suppressed tyrosine phosphorylation of 70-kDa protein, whereas HA1004, a structural analogue of H-7, did not. These results suggest that MCP-1 gene expression in cultured monocytes is regulated by the cell density at the transcriptional level and that the signaling pathways leading to the gene transcription are mediated through PTK and PKC. It is also suggested that PKC activity plays a critical role in tyrosine phosphorylation of 70-kDa protein, which may mediate signals regulating the cell density-dependent expression of the MCP-1 gene.

Position-independent, high-level, and correct regional expression of the rat aldolase C gene in the central nervous system of transgenic mice

Aldolase C is mainly expressed in the central nervous system (CNS). To clarify the regulatory mechanisms for the CNS-specific expression, transgenic mice were created using two constructs of the rat aldolase C gene. A fusion gene comprising the 5' regulatory region of the aldolase C gene was expressed in a CNS-specific manner. However, the expression levels and the cellular localization of the gene varied among transgenic mice. The other construct, including both 5' and 3' regulatory regions of the gene, showed position-independent and high-level expression as well as the correct regional distribution in the CNS. These results indicate that the 13-kb sequence of the rat aldolase C gene contains sufficient information for faithful expression of the gene.

What's new with lactose permease

The lactose permease of Escherichia coli is a paradigm for polytopic membrane transport proteins that transduce free energy stored in an electrochemical ion gradient into work in the form of a concentration gradient. Although the permease consists of 12 hydrophobic transmembrane domains in probable alpha-helical conformation that traverse the membrane in zigzag fashion connected by hydrophilic "loops", little information is available regarding the folded tertiary structure of the molecule. In a recent approach site-directed fluorescence labeling is being used to study proximity relationships in lactose permease. The experiments are based upon site-directed pyrene labeling of combinations of paired Cys replacements in a mutant devoid of Cys residues. Since pyrene exhibits excimer fluorescence if two molecules are within about 3.5A, the proximity between paired labeled residues can be determined. The results demonstrate that putative helices VIII and IX are close to helix X. Taken together with other findings indicating that helix VII is close to helices X and XI, the data lead to a model that describes the packing of helices VII to XI.

Protein kinase C-mediated inhibition of cyclin A expression in human vascular endothelial cells

Proliferation of cultured human vascular endothelial cells may be negatively regulated by the protein kinase C (PKC) pathway, because phorbol 12-myristate, 13-acetate (PMA) inhibits DNA synthesis and cell population doubling in PKC-retaining cells, but not in cells depleted of PKC by a long-term exposure to PMA. We investigated the mechanism through which PKC arrests the cell cycle with regard to cyclin A, which has been reported to play a key role in G1/S progression activating CDK2. Cyclin A mRNA was elevated from late G1 in accordance with the protein expression, which reached the maximal level during the S phase. PMA added at late G1 potently reduced the levels of cyclin A mRNA and the protein in concentration-dependent manners parallel to its effect on the proliferation. However, it failed to inhibit the expression in PKC-depleted cells. The mRNA reduction by PMA was due to inhibition of the transcription. The PMA effects were mimicked by multiple doses of 1,2-dioctanoylglycerol. These findings suggest that PKC inhibits G1/S progression through suppression of cyclin A gene transcription in endothelial cells.

Interferon-gamma suppresses PDGF production from THP-1 cells and blood monocyte-derived macrophages

Involvement of the immunological mechanisms in atherogenesis has recently been suggested by immunohistological detection of macrophages and T lymphocytes in atherosclerotic lesions. In the present study, we have investigated the regulatory effect of interferon-gamma (IFN-gamma), a cytokine secreted by activated T cells, on the production and secretion of platelet-derived growth factor (PDGF) from macrophages in culture. The human monocytic leukemia cell line, THP-1, was treated with phorbol 12-myristate 13-acetate (PMA) for 24 h to induce macrophage differentiation and PDGF production, and then various doses of recombinant human IFN-gamma (0-1000 I.U./ml) were added to the culture. After 48 h, the conditioned medium and the cells were harvested and analyzed for PDGF production. PDGF-dependent mitogenic activity in the conditioned medium, estimated by neutralization of mitogenic activity with anti-PDGF antibody, was suppressed by IFN-gamma treatment. Radioimmunoassays for PDGF also revealed a decrease in both PDGF-AA and -BB in the conditioned medium with IFN-gamma treatment, whereas neither total cell DNA as an indication of cell number nor overall protein synthesis based on [3H]leucine incorporation were decreased. Northern analysis of total RNA extracted from the cells demonstrated that IFN-gamma suppressed the level of PDGF mRNA. Analysis of mRNA degradation in the presence of actinomycin D demonstrated that the decrease in PDGF mRNA was not due to enhanced degradation of mRNA. A similar inhibitory effect of IFN-gamma on PDGF mRNA levels was also found in monocyte-derived macrophages cultured in the presence of granulocyte-macrophage colony stimulating factor. These results suggest that IFN-gamma modulates production and secretion of PDGF from macrophages and that the functions of macrophages in atherogenesis may be regulated by the cellular interactions between T cells and macrophages through the action of cytokines such as IFN-gamma.

Second messengers regulate endosomal acidification in Swiss 3T3 fibroblasts

Acidification of the endosomal pathway is important for ligand and receptor sorting, toxin activation, and protein degradation by lysosomal acid hydrolases. Fluorescent probes and imaging methods were developed to measure pH to better than 0.2 U accuracy in individual endocytic vesicles in Swiss 3T3 fibroblasts. Endosomes were pulse labeled with transferrin (Tf), alpha 2-macroglobulin (alpha 2M), or dextran, each conjugated with tetramethylrhodamine and carboxyfluorescein (for pH 5-8) or dichlorocarboxyfluorescein (for pH 4-6); pH in individual labeled vesicles was measured by ratio imaging using a cooled CCD camera and novel image analysis software. Tf-labeled endosomes acidified to pH 6.2 +/- 0.1 with a t1/2 of 4 min at 37 degrees C, and remained small and near the cell periphery. Dextran- and alpha 2M-labeled endosomes acidified to pH 4.7 +/- 0.2, becoming larger and moving toward the nucleus over 30 min; approximately 15% of alpha 2M-labeled endosomes were strongly acidic (pH less than 5.5) at only 1 min after labeling. Replacement of external Cl by NO3 or isethionate strongly and reversibly inhibited acidification. Addition of ouabain (1 mM) at the time of labeling strongly enhanced acidification in the first 5 min; Tf-labeled endosomes acidified to pH 5.3 without a change in morphology. Activation of phospholipase C by vasopressin (50 nM) enhanced acidification of early endosomes; activation of protein kinase C by PMA (100 nM) enhanced acidification strongly, whereas elevation of intracellular Ca by A23187 (1 microM) had no effect on acidification. Activation of protein kinase A by CPT-cAMP (0.5 mM) or forskolin (50 microM) inhibited acidification. Lysosomal pH was not affected by ouabain or the protein kinase activators. These results establish a methodology for quantitative measurement of pH in individual endocytic vesicles, and demonstrate that acidification of endosomes labeled with Tf and alpha 2M (receptor-mediated endocytosis) and dextran (fluid-phase endocytosis) is sensitive to intracellular anion composition, Na/K pump inhibition, and multiple intracellular second messengers.