Impact of synovial membrane-derived stem cell transplantation in a rat model of myocardial infarction

To explore a new source of cell therapy for myocardial infarction (MI), we assessed the usefulness of mesenchymal stem cells derived from synovial membrane samples (SM MSCs). We developed a model of MI by ligation of the proximal left anterior descending coronary artery (LAD) in Lewis rats. Two weeks after ligation, 5 x 10(6) SM MSCs were injected into the MI scar area (T group, n = 9), while buffer was injected into the control group (C group, n = 9). Cardiac performances measured by echocardiography at 4 weeks after transplantation were significantly increased in the T group as compared with the C group. Masson's trichrome staining showed that SM MSC transplantation decreased collagen volume in the myocardium. Engrafted SM MSCs were found in the border zone of the infarct area. Immunohistological analysis showed that these cells were positive for the sarcomeric markers alpha-actinin and titin, and negative for desmin, troponin T, and connexin 43. SM MSC transplantation improved cardiac performance in a rat model of MI in the subacute phase, possibly through transdifferentiation of the engrafted cells into a myogenic lineage, which led to inhibition of myocardial fibrosis. Our results suggest that SM MSCs are a potential new regeneration therapy candidate for heart failure.

A novel catheter system for percutaneous intracoronary artery cardiomyoplasty

BACKGROUND

Current medical and invasive treatment strategies are often found to be inadequate to treat patients with acute myocardial infarction. Cell and tissue therapies are a promising treatment alternative for patients with severe ischemic heart disease.

OBJECTIVES

The objective of this study was to evaluate the efficacy of a new means of direct myocardial access using the percutaneous coronary intervention (PCI) technique.

METHODS

We used a system consisting of an injection needle catheter that implants cells and the injection guide catheter that delivers the injection needle catheter into the target lesion. We harvested skeletal myoblasts from Yorkshire swine (n = 8; 50-60 kg), expanded them in culture and labeled them with a fluorescent cell-linker kit. The myoblasts (106 cells), along with green dye, were injected into the normal heart of swine using this novel system. Histological analysis was performed on Days 0 (n = 4) and 14 (n = 4) after injection.

RESULTS

Working along the coronary artery, the catheter was easily delivered to the left anterior descending (LAD) coronary artery with the conventional PCI technique. No events of death, cardiac tamponade or other procedural complication occurred. Electrocardiography did not detect cardiac arrhythmia during the 14 days following the injection. On gross inspection, the heart was observed through its outer surface, and the myoblasts and green dye were well localized in the LAD area.

CONCLUSIONS

The present study demonstrates the feasibility of a new means of a direct myocardial injection system without any adverse outcomes.

Novel method of decellularization of porcine valves using polyethylene glycol and gamma irradiation

BACKGROUND

Recent tissue-engineered valves are in need of a breakthrough to overcome several limitations against clinical applications. We have developed a new method of decellularization using polyethylene glycol and gamma irradiation.

METHODS

Fresh porcine aortic valves were decellularized using polyethylene glycol and gamma irradiation. These were evaluated by histologic, biochemical (DNA, solubilized protein and collagen content), mechanical (strength test, transmission electron microscopy) and immunologic (porcine endogenous retrovirus and the alpha-1.3 galactosyl epitope) analyses. Implantations into the subcutaneous tissue of rats (1 week, n = 10; 2 months, n = 10) and into the descending aorta of dogs (2 months, n = 6; 6 months, n = 3) were used as in vivo studies.

RESULTS

Complete decellularization was confirmed by histologic examination and by determining the DNA and solubilized protein content. The decellularized valve showed no significant differences in its mechanical strength or collagen content compared with native porcine tissues. The ultrastructure was well preserved in transmission electron microscope images. The DNA sequence of a porcine endogenous retrovirus and the alpha-1.3 galactosyl epitope were eliminated after the decellularizing process. No acute rejection and little calcification was noted in the rat model. In the dog model at 2 months, the surface of the graft was completely covered with a monolayer of endothelial cells. In addition, several layers of vimentin-positive cells lay under the endothelial cells. At 6 months after implantation, many smooth muscle cells, monolayer endothelial cells, and some vasculogenesis were seen.

CONCLUSIONS

The decellularizing method provided low immunogenicity, low risk of unknown infections, and was little subject to calcification. The decellularized tissues showed acceptable durability and recellularization.

Novel tissue-engineered biodegradable material for reconstruction of vascular wall

BACKGROUND

To solve several problems with artificial grafts, we sought to develop a novel bioengineered material that can promote tissue regeneration without ex vivo cell seeding and that has sufficient durability to be used for artery reconstruction. Here, we tested whether this biodegradable material could accelerate the in situ regeneration of autologous cardiovascular tissue, especially of the arterial wall, in various models of cardiovascular surgeries.

METHODS

The tissue-engineered patch was fabricated by compounding a collagen-microsponge with a biodegradable polymeric scaffold composed of polyglycolic acid knitted mesh, reinforced on the outside with woven polylactic acid. Tissue-engineered patches without precellularization were grafted into the porcine descending aorta (n = 5), the porcine pulmonary arterial trunk (n = 8), or the canine right ventricular outflow tract (as the large graft model; n = 4). Histologic and biochemical assessments were performed 1, 2, and 6 months after the implantation.

RESULTS

There was no thrombus formation in any animal. Two months after grafting, all the grafts showed good in situ cellularization by hematoxylin/eosin and immunostaining. The quantification of the cell population by polymerase chain reaction showed a large number of endothelial and smooth muscle cells 2 months after implantation. In the large graft model, the architecture of the patch was similar to that of native tissue 6 months after implantation.

CONCLUSIONS

A tissue-engineered patch made of our biodegradable polymer and collagen-microsponge provided good in situ regeneration at both the venous and arterial wall, suggesting that this patch can be used as a novel surgical material for the repair of the cardiovascular system.

Angiogenic Gene Cell Therapy using Suicide Gene System Regulates the Effect of Angiogenesis in Infarcted Rat Heart

BACKGROUND

Although angiogenic gene therapy has been reported to be effective in restoring ischemic heart function, there are several obstacles to its clinical application, such as unreliable efficiency of transfection and uncontrollable expression. We developed human HGF (hHGF)-producing cells that regulated hHGF production using the thymidine kinase gene of Herpes Simplex Virus (TK) and the Ganciclovir (GCV) system. We tested whether these cells induced and regulated angiogenic effects in infarcted myocardium.

METHODS

NIH3T3 cells were stably transfected with an hHGF cDNA expression plasmid (NIH/HGF). Next, the NIH/HGF cells were stably transfected with TK (NIH/HGF/TK). The left anterior descending artery was ligated in the heart of severe combined immunodeficiency rats, and four materials were transplanted: 1) NIH/HGF (n=10), 2) NIH/HGF/TK, with orally administered GCV (n=10), 3) NIH3T3 (n=10), and 4) culture medium (n=10).

RESULTS

In vitro, the proliferation of NIH/HGF/TK cells was suppressed by GCV. In vivo, significant increases in cardiac performance and angiogenesis were observed in the NIH/HGF and NIH/HGF/TK groups 4 weeks after transplantation. Although tumorous lesions were detected in the NIH/HGF group, their growth was completely controlled in the NIH/HGF/TK group.

CONCLUSIONS

Angiogenic gene cell therapy using the TK-GCV suicide gene system induces and regulates angiogenesis under the control of cell growth, suggesting it as a promising system for therapeutic angiogenesis.

Tissue cardiomyoplasty using bioengineered contractile cardiomyocyte sheets to repair damaged myocardium: their integration with recipient myocardium

BACKGROUND

We hypothesized that tissue-engineered contractile cardiomyocyte sheets without a scaffold would show histological and electrical integration with impaired myocardium, leading to the regeneration of infarcted myocardium.

METHODS

Neonatal rat cardiomyocytes were cultured on Poly(N-isopropylacrylamide)-grafted polystyrene dishes and detached as a square cell sheet at 20 degrees C. Two sheets were stacked to make thicker contractile cardiac sheets. In cross-section, the stacked sheets looked like homogeneous heart-like tissue. Two weeks after rats were subjected to left anterior descending (LAD) ligation, two treatments were conducted: 1) cardiomyocyte sheet implantation (T group, n=10), and 2) fibroblast sheet implantation (F group, n=10). The control group underwent no additional treatment (C group, n=10).

RESULTS

Echocardiography demonstrated that cardiac performance was significantly ameliorated in the T group 2, 4, and 8 weeks after implantation. The cardiomyocyte sheets became attached to the infarcted myocardium, showed angiogenesis, expressed connexin-43, and appeared as homogeneous tissue in the myocardium Electrophysiological experiments showed a QRS complex with one peak in the treated scar area in the T group, but two peaks, indicative of branch block, in that of the other groups. Furthermore, the threshold for pacing of the recipient heart was lower in the T group than in the other groups.

CONCLUSIONS

Cardiomyocyte sheets integrated with the impaired myocardium and improved cardiac performance in a model of ischemic myocardium. Techniques using such tissue-engineered cell sheets are introducing the promising concept of tissue cardiomyoplasty to the field of regenerative medicine.

Repair of impaired myocardium by means of implantation of engineered autologous myoblast sheets

OBJECTIVES

Autologous skeletal myoblast cell transplantation by means of the injection method is subject to the loss of intercellular communication, extracellular matrix, and cell numbers. We hypothesize that the implantation of skeletal myoblast cell sheets might be more advantageous in repairing the impaired heart by providing uniform and stable cell delivery with less cell loss and without disrupting the cell-cell microenvironment.

METHODS

Left anterior descending coronary artery-ligated Lewis rat hearts (2 weeks, total n = 173) received 1 x 10(7) autologous skeletal myoblasts by means of cell transplantation either through myoblast injection or implantation of 2 monolayer-constructed myoblast sheets (5 x 10(6) cells per sheet) or through medium injection. Myoblast sheets were constructed with temperature-responsive, polymer-grafted cell-culture dishes, which release the confluent cells from the dish surface at less than 20 degrees C.

RESULTS

Echocardiographic results indicated higher improvement of cardiac performance in the myoblast sheet group than among the other groups until 8 weeks after cell transplantation. Histologic comparison revealed greater cellularity and abundant widespread neocapillaries within the noticeable uniform thickened wall in myoblast sheet group hearts only. Fibrosis was substantially reduced with skeletal myoblast sheet implantation compared with skeletal myoblast cell injection. Obviously higher numbers of hematopoietic stem cells (c-kit, stem cell antigen 1, and CD34) were observed in the myoblast sheet group infarct heart region. Reverse transcription-polymerase chain reaction results showed expression of stromal-derived factor 1, hepatocyte growth factor, and vascular endothelial growth factor as follows: myoblast sheets > myoblast injection > control.

CONCLUSIONS

Myoblast sheets repaired the impaired myocardium, reduced fibrosis, and prevented remodeling in association with recruitment of hematopoietic stem cells through the release of stromal-derived factor 1 and other growth factors. Our experiment indicates a therapy for patients with severe heart failure.

Combined autologous cellular cardiomyoplasty with skeletal myoblasts and bone marrow cells in canine hearts for ischemic cardiomyopathy

OBJECTIVES

Cellular cardiomyoplasty with isolated skeletal myoblasts and bone marrow mononuclear cells is an encouraging therapeutic strategy for heart failure. We investigated the achievements accomplished with combined cell therapy of skeletal myoblast and bone marrow mononuclear cell transplantation to the ischemic canine myocardium.

METHODS

Autologous skeletal myoblasts (1 x 10(8)) and autologous bone marrow mononuclear cells (3 x 10(6)) were injected directly into the damaged myocardium of canine hearts that had undergone 2 weeks of left anterior descending coronary artery ligation. Treatment groups were as follows: skeletal myoblasts plus bone marrow mononuclear cells (combined cell therapy, n = 4), myoblasts (n = 4), bone marrow mononuclear cells (n = 4), and medium only (n = 4). In similarly designed supporting experiments, angiogenic factor expression was evaluated by enzyme-linked immunosorbent assay after cell transplantation in rat hearts that had undergone left anterior descending coronary artery ligation.

RESULTS

Four weeks after cell implantation, echocardiography demonstrated better cardiac performance with reduced left ventricular dilation and significantly improved ejection fraction in the combined cell therapy group compared with that seen in the other groups (pretreatment, 37.7% +/- 1.1%, vs combined cell therapy, 55.4% +/- 8.6%; myoblasts, 47.4% +/- 7.4%; bone marrow mononuclear cells, 44.4% +/- 6.7%; medium only [control], 34.4% +/- 5.4%; P < .05). A significantly high number of neovessels were observed in the group receiving combined cell therapy only (combined cell therapy, 45.5 +/- 12 x 10(2)/mm2; myoblasts, 26.5 +/- 8 x 10(2)/mm2; bone marrow mononuclear cells, 30.7 +/- 15 x 10(2)/mm2; medium only [control], 7.1 +/- 1 x 10(2)/mm2; P < .05). Immunostained sections expressed the skeletal specific marker myosin heavy chain, although they did not express the cardiac specific marker troponin T. Results of enzyme-linked immunosorbent assay showed the highest expression of vascular endothelial growth factor (combined cell therapy, 2.9 +/- 0.7 ng/g tissue; myoblasts, 0.24 +/- 0.7 ng/g tissue; bone marrow mononuclear cells, 1.9 +/- 0.2 ng/g tissue; medium only [control], 0.19 +/- 0.004 ng/g tissue; P < .05) and hepatocyte growth factor in the combined cell therapy hearts.

CONCLUSIONS

Combined autologous cellular therapy induced both myogenesis and angiogenesis with enhancement of cardiac performance and reduction of cardiac remodeling, suggesting a capable strategy for treating severe ischemic cardiomyopathy clinically.

Biodegradable polymer with collagen microsponge serves as a new bioengineered cardiovascular prosthesis

OBJECTIVE

Biodegradable materials with autologous cell seeding have attracted much interest as potential cardiovascular grafts. However, pretreatment of these materials requires a complicated and invasive procedure that carries the risk of infection. To avoid these problems, we sought to develop a biodegradable graft material containing collagen microsponge that would permit the regeneration of autologous vessel tissue. The ability of this material to accelerate in situ cellularization with autologous endothelial and smooth muscle cells was tested with and without precellularization.

METHODS

Poly(lactic-co-glycolic acid) as a biodegradable scaffold was compounded with collagen microsponge to form a vascular patch material. These poly(lactic-co-glycolic acid)-collagen patches with (n = 10) or without (n = 10) autologous vessel cellularization were used to patch the canine pulmonary artery trunk. Histologic and biochemical assessments were performed 2 and 6 months after the implantation.

RESULTS

There was no thrombus formation in either group, and the poly(lactic-co-glycolic acid) scaffold was almost completely absorbed in both groups. Histologic results showed the formation of an endothelial cell monolayer, a parallel alignment of smooth muscle cells, and reconstructed vessel wall with elastin and collagen fibers. The cellular and extracellular components in the patch had increased to levels similar to those in native tissue at 6 months.

CONCLUSIONS

The poly(lactic-co-glycolic acid)-collagen microsponge patch with and without precellularization showed good histologic findings and durability. This patch shows promise as a bioengineered material for promoting in situ cellularization and the regeneration of autologous tissue in cardiovascular surgery.

Novel method of preparing acellular cardiovascular grafts by decellularization with poly(ethylene glycol)

We have developed a new method of preparing acellular vascular grafts. Cellular components, including cell membranes and proteins in cytosol, were efficiently extracted from the vessels in a concentrated aqueous solution of poly(ethylene glycol), an amphiphilic biocompatible polymer. The residual DNA was digested by deoxyribonuclease I treatment after extraction with poly(ethylene glycol). The two-step extraction process proved quite effective at removing the cellular components while causing little damage to the extracellular matrices. We did not use any detergent that would damage the extracellular matrices. Therefore, vascular endothelial cells grew well on the acellular vessels after recellularization, promising longi-patent cardiovascular grafts.

[Myocardial regeneration therapy for heart failure: hepatocyte growth factor enhances the effect of cellular cardiomyoplasty]

BACKGROUND

We hypothesized that transfection of the gene for human hepatocyte growth factor(hHGF) combined with cellular cardiomyoplasty might regenerate the impaired myocardium.

METHODS AND RESULTS

We used a ligation model of proximal left anterior descending coronary artery of Lewis rats. Two weeks after left anterior descending coronary artery ligation, three different treatments were conducted; 1) neonatal rat cardiomyocytes group(10(6) cells, T group, n = 11), 2) HVJ-liposomes bearing the hHGF gene group (H group, n = 10), and 3) combined(T-H group, n = 10). The injection site was the scar area of myocardial infarction. For control, culture medium was injected (C group, n = 13). Echocardiography demonstrated that cardiac performance was significantly ameliorated in the T-H group 4 and 8 weeks after injection. Contrast echocardiography also showed a marked increase in myocardial perfusion in the T-H group but not in the other groups. In the T-H group, neovascularization and a marked reduction of fibrosis were observed histologically. In an immunohistochemical study, strong staining for beta 1-integrin, alpha- and beta-dystroglycan were found principally in the basement membrane of myocytes in the T-H group 8 weeks after transplantation, although there was weak immunoreactivity in the T group.

CONCLUSIONS

hHGF gene transfection enhanced the cellular cardiomyoplasty possibly by stimulating angiogenesis, restoring the impaired extracellular matrix, and promoting the integration of the dissociated grafted myocytes. The combined effects might have lead to the improved cardiac performance. Thus, combined therapy may be a promising strategy for the treatment of heart failure caused by myocardial infarction.

Cloning and expression of a Porphyromonas gingivalis gene for protoporphyrinogen oxidase by complementation of a hemG mutant of Escherichia coli

Porphyromonas gingivalis, a bacterium implicated in periodontal pathogenesis, has a growth requirement for iron protoporphyrin IX. By complementation with a P. gingivalis 381 chromosomal DNA library, we were able to isolate a clone that enhanced the poor growth of a hemG mutant of Escherichia coli. The DNA sequence analysis of this clone revealed three open reading frames (ORFs). ORF3 encoded a protein of 466 amino acids with a calculated molecular weight of 51 695 Da. The deduced amino acid sequence of the ORF3 gene had significant similarity to sequences of protoporphyrinogen oxidase (PPO) from Myxococcus xanthus (30% identical residues). When the ORF3 gene was overexpressed in E. coli, the extract had much higher PPO activity than a control extract, and this activity was inhibited by acifluorfen, a specific inhibitor of PPO. Thus, ORF3 was named PgHemG. Furthermore, several porphyrin-related genes, including hemD, hemN and hemH, were identified in the data bases on the websites available on-line. We postulated that a porphyrin biosynthetic pathway to heme from preuroporphyrin may be conserved in P. gingivalis.

Myocardial regeneration therapy for heart failure: hepatocyte growth factor enhances the effect of cellular cardiomyoplasty

BACKGROUND

We hypothesized that transfection of the gene for human hepatocyte growth factor (hHGF) combined with cellular cardiomyoplasty might regenerate the impaired myocardium.

METHODS AND RESULTS

We used a ligation model of proximal left anterior descending coronary artery (LAD) of Lewis rats. Two weeks after LAD ligation, 3 different treatments were conducted: (1) neonatal rat cardiomyocytes group (10(6) cells, T group, n=11), (2) HVJ-liposomes bearing the hHGF gene group (H group, n=10), and (3) combined (T-H group, n=10). The injection site was the scar area of myocardial infarction. For control, culture medium was injected (C group, n=13). Echocardiography demonstrated that cardiac performance was significantly ameliorated in the T-H group 4 and 8 weeks after injection. Contrast echocardiography also showed a marked increase in myocardial perfusion in the T-H group but not in the other groups. In the T-H group, neovascularization and a marked reduction of fibrosis were observed histologically. In an immunohistochemical study, strong staining for beta(1)-integrin, alpha-, and beta-dystroglycan were found principally in the basement membrane of myocytes in the T-H group 8 weeks after transplantation, although there was weak immunoreactivity in the T group.

CONCLUSIONS

hHGF gene transfection enhanced the cellular cardiomyoplasty possibly by stimulating angiogenesis, restoring the impaired ECM, and promoting the integration of the dissociated grafted myocytes. The combined effects might have lead to the improved cardiac performance. Thus, combined therapy may be a promising strategy for the treatment of heart failure caused by myocardial infarction.

Analysis of sympathetic nerve activity in end-stage cardiomyopathy patients receiving left ventricular support

BACKGROUND

The left ventricular assist system (LVAS) has been used increasingly for patients with end-stage heart failure who are awaiting transplantation. Sympathetic nerve activity is known to correlate with cardiac function in chronic heart failure patients, but little is known about sympathetic nerve activity during LVAS support. In this study, we examined the status of sympathetic nerve activity in relation to mechanical support.

METHODS

In this study, we included 10 consecutive patients with end-stage cardiomyopathy who were on LVAS support for at least 2 months (duration, 222 +/- 59 days). None of these patients achieved enough functional recovery to be taken off LVAS. In these patients, we used iodine-125-metaiodobenzylguanidine (125I-MIBG) scintigraphy to examine the change of sympathetic nerve activity after LVAS implantation, and compared the results with the change of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) levels as well as with histologic optional findings. Samples for ANP and BNP measurement were obtained before and 30 days after LVAS implantation. Specimens for histologic analysis were obtained at the time of LVAS implantation and at the time of cardiac transplantation or autopsy.

RESULTS

We observed marked decrease in serum levels of ANP and BNP 1 month after LVAS implantation. But myocardial sympathetic nerve function, which was evaluated with 125I-MIBG scintigraphy and expressed as the heart-to-mediastinum activity ratio, remained below normal even 2 months after the LVAS implantation (1.57 +/- 0.19; normal, 2.34 +/- 0.36). Serial histologic analysis in these 10 patients showed continuous increase in percentage of fibrosis and cell diameter despite ventricular unloading by the LVAS.

CONCLUSIONS

Sympathetic nerve function, which was evaluated on 125I-MIBG scintigraphy, did not improve during left ventricular support. Because none of the patients included in our study showed improvement in cardiac function or histologic findings, the recovery of myocardial sympathetic nerve function may be an important factor in myocardial recovery for cardiomyopathy patients on LVAS support.

Involvement of PLAGL2 in activation of iron deficient- and hypoxia-induced gene expression in mouse cell lines

We searched iron-deficient inducible cDNA, using subtraction cloning and mRNA from desferrioxamine-treated mouse macrophage Raw264.7 cells. We identified a pleomorphic adenoma gene like 2 (PLAGL2), one of PLAG superfamily proteins exhibiting antiproliferative properties on tumor cells. Mouse PLAGL2 consists of 496 amino acids with seven C2H2 zinc-fingers. PLAGL2 mRNA was induced in RAW264.7 cells, mouse erythroleukemia cells and Balb/c 3T3 cells when they were treated with desferrioxamine. Hypoxia also increased PLAGL2 mRNA. Expression of PLAGL2 in COS-7 cells led to nuclear localization. PLAGL2 had potential binding ability to GC-rich oligonucleotide and activated transcription of a gene with the binding sequence in transient reporter assay, a finding consistent with a case seen in a PLAGL2 homolog, ZAC-1. Transient co-transfection of PLAGL2 or ZAC1 cDNA and a reporter containing a lactate dehydrogenase A (LDHA) promoter carrying the hypoxia inducible factor-1 responsive element led to an increase in the basal transcription in Balb/c 3T3 and HepG2 cells. Activation in transcription from the LDHA promoter increased by desferrioxamine treatment or hypoxia was further enhanced when PLAGL2 was expressed. We propose that PLAGL2 is involved in the cell cycle arrest and apoptosis of tumor cells by regulating iron depletion- or hypoxia-inducible gene expression.

Proteasome inhibitor 1 enhances paclitaxel-induced apoptosis in human lung adenocarcinoma cell line

Paclitaxel is a chemotherapeutic drug that induces apoptosis in tumor cells by stabilizing microtubules, prevents normal mitosis, and blocks the cell cycle at the G2/M phase. We have previously reported that the activation of caspase-3 and caspase-8 plays a crucial role in paclitaxel-induced apoptosis. Anti-tumor reagents including paclitaxel, irradiation, and other stimuli activate the transcription factor NF-kappaB, which has the ability to suppress the apoptotic potential of those stimuli. Using a human lung adenocarcinoma cell line (LC-2-AD), we therefore examined whether the inhibition of NF-kappaB activity by proteasome inhibitor 1 (PS1) could become a new adjuvant therapy for cancer. A synergistic effect on apoptosis induction was observed with the combination of more than 0.1 microg/ml paclitaxel and 0.5 microM PS1. An increase in the cell number of apoptotic cells is correlated with the loss of Deltaphim and the activation of caspase-3 and caspase-8. Furthermore, augmented apoptosis is related to NF-kappaB activation. Based on these findings, we propose that the combination of paclitaxel with PS1 could be a new strategy for cancer treatment.

Major histocompatibility complex restriction between hematopoietic stem cells and stromal cells in vitro

We have previously found that a significant number of hematopoietic progenitors accumulate in engrafted bones with the same major histocompatibility complex (MHC) as the transplanted bone marrow cells. In the present study, to further clarify the MHC restriction between hematopoietic stem cells (HSC) and microenvironment, we carried out cobblestone colony formation assays by culturing HSCs with MHC-matched or -mismatched stromal cell monolayers. The formation of cobblestone colonies under MHC-mismatched stromal cells significantly decreased in comparison with MHC-matched stromal cells. However, the decrease in cobblestone colony formation under MHC-mismatched stromal cells was not significant when using MHC class I-deficient HSC or stromal cells. Taken together with the results using B10 congenic strains, it is suggested that the MHC preference is restricted by MHC class Ia molecules. Treatment with monoclonal antibodies (mAbs) against MHC class Ia molecules of stromal cell phenotypes significantly enhanced the cobblestone colony formation, whereas treatment with mAbs against HSC phenotypes significantly inhibited it. The expression of cytokines to promote hematopoiesis was enhanced by the mAbs against stromal cell phenotypes. The enhancement of cytokine expression was also observed when stromal cells and HSCs were MHC-matched. These results suggest that signaling via the MHC molecules augments stromal cell activity and elicits the MHC restriction.

Measurement of ferrochelatase activity

Ferrochelatase is the terminal enzyme in the heme biosynthesis pathway. Under anaerobic conditions it catalyzes the insertion of ferrous iron into the protoporphyrin IX ring to form protoheme. In the absence of iron and under aerobic conditions, the enzyme will use zinc or mercury as a substitute. The assay described in this unit uses zinc under aerobic conditions and the artificial substrate mesoporphyrin to analyze the formation of zinc-mesoporphyrin by HPLC with UV or fluorescence detection.

Homozygous variegate porphyria: 20 y follow-up and characterization of molecular defect

The long-term follow-up of a homozygous variegate porphyria patient revealed severe photosensitivity accompanied by mild sensory neuropathy and IgA nephropathy. A 35T to C transition in exon 2 (I12T) and a 767C to G transversion in exon 7 (P256R) of the protoporphyrinogen oxidase gene were identified from both alleles of the patient's cDNA and genomic DNA samples. Both prokaryotic and eukaryotic expression studies showed that the first mutation in the evolutionary conserved region resulted in a decrease in the protoporphyrinogen oxidase activity in contrast to the polymorphic substitution in exon 7, which affected the function of the enzyme assayed in Escherichia coli but not COS-1 cells.

Change of c-Myc expression and cardiac hypertrophy in patients with aortic valve replacement

BACKGROUND

Long-term volume overload to the left ventricle (LV) due to aortic regurgitation (AR) tends to cause severe impairment in LV function that cannot be reversed even with aortic valve replacement (AVR). Recently, we reported that the protooncogene c-myc is related to the onset of the cardiac hypertrophy and LV dysfunction in patients with chronic AR. However, it is still unclear whether c-myc is related to reversibility of the cardiac hypertrophy or LV dysfunction after AVR.

METHODS AND RESULTS

Twenty patients with isolated chronic AR who underwent AVR were included in this study. LV function was calculated before and after AVR. After AVR, end-systolic volume index (ESVI) and enddiastolic volume index (EDVI) were improved, but not mass index (LVMI). However, normalization of ESVI and EDVI was observed only in 12 and 9 patients, respectively. Preoperatively, c-Myc protein was expressed in the myocardium of 16 out of 20 patients with an average point count of 35+/-30%. After AVR, c-Myc protein was observed only in 2 patients. Preoperative ejection fraction (EF), ESVI, and postoperative end-systolic stress (ESS)/ESVI had significant correlation to postoperative cell diameter (CD). Percent c-Myc protein expression before the operation was significantly correlated to postoperative CD, ESVI, and ESS/ESVI. Average c-Myc expression was higher in patients who showed normalization of CD and ESS/ESVI after AVR than the patients who did not.

CONCLUSIONS

These data suggest that preoperative expression of c-Myc can be indicative of the reversibility of myocardial cellular hypertrophy and LV dysfunction.

Expression of coproporphyrinogen oxidase and synthesis of hemoglobin in human erythroleukemia K562 cells

Coproporphyrinogen oxidase (CPOX), the sixth enzyme in the heme-biosynthetic pathway, catalyzes oxidative decarboxylation of coproporphyrinogen to protoporphyrinogen and is located in the intermembrane space of mitochondria. To clarify the importance of CPOX in the regulation of heme biosynthesis in erythroid cells, we established human erythroleukemia K562 cells stably expressing mouse CPOX. The CPOX cDNA-transfected cells had sevenfold higher CPOX activity than cells transfected with vector only. Expression of ferrochelatase and heme content in the transfected cells increased slightly compared with the control. When K562 cells overexpressing CPOX were treated with delta-aminolevulinic acid (ALA), most became benzidine-positive without induction of the expression of CPOX or ferrochelatase, and the heme content was about twofold higher than that in ALA-treated control cells. Increases in cellular heme concomitant with a marked induction of the expression of heme-biosynthetic enzymes, including CPOX, ferrochelatase and erythroid-specific delta-aminolevulinic acid synthase, as well as of alpha-globin synthesis, were observed when cells were treated with transforming growth factor (TGF)beta 1. These increases in the transfected cells were twice those in control cells, indicating that overexpression of CPOX enhanced induction of the differentiation of K562 cells mediated by TGF beta 1 or ALA. Conversely, the transfection of antisense oligonucleotide to human CPOX mRNA into untreated and TGF beta 1-treated K562 cells led to a decrease in heme production compared with sense oligonucleotide-transfected cells. These results suggest that CPOX plays an important role in the regulation of heme biosynthesis during erythroid differentiation.

Lateral clustering of cadherin-4 without homophilic interaction: possible involvement in the concentration process at cell-cell adhesion sites as well as in the cell adhesion activity

It is thought that the concentration of classic cadherins at cell-cell adhesion sites is essential for generating strong cell-cell adhesion activity, but the mechanism is not well understood. To clarify the structural basis of the concentration process and the cell adhesion activity, we constructed various mutants of cadherin-4 and examined the adhesion properties of the transfectants. A deletion mutant lacking the entire cytoplasmic domain had weak, but significant Ca(2+)-dependent cell adhesion activity. Interestingly, the deletion mutant showed intrinsic cluster formation in the absence of cell-cell adhesion, possible lateral cluster formation. The cytoplasmic domain-deleted cadherin-4 containing the mutation of Trp-2 to Ala, which is known to inhibit the strand dimer formation required for the cell-cell adhesion, retained the possible activity of lateral cluster formation, supporting this notion. These results suggest that the extracellular domain has intrinsic activity of lateral cluster formation. Indeed, deletion of a cadherin repeat in the extracellular domain significantly reduced or abolished the lateral cluster formation as well as the concentration of cadherin-4 at cell-cell contact sites and cell adhesion activity. When transfectants of the cytoplasmic domain-deleted cadherin-4 made cell-cell contact and formed intimate cell-cell adhesion, the lateral clusters of cadherin-4 initially gathered at cell-cell contact sites, and a smooth linear concentration was gradually formed along the cell-cell adhesion interface. The results suggest that the lateral cluster formation is involved in the concentration process of cadherin-4 at cell-cell adhesion sites, hence in the strong cell adhesion activity of cadherin-4 as well.

Reduction in myocardial apoptosis associated with overexpression of heat shock protein 70

It is reported that ischemia-reperfusion induces apoptotic cell death in myocardium. It is also demonstrated that heat shock protein 70 (HSP70) enhances myocardial tolerance. Therefore, it is hypothesized that HSP70 may play a role in the attenuation of myocardial apoptosis. To elucidate this goal, HSP70-overexpressing and control-transfected rat hearts were prepared using gene transfection by intra-coronary infusion of the hemagglutinating virus of Japan-liposome. In vivo experiment Hearts of both groups were subjected to global ischemia, followed by reperfusion in situ. Shorter recovery time to spontaneous beating (HSP70-transfected vs. control-transfected; 46.7+/-4.6 vs. 67.5+/-7.0 s, p = 0.033) and lower serum CPK levels (415+/-27 vs. 533+/-36 IU, p = 0.027) were observed in the HSP70-transfected group. The HSP70-transfected group also showed a lower percentage of cardiac myocytes positively stained by nick end labeling after ischemia-reperfusion (17.5+/-4.9 vs. 40.0+/-5.1%, p = 0.010). In vitro experiment Cardiac myocytes isolated from the hearts of both groups (prepared separately from the in vivo experiment) were subjected to hypoxia-reoxygenation. Flow cytometry was used to identify the cells that showed sub-G1 DNA content as apoptotic cells. Apoptotic cells as a percentage of viable cells increased more in the control-transfected group after hypoxia-reoxygenation (13.0+/-0.77 vs. 21.9+/-1.18%, p<0.0001). In conclusion, we demonstrated that apoptosis after ischemia-reperfusion was decreased in the HSP70-overexpressing heart in vivo and in vitro, leading to the suggestion that HSP70 could be associated with the reduction in myocardial apoptosis.

Analysis of the candidate genes responsible for non-syndromic cleft lip and palate in Japanese people

In order to assess the association of alleles for candidate genes with non-syndromic cleft lip and palate, DNA samples from 43 Japanese patients were compared with those from 73 control subjects with respect to the genes encoding transforming growth factor alpha (TGFalpha), TGFbeta and gamma-aminobutyric acid type A receptor beta3 (GABRB3). The restriction fragment length polymorphisms of the 3'-non-coding region of the TGFalpha gene K-primer region were observed after digestion with NcoI and HinfI. Allele 4 was the most common among cases of cleft lip with or without cleft palate, whereas allele 2 was the most common among controls. A significant difference was found in this region between groups with cleft lip (with or without cleft palate) and controls (chi2=10.190; P=0.017). Three alleles of the TGFbeta2 gene were tested, and allele 2 was the most common in both cases and controls. The proportion of allele 2 in the case group was greater than that in the control group, showing a significant difference between cases of cleft lip (with or without cleft palate) and controls (chi(2)=19.208; P<0.0001). No significant differences in variants of TGFbeta3 or GABRB3 between case and control populations were observed. Thus it is concluded that TGF genes play a role in craniofacial development, and that alleles of TGFalpha or/and TGFbeta2 are associated with cleft lip and cleft palate in Japanese populations.

Coronary artery bypass graft in a renal transplant recipient

A 47-year-old woman receiving predonine after renal transplantation underwent coronary artery bypass graft (CABG) surgery because of medically angina uncontrollable since 1996. Although she had an episode of acute renal rejection successfully treated with steroid pulse therapy, she had no angina or hemodialysis for over 2 years after CABG. We discuss postoperative management of renal recipient after cardiac surgery using lymphocyte-subpopulation monitoring.

Regulation of the expression of human ferrochelatase by intracellular iron levels

Mammalian ferrochelatase, the terminal enzyme of the heme biosynthetic pathway, catalyzes the insertion of a ferrous ion into protoporphyrin and contains a labile [2Fe-2S] cluster center at the C-terminus. To clarify the roles of the iron-sulfur cluster in the expression of mammalian ferrochelatase, enzyme activity in human erythroleukemia K562 cells under iron-depleted conditions was examined. Treatment of cells with an iron chelator, desferrioxamine, resulted in a decrease in enzyme activity, in a dose- and time-dependent manner. Heme content decreased during desferrioxamine treatment of the cells. Addition of ferric ion-nitrilotriacetate [Fe (III)NTA] to desferrioxamine-containing cultures led to restoration of the reduction in the enzyme activity. While RNA blots showed that the amount of ferrochelatase mRNA remained unchanged during these treatments, the amount of ferrochelatase decreased with a concomitant decrease in enzyme activity. When full-length human ferrochelatase was expressed in Cos7 cells, the activity was found mainly in the mitochondria and was decreased markedly by treatment with desferrioxamine. The activity in Cos7 cells expressing human ferrochelatase in cytoplasm decreased with desferrioxamine, but to a lesser extent. When Escherichia coli ferrochelatase, which lacks the iron-sulfur cluster, was expressed in Cos7 cells, the activity did not change following any treatment. Conversely, the addition of Fe (III)NTA to the culture of K562 and Cos7 cells led to an increase in ferrochelatase activity. These results indicate that the expression of mammalian ferrochelatase is regulated by intracellular iron levels, via the iron-sulfur cluster center at the C-terminus, and this contributes to the regulation of the biosynthesis of heme at the terminal step.

Cloning of a coproporphyrinogen oxidase promoter regulatory element binding protein

Coproporphyrinogen oxidase [CPO] gene promoter regulatory element (CPRE) plays an important role in CPO gene regulation. To isolate a CPRE binding protein, we performed Southwestern screening of K562 cDNA expression library using CPRE as a probe and isolated a cDNA clone which encoded a novel protein, Klp1 (K562 cell-derived leucine-zipper-like protein 1). Klp1 mRNA was highly expressed in K562 cells, HeLa cells, and brain as a single transcript (1.4 kb). Gel mobility shift assays revealed that Klp1 specifically binds to CPRE. Computational analysis revealed that Klp1 has a leucine-zipper-like structure, a Leu-X-X-Leu-Leu motif, and a putative nuclear localization signal in the basic amino acid rich region. Transfection of the Klp1 expression vector into THP-1 cells resulted in transcriptional activation of a reporter construct containing CPRE. These results indicate that Klp1 is a DNA sequence-specific transcription factor that regulates gene expression of genes that contain CPRE in their regulatory region.

Morphological change, loss of deltapsi(m) and activation of caspases upon apoptosis of colorectal adenocarcinoma induced by 5-FU

Apoptosis is clearly distinguished from necrosis, morphologically and chemically. Morphologically, apoptosis is characterized by a condensed nucleus and the disappearance of microvilli without disruption of the cytoplasm. In this report, we demonstrate that 5-fluorouracil (5-FU)-induced early apoptotic cells are characterized by (i) ultracondensed mitochondria, (ii) no change in the microvilli or nucleus, (iii) a high mitochondrial transmembrane potential (Deltapsi(m)), and (iv) being annexin V(negative). The early apoptotic cells also show the active forms of caspase 8 and caspase 9. They rapidly lose Deltapsi(m) after further incubation. Therefore, we conclude that the ultracondensation of mitochondria precedes the loss of Deltapsi(m) and the exposure of phosphatidylserine to the outer leaflet of the cell membrane.

Mutation analysis of cadherin-4 reveals amino acid residues of EC1 important for the structure and function

To clarify the structural basis of the cell adhesion activity of cadherins, we examined the effects of point mutations of well-conserved amino acid residues in the extracellular domain 1 of cadherin-4 (Cdh4) on the adhesion properties by alanine scanning mutagenesis. Mutations of two well-conserved aromatic amino acid residues in the extracellular domain 1 resulted in abnormal processing of Cdh4 molecules and no cell adhesion activity, whereas mutations of the corresponding aromatic amino acids in the extracellular domain 2 did not show these effects, suggesting a role for the two residues in the extracellular domain 1 in the folding and/or intracellular transport processes of Cdh4. Mutations of the amino acid residues suspected to be involved in strand dimer formation resulted in loss or significant decrease in cell adhesion activity. The mutant Cdh4s showed weak concentration at cell-cell adhesion sites and chemical cross-linking suggested that the strand dimer formation was actually impaired in the mutants. These results are consistent with the zipper model, in which the extracellular domain 1 of Cdh4 has intrinsic strand dimer formation activity in addition to adhesion dimer formation activity, both of which are involved in cell adhesion activity. The zipper model, however, needs further improvement to fully account for the present results.

ELISA for urinary trehalase with monoclonal antibodies: a technique for assessment of renal tubular damage

BACKGROUND

alpha,alpha-Trehalase, located on renal proximal tubules, is a glycoprotein that hydrolyses alpha,alpha-trehalose to two glucose molecules. Urinary trehalase reflects damage to renal proximal tubules, but its activity has not been measured routinely because measurement of catalytic activity is rather complicated and because conventional assays for enzyme activity might not reflect all of the trehalase protein because of enzyme inactivation in urinary samples.

METHODS

We established novel monoclonal antibodies for human trehalase and a sandwich ELISA for quantification of urinary trehalase. We determined the urinary trehalase protein concentration with this ELISA and trehalase catalytic activity, and the results of these two methods were compared.

RESULTS

The ELISA system was more sensitive than the detection of enzyme activity and could detect a subtle difference in the amount of trehalase present in renal diseases. The within- and between-assay CVs in the ELISA were 6.7-7.6% and 6.2-8.2%, respectively. Highly significant increases in both the quantity and activity were seen in patients with nephrotic syndrome (acute phase), Lowe syndrome, and Dent disease. The quantities were 70- to 200-fold greater, whereas enzyme activities were, at most, 10-fold higher than those of control subjects. In the detection of small amounts of trehalase in patients with chronic glomerulonephritis and renal anomalies, quantities were better than enzyme activities.

CONCLUSIONS

We have established an ELISA system for quantification of urinary trehalase that uses novel monoclonal antibodies. Our ELISA system is simpler and more sensitive than a conventional activity assay and reflects trehalase protein. This ELISA can be a useful as a common tool for clinical assessment of renal proximal tubular damage.

Differentiation from thymic B cell progenitors to mature B cells in vitro

The role of the thymic microenvironment in the development of murine thymic B cells has yet to be fully clarified. We therefore investigate the microenvironment that supports the development of mature thymic B cells (sIg+/B220+/CD43-B cells) from thymic B cell progenitors with immunophenotypes of sIg-/B220med/CD43+ cells. As we have previously reported, thymic B cells generated from these progenitors in the thymus are CD5+ B cells. We next study the in vitro condition that supports the differentiation of thymic B cell progenitors. Stromal cells (from the bone marrow or thymus), thymus-derived cell lines with the character of thymic nurse cells (TNCs) or thymic epithelial cells (TECs), or the bone marrow-derived cell line (MS-5) are tested for their ability to support B-lymphopoiesis from thymic B cell progenitors. Interestingly, thymic stromal cells (but neither stromal cells from the bone marrow nor stromal cell lines) support the differentiation of thymic B cell progenitors into thymic B cells in the presence of IL-7. Cortical epithelia (but not medullary epithelia, thymic macrophages or dendritic cells) are found to contribute to thymic B cell differentiation. Surface phenotype and Ig rearrangement analyses reveal that mature B cells generated in this condition are primarily CD5+ B cells, indicating that the thymic microenvironment (particularly cortical epithelia) determines the differentiation of thymic B cells.

Age-dependent abnormalities of hematopoietic stem cells in (NZW x BXSB)F1 mice

The (NZW x BXSB)F1 (W/BF1) mouse is known as an autoimmune-prone strain which develops lupus nephritis, thrombocytopenia due to platelet-specific autoantibodies, leukocytosis, and myocardial infarction. In this experiment, we investigated the age-dependent abnormalities of the hematopoietic stem cells (HSCs) and hematopoiesis in this mouse. White blood cell counts (especially Mac-1- or Gr-1-positive cells) in the peripheral blood of 12-week-old W/BF1 mice increased in comparison with those of four-week-old W/BF1 or normal mice. To investigate whether the abnormal hematopoiesis can be attributed to the HSCs of W/BF1 mice, colony-forming unit in spleen (CFU-S) and colony-forming unit in culture (CFU-C) assays were performed. Day 12 CFU-S counts of 12-week-old W/BF1 mice significantly increased in comparison with those of four-week-old W/BF1 mice or normal mice. In the CFU-C assay, CFU-GEMM and CFU-GM counts in 12-week-old W/BF1 mice increased in comparison with those of four-week-old W/BF1 or control mice. The bone marrow cells (BMCs) from 12-week-old W/BF1 mice showed a high level of G-CSF and a low level of GM-CSF in mRNA expression. To examine the effect of HSCs from 12-week-old W/BF1 mice on the onset of autoimmune diseases and the abnormal hematopoiesis, T- and B-cell-depleted BMCs of four-week-old or 12-week-old W/BF1 mice were transplanted to C3H mice. Recipient C3H mice that had received the BMCs from 12-week-old W/BF1 mice showed an earlier onset of autoimmune diseases and a shorter survival rate than those that had received the BMCs from four-week-old W/BF1 mice. These data suggest that the HSCs from 12-week-old W/BF1 mice showing the symptoms of autoimmune diseases have the capacity to induce autoimmune diseases earlier than the HSCs from four-week-old W/BF1 mice.

Activated Rac1 selectively up-regulates the expression of integrin alpha6beta4 and induces cell adhesion and membrane ruffles of nonadherent colon cancer Colo201 cells

Functions of small GTPases in integrin expression were investigated when the interaction of nonadherent human colon carcinoma 201 cells with the extracellular matrix (ECM) was examined. By transfection of the constitutively active form of a small GTPase Rac1, Rac V12, adhesion of cells to the ECM increased with concomitant cell spreading and formation of membrane ruffles. Activated Cdc42 and Cdc42 V12, but not wild-type Rac1, Cdc42, or RhoA, also induced the adhesion and spreading of Colo201 cells. This adhesion is integrin beta4 dependent since an antibody for integrin beta4 inhibited the RacV12-dependent cell adhesion and numbers of adhesive cells on laminin-coated plates exceeded those on collagen- and fibronectin-coated plates. By immunofluorescence, in addition to clustering of integrin molecules, expression of integrin alpha6beta4 on the cell surface of Rac V12- and Cdc42 V12-expressing cells was selectively up-regulated without an increase in biosynthesis of alpha6beta4 integrin. Treatment of Rac V12-expressing cells with wortmannin or LY294002, specific inhibitors of phosphoinositide 3-OH kinase, decreased the up-regulated alpha6beta4 and cell adhesion. In light of this evidence, we propose that the regulation of integrin alpha6beta4 expression induced by Rac1 and Cdc42 may play an important role in cell adhesion and tumorigenesis of colon carcinoma cells.

Apoptosis of colorectal adenocarcinoma induced by 5-FU and/or IFN-gamma through caspase 3 and caspase 8

The cytotoxic effect of 5-FU has been shown by the induction of apoptosis in cancer cells, and reported to be enhanced by IFN-gamma. We examined the role of caspases on the apoptosis induction of 5-FU and IFN-gamma using a colorectal adenocarcinoma cell line. The activities of caspase 3 and caspase 8 increased when apoptosis was induced by 5-FU and/or IFN-gamma. Moreover, all apoptotic cells showed high caspase 3 activity in these conditions. Although the inhibitors of caspase 3 and caspase 8 inhibit apoptosis, anti-Fas ligand antibody does not affect the apoptosis induced by 5-FU. Thus, caspase 3 and caspase 8 play crucial roles in apoptosis induced by 5-FU and/or IFN-gamma, regardless of the Fas-Fas ligand system.

Detection of a variety of Ser/Thr protein kinases using a synthetic peptide with multiple phosphorylation sites

A novel peptide with multiple phosphorylation sites, which we designated as multide, was developed to detect a wide variety of protein kinases in crude cell extracts. Multide, KKRKSSLRRWSPLTPRQMSFDC, has been designed to contain consensus sequences for various Ser/Thr protein kinases including cAMP-dependent protein kinase, protein kinase C, MAP kinases, and Ca(2+)/calmodulin-dependent protein kinases in a single peptide. In-gel protein kinase assay using multide was found to be very useful for analyzing the activities of protein kinases that are altered in response to various extracellular stimuli. The substrate specificities of the protein kinases thus detected were further determined by using five multide analogs with different phosphorylation sites.

A crucial role of caspase 3 and caspase 8 in paclitaxel-induced apoptosis

The anticancer drug paclitaxel is well known as an inhibitor of microtubule depolymerization, resulting in mitosis arrest. We investigated the mechanism underlying antitumor effects of paclitaxel on the lung adenocarcinoma cell line LC-2-AD. Less than 10 microg/ml paclitaxel induced mitosis arrest upon LC-2-AD, followed by apoptosis, but more than 30 microg/ml paclitaxel induced apoptosis without mitosis arrest. LC-2-AD with less than 1 microg/ml paclitaxel showed a loss of mitochondrial transmembrane potential (deltapsim), which correlated with antitumor effects. However, LC-2-AD with more than 10 microg/ml paclitaxel showed slight changes in the loss of deltapsim in spite of its ability to induce apoptosis significantly. The cleavage of caspase 3, caspase 8, and DFF45/ICAD was also observed in paclitaxel-induced apoptosis, and the inhibitor of caspase 3 and caspase 8 inhibited both antitumor effects and apoptosis induced by paclitaxel. These results suggest that activation of caspase 3 and caspase 8 plays a crucial role in paclitaxel-induced apoptosis under any concentrations of paclitaxel.

Oxidation of protoporphyrinogen IX in Escherichia coli is mediated by the aerobic coproporphyrinogen oxidase

Protoporphyrinogen oxidase, the penultimate enzyme involved in the biosynthetic pathway for heme, catalyzes the removal of six electrons from protoporphyrinogen IX to generate protoporphyrin IX. In Escherichia coli, this enzyme is encoded by the hemG gene. In this study we examined possible alternate pathways for the oxidation of protoporphyrinogen IX to protoporphyrin IX, by isolating and investigating E. coli mutants that can still grow normally when the hemG gene is disrupted. One of these mutants was characterized in detail and had a mutation in the promoter region of the hemF gene, which encodes aerobic coproporphyrinogen oxidase, the enzyme involved in the step immediately before protoporphyrinogen oxidase. Measurement of the promoter activity of the hemF gene showed that the level of transcription was elevated by the mutation. Overexpression of a wild-type hemF gene cloned in a multicopy plasmid also restored the growth of deltahemG strain. Extracts from cells that overexpress hemF exhibited an increased ability to oxidize protoporphyrinogen IX to protoporphyrin IX. These findings suggest that the E. coli aerobic coproporphyrinogen oxidase has an intrinsic capacity to oxidize not only coproporphyrinogen III but also protoporphyrinogen IX.

MAP kinase-independent induction of proto-oncogene c-fos mRNA by hemin in human cells

Treatment of HeLa cells or human skin fibroblast cells with hemin led to a time- and dose-dependent rapid induction of c-fos mRNA. This induction was absent in the cells treated with actinomycin D, indicating that the c-fos induction by hemin occurs at the level of transcription. Metalloporphyrins, including zinc-, cobalt-, and tin-protoporphyrin, ferric ion, and protoporphyrin also induced c-fos mRNA. Transient reporter assay with the reporter constructs of the human c-fos gene promoter up to -404 bp connected to the luciferase gene showed high activity but no induction by hemin, suggesting that cis-acting elements, including the serum response element located about -310 bp upstream of the human c-fos gene promoter, may not contribute to the heme-dependent induction. With in-gel assay of protein kinases, the activity of the mitogen-activated protein (MAP) kinases such as extracellular signal-regulated kinase 12 or p38 MAP kinase in hemin-treated HeLa cells was not stimulated. Stimulation of c-Jun N-terminal kinase by hemin was nil. Furthermore, PD58059 and SB203580, inhibitors for MAP kinases, did not affect the hemin-dependent c-fos induction. Of the inhibitors for protein kinases so far tested, KN-62, a specific inhibitor for calmodulin-dependent protein kinase II (CaMK II), inhibited the induction of c-fos mRNA by hemin. Phosphorylation of CaMK II in hemin-treated cells increased. With gel mobility assay, the DNA AP-1 binding activity transiently increased when treating HeLa cells with hemin. Therefore, induction of c-fos led to an activation of AP-1 in the presence of hemin. We suggest that calmodulin-dependent protein kinase II rather than the MAP kinase family regulates the induction of the human c-fos gene expression by hemin.

HGF activates signal transduction from EPO receptor on human cord blood CD34+/CD45+ cells

Hepatocyte growth factor (HGF) is a multifunctional cytokine with early hematopoiesis-stimulatory activity. Here, we focus on its erythropoiesis-stimulatory effect on highly purified human hematopoietic progenitor cells (CD34+/CD45+ cells) derived from the cord blood. In immunoblot analyses, c-met protein (a receptor of HGF) was detected in the CD34+/CD45+ cells, although the expression levels were different among samples. The c-met expression was facilitated by incubation of the cells with stem cell factor (SCF) or interleukin 3 (IL-3), even if the expression level had been low. IL-6, G-CSF, or erythropoietin (EPO) did not show such a stimulatory effect on the c-met expression of the cells. When HGF was added to the CD34+/CD45+ cells in the presence of SCF, the numbers of CD36+/CD11b- cells (very early erythroid lineage cells) and BFU-E increased. EPO-dependent tyrosine phosphorylation of Stat 5 also increased, but the EPO receptor (EPO-R) expression remained unchanged in the CD34+/CD45+ cells treated with SCF + HGF. Our present study suggests that stimulation of the HGF/c-met signal is concomitant with induction of c-met protein by SCF. The subsequent enhancement of signal transduction via the activation of Stat 5 from the EPO-R plays a crucial role in the commitment of hematopoietic stem cells into erythroid lineage cells.

Ischemia induces metallothionein III expression in neurons of rat brain

Metallothionein III (MT-III) is a brain-specific member of the metallothionein family and binds zinc in vivo. In order to confirm the precise localization of MT-III in normal rat brain and the change of MT-III expression after transient whole brain ischemia, we raised a high affinity phagemid-antibody specific for rat MT-III. Immunohistochemical analysis revealed that MT-III in normal brain is localized abundantly in neuronal cell bodies in CA1-3 regions of hippocampus, dentate gyrus, cerebral cortex, olfactory bulb and Purkinje cells in cerebellum. This expression pattern of MT-III was similar to that of MT-III mRNA observed by in situ hybridization studies. ELISA and Northern blot analysis revealed that MT-III protein as well as mRNA levels were up-regulated in cerebrum soon after ischemic stress. Immunohistochemical analysis also demonstrated intense staining in neurons in injured brain after ischemia, which distributed in the same regions as in normal brain. These results suggest that MT-III plays an important role in protecting neurons from ischemic insult by reducing neurotoxic zinc levels and inhibits uncontrolled growth of neurites after ischemia.

Structure and transcriptional regulation of the mouse ferrochelatase gene

Ferrochelatase (EC.4.99.1.1), the final step in the biosynthesis of heme, is widely expressed in various tissues and is induced in erythroid cells. We determined the structure of the mouse ferrochelatase gene after isolation and characterization of lambda phage clones mapping discrete regions of the cDNA. The gene spans about 25 kb and consists of 11 exons. The exon/intron boundary sequences conform to consensus acceptor (GTn)/donor (nAG) sequences, and exons in the gene encode functional protein domains. The promoter region contains multiple Sp1 sites, a CACCC box and GATA-1 binding sites. Function analysis of the promoter by transient transfection assay demonstrated that one Sp1 binding site located at -37/-32 is essential for basic expression of the ferrochelatase gene in both mouse erythroleukemia (MEL) and non-erythroid EL4 cells. In addition, the region (-66/-51) containing a CACCC box and the neighboring GC box partly contributes to the inducible activity of the reporter in MEL cells upon induction with dimethylsulfoxide. It appears that at least two promoter regions of the mouse ferrochelatase gene function in basic and inducible expression.

Facile degradation of apolipoprotein B by radical reactions and the presence of cleaved proteins in serum

A facile cleavage of peptide bonds of apolipoprotein B (apoB) by radical reaction is reported. When human LDL was subjected to oxidative damage using Cu2+, extensive degradation of apoB was observed based on immunoblotting. The degradation of apoB was inhibited by radical scavengers (beta-mercaptoethanol, butylated hydroxytoluene, and probucol) and promoted by a radical initiator [2, 2'-azobis(2-amidinopropane)dihydrochloride]. When human serum was treated with Cu2+, a similar cleavage pattern of apoB was observed. The cleaved apoB proteins were also detected in normal serum on the basis of immunoblots. These results suggest that apoB is highly reactive toward radicals in vitro and in vivo, with reaction resulting in the cleavage of peptide bonds.

Molecular characterization of a newly identified heme-binding protein induced during differentiation of urine erythroleukemia cells

A heme-binding protein with a molecular mass of 22 kDa, termed p22 HBP, was purified from mouse liver cytosol, using blue Sepharose CL-6B. We identified a cDNA encoding p22 HBP, and sequence analysis revealed that p22 HBP comprises 190 amino acid residues (Mr 21,063) and has no homology to any other known heme-binding protein. The p22 HBP mRNA (approximately 1.0 kilobases) is ubiquitously expressed in various tissues and is extremely abundant in the liver. cDNA allows for expression of active p22 HBP, with a high affinity for 55Fe-hemin, with a Kd of 26 +/-1.8 nM. The Bmax of hemin binding to p22 HBP was 0.55 +/- 0.021 mol/mol of protein, a value consistent with one heme molecule binding per molecule of protein. The order of potency of different ligands to compete against 55Fe-hemin binding to p22 HBP was hemin = protoporphyrin IX > coproporphyrin III > bilirubin > palmitic acid > all-trans-retinoic acid. Treatment of mouse erythroleukemia (MEL) cells with dimethyl sulfoxide or hemin resulted in an increase in p22 HBP mRNA. The immunoblot analysis showed that p22 HBP increased with time in dimethyl sulfoxide- and hemin-induced MEL cells. Conversely, transfer of antisense oligonucleotides to p22 HBP cDNA resulted in a decrease of p22 HBP in dimethyl sulfoxide-treated MEL cells, and the heme content in these cells decreased to 66-71% of sense oligonucleotides-transferred cells. Thus, this newly identified heme-binding protein, p22 HBP, may be involved in heme utilization for hemoprotein synthesis and even be coupled to hemoglobin synthesis during erythroid differentiation.