Flow cytometric estimation of cytotoxic activity of rhodexin A isolated from Rhodea japonica in human leukemia K562 cells

We have examined the cytotoxic effect of rhodexin A isolated from the extract of Rhodea japonica on human leukemia K562 cells using a flow cytometer and compared it with that of ouabain. Rhodexin A at 30 nM started to attenuate growth without affecting viability and further increases in the concentration of rhodexin A (100 nM or more) completely inhibited growth with decreasing viability. Rhodexin A at 30-100 nM increased the G(2)M population, but decreased the G(0)G(1) population, suggesting cell cycle arrest in the G(2)M phase. Rhodexin A at 100 nM increased the number of cells with hypodiploid DNA, indicating that rhodexin A induced apoptosis. The potency of rhodexin A to inhibit growth was greater than that of ouabain. The results indicate that rhodexin A exerts a potent inhibitory action on the growth of human leukemia K562 cells by inducing cell cycle arrest and apoptosis. Rhodexin A may also be a candidate for cancer treatment because there have been clinical reports of tumor regression in patients taking cardiac glycosides.

Search for supernova relic neutrinos at Super-Kamiokande

A search for the relic neutrinos from all past core-collapse supernovae was conducted using 1496 days of data from the Super-Kamiokande detector. This analysis looked for electron-type antineutrinos that had produced a positron with an energy greater than 18 MeV. In the absence of a signal, 90% C.L. upper limits on the total flux were set for several theoretical models; these limits ranged from 20 to 130 macro nu(e) cm(-2) s(-1). Additionally, an upper bound of 1.2 macro nu(e) cm(-2) s(-1) was set for the supernova relic neutrino flux in the energy region E(nu)>19.3 MeV.

Indications of neutrino oscillation in a 250 km long-baseline experiment

The K2K experiment observes indications of neutrino oscillation: a reduction of nu(mu) flux together with a distortion of the energy spectrum. Fifty-six beam neutrino events are observed in Super-Kamiokande (SK), 250 km from the neutrino production point, with an expectation of 80.1(+6.2)(-5.4). Twenty-nine one ring mu-like events are used to reconstruct the neutrino energy spectrum, which is better matched to the expected spectrum with neutrino oscillation than without. The probability that the observed flux at SK is explained by statistical fluctuation without neutrino oscillation is less than 1%.

Effects of A23187 and CaCl(2) on tri-n-butyltin-induced cell death in rat thymocytes

As tri-n-butyltin (TBT), one of the environmental pollutants, is accumulated in wild animals, concern regarding the toxicity of TBT in both wildlife and human is increasing. TBT has been reported to increase intracellular Ca(2+) concentration in several types of cells. In order to examine how Ca(2+) is involved in TBT-induced cell death, the effect of TBT on rat thymocytes has been compared with that of A23187, a calcium ionophore, under various concentrations of external Ca(2+) using a flow cytometer and fluorescent probes. Although both TBT and A23187 were toxic to cells under normal Ca(2+) condition, under external Ca(2+)-free condition the cytotoxic action of TBT was potentiated without changing the threshold concentration while that of A23187 was completely abolished. A23187 attenuated the TBT-induced descent in cell viability under normal Ca(2+) concentration despite intracellular Ca(2+) concentration was increased. As external Ca(2+) concentration increased, the TBT-induced increase in number of dead cells gradually decreased whereas the number of cells in an early stage of apoptosis increased. Results suggest that Ca(2+) has contradictory actions on the process of TBT-induced cell death in rat thymocytes.

Formaldehyde-induced shrinkage of rat thymocytes

To test the possibility that micromolar formaldehyde, a metabolite of methanol derived from aspartame, exerts cytotoxicity, its effect on rat thymocytes was examined under the in vitro condition using a flow cytometer. Incubation of thymocytes with formaldehyde at 100 micro M or more for 24 h significantly increased the populations of shrunken cells and cells with hypodiploid DNA. The peak blood concentration of methanol in human subjects administered abuse doses of aspartame has been reported to exceed 2 mg/dL (625 micro M). It would increase the population of thymocytes undergoing apoptosis if formaldehyde at 100 micro M or more appears in the blood after administration of aspartame.

Cellular component of vascular calcification. Fibroblasts are essential for calcium deposition in cultured cells

It has been reported that calcium deposition and calcium content in cultured human aortic smooth muscle cells (SMC) increased when the cells are incubated in a medium with a high phosphate concentration (2 mM). To determine the cellular components or soluble factors contributing to the deposition, we cultured commercially available SMC, fibroblasts (Fb) and endothelial cells (Ed). These cells and their mixtures were incubated for 10 days in normal or high-phosphate media. Calcium crystals were stained by the von-Kossa staining and counted in the defined area. Calcium content was measured by a colorimetric assay. SMC were incubated in high-phosphate media (up to 2 mM) or beta-glycerophosphate (beta-GP) media, resulting in no obvious deposition of calcium crystals, irrespective of the coating of type I collagen on the dish. Next, various combinations of cells were cultured, and a significant number of depositions were observed only when Fb were included in the combination. The calcium content was significantly higher in cultures of SMC and Fb. The calcium deposition on single or mixture of the cells did not increase compared with control when cells were incubated in a high concentration of phosphate, cultured in the existence of beta-GP or uremic serum. We therefore conclude that Fb, rather than SMC or Ed, are essential for calcium deposition and calcium accumulation in culture. Phosphate concentration in the medium and uremic serum did not influence the deposition of calcium.

Reassessing the definition of myeloid engraftment after autotransplantation: it is not necessary to see 0.5 x 10(9)/l neutrophils on 3 consecutive days to define myeloid recovery

The time to myeloid recovery after autologous hematopoietic stem cell transplantation (HSCT) is usually defined as the first of 3 consecutive days with an absolute neutrophil count (ANC) of >or=0.5 x 10(9)/l (ANC500). Universal documentation of ANC500 for 3 consecutive days, historically required to ensure robust myeloid recovery, has become difficult with a trend towards early discharge and outpatient HSCT. We studied 90 autografted patients to see how frequently ANC declined after having reached >or=0.5 x 10(9)/l. ANC500 was documented on 2 and 3 consecutive days in 14 and 63 patients, respectively. ANC increased by a median of 213% from the 1st to the 2nd day (rise in 75 and unchanged in two), and by a median of 142% from the 2nd day to the 3rd (rise in 60, unchanged in one, and decline in two; higher than the 1st day in the latter three). The increase from the 1st to the 3rd day was 13-3433% (median, 557%). Thus, in all 63 patients, no decline below ANC500 was seen, and the first day with ANC500 was also the first of 3 consecutive days with ANC500. The remaining 13 patients had repeat counts 2-7 days after the 1st day with ANC500 documenting further increase in ANC with no evidence of failed engraftment. These data show that the first day with ANC500 is also consistently the first of 3 consecutive days with ANC500 in autografted patients. Therefore, the traditional definition of myeloid engraftment should be changed to consider the first day with ANC500 as the day of engraftment without necessarily documenting ANC500 on the subsequent 1-2 days. This simple change in definition has significant implications for how data are reported to transplant registries and how peer-review organizations such as the Foundation for the Accreditation of Hematopoietic Cell Therapy (FAHCT) define completeness of data.

Cytotoxic effects of methanol, formaldehyde, and formate on dissociated rat thymocytes: a possibility of aspartame toxicity

Aspartame is a widely used artificial sweetener added to many soft beverages and its usage is increasing in health-conscious societies. Upon ingestion, this artificial sweetener produces methanol as a metabolite. In order to examine the possibility of aspartame toxicity, the effects of methanol and its metabolites (formaldehyde and formate) on dissociated rat thymocytes were studied by flow cytometry. While methanol and formate did not affect cell viability in the physiological pH range, formaldehyde at 1-3 mmol/L started to induce cell death. Further increase in formaldehyde concentration produced a dose-dependent decrease in cell viability. Formaldehyde at 1 mmol/L or more greatly reduced cellular content of glutathione, possibly increasing cell vulnerability to oxidative stress. Furthermore, formaldehyde at 3 mmol/L or more significantly increased intracellular concentration of Ca2+ ([Ca2+]i) in a dose-dependent manner. Threshold concentrations of formaldehyde, a metabolite of methanol, that affected the [Ca2+]i and cellular glutathione content were slightly higher than the blood concentrations of methanol previously reported in subjects administered abuse doses of aspartame. It is suggested that aspartame at abuse doses is harmless to humans.

Cytokinesis arrest and nuclear fission in low density populations of trichomonad protozoan

Cell growth of anaerobic protozoan Tritrichomonas foetus was analyzed. This protozoan usually proliferates in extremely high density, but protozoan parasites were dispersed uniformly in F-bouillon medium and cell division stopped temporarily. However, nuclear fission continued and giant polynucleated cells formed. Later, cell division resumed and cells returned to normal form. In conditioned medium, cytokinesis of the dispersed parasites did not stop. Results indicated that T. foetus cells secreted an extracellular factor that influenced cytokinesis.

Cytotoxic effects of triphenylbismuth on rat thymocytes: comparisons with bismuth chloride and triphenyltin chloride

The biomedical and industrial uses of organobismuth compounds have become widespread, although there is limited information concerning their cytotoxicity. Therefore, the actions of triphenylbismuth on rat thymocytes were examined using a flow cytometer with ethidium bromide, annexin V-FITC, fluo-3-AM, and 5-chloromethylfluorescein (5CMF) diacetate. Triphenylbismuth at 3-30 microM increased the population of cells stained with ethidium, indicating a decrease in cell viability. Organobismuth at 30 microM increased the population of cells positive to annexin V, suggesting an increase in the population of apoptotic cells. Triphenylbismuth at 3 microM or more decreased cellular glutathione content (5CMF fluorescence intensity) and increased intracellular Ca(2+) concentration ([Ca(2+)](i), fluo-3 fluorescence intensity) in a dose-dependent manner. Because an increase in [Ca(2+)](i) is linked to cell death or cell injury and a decrease in cellular glutathione content increases cell vulnerability to oxidative stress, the triphenylbismuth-induced changes in cellular parameters may be responsible for triphenylbismuth-induced cytotoxicity. Bismuth chloride at 10-30 microM did not significantly affect cell viability. These results suggest that triphenylbismuth at micromolar concentrations exerts cytotoxic action on rat thymocytes, possibly related to a health hazard. Although the cytotoxicity of triphenylbismuth was less than that of triphenyltin, one of the environmental pollutants, it is necessary to direct our attention to the use and disposal of organobismuth compounds.

Flow cytometric estimation on cytotoxic activity of leaf extracts from seashore plants in subtropical Japan: isolation, quantification and cytotoxic action of (-)-deoxypodophyllotoxin

The cytotoxic activity of methanol extracts of leaves collected from 39 seashore plants in Iriomote Island, subtropical Japan was examined on human leukaemia cells (K562 cells) using a flow cytometer with two fluorescent probes, ethidium bromide and annexin V-FITC. Five extracts (10 microg/mL) from Hernandia nymphaeaefolia, Cerbera manghas, Pongamia pinnata, Morus australis var. glabra and Thespesia populnea greatly inhibited the growth of K562 cells. When the concentration was decreased to 1 microg/mL, only one extract from H. nymphaeaefolia still inhibited the cell growth. A cytotoxic compound was isolated from the leaves by bioassay-guided fractionation and was identified as (-)-deoxypodophyllotoxin (DPT). The fresh leaves of H. nymphaeaefolia contained a remarkably high amount of DPT (0.21 +/- 0.07% of fresh leaf weight), being clarified by a quantitative HPLC analysis. DPT at 70-80 pM started to inhibit the growth of K562 cells in an all-or-none fashion and at 100 pM or more it produced complete inhibition in all cases. Therefore, the slope of the dose-response curve was very steep. DPT at 100 pM or more decreased the cell viability to 50%-60% and increased the number of cells undergoing apoptosis (annexin V-positive cells). The results indicate that DPT contributes to the cytotoxic action of the extract from the leaves of H. nymphaeaefolia on K562 cells.

Modification of NMDA responses by tri-n-butyltin in rat brain neurons

1. The effects of the organotin, tri-n-butyltin (TBT), on N-methyl-D-aspartate (NMDA) induced membrane currents were investigated in order to evaluate possible neuronal actions of this toxic environmental pollutant. Experiments were conducted on neurons acutely dissociated from the rat dorsal motor nucleus of vagus (DMV) using the nystatin-perforated patch clamp recording technique. 2. In Mg(2+)-free physiological recording solutions, the application of NMDA to single DMV neurons held at a holding potential (V(H)) of -40 mV evoked an inward current which rapidly reached a peak before declining to a steady-state inward current. This was followed, immediately after NMDA washout, by a transient outward current. TBT (100 nM) reversibly caused a slight reduction in the inward currents and greatly increased the amplitude of the outward currents. 3. The reversal potential of the NMDA-induced outward current in the presence of TBT was -86.7 mV, close to the theoretical K(+) equilibrium potential of -85.7 mV. 4. The NMDA-induced outward current was completely blocked when the K(+) in the internal solution was replaced with equimolar Cs(+). Under these conditions, the NMDA induced current was more sustained and was unaffected by TBT. 5. The NMDA-induced outward current was markedly inhibited by 5 mM tetraethylammonium chloride and 300 nM charybdotoxin, and it was abolished by removal of extracellular Ca(2+), suggesting that the outward current was due to the activation of Ca(2+)-activated K(+) channels by Ca(2+) influx through NMDA receptors. 6. In conclusion, in rat DMV neurons, TBT potentiates the Ca(2+)-activated K(+) current induced by NMDA application without having any direct effects on the NMDA-induced inward current. Given the significant role of NMDA receptor mediated excitation in various physiological and pathological processes, the modulation of this response by TBT may have an important influence on neuronal function.

Ultrastructural characteristics of diabetic nephropathy

Diabetic nephropathy is a major cause of chronic renal failure in Japan, and the prevalence rate has markedly increased during the past decade. Diabetic nephropathy shows various specific histological changes not only in glomeruli but also in the interstitial region. Nodular, diffuse, and exudative lesions, so-called diabetic glomerulosclerosis, are well known as glomerular lesions. At first, they were historically evaluated only by light microscopy, and thus which components of the glomeruli were modified was not sufficiently clear. Subsequent electron microscopic studies clarified that the expansion of the mesangial matrix was the true form of nodular and diffuse lesions, and that insudated serum substance was the real appearance of an exudative lesion. Interstitial lesions also exhibit specific features in diabetic nephropathy. In electron microscopic studies, it was proved that the size of mitochondria and thickness of the tubular basement membrane were increased in diabetic nephropathy. In this review, we introduce typical electron microscopic findings in diabetic nephropathy and recent opinions on the progression of diabetic nephropathy.

Cobe Spectra is superior to Fenwal CS 3000 Plus for collection of hematopoietic stem cells

One hundred and seventy-seven stem cell apheresis procedures performed on 91 patients using the Fenwal CS 3000 Plus cell separator and 61 procedures performed on 37 patients using the Cobe Spectra cell separator were studied to compare the CD34(+) cell collection efficiencies (CE; the proportion of the total CD34(+) cell content in the blood volumes processed that is harvested) of the two machines. The absolute peripheral blood CD34(+) cell count was comparable for the two groups (P = 0.27). A strong correlation was seen between the blood CD34(+) cell count and the total number of CD34(+) cells collected for the Spectra (r(2) = 0.59; P < 10(-6)) and for the CS 3000 Plus (r(2) = 0.60; P < 10(-6)). No significant correlation emerged between the peripheral blood CD34(+) cell count and the CE of either machine. The total number of CD34(+) cells collected per procedure was comparable (P = 0.51): median 113 x 10(6) for CS 3000 Plus and median 218 x 10(6)for Spectra. CE was significantly higher with the Spectra (median 45.7%, range 9.8-98.6%) than the CS 3000 Plus (median 30.3%, range 1.7-89.3%; P < 0.00001). We conclude that the CD34(+) cell CE of the Spectra is superior to that of the CS 3000 Plus. Therefore, under the usual clinical conditions, Cobe Spectra should be used preferentially for peripheral blood progentor cell collection to maximize the number of hematopoietic stem cells collected.

Estimation of increased concentration of intracellular Cd(2+) by fluo-3 in rat thymocytes exposed to CdCl(2)

Cadmium, an environmental pollutant, has been reported to induce apoptosis in murine lymphocytes. To reveal the mechanism of cadmium-induced apoptosis, one of important questions is whether cadmium increases intracellular concentration of Ca(2+) ([Ca(2+)](i)), Cd(2+) ([Cd(2+)](i)) or both. It is difficult to detect the increase in [Ca(2+)](i) using Ca(2+)-chelator-based fluorescent Ca(2+) indicators in the presence of Cd(2+) because of their sensitivity to Cd(2+). Therefore, the study on membrane response such as Ca(2+)-dependent hyperpolarization gives a clue to reveal whether the [Ca(2+)](i) or [Cd(2+)](i) is increased. Cadmium at concentrations of 3 μM or more dose-dependently augmented fluo-3 fluorescence in rat thymocytes, presumably suggesting an increased [Ca(2+)](i). However, the membranes were not hyperpolarized although the cells possess Ca(2+)-dependent K(+) channels. One may argue that cadmium inhibits Ca(2+)-dependent K(+) channels so that cadmium fails to hyperpolarize the membranes. It is unlikely because the [Ca(2+)](i) increased by A23187, a calcium ionophore, elicited the hyperpolarization in the presence of Cd(2+). Furthermore, the profile of cytotoxicity induced by cadmium, examined by ethidium bromide and annexin V-FITC, was different from that induced by A23187. Taken together, it is concluded that the application of cadmium increases the [Cd(2+)](i) rather than the [Ca(2+)](i) in rat thymocytes, resulting in the induction of cytotoxicity.

Engraftment syndrome: a common cause for rash and fever following autologous hematopoietic stem cell transplantation for multiple sclerosis

Autologous hematopoietic stem cell transplantation (HSCT) is currently being evaluated as a therapy for patients with progressive multiple sclerosis (MS) at risk of debilitating neurological impairment. While preliminary results from a few studies have been reported, little is known about toxicities or outcome of HSCT for MS. We report a relatively frequent triad of non-infectious fever, rash and fatigue or lassitude that may also be associated with pruritus, pulmonary symptoms, and eosinophilia and frequently occurs around engraftment. This syndrome occurred in 26% of our series of patients (5/19) undergoing HSCT for multiple sclerosis. The engraftment syndrome is usually self-limited but may require intervention with systemic corticosteroids.

Isolation and antioxidant activity of galloyl flavonol glycosides from the seashore plant, Pemphis acidula

Four kinds of galloyl flavonol glycosides were found in the leaf extract of Pemphis acidula, a plant growing on the subtropical seashore. Their chemical structures were elucidated to be quercetin or kaempferol 6"-O-galloyl-beta-D-glycosides by using spectroscopic and chemical analyses. One of the flavonols, kaempferol-3-O-(6-O-galloyl-beta-D-galactopyranoside), was newly isolated from natural sources and its structure was completely determined in this investigation. The antioxidant-related activities of the galloyl flavonoids were examined by the DPPH antiradical activity, inhibition of methyl linoleate oxidation, and inhibition of oxidative cell death. These results were compared with those of the corresponding non-galloylated flavonol glycosides and their aglycones. The galloyl flavonoids showed more efficient activity than that of the corresponding flavonol glycosides, but not more than that of the corresponding aglycones in the three assays applied.

Allogeneic stem cell transplantation for Evans syndrome

Evans syndrome is a rare disorder characterized by combined autoimmune thrombocytopenia (ITP) and autoimmune hemolytic anemia (AIHA). Standard treatments consist of transfusions, corticosteroids, splenectomy, IVIG, anabolic steroids, vincristine, alkylating agents, or cyclosporine. In a patient with refractory disease, an allogeneic hematopoietic stem cell transplant (HSCT) resulted in complete clinical and serologic remission for more than 30 months. Allogeneic HSCT may be the only current curative therapy for Evans syndrome but may also be complicated by significant toxicities.

Future strategies in hematopoietic stem cell transplantation for rheumatoid arthritis

Patients with coincidental rheumatoid arthritis (RA) treated by allogeneic hematopoietic stem cell transplantation (HSCT) for drug induced aplastic anemia have been fortuitously cured of RA. Other than these examples with allogeneic HSCT, there is no known curative therapy for RA. Despite its potential to cure, allogeneic transplantation is not being offered to patients with RA due to transplant related mortality. Advances in HSCT conditioning regimens and better prevention of graft-versus-host disease should allow consideration of allogeneic HSCT as therapy for severe RA. We propose a new, well tolerated, nonmyeloablative allogeneic stem cell transplant regimen as treatment for RA.

Nanomolar concentrations of tri-n-butyltin facilitate gamma-aminobutyric acidergic synaptic transmission in rat hypothalamic neurons

Tri-n-butyltin (TBT), an environmental pollutant, is accumulated in edible mollusks and fishes. It has also become a health concern in today's society. In the present study, to elucidate the possible neurotoxic action of TBT, the effect on spontaneous gamma-aminobutyric acid (GABA) release from GABAergic nerve terminals projecting to rat ventromedial hypothalamic neurons was examined using "synaptic bouton" preparation with a nystatin perforated patch recording mode under voltage-clamp conditions. The threshold concentration of TBT to affect the synaptic transmission was 10 to 30 nM. TBT at 30 nM or higher concentrations increased the frequency of GABAergic miniature inhibitory postsynaptic currents in a dose-dependent manner, whereas the current amplitude and current kinetics were not affected. The removal of either external Ca2+ or application of Cd2+ attenuated the TBT-induced facilitation of neurotransmission. TBT at 1 microM induced an inward current in more than one-half of the cells. This current persisted even after TBT was washed out. The present results indicate that TBT at environmentally relevant concentrations (30-100 nM) facilitates the GABAergic neurotransmission in the mammalian brain and the external Ca2+ is needed in this facilitation. Because the concentration of TBT accumulated in some mollusks and fishes has been reported to reach levels of 100 nM or more, such accumulation of TBT in some mollusks and fishes is thus suggested to be hazardous to the health of humans.

Treatment of relapse after autologous blood stem cell transplantation for severe rheumatoid arthritis

There is little information about the clinical course of patients with rheumatoid arthritis (RA) who relapse after autologous blood stem cell transplantation (ASCT). We describe 6 patients with severe RA who received ASCT in 3 US centers. Duration of followup was between 24 and 42 months posttransplant. Five patients achieved major responses but relapsed 3-22 months posttransplant. Two patients with relapse improved remarkably after restarting disease modifying antirheumatic drugs (DMARD). Two patients developed a mild RA flare at 3 and 5 months posttransplant and improved spontaneously. All 4 patients who improved after an initial disease flare remained highly functional at 14-22 months posttransplant. All patients in this study were anti-tumor necrosis factor (TNF) drug naive; all received a TNF blocker as a second line posttransplant salvage therapy, but only 3 responded. Future ASCT strategies need to focus on improving the durability of the early posttransplant responses.

CD34(+) cell collection efficiency does not correlate with the pre-leukapheresis hematocrit

One hundred and seventy-seven large-volume leukapheresis procedures performed on 91 patients over a 15 month period were reviewed to see if the pre-apheresis hematocrit (Hct) affected the CD34(+) cell collection efficiency (CE) of the Fenwal CS 3000 Plus cell separator. The Hct was 0.174-0.461 (median 0.317), and the peripheral blood CD34(+) cell count 2-2487 per microl (median 21). The total CD34(+) cell quantity collected was 3.0-2677.2 x 10(6) (median 113.0). Based on the number of CD34(+)cells contained in the blood volume processed (23.3-37303.2 x 10(6); median 318.0), the CE was 1.7-87.5% (median 30.3). No correlation was found between the Hct and CE (r(2) = 0.0034; P = 0.44) or the total CD34(+) cell quantity collected (r2 = 0.0040; P = 0.40). CEs for Hct <0.25 (median CE 36%), Hct 0.25-0.299 (median CE 30%) and Hct 0.30 (median CE 30%) were comparable. As expected, highly significant correlations were seen between the CD34(+) cell quantities collected and quantities processed (r2 = 0.59; P < 10(-6)) as well as the peripheral blood CD34(+) cell counts (r2= 0.60; P < 10(-6)). We conclude that the minimum acceptable Hct or hemoglobin level for leukapheresis should be dictated by clinical circumstances because it does not affect stem cell collection.

Troglitazone, a PPARgamma ligand, inhibits osteopontin gene expression in human monocytes/macrophage THP-1 cells

Peroxizome proliferator-activated receptor-gamma (PPARgamma) is a member of the nuclear receptor family of transcription factors that regulate adipocyte differentiation. Recent studies indicate that liganded PPARgamma not only promotes differentiation but also inhibits the activation of macrophages. Osteopontin, a component of extracellular matrix, is synthesized by macrophages in atherosclerotic plaques. In this study, we examined whether PPARgamma ligand regulates osteopontin gene expression in THP-1 cells, a cell line derived from human monocytic leukemia cells which can differentiate to macrophage upon stimulation with phorbol ester PMA. Northern blot analysis showed that osteopontin expression is markedly induced in response to PMA. Troglitazone, a PPARgamma ligand, dramatically attenuated the PMA-induced osteopontin expression. Transient transfection assays of the human osteopontin promoter/luciferase construct which contains a 5'-flanking region between -1500 and +87 relative to the transcription start site demonstrate that either treatment with troglitazone or cotransfection of PPARgamma expression vector inhibits osteopontin promoter activity. These data indicate that troglitazone reduces osteopontin gene expression at transcriptional level through PPARgamma activation, and suggest the role of troglitazone in inhibiting the ability of macrophages to produce extracellular matrix, which is particularly relevant to atherosclerotic plaque formation.