Biomedical subjects

M Tsuboi

Publications and source records attributed to M Tsuboi.

At least 19 recordsLinked to original sources

PubMed2005

Induction of apoptosis by carbazole alkaloids isolated from Murraya koenigii.

In the current study, we isolated 10 carbazole alkaloids from the plant species Murraya koenigii (Rutaceae), and examined their effects on the growth of the human leukemia cell line HL-60. Three carbazole alkaloids, mahanine (6), pyrayafoline-D (7) and murrafoline-I (9), showed significant cytotoxicity against HL-60 cells. Fluorescence microscopy with Hoechst 33342 staining revealed that the percentage of apoptotic cells with fragmented nuclei and condensed chromatin was increased in a time-dependent manner after treatment with each alkaloid. Interestingly, each carbazole alkaloid induced the loss of mitochondrial membrane potential. In addition, both caspase-9 and caspase-3 were also time-dependently activated upon treatment with the alkaloids. Caspase-9 and caspase-3 inhibitors suppressed apoptosis induced by these alkaloids. The results suggest that these three alkaloids induced apoptosis in HL-60 cells through activation of the caspase-9/caspase-3 pathway, through mitochondrial dysfunction.

Apoptosis↗

PubMed2004

Treatment of non-small-cell lung cancer: a perspective on the recent advances and the experience with gefitinib.

Worldwide, non-small-cell lung cancer (NSCLC) is a leading cause of cancer-related mortality and, until screening detects early disease, treatment for the majority of patients will consist of radiation therapy, chemotherapy or combinations thereof. Modern mono and doublet chemotherapy regimens have translated into modest increases in life expectancy and improved quality of life, but at the expense of systemic and pulmonary adverse events (AEs). There is a great unmet need to provide effective therapy for advanced NSCLC that does not have the toxicity burden of conventional chemotherapy and radiotherapy. Novel drugs that inhibit a range of growth factor receptors, such as the epidermal growth factor receptor tyrosine kinase inhibitors gefitinib ('Iressa') and erlotinib ('Tarceva') or the monoclonal antibody cetuximab ('Erbitux'), have recently been evaluated. Having demonstrated antitumour activity and rapid symptom improvement in pretreated patients with advanced NSCLC, gefitinib was approved in the USA, Japan and other countries. Gefitinib is well tolerated with a low incidence of grade 3/4 AEs. Interstitial lung disease has been reported in a small number of patients receiving gefitinib, although this may be attributed to other treatments and conditions. Nevertheless, although the use of novel treatments requires vigilance for unexpected AEs such as pulmonary toxicity, in this area of high unmet clinical need, the benefits outweigh the risks in patients for whom no other proven effective treatment exists.

Adult↗

PubMed2001

Orientations of Tyr 21 and Tyr 24 in the capsid of filamentous virus Ff determined by polarized Raman spectroscopy.

The capsid of filamentous virus Ff is assembled from approximately 2750 copies of a 50-residue alpha-helical subunit, the two tyrosines of which (Tyr 21 and Tyr 24) are located within a hydrophobic sequence that constitutes the subunit interface. We have determined the side chain orientations of Tyr 21 and Tyr 24 by polarized Raman microspectroscopy of oriented Ff fibers, utilizing a novel experimental approach that combines site-specific mutation and residue-specific deuteration of capsid subunits. The polarized Raman signature of Tyr 21 was obtained by incorporating C(delta 1),C(delta 2),C(epsilon 1),C(epsilon 2)-tetradeuteriotyrosine at position 21 in an Ff mutant in which Tyr 24 is replaced with methionine. Similarly, the polarized Raman signature of Tyr 24 was obtained by incorporating C(delta 1),C(delta 2),C(epsilon 1),C(epsilon 2)-tetradeuteriotyrosine at position 24 in the analogous Tyr 21 --> Met mutant. Polarizations of the corresponding C-D stretching bands in the 2200-2400 cm(-1) interval of the Raman spectrum were measured and interpreted using tensors transferred from a polarized Raman analysis of L-tyrosine-2,3,5,6-d(4) single crystals. Polarized Raman analysis was extended to the bands of Ff near 642 and 855 cm(-1), which originate from vibrational modes of the tyrosine phenolic ring. The results indicate the following: (i) For both Tyr 21 and Tyr 24, the phenolic 2-fold axis (C(1)-C(4) line) is inclined at 41 +/- 5 degrees from the virion axis and the normal to the plane of the phenolic ring is inclined at 71 +/- 5 degrees from the virion axis; (ii) the mutation of Tyr 24, but not the mutation of Tyr 21, perturbs Raman markers of the subunit tryptophan (Trp 26), suggesting interdependence of Tyr 24 and Trp 26 orientations in native Ff; and (iii) polarization anisotropies observed for Raman markers of Ff DNA bases are unperturbed by mutation of either Tyr 21 or Tyr 24, indicating that nonrandom base orientations of packaged Ff DNA are independent of the mutation of either Tyr 21 or Tyr 24. A molecular model consistent with these findings is proposed.

Amino Acid Sequence↗

PubMed2001

Potential use of Amplicor PCR kit in diagnosing pulmonary tuberculosis from gastric aspirate.

Polymerase chain reaction (PCR) detection of mycobacteria from gastric aspirate for the diagnosis of tuberculosis is not fully evaluated up to now. A total of 116 gastric aspirate specimens were collected from patients with suspected pulmonary tuberculosis. The breakdown of diagnosis was 67 pulmonary tuberculosis, 16 nontuberculous mycobacterial infection, 5 extra pulmonary tuberculosis, and 28 other lung diseases. The conventional methods were shown to have a sensitivity of 47.8% and a specificity of 79.6%; on the other hand, Amplicor had 34.9% and 97.0%, respectively. The Amplicor provided a more rapid and specific method for diagnosing tuberculosis and was more useful than the conventional.

Adult↗

PubMed2001

Novel immunosuppressive effect of FK506 by augmentation of T cell apoptosis.

We have recently reported the accumulation of oligoclonal activated T cells in the spontaneously developed autoimmune pancreatitis in aly/aly mouse. In this study, we examined the effects of FK506 in this mouse model in preventing autoimmune pancreatitis and investigated its action on calcium signalling apoptosis of alymphoplasia (aly) lymphocytes in vitro. Mice were treated with FK506 from 8 to 25 weeks of age. At the age of 15 weeks, minimal mononuclear cell infiltration was observed in the pancreas in both the FK506 treated group and the control group. Furthermore, a marked cell infiltration associated with destruction of acini and partial fatty changes were observed in 25-week-old control mice. In contrast, FK506 treated mice showed almost no tissue destruction or mononuclear cell infiltration at the age of 25 weeks. Furthermore, at 15 weeks of age, most mononuclear cells in FK506-treated mice were TUNEL positive, whereas only a few were positive in control mice. This augmentation of T cell apoptosis by FK506 was confirmed using naive splenocytes activated by PMA and ionomycin in vitro. Finally, a suppressive effect of FK506 on Bcl-2 production but not on Bax production was confirmed by Western blotting. This unique effect of FK506 on the augmentation of T cell apoptosis is probably one of the mechanisms explaining its beneficial effect on aly autoimmune pancreatitis.

Animals↗

PubMed2001

Mitochondrial DNA deletion associated with the reduction of adenine nucleotides in human atrium and atrial fibrillation.

BACKGROUND: Structural changes in the number, size, and shape of mitochondria (mt) have been observed in the atrial muscles of patients with atrial fibrillation (AF) and of animals with rapid atrial pacing, however, it is not known whether the mitochondrial function is impaired in human atrium with AF. MATERIALS AND METHODS: We determined adenine nucleotides concentrations and mtDNA deletions in 26 human right atria obtained at the time of cardiac surgery, using HPLC and PCR amplification, and studied the relationship between mtDNA deletions and clinical manifestations, the haemodynamic parameters of the patients and adenine nucleotide concentrations in their atrium. RESULTS: The age and the prevalence of AF were significantly higher in the patients with a mtDNA deletion of 7.4 kb than in those without a deletion; there were no significant differences regarding haemodynamic parameters between the two groups. The concentrations of ATP, ADP, AMP and total adenine nucleotides in the right atrium were significantly lower in the patients with mtDNA deletions than the patients without a deletion. In a gender- and diseased-matched population, the mtDNA deletion was still significantly associated with age and a decreased concentration of adenine nucleotides in the atrium. Using quantitative PCR analysis, the proportion of mtDNA deletion to normal mtDNA of the atrium, was estimated to be 0.3-2% in four cases. CONCLUSION: These results suggest that the deletion of mtDNA associated with ageing or AF can lead to a bioenergetic deficiency due to an impaired ATP synthesis in the human atrium; however, no conclusion can be made whether mtDNA deletion were the result or the cause of an impaired ATP synthesis, ageing, hemodynamic deterioration, or AF.

Adenine Nucleotides↗

PubMed2001

Completely resected stage IIIA non-small cell lung cancer: the significance of primary tumor location and N2 station.

BACKGROUND: The number of N2 stations (single vs multiple N2 stations) is an important prognostic factor in patients with completely resected stage IIIA-N2 non-small cell lung cancer. However, the significance of both the N2 station(s) actually involved and the primary tumor location remains unclear. METHODS: The database was built with the use of a questionnaire survey on the survival of patients with pathologic stage IIIA-N2 non-small cell lung cancer completely resected between January 1992 and December 1993. The survey was performed by the Japan Clinical Oncology Group as of July 1999. The data include information on the survival and N2 stations of 402 patients. RESULTS: A frequently metastasized single N2 station was the lower pretracheal station in primary tumors in the right upper lobe, the subaortic station in the left upper lobe, and the subcarinal station in the right middle or lower lobe and the left lower lobe. In multiple N2 stations, the frequency of metastasis of the N2 station observed in a single N2 station was as high as 72% to 89%, and one or two other frequently metastasized stations were added to each group. Regarding the survival of patients with a primary tumor in each lobe except for the left lower lobe, a single N2 station resulted in a significantly better survival than did multiple N2 stations. Furthermore, the overall survivals classified according to each primary site showed a significant difference among the four primary sites (P =.04). CONCLUSIONS: The primary tumors in each lobe showed a prevalence of N2 station(s). The number of N2 stations is a good prognosticator except in patients with a primary tumor in the left lower lobe. In addition, the site of a primary tumor itself is also considered to influence the survival of the patients.

Adult↗

PubMed2001

Viewing of complex molecules of ethidium bromide and plasmid DNA in solution by atomic force microscopy.

Tertiary structure changes in plasmid DNA, induced by ethidium bromide intercalation, have been observed in aqueous solutions by the use of an atomic force microscope. A relaxed closed circular pBR322 molecule became a positively supercoiled complex on the drug binding. The supercoiling always resulted in an interwound (or a plectonemic) form, but never a solenoidal (or a toroidal) form. A quantitative analysis of the compactness of such supercoiled complexes has been carried out.

DNA↗

PubMed2001

Vagal stimulation prior to atrial rapid pacing protects the atrium from electrical remodeling in anesthetized dogs.

Atrial electrical remodeling is thought to be the cause of the maintenance of atrial fibrillation (AF). Although the initiation and maintenance of AF is partially associated with autonomic nervous tone, vagally mediated AF does not tend to become permanent. Therefore, the effects of preceding vagal stimulation (VS) on the atrial effective refractory period (ERP) under electrical remodeling conditions were investigated in anesthetized dogs. Atrial ERPs were measured at 5 sites before and after a 7-h period of atrial rapid pacing in the control group. In the VS group, the vagus nerve was stimulated for 20 min before a period of atrial rapid pacing. Atrial rapid pacing shortened the ERP at each site in the control group (electrical remodeling). On the other hand, atrial rapid pacing after VS did not shorten the ERP at any site in the VS group. Tetrodotoxin, which was administered into the fatty tissue overlying the right atrial side of the right pulmonary vein junctions, blocked the protective effect of VS against the shortening of the ERP induced by atrial rapid pacing. In contrast, atropine did not interfere with such protective effects. These results suggest that VS prior to atrial rapid pacing protects the atrium from atrial electrical remodeling.

Anesthesia↗

PubMed2001

Dominant anti-vagal effect of pentobarbital on cardiac responses to intracardiac autonomic nerve stimulation in the dog.

The isolated canine atrium was perfused by heparinized blood of the donor dog. An adequate dose of pentobarbital that induced a potent hypotension in the donor did not produce any significant change in the atrial rate and developed tension in the isolated atrium perfused with donor's blood. Pentobarbital in doses that modified neither cardiac responses to intracardiac adrenergic nerve stimulation nor exogenously given norepinephrine or acetylcholine significantly inhibited intracardiac vagal responses. From these results, it is concluded that a large dose of pentobarbital has a dominant antivagal effect in the heart.

Animals↗

PubMed2001

[Intravascular lymphomatosis: a case report].

We report a case of a 64-year-old man with intravascular lymphomatosis. He had dementia and generalized seizure. Computed tomogram scan and magnetic resonance imaging showed multiple infarctions in the right frontal lobe, right cerebellar hemisphere and left occipital lobe. A month after admission he had a daily high fever and frequent convulsions. The level of serum LDH was progressively getting higher and the level of beta 2-microglobulin in both serum and CSF was high. One and a half months after admission we performed an open biopsy for making a definite diagnosis by pathological examination. Histological diagnosis was intravascular lymphomatosis (angiotrophic lymphoma) of large B cell type. He was treated with regimens of combined chemotherapy with M-CHOP (methotrexate, cyclophosphamide, adriamycin, vincristine, prednisolone). After chemotherapy his consciousness was gradually improving better and the level of serum LDH and beta 2-microglobulin was reduced to a low level. Three months after admission he died of respiratory failure. After a review of the literature and experience with this case, it is obrious that early diagnosis of this disease is difficult. However, we think that multiple cerebral infarctions on neuroradiological examinations and high levels of serum LDH (especially LDH2 and LDH3) and beta 2-microglobulin in CSF and serum should lead to a presumptive diagnosis of this disease, and biopsy should be used to make a difinite diagnosis.

Antineoplastic Combined Chemotherapy Protocols↗

PubMed2000

Lipase-catalyzed transesterification of 2-hydroxy-2-(pentafluorophenyl)acetonitrile leading to (1R,2R)- and (1S,2S)-bis(pentafluorophenyl)ethane-1,2-diol

Optically pure (1R,2R)- and (1S,2S)-1,2-bis(pentafluorophenyl)ethane-1,2-diol (1) were synthesized from key intermediates (R)- and (S)-2-hydroxy-2-(pentafluorophenyl)acetonitrile (2), both of which were prepared by the lipase LIP-catalyzed transesterification (E = 465). The absolute configuration of (S)-2 was determined by X-ray structural analysis after transformation into (S)-alpha-cyano-2,3,4,5,6-pentafluorobenzyl (S)-6-methoxy-alpha-methyl-2-naphthaleneacetate (S,S)-9. In addition, the crystal structure of (S,S)-9 has an interesting well-ordered packing pattern which shows face-to-face stacking interactions and end-to-end parallel contacts between the pentafluorophenyl and 6-methoxynaphthyl groups of the adjacent molecules.

Journal Article↗

PubMed2000

Intensity of the polarized Raman band at 1340-1345 cm-1 as an indicator of protein alpha-helix orientation: application to Pf1 filamentous virus.

Raman spectra of oriented alpha-helical protein molecules exhibit a prominent band near 1340-1345 cm(-)(1), the intensity of which is highly sensitive to molecular orientation. Polarization of the 1340-1345 cm(-)(1) marker is evident in Raman spectra of alpha-helical poly-L-alanine (alphaPLA) and alpha-helical poly-gamma-benzyl-L-glutamate (alphaPBLG). Corresponding polarization is also observed in Raman spectra of the filamentous virus Pf1, which is an assembly of alpha-helical coat protein molecules. In alphaPLA and alphaPBLG, we assign the band to a normal mode of symmetry type E(2) and specifically to a vibration localized in the (O=C)-C(alpha)-H linkages of the main chain peptide group. Although strict helical symmetry does not apply to coat subunits of filamentous viruses, an approximate E(2)-type mode may be presumed to account for a corresponding Raman band of Pf1 and fd filamentous viruses. Spectroscopic studies of N-methylacetamide and isotopically-edited fd viruses support the present assignment of the 1340-1345 cm(-)(1) band. Polarization anisotropy indicates that this band may be exploited as a novel indicator of protein alpha-helix orientation. Application of this approach to the polarized Raman spectrum of Pf1 suggests that, on average, the axis of the alpha-helical coat protein subunit in the native virion structure forms an angle of 20 +/- 10 degrees with respect to the virion axis.

Alanine↗

PubMed2000

Effects of the aromatase inhibitor anastrozole on serum oestrogens in Japanese and Caucasian women.

PURPOSE: Substantial differences in plasma oestrogen disposition have been reported between Japanese and Caucasian women, but there are currently few data available on the relative endocrinological effects of aromatase inhibitors in these two groups. Hence, the effects of the nonsteroidal aromatase inhibitor anastrozole on serum oestrogen concentrations were compared in 24 healthy postmenopausal Japanese women and 24 healthy postmenopausal Caucasian women. METHODS: Anastrozole, 1 mg/day, was given once daily for 16 days. Serum oestradiol and oestrone sulphate levels were measured on three consecutive days beginning 2 days before the first dose, and on a further three consecutive days beginning on the penultimate day of dosing. Trough concentrations of anastrozole (measured 24 h after dosing) were also determined during the same periods. RESULTS: There were no substantial differences in plasma oestrogen concentrations between the Japanese and Caucasian women at baseline. On average, anastrozole suppressed serum oestradiol and oestrone sulphate levels by approximately 87% and 93%, respectively, for both Japanese and Caucasian women, and minimum plasma anastrozole concentrations at steady-state (anastrozole C(min)) were also similar in both groups. Statistical analysis of serum oestradiol and serum oestrone sulphate levels, and plasma anastrozole C(min) showed that there were no statistically significant differences between the Japanese and Caucasian women. CONCLUSION: Neither the pharmacodynamic effects of anastrozole on serum oestrogens nor the pharmacokinetics of anastrozole differ between postmenopausal Japanese and Caucasian women. Hence, these findings suggest that the therapeutic benefits of anastrozole in Caucasians will be predictive of the drug's effect in Japanese women and support the use of anastrozole in postmenopausal Japanese women with breast cancer.

Aged↗

PubMed2000

Molecular cloning and DNA analysis of the orotidine-5'-phosphate decarboxylase gene from the yeast Saccharomyces exiguus Yp74L-3.

The orotidine-5'-phosphate decarboxylase gene of Saccharomyces exiguus Yp74L-3 was cloned as a DNA fragment complementing a ura4 mutation of this yeast. The coding region of the gene is 807 bp in length, and represents 68.7% similarity to the corresponding gene of S. cerevisiae (URA3). The cloned URA4 gene was shown to be located on the 790-kbp Chromosome (chr) VIII of S. exiguus Yp74L-3. The neighbor-joining phylogenetic tree based on the orotidine-5'-phosphate decarboxylase coding sequences indicates that S. exiguus Yp74L-3 is closely related to Kluyveromyces yeasts, as well as to a S. cerevisiae laboratory strain.

Chromosome Mapping↗

PubMed2000

Effects of phosphorus-containing calcium preparation (bone meal powder) and calcium carbonate on serum calcium and phosphorus in young and old healthy volunteers: a double-blinded crossover study.

To evaluate the effects of bone meal powder (BEC) on calcium and phosphorus metabolism, a calcium absorption test was conducted using a preparation of calcium carbonate (CAC) as the control drug. A total of 12 healthy volunteers, consisting of 6 younger (aged 20-29 years, 3 men and 3 women) and 6 older (aged 60-69 years, 3 men and 3 women) persons, were subjected to a double-blinded crossover study. Serum calcium (s-Ca) level significantly increased to 105.3% +/- 1.9% (P < 0.01 vs the basal value; mean +/- SD) from the basal value in the BEC group and to 104.4% +/- 2.7% (P < 0.01) in the CAC group at 3h post load. Urinary excretions of calcium (u-Ca/glomerular filtration rate, u-Ca/GF) after BEC and CAC load rose to 226.6% +/- 154.5% (P < 0.05) and 211.1% +/- 148.0% (P < 0.05), respectively. Serum phosphorus (s-P) levels after BEC load increased to 110.0% +/- 15.1% (P < 0.05), whereas that after CAC load showed no significant change (99.3% +/- 7.9%). On the other hand, urinary excretion of phosphorus (u-P/GF) after CAC load decreased to 60.0% +/- 32.4% (P < 0.01) and that in the BEC group showed no significant change (92.5% +/- 49.5%). The increase in s-Ca led to decrease in serum intact parathyroid hormone (i-PTH) level [77.3% +/- 33.4% (P < 0.05) for BEC and 69.5% +/- 20.3% (P < 0.01) for CAC] although s-P was increased by the BEC load. The responses to BEC and CAC administration were compared in the younger and the older groups. The responses in the younger and the older group showed fundamentally the same trends and to the same extent. However, the changes in serum ionized calcium (i-Ca) and i-PTH levels at 1.5 h post load were significantly smaller in the older group than in the younger group (P < 0.01; P < 0.05). The increment in s-P level after BEC load in the older group was larger than that in the younger group. In conclusion, BEC can modulate not only calcium but also phosphorus metabolism in both younger and older subjects. Further investigations are required to evaluate the effects of BEC on bone density and safety for renal function in long-term observations.

Adult↗

PubMed2000

Block of sodium channels by divalent mercury: role of specific cysteinyl residues in the P-loop region.

Divalent mercury (Hg(2+)) blocked human skeletal Na(+) channels (hSkM1) in a stable dose-dependent manner (K(d) = 0.96 microM) in the absence of reducing agent. Dithiothreitol (DTT) significantly prevented Hg(2+) block of hSkM1, and Hg(2+) block was also readily reversed by DTT. Both thimerosal and 2,2'-dithiodipyridine had little effect on hSkM1; however, pretreatment with thimerosal attenuated Hg(2+) block of hSkM1. Y401C+E758C rat skeletal muscle Na(+) channels (mu1) that form a disulfide bond spontaneously between two cysteines at the 401 and 758 positions showed a significantly lower sensitivity to Hg(2+) (K(d) = 18 microM). However, Y401C+E758C mu1 after reduction with DTT had a significantly higher sensitivity to Hg(2+) (K(d) = 0.36 microM) than wild-type hSkM1. Mutants C753Amu1 (K(d) = 8.47 microM) or C1521A mu1 (K(d) = 8.63 microM) exhibited significantly lower sensitivity to Hg(2+) than did wild-type hSkM1, suggesting that these two conserved cysteinyl residues of the P-loop region may play an important role in the Hg(2+) block of the hSkM1 isoform. The heart Na(+) channel (hH1) was significantly more sensitive to low-dose Hg(2+) (K(d) = 0.43 microM) than was hSkM1. The C373Y hH1 mutant exhibited higher resistance (K(d) = 1.12 microM) to Hg(2+) than did wild-type hH1. In summary, Hg(2+) probably inhibits the muscle Na(+) channels at more than one cysteinyl residue in the Na(+) channel P-loop region. Hg(2+) exhibits a lower K(d) value (<1. 23 microM) for inhibition by forming a sulfur-Hg-sulfur bridge, as compared to reaction at a single cysteinyl residue with a higher K(d) value (>8.47 microM) by forming sulfur-Hg(+) covalently. The heart Na(+) channel isoform with more than two cysteinyl residues in the P-loop region exhibits an extremely high sensitivity (K(d) < 0. 43 microM) to Hg(+), accounting for heart-specific high sensitivity to the divalent mercury.

2,2'-Dipyridyl↗

PubMed2000

CD4+ T cell-mediated cytotoxicity toward thyrocytes: the importance of Fas/Fas ligand interaction inducing apoptosis of thyrocytes and the inhibitory effect of thyroid-stimulating hormone.

The accumulation of activated CD4+ T cells and antigen (Ag)-dependent cellular interactions between thyrocytes and CD4+ T cells have been determined in thyroid gland from patients with Graves' disease. The Fas/Fas ligand (FasL) interaction between antigen-presenting cells and T cells regulates the apoptosis of the former cells triggered by the latter cells. The inhibition of Fas-mediated apoptosis in thyrocytes could be a underlying mechanism of hyperplasia of thyrocytes in patients with Graves' disease. We investigated the potential role of Fas/FasL interaction between thyrocytes and CD4+ T cells in the induction of Fas-mediated apoptosis of the former cells induced by the latter cells. The presence of only a few specific T cells responsive to a putative autoantigen has hampered the investigation of specific T cell activation toward antigen-presenting cells (APCs). Therefore, we used a superantigen, staphylococcal enterotoxin B (SEB), to examine specific T cell activation toward thyrocytes in vitro since it stimulates a large proportion of T cells with particular Vbeta elements. Spontaneous apoptosis of thyrocytes in culture was not found even in the presence of various kinds of cytokines. In contrast, a clear induction of Fas-mediated apoptosis by anti-Fas IgM was determined in interferon-gamma (IFN-gamma)-stimulated thyrocytes. In addition, a significant cytotoxicity of purified CD4+ T cells toward IFN-gamma-stimulated thyrocytes in the presence of SEB was induced, and the addition of anti-HLA-DR and -DQ monoclonal antibodies (mAbs) or blockade of the Fas/FasL interaction reduced this cytotoxicity. FasL expression of CD4+ T cells cocultured with IFN-gamma-stimulated thyrocytes in the presence of SEB was clearly induced. Furthermore, the addition of mAbs against CD54 and CD58 inhibited both cytotoxicity and FasL expression of CD4+ T cells. The cytotoxicity of CD4+ T cells toward IFN-gamma-stimulated, SEB-pulsed thyrocytes was markedly inhibited when we used thyrocytes cultured with IFN-gamma in the presence of thyroid-stimulating hormone (TSH) as target cells. Our results suggest that 1) CD4+ T cells were activated by thyrocytes expressing MHC class II molecules in an SEB-dependent manner and then expressed FasL. 2) These activated FasL+ CD4+ T cells killed thyrocytes by interacting with Fas on thyrocytes and FasL on activated CD4+ T cells. The presence of costimulating molecules such as CD54 and CD58 on thyrocytes was also necessary to generate activated FasL+ CD4+ T cells. 3) Since the actions of thyroid stimulating antibody (TSAb) toward thyrocytes are similar to those of TSH, one goitrogenic activity of TSAb may, in part, be due to the inhibitory effect on Fas-mediated apoptosis of thyrocytes triggered by activated CD4+ T cells.

Apoptosis↗