[An autopsied case of subacute progressive dementia with flactuated disturbance of consciousness, myoclonus and periodic synchronous discharges on EEGs]

We present an autopsied case which developed progressive dementia at the age of 45. EEGs showed periodic synchronous discharges (PSD) when he showed fluctuated cloudy consciousness with myoclonus. Cerebrospinal fluid examination showed mild to moderate increase in protein and monocytes for duration of illness, but antivirotics and antibiotics were not effective. He was not apallic even at the terminal stage when computed tomography (CT) revealed marked cerebral atrophy, and died of pneumonia 27 months after onset. He was clinically diagnosed as having Creutzfeldt-Jakob disease (CJD) because of subacute progressive dementia, myoclonus and PSD. Neuropathological examination revealed marked brain atrophy with severe neuronal loss and gliosis in the cerebral cortex and subcortical nuclei, although no spongiform degeneration was found. Senile plaques, neurofibrillaly tangles, argyrophilic glial inclusions and glial nodules were not detected. Prion protein immunoreactivity was negative. Therefore, this case can not be neuropathologically diagnosed as having CJD, Alzheimer's disease, non-Alzheimer-type degenerative dementias or any encephalitis. This case might have suffered from an unknown new disease.

Analysis of Fas system in pulmonary injury of graft-versus-host disease after rat intestinal transplantation

The lung is one of the primary targets of acute graft-versus-host disease (GVHD), which is the principal complication that occurs after allogeneic intestinal transplantation. The purpose of this study is to investigate the involvement of Fas/Fas ligand system in pulmonary injury after rat semi-allogeneic intestinal transplantation. The lungs were serially harvested from LEW x BN F1(LBNF1) recipients of either LEW heterotopic intestinal allografts or LBNF1 isografts, on days 1, 3, 5, 9, and 13 posttransplant. In light microscopy, pulmonary injury became apparent on day 13 in the allogeneic combination, showing a thickening of the alveolar septa. The incidence of apoptosis, examined by terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate (dUTP) biotin nick end-labeling, was observed to increase steadily in the alveolar cells accompanied by a progression of GVHD. In an immunohistochemical study, Fas was constitutively expressed in the lung, although Fas ligand was expressed most extensively on day 9. The immunoreactivity of both Fas and Fas ligand were observed in alveolar cells, in addition to leukocytes. An analysis by reverse transcription polymerase chain reaction also revealed that the expression of Fas mRNA was constitutive without any significant change, although that of Fas ligand mRNA increased substantially and peaked on day 9, which was significant compared to the isogeneic combination. In conclusion, transcriptionally up-regulated Fas ligand and increased number of apoptosis suggests that the Fas system may play a role in the pathophysiology of GVHD-induced pulmonary injury.

Effect of linear polarized near-infrared ray irradiation on the chemiluminescence of human neutrophils and serum opsonic activity

The purpose of this study was to investigate the in vitro effects of linear polarized near-infrared ray irradiation on neutrophil chemiluminescence (CL) and serum opsonic activity. We used luminol- and lucigenin-dependent CL to detect the affected reactive oxygen species production process of human neutrophils and measured serum opsonic activity based on luminol-dependent CL. The linear polarized near-infrared ray irradiation suppressed a maximum light emission (peak height) of luminol- and lucigenin-dependent CL in a dose-dependent manner. The findings suggested that the linear polarized near-infrared ray irradiation suppressed the superoxide anion and hypochlorite production of human neutrophils. The serum opsonic activity was decreased by linear polarized near-infrared ray irradiation, and this suppressive effect might be caused by inhibiting the activation of the classical and alternative complement pathway. Therefore, it is suggested that near-infrared ray irradiation may have an inhibitory effect against chronic pain via reduction of reactive oxygen species production and opsonic activity.

[Lung volume reduction surgery for pulmonary emphysema]

Surgical treatment for pulmonary emphysema has received renewed attention, because many studies have demonstrated improvements in dyspnea and pulmonary function. After lung volume reduction surgery (LVRS) for carefully selected advanced pulmonary emphysema, pulmonary functional impairments, such as expiratory flow limitation, increase in lung volume, decrease in lung elastic recoil, impaired gas exchange are improved. Improvements of dynamic hyperinflation, respiratory muscle function and exercise tolerance were also demonstrated after LVRS for pulmonary emphysema. Finally these functional effects may improve symptom and prognosis of pulmonary emphysema with better quality of life. Although the basic mechanism responsible for the improvements are not well known yet, physiological mechanisms which brought improvement after surgical treatment for pulmonary emphysema should be further investigated.

Early detection of apoptosis and fas ligand expression in hepatic graft-versus-host disease after rat small bowel transplantation

BACKGROUND

The liver is one of the primary targets of acute graft-versus-host disease (GVHD), which is the principal complication that occurs after allogeneic intestinal transplantation. The purpose of this study is to investigate the involvement of the Fas/Fas ligand system in hepatic GVHD after rat semiallogeneic intestinal transplantation.

MATERIALS AND METHODS

Liver samples were serially harvested from LEW x BN F(1) (LBNF(1)) recipients of either LEW heterotopic intestinal allografts (group 1) or LBNF(1) isografts (group 2), on Days 1, 3, 5, 9, and 13 posttransplant.

RESULTS

In group 1, hepatic injuries as assessed by either serum aspartate aminotransferase (AST) level, alanine aminotransferase (ALT) level, or cellular infiltration on HE staining became apparent after Day 13. The incidence of apoptosis, examined by terminal deoxynucleotidyl transferase-mediated dUTP biotin nick end-labeling (TUNEL), was observed to steadily increase in the liver from Day 5 accompanied by a progression of GVHD: 17.5 +/- 3.1 and 3.1 +/- 0.4 cells/field (200x) in groups 1 and 2, respectively. In an immunohistochemical study, Fas was constitutively expressed in the liver in both groups, while Fas ligand was expressed most extensively on Day 13 in group 1. Immunoreactivity of both Fas and Fas ligand was observed in hepatocytes, in addition to leukocytes. Analysis by reverse transcription polymerase chain reaction also revealed the expression of Fas mRNA to be constitutive in both groups, while that of Fas ligand mRNA increased significantly from Day 5 and peaked on Day 13 in group 1, and the expression was 10 times stronger than that for isogeneic combination (group 2).

CONCLUSION

Early detection of upregulated Fas ligand and increased apoptosis is thus considered to be potentially a useful tool for the diagnosis of hepatic GVHD.

Tight interaction between densely methylated DNA fragments and the methyl-CpG binding domain of the rat MeCP2 protein attached to a solid support

In a previous report we have found that a number of short DNA fragments methylated at CpG sequences bound more tightly to a methyl-CpG binding column than DNA fragments having a larger number of methyl-CpG sequences. The column consists of a polypeptide comprising the DNA binding domain of the rat MeCP2 protein attached to a solid support. In the present study, we have investigated the features of short DNA fragments which bind tightly to a methyl-CpG binding column. Tight binding was observed when the DNA fragment had a high density of methyl-CpG sequences. Many of these fragments, derived from human genomic DNA, contained Alu repeated sequences supporting the previous observation that the highly-abundant Alu sequences are highly methylated. Our results suggest that methyl-CpG density is an important factor in the interaction between DNA fragments and the DNA binding domain of MeCP2 attached to a solid support.

Microsatellite instability in double cancers of the esophagus and head and neck

It is generally accepted that patients with squamous cancers of the esophagus are known to have a high risk of concomitant head and neck cancer. However, there have been only a few reports describing microsatellite instability (MSI) in patients with both esophageal squamous cell carcinoma and head and neck cancers. To evaluate the role of genetic instability in carcinogenesis in such patients, we analyzed six microsatellite loci in 21 tumors from 10 patients who had developed primary cancers of both the esophagus and the head and neck. MSI was detected in 6 out of 10 patients. In five patients with double cancer, MSI was observed at the same microsatellite loci in both the esophageal and the head and neck tumors obtained from the same individuals. These data suggest that such patients may have the same underlying defect in the mismatch repair system, providing insight into possible mechanisms for field carcinogenesis.

Vascular reconstruction of the hepatic artery using the gastroepiploic artery: a case report

A 59 year-old woman with obstructive jaundice secondary to proximal bile duct carcinoma underwent percutaneous transhepatic biliary drainage (PTDB). This revealed complete obstruction of the bifurcation of the hilar hepatic duct and encasement of the right hepatic artery. Wedged hilar hepatectomy with combined resection of the extrahepatic bile duct, gallbladder, and the encased right hepatic artery was performed. The hepatic artery was reconstructed using an in situ right gastroepiploic artery (GEA) pedicle graft. The anastomosis was protected with fatty tissue from the greater omentum. This technique can be used to reconstruct the hepatic artery after radical surgery for malignant hepatobiliary and pancreatic disease.

Percutaneous transhepatic cholangioscopic lithotripsy and change of biliary manometry patterns

BACKGROUND/AIMS

Percutaneous transhepatic cholangioscopic lithotripsy (PTCSL) is used to remove bile duct stones. This work aims to evaluate the clinical usefulness of PTCSL and the reversibility of the terminal bile duct dysfunctions after PTCSL.

METHODOLOGY

Thirty patients who underwent PTCSL using mechanical and/or electrohydraulic lithotripsy over the past 10 years (20 patients with common bile duct stones and 10 with intrahepatic bile duct stones) were evaluated. Terminal bile ductal pressure was measured using the percutaneous transhepatic biliary drainage (PTBD) tube prior to and after lithotripsy by means of variable-load cholangiomanometry.

RESULTS

Complete stone extraction was possible in 26 patients (86.7%). The other 4 patients had intrahepatic stones. Complications included 2 cases of hemobilia, one of pneumonia, and 3 of localized peritonitis. Of 26 patients without residual stones, only 4 patients had a linear pressure flow (P-F) pattern which indicates normal biliary tract function prior to lithotripsy. In 17 of 22 patients with other type P-F patterns, however, these types also changed to a linear pattern after complete removal of stones. The P-F pattern of the other 5 patients remained unchanged.

CONCLUSIONS

PTCSL is a safe and efficient method treating biliary tract lesions while preserving the function of the sphincter of Oddi. The terminal biliary tract function normalized after stone removal. Thus, PTCSL was useful for patients with complicated bile duct stones not accessible to endoscopic retrograde management.

Analysis of the Fas system and Bcl-2 in rat liver allograft rejection

BACKGROUND

Apoptosis is involved in the mechanism of cell death observed in liver allograft rejection. The liver cells are sensitive to Fas-mediated apoptosis; however, little is known about the involvement of the Fas system in liver allograft rejection. We used rat models to investigate the expression of Fas/Fas ligand and apoptosis-related proteins during liver allograft rejection.

MATERIALS AND METHODS

DA rats to Lewis, and Lewis to Lewis orthotopic liver transplantation were performed; liver samples were collected on days 1, 3, 5, 7, and 9 postoperatively (each n = 3). Apoptosis was monitored by TUNEL and electron microscopy. The expression of Fas, FasL, bcl-2, and bax was examined at the mRNA level and by means of immunohistochemistry.

RESULTS

The TUNEL index in the allografts and isografts on day 7 was 20.1 +/- 1.5 and 7.7 +/- 2.6/1000 cells, respectively. Fas and bax mRNA were constitutively expressed in both of the groups. The expression of Fas ligand mRNA in the allografts which rose on day 5 was 10 times stronger compared to that in the isografts. On the other hand, bcl-2 mRNA was generally expressed in the isografts while it decreased in the allografts. The immunohistochemical analysis also showed an increased reactivity of Fas ligand on day 5 in the allograft, which was observed both in parenchymal and nonparenchymal cells.

CONCLUSIONS

These results strongly suggest that Fas/Fas ligand interaction mediates the liver injury during allograft rejection. In addition, other regulatory factors of apoptosis, such as bcl-2, might also be involved in this pathogenesis.

Stable gene expression with VSV-G pseudotyped-retrovirus vector in the rat liver

BACKGROUND

Pseudotyped-retrovirus-mediated gene transfer to the regenerating rat liver was investigated in vivo and the findings were compared with those for retrovirus-mediated gene transfer.

MATERIALS AND METHODS

Four weeks prior to gene transfer, the spleen was transpositioned to the left subcutaneous position to develop a port-splenic shunt. Twenty-four hours after a partial hepatectomy (68%) was performed, the liver was perfused in situ and kept in contact with either a pseudotyped-retrovirus vector encoding LacZ (7 x 10(7) cfu/ml, Group 1) or a retrovirus vector encoding LacZ (1 x 10(4) cfu/ml, Group 2) for 30 min. The animals were sacrificed at various points after gene transfer, and X-gal staining, reversed polymerase chain reaction (RT-PCR), and ONPG assay were performed to detect the transferred LacZ cDNA.

RESULTS

In X-gal staining, the transferred LacZ cDNA started to show a strong beta-galactosidase activity in 30 to 50% of the hepatocytes at 3 days after gene transfer. Positive staining continued to be recognized until 28 days with a slight decrease in its intensity thereafter. On the other hand, Group 2 animals showed weak staining, which was observed in about 10 to 15% of the hepatocytes from 3 days after gene transfer and then decreased thereafter. In RT-PCR, positive mRNA of LacZ was detected constitutively until 28 days after gene transfer in Group 1, whereas two-thirds of the samples showed a negative band in Groups 2 at 3 days after gene transfer.

CONCLUSION

In conclusion, the pseudotyped-retrovirus vector was useful in establishing a stable and strong expression of the in vivo gene transfer, while targeting the regenerating liver.

Anesthetic management for pheochromocytoma resection using spinal cord stimulation and intravenous nicardipine--a case report

We have used spinal cord stimulation (SCS), diazepam and nitrous oxide for maintenance of general anesthesia. Blood pressure was maintained by bolus administration of nicardipine for the removal of pheochromocytoma. Both SCS and nicardipine reduced systemic vascular resistance and SCS increased cardiac output. However, neither SCS nor nicardipine could inhibit the release of norepinephrine. SCS proved to be useful as one of anesthetic technique during the removal of pheochromocytoma, and also in the management of postoperative pain and the prevention of complications.

Common bile duct blood clot: an unusual cause of ductal filling defects for calculi

We report a case of obstructive jaundice caused by a blood clot in the common bile duct in a 75-year-old man with cirrhosis. Five years prior to his admission, he had undergone a left hepatectomy for hepatocellular carcinoma. At the present admission, he appeared icteric, and endoscopic retrograde cholangiography revealed filling defects in the common bile duct. Choledochotomy was therefore performed for possible common duct stones, and exploration of the duct showed blood clot casts filling the duct. The casts were easily removed, and the patient's postoperative course was uneventful. However, he developed ascites and jaundice 1 month later and died of liver failure approximately 3 months after undergoing the choledochotomy. Autopsy revealed hemorrhagic necrosis in the proximal intrahepatic duct of the posterior segment, which was considered to be the cause of the observed hemobilia, as well as the blood clot in the common bile duct at surgery. We report this rare case and discuss the cause of hemobilia.

A small-molecule, nonpeptide CCR5 antagonist with highly potent and selective anti-HIV-1 activity

The beta-chemokine receptor CCR5 is considered to be an attractive target for inhibition of macrophage-tropic (CCR5-using or R5) HIV-1 replication because individuals having a nonfunctional receptor (a homozygous 32-bp deletion in the CCR5 coding region) are apparently normal but resistant to infection with R5 HIV-1. In this study, we found that TAK-779, a nonpeptide compound with a small molecular weight (Mr 531.13), antagonized the binding of RANTES (regulated on activation, normal T cell expressed and secreted) to CCR5-expressing Chinese hamster ovary cells and blocked CCR5-mediated Ca2+ signaling at nanomolar concentrations. The inhibition of beta-chemokine receptors by TAK-779 appeared to be specific to CCR5 because the compound antagonized CCR2b to a lesser extent but did not affect CCR1, CCR3, or CCR4. Consequently, TAK-779 displayed highly potent and selective inhibition of R5 HIV-1 replication without showing any cytotoxicity to the host cells. The compound inhibited the replication of R5 HIV-1 clinical isolates as well as a laboratory strain at a concentration of 1.6-3.7 nM in peripheral blood mononuclear cells, though it was totally inactive against T-cell line-tropic (CXCR4-using or X4) HIV-1.

[Thromboxane A2 antagonist--discovery of seratrodast]

We were interested in RCS (rabbit aorta contracting substance) and SRS-A (slow reacting substance of anaphylaxis) and their involvement in human bronchial asthma. When we started our anti-asthmatic drug research in the 1970's. We synthesized a lot of chemical compounds and eventually discovered that AA-861 inhibited the generation of SRS-A from the lung tissue of actively sensitized guinea pigs. AA-861 was found to be a potent 5-lipoxygenase inhibitor. This compound reduced experimental allergic asthma in guinea pigs, but it is easily metabolized in the body. More recently, we found a novel compound, AA-2414 (seratrodast), which is not metabolized in the body. AA-2414 proved to be not a 5-lipoxygenase inhibitor, but a thromboxane A2 (TXA2) receptor antagonist. Seratrodast is the first receptor antagonist that is being developed as an anti-asthmatic drug. Seratrodast inhibits both immediate-, late asthmatic responses in guinea pigs, and also reduces airway hyperresponsiveness in dogs. The anti-asthmatic action of seratrodast in animal models indicates that the drug should be of use in the treatment of human asthmatics. In clinical studies, seratrodast showed a marked effect to improve clinical parameters in bronchial asthma. It is also reported that seratrodast is free from harmful aftereffects. Clinical trials are under way in the US.

Bronchoscopic removal of bronchial foreign bodies through the laryngeal mask airway in pediatric patients

The laryngeal mask airway was used to perform fiberoptic removal of bronchial foreign bodies (peanuts) in two pediatric patients. Laryngeal mask airway offers easy access to the airway, safe respiratory management and direct visualization of the airway during bronchoscopic procedures. Laryngeal mask airway allows the use of larger bronchoscopes than can usually be used for children when bronchoscopy is performed through an endotracheal tube. In each case, the peanuts were removed safely and easily using a Fogarty catheter through the fiberoptic bronchoscope. These cases suggest that laryngeal mask airway is useful in maintaining a secure airway during the removal of bronchial foreign bodies in children.

Mucosa-associated lymphoid tissue (MALT) of the gallbladder: a clinicopathological correlation

OBJECTIVE

Lymph follicles are frequently found on histological examination of a surgically removed gallbladder. The significance of these lymph follicles is not clearly understood. The aim of this study was to examine the clinicopathological correlation between the lymph follicles in the gallbladder morphologically and the mucosa-associated lymphoid tissue (MALT) in the gut.

METHODS

The gallbladders were fixed and cut serially. The tissue slices were processed in the routine manner for a histological examination. The histological criteria for MALT in this study was defined as the presence of lymph follicles with germinal centers in the lamina propria mucosae in approximately equal numbers in all portions of the gallbladders from the neck to the fundus. Biliary bile obtained at surgery was cultured for a bacteriological examination in the hospital laboratory. The types of gallstones were classified according to the Classification of Gallstones by the Japanese Society of Gastroenterology.

RESULTS

Of the 1341 patients, 158 (11.8%) patients fulfilled the histological criteria, including 64 men and 94 women with an average age of 64.2 years. Gallstones were present in 89.2% of the patients, and 74.5% of these were calcium bilirubinate gallstones. Cultures of the bile were positive in 95.4% of the patients. A variety of bacterial species were thus found, most commonly Escherichia coli and Klebsiella spp. Grossly, the gallbladders usually showed a granular appearance of the mucosa.

CONCLUSION

The MALT in the gallbladder is not a rare condition and is frequently encountered in clinical practice. This lymphoid tissue may represent a mucosal and morphological immune phenomenon for infection rather than a substrate for the development of low-grade B-cell lymphoma.

Isolation of DNA fragments associated with methylated CpG islands in human adenocarcinomas of the lung using a methylated DNA binding column and denaturing gradient gel electrophoresis

We have constructed a library of DNA fragments heavily methylated in human adenocarcinomas of the lung to permit the comprehensive isolation of methylated CpG islands in cancer. Heavily methylated genomic DNA fragments from tumors of nine male patients were enriched using a methylated DNA binding column and used for construction of the library. From this library, DNA fragments having properties of CpG islands were isolated on the basis of their reduced rate of strand dissociation during denaturing gradient gel electrophoresis. Approximately 1,000 clones, corresponding to 0.3% of the library were analyzed, and nine DNA fragments were identified as being associated with CpG islands that were methylated in tumor DNA. One CpG island was methylated specifically in tumor DNA, whereas the remaining eight CpG islands were methylated both in normal and tumor DNA derived from the same patients. Our results suggest that the number of CpG islands methylated specifically in tumors is not large. The library, which contains DNA fragments from methylated CpG islands comprehensively, is expected to be valuable when elucidating epigenetic processes involved in carcinogenesis.

Protective effects of ulinastatin against ischemia-reperfusion injury

We investigated the protective effect of urinary trypsin inhibitor (ulinastatin: UTI) in vitro, in relation to the neutrophil activity in hepatic ischemia/reperfusion (I/R) injury. The rat liver was removed and preserved in cold Ringer's lactate solution for 60 min, followed by 120 min of reperfusion with oxygenated perfusate. The rats were divided into four groups (n = 8 in each group). The livers were perfused with Krebs-Henseleit (K-H) solution containing no additives in group 1, 50,000 U/kg of UTI in group 2, 3.5 x 10(6) of neutrophils in group 3, and both neutrophils and UTI in group 4. In group 3, the AST and ALT levels were always higher than those in other three groups at any point evaluated (P < 0.01) and the LDH levels were observed to be significantly higher than those in other three groups at 0, 5, 10, 60, and 90 min after reperfusion (P < 0. 01). These increase were suppressed by additional pretreatment with UTI in group 4. The bile flow during reperfusion was significantly suppressed in group 3 compared to that of group 4, at both 30 (P < 0. 01) and 60 (P < 0.05) min after reperfusion. The MPO activity after reperfusion in group 3 also significantly increased compared to other three groups (P < 0.01). These data thus suggest that UTI ameliorated the ischemia/reperfusion injury in vitro by inhibiting of neutrophil accumulation in the postischemic liver.

Characteristics of hepatocellular carcinoma in patients with negative virus markers: clinicopathologic study of resected tumors

Fifty-one cases of resected hepatocellular carcinoma (HCC) were retrospectively analyzed to evaluate the clinicopathologic features of HCC in patients with negative virus markers. The data were compared between three groups: hepatitis B surface antigen positive (HB, n = 11), hepatitis C virus antibody positive (HC, n = 21), and non-BC (both HbsAg and HCVAb negative, n = 12). Seven patients were excluded from the study because of operative death (n = 3), a history of alcohol abuse (n = 3), or the presence of dual positive HB and HC virus markers (n = 1). The data were analyzed by either an analysis of variance (ANOVA) or a contingency table. The age of the non-BC patients was higher (63.0 +/- 4.1, +/- SE) than that of HB patients (54.0 +/- 3.2, p < 0.05) but was identical to that of the HC group (62.0 +/- 1.8). Among the preoperative laboratory data, the serum glutamic oxaloacetate and glutamate pyruvate transaminoses (GOT, GPT) levels were statistically lower in the non-BC patients (32.8 +/- 4.8 and 28.0 +/- 4.4 IU/L, respectively) than in the HB and HC patients. The pathologic features of the resected specimens in the non-BC patients showed more invasive growth than in specimens from the HB or HC patients. The clinical stages (defined based on the criteria of the Japanese Association of Hepatocellular Carcinoma) were also more advanced in the non-BC patients than in the other groups. Postoperative survival time showed no significant difference among the groups. In conclusion, the non-BC patients had comparatively greater invasive growth and more advanced clinical stages than the HB and HC patients, despite the absence of liver cirrhosis, and so demonstrated the same poor survival data as observed in the HB and HC patients.

Pedunculated exogastric leiomyosarcoma: case report and brief literature review

A case report and review of the literature on pedunculated exogastric leiomyosarcomas are presented. Although about one-fourth of the stromal tumors (common leiomyomas and leiomyosarcomas) of the stomach grow in an exogastric configuration, pedunculated exogastric leiomyosarcomas are extremely rare. At present there is no evidence of intraperitoneal seeding from exogastric leiomyosarcomas. Consequently, a local resection with an adequate margin is sufficient when no invasion to the adjacent structures, is observed.

Fas ligand induction in human NK cells is regulated by redox through a calcineurin-nuclear factors of activated T cell-dependent pathway

Fas ligand (FasL) on cytotoxic lymphocytes is important for mediating apoptosis of activated lymphocytes and other target cells. We have reported that NK cell functions, such as proliferation, cell death, and killing activity, are subject to regulation by cellular redox status. Here, we report that expression of FasL protein and mRNA in activated NK cells is also regulated by redox. Ligation of CD16 on IL-2-preactivated NK cells resulted in reduction of intracellular peroxide level as well as induction of FasL expression. This CD16-induced FasL expression was suppressed by oxidative stress, including thiol deprivation or treatment with hydrogen peroxide (H2O2). Addition of thiol-reducing compounds, such as L-cystine, 2-ME, or N-acetyl cysteine, restored FasL expression. These data suggest that CD16 stimulation requires cellular reducing status for FasL induction in NK cells. Because FasL gene activation following CD16 cross-linking is regulated by the NF of activated T cells (NFAT), we examined the effect of oxidative stresses on NFAT activation. Electrophoretic mobility shift assays revealed that both thiol insufficiency and H2O2 treatment suppressed DNA-binding activity of NFAT and that addition of thiol-reducing compounds reversed or even enhanced it. Furthermore, these oxidative stresses inhibited activity of calcineurin, a serine/threonine phosphatase that regulates NFAT activation. These results suggest that suppression of calcineurin and NFAT activation is a mechanism by which oxidative stress inhibits FasL induction in activated NK cells and further support the hypothesis that thiol-reducing compounds might be required for maintenance of optimal NK functions under physiologic oxidative conditions.