Biomedical subjects

Yoshihiro Minamiya

Publications and source records attributed to Yoshihiro Minamiya.

At least 19 recordsLinked to original sources

PubMed2025

Stratifying Lung Adenocarcinoma Risk with Multi-ancestry Polygenic Risk Scores in East Asian Never-Smokers.

BACKGROUND: Lung adenocarcinoma (LUAD) in never-smokers is a major public health burden, especially among East Asian women. Polygenic risk scores (PRSs) are promising for risk stratification but are primarily developed in European-ancestry populations. We aimed to develop and validate single- and multi-ancestry PRSs for East Asian never-smokers to improve LUAD risk prediction. METHODS: PRSs were developed using genome-wide association study summary statistics from East Asian (8,002 cases; 20,782 controls) and European (2,058 cases; 5,575 controls) populations. Single-ancestry models included PRS-25, PRS-CT, and LDpred2; multi-ancestry models included LDpred2+PRS-EUR128, PRS-CSx, and CT-SLEB. Performance was evaluated in independent East Asian data from the Female Lung Cancer Consortium (FLCCA) and externally validated in the Nanjing Lung Cancer Cohort (NJLCC). We assessed predictive accuracy via AUC, with 10-year and (age 30-80) absolute risks estimates. RESULTS: The best multi-ancestry PRS, using East Asian and European data via CT-SLEB (clumping and thresholding, super learning, empirical Bayes), outperformed the best East Asian-only PRS (LDpred2; AUC=0.629, 95% CI:0.618,0.641), achieving an AUC of 0.640 (95% CI:0.629,0.653) and odds ratio of 1.71 (95% CI:1.61,1.82) per SD increase. NJLCC Validation confirmed robust performance (AUC =0.649, 95% CI: 0.623, 0.676). The top 20% PRS group had a 3.92-fold higher LUAD risk than the bottom 20%. Further, the top 5% PRS group reached a 6.69% lifetime absolute risk. Notably, this group reached the average population 10-year LUAD risk at age 50 (0.42%) by age 41, nine years earlier. CONCLUSIONS: Multi-ancestry PRS approaches enhance LUAD risk stratification in East Asian never-smokers, with consistent external validation, suggesting future clinical utility.

East Asian never smokers↗

PubMed2006

Tumor-derived TGFbeta-1 induces dendritic cell apoptosis in the sentinel lymph node.

Lymphatic flux from a primary tumor initially flows into a tumor-draining lymph node (LN), the so-called sentinel LN (SLN). Carried by the lymph fluid are a variety of mediators produced by the tumor that can influence immune responses within the SLN, making it a good model with which to investigate tumor-related immunology. For instance, dendritic cell (DC) numbers are reduced in SLNs from melanoma and breast cancer patients. In the present study, we investigated the mechanism by which DC numbers were reduced within SLNs from patients with non-small cell lung cancer. We found that the incidence of apoptosis among DCs was higher in SLNs than in non-SLNs, as were levels of TGFbeta-1. In contrast, levels of TGFbeta-1 mRNA did not differ between SLNs and non-SLNs, but were 30 times higher in tumors than in either LN type. In vitro, incubation for 2 days with TGFbeta-1 induced apoptosis among both cultured DCs and DCs acutely isolated from normal thoracic LNs, effects that were blocked by the TGFbeta-1 inhibitor DAN/Fc chimera. Taken together, these results suggest that tumor-derived TGFbeta-1 induces immunosuppression within SLNs before the movement of tumor cells into the SLNs, thereby facilitating metastasis within those nodes.

Apoptosis↗

PubMed2006

Intraoperative sentinel lymph node mapping using a new sterilizable magnetometer in patients with nonsmall cell lung cancer.

PURPOSE: We recently developed a novel method for sentinel lymph node mapping using magnetic force. However, problems with the sterility and sensitivity of the magnetometer made intraoperative sentinel lymph node mapping impossible. The purpose of this study was to test the utility of a new, more sensitive, sterilizable magnetometer developed in our institute for in vivo sentinel lymph node mapping in patients with nonsmall cell lung cancer. DESCRIPTION: Ferumoxides (magnetite) served as the tracer. Twenty patients with nonsmall cell lung cancer participated in the study. Each received 5 mL of ferumoxides, which were injected around their tumor. Magnetic force was then measured intraoperatively using the new sterilizable magnetometer. EVALUATION: The in vivo sentinel lymph node detection rate was 80.0% (16 of 20). The accuracy, sensitivity, and false-negative rates were 100% (16 of 16), 100% (4 of 4) and 0% (0 of 12), respectively. Our preliminary study indicates that our new magnetometer enables in vivo sentinel lymph node mapping in patients with nonsmall cell lung cancer. CONCLUSIONS: This device safely and accurately detected sentinel lymph nodes in nonsmall cell lung cancer patients.

Aged↗

PubMed2005

Estrogen receptor alpha and beta are prognostic factors in non-small cell lung cancer.

PURPOSE: Estrogen receptor-alpha (ER-alpha) and -beta (ER-beta) play important roles in the carcinogenesis of breast tumors. Similarly, there have been several reports of ER expression in lung cancers, but the results have not been consistent, and the receptors' prognostic value remains unclear. Our goal was to investigate ER expression in non-small cell lung cancer (NSCLC) and to assess whether their expression correlates with prognosis. EXPERIMENTAL DESIGN: ER expression was examined using immunohistochemical methods with sections from 132 resected NSCLC specimens. Kaplan-Meier survival curves were analyzed to determine the significance of ER expression in the prognosis of NSCLC patients. RESULTS: ER-alpha was detected in the cytoplasm of 73% of the specimens analyzed, whereas ER-beta was detected in the nucleus of 51%. ER-alpha expression correlated with poorer overall survival (P < 0.001), as did the absence of ER-beta expression (P = 0.048). Likewise, at histopathologic stage I, ER-alpha expression (P = 0.028) or the absence of ER-beta (P = 0.037) correlated with a poorer prognosis, and ER-alpha(+)ER-beta(-) patients had a significantly worse prognosis than ER-alpha(-)ER-beta(+) patients (P = 0.00007). Multivariate Cox regression analysis revealed the absence of ER-beta to be an independent factor predictive of poor disease outcome (hazard ratio, 1.9; 95% confidence interval, 1.1-3.4; P = 0.0264). CONCLUSIONS: ER-alpha expression and the absence of ER-beta expression are associated with a poorer prognosis among NSCLC patients. In particular, the absence of ER-beta could serve as a marker identifying patients at high risk even at an early clinical stage.

Adult↗

PubMed2005

Effect of antithrombin III on neutrophil deformability.

As the spherical diameter of pulmonary capillaries is smaller than that of neutrophils, increased neutrophil stiffness or conversely, decreased neutrophil deformability is a key step in the initial sequestration of neutrophils within the lungs during inflammatory processes. Antithrombin III (AT) is known to exert a therapeutic effect against disseminated intravascular coagulation, and accumulating evidence suggests that AT also has anti-inflammatory properties. The mechanisms of its anti-inflammatory effects remain unclear, but in a rat endotoxin model, AT apparently inhibited neutrophil sequestration in the lung. In the present in vitro study, therefore, we examined the effect of AT on the deformability of human neutrophils and correlated those findings with their F-actin content. Isolated human neutrophils were stimulated with formyl-Met-Leu-Phe (1 muM, 2 min) in the presence or absence of the alpha, beta, or low heparin-affinity isoforms of AT (1 IU/ml, 20 min), and deformability was evaluated using a filter assay system. Neutrophils were also stained with fluorescein isothiocyanate-phalloidin and subjected to a fluorescein-activated cell sorter scan to assess F-actin content. The results showed that pretreatment with any of the three AT isoforms similarly inhibited the decreased neutrophil deformability and increased F-actin content of stimulated cells. Notably, heparinase had no effect on deformability or F-actin content in the presence or absence of AT, which was somewhat unexpected, as heparin sulfate proteoglycans likely function as AT receptors. These findings suggested that AT inhibits the increase in neutrophil stiffness seen during inflammatory processes by inhibiting actin polymerization via a heparin-independent pathway.

Actins↗

PubMed2005

Increased expression of myosin light chain kinase mRNA is related to metastasis in non-small cell lung cancer.

BACKGROUND: The invasiveness of tumor cells depends in large part on their motility, which in turn depends on cytoskeletal function. A major cytoskeletal component involved in cell motility is myosin II, the classical form of myosin first identified in muscle but also expressed in nonmuscle cells. Myosin II is activated by myosin light chain kinase (MLCK), which phosphorylates it on its regulatory light chain. In this context, the contribution made by MLCK to tumor cell motility and invasiveness has been investigated extensively in vitro, but clinical evidence of such a contribution has been lacking. In the present study, therefore, we examined the role of MLCK in the metastasis of non-small cell lung cancer (NSCLC) in a clinical setting. METHODS: We measured MLCK mRNA expression in tumor samples from 39 NSCLC patients using real-time semiquantitative reverse transcription polymerase chain reaction carried out in a LightCycler. We then correlated MLCK mRNA expression with known clinicopathological factors. RESULTS: We found that levels of MLCK mRNA expression were higher in patients who showed disease recurrence and distant metastasis than in those who did not. Moreover, the 3-year disease-free survival rate among patients showing lower levels of MLCK mRNA expression [log10(MLCK/GAPDH) <1.4] was significantly greater than among those showing higher MLCK mRNA expression [log10(MLCK/GAPDH) > or =1.4] (87.5 vs. 50.0%; log-rank test, p = 0.021). CONCLUSION: These findings are the first clinical evidence that expression of MLCK is correlated with disease recurrence and distant metastasis in NSCLC.

Adult↗

PubMed2005

Pulmonary reexpansion causes xanthine oxidase-induced apoptosis in rat lung.

The pathogenesis of reexpansion pulmonary edema is not yet fully understood. We therefore studied its mechanism in a rat model in which the left lung was collapsed by bronchial occlusion for 1 h and then reexpanded and ventilated for an additional 3 h. We then evaluated the production of reactive oxygen species in the lungs using fluorescent imaging and cerium deposition electron microscopic techniques and the incidence of apoptosis using the TdT-mediated dUTP-digoxigenin nick end labeling (TUNEL) method. We found that pulmonary reexpansion induced production of reactive oxygen species and then apoptosis, mainly in endothelial and alveolar type II epithelial cells. Endothelial cells and alveolar type I and II epithelial cells in the reexpanded lung were positive for TUNEL and cleaved caspase-3. DNA fragmentation was also observed in the reexpanded lung. In addition, wet-dry ratios obtained with reexpanded lungs were significantly higher than those obtained with control lungs, indicating increased fluid content. All of these effects were attenuated by pretreating rats with a specific xanthine oxidase inhibitor, sodium (-)-8-(3-methoxy-4-phenylsulfinylphenyl) pyrazolo[1,5-a]-1,3,5-triazine-4(1H)-one. It thus appears that pulmonary reexpansion activates xanthine oxidase in both endothelial and alveolar type II epithelial cells and that the reactive oxygen species produced by the enzyme induce apoptosis among the endothelial and alveolar type I and II epithelial cells that make up the pulmonary water-air barrier, leading to reexpansion pulmonary edema.

Animals↗

PubMed2005

Nocturnal hypoxemia after lobectomy for lung cancer.

BACKGROUND: Although nocturnal episodic hypoxemia after major abdominal surgery has been reported, the condition of nocturnal oxygen saturation after lung surgery is largely unknown. We evaluated nocturnal oxygen saturation during the perioperative period after lobectomy for lung cancer. This study also compared the postoperative course of nocturnal oxygen saturation after standard lobectomy with posterolateral thoracotomy and lobectomy with video-assisted thoracic surgery. METHODS: Twenty-one consecutive patients who had undergone lobectomy for lung cancer by either the posterolateral thoracotomy approach (n = 11) or the video-assisted thoracic surgery approach (n = 10) were studied. Fifteen consecutive patients who had undergone gastrectomy for gastric cancer were also studied. Overnight oxygen saturation was measured on the third and 14th postoperative days. RESULTS: The frequency of hypoxemia in the lobectomy group was higher than that in the gastrectomy group (p = 0.043). The frequency of hypoxemia on the 14th postoperative day (p = 0.009) and the severity of hypoxemia on the third and 14th postoperative days (p = 0.041, 0.046) for the video-assisted thoracic surgery approach were lower than those for the posterolateral thoracotomy approach. In terms of mean arterial oxygen saturation, heart rate, forced vital capacity, and forced expiratory volume in 1 second, there were no statistically significant differences between the video-assisted thoracic surgery group and the posterolateral thoracotomy group. CONCLUSIONS: Video-assisted thoracic surgery lobectomy was superior in terms of early postoperative nocturnal oxygen saturation. We conclude that the video-assisted thoracic surgery approach is more beneficial than the posterolateral thoracotomy approach for high-risk patients.

Aged↗

PubMed2005

Intraoperative detection of lymph node micrometastasis with flow cytometry in non-small cell lung cancer.

OBJECTIVE: We sought to determine whether cytokeratin-positive cells can be detected as markers of lymph node metastasis by using flow cytometry within a time frame suitable for intraoperative decision making in non-small cell lung cancer. METHODS: Five lymph nodes from each of 20 patients with non-small cell lung cancer were randomly selected for study. Each node was divided longitudinally into 3 pieces: one piece for flow cytometry, one for immunohistochemical staining, and the last for conventional hematoxylin and eosin staining. In both flow cytometry and immunohistochemistry, cytokeratin-positive cells were detected with the fluorescein isothiocyanate-conjugated anti-cytokeratin antibody AE1/AE3. RESULTS: Cytokeratin-positive nodes were detected by means of flow cytometry within 40 minutes. Eight (8%) of the 100 lymph nodes from 4 (20%) of the 20 patients were deemed positive for metastasis on the basis of conventional histologic examination. By contrast, 33 (33%) lymph nodes from 13 (65%) patients were deemed positive on the basis of immunohistochemical cytokeratin staining, and 38 (38%) lymph nodes from 14 (70%) patients were deemed positive on the basis of flow cytometric cytokeratin-positive cell detection. All nodes deemed positive for metastasis on the basis of conventional and immunohistochemical methods were also positive on flow cytometry. CONCLUSIONS: Flow cytometry enables rapid intraoperative diagnosis of nodal metastasis in patients with non-small cell lung cancer. Flow cytometric detection of cytokeratin-positive cells within lymph nodes correlates with their immunohistochemical detection, and its level of sensitivity is greater than that of conventional histologic staining and about equal to that of immunohistochemical staining.

Biomarkers, Tumor↗

PubMed2005

The current status of sentinel lymph node mapping in non-small cell lung cancer.

Sentinel lymph node (SLN) mapping has become a common procedure in the treatment of breast cancer and malignant melanoma. Its primary benefit is that it enables surgeons to avoid nontherapeutic lymph node dissection and the complications that follow. There are also several studies of the use of SLN mapping in the treatment of non-small cell lung cancer (NSCLC) reported in the English literature, and all present evidence for the existence of SLNs in NSCLC. Nevertheless, SLN mapping is not widely used in the treatment of NSCLC for several reasons: first, special precautions are required to minimize exposure when radioisotopes are used as tracers; second, it is difficult to detect the blue dyes used as tracers within anthoracotic thoracic lymph nodes; and third, major complications comparable to the arm edema seen in breast cancer or the lymphedema and nerve injury seen in melanoma are not seen with mediastinal lymph node dissection (MLND). To address these issues, new techniques are being developed by groups at several institutes, including our own. We believe that SLN mapping will enable surgeons to more precisely stage NSCLC, after which more sensitive techniques can be employed on a limited amount of tissue to detect occult micrometastatic disease with less cost and effort. SLN mapping can also be applied to video-assisted thoracic surgery (VATS) for NSCLC, enabling surgeons to avoid nontherapeutic and technically difficult MLND often necessary with traditional open surgery. For all of these reasons, we think that SLN mapping will be useful in the treatment of NSCLC, and that further development aimed at making SLN mapping a practical surgical procedure is warranted.

Carcinoma, Non-Small-Cell Lung↗

PubMed2004

Expression of tissue factor mRNA and invasion of blood vessels by tumor cells in non-small cell lung cancer.

PURPOSE: Tissue factor (TF), an initiator of the extrinsic coagulation cascade, is also expressed in a wide range of cancer cells and plays an important role in cancer progression and metastasis, as well as in processes independent of the blood coagulation pathway. For example, by acting as an adhesion molecule enabling tissue invasion, TF may play a key role in the metastatic process and angiogenesis in non-small cell lung cancer (NSCLC). METHODS: To further investigate the role of TF on tumor cell invasion in NSCLC, we measured the TF mRNA expression in the tumors of 42 NSCLC patients using real-time quantitative reverse transcription - polymerase chain reaction carried out in a LightCycler. We then compared the TF mRNA expression with histological evidence of invasion of blood and lymphatic vessels by tumor cells. RESULTS: Although there was no significant relationship between the TF mRNA expression and the invasion of lymphatic vessels, the TF mRNA expression was significantly higher in tumors that invaded blood vessels (Log(10) TF mRNA/GAPDH mRNA = 2.16 +/- 0.18) than in those that did not (1.59 +/- 0.16; P = 0.03). CONCLUSION: These results suggest that TF plays a major role in blood vessel invasion by tumor cells in NSCLC.

Adult↗

PubMed2004

Soluble and cell-associated forms of some yet to be identified factor in transfused blood which promotes solid tumor growth in mice.

PURPOSE: The mechanism underlying the immunomodulation caused by blood transfusion has yet to be elucidated. The aim of the present study was to determine whether the transfusion of a soluble or insoluble factor present in stored blood can induce immunomodulation, which would thereby promote solid tumor growth. METHODS: C57Bl/6J mice were subcutaneously inoculated with B16-CG melanoma cells, which secrete beta-human chorionic gonadotropin (beta-hCG). Following inoculation, each of three different products of allogeneic and syngeneic blood were transfused on days 0 and 1: fresh whole blood, stored whole blood, and supernatants from the stored blood. Tumor growth was then monitored by measuring urinary beta-hCG. All mice were killed on day 15, and the tumor weight and volume were measured. RESULTS: Transfusion of all allogeneic blood products enhanced tumor growth, as did the stored syngeneic whole blood. Neither fresh syngeneic blood nor the supernatant from stored syngeneic blood promoted tumor growth. Although the tumors were not visually detectable until day 10 after inoculation, by day 7 the levels of urinary beta-hCG were significantly higher in the mice that received allogeneic blood supernatant than in the mice that received saline. CONCLUSIONS: A soluble alloantigen enhances solid tumor growth, as does an insoluble factor present in stored syngeneic whole blood. The immunomodulation associated with this factor begins to enhance tumor growth within 7 days after transfusion.

Animals↗

PubMed2004

Mediastinal neurofibroma originating from the left intrathoracic phrenic nerve: report of a case.

We report a case of mediastinal neurofibroma originating from the left phrenic nerve in a 42-year-old woman who was referred to us after a routine chest X-ray showed a smooth, round abnormal shadow in the left middle lung field adjacent to the heart. We resected a 25 x 20 x 20-mm tumor by video-assisted thoracic surgery. Histopathological examination confirmed that the lesion was a mediastinal neurofibroma originating from the left phrenic nerve without von Recklinghausen's disease. Neurogenic mediastinal tumors originating from the phrenic nerve are very rare, and to the best of our knowledge, no other case of a mediastinal neurofibroma originating from the phrenic nerve in a patient without von Recklinghausen's disease has ever been reported.

Adult↗

PubMed2004

Superior mediastinal and neck lymphatic mapping in mid- and lower-thoracic esophageal cancer as defined by ferumoxides-enhanced magnetic resonance imaging.

OBJECTIVE: The purpose of this study was to detect lymphatic drainage into the superior mediastinum and neck in thoracic esophageal cancer patients using ferumoxides-enhanced magnetic resonance imaging (MRI), and to have this information assist in determining the appropriate extent of lymphadenectomy. METHODS: Nine male patients with T2-T3 mid- and lower-thoracic esophageal cancer with lymph node metastasis were examined. The day before surgery, ferumoxides was endoscopically injected into the submucosal layer of the peritumoral lesion. Thereafter, lymph nodes in the superior mediastinum and neck, which were shown to be ferumoxides-enhanced on MRI, were harvested and evaluated; magnetic force from all harvested lymph nodes was measured ex vivo. RESULTS: MRI of the superior mediastinum and neck revealed 1(median) ferumoxides-enhanced lymph nodes in eight (89%) patients, and there was laterality in the lymphatic mapping in both areas. Of the 15 lymph nodes into which drainage was detected by enhanced MRI, 12 (80%) were magnetite-positive. In six patients (67%), magnetic resonance enhanced lymph nodes corresponded completely with the ex vivo magnetite examination, and in 3 patients (33%) there was partial agreement. In 3 (60%) of the 5 patients that showed paratracheal and/or supraclavicular lymph node metastases, all of the affected nodes were detected by MRI; in one patient some of the affected nodes were detected. CONCLUSION: Ferumoxides-enhanced MRI is useful for visualizing lymphatic drainage to the superior mediastinum and neck in thoracic esophageal cancer. It is an adequate procedure to form an estimate on the appropriate extent of lymphadenectomy.

Adult↗

PubMed2004

Antithrombin III diminishes production of oxygen radical in endotoxin-infused rat lung.

The interaction of antithrombin III (AT) with cell surface glycosaminoglycans is known to have an inhibitory effect on inflammatory processes. We evaluated the effect of AT on endotoxin-induced production of oxygen radical in the pulmonary circulation using a fluorescent imaging technique. Also measured was the myeloperoxidase content of the lung, which served as an index of neutrophil accumulation, and neutrophil F-actin levels. Four groups of rats were infused for 2 h with endotoxin at 4.5 mg/kg/h (Et group), physiological saline (CT group), 100 U/kg of AT + endotoxin (AT group), or 100 U/kg of low-heparin-affinity latent-AT + endotoxin (L-AT group), respectively. Production of oxygen radical, neutrophil accumulation, and neutrophil F-actin levels were all significantly higher in the ET and L-AT groups than in the CT or AT group. Moreover; the levels of myeloperoxidase within the lung were well correlated with levels of oxygen radical production, which was consistent with the electron microscopic finding that cerium was deposited almost exclusively around neutrophils. Thus, it appears that AT most likely reduces F-actin formation in neutrophil by binding to glycosaminoglycans (e.g., syndecan-4) on the neutrophil, thereby reducing neutrophil accumulation in the lung, which would in turn inhibit oxygen radical production in the lung.

Actins↗

PubMed2004

Hydrogen peroxide derived from intestine through the mesenteric lymph induces lung edema after surgical stress.

Compelling evidence indicates that the small intestine is the primary source of factors inducing lung injury after major surgery and that the lymphatic system is the major route by which these gut-derived factors reach the pulmonary circulation. This study investigated the mechanism of lung edema induced by surgical stress. After subjecting male, fasted, pathogen-free Sprague-Dawley rats to surgical stress (laparotomy and intestinal handling for 5 min), followed by ventilation for 5 h, we measured H2O2 production in the mucosa of small intestine and in the lung using 2',7'-dichlorofluorescein and intravital fluorescence microscopy. In addition, H2O2 in mesenteric lymph was measured using a quantitative assay; lung permeability was assessed as a function of extravasation of Evans blue dye; neutrophil accumulation was visualized by intravital fluorescence microscopy and assessed as a function of myeloperoxidase activity; and TNF-alpha levels were measured using a specific ELISA. The intensity of 2',7'-dichlorofluorescein fluorescence in the mucosa of small intestine, H2O2 levels of mesenteric lymph, and lung permeability were all significantly higher in rats subjected to surgical stress than in control animals. Moreover, all of these effects were blocked by pretreatment with a specific xanthine oxidase inhibitor. Surgical stress did not increase neutrophil accumulation or TNF-alpha production in the lung. In conclusion, surgical stress induces xanthine oxidase-dependent H2O2 production in the small intestine. The H2O2 then enters the mesenteric lymph and travels to the lung, where it increases capillary permeability and thus induces edema.

Animals↗

PubMed2004

Methylprednisolone-induced expression of mitochondrial heat shock protein 60 protects mitochondrial membrane potential in the hypoxic rat liver.

This study investigated the contribution made by mitochondrial heat shock protein (hsp) 60 to methylprednisolone-mediated protection against mitochondrial membrane depolarization under hypoxic conditions. A low-flow hypoxia model was generated in isolated male, fasted, pathogen-free Sprague-Dawley rat livers by reducing perfusate inflow pressure from 10 to 2.5 cm H2O for 2 h. The effects of methylprednisolone on mitochondrial membrane potential and expression of mitochondrial hsp 60 protein and mRNA were determined. We measured mitochondrial membrane potential by imaging rhodamine 123 fluorescence. Induction of mitochondrial hsp 60 was detected using two different anti-hsp 60 antibodies: one against the N-terminal signal sequence, which reacted exclusively with cytoplasmic hsp 60, and one against a different epitope, which reacted with cytoplasmic and mitochondrial hsp 60. In addition, the distribution of hsp 60 mRNA was examined using in situ hybridization. We found that under hypoxic conditions, there was a significant decline in mitochondrial membrane potential that was accompanied by a mild decline in the level of mitochondrial hsp 60, and that cytosolic hsp 60 was translocated into mitochondria. Pretreatment with methylprednisolone inhibited the declines in mitochondrial membrane potential and hsp 60 protein, as well as the translocation of cytosolic hsp 60. This raises the possibility that one way in which methylprednisolone protects the mitochondrial membrane potential under hypoxic conditions is to induce expression of mitochondrial hsp 60.

Animals↗

PubMed2003

Hydrogen peroxide-dependent declines in Bcl-2 induces apoptosis in hypoxic liver.

BACKGROUND: Low-flow hypoxia induces xanthine oxidase-dependent hydrogen peroxide production by hepatocytes in the midzone of blood-perfused rat livers and apoptosis in sinusoidal endothelial cells (SECs). As Bcl-2 is a potent inhibitor of apoptotic cell death and is localized mainly in the inner mitochondrial membrane and crista, the purpose of this study was to determine whether cell-specific changes in mitochondrial Bcl-2 levels could account for the hypoxia-induced apoptosis in SECs. MATERIALS AND METHODS: A low-flow hypoxia model was generated in isolated rat livers by reducing perfusate inflow pressure from 10 to 2.5 cmH2O for 2 h. Apoptosis was then evaluated using the TdT-mediated dUTP-digoxigenin nick end-labeling (TUNEL) method. Mitochondrial Bcl-2 protein levels were determined in hepatocytes and SECs using cryosectioning immunogold labeling electron microscopy.Results. TUNEL-positive nonparenchymal cells, identified as SECs, were observed predominantly in the midzone of low-flow hypoxic rat livers, whereas few parenchymal cells were stained. Mitochondrial Bcl-2 levels were higher in SECs than in hepatocytes under control conditions, but they declined significantly during hypoxia, though no morphological signs of apoptosis were apparent. In hepatocytes, by contrast, Bcl-2 levels were unaffected by hypoxia. Pretreatment with a specific xanthine oxidase inhibitor, sodium (-)-8-(3-methoxy-4-phenylsulfinylphenyl) pyrazolo [1,5-a]-1,3,5-triazine-4-olate monohydrate, which blocks production of hydrogen peroxide, also blocked both the hypoxia-induced apoptosis and the decline in mitochondrial Bcl-2 in SECs. CONCLUSION: Hydrogen peroxide-dependent declines in Bcl-2 induce apoptosis in SECs in the hypoxic rat liver.

Animals↗