Nuclear accumulation of MLKL induces necroptosis in cardiomyocytes: potential implication in Doxorubicin-induced cardiotoxicity

Background

The treatment with doxorubicin, a powerful chemotherapeutic agent, has been shown to be associated with an increased risk of lethal heart failure. Although various types of cell death pathway such as apoptosis and ferroptosis have been shown to be involved in the development of doxorubicin-induced cardiotoxicity, DIC, the involvement of necroptosis, a novel programmed necrosis induced by translocation of activated mixed lineage kinase domain-like protein, MLKL, to plasma membrane, remains unclear.

Purpose

The aim of this study was to determine whether necroptosis is involved in the development of DIC.

Methods and results

DIC was induced in C57BL/6J mice by intraperitoneal injection of doxorubicin at a dose of 10 mg/kg 3 times for a week. Eight days after the commencement of injection, echocardiographic analyses showed that left ventricular ejection fraction assessed by echocardiography was significantly lower in the doxorubicin-treated mice than in the vehicle-treated mice (44.0±13.7 vs. 70.5±3.7%), indicating the development of DIC. Immunoblot analysis showed that MLKL protein level was higher by 1.6 fold in the doxorubicin-treated mice than in the vehicle-treated mice. Interestingly, immunohistochemical analysis showed that signals of phospho-Ser345-MLKL, an activated form of MLKL, was found in the nuclei in addition to cytosol and intercalated discs of cardiomyocytes in the doxorubicin-treated mice. To get novel insight into significance of nuclear MLKL accumulation, a leucine-rich nuclear export signal (NES) spanning amino acids 280–284 of rat MLKL was identified by site-directed mutation analyses, and H9c2 cells, cultured rat cardiomyoblasts, were transfected with expression constructs for nucleus-directed MLKL (FLAG-mtNES-MLKL) or its wild type (FLAG-WT-MLKL). Percentage of FLAG-positive cells stained with Zombie Red, a fluorescent dye that is non-permeant to live cells, was higher in FLAG-mtNES-MLKL-transfected cells than in FLAG-WT-MLKL-transfected cells (80.0±3.5% vs. 6.3±1.3%, p<0.05), whereas percentage of cells immunostained with cleaved caspase-3 to FLAG-positive cells was similar in the two groups. The effect of the MLKL mutant on necroptosis was attenuated by treatment with GppNHp, an inhibitor of Ran-mediated nuclear protein import.

Conclusion

Nuclear accumulation of MLKL induces necroptosis in cardiomyocytes, which may contribute to progression of DIC.

Funding Acknowledgement

Type of funding sources: None.

Intracellular localization of AMP deaminase and its novel role in BCAA and lipid metabolism in diabetic cardiomyopathy

Background

A metabolomic study in the human heart suggested a pivotal role of amino acid (AA) metabolism in fatty acid oxidation, which is dysregulated in type 2 diabetes mellitus (T2DM) and heart failure. We previously reported that aberrant up-regulation of AMP deaminase 3 (AMPD3) impairs cardiac energetics in T2DM hearts, and AMPD3 was recently shown to be activated by fasting and to promote AA metabolism and fatty acid oxidation in skeletal muscle. A sodium glucose cotransporter 2 inhibitor (SGLT2i) has been shown to augment systemic AA metabolism, but its effect on cardiac AA metabolism remains unknown.

Purpose

We hypothesized that AMPD3 has a role in AA and lipid metabolism in cardiomyocytes and that the protective effect of an SGLT2i in diabetic hearts is mediated by modification of AA and lipid metabolism.

Methods and results

Proteomic analyses of AMPD3 immunoprecipitates in rat hearts revealed that AMPD3 interacted with the E1α and E2 components of the BCKDH complex, a rate-limiting enzyme of branched-chain AA (BCAA) catabolism. Immunoblotting using subcellular fractions revealed that BCKDH localized not only in the mitochondria matrix but also in the cytosol and endoplasmic reticulum (ER) and that AMPD3 interacted with BCKDH in the cytosol and ER. Despite comparable expression of BCKDH components and phosphorylation of E1α at Ser293, significant accumulation of BCAA was observed in T2DM rats (OLETF; 317±30 nmol/g) compared to that in control rats (LETO; 213±16 nmol/g), and the accumulation of BCAA was accompanied by up-regulation of AMPD3 in the cytosol and ER by 98% and 231%, respectively. In cardiomyocytes, disruption of BCAA catabolism by knockdown of BCKDH-E1α resulted in a 5.8-fold increase in AMPD3 at the transcriptional level and blunted lipid droplet biogenesis in response to a long-chain fatty acid challenge. Next, myocardial infarction (MI) was induced in LETO and OLETF pretreated with empagliflozin (10 mg/kg/day, 14 days) or a vehicle. Pathway analysis of cardiac metabolites revealed arginine biosynthesis and BCAA metabolism as the most significantly changed pathways with empagliflozin, with BCAA (791±187 nmol/g), glutamate, glutamine and urea being significantly increased. Empagliflozin restored myocardial ATP and survival after MI in OLETF to levels comparable to those in LETO. Electron microscopy showed a significantly higher prevalence of myocardium lipid droplets in OLETF, which was further increased by empagliflozin.

Conclusions

The results support the hypotheses that imbalance of extra-mitochondrial AMPD3-BCKDH interaction underlies dysregulated BCAA metabolism in T2DM hearts and that activation of cardiac AA metabolism by an SGLT2i normalizes fatty acid overload through sequestration into intracellular lipid droplets.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Boehringer Ingelheim

Is GLP-1 insufficiency a coronary risk factor? A multicenter observational study, BOREAS-CAD2

Background and aim

Glucagon-like peptide-1 (GLP-1) regulates insulin secretion and also affords pleiotropic effects including protective effects on blood vessels. Multiple factors regulate GLP-1 secretion after meals, but a group of apparently healthy subjects showed blunted responses of GLP-1 secretion in our previous study. In this study, we examined the possibility that the reduced capacity of GLP-1 secretion is associated with increased extent of coronary artery stenosis in non-diabetic patients.

Methods and results

Non-diabetic patients who were admitted for coronary angiography without a history of coronary interventions were enrolled. Coronary artery stenosis was quantified by Gensini score (GS), and GS ≥10 was used as an outcome variable based on results of earlier studies indicating its predictive value for cardiovascular events. The patients (mean age, 66.5±8.8 years; 71% males, n=173) underwent oral 75 g-glucose tolerant tests for determination of glucose, insulin and active GLP-1 levels. The area under the curve of plasma active GLP-1 (AUC-GLP-1) was determined as an index of GLP-1 secretion capacity. AUC-GLP-1 was not correlated with fasting glucose, AUC-glucose, serum lipids, indices of insulin sensitivity or estimated glomerular filtration rate. In multivariate logistic regression analysis for GS ≥10, AUC-GLP-1 < median, age and hypertension were selected as explanatory variables, though fasting GLP-1 level was not selected.

Conclusion

The findings indicate significant association of reduced GLP-1 secretion capacity with increased extent of coronary artery stenosis in non-diabetic patients. A causal relationship between change in GLP-1 secretion capacity and coronary stenosis remains to be examined by a longitudinal study

Funding Acknowledgement

Type of funding sources: Private company. Main funding source(s): This study was supported in part by a research grant from Investigator-Initiated Studies Program of Merck Sharp & Dohme Corp./MSD K.K.

Inhibition of xanthine oxidase ameliorates functional and metabolic impairment in type 2 diabetic hearts under pressure overload

Background

We recently reported that upregulated AMP deaminase (AMPD), via reduction in the tissue adenine nucleotide pool, contributes to exacerbation of diastolic dysfunction under pressure overload in OLETF, a rat model of obese type 2 diabetes (T2DM). Upregulated AMPD also possibly promotes xanthine oxidase (XO)-mediated ROS production, since AMPD deaminases AMP to IMP, which is further converted to inosine, providing substrates of XO, hypoxanthine and xanthine. Here, we examined the hypothesis that inhibition of XO ameliorates the pressure overload-induced diastolic dysfunction by suppression of ROS-mediated mitochondrial dysfunction and/or vascular dysfunction in T2DM rats.

Methods and results

Metabolomic analyses revealed that levels of xanthine and uric acid in the LV myocardium were significantly higher by 37% and 51%, respectively, in OLETF than in LETO, non-diabetic control rats, under the condition of phenylephrine-induced pressure overloading (200–230 mmHg). Myocardial XO activity in OLETF was 57.9% higher than that in LETO, which may be attributed to 31% higher level of inosine, a positive regulator of XO, in OLETF than in LETO. The activity of XO was significantly attenuated by administration of topiroxostat, an XO inhibitor at 0.5 mg/kg/day for 14 days. Pressure volume loop analyses showed that the pressure overloading resulted in significantly higher LVEDP in OLETF than in LETO (18.3±1.5 vs. 12.2±1.3 mmHg, p<0.05, n=7), though LVEDPs at baseline were comparable in OLETF and LETO (5.6±0.4 vs. 4.7±0.7 mmHg). Treatment with topiroxostat significantly suppressed the pressure overload-induced elevation of LVEDP in OLETF (18.3±1.5 vs. 11.3±1.1 mmHg, p<0.05) but not in LETO. Under the condition of pressure overloading, Ea/Ees, an index for ventricular-arterial coupling, was higher in OLETF than in LETO (2.3±0.3 vs. 1.6±0.3, p<0.05), and it was also improved by topiroxostat in OLETF (1.2±0.2, p<0.05). Myocardial ATP content was lower in OLETF than in LETO (2966±400 vs. 1818±171 nmol/g wet tissue, p<0.05), and treatment with topiroxostat significantly restored the ATP level (2629±307 nmol/g wet tissue). The LV myocardium of OLETF under pressure overload showed significantly higher level of malondialdehyde and 4-hydroxynonenal, an indicator of lipid peroxidation, than that of LETO. Measurement of oxygen consumption rate by Seahorse XFe96 Analyzer in mitochondria isolated from LV tissues revealed that state 3 respiration was significantly suppressed in OLETF by 43% compared to LETO, and it was restored by treatment with topiroxostat.

Conclusion

Both activity and substrates of XO are increased in T2DM hearts, in which upregulation of AMPD may play a role. Inhibition of XO ameliorates pressure overload-induced diastolic dysfunction and improves ventricular-arterial coupling in diabetic hearts, most likely through protection of mitochondrial function from ROS-mediated injury.

Funding Acknowledgement

Type of funding source: Public grant(s) – National budget only. Main funding source(s): Grant-in-aid for Scientific Research (#26461132, #17K09584) from the Japanese Society for the Promotion of Science

P207 Synergetic effect of amino acid and ketone metabolism underlies empagliflozin-mediated cardioprotection in the type 2 diabetic heart

Funding Acknowledgements

Boehringer Ingelheim

Background

 Although emerging evidence has indicated that sodium glucose cotransporter 2 (SGLT2) inhibitors restore impaired cardiac energetics in type 2 diabetes mellitus (T2DM), the underlying molecular mechanisms have yet to be established.  Augmented utilization of ketone is one proposed hypothesis, but depletion of succinyl-CoA triggered by the conversion of ketone back to acetyl-CoA by SCOT (succinyl-CoA:3-oxoacid CoA transferase) may hamper oxidative capacity of the tricarboxylic acid (TCA) cycle, which also requires succinyl-CoA.  The recent finding that empagliflozin augments systemic amino acid metabolism in patients with T2DM led us to hypothesize that the anaplerotic effect of amino acid on the TCA cycle complements ketone oxidation.

Methods and Results

 Myocardial infarction (MI) was induced in T2DM rats (OLETF) and control rats (LETO).  Survival rate at 48 hours after MI was significantly lower in OLETF than in LETO (40% vs 84%), and empagliflozin treatment (10 mg/kg/day, 14 days) before MI improved the survival rate in OLETF to 70%.  Metabolome analysis was performed using heart tissues from the non-infarct region 12 hours after MI.  Using principal component analysis, data from 92 metabolites that were detected were compressed into 2 dimensions, and the first component (PC1) clearly separated empagliflozin-treated OLETF from non-treated LETO and OLETF.  Analysis of factor loading of each metabolite for PC1 revealed that branched chain amino acids leucine, isoleucine and valine, the latter two of which can be oxidized to succynyl-CoA, and β-hydroxybutyrate were the top four metabolites that characterized empagliflozin treatment.  Furthermore, in comparison to LETO, OLETF treated with empagliflozin showed 50% higher levels of glutamine and glutamate, both of which can replenish the TCA cycle at the level of α-ketoglutarate.  In OLETF, empagliflozin significantly increased the TCA cycle intermediates citrate, cis-aconitate and malate by 74%, 119% and 59%, respectively.  OLETF showed 86% higher lactate and 38% lower ATP than those in LETO, but levels of the metabolites were normalized by empagliflozin, suggesting improved glucose oxidation.

Conclusions

  The present analyses showed that amino acid and ketone metabolism are metabolic pathways that are most affected by empagliflozin.  Coordination of these "starvation-induced pathways" may underlie the favorable metabolic effect of empagliflozin in T2DM hearts.

P121 Pressure overload-induced functional and metabolic impairments in type 2 diabetic hearts are ameliorated by inhibition of xanthine oxidase

Funding Acknowledgements

SANWA KAGAKU KENKYUSHO Co., Ltd.

Background

  We have recently demonstrated that AMP deaminase (AMPD) is upregulated in OLETF, obese type 2 diabetic (T2DM) rats, and that the upregulated AMPD contributes to depletion of myocardial ATP at the time of pressure overload, leading to diastolic dysfunction.  On the other hand, AMPD promotes the formation of IMP from AMP, and IMP is in turn further converted to hypoxanthine and xanthine, substrates of xanthine oxidase (XO), which produces uric acid with ROS as a byproduct.  Based on these findings, we tested the hypothesis that inhibition of XO ameliorates the pressure overload-induced diastolic dysfunction in T2DM rats. 

Methods and results

Metabolomic analyses of the left ventricular myocardium revealed that levels of myocardial hypoxanthine and xanthine were significantly higher by 30% and 28%, respectively, in OLETF than in LETO, non-diabetic control rats, under the condition of pressure overloading (200-230 mmHg) induced by phenylephrine infusion. Myocardial XO activity in OLETF was 57.9% higher than that in LETO, and the activity was significantly attenuated by oral administration of topiroxostat, an XO inhibitor, at 0.1-0.5 mg/kg/day for 14 days in a dose-dependent manner.  Pressure volume loop analyses showed that the pressure overloading induced by phenylephrine infusion resulted in significantly higher LVEDP in OLETF than in LETO (18.3 ± 1.5 vs. 12.2 ± 1.3 mmHg, p < 0.05, n = 7), though LVEDPs at baseline were comparable in OLETF and LETO (5.6 ± 0.4 vs. 4.7 ± 0.7 mmHg).  Treatment with topiroxostat significantly suppressed the pressure overload-induced elevation of LVEDP in OLETF (18.3 ± 1.5 vs. 11.3 ± 1.1 mmHg, p < 0.05) but not in LETO.  Tau, the time constant of LV pressure decay, was significantly prolonged to 14.7 ± 0.7 ms (p < 0.05) by pressure overloading in OLETF but not in LETO, though baseline Tau values were similar in LETO and OLETF (6.1 ± 0.2 vs. 8.0 ± 0.4 ms).  The prolongation of Tau by pressure overloading in OLETF was significantly attenuated by treatment with topiroxostat.  Ea/Ees, an index for ventricular-arterial coupling, was higher in OLETF than in LETO (2.3 ± 0.3 vs. 1.6 ± 0.3, p < 0.05) under the condition of pressure overloading, and it was also improved by topiroxostat in OLETF (1.2 ± 0.2, p < 0.05).  Myocardial ATP content was lower in OLETF than in LETO under the condition of pressure overloading (2966 ± 400 vs. 1818 ± 171 nmol/g wet tissue, p < 0.05), but treatment with topiroxostat significantly restored the ATP level (2629 ± 307 nmo/g wet tissue). Conclusion:  In T2DM hearts, not only XO activity but also XO substrates are upregulated and upregulated AMPD may be involved in the upregulation.  Inhibition of XO ameliorates pressure overload-induced diastolic dysfunction and improves ventricular-arterial coupling most likely through augmented ATP preservation.

P6453Activation of necroptotic pathway by downregulated caspase-8 expression is associated with progression of left ventricular remodeling in nonischemic dilated cardiomyopathy

Background

Necroptosis, a form of programmed necrosis, has been suggested to be involved in the pathogenesis of various pathological conditions including heart failure. Protein expression of caspase-8, an endogenous inhibitor of necroptosis, is reported to be downregulated in human failing hearts, but its clinical significance remains unclear.

Methods

Endomyocardial biopsy specimens were obtained from patients with nonischemic dilated cardiomyopathy (n=57, 56.2±14.5 years old, 70% male). The area stained with antibodies against caspase-8 and phospho-MLKL-Ser358 was calculated using an image analyzer, and fibrotic and cardiomyocyte areas were determined by Masson's Trichrome staining. Using a level of median caspase-8 expression (6.04% of the area of the myocardium with caspase-8 signal), patients were classified into a high caspase-8 expression group (H-cas8) and a low caspase-8 expression group (L-cas8).

Results

Caspase-8 signals were detected in cytoplasm and intercalated disks of cardiomyocytes. Patients in the L-cas8 group was younger (51.3±13.1 vs. 61.2±14.3 years old) and had larger left ventricular end-diastolic volume (LVEDV: 174±49 vs. 131±41 ml), larger left ventricular end-systolic volume (LVESV: 123±51 vs. 87±39 ml), and higher ratio of mitral peak velocity of early filling to late diastolic filling (E/A: 1.94±1.48 vs. 1.12±0.66) compared with the H-cas8 group. Caspase-8 expression level was positively correlated with age (r=0.34, p=0.01) and negatively correlated with LVEDV (r=−0.47, p<0.01), LVESV (r=−0.40, p<0.01), and E/A (r=−0.39, p<0.01) in simple linear regression analysis. The extent of myocardial fibrosis was not correlated with caspase-8 expression level. Multiple regression analysis indicated that LVEDV, LVESV, and E/A were independent explanatory factors of caspase-8 expression level after adjusting age and sex. Phospho-MLKL signals, an index of activation of necroptotic pathway, were frequently observed in cytoplasm, intercalated disks, and nuclei in the L-cas8 group but not in the H-cas8 group.

Conclusion

Lower caspase-8 expression in cardiomyocytes was associated with increased phosphorylation of MLKL and larger left ventricular volume, suggesting that downregulated caspase-8 may contribute to progression of myocardial remodeling via activation of MLKL in human dilated cardiomyopathy.

P6273Inhibitory phosphorylation of RIP1 at Ser320 induces nuclear translocation of TFEB, leading to suppression of necroptosis in cardiomyocytes

Background

Necroptosis, a form of programmed necrosis, has been shown to contribute to the pathogenesis of various diseases including ischemia/reperfusion injury and heart failure. We recently reported that necroptotic signals suppresses autophagy in cardiomyocytes and that rapamycin, an mTORC1 inhibitor, not only promotes autophagy but also protect the cells from necroptosis.

Purpose

We examined the mechanism by which rapamycin suppresses necroptosis of cardiomyocytes, focusing on regulation of RIP1 activity and autophagic flux.

Methods and results

In H9c2 cardiomyoblasts, necroptosis was induced by treatment with TNF and z-VAD-fmk (zVAD) for 24 h, and cell death was determined by LDH release (as % of total). The treatment with TNF/zVAD increased LDH release from 3.4±1.3% to 46.1±2.3%, and LDH release was suppressed by necrostatin-1 (5.9±0.9%), a RIP1 inhibitor, and by rapamycin (23.5±1.4%). The protective effect of rapamycin was mimicked by Ku-0063794, an mTORC1/2 inhibitor. TNF/zVAD induced RIP1-RIP3 complex formation, together with suppression of TNF-induced RIP1 cleavage, which was mitigated by rapamycin. In addition, rapamycin not only suppressed TNF/zVAD-induced phosphorylation of RIP1-Ser166, an index of RIP1 activation, but also increased phosphorylation of RIP1-Ser320, an inhibitory phosphorylation site. In cells transfected with RIP1-S320A, which lack Ser320 for inhibitory phosphorylation, rapamycin failed to suppress TNF/zVAD-induced RIP1-RIP3 binding and cell death. Immunoblot analyses showed that TNF/zVAD significantly increased level of LC3-II. The accumulation of LC3-II protein was not further increased by bafilomycin A1 (100 nM), an inhibitor of lysosomal protein degradation, indicating that accumulation of LC3-II by TNF/zVAD reflected suppression of autophagic flux. Inhibition of RIP1 by necrostatin-1 attenuated TNF/zVAD-induced accumulation of LC3 II. The restoration of autophagic flux in TNF/zVAD-treated cells by necrostatin-1 was confirmed by monitoring tandem RFP-GFP-LC3 transfected cells; necrostatin-1 increased a ratio of RFP-LC3-puncta (autolysosomes) to RFP-GFP-LC3-puncta (autophagosomes) in TNF/zVAD-treated cells. In addition, necrostatin-1 and rapamycin induced nuclear translocation of TFEB, a regulator of lysosome biogenesis, which was associated with upregulation of MCOLN1 mRNA, a downstream target of TFEB. Restoration of autophagic flux in TNF/zVAD-treated cells by necrostatin-1 was inhibited by siRNA-mediated knockdown of TFEB.

Conclusion

Activation of TFEB by inhibitiory phosphorylation of RIP1-Ser320 is a primary mechanism of cytoprotection afforded by mTORC1 inhibition against necroptosis.

Effect of sodium-glucose co-transporter-2 inhibitors on impaired ventricular repolarization in people with Type 2 diabetes

AIMS

To test the hypothesis that treatment with a sodium-glucose co-transporter-2 inhibitor would reverse ventricular repolarization heterogeneity, a predictor of cardiovascular mortality, in people with Type 2 diabetes.

METHODS

We retrospectively analysed changes in indices of ventricular repolarization before and after treatment with a sodium-glucose co-transporter-2 inhibitor in 46 people with Type 2 diabetes.

RESULTS

Sodium-glucose co-transporter-2 inhibitor treatment reduced HbA_1c concentration [62±13 mmol/mol (7.7±1.2%) vs 59±16 mmol/mol (7.5±1.4%)], body weight (77.8±13.9 vs 74.7±12.5 kg) and systolic blood pressure (133±18 vs 126±12 mmHg) in the study participants. Heart rate and QTc interval were not changed by sodium-glucose co-transporter-2 inhibitor treatment, but QTc dispersion was significantly reduced (median, 48.8 vs 44.2 ms). Sodium-glucose co-transporter-2 inhibitor treatment reversed QTc dispersion more in participants who had larger QTc dispersion before the treatment. Changes in systolic blood pressure (Spearman's ρ= 0.319; P=0.031), but not in HbA_1c concentration, were correlated with changes in QTc dispersion after sodium-glucose co-transporter-2 inhibitor treatment.

CONCLUSIONS

The findings suggest that sodium-glucose co-transporter-2 inhibitor treatment reverses ventricular repolarization heterogeneity in people with Type 2 diabetes, independently of its effect on glycaemic control. The favourable effect on ventricular repolarization heterogeneity could be the mechanism by which empaglifozin reduced cardiovascular events in a recent study.

Age-related changes in cortical and trabecular bone mineral status: A quantitative CT study in lumbar vertebrae

Purpose: To investigate the age and sex dependence of the bone mineral status of human lumbar vertebrae with special regard to differences between cortical and trabecular bone.

Material and Methods: The study group comprised 125 normal Japanese healthy volunteers (54 males and 71 females), and was subdivided into adult male and female groups (subjects younger than 40 years), intermediate male and female groups (ages ranging between 41 and 64 years) and old male and female groups (subjects older than 65 years). The cortical bone mineral status was estimated using a single-energy quantitative CT (SE-QCT) technique, whereas trabecular bone mineral density (BMD) was estimated using a dual-energy (DE-QCT) technique.

Results: A considerable gender difference in the age-related cortical bone status was found. There was a significant reduction of the mean values of the cortical volume and BMD in the old female group compared with those obtained in the old male group.

Conclusion: The results suggest that in men, cortical and trabecular bone volume decrease very little with age. In women, cortical volume and BMD and trabecular BMD decrease with age while trabecular bone volume does not. The study showed that all variables had higher values in men than in women and that the difference increased with age.

Chronic Effects of Norepinephrine and Vasopressin on Urinary Prostaglandin E and Kallikrein Excretions in Conscious Rats

To assess in vivo functional interactions of vasopressor substances, norepinephrine and vasopressin, with renal prostaglandins and kallikrein-kinin system which are responsible for the vasodepressor mechanism in the kidney, we evaluated chronic effects of norepinephrine (1.8 mg/kg/day ip) and vasopressin (7.2 U/kg/day ip) on urinary prostaglandin E excretion and urinary kallikrein excretion in conscious rats. Both norepinephrine and vasopressin induced a sustained increase in systolic blood pressure. Norepinephrine induced slight but significant increases in urinary prostaglandin E excretion and urinary kallikrein excretion which were sustained for up to 6 days. Vasopressin induced a marked increase in urinary prostaglandin E excretion which was sustained for up to 6 days, whereas it induced a sustained decrease in urinary kallikrein excretion. Circulating angiotensin II levels was not changed by norepinephrine, but was decreased by vasopressin. These results indicate that renal prostaglandin E may not correlate with renal kallikrein-kinin and renin-angiotensin system in the responses to norepinephrine and vasopressin, and that vasopressin may be a more potent stimulator of the synthesis or release of renal prostaglandin E.

Mirthful laughter differentially affects serum pro- and anti-inflammatory cytokine levels depending on the level of disease activity in patients with rheumatoid arthritis

OBJECTIVES

To examine the effect of mirthful laughter in rheumatoid arthritis (RA), we evaluated the levels of serum cytokines before and after patients experienced mirthful laughter.

METHODS

Forty-one patients with RA and 23 healthy subjects were enrolled. They listened to 'Rakugo', a traditional Japanese comic story, to induce mirthful laughter. We measured serum IL-6, IL-1beta, TNF-alpha, IL-4 and IL-1 receptor antagonist (IL-1Ra) concentrations before and after patients listened to the story. The RA subjects were divided into two groups. One was designated the 'difficult-to-control RA' group (CRP > or =1.0 mg/dl); The other group was regarded as the 'easily controlled RA' group (CRP <1.0 mg/dl).

RESULTS

The basal levels of serum IL-6 and TNF-alpha in the RA patients were significantly higher than those in the healthy group. After experiencing mirthful laughter, the levels of serum IL-6 decreased significantly in the RA group but not in the healthy subjects. Interestingly, the level of serum TNF-alpha decreased only in the easily controlled RA group. Serum IL-4 concentration in the RA group was significantly higher than that in healthy subjects before the story. After the story, the level of serum IL-4 significantly decreased in the RA group, especially in the difficult-to-control RA group. In contrast, serum IL-1Ra concentration was statistically higher in the RA group than that in healthy subjects before the story, and a further increase was observed after the story, especially in the easily controlled RA group.

CONCLUSIONS

Our findings suggest that mirthful laughter affects the levels of serum pro- and anti-inflammatory cytokines differentially, depending on the RA disease activity.

Effects of mirthful laughter on growth hormone, IGF-1 and substance P in patients with rheumatoid arthritis

OBJECTIVE

Growth hormone (GH) plays an ancillary role in the regulation of immune function. GH has been shown to be associated with joint symptoms such as pain and swelling. On the other hand, mirthful laughter has favorable effects on the neuroendocrine-immune system. We evaluated the levels of serum GH, insulin-like growth factor-1 (IGF-1) in RA patients and evaluated the effect of mirthful laughter on GH and IGF-1.

METHODS

We compared with the levels of serum GH, IGF-1 and substance P (SP) in patients with RA and healthy subjects (control group) before and after exposure to "Rakugo", a traditional Japanese comical story that induces mirthful laughter.

RESULTS

The basal level of serum GH in the RA group was significantly higher than in the control group. After experiencing mirthful laughter, the level of serum GH in the RA group significantly decreased, approaching that in the control group. The serum IGF-1 level was lower in the RA group than in the control group. There was no significant difference in the level of serum SP between the RA group and the control group.

CONCLUSION

The basal level of serum GH in the RA group was significantly higher than in the control group, and the level of serum GH significantly decreased after experiencing mirthful laughter These results suggest that the homeostasis of GH in patients with RA is disturbed, and the increased serum GH levels in RA patients may be associated with their stress condition.

Effect of general anesthesia on the abnormal immune response in patients with rheumatoid arthritis

OBJECTIVE

To evaluate the influence of mental stress on the neuroendocrine-immune system in patients with rheumatoid arthritis (RA).

METHODS

Twenty-four patients with RA and 10 patients with osteoarthritis (OA) who underwent total knee or hip arthroplasty under general anesthesia were enrolled in this study. The blood levels of interleukin-6 (IL-6), IL-1 receptor antagonist (IL-1Ra), tumor necrosis factor-alpha (TNF-alpha), soluble TNF receptors (TNF-Rs) and other substances related to stress were measured just before administering anesthesia on the day of the operation when the patients lay on the operating table and roughly 30 min later when the patients were under general anesthesia without mental stress. These values were compared with those at the same time on the day before the operation, which were considered as controls.

RESULTS

In patients with RA under general anesthesia, the levels of IL-6, TNF-alpha, and TNF-R1 and TNF-R2 in the peripheral blood were significantly decreased compared with the levels before anesthesia (p < 0.01). Before anesthesia the levels of IL-1Ra in the peripheral blood were significantly higher, and the level of IL-1Ra was enhanced after the administration of general anesthesia, when compared with the level on the day before the operation (p < 0.01). Such changes were not apparent in patients with OA.

CONCLUSION

In patients with RA, excessive mental stress should be eliminated to modify the interaction between the stress-immune system and stress-endocrine system as a method to better control disease activity.

Uni-axial cyclic stretch induces Cbfa1 expression in spinal ligament cells derived from patients with ossification of the posterior longitudinal ligament

Ossification of the posterior longitudinal ligament of the spine (OPLL) is characterized by ectopic bone formation in the spinal ligaments. Mechanical stress, which acts on the posterior ligaments, is thought to be an important factor in the progression of OPLL. To clarify this mechanism, we investigated the effects of in vitro cyclic stretch (120% peak to peak, at 0.5 Hz) on cultured spinal ligament cells derived from OPLL (OPLL cells) and non-OPLL (non-OPLL cells) patients. The mRNA expressions of Cbfa1 (an osteoblast-specific transcription factor), type I collagen, alkaline phosphatase (ALP), osteocalcin and integrin beta1 (a mechanotransducer) were increased by cyclic stretch in OPLL cells, whereas no change was observed in non-OPLL cells. The effects of cyclic stretch on the spinal ligament tissues derived from OPLL and non-OPLL patients were also analyzed by immunohistochemistry using an antibody against Cbfa1. The expression of Cbfa1 was increased by cyclic stretch at the center of the spinal ligament tissues of OPLL patients, whereas no change was observed in the tissues of non-OPLL patients. Furthermore, U0126, a specific inhibitor of MAPK kinase (MEK), suppressed the stretch-induced mRNA expressions of Cbfa1, ALP and type I collagen in OPLL cells. These results suggest that in OPLL cells, mechanical stress is converted by integrin beta1 into intracellular signaling and that Cbfa1 is activated through the MAP kinase pathway. Therefore, we propose that mechanical stress plays a key role in the progression of OPLL through an increase in Cbfa1 expression.

Uniaxial cyclic stretch induces osteogenic differentiation and synthesis of bone morphogenetic proteins of spinal ligament cells derived from patients with ossification of the posterior longitudinal ligaments

Ossification of the posterior longitudinal ligament of the spine (OPLL) is characterized by ectopic bone formation in the spinal ligaments. Mechanical stress, which acts on the posterior ligaments, is thought to be an important factor in the progression of OPLL. To elucidate this mechanism, we investigated the effects of in vitro sinusoidal cyclic stretch (120% peak to peak, at 1 Hz) on cultured spinal ligament cells derived from OPLL and non-OPLL patients. The mRNA expressions of alkaline phosphatase (ALP), osteopontin, bone morphogenetic protein (BMP)-2, BMP-4, and BMP receptors as well as ALP activity in cell layers and production of BMPs into the conditioned medium were significantly increased by cyclic stretch in OPLL cells, whereas no change was observed in non-OPLL cells. A stretch-activated Ca(2+) channel blocker, Gd(3+), the voltage-dependent L-type Ca(2+) channel blockers diltiazem and nifedipine, and Ca(2+)-free medium suppressed stretch-induced ALP activity, which suggests a role of Ca(2+) influx in the signal transduction of mechanical stress to the osteogenic response of OPLL cells. Our study provides first evidences that mechanical stress plays a key role in the progression of OPLL through the induction of osteogenic differentiation in spinal ligament cells and the promotion of the autocrine/paracrine mechanism of BMPs in this lesion.

Does being easily moved to tears as a response to psychological stress reflect response to treatment and the general prognosis in patients with rheumatoid arthritis?

OBJECTIVE

Psychological stress affects the condition of patients with rheumatoid arthritis (RA). We evaluated the neuroendocrine and immune responses (NEIRs) in the peripheral blood to psychological stress induced by deep emotion with tears in patients with RA.

METHODS

We compared the levels of plasma cortisol and interleukin-6 (IL-6), the CD4/CD8 ratio, and natural killer (NK) cell activity in peripheral blood between the patients with easily controlled RA (CRP < 1.0 mg/dl) and those with difficult-to-control RA (CRP > or = 1.0 mg/dl) before and after the stress session.

RESULTS

Psychological stress induced by deep emotion with tears had a greater influence on NEIRs in patients with difficult-to-control RA (CRP > or = 1.0 mg/dl) than in those with easily controlled RA (CRP < 1.0 mg/dl). The levels of plasma cortisol, IL-6, and the CD4/CD8 ratio were lower, while NK cell activity in the peripheral blood was higher in those who were not moved to tears than in those who were moved to tears. Patients who were moved to tears were apt to obtain good control of RA (CRP < 1.0 mg/dl) within one year.

CONCLUSION

The patients with better RA control are easily moved to tears as an emotional expression; shedding tears is considered to suppress the influence of stress on the NEIRs, thus preventing the buildup of stress. Patients who were moved to tears had a more easily controlled RA compared with those who were emotionally affected but not moved to tears.

[Nitric oxide (NO) donor]

Nitric oxide (NO), which is synthesized from L-arginine by nitric oxide synthase (NOS) in mammals, acts as a signal molecule for vasorelaxation, cytotoxicity and neurotransmission. The difficulty in handling of a gaseous and labile NO causes problems with the effective and precise studies using NO. The increasing interest in the biological roles of NO requires the use of NO donors which releases NO under the various desirable conditions. We systematized the most commonly used NO donors in this article to support the biological investigation. NO donors were classified according to the functional groups based on NO-donating characteristics. The preparation, chemical properties and NO-donating ability of these NO donors are summarized. It is particularly described in some detail on the stability both as a solid and in solution and the handling of the compounds.

Contribution of both the sarcolemmal K(ATP) and mitochondrial K(ATP) channels to infarct size limitation by K(ATP) channel openers: differences from preconditioning in the role of sarcolemmal K(ATP) channels

The roles of sarcolemmal ATP-sensitive K+ (sarcK(ATP)) and mitochondrial ATP-sensitive K+ (mitoK(ATP)) channels in the cardioprotection induced by K(ATP) channel openers remain unclear, though the mitoK(ATP) channel has been proposed to be involved as a subcellular mediator in cardioprotection afforded by ischemic preconditioning (PC). In the present study, selective inhibitors of the sarcK(ATP) and mitoK(ATP) channels were used to examine the role of each channel subtype in infarct size limitation by KATP channel openers. Isolated rabbit hearts were perfused in the Langendorff mode with monitoring of the activation recovery interval (ARI) and subjected to 30-min global ischemia/2-h reperfusion to induce infarction. Before ischemia, hearts received 10 microM pinacidil, 100 microM diazoxide, or PC with or without preceding infusion of a sarcK(ATP) channel-selective blocker (5 microM HMR1098) or a mitoK(ATP) channel-selective blocker (100 microM 5-hydroxydecanoate, 5-HD). ARI, an index of action potential duration, was shortened from 118+/-3 ms to 77+/-5 ms after 10 min of ischemia in untreated control hearts. Pinacidil shortened ARI before ischemia from 113+/-2 ms to 78+/-5 ms and enhanced the ARI shortening during ischemia. Diazoxide did not affect ARI before ischemia but accelerated ischemia-induced shortening of ARI. Infarct size as a percentage of the left ventricle (%IS/LV) was reduced by pinacidil and diazoxide from the control value of 47.2+/-4.0% to 4.5+/-1.5% and 5.2+/-1.2%, respectively. HMR1098 significantly inhibited the shortening of ARI by ischemia, pinacidil and diazoxide and partially blocked infarct size limitation by these K(ATP) channel openers (%IS/LV=32.6+/-4.2% and 23.4+/-5.3%, respectively). Infusion of 5-HD did not modify the change in ARI caused by the K(ATP) channel openers but completely abolished cardioprotection (%IS/LV=46.0+/-6.2% with pinacidil and 57.2+/-7.0% with diazoxide). PC with two episodes of 5-min ischemia limited %IS/LV to 21.6+/-4.0%, and this protection was not inhibited by HMR1098. Neither HMR1098 nor 5-HD alone modified infarct size. In conclusion, both sarcK(ATP) and mitoK(ATP) channels may contribute to the anti-infarct tolerance afforded by pinacidil and diazoxide.

Critical timing of mitochondrial K(ATP) channel opening for enhancement of myocardial tolerance against infarction

OBJECTIVE

The present study was designed to assess the relationship between the timing of a mitoK(ATP) channel opener, diazoxide, and its infarct size-limiting effect.

METHODS

In isolated rabbit hearts, infarction was induced by 30 min of global ischemia and 2 h of reperfusion, and infarct size was determined by tetrazolium staining and expressed as a percentage of the left ventricle (%IS/LV). Diazoxide, a mitoK(ATP) channel selective opener, and/or 5-hydroxydecanoate (5-HD), a mitoK(ATP) channel blocker, were infused before or after the onset of ischemia. When these agents were infused during the ischemic period, they were dissolved in a hypoxic buffer at concentrations 10-fold higher than those in the pre-ischemic period, and the infusion rate was set at 2% of the pre-ischemic coronary flow.

RESULTS

In untreated controls, %IS/LV was 53.2+/-4.1 (SE). Pretreatment with diazoxide (100 microM) with a 10-min washout period reduced %IS/LV to 7.8+/-2.4 and this protection was abolished by co-infusion of 5-HD (50 microM). Pre-ischemic infusion of diazoxide without a washout period reduced %IS/LV to 7.3+/-1.4, and infusion of diazoxide from 10 min after the onset of ischemia also limited %IS/LV to 14.9+/-4.6. However, diazoxide infusion from 25 min after the onset of ischemia failed to reduce infarct size (%IS/LV = 54.5+/-7.2). Furthermore, pretreatment with 5-HD (50 microM) also completely abolished the protection afforded by early post-ischemic diazoxide infusion (%IS/LV = 48.3+/-6.5). Neither infusion of 5-HD nor the anoxic vehicle alone during ischemia modified %IS/LV.

CONCLUSION

These findings suggest that opening of mitoK(ATP) channels before ischemia and during early ischemia, but not that upon reperfusion, is important for enhancement of myocardial tolerance against infarction.

Infarct size limitation by bradykinin receptor activation is mediated by the mitochondrial but not by the sarcolemmal K(ATP) channel

Earlier studies have shown that activation of bradykinin B2 receptor triggers protein kinase C (PKC)-mediated cardioprotective mechanism in ischemic preconditioning (PC). In the present study, we examined whether the effector in this B2-receptor triggered pathway of PC is the ATP sensitive potassium (K(ATP)) channel in the mitochondria (mito-K(ATP) channel) or K(ATP) channel in the sarcolemma (sarc-K(ATP) channel). Isolated rabbit hearts were perfused with modified Krebs-Henseleit buffer in a Langendorff mode, and regional myocardial ischemia was induced by occluding a left coronary artery for 30 min and then reperfusing for 2 hours. Infarct size was determined by triphenyltetrazolium chloride staining and expressed as a percentage of area at risk (% IS/AR). Infusion of bradykinin (500 nmol/L) for 15 min prior to ischemia significantly reduced % IS/AR from 37.4 +/- 2.9 (SE) of the untreated controls to 12.0 +/- 3.3%. This protective effect of bradykinin was completely abolished by coinfusion of 5-hydroxydecanoate (5-HD, 50 micromol/L), a selective mito-K(ATP) channel blocker (% IS/AR = 44.2 +/- 6.4). In contrast, a high dose of HMR1098 (20 micromol/L), which is a newly developed sarc-K(ATP) channel selective blocker with IC50 of 0.6 micromol/L, failed to modify the infarct size limitation by preischemic infusion of bradykinin (% IS/AR = 11.7 +/- 3.4). Neither 5-HD nor HMR1098 alone modified infarct size (% IS/AR = 37.8 +/- 3.8 and 35.1 +/- 6.2, respectively). These results suggest that opening of the mito-K(ATP) channel but not the sarc-K(ATP) channel is involved in infarct size limitation by a mechanism triggered by bradykinin B2 receptor activation.

Changes in liver fatty acid unsaturation after partial hepatectomy in the rat

The purpose of this study was to assess changes in the degree of fatty acid unsaturation in rat liver after partial hepatectomy. This is the first study in which liver fatty acid unsaturation has been analyzed over a long period of regeneration until day 28 after operation. The relationship between changes in unsaturation and fatty acid composition in the regenerating liver were also investigated in this study. Proton nuclear magnetic resonance spectroscopy revealed significantly elevated levels of unsaturation with a maximum on day 5 after partial hepatectomy, compared with untreated controls (11.72+/-0.55 vs. 11.05+/-0.26%, P < 0.05). No significant changes in unsaturation were found in day 1 regenerating liver, which is rich in absolute amounts of fatty acids. Based on gas-liquid chromatography, the relative amounts of oleic acid (18:1n-9) and linoleic acid (LA; 18:2n-6) were increased, while polyunsaturated fatty acids such as arachidonic acid (20:4n-6) and docosahexaenoic acid (DHA; 22:6n-3) were decreased on day 1. On the other hand, on day 5 of regeneration, while most fatty acids were returning to their preoperative control levels, only DHA was higher than the control value (7.69+/-0.58 vs. 5.57+/-0.37%, P < 0.001). The high levels of unsaturation on day 5 were found to be partly due to the increase in DHA. The findings suggest that some significant signals are transmitted during the regeneration process owing to alterations in the membrane structure by the high levels of fatty acid unsaturation and the increase in DHA levels on day 5 after partial hepatectomy.

Roles of tyrosine kinase and protein kinase C in infarct size limitation by repetitive ischemic preconditioning in the rat

In this study, we examined the possibility that infarct-size limitation by repetitive preconditioning (PC) is achieved by activation of both protein kinase C (PKC) and tyrosine kinase. In addition, we assessed whether such kinase activation is triggered by angiotensin II type 1 (AT1) and alpha1-adrenergic receptors and whether sarcolemmal and mitochondrial adenosine triphosphate (ATP)-sensitive potassium (K(ATP)) channels play roles as effectors of cardioprotection in the rat. Under pentobarbital anesthesia, myocardial infarction was induced by 20-min coronary occlusion and 3-h reperfusion in the rat. Infarct size was determined by tetrazolium and expressed as a percentage of area at risk (%IS/AR). PC with one cycle of 5-min ischemia/5-min reperfusion before 20-min ischemia significantly reduced %IS/AR from the control value of 49.4 +/- 2.0 to 35.4 +/- 2.8, and repetitive PC with two cycles of 5-min ischemia/5-min reperfusion further limited %IS/AR to 3.2 +/-0.9. Infarct-size limitation by single-cycle PC was completely abolished by a PKC inhibitor, staurosporine (100 microg/kg; %IS/ AR, 45.7 +/- 5.0). In contrast, the cardioprotection by repetitive PC was only partially blocked by staurosporine (%IS/AR, 19.8 +/- 2.4), another PKC inhibitor, polymyxin B (5 mg/kg; %IS/AR, 16.2 +/- 3.1), or a tyrosine kinase inhibitor, genistein (5 mg/kg; %IS/AR, 21.8 +/- 1.4). However, a combined injection of genistein and staurosporine additively inhibited protection of repetitive PC (%IS/AR, 36.4 +/- 1.7). Staurosporine, polymyxin B, or genistein alone did not modify %IS/AR in nonpreconditioned rat hearts. Infarct-size limitation by repetitive PC was not attenuated by pretreatment with a selective AT1-receptor blocker (CV11974, 10 mg/kg), prazosin (0.6 mg/kg; %IS/AR, 6.4 +/- 3.2 and 1.6 +/- 0.5, respectively). A selective blocker of mitochondrial K(ATP) channels, 5-hydroxydecanoate (3 mg/kg), completely abolished the cardioprotective effect (%IS/AR, 50.8 +/-3.5), but HMR1883 (3 mg/kg), a selective blocker of sarcolemmal K(ATP) channels, failed to inhibit the preconditioning effect (%IS/AR, 4.4 +/- 0.7). These findings suggest that repetition of PC provokes activation of both PKC and tyrosine kinase, leading to enhanced antiinfarct tolerance by opening of mitochondrial but not sarcolemmal K(ATP) channels. It is unlikely that activation of either AT1 or alpha1-adrenergic receptor alone is crucial to trigger preconditioning. Key Words: Tyrosine kinase-Genistein-Angiotensin II-alpha1-Adrenergic receptor-Sarcolemmal K(ATP) channel-Mitochondrial K(ATP) channel.

Proliferating cell nuclear antigen in normal and regenerating rat livers

Immunohistochemical analysis using proliferating cell nuclear antigen (PCNA) antibody shows a negligible number of cells stained in normal liver, but much higher numbers in regenerating liver 24 and 48 h after surgery. We also verified different results by biochemical analysis. Two forms of PCNA, L type (eluted at low concentrations of KCl from a phosphocellulose column) and H type (eluted at high KCl concentrations), were observed in the nucleoplasm of regenerating livers 24 and 48 h after surgery. Treatment of the H type fraction with nuclease caused the H type to disappear and the amount of L type to increase. PCNAs in the cytoplasm are P type (eluted in the pass through fraction) and L type. Surprisingly, the total amounts of P type and L type in cytoplasmic extracts are comparable to those of L type and H type in the nucleoplasm. These results suggest that newly synthesized PCNA is immediately converted into the P and L complex forms. The P type and some of the L type that lacks a nuclear localization signal remain in the cytoplasm; the rest of the L type with a nuclear localization signal is transferred into the nuclei. Then, some of the L type in the nucleoplasm forms the H type, which binds to DNA. These three types of PCNA are also found in significant amounts in the nucleoplasm and cytoplasm of normal rat liver despite its nonproliferating state.

Role of the monocarboxylic acid transport system in the intestinal absorption of an orally active beta-lactam prodrug: carindacillin as a model

Transport of carbenicillin (CBPC) and its orally active prodrug (carindacillin, CIPC) was studied with rat intestinal brush border membrane vesicles (BBMV). CIPC was transported uphill into BBMV in the presence of a H(+) gradient, indicating that CIPC absorption is carrier-mediated. Indeed, CIPC was predominantly transported by the monocarboxylic acid transport system, although it might be possible that CIPC possesses some affinity to the oligopeptide transporter. In contrast, CBPC exhibited no affinity to either the oligopeptide or the monocarboxylic acid transport system. Apparent uptake clearance of CIPC was approximately 70-fold greater than that of CBPC. It was clarified that the modification of the chemical structure of CBPC (a dicarboxylic acid) to CIPC (a monocarboxylic acid) by ester formation may have resulted in the increased affinity to the monocarboxylic acid transport system, which, in turn, led to improved absorption of the prodrug.

[Evaluation of epidural blood patch in the treatment of two cases of spontaneous intracranial hypotension]

We evaluated the effect of epidural blood patch (EBP) in the treatment of two cases of spontaneous intracranial hypotension (SIH). Both case 1 (53-year old female) and case 2 (44-year old female) had severe postural headache and showed meningeal thickening by cranial MRI, and were diagnosed as SIH. Case 1: Although her intracranial pressure remained within normal ranges, an extradural leakage was shown in the middle thoracic region on isotope cisternography using indium-111 labeled DTPA. She underwent epidural blood patch with autologous blood at Th 6-7 level twice (10 ml and 15 ml, respectively) but without remarkable pain relief. Case 2: Her intracranial pressure was low (0 mmH2O on supine position), but, isotope cisternography using DTPA showed only the early appearance of isotope in the bladder but failed to disclose the site of the CSF leak. Epidural blood patch with 30 ml of autologous blood was performed at Th 12-L 1 level which only resulted in severe backache without clinical improvement. In conclusion, we could not find the effectiveness of EBP on the two cases of SIH, although there are many reports on its efficacy.

Time window for the contribution of the delta-opioid receptor to cardioprotection by ischemic preconditioning in the rat heart

The present study aimed to examine (1) whether the role of the opioid receptor in ischemic preconditioning (PC) is consistent regardless of the duration of ischemic insult and (2) which opioid receptor subtype contributes to PC. In the first series of experiments, the effects of PC, a nonselective opioid receptor antagonist (naloxone), and their combination on the infarct size after various durations of ischemia were assessed. In anesthetized, open-chest rats, the coronary artery was occluded for 20, 30, or 40 minutes to induce infarction and was reperfused for 3 hours, PC was performed with two cycles of 5-minute ischemia followed by 5-minute reperfusion before the sustained ischemia. At 25 minutes before the ischemia, naloxone was injected alone or in combination with subsequent PC. Infarct size was determined by tetrazolium staining and was expressed as a percentage of the risk area size (%IS/RA). In the second series of experiments, the effects of a delta-receptor-selective antagonist, naltrindole (NTI), and a kappa-receptor selective antagonist, nor-binaltrophimine (nor-BNI), on PC before 30-minute coronary occlusion were assessed. In untreated controls, %IS/RA was 53.1 +/- 3.2 after 20 minutes, 67.9 +/- 3.9 after 30 minutes, and 87.8 +/- 2.0 after 40 minutes of ischemia, respectively. PC significantly reduced %IS/RA after 20, 30, and 40 minutes of ischemia to 3.1 +/- 0.8, 12.8 +/- 1.1, and 42.1 +/- 4.3, respectively (P < 0.05 vs. each control). Naloxone (6 mg/kg) partially attenuated the protection afforded by PC when the sustained ischemia was 30 minutes (%IS/RA = 27.4 +/- 4.5; P < 0.05 vs. PC), but this inhibitory effect of naloxone was not detected when the duration of the ischemia was 20 or 40 minutes. NTI (10 mg/kg) also attenuated infarct size limitation by PC after 30 minutes of ischemia (%IS/RA = 25.6 +/- 3.7), but nor-BNI (10 mg/kg) failed to modify infarct size limitation by PC (%IS/RA = 13.3 +/- 3.2). The present results suggest that activation of the opioid delta-receptor partly contributes to preconditioning against infarction in the rat and that there may be a time window (at around 30 minutes after the onset of ischemia) for this opioid receptor-mediated protective mechanism.

[Study of N-nitroso compounds which have NO-release ability]

Nitric oxide (NO), which plays an important role in the vital functions of organisms, is gaseous and labile molecule. Much attention has been paid to the stability and easily handling of NO donors, for careful handling of NO is required during experimental work. We synthesized a series of aromatic N-nitrosoureas and N-nitrosamides which efficiently liberates NO at room temperature. Generation of NO from the aromatic N-nitroso compounds was chemically confirmed by the trapping of NO as a nitrosyl complex of tetraphenylporphyrinatocobalt (II) and spectrophotometrically quantified by means of the Griess reaction using a newly designed test apparatus. 3,3-Dibenzyl-1-(4-tolyl)-1-nitrosourea showed the greatest NO-generating ability among the synthesized N-nitroso compounds. Further, the NO-generating ability was related to the reciprocal of the ID50 value for growth inhibition of cultured L-5178Y cell by the aromatic N-nitroso compounds.

Characterization of the cytotoxic activity of nitric oxide generating N-nitroso compounds

The NO-generating abilities of aromatic N-nitroso compounds (nitrosoureas, nitrosamides and nitrosamines), and N-acetyl-S-nitroso-DL-penicillamine at ambient temperature were compared by employing the Griess reaction. 3,3-Dibenzyl-1-(4-tolyl)-1-nitrosourea showed the greatest NO-generating ability among the tested compounds. The NO-generating ability of the aromatic N-nitrosoureas and N-nitrosamides was greater than that of the N-nitrosamines, presumably reflecting differences in electrostatic repulsion between the carbonyl oxygen and nitroso oxygen in these compounds. In addition, a conjugative effect between the aromatic ring carbon and neighboring nitrogen influences the NO-generating ability; the conjugative effect in the case of N-nitrosoureas and N-nitrosamides having an ortho-alkyl substituted aromatic ring, or N-nitrosamines having a bulky N-group, such as tert-butyl, is decreased by an increase in steric hindrance around the nitroso group. The N-NO bond then becomes more stable. The NO-generating ability was related to the reciprocal of the ID50 value for growth inhibition of cultured L-5178 Y cells by the aromatic N-nitroso compounds. On the other hand, NO production from the aliphatic N-nitroso compounds was not observed under our conditions, and these N-nitroso compounds did not show effective cytotoxic activity.

Age-related changes in proliferating cell nuclear antigen levels

To clarify the effect of aging on rat liver regeneration, we compared proliferating cell nuclear antigen (PCNA) levels in control and regenerating livers from young and aged rats 48 h after partial hepatectomy. The nucleoplasm and cytoplasm from regenerating livers of 2-month and 24 month-old rats were fractionated by phosphocellulose column chromatography, aliquots of fractions were transferred to nitrocellulose filters and the amounts of PCNA in each fraction were measured by an immunostaining method. Two forms of PCNA, L type (eluted at low concentrations of KC1) and H type (eluted at high KC1 concentrations) were observed in the nucleoplasm from both control and regenerating young rat liver. On the other hand, the cytoplasm contained P type (eluted in the pass-through fraction), L type and H type PCNA. In control liver from aged rats, three types of PCNA in the cytoplasm and two types in the nucleoplasm were present at decreased levels. In regenerating liver from young rats, the increases in L type in the cytoplasm and H type in the nucleoplasm were remarkable. However, none of the three PCNA types increased significantly during liver regeneration in aged rats. Treatment with DNase resulted in the disappearance of the H type with a concomitant increase in the P and L types. These results suggest that the H type is a complex form consisting of the P and L types of PCNA and DNA. These results suggest that the increase in the L type in the cytoplasm reflects newly synthesized PCNA production for cellular proliferation and that the increase in the H type in the nucleoplasm is a reflection of binding to DNA and the fundamental role of PCNA itself in liver regeneration in young rats. On the other hand, there was little increase in any of the three types in regenerating liver from 24-month-old rats. Thus, PCNA content may be closely related to the decrease in the rate of cellular proliferation in aged animals.

Myocardial viability in cases with persistent perfusion defects on the dipyridamole thallium-201 scintigram. A comparative study with autopsy findings

The aim of this study was to assess the incidence of myocardial infarction among persistent perfusion defects in dipyridamole-stress thallium scintigraphy by inspecting autopsied hearts and to evaluate whether the regional thallium activity of a scintigraphic defect can predict the presence of infarction. Autopsied hearts were compared with dipyridamole myocardial scintigrams undertaken during life in 27 patients (mean age 85 +/- 8 years). The time interval from stress testing until death was 428 +/- 351 days. Regional thallium uptake of delayed perfusion defect was calculated on the short axis images. The grade of regional myocardial fibrosis in autopsy specimens was also quantified to correlate with the corresponding regional thallium uptake. In 6 of 15 (40%) regions with persistent defects on the scintigram, myocardial infarction was not found at autopsy. Regional thallium-201 uptake of delayed defects < 50% diagnosed infarction with a sensitivity of 82% and a specificity of 80%. A linear correlation (r = -0.67) was observed between percent thallium-201 uptake and the degree of myocardial fibrosis. In conclusion, perfusion defects at 4-hour imaging in dipyridamole-stress testing may overestimate the presence of myocardial infarction and regional thallium-201 activity is helpful in distinguishing between defects with and without infarction.

Comparative study of bone mineral density estimated by various methods of single- and dual-energy quantitative computed tomography: the capability of the four-equation four-unknown method

A dual-energy (DE) quantitative computed tomography (QCT) method, the four-equation four-unknown method (DEQCT 4E-4U), was assessed and compared to single-energy (SE) QCT and standard DEQCT (two-line method). The results of this study indicate that bone mineral density (BMD) was more accurately estimated by the present method than by the SEQCT or standard DEQCT techniques on the basis of a phantom study when a large fat content was present. The results of both the phantom study and a human study also showed that the present method corrected for fat in estimating BMD in the presence of high-fat content. These findings suggest that use of this method for estimating BMD can provide useful information in studies assessing the metabolic state of bone. We propose that CT numbers estimated from excised vertebral bone marrow can serve as a soft-tissue correction for the present method.

Juvenile hyaline fibromatosis. Case report with five years' follow-up

Juvenile hyaline fibromatosis (JHF) is a rare hereditary disorder named by Drescher et al. in 1969. As recently as 1985, only 30 cases had been reported worldwide. We report the case of a 9-year-old girl who was diagnosed with JHF at age 3 and has been closely followed since. She initially had slowly growing multiple soft tumors over her entire body as well as hypertrophic gingiva and mild bone deformities. She was originally misdiagnosed with infantile myofibromatosis at age 3. However, at age 6, because of the light and electron microscopic findings of the tumors, she was diagnosed as having JHF. Currently, at age 9, she has nodular lesions developing over her body as well as bone changes that are progressing with no evidence of regression.

Magnetic resonance imaging study of the brain in aged volunteers: T2 high intensity lesions and higher order cortical function

The aims of the present study were to clarify the findings of magnetic resonance imaging (MRI) in the aging brain, and to relate the MRI findings to higher order cortical function. A total of 118 healthy aged volunteers (41 men, 77 women) underwent cranial MRI electroencephalography (EEG), Benton visual retention test (BVRT) and interview. The subjects had no past history or clinical evidence of cerebrovascular disorder, head trauma or dementia and were living at home without any difficulty. The majority of the subjects have participated in this series of studies since 1982. Using a 1.5 T superconductive MR instrument, T1-weighted, proton density and T2-weighted images were obtained. The MRI data were rated visually by regarding 12 items according to fixed criteria. T2 high signal intensity (T2HSI) lesions were found in 69.5% of subjects, the prevalence of which increased with age. T2HSI lesions were most frequently found in the basal ganglia (61.9%), followed by the thalamus (39.0%), parietal lobe (37.0%), temporal lobe (12.7%) and pons (8.5%). Among these lesions, lacunar infarction showed low signal intensity in T1-weighted images and was found in 24.6% of subjects, the prevalence also increasing with age. These findings, including brain atrophy determined according to similar criteria, were correlated closely with the subjects' age. The results of BVRT showed a close relation with T2HSI, suggesting that T2HSI may influence cognitive function. When the subjects were classified according to the presence of T2HSI, lacunar infarction and EEG abnormalities, brain atrophy was significantly milder in a group of subjects with T2HSI(-), lacunar infarction(-) and normal EEG than in the other groups. This suggests that changes seemingly representing physiological aging may be promoted by another pathological which also exerts influences on higher order cerebral function.

Stimulation of DNA polymerase gamma activity by proliferating cell nuclear antigen

DNA polymerase was partially purified from mitochondrial extracts of rat liver by phosphocellulose, DEAE-cellulose, heparin-Sepharose CL-6B and DNA-agarose column chromatography. By these purification steps, DNA polymerase and proliferating cell nuclear antigen (PCNA) were completely separated at the step of heparin-Sepharose CL-6B column chromatography. The isolated DNA polymerase was inhibited by ddTTP, but not by aphidicolin. The enzyme sedimented at about 8 S on 5-20% analytical sucrose density gradient centrifugation. These data showed that the DNA polymerase isolated from mitochondria is gamma in type. After the separation of DNA polymerase gamma and PCNA, the two fractions were remixed and DNA polymerase gamma activity was measured. DNA polymerase gamma activity was stimulated about three-fold or more in the presence of the PCNA fraction. This stimulation was inhibited by the addition of anti-PCNA rabbit IgG2a. In addition, highly purified human recombinant PCNA stimulated the DNA polymerase gamma activity. These results indicate that DNA polymerase gamma, like DNA polymerase delta, is activated by PCNA.

Efficacy of interferon alfa therapy in chronic hepatitis C patients depends primarily on hepatitis C virus RNA level

To clarify the viral factors that may predict the therapeutic effect of interferon (IFN) in chronic hepatitis C (CHC) patients, we investigated the quantitative serum hepatitis C virus (HCV) RNA level, genotype, and liver biopsy histological features in 60 patients who were treated with 360 x 10(6) U of natural IFN-alpha for 36 to 48 weeks and for more than 12 months after therapy. A branched DNA (bDNA) assay was used to measure HCV RNA levels. All responders, defined as those individuals with normal alanine transaminase (ALT) levels at 48 weeks after therapy, had less than 2 x 10(6) HCV RNA Eq/mL before administration of IFN. Of 39 patients with RNA levels (less than 2 x 10(6) Eq/L) 23 (59.0%) were responders. The genotype was determined for each patient using type-specific polymerase chain reaction (PCR) primers. There was a significant difference in rate of response between subtype 1b and subtypes 2a and 2b (P < .0002); however, all responders had less than 2 x 10(6) Eq/L independent of genotype. In a multivariate analysis, RNA level was the most statistically significant factor affecting response to IFN. Although disease severity, as defined by histological features, was not statistically correlated with nonresponse, patients that responded to IFN tended to have less severe disease.

Malignant hypercalcemia due to gastric endocrine cell carcinoma

A 62-year-old man was admitted to our Neurology Unit due to consciousness disturbance. Laboratory data showed marked hypercalcemia and azotemia. Serum parathyroid hormone-related protein (PTHrP) level was extremely high. We performed intensive hemodialysis for renal failure, but his condition deteriorated rapidly. On day 10, he died of multiple organ failure. The autopsy revealed gastric undifferentiated adenocarcinoma with systemic dissemination. Immunohistological study showed positive PTHrP staining in carcinoid-like parts of the tumor. This is the first reported case of malignant hypercalcemia due to PTHrP-producing carcinoid or endocrine cell carcinoma of the stomach.