Sex differences in terms of recurrent atrial fibrillation after catheter ablation according to the history of heart failure: insights from the Kansai Plus Atrial Fibrillation (KPAF) registry

Background

There are significant differences in the prevalence and prognosis of cardiovascular diseases between male and female. We previously reported that catheter ablation (CA) of atrial fibrillation (AF) was less effective in female than male, but whether their history of heart failure influence the recurrence after CA of AF remains still unknown.

Purpose

We sought to clarify sex differences in terms of AF recurrence after RFCA of AF according to the history of heart failure.

Methods

We conducted a large-scale, prospective, multicenter, observational study (Kansai Plus Atrial Fibrillation Registry). We enrolled 5010 consecutive patients who underwent an initial RFCA of AF at 26 centers (64±10 years; 1369 [27.3%] females; non-paroxysmal AF, 35.7%). The median follow-up duration was 2.9 years.

Results

Fourteen % of female had a history of heart failure prior to CA, while 12.8% of male had a history of heart failure at baseline (p=0.29). The 3-year cumulative incidence of AF recurrence after a single procedure was 43.3% in female and 39.0% in male (log rank P=0.0046). In patients with the history of heart failure, AF recurrence rates were 42.2% in female and 45.8% in male (log rank P=0.51). On the other hand, in patients without history of heart failure, more females experienced AF recurrence (female vs. male, 43.5% vs. 38.0%, log rank P=0.001).

The rate of AF recurrence after multiple procedures was higher in female (24.2% vs. 19.6%, log rank P<0.0001). AF recurrence rates were similar between sexes in patients with history of heart failure (female vs. male, 26.0% vs. 26.7%, log rank P=0.86), while AF recurrence rates were higher in female without history of heart failure than those in male (females vs. males, 23.9% vs. 18.5%, log rank P<0.0001).

Conclusion

The Kansai Plus Atrial Fibrillation Registry revealed a distinct sex difference in terms of the AF recurrence after CA of AF. Females had higher recurrence rates compared with males in patients without history of heart failure, while recurrence rates were similar between sexes in patients with history of heart failure.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Research Institute for Production Development in Kyoto, Japan.

Predictive factors of recurrent atrial tachyarrhythmia after multiple procedures of radiofrequency catheter ablation for paroxysmal atrial fibrillation: Kansai Plus Atrial Fibrillation Registry (KPAF)

Background

The predictors of arrhythmia recurrence after radiofrequency catheter ablation (RFCA) for paroxysmal atrial fibrillation (PAF) have not yet been fully evaluated.

Purpose

The aim of this study was to develop and validate a risk scoring system to predict the incidence of recurrence of atrial tachyarrhythmia after the final RFCA for PAF.

Methods

The study population consisted of 3223 consecutive patients undergoing first-time RFCA for PAF from November 2011 to March 2014 in 26 cardiovascular centers in Japan who were enrolled in the Kansai Plus Atrial Fibrillation (KPAF) registry. We developed a scoring system in a derivation cohort with 2149 patients and assessed its reproducibility in a validation cohort with 1074 patients. The primary endpoint was recurrent atrial tachyarrhythmia lasting for ≥30 seconds after 91 days post the final ablation.

Results

During a median follow-up period of 3.1 years, 404 (18.8%) patients of the derivation cohort had AF recurrence after the final RFCA. The baseline patient characteristics of the derivation cohort were as follows: mean age 64.7 years, male 1480 (68.9%), mean body mass index (BMI) 23.6 kg/m2, hypertension 1122 (52.2%), prior heart failure 182 (8.5%), diabetes mellitus 203 (9.5%), prior stroke and/or transient ischemic attack 21 (1.0%), prior vascular disease 209 (9.7%), prior valvular disease 105 (4.9%), median CHADS2 score 1.1, median CHA2DS2-VASc score 2.1, mean number of ineffective antiarrhythmic drugs (AAD) 0.80, median duration of history of AF episodes 2.1 years, mean left atrial diameter (LAD) 38.2 mm, mean left ventricular ejection fraction (LVEF) 65.3%, and mean eGFR 68.7 mL/min/1.73m2. There was no significant difference in the baseline characteristics between derivation and validation cohorts. The results of the multivariate logistic regression models identified 5 independent variables of recurrent atrial tachyarrhythmia after the final RFCA: female (odds ratio (OR) = 1.45, p=0.0017), BMI <25 kg/m2 (OR=1.40, p=0.0081), duration of AF history 3 years≤ (OR=1.39, p<0.0034), chronic kidney disease (CKD) (OR=2.1, p=0.005, for stage 2/3CKD, OR=2.6, p=0.018 for stage 4/5 CKD), and LVEF (OR=2.1, p=0.039 for LVEF <50%, OR=1.5, p=0.022 for LVEF 50–60%). The predictive score for each factor was 3 points for CKD stage 4/5, 2 for CKD stage2/3 and LVEF <50%, and 1for the others (11 points in total). The arrhythmia-free rates after the final RCFA in the derivation cohort according to the score were as follows: 0–2 points = 91.7%, 3–4 = 80.7%, 5< = 72.6%, respectively. The similar results were reproduced in the validation cohort (Figure 1).

Conclusion

Our newly developed scoring system, composed of female, BMI, AF duration, CKD, and LVEF, could reproducibly predict arrhythmia recurrence after the final RFCA for PAF.

Funding Acknowledgement

Type of funding source: None

Sex differences in the predictors of recurrent atrial fibrillation after catheter ablation: insights from the Kansai Plus Atrial Fibrillation (KPAF) registry

Background

The impact of sex differences on the clinical outcomes of radiofrequency catheter ablation (RFCA) of atrial fibrillation (AF) is controversial. We previously reported that females experienced more frequent AF recurrences than males after the index and last RFCA procedures.

Purpose

To identify the risk factors associated with recurrent AF in females and males after RFCA of AF.

Methods

We conducted a large-scale, prospective, multicenter, observational study (Kansai Plus Atrial Fibrillation Registry). We enrolled 5010 consecutive patients who underwent an initial RFCA of AF at 26 centers (64±10 years; 1369 [27.3%] females; non-paroxysmal AF, 35.7%). The median follow-up duration was 2.9 years.

Results

The incidence of AF recurrences after a single procedure was 43.3% in females and 39.0% in males. After a multivariate adjustment at baseline, the significant predictors of AF recurrence in females after the index RFCA were non-paroxysmal AF (hazard ration [HR],1.59; 95% confidence interval [CI],1.31–1.93, p<0.0001), a history of AF ≥2 years (HR,1.47; 95% CI,1.24–1.74, p<0.0001), coronary artery disease (HR,1.43; 95% CI,1.03–1.98, p=0.0035), and an estimated glomerular filtration rate (eGFR)<60 mL/min/1.73m2 (HR,1.46; 95% CI,1.10–1.95, p=0.0086). On the other hand, significant predictors of AF recurrence in males after the index RFCA were non-paroxysmal AF (HR,1.54; 95% CI,1.37–1.73, p<0.0001), a history of AF ≥2 years (HR,1.40; 95% CI,1.26–1.56, p<0.0001), the number of antiarrhythmic drugs (HR,1.06; 95% CI,1.003–1.13, p=0.040), a left atrial diameter≥40mm (HR,1.13; 95% CI,1.007–1.27, p=0.038), and dilated cardiomyopathy (HR,1.55; 95% CI,1.07–2.26, p=0.021), however, an eGFR<60 mL/min/1.73m2 was not associated with AF recurrence in males (HR, 1.00; 95% CI, 0.88–1.13, p=0.97).

Conclusion

The Kansai Plus Atrial Fibrillation Registry revealed a distinct sex difference in terms of the predictors of recurrent AF after RFCA. Non-Paroxysmal AF and a long history of AF were common risk factors both in females and males. However, renal dysfunction was a significant predictor of AF recurrence in females, while it was not a risk of recurrence in males.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): Research Institute for Production Development in Kyoto, Japan.

Catheter ablation of atrial fibrillation benefits the patients with heart failure and preserved ejection fraction as well as those with heart failure and reduced ejection fraction

Background

Although catheter ablation of atrial fibrillation (AF) has recently been shown to improve the cardiac function and even mortality in patients with heart failure (HF) and reduced ejection fraction (HFrEF), few studies have examined the outcomes of AF catheter ablation in patients with HF with preserved ejection fraction (HFpEF).

Purpose

To verify the impact of AF catheter ablation on the cardiac function and HF status in patients with HFpEF.

Methods

We studied 306 patients with HF who had a history of an HF hospitalization and/or preprocedural serum BNP levels >100pg/ml (age, 68.9±8.2 years old; male, 66.3%; non-paroxysmal AF, 63.1%, left atrial diameter [LAD], 42.5±6.3 mm; left ventricular ejection fraction [LVEF], 60.6±12.0%) out of 596 consecutive patients who underwent pulmonary vein isolation-based catheter ablation of AF. The patients with an LVEF ≥50% were defined as having HFpEF (n=262; age, 69.0±8.2 years old; male, 64.5%; non-paroxysmal AF, 61.8%, LAD, 42.1±5.9 mm; left LVEF, 64.0±8.2%) and the remaining patients with an LVEF <50% were defined as having HFrEF (n=44, age, 67.9±8.7 years old; male, 77.0%; non-paroxysmal AF, 70.5%, LAD, 44.9±8.2 mm; LVEF, 40.1±10.2%). The patients received periodic follow-ups for 12 months after the catheter ablation. The cardiac function parameters including the echocardiographic findings and HF functional status of the patients were compared between baseline and 12 months, stratified by the HF subgroup.

Results

AF recurred in 60 patients with HFpEF (22.9%) and in 14 with HFrEF (31.8%) during the 12 month follow-up (p=0.27), however, sinus rhythm was maintained at 12 months in most of the patients (253 patients with HFpEF [96.6%] and 42 patients with HFrEF [95.5%]) (p=0.71). Figure 1 compares the changes in the cardiac function parameters and NYHA functional class from baseline to the 12-month follow-up stratified by the HF subgroup. Both the patients with HFpEF and HFrEF had significant improvements in the serum BNP levels, chest thorax ratio, and LVEF determined by echocardiography. LA reverse remodeling as shown by a significant reduction in the LAD was observed in both HF subgroups, however, the E/E', an index of the LV diastolic function, did not significantly change in either of the subgroups. Similar to the patients with HFrEF, an improvement in the NYHA functional class was seen in those with HFpEF.

Conclusions

Catheter ablation of AF may benefit patients with HFpEF as well as those with HFrEF. Sinus rhythm maintenance achieved by AF catheter ablation in patients with HFpEF may lead to LA reverse remodeling and a better LV systolic function, thereby improving the NYHA functional class. It is unclear whether changes in the LV diastolic function may contribute to this favorable process.

Funding Acknowledgement

Type of funding source: None

The impact of catheter ablation for patients with asymptomatic atrial fibrillation: subanalysis of kansai plus atrial fibrillation (kpaf) registry

Background

Catheter ablation (CA) of atrial fibrillation (AF) for symptomatic patients improves the quality of life and prognosis of patients with heart failure. However, the impact of CA for asymptomatic patients is still controversial.

Purpose

We aimed to investigate the clinical outcomes of CA of AF for asymptomatic patients compared to those for symptomatic patients.

Methods

A total of 5,013 patients from the Kansai Plus Atrial Fibrillation (KPAF) Registry who underwent CA were screened. The patients were divided into three groups by type of AF; paroxysmal (PAF), persistent (PEAF) and long standing (LSAF) and the patients in each type of AF were divided into two groups: asymptomatic and symptomatic. The primary endpoint was recurrent supraventricular tachyarrhythmias lasting for more than 30 seconds during follow-up 4 years after CA. The secondary endpoint was a composite of cardiovascular, cerebral, and gastrointestinal events during follow-up 4 years after CA. The incidence of complications related to CA between asymptomatic and symptomatic patients was also evaluated. Kaplan–Meier analysis was employed to estimate the primary and secondary endpoints. The statistical differences in primary and secondary endpoints between asymptomatic and symptomatic patients were evaluated using a log–rank test. The impact of symptom due to AF on the primary and secondary endpoint was evaluated using a Cox hazard analysis. The difference in incidence of complications between asymptomatic and symptomatic patients was evaluated using a chi–square test.

Results

In this study population, PAF was the most frequent at 64.4%, followed by PEAF (22.7%) and LSAF (13.0%). There were some significant differences in the baseline characteristics between asymptomatic and symptomatic patients in each type of AF. The proportion of male was significantly higher in asymptomatic patients than symptomatic patients in PAF (81.2% versus 67.2%, p<0.001) and PEAF (86.4% versus 74.3%, p<0.001). Left atrial diameter was larger in asymptomatic patients than symptomatic patients only in PAF (40±6mm versus 38±6mm, p<0.001). In all types of AF, there was no significant difference in primary endpoint between asymptomatic and symptomatic patients as follows: 37.5% versus 40.6% (p=0.6) in PAF, 45.2% versus 55.1% (p=0.09) in PEAF and 59.3% versus 63.6% (p=1.0) in LSAF. There was also no significant difference in secondary endpoint between asymptomatic and symptomatic patients: 7.1% versus 6.8% (p=0.7) in PAF, 5.4% versus 8.7% (p=0.3) in PEAF and 4.4% versus 5.1% (p=0.5) in LSAF. In a Cox hazard analysis, the symptom did not affect both of the primary and secondary endpoints in each type of AF. In regard to the incidence of complications related to CA, there was no significant difference between asymptomatic and symptomatic patients in each type of AF.

Conclusion

CA of AF for asymptomatic patients can be safe and can lead to equivalent outcomes as well as symptomatic patients.

Funding Acknowledgement

Type of funding source: None

P5652Catheter ablation outcome and heart failure hospitalization in atrial fibrillation patients with preserved left ventricular ejection fraction: insights from the Kansai plus atrial fibrillation (KPAF)

Background

Heart failure (HF) is the leading cause of death in patients with atrial fibrillation (AF), and AF is an independent prognostic factor in HF patients with preserved left ventricular ejection fraction (LVEF). Radiofrequency catheter ablation (RFCA) for AF is effective to maintain sinus rhythm.

Purpose

We sought to clarify incidence of HF hospitalization and whether AF ablation outcome influenced incidence of HF hospitalization after the procedures in patients with preserved LVEF.

Methods

We conducted a large-scale, prospective, multicenter, observational study. A total of 4522 consecutive patients with normal LVEF (>/- 50%) who underwent an initial RFCA for AF in 26 centers were enrolled (average age, 64±10 years; non-paroxysmal AF, 33.7%). The median follow-up duration was 2.9 years.

Results

The 3-year cumulative incidence of AF recurrence after a single procedure was 40.3%. Hospitalization for HF was observed in 60 patients (1.3%) and was significantly higher in patients with AF recurrence than those without it (2.63% vs 0.44%, log-rank p<0.001). After adjustment by age ≥65 years, estimated glomerular filtration rate ≤60ml/min, history of HF, and female, all of which were statistically associated with a risk of HF hospitalization, AF recurrence after the index RFCA was an independent predictor of HF hospitalization (hazard ratio; 4.75, 95% confidence interval; 2.59–9.42, p<0.001).

Conclusions

Recurrence after RFCA for AF was a significant risk of HF hospitalization among AF patients with preserved LVEF.

Acknowledgement/Funding

This study was supported by the Research Institute for Production Development in Kyoto, Japan.

P1035Factors associated with quality-of-life improvement after catheter ablation of atrial fibrillation: insights from the Kansai Plus Atrial Fibrillation (KPAF) registry

Background

Improving the quality of life (QoL) is one of the main purposes of catheter ablation (CA) of persistent atrial fibrillation (AF). Factors associated with QoL improvement after CA of AF patients have not been clarified. The Kansai Plus Atrial Fibrillation (KPAF) Registry is a multi-center registry enrolling more than 5,000 consecutive patients undergoing the first radiofrequency catheter ablation of AF.

Purpose

The aim of this study was to investigate the QoL change after AF ablation and its associated factors.

Methods

A total of 2030 patients in whom the QoL score was assessed before and one year after the ablation were enrolled from the KPAF registry (age 64±10 years, 75% male, paroxysmal 66%, CHADS2 score 1.1±1.1). The QoL was evaluated using the AF specific QoL evaluation method (AFQLQ), which scores the patient QoL within a range of 0–98 points.

Results

Overall, catheter ablation showed a significant increase in the AFQLQ score (68±19 vs. 86±13 points, P<0.01). AF recurrence was observed in 372 cases (18%) during a 1-year follow-up period. A multivariate analysis showed that AF recurrence, symptomatic AF, long AF duration, high preprocedural heart rate (>110 bpm) and small left atrial diameter were independent predictors of a QoL improvement defined as a >10% score increase.

Multivariate analysis

Conclusions

CA of AF significantly improved the QoL. AF recurrence was one of the strong factors associated with QoL improvement. Symptomatic AF, long AF duration, high preprocedural heart rate and small left atrial diameter were independent predictors of QoL improvement.

P1029Catheter ablation outcome and heart failure hospitalization in atrial fibrillation patients: insights from the Kansai plus atrial fibrillation (KPAF) registry

Background

Heart failure (HF) is the leading cause of death in patients with atrial fibrillation (AF). Radiofrequency catheter ablation (RFCA) for AF is effective to maintain sinus rhythm.

Purpose

We sought to clarify whether AF ablation outcome influenced incidence of HF hospitalization after the procedures.

Methods

We conducted a large-scale, prospective, multicenter, observational study. A total of 5010 consecutive patients who underwent an initial RFCA for AF in 26 centers were enrolled (average age, 64±10 years; non-paroxysmal AF, 35.6%). The median follow-up duration was 2.9 years.

Results

The 3-year cumulative incidence of AF recurrence after a single procedure was 40.2%. The 3-year incidence of hospitalization for HF was observed in 92 patients (1.8%) and was significantly higher in patients with AF recurrence than those without it (3.3% vs 0.84%, log-rank p<0.001). After adjustment by advanced age,(≥65 years), reduced left ventricular ejection fraction (≤50%), low estimated glomerular filtration rate (≤60ml/min), and history of HF, all of which were statistically associated with a risk of HF hospitalization (p<0.1, respectively), AF recurrence after the index RFCA was an independent predictor of HF hospitalization (hazard ratio [HR]; 3.17, 95% confidence interval [CI]; 2.06–5.04, p<0.001).Even after multiple procedures (1425 re-ablation sessions in 1274 patients [25.4%]), AF recurrence after the last procedure was an independent predictor of HF hospitalization (HR; 2.83, 95% CI; 1.89–4.24, p<0.001).

Conclusions

Among AF patients receiving RFCA, those with AF recurrence were at greater risk of heart failure hospitalization than were patients without AF recurrence. These differences should be noted when treating AF patients in actual clinical practice.

Acknowledgement/Funding

This study was supported by the Research Institute for Production Development in Kyoto, Japan.

P5650Improvement in ejection fraction predicts heart failure after catheter ablation for atrial fibrillation in patients with left ventricular systolic dysfunction: from the KPAF registry

Introduction

The presence of atrial fibrillation (AF) in patients with reduced left ventricular ejection fraction (LVEF) is associated with increased risks of mortality and hospitalization for heart failure (HF). Although prior studies reported that catheter ablation (CA) for AF in low LVEF patients reduced risks of all-cause mortality and HF hospitalization, the predictors of worsening HF after ablation has not been adequately evaluated.

Purpose

The purpose of this study was to investigate the impact of improvement in LVEF after AF ablation on the incidence of subsequent HF hospitalization in patients with low LVEF.

Methods

The Kansai Plus Atrial Fibrillation (KPAF) Registry is a multicenter registry enrolling 5,013 consecutive patients undergoing first-time ablation for AF. The current study population consisted of 1,031 patients with reduced LVEF of <60%. We divided the study population into 3 groups according to LVEF at follow-up; 678 patients (65.8%) with improved LVEF (≥5 U change in LVEF), 288 patients (27.9%) with unchanged LVEF (−5 U ≤ change in LVEF <5 U) and 65 patients (6.3%) with worsened LVEF (<−5 U change in LVEF).

Results

During the median follow-up of 1067 [879–1226] days, patients improved LVEF had lower rate of HF hospitalization, compared with those with unchanged and worsened LVEF (2.1%, 8.0%, and 21.5%, respectively, P<0.0001). Recurrent atrial tachyarrhythmias were documented in 43.5%, 47.2% and 67.7%, respectively (P=0.0008).

Figure 1

Conclusion

Among patients with reduced LVEF undergoing AF ablation, patients with subsequently improved LVEF in association with maintained sinus rhythm had markedly lower risk of HF hospitalization during follow-up as compared with those with unchanged or worsened LVEF.

P1038Device implantation after catheter ablation of paroxysmal atrial fibrillation with coexisting sick sinus syndrome: Insights from the Kansai Plus Atrial Fibrillation (KPAF) study

Background

Sick sinus syndrome (SSS) and atrial fibrillation (AF) frequently coexist and interact to initiate and perpetuate each other. Several retrospective or small cohort studies have suggested that successful catheter ablation of AF may help to waive device implantations in patients with paroxysmal AF plus SSS, however, no prospective large studies are so far available on this scenario.

Purpose

We aimed to elucidate the device implantation-free survival after catheter ablation of paroxysmal AF with coexisting SSS in a prospective large-scale registry. We also determined the risk factors for device implantations after catheter ablation of paroxysmal AF.

Methods

The Kansai Plus Atrial Fibrillation (KPAF) study is a multi-center prospective registry that enrolled 5,019 consecutive patients that underwent an initial pulmonary vein isolation-based radiofrequency catheter ablation of AF. This study was comprised of 3,226 patients with paroxysmal AF registered in the KPAF study (age, 64.8±10.5 years old; female, n=999 [31.0%]; left atrial diameter [LAD], 37.5±8.0 mm; left ventricular ejection fraction [LVEF], 65.3±8.4%, CHADS2 score, 1.09±1.05). The atrial tachyarrhythmia-free and device-free survivals after catheter ablation were compared between patients with SSS (n=368; tachy-brady syndrome, 88%) and without SSS (control; n=2,858).

Results

The atrial tachyarrhythmia-free survival was almost identical between the two groups both after the first ablation session (Fig.1A) and after the last procedure with an average of 1.3±0.5 sessions. At baseline, the devices had already been implanted in 53 (14.4%) SSS and 36 (1.3%) control patients. In the remaining patients, devices were newly implanted in 54 (17.1%) SSS and 62 (2.2%) control patients during the follow-up of 3 years after the catheter ablation (Figure 1B). In the SSS group, devices were implanted predominantly within 6 months after the catheter ablation, and atrial tachyarrhythmia recurrence preceded the device implantation in 48 (89%) patients. Multivariate predictors of device implantations after the paroxysmal AF ablation included: SSS (hazard ratio [HR] 6.85, 95% confidence interval [CI] 4.61–10.19, p<0.001), an age>75 years old (HR 1.69, 95% CI 1.08–2.64, p=0.019), a female gender (HR 2.16, 95% CI 1.44–3.24, p<0.001), the LAD (mm) (HR 1.05, 95% CI 1.02–1.08, p=0.006), and the LVEF (%) (95% CI 0.96, 95% CI 0.94–0.98, p<0.001).

Figure 1

Conclusions

Device implantations could be waived in >80% of patients with SSS at 3 years of follow-up after the catheter ablation of paroxysmal AF in this real world all comer prospective registry. In addition to coexisting SSS, predictors of device implantations after paroxysmal AF ablation included: the elderly, a female gender, a large LA, and a reduced LVEF.

Acknowledgement/Funding

None

A novel spermatogenesis-related factor-1 gene expressed in maturing rat testis

A rat gene with testis-specific expression coinciding with spermatogenesis was cloned by differential display. This spermatogenesis-related factor-1 (SRF-1) gene was not expressed in other organs. Testicular expression was detected from 5 weeks of age and increased up to 15 weeks; this level of expression was maintained for 63 weeks. The 750-bp cloned gene was coded for an open reading frame of 202 amino acids. According to in situ hybridization at 7 weeks, this gene was expressed mainly in spermatocyte. The gene product may function as a molecular motor in meiosis, as the deduced amino acid sequence showed partial homology with kinesin-related proteins. The action of this gene and its product with respect to division of reproductive cells requires further investigation.

Intra- and intermolecular beta-pleated sheet formation in glutamine-repeat inserted myoglobin as a model for polyglutamine diseases

An aberrant structure of the expanded polyglutamine might be involved in the formation of aggregates in CAG repeat diseases. To elucidate structural properties of the expanded polyglutamine, we prepared sperm whale myoglobin (Mb) mutants, in which 12, 28, 35, and 50 repeats of glutamine were inserted at the corner between the C and D helices (Gln(12), Gln(28), Gln(35), and Gln(50), respectively). Circular dichroism and IR spectroscopies showed that the expanded polyglutamine, which was recognized by the monoclonal antibody 1C2 in Gln(28), Gln(35), and Gln(50) Mb forms an antiparallel beta-pleated sheet structure. Gln(50) Mb aggregates were found to comprise an intermolecular antiparallel beta-pleated sheet. Fluorescence together with (1)H NMR spectra revealed partial unfolding of the protein surface in Gln(35) and Gln(50) Mb, although the structural changes in the protein core were rather small. The present results indicate that the fluctuating beta-pleated sheet of the expanded polyglutamine exposed on the protein surface facilitates the formation of aggregates through intermolecular interactions. The present study has first established and characterized structural properties of a molecular model for polyglutamine diseases in which various lengths of polyglutamine including a pathologically expanded glutamine repeat were inserted into a structurally known protein.

The role of water molecules in the association of cytochrome P450cam with putidaredoxin. An osmotic pressure study

We have investigated the osmotic pressure dependence of the association between ferric cytochrome P450cam and putidaredoxin (Pdx) to gain an insight into the role of water molecules in the P450cam-reduced Pdx complexation amenable to physiological electron transfer. The association constant was evaluated from the electron transfer rates from reduced Pdx to P450cam. The natural logarithm of the association constant K(a) was linearly reduced by the osmotic pressure, and osmotic stress yields uptake of 25 waters upon association. In contrast, uptake of only 13 waters is observed from the osmotic pressure dependence of the association in the nonphysiological redox partners P450cam and oxidized Pdx. Although general protein-protein associations proceed through dehydration around the complex interface, the interfacial waters could mediate hydrogen-bonding interactions. Therefore, about 10 more interfacial waters imply an additional water-mediated hydrogen-bonding network in the P450cam.reduced Pdx complex, which does not exist in the complex with oxidized Pdx. It is also possible that the water-mediated hydrogen-bonding interactions support a high P450cam affinity for reduced (K(a) = 0.83 microm(-1)) relative to oxidized (K(a) = 0.058 microm(-1)) Pdx. This study points to a novel role of solvents in assisting redox state-dependent interaction between P450cam and Pdx.

Binding of CO at the Pro2 side is crucial for the activation of CO-sensing transcriptional activator CooA. (1)H NMR spectroscopic studies

CooA is a heme-containing transcriptional activator that anaerobically binds to DNA at CO atmosphere. To obtain information on the conformational transition of CooA induced by CO binding to the heme, we assigned ring current-shifted (1)H NMR signals of CooA using two mutants whose axial ligands of the heme were replaced. In the absence of CO, the NMR spectral pattern of H77Y CooA, in which the axial histidine (His(77)) was replaced with tyrosine, was similar to that of wild-type CooA. In contrast, the spectra of CooADeltaN5, in which the NH(2) termini including the other axial ligand (Pro(2)) were deleted, were drastically modulated. We assigned three signals of wild-type CooA at -4.5, -3.6, and -2.8 ppm to delta(1)-, alpha-, and delta(2)-protons of Pro(2), respectively. The Pro(2) signals were undetectable in the upfield region of the spectrum of the CO-bound state, which confirms that CO displaces Pro(2). Interestingly, the Pro(2) signals were observed for CO-bound H77Y CooA, implying that CO binds to the trans position of Pro(2) in H77Y CooA. The abolished CO-dependent transcriptional activity of H77Y CooA is therefore the consequence of Pro(2) ligation. These observations are consistent with the view that the movement of the NH(2) terminus triggers the conformational transition to the DNA binding form.

Protein purification, cDNA cloning and gene expression of lysozyme from eri-silkworm, Samia cynthia ricini

Lysozyme was isolated from immunized hemolymph of Samia cynthia ricini larvae by heat treatment, cation exchange and reverse-phase chromatography. A cDNA encoding lysozyme was cloned by screening the cDNA library from immunized fat body using, as a probe, a DNA fragment obtained by PCR-based differential display method. The deduced amino acid sequence showed high homology with other chicken-type lysozymes. The calculated molecular mass of the mature peptide was 13785, which agreed precisely with that obtained by MALDI-TOF mass spectrometry of the isolated protein. The lysozyme transcripts were detected at a significant level in naïve fat body, and the level increased 5-10-fold upon injection of the larvae with UV-killed bacteria or peptidoglycan.

Ligand migration in human myoglobin: steric effects of isoleucine 107(G8) on O(2) and CO binding

To investigate the ligand pathway in myoglobin, some mutant myoglobins, in which one of the amino acid residues constituting a putative ligand-docking site, Ile107, is replaced by Ala, Val, Leu, or Phe, were prepared and their structural and ligand binding properties were characterized. The kinetic barrier for the ligand entry to protein inside was lowered by decreasing the side-chain volume at position 107, indicating that the bulky side chain interferes with the formation of the activation state for the ligand migration and the free space near position 107 would be filled with the ligand in the activation state. Another prominent effect of the reduced side-chain volume at position 107 is to stabilize the ligand-binding intermediate state. Because the stabilization can be ascribed to decrease of the positive enthalpy, the enlarged free space near position 107 would relieve unfavorable steric interactions between the ligand and nearby amino acid residues. The side-chain volume at position 107, therefore, is crucial for the kinetic barrier for the ligand migration and free energy of the ligand-binding intermediate state, which allows us to propose that some photodissociated O(2) moves toward position 107 to be trapped and then expelled to the solvent.

Time-resolved hole-burning study on myoglobin: fluctuation of restricted water within distal pocket

We have studied the equilibrium fluctuation dynamics of Zn-substituted myoglobin and its His64-->Leu (H64L) mutant in the pH range from 5 to 9 by using time-resolved transient-hole-burning (TRTHB) spectroscopy. In the H64L mutant, we have observed a largely reduced width of the absorption spectrum and only a slight temporal shift of the hole-burning spectrum. These observations both reflect the suppressed conformational fluctuation in the mutant. On the other hand, the pH-dependent change in the absorption spectrum could not be solely explained by the change in the protonation state of His64 induced by the pH change. These results suggest that although the fluctuation dynamics observed by the TRTHB experiment of the native sample mainly reflects the conformational motion around His64, the interconversion process of His64 between its protonated and unprotonated states has a minor contribution. Instead, we have proposed a tentative interpretation that the motion of the water molecule around His64 is the main source of the observed dynamics in the TRTHB technique.

Proximal cysteine residue is essential for the enzymatic activities of cytochrome P450cam

To investigate the functional and structural roles of the proximal thiolate ligand in cytochrome P450cam, we prepared the C357H mutant of the enzyme in which the axial cysteine residue (Cys357) was replaced with a histidine residue. We obtained the unstable C357H mutant by developing a new preparation procedure involving in vitro folding of P450cam from the inclusion bodies. The C357H mutant in the ferrous-CO form exhibited the Soret peak at 420 nm and the Fe-CO stretching line at 498 cm-1, indicating a neutral histidine residue as the axial ligand. However, another internal ligand is coordinated to the heme iron as the sixth ligand in the ferric and ferrous forms of the C357H mutant, suggesting the collapse of the substrate-binding site. The C357H mutant showed no catalytic activity for camphor hydroxylation and the reduced heterolytic/homolytic ratio of the O-O bond scission in the reaction with cumene hydroperoxide. The present observations indicate that the thiolate coordination in P450cam is important for the construction of the heme pocket and the heterolysis of the O-O bond.

The electronic and vibrational structures of iron-oxo porphyrin with a methoxide or cysteinate axial ligand

Hybrid density functional theory (DFT) calculations for the electronic and vibrational structures of compound I species with a methoxide (MeO-) (1) or cysteinate (CysS-) (2) axial ligand are carried out in order to elucidate the natures of a methoxide-coordinating new type of compound I species (Bull. Chem. Soc. Jpn. 71 (1998) 1343) and cysteinate-coordinating compound I species of chloroperoxidase (CPO-I) and cytochrome P450s (P450-I). DFT computations of 1 and 2 demonstrate that these "anionic" ligands are a spin carrier; 70% (80%) of a spin density resides on the O (S) atom of the axial ligand and 30% (20%) is distributed on the porphyrin ring. These results suggest that for the generation of the compound I species, one electron is removed from the iron centers and the rest of the one electron is supplied from the oxidizable axial ligands instead of the iron centers or the porphyrin ring. Vibrational analyses demonstrate that the Fe=O bond is more strongly activated in 1 compared with 2 with the stretching mode at 849 cm(-1) (878 cm(-1)) for the doublet state1a (2a) and at 814 cm(-1) (875 cm(-1)) in the quartet state 1b (2b). This reverse order of the Fe=O bond strength with respect to the axial donor strength should have relevance to the significantly oxidized character of the CysS- axial ligand. In conjunction with the recent results of the extensive resonance Raman (RR) studies, some interpretations of unsettled RR results for compound I of chloroperoxidase (CPO-I) and a synthetic compound I species [O=FeIV(TMP*+)(alcohol)] (J. Am. Chem. Soc. 113 (1991) 6542) concerning the O=Fe stretching frequencies are discussed.

Identification of histidine 77 as the axial heme ligand of carbonmonoxy CooA by picosecond time-resolved resonance Raman spectroscopy

The heme proximal ligand of carbonmonoxy CooA, a CO-sensing transcriptional activator, in the CO-bound form was identified to be His77 by using picosecond time-resolved resonance Raman spectroscopy. On the basis of the inverse correlation between Fe-CO and C-O stretching frequencies, we proposed previously that His77 is the axial ligand trans to CO [Uchida et al. (1998) J. Biol. Chem. 273, 19988-19992], whereas later a possibility of displacement of His77 by CO with retention of another unidentified axial ligand was reported [Vogel et al. (1999) Biochemistry 38, 2679-2687]. Although our previous resonance Raman study failed to detect the Fe-His stretching [nu(Fe-His)] mode of CO-photodissociated CooA of the carbonmonoxy adduct due to the rapid recombination, application of the picosecond time-resolved resonance Raman technique enabled us to observe a new intense line assignable to nu(Fe-His) at 211 cm(-)(1) immediately after photolysis, while it became nondiscernible after 100-ps delay. The low nu(Fe-His) frequency of photodissociated CooA indicates the presence of some strain in the Fe-His bond in CO-bound CooA. This and the rapid recombination of CO characterize the heme pocket of CooA. The 211 cm(-)(1) band was completely absent in the spectrum of the CO-photodissociated form of the His77-substituted mutant but the Fe-Im stretching band was observed in the presence of exogenous imidazole (Im). Thus, we conclude that His77 is the axial ligand of CO-bound CooA and CO displaces the axial ligand trans to His77 with retention of ligated His77 to activate CooA as the transcriptional activator.

Angiographic no-reflow phenomenon as a predictor of adverse long-term outcome in patients treated with percutaneous transluminal coronary angioplasty for first acute myocardial infarction

OBJECTIVES

We sought to elucidate the long-term prognostic importance of angiographic no-reflow phenomenon after percutaneous transluminal coronary angioplasty (PTCA) for acute myocardial infarction (AMI).

BACKGROUND

Angiographic no-reflow phenomenon, a reduced coronary antegrade flow (Thrombolysis in Myocardial Infarction [TIMI] flow grade < or =2) without mechanical obstruction after recanalization, predicts poor left ventricular (LV) functional recovery and survival in the early phase of AMI. We hypothesized that angiographic no-reflow phenomenon also predicts long-term clinical outcome.

METHODS

We studied 120 consecutive patients with their first AMI treated by PTCA without flow-restricting lesions. The patients were classified as either no-reflow (n = 30) or reflow (TIMI-3) (n = 90) based on post-PTCA cineangiograms to follow up (5.8 +/- 1.2 years) for cardiac death and nonfatal events.

RESULTS

Patients with no-reflow had congestive heart failure (p < 0.0001), malignant arrhythmia (p = 0.038), and cardiac death (p = 0.002) more often than did those with reflow. Kaplan-Meier curves showed lower cardiac survival and cardiac event-free survival (p < 0.0001) in patients with no-reflow than in those with reflow. Multivariate analyses disclosed that no-reflow phenomenon was an independent predictor of long-term cardiac death (relative risk [RR] 5.25, 95% confidence interval [CI] 1.85 to 14.9, p = 0.002) and cardiac events (RR 3.71, 95% CI 1.79 to 7.69, p = 0.0004). At follow-up, survivors with no-reflow had higher end-diastolic and end-systolic LV volume indices and plasma brain natriuretic peptide levels, and lower LV ejection fractions (p = 0.0002, p < 0.0001, p = 0.002, p < 0.0001, respectively) than did those with reflow, indicating that no-reflow may be involved in LV remodeling.

CONCLUSIONS

Angiographic no-reflow phenomenon strongly predicts long-term cardiac complications after AMI; these complications are possibly associated with LV remodeling.

Unusual pressure effects on ligand rebinding to the human myoglobin Leucine 29 mutants

Using high pressure flash photolysis, we revealed that the side chain of Leu(29) controls the reaction volume of the ligand migration process in myoglobin, which is the primary factor for the unusual activation volume of ligand binding in some Leu(29) mutants. As we previously reported (Adachi, S., Sunohara, N., Ishimori, K., and Morishima, I. (1992) J. Biol. Chem. 267, 12614-12621), CO bimolecular rebinding in the L29A mutant was unexpectedly decelerated by pressurization, suggesting that the rate-determining step is switched to ligand migration. However, very slow CO bimolecular rebinding of the mutants implies that bond formation is still the rate-determining step. To gain further insights into effects of the side chain on ligand binding, we prepared some new Leu(29) mutants to measure the CO and O(2) rebinding reaction rates under high hydrostatic pressure. CO bimolecular rebinding in the mutants bearing Gly or Ser at position 29 was also decelerated upon pressurization, resulting in apparent positive activation volumes (DeltaV), as observed for O(2) binding. Based on the three-state model, we concluded that the increased space available to ligands in these mutants enhances the volume difference between the geminate and deoxy states (DeltaV(32)), which shifts the apparent activation volume to the positive side, and that the apparent positive activation volume is not due to contribution of the ligand migration process to the rate-determining step.

Electron transfer reactions in Zn-substituted cytochrome P450cam

We have investigated photoinduced electron transfer (ET) reactions between zinc-substituted cytochrome P450cam (ZnP450) and several inorganic reagents by using the laser flash photolysis method, to reveal roles of the electrostatic interactions in the regulation of the ET reactions. The laser pulse irradiation to ZnP450 yielded a strong reductant, the triplet excited state of ZnP450, (3)ZnP450, which was able to transfer one electron to anionic redox partners, OsCl(6)(2-) and Fe(CN)(6)(3-), with formation of the porphyrin pi-cation radical, ZnP450(+). In contrast, the ET reactions from (3)ZnP450 to cationic redox partners, such as Ru(NH(3))(6)(3+) and Co(phen)(3)(3+), were not observed even in the presence of 100-fold excess of the oxidant. One of the possible interpretations for the preferential ET to the anionic redox partner is that the cationic patch on the P450cam surface, a putative interaction site for the anionic reagents, is located near the heme (less than 10 A from the heme edge), while the anionic surface is far from the heme moiety (more than 16 A from the heme edge), which would yield 8000-fold faster ET rates through the cationic patch. The ET rate through the anionic patch to the cationic partner would be substantially slower than that of the phosphorescence process in (3)ZnP450, resulting in no ET reactions to the cationic reagents. These results demonstrate that the asymmetrical charge distribution on the protein surface is critical for the ET reaction in P450cam.

Roles of the axial push effect in cytochrome P450cam studied with the site-directed mutagenesis at the heme proximal site

To examine the roles of the axial thiolate in cytochrome P450-catalyzed reactions, a mutant of cytochrome P450cam, L358P, was prepared to remove one of the conserved amide protons that are proposed to neutralize the negative charge of the thiolate sulfur. The increased push effect of the thiolate in L358P was evidenced by the reduced reduction potential of the heme. The 15N-NMR and resonance Raman spectra of the mutant in the ferric-CN and in the ferrous-CO forms, respectively, also supported the increased push effect. The maintenance of stereo- and regioselectivities for d-camphor hydroxylation by the mutant suggests the minimum structural change at the distal site. The heterolysis/homolysis ratios of cumene hydroperoxide were the same for wild-type and L358P. However, we observed the enhanced monooxygenations of the unnatural substrates using dioxygen and electrons supplied from the reconstituted system, which indicate the significant role of the push effect in dioxygen activation. We interpret that the enhanced push effect inhibits the protonation of the inner oxygen atom and/or promotes the protonation of the outer oxygen atom in the putative iron-hydroperoxo intermediate (Fe3+ -O-OH) of P450cam. This work is the first experimental indication of the significance of the axial cysteine for the P450 reactivity.

Melatonin scavenges hydroxyl radical and protects isolated rat hearts from ischemic reperfusion injury

During postischemic reperfusion, free radicals are produced and have deleterious effects in isolated rat hearts. We investigated whether melatonin (MEL) reduces the production of hydroxyl radical (*OH) in the effluent and aids in recovery of left ventricular (LV) function. Hearts were subjected to 30 min of ischemia followed by 30 min of reperfusion. Salicylic acid (SAL) was used as the probe for *OH, and its derivatives 2,5- and 2,3-dihydroxybenzoic acid (DHBA) were quantified using HPLC. In addition, thiobarbituric acid reactive substances (TBARS) in the myocardium was measured. Plateaus in the measurement of 2,5- and 2,3-DHBA were seen from 3 to 8 min after reperfusion in each group. The group that received 100 microM MEL+ SAL had significantly reduced amounts of 2,5- and 2,3-DHBA by multiple folds, compared to the SAL group. TBARS was significantly decreased in the 100 microM MEL group (1.20+/-0.36 vs 1.85+/-0.10 micromol/g of drug-free group, p<0.001). More importantly, the 100 microM MEL group significantly recovered in LV function (LV developed pressure, +dp/dt, and -dp/dt; 63.0%, 60.3%, and 59.4% in the 100 microM MEL group; 30.2%, 29.7%, and 31.5% in the drug-free group, respectively; p<0.05). Duration of ventricular tachycardia or ventricular fibrillation significantly decreased in the 100 microM MEL group (100 microM MEL, 159+/-67 sec; drug-free, 1244+/-233 sec; p<0.05). As a result of scavenging *OH and reducing the extent of lipid peroxidation, MEL is an effective agent for protection against postischemic reperfusion injury.

Stepwise formation of alpha-helices during cytochrome c folding

Two models have been proposed to describe the folding pathways of proteins. The framework model assumes the initial formation of the secondary structures whereas the hydrophobic collapse model supposes their formation after the collapse of backbone structures. To differentiate between these models for real proteins, we have developed a novel CD spectrometer that enables us to observe the submillisecond time frame of protein folding and have characterized the timing of secondary structure formation in the folding process of cytochrome c (cyt c). We found that approximately 20% of the native helical content was organized in the first phase of folding, which is completed within milliseconds. Furthermore, we suggest the presence of a second intermediate, which has alpha-helical content resembling that of the molten globule state. Our results indicate that many of the alpha-helices are organized after collapse in the folding mechanism of cyt c.

Functions of fluctuation in the heme-binding loops of cytochrome b5 revealed in the process of heme incorporation

Cytochrome b(5) (cyt b(5)) holds heme using two axial histidines, His63 and His39, that are located in the centers of the two heme-binding loops. The previous NMR study on the apo form of cyt b(5) (apocyt b(5)) revealed that the loop including His63 exhibits a larger fluctuation compared to the other loop including His39 [Falzone, C. J., Mayer, M. R., Whiteman, E. L., Moore, C. D., and Lecomte, J. T. (1996) Biochemistry 35, 6519-6526]. To understand the significance of the fluctuation, the heme association and dissociation rates of the two loops were compared using two mutants of cyt b(5) in which one of the axial histidines was replaced with leucine. It was demonstrated that the fluctuating loop possesses a significantly slower heme dissociation rate and a faster heme association rate than the other loop. To further verify the importance of the fluctuating loop, the heme association process of wild-type apocyt b(5) was investigated using optical absorption and CD spectroscopies. It was indicated that the process proceeds through the two pathways, and that the dominant pathway involves the initial coordination of His63 located in the fluctuating loop. The urea concentration dependency of the rate constants revealed that the folding of the fluctuating loop is associated with the coordination of His63. It was suggested that the fluctuation enables the loop to have a larger heme-loop contact in the heme-bound conformation. The fluctuating heme-binding loops might be useful for the artificial design of heme-binding proteins.

Substitution of the heme binding module in hemoglobin alpha- and beta-subunits. Implication for different regulation mechanisms of the heme proximal structure between hemoglobin and myoglobin

In our previous work, we demonstrated that the replacement of the "heme binding module," a segment from F1 to G5 site, in myoglobin with that of hemoglobin alpha-subunit converted the heme proximal structure of myoglobin into the alpha-subunit type (Inaba, K., Ishimori, K. and Morishima, I. (1998) J. Mol. Biol. 283, 311-327). To further examine the structural regulation by the heme binding module in hemoglobin, we synthesized the betaalpha(HBM)-subunit, in which the heme binding module (HBM) of hemoglobin beta-subunit was replaced by that of hemoglobin alpha-subunit. Based on the gel chromatography, the betaalpha(HBM)-subunit was preferentially associated with the alpha-subunit to form a heterotetramer, alpha(2)[betaalpha(HBM)(2)], just as is native beta-subunit. Deoxy-alpha(2)[betaalpha(HBM)(2)] tetramer exhibited the hyperfine-shifted NMR resonance from the proximal histidyl N(delta)H proton and the resonance Raman band from the Fe-His vibrational mode at the same positions as native hemoglobin. Also, NMR spectra of carbonmonoxy and cyanomet alpha(2)[betaalpha(HBM)(2)] tetramer were quite similar to those of native hemoglobin. Consequently, the heme environmental structure of the betaalpha(HBM)-subunit in tetrameric alpha(2)[betaalpha(HBM)(2)] was similar to that of the beta-subunit in native tetrameric Hb A, and the structural conversion by the module substitution was not clear in the hemoglobin subunits. The contrastive structural effects of the module substitution on myoglobin and hemoglobin subunits strongly suggest different regulation mechanisms of the heme proximal structure between these two globins. Whereas the heme proximal structure of monomeric myoglobin is simply determined by the amino acid sequence of the heme binding module, that of tetrameric hemoglobin appears to be closely coupled to the subunit interactions.

Protective effects of carvedilol against doxorubicin-induced cardiomyopathy in rats

Carvedilol (CAR) is a vasodilating beta-blocker which also has antioxidant properties. CAR produces dose-related reduction in mortality in patients with congestive heart failure. In the present study, we tested the hypothesis that CAR protects against doxorubicin (DOX)-induced cardiomyopathy in rats. Sprague-Dawley rats were treated with DOX, CAR, CAR+DOX, or atenolol (ATN)+DOX. DOX (cumulative dose, 15 mg/kg) was administered intraperitoneally, and CAR (30 mg/kg daily) or ATN (150 mg/kg daily) was administered orally. Three weeks after the completion of these treatments, cardiac performance and myocardial lipid peroxidation were assessed. Mortality was observed in the DOX (25%) and ATN+DOX (12.5%) groups. Compared with control rats, DOX significantly decreased systolic blood pressure (104+/-4 vs. 120+/-4 mmHg, P<0.05) and left ventricular fractional shortening (38.8+/-3.1 vs. 55.4+/-1.3%, P<0.01), and resulted in a significant accumulation of ascites (14.4+/-4.9 vs. 0 ml, P<0.01). CAR significantly prevented the cardiomyopathic changes caused by DOX, while ATN did not. The myocardial thiobarbituric acid reactive substances (TBARS) content was significantly higher in DOX-treated rats than in control rats (80.4+/-7.1 vs. 51.5+/-1.2 nmol/g heart, p<0.01). CAR prevented the increase in TBARS content (48.8+/-3.0 nmol/g heart, P<0.01 vs. DOX group), whereas ATN had no significant effect (74.3+/-5.2 nmol/g heart). CAR also significantly prevented the increase in both myocardial and plasma cholesterol concentrations caused by DOX. These data indicate that CAR protects against DOX-induced cardiomyopathy and that this effect may be attributed to the antioxidant and lipid-lowering properties of CAR, not to its beta-blocking property.

Luminol activity of horseradish peroxidase mutants mimicking a proposed binding site for luminol in Arthromyces ramosus peroxidase

To enhance the oxidation activity for luminol in horseradish peroxidase (HRP), we have prepared three HRP mutants by mimicking a possible binding site for luminol in Arthromyces ramosus peroxidase (ARP) which shows 500-fold higher oxidation activity for luminol than native HRP. Spectroscopic studies by (1)H NMR revealed that the chemical shifts of 7-propionate and 8-methyl protons of the heme in cyanide-ligated ARP were deviated upon addition of luminol (4 mM), suggesting that the charged residues, Lys49 and Glu190, which are located near the 7-propionate and 8-methyl groups of the heme, are involved in the specific binding to luminol. The positively charged Lys and negatively charged Glu were introduced into the corresponding positions of Ser35 (S35K) and Gln176 (Q176E) in HRP, respectively, to build the putative binding site for luminol. A double mutant, S35K/Q176E, in which both Ser35 and Gln176 were replaced, was also prepared. Addition of luminol to the HRP mutants induced more pronounced effects on the resonances from the heme substituents and heme environmental residues in the (1)H NMR spectra than that to the wild-type enzyme, indicating that the mutations in this study induced interactions with luminol in the vicinity of the heme. The catalytic efficiencies (V(max)/K(m)) for luminol oxidation of the S35K and S35K/Q176E mutants were 1.5- and 2-fold improved, whereas that of the Q176E mutant was slightly depressed. The increase in luminol activity of the S35K and S35K/Q176E mutants was rather small but significant, suggesting that the electrostatic interactions between the positive charge of Lys35 and the negative charge of luminol can contribute to the effective binding for the luminol oxidation. On the other hand, the negatively charged residue would not be so crucial for the luminol oxidation. The absence of drastic improvement in the luminol activity suggests that introduction of the charged residues into the heme vicinity is not enough to enhance the oxidation activity for luminol as observed for ARP.

Relationship between the apolipoprotein E and angiotensin-converting enzyme genotypes and LDL particle size in Japanese subjects

We investigated whether the apolipoprotein E (apoE) and the angiotensin-converting enzyme (ACE) genotypes contribute to the variance in low-density lipoprotein (LDL) particle size in Japanese subjects (n = 136; M/F= 106/30). ACE polymorphism was associated with neither LDL size nor individual lipid levels. In contrast, the subjects with the epsilon2 allele of the apoE genotype had significantly lower levels of total cholesterol (P = 0.002) and LDL cholesterol (P = 0.004) compared with those without the epsilon2 allele. The subjects with the epsilon4 allele had a significantly smaller LDL particle size than those without the epsilon4 allele (P = 0.012). Separate analyses of the male subjects showed similar associations. A stepwise regression analysis revealed the epsilon4 allele to be an independent contributing variable that could affect LDL particle size. Our results suggest that the apoE genotype is associated with the development of atherosclerotic disease, since the epsilon2 and epsilon4 alleles relate to a decrease in LDL cholesterol levels and a decrease in LDL particle size, respectively.

Zinc accumulation in adriamycin-induced cardiomyopathy in rats: effects of melatonin, a cardioprotective antioxidant

We have recently reported that melatonin protects against adriamycin-induced cardiomyopathy whose pathogenesis may involve free radicals and lipid peroxidation. Melatonin has also been shown to affect zinc turnover. Since zinc may act as an antioxidant, we investigated the role of zinc in the pathogenesis of adriamycin-induced cardiomyopathy as well as in the treatment of melatonin against this disorder. Sprague-Dawley rats were given adriamycin (cumulative dose, 15 mg/kg); melatonin (cumulative dose, 84 mg/kg); adriamycin plus melatonin; adriamycin plus probucol, another antioxidant (cumulative dose, 90 mg/kg); or vehicle alone, according to previously-used regimens. Cardioprotective effects of both antioxidants (melatonin and probucol) were confirmed by the parameters of fractional shortening, heart weight, heart/body weight ratio, ascites volume, and mortality. Adriamycin increased both the myocardial and plasma levels of thiobarbituric acid reactive substances (TBARS) and myocardial zinc levels, and decreased plasma zinc levels. The significant negative correlation observed between the myocardial and plasma zinc levels (r = 0.73, P < 0.01) among the samples of adriamycin-treated and control rats suggested an internal redistribution of zinc. Melatonin and probucol were equally effective in inhibiting the increase in myocardial TBARS as well as zinc levels, suggesting that myocardial zinc accumulation might be a protective response against adriamycin-induced oxidative stress. Melatonin also inhibited the adriamycin-induced decrease in plasma zinc levels; probucol was not as effective in doing so. In addition to melatonin's antioxidative effect, it may have the effect of maintaining the plasma zinc levels.

Crystal structure of a protein with an artificial exon-shuffling, module M4-substituted chimera hemoglobin beta alpha, at 2.5 A resolution

The crystal structure of the homotetramer of a chimera beta alpha-subunit of human hemoglobin was refined at 2.5 A resolution. The chimera subunit was constructed by replacing an exon-encoded module M4 of the beta-subunit with that of the alpha-subunit, simulating an exon-shuffling event. The implanted module M4 retained the native alpha-subunit structure, while module M3 was disturbed around the site where a new type of intron was recently found. Some of the residues were found in alternative conformations that avoid steric hindrance at the subunit interface. The modules are modestly rigid in their backbone structures by using side-chains to compensate for interface incompatibility.

Minimum structure of peptidoglycan required for induction of antibacterial protein synthesis in the silkworm, Bombyx mori

Various peptidoglycan fragments, different in mode of cross-linking and molecular size, were isolated, and the elicitor activity was tested for induction of antibacterial protein synthesis in larvae of Bombyx mori. Linear uncross-linked peptidoglycans from Bacillus licheniformis and Micrococcus luteus were effective elicitors, similar to the directly cross-linked peptidoglycan from B. licheniformis cell wall. The fragments of uncross-linked peptidoglycan with a sugar chain length of four or more were active elicitors, but the disaccharide unit had no elicitor activity. The minimum structure of peptidoglycan required for induction of antibacterial protein synthesis was determined to be two repeating N-acetylglucosamine-N-acetylmuramic acid units with peptide side chains.

The artificial alpha1beta1-contact mutant hemoglobin, Hb Phe-35beta, shows only small functional abnormalities

It was previously reported that Hb Philly with a mutation of Phe for Tyr at 35(C1)beta showed non-cooperative oxygen binding with a very high affinity and instability leading to hemolysis. Further, it lacked the 1H-NMR signal at 13.1 ppm from 2,2-dimethyl-2-silapentane-5-sulfonate in normal hemoglobin (Hb A), so that this signal was assigned to a hydrogen bond formed by Tyr-35(C1)beta. Surprisingly, our artificial mutant hemoglobin with the same mutation as Hb Philly showed slightly lowered oxygen affinity, almost normal cooperativity, the 1H-NMR signal at 13.1 ppm and no sign of instability. Our results indicate that the mutation reported for Hb Philly and the assignment of the 13.1 ppm signal need reexamination.