Tsuneo Konta

Unexpected transcriptional induction of monocyte chemoattractant protein 1 by proteasome inhibition: involvement of the c-Jun N-terminal kinase-activator protein 1 pathway.

Proteasome inhibitors, the well-known inhibitors of NF-κB, are recently considered therapeutic agents for inflammation. However, the anti-inflammatory properties of these agents have not been fully evaluated. In this report we describe a novel effect of proteasome inhibitors on the expression of monocyte chemoattractant protein 1 (MCP-1) in mesangial cells. We found that proteasome inhibitor MG132 dose-dependently induced expression of MCP-1 at the transcriptional level. The stimulatory effect was similarly observed with other proteasome inhibitors (proteasome inhibitor 1 and lactacystin) and in other cell types (NRK fibroblasts). The 5′-flanking region of the MCP-1 gene contains multiple AP-1 sites. To explore the mechanisms involved, we examined the effects of proteasome inhibition on the AP-1 pathway. Northern blot analysis showed that MG132 rapidly induced the expression of c-jun, but not c-fos. Immunoblot analysis showed that MG132 prevented degradation of c-Jun protein. Kinase assay revealed that c-Jun N-terminal kinase (JNK) was rapidly activated by MG132. Consistent with these results, a reporter assay showed that AP-1 activity was up-regulated after treatment with MG132. Curcumin, a pharmacological inhibitor of the JNK-AP-1 pathway, abrogated the induction of MCP-1 by MG132. Similarly, stable transfection with a dominant-negative mutant of c-Jun attenuated both MG132-induced activation of AP-1 and expression of MCP-1. The transcriptional activation by proteasome inhibitors was observed not only in MCP-1, but also in other AP-1-dependent genes, including stromelysin and mitogen-activated protein kinase phosphatase 1. These data revealed that proteasome inhibition triggered the expression of MCP-1 and other genes via the multistep induction of the JNK-c-Jun/AP-1 pathway.

Transcriptional Induction of Mitogen-activated Protein Kinase Phosphatase 1 by Retinoids SELECTIVE ROLES OF NUCLEAR RECEPTORS AND CONTRIBUTION TO THE ANTIAPOPTOTIC EFFECT

All-trans-retinoic acid (t-RA) inhibits hydrogen peroxide (H2O2)-induced apoptosis by inhibiting the c-Jun N-terminal kinase (JNK)-activator protein 1 (AP-1) pathway. In this report, we examined the involvement of mitogen-activated protein kinase phosphatase 1 (MKP-1) in suppression of JNK and the antiapoptotic effect of t-RA and the roles of nuclear receptors in the regulation of MKP-1 by t-RA. We found that not only t-RA, but also a selective agonist of retinoic acid receptor (RAR), a selective agonist of retinoid X receptor (RXR), and a pan-agonist of RAR and RXR all induced MKP-1 at the transcriptional level. Activation of RAR was required for all of these triggering effects, but activation of RXR was required only for the RXR agonist-induced MKP-1 expression. Among the three RAR subtypes, RARα and RARγ, but not RARβ, mediated the t-RA-induced MKP-1 expression. The antiapoptotic effect of t-RA on H2O2-induced apoptosis in several cell types was correlated with the inducibility of MKP-1 by t-RA. Inhibition of MKP-1 by vanadate enhanced JNK phosphorylation and attenuated the antiapoptotic effect of t-RA. Furthermore, overexpression of MKP-1 inhibited H2O2-induced JNK phosphorylation and apoptosis. To our knowledge, this is the first to demonstrate that 1) MKP-1 is inducible by retinoids at the transcriptional level, 2) RXR and individual RAR subtypes have different roles in this process, and 3) the induced MKP-1 plays a significant role in mediating both JNK inhibition and the antiapoptotic effect of t-RA in oxidative stress.

Clinical utility of trace proteinuria for microalbuminuria screening in the general population

BackgroundThe urine dipstick test that regards > 1+ proteinuria as positive is unsuitable for microalbuminuria screening owing to its low sensitivity in the general population. We conducted a cross-sectional survey to examine whether trace proteinuria could be an indicator of microalbuminuria.MethodsThe subjects were 2321 participants in a community-based health check-up in Takahata, Japan. Dipstick tests for proteinuria and the urine albumin–creatinine ratio (UACR) measurement were performed with single-spot urine specimens collected early in the morning. The results of the dipstick tests were recorded as (−), trace, (1+), (2+), and (3+). Micro- and macroalbuminuria were defined as UACR 30–300 mg/g and > 300 mg/g, respectively.ResultsOverall, the prevalence and median UACR levels of urine protein (−), trace, (1+), (2+), and (3+) were 92.0% (8.8 mg/g), 3.5% (43 mg/g), 2.6% (81 mg/g), 1.4% (315 mg/g), and 0.5% (1073 mg/g), respectively. Within the trace proteinuria category, the prevalence of microalbuminuria in all subjects, men, subjects ≥60 years, diabetic subjects, and hypertensive subjects was 59.3%, 73.8%, 71.2%, 88.9%, and 68.0%, respectively. By regarding trace proteinuria as positive, the sensitivity of the urine protein dipstick test for micro- and macroalbuminuria was improved (from 23.3% to 37.1%), while its specificity was not significantly changed (from 98.9% to 97.3%).ConclusionTrace proteinuria could be a useful indicator of microalbuminuria in the general population, and especially in subjects at high risk of cardiovascular disease.

Association between prehypertension and chronic kidney disease in the Japanese general population

The increased prevalence of chronic kidney disease (CKD) is a consequence of the accumulation of risk factors, one of which is hypertension. Here we assessed the prevalence of CKD according to blood pressure among 232,025 patients in a Japanese nationwide database with a focus on the prevalence and risk factors of CKD in prehypertension. Patients were stratified by blood pressure and included 75,474 with optimal blood pressure (less than 120/80 mm Hg); 59,194 with prehypertension and a normal blood pressure (120-129/80-84 mm Hg) or 46,547 patients with high-normal blood pressure (130-139/85-89 mm Hg); and 50,810 with hypertension (over 140/90 mm Hg without anti-hypertensive drugs). CKD was defined as an estimated glomerular filtration rate of stage 3 or lower or having proteinuria greater than 1+ by a dipstick method. The prevalence of CKD among patients with optimal blood pressure, prehypertension having normal or high-normal blood pressure, and hypertension was 13.9, 15.6, 18.1, and 20.7% in men, and 10.9, 11.6, 12.9, and 15.0% in women, with a significant difference between genders at each strata of blood pressure. In men, but not in women, whose blood pressure was high-normal, the CKD risk was significantly greater (odds ratio 1.11) than those with optimal blood pressure. Obesity (body mass index over 25) was significantly associated with an increased risk of CKD in both men and women (odds ratio 1.43 and 1.26, respectively), and there was an additive effect of obesity and pre-hypertension on CKD risk in men compared with men with optimal blood pressure. Thus, the prevalence of CKD increased with the severity of blood pressure. Prehypertension with high-normal blood pressure, particularly in conjunction with obesity, was found to be an independent risk factor of CKD in men.

Long-Term Blood Pressure Variability, New-Onset Diabetes Mellitus, and New-Onset Chronic Kidney Disease in the Japanese General Population

Whether long-term blood pressure (BP) variability among individuals without diabetes mellitus is associated with new-onset chronic kidney disease (CKD) risk, independently of other BP parameters (eg, mean BP, cumulative exposure to BP) and metabolic profile changes during follow-up, remains uncertain. We used data from a nationwide study of 48 587 Japanese adults aged 40 to 74 years (mean age, 61.7 years; 39% men) without diabetes mellitus or CKD (estimated glomerular filtration rate <60 mL/min per 1.73 m2 or proteinuria by dipstick). BP was measured at baseline and during 3 annual follow-up visits (4 visits). BP variability was defined as standard deviation (SD) and average real variability during the 4 visits. At the year 3 follow-up visit, 6.3% of the population had developed CKD. In multivariable-adjusted logistic regression models, 1 SD increases in SDSBP (per 5 mmHg), SDDBP (per 3 mmHg), average real variabilitySBP (per 6 mmHg), and average real variabilityDBP (per 4 mmHg) were associated with new-onset CKD (odds ratios [ORs] and 95% confidence intervals, 1.15 [1.11–1.20], 1.08 [1.04–1.12], 1.13 [1.09–1.17], 1.06 [1.02–1.10], respectively; all P<0.01) after adjustment for clinical characteristics, and with mean BP from year 0 to year 3. The associations of SDBP and average real variabilityBP with CKD remained significant after additional adjustments for metabolic parameter changes during follow-up (ORs, 1.06–1.15; all P<0.01). Sensitivity analyses by sex, antihypertensive medication use, and the presence of hypertension showed similar conclusions. Among those in the middle-aged and elderly general population without diabetes mellitus, long-term BP variability during 3 years was associated with new-onset CKD risk, independently of mean or cumulative exposure to BP and metabolic profile changes during follow-up.

MAP kinase-dependent, NF-κB-independent regulation of inhibitor of apoptosis protein genes by TNF-α

The inhibitor of apoptosis protein (IAP) family of molecules regulates apoptotic processes triggered by various stimuli. However, the mechanisms involved in the regulation of the IAP genes are not fully understood. In this report, we examined roles of nuclear factor‐κB (NF‐κB) and mitogen‐activated protein (MAP) kinases in tumor necrosis factor‐α (TNF‐α)‐induced expression of IAP genes. In human endothelial cells, TNF‐α induced c‐IAP1 and c‐IAP2, but not XIAP and TIAP/Survivin, at the transcriptional level. Inactivation of NF‐κB by overexpression of a super‐repressor mutant of IκBα did not affect the induction of IAPs by TNF‐α. In contrast, extracellular signal‐regulated kinase, p38 MAP kinase, and c‐Jun N‐terminal kinase were activated after stimulation with TNF‐α, and inhibition of each kinase by PD098059, SB203580, curcumin, or SP600125 substantially attenuated the TNF‐α‐induced c‐IAP1 and c‐IAP2 expression. To examine whether the MAP kinases‐mediated induction of IAPs contributes to survival of TNF‐α‐exposed cells, cells were pretreated with MAP kinase inhibitors and stimulated with TNF‐α. Treatment with kinase inhibitors alone did not induce apoptosis but enhanced markedly TNF‐α‐triggered apoptosis. Furthermore, overexpression of either c‐IAP1 or c‐IAP2 diminished the apoptosis‐promoting effects of MAP kinase inhibitors. These data indicated that TNF‐α induced expression of c‐IAP1 and c‐IAP2 via MAP kinases, but not via NF‐κB, and that MAP kinases participated in the inhibition of apoptosis by induction of c‐IAPs in TNF‐α‐stimulated endothelial cells. J. Cell. Physiol. 210: 703–710, 2007.

A Lower Level of Forced Expiratory Volume in 1 Second Is a Risk Factor for All-Cause and Cardiovascular Mortality in a Japanese Population: The Takahata Study

Chronic obstructive pulmonary disease is a known risk factor for cardiovascular death in Western countries. Because Japan has a low cardiovascular death rate, the association between a lower level of forced expiratory volume in 1 s (FEV1) and mortality in Japan’s general population is unknown. To clarify this, we conducted a community-based longitudinal study. This study included 3253 subjects, who received spirometry from 2004 to 2006 in Takahata, with a 7-year follow-up. The causes of death were assessed on the basis of the death certificate. In 338 subjects, airflow obstruction was observed by spirometry. A total of 127 subjects died. Cardiovascular death was the second highest cause of death in this population. The pulmonary functions of the deceased subjects were significantly lower than those of the subjects who were alive at the end of follow-up. The relative risk of death by all causes, respiratory failure, lung cancer, and cardiovascular disease was significantly increased with airflow obstruction. The Kaplan–Meier analysis showed that all-cause and cardiovascular mortality significantly increased with a worsening severity of airflow obstruction. After adjusting for possible factors that could influence prognosis, a Cox proportional hazard model analysis revealed that a lower level of FEV1 was an independent risk factor for all-cause and cardiovascular mortality (per 10% increase; hazard ratio [HR], 0.89; 95% confidence interval [CI], 0.82–0.98; and HR, 0.72; 95% CI, 0.61–0.86, respectively). In conclusion, airflow obstruction is an independent risk factor for all-cause and cardiovascular death in the Japanese general population. Spirometry might be a useful test to evaluate the risk of cardiovascular death and detect the risk of respiratory death by lung cancer or respiratory failure in healthy Japanese individuals.

Protein kinase C and extracellular signal regulated kinase are involved in cardiac hypertrophy of rats with progressive renal injury

Increased cardiovascular mortality is an unresolved problem in patients with chronic renal failure. Cardiac hypertrophy is observed in the majority of patients with chronic renal failure undergoing haemodialysis. However, the mechanisms, including signal transduction pathways, responsible for cardiac hypertrophy in renal failure remain unknown. We examined the subcellular localization of protein kinase C (PKC) isoforms and phosphorylation activities of 3 mitogen‐activated protein (MAP) kinase families in hypertrophied hearts of progressive renal injury rat model by subtotal nephrectomy (SNx). We also examined the effects of a novel angiotensin II type‐1 receptor antagonist, CS‐866, on the PKC translocation, MAP kinase activity and cardiac hypertrophy in SNx rats. The left ventricle/body weight ratios were significantly larger in SNx rats than in sham rats at 1, 2, and 4 weeks after surgery. The translocation of PKCα and ɛ isoforms to membranous fraction was observed in SNx rat hearts at 1, 2, and 4 weeks after surgery. Activation of extracellular signal regulated kinase (ERK) 1/2, but not p38 MAP kinase and c‐Jun N‐terminal kinase (JNK), was observed at 1 and 2 weeks after surgery. Angiotensin II receptor blockade with CS‐866 (1 mg kg−1 day−1) prevented cardiac hypertrophy, PKC translocation and ERK1/2 activation in SNx rats without significant changes in blood pressure. These data suggest that PKC and ERK1/2 are activated by an angiotensin II receptor‐mediated pathway and might play an important role in the progression of cardiac hypertrophy in renal failure.

Association between Combined Lifestyle Factors and Non-Restorative Sleep in Japan: A Cross-Sectional Study Based on a Japanese Health Database

Background Although lifestyle factors such as cigarette smoking, excessive drinking, obesity, low or no exercise, and unhealthy dietary habits have each been associated with inadequate sleep, little is known about their combined effect. The aim of this study was to quantify the overall impact of lifestyle-related factors on non-restorative sleep in the general Japanese population. Methods and Findings A cross-sectional study of 243,767 participants (men, 39.8%) was performed using the Specific Health Check and Guidance System in Japan. A healthy lifestyle score was calculated by adding up the number of low-risk lifestyle factors for each participant. Low risk was defined as (1) not smoking, (2) body mass index<25 kg/m2, (3) moderate or less alcohol consumption, (4) regular exercise, and (5) better eating patterns. Logistic regression analysis was used to examine the relationship between the score and the prevalence of non-restorative sleep, which was determined from questionnaire responses. Among 97,062 men (mean age, 63.9 years) and 146,705 women (mean age, 63.7 years), 18,678 (19.2%) and 38,539 (26.3%) reported non-restorative sleep, respectively. The prevalence of non-restorative sleep decreased with age for both sexes. Compared to participants with a healthy lifestyle score of 5 (most healthy), those with a score of 0 (least healthy) had a higher prevalence of non-restorative sleep (odds ratio, 1.59 [95% confidence interval, 1.29–1.97] for men and 2.88 [1.74–4.76] for women), independently of hypertension, hypercholesterolemia, diabetes, and chronic kidney disease. The main limitation of the study was the cross-sectional design, which limited causal inferences for the identified associations. Conclusions A combination of several unhealthy lifestyle factors was associated with non-restorative sleep among the general Japanese population. Further studies are needed to establish whether general lifestyle modification improves restorative sleep.

Retinoic Acid Regulation of Mesangial Cell Apoptosis

Retinoic acid (RA) is recently used for the treatment of experimental glomerular diseases. However, mechanisms underlying its therapeutic effects are largely unknown. We recently reported that RA has the potential for protecting certain cells from particular injury. A typical example is its effect on oxidant-induced apoptosis of mesangial cells. Mesangial cells exposed to hydrogen peroxide undergo apoptosis through activation of the c-Jun N-terminal kinase activator protein 1 pathway. RA dramatically inhibits this process via suppression of c-fos/c-jun expression and inhibition of the c-Jun N-terminal kinase activation. The anti-apoptotic effect of RA is mediated by both nuclear receptor dependent and nuclear receptor independent mechanisms and is, at least in part, mediated by induction of mitogen-activated protein kinase phosphatase 1. In this review, we briefly summarize the current knowledge on molecular mechanisms involved in the anti-apoptotic effects of RA.