Identification of pyridinoline, a collagen crosslink, as a novel intrinsic ligand for the receptor for advanced glycation end-products (RAGE).

Advanced glycation end-products (AGEs) elicit inflammatory responses via the receptor for AGEs (RAGE) and participate in the pathogenesis of diabetic complications. An earlier study showed that 3-hydroxypyridinium (3-HP), a common moiety of toxic AGEs such as glyceraldehyde-derived pyridinium (GLAP) and GA-pyridine, is essential for the interaction with RAGE. However, the physiological significance of 3-HP recognition by RAGE remains unclear. We hypothesized that pyridinoline (Pyr), a collagen crosslink containing the 3-HP moiety, could have agonist activity with RAGE. To test this hypothesis, we purified Pyr from bovine achilles tendons and examined its cytotoxicity to rat neuronal PC12 cells. Pyr elicited toxicity to PC12 cells in a concentration-dependent manner, and this effect was attenuated in the presence of either the anti-RAGE antibody or the soluble form of RAGE. Moreover, surface plasmon resonance-based analysis showed specific binding of Pyr to RAGE. These data indicate that Pyr is an intrinsic ligand for RAGE. ABBREVIATIONS: AGEs: advanced glycation end-products; RAGE: receptor for advanced glycation end-products; DAMPs: damage-associated molecular patterns; PRR: pattern recognition receptor; TLR: toll-like receptor; GLAP: glyceraldehyde-derived pyridinium; 3-HP: 3-hydroxypyridinium; Pyr: pyridinoline; HFBA: heptafluorobutyric acid; GST: glutathione S-transferase; SPR: surface plasmon resonance; ECM: extracellular matrix; EMT: epithelial to mesenchymal transition.

Receptor for advanced glycation end products (RAGE)-mediated cytotoxicity of 3-hydroxypyridinium derivatives.

Advanced glycation end products (AGEs) formed from glyceraldehyde (Gcer) and glycolaldehyde (Gcol) are involved in the pathogenesis of diabetic complications, via interactions with a receptor for AGEs (RAGE). In this study, we aimed to elucidate the RAGE-binding structure in Gcer and Gcol-derived AGEs and identify the minimal moiety recognized by RAGE. Among Gcer and Gcol-derived AGEs, GLAP (glyceraldehyde-derived pyridinium) and GA-pyridine elicited toxicity in PC12 neuronal cells. The toxic effects of GLAP and GA-pyridine were suppressed in the presence of anti-RAGE antibody or the soluble form of RAGE protein. Furthermore, the cytotoxicity test using GLAP analog compounds indicated that the 3-hydroxypyridinium (3-HP) structure is sufficient for RAGE-dependent toxicity. Surface plasmon resonance analysis showed that 3-HP derivatives directly interact with RAGE. These results indicate that GLAP and GA-pyridine are RAGE-binding epitopes, and that 3-HP, a common moiety of GLAP and GA-pyridine, is essential for the interaction with RAGE.

Hemocholecyst complicated in a hemodialysis patient with microscopic polyangiitis.

Microscopic polyangiitis (MPA) is a systemic vasculitis associated with antineutrophil cytoplasmic antibodies, and it involves multiple organs, including the kidneys and lungs. We report on the case of a 72-year-old woman with MPA who developed hemocholecyst in addition to alveolar hemorrhage and rapidly progressive glomerulonephritis. Although her renal function was not salvaged, the alveolar hemorrhage and hemocholecyst were treated conservatively. Clinicians should consider the possibility of hemocholecyst in patients with MPA complaining of abdominal pain.

Insight into specific pro-arrhythmic triggers in Brugada and early repolarization syndromes: results of long-term follow-up.

The pro-arrhythmic triggers in Brugada and early repolarization syndromes (BrS, ERS) have not been analyzed systematically except for case reports. We clinically investigated the circumstances which precede/predispose to arrhythmic events in these syndromes during long-term follow-up. A detailed history from the patients/witnesses was taken to investigate the antecedent events in the last few hours that preceded syncope/ventricular fibrillation (VF); medical records, ECG and blood test from the emergency room (ER) were reviewed. 19 patients that fulfilled the investigation criteria were followed up for 71 ± 49 months (34-190 months). Prior to the event (syncope/VF), the patients were partaking different activities in the following decreasing order; drinking alcoholic beverage, having meal, and getting up from sleep, exercise. 3 patients reported mental/physical stress prior to the event and 2 patients developed VF several days after starting oral steroid for treatment of bronchial asthma. In the ER, elevated J-wave amplitude (0.27 ± 0.15 mV) was found with 58 % of the patients having hypokalemia. After electrolyte correction and cessation of steroids, the following day plasma K+ (4.2 ± 0.3 mEq/L, P < 0.001) was significantly increased and J-wave amplitude (0.13 ± 0.1 mV, P < 0.001) was remarkably reduced. Three patients were kept on oral spironolactone/potassium supplements. During follow-up for 71 ± 49 (34-190) months, among 4 patients with VF recurrence, one patient developed VF after taking oral steroid. In ERS and BrS, hypokalemia and corticosteroid therapy add substantial pro-arrhythmic effects, but potentially treatable. Stopping steroid therapy and avoiding hypokalemia had excellent long-term outcome.

Late Gadolinium Enhancement on Cardiac MRI Correlates with QT Dynamicity Represented by QT/RR Relationship in Patients with Ventricular Arrhythmias.

BACKGROUND: The distribution of late gadolinium enhancement (LGE) on the cardiac MRI (CMR) indicates myocardial fibrosis and provides information of possible reentry substrates. QT dynamicity reflecting repolarization abnormalities has gained attention as a potential prognostic predictive factor. OBJECTIVE: To clarify the correlation between the LGE distribution on CMR and QT dynamicity represented by the QT/RR relationship. METHODS: CMR and QT/RR analyses using Holter monitoring were performed in 34 patients (24 males, 60 ± 11 years) with ventricular tachycardia (VT) and/or ventricular fibrillation (VF). The LGE on CMR was scored using a 4-point score in 17 left ventricular segments. The sum of the LGE scores was calculated for each patient. The QT/RR slope and daytime/nighttime QT/RR ratio (day/night ratio) were calculated. The correlation between the slope or the day/night QT/RR ratio and late enhancement findings was analyzed. RESULTS: All patients were divided into 23 LGE positive (LGE(+)) and 11 LGE negative (LGE(-)) patients. The slopes of the QTe/RR and QTa /RR were significantly steeper in the LGE(+) than in LGE(-) patients (0.21 ± 0.03 vs 0.13 ± 0.02; P < 0.001, 0.19 ± 0.03 vs 0.13 ± 0.02; P < 0.001, respectively), and both slopes were significantly correlated with the total LGE scores (r = 0.83, P < 0.001; r = 0.71, P < 0.001, respectively). In the LGE(+) patients, the QTe day/night (1.37 ± 0.38 vs 0.91 ± 0.33; P = 0.002) and QTa day/night ratios (1.33 ± 0.26 vs 1.06 ± 0.30; P = 0.011) were significantly greater than those in the LGE(-) patients. CONCLUSION: The LGE distribution was closely related to the QT dynamicity, suggesting that a combination of these markers can be a powerful tool for understanding the background pathophysiology.

Alteration of histone H3K4 methylation in glomerular podocytes associated with proteinuria in patients with membranous nephropathy.

BACKGROUND: Histone H3K4 trimethylation (H3K4 me3) is found in active euchromatic regions and plays an important role in podocyte function in which actin filaments are abundant in the foot processes. The pathogenesis of membranous nephropathy (MN), the most prevalent cause of primary nephrotic syndrome in the middle-aged and elderly, is podocyte dysfunction. METHODS: We investigated the role of H3K4 me3 in podocyte dysfunction in nephrotic syndrome using cultured podocytes and a mouse proteinuria model induced by LPS. We examined renal biopsy specimens from six patients with nephrotic syndrome caused by Phospholipase-A2-Receptor-positive primary MN. RESULTS: H3K4 me3 exhibited a pattern of nuclear expression in podocytes of the kidneys from patients with MN. The overlapping expression of H3K4 me3 and cathepsin L (a potent endoprotease causing the breakdown of actin-associated protein within lysosomal compartments in kidney podocytes) were higher in patients with MN compared with the controls. Histone H3K4 me3 in kidney podocytes was negatively correlated with synaptopodin, an actin-associated protein in podocytes, and the expression was positively correlated with the proteinuria levels in patients with MN. Histone H3K4 me3 levels were elevated in podocytes of LPS-treated mice, combined with an increase in podocyte swelling, an elevation of serum creatinine and urine albumin, increased cathepsin L, and decreased synaptopodin expression. Histone H3K4 me3 levels at the cathepsin L promoter were elevated in LPS-exposed mouse kidneys. The administration of shRNA against MLL3 (an H3K4 methyltransferase) to LPS-treated mice and cultured podocytes co-cultured with LPS-stimulated macrophages ameliorated podocyte swelling, an elevation in the serum creatinine and urine albumin levels and an increased expression of histone H3K4 me3 and cathepsin L, and a decreased expression of synaptopodin and increase in histone H3K4 me3 levels at the cathepsin L promoter. CONCLUSIONS: Histone H3K4 me3 upregulation may be involved in podocyte dysfunction and the pathophysiology of MN. Targeting this epigenetic signature of histone H3K4 me3 followed by modulating the actin dynamics may be an effective strategy to ameliorate the consequences of MN.

Successful percutaneous transluminal angioplasty for the treatment of renovascular hypertension with an atrophic kidney.

Renovascular hypertension is an important cause of secondary hypertension. We present the case of a 61-year-old man with renovascular hypertension caused by chronic total occlusion of the left renal artery resulting in an atrophic kidney. Although renography indicated almost no residual function of the left kidney, renal vein sampling showed a significant increase of renin secretion in the left kidney. The endocrine function of the left kidney was believed to be preserved; thus, we performed percutaneous transluminal renal angioplasty with stent placement. After the procedure, the patient's blood pressure decreased gradually to within the normal range without adverse events. The laboratory data on endocrine function and the renography findings drastically improved. Percutaneous transluminal renal angioplasty is a promising therapeutic procedure for renovascular hypertension with an atrophic kidney.

Repolarization characteristics in early repolarization and brugada syndromes: insight into an overlapping mechanism of lethal arrhythmias.

INTRODUCTION: We reported impaired QT-rate dependence in early repolarization syndrome (ERS); however, contemporary data have shown peak incidence of sudden cardiac death (SCD) in ERS and Brugada syndrome (BrS) at mid-night and early morning. Taken together, we analyzed the nocturnal QT-rate dependence in both syndromes. METHODS AND RESULTS: A total of 172 subjects were enrolled: 11 ERS, 11 BrS patients, 50 subjects with an uneventful ER pattern (ERP), and 100 non-J-wave control subjects. Ambulatory ECG-derived parameters (QT, QTc, and QT/RR slope) and day-night QT difference were analyzed and compared. Among the groups, there was no significant difference in the average QT or QTc; however, the 24-hour QT/RR slope was significantly smaller in ERS and BrS patients (0.103 ± 0.01 and 0.106 ± 0.01, respectively) than in the control group (0.156 ± 0.03, P < 0.001). Detailed analysis showed a lower day-night QT difference in ERS and BrS patients (19 ±18.7 and 24 ±14 milliseconds, respectively) than in the controls (40 ± 22 milliseconds, P = 0.007) with the lowest QT/RR slopes seen in the ERS and BrS groups from 0 to 3:00 am (QT/RR; 0.076 ± 0.02 vs. 0.092 ± 0.04 vs. 0.117 ± 0.04, for the ERS, BrS, and controls, respectively, P = 0.004) and from 3 to 6 am (QT/RR 0.074 ± 0.03 vs. 0.079 ± 0.02 vs. 0.118 ± 0.04, P < 0.001). CONCLUSION: In a large population of age- and gender-matched groups, both ERS and BrS patients showed attenuated QT-rate dependence and impaired QT day-night modulation that may provide a baseline reentrant substrate. Importantly, QT/RR maladaptation was most evident at mid-night and early morning, which may explain the propensity of such patients to develop SCD during this critical period.

Silencing of p53 RNA through transarterial delivery ameliorates renal tubular injury and downregulates GSK-3ß expression after ischemia-reperfusion injury.

p53, a pivotal protein in the apoptotic pathway, has been identified as a mediator of transcriptional responses to ischemia-reperfusion (IR) injury. The characteristics and functional significance of the p53 response in vivo are largely unknown in IR-induced kidney injury. Therapeutic opportunities of delivering small interfering RNA (siRNA) via venous injection have gained recognition; however, systemic adverse effects of siRNA therapy should be considered. To prevent IR-induced kidney injury, we tested the efficacy of transarterial administration of siRNA targeting p53 (p53 siRNA). Female C57BL/6 mice underwent unilateral renal artery ischemia for 30 min, followed by reperfusion. siRNA experiments utilized short hairpin (sh) RNA plasmid-based approaches. Transfection of shRNA was performed using cationic polymer transfection reagent. Injection of synthetic p53 shRNA into the left renal artery just after ischemia improved tubular injury, apoptosis, and the swelling of mitochondria in cells of the thick ascending limb of Henle (mTALH) at the outer medullary regions. Staining of upregulated p53 was colocalized with the inducible expression of glycogen synthase kinase-3ß (GSK-3ß) at mTALH after IR injury. p53 shRNA inhibited GSK-3ß expression and restored ß-catenin expression at mTALH. For IR-induced kidney injury, transarterial delivery of p53 siRNA is an effective pharmacological intervention. Targeting siRNA to p53 leads to an attenuation of apoptosis and mitochondrial damage through the downregulation of GSK-3ß expression and upregulation of ß-catenin. Local delivery of vectors such as p53 siRNA through a transaortic catheter is clinically useful in reducing the adverse effect of siRNA-related therapy.

Epicardial adipose tissue is associated with prevalent atrial fibrillation in patients with hypertrophic cardiomyopathy.

Prevalent atrial fibrillation (AF) in patients with hypertrophic cardiomyopathy (HCM) represents an important issue with regard to stroke events caused by embolization and is associated with high mortality. Increased epicardial adipose tissue (EAT), which shows high metabolic activity, can locally influence the activity of the autonomic ganglia, enhancing autonomic dysregulation and increasing the likelihood of AF. We tested the hypothesis that EAT is associated with prevalent AF in HCM patients. Sixty-two patients with idiopathic HCM diagnosed on the basis of ultrasound cardiography findings and histopathological evaluation of myocardium obtained by right ventricular biopsy underwent cardiac magnetic resonance imaging to estimate the extent of EAT. EAT area was significantly higher in the group with AF episodes than in the group without. An increased incidence of AF was found to be significantly related to an increase in EAT, and this association persisted after adjustment for body mass index, sex, and age. Time domain measures of heart rate variability measured by Holter electrocardiography, standard deviation of normal to normal, and standard deviation of the average of normal to normal were negatively related to EAT area. EAT was positively correlated with intraventricular septal thickness and cystatin C level and negatively correlated with the 24-hour creatinine clearance rate. Increased EAT area in HCM patients is significantly related to the presence of AF, which is associated with changes in baseline autonomic nervous tone, left ventricular mass, and chronic kidney disease.

Mizoribine for crescentic glomerulonephritis with sarcoidosis: effectiveness not only for urinalysis abnormalities but also for hilar lymph node enlargement.

Sarcoidosis is a multisystem disease related to helper T cell responses. We recently experienced the case of a 57-year-old woman with sarcoidosis complicated by crescentic glomerulonephritis with low levels of myeloperoxidase-antineutrophil cytoplasmic antibody. We herein describe the details of her clinical course and discuss the effectiveness of mizoribine, which has an immunosuppressive effect equivalent to that of mycophenolate mofetil, not only for urinalysis abnormalities but also for hilar lymph node enlargement.

The intrinsic prostaglandin E2-EP4 system of the renal tubular epithelium limits the development of tubulointerstitial fibrosis in mice.

Inflammatory responses in the kidney lead to tubulointerstitial fibrosis, a common feature of chronic kidney diseases. Here we examined the role of prostaglandin E(2) (PGE(2)) in the development of tubulointerstitial fibrosis. In the kidneys of wild-type mice, unilateral ureteral obstruction leads to progressive tubulointerstitial fibrosis with macrophage infiltration and myofibroblast proliferation. This was accompanied by an upregulation of COX-2 and PGE(2) receptor subtype EP(4) mRNAs. In the kidneys of EP(4) gene knockout mice, however, obstruction-induced histological alterations were significantly augmented. In contrast, an EP(4)-specific agonist significantly attenuated these alterations in the kidneys of wild-type mice. The mRNAs for macrophage chemokines and profibrotic growth factors were upregulated in the kidneys of wild-type mice after ureteral obstruction. This was significantly augmented in the kidneys of EP(4)-knockout mice and suppressed by the EP(4) agonist but only in the kidneys of wild-type mice. Notably, COX-2 and MCP-1 proteins, as well as EP(4) mRNA, were localized in renal tubular epithelial cells after ureteral obstruction. In cultured renal fibroblasts, another EP(4)-specific agonist significantly inhibited PDGF-induced proliferation and profibrotic connective tissue growth factor production. Hence, an endogenous PGE(2)-EP(4) system in the tubular epithelium limits the development of tubulointerstitial fibrosis by suppressing inflammatory responses.

Thromboxane A2 and prostaglandin F2alpha mediate inflammatory tachycardia.

Systemic inflammation induces various adaptive responses including tachycardia. Although inflammation-associated tachycardia has been thought to result from increased sympathetic discharge caused by inflammatory signals of the immune system, definitive proof has been lacking. Prostanoids, including prostaglandin (PG) D(2), PGE(2), PGF(2alpha), PGI(2) and thromboxane (TX) A(2), exert their actions through specific receptors: DP, EP (EP(1), EP(2), EP(3), EP(4)), FP, IP and TP, respectively. Here we have examined the roles of prostanoids in inflammatory tachycardia using mice that lack each of these receptors individually. The TXA(2) analog I-BOP and PGF(2alpha) each increased the beating rate of the isolated atrium of wild-type mice in vitro through interaction with TP and FP receptors, respectively. The cytokine-induced increase in beating rate was markedly inhibited in atria from mice lacking either TP or FP receptors. The tachycardia induced in wild-type mice by injection of lipopolysaccharide (LPS) was greatly attenuated in TP-deficient or FP-deficient mice and was completely absent in mice lacking both TP and FP. The beta-blocker propranolol did not block the LPS-induced increase in heart rate in wild-type animals. Our results show that inflammatory tachycardia is caused by a direct action on the heart of TXA(2) and PGF(2alpha) formed under systemic inflammatory conditions.

Prostaglandin I2 promotes recruitment of endothelial progenitor cells and limits vascular remodeling.

OBJECTIVE: Endothelial progenitor cells (EPCs) play an important role in the self-healing of a vascular injury by participating in the reendothelialization that limits vascular remodeling. We evaluated whether prostaglandin I(2) plays a role in the regulation of the function of EPCs to limit vascular remodeling. METHODS AND RESULTS: EPCs (Lin(-)cKit(+)Flk-1(+) cells) were isolated from the bone marrow (BM) of wild-type (WT) mice or mice lacking the prostaglandin I(2) receptor IP (IP(-/-) mice). Reverse transcription-polymerase chain reaction analysis showed that EPCs among BM cells specifically express IP. The cellular properties of EPCs, adhesion, migration, and proliferation on fibronectin were significantly attenuated in IP-deficient EPCs compared with WT EPCs. In contrast, IP agonists facilitated these functions in WT EPCs, but not in IP-deficient EPCs. The specific deletion of IP in BM cells, which was performed by transplanting BM cells of IP(-/-) mice to WT mice, accelerated wire injury-mediated neointimal hyperplasia in the femoral artery. Notably, transfused WT EPCs, but not IP-deficient EPCs, were recruited to the injured vessels, participated in reendothelialization, and efficiently rescued the accelerated vascular remodeling. CONCLUSIONS: These findings clearly indicate that the prostaglandin I(2)-IP system is essential for EPCs to accomplish their function and plays a critical role in the regulation of vascular remodeling.

Comparison between unattended automated office blood pressure and conventional office blood pressure under the environment of health checkup among Japanese general population.

Unattended automated office blood pressure (AOBP) measurement has been endorsed as the preferred in-office measurement modality in recent Canadian and American clinical practice guidelines. However, the difference between AOBP and conventional office blood pressure (CBP) under the environment of a health checkup remains unclear. We aimed to identify the clinical significance of AOBP as compared to CBP under the environment of a health checkup. There were 491 participants (333 females, mean age of 62.5 years) who were at least 20 years old, including 179 participants who were previously diagnosed with hypertension. Mean AOBPs were 131.8 ± 20.9/76.6 ± 11.7 mm Hg, and CBPs were 135.6 ± 21.6/77.3 ± 11.5 mm Hg. There was a difference of 3.9 mm Hg in systolic blood pressure (SBP) and 0.8 mm Hg in diastolic BP between AOBP and CBP. In all participants, SBP and pulse pressure, as well as the white coat effect (WCE), increased with age. The cutoff value used was 140/90 mm Hg for CBP and 135/85 mm Hg for AOBP, and the prevalence of WCE and masked hypertension effect (MHE) was 12.4% and 14.1%, respectively. Even in a health checkup environment of the general population, there was a difference between the AOBP and CBP, and the WCE was observed more strongly in the elderly with a history of hypertension, suggesting that a combination of AOBP with CBP may be useful in detecting WCE and MHE in all clinical scenarios including health checkups, and help solve the "hypertension paradox" not only in Japan but in all over the world.

Decreased susceptibility to renovascular hypertension in mice lacking the prostaglandin I2 receptor IP.

Persistent reduction of renal perfusion pressure induces renovascular hypertension by activating the renin-angiotensin-aldosterone system; however, the sensing mechanism remains elusive. Here we investigated the role of PGI2 in renovascular hypertension in vivo, employing mice lacking the PGI2 receptor (IP-/- mice). In WT mice with a two-kidney, one-clip model of renovascular hypertension, the BP was significantly elevated. The increase in BP in IP-/- mice, however, was significantly lower than that in WT mice. Similarly, the increases in plasma renin activity, renal renin mRNA, and plasma aldosterone in response to renal artery stenosis were all significantly lower in IP-/- mice than in WT mice. All these parameters were measured in mice lacking the four PGE2 receptor subtypes individually, and we found that these mice had similar responses to WT mice. PGI2 is produced by COX-2 and a selective inhibitor of this enzyme, SC-58125, also significantly reduced the increases in plasma renin activity and renin mRNA expression in WT mice with renal artery stenosis, but these effects were absent in IP-/- mice. When the renin-angiotensin-aldosterone system was activated by salt depletion, SC-58125 blunted the response in WT mice but not in IP-/- mice. These results indicate that PGI2 derived from COX-2 plays a critical role in regulating the release of renin and consequently renovascular hypertension in vivo.

Augmented cardiac hypertrophy in response to pressure overload in mice lacking the prostaglandin I2 receptor.

BACKGROUND: In the heart, the expressions of several types of prostanoid receptors have been reported. However, their roles in cardiac hypertrophy in vivo remain unknown. We intended to clarify the roles of these receptors in pressure overload-induced cardiac hypertrophy using mice lacking each of their receptors. METHODS AND RESULTS: We used a model of pressure overload-induced cardiac hypertrophy produced by banding of the transverse aorta in female mice. In wild-type mice subjected to the banding, cardiac hypertrophy developed during the observation period of 8 weeks. In mice lacking the prostaglandin (PG) I2 receptor (IP(-/-)), however, cardiac hypertrophy and cardiomyocyte hypertrophy were significantly greater than in wild-type mice at 2 and 4 weeks but not at 8 weeks, whereas there was no such augmentation in mice lacking the prostanoid receptors other than IP. In addition, cardiac fibrosis observed in wild-type hearts was augmented in IP(-/-) hearts, which persisted for up to 8 weeks. In IP(-/-) hearts, the expression level of mRNA for atrial natriuretic peptide, a representative marker of cardiac hypertrophy, was significantly higher than in wild-type hearts. In vitro, cicaprost, an IP agonist, reduced platelet-derived growth factor-induced proliferation of wild-type noncardiomyocytes, although it could not inhibit cardiotrophin-1-induced hypertrophy of cardiomyocytes. Accordingly, cicaprost increased cAMP concentration efficiently in noncardiomyocytes. CONCLUSIONS: IP plays a suppressive role in the development of pressure overload-induced cardiac hypertrophy via the inhibition of both cardiomyocyte hypertrophy and cardiac fibrosis. Both effects have been suggested as originating from the action on noncardiomyocytes rather than cardiomyocytes.

Oral pretreatment with ebselen enhances heat shock protein 72 expression and reduces myocardial infarct size.

Reactive oxygen species (ROS) enhance myocardial ischemia-reperfusion (I/R) injury. Ebselen, a seleno-organic glutathione peroxidase (GPx) mimetic, has a protective effect against tissue injury induced by ROS. However, the cardio-protective effect of orally administered ebselen has never been investigated in cardiac I/R injury. We investigated the effects and mechanisms of orally administered ebselen on experimental myocardial infarction. Isolated perfused rabbit hearts underwent 30 min of global ischemia and 60 min of reperfusion, with or without oral administration of ebselen 24 h before I/R, with or without enhanced oxidative stress by H202 infusion for the first 1 min of reperfusion. The recovery of left ventricular developed pressure (LVDP) was significantly improved, and the myocardial infarct size was significantly reduced by ebselen. The recovery of LVDP and the myocardial infarct size were markedly aggravated by H202 infusion. These enhancements by H202 were dose-dependently suppressed by ebselen, along with a reduction in myocardial 8-hydroxydeoxyguanosine levels, a marker for oxidative DNA damage. The myocardial reduced glutathione (GSH) level was preserved by ebselen. Ebselen markedly enhanced myocardial heat shock protein (HSP) 72 expression. The cardioprotective effect of ebselen-induced HSP72 was confirmed by MTT assay in isolated cardiomyocytes using KNK437, a novel HSP inhibitor. In conclusion, an oral administration of ebselen 24 h before I/R provided excellent cardioprotective effects, at least in part through HSP72 induction and GSH preservation.

Prostaglandin E2 protects the heart from ischemia-reperfusion injury via its receptor subtype EP4.

BACKGROUND: In the heart with acute myocardial infarction, production of prostaglandin (PG) E2 increases significantly. In addition, several subtypes of PGE2 receptors (EPs) have been reported to be expressed in the heart. The role of PGE2 in cardiac ischemia-reperfusion (I/R) injury, however, remains unknown. We intended to clarify the role of PGE2 via EP4, an EP subtype, in I/R injury using mice lacking EP4 (EP4-/- mice). METHODS AND RESULTS: In murine cardiac ventricle, competitive reverse transcription-polymerase chain reaction revealed the highest expression level of EP4 mRNA among EP mRNAs. EP4-/- mice had larger infarct size than wild-type mice in a model of I/R; the left anterior descending coronary artery was occluded for 1 hour, followed by 24 hours of reperfusion. In addition, isolated EP4-/- hearts perfused according to the Langendorff technique had greater functional and biochemical derangements in response to I/R than wild-type hearts. In vitro, AE1-329, an EP4 agonist, raised cAMP concentration remarkably in noncardiomyocytes, whereas the action was weak in cardiomyocytes. When 4819-CD, another EP4 agonist, was administered 1 hour before coronary occlusion, it reduced infarct size significantly in wild-type mice. Notably, a similar cardioprotective effect was observed even when it was administered 50 minutes after coronary occlusion. CONCLUSIONS: Both endogenous PGE2 and an exogenous EP4 agonist protect the heart from I/R injury via EP4. The potent cardioprotective effects of 4819-CD suggest that the compound would be useful for treatment of acute myocardial infarction.

Thromboxane A2 regulates vascular tone via its inhibitory effect on the expression of inducible nitric oxide synthase.

BACKGROUND: Circulatory failure in sepsis arises from vascular hyporesponsiveness, in which nitric oxide (NO) derived from inducible NO synthase (iNOS) plays a major role. Details of the cross talk between thromboxane (TX) A2 and the iNOS-NO system, however, remain unknown. We intended to clarify the role of TXA2, via the cross talk, in vascular hyporesponsiveness. METHODS AND RESULTS: We examined cytokine-induced iNOS expression and NO production in cultured vascular smooth muscle cells (VSMCs) and cytokine-induced hyporesponsiveness of the aorta from mice lacking the TXA2 receptor (TP-/- mice). The cytokine-induced iNOS expression and NO production observed in wild-type VSMCs were significantly augmented in TP-/- VSMCs, indicating an inhibitory effect of endogenous TXA2 on iNOS expression. Furthermore, in indomethacin-treated wild-type VSMCs, U-46619, a TP agonist, inhibited cytokine-induced iNOS expression and NO production in a concentration-dependent manner, effects absent from TP-/- VSMCs. In an ex vivo system, the cytokine-induced hyporesponsiveness of aortas to phenylephrine was significantly augmented in TP-/- aorta but was almost completely canceled by aminoguanidine, an iNOS inhibitor. Accordingly, cytokine-induced NO production was significantly higher in TP-/- aorta than in wild-type aorta. Moreover, U-46619 significantly suppressed lipopolysaccharide-induced NO production in vivo only in wild-type mice. CONCLUSIONS: These results suggest that TXA2 has a protective role against the development of vascular hyporesponsiveness via its inhibitory action on the iNOS-NO system under pathological conditions such as sepsis.