Motoi Kobayashi

A newly estimated glomerular filtration rate is independently associated with arterial stiffness in Japanese patients.

Chronic kidney disease (CKD) is associated with an increased risk of cardiovascular disease, and thus is a major worldwide public health problem. Recently, an estimated glomerular filtration rate (eGFR) using the Modification of Diet in Renal Disease equation for Japanese patients was proposed by the Japanese Society of Nephrology. However, the role of eGFR in the assessment of atherosclerosis is not well understood in Japanese patients. We analyzed the relationship between eGFR and severity of arterial stiffness using brachial-ankle pulse wave velocity (baPWV) in 647 adult Japanese patients. baPWV correlated significantly and positively with age, hypertension, diabetes, prior cardiovascular disease, blood pressure, pulse pressure and heart rate, and negatively with eGFR (r=−0.405, p<0.0001). A multiple regression analysis revealed that baPWV correlated independently with eGFR. Furthermore, there was a stepwise increase in baPWV, corresponding to advances in CKD through stages 1 to 5. When CKD stage 3 was divided at eGFR 45 mL/min/1.73 m2, the baPWV of stage 3b (eGFR 30 to 44) was significantly higher than that of stage 3a (eGFR 45 to 59) independent of traditional risk factors, suggesting that an eGFR of 45 mL/min/1.73 m2 may be a critical cut off value to predict arterial stiffness in CKD. In conclusion, the newly proposed eGFR is significantly associated with arterial stiffness, independent of traditional risk factors for cardiovascular disease.

NLRP3 Deficiency Reduces Macrophage Interleukin-10 Production and Enhances the Susceptibility to Doxorubicin-induced Cardiotoxicity.

NLRP3 inflammasomes recognize non-microbial danger signals and induce release of proinflammatory cytokine interleukin (IL)-1β, leading to sterile inflammation in cardiovascular disease. Because sterile inflammation is involved in doxorubicin (Dox)-induced cardiotoxicity, we investigated the role of NLRP3 inflammasomes in Dox-induced cardiotoxicity. Cardiac dysfunction and injury were induced by low-dose Dox (15 mg/kg) administration in NLRP3-deficient (NLRP3−/−) mice but not in wild-type (WT) and IL-1β−/− mice, indicating that NLRP3 deficiency enhanced the susceptibility to Dox-induced cardiotoxicity independent of IL-1β. Although the hearts of WT and NLRP3−/− mice showed no significant difference in inflammatory cell infiltration, macrophages were the predominant inflammatory cells in the hearts, and cardiac IL-10 production was decreased in Dox-treated NLRP3−/− mice. Bone marrow transplantation experiments showed that bone marrow-derived cells contributed to the exacerbation of Dox-induced cardiotoxicity in NLRP3−/− mice. In vitro experiments revealed that NLRP3 deficiency decreased IL-10 production in macrophages. Furthermore, adeno-associated virus-mediated IL-10 overexpression restored the exacerbation of cardiotoxicity in the NLRP3−/− mice. These results demonstrated that NLRP3 regulates macrophage IL-10 production and contributes to the pathophysiology of Dox-induced cardiotoxicity, which is independent of IL-1β. Our findings identify a novel role of NLRP3 and provided new insights into the mechanisms underlying Dox-induced cardiotoxicity.

The balance of fetuin-A and osteoprotegerin is independently associated with diastolic dysfunction in hemodialysis patients

Fetuin-A and osteoprotegerin (OPG) are arterial calcification regulators, which are related to cardiovascular survival in hemodialysis patients. We hypothesized that a balance of these calcification regulators might mediate the progression of left ventricular (LV) diastolic dysfunction in hemodialysis patients. We recruited 63 hemodialysis patients and measured their serum fetuin-A, OPG, arterial stiffness, aortic calcification and echocardiographic parameters, including the transmitral early diastolic velocity/tissue Doppler mitral annular early diastolic velocity ratio (E/E′), and analyzed the relationships between these variables. Fetuin-A levels were significantly and negatively correlated with the ankle–brachial pulse wave velocity (baPWV), aortic calcification score (AOCS), left atrial volume index (LAVI), LV mass index (LVMI) and E/E′. OPG levels and the ratio of OPG to fetuin-A levels were significantly and positively correlated with the baPWV, AOCS, LAVI and E/E′. A stepwise multiple regression analysis revealed that E/E′ was independently correlated with fetuin-A levels (β=−0.334, P=0.02), OPG levels (β=0.367, P=0.01) and the ratio of OPG to fetuin-A (β=0.295, P=0.04). Categorizing the patients according to their serum fetuin-A and OPG levels revealed that patients with low fetuin-A and high OPG levels had the highest LAVI, LVMI and E/E′ values after adjusting for potential confounders. Serum fetuin-A levels negatively reflected, whereas OPG levels and the ratio of OPG to fetuin-A positively reflected an increase in vascular and ventricular stiffness, leading to the aggravation of diastolic dysfunction. Therefore, based on our results, the balance of the tissue calcification regulators fetuin-A and OPG could mediate the progression of LV diastolic dysfunction in hemodialysis patients.

The cardiac glycoside ouabain activates NLRP3 inflammasomes and promotes cardiac inflammation and dysfunction

Cardiac glycosides such as digoxin are Na+/K+-ATPase inhibitors that are widely used for the treatment of chronic heart failure and cardiac arrhythmias; however, recent epidemiological studies have suggested a relationship between digoxin treatment and increased mortality. We previously showed that nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing 3 (NLRP3) inflammasomes, which regulate caspase-1-dependent interleukin (IL)-1β release, mediate the sterile cardiovascular inflammation. Because the Na+/K+–ATPase is involved in inflammatory responses, we investigated the role of NLRP3 inflammasomes in the pathophysiology of cardiac glycoside-induced cardiac inflammation and dysfunction. The cardiac glycoside ouabain induced cardiac dysfunction and injury in wild-type mice primed with a low dose of lipopolysaccharide (LPS), although no cardiac dysfunction was observed in mice treated with either ouabain or LPS alone. Ouabain also induced cardiac inflammatory responses, such as macrophage infiltration and IL-1β release, when mice were primed with LPS. These cardiac manifestations were all significantly attenuated in mice deficient in IL-1β. Furthermore, deficiency of NLRP3 inflammasome components, NLRP3 and caspase-1, also attenuated ouabain-induced cardiac dysfunction and inflammation. In vitro experiments revealed that ouabain induced NLRP3 inflammasome activation as well as subsequent IL-1β release from macrophages, and this activation was mediated by K+ efflux. Our findings demonstrate that cardiac glycosides promote cardiac inflammation and dysfunction through NLRP3 inflammasomes and provide new insights into the mechanisms underlying the adverse effects of cardiac glycosides.

Three cases of corticosteroid therapy triggering ventricular fibrillation in J-wave syndromes

We describe three cases of J-wave syndrome in which ventricular fibrillation (VF) was probably induced by corticosteroid therapy. The patients involved were being treated with prednisolone for concomitant bronchial asthma. One of the three patients had only one episode of VF during her long follow-up period (14 years). Two patients had hypokalemia during their VF episodes. Corticosteroids have been shown to induce various types of arrhythmia and to modify cardiac potassium channels. We discuss the possible association between corticosteroid therapy and VF in J-wave syndrome based on the cases we have encountered.