Background-Inflammation plays a key role in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury; however, the mechanism by which myocardial I/R induces inflammation remains unclear. Recent evidence indicates that a sterile inflammatory response triggered by tissue damage is mediated through a multiple-protein complex called the inflammasome. Therefore, we hypothesized that the inflammasome is an initial sensor for danger signal(s) in myocardial I/R injury. Methods and Results-We demonstrate that inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes, is crucially involved in the initial inflammatory response after myocardial I/R injury. We found that inflammasomes are formed by I/R and that its subsequent activation of inflammasomes leads to interleukin-1␤ production, resulting in inflammatory responses such as inflammatory cell infiltration and cytokine expression in the heart. In mice deficient for apoptosis-associated speck-like adaptor protein and caspase-1, these inflammatory responses and subsequent injuries, including infarct development and myocardial fibrosis and dysfunction, were markedly diminished. Bone marrow transplantation experiments with apoptosis-associated speck-like adaptor protein-deficient mice revealed that inflammasome activation in bone marrow cells and myocardial resident cells such as cardiomyocytes or cardiac fibroblasts plays an important role in myocardial I/R injury. In vitro experiments revealed that hypoxia/reoxygenation stimulated inflammasome activation in cardiac fibroblasts, but not in cardiomyocytes, and that hypoxia/reoxygenation-induced activation was mediated through reactive oxygen species production and potassium efflux. Conclusions-Our results demonstrate the molecular basis for the initial inflammatory response after I/R and suggest that the inflammasome is a potential novel therapeutic target for preventing myocardial I/R injury. (Circulation. 2011;123:594-604.)Key Words: cytokine Ⅲ heart Ⅲ hypoxia Ⅲ inflammation Ⅲ leukocyte I ncreasing evidence indicates that inflammation is involved in the pathophysiology of myocardial ischemia/reperfusion (I/R) injury. 1 One prominent and early mediator for inflammation in I/R injury is interleukin-1␤ (IL-1␤). 2,3 I/R induces IL-1␤ expression in the heart, and the inhibition of IL-1␤ prevents myocardial injury after I/R, 3 suggesting that the deleterious effects of myocardial I/R are mediated, at least in part, by IL-1␤. In the generation of IL-1␤, pro-IL-1␤, an inactive precursor, undergoes proteolysis by the converting enzyme caspase-1. Caspase-1 is activated within a cytosolic multiprotein complex, the inflammasome. The inflammasome contains cytoplasmic receptors of the NACHT leucine-rich-repeat protein family that are associated with the apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC), which in turn recruits and activates caspase-1. 4,5 Increasing evidence indicates that several sterile inflammatory responses triggered by tissue damage are mediated by th...

Glutamate released by activated microglia induces excitoneurotoxicity and may contribute to neuronal damage in neurodegenerative diseases, including Alzheimer disease, Parkinson disease, amyotrophic lateral sclerosis, and multiple sclerosis. In addition, tumor necrosis factor-␣ (TNF-␣) secreted from activated microglia may elicit neurodegeneration through caspasedependent cascades and silencing cell survival signals. However, direct neurotoxicity of TNF-␣ is relatively weak, because TNF-␣ also increases production of neuroprotective factors. Accordingly, it is still controversial how TNF-␣ exerts neurotoxicity in neurodegenerative diseases. Here we have shown that TNF-␣ is the key cytokine that stimulates extensive microglial glutamate release in an autocrine manner by up-regulating glutaminase to cause excitoneurotoxicity. Further, we have demonstrated that the connexin 32 hemichannel of the gap junction is another main source of glutamate release from microglia besides glutamate transporters. Although pharmacological blockade of glutamate receptors is a promising therapeutic candidate for neurodegenerative diseases, the associated perturbation of physiological glutamate signals has severe adverse side effects. The unique mechanism of microglial glutamate release that we describe here is another potential therapeutic target. We rescued neuronal cell death in vitro by using a glutaminase inhibitor or hemichannel blockers to diminish microglial glutamate release without perturbing the physiological glutamate level. These drugs may give us a new therapeutic strategy against neurodegenerative diseases with minimum adverse side effects.

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Background— AL amyloidosis with heart failure is associated with decreased longitudinal myocardial contraction measured by pulsed tissue Doppler imaging. We sought to clarify whether new modalities of myocardial strain Doppler (change in length per unit length) or strain rate (the temporal derivative of strain) were more sensitive than tissue Doppler and could detect early regional myocardial dysfunction before the onset of congestive heart failure (CHF) in patients with AL (primary) amyloidosis. Methods and Results— Ninety-seven biopsy-proven patients with AL amyloidosis were divided into 3 groups. Group 1 patients had no cardiac involvement (n=36), group 2 had heart involvement but no CHF (n=32), and group 3 had heart involvement and CHF (n=29). All patients underwent tissue velocity (TV) imaging, strain, and strain rate imaging (SR) at the basal, mid, and apical ventricle in 2 apical views. With the use of TV, differences in systolic function were only apparent between group 3 (basal mean value, 3.0±1.1 cm/s) and groups 1 and 2 (5.0±1.3 and 4.6±1.2 cm/s, respectively). In contrast, basal peak systolic SR (l/s) showed significant differences among all 3 groups (−2.0±0.4, −1.55±0.6, and −0.76±0.3 for groups 1 to 3, respectively. P <0.01). Basal strain also demonstrated statistically significant differences among the groups (−19±4%, −15±4.5%, and −8.0±5%; P <0.01). Conclusions— Cardiac amyloidosis is characterized by an early impairment in systolic function at a time when fractional shortening remains normal. This abnormality precedes the onset of CHF and can be detected by strain and SR but is not apparent by TV imaging.