Takeki Hata

Inflammasome Activation of Cardiac Fibroblasts Is Essential for Myocardial Ischemia/Reperfusion Injury

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&bgr; 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.

Bone marrow CXCR4 induction by cultivation enhances therapeutic angiogenesis

AIMS The chemokine stromal cell-derived factor-1 (SDF-1) and its receptor (CXCR4, CXC chemokine receptor 4) play a critical role in the process of post-natal neovascularization. Here, we investigated the role of CXCR4(+) bone marrow cells (BMCs) in neovascularization in a murine hindlimb ischaemia model. METHODS AND RESULTS We found that the expression of CXCR4 in BMCs was specifically upregulated by cultivation; therefore, we used freshly isolated BMCs and cultivated BMCs, designated as BMC(Fr) and BMC(Cul), respectively. The increased CXCR4 expression corresponded to the migratory capacity in response to SDF-1 alpha. Real-time reverse transcription-polymerase chain reaction and immunohistochemical analyses revealed that SDF-1 alpha expression was significantly increased in the ischaemic limbs of mice. Blood flow perfusion and capillary density were significantly accelerated in mice implanted with BMC(Cul) as compared with those in mice implanted with BMC(Fr). The stimulatory effect of BMC(Cul) on neovascularization was significantly impaired when BMC(Cul) derived from CXCR4(+/-) mice were implanted. The implanted BMC(Cul) showed high retention in the ischaemic limbs. Further, the implantation of BMC(Cul) significantly increased the expression of interleukin (IL)-1 beta and vascular endothelial growth factor-A in the ischaemic limbs. CONCLUSION The upregulation of CXCR4 expression by cultivation may serve as a useful source of BMCs for accelerating therapeutic angiogenesis in ischaemic cardiovascular diseases.

Critical role of Th17 cells in inflammation and neovascularization after ischaemia

AIMS Increasing evidence suggests that CD4(+) T cells contribute to neovascularization in ischaemic tissue. However, the T cell subset responsible for neovascularization after ischaemia remains to be determined. Here, we investigated the role of Th17 cells secreting interleukin (IL)-17, a newly identified subset of CD4(+) T cells, in the neovascularization after murine hindlimb ischaemia. METHODS AND RESULTS Unilateral hindlimb ischaemia was produced in wild-type (WT) C57BL/6 mice. Depletion of CD4(+) T cells resulted in significantly reduced blood flow perfusion in the ischaemic limbs. The expression of IL-17 and retinoic acid receptor-related orphan receptor γt (RORγt) was up-regulated in the ischaemic limbs. IL-17-deficient mice showed a significant reduction in blood flow perfusion, inflammatory cell infiltration, and production of angiogenic cytokines in the ischaemic limbs compared with WT mice. In bone marrow transplantation experiments, the absence of IL-17 specifically in bone marrow cells diminished the neovascularization after ischaemia. Furthermore, IL-17-deficient CD4(+) T cells transferred into the ischaemic limbs of T cell-deficient athymic nude mice evoked a significantly limited neovascularization compared with WT CD4(+) T cells. CONCLUSION These findings identify Th17 cells as a new angiogenic T cell subset and provide new insight into the mechanism by which T cells promote neovascularization after ischaemia.

Endomyocardial biopsy in a patient with hemorrhagic pheochromocytoma presenting as inverted Takotsubo cardiomyopathy.

A 29-year-old female patient presented with shock and dyspnea due to heart failure and pulmonary edema. Echocardiography indicated excessive contraction limited to the left ventricular apex and akinesis of the basal and middle ventricle, which were confirmed by emergency left ventriculography. The finding was diagnostic of inverted Takotsubo cardiomyopathy. An abdominal computed tomography scan showed a tumor in the left adrenal gland with a central low-density area, and the plasma and urinary catecholamines were strikingly elevated. Taken together, these findings suggested the presence of a hemorrhagic pheochromocytoma. A myocardial biopsy in the very acute stage on the day of admission revealed neutrophilic infiltration and contraction-band necrosis, which was indistinguishable from the previously reported pathology in the acute phase of idiopathic Takotsubo cardiomyopathy without pheochromocytoma. The diagnosis of pheochromocytoma in this case was confirmed 7 weeks later by surgical removal of the left adrenal gland with massive hemorrhage at the center of the pheochromocytoma. The marked similarity of the endomyocardial pathology between this case and cases with idiopathic Takotsubo cardiomyopathy strongly points to catecholamine excess as a common causality for Takotsubo cardiomyopathy with or without pheochromocytoma.