Yanjuan Yang

Deletion of Interleukin-6 Attenuates Pressure Overload-Induced Left Ventricular Hypertrophy and Dysfunction

RATIONALE The role of interleukin (IL)-6 in the pathogenesis of cardiac myocyte hypertrophy remains controversial. OBJECTIVE To conclusively determine whether IL-6 signaling is essential for the development of pressure overload-induced left ventricular (LV) hypertrophy and to elucidate the underlying molecular pathways. METHODS AND RESULTS Wild-type and IL-6 knockout (IL-6(-/-)) mice underwent sham surgery or transverse aortic constriction (TAC) to induce pressure overload. Serial echocardiograms and terminal hemodynamic studies revealed attenuated LV hypertrophy and superior preservation of LV function in IL-6(-/-) mice after TAC. The extents of LV remodeling, fibrosis, and apoptosis were reduced in IL-6(-/-) hearts after TAC. Transcriptional and protein assays of myocardial tissue identified Ca(2+)/calmodulin-dependent protein kinase II (CaMKII) and signal transducer and activator of transcription 3 (STAT3) activation as important underlying mechanisms during cardiac hypertrophy induced by TAC. The involvement of these pathways in myocyte hypertrophy was verified in isolated cardiac myocytes from wild-type and IL-6(-/-) mice exposed to prohypertrophy agents. Furthermore, overexpression of CaMKII in H9c2 cells increased STAT3 phosphorylation, and exposure of H9c2 cells to IL-6 resulted in STAT3 activation that was attenuated by CaMKII inhibition. Together, these results identify the importance of CaMKII-dependent activation of STAT3 during cardiac myocyte hypertrophy via IL-6 signaling. CONCLUSIONS Genetic deletion of IL-6 attenuates TAC-induced LV hypertrophy and dysfunction, indicating a critical role played by IL-6 in the pathogenesis of LV hypertrophy in response to pressure overload. CaMKII plays an important role in IL-6-induced STAT3 activation and consequent cardiac myocyte hypertrophy. These findings may have significant therapeutic implications for LV hypertrophy and failure in patients with hypertension.

PRESSURE-OVERLOAD INDUCED LV HYPERTROPHY AND DYSFUNCTION: CRITICAL ROLES OF CAMKII AND P38 MAP KINASE IN ER STRESS SIGNALING PATHWAY

The role of endoplasmic reticulum (ER) stress in pressure overload-induced LV hypertrophy and dysfunction is poorly understood. The specific roles of CaMKII and p38 signaling remain unclear. Transverse aortic constriction (TAC) was performed in age-matched CHOP knockout (KO) mice and controls.

NF-KB INHIBITION PROTECTS AGAINST MYOCARDIAL ISCHEMIA/REPERFUSION INJURY VIA ACTIVATION OF ANTIAPOPTOTIC SIGNALING

The molecular details of nuclear factor-kappaB (NF-kB) signaling during myocardial ischemia/reperfusion (I/R) injury remain poorly understood. We hypothesized that inhibition of NF-kB would prevent cell death. We used transgenic mice overexpressing a mutant IkBα with consequent cardiac-specific

CARDIAC-SPECIFIC TRANSGENIC INHIBITION OF NF-KB ACTIVATION PROTECTS AGAINST MYOCARDIAL ISCHEMIA/REPERFUSION INJURY

Nuclear factor-kappaB (NF-kB), a stress-responsive transcription factor, has been implicated in various cardiovascular pathologies. Although NF-kB is necessary for late preconditioning, its summative role in myocardial ischemia/reperfusion (I/R) injury remains unclear. Using mice with cardiac-

CARDIAC-SPECIFIC TRANSGENIC SILENCING OF NF-KB AMELIORATES LEFT VENTRICULAR DYSFUNCTION AND REMODELING AFTER ACUTE MYOCARDIAL INFARCTION

After an acute myocardial infarction (MI), the left ventricle (LV) undergoes remodeling with progressive deterioration in function. The role of nuclear factor-kappaB (NF-kB) signaling in the genesis of ischemic heart failure remains unclear. We examined the role of NF-kB in post-MI cardiomyopathy