Activation of acetylcholine receptor elicits intracellular Ca2+ mobilization, transient cytotoxicity, and induction of RANKL expression

Acetylcholine receptors (AChR) including muscarinic and nicotinic AChR are widely expressed and mediate a variety of physiological cellular responses in neuronal and non-neuronal cells. Notably, a functional cholinergic system exists in oral epithelial cells, and nicotinic AChR (nAChR) mediates cholinergic anti-inflammatory responses. However, the pathophysiological roles of AChR in periodontitis are unclear. Here, we show that activation of AChR elicits increased cytosolic Ca²⁺ ([Ca²⁺]ᵢ), transient cytotoxicity, and induction of receptor activator of nuclear factor kappa-B ligand (RANKL) expression. Intracellular Ca²⁺ mobilization in human gingival fibroblast-1 (hGF-1) cells was measured using the fluorescent Ca²⁺ indicator, fura-2/AM. Cytotoxicity and induction of gene expression were evaluated by measuring the release of glucose-6-phosphate dehydrogenase and RT-PCR. Activation of AChR in hGF-1 cells by carbachol (Cch) induced [Ca²⁺]ᵢ increase in a dose-dependent manner. Treatment with a high concentration of Cch on hGF-1 cells caused transient cytotoxicity. Notably, treatment of hGF-1 cells with Cch resulted in upregulated RANKL expression. The findings may indicate potential roles of AChR in gingival fibroblast cells in bone remodeling.

Relationship between Systolic Anterior Motion of the Mitral Valve and the Left Ventricular Outflow Pressure Gradient in Patients with Hypertrophic Obstructive Cardiomyopathy

To analyze the effects of the characteristics of the systolic anterior motion(SAM) of the mitral valve on the left ventricular outflow pressure gradient and to determine the relation between the anatomical characteristics of the left ventricle and the left ventricular outflow pressure gradient, mitral valve and left ventricular M mode echocardiogram and continuous wave Doppler echocardiogram of the left ventricular outflow tract were recorded in 7 patients with hypertrophic obstructive cardiomyopathy(HOCM), aged 19 to 66 years(mean 37 years). Mitral-septal distance at the closest apposition(S-SAM;1.1+/-2mm), duration of mitral-septal apposition(89+/-20 msec), time interval from the peak of the R-wave to initial apposition of the mitral valve against the interventricular septum(R-SAM interval ; 222+/-32 msec) and left ventricular posterior wall thickness(LVPWT; 1.1+/-0.5mm) were observed on mitral valve and left ventricular M-mode echocardiograms and peak flow velocity in the left ventricular outflow(V-LVOT; 3.5+/-1.5 m/sec) was measured from the Doppler echocardiograms of the left ventricular outflow tract. V-LVOT was correlated significantly with degree of mitral-septal apposition(r=-0.70, p<0.05), duration of mitral-septal apposition(r=0.74, P<0.05), R-SAM interval(r=-0.80, p<0.05) and LVPWT(r=0.78, p<0.05). These results suggest that the closer apposition of mitral valve against interventricular septum, the more prolonged mitral-septal apposition, the earlier onset of SAM of the mitral valve and the thicker the left ventricular posterior wall, the more increase the LV outflow pressure gradient in HOCM.