Intracellular calcium changes induced by the endozepine triakontatetraneuropeptide in human polymorphonuclear leukocytes: role of protein kinase C and effect of calcium channel blockers

BACKGROUND: The endozepine triakontatetraneuropeptide (TTN) induces intracellular calcium ([Ca(++)](i)) changes followed by activation in human polymorphonuclear leukocytes (PMNs). The present study was undertaken to investigate the role of protein kinase (PK) C in the modulation of the response to TTN by human PMNs, and to examine the pharmacology of TTN-induced Ca(++ )entry through the plasma membrane of these cells. RESULTS: The PKC activator 12-O-tetradecanoylphorbol-13-acetate (PMA) concentration-dependently inhibited TTN-induced [Ca(++)](i )rise, and this effect was reverted by the PKC inhibitors rottlerin (partially) and Ro 32-0432 (completely). PMA also inhibited TTN-induced IL-8 mRNA expression. In the absence of PMA, however, rottlerin (but not Ro 32-0432) per se partially inhibited TTN-induced [Ca(++)](i )rise. The response of [Ca(++)](i )to TTN was also sensitive to mibefradil and flunarizine (T-type Ca(++)-channel blockers), but not to nifedipine, verapamil (L-type) or ω-conotoxin GVIA (N-type). In agreement with this observation, PCR analysis showed the expression in human PMNs of the mRNA for all the α1 subunits of T-type Ca(++ )channels (namely, α1G, α1H, and α1I). CONCLUSIONS: In human PMNs TTN activates PKC-modulated pathways leading to Ca(++ )entry possibly through T-type Ca(++ )channels

Demographic and clinical characteristics of the subjects classified by Lp-PLA2 activity quartiles.

<p>Results are expressed as mean ± SD. BMI, body mass index; K⁺, potassium; Na⁺, sodium; BP, Blood Pressure; HDL, high density lipoprotein; LDL, low density lipoprotein; EF, ejection fraction; CAD, coronary artery disease.</p

Cardiovascular events by Lp-PLA2 mass.

<p>The bar graphs show cardiovascular death and events rate by quartiles of Lp-PLA2 mass (the absolute number of events is shown above each column). Cardiovascular deaths (p = 0.020) were significantly different across Lp-PLA2 mass quartiles. AMI: acute myocardial infarction.</p

Stepwise linear regression analysis of determinants of Lp-PLA2 mass and activity.

<p>Significant predictors of Lp-PLA2 mass were creatinine, HDL- and LDL. Significant predictors of Lp-PLA2 activity were gender, HDL- and LDL-cholesterol, and homocysteinemia.</p

Cardiovascular events by Lp-PLA2 activity.

<p>The bar graphs show cardiovascular death and events rate by quartiles of Lp-PLA2 activity (the absolute number of events is shown above each column). Cardiovascular deaths (p = 0.012), events (p = 0.016), acute myocardial infarction (AMI) (p = 0.019) were significantly different across Lp-PLA2 activity quartiles.</p

Demographic and clinical characteristics of the subjects classified by Lp-PLA2 mass quartiles.

<p>Results are expressed as mean ± SD. BMI, body mass index; K⁺, potassium; Na⁺, sodium; BP, Blood Pressure; HDL, high density lipoprotein; LDL, low density lipoprotein; EF, ejection fraction; CAD, coronary artery disease.</p

Data analysis flow chart.

<p>The flow chart shows the selection process by which the patients were submitted to statistical analysis.</p

Cardiovascular events- and acute coronary syndromes-free survival.

<p>Kaplan-Meier curves show cardiovascular (CV) events- (left Panel) and acute coronary syndromes (ACS)-free survival (right Panel) in the propensity score-matched high-risk patients divided into the high and low Lp-PLA2 activity group. Patients with high Lp-PLA2 activity had a significantly lower CV events-free survival and a significantly lower ACS-free survival.</p