Detection of the full-length transcript variant for neurokinin-1 receptor in human whole blood associated with enhanced reinforcement of clot by substance-P

Involvement of superoxide generated by NADPH oxidase in the shedding of procoagulant vesicles from human monocytic cells exposed to bupivacaine

It is known that a variety of sized procoagulant vesicles that express tissue factor are released from several types of cells including monocytes by mechanisms related to the induction of apoptosis, while it has not yet been evaluated whether superoxide is involved in the production of such vesicles. Here, we report that a local anesthetic bupivacaine induces apoptosis in human monocytic cells THP-1 within a short observation period, where the shedding of procoagulant vesicles is associated. The property as procoagulant vesicles was evaluated using flow cytometry by the binding of FITC-conjugated fibrinogen to vesicles in the presence of fresh frozen plasma and the suppression of this binding by heparin. Bupivacaine (1 mg/ml) increased the apoptotic cells and procoagulant vesicles. LY294002 (100 µM), that inhibits the recruiting of intracellular component of NADPH oxidase to construct the activated form of this enzyme complex, or superoxide dismutase (1500 unit/ml) suppressed bupivacaine-provoked induction of apoptosis and the increase of procoagulant vesicles. We suggest that this simple experimental system is useful to explore the molecular mechanisms of action of superoxide in the shedding of procoagulant vesicles from human monocytic cells.

Truncation of neurokinin-1 receptor-Negative regulation of substance P signaling

Substance P (SP) is a tachykinin peptide, which triggers intracellular signaling in the nervous and immune systems, as well as, other local and systemic events. The interaction between SP and its receptor, neurokinin-1 receptor (NK1R), results in major downstream cellular actions, which include changes in calcium fluxes, ERK, and p21-activated kinase phosphorylation and NFκB activation. Two naturally occurring variants of the NK1R, the full-length, 407 aa receptor (NK1R-F) and the truncated, 311 aa isoform (NK1R-T), mediate the actions of SP. Receptor truncation partially disrupts signaling motifs of the carboxyl tail, a critical site for mediating NK1R signaling, resulting in a "less-efficient" receptor. Although NK1R-F is the predominant isoform in the central and peripheral nervous systems, NK1R-T is expressed in several tissues and cells, which include monocytes, NK cells, and T-cells. The SP binding domain is not affected by truncation and this site is identical in both NK1R receptor isoforms. However, while cells expressing NK1R-F respond to nanomolar concentrations of SP, monocyte and macrophage activation, mediated through NK1R-T, requires micromolar concentrations of SP in order to elicit signaling responses. Elevated plasma levels of SP are associated with increased inflammatory responses and NK1R antagonists reduce inflammation and cytokine production in vivo. This mini review presents and discusses the novel hypothesis that the expression of NK1R-T on immune system cells prevents immune activation in a milieu, which usually contains low concentrations of SP and, thus, maintains immune homeostasis. In contrast, in the activated neuronal microenvironment, when SP levels reach the threshold at tissue sites, SP promotes immune activation and modulates monocyte/macrophage polarization.

Pro-substance p for evaluation of risk in acute myocardial infarction

BACKGROUND

Pro-substance P (ProSP) is a stable surrogate marker for labile substance P, which has pro-inflammatory effects, increases platelet aggregation and clot strength, and reduces fibrinolysis.

OBJECTIVES

This study assessed whether ProSP was associated with poor prognosis after acute myocardial infarction (AMI) to identify novel pathophysiological mechanisms.

METHODS

ProSP was measured in 1,148 AMI patients (825 men, mean age 66.2 ± 12.8 years). Endpoints were major adverse cardiac events (composite of death, reinfarction, and heart failure [HF] hospitalization), death/reinfarction, and death/HF. GRACE (Global Registry of Acute Coronary Events) scores were compared with ProSP for death and/or reinfarction at 6 months.

RESULTS

During 2-year follow-up, there were 140 deaths, 112 HF hospitalizations, and 149 re-AMI. ProSP levels were highest on the first 2 days after admission and related to estimated glomerular filtration rate, age, history of diabetes, ischemic heart disease or hypertension, Killip class, left ventricular wall motion index, and sex. Multivariate Cox regression models showed ProSP level was a predictor of major adverse events (hazard ratio [HR]: 1.30; 95% confidence interval [CI]: 1.10 to 1.54; p < 0.002), death and/or AMI (HR: 1.42; 95% CI: 1.20 to 1.68; p < 0.0005), death and/or HF (HR: 1.38; 95% CI: 1.14 to 1.67; p < 0.001). ProSP levels with GRACE scores were independent predictors of 6-month death and/or reinfarction (p < 0.0005 for both). ProSP-adjusted GRACE scores reclassified patients significantly (overall category-free net reclassification improvement of 31.6 (95% CI: 14.3 to 49.0; p < 0.0005) mainly by down-classifying those without endpoints.

CONCLUSIONS

ProSP levels post-AMI are prognostic for death, recurrent AMI, or HF, and they improve risk prediction of GRACE scores, predominantly by down-classifying risk in those without events.