RNA-based thermoregulation of a Campylobacter jejuni zinc resistance determinant.

RNA thermometers (RNATs) trigger bacterial virulence factor expression in response to the temperature shift on entering a warm-blooded host. At lower temperatures these secondary structures sequester ribosome-binding sites (RBSs) to prevent translation initiation, whereas at elevated temperatures they "melt" allowing translation. Campylobacter jejuni is the leading bacterial cause of human gastroenteritis worldwide yet little is known about how it interacts with the host including host induced gene regulation. Here we demonstrate that an RNAT regulates a C. jejuni gene, Cj1163c or czcD, encoding a member of the Cation Diffusion Facilitator family. The czcD upstream untranslated region contains a predicted stem loop within the mRNA that sequesters the RBS to inhibit translation at temperatures below 37°C. Mutations that disrupt or enhance predicted secondary structure have significant and predictable effects on temperature regulation. We also show that in an RNAT independent manner, CzcD expression is induced by Zn(II). Mutants lacking czcD are hypersensitive to Zn(II) and also over-accumulate Zn(II) relative to wild-type, all consistent with CzcD functioning as a Zn(II) exporter. Importantly, we demonstrate that C. jejuni Zn(II)-tolerance at 32°C, a temperature at which the RNAT limits CzcD production, is increased by RNAT disruption. Finally we show that czcD inactivation attenuates larval killing in a Galleria infection model and that at 32°C disrupting RNAT secondary structure to allow CzcD production can enhance killing. We hypothesise that CzcD regulation by metals and temperature provides a mechanism for C. jejuni to overcome innate immune system-mediated Zn(II) toxicity in warm-blooded animal hosts.

Time-to-reperfusion therapy influences outcome of patients with myocardial infarction subjected to facilitated PCI.

AIM: The purpose of this study was to evaluate the impact of time-to-reperfusion on outcome after facilitated percutaneous coronary intervention (PCI) i.e. PCI following early pharmacological reperfusion therapy in ST-segment elevation myocardial infarction (STEMI). METHODS AND RESULTS: The study population consisted of 262 consecutive patients with STEMI, aged <75 years, without cardiogenic shock, presenting <12 hours of chest pain onset, transferred from community hospitals to a catheterization laboratory with time delay >90 min after pharmacological reperfusion therapy (alteplase i.v. bolus 15 mg followed by an infusion - 35 mg/60 min; abciximab i.v. bolus 0.25 mg/kg followed by a 12-hour infusion - 0.125 microg/kg/min; unfractionated heparin i.v. bolus 40 U/kg [maximum 3000 U]). One hundred seventeen patients (44.7%) received pharmacological reperfusion therapy <3 h after chest pain onset, 101 (38.5%) at 3-6 h and 44 patients (16.8%) >6 h. Patent infarct-related artery rates at initial angiography were similar among the study groups. PCI significantly improved epicardial flow in all three groups. Mortality at 12 months was significantly related to time-to-pharmacological reperfusion (3.4% [<3 h], 4.0% [3-6 h], 13.6% [>6 h], p = 0.027). At 6 months left ventricular ejection fraction was significantly improved in the two groups of patients with time-to-pharmacological reperfusion <6 hours and the time-to-pharmacological reperfusion was the independent predictor of lack of left ventricular ejection fraction recovery. CONCLUSION: Our study shows that among STEMI patients undergoing facilitated PCI, time-to-pharmacological reperfusion significantly affects left ventricular function recovery and long-term mortality.