Remote ischemic preconditioning in patients undergoing cardiac surgery with six ischemic cycles.

BACKGROUND: We have previously shown that remote ischemic preconditioning (RIP), which utilizes in part the extracellular RNA (eRNA)/RNase1 pathway, can induce ischemic tolerance in humans. Because RIP has thus far been tested only with four cycles of extremity ischemia/reperfusion, we investigated the influence of six cycles of ischemia on the eRNA/RNase1 pathway in cardiac patients. METHODS: Six cycles of RIP were carried out in 14 patients undergoing cardiac surgery. Blood samples were taken at 13 timepoints during surgery and at three timepoints after surgery for determining serum levels of RNase1, eRNA, and TNF-α. Trans-cardiac gradients between the myocardial blood inflow and outflow were calculated. RESULTS: Between the fourth and the sixth RIP cycles, a noticeable increase in the levels of eRNA (fourth: 151.6 (SD: 44.2) ng/ml vs sixth: 181.8 (SD: 87.5) ng/ml, p = .071), and a significant increase in RNase1 (fourth: 151.1 (SD: 42.6) U/ml vs sixth: 175.3 (SD: 41.2) U/ml, p = .001), were noted. The trans-cardiac gradients of RNase1 and eRNA before and after ischemia were not significantly different (p = .158 and p = .221; p = .397 and p = .683, respectively). Likewise, the trans-cardiac gradient of TNF-α was similar before and after ischemia. During the first 48 h after the surgery, RNase1 activity rose significantly and exceeded baseline values (135.7 (SD: 40.6) U/ml before and 279.2 (SD: 85.6) U/ml after surgery, p = .001) as did eRNA levels (148,6 (SD: 35.4) ng/ml before and 396.5 (SD: 154.5) ng/ml after surgery, p = .005), whereas TNF-α levels decreased significantly (91.7 (SD: 47.7) pg/ml before and 35.7 (SD: 36.9) pg/ml after surgery, p = .001). CONCLUSION: Six RIP cycles increased the RNase1 levels significantly above those observed with four cycles. More clinical data are required to show whether this translates into a benefit for patients.

Thrombin Promotes Macrophage Polarization into M1-Like Phenotype to Induce Inflammatory Responses.

Despite strong evidence supporting the cellular interplay between haemostasis and innate immunity, humoral connections between blood coagulation and the behavior of inflammatory macrophages are not well understood. In this study, we investigated changes in gene expression of selected cytokines and chemokines and their secretion profiles following thrombin stimulation of murine macrophages. Thrombin promoted differentiation of macrophages into an M1-like phenotype that was associated with the expression of classical pro-inflammatory markers. The cellular actions of thrombin on macrophages were mediated in part by protease-activated receptor-1 (PAR-1) and were dependent on phosphoinositide 3-kinase/AKT and nuclear factor-κB. Moreover, heat-denatured thrombin stimulated the secretion of some pro-inflammatory mediators to the same magnitude indicating that different receptors transmit cellular signals of enzymatically active thrombin and nonactive thrombin, the latter remaining so far undefined. Finally, pretreatment of macrophages with thrombin resulted in tolerance against secondary stimulation by lipopolysaccharide with regard to expression of tumor necrosis factor-α. These results provide new insights into the molecular link between the key enzyme of haemostasis and innate immunity responses.

Responses of Endothelial Cells Towards Ischemic Conditioning Following Acute Myocardial Infarction.

One of the primary therapeutic goals of modern cardiology is to design strategies aimed at minimizing myocardial infarct size and optimizing cardiac function following acute myocardial infarction (AMI). Patients with AMI who underwent reperfusion therapy display dysfunction of the coronary endothelium. Consequently, ischemic endothelial cells become more permeable and weaken their natural anti-thrombotic and anti-inflammatory potential. Ischemia-reperfusion injury (IRI) is associated with activation of the humoral and cellular components of the hemostatic and innate immune system, and also with excessive production of reactive oxygen species (ROS), the inhibition of nitric oxide synthase, and with inflammatory processes. Given its essential role in the regulation of vascular homeostasis, involving platelets and leukocytes among others, dysfunctional endothelium can lead to increased risk of coronary vasospasm and thrombosis. Endothelial dysfunction can be prevented by ischemic conditioning with a protective intervention based on limited intermittent periods of ischemia and reperfusion. The molecular mechanisms and signal transduction pathways underlying conditioning phenomena in the coronary endothelium have been described as involving less ROS production, reduced adhesion of neutrophils to endothelial cells and diminished inflammatory reactions. This review summarizes our current understanding of the cellular and molecular mechanisms regulating IRI-affected and -damaged coronary endothelium, and how ischemic conditioning may preserve its function.

Antitumor Macrophage Response to Bacillus pumilus Ribonuclease (Binase).

Extracellular bacterial ribonucleases such as binase from Bacillus pumilus possess cytotoxic activity against tumor cells with a potential for clinical application. Moreover, they may induce activation of tumor-derived macrophages either into the M1-phenotype with well-documented functions in the regulation of the antitumor immune response or into M2-macrophages that may stimulate tumor growth, metastasis, and angiogenesis. In this study, binase or endogenous RNase1 (but not RNA or short oligonucleotides) stimulated the expression of activated NF-κB p65 subunit in macrophages. Since no changes in MyD88 and TRIF adaptor protein expression were observed, toll-like receptors may not be involved in RNase-related NF-κB pathway activation. In addition, short exposure (0.5 hr) to binase induced the release of cytokines such as IL-6, МСР-1, or TNF-α (but not IL-4 and IL-10), indicative for the polarization into antitumor M1-macrophages. Thus, we revealed increased expression of activated NF-κB p65 subunit in macrophages upon stimulation by binase and RNase1, but not RNA or short oligonucleotides.