Hemorrhagic shock and reperfusion injury: the critical interplay of fibrin fragments, leukocytes, and vascular endothelial-cadherin

Biomimetic Strategies To Treat Traumatic Brain Injury by Leveraging Fibrinogen

There were over 27 million new cases of traumatic brain injuries (TBIs) in 2016 across the globe. TBIs are often part of complicated trauma scenarios and may not be diagnosed initially because the primary clinical focus is on stabilizing the patient. Interventions used to stabilize trauma patients may inadvertently impact the outcomes of TBIs. Recently, there has been a strong interest in the trauma community toward administrating fibrinogen-containing solutions intravenously to help stabilize trauma patients. While this interventional shift may benefit general trauma scenarios, fibrinogen is associated with potentially deleterious effects for TBIs. Here, we deconstruct what components of fibrinogen may be beneficial as well as potentially harmful following TBI and extrapolate this to biomimetic approaches to treat bleeding and trauma that may also lead to better outcomes following TBI.

Effects of tirofiban on the reperfusion-related no-reflow in rats with acute myocardial infarction

Objective

To investigate the effects of tirofiban on the no-reflow phenomenon of acute myocardial infarction (AMI) rats received reperfusion, as well as the underlying mechanisms.

Methods

Fifty-six male Sprague-Dawley rats were randomly divided into four groups: Sham operation group (Sham), AMI/reperfusion group (AMI/R), Tirofiban group (Tiro) and Tiro+N-nitro-L-arginine group (L-NNA; an endothelial nitric oxide synthase inhibitor). To generate the animal model mimicking the no-reflow phenomenon, the rats first received occlusion of the left anterior descending coronary artery for 60 min and then followed by reperfusion for 120 min. Area of no-reflow, area at risk and area of necrosis were measured by thioflavine S, Evans blue and triphenyl tetrazolium chloride staining, respectively. Haemodynamic function was measured at the end. In the meantime, nitric oxide synthase (NOS) activity was determined by a NOS assay kit. The expression of myocardial endothelial nitric oxide synthase (eNOS) was determined by an enzyme-linked immunosorbent assay (ELISA). The expression of phosphorylated eNOS at Ser¹¹⁷⁷ (p-eNOS Ser¹¹⁷⁷) and vascular endothelial-cadherin (VE-cadherin) were determined by western blot.

Results

Compared with AMI/R group, tirofiban significantly reduced the no-reflow area and infarct size (all P < 0.05). Tirofiban elevated eNOS activity, lessen inducible nitric oxide synthase (iNOS) activity and increased the expression of Ser¹¹⁷⁷ phosphorylated eNOS and VE-cadherin in the ischemic myocardium (all P < 0.05). No statistical differences were found in the expression of eNOS among the four groups. Also, tirofiban improved cardiac function with significantly higher levels of left ventricular end systolic pressure, maximum change rate of left ventricular pressure rise and fall, heart rate, and lower level of left ventricular end diastolic pressure than those of the AMI/R group (all P < 0.05). Whereas, these effects of tirofiban were partially abolished by L-NNA.

Conclusions

Tirofiban could reduce the size of no-reflow and infarct. A possible mechanism underlying this effect is that tirofiban could protect the structural and functional integrity of microvascular endothelium which is partially regulated by eNOS activity.

Recombinant factor XIII mitigates hemorrhagic shock-induced organ dysfunction

BACKGROUND

Plasma factor XIII (FXIII) is responsible for stabilization of fibrin clot at the final stage of blood coagulation. Since FXIII has also been shown to modulate inflammation, endothelial permeability, as well as diminish multiple organ dysfunction (MOD) after gut ischemia-reperfusion injury, we hypothesized that FXIII would reduce MOD caused by trauma-hemorrhagic shock (THS).

MATERIALS AND METHODS

Rats were subjected to a 90 min THS or trauma sham shock (TSS) and treated with either recombinant human FXIII A(2) subunit (rFXIII) or placebo immediately after resuscitation with shed blood or at the end of the TSS period. Lung permeability, lung and gut myeloperoxidase (MPO) activity, gut histology, neutrophil respiratory burst, microvascular blood flow in the liver and muscles, and cytokine levels were measured 3 h after the THS or TSS. FXIII levels were measured before THS or TSS and after the 3-h post-shock period.

RESULTS

THS-induced lung permeability as well as lung and gut MPO activity was significantly lower in rFXIII-treated than in placebo-treated animals. Similarly, rFXIII-treated rats had lower neutrophil respiratory burst activity and less ileal mucosal injury. rFXIII-treated rats also had a higher liver microvascular blood flow compared with the placebo group. Cytokine response was more favorable in rFXIII-treated animals. Trauma-hemorrhagic shock did not cause a drop in FXIII activity during the study period.

CONCLUSIONS

Administration of rFXIII diminishes THS-induced MOD in rats, presumably by preservation of the gut barrier function, limitation of polymorphonuclear leukocyte (PMN) activation, and modulation of the cytokine response.