Hemoglobin encapsulated poly(ethylene glycol) surface conjugated vesicles attenuate vasoactivity of cell-free hemoglobin

An ex vivo method to evaluate vasoactivity induced by hemoglobin-based oxygen carriers in resistance vessels

Red blood cell substitutes offer a solution to the problem of blood shortage and side effects of blood transfusion. Hemoglobin-based oxygen carriers (HBOCs) are one of the promising substitutes for red blood cells. Vasoactivity, which refers to the side effect of HBOCs that causes vasoconstriction and subsequent hypertension, limits the clinical application of HBOCs. In this study, an ex vivo method for the evaluation of vasoactivity induced by HBOCs was established based on isolated rat mesenteric artery vessels and the DMT120CP system. The DMT120CP system, equipped with a flowmeter, permits the control of intravascular pressure, pressure gradient, and flow conditions with high accuracy, simulating the physiological conditions for isolated vessels. The concentration of noradrenaline was optimized to 1 × 10-6∼3 × 10-6 M. PEGylated bovine hemoglobin (PEG-bHb) was synthesized and perfused into the vessel for vasoactivity evaluation, with bHb as the positive control and PSS buffer solution as the negative control. PEG-bHb showed a hydration diameter of 15.5 ± 1.4 nm and a P50 value of 6.99 mmHg. PEG-bHb exhibited a colloid osmotic pressure of 64.1 mmHg and a viscosity of 1.73 cp at 40 mg/mL. The established vasoactivity evaluation method showed significant differences in samples (bHb or PEG-bHb) with different vasoactivity properties. The vasoconstriction percentage induced by PEG-bHb samples synthesized in different batches showed coefficients of variation less than 5%, indicating good applicability and repeatability. The established evaluation method can be applied to study the vasoactivity induction and elimination strategies, promoting the clinical application of HBOCs.

Nanovesicular liposome-encapsulated hemoglobin (LEH) prevents multi-organ injuries in a rat model of hemorrhagic shock

The goals of resuscitation in hemorrhagic shock are to correct oxygen deficit and to maintain perfusion pressure to the vital organs. We created liposome-encapsulated hemoglobin (LEH) as a nanoparticulate oxygen carrier (216±2nm) containing 7.2g/dl hemoglobin, and examined its ability to prevent the systemic manifestations of hemorrhagic shock (45% blood loss) in a rat model. We collected plasma after 6h of shock and LEH resuscitation, and determined the circulating biomarkers of systemic inflammation and functions of liver, gut, heart, and kidney. As is typical of the shock pathology, a significant increase in the plasma levels of cardiac troponin, liver function enzymes, soluble CD163 (macrophage activation), and creatinine, and the liver/gut myeloperoxidase activity was observed in the hemorrhaged rats. The plasma levels of TNF-α, IL-6, IL-1α, CINC-1, and IL-22 also increased after hemorrhagic shock. LEH administration prevented the hemorrhagic shock-induced accumulation of the markers of injury to the critical organs and pro-inflammatory cytokines. LEH also decreased the plasma levels of stress hormone corticosterone in hemorrhaged rats. Although saline also reduced the circulating corticosterone and a few other tissue injury markers, it was not as effective as LEH in restraining the plasma levels of creatinine, alanine transaminase, CD163, TNF-α, IL-6, and IL-1α. These results indicate that resuscitation with nanoparticulate LEH creates a pro-survival phenotype in hemorrhaged rats, and because of its oxygen-carrying capacity, LEH performs significantly better than saline in hemorrhagic shock.