Fluid resuscitation with hemoglobin vesicles prevents Escherichia coli growth via complement activation in a hemorrhagic shock rat model

Branched PEG-modification: A new strategy for nanocarriers to evade of the accelerated blood clearance phenomenon and enhance anti-tumor efficacy

PEGylation is one of the most successful technologies for reducing immunogenicity, improving the stability and circulation time of nanocarriers, and has been applied in the clinic for over three decades. However, linear PEG-modified nanocarriers have been found to induce anti-PEG IgM at the first injection, which triggers the accelerated blood clearance (ABC) phenomenon upon repeated injections. Furthermore, clinical and research evidence has revealed that anti-PEG antibodies also cause serious complement activation-related pseudoallergies (CARPA), which greatly reduce the safety of linear PEGylated nanocarriers. In this study, as an alternative to linear PEG, branched PEG was selected owing to its low antigenicity. We pioneer the use of branched PEG lipid derivatives [DSPE-mPEG_2,n (n = 2, 10, and 20 kDa)] to modify nanoemulsions (PE_2,n) and liposomes (PL_2,n). Upon characterization, PE_2,n and PL_2,n showed similar physicochemical properties to linear DSPE-mPEG₂₀₀₀-modified nanocarriers in terms of size, polydispersity index (PDI), and zeta potential. However, our pharmacokinetics study surprisingly indicated that PE_2,n and PL_2,n did not induce the ABC phenomenon after repeated injection. This may be attributed to the fact that PE_2,n and PL_2,n induced noticeably lower levels of anti-PEG IgM than linear PEG-modified nanocarriers and did not activate the complement system. Furthermore, we are the first to investigate the anti-tumor efficacy of DSPE-mPEG_2,n-modified liposomal doxorubicin (DOX). The pharmacodynamic experiments showed that DSPE-mPEG_2,n-m-modified liposomal DOX had better in vivo anti-tumor effects than linear DSPE-mPEG₂₀₀₀-modified liposomes. Therefore, we speculate that DSPE-mPEG_2,n-modified nanocarriers possess promising prospects in avoiding the ABC phenomenon, reducing CARPA, and improving the anti-tumor efficacy of encapsulated drugs.

Evasion of the accelerated blood clearance phenomenon by branched PEG lipid derivative coating of nanoemulsions

PEGylation increases the circulation time of the nanocarrier, but also triggers accelerated blood clearance (ABC) phenomenon. It is well-known that the ABC phenomenon results in shortened blood circulation and aberrant increase in liver and spleen accumulation, which greatly limits the application of PEGylated nano-preparations. For many years, researchers have been working hard to find ways to reduce or eliminate the ABC phenomenon. Previous studies have focused on PEG molecular weight and PEG alternative materials, but there has never been any research on the effect of different PEG chain types on the ABC phenomenon. Therefore, 40 kDa molecular weight of linear PEG lipid derivatives (DSPE-mPEG_40k) and branched PEG lipid derivatives (DSPE-mPEG_2,40k) were selected to modify nanoemulsions to explore the influence of distinct PEG chain types on avoiding the ABC phenomenon for the first time. We pioneer the use of linear and branched PEG lipid derivatives (DSPE-mPEG_40k and DSPE-mPEG_2,40k) to modify nanoemulsions (PE_40k and PE_2,40k). Upon characterization, PE_40k and PE_2,40k showed good physicochemical properties in the aspect of size, polydispersity index (PDI value), and zeta potential. Surprisingly, the pharmacokinetics study indicated that repeated injection of PE_40k and PE_2,40k did not trigger the ABC phenomenon. More importantly, PE_2,40k possessed a long circulation time and did not cause ABC phenomenon after repeated injection. This may be attributed to the fact that PE_2,40k induced noticeably lower anti-PEG IgM levels compared to linear PEG-modified nanocarriers and did not activate the complement system. Therefore, we speculate that DSPE-mPEG_2,40k-modified nanocarriers possess promising prospects in avoiding the ABC phenomenon, which may improve the possibility of wide application of nanoformulations.

Effects of Hypertonic Saline and Hydroxyethyl Starch on Myeloid-Derived Suppressor Cells in Hemorrhagic Shock Mice under Secondary Bacterial Attack

Objectives

The primary target is to reveal whether the resuscitation with hypertonic saline (HTS) or hydroxyethyl starch (HES) would have different effects on the myeloid-derived suppressor cell (MDSC) count and monocytic MDSC (M-MDSC)/granulocytic/neutrophilic MDSC (G-MDSC) rate in the peripheral blood, spleen, and bone marrow nucleated cells (BMNC) in a controlled hemorrhagic shock mouse model under secondary Escherichia coli bacterial infection attack, comparing to resuscitation with normal saline (NS) in 72 hours.

Method

After hemorrhagic shock with bacteremia, which is induced by Escherichia coli bacterial infection attack, comparing to resuscitation with normal saline (NS) in 72 hours. Method. After hemorrhagic shock with bacteremia, which is induced by Escherichia coli 35218 injection, the mice were distributed into control, NS, HTS, and HES groups. The peripheral blood nucleated cells (PBNC), spleen single-cell suspension, and bone marrow nucleated cells were collected. The flow cytometry was used to detect the MDSC, M-MDSC, and G-MDSC.

Result

In PBNC, after resuscitation with NS, the MDSC was continuously higher, while the rate of M-MDSC/G-MDSC were continuously lower (P < 0.05). In HTS, the MDSC varied, higher at 24 and 72 hours (P < 0.05). In HTS, the MDSC varied, higher at 24 and 72 hours (P < 0.05). In HTS, the MDSC varied, higher at 24 and 72 hours (P < 0.05). In HTS, the MDSC varied, higher at 24 and 72 hours (P < 0.05). In HTS, the MDSC varied, higher at 24 and 72 hours (P < 0.05), the M-MDSC/G-MDSC were continuously lower (P < 0.05). In the spleen, resuscitation with HTS, the M-MDSC/G-MDSC were continuously lower (P < 0.05). In BMNC, after resuscitation with HES, the M-MDSC/G-MDSC were lower at 24 and 72 hours (P < 0.05).

Conclusion

In mouse hemorrhagic shock model with bacterial infection, the resuscitation with NS, HTS, or HES induced difference changes in MDSC and M-MDSC/G-MDSC, which were time-dependent and organ-specific. Resuscitation with crystalloid, like NS or HTS, showed longer effects on the MDSC and M-MDSC/G-MDSC in peripheral blood; while HTS has a longer effect on M-MDSC/G-MDSC in the spleen, HES has a stronger impact on the differentiation regulation of MDSC to G-MDSC in the bone marrow.

Effects of arterial hemorrhage speed on the blood coagulation/fibrinolysis system and hemodynamics in rats

: The effects of rapid hemorrhage on coagulopathy have been reported. However, the effects of different hemorrhage speeds on the blood coagulation/fibrinolysis system have not been investigated. This study aimed to compare different hemorrhage speeds for clarifying their effects on the coagulation/fibrinolysis system and circulation disorders in rats. Male Sprague-Dawley rats (301-396 g) were randomly assigned to five groups depending on hemorrhage speed and length of procedure: first, rapid (1.4 ml/min, 30-min bleeding); second, rapid-L (1.4 ml/min, 30-min bleeding and observation until 6 h); third, slow (0.1 ml/min, intermittently, 6-h bleeding); fourth, control (30-min observation); and fifth, control-L (6-h observation). Hemorrhage was induced by withdrawing blood until 40% of the estimated blood volume from the femoral artery. We measured vital signs, hematology, general chemistry, blood gas status, coagulation parameters, fibrinolytic markers [tissue-type plasminogen activator and plasminogen activator inhibitor one (PAI-1)], vascular endothelial damage (syndecan-1), and liver PAI-1 mRNA expression. Rapid hemorrhage induced elevation of lactate and syndecan-1 levels and prolonged prothrombin time and activated partial thromboplastin time in the rapid group. In contrast, slow hemorrhage did not induce these changes. Hemorrhage speed had no effect on plasma tissue-type plasminogen activator and hematology. Plasma PAI-1 levels were significantly increased in the rapid-L group, while liver PAI-1 mRNA levels were increased in the slow group. This study shows changes in the circulatory and fibrinolysis systems, depending on the hemorrhage speed. Hemorrhage might promote production of PAI-1, while tissue hypoxia due to rapid hemorrhage might promote release of PAI-1.

Effects of renal denervation on blood-pressure response to hemorrhagic shock in spontaneously hypertensive rats

PURPOSE

Renal denervation (RD) has been demonstrated to be an effective approach to reduce blood pressure for those with resistant hypertension. Yet, we aimed to explore the effect and possible mechanism of RD on blood-pressure response to hemorrhagic shock in spontaneously hypertensive rats.

METHODS

A total of 48 male spontaneously hypertensive rats were randomized to three groups: study group, sham-operation group and control group. RD was achieved by cutting off renal nerves and swabbing phenol on it. Ten weeks after RD, 8 rats in each group were sacrificed to collect the kidney and heart tissues. The remaining rats were subjected to an operation to induce hemorrhagic shock which would lead to 40% loss of total blood volume, and observed for 120 min. The serum concentration of norepinephrine was measured before and three weeks after RD.

RESULTS

The blood-pressure and norepinephrine levels were reduced significantly after RD (p < 0.05). Systolic blood pressure and diastolic blood pressure of the surgery group were higher than those in the sham and control groups at 15, 30 and 45 min after hemorrhagic shock (p < 0.05), while no significant difference was observed at 60, 90 and 120 min (p > 0.05). Additionally, the beta-1 adrenergic receptor (β1-AR) in the study group was significantly higher than those in the other two groups (p < 0.05) after hemorrhagic shock.

CONCLUSION

This study demonstrated that RD could to some extent improve blood-pressure response to hemorrhagic shock in an established model of severe hemorrhagic shock in spontaneously hypertensive rats. The mechanism might be associated with up-regulation of β1-AR.

The Use of Hemoglobin Vesicles for Delivering Medicinal Gas for the Treatment of Intractable Disorders

Bioactive gaseous molecules, such as oxygen (O₂) and carbon monoxide (CO), are essential elements for most living organisms to maintain their homeostasis and biological activities. An accumulating body of evidence suggests that such molecules can be used in clinics as a medical gas in the treatment of various intractable disorders. Recent developments in hemoglobin-encapsulated liposomes, namely hemoglobin vesicles (HbV), possess great potential for retaining O₂ and CO and could lead to strategies for the development of novel pharmacological agents as medical gas donors. HbV with either O₂ or CO bound to it has been demonstrated to have therapeutic potential for treating certain intractable disorders and has the possibility to serve as diagnostic and augmenting product by virtue of unique physicochemical characteristics of HbV. The present review provides an overview of the present status of the use of O₂- or CO-binding HbV in experimental animal models of intractable disorders and discusses prospective clinical applications of HbV as a medical gas donor.

Effects of different types of fluid resuscitation on hepatic mitochondria and apoptosis

The aim of this study was to observe the effects of different types of fluid resuscitation on hepatic mitochondria and apoptosis in hemorrhagic shock, and the corresponding mechanisms. Forty rats were divided into five groups: Sham surgery (Sham group), shock (Shock group), Ringer's lactate resuscitation (RL group), hydroxyethyl starch resuscitation (HES group) and autologous blood resuscitation (BL group). A model of hemorrhagic shock was successfully induced in the latter four groups. The recovery objective was to maintain the mean arterial pressure (MAP) of the rats at 80 mmHg. Two hours after the end of the recovery experiment, fresh liver samples were examined in order to observe the changes in the morphology and mitochondrial membrane potential (ΔΨm). In addition, the levels of succinate dehydrogenase (SDH) activity were assessed, and a terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) assay was conducted to evaluate the level of apoptosis in the liver cells. In the Shock, RL, HES and BL groups, mitochondrial ultrastructural damage in the liver cells, significant reductions in liver cell function, liver ΔΨm and SDH activity, and the apoptosis of hepatocytes were more apparent compared with those in the Sham group. In the BL group, compared with the RL and HES groups, the injuries to the mitochondrial ultrastructure and liver cell function were significantly reduced, the hepatic ΔΨm and SDH activity were significantly increased and the hepatocyte apoptosis index (AI) was significantly reduced (P<0.05). In conclusion, in a rat model of hemorrhagic shock, different methods of fluid resuscitation may improve the liver cells with regard to mitochondrial ultrastructure and function, the stability of liver ΔΨm, the activity of SDH and the inhibition of liver cell apoptosis. The results indicate that infusion with autologous blood followed by RL solution is a preferable method of fluid resuscitation compared with HES.