Heterogeneity in the Effect of Albumin and Other Resuscitation Fluids on Intracellular Oxygen Free Radical Production

Non-oncotic properties of albumin. A multidisciplinary vision about the implications for critically ill patients

INTRODUCTION

Effective resuscitation with human albumin solutions is achieved with less fluid than with crystalloid solutions. However, the role of albumin in today's critical care unit is also linked to its multiple pharmacological effects. Areas covered: The potential clinical benefits of albumin in select populations of critically ill patients like sepsis seem related to immunomodulatory and anti-inflammatory effects, antibiotic transportation and endothelial stabilization. Albumin transports many drugs used in critically ill patients. Such binding to albumin is frequently lessened in critically ill patients with hypoalbuminemia. These changes could result in sub-optimal treatment. Albumin has immunomodulatory capacity by binding several bacterial products. Albumin also influences vascular integrity, contributing to the maintenance of the normal capillary permeability. Moreover, the albumin molecule encompasses several antioxidant properties, thereby significantly reducing re-oxygenation injury, which is especially important in sepsis. In fact, most studies of albumin administration are a combination of a degree of resuscitation with a degree of maintenance or supplementation of albumin. Expert commentary: The potential clinical benefits of the use of albumin in selected critically ill patients such as sepsis seem related to its immunomodulatory and anti-inflammatory effects, antioxidant properties, antibiotic transportation and endothelial stabilization. Additional studies are warranted to further elucidate the underlying physiologic and molecular rationale.

Fluorine-19 Labeling of Stromal Vascular Fraction Cells for Clinical Imaging Applications

Stromal vascular fraction (SVF) cells are used clinically for various therapeutic targets. The location and persistence of engrafted SVF cells are important parameters for determining treatment failure versus success. We used the GID SVF-1 platform and a clinical protocol to harvest and label SVF cells with the fluorinated ((19)F) agent CS-1000 as part of a first-in-human phase I trial (clinicaltrials.gov identifier NCT02035085) to track SVF cells with magnetic resonance imaging during treatment of radiation-induced fibrosis in breast cancer patients. Flow cytometry revealed that SVF cells consisted of 25.0% ± 15.8% CD45+, 24.6% ± 12.5% CD34+, and 7.5% ± 3.3% CD31+ cells, with 2.1 ± 0.7 × 10⁵ cells per cubic centimeter of adipose tissue obtained. Fluorescent CS-1000 (CS-ATM DM Green) labeled 87.0% ± 13.5% of CD34+ progenitor cells compared with 47.8% ± 18.5% of hematopoietic CD45+ cells, with an average of 2.8 ± 2.0 × 10¹² ¹⁹F atoms per cell, determined using nuclear magnetic resonance spectroscopy. The vast majority (92.7% ± 5.0%) of CD31+ cells were also labeled, although most coexpressed CD34. Only 16% ± 22.3% of CD45-/CD31-/CD34- (triple-negative) cells were labeled with CS-ATM DM Green. After induction of cell death by either apoptosis or necrosis, >95% of ¹⁹F was released from the cells, indicating that fluorine retention can be used as a surrogate marker for cell survival. Labeled-SVF cells engrafted in a silicone breast phantom could be visualized with a clinical 3-Tesla magnetic resonance imaging scanner at a sensitivity of approximately 2 × 10⁶ cells at a depth of 5 mm. The current protocol can be used to image transplanted SVF cells at clinically relevant cell concentrations in patients.

SIGNIFICANCE

Stromal vascular fraction (SVF) cells harvested from adipose tissue offer great promise in regenerative medicine, but methods to track such cell therapies are needed to ensure correct administration and monitor survival. A clinical protocol was developed to harvest and label SVF cells with the fluorinated (¹⁹F) agent CS-1000, allowing cells to be tracked with (19)F magnetic resonance imaging (MRI). Flow cytometry evaluation revealed heterogeneous ¹⁹F uptake in SVF cells, confirming the need for careful characterization. The proposed protocol resulted in sufficient ¹⁹F uptake to allow imaging using a clinical MRI scanner with point-of-care processing.

Soybean oil: a potentially new intravascular perfusate

BACKGROUND

Given that micelles of lipids are colloids, the hypothesis was generated that the rapid administration of large volumes of soybean oil micelles would be an effective perfusion fluid. We also hypothesized that oxygen loading would be enhanced due to the greater solubility of oxygen in lipids compared to water.

METHODS

A 100% lethal mouse model of blood loss was used to compare the ability of soybean oil micelles to that of Ringer's lactate, blood and other fluids, with respect to raising and maintaining the blood pressure for one hour. Oxygen on- and off-loading of various concentrations of soybean oil micelles was determined using mass spectroscopy. Nitric oxide uptake by micelles was also determined in a similar fashion.

RESULTS

A 20% soybean oil emulsion was superior to Ringer's lactate in raising and maintaining blood pressure. A 20% soybean oil emulsion with 5% albumin added was superior to shed blood as well as solutions comprised of 5% albumin added to either normal saline or Ringer's lactate. There was a linear relationship between oxygen content and micelle concentration between 10% and 30%. Off-loading of oxygen from the micelles was nearly as fast as off-loading from water. Nitric oxide also loaded preferentially onto soybean oil micelles.

CONCLUSIONS

(1) Soybean oil emulsions were superior to other fluids in restoring and maintaining the blood pressure; (2) oxygen-carrying ability of soybean oil micelles exceeds that of water and follows Henry's law between 10% and 30% w/v oil content; (3) nitric oxide was carried by the micelles; (4) animals receiving soybean oil micelles did not exhibit fat embolization; (5) colloids comprised of soybean oil-containing micelles may be used to replace blood loss and may be used to deliver oxygen and other potentially therapeutic gases such as nitric oxide to tissues.

Resuscitation fluids and endotoxin-induced myocardial dysfunction: is selection a load-independent differential issue?

Along with redistributive shock, myocardial dysfunction is now recognized as highly prevalent in early severe sepsis. Indeed, aside from their distinct loading potency, resuscitation fluids have been poorly investigated as to their specific molecular impact on myocardial dysfunction. The objective of this study was to evaluate the load-independent biological impact of different resuscitation fluids on endotoxin-induced myocardial dysfunction. Adult rats implanted with a central venous catheter were given an intraperitoneal injection of endotoxin (lipopolysaccharides [LPSs], Escherichia coli, 10 mg/kg) or normal saline (sham) and subsequently infused or not with similar "fluid potency" loading resuscitation fluid (normal saline, albumin [Alb], or hypertonic saline solution) for 6 to 24 h, followed by echocardiographic and hemodynamic monitoring together with biochemical and histopathologic evaluation. Intervention was to assess the selective influence of load-independent fluid infusion on the aforementioned parameters in groups of animals challenged or not with LPS. At comparative plasma volumes, Alb improved myocardial homeostasis after LPS challenge by (i) reducing left ventricular relative wall diastolic thickness, interstitial space enlargement, and endogenous Alb content; (ii) limiting cardiac apoptosis and sustaining extracellular signal-regulated mitogen-activated protein kinase activation; and (iii) enhancing the expression pattern of heme-oxygenase 1/inducible nitric oxide synthase. Hypertonic saline solution was also cardioprotective by early prevention of myocardial dysfunction and by reducing cardiac apoptosis. Fluid infusions have distinct load-independent structural/biological impacts on endotoxin-induced myocardial dysfunction. Albumin and hypertonic saline solution are the most pleiotropic fluids in protecting the heart after a "sepsis" hit.

Lack of plasma albumin impairs intravascular lipolysis and explains the associated free fatty acids deficiency and hypertriglyceridemia

BACKGROUND

Abnormalities in lipid metabolism and transport are hallmarks in analbuminemic Nagase rats (NAR) and humans. Triglyceridemia is nearly 3- to 5-fold higher in female NAR than in control Sprague-Dawley rats (SDR). Also, NAR present with a severe plasma free fatty acid (FFA) deficit. There are conflicting results regarding the mechanisms underlying NAR hypertriglyceridemia.

OBJECTIVE

We aimed at investigating whether liver lipogenesis and triglyceride secretion rates into the plasma contribute to the hypertriglyceridemia in NAR. We also studied whether heparin or albumin administration would release the hypothesized lipolysis inhibition in NAR.

METHODS

The incorporation of tritiated water into lipids and the linear accumulation rate of plasma triglycerides after Triton WR1339 injection were the measures of liver lipogenesis and triglyceride secretion rates.

RESULTS

Lipogenesis (596 ± 40 vs. 929 ± 124 μmol 3H2O/g/h) and triglyceride (4.25 ± 1.00 vs. 7.04 ± 1.68 mg/dL/min) secretion rates were slower (P ≤ 0.05) in fasted NAR than in control SDR. The injection of either heparin or albumin elicited an increase in NAR plasma FFA levels over time. FFA levels reached control levels 90 min after the albumin administration, increasing from 0.36 ± 0.05 to 1.34 ± 0.16 mEq/L (P ≤ 0.05). These results indicate that the lack of plasma albumin inhibits intravascular lipolysis and causes the FFA deficit observed in NAR.

CONCLUSION

NAR hepatic triglyceride synthesis and output do not contribute to NAR hypertriglyceridemia. We propose that the lack of albumin diminishes intravascular lipolysis which reduces the plasma triglyceride removal rate and explain both NAR hypertriglyceridemia and FFA deficiency.

Histidine inhibits the degradation of cells suspended in Ringer's lactate

BACKGROUND

We previously demonstrated that the degradation of a suspension of Jurkat cells in Ringer's lactate (RL) was inhibited by the addition of a 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid/Tris buffer. Given the ability of histidine to buffer protons in the physiologic range (pKa = 6.0), we hypothesized that this amino acid would have the same effect.

METHODS

RL was made in our laboratory using sodium l-lactate. Jurkat cells were suspended in RL alone or RL with various concentrations of histidine or other test reagents at 37 degrees C for 4 hours or 24 hours in an atmosphere of 95% air and 5% CO2. Using flow cytometry, we measured cell shrinkage, phosphatidylserine translocation, propidium iodide uptake, and intracellular oxygen free radical production.

RESULTS

Cell shrinkage was induced by suspension in RL after 4 hours incubation. At 4 hours, cell shrinkage was inhibited by all concentrations of histidine tested, 7.8 mumol/L to 10 mmol/L. There was no statistical difference between cells suspended in medium and cells suspended in 1 mmol/L or 10 mmol/L histidine. After 24 hours incubation, 100% of the cells in RL had undergone cell shrinkage whereas in 10 mmol/L histidine only a mean of 20% of the cells had undergone cell shrinkage. The inhibitory effect of 1 mmol/L histidine at pH 7.4 was compared with that at pH 6.8. After 4 hours incubation, there was no difference. After 24 hours incubation, the inhibitory effect at pH 7.4 was significantly greater that that at pH 6.8. Histidine at 1 mmol/L to 10 mmol/L significantly reduced the percentage of cells that underwent phosphatidylserine translocation and propidium iodide uptake. The effect of the dipeptide buffer, glycylglycine, and the two other positively charged amino acids, arginine and lysine, after 4 hours incubation was compared with histidine at 1 mmol/L. At 1 mmol/L, histidine was superior to arginine and lysine and indistinguishable from glycylglycine. Intracellular free radical production was measured at 0.5 mmol/L, 1.0 mmol/L, and 10 mmol/L histidine concentrations. There was significant inhibition only at 10 mmol/L.

CONCLUSIONS

Characteristics of apoptotic cell death that occur in cells suspended in RL are inhibited by the addition of histidine, arginine, and lysine as well as the dipeptide glycylglycine, which, with a pKa of 8.25, also buffers in the physiologic range. Histidine is superior to lysine and arginine at 1 mmol/L. The salutary effect of histidine at 0.5 mmol/L and 1 mmol/L is caused by a mechanism other than the inhibition of oxygen free radicals. Moreover, the buffering of protons may play a role at 24 hours but made no difference at 4 hours.

Albumin attenuates neutrophil activation induced by stimulators including antibodies against neutrophil-specific antigens

As neutrophil activation is related to several adverse transfusion reactions, we studied about the activation induced by anti-neutrophil antibodies and the stabilizing effects of albumin pretreatment by means of flow cytometry. Anti-neutrophil monoclonal antibody (anti-HNA-1a, 1b, 2a) alone induced CD11b expression and shedding of L-selectin, and anti-HNA-1a reinforced reactive oxygen species (ROS) production. Albumin pretreatment significantly reduced CD11b expression and L-selectin shedding induced by fMLP and ROS production induced by PMA, G-CSF combined with PMA or LPS-fMLP, or anti-HNA-1a combined with PMA. These findings suggest that anti-HNA-1a is related to adverse reactions and albumin has a regulating effect on neutrophil activation.