The finding that HSA exerts a plasma antioxidant force also is important regarding its possible therapeutic effects, because it may provide the opportunity to enhance endogenous antioxidant protection in pathological conditions by HSA infusion [
61]. Commercially available HSA solutions are complex products that contain not only native HSA but also various species of HSA under different redox states, as well as several minor degradation products [
46,
62]. Significant HSA variability has been reported between the commercial HSA solutions (Table
1). Bioprocesses and storage conditions increase heterogeneity of HSA: truncated, cysteinylated, nitrosylated, and glycosylated forms or HSA-HSA dimers may be found in commercialized products [
29]. These frequently encountered modifications can change HSA antioxidant properties and its binding capacity to endogenous or exogenous molecules [
29,
51,
63]. The observed heterogeneity also can potentially influence clinical outcome and should be correlated with morbidity/mortality in randomized trials [
47,
63,
64]. The use of an antioxidant for the treatment of sepsis has been considered a new, interesting, adjunctive therapy and constitutes a challenge in the clinical management of these patients [
17]. However, it is still unclear whether the administration of commercially available HSA that is largely oxidized, increases or decreases oxidative stress burden in critically ill patients [
52].
Table 1
Characteristics of commercial HSA (available solutions for infusion in France)[
29]
Manufacturer | Baxter | Octapharma | LFB |
Available presentations |
Newborns and infants:
|
| 20% (200 mg/ml): 10 ml vial (2 g) |
Adults:
|
20% (200 mg/ml):
|
20% (200 mg/ml):
|
20% (200 mg/ml):
|
50 ml vial (10 g) | 50 ml vial (10 g) | 50 ml vial (10 g) |
100 ml vial (20 g) | 100 ml vial (20 g) | 100 ml vial (20 g) |
5% (50 mg/ml):
|
5% (50 mg/ml):
|
100 ml vial (5 g) | 250 ml vial (12.5 g) |
250 ml vial (12.5 g) | 500 ml vial (25 g) |
500 ml vial (25 g) | |
| |
4% (40 mg/ml):
|
4% (40 mg/ml):
|
100 ml vial (4 g) | 100 ml vial (4 g) |
250 ml vial (10 g) | 250 ml vial (10 g) |
500 ml vial (20 g) | 500 ml vial (20 g) |
Indications (EMA) | Restoration and maintenance of circulating blood volume where volume deficiency has been demonstrated and the use of a colloid is appropriate. The choice of albumin rather than an artificial colloid will depend on the clinical situation of the individual patient, based on official recommendations. |
Until now, several analytical techniques have been employed to monitor the heterogeneity or the degradation profiles of HSA. High-Performance Liquid Chromatography (HPLC), Mass Spectrometry (MS), Sodium Dodecyl Sulfate-PolyAcrylamide Gel Electrophoresis (SDS-PAGE) and Western blot analyses, or Capillary Zone Electrophoresis (CZE) have contributed to point out this heterogeneity of commercial HSA [
51,
62]. Aggregation or chemical degradation can be induced during sample preparation or purification. Procedures, such as temperature variations, freeze-thawing process, mechanical agitation, or lyophilization, may affect HSA structure and composition of therapeutic HSA. Anraku et al
. studied the protective effect of sodium N-acetyl-L-tryptophanate against albumin oxidation, using HPLC. They partially resolved mercaptalbumin (reduced form of HSA) from two populations of non-mercaptalbumin (oxidized forms), demonstrating that it is possible to improve the quality of the solutions [
65]. Ogasawara et al. used SDS-PAGE and Western blot analyses to detect albumin disulfide dimers in plasma, considered to be a biomarker of oxidative stress [
66]. More recently, Qian et al. (2008) reported a size exclusion HPLC method to estimate the proportion of HSA dimers and oligomers suitable for a quality control [
67]. MS and MS coupled to HPLC also have been employed to characterize different variants of HSA in commercial HSA preparations. In particular, six related proteins have been identified but the method provided only qualitative data and did not detect any dimer form of HSA [
52]. Finally, Alahmad et al. developed a reproducible CZE method to separate HSA from most of its variants. This method proved to be useful in detecting quantitative differences in the proportion of native HSA present in batches produced according to different fractionation ways [
51]. Because an increased percentage of oxidized HSA is responsible for impaired HSA functions [
28], the development of a reliable method providing qualitative and quantitative data on HSA variants in commercial preparations, especially the ratio of native HSA to degraded forms, is of paramount importance for optimizing the clinical use of HSA.