Delipidated serum abolishes the inhibitory effect of serum on in vitro liposome-mediated transfection

All the standard in vitro lipofection has been routinely performed in serum-free medium as the transfection activity of liposome/DNA complexes is sensitive to the presence of serum. In this study, we have demonstrated that lipid-rich serum lipoprotein included in the transfection medium strongly inhibited the transfection activity of DC-chol liposome/DNA complexes in five different cell types (CHO, 293, A2780CP, A431 and SKBR3). The levels of inhibition by serum lipoprotein were rather greater than those by serum and varied with cell types. However, this inhibition was completely abolished by delipidation of serum. Thus, delipidated serum can be included in the transfection medium. The complexes formed in the presence of serum (zeta=-18.2+/-1.07 mV), delipidated serum (zeta=-19.6+/-0.54 mV), IgG (zeta=-21.6+/-1.92 mV) or serum lipoprotein (zeta=-10.5+/-2.33 mV) were as much negatively charged as those in serum-free medium (zeta=-21.3+/-1.60 mV). The results suggest that the inhibition of liposome-mediated transfection by serum was not associated with charges of serum proteins but with lipids or lipid-associated proteins present in serum.     

Studies on the antigenic properties of serum albumins

Summary Bovine serum albumin (BSA) is one of the most widely studied proteins; its structure is well known and its antigenic properties have been described in animal models. The aim of our work was to evaluate the role of conformation on antigenicity of serum albumins. This study was performed using electrophoresis associated with the immunoblotting technique, where sera from children allergic to BSA were used. Data obtained in this research indicate that serum albumin antigenicity is only partially correlated to its native three-dimensional structure. Heat treatment and chemical denaturation (SDS treatment) are not able to significantly decrease its capability to bind circulating IgEs. Only the reducing treatment is able to modify the antigenicity of this protein. Moreover, a direct correlation between the cross-reactivity observed in immunoblotting between different serum albumins and the percentage of their sequence identity (phylogenetic similarity of the species) was shown.     

Studies on the antigenic properties of serum albumins

Bovine serum albumin (BSA) is one ofthe most widely studied proteins; its structure iswell known and its antigenic properties have beendescribed in animal models. The aimof our work was to evaluate the role of conformationon antigenicity of serum albumins. This study was performed using electrophoresisassociated with the immunoblotting technique, wheresera from children allergic to BSA were used.Data obtained in this research indicatethat serum albumin antigenicity is only partiallycorrelated to its native three-dimensional structure.Heat treatment and chemical denaturation(SDS treatment) are not able to significantly decrease its capability to bind circulating IgEs. Only thereducing treatment is able to modify the antigenicityof this protein. Moreover, a direct correlationbetween the cross-reactivity observed inimmunoblotting between different serum albumins andthe percentage of their sequence identity(phylogenetic similarity of the species) was shown.     

Effect of hemodialysis on the antioxidative properties of serum

In patients with chronic renal failure undergoing regular hemodialysis (HD), oxidative stress is involved in the development of dialysis-related pathologies. The aim of the study was to measure the effect of HD treatment on the general antioxidative status of serum with special consideration of the specific oxidizability of lipids and proteins. Indicators for the oxidative/antioxidative status of plasma were monitored at the beginning and at the end of a dialysis session on the arterial and venous side of the dialyzer. A decrease in the antioxidant status was accompanied by an increased oxidizability of proteins as well as lipids during HD treatment. During the first passage of the dialyzer, the lag time of lipid oxidation decreased from 114.0+/-19.8 to 81.5+/-18.9 min, the lag time of protein oxidation decreased from 105.0+/-24.6 to 72.9+/-21.3 min and the total antioxidative status decreased from 518+/-24 to 252+/-124 microM trolox equivalents. The carbonyl content of serum proteins was high in patients with end stage renal disease (ESRD) (3.9+/-1.1 vs. 0.9+/-0.1 nmol/mg in controls) but did not change significantly during dialysis procedure. Our data demonstrate that the susceptibility of serum lipids and proteins to oxidative modification is severely increased by HD treatment.