Effect of Glyoxal on Plasma Membrane and Cytosolic Proteins of Erythrocytes

Abstract

Glyoxal (GO) is a reactive dicarbonyl derived endogenously from sugars and other metabolic reactions within cells. Numerous exogenous sources of this compound include tobacco smoking, air pollution, and food processing. GO is toxic to cells mainly due to its high levels and reactivity towards proteins, lipids, and nucleic acids. We speculate that glyoxal could be involved in erythrocyte protein damage and lead to cell dysfunction. The osmotic fragility and level of amino and carbonyl groups of membrane proteins of erythrocytes incubated for 24 h with GO were identified. The amount of thiol, amino, and carbonyl groups was also measured in hemolysate proteins after erythrocyte treatment with GO. In hemolysate, the level of glutathione, non-enzymatic antioxidant capacity (NEAC), TBARS, and activity of antioxidant enzymes was also determined. The study's results indicated that GO increases erythrocyte osmotic sensitivity, alters the levels of glutathione and free functional groups in hemolysate proteins, and modifies the activity of antioxidant enzymes. Our findings indicate that GO is a highly toxic compound to human erythrocytes. Glyoxal at concentrations above 5 mM can cause functional changes in erythrocyte proteins and disrupt the oxidoreductive balance in cells.

Keywords: antioxidant enzymes; erythrocyte; glutathione; glyoxal; hemoglobin.

Figure 1

The osmotic fragility of the RBCs after incubation with GO (C₅₀—NaCl concentration at which 50% of RBCs undergo hemolysis). Data were presented as median with a boxplot bounded by quartiles, n = 10, * p < 0.05—GO (10 mM) versus control.

Figure 2

The level of (A) carbonyl and (B) amino groups in erythrocyte plasma membrane proteins after incubation of whole erythrocytes with GO. Data were presented as median with a boxplot bounded by quartiles, n = 10.

Figure 3

The level of (A) carbonyl and (B) amino groups in hemolysate proteins of erythrocytes after incubation of whole erythrocytes with GO. Data were presented as median with a boxplot bounded by quartiles, n = 10 for carbonyl groups, and n = 9 for amino groups. * p < 0.05—GO (5 mM) vs. control and GO (10 mM) vs. control.

Figure 4

The level of (A) thiol group and (B) GSH in hemolysate proteins of erythrocytes after incubation of whole erythrocytes with GO. Data were presented as median with a box plot bounded by quartiles, n = 10. * p < 0.05—GO (5 mM) vs. control and GO (10 mM) vs. control.

Figure 5

(A) The total non-enzymatic antioxidant capacity and (B) the concentration of thiobarbituric acid-reactive substances (TBARS) in hemolysate proteins of erythrocytes incubated with GO. Data were presented as median with a boxplot bounded by quartiles, n = 9 for TBARS and n = 10 for NEAC, * p < 0.05—GO (10 mM) vs. control.

Figure 6

Alterations in the SOD (A) and catalase (B) activity in hemolysate after incubation of whole erythrocytes with GO. Data are expressed as median with a box plot bounded by quartiles, n = 9. * p < 0.05—GO (10 mM) vs. control.