In the current study SA was assessed

In the current study, SA was assessed to confirm the safety of CS addition to erythrocytes SA as well as SA elicits antioxidant action. It has been reported that, ROS induced desialylation by depletion of SA content from cell surfaces (Pawluczyk et al., 2014, Harisa, 2015). Therefore, significant decrease in SA content was noticed in SKL2001 receptor incubated with high cholesterol. The decreases of erythrocytes SA content increase their friction among themselves and endothelial cells; this may trigger vascular dysfunction (Fan et al., 2012). By contrast, treatment with CS keeps SA levels at values near that of control. This is in agreement with many studies which demonstrated that CS preserves antioxidants capacity (Anandan et al., 2013). In the present study, plasma TAC levels were significantly decreased by HC incubation. Likewise, several studies reported that oxidative stress exposure induced decline of TAC levels. The decrease in plasma TAC was demonstrated in HC induced oxidative stress (Devrim et al., 2008). Oxidative stress environment causes a plethora of changes in erythrocytes including loss of antioxidant power and enhances proteins and lipids oxidation. Ramírez-Zamora et al. (2013), reported that erythrocyte membranes are the most targets for deleterious actions of ROS. The equilibrium between SOD as hydrogen peroxide producing agent as well as CAT, and GPx as hydrogen peroxide degrading agents is essential for the removal of ROS. The activity ratios were calculated to better assess antioxidant defenses. Herein, oxidative stress in erythrocytes was increased as confirmed by increase of SOD/CAT and SOD/GPx ratios, GSSG, PCC and MDA in erythrocytes exposed to HC. Similarly, several studies demonstrated that exposure of erythrocytes to HC induced a decrease of antioxidant power; however, biomolecular damage was increased (Devrim et al., 2008, Franiak-Pietryga et al., 2009, Uydu et al., 2012). This attributed to elevation of ROS that consumes antioxidant machinery. Consequently, oxidized GSH, MDA and PCC levels were increased. CS treatment ameliorates these oxidative alterations in erythrocytes by its antioxidant activity. Antioxidant properties of CS are not only confirmed by in vitro studies, but also demonstrated in many in vivo studies using animal models as well as clinical trials. Treatment with CS preserves antioxidant enzymes, particularly glutathione-dependent system, increases in antioxidant potential, and restores redox balance. Therefore, CS decreases lipids and proteins oxidation and attenuates cellular damage (Luo and Wang, 2013). HC disrupts NO homeostasis through increase of ROS formation, depletion of NOS substrate, and oxidation of cofactors (Li and Förstermann, 2013). Furthermore, several previous studies have demonstrated that inhibition of arginase increases NO level, and decreases risk of ischemic heart diseases (Pernow and Jung, 2013). The finding of the present study confirmed that HC induced NOS inactivation compared to control cells. These results are in agreement with the finding of Devrim et al. (2008) who reported that HC decreases NOS activity and NO production. Likewise, Ramírez-Zamora et al. (2013) reported ROS inactivates NOS. The increase of cholesterol inclusion into cell membrane impairs entry of l-Arginine as NOS substrate into the cells (Eligini et al., 2013). Conversely, CS restores NOS activity and nitrite level compared to HC treated cells. These results were concurred with several studies which demonstrated that CS improves NO level (Ozcelik et al., 2014, Zhang et al., 2014). Moreover, numerous studies reported that cholesterol lowering therapy improves NO bioavailability (Harisa et al., 2012, Li and Förstermann, 2013). The current investigations revealed that arginase activity and arginase/NOS ratio were increased by HC exposure. Similarly, Ramírez-Zamora et al. (2013) reported that oxidative stress induced arginase activation. Furthermore, Yang et al. (2013) indicated that ROS augments arginase activity. In such cases, l-arginine availability was limited; therefore, NO production decreases. On the contrary, treatment of HC with CS or CS plus l-arginine prevents HC-induced arginase activation. Similar observation was indicated by Schnorr et al. (2008), who suggested antioxidants treatment diminishes arginase activity in erythrocytes with an increase of NO bioavailability.