Ter 12 weeks administration of astaxanthin (N = 30). X-axis is the concentration of RBC Ab. Y-axis is concentration of RBC astaxanthin that had been measured in our former human study [12]. doi:10.1371/journal.pone.0049620.gAmyloid b PHCCC site determination in Human ErythrocytesTable 2. Changes in Amyloid b levels in RBC and plasma before and after a 12 week administration of 0, 6 or 12 mg astaxanthin.Parameters Age Total number of subjects Males Females RBC Ab40 (pmol/g hemoglobin) Before administration After administration RBC Ab42 (pmol/g hemoglobin) Before administration After administration Plasma Ab40 (pmol/g protein) Before administration After administration Plasma Ab42 (pmol/g protein) Before administration After administration0 mg 56.661.4 10 56 mg 56.362.1 10 512 mg 56.161.6 10 57.8960.46 8.2360.8.1360.65 7.0860.8.3660.55 6.3160.53*3.9060.29 3.6960.4.2460.37 3.6060.4.0860.55 2.4060.47*0.79760.050 0.80460.0.81760.051 0.78660.0.80260.034 0.74760.0.22360.011 0.23260.0.23660.031 0.20460.0.26660.020 0.24360.Means 6 SE are shown. Significantly different between before and after astaxanthin administration: *P,0.05. Blood samples (RBC and plasma) that had been obtained from our former human study [12] were subjected to Ab determination. doi:10.1371/journal.pone.0049620.tFigure 3. Correlation between RBC PLOOH and Ab40 (A) or Ab42 (B) concentration after 12 weeks administration of astaxanthin (N = 30). X-axis is concentration of RBC Ab. Y-axis is concentration of RBC PLOOH [phosphatidylcholine hydroperoxide (PCOOH) and phosphatidylethanolamine hydroperoxide (PEOOH)] that had been measured in our former human study [12]. doi:10.1371/journal.pone.0049620.gAlthough plasma Ab has been investigated thoroughly in previous studies [1,5,21,28], little attention has been paid to RBC Ab. In the present study, we provide evidence that Ab is indeed present in human RBC. We found that RBC Ab40 and Ab42 levels in healthy human volunteers were about 8- and 14-times higher 1676428 than plasma Ab40 and Ab42, respectively (Table 1), when RBC Ab levels per g hemoglobin were compared to plasma Ab levels per g protein. These results suggested that plasma Ab42 and Ab40 readily bind to RBC, and this may provide an explanation for lower concentrations of “unbound” Ab42 and Ab40 in human plasma [3]. In addition, the experiments confirmed that the RBC Ab42/Ab40 ratio was about 1.8-times higher than in plasma (Table 1). This may be related to the fact that Ab42 interacts with RBC more avidly than Ab40 [9,29], probably because two additional hydrophobic amino acids at the C-terminus of Ab42 increase the rate of Ab insertion into the RBC bilayer [30]. We also found that RBC Ab40 and Ab42 levels in healthy elderly subjects were higher than in young volunteers. It was reported that brain as well as plasma Ab (Ab40 and Ab42) levelstend to increase according to age [31]. The age-related increase in plasma Ab could be connected to increases in Ab production or a reduction in Ab clearance in the brain. These shifts may be related to changes in the central or peripheral activity of Ab synthetic enzymes (e.g., b-secretase or c-secretase) or Ab catabolic enzymes (e.g., insulin-degrading enzyme or neprilysin) associated with aging. Therefore, the age-related enhanced binding of Ab to RBC may purchase Tubastatin A reflect age-dependent 1662274 changes in Ab metabolism. Since significant positive correlations were observed between RBC and plasma Ab concentrations (Fig. 1), this may strengthen the hypothesis. In order to.Ter 12 weeks administration of astaxanthin (N = 30). X-axis is the concentration of RBC Ab. Y-axis is concentration of RBC astaxanthin that had been measured in our former human study [12]. doi:10.1371/journal.pone.0049620.gAmyloid b Determination in Human ErythrocytesTable 2. Changes in Amyloid b levels in RBC and plasma before and after a 12 week administration of 0, 6 or 12 mg astaxanthin.Parameters Age Total number of subjects Males Females RBC Ab40 (pmol/g hemoglobin) Before administration After administration RBC Ab42 (pmol/g hemoglobin) Before administration After administration Plasma Ab40 (pmol/g protein) Before administration After administration Plasma Ab42 (pmol/g protein) Before administration After administration0 mg 56.661.4 10 56 mg 56.362.1 10 512 mg 56.161.6 10 57.8960.46 8.2360.8.1360.65 7.0860.8.3660.55 6.3160.53*3.9060.29 3.6960.4.2460.37 3.6060.4.0860.55 2.4060.47*0.79760.050 0.80460.0.81760.051 0.78660.0.80260.034 0.74760.0.22360.011 0.23260.0.23660.031 0.20460.0.26660.020 0.24360.Means 6 SE are shown. Significantly different between before and after astaxanthin administration: *P,0.05. Blood samples (RBC and plasma) that had been obtained from our former human study [12] were subjected to Ab determination. doi:10.1371/journal.pone.0049620.tFigure 3. Correlation between RBC PLOOH and Ab40 (A) or Ab42 (B) concentration after 12 weeks administration of astaxanthin (N = 30). X-axis is concentration of RBC Ab. Y-axis is concentration of RBC PLOOH [phosphatidylcholine hydroperoxide (PCOOH) and phosphatidylethanolamine hydroperoxide (PEOOH)] that had been measured in our former human study [12]. doi:10.1371/journal.pone.0049620.gAlthough plasma Ab has been investigated thoroughly in previous studies [1,5,21,28], little attention has been paid to RBC Ab. In the present study, we provide evidence that Ab is indeed present in human RBC. We found that RBC Ab40 and Ab42 levels in healthy human volunteers were about 8- and 14-times higher 1676428 than plasma Ab40 and Ab42, respectively (Table 1), when RBC Ab levels per g hemoglobin were compared to plasma Ab levels per g protein. These results suggested that plasma Ab42 and Ab40 readily bind to RBC, and this may provide an explanation for lower concentrations of “unbound” Ab42 and Ab40 in human plasma [3]. In addition, the experiments confirmed that the RBC Ab42/Ab40 ratio was about 1.8-times higher than in plasma (Table 1). This may be related to the fact that Ab42 interacts with RBC more avidly than Ab40 [9,29], probably because two additional hydrophobic amino acids at the C-terminus of Ab42 increase the rate of Ab insertion into the RBC bilayer [30]. We also found that RBC Ab40 and Ab42 levels in healthy elderly subjects were higher than in young volunteers. It was reported that brain as well as plasma Ab (Ab40 and Ab42) levelstend to increase according to age [31]. The age-related increase in plasma Ab could be connected to increases in Ab production or a reduction in Ab clearance in the brain. These shifts may be related to changes in the central or peripheral activity of Ab synthetic enzymes (e.g., b-secretase or c-secretase) or Ab catabolic enzymes (e.g., insulin-degrading enzyme or neprilysin) associated with aging. Therefore, the age-related enhanced binding of Ab to RBC may reflect age-dependent 1662274 changes in Ab metabolism. Since significant positive correlations were observed between RBC and plasma Ab concentrations (Fig. 1), this may strengthen the hypothesis. In order to.
