title: Inverse relationship between erythrocyte size and platelet reactivity in elderly.
abstract: Previous work indicates that erythrocytes (RBCs) accumulate β-amyloid X-40 (Aβ40) in individuals with Alzheimer disease (AD) and to a lesser extent in healthy elderly. The toxin damages RBCs and increases their mean corpuscular volume (MCV). Furthermore, AD platelets demonstrate lower reactivity. This study investigated interactions between RBCs and platelets. Older individuals with moderate hypertension (n = 57) were classified into two groups, depending on MCV in whole blood: The MCVhighgroup comprised individuals with higher MCV (n = 27; 97 ± 3(SD) fl) and MCVlowgroup had relatively lower MCV (n = 30; 90 ± 3(SD) fl). Flow cytometry was used to determine platelet reactivity, i.e., the surface binding of fibrinogen after provocation. Adenosine diphosphate (ADP) and a thrombin receptor-activating protein (TRAP-6) were used as agonists. Subsequently, blood cells were divided according to density into 17 subfractions. Intra-RBC Aβ40content was analyzed and in all platelet populations surface-bound fibrinogen was determined to estimate platelet in vivo activity. We found Aβ40inside RBCs of approximately 50% of participants, but the toxin did not affect MCV and platelet reactivity. In contrast, MCV associated inversely with platelet reactivity as judged from surface-attached fibrinogen after ADP (1.7 μmol/L) (p < 0.05) and TRAP-6 provocation (57 μmol/L (p = 0.01) and 74 μmol/L (p < 0.05)). In several density fractions (nos. 3, 4, 8, 11-13 (p < 0.05) and nos. 5-7 (p < 0.01)) MCV linked inversely with platelet-attached fibrinogen. In our community-dwelling sample, enhanced MCV associated with decreased platelet reactivity and lower in vivo platelet activity. It resembles RBCs and platelet behavior in AD-type dementia.
authors.affiliation: a Department of Internal Medicine, Vrinnevi Hospital , Norrköping , Sweden.|b Department of Social and Welfare , Linköping University , Linköping , Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Milovanovic
authors.affiliation: c Primary Health Care and Department of Medical and Health Sciences , Linköping University , Norrköping , Sweden.
authors.forename: S
authors.initials: S
authors.lastname: Nilsson
authors.affiliation: d Department NVS, Center for Alzheimer Research, Division for Neurogeriatrics , Karolinska Institutet , Huddinge , Sweden.|e Karolinska University Hospital, Geriatric Clinic, Clinical Trial Unit , Huddinge , Sweden.
authors.forename: B
authors.initials: B
authors.lastname: Winblad
authors.affiliation: d Department NVS, Center for Alzheimer Research, Division for Neurogeriatrics , Karolinska Institutet , Huddinge , Sweden.|e Karolinska University Hospital, Geriatric Clinic, Clinical Trial Unit , Huddinge , Sweden.
authors.forename: V
authors.initials: V
authors.lastname: Jelic
authors.affiliation: d Department NVS, Center for Alzheimer Research, Division for Neurogeriatrics , Karolinska Institutet , Huddinge , Sweden.
authors.forename: H
authors.initials: H
authors.lastname: Behbahani
authors.affiliation: a Department of Internal Medicine, Vrinnevi Hospital , Norrköping , Sweden.|d Department NVS, Center for Alzheimer Research, Division for Neurogeriatrics , Karolinska Institutet , Huddinge , Sweden.
authors.forename: T
authors.initials: T
authors.lastname: Shahnaz
authors.affiliation: a Department of Internal Medicine, Vrinnevi Hospital , Norrköping , Sweden.
authors.forename: M
authors.initials: M
authors.lastname: Oweling
authors.affiliation: a Department of Internal Medicine, Vrinnevi Hospital , Norrköping , Sweden.|d Department NVS, Center for Alzheimer Research, Division for Neurogeriatrics , Karolinska Institutet , Huddinge , Sweden.
authors.forename: P
authors.initials: P
authors.lastname: Järemo
mesh_terms: D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000097:blood*; D015415:Biomarkers; D001792:Blood Platelets / Q000502:physiology*; D048429:Cell Size; D004909:Erythrocyte Indices; D004912:Erythrocytes / Q000166:cytology*; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D008297:Male; D015539:Platelet Activation
chemical_list: D015415:Biomarkers
keywords: Alzheimer´s disease; elderly; erythrocytes; fibrinogen; mean corpuscular volume; platelet activity; platelet density; platelet reactivity; β-amyloid