Blueberry Antagonism of C-2 Ceramide Disruption of CA2+ Responses and Recovery in MAChR-Transfected COS-7 Cells

Authors: Joseph, James; NEUMAN, ANNA - CORTIVA INSTITUTE; BIELINSKI, DONNA - TUFTS UNIVERSITY; Fisher, Derek

Submitted to: Journal of Alzheimer's Disease
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/28/2008
Publication Date: 11/15/2008
Citation: Joseph, J.A., Neuman, A., Bielinski, D.F., Fisher, D.R. 2008. Blueberry Antagonism of C-2 Ceramide Disruption of CA2+ Responses and Recovery in MAChR-Transfected COS-7 Cells. Journal of Alzheimer's Disease.15:429-441.

Interpretive Summary: Muscarinic receptors are a type of signal receiver that are involved in memory formation, blood vessel function and the regulation of the precursor to amyloid beta (the characteristic plaques found in the brains of Alzheimer’s Disease patients). Research indicates that muscarinic receptors decline in terms of sensitivity during the aging process. This loss of sensitivity may be related to oxidative stress sensitivity since the different types of muscarinic receptors exhibit differential responses to oxidative stress as assessed by the ability of the cell to return to normal after being stressed. Our previous research demonstrated that the polyphenolic compounds found in blueberry extract prevented certain deficits in calcium buffering in the cell. The deficits induced by oxidative stress via dopamine (a neurotransmitter) or amyloid beta exposure that was seen in these experiments is similar to that reported in many studies with respect to aging, and results in a loss of cell function. It also appears that alterations in the lining of the cell may contribute to the losses in receptor responsiveness. Ceramide has been shown to affect calcium buffering and the rate of senescence in several types of cells and tissues. It is of interest in the present experiments to determine the effects of dopamine or amyloid beta on calcium levels in the presence or absence of ceramide and to determine whether the addition of blueberry would prevent any functional deficits in the above parameters induced by these stressors. Results indicate that while ceramide did not produce profound deficits in one test, significant decrements were seen in the cells ability to initially respond, regardless of dopamine or amyloid beta exposure. Blueberry treatment prior to ceramide had a greater effect that ceramide treatment prior to blueberry in one type of cells compared to another. This difference in order of blueberry application was not observed when amyloid beta was used as the stressor. Results are discussed in terms of the effects on stress signaling by the various treatments.

Technical Abstract: Muscarinic receptors (MAChRs) are involved in memory formation, vascular function, and amyloid precursor protein regulation. Research indicates that MAChRs decline in terms of sensitivity during the aging process. This loss of receptor sensitivity may be related to oxidative stress sensitivity (OSS) since MAChR subtypes exhibit differential responses to OS as assessed by the ability of the cell to extrude or sequester Ca2+ following oxotremorine-induced depolarization in COS-7 cells. Our previous research demonstrated that the polyphenolic compounds found in blueberry (BB) extract treatment prevented deficits in cellular calcium regulation. The loss of calcium buffering induced by OS via dopamine (DA) or A beta exposure that was seen in these experiments is similar to that reported in many studies with respect to aging, and results in a loss of cell function. It also appears that alterations in lipid membranes (e.g., via ceramide, Cer) may contribute to the losses in receptor responsiveness. Ceramide has been shown to affect calcium buffering and the rate of senescence in several cell lines and tissue culture models. Since, in aging, oxidative stressors impinge upon receptor-containing membranes that may have altered lipids, it became of interest in the present experiments to determine the effects of DA or A beta 42 on calcium baseline, response, and buffering in the presence or absence of ceramide and to determine whether BB pre-treatment would prevent any functional deficits in the above parameters induced by these stressors. Results indicate that while ceramide did not produce profound deficits in Recovery, in either M1- or M3-transfected COS-7 cells, significant decrements were seen in the ability of both types of transfected cells to initially respond to oxotremorine, regardless of DA or A beta 42 exposure. BB pre-treatment (prior to ceramide) had a greater effect than ceramide treatment prior to BB in M1-transfected cells compared to M3-transfected cells. This difference in order of BB application was not observed when A beta 42 was used as the stressor. Results are discussed in terms of the effects on stress signaling by the various treatments.