Differential protection among fractionated blueberry polyphenolic families against DA-, Abeta(42)- and LPS-induced decrements in Ca(2+) buffering in primary hippocampal cells

Abstract

It has been postulated that at least part of the loss of cognitive function in aging may be the result of deficits in Ca(2+) recovery (CAR) and increased oxidative/inflammatory (OX/INF) stress signaling. However, previous research showed that aged animals supplemented with blueberry (BB) extract showed fewer deficits in CAR, as well as motor and cognitive functional deficits. A recent subsequent experiment has shown that DA- or Abeta(42)-induced deficits in CAR in primary hippocampal neuronal cells (HNC) were antagonized by BB extract, and (OX/INF) signaling was reduced. The present experiments assessed the most effective BB polyphenol fraction that could protect against OX/INF-induced deficits in CAR, ROS generation, or viability. HNCs treated with BB extract, BB fractions (e.g., proanthocyanidin, PAC), or control medium were exposed to dopamine (DA, 0.1 mM), amyloid beta (Abeta(42), 25 muM) or lipopolysaccharide (LPS, 1 microg/mL). The results indicated that the degree of protection against deficits in CAR varied as a function of the stressor and was generally greater against Abeta(42) and LPS than DA. The whole BB, anthocyanin (ANTH), and PRE-C18 fractions offered the greatest protection, whereas chlorogenic acid offered the lowest protection. Protective capabilities of the various fractions against ROS depended upon the stressor, where the BB extract and the combined PAC (high and low molecular weight) fraction offered the best protection against LPS and Abeta(42) but were less effective against DA-induced ROS. The high and low molecular weight PACs and the ANTH fractions enhanced ROS production regardless of the stressor used, and this reflected increased activation of stress signals (e.g., P38 MAPK). The viability data indicated that the whole BB and combined PAC fraction showed greater protective effects against the stressors than the more fractionated polyphenolic components. Thus, these results suggest that, except for a few instances, the lesser the polyphenolic fractionation, the greater the effects, especially with respect to prevention of ROS and stress signal generation and viability.

Figure 1

This figure shows a typical Baseline (A), peak depolarization following 30 mM KCl (B), and Recovery (C) and in control cells that were not treated with DA, LPS or Aβ₄₂.

Figure 2

Differences in the values of Calcium Recovery in whole BB, fraction pre-treated, or control (Cont) cells exposed to DA (A), Aβ42 (B), or LPS (C). b= p<0.05 from stressor control; c= p<0.05 from own treated control.

Figure 3

Differences in viability in whole BB, fraction pre-treated, or control (Cont) cells exposed to DA (A), Aβ42 (B), or LPS (C). a=p<0.05 from control; b=p<0.05 from stressor control; c= p<0.05 from own treated control.

Figure 4

Differences in ROS in whole BB, fraction pre-treated, or control (Cont) cells exposed to DA (A), Aβ42 (B), or LPS (C). a=p<0.05 from control; b=p<0.05 from stressor control; c= p<0.05 from own treated control.

Figure 5

Cellular changes in the level of activation of a subset of protective (MAPK, Figure 5A) and stress signals (JNK, Figure 5B; P38MAPK, Figure 5C; NfκB, Figure 5D) in whole BB, fraction pre-treated, or control (Cont) cells exposed to DA and analyzed by fluorescence immunocytochemistry. a=p<0.05 from control; b=p<0.05 from DA control; c= p<0.05 from own treated control.