Figure 4.

Caffeine blocks high cholesterol diet-induced down-regulation of tight junction proteins. (A) Schematic draft of a section of olfactory bulb, the green square indicated where the fluorescent images were taken for measures of the expression of occludin and ZO-1. (B) Decreased occludin immunostaining was observed in olfactory bulb from cholesterol-fed rabbits and this effect was blocked by caffeine. Caffeine alone had no effect on occludin immunostaining in normal rabbit brain. Representative images taken from 2 rabbits in each group with 6 sections from each animal are shown. Bar = 100 μm. (C) Quantitative data from B shows that high cholesterol diet significantly decreased occludin immunopositive staining in olfactory bulb, and this effect is blocked by caffeine. (D) Cholesterol-enriched diet decreased significantly protein levels of occludin, and these effects were blocked by caffeine at the dose of 3 mg/day. Caffeine alone did not significantly change protein levels of occludin in normal rabbit olfactory bulb (n = 4, *p < 0.05). (E) Decreased ZO-1 immunostaining was observed in olfactory bulb from cholesterol-fed rabbits and this effect was blocked by caffeine. Caffeine alone had no effect on ZO-1 immunostaining in normal rabbit brain. Representative images taken from 2 rabbits in each group with 6 sections from each animal are shown. Bar = 100 μm. (F) Quantitative data from E shows that high cholesterol diet significantly decreased ZO-1 immunopositive staining in olfactory bulb, and this effect is blocked by caffeine. (G) Cholesterol-enriched diet decreased significantly protein levels of ZO-1, and these effects were blocked by caffeine at the dose of 3 mg/day. Caffeine alone did not significantly change protein levels of ZO-1 in normal rabbit olfactory bulb. n = 4, *p < 0.05.