Quercetin alleviates cognitive decline in ovariectomized mice by potentially modulating histone acetylation homeostasis.

The synergism between estrogen and histone tail acetylation-mediated memory formation is not clearly understood. Here, we attempt to study the altered histone acetylation homeostasis mediated changes in cognition following ovariectomy and evaluate the protective effect of quercetin. A significant reduction in estradiol levels with subsequent depletion in spatial memory and learning functions assessed by Morris water maze, novel object recognition test and elevated plus maze was observed in ovariectomized (OVX) mice. Correspondingly, a significant decline in neuroplasticity markers like brain-derived neurotrophic factor (BDNF), synaptophysin (SYP) and postsynaptic density-95 (PSD-95) was observed in cortex and hippocampus of OVX animals. Notably, histone acetyltransferase (HAT)/histone deacetylase (HDAC) balance was significantly disrupted in cortex and hippocampus of OVX mice. Lowered extracellular signal regulated kinases (ERK) and cAMP response element binding protein activation observed in OVX brain regions might account for HAT/HDAC imbalance. Altered HAT/HDAC homeostasis results in lowered histone 3 acetylation in OVX brain that suppressed transcriptional activation of neuroplasticity-related genes. Quercetin supplementation to OVX mice for 4 weeks was able to ameliorate cognitive impairment by restoring HAT/HDAC homeostasis through ERK activation and reversing alterations in neuroplasticity markers in cortex and hippocampus of OVX mice. Taken together, our results suggest that quercetin alleviates ovariectomy-induced cognitive decline by modulating histone acetylation homeostasis.