Hyperhomocysteinemia-induced autophagy and apoptosis with downregulation of hairy enhancer of split 1/5 in cortical neurons in mice

It has been reported that hyperhomocysteinemia (HHcy) is associated with neurodegenerative and cardiovascular diseases. However, little is known about brain histomorphology, neuronal organelles, and hairy enhancer of split ( hes) expression under HHcy. In this study, non-HHcy and HHcy induced by high-methionine diet in apolipoprotein E-deficient (Apo E-/-) mice were comparatively investigated. The histomorphology, ultrastructure, autophagosomes, apoptosis, and expression of proteins, HES1, HES5 and P62, were designed to assess the effects of HHcy on brain. The results showed that compared to the non-HHcy mice, the HHcy group had an increase in autophagosomes, vacuolization in mitochondria, and neuron apoptosis; treatment with folate and vitamin B12 reduced the extent of these lesions. However, the elementary histomorphology, the numbers of cortical neurons, and Nissl bodies had no significant difference between the HHcy and the non-HHcy groups or the group treated with folate and vitamin B12. Immunohistochemistry and immunofluorescence demonstrated a decrease in HES1- or HES5-positive neurons in the HHcy group when compared to the non-HHcy groups, wild-type, and Apo E-/- controls, or the HHcy mice with folate and vitamin B12 supplement. Western blots showed that HHcy induced a decreased expression of HES1 and HES5, or P62, in which the expression of HES1 and P62 was elevated by treating with folate and vitamin B12 supplement. These results suggest that HHcy-enhanced brain damage is associated with increased autophagy and neuronal apoptosis in Apo E-/- mice, in which downregulation of hes1 and hes5 is involved.