Effects of Pyridoxine Deficiency on Hippocampal Function and Its Possible Association with V-Type Proton ATPase Subunit B2 and Heat Shock Cognate Protein 70

Abstract

Pyridoxine, one of the vitamin B6 vitamers, plays a crucial role in amino acid metabolism and synthesis of monoamines as a cofactor. In the present study, we observed the effects of pyridoxine deficiency on novel object recognition memory. In addition, we examined the levels of 5-hydroxytryptamine (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), 3,4-dihydroxyphenethylamine (DA), 3,4-dihydroxyphenylacetic acid, and homovanillic acid and the number of proliferating cells and neuroblasts in the hippocampus. We also examined the effects of pyridoxine deficiency on protein profiles applying a proteomic study. Five-week-old mice fed pyridoxine-deficient diets for 8 weeks and showed a significant decrease in the serum and brain (cerebral cortex, hippocampus, and thalamus) levels of pyridoxal 5′-phosphate, a catalytically active form of vitamin-B6, and decline in 5-HT and DA levels in the hippocampus compared to controls fed a normal chow. In addition, pyridoxine deficiency significantly decreased Ki67-positive proliferating cells and differentiated neuroblasts in the dentate gyrus compared to controls. A proteomic study demonstrated that a total of 41 spots were increased or decreased more than two-fold. Among the detected proteins, V-type proton ATPase subunit B2 (ATP6V1B2) and heat shock cognate protein 70 (HSC70) showed coverage and matching peptide scores. Validation by Western blot analysis showed that ATP6V1B2 and HSC70 levels were significantly decreased and increased, respectively, in pyridoxine-deficient mice compared to controls. These results suggest that pyridoxine is an important element of novel object recognition memory, monoamine levels, and hippocampal neurogenesis. Pyridoxine deficiency causes cognitive impairments and reduction in 5-HT and DA levels, which may be associated with a reduction of ATP6V1B2 and elevation of HSC70 levels in the hippocampus.

Pyridoxine Deficiency Exacerbates Neuronal Damage after Ischemia by Increasing Oxidative Stress and Reduces Proliferating Cells and Neuroblasts in the Gerbil Hippocampus

“…PDD-fed gerbils showed a significant reduction in serum PLP levels in sham-operated animals as well as ischemic animals three and four days after ischemia. This result is consistent with our previous study that PDD-fed mice showed a significant reduction in serum and hippocampal PLP levels [ 20 ]. In contrast, pyridoxine deficiency significantly increased serum homocysteine levels in sham- and ischemia-operated animals and showed hyperhomocysteinemia, which is characterized by > 15 µmol/L homocysteine levels in the blood.…”

“…Vitamin B 6 is one of the essential vitamins that maintain the health of the nervous system in mammals, which should be taken in sufficient quantity from the food because it is not synthesized in mammals [ 25 , 26 ]. Deficiency of vitamin B 6 causes cognitive function impairment, hippocampal neurogenesis reduction, cardiovascular disease, and Alzheimer’s disease [ 20 , 27 ]. In the present study, we observed the effects of pyridoxine deficiency on cell death in the hippocampal CA1 region and on neuroblasts in the dentate gyrus after transient forebrain ischemia.…”

“…In this study, we also observed the effects of pyridoxine deficiency on regenerative potentials based on proliferating cells and neuroblasts in the dentate gyrus because we observed the reduction of neuroblasts in the mice hippocampus [ 20 ]. In gerbil brain, the proliferating cells and neuroblasts were reduced in the dentate gyrus of sham- and ischemia-operated animals, and this result suggests that pyridoxine deficiency reduces the regeneration potentials in ischemic brain.…”

“…After a week of acclimation, gerbils were fed with pyridoxine-deficient diet (PDD, D10001, Research Diets) and its control diet (CD, D15501R, control, Research Diets, New Brunswick, NJ, USA) for 56 days as described in the previous study [ 20 ] since the half-life of the elimination of pyridoxine exceeds 15 to 20 days [ 56 ]. All animals used in this study were sacrificed on the 56th day of diet feeding.…”

“…To show the morphological evidence of the changes in neurons, astrocytes, and microglia in the hippocampus, immunohistochemical staining was conducted for NeuN, GFAP, and Iba-1, respectively, as previously described [ 20 , 57 ]. In addition, proliferating cells and neuroblasts were visualized with the immunohistochemistry of Ki67 and DCX.…”