ABSTRACT
Disturbances in calcium homeostasis have been observed to be associated with Alzheimer's and other neurodegenerative diseases. Increased total calcium levels and decreased levels of calcium binding proteins have been found in Alzheimer brain tissue. However, the mechanism behind these disturbances remain unknown. In situ hybridization with tritiated antisense RNA probes for the calcium binding proteins, calbindin-28k and calmodulin, was used to examine the expression of genes coding for these proteins in Alzheimer and Huntington brain tissues matched for age, agonal process and autopsy interval. mRNA levels for calbindin-28k were reduced by 35% in CA1 and CA2 regions of Alzheimer hippocampus, as compared to Huntington control. In contrast, calmodulin expression was unchanged in CA1 but reduced by 30% in CA2. mRNA expression of calbindin-28k and calmodulin in Alzheimer temporal cortex did not differ from control. There were no significant differences in calcium binding protein message levels in cerebellar Purkinje cells between Alzheimer and Huntington control. There was no correlation between calcium binding protein message levels and brain weight, autopsy interval, patient age or the extent of neurofibrillary degeneration. Instead, decreased calbindin-28k expression in Alzheimer-affected hippocampus was due to an increase in the percentage of neurons expressing lower message levels for these proteins.
Subject(s)
Alzheimer Disease/metabolism , Hippocampus/chemistry , Huntington Disease/metabolism , Nerve Tissue Proteins/deficiency , S100 Calcium Binding Protein G/analysis , Aged , Animals , Calbindins , Calcium/metabolism , Cerebellum/chemistry , Homeostasis , Humans , In Situ Hybridization , Middle Aged , Nerve Tissue Proteins/analysis , Neurons/chemistry , RNA, Messenger/analysis , Rats , Temporal Lobe/chemistryABSTRACT
Receptors for vitamin D hormone (VDR) and the calcium binding protein, calbindin-28k, have been localized in many tissues, including brain. In brain, VDR and calbindin-28k were reported to colocalize in hippocampal CA1 cells. We have shown that mRNA pool size for calbindin-28k was reduced, on average, by 35% in Alzheimer hippocampal CA1 cells, as compared to Huntington control (manuscript in preparation). In the present study, in situ hybridization with tritiated antisense RNA probes was used to examine VDR expression in paired Alzheimer and Huntington brain tissue. Message levels for VDR were reduced, on average, by 34% and 31%, respectively, in Alzheimer hippocampal CA1 and CA2 pyramidal cells, as compared to Huntington control. However, VDR message levels were not significantly different from control in Alzheimer temporal cortex or cerebellum. There was no correlation between VDR message levels and brain weight, autopsy interval, patient age or the extent of neurofibrillary degeneration. Instead, VDR mRNA pool size in hippocampal CA1 cells correlated significantly with calbindin-28k message levels (r = 0.52, P less than 0.001). Decreased message levels for VDR and calbindin-28k in these cells were due to an increased percentage of cells expressing lower message levels for these proteins. These results show that in Alzheimer hippocampal CA1 cells, VDR mRNA pool size is downregulated and that this downregulation may play a role in the reduction of calbindin-28k expression.
Subject(s)
Alzheimer Disease/metabolism , Hippocampus/metabolism , Huntington Disease/metabolism , Nerve Tissue Proteins/biosynthesis , S100 Calcium Binding Protein G/biosynthesis , Vitamin D-Binding Protein/biosynthesis , Alzheimer Disease/pathology , Calbindins , Cerebellum/metabolism , Cerebellum/pathology , Gene Expression Regulation , Hippocampus/pathology , Humans , Huntington Disease/pathology , Infant, Newborn , Middle Aged , Nerve Tissue Proteins/genetics , RNA, Messenger/analysis , S100 Calcium Binding Protein G/genetics , Temporal Lobe/metabolism , Temporal Lobe/pathology , Vitamin D/physiology , Vitamin D-Binding Protein/geneticsABSTRACT
The technique of in situ hybridization with tritiated RNA probes was used to study the expression of the 68 kDa neurofilament (NF68) gene and the superoxide dismutase-1 (SOD-1) gene in the brains of Alzheimer's disease (AD) patients. Messenger RNA (mRNA) for these proteins was localized and quantified in single cells of formalin-fixed, paraffin-embedded sections of 4 pairs of AD and Huntington's disease (HD) brains from patients matched for age at death and autopsy interval. The cerebellar cortex and hippocampal CA1 and CA2 regions were compared in these two groups of subjects, since in AD the CA2 region of the hippocampus and the cerebellum have been found to be relatively unaffected by the Alzheimer process in comparison to the hippocampal CA1 region. The amount of NF68 mRNA was reduced by approximately 50% in pyramidal cells of both the CA1 and CA2 of AD hippocampus (P less than 0.001), and by 15% in the Purkinje cells of AD cerebellum (P less than 0.05) relative to that of the HD individuals. SOD-1 mRNA was reduced by about 22% in the CA1 of AD brains (P less than 0.001) with no corresponding reduction in the CA2, and by only 5% in the AD cerebellum (P greater than 0.5). The paired design of the study suggests that these results are not simply attributable to the effects of autopsy interval or the agonal process in each patient's death.
