Immunohistochemical study of the hnRNP A2 and B1 in the hippocampal formations of brains with Alzheimer's disease

To elucidate the post-transcriptional regulation in the subjects with Alzheimer's disease (AD), we employed immunohistochemical techniques and examined the expression of the heterogeneous nuclear ribonucleoprotein (hnRNP) A2 and B1 in the hippocampus with neurofibrillary tangle (NFT) neuropathology. In the mildly affected subjects (Braak stages I and II), the most intense A2 immunoreactivity was observed in the CA3 to CA1 neurons. In the moderately (Braak stages III and IV) and severely affected subjects (Braak stages V and VI), the CA1 region demonstrated a decrease in the number of A2 immunoreactive neurons and in immunoreactivity in the remaining neurons, while within the CA4 to CA2 in the severely affected subjects, the majority of neurons showed increased A2 immunoreactivity. An intense B1 immunoreactivity was observed throughout the CA subfields. In the CA1 subfield of the moderately affected subjects and in the extensive hippocampal regions of the severely affected subjects, a decrease in B1 immunoreactivity was observed. Double-immunolabeling studies demonstrated that tangle-bearing neurons reduced A2 and B1 immunoreactivity. Our study suggests that hnRNP A2 and B1 display different responses in the AD hippocampus, and further suggests that the post-transcriptional regulation is disturbed in neurons of the AD hippocampus.