Distinctly altered TRPC3 and TRPC6 expression patterns in human Alzheimer's disease cortex and hippocampus.

Abstract

Calcium dysregulation is increasingly recognized as a convergent mechanism underlying neuronal vulnerability and glial overactivation in Alzheimer's disease (AD). Transient Receptor Potential Canonical (TRPC) channels are potential key modulators of Ca²⁺ signaling in multiple cell types in central nervous system (CNS), mediating different pathophysiological roles. However, their cell type-specific remodeling and cellular origins of these changes in human AD tissue remain poorly defined. This study investigated their expression patterns with main focus on the two closely related members of TRPC3 and TRPC6 across human AD brains and two relevant mouse models. Formalin-fixed paraffin-embedded cortical and hippocampal tissues from AD patients and age-matched controls were examined using immunohistochemistry. Spatial relationships between TRPC3/TRPC6 and glial fibrillary acidic protein (GFAP)-positive astrocytes were assessed in adjacent serial sections. TRPC3 expression was markedly increased in AD cortex and hippocampus whereas TRPC6 was significantly reduced primarily in pyramidal neurons. TRPC3-positive regions showed close spatial correspondence with reactive astrocytes, particularly in the hippocampal and subcortical white matter regions, suggesting a partial astrocytic origin. TRPC6 exhibited negligible overlap with GFAP. These observations were reproduced in brain sections of both 5xFAD and PS19 transgenic (Tg) mice compared to their littermate controls. Our findings reveal a conserved pattern of divergent TRPC remodeling across human and mouse models with AD pathology. In addition, TRPC1 expression was significantly reduced in AD samples while TRPC4 and TRPC5 had no significant change in expression. Taken together, selected TRPC family members may undergo differential remodeling during AD pathogenesis, with TRPC3 and TRPC6 showing the most prominent and consistent alterations.